How many welding processes are there? What are the common ones? How are they defined? And what are their English abbreviations and full names?

Commonly used are electric welding, gas welding, laser welding, brazing, hot melt welding, electron beam welding, explosion welding and so on.

Introduction of 17 welding method

1. Manual arc surfacing

Manual arc welding is the earliest developed welding method among all kinds of arc welding methods and is still widely used today. It uses covered electrode coated with paint as covered electrode and filler metal, and the arc burns between the end of covered electrode and the surface of the workpiece to be welded. On the one hand, the coating can produce gas shielded arc under the action of arc heat, on the other hand, it can produce slag to cover the surface of molten pool and prevent the interaction between molten metal and surrounding gas. The more important function of slag is to produce physical and chemical reaction with molten metal or add alloying elements to improve the properties of weld metal.

Manual arc welding equipment is simple, portable and flexible. It can be used for short weld welding in maintenance and assembly, especially for hard-to-reach parts. Manual arc welding and corresponding covering electrodes can be applied to most industrial carbon steel, stainless steel, cast iron, copper, aluminum, nickel and their alloys.

2. Tungsten gas shielded arc welding

This is a kind of gas shielded arc welding without melting electrode, which uses the arc between tungsten electrode and workpiece to melt the metal and form a weld. Tungsten electrode does not melt during welding, but only acts as an electrode. At the same time, argon or helium is sent to the nozzle of the welding torch for protection. Additional metals can be added as needed. It is called TIG welding internationally.

Tungsten gas shielded welding (GTAW) can control the heat input well, and it is an excellent method to connect metal plate and backing weld. This method can be used to connect almost all metals, especially to weld refractory oxides such as aluminum and magnesium and active metals such as titanium and zirconium. This welding method has high weld quality, but compared with other arc welding, its welding speed is slow.

3. Metal electrode gas shielded arc welding

This welding method uses the burning arc between the continuously fed welding wire and the workpiece as the heat source, and the gas sprayed from the nozzle of the welding gun protects the arc for welding.

The shielding gas commonly used in MIG arc welding is argon, helium, CO2 or their mixture. When argon or helium is used as shielding gas, it is called MIG welding (MIG welding for short internationally); When the mixture of inert gas and oxidizing gas (O2, CO2) is used as shielding gas, or when CO2 gas or CO2+O2 mixture is used as shielding gas, or when CO2 gas or CO2+O2 mixture is used as shielding gas, it is collectively called MIG welding (internationally known 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 fast welding speed and high deposition rate. MIGMAW can be used for most major metals, including carbon steel and alloy steel. Metal inert gases are suitable for stainless steel, aluminum, magnesium, copper, titanium, zirconium and nickel alloys. This welding method can also be used for arc spot welding.

4. Plasma arc welding

Plasma arc welding is also a kind of non-melting arc welding. It uses the compressed arc (called transfer arc) between the electrode and the workpiece to realize welding. The electrode used is usually a tungsten electrode. The plasma gas used to generate the plasma arc can be argon, nitrogen, helium or their mixture. At the same time, through the nozzle with inert gas protection. When welding, filler metal can be added or not.

In plasma arc welding, the arc is straight, the energy density is high and the arc penetration ability is strong. The keyhole effect produced in plasma arc welding can be used for the butt joint of most metals in a certain thickness range, and can ensure the penetration depth and weld uniformity. Therefore, plasma arc welding has high productivity and good welding quality. However, plasma arc welding equipment (including nozzle) is more complicated and requires higher control of welding process parameters.

Most metals that can be welded by gas tungsten arc welding can be welded by plasma arc welding. In contrast, plasma arc welding can be carried out more easily for the welding of extremely thin metals below1mm.

5. Tubular wire arc welding

Tubular wire arc welding is also welded by using the combustion arc between the continuously fed welding wire and the workpiece as the heat source, which can be considered as a type of gas shielded metal welding. The welding wire used is tubular welding wire, and the tube is filled with flux of various components. When welding, protective gas, mainly CO2, is added. Flux is decomposed or melted by heat, which plays a role in slagging, protecting molten pool, alloying and stabilizing arc.

