How to cook stainless steel semi-automatically

How to cook stainless steel semi-automatically in a carbon dioxide environment: video, tips

Welding stainless steel with a semi-automatic machine can be quite difficult not only for a beginner, but also for an experienced specialist. Such difficulties are primarily associated with the characteristics of the metal itself, for high-quality welding of which it is necessary to correctly select the operating welding modes and the appropriate consumables.

Semi-automatic welding machine for metal welding in a protective gas environment

Types of stainless steels

The main alloying element of steels classified as stainless steels is chromium. It is thanks to this element, which stainless steel must contain at least 12%, that an oxide film is created on its surface.

Despite the very small thickness of such a film, sometimes not exceeding the size of several atoms, it provides reliable protection of the metal from corrosion.

In addition, if this protective film is accidentally or intentionally damaged by mechanical force, then after some time it will restore its integrity.

The chemical composition of the vast majority of stainless steel grades, in addition to iron, carbon and chromium, may contain chemical elements such as nickel, titanium, niobium and molybdenum. These elements, found in stainless steel in fairly small quantities, improve both the anti-corrosion and mechanical characteristics of the alloy.

Chemical composition of the main grades of stainless steel

Stainless steels, depending on the characteristics of their internal structure, can belong to one of the following types. Martensitic

These are alloys containing 17% chromium and 0.5% carbon. Stainless steel with this structure is hard and highly brittle and can only be successfully used in slightly aggressive environments.

Austenitic

The chemical composition of such steels, in addition to chromium and carbon, also contains nickel, which increases the austenitic region in their structure. The distinctive qualities of such alloys, classified as non-magnetic, are high corrosion resistance and strength, optimally combined with good ductility.

Ferritic

This includes stainless steel alloys containing no more than 0.12% carbon and up to 30% chromium. This stainless steel, characterized by a good ratio of high strength and ductility, is resistant to thermal hardening and can be successfully used in conditions of exposure to aggressive environments.

Semi-automatic welding of stainless steel in a protective environment ensures high-quality connection of products

Properties and weldability of stainless steel

Steels classified as stainless steels are difficult to weld materials, which is explained by a number of their physical and chemical characteristics. When you decide to cook stainless steel with a semi-automatic machine, you must take into account a number of important parameters. Only in this case can you count on the resulting welded joint being of the required quality and reliability.

Compared to steels of other categories, stainless steel has a fairly low (on average two times) thermal conductivity. Because of this, heat is removed from the welding zone very poorly, as a result of which the metal is subjected to significant overheating, which negatively affects its corrosion resistance. To avoid such negative consequences, welding of stainless steel using a semi-automatic machine is performed at a reduced current (by 15–20%), and the parts to be joined are subjected to additional cooling.

Approximate modes of semi-automatic welding in a shielding gas environment

With significant heating (over 500°), carbide compounds are formed at the boundaries of the crystal lattice of stainless metal, which cause a phenomenon such as intergranular corrosion. As a result, delamination of the internal structure of the metal occurs and corrosion processes develop. To avoid this, they resort to more intensive cooling of the products being joined, for which ordinary water can be used.

It is also difficult to cook stainless steel (including in a protective gas environment) because it has a tendency to thermal expansion. Significant expansion of the joined products that occurs during semi-automatic welding leads to the formation of cracks both in the weld and in the base metal. Meanwhile, this phenomenon can be avoided if a wider gap is left between the parts being welded.

A high-quality stainless steel weld may be slightly grayish, but not dark

Stainless steel, due to the characteristics of its chemical composition, has a fairly high electrical resistance, which causes significant heating of the electrodes used for semi-automatic welding. In this regard, for welding stainless steel, electrodes made of wire with a certain chemical composition are used, and the length of the rods, if they contain chromium and nickel, should not exceed 350 mm.

Consumables

Good results in joining stainless steel parts can be achieved by welding performed in a shielding gas environment. To weld using this technology, naturally, you will need both special equipment and appropriate consumables, which are filler wire and the gas itself.

The purpose of gas in semi-automatic welding is to protect the molten metal in the weld pool from oxidation. The gas used for such protection should not itself react with the molten metal so as not to have a harmful effect on it. That is why inert argon mixed with a small amount of carbon dioxide is predominantly used as a protective medium.

On the left is a weld made in a carbon dioxide environment. On the right - in argon (98%)

The standard composition of the gas mixture used when welding stainless steel with a semi-automatic machine includes 98% argon and 2% carbon dioxide. In some cases, in order to reduce the cost of welding, it is possible to use a gas mixture consisting of 70% argon and 30% carbon dioxide.

To weld stainless steel while obtaining a high-quality and reliable weld, it is very important to choose the right filler wire, which should also be made of stainless steel. In cases where it is not possible to use shielding gas, semi-automatic welding is carried out in a normal environment, but special flux-cored wire is used to perform it. Meanwhile, the use of the latter leads to the fact that the welds may become covered with a layer of rust over time.

Some features of the technology

The use of special semi-automatic welding machines mentioned above can significantly improve the quality of stainless steel welding, as well as simplify the process of its implementation. The use of such equipment allows you to solve several technological problems at once, including:

• supply of filler wire to the joint formation zone;
• supply of shielding gas to the welding zone;
• cooling of the welding torch;
• ensuring the convenience of making welded joints in hard-to-reach places.

Semi-automatic welding equipment

In products made of stainless steels, during the welding process, significant internal stresses are formed, which are removed by their further heat treatment - heating to a temperature of 660–760° and slow cooling in the open air.

Preparation for welding work

Before welding products made from stainless steel using a semi-automatic machine, they must be properly prepared in order to obtain a high-quality and reliable connection. The process of such preparation is as follows.

• The surface of the parts to be joined is thoroughly cleaned using a metal brush and then degreased, for which the most common solvents can be used.
• To remove residual moisture from the surface of the product, it is heated to a temperature of 100°.

Preparing stainless steel for welding the manifold

Welding rules and methods

As mentioned above, in order to qualitatively weld stainless steel using a semi-automatic machine, it is necessary to correctly select the filler wire from which the weld will be formed. It is optimal if the degree of alloying of the wire exceeds that of the base metal. This is explained by the fact that alloying elements contained in the chemical composition of the wire will burn out of the metal during its melting, therefore their content must be taken into account with a reserve.

