How and with what to cook titanium? Titanium welding: technology and features

Issues discussed in the material:

• What you need to know about welding titanium with argon
• How to properly prepare for the titanium argon welding process
• How to weld titanium with argon
• What defects can appear during welding of titanium with argon and how to eliminate them

Among other metals, titanium stands out for its low weight and ability to resist corrosion. For this reason, it is actively used in the production of complex components for the needs of aviation, shipbuilding, and mechanical engineering. In this article we will talk about this type of processing, such as titanium argon welding.

Technology and features of titanium argon welding

Welding titanium is challenging because it requires very high temperatures to melt it. However, when heated strongly, this metal becomes chemically very reactive to the gases contained in the air.

Not everyone knows, but titanium, being one of the strongest metals on our planet, is quite often found in nature - even more often than, for example, zinc or copper. This dull gray metal melts at 1700 °C. From a technical point of view, its main value, as we have already said, is its high resistance to rust, as well as relatively low heat during welding.

The melting point of titanium alloys depends on the grade and ranges from 1470 – 1825 °C. Compared to other types of metals, they are lightweight (due to low density) with high strength, which is why they are used as a material for bicycle frames and racing car parts. But you need to understand that the specific properties of alloys turn their welding into a complex process.

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It should be noted that the metal can be in one of the stable phases; they are denoted by the Latin letters α and β:

• The α phase is a state at ambient temperature, while the metal has a fine-grained structure and is completely inert to the cooling rate.
• Phase β is reached at temperatures above 880 0C: the grain becomes larger, and sensitivity to cooling (process speed) occurs.

These phases are stabilized with the help of additives and alloying elements: O, N, Al (for α) or V, Cr, Mn (for β). For this reason, all titanium alloys are usually divided into groups according to the type of additives used:

• VT1 – VT5.1 These are the so-called α-alloys. They are distinguished by their ductility and weld well, but their strength is not increased by heat treatment.
• VT 15 – 22. β-alloys that weld less well, often with the appearance of cold cracks. The quality of the connection of segments is negatively affected by the fact that during welding the grains of the structure increase in size. However, heat treatment can partially increase the strength of the alloy.
• VT4 – 8, OT4. Group α + β. The properties of such intermediate alloys depend on the type and proportion of additives used.

It is worth dwelling in more detail on the properties of titanium, which make welding work difficult:

• density 4.51 g/cm³;
• strength 267 – 337 MPa;
• melting point 1668 0C;

• low thermal conductivity;
• possibility of spontaneous combustion when heated to 400 °C and in contact with oxygen;
• oxidation with carbon dioxide;
• formation of hard but brittle nitride compounds when heated to 600 °C and direct contact with nitrogen;
• ability to absorb hydrogen when reaching 250 °C;
• grain increase at 880 °C and above.

An increase in temperature to 400 – 500 °C or more is critical for titanium. Strong heating entails a sharp increase in chemical activity, due to which the metal reacts with atmospheric air. All this negatively affects the strength of the weld; hydrides, nitrides, carbides, etc. are formed. Failure to comply with GOST may result in the seam not being able to withstand even a light blow.

Argon welding carried out according to all the rules ensures a weld strength of 0.6 - 0.8 of the metal itself.

For welds, GOST R ISO 5817-2009 applies; it fixes the quality of welding of the following metals: steel, titanium, nickel, their alloys, and the maximum permissible levels of product defects.

Pure titanium is little used in production due to insufficient strength. Therefore, if we are talking, for example, about welding titanium with argon, we mean some kind of alloy, in other words, titanium and an alloying element.

Quality

After welding work, quality control must be performed. To do this, it is necessary to inspect the seam: the main parameters here are the color and its structure.

Seam color

Silver color with a characteristic bright tint

Very high quality seam. Under natural conditions, pure titanium has a white-silver color. Therefore, the silver color of the seam indicates that no foreign impurities entered the metal during welding. Such a seam will not crack over time, will not become corroded, and will not deform under high loads.

