Technology for welding cast iron with a coated electrode using an inverter at home

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• Cast iron: types, application Features of welding cast iron

Cast iron: types, application

Cast iron is a kind of mixture of iron and carbon. The material is hard and wear-resistant, but, paradoxically, quite fragile if not handled correctly. This is why welding cast iron with an electrode at home using an inverter should only be done after careful preparation (this will be discussed below).

Cast iron has been known in the world for a long time - it is believed that it appeared in the 6th century BC.

The average melting point is over 1000 degrees Celsius. You can work with the material when heated to 600 degrees.

By type, cast iron metal is divided into the following categories:

• white;
• half-hearted;
• grey;
• high strength;
• malleable.

Over time, cast iron does not lose its relevance; it is used in various spheres of human activity. The material is used for the following purposes and tasks:

• forging fences;
• production of machine tools;
• production of frying pans for household use;
• manufacturing of heating radiators, pipes, plumbing connections;
• creating baths;
• in the automotive industry - for the production of crankshafts, cylinders, engines and other things.

This is only a small part of the tasks that ordinary cast iron can successfully cope with. An important feature is that surfacing cast iron with electrodes can be done at home without the help of a professional welder.

Features of cast iron welding

Depending on the form in which carbon is present, cast iron is divided into several types:

1. White cast iron. It contains carbon in the form of cementite. It is characterized by high hardness and cannot be processed with cutting tools. It is extremely difficult to cook.
2. Gray cast iron. It contains carbon in the form of graphite. The alloy is quite easy to process. When welding cast iron with an electrode at home with an inverter, a reliable connection is ensured.
3. Malleable type. It is produced by specially treating white cast iron to convert the carbon into flake graphite form. This alloy is actively used in mechanical engineering. It can be welded with special electrodes.
4. Half cast iron. Contains carbon in both forms - cementite and graphite. Used for the manufacture of products with increased wear resistance.
5. High strength cast iron. The carbon in it has a spherical shape, acquired during crystallization. Metal is used for especially critical products, including pipes.

The last 2 types of alloy can be welded with an electrode, but require a special approach. Welding technology for different types of cast iron differs significantly, which must be taken into account when working.

Welding cast iron is associated with the following difficulties:

1. Some alloy components are easily oxidized upon melting to form refractory oxides. They lead to inhomogeneity of the weld and the appearance of unwelded areas.
2. With rapid cooling of the heat-affected zone, cementite is formed, which subsequently cannot be machined.
3. The cast iron melt has increased fluidity, which makes it difficult to form a seam and retain it in the weld pool.
4. Any uneven heating and cooling of the welding zone leads to cracking of the metal.
5. When cast iron melts, gases are released that can cause pores to appear in the weld.

Important! The special structure and properties of cast iron lead to poor weldability at home. However, if you follow the regimes, choose the right method and consumables, you can brew most cast iron products used at home with high quality.

Cast iron as a material

Cast iron is divided into two types. The lighter one is usually called white: at the break it has a light gray almost white color. Carbon in its composition is presented in the form of cementite. This material is characterized by high fragility and cannot be machined. It is rarely used for the production of various types of products and cannot be welded.

After additional processing of white cast iron, namely long-term melting at a temperature of 1000 degrees Celsius, another type of cast iron is obtained - gray. Unlike the first, the product is more technologically advanced and can be machined and welded. It is used to produce a wide range of parts that are resistant to vibration and mechanical stress. Malleable cast iron is in demand in the production of agricultural machinery, machinery, machine tools, ships and many other equipment.

If a certain amount of alloying additives is added to the composition of a malleable material, high-strength cast iron will be obtained. The material is used in the production of high-pressure pipes, critical parts for the automotive industry and mechanical engineering. When fractured, the color of such cast iron will have a silver-gray tint. Carbon in its composition is represented by graphite. This type is widely used as a structural material, processed by cutting turning tools, has wear resistance, excellent casting performance, vibration resistance.

Types of welding

To know how to weld cast iron with a conventional electrode, it is important to understand the types of welding in general. They are divided into:

• hot;
• semi-hot;
• cold.

Hot is indeed such, occurring at temperatures between 600 and 700 degrees Celsius. The metal is heated in industrial furnaces, which are considered heavy-duty equipment. Cast iron becomes flexible, like plasticine, and is easy to work with. During the process, no cracks or pores appear on the product that would interfere with normal operation in the future.

Experts call this welding method the most ideal for cast iron. Naturally, to the question: is it possible to cook cast iron using conventional electrodes at home using the hot welding method, the answer will be negative. Creating such a colossal temperature in an apartment or garage, for example, is dangerous to life and health.

Semi-hot welding is also impossible at home. It is carried out at a temperature of 300-400 degrees Celsius. For heating, special hair dryers or heating elements are used. This method is used in industry. Its main advantage is faster cooling compared to the hot method. For a novice master, the semi-hot technology of welding cast iron with electrodes is practically impossible.

Cold welding is suitable for home use. It occurs at a maximum temperature of 80 degrees Celsius.

Alloy characteristics

The welding process of cast iron parts directly depends on the characteristics and properties of the alloy. In fact, this metal consists of two metals - iron and carbon. But if we compare it with steel, then it contains almost 2.14% more iron.

As mentioned above, depending on the composition, cast iron can be of different types - white, gray, half-cast, high-strength. The properties of each type are determined by the constituent components.

Welding on cast iron has some difficulties. During this process, it is quite difficult to achieve high strength of the weld. This occurs due to the presence of problems from the list:

• Due to the fact that cast iron has a non-uniform structure, the seam can crack severely when welded. This is due to the influence of the increased arc temperature on it. As a result, bleaching occurs, a change in composition in the area of ​​metal welding;
• welding work on cast iron using the high-temperature influence of an electric arc causes the burnout of part of the carbon from the alloy composition. All this can cause the formation of pores in the weld. As a result, the strength of the weld is greatly reduced and quality characteristics deteriorate;
• When melted, cast iron acquires a highly fluid structure, which causes difficulties in forming a normal seam. The higher the carbon content, the higher the degree of fluidity of the alloy;
• When welding cast iron with steel, oxide may appear in the weld, which causes a decrease in strength.

The above features of the metal significantly complicate the welding process on cast iron. The main difficulty is that the outcome may not be what is expected. Often, pores and cracks appear on the surface of the weld as the alloy cools.