For semi-automatic welding of stainless steel, wire with an ultra-low carbon content and high silicon content, resistant to oxidizing environments, is used

For welding products made of stainless steel, three main methods are used:

• short arc method (used in cases where small thickness products are welded);
• jet transfer method (allows you to weld parts even of very significant thickness);
• pulsed (the most universal technology that allows you to perform welding work with high productivity and at the same time save wasted resources).

Each of the listed methods has certain features, but there are also general rules that should be followed when using each of them. Let's look at these rules.

• The torch body is located at the opposite angle to the progress of the seam to provide a high-quality overview of the latter.
• The torch nozzle, through which shielding gas and welding wire are supplied, is located at a distance of approximately 12 mm from the surface of the products.
• The filler wire, melted as a result of the burning of an electric arc, is fed into the zone of the weld being formed in small drops.

Burner position: approximately 11 o'clock

In addition, there are general recommendations for welding work that uses shielding gas.

• Stainless steel should only be cooked with reverse polarity.
• The angle at which the welding machine nozzle is located should ensure good penetration of the joint and a small width of the seam being formed.
• The protrusion of the wire from the nozzle of the welding machine should not exceed 12 mm.
• The gas flow rate that forms the protective environment should be in the range of 6–12 m3/min.
• The gas supplied to the welding zone must first be passed through a drying agent, which is copper sulfate.
• To minimize the splashing of molten metal from the welding area, the surface of the products to be joined is treated with an aqueous solution of chalk.
• To get a beautiful and high-quality weld, it should not start and end at the very edge of the parts being joined. It's better to retreat some distance. The welding itself, which is important, is performed without oscillatory movements to the sides of the seam being formed.

Elimination of deformations

During the welding process, stainless steel products can become deformed, which is associated with their significant heating during this procedure. In order to correct such defects, you can use one of two methods.

• Using a hammer and a smoother, the “bubble” formed on the surface of the stainless steel is simply tapped, moving from the edge of the part.
• Straightening the formed warping by tapping will be more effective if you combine it with heating the parts, for which you can use a regular gas burner.

In order to cook stainless steel with high quality using a semi-automatic machine, it is not enough just to get acquainted with the theoretical basis; it is very advisable to watch a training video on this topic.

Source: http://met-all.org/obrabotka/svarka/svarka-nerzhavejki-poluavtomatom-srede-uglekislogo-gaza-video.html

How to cook stainless steel yourself using a semi-automatic machine?

Stainless steels are subjected to welding quite often; this process requires care. Before you start cooking stainless steel, you need to read the process instructions and the features of using the burner. The semi-automatic welding scheme for stainless steel is simple, although compliance with all standards and conditions is required. For welding, a special wire is used, which contains nickel, which improves the characteristics of the seam.

Welding process diagram.

The welding torch itself and the work diagram are:

• the burner body, which must be tilted at a certain angle;
• a nozzle, which must be at a strictly defined angle and at an optimal distance so that the seam heats up perfectly;
• a conductive tip located inside the nozzle;
• electrode welding wire inserted into the conductive tip;
• welding arc acting on metal;
• the weld seam that remains after the process of welding parts;
• weld pool, i.e. an area of ​​molten metal that is formed under the influence of high temperatures;
• electrode drops that are fed into the bath;
• gas protection.

Semi-automatic welding techniques

Melt and transfer of electrode material: A. Drop method. B. Jet method.

Welding stainless steel is possible in several ways:

• pulse welding;
• welding using a short arc;
• welding, during which so-called jet transfer is used.

A short arc is used when the work is done on thin metal. Using jet transfer is effective for joining thick parts. Pulse welding technology is a controlled process.

The metal for the wire is introduced into the bath in pulses, and the supply is carried out one drop at a time.

The arc operates at an average current level, heat input is reduced, as is the overall thermal effect zone. The size of the weld pool is optimal, and this is important for stainless steel. With pulse technology, there is also almost no splash of molten metal. This saves materials and the process itself is safer. The time for cleaning the seam is reduced, and the surface is of high quality.

Is it possible to weld ferrous metal and stainless steel? Yes, such a process is possible, but only if certain conditions are met. It is necessary to take into account why stainless steel is used and what kind of ferrous metal will be used. It is important to choose the right filler wire; you should not use the usual one, as the quality of the weld will be poor. When using an arc and an argon mixture, special stainless steel additives are required.

How to create a landscape design yourself and beautifully?

Semi-automatic welding technology in a protected environment

To answer the question of how to semi-automatically weld stainless steel, it is necessary to clearly define all the requirements for such a process.

Preparatory work:

Gas shielded welding diagram.

1. The gas for welding is taken with the following composition: 70% special welding carbon dioxide (you can use food grade carbon dioxide), 30% argon B.
2. Reverse polarity is applicable during operation. Straight polarity is only possible when working under flux.
3. The welding wire overhang should be 6-12 mm. When welding, the distance from the nozzle should be 5-15 mm. The working flow rate of the gas welding mixture will be 6-12 m³/min while maintaining a pressure of 0.05-0.2 atmospheres. It is impossible to reduce the amount of gas, since in this case the seam will be insufficient and its quality will be poor. A situation is also possible in which carbon begins to burn out strongly, as do alloying additives.
4. The welding angle must be maintained so that it faces backwards. It is recommended to tilt the electrode in the direction opposite to the direction of the seam. The tilt is maintained at 5-10 degrees. This gives a good penetration depth, the seam is of better quality and smoother. If the angle is tilted forward, the seam becomes wide and the penetration depth is shallower. The latter option is best suited for thin metal.
5. During the welding process it is necessary to use a desiccant. This is required for the reason that the composition of the cylinder consists of 60% water; upon exiting at the seam, acid is formed under the influence of high temperature and carbon dioxide. But this acid greatly worsens the quality of the seam, and a desiccant can solve this problem. It uses silica gel or copper sulfate, which are calcined at a temperature of 200°C in about 15 minutes. For 3-4 working volumes of cylinders you need to take only 100 g of such a desiccant.
6. It is required to provide protection from metal splashes. Usually it is recommended to use a chalk aqueous solution for this.

Welding Process Basics

The special stainless steel welding wire itself is an electrode, which simplifies the welding process.

Stainless steels are available in 3 grades; the welding process will greatly depend on the choice of this grade:

• food grade stainless steel, low alloy;
• food grade, chemical stainless steel, medium alloy;
• heat-resistant, high-pressure-resistant, chemical-grade stainless steel, high-alloy.

To cook with a semi-automatic machine correctly, you need to use a special wire:

1. The first two types of such welding wire ensure the mixing of all alloying elements during welding, but the metal burns out, especially chromium. A process called corrosion occurs when aggressive environments occur.
2. The third type of welding wire is special; during welding, no cracks or stresses are formed in the seam, i.e. the joint is of high quality.

Preparatory work for metal:

1. The surface of the parts to be welded must be degreased and all traces of the oxide film must be completely removed. This is done mechanically or using special acids.
2. Before welding itself, it is necessary to dehydrate the future seam, for which it is heated to 100°C with a torch. But during welding, all remaining excess boils away automatically, especially if a continuous seam is made.
3. There is a preparation option in which the area of ​​metal around the future weld is heated to 200°C; in some cases, this procedure is carried out for the entire workpiece. This allows you to reduce the impact on the metal near the seam during its heating during welding.
4. It is not recommended to heat 2 different types of steel, only one type.

For the sides, it is best to overlap with welding on both sides; the edges themselves can be bent outward, the inner corner is not welded. The outer edges are often processed using rollers using the pressing method.

How to relieve tension?

When welding semi-automatically, it is important to relieve stress from the metal; the following actions are used:

1. The stress is removed during tempering at 560-660°C. This process involves heating the part to be welded to the required temperature, after which the part itself is cooled in the open air.
2. If a temperature of 760°C is reached, then a process such as the reduction of chromium on the weld is observed. This allows stress to be quickly relieved to ensure the required weld quality.
3. For thin-walled parts, stress is perfectly relieved. If you start piercing the seam with hammers after welding, then the operating temperature is maintained at only 100°C.

Straightening deformities

After welding is completed, it is necessary to perform the following actions aimed at removing possible deformations:

1. Using a special smoother, a hammer is used to process the part, which should fit tightly to the anvil.
2. If a bubble has formed on the surface, then you need to tap it along the edge with a hammer, carefully approaching the bubble itself. On the other hand, this area can also be heated with a burner, moving in a circle of 30-60 mm. You just need to move in a checkerboard pattern and don’t stop tapping with the hammer.

Welding stainless steel semi-automatically requires certain skills. The process itself includes preparing the welding area and wire for work. After welding, if necessary, work is performed to eliminate deformations.

Source: https://moyakovka.ru/process/kak-poluavtomatom-varit-nerzhaveiku.html

How to cook stainless steel semi-automatically

Unlike ordinary steel, not every craftsman can perform high-quality semi-automatic welding of stainless steel. To obtain a reliable connection, it is necessary to take into account its features, correctly set the operating mode parameters and select consumables. The success of the work largely depends on the quality of the equipment.

Features of stainless steel welding

Alloying additives make stainless steel resistant to corrosion and acids, but at the same time it acquires properties that make welding difficult. Compared to conventional steel, thermal conductivity is reduced by half. This makes it difficult to remove heat from the welding site, which leads to overheating of the metal, burn-through and burnout of chrome. To prevent this phenomenon, welding is performed with a current 15 - 20% less than the standard one with additional cooling of the workpieces.

Stainless steel has a high coefficient of thermal expansion, which leads to cracking of the seam and the metal next to it. To neutralize it, a large gap is left between the workpieces. Due to the high electrical resistance of the material, the electrodes for welding stainless steel overheat, which does not have the best effect on the quality of the seam. Therefore, they are cut to the minimum possible size so that they do not have time to heat up.

Having learned about the difficulties, beginners ask the question: “Is it possible to weld stainless steel semi-automatically at home?” The answer, of course, is yes. Three methods are used to connect workpieces:

• short arc;
• impulse method;
• jet transfer.

Thin stainless steel is welded with a short arc, as it reduces the likelihood of burning through. The jet transfer method is used to join thick-walled parts made of stainless alloys in production. Welding is carried out using flux-cored wire and special heads.

To create a protective environment during pulse welding, a mixture of argon and carbon dioxide is used. The advantages of the method include:

• the ability to connect both thin and thick workpieces;
• feeding the wire in short pulses prevents splashing of molten metal;
• saving of filler material;
• excellent connection quality;
• high performance.

Selection of materials for welding

To obtain a high-quality weld, the composition of the filler wire must be the same as that of the metal being welded. It is better if the content of alloying elements is slightly higher. If you use regular brands, the connection will quickly rust. For welding stainless steel alloyed with chromium, flux-cored and wire with a high nickel content are produced.

Source: https://svarkaprosto.ru/tehnologii/kak-varit-nerzhavejku-poluavtomatom

Semi-automatic welding of stainless steel in a carbon dioxide environment

Welding stainless steel semi-automatically in a carbon dioxide environment is not the easiest process even for very experienced welders. It's all about the metal being welded, because stainless steel is steel that, in addition to carbon, also contains chromium (12%).

So, it is chromium, in contact with oxygen in the air, that forms an oxide film just a few atoms thick on the surface of the workpiece. But it is this film that prevents the welding process from being carried out, because it is refractory. By the way, it is this that reflects such a high indicator as resistance to corrosion.

It can be easily removed using, for example, a wire brush or sandpaper. But the film is quickly restored.

All these features of stainless steel affect the method of its processing and welding, the correct choice of welding mode and selection of consumables. But it is also necessary to take into account the fact that stainless steel manufacturers today offer not only an alloy of iron and chromium. There are three classes that have different properties.

• Ferritic - it contains only chromium. This metal is used in aggressive environments. One of its features is resistance to thermal hardening.
• Austenitic - in addition to chromium, the composition also includes nickel. This steel has increased strength and ductility.
• Martensitic – composed of chromium and carbon. Despite its sufficiently high strength, this stainless steel is very fragile, so it is used only in slightly aggressive environments.