White or yellowish

High or good quality. The yellow color of the weld indicates that oxidation occurred in the metal during welding to form simple titanium-based oxides. However, not too many such oxides were formed in the metal. Therefore, the quality of the weld is at a fairly high level. That is, such a seam will easily withstand medium and high physical loads and will not crack over time. Will withstand exposure to non-aggressive corrosive environments.

Red, brown, gray, black, bluish

Poor seam quality. This color indicates that a large amount of oxides, as well as nitrogen- and titanium-based compounds, were formed during welding. This type of seam is extremely unreliable. It will crack under overload and may become covered with rust and scale. According to GOST, parts with such weld quality are not allowed for use. It is necessary to dismantle the seam, re-weld with removal of the damaged fragment, and remelt the welded structure.

Structure

In the case of high-quality welding, the seam should be smooth and uniform, without any compaction and without deformed areas. If a large number of irregularities have formed in the weld area (small dents, compactions, bumps, dots, etc.), this may indicate that during welding air bubbles (oxygen, nitrogen, carbon dioxide) penetrated into the thickness of the alloy. This scenario is quite negative, since air bubbles have a bad effect on the hardness of the weld.

How to properly prepare parts for welding titanium with argon

Welding titanium with argon is carried out with complete isolation of the welded surfaces from the atmosphere, therefore automatic or semi-automatic technology is most often used.

Of course, manual welding of this metal is possible, but it uses a special torch with a ceramic nozzle: through it, an inert gas, argon, is supplied under pressure, which displaces the air.

The diagram shows devices for protecting the seam with gas and supplying it in an increased volume.

Before welding titanium with argon, edges and additives are prepared, so we also provide a table for preparing edges.

It is necessary to clean metal surfaces with a steel brush, sandpaper, and degrease.

One of the most common solvents for degreasing metal surfaces is acetone, but it has a strong odor and is quite toxic. This is evidenced by the fact that acetone belongs to hazard class 4. When inhaled for short periods of time, its moderate and high concentrations cause irritation of the eyes, respiratory tract, increased heart rate, headaches, nausea, vomiting, and even clinical coma is possible.

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Therefore, it is worth choosing safer but more effective compositions for cleaning metal surfaces. One option is denatured alcohol, which is applied to the metal with a lint-free cloth. This is alcohol with additives that make it impossible to consume. On the one hand, they have a terrible taste, and on the other, they cause vomiting and can even cause blindness.

Before joining, titanium parts are etched with a mixture of hydrochloric acid, water and sodium fluoride in the following proportion: 350 ml HCl, 650 ml distilled water, 50 g sodium fluoride. Etching takes about 10 minutes at 60 – 65 °C.

Another method that allows you to remove the oxide film is a mixture of 2 - 4% hydrofluoric acid and 30 - 40% nitric acid. Etching lasts 30 seconds and the temperature does not exceed 60 °C.

After this, the metal is thoroughly polished using sandpaper up to No. 12, wire brushes, and a scraper. It is important to make sure that the edges of the parts are smooth and free of burrs and cracks. The filler wire for welding titanium with argon is also cleaned in the same way. Next, it's time to move on to welding.

Work in an argon protective gas environment is carried out using filler materials. The latter are divided into groups according to composition (palladium, vanadium, aluminum) and the proportion of oxygen contained in them. The table contains the characteristics of additives made of titanium and its alloy:

It is very important that the rods and wires when welding titanium do not come out from under the gas protection, since the additives become contaminated in the air.

Argon-arc technology requires the use of direct current of direct polarity and tungsten electrodes. Sometimes you have to use special devices into which inert gas enters, displacing the air.

It is possible to weld titanium with argon using copper and steel pads. They have holes for gas supply.

To connect pipes, special aprons with different curves are used, whose characteristics are determined by the diameter of the pipe.

Semi-automatic or automatic technologies are carried out in a special capsule filled with argon or helium. When it comes to pipes, they are not placed in a protective environment, but are sealed and filled with argon.

Another important requirement for such work is the presence of gloves on your hands, because even clean hands leave sweat marks on the edges. The latter negatively affect the quality of the weld.

Selecting a mask

No matter how welding is performed, it is an unsafe process that can cause significant damage to the health, in particular the vision of the welder. A necessary accessory is a mask that will protect against possible sparks hitting the face, neck and eyes and causing burns.

The mask protects against ultraviolet and infrared radiation. It will also protect against the possibility of hot metal particles getting on the skin and eyes and from harmful gas fumes. A mask is an integral part of a welder’s equipment, regardless of whether he has many years of experience or whether he is taking on such work for the first time.

There is a large selection of masks on sale. However, in addition to the type of this type of protection, it is necessary to choose the right size. The mask should fit tightly on your head and not fall off at the most inopportune serious moment. Otherwise, instead of protection, it will become a thing that poses additional danger.

A mask that is small for a particular person will also not work. Ideally, the mask should fit tightly on your head and not fall off. Therefore, it makes sense to purchase it not online, but during a personal visit to the store.

The welding helmet contains a transparent viewing window through which it is possible to observe the welding process. This window is covered with plastic or tinted glass. The most basic types of masks include welding goggles.

The open look is similar to regular glasses that have special lenses. The closure type has the ability to be fixed with an elastic band. Mineral glass or polycarbonate are used to cover the window. Most models have glass anti-fog protection. The disadvantage is the exposed areas of the face and neck. In order to learn welding, it is recommended to purchase other types of face protection. A good protection option is protective masks.

The advantage of a welding helmet is complete protection of the face, eyes and neck. Preference should be given to those types that are mounted on the head, rather than those that have to be held in the hand.

It must be taken into account that during welding, from time to time it is necessary to inspect the intermediate results of the work or replace a burnt electrode. To do this, you have to free your face from the mask, which is extremely inconvenient. This type of protective mask, such as the “Chameleon”, solves this problem.

This can be considered a breakthrough in the field of welder equipment, and gives him a lot of convenience, being the most convenient option that uses automatic adjustment of glass tinting. A crystal-based filter allows only visible rays to pass through, and blocks ultraviolet and infrared rays. There is thorough neck protection. The mask fits tightly on the head, but without unnecessary tension, thanks to the position regulator. The presence of ventilation prevents the glass from fogging up.

The main important function is performed by the auto-dimming regulator. Thanks to its presence, the welder can not remove the mask from his head or lift it. The mask itself monitors the light level thanks to the presence of polarizing filters. When welding occurs, the glass acquires maximum darkness, and when exposure to bright light ceases, it becomes more transparent. The filter will also react to changes in the brightness of the arc.

Masks of this class are lightweight. The advantages include the possibility of a wide overview. Welding work for beginners is recommended to be done in such universal masks, which will ensure maximum safety.

You should not leave anything unprotected, so in addition to the mask, you should take care of thick clothing, canvas mittens, strong shoes and a durable hat. The ideal option would be to purchase a special suit made for protection during welding.

Methods for welding titanium with argon

Titanium welding is carried out using both the “cold” method and the flux-arc method or using plasma-arc welding. However, the most widely used method is welding titanium with argon, that is, by melting in an isolated argon environment, the so-called TIG welding.

To connect large cross-section parts, the method of electroslag welding with argon is used.

The type of alloy plays an important role. So, let us remind you that titanium grades VT1-VT5 are excellent for welding, although they cannot be hardened. Alloys VT15 - VT22 weld much worse, forming a coarse-grained, relatively weak weld, but hardening can increase its strength. Other types of titanium alloys are considered intermediate.

Today the following types of resistance welding with argon are used:

• butt;
• point;
• roller;
• condenser butt (for pipes).

When working with flux, oxygen-free flux AN-11 or AN-T2 is used.

Manual welding of alloys with titanium argon is carried out with direct current of direct polarity in the range of 90 - 200 A. Note that this indicator depends on the thickness of the parts being joined, the caliber of the electrode and the diameter of the filler wire.

Watch the color of the resulting seam. If you have a bright silver seam in front of you, everything is fine. Whereas a yellowish or blue tint indicates that the supply of shielding gas was stopped early. The worst option is gray, dark blue or whitish joints, since they need to be completely removed and the joints thoroughly cleaned for rejoining. For cleaning, use a stainless steel metal brush.

GAS PROTECTION OF THE WELD BATH

There are three protection options:

• inkjet using special devices
• local in sealed chambers of small volume
• general in chambers with a controlled atmosphere (VKS-1, VUAS-1, USB-1)

When argon arc welding of titanium with a W-electrode, welding torches with the largest possible gas nozzle should be used, creating a wide protection zone. The flow of argon through the nozzle must be laminar, which is achieved by gas lenses installed inside the nozzle. Gas consumption, depending on the welding mode, ranges from 8 to 20 l/min. If the burner nozzle does not guarantee reliable protection, then it is supplemented with a special nozzle, box or other device. Additional protective devices are made of stainless steel. Inside there are splitters and gas lenses. The nozzle attached to the gas torch to protect the crystallizing weld pool should have a width of 40-50 mm and a length of 60-120 mm, depending on the welding mode. For welding tubular structures, circular rotary and non-rotary joints, local or small-sized protective chambers are used.

1- additional nozzle; 2 - gas lens

The quality of protection is determined by the appearance of the weld metal. A silver or straw-colored seam surface indicates good protection. The yellow-blue color indicates a violation of protection, although in some cases such seams are considered acceptable. A dark blue or bluish-gray color with spots of gray coating characterizes the poor quality of the seam.

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Nuances of manual welding of titanium in argon

It is possible to achieve a strong weld when welding titanium with argon by ensuring the cleanliness of the surface of the parts and the additive. Another prerequisite is the correct setting of the welding machine. If the argon welding technique is not followed, welding defects always appear at the weld site. Before starting work, purge and clean the burner and protective nozzle. Do not forget about the backing pads for the back of the seam - with their help you can check the presence of air in the system.

Welding is carried out without preheating. The exception is situations when humidity or condensation on titanium is possible - then heating to 70 °C is required.

With TIG technology, high-frequency arc ignition is recommended. When you work with an additive, the arc length is equal to 1 - 1.5 times the electrode cross-section. If argon welding is performed without an additive, this parameter corresponds to the diameter of the tungsten electrode. Remember that tungsten particles remain in the scratches that form on the metal when touching the tungsten electrodes. When all work is completed, the arc should fade out gradually; to do this, gradually reduce the current. Protection of the weld and heat-affected zone is also ensured after the arc is turned off, when the temperature drops to 427 °C.

When connecting thin-walled parts with argon, the gap between the edges should be 0.5 - 1.5 mm. In this case, you can avoid forming edges and dispense with filler wire. By the way, the latter must match the composition of the main metal being welded.

Welding titanium with argon involves the following modes: if a tungsten electrode with a diameter of 1.5 - 2 mm and a filler wire with a diameter of 2 mm are used, and the thickness of the workpieces being welded is 2 mm, a current of 90 - 100 amperes must be maintained. Increasing the thickness of the metal to 4 mm allows it to be welded with a current of 120 - 140 amperes. And the most important thing to remember: to work with titanium and its alloys, alternating current of constant polarity is used.

There are also a number of other essential conditions for high-quality welding of titanium with argon:

• For manual technology, a short arc is used, vibrations of the electrode and additives are not allowed. The welder moves along the seam.
• Welding is carried out at an angle forward, that is, the electrode should be directed in the direction opposite to the direction of movement.
• The angle between the additive and the electrode is 90°.
• The additive is fed into the weld pool continuously.
• After the arc is extinguished, the shielding gas continues to flow, providing cooling below 400 0C, on average this takes a minute.

Further cooling of the metal is a guarantee of a high-quality weld. You can tell by the color. Normally, the seam is light, straw, yellow. But grey, bluish or black indicate oxidation, which has a bad effect on quality.

The technology of semi-automatic or automatic argon welding is the same as manual welding. The only nuance that should not be forgotten is the holes in the burner nozzle. In accordance with GOST, their diameter is 12 - 15 mm. It is recommended to light and extinguish the burner on special linings and slats.

Equipment used

Automatic and semi-automatic machines are used for work; the type of mechanized welding equipment depends on the required degree of human participation in the welding process. A mechanized automatic apparatus carries out:

• arc ignition;
• mechanized supply of additive, flux or gas;
• control of current parameters;
• movement of the arc relative to the edges along a given trajectory.

The operator only monitors the operation of the machines, which consist of a tractor (self-propelled welding head) and a control unit (processor).

Mechanized tractor-type devices feed wire using pressure and feed rollers. The arc is moved in the direction of the seam manually by the welder. The main element of semi-automatic mechanization is the electric holder. Through this device, electric current is supplied to the welding zone. The arc is ignited when the circuit is closed using a start button located on the handle of the holder.

Tractor-type equipment can perform work in a fully automatic process

To supply and remove the remaining flux, bins with regulators (dispensers) are installed. Mechanized semi-automatic machines for welding in shielding gases have a special gas-electric torch, from which gas and conductive filler wire are simultaneously supplied.

How is automatic titanium welding performed?

A tungsten electrode is used for this. Moreover, the size of the welding torch holes should be in the range of 12 – 15 mm. It is also necessary to take into account that it is better to make a connection with a non-consumable electrode using direct current of straight polarity.

The high activity of titanium forces the burner to be lit and extinguished on special strips, outside the product. As with manual technology, gas is supplied for another 1 minute after extinguishing the arc, protecting the seam and transition zone from oxidation. The following are the modes for automatic welding of titanium with argon in shielding gases and submerged arc:

Submerged arc operating modes:

Preliminary preparation

Titanium, unlike other metals, is very demanding in terms of surface cleanliness before welding. Therefore, preliminary preparation for argon arc welding plays a primary role. To get a stronger, more beautiful welding seam, you will need to carefully study a few simple rules. To begin with, be sure to degrease the surface of the metal, because titanium, its alloys, as well as some other metals react negatively even to the fatty secretions of the hands. Also, it's best to wear lint-free gloves when cleaning and working metal, so don't forget that. Small greasy spots can negatively affect the quality of the weld. The same applies to the cleanliness of gloves and leggings. Now let's turn directly to processing, having first discussed the issue of security.

Dangers in Preparation

Acetone is a very popular solvent for degreasing metal surfaces. However, this substance is very toxic. Firstly, acetone has an unpleasant odor and is very dangerous. It belongs to the fourth class of danger to the human body. Inhalation of moderate to high concentrations of acetone for short periods of time may cause irritation to the eyes, nose, throat, and lungs. In addition, this substance provokes an increase in heart rate, headaches, nausea, and vomiting. In particularly difficult cases, clinical coma is possible. Secondly, there are safer and no less effective means for preparing the surface of the weld. Welders with many years of experience recommend using denatured alcohol for such purposes. It is applied to the metal using a lint-free cloth. Denatured alcohol is basically pure alcohol with additives that make it taste quite terrible. Other additives included in the composition cause vomiting, which prevents drunkards from consuming denatured alcohol (as it can cause blindness). Welding titanium with argon requires cleaning the metal from oxide. To do this, use a stainless steel brush. It should only be used for titanium. Professional welders try to keep such brushes in a separate container. This keeps them clean. If there is no designated container, you can simply label any other one.

Shielding gas

Titanium is very sensitive to other gases and is characterized by high chemical activity. Because of this, welding requires the use of pure inert gases.

By using argon as a shielding gas, we obtain deeper penetration and a relatively narrow zone of temperature influence on the base metal.

If helium is used, the transition zone between the weld and the base metal will be smoother. This gas provides more heat, increasing productivity when welding parts with medium and large thickness. Unlike argon, helium has a consumption of 1.5 - 2 times more. Sometimes a mixture of these shielding gases may be used. They can provide additional benefits.

Welding titanium with argon - TIG welding technology

Good results when welding titanium can be obtained only by maintaining the cleanliness of the surface of the parts being welded (edges) and the filler metal itself. In addition, correct settings and selection of appropriate welding machine parameters are required. Improper welding technique in almost 100% of cases will be accompanied by the appearance of welding defects. Before starting work, first purge the burner itself, clean it and the protective nozzle. Don't forget about the backing pads used on the back side of the weld. They make it possible to check whether there is still air in the system.

Typically, welding titanium with argon does not require preheating. If there is any suspicion of metal moisture or condensation, you should definitely heat it up (up to 70 °C).

To ignite the arc when TIG welding titanium, it is best to use high-frequency ignition. The length of the welding arc itself in the case of using filler wire is 1 -1.5 cross-section of the electrode. If there is no additive, then the length of the arc should be equal to the diameter of the tungsten electrode used. Do not forget, scratches that can result from touching the tungsten electrodes to the metal during welding can retain tungsten particles. The attenuation of the arc upon completion of work should be gradual. In other words, gradually reduce the current. Protection of the weld and heat-affected zone is carried out even after the arc is turned off, bringing the temperature below 427 °C.

Possible defects when welding titanium with argon and ways to eliminate them

The only way to avoid defects when joining titanium elements with argon is to use a laser; in all other cases, errors are possible. GOST determines that defects appear due to non-compliance with technical conditions, violation of technology, as a result of which the design becomes unsuitable for use.

According to GOST, defects are divided into the following types:

• cracks;
• pores;
• solid formations;
• lack of fusion;
• wrong seam;
• other varieties.

GOST does not allow the presence of cracks in the seam or adjacent areas, since they form the center of destruction.

The reason for the appearance of ruptures usually lies in the high content of carbon, nickel, hydrogen, and phosphorus in the molten metal. Let’s say right away that when joining with a laser, there is no chance of cracks forming. To remove cracks that have appeared, it is necessary to drill the ends of the defect, then eliminate the crack mechanically and by gouging, clean and weld the area.

GOST defines pores as cavities filled with gas. It is quite logical that this defect is formed when welding titanium with argon due to high gas formation. A place with pores weakens the entire structure, so it is digested, having previously been cleaned mechanically.

Solid inclusions are foreign metallic and non-metallic substances included in the weld, reducing its strength and concentrating stress. Therefore, the area with the defect is completely cut down, removed by planing, and welded.

Non-fusion is the lack of connection between the metal and the weld, caused by the failure to melt part of the edge of the joint. This defect can appear if the corner shape or welding mode is chosen incorrectly, or if the edges are poorly pretreated. Since lack of fusion negatively affects the strength of the seam, the defect site is cut out, cleaned, and then welded.

Violation of the shape is a discrepancy between the shape of the seam and the established requirements. This deficiency appears due to power surges in the network, incorrect angle of inclination, etc. It can lead to internal defects in the seam, so they resort to welding the area with a thin seam with a small-diameter electrode.

Necessary equipment

Although the technology for thermite welding is not complicated, to perform it you still need to have the following equipment:

1. Crucible. It is made from refractory metals or ceramics and is equipped with a device that ensures safe drainage of the melt.
2. Mold and matrix for creating castings. They can be single or reusable. To limit the area of ​​the melt and prevent it from spreading over the surface, a special clay coating is used.
3. Vise or clamps. They fix and compress the parts to be welded.
4. Thermite compound, cartridge or pencil.
5. Tools for cleaning the surfaces to be joined and the resulting seams.

