How to cook cast iron. Welding cast iron at home with an electrode and welding methods

Cast iron is an alloy of carbon and iron, which also contains alloying additives and impurities.
Cast iron parts are widely used not only in industrial and production areas, but also in everyday life. Cast iron products for private use: plumbing elements, fence structures, car parts and much more. The active use of this alloy leads to the need for welding work. The main difficulties in welding cast iron that home craftsmen encounter:

due to the fluidity of the alloy, it is recommended to carry out welding in the lower spatial position;
non-compliance with temperature conditions leads to overheating of cast iron, which can cause the formation of pores and stress in welds;
cast iron in a molten state can release gases , which will negatively affect the quality of the connection;
Accelerated or uneven heating or cooling can promote cracking .

In order to obtain a high-quality connection of cast iron products at home, it is necessary to take into account these specific characteristics, as well as correctly prepare the working surface, select the correct welding mode and electrode.

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:

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

Methods for avoiding basic mistakes

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

The mode and materials are selected according to the most difficult to weld alloy, i.e. on cast iron.
In the absence of increased requirements for joint strength, filler material made of pure nickel is used.
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.
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.
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.
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.

Properties of cast iron

Cast iron is an alloy of iron and carbon. The carbon content in cast iron ranges from 2.14% to 6.67%. Carbon gives iron alloys hardness and reduces ductility and toughness. Carbon in cast iron is contained in the form of cementite and graphite.

The melting point of cast iron is from 1,150 to 1,200 °C, which is 300 °C lower than that of pure iron. The thermal conductivity of cast iron is lower than that of steel, and the coefficient of thermal expansion is the same. The electrical conductivity of cast iron depends on the distribution of graphite inclusions.

When cast iron is rapidly cooled from a metal temperature of more than 750°C, graphite turns into cementite, and the cast iron turns from gray to white. A hardened structure is formed with internal stresses leading to cracks.

Features of welding cast iron.

This material is a compound of iron (F), carbon (C) and impurities: silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), etc.

In the marking designation: the first numbers are the tensile strength in kg/mm2, and the second numbers are for gray cast iron, the bending strength, for malleable and high-strength, relative elongation in%.

By annealing at high temperature - 1000º C, due to graphitization, white turns into malleable cast iron. To increase wear resistance, chromium (Cr), nickel (Ni), tungsten (W), etc. is added. This metal is called alloyed.

For alloyed grades, letters indicate alloying elements, and numbers indicate their average percentage content. For example: ChN19X3 – cast iron containing 19% nickel and 3% chromium. If there is a spherical form of graphite, the letter Ш is placed at the end of the marking.

Due to increased fragility and hardness, the process becomes more complicated. But welding cast iron with an electrode in home workshops is possible under certain conditions. By following the technology and having some skills, you can achieve a high-quality result, but the structure of the seam will differ greatly from the structure of the base material.

What technologies are used

Welding of materials is carried out in several ways. The choice depends on the thickness of the workpieces, steel grade, and available equipment.

With consumable electrodes

These consumables are designed for manual arc welding. During operation, the core metal melts and is transferred to the weld pool.

In order to prevent contact of the materials being joined with nitrogen and oxygen from atmospheric air, a coating is applied to the rods. When burned, it produces a cloud of gases surrounding the weld pool. To connect cast iron and steel, an electrode with a basic type of coating is used. Unlike other coatings containing organic matter, it does not emit hydrogen.

Consumable electrodes are designed for manual welding.

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Welding cast iron with an electrode

Cold welding

According to the method of preliminary preparation of parts, 3 types of welding are distinguished:

With heating up to +600…+700°С (hot technology). Small workpieces are placed in the oven as a whole; for large ones, the edges are heated with a blowtorch. Upon reaching the specified temperature, the cast iron emits a crimson glow.
Heated to +200…+300°С (semi-hot).
Without preheating (cold).

The first method allows you to get the most reliable connection. Preheating reduces the uneven temperature distribution in the workpiece mass and thereby reduces the risk of cracks opening.

A lower temperature (second method) is allowed with a large number of alloying elements in the workpiece material. They increase the strength and ductility of the seam.

Cold welding is the least energy-consuming. But the connection turns out to be unreliable. This method can only be used if the seam will work in compression.

Using argon arc welding

This method involves the use of refractory electrodes.

Argon arc welding occurs in an inert gas environment.