Properties of stainless steel

Before you cook stainless steel with carbon dioxide, you need to understand that this is not ordinary steel. This is a difficult alloy to weld, so it is recommended to pay attention to its physical properties.

• Compared to the same ordinary steel, stainless steel has two times lower thermal conductivity. That is, in order to weld it, it is necessary to reduce the welding current. At high current, a burn-through may occur, because the metal itself will conduct heat through its entire mass with difficulty. In addition, an overheated area is a guarantee of a decrease in the anti-corrosion abilities of the metal. Therefore, there is only one way out - to increase the cooling of the weld and reduce the current by 20-30%.
• There is such a thing as intergranular corrosion of metal. Essentially, this is when, when heated, carbide forms inside the steel as a result of the combination of iron and chromium. This can happen if the heating temperature reaches +500C. The carbides themselves from inside the metal lead to its cracking. And, as a result, corrosion. Therefore, it is impossible to allow the temperature to remain at this value for a long time. The way out of this situation is to cool the welding zone by any means, even water.
• Stainless steel is a steel with high linear expansion. When heated, the metal expands very strongly, and when cooled, accordingly, it contracts greatly. This enormous shrinkage causes the weld to crack. Therefore, when welding stainless steel even semi-automatically, it is necessary to leave an increased gap between the workpieces. It will compensate for the amount of shrinkage.
• There is such an indicator - electrical resistance. It is quite high in stainless steel. It is this property that affects the overheating of an electrode made of high-alloy steel. That is why such consumables are short in length - within 35 cm.

How to cook stainless steel with a semi-automatic machine

To weld stainless steel semi-automatically, it is necessary to select the correct composition of the shielding gas. It is considered optimal if the gas should consist of argon - 98% and carbon dioxide - 2%. Although many welders, in order to reduce the cost of work, increase the percentage in favor of cheap carbon dioxide. For example, 30% is carbon dioxide and 70% is argon.

As for the filler wire, it is recommended to use exactly the same as the metal being welded. For example, if workpieces made of 304 stainless steel are welded, it is recommended to use a Y308 brand additive to join them.

With a non-consumable tungsten electrode everything is just as simple. Its diameter will depend on the thickness of the parts being welded. For example, if their thickness does not exceed 1 mm, then an electrode with a diameter of 1 mm is used. Thickness 1-4 – diameter 1.6. Thickness over 4 mm, diameter 2.5 mm.

Welding nuances

Semi-automatic welding machines for stainless steel provide several functions of the technological welding process.

• uniform feed rate of filler material into the welding zone;
• the ability to adjust the exact strength of the welding current;
• burner cooling.

All this ensures high quality of the weld, plus the speed of the welding process increases. Of course, it must also be said that in a carbon dioxide environment, the filler wire melts more intensely, so heating of the welded area will occur at low (relatively) temperatures.

All other operations are carried out in exactly the same way as when semi-automatically welding conventional steels.

• Stainless steel workpieces to be welded are being prepared. They are cleaned with an iron brush to remove dirt, paints and other materials. If necessary, then degrease it. To do this, you can use alcohol, acetone, gasoline, and so on. If parts with a thickness of more than 4 mm are connected, then edges are necessarily formed. It is necessary to heat up to +100C in order to completely remove moisture from the surfaces.
• And the welding process itself.

It is very important to follow the exact scheme of semi-automatic welding. The burner should be approached to the gap between the workpieces at a slight angle. The filler wire is fed at an opposite angle. In this case, the burner nozzle should be at a distance of 10-12 mm from the surface of the weld.

It turns out that the arc that occurs between the tungsten non-consumable electrode and the metal of the workpiece melts the metal of the filler wire. It falls in drops between the workpieces, forming a seam. In this case, under the influence of shielding gas pressure, droplets spread throughout the weld pool. And all this happens evenly. This can be seen very clearly in the video.

To summarize all of the above, it is necessary to identify the positions that affect the quality of the final result when welding stainless steel with a semi-automatic machine in a protective carbon dioxide environment.

• Welding is performed using direct current of reverse polarity.
• The burner tilts forward, the additive tilts back.
• The maximum extension of the tungsten electrode is 12 mm.
• The consumption of shielding gas is very important. Its range is 6-12 m³/min. An increase in the consumed volume leads to a decrease in the quality of the seam.
• Be sure to add a desiccant to the gas cylinder, for example, copper sulfate. The thing is that when carbon dioxide comes into contact with metal, an acid is formed, which, when supplied to the welding zone, will destroy the carbon. Therefore, acid cannot be allowed to form.
• The deposition process itself must be carried out smoothly.
• It is also recommended to tap the weld seam with a hammer after finishing work. In this way, bubbles formed on the surface of the seam during welding are removed.

And yet, despite its apparent simplicity, welding stainless steel with a semi-automatic machine is not the easiest process, and it is very responsible. It requires skills and experience to carry it out. So it is not suitable for beginner welders. Watch the video on how to properly cook stainless steel using a semi-automatic machine in a protective carbon dioxide environment.

Source: https://svarkalegko.com/tehonology/svarka-nerzhavejki-poluavtomatom.html

Semi-automatic welding of stainless steel: properties of the alloy, welding in carbon dioxide and argon - Machine

How stainless steel is welded semi-automatically in a carbon dioxide environment is the topic of our publication.

What you need for welding

• Current source (semi-automatic);
• welding wire;
• shielding gas.

The welding wire must be identical to the metal being welded. In our case, choose stainless steel for a semi-automatic machine.

Stainless steel welding wire for semi-automatic machine

There is wire from Russian and foreign manufacturers on the market, which is divided into flux-cored and solid wire. Diameter from 0.13 to 6.0 mm. At home, diameters of 0.6 and 0.8 mm are used, and over 1.0 mm in production.

1. Solid wire is used for gas shielded and submerged arc connections. This method eliminates the entry of air into the welding zone, thereby improving the quality of the weld.
2. Corroded stainless steel wire (self-shielding) is a thin-walled tube filled with flux and gas. The mixture of components allows you to weld products without protective gases (carbon dioxide and argon).