In addition to the above advantages, tubular wire arc welding has more metallurgical advantages due to the role of flux in the tube. Tubular wire arc welding can be used to weld most ferrous metal joints. Tubular wire arc welding has been widely used in some industrialized countries.

"Tubular welding wire" is now called "flux-cored welding wire"-attention to the poster.

6. Resistance welding

This is a 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. Because electroslag welding has more unique characteristics, it will be introduced later. This paper mainly introduces several kinds of resistance welding with solid resistance heat as energy source, including spot welding, seam welding, projection welding and butt welding.

Resistance welding is generally a welding method that uses the resistance heat generated when the current passes through the workpiece to make the workpiece under a certain electrode pressure and melt the contact surface between the two workpieces to realize the connection. Large current is usually used. In order to prevent electric arc on the contact surface and forge welding metal, pressure is always applied during welding.

When this kind of resistance welding is carried out, the good surface of the workpiece to be welded is very important to obtain stable welding quality. Therefore, before welding, it is necessary to clean the contact surfaces between the electrode and the workpiece and between the workpieces.

The disadvantages of spot welding, seam welding and projection welding are that the welding current (single phase) is large (thousands to tens of thousands of amperes), the power-on time is short (several cycles to several seconds), the equipment is expensive and complicated, and the productivity is high, which is suitable for mass production. It is mainly used for welding thin plate members with thickness less than 3 mm, and can weld various non-ferrous metals such as steel, aluminum, magnesium and their alloys, stainless steel, etc.

7. Electron beam welding

Electron beam welding is a method of welding by using the heat energy generated when concentrated high-speed electron beams bombard the workpiece surface.

In the process of electron beam welding, the electron beam is generated and accelerated by the electron gun. 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. Welding preparation time (mainly vacuumizing time) is long, and the size of workpiece is limited by the size of 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 not only for precision welding of very thin materials, but also for welding of very thick parts (up to 300 mm thick). All metals and alloys that can be welded by other welding methods can be welded by electron beam. Mainly used for welding products with high quality requirements. It can also solve the welding of dissimilar metals, oxidizable metals and refractory metals. But it is not suitable for mass production.

8. Laser welding

Laser welding is welding with a laser beam focused by a high-power coherent monochromatic optical sub-stream as a heat source. This welding method usually includes 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 vacuum, but the disadvantage is that the penetration is not as strong as that of electron beam welding. Accurate energy control can be carried out during laser welding, so as to realize the welding of precision micro-devices. It can be applied to a variety of metals, especially to solve the welding of some difficult-to-weld metals and dissimilar metals.

9. Brazing

The energy of brazing can be chemical reaction heat or indirect heat energy. It uses metal whose melting point is lower than that of the material to be welded as brazing filler metal, which is melted by heating, and enters the gap of the contact surface of the joint through capillary action to wet the surface of the welded metal, so that the liquid phase and the solid phase diffuse with each other to form a brazed joint. Therefore, brazing is a solid and liquid welding method.

The brazing heating temperature is low, the base material does not melt, and no pressure is needed. However, some measures must be taken to remove oil, dust and oxide film on the surface of the workpiece before welding. This is an important guarantee to make the workpiece wet well and ensure the quality of the joint.

When the liquidus humidity of solder is higher than 450℃ and lower than the melting point of base metal, it is called brazing; When the temperature is lower than 450℃, it is called brazing.

Brazing can be divided into flame brazing, induction brazing, furnace brazing, immersion brazing and resistance brazing according to different heat sources or heating methods.

Because of the low heating temperature during brazing, it has little influence on the properties of workpiece materials, and the stress and deformation of weldments are also small. However, the strength and heat resistance of brazed joints are generally low.

Brazing can be used to weld carbon steel, stainless steel, superalloys, aluminum, copper and other metallic materials, as well as to connect dissimilar metals, metals and nonmetals. It is suitable for welding joints with small load or normal temperature operation, especially for precision, miniature and complex multi-brazed joints.

