Arc welding technology is divided into six welding methods: manual arc welding, submerged arc welding, gas tungsten arc welding, gas metal arc welding, plasma arc welding and tubular wire arc welding. The following is the introduction of these six different welding methods:
1.Manual Arc Welding/Full Automatic Welding
Manual arc welding is one of the earliest and still widely used welding methods among various arc welding methods. It uses the coated electrode as the electrode and filler metal, and the arc burns between the end of the electrode and the surface of the workpiece to be welded.
Under the action of arc heat, on the one hand, the coating can produce gas to protect the arc, on the other hand, it can produce 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 reaction with molten metal or add alloying elements to improve the energy of weld metal.
Manual arc welding equipment is simple, light and flexible. It can be applied to the welding of short joints in maintenance and assembly, especially for the welding of parts that are difficult to reach. Manual arc welding with corresponding electrodes can be applied to most industrial carbon steel, stainless steel, cast iron, copper, aluminum, nickel and their alloys.
This is a non-melting electrode gas shielded arc welding, which uses the arc between tungsten electrode and workpiece to melt the metal and form weld. In the welding process, the tungsten electrode does not melt and only acts as an electrode. At the same time, argon or helium is sent into the nozzle of the welding torch for protection.
Additional metals can also be added as needed. It is commonly known as TIG welding in the world. Gas tungsten arc welding is an excellent method for connecting sheet metal and backing welding because it can well control heat input.
This method can be used to connect almost all metals, especially for welding metals such as aluminum and magnesium, which can form refractory oxides, and active metals such as titanium and zirconium. This welding method has high weld quality, but its welding speed is slower than other arc welding.
4.Gas metal arc welding / CO2 carbon arc welding
Gas metal arc welding is a fusion welding method using the arc as the heat source. The arc is established between the continuously fed welding wire and the molten pool. The molten pool formed by the mixing of the molten welding wire metal and the base metal crystallizes to form the weld after the arc heat source is removed, and the separated base metal is connected by metallurgy.
Oxidation of alloy elements during CO2 welding, under the action of arc high temperature, CO2 will decompose into CO, O2 and O. under welding conditions, CO is insoluble in metal and does not participate in the reaction, while CO2 and o have strong oxidation, which oxidizes Fe and other alloy elements.
Deoxidation and alloying of weld metal. Usually, a certain amount of deoxidizer is added into the welding wire for deoxidation. In addition, the remaining deoxidizer is left in the weld as alloy elements to make up for the loss of oxidation and burning loss and ensure the chemical composition requirements of the weld.
At present, CO2 gas shielded welding is widely used in locomotive manufacturing, ship manufacturing, automobile manufacturing, coal mining machinery manufacturing and other fields. It is suitable for welding low carbon steel, low alloy steel and low alloy high strength steel, but it is not suitable for welding non-ferrous metals and stainless steel. Although some data show that CO2 gas shielded welding can be used for stainless steel welding, it is not the first choice for stainless steel welding.
Submerged arc welding is a melting electrode welding method with granular flux as the protective medium and the arc hidden under the flux layer. The welding process of submerged arc welding consists of three links:
Sufficient granular flux shall be evenly deposited at the joint to be welded of the weldment → the conductive nozzle and weldment shall be connected with the welding power supply for two stages respectively to generate the welding arc → the welding wire shall be automatically fed and the arc shall be moved for welding.
Submerged arc welding has the characteristics of unique arc performance, high electric field intensity of arc column and high production efficiency; The flux participates in the metallurgical reaction, Si and Mn are reduced, and part C is burned, limiting the removal of impurities s and P to h and preventing the generation of hydrogen pores.
Due to the large penetration, high productivity and high degree of mechanical operation, submerged arc welding is suitable for welding long welds of medium and thick plate structure. It is widely used in shipbuilding, boilers and pressure vessels, bridges, overweight machinery, nuclear power plant structure, marine structure, weapons and other manufacturing departments. It is one of the most commonly used welding methods in today's welding production.