Wire for welding stainless steel semi-automatically, produced with heat treatment or cold drawn. And it is divided into oxidized (T) and light (white, TS).

Stainless steel wire is available in 2 accuracy classes:

• increased accuracy (P);
• normal accuracy.

Wire with increased precision is used to improve the quality of the seam.

Stainless steels are divided into different grades based on their chemical composition, and the wire also has different markings. The table (below) will introduce the brands, diameter and weight of stainless steel wires:

Cost of stainless wire for semi-automatic machine

The price varies depending on the manufacturer and the region of residence of the buyer.

Averages:

• ER 308 LSI 0.8mm 1kg - 825 RUR;
• ER 308 LSI 0.8mm 5kg — 4237 rub.

Gas selection

Semi-automatic cooking without gas is prohibited, except when using cored wires. Semi-automatic welding of stainless steel can be performed in an environment of carbon dioxide or a mixture of carbon dioxide and argon.

Carbon dioxide is a readily available and cheap gas for joining stainless steels. When used cleanly, the welder is faced with excessive spattering of metal and a clumsy weld.

It is more convenient to use a mixture of argon and carbon dioxide, percentage ratio 98/2 (Ar-98%, CO2-2%). Experienced welders vary the composition of the mixture depending on the brand of stainless steel and their preferences.

The percentage of carbon dioxide and argon can be adjusted using two separate cylinders. Connect the outputs from the two gearboxes using a tee taken from the windshield wiper of a domestic car. Details of this design are in the video:

That's it, all you have to do is select the shielding gas and connect the wire to the device. Be aware: the conductive tip must be the same diameter as the wire.

Buy tips with a reserve; during operation they burn out and the device then cooks worse.

how to set up a semi-automatic machine for operation (for beginners).

How to weld stainless steel in a carbon dioxide environment

Use a grinder to clean the working surface of the product, and when connecting metal with a thickness of 4 mm or more, make edges (grooves for depositing metal). This article talks about marking stainless steels and preparing surfaces.

After cutting the chamfers, join the parts together using clamping pliers, leaving a gap between the products (at least 1.5 mm).

The gap should be along the entire length of the workpiece; it will allow the metal to be welded to its full thickness. Connect the ground and set your settings on a semi-automatic device depending on the design of your device and the thickness of the metal.

Simple semi-automatic machines on the front panel have 2 adjustments:

• welding voltage;
• wire feed speed.

Advanced models are equipped with an inductance adjustment knob. Also, the wire feed speed depending on the diameter can be adjusted by a switch.

Setting the inductance changes the arc rigidity, penetration depth and bead shape:

1. With low inductance: the arc is cold - we get a thin bead with deep penetration;
2. With high inductance: the arc is hot - a wide bead with shallow penetration.

Holding the torch with a slope of 20-60 degrees (the distance from the nozzle to the weld pool is 10-20 mm), use short tacks to make a stainless steel connection. They pulled the trigger, released it, pressed it and released it, and this is how the cut edges are slowly filled with metal. You can cook either with an angle back (toward you) or with an angle forward (away from you).

The tables (below) will help you decide on the settings of the semi-automatic machine:

When welding with an overlap, there is no need to cut chamfers; it is enough to clean the surface, place the parts on top of each other and make the connection.

During the welding process, before making a new seam, bite off the weld bead at the tip of the wire.

• In the process of joining stainless steel semi-automatically in a carbon dioxide environment, change the wire feed speed, with such manipulations you will achieve a high-quality seam.

Source: https://regionvtormet.ru/beton/svarka-nerzhavejki-poluavtomatom-svojstva-splava-svarivanie-v-srede-uglekislogo-gaza-i-argona.html

Features of semi-automatic stainless steel welding

Stainless steel is used in many industries, as well as in everyday life. When eliminating possible breakdowns of parts and connecting individual parts, semi-automatic stainless steel welding is used. Special equipment and a protective gas environment will help avoid the appearance of defects at the joint.

Semi-automatic welding of stainless steel

Features of stainless steel

The process of joining stainless steel by welding is considered complex. This is due to the composition of stainless alloys, as well as their characteristic properties.

Semi-automatic stainless steel welding technology

To improve the quality of the connection, as well as reduce the level of falsity in the welding process of stainless alloys, semi-automatic devices are used. The equipment gives:

• providing the weld pool with gas to protect it from outside influences;
• feed of filler wire;
• forced cooling;
• the ability to perform work in hard-to-reach places.

During the welding process, areas of increased internal stress are formed on the metal surface. To prevent this phenomenon, it is recommended to carry out processing by heating the part to a temperature of 760°C and further self-cooling.

Materials and equipment

Semi-automatic machines are used in the welding process. They are provided with a wire feed system as well as shielding gas. A semi-automatic welding machine must have the ability to switch polarity, as well as control and adjust basic parameters.

Wire for welding stainless steel

To ensure a reliable seam, it is necessary to use semi-automatic stainless steel welding wire. It is also made from stainless steel materials. If it is not possible to use a gas environment, it is recommended to use cored wire; it has a hollow structure, the void is filled with flux. The disadvantage of the latter is the subsequent appearance of cracks in the structure of the seam.

How to cook stainless steel semi-automatically

Often, connection parts may be located in hard-to-reach places. Semi-automatic welding of stainless steel provides a reliable seam that is protected from premature wear.

Metal preparation

Before performing work on connecting with filler wire, it is necessary to prepare the parts:

• remove all contaminants at the connection point;
• degreasing the metal is carried out to ensure the reliability of the seam and protection from cracks; solvents will help with this;
• To remove excess moisture, it is recommended to heat the parts to 100°C.

Welding technical diagram

Three methods are used to join stainless alloys by welding:

• for parts of small thickness, the short arc method is required;
• with jet transfer, a welded stainless steel joint is obtained for parts of large thickness;
• The impulse method is considered universal.

The technological process requires following certain rules:

• for a good view it is necessary to place the burner at a negative angle to the seam;
• the head should be kept at a distance of 12 mm from the metal surface;
• the wire should melt in small portions, without large drops.

