What to cook stainless steel? Welding technology, equipment

What to cook stainless steel - a very relevant issue for modern industry. It is worth noting that this type of steel is a fairly strong material, so its processing has certain nuances. The choice of welding method depends on the thickness of the workpieces, and on the chemical composition.

Stainless steel. Main characteristics

Stainless steel is an alloy of carbon and iron, alloyed with chromium. The high content of the last element ensures high resistance of the material in a corrosive environment. Chromium oxides form a special protective film, due to which the base metal maintains its durability. In addition, steel is alloyed with nickel, cobalt, and titanium. The main advantages of stainless steel are high resistance to contact with an aggressive environment, high strength, respectively, and a long period of operation. In addition, steel has a good aesthetic appearance.

Features of welding steel, resistant to corrosion

This material has a large linear expansion. As a consequence, with the thermal effect of the workpiece can deform, change its size. To avoid such a situation, it is necessary to clearly adhere to the optimal gap between the parts that connect. The action of high temperature can lead to the fact that the alloyed steel somewhat loses its properties, the resistance to corrosion decreases. In this case, the weld should be cooled in time. Low thermal conductivity of steel requires a reduction in current strength of about 25%. It is also worthwhile to select the welding electrodes correctly, since they can overheat if they are long. Another difficulty is the appearance of refractory carbides on the surface, intergranular corrosion.

Ways of cooking stainless steel

There are many methods of welding corrosion-resistant steel. With a small thickness of metal (1.5 mm), it is advisable to use arc welding (in an inert gas environment). What to cook stainless steel with a thickness of less than 0.8 mm? In this case, a pulsed arc method is used. Thin metals are also connected by an arc with a jet transfer of material. Increasingly, the plasma method of welding is used. It can be used for a wide range of thickness of blanks. Cross sections of more than 10 mm are cooked under a ball of flux. Still use welding with high-frequency currents, laser method.

Argon material welding

This process occurs in the protective gas environment - argon. It protects the material from the effects of oxygen. In the special device an arc is formed between the part and the tungsten electrode. In the process of heating, the edges melt, a protected welding bath arises. A special wire for welding stainless steel is also continuously fed into the arc. The joining process itself is made at an angle of 90 °. For the best quality work, it is necessary to exclude any oscillating motion of the electrode. As a result, a seam free from slags is obtained. Such a connection is of high quality, durability, satisfies all aesthetic demands. Welding of stainless steel gas is used in many sectors: chemical, food industry, automotive, aviation, and power engineering. Among the shortcomings can be identified only a large expenditure of time on the process itself. Also, technology requires special skills and experience from employees.

Equipment for argon-arc welding

First of all, an inverter is needed for this type of metal connection. Its modifications and models are pretty much: "Svarog", KEMPPI Master, BRIMA, etc. The main advantages of the device are ease of operation, small size and weight, stable arc. Inverters can be used for welding almost any metal, with the connections being of high quality. How to cook stainless steel inverter and what should I consider? First of all, it is necessary to choose the correct operating temperature range. Some models do not work in the open space during cold weather. Also worth considering the power of the device. For household use, an inverter with current up to 160 A (for example, "Svarog TIG 200 P", PRO TIG 200 P) is suitable. The parts are cleaned before cleaning, degreased. For welding, a gas cylinder with argon is required. Although in practice it is allowed to use dilute gas. A gas burner is attached to the gas hose , into which a tungsten electrode is inserted. On the burner handle there are buttons for supplying current and gas. You also need a welding wire from the same material as the parts to be connected.

How Semiautomatic Welding Works

Than to cook a stainless steel at repair of the car, in a life? In this case, often use the method of welding semi-automatic. It can occur both in a protective environment and without the use of gas. Semiautomatic machines are also used in large automobile enterprises, which indicates the high quality of the welded joint. The electrode and the filler material in this case is a special wire. You can work with equipment in several ways: short arc, jet transfer, pulse welding of stainless steel. The technology provides operation without protective gas, however in this case it is necessary to choose special powder electrodes. This method is suitable for work in the air. There is no need to buy (and, accordingly, spend additional funds) a gas cylinder. This has its drawback - over time, the welded joint can become rusted. Therefore, experts recommend using special electrodes on stainless steel and welding using argon. To date, there are many varieties of semiautomatic devices, both domestic ("FEB", "Svarog"), and foreign (BRIMA, EWM, TRITON, etc.). The choice of apparatus depends on the tasks assigned, the amount of welding and the characteristics of the materials to be connected.

Use of electrode welding

How to cook stainless steel, if special requirements to the quality of the seam is not provided? As a rule, electrode welding is used in domestic conditions, when connecting all kinds of pipes, in small-scale production, and also for obtaining a short weld. The essence of this process is the formation of a connection from the material of the workpiece and the metal of the electrode. The advantages of the technique include simplicity of execution, the ability to combine different metals (both thin and rather large cross sections). There is no need to use gas, which makes the process cheaper. Also welding with electrodes makes it possible to approach hard-to-reach parts of the part. There are certain disadvantages of this technology. First, the weld seam requires cleaning from the formed slags. Secondly, the welding speed is small.

How to choose welding electrodes

Electrodes for stainless steel are widely used for joining corrosion resistant alloys that operate at high temperatures. As a rule, the rods are made on the basis of nickel, chromium. With manual arc welding , two types of electrodes can be used. The first - work under conditions of direct current. The main coating most often consists of magnesium, calcium carbonate. Welding electrodes with rutile coating can work with alternating current. When welding using argon, various tungsten rods are used. Due to their high operating temperature, they do not melt. There are many of their varieties. Green electrodes (WP) consist of pure tungsten. They provide a sufficiently high stability of the arc. White - WZ-8 - doped with zirconium oxide. Thorium oxide is added to the red electrodes. This is the most common group, the rods have a high resistance. Also, tungsten electrodes can include lanthanum, cerium.

Welded joint processing

After the end of the process of joining the parts it is necessary to clean the seam. This should be done in order to improve the appearance, extend the life. Otherwise, corrosion may occur in this area. First of all, mechanical cleaning of the welded joint is carried out. More aesthetically, the joints look after sandblasting. The next step involves grinding the surface. It is not recommended to use abrasives based on corundum, as it can provoke the appearance of corrosion. It should be noted that all these manipulations are aimed at improving the appearance of the part. Protect the weld seam from damage by etching, passivation. Etching is the surface treatment with special chemicals that destroy the scales formed. When passivated, a special substance is applied to the joint site. Under its influence, a protective film (of chromium oxide) appears.

Laser method of welding alloys

One of the most modern and technological methods of connection is laser welding of stainless steel. The essence of this method is the use of a laser beam as a source of heating. This welding is characterized by high speed, high concentration of energy at the junction. The thermal effect on the zone, which is in the immediate vicinity of the seam, is insignificant. Therefore, the risk of formation of hot or cold cracks is minimal. The seam obtained as a result is distinguished by its strength, porosity is absent. It is also possible to deliver the alloying elements, shielding gas, to the connection site. Since there are no welding electrodes, foreign compounds do not enter the seam. Laser welding can be used even for jewelry, as all the seams are thin, neat and durable. The only drawback is that the equipment is quite expensive, so the mass use of such installations is not yet possible.