In addition to the connection of components in metal structure, submerged arc welding can also weld wear-resistant or corrosion-resistant alloy layer on the surface of base metal. With the development of welding metallurgy technology and welding material production technology, the materials that can be welded by submerged arc welding have developed from carbon structural steel to low-alloy structural steel, stainless steel, heat-resistant steel and some non-ferrous metals, such as nickel base alloy, titanium alloy, copper alloy and so on.
The water-cooled nozzle and other measures can reduce the cross-sectional area of the arc column area of the arc, and significantly improve the temperature, energy density and plasma flow rate of the arc. This kind of arc that compresses the arc column with external constraints is called plasma arc.
Plasma arc is a special form of arc. It is an arc with high energy density. It is still a gas conduction phenomenon. Plasma arc welding is a method that uses the heat of plasma arc to heat and melt the workpiece and base metal.
Plasma arc welding is widely used in industrial production, especially in the welding of copper and copper alloy, titanium and titanium alloy, alloy steel, stainless steel, molybdenum and other metals used in military and cutting-edge industrial technologies such as aerospace, such as missile shell of titanium alloy, some thin-walled containers on aircraft, etc.
6.Tubular wire arc welding
Tubular welding wire arc welding also uses the arc burning between the continuously fed welding wire and the workpiece as the heat source for welding, which can be considered as a type of GMAW. The welding wire used is tubular welding wire, which is filled with flux of various components.
When welding, add shielding gas, mainly CO2. The flux decomposes or melts when heated, which plays a role in slagging, protecting the solution pool, alloying and stabilizing the arc. In addition to the advantages of the above-mentioned GMAW, tubular wire arc welding has more advantages in metallurgy due to the action of flux in the pipe.
Tubular wire arc welding can be applied to the welding of most ferrous metal joints. Tubular wire arc welding has been widely used in some industrial advanced countries. "Tubular welding wire" is now called "flux cored welding wire".
What kind of process makes the electric cabinet to get a perfect stud weld?
The production mode of electrical cabinet using stud welding includes cabinet body type and flat plate type. If the cabinet type production is adopted, the cabinet is assembled and welded first, and then the stud welding is carried out. Plate type is the opposite. First weld the studs on the plate, and then assemble them. According to the production demand, manual welding and robot automatic welding are widely used in the electrical cabinet industry.
Stud welding is required for medium and high pressure gas filled cabinets involving the use of gas insulation, such as SF6 sulfur hexafluoride gas. Some manufacturers used energy storage welding before. Due to the shallow penetration depth of energy storage welding, there are high requirements for the accuracy of welding studs, the cleanliness of plate surface and the proficiency of operators. If any link is not well controlled, there is a risk of nail falling, which requires additional TIG repair welding. If the stud is found to fall off during transportation to the site for installation or use, the hidden danger is very large and the repair cost is quite high. In addition, the sound of energy storage welding M8 stud is relatively loud, which will affect the hearing of operators who do not wear ear muffs.
Pull arc welding has the advantages of low noise, less splash and large penetration. It is the preferred process method for stud welding of electrical cabinet. The conventional short cycle pull arc welding process can meet the requirements of most manufacturers. However, in order to ensure and obtain better welding effect, SRM patented technology (balanced magnetic field welding technology) of German Soyer can be adopted for studs with large diameter of M10 and above and multi angles of welding position. This process is based on the arc drawing process with a unique adjustable magnetic field. SRM process technology can effectively reduce heat input, welding deformation and welding back marks. Due to the high-speed rotation of the arc under the influence of the controllable magnetic field, the weld formation is uniform, reducing the chance of magnetic bias blowing and the situation of molten metal falling down during transverse welding.
How to choose the welding equipment to make the electric cabinet get a perfect stud weld?
The equipment can be selected only after the process is determined. Stud welding equipment in electrical cabinet industry is generally divided into manual welding and automatic welding. Manual welding is the choice of many small and medium-sized manufacturers, because the production quantity is small, the investment capital required is less, and it can weld different kinds of products more flexibly. Considering the advantages of continuous welding, saving labor cost and improving welding stability, most large manufacturers of electrical cabinets use automatic welding.
Manual welding of plug nails, positioning, loading and unloading and other actions are completed by workers. Stud welding equipment is relatively simple, which only needs welding machine and welding gun. Automatic welding in the electrical cabinet industry generally uses robot positioning welding. