1. Hand arc welding

Hand arc welding is the earliest developed and most widely used welding method in various arc welding methods. It is coated with the outside of the electrode electrode and filler metal, the arc is burning between the end of the electrode and the surface of the welded workpiece.

Under the action of arc heat, the coating can generate gas to protect the arc on the one hand, and on the other hand, it can generate slag to cover the surface of the molten pool to prevent the interaction between the molten metal and the surrounding gas. The more important role of slag is to produce physical and chemical reactions with molten metal or to add alloying elements to improve the properties of weld metal.

Hand arc welding equipment is simple, light, flexible operation. It can be applied to the welding of short seams in maintenance and assembly, especially for welding of difficult to reach parts. Hand arc welding with the corresponding electrode can be applied to most industrial carbon steel, stainless steel, cast iron, copper, aluminum, nickel and its alloys.

2. Gas tungsten arc welding

This is a non-melting gas shielded arc welding, which uses the arc between the tungsten electrode and the workpiece to melt the metal to form a weld. The tungsten pole does not melt during the welding process and only acts as an electrode. At the same time by the torch nozzle into argon or helium for protection. A metal may be additionally added as needed.

(Internationally known as TIG welding).

Gas tungsten arc welding is an excellent method for joining sheet metal and backing due to its good control of heat input. This method can be used to join almost all metals, especially for welding aluminum, magnesium, which can form refractory oxides, and active metals such as titanium and zirconium. The weld quality of this welding method is high, but compared with other arc welding, the welding speed is slow.

3. MIG shielded arc welding

This welding method is the use of continuous feeding of the welding wire and the workpiece burning between the arc as a heat source, by the torch nozzle of the gas protection arc to welding.

The shielding gases commonly used in gas shielded arc welding are argon, helium, CO2 or a mixture of these gases. When argon or helium is used as shielding gas, it is called metal inert gas shielded arc welding.

(known internationally as MIG welding).

When inert gas and oxidizing gas (O2,CO2) mixed gas is used as protective gas, or when CO2 gas or CO2 + O2 mixed gas is used as protective gas, or when CO2 gas or CO2 + O2 mixed gas is used as protective gas, it is collectively referred to as melting electrode active gas shielded arc welding.

(known internationally as MAG welding).

The main advantage of MIG arc welding is that it can be easily welded in various positions, and it also has the advantages of faster welding speed and high deposition rate.

Melt electrode active gas shielded arc welding can be applied to most major metals, including carbon steel, alloy steel. MIG welding is suitable for stainless steel, aluminum, magnesium, copper, titanium, zirconium and nickel alloys. Arc spot welding is also possible with this welding method.

4. Plasma arc welding

Plasma arc welding is also a non-melting arc welding. It is the use of electrode and workpiece between the compression arc (called forward transfer arc) to achieve welding. The electrode used is usually a tungsten electrode. The plasma gas used to generate the plasma arc may be argon, nitrogen, helium, or a mixture of the two. At the same time, it is also protected by an inert gas through a nozzle. Filler metal can be added during welding, or no filler metal can be added.

Plasma arc welding welding, because of its straight arc, energy density, and thus the arc penetration ability. The keyhole effect produced during plasma arc welding can be carried out without beveling for most metals within a certain thickness range, and can ensure uniform penetration and weld.

Therefore, plasma arc welding has high productivity and good weld quality. However, plasma arc welding equipment (including nozzles) is more complex, the control of welding process parameters is higher.

Most of the metals that can be welded by gas tungsten arc welding can be plasma arc welding. In contrast, welding of extremely thin metals of 1mm or less can be easily performed by plasma arc welding.

5. Tubular welding wire arc welding

Tubular welding wire arc welding is also the use of continuous feeding of the welding wire and the workpiece burning between the arc as a heat source for welding, can be considered as a type of MIG welding. The welding wire used is a tubular welding wire, the tube containing various components of the flux.

During welding, a protective gas, mainly CO2, is applied. The flux is decomposed or melted by heat, which plays the role of slag forming to protect the solution pool, alloy infiltration and arc stabilization.

Tubular welding wire arc welding in addition to the above-mentioned advantages of gas shielded arc welding, due to the role of the flux in the tube, so that it has more advantages in metallurgy. Tubular wire arc welding can be applied to the welding of various joints of most ferrous metals. Tubular wire arc welding has been widely used in some advanced industrial countries.

"Tubular welding wire" is now referred to as "flux-cored welding wire".

6. Resistance welding

This is a kind of welding method with resistance heat as energy source, including electroslag welding with slag resistance heat as energy source and resistance welding with solid resistance heat as energy source. Since electroslag welding has more unique characteristics, it is introduced later. Here mainly introduces several kinds of solid resistance heat for energy resistance welding, mainly spot welding, seam welding, projection welding and butt welding.

Resistance welding is generally a welding method that makes the workpiece under a certain electrode pressure and uses the resistance heat generated when the current passes through the workpiece to melt the contact surface between the two workpieces and realize the connection. Larger currents are usually used.

In order to prevent arcing on the contact surfaces and in order to forge the weld metal, pressure is always applied during the welding process. When performing this type of resistance welding, the surface of the workpiece being welded is of paramount importance for obtaining a stable welding quality. Therefore, the contact surface between the electrode and the workpiece and the workpiece must be cleaned before welding.

The contradiction of spot welding, seam welding and projection welding is that the welding current (single phase) is large (thousands to tens of thousands of amperes), the power-on time is short (a few weeks to a few seconds), the equipment is expensive, complex, and the productivity is high, so it is suitable for mass production. It is mainly used for welding thin plate components with thickness less than 3mm. All kinds of steel, aluminum, magnesium and other non-ferrous metals and their alloys, stainless steel can be welded.

7. Electron beam welding

Electron beam welding is a method of welding with the heat energy generated when the concentrated high-speed electron beam bombards the surface of the workpiece.

In electron beam welding, an electron beam is generated by an electron gun and accelerated. Commonly used electron beam welding are: high vacuum electron beam welding, low vacuum electron beam welding and non-vacuum electron beam welding. The first two methods are carried out in a vacuum chamber. The welding preparation time (mainly the vacuum time) is longer, and the workpiece size is limited by the size of the vacuum chamber.

Compared with arc welding, the main characteristics of electron beam welding are large weld penetration, small weld width and high weld metal purity. It can be used for precision welding of very thin materials and for welding of very thick (up to 300mm thick) components.

All metals and alloys that can be fusion welded by other welding methods can be welded by electron beam welding. It is mainly used for welding of products requiring high quality. It can also solve the welding of dissimilar metals, easily oxidized metals and refractory metals. But not suitable for high-volume products.

8. Laser welding

Laser welding is the use of high-power coherent monochromatic photon flow focused by the laser beam as a heat source for welding. This welding method usually has continuous power laser welding and pulsed power laser welding.

The advantage of laser welding is that it does not need to be carried out in a vacuum, but the disadvantage is that the penetration is not as strong as the electron beam welding. Laser welding can be precise energy control, which can achieve precision micro-device welding. It can be applied to many metals, especially to solve some difficult to weld metal and dissimilar metal welding.

9. Brazing

The energy source for brazing can be chemical reaction heat or indirect heat energy. It uses a metal with a melting point lower than that of the material to be welded as a brazing filler metal. After heating, the brazing filler metal is melted. * Capillary action brings the brazing filler metal into the gap of the contact surface of the joint, wetting the surface of the metal to be welded, and mutual diffusion between the liquid phase and the solid phase to form a brazing joint. Therefore, brazing is a solid phase and liquid phase welding method.

The brazing heating temperature is low, the base metal does not melt, and there is no need to apply pressure. However, before welding, certain measures must be taken to remove the oil, dust and oxide film on the surface of the welded workpiece. This is an important guarantee for the good wettability of the workpiece and the quality of the joint.

When the liquidus humidity of the solder is higher than 450 ℃ and lower than the melting point of the base metal, it is called brazing; when it is lower than 450 ℃, it is called soldering. According to the heat source or heating method, brazing can be divided into: flame brazing, induction brazing, furnace brazing, dip brazing, resistance brazing and so on.

Due to the low heating temperature during brazing, the performance of the workpiece material is less affected, and the stress deformation of the weldment is also small. However, the strength of the brazed joint is generally low and the heat resistance is poor.

Brazing can be used for welding carbon steel, stainless steel, high temperature alloy, aluminum, copper and other metal materials, but also can connect dissimilar metal, metal and non-metal. Suitable for welding joints with little load or working at room temperature, especially for precision, miniature and complex multi-brazed weldments.

10. Electroslag welding

Electroslag welding is a welding method using the resistance heat of slag as energy source. The welding process is carried out in the vertical welding position in the assembly gap formed by the end faces of the two workpieces and the water-cooled copper sliders on both sides. During welding, the end of the workpiece is melted by the resistance heat generated by the current through the slag. According to the shape of the electrode used in welding, electroslag welding is divided into wire electroslag welding, plate electroslag welding and melting tip electroslag welding.