For welding, you should not use dark gray or black cast iron (it has a high graphite content). These types of alloys should not be cooked at home, as this often causes cracking of the joint and the part itself.

Features of the welding process

Now we’ll tell you how to weld cast iron using electric welding. When the master is convinced of the reliability of the equipment, he can begin the process. To do this, you need to choose how to cook cast iron with simple electrodes:

• on studs;
• multi-layered.

In the first case, the master first installs the pins themselves, and forms a seam around them. Experienced welders recommend performing the procedure in a staggered manner to prevent overheating of the material. The work is completed with a connecting seam - it goes from one pin and its “surroundings” to the other.

The multilayer method is as follows: chamfers are created, then the initial layer is fused, it is hammered, then a second layer is laid, tapped again, and so on. After the seam has cooled, it must be sanded to give the product an aesthetic appearance. If it is possible to access the inside of the product, then the initial layer in the multilayer method is placed on the outside and inside. This makes the connection even stronger.

In general, there is nothing complicated about how to properly cook cast iron with electrodes. The main thing is to follow safety rules.

Welding cast iron using steel studs

The weld metal can peel off, making the melting zone the most vulnerable area. To more evenly distribute the load during cooling and associated shrinkage, so-called “wraps” are used - steel studs. If the wall thickness of the workpiece exceeds 6 mm, then the edges are pre-cut at an angle of 45 degrees.

Then holes are drilled in a checkerboard pattern into which steel pins are screwed. They partially protrude on the surface. The wrappers are scalded in a circle, after which a fusion layer is formed by applying annealing rollers. The peculiarity of the seam is that most of the mechanical loads are borne by steel studs, while the seam is subject to a small force.

Safety precautions

Even before cooking cast iron with a conventional electrode, it is important to take care of following safety precautions:

• Place a fire extinguisher near your workplace;
• make sure the welding machine is in good working order;
• put on special protective gloves for welding activities;
• cover your face with a mask or at least glasses;
• work exclusively in thick clothing so that particles of hot metal do not have the opportunity to come into contact with the skin;
• it is important that fresh air always flows into the room where welding is performed;
• if you are welding for the first time, it is wise to invite an assistant or at least an outside observer, so that in case of an emergency, there will be someone to help.

Naturally, it is advisable to work during daylight hours or at least in sufficient lighting, in an absolutely sober and healthy state.

Security measures

Carrying out welding work at home requires careful and precise adherence to safety precautions. The most important points:

• the room in which welding work is carried out must be illuminated and ventilated ;
• It is mandatory to use means for grounding ;
• Cast iron does not respond well to rapid cooling, so its surface must be protected from moisture ;
• personal protective equipment when working .

Preparation for welding

Preparatory operations must be carried out carefully and carefully, as this is one of the fundamental principles of obtaining a high-quality connection:

• the structure is cleaned of dirt, debris and dust;
• then you should degrease the parts with a solvent, for example, acetone;
• when working with thin cast iron, you need to use pads to remove heat;
• edge cutting should be done before welding thick-walled products; for this, a file or grinder is used;
• cracks must be drilled along the edges and cut to their entire length; an alternative method is to cut out the cracks and round the ends;
• depending on the chosen welding method (hot or cold), the product is heated or not. The part can be heated using various equipment: ovens, gas burners, or using improvised means: a blowtorch.

Cutting and edging

This operation is mandatory when welding cast iron by any method. To do this, the edges are cleaned with a file or a grinder with a metal attachment. When cutting the edges, cracks are cut out. If it is necessary to install studs, the edges are cut at an angle. Holes are drilled at the ends and threads are formed. After this, screw in the studs. The outer ends of the elements must be welded to each other.

Preparation

The presence or absence of defects largely depends on how competently the preparatory work is carried out. Cracks in cast iron have a thin and deep structure. To get rid of them, you need to cut the edges to the full depth. For these purposes, you can resort to simple mechanical methods - grinding or cutting, or you can use heat treatment - arc or oxygen cutting.

The length of the groove should be approximately 5 millimeters longer than the visible part of the crack on each side. Closer to the edge, the cutting groove should become shallower so that it eventually comes out flush with the surface of the workpiece. The depth of cutting through defects is 1-2 mm less than the thickness of the walls of the product. Regarding non-through cracks, it’s the other way around: the cutting should exceed the depth of the crack by at least 1-2 mm.

Proper cutting of edges eliminates overheating of cast iron. If everything is done correctly, the metal will heat up evenly throughout the entire area. To do this, you need to ensure that the bevel of the edges is exactly 45 degrees. It is important that the edges are free of sharp corners. It is advisable to clean the surface with sandpaper, a sandblaster, a grinder or a regular metal brush. If some contaminants cannot be removed mechanically, then you can resort to heat treatment.

Cast iron parts with thin walls are welded using graphite molds. They serve as a lining. Thanks to this technique, the temperature is evenly distributed throughout the entire volume and the original shape of the workpiece is preserved.

Devices and consumables

To carry out welding work, you need to use special equipment. Experts recommend using devices that generate direct current (inverters). Welding equipment that uses transformers has low efficiency and worsens the final result.

To operate the inverter you will need consumables in the form of electrodes. Their diameter must be at least 3 mm. Welding cast iron with electrodes allows you to make a better-quality seam than when working with a semi-automatic machine. The best consumables for this alloy are considered to be OZCh-2 and MNCh-2.

Cast iron can be cooked with argon. For this, copper-plated wire is used. The process of working with this equipment is similar to using an inverter. Using argon welding, plates up to 4 mm thick can be welded.

Surfacing of cast iron

The work is performed with electrodes of the following brands:

1. OZZHN-1. Suitable for eliminating serious casting or processing defects.
2. MNC-2. Used for surfacing critical connections. Pre-heating of the surface is not required.
3. OZCH-2. Surfacing of gray and ductile cast iron.

The operation of gas surfacing is based on thermal energy, which is released as a result of the combustion of acetylene, as well as its substitutes, and oxygen. Consumable materials are fluxes and light rods.