The welder is recommended to fulfill a number of requirements:

• welding is carried out with reverse polarity of the terminals;
• the angle value regulates the quality and width of the seam;
• the extension length of the filler wire should be no more than 12 mm;
• dried gas must be supplied to the weld site at a flow rate of up to 12 m3/min;
• to prevent splashes, the surfaces are treated with a chalk solution;
• It is recommended to make the beginning and end of the seam at some distance from the edge of the parts.

Correction of defects

When performing welding work, deformations may occur at the joints; this occurs as a result of heating. To resolve this, do the following:

• when bubbles form at the seam, use the method of tapping with a hammer from the edge of the parts;
• warped metal must be straightened by heating the part with a torch, as well as tapping with a hammer.

To obtain a seam, it is necessary to study the theoretical part, as well as perform test welding on samples.
Semi-automatic welding of stainless steel. Argon, carbon dioxide and mixture.

Features of semi-automatic stainless steel welding Link to main publication

Source: https://metalloy.ru/obrabotka/svarka/nerzhavejki-poluavtomatom

Semi-automatic welding of stainless steel: properties of the alloy, welding in carbon dioxide and argon

The colloquially used word “stainless steel” refers to low-carbon steel with the addition of chromium. As a result of interaction with oxygen, chromium creates a protective oxide film that prevents the metal from rusting.

If a metal alloy contains at least 12% chromium, then it already belongs to the category of stainless steel and is resistant to corrosion. At the same time, working with this material requires certain preparation of the metal before welding. The quality of welding work is influenced by the choice of operating welding mode and the correct selection of consumables.

The surface anti-corrosion layer of the metal is resistant to restoration. Modern anti-corrosion alloys may contain in small quantities: carbon, titanium, nickel, molybdenum, niobium. All these elements also increase corrosion resistance and improve the quality of the steel.

Depending on the microstructure, stainless steel can have different properties and be used in different environments:

1. Steel containing chromium and nickel belongs to the austenitic class. It is distinguished by high levels of rust resistance, ductility, strength and non-magneticity.
2. An alloy containing chromium and iron is called ferritic. It is resistant to thermal hardening and can be used in aggressive environments.
3. An alloy containing carbon and chromium is called martensitic and is used in slightly aggressive environments. This use is explained by the high hardness and at the same time brittleness of the alloy.

Properties of stainless alloy

It is recommended that a novice welder take into account certain properties of the chemical composition of the steel alloy in order to complete the job efficiently. The main parameters usually include:

1. Low thermal conductivity . The thermal conductivity of stainless steel is two times lower compared to other metals. During the welding process, the metal may melt more than necessary. Corrosion resistance will be reduced as a result. To eliminate the negative consequences, craftsmen reduce the current strength by 20% and additionally cool the seam.
2. Minimum melting point level. To maintain resistance to rust, the optimal temperature regime is maintained during work.
3. Intergranular corrosion . It is the result of the formation of a carbide compound of chromium and iron. Spreading, leading to metal corrosion, occurs when the temperature rises above 500 degrees. To eliminate undesirable effects, various methods of cooling the structures being welded are used.
4. High level of linear expansion of steel. Casting shrinkage of steel occurs due to high temperatures. Exceeding the temperature can lead to deformation of the metal and the appearance of cracks between the parts being welded. For this purpose, when working with stainless steel, it is recommended to leave small gaps for expansion.
5. High electrical resistance . This indicator can cause heating of electrodes made of high-alloy steel. To prevent high heating, the length of nickel and chromium electrodes does not exceed 350 mm.

Semi-automatic welding

When using different methods for welding stainless steel, different quality results can be obtained. For welding in a gas-free environment, flux-cored wire is used. This method ensures an even and beautiful seam. But such a seam may rust during use of the product.

To prevent such consequences and obtain a high-quality result, welders use a semi-automatic machine using steel wire and carbon dioxide. The ideal gas composition is 2% carbon dioxide and 98% argon. To reduce the cost of the work performed, the gas proportions are changed to the ratio of 30% carbon dioxide and 70% argon.

The use of a semi-automatic machine allows the wire to be fed into the welding area by mechanization. The semi-automatic machine allows you to cool the torch, make high-quality connections in an argon environment, adjust the filler wire feed speed and weld in hard-to-reach places.

Before carrying out welding work, the surface of the parts to be welded is prepared:

1. Clean the surface with a metal brush and degrease using special products: white spirit, acetone or aviation gasoline.
2. Heat the parts to be welded to 100 degrees so that the welding zone is dry and free of moisture.

The most reliable and effective is welding using argon and carbon dioxide . This method of welding metal allows you to preserve all the properties of steel. During the welding process, nickel alloy wire burns more intensely, which improves welding performance.

When using regular wire, the performance may be worse. Methods of modern welding of stainless metals:

1. Thin sheet metals are connected using the short arc method.
2. Thick sheet metals are joined using the jet transfer method.
3. Saving resources of high productivity is carried out by the pulse welding method. This method allows the wire to be fed in short bursts.

In an argon environment

Semi-automatic welding in an argon environment allows you to increase productivity. The technology of such welding allows not only welding thick metals, but also obtaining reliable, high-quality joints that are attractive in appearance.

The composition of the welding wire should include nickel to improve the quality of the work performed. For welding thick-walled metals, a mixture of argon and carbon dioxide is used.

The welder should remember that products may become deformed during operation due to prolonged heating. This problem can be solved by tapping and heating the parts. For this purpose, you can use a household gas burner.

In a carbon dioxide environment

When carrying out welding work in a carbon dioxide environment with a semi-automatic machine, the following requirements must be met:

1. Application of reverse polarity.
2. Holding the electrode angle. Thin metals can be welded by tilting the wire forward. This method makes the seam wider and the penetration depth shallower.
3. The amount of wire protrusion should not exceed 12 mm.
4. Ensuring control over gas consumption. Too little or too much gas consumption can negatively affect the final result.
5. Using a dehumidifier. During the process of welding metal at high temperatures, water is released from cylinders with a gas mixture, which, when interacting with carbon dioxide, reduces the strength of the seam. Copper sulfate, used as a drying agent, helps maintain the quality of the weld.
6. Welding should not begin or end at the edge of the part. This can lead to hydrogen cracks. It is recommended to retreat at least 5 cm from the edge of the product.

Source: https://tokar.guru/svarka/svarka-nerzhaveyki-poluavtomatom-v-srede-argona-i-uglekislym-gazom.html

Semi-automatic stainless steel welding technology

Today, in addition to industrial-grade semi-automatic machines, semi-automatic welding machines have appeared, so-called. hobby class, allowing you to cook stainless steel semi-automatically almost at home. Such hobby-class welding machines include, for example, the MDT series. But, nevertheless, welding stainless steel with a modern semi-automatic machine still remains a complex and responsible process even for an experienced welder.

And this complexity is associated, firstly, with the different chemical composition of stainless steel alloys, and secondly, with a number of characteristic properties of stainless steel, which further complicate welding work.

Special welding properties of stainless steel

Stainless steel has the following properties that affect the welding process:

Low thermal conductivity

The thermal conductivity of stainless steel is 2 times lower than that of low-carbon alloys. Because of this, the weld pool overheats and the steel melts, which, in turn, leads to a deterioration in the anti-corrosion properties of stainless steel. To prevent these negative processes, it is recommended to reduce the current strength by 20% and use means of forced cooling of the weld pool.

Low melting point

A low melting point combined with low thermal conductivity leads to the formation of a liquid melt in the weld pool with a temperature of over 500 degrees. Under these conditions, intergranular corrosion begins to occur - the formation of iron and chromium carbides. Subsequently, microcracks form in places where carbides are concentrated, into which water penetrates, provoking corrosion processes.

The recipe for preventing intergranular corrosion is forced cooling of the weld pool (water, a jet of inert gas, etc.).

High thermal expansion rate

Under conditions of low thermal conductivity, this factor leads to linear shrinkage and thermal deformation of the crystalline structure of stainless steel. To prevent shrinkage, a sufficiently wide gap is left between the parts being welded, into which the overheated stainless steel will expand.

Low electrical conductivity

Compared to other iron alloys, stainless steel can be called an insulating material, because stainless steel conducts electricity so poorly. Because of this property, overheating of the electrodes occurs during welding, especially if they are highly alloyed varieties, i.e., contain a large amount of nickel and chromium.

Features of semi-automatic welding of stainless steel in an argon flow

There are several technologies for welding work with stainless steel, for example, using special flux-cored wire. But they all have certain disadvantages. Thus, welding seams created using flux-cored wire crack over time.

Semi-automatic welding of stainless steel with argon is the most effective and high-quality method of thermal connection of two stainless steel parts. To cool the weld pool, a flow of inert gas argon with the addition of carbon dioxide is most often used.

Please note that the ratio of argon and carbon dioxide varies depending on the nature of the stainless alloys with which welding work is performed. This ratio is regulated using two cylinders with argon and carbon dioxide, whose valves are unscrewed differently, thereby achieving different ratios of the cooling gas mixture.

To improve the quality and appearance of the resulting weld, stainless steel nickel alloy wire is used, which is fed into the welding zone mechanically.

Like the ratio of the cooling mixture, the chemical composition of the wire depends on the chemical composition of the stainless alloys and the characteristics of the welding work.

So, how to cook stainless steel with a modern semi-automatic machine? This procedure is performed in several ways:

1. Short arc. Used for joining thin sheet parts.
2. Jet transfer. Used for joining thick-walled parts.
3. Pulse welding technology. It is widely used in industrial production, as it is characterized by high speed of welding work with low energy consumption.

So, before starting welding work:

• Reverse polarity is established;
• The electron inclination and the angle of wire feed into the welding area are set. For example, when the wire is tilted forward, the depth of penetration decreases and the width of the weld seam increases. This combination is used for cooking thin-leaved parts;
• The permissible wire overhang is set. Typically this figure is limited to a distance of 12 mm;
• The strength of the cooling gas flow is set in the range from 6 to 12 m3/min. If the strength of the cooling gas flow is not set within the specified limits, the welding quality will significantly deteriorate as a result;
• The operating procedure of the dryer is determined, the task of which is to remove water vapor from the gas mixture. The fact is that water molecules, entering the weld pool, react with carbon dioxide and metals, as a result of which first carbonic acid and then carbon dioxide salts of metals are sequentially formed. Copper sulfate is usually used as a drying agent, which is heated to 200 degrees 20 minutes before welding. The average consumption of copper sulfate is 100 grams per 4 cylinders of the gas mixture;
• To protect against splashes of molten metal, a container with a water-chalk solution is connected to the semiautomatic device;
• The speed and trajectory of movement are set. Semi-automatic welding must begin at least 5 cm from the edge of the part, otherwise there is a risk of the formation of the so-called. hydrogen cracks.

Completion of welding work

Welding stainless steel with a semi-automatic machine does not guarantee an ideal result. At the end of welding work, bubbles may appear on the surface of the welded parts, which should be smoothed out with a hammer. To do this, you need to heat the bubble with a burner and, gently tapping it with a hammer, straighten it.

Source: https://electrod.biz/oborudovanie/poluavtomat/svarka-nerzhaveyki-poluavtomatom.html

How to cook stainless steel semi-automatically

How stainless steel is welded semi-automatically in a carbon dioxide environment is the topic of our publication.

Semi-automatic welding of stainless steel (MIG) | Tiberis

Semi-automatic welding of stainless steel is the most popular method of welding in a protective gas environment, which is used both in car repair shops and in large industrial production. From our article you will learn what the technology of the semi-automatic welding method of stainless steels is, what features it has, and what you should remember during the welding process in order to achieve ideal quality of the weld.

What is the semi-automatic welding method for stainless steel?

Semi-automatic welding of stainless steel (MIG) in a shielding gas environment is a high-tech process during which a wire is automatically fed into the welding zone, which simultaneously acts as an electrode and a filler metal, then it melts under the influence of the heat of the arc.

The quality of the arc is largely influenced by the correct choice of operating modes of the semiautomatic device: current, wire feed speed, choice of shielding gas and its consumption. The weld seam is formed quickly and is even. As a rule, during welding work this method uses a protective gas mixture of argon and carbon dioxide.