10. Electroslag welding

Electroslag welding is a welding method which uses the resistance heat of slag as energy source. The welding process is carried out in the vertical welding position and the assembly gap formed by the end faces of two workpieces and the water-cooled copper sliders on both sides. When welding, the end of the workpiece is melted by the resistance heat generated by the current passing through the slag.

According to the electrode shape used in welding, electroslag welding can be divided into wire electrode electroslag welding, plate electrode electroslag welding and nozzle electroslag welding.

The advantages of electroslag welding are: the thickness of weldable parts is large (from 30mm to 1000mm or more) and the productivity is high. It is mainly used to weld butt joints and T-joints in profiles.

Electroslag welding can be used to weld various steel structures and castings. Electroslag welding joints are usually normalized after welding because of their slow heating and cooling speed, wide heat affected zone, coarse structure and poor toughness.

1 1. High frequency welding

High frequency welding uses solid resistance heat as energy source. During welding, the resistance heat generated by high-frequency current in the workpiece is used to heat the surface layer of the welding zone of the workpiece to a molten or nearly plastic state, and then upsetting force is applied (or not applied) to realize metal bonding. Therefore, it is a solid resistance welding method.

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

High-frequency welding is a very professional welding method, and special equipment should be equipped according to the product. The productivity is high, and the welding speed can reach 30m/min. It is mainly used for welding longitudinal seam or spiral seam when manufacturing pipeline.

12. Gas welding

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

Gas welding can be used to weld many ferrous metals, nonferrous metals and alloys. Generally suitable for maintenance and single-chip welding.

13. Pneumatic welding

Gas welding, like gas welding, also uses gas flame as heat source. When welding, the ends of two butted workpieces are heated to a certain temperature, and then sufficient pressure is applied to obtain a firm joint. This is a solid state welding.

Air pressure welding is often used for rail welding and steel bar welding without filler metal.

14. explosive welding

Explosive welding is another solid-state welding method with chemical reaction heat as energy source. But it uses the energy generated by explosive explosion to realize metal connection. Under the action of shock wave, two metals can accelerate the formation of metal combination in less than one second.

Among all kinds of welding methods, explosive welding can weld the widest range of dissimilar metals. Explosive welding can be used to weld two metallurgically incompatible metals into various transition joints. Explosive welding is mainly used to coat flat plates with considerable surface area, and it is an effective method to manufacture composite plates.

15 friction welding

Friction welding is a kind of solid welding with mechanical energy as energy source. It uses the heat generated by mechanical friction between two surfaces to realize metal connection.

The heat of friction welding is concentrated on 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 at the end of heating, so that the hot metal can be combined by upsetting, and generally the joint surface will not melt.

Friction welding has high productivity. In principle, almost all metals that can be hot forged can be friction welded. Friction welding can also be used to weld different metals. It should be suitable for workpieces with circular cross-section, and the maximum diameter is100 mm.

16. Ultrasonic welding

Ultrasonic welding is also a solid-state welding method with mechanical energy as energy source. During ultrasonic welding, the high-frequency vibration of the sonotrode can cause strong crack friction on the joint surface, which is heated to the welding temperature and forms a joint under low static pressure.

Ultrasonic welding can be used for welding between most metal materials, and can realize welding between metals, between dissimilar metals and between metals and nonmetals. It is suitable for the repeated production of metal wire, foil or thin metal joint below 2 ~ 3 mm

17. Diffusion welding

Diffusion welding is generally a solid-state welding method with indirect heat energy as energy source. Usually in a vacuum or protective atmosphere. When welding, the surfaces of the two welded parts are in contact at high temperature and high pressure and kept warm for a certain time, so as to reach the distance between atoms and combine through the childish mutual diffusion of atoms. Before welding, not only impurities such as oxides on the workpiece surface should be removed, but also the surface roughness should be lower than a certain value to ensure the welding quality.

Diffusion welding has little harmful effect on the properties of welding materials. It can weld many same and different metals and some nonmetallic materials, such as ceramics.

Diffusion welding can weld workpieces with complex structure and large thickness difference.