The advantages of electroslag welding are:

Weldable workpiece thickness is large (from 30mm to more than 1000mm), high productivity.

It is mainly used for welding of butt joints and T-joints in section.

Electroslag welding can be used for the welding of various steel structures, and can also be used for the welding of castings. Due to the slow heating and cooling of electroslag welding joints, the heat affected zone is wide, the microstructure is coarse and tough, so it is generally necessary to normalize after welding.

11. High frequency welding

High frequency welding is based on solid resistance heat as energy. During welding, the resistance heat generated by high-frequency current in the workpiece heats the surface of the welding zone of the workpiece to a molten or nearly plastic state, and then applies (or does not apply) a forging force to achieve metal bonding. Therefore, it is a solid-phase resistance welding method.

High frequency welding can be divided into contact high frequency welding and induction high frequency welding according to the way high frequency current generates heat in the workpiece. In contact high-frequency welding, high-frequency current is transmitted to the workpiece through mechanical contact with the workpiece. In induction high-frequency welding, high-frequency current generates an induced current in the workpiece through the coupling effect of the external induction coil of the workpiece.

High frequency welding is a specialized welding method, which should be equipped with special equipment according to the product. High productivity, welding speed up to 30 m/min. Mainly used in the manufacture of pipe longitudinal seam or spiral seam welding.

12. Gas welding

Gas welding is a welding method using gas flame as heat source. The most widely used is oxygen-acetylene flame with acetylene gas as fuel. Because the equipment is simple and convenient to use, but the heating speed and productivity of gas welding are low, the heat affected zone is large, and it is easy to cause large deformation.

Gas welding can be used for the welding of many ferrous metals, non-ferrous metals and alloys. Generally applicable to maintenance and single sheet welding.

13. Gas pressure welding

Gas pressure welding and gas welding, gas pressure welding is also a gas flame as a heat source. During welding, the ends of the two abutting workpieces are heated to a certain temperature, and then sufficient pressure is applied to obtain a firm joint. Is a solid phase welding. Gas pressure welding without filler metal, commonly used in rail welding and steel welding.

14. Explosive welding

Explosive welding is also another solid-phase welding method using chemical reaction heat as energy source. But it uses the energy generated by the explosion of explosives to achieve metal connections. Under the action of the explosive wave, two pieces of metal can be accelerated to form a metal combination in less than a second.

Among the various welding methods, explosive welding can weld the widest range of combinations of dissimilar metals. Two metallurgically incompatible metals can be welded into various transition joints by explosive welding. Explosive welding is mostly used for plate cladding with considerable surface area and is an efficient method for manufacturing composite plates.

15. Friction welding

Friction welding is a solid-phase welding that uses mechanical energy as an energy source. It uses the heat generated by the mechanical friction between the two surfaces to achieve the metal connection. The heat of friction welding is concentrated at the joint surface, so the heat affected zone is narrow. Pressure must be applied between the two surfaces. In most cases, the pressure is increased when the heating is terminated, so that the hot metal is combined by upsetting, and the joint surface is generally not melted.

Friction welding productivity is high, in principle, almost all hot forging metal can be friction welding. Friction welding can also be used for welding dissimilar metals. To be applied to the cross section of the circular maximum diameter of 100mm workpiece.

16. Ultrasonic welding

Ultrasonic welding is also a solid-phase welding method that uses mechanical energy as an energy source. When ultrasonic welding is carried out, the welding workpiece is under low static pressure, and the high-frequency vibration emitted by the sound pole can make the joint surface produce strong crack friction and heat to the welding temperature to form a bond.

Ultrasonic welding can be used for welding between most metal materials, and can realize the welding between metal, dissimilar metal and metal and non metal. It can be applied to the repeated production of metal wire, foil or sheet metal joints below 2 -- 3mm.

17. Diffusion welding

Diffusion welding is generally a solid-phase welding method using indirect heat energy as energy. It is usually carried out under vacuum or a protective atmosphere. During welding, the surfaces of the two welded workpieces are contacted and held for a certain period of time under high temperature and high pressure to reach the distance between atoms, which are combined by simple diffusion of atoms. Before welding, it is not only necessary to clean the impurities such as oxides on the surface of the workpiece, but also the surface roughness should be lower than a certain value to ensure the welding quality.

Diffusion welding has almost no harmful effect on the properties of the material to be welded. It can weld many homogeneous and heterogeneous metals and some non-metallic materials, such as ceramics. Diffusion welding can weld complex structures and workpieces with very different thicknesses.