Welding methods

Three methods have been developed to create strong seams:

1. Hot welding technology is complex, but practically eliminates the formation of cracks. It is performed with preheating to a temperature of 600 - 650⁰C with subsequent slow cooling. In production, this procedure is performed on induction installations. Some beginners doubt whether it is possible to cook cast iron using this method on their own. This is possible if you use a forge, gas burner, or blowtorch for heating, and hot sand for slow cooling.
2. Semi-hot welding is similar to the previous method, but the heating temperature is 300 - 350⁰C.
3. Cold welding is carried out with special electrodes without preheating the parts. However, in order to brew cast iron using this method, it is necessary to take into account the technological features of the material.

Preheat

All cast irons are susceptible to stress cracking. Temperature control is the only way to prevent cracks. Creating a weld, from the point of view of thermal processes, consists of three steps:

• preheating;
• heat input;
• slow cooling.

The main task of thermal control is expansion control. Stress does not occur in metal when the entire object heats up or expands at the same time and at the same rate. The risk of cracks is high if the heat is localized in a small heat-affected zone. Preheating reduces the thermal gradient between the casting body and the weld site. In theory, higher temperature welding methods require higher preheat temperatures. If the latter cannot be provided, the best strategy would be to minimize heat input - to use low-temperature welding methods with low-melting electrodes.

The cooling rate is another factor that directly affects the occurrence of stress in the welded zone. Rapid cooling due to the reduction of the cooling zone creates brittle, easily cracked seams.

How to weld cast iron using electric welding

Correctly welding cast iron by electric welding is possible only if you use the correct electrodes, as well as the necessary equipment. The peculiarity of the work is that in the area where the seam is applied, the fragility of the metal increases.

The fragility is due to the fact that during work, cast iron experiences excessive and intense hardening. For this reason, the technology for welding cast iron with electrodes in industrial conditions differs significantly from the conventional processing of other metals and requires heating the material to a temperature of about 600-650° degrees.

The following types of electrodes are used for work:

1. OZCH-2 – have a copper rod coated with a special composition that includes graphite.
2. MNCh-2 - an alloy of metals from nickel, copper, manganese and iron is used for the rod. MNCh-2 electrodes are the optimal solution, but they are significantly more expensive.

Electric welding of cast iron products using the cold method requires compliance with a certain rate of welding and control so that the surface does not heat up above the required levels. The welder performs work “randomly”, in small sections with mandatory forging and breaks.

Since the peculiarity of cast iron is its slow cooling, welding a cast iron part may require a large amount of time. When restoring small defects, it is mandatory to use a graphite substrate to avoid metal leakage.

How to brew cast iron correctly

The special properties of the metal cause increased demands on the welding process. The right approach requires careful preparation. The work area must be well cleaned of any contamination. Used: grinder, metal brushes, sandpaper. Oil stains are removed with solvents. For severe contamination, use torches or sandblasting.

A common occurrence is cracks on the surface along the edges of cast iron products. Their sealing requires a special approach. The cracks are cut and cleaned to their full length to ensure complete filling with the melt. If necessary, the workpieces are drilled along the edges, and the ends are cut at the angle required for welding.

Cast iron can be brewed in several ways, and it is important to choose the right option.

Welding technology and methods

There are 3 main methods of welding cast iron, depending on preheating:

1. Hot method. Before welding, parts are heated to 600-680 °C, which increases the plasticity of the metal and reduces the risk of cracking. This technique is ideal for production environments where special ovens are available. It is extremely difficult and dangerous to provide such heating in a house.
2. Semi-hot technology. The metal is preheated to 320-360 °C. Heating is done with special hair dryers. It is difficult to implement this method at home, but if you have a separate workshop, you can carry out the process.
3. Cold welding. This is the most common technique for working at home. Preheating is not performed or does not exceed 60–80 °C. With this method, you will have to take into account all the difficulties of working with cast iron.

When choosing a method, you must take into account safety, the type of metal and the availability of the necessary equipment.

Stud welding

The grain structure of the alloy does not always allow parts to be welded in a multilayer manner. In difficult cases, threaded studs are installed. They are mounted in a checkerboard pattern along the edges of the workpieces being joined.

When choosing the size of studs, consider the following recommendations:

1. The diameter of the fastening element should be 30-40% of the thickness of the workpieces being connected. The maximum value is 1.2 cm.
2. The pin is screwed in 1.5 times the diameter. However, the length of the screwed-in section should not exceed half the thickness of the parts being welded;
3. The size of the protruding part should be 0.7-1.2 times the cross-section of the stud.

After placing the studs, several layers are welded along their perimeter.

To avoid overheating, the operation is performed alternately on different sides. At the final stage, the deposited metal is welded in several seams.

Cold welding of cast iron

Cold welding for cast iron is performed mainly in domestic conditions. The advantage of the cold method is that there is no need for additional equipment to complete the work. When applying a seam, the following types of electrodes for cold welding are used:

• Copper-iron.
• Copper-nickel.
• Iron-nickel.
• Steel.
• Cast iron.

Surfacing is performed by laying one or more weld beads. When using steel electrodes, it is necessary to install studs to increase the strength of the connection. Any electrodes that contain iron and nickel are mainly used to repair minor damage.

The technology of cold welding of cast iron also involves the correction of large surface defects. For these purposes, cast iron electrodes coated with graphite are used.

The cold method cannot provide a high-quality and long-lasting seam. The use of the cold method is limited to parts with minor defects and non-load-bearing structures.

In a gas environment

Gas is used to protect and heat the treated area. When welding cast iron, a propane-butane mixture or acetylene is often used. The electrode is replaced with a filler wire made of the same metal or nickel. To reduce the likelihood of oxidation, the rod is treated with flux. Sometimes the wire is heated by the reducing part of the burner.

To obtain a welded joint using the gas method, perform the following steps:

1. Gradually heat up the welding area. The appropriate temperature is selected empirically.
2. Once the desired temperature is achieved, a connection is formed. Gradually remove the burner, achieving slow cooling.
3. Clean the welded joint from slag and grind it if necessary.

Arc welding with electrodes

This method is approved for use, but it is characterized by high cost and lack of advantages over other methods. Cast iron does not require careful protection from oxidation.

When arc welding with argon, the following rules are observed:

• prevent overheating of the treated areas;
• gradually increase the temperature of the weld pool;
• slowly cool the finished structure.

The welding process includes the following steps:

• fixing parts in the correct position using a vice or clamp;
• formation of a protective gas cloud (argon supply starts 15 seconds before arc initiation, stops 7 seconds after completion of work);
• setting up the machine (current strength and supply speed of consumables are selected taking into account the thickness of the workpieces being welded);
• suture placement (the electrode is guided in the direction of the connection);
• completion of welding by gradually reducing the arc power with a rheostat.