What other types of welding are suitable for titanium besides argon?

1. Electroslag welding
   Recently, this type of connection of titanium elements has been actively used in industry. For example, it is used for the VT5-1 alloy, that is, titanium alloyed with up to 5% aluminum and up to 3% tin. The alloy is produced by pressing and rolling into thin sheets, or by forging blanks with a large cross-section.

   The method used for large sections is considered very complex, but it is quite suitable for electroslag submerged arc welding AN-T2 in argon. The role of the alternating current source is played by a three-phase transformer with a rigid characteristic.

   For working with small forgings (60x60 mm), the following modes are recommended: current strength 1600 - 1800 A, arc voltage 14 - 16 V. Normally, the distance between the edges of the forgings is 26 mm, the mass of the filled flux is 130 g, the argon flow rate is 8 l/min.

   The use of a plate electrode measuring 12x60 mm in these modes allows us to achieve a stable process and a strong weld. The latter is comparable in strength to the base metal.

   When connecting extruded profiles with a large cross-section with an 8 mm thick electrode, a welded joint is obtained with slightly worse strength - 80 - 85% of that of the base metal. This feature is caused by the use of plate electrodes made of unalloyed VT1-1 alloy. Let us explain that it is not recommended to work with alloyed electrode alloys, because they do not provide the necessary ductility of the connection due to the high content of gases in the pressed metal.

2. contact welding
   GOST allows the use of this technology, since the optimal titanium welding speed is 2 – 2.5 mm/sec. Exceeding it will result in a decrease in the strength of the metal filling the gap. Note that this indicator is very important when work is carried out using the contact method, because all operations here are carried out very quickly. You should not clean the welded edges, much less mill them.

   In practice, several variants of the contact method are used, and all of them are suitable for working with titanium workpieces. Namely, we are talking about point, linear and capacitor technology. For each of them, their own mode is selected, which depends on the thickness of the workpieces being welded, the pressure and diameter of the electrodes or on the dimensions of the welding plate, compression time, and the duration of current passage through the metal. As you understand, this process requires competent selection of all the above parameters.

   Below you can familiarize yourself with the approximate modes of butt welding of titanium at an initial melting speed of 0.5 mm/sec:

   Area of ​​welded section, mm	Upsetting pressure, MN/M2	Departure of the workpiece from the electrodes, mm	Allowance, mm per		Reflow speed, mm/sec	Reflow current, A
   			reflow	draft
   150	2,9	less than 25	8	3	6	1,5 – 2,0
   250	4,9 – 7,8	25-40	10	6	6	2,5 – 3,0
   500	9,8 – 14,7	45	10	6	6	5,0 – 7,0
   1000	20 – 24	50	12	10	5	5
   1500	29 – 59	60	15	10	5	7,5
   2000	39 – 98	65	18	12	5	10
   2500	49 – 147	70	20	12	5	12,5
   3000	98 – 196	100	22	14	4	15,0
   4000	147 – 294	110	24	15	4	20,0
   5000	196 – 392	130	26	15	3,5	25,0
   6000	343 – 490	140	28	15	3,5	30,0
   7000	294 – 490	150	30	15	3,0	35,0
   8000	343 – 588	165	35	15	3,0	40,0
   9000	441 – 882	180	40	15	2,5	45,0
   10000	490 – 981	180-200	40	15	2,5	50,0

   Spot and seam (roller) welding is suitable for joining titanium sheets and plates up to 4 mm thick. The height of the cast core is 80–90% of the total thickness of the sheets. Below are approximate modes of this type of processing:

   Sheet thickness, mm	Electrode contact surface diameter, MN/m2	Force on electrodes, N	Duration of current passage, s	Compression time of parts, s	Current strength, A
   0,8	4,0 – 4,5	1960-2450	0,1 – 0,15	0,1	7000
   1,0	4,5 – 5,0	2450 – 2950	0,15 – 0,2	0,3	8000
   1,2	5,0 – 5,5	3150 – 3440	0,2 – 0,25	0,3	8500
   1,5	5,5 – 6,0	3935 – 4915	0,25 – 0,3	0,4	9000
   2,0	6,0 – 7,0	4915 – 5895	0,25 – 0,3	0,4	10000
   2,5	7,0 – 8,0	5895 – 6875	0,3 – 0,4	0,4	12000

   Modes of suture (roller) technology:

   Sheet thickness, mm	Seam width, mm	Roller force, N	Welding duration, s		Welding speed, m/min	Current strength, A
   			pulse	pause
   0,8+0,8	3,5 – 4,0	2950	0,1 – 0,12	0,18 – 0,20	0,8 – 1,0	6000
   1,0+1,0	4,5 – 5,5	3935	0,14 – 0,16	0,24 – 0,28	0,6 – 0,8	7500
   1,5+1,5	5,5 – 6,5	4915	0,20 – 0,24	0,3 – 0,4	0,5 – 0,6	10000
   2,0+2,0	6,5 – 7,5	6385	0,24 – 0,28	0,4 – 0,5	0,4 – 0,5	12000
   2,5+2,5	7,0 – 8,0	7855	0,28 – 0,32	0,6 – 0,8	0,3 – 0,4	15000

   Pipes made of titanium grade VT1-2, with a diameter of 10 - 23 mm and a wall thickness of 1.0 - 1.5 mm, can be welded using capacitor butt technology without the use of gas protection. Before this, we remind you that the welded edges are etched and work with the following modes:

   Pipe diameter, mm	Capacity, uF	Charging voltage, V	Upsetting force, N	Pipe extension from liners, mm	Transformation ratio
   10x1	5000	850 – 900	8935 – 9805	1,0 – 1,5	84
   23x1.5	7000	2000 – 2100	22565 – 24035	1,2 – 1,8	84

   The optimal overhang for pipes with a diameter of 10 mm is 1 - 1.5 mm, while for pipes with a diameter of 23 mm this figure is 1.2 - 1.8 mm. When the pipe protrusion is less than 0.8 mm, a splash of molten metal occurs, and when the limit of 2.2 mm is exceeded, the ends shift, resulting in lack of penetration. When the upsetting force is less than 20.7 kN, lack of penetration also results. It is also possible at a charging voltage of less than 1900 V, and at a voltage above 2200 V, liquid metal splashes out. Melting occurs inside the pipe in the form of a rim with a height of up to 1.5 mm and a maximum thickness of 0.3 mm.

3. Cold welding of titanium
   This technology involves the destruction of the crystal lattice and the formation of a new one by combining layers of titanium; the process occurs in a solid state in the open air.

   It is worth mentioning separately about working with white titanium, since such welding is carried out under pressure without external heating. The corresponding instructions allow you to use the technology at any air temperature.

   With the application of normal forces, this method of joining titanium sheets is overlapped using clamps for fixation. Next, you can begin the welding process. After removing the clamps, the sheets are deformed and firmly fastened together.

Electroslag

For titanium alloys with high tin or aluminum content, electroslag welding technology can be very often used. This technology is quite complex, and to master it it is recommended to obtain appropriate education. Main features of electroslag technology:

• For large parts with large cross-sections, it is recommended to use fluxes in argon. This will ensure high quality protection of parts.
• When welding small parts, fluxes do not need to be used. Optimal technical operating parameters: current - 1700 amperes, voltage - 15 volts, argon flow - about 7 liters per minute.
• For extruded profiles, it is better not to use electroslag welding. The strength in this case will be quite low compared to alternative technologies.