Oxygen is sometimes used instead of carbon dioxide, in which case the wettability at the edges of the weld increases (that is, the contact angle becomes sharper). Semi-automatic welding technology takes into account the structural features of the metal, its structure and chemical properties.

The question of how to cook stainless steel with a semi-automatic machine may have several answers. You can work with a semi-automatic machine in three different ways:

• Short arc (for stainless steel with a thickness equal to or less than 0.8 mm);
• Using jet transfer, the thickness of stainless steel ranges from 0.8 mm to 3 mm);
• Pulse welding (stainless steel thickness more than 3 mm. But can also be used for thinner sheet steel).

Where is this method most often used?

Stainless steel is actively used in many areas of our lives, and, of course, in the process of working with this metal, as well as in the process of making certain parts from it, we have to resort to welding. The MIG method is rightfully considered universal.

The high efficiency of the method allows it to be used in garage conditions, and in the manufacture of household appliances and dishes, for example, in the case of installation and welding of various fences, metal tanks in the country, and in large production facilities in the automotive industry with serious requirements for the quality of the weld seam and efficiency welding process.

Is it necessary to use shielding gas?

It is possible to weld stainless steel semi-automatically without using gas. This welding method is characterized by the fact that a special flux-cored wire is involved in the process. The result is a high-quality seam. But the disadvantage of this method is that the suture material will become rusty over time. Therefore, when working with stainless steel, it is better to use stainless steel wire and supply of shielding gas to the weld pool.

What are the advantages and disadvantages of this method in contrast to MMA and TIG welding?

When compared with other welding methods, such as TIG welding, manual welding of stainless steel MMA, the semi-automatic method of welding stainless steel (MIG) (with gas) has the following advantages:

• High performance;
• A small amount of smoke.

The disadvantages of this method include:

• The need to purchase a gas cylinder;
• Limited outdoor use.

The gasless MIG method using cored wire has its pros and cons. So the advantages of this method include

• Lack of gas cylinders;
• Ideal for outdoor welding processes.

And among the shortcomings there are:

• The need to remove waste;
• Costs for cored wire.

Conclusion : High performance outweighs the inconvenience of having to use a gas cylinder, which is why the gas method is the most popular, especially indoors.

Welding materials and equipment for semi-automatic stainless steel welding

In order to weld stainless steel semi-automatically you will need:

Although it is possible, as mentioned above, to cook without gas, then it will be necessary to purchase self-protecting flux-cored wire.

Many people are interested in what kind of wire to weld stainless steel with. The electrode wire is selected depending on the thickness of the parts being welded (Table 1). Thin wire ensures stable arc burning to achieve greater penetration depth. Thick wire requires significant amounts of welding current, on average 100 A for each additional mm of diameter.

Sheet thickness, mm	Wire diameter, mm	Current strength, A
1	0,8	65
1,5	0,8	115
2	0,8	130
3	1	215
3	1	210
4	1	220
4	1,2	280
5	1,2	300
5	1,2	190
6	1,2	300
6	1	115
8	1,2	300
8	1	130
10	1,2	300

What types of metals (steel) can be welded with stainless steel

The MIG-MAG method is used when it is necessary to weld low- and high-alloy (stainless) steels, as well as aluminum and its alloys. A fairly new use of the method is semi-automatic soldering MIG-Brazing in a protective gas environment. Moreover, various combinations of welded materials are possible: copper-copper, steel-steel, copper-steel, etc.

Features of the welding process and recommendations

There are several features of the MIG welding process that must be taken into account in order to achieve the best result. Here are recommendations from experienced welders:

1. The gas mixture for welding should include: 30% argon and 70% special welding carbon dioxide (food grade can be used).
2. The protrusion of the electrode wire should be within 6-12 mm. When welding, the distance from the nozzle should be 5-15 mm. The working flow rate of the gas welding mixture will be 6-12 m³/min at a pressure of 0.05-0.2 atm. If the amount of gas is reduced, the weld will be of poor quality.
3. When operating, reverse polarity is used. Straight polarity is only possible with submerged arc welding.
4. The welding angle must be maintained in such a way that it looks backward, that is, the welder moves from left to right. The slope should be approximately 5-10 degrees. This gives a good penetration depth, the seam is smoother and of higher quality. When the angle is tilted forward, a wide seam is obtained, and the penetration depth decreases. This option is more suitable for thin sheets of metal.

Conclusion : Attention to the details of the welding process directly affects its result, in other words, the quality of the weld.

Semi-automatic processing of stainless steel after welding

In the process of welding stainless steel by any method, including the MIG/MAG method, a porous layer of oxide appears, and the chromium contained in the steel weakens the metal, increasing its ability to rust. Therefore, it is necessary to carefully process the product after welding.

What models of semi-automatic machines are best suited for welding stainless steel?

Today, the welding equipment market offers a wide range of semi-automatic units of Russian and foreign production,

Depending on the required voltage, you can choose:

• Models of semi-automatic welding machines (MIG/MAG) for 220V mains voltage:

Inexpensive models - Svarog EASY MIG 160 (N219), FEB NORMA-205MP, These are fairly compact welders that, despite their affordable cost, can be used for MIG welding with or without gas.

Premium models - EWM Picomig 180 Puls, KEMPPI MinarcMIG EVO 170, KEMPPI MinarcMIG EVO 200, Lincoln Electric Speedtec 200C. These are devices of the latest generation of welding equipment, created for professional welding, providing solutions to a wide range of problems. Inverters remain functional even with falls and shocks.

• Models of semi-automatic welding machines (MIG/MAG) for 380V mains voltage:

Among the budget options are BRIMA MIG 250, TRITON MIG 300, characterized by high performance characteristics despite their compact size.

And premium models for professional welding, characterized by versatility and high quality from reputable European manufacturers EWM Phoenix 351 Puls, KEMPPI FastMig Pulse 450.

Conclusion : The choice of a specific model of welder depends on the task being pursued, working conditions and the material capabilities of the welder. In Tiberis you can easily select the unit that suits you in all respects. Here you can get professional advice from experienced specialists on all issues related to the MIG welding method.

Source: https://www.tiberis.ru/stati/svarka-nerzhavejki-poluavtomatom-mig-mag