With argon-arc technology, a semi-automatic device with nickel wire or non-consumable electrodes is used.

Features of welding at home with an inverter

For electric welding at home, you can use a regular inverter or a special home semi-automatic machine. The most common method is cold welding with electrodes, when an inverter is used as a current source. When connecting the device, the polarity is reversed. It is turned on at the minimum power for this type of electrode. Welding is done with short seams 40–50 mm long.

There are 2 ways to ensure the strength of the weld:

1. Welding with studs. As a rule, steel studs with a diameter of up to 0.4 times the thickness of the cast iron workpiece are used. They are inserted into holes drilled along the edges. Their projection does not exceed 4–5 mm, and the installation pitch is up to 5 diameters. At the initial stage, the protruding part is scalded around, and the melt fills the seam. Then, the metal is welded from stud to stud, forming a circular weld. Gradually, the entire surface at the joint should be evenly filled with the deposited metal.
2. Multilayer welding. After careful preparation of the edges of the workpieces and the formation of chamfers, the parts are joined and the layer-by-layer formation of the weld begins. After applying the first layer, it is carefully forged with a hammer. Then, the procedure is repeated with the second layer, etc. If flat workpieces are to be cooked, then after applying each layer, the parts are turned over and the layer is applied on the reverse side.

Reference! When welding, it is important to remember that the metal cannot be overheated, and therefore frequent stops of the process are necessary.

What electrodes are used for welding cast iron

The peculiarity of welding cast iron using electrodes is that when the electrode burns out, a certain amount of carbon located in the metal itself also burns out. When burned out, pores are formed that affect the quality and strength of the weld joint.

Therefore, for welding cast iron products, electrodes containing nickel and copper are used. There is a reasonable explanation for this, related to the characteristics of these metals:

• Nickel - dissolves without residue in the iron that is part of cast iron. In this case, nickel is completely neutral with respect to carbon and enters into a chemical reaction with it. This provides certain advantages. The weld seam applied with a nickel electrode is not hardened during the work and remains soft and pliable for further processing.
• Copper - the special electrodes used for welding heat-resistant cast iron are made of this metal. Copper does not dissolve in iron and as a result forms a harder weld, which is often required when processing the material.

If we talk about brands of electrodes for welding and surfacing, then there are about a dozen types of products on the market designed for specific purposes and having their own specific properties. Namely:

• Welding electrodes for cast iron SCh 20 – for work with gray cast iron, electrodes with a graphite coating are used. Electrodes SCh 20 allow you to obtain a weld that is completely identical in structure and chemical composition to the metal being processed.
• Electrodes for cast iron TsCh 4 - used for cold work. The main purpose of TsCh 4 electrodes is to carry out minor repairs of surface defects. It is also recommended to use TsCh 4 electrodes for welding cast iron with steel, provided that low-polarity direct current is supplied.
• Welding cast iron with a stainless steel electrode is another effective way to process black cast iron. The technology for working with a stainless steel electrode includes mandatory heating of the workpiece and the application of several welds.
• Welding with copper electrodes - this class includes the most “rare” MNCh-2 consumables. MNCh-2 electrodes allow you to obtain the highest quality seam. MNCh-2 can be used for both cold and hot welding.

You can independently make electrodes similar in composition to those listed above. Especially considering that MNC-2 is rare and in short supply, making its analogue at home is quite justified. For production you will need to do the following:

• Remove the coating from the conventional electrode. Grind the resulting composition and mix in equal proportions of iron powder. Small chips can be used.
• Liquid glass is poured into a separate container. The mixture is gradually poured into liquid glass, bringing the composition to the consistency of thick sour cream. Welding with copper electrodes is quite expensive, and making homemade coating significantly reduces the cost of repair work.
• Take copper wire marked M2, M3. The wire is cleaned with sandpaper, then degreased and cut to the required length.
• The resulting blanks are dipped in coating. The result should be an electrode with copper wire no more than 1.5 mm thick. In order for the properties of manufactured consumables to be almost identical, they must be processed for the same time.
• The blanks are hung in a vertical position and wait for the mixture to dry completely and harden.

It is strictly forbidden to use brass wire as a rod. Brass wire contains a large amount of zinc, which is poisonous. When the electrode is burned, a toxic substance will evaporate, which can cause serious poisoning.

What markings are used to indicate electrodes that can be used for welding?

• OZCH-2, OZCH-6 - these electrodes are made by applying ferrite powder to a copper rod. The purpose of the OZCh-2 and OZCH-6 electrodes is to eliminate small defects using cold work. According to their characteristics, copper electrodes for OZCh-2 and OZCH-6 cast iron resemble home-made products that can be made at home.
• OZZHN-1, OZCH-3, OZCH-4 - these consumables contain a large amount of nickel. According to GOST, the percentage of nickel can reach 90% of the total mass. The group OZZHN-1, OZCh-3, OZCh-4 includes both nickel and nickel-iron electrodes.
• MNC-2 are the rarest of all types of products. The composition of MNP-2 includes nickel, copper, and iron. This ensures a high-quality and even seam of high strength.

Welding cast iron with simple electrodes (on steel)

Welding cast iron with conventional steel electrodes does not provide good weld quality.
Consumables of this type are used due to their availability and low cost. To reduce the negative consequences of using steel electrodes, it is necessary to use special TsCh-4 rods. This brand is one of the most popular and in demand among welders. Therefore, it is important to know how to properly cook cast iron with TsCh-4 electrodes. This grade is intended for surfacing the first cladding layers with subsequent continuation of the welding process with conventional materials (in the picture). In addition, TsCh-4 is suitable for both hot and cold welding of cast iron, sealing defects and joining steel to cast iron.

As for the SSSI. Often performers wonder about UONI electrodes, whether it is possible to cook cast iron with this brand. It should be noted that conventional electrodes can only be used when welding small defects in non-critical structures. Since the quality of the connection will not be high. To obtain more or less satisfactory quality, you should follow the same rules as when welding with special electrodes. Another effective way to improve the quality of the connection is a slight preheating to 150-200°C and slow cooling.

Welding electrodes "UONI-13/55" in packaging.