They are made from the following materials:

Tungsten.
Pressed graphite of artificial origin.
Electrical coal.

A non-consumable consumable has no coating and does not serve as a source of metal for the weld pool. Therefore, the following is supplied to the work area:

Shielding gas. In most cases it is argon, sometimes it is mixed with carbon dioxide.
Filler material in the form of wire or plates. In the first embodiment, the product can be hollow with flux content inside.

Welding cast iron with steel with a non-consumable type electrode is carried out in one of the following ways:

Semi-automatic. The welder holds the torch with one hand and feeds the filler material with the other.
Automatic. The welding process takes place without human intervention.

The shielding gas nozzle is built into the torch. A refractory consumable is installed in it.

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;
Read also: Welding designation in a drawing according to GOST: using an example, we look at why symbols are needed and how to read them correctly

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):

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.
Argon is used as a protective atmosphere; it saves the seam from oxidation.
Refractory tungsten electrodes are chosen for work.
To work with thin-walled elements, experienced welders use small thin pieces of cast iron instead of wire.
For connections that experience only static loads (compression), nickel alloys can be used. They adhere perfectly to any grade of steel.

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.

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.

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:

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.
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.
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:

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.
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;
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:

Gradually heat up the welding area. The appropriate temperature is selected empirically.
Once the desired temperature is achieved, a connection is formed. Gradually remove the burner, achieving slow cooling.
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:

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.
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 weld with electric welding

Before you start welding using electrodes, you must carefully study the features of welding cast iron of this type. First of all, you need to select the right electrodes and special equipment. The main feature of this method is that the degree of fragility of the metal increases in the area of the weld.

The increase in fragility is due to the fact that during welding work the alloy on the cast iron alloy is highly hardened. For this reason, electrode welding of a cast iron boiler and other parts in an industrial environment has significant differences compared to the conventional processing of other products. During it, it is necessary to heat the material to a temperature of almost 600-650 degrees Celsius.

Typically, two types of electrodes are used in electric welding:

OZCH-2. The electrodes of this model have a copper metal rod, which is coated with a special composition containing graphite;
MNC-2. For the rod of this type of electrode, different types of metals are used - nickel, copper, manganese and iron. This model is the most suitable option for electric welding of cast iron, but it has a high cost.

Features of welding cast iron parts using electrodes:

during cold electric welding, it is necessary to maintain a certain pace of sutures;
control of the welding process is required, this will help to avoid overheating of the surface above the established values;
The welder must carry out work “randomly”, in small parts. In this case, forging must be performed and breaks must be taken;
due to the fact that the main feature of cast iron is that it cools quite slowly, so welding a cast iron part may require some period of time;
if small defects are being restored, then an additional graphite substrate may be required; this will prevent metal leakage.

Surfacing of cast iron

Surfacing of cast iron can be done using special electrodes of the following brands:
MNCh-2, used for critical joints, surfacing is performed without heating. OZZHN-1 are intended for repairing serious defects. OZCH-2 are used for surfacing ductile and gray cast iron. The technology of cast iron surfacing is presented in the article “Metal surfacing: electrode and others.”

Gas surfacing is carried out using the heat generated by the combustion of a mixture of acetylene (acetylene substitutes) and oxygen. Cast rods and fluxes are used as consumables.

Welding of thick-walled elements with alloy inserts

The connection of such workpieces is carried out according to the following rules:

Cold welding is used.
The seam is picked up with short tacks 2.5 mm long.
Each subsequent one is performed after the previous one has cooled.

Despite the fact that the tacks follow one after another, this technology does not ensure a tight connection. This is explained by the fact that the new seam lies on the already hardened one, so they do not merge together.

In addition, the connection is fragile. For this reason, the method is not suitable if mechanical processing of the seam is planned in the future.

Safety precautions when welding cast iron

Carrying out work with cast iron requires compliance with safety measures aimed at ensuring proper conditions in the workplace. In this case, the following nuances must be taken into account:

Electric welding of cast iron at home should be carried out in a well-lit and ventilated area.
The device must be grounded.
Metal does not respond well to rapid cooling. It is necessary to protect its surface from moisture.
It is mandatory to use personal protective equipment:
points
workwear

When working with cast iron using the electric welding method, all basic requirements apply to all welding work without exception. The master is required to adhere to the rules for the safe operation of electrical welding equipment.