When welding cast iron with general purpose electrodes, the weakest point is the heat-affected zone at the fusion boundary. This zone is characterized by fragility and the presence of cracks. These defects often lead to peeling of the deposited layer from the base metal. To avoid this, you must use steel studs or bolts.

The studs are threaded and screwed into the surface to be welded. The dimensions depend on the thickness of the work product. There are recommendations regarding stud sizes:

• the diameter should be 0.3-0.4 of the thickness of the part, but not more than 12 mm;
• screw-in depth - 1.5 times the diameter of the stud, but not more than half the thickness of the products being welded;
• the height of the protruding part of the pin is 0.75-1.2 of its diameter.

The studs are placed in the beveled edges of the parts in a checkerboard pattern at a distance of 4-6 diameters.
The protruding parts of the studs are scalded around the perimeter, gradually filling the seam. First of all, all studs are welded with circumferential seams using electrodes whose diameter is 3 mm. A low voltage is used. Welding is done randomly to avoid severe overheating. Afterwards, circular seams are placed around the welding site until the entire surface is covered with a layer of deposited metal.

We hope that presenting here the above rules and recommendations will help you figure out how to weld cast iron correctly with electrodes and successfully complete the work.

Welding cast iron with non-consumable electrodes

Cast iron can be welded with different types of non-consumable electrodes: tungsten, carbon or graphite. Cast iron or special filler rods containing nickel, aluminum, copper and other metals are used as filler material. To protect the welding zone, inert gases are used, most often argon or fluxes, the main component of which is borax. The most popular technology is AC TIG - welding with a tungsten electrode using alternating current in an argon environment.

Welding cast iron with coated electrodes

Cast iron electrodes are special materials for correcting defects in cast iron, which are cast round rods coated with different compositions. In most cases, the connection is made using direct current, but it is also possible to use alternating current. The current value is determined at the rate of 50-60 A per 1 mm. electrode.

The quality of the seam obtained as a result of cold welding with cast iron electrodes is heterogeneous. Therefore, semi-hot welding should be performed.

How to properly cook cast iron with electrodes, the video is presented below.

After reviewing the entire range of information, the performer will be able to choose the best electrode for cast iron.

How to cook cast iron with electrodes

Since cast iron is a brittle metal, it cannot be overheated too much during the welding process. It is also important not to cool welded workpieces too quickly, which can lead to cracks and deformations.

When welding cast iron with electrodes, you should adhere to the following rules:

• Switch the inverter to reverse polarity. The positive terminal must be connected to the electrode, and the negative terminal to the cast iron being welded.
• Set the lowest welding current that is permissible for a specific electrode diameter.
• When welding cast iron with electrodes, the metal must not be overheated. Therefore, the length of one continuous seam should not be more than 3 cm.
• The workpiece should be allowed to cool all the time to prevent overheating of the metal.

As you can see, the technology of welding cast iron is quite complex. You need to know what and how to do, in what sequence. Be sure to hammer the first and last seams without using too much force.

Operating the inverter in pulse mode

The essence of the method is that the main welding current is supplemented by high-frequency pulses of greater strength superimposed on top of it. The ratio of current strength and pulse duration is adjusted in the device settings and is maintained automatically. Technology contributes to:

• improving the quality and strength of the welded joint;
• increasing the level of arc control and process control;
• welding efficiency increases;
• the likelihood of burning through the metal is reduced;
• the seam is neat.

Alternating impulses and pauses replaces the need to perform complex actions with the tip of the rod. The method is not suitable for joining parts that will experience vibration, shaking and shock.

How to weld cast iron with an electrode at home

The service life of cast iron is twice as long as that of steel, however, due to the high carbon content, repairs by conventional electric welding of parts made of this material are ineffective. Microcracks form at the junction, and pores form at the seam. In industry, this problem is solved by special training, which is not applicable for welding cast iron at home. However, creating strong connections is also possible with self-repair using electrodes for welding cast iron.

Cast iron is an alloy of carbon and iron, where the carbon content is 2.14%. Which negatively affects the quality of the connection.

The process is labor intensive due to:

• formation of cracks and pores;
• during processing, the appearance of hardened structures and rapid dulling of the tool;
• thin material crumbles from overheating.

According to its composition, cast iron is divided into gray and white:

1. White ones cannot be welded due to their fragility and hardness. Suitable for grinding;
2. Gray (high strength, malleable) are easy to machine and have limited weldability.

There are 2 methods of welding cast iron - hot and cold.

Hot also includes semi-hot.

When hot joining, the part is heated to a temperature of 600-700°C, welding is performed and the cast iron product is slowly cooled in the furnace. With a semi-hot connection, the temperature is maintained at 300-400°C.

Hot and semi-hot welding requires additional equipment. In domestic conditions, a cold connection is used.

Welding cast iron with an electrode at home requires chamfering. There is no need to degrease or clean the parts.

Chamfering is performed:

• file;
• emery;
• Bulgarian

Note: sharp edges are not allowed. The sharpness is removed with a suitable tool.

When connecting, do not overheat the heat-affected area (no more than 80°C). Take frequent breaks between passes. Use multi-pass welding.

1. first perform surfacing along the edges of the chamfers;
2. then gradually filling the seam;
3. After each pass, hot forge the roller.

Make rollers 40 mm long, scattered to reduce heating of the part.

How to weld cast iron using electric welding at home. What you will need:

• current source (inverter);
• electrodes 3 mm;
• seam cleaning brush;
• hammer for forging and removing slag;
• cutter or cutter for cutting chamfers;
• shield and gloves.

1. first, cutting edges and blunting sharp corners;
2. then surfacing along the edges of the chamfers;
3. then gradually fill the seam.

Forge each roller hot. Don’t rush, give the part time to cool (heating of the heat-affected zone is no more than 80°C).

After filling the weld, turn the part over and cut the edges on the reverse side. Perform welding as described above. Observing the temperature regime and forging each roller. At the end of the process, grind the deposited surface if desired.

Video:

Cold welding is used to repair batteries, vices, engine cylinder blocks and other structures made of gray cast iron.

You can get acquainted with factory electrodes and homemade ones for connecting different types of cast iron.

The table below will help you set the current on the device for different diameters of electrode brands:

• TsCh-4;
• OZCh-2;
• OZZHN-1;
• MNC-2.

The current values ​​are indicated for the lower position of the electrode. For a vertical position, the current is reduced by 15-20 A, except for TsCh-2.

In order to save money, home craftsmen have adapted to welding cast iron with a conventional electrode with copper wire. Video below:

Also, copper wire will help in welding cast iron with steel.

Some craftsmen ask how to cook cast iron with a semi-automatic machine? On metalworking forums, experienced welders advise using PUNCH 11 wire. The connection is made with 2-5 cm stitches with forging, without gas protection on straight polarity. Current 90-110 Amperes depending on the thickness of the metal.

Types of cutting are divided into thermal and mechanical. List of tools and methods:

1. The grinder is a simple and affordable way. Minus: the cut occurs in a straight line.
2. Pipe cutters have proven themselves well when working with pipes.
3. Reciprocating saw.
4. Electrode.
5. Oxy-fuel cutting is a good option. Oxygen flux will improve the quality of cutting cast iron.
6. Mobile installations Thermal cutter 2M (weight up to 5 kg).
7. Oxygen-lance cutting and plasma.

DIY electrodes for cast iron

In the absence of special electrodes for welding cast iron, you can independently make consumables that are similar in characteristics to the OZCH-2 and OZCH-6 grades. Next, we will look at two ways to make electrodes for cast iron with your own hands.

1. The production of electrodes for cast iron is carried out using the following technology:

Warning! We have not yet tried this method in practice, it was found in open sources, we are not responsible for the result. If you do, it is at your own peril and risk. Please share your results in the comments to this article. The next method is more traditional and has been tested by many, as shown in the video below.

• It is necessary to take copper wire with a diameter of 2-5 mm, sand it with sandpaper, degrease it and cover it with homemade coating; The easiest way is to prepare a coating from the coating of conventional electrodes (ANO-4, UONI-13/55).
• The coating of general purpose consumables is scraped off the rod, crushed and mixed with steel filings or iron powder in a 1:1 ratio. Then silicate glue is added to the resulting mixture, after which all components are thoroughly mixed.
• The wire is lowered into a homemade coating until the applied coating thickness is 1.5-2.0 mm. Then you need to wait until the excess mixture drains.
• The next stage is drying, which is carried out in the open air; the electrodes are dried in a vertical position.
• The final procedure - calcination is performed in the oven or on the stove at a temperature of 200-250°C.
• Homemade electrodes for cast iron are ready for welding. The welding mode with self-made electrodes does not differ from the operating mode with branded consumables.

2. There is another way to make a cast iron electrode. The welder will need a drill, a steel electrode (ANO-4, UONI-13/45) and copper wire with a diameter of 2 mm.

To make an electrode for cast iron with your own hands using this technology, you should perform the following steps: the wire is wound onto the steel base of a conventional electrode by rotating it clamped in the drill parton. To visually familiarize yourself with the production process, we recommend watching the video.

Do-it-yourself cast iron electrodes will allow you to save money and also perform welding work without downtime. But the quality will be lower than from using special electrodes for cast iron.

Making electrodes at home using cast iron can be done by a performer of any level.

Difficulties in welding cast iron

Before starting work, the contractor must take into account the features of welding cast iron with electrodes. These specific features are due to the unique properties of cast iron.

One of the main disadvantages of cast iron is poor weldability, which is due to the following factors:

• poor connection of cast iron by welding is explained by its chemical structure and properties;

  
  In the photo: time in the welding bead

• Various elements, in particular silicon, are oxidized in the weld pool, resulting in the formation of oxides. The refractoriness of these oxides leads to the appearance of uncooked areas;
• rapid cooling of the joint and heat-affected zone leads to the formation of areas of cementite characterized by increased hardness. These areas are difficult to machine;
• cast iron is characterized by high fluidity, which makes it difficult to retain the molten metal in the bath and complicates the formation of a seam;
• uneven heating and cooling of brittle cast iron can most likely lead to cracks;
• molten cast iron tends to release gases, which can cause pores to form in the weld.

Specific qualities of cast iron

Compared to conventional metals, such a structure requires a special approach and special preparatory work. Otherwise, the material overheats and becomes more brittle. Cast iron as a special metal has several varieties, determined primarily by its structure. Experienced welders can easily determine how and in what way to weld a particular sample, based on just one section.

With a fine-grained structure and a color close to a gray tint, welding cast iron with an inverter is much easier than similar parts with large grains of a dark color. There are other factors to consider as well. For example, cast iron workpieces that have been in oil for a long time or are subject to constant oxidation in wet soils, water and other similar environments are completely unsuitable for welding.

Thus, the possibilities for welding this material are quite limited due to its physical properties and specific features:

• Cast iron has increased fluidity, so all parts made of this material can only be welded in a horizontal position.
• If the temperature regime is not observed, in most cases overheating occurs. As a result of carbon burnout, voids appear in the internal structure of the metal.
• In places of welding seams, metal stresses often form due to its low ductility and under the influence of too high or low ambient temperatures.
• When molten cast iron comes into contact with the environment, oxides may appear whose melting point exceeds that of the original material.
• As the part cools, cracks may form in the area of ​​the weld, which indicates non-compliance with the work technology.

What electrodes are used

Not all types of consumables can be used for welding brittle alloy. Before starting work, you should study the basic characteristics of the electrodes.

Non-melting

You can cook cast iron parts using different types of elements:

• tungsten;
• graphite;
• coal.

Cast iron or filler electrodes containing alloying additives (copper, nickel) are used as consumables involved in the formation of the seam. The weld pool is protected with argon or borax-based fluxes. The most common technology is TIG welding with a tungsten rod under alternating current.

Simple for steel

Welding cast iron elements with conventional electrodes does not allow obtaining a high-quality seam. Such consumables are used due to their low cost. To reduce the likelihood of defect formation, filler rods of the TsCh-4 brand are used. They are designed to form the first cladding layer with further continuation of welding with simple materials.

UONI electrodes are used only to eliminate small defects in structures that do not experience high loads.

Covered with additional metal

Such elements are used for welding cast iron with an electrode at home when it is necessary to eliminate casting defects. They have the form of round bars coated with protective materials. Most often, the welding process is carried out with direct current. Variable is used less frequently. The required current strength is calculated using the formula 50-60 A per 1 mm of electrode. When electric welding with coated elements, the seam turns out to be non-uniform.

Welding with non-consumable electrodes

Welding cast iron using this technology is carried out in a protective environment of argon or fluxes, the main component of which is borax. Cast iron or special rods containing nickel, aluminum and copper are used as filler materials. Welding cast iron is carried out using tungsten, carbon and graphite electrodes.

The most common method is argon arc welding (AC TIG). In order for the work to be successful, you should adhere to several rules:

• Thorough cleaning of the surface from debris and dirt;
• the workpiece must be fixed at several points;
• It is recommended to use slight preheating of the product; for this you can use improvised means. It should be remembered that the presence or absence of heating depends on the type of cast iron being welded;
• the additive is supplied at an angle of 20-30 degrees;
• it is necessary to use small amounts of current;
• the connection should be carried out in stages : the performer welds a small section of 2-3 cm and forges the deposited metal so that
• avoid residual stress. Forging is done with a small hammer, the weight of which does not exceed 1.2 kg, the hammer is of a rounded type.
• Cooling of the part after welding is carried out gradually .

This method is not the main one when connecting cast iron products. This is due to certain difficulties that arise during the work process, as well as an increased level of labor and financial costs.

Welding modes, currents, operating techniques

Cast iron is cooked with direct current, mainly of reverse polarity, although for some brands of electrodes (MNC-2) it may be necessary to switch the negative to the holder. Due to the high fluidity of cast iron, it should always be welded only in the lower position of the seam.

At home, you can use two types of welding: with partial heating and without it. This is determined individually for each brand of electrodes. The part is heated up long before welding begins, using a soldering gasoline or gas lamp, or acetylene torches. The heating of the cast iron part must continue during the welding process, so the work is performed by two people.

Cast iron is welded with short seams (2–4 cm each) with an indentation of 2–3 seam lengths. Each “stitch” is performed with numerous tacks with an arc burning duration of 0.5 to 1.5 seconds, depending on the thickness of the metal and the brand of electrodes.

The area where the seam is being applied is heated for 2-3 minutes, then the welder applies metal to the root of the cut seam, and an assistant carefully heats up the welding site. When the “stitch” is completed, it is covered with dry sand or covered with asbestos cloth and the flame is removed.

Slow cooling is critical when welding cast iron. Without it, the metal may immediately become covered with a web of cracks radiating from the weld pool, and the product will be hopelessly damaged. Thermal insulating lining can also be laid on the back side of the seam in advance, but even in this case, each welding crater must be immediately protected from direct contact with air. It is recommended to place small parts in a hot oven for an hour.

When welding, the root of the seam is first filled; complete filling is carried out after the part has completely cooled using exactly the same technology with a smooth tempering. If a tight connection is required, a few more intermediate stitches are made between the “stitches”, and then the seam is completely sealed. However, it is much better to use polymer or epoxy sealants to ensure tightness.

Cleaning parts

The environment in which the casting was located affects weldability no less than the grade of the alloy due to the absorbent properties of cast iron. For example, exhaust manifolds that have been exposed to heated combustion products for many years will be very difficult to weld. Regardless of the brand of alloy and origin, it is necessary to completely clean the casting in the weld area - remove paint, grease, oil, and scale. It is helpful to gently and slowly heat the weld for a short period of time to evaporate volatile impurities from the area being treated.

Technology of welding cast iron with steel using a consumable electrode

There are several methods of welding cast iron; they are used to join cast iron alloys with other metals:

1. Hot - before joining the parts, the ovens are preheated to 600°C completely. Heating with a blowtorch is allowed only in the work area (cast iron becomes crimson in color). Used for reliable connections.
2. Semi-hot, good for alloys. The parts to be joined are partially or completely heated to 200–300°C.
3. Cold - parts are connected without heating, used for overlays - seams working under compression.

Joining metals by manual electric welding involves preliminary preparation of surfaces. Cast iron alloy is porous and absorbs oil well. It is not enough to degrease the stain; it must be cleaned to a clean layer, otherwise the seam will turn out loose.

How to weld steel to cast iron:

1. First you need to select the current parameters. If the welding machine only works on constant, switch the Polarity to reverse. It is necessary to take into account the no-load indicator (voltage between the poles without an arc), the permissible value is up to 54 V. Operating on alternating current is allowed only with no-load from 54 V.
2. Welding is carried out in small sections, the beads are made no more than 3 cm long. First, cast iron is deposited, then a steel part is welded to the buffer layer.
3. Thick-walled seams are welded in multi-layers, each one is hammered before applying the next. It is made perpendicular to the first - this is how the strength of the connection is achieved.
4. After joining the cast iron alloy with steel using hot and semi-hot methods, it is important to observe the cooling regime of the surfacing zone. The seam is periodically heated so that it cools gradually. When suddenly cooled, the cast iron alloy cracks due to internal stresses.

Multilayer welding using annealing bead technology

The method is used to eliminate cracks on parts with thin walls - up to 8 millimeters. Rollers are formed sequentially in such a way that each new one thermally affects the previous layer. This reduces the hardness of the deposit.

The crack is pre-cut: V-shaped processing, opening angle is 45 degrees. Preparatory beads are first welded onto each edge, and annealing beads are welded onto them. The rollers are applied in small sections up to 50 mm long.

Each transition from one area to another should be leisurely, so that the metal has time to cool to a temperature of 50-60 degrees Celsius. At this point, the rollers need to be forged and the scale removed. Preparatory rollers are applied earlier, and therefore warm up better and cool down more slowly. In the hardened part, the metal is partially tempered and normalized. When the formation of the beads on both sides of the crack is completed, the weld itself is applied. It is also formed in the same small segments.

Applications of argon arc welding

The use of refractory electrodes and copper-nickel filler wire gives good results.

How to weld steel to cast iron (several recommendations):

1. The additive is selected according to the type of metal and type of cast iron. Nickel-based flux-cored wire is most often chosen; the coating is first removed from it.
2. Argon is used as a protective atmosphere; it saves the seam from oxidation.
3. Refractory tungsten electrodes are chosen for work.
4. To work with thin-walled elements, experienced welders use small thin pieces of cast iron instead of wire.
5. For connections that experience only static loads (compression), nickel alloys can be used. They adhere perfectly to any grade of steel.

Argon welding

Welding cast iron with argon is used by many novice welders on the advice of experienced comrades, and they often resort to semi-automatic welding in an argon environment. This method is not justified for products made of cast iron alloys. The connection is obtained as in heated air, but the costs increase greatly.

The technology for welding cast iron and steel with argon usually requires the presence of a neutral environment. Of course, a seam can be obtained in an atmospheric environment, but its quality will greatly deteriorate. When welding in this environment, microcracks may form in the joint, and uneven hardening will also be observed.

If, in addition to welding, the inert gas argon is supplied, the chemical composition in the weld pool will not change in any way. If argon is used, the welding method does not matter at all. The quality of the welds is equally good for any connection of parts - butt, overlap, patch.

TIG welding of cast iron using argon is considered the most optimal option, which allows you to make a strong seam. Using gas you can cook almost any combination. If there are some difficulties in purchasing argon, then it is better to leave it for joining cast iron and steel.

Methods for avoiding basic mistakes

When connecting a steel part to a cast iron part, the following recommendations must be observed:

1. The mode and materials are selected according to the most difficult to weld alloy, i.e. on cast iron.
2. In the absence of increased requirements for joint strength, filler material made of pure nickel is used.
3. Overheating of workpieces should be avoided. The dimensions of the weld pool should be minimal. An overheated alloy cracks as it cools and cracks appear in the seam.
4. It is not recommended to try to weld steel and cast iron with the highest carbon content. It is prone to cracking and is therefore considered non-weldable. It is necessary to resort to alternative connection options.
5. When repairing structures subject to high loads, steel is not welded directly to cast iron. First, nickel filler material is deposited on it, forming the so-called. buffer zone.
6. Work must be carried out at a moderate speed. Rapid welding creates hot and cold fractures.

The most reliable seams are obtained under the following conditions:

• using small diameter electrodes;
• applying surfacing in 5 cm sections, allowing the cast iron to cool.

  
  The mode and materials are selected based on cast iron.

The arc is biased towards the welded area, trying not to affect the base metal.

Characteristics of cast iron

The material is an iron alloy containing a large amount of carbon.
The substance gives cast iron hardness. Carbon, which is not a metal, is not capable of forming bonds with iron; it is contained in the alloy in the form of graphite inclusions.

The alloy has the following characteristics:

1. Porosity of the structure. The voids quickly fill with gases or absorb oil.
2. Relatively low melting point (1200-1250 °C). This explains the high fluidity of the alloy when heated.
3. Fragility. Cast iron is not recommended for the manufacture of structures subject to high loads.
4. Low ductility.
5. Resistant to acids and alkalis. At the same time, the material is sensitive to prolonged exposure to moisture.

Cast iron welding options and their brief characteristics

Depending on the strength requirements and the nature of damage to cast iron parts, one of several welding methods is used.

Hot welding

Hot welding is used in cases where it is necessary to obtain high machinability of the seam and the proximity of its composition and structure to the rest of the cast iron. The parts to be welded are prepared as described above and heated to a temperature of 700°C. If necessary, before heating, a mold is made from materials used in foundry. This is required for through and edge (chip) damage. Sanded surfaces and threads should be protected with clay.

Gas welding

Gas welding of cast iron is mainly used in cases where it is required to obtain a high-strength weld, but subject to a small penetration of the surface of the base metal. At the same time, the technology of gas welding of cast iron is accompanied by the use of several welding modes, on which the quality of the final joint will depend.

The quality indicator of a welded joint is influenced by the following components:

• types of supply voltage modes;
• type of technique of the superimposed welded joint;
• current indicator;
• passing speed.

How to weld cast iron and steel using gas arc welding in order to ultimately obtain a connection with high strength without cracks, pores and other defects? To do this, you need to comply with some requirements during the workflow:

• the arc voltage indicator should be from 18 to 21 V;
• current strength - 100-120 A;
• travel speed no more than 12 m per hour;
• Welding work must be carried out using special welding wires 09G2SA or PANCH 11 with a diameter of 1 mm.

Welding with inverter

Many inexperienced welders often wonder whether it is possible to weld cast iron and steel with an inverter welding machine? Of course you can, but you should prepare first. The cast iron preparation process should be carried out taking into account the following recommendations:

• First of all, the required area is cleaned with a grinder. For stripping, it is recommended to use a flap wheel or other most suitable attachment;
• After the top layer has been stripped down to non-oxidized metal, degreasing is required. This process can be performed using gasoline or any other solvent;
• If it is necessary to repair a crack, then it must be cleared until it is completely finished. After this, a hole with a diameter of 10 mm must be drilled in this place.

Welding cast iron with an inverter can be carried out layer by layer and using support elements - studs. They are entirely made of steel. The use of these support elements must be accompanied by taking into account the following important requirements:

• the dimensions of these elements must be accurate, their diameter should not be more than 40% of the thickness of the cast iron;
• the protrusion of the stud above the metal is no more than 4-6 mm;
• the distance between them should not exceed 6 mm;
• the number of studs used should depend on the connection parameters, but they should not exceed 25% of the fracture area.

Electrodes can also be used, but they must be special. It is not recommended to brew cast iron with conventional electrodes. For this type of alloy, electrodes with the addition of nickel, copper, chromium and other alloys are suitable, which contribute to durable deposition of cast iron.

How is it carried out?

How to weld cast iron using an inverter to get a good and high-quality weld? To do this, you will need to study important recommendations:

• the polarity of the connection must be reversed;
• the operation of the welding machine must be carried out at minimum power, it must correspond to the thickness of the cast iron element;
• the length of one continuous weld should not be more than 3-5 centimeters;
• there should be no overheating of the metal, which can occur as a result of frequent breaks;
• The first and last layers in multi-layer welding should be forged with a hammer with little force.

The welding process itself can be multi-layer or using studs. After the studs are installed correctly, each layer is welded. Metal must be placed around each stud to create a patch. At the end, a weld is made that connects the welded metal between the studs.

Multilayer welding is performed using electrodes. After fusing the first layer, forging is carried out with a hammer; it should be done hot. If there is access to the back side of the product, then a layer is also applied to it, and then it is forged. At the end, the following layers of metal are applied.

Before answering the question of whether cast iron can be welded, it is worth considering the main features of this alloy. The choice of a certain type of welding depends on its type and structure. Different types of welding can be used for it - electric, semi-automatic, gas, argon, inverter. But for the process to be successful, preliminary preparation of cast iron and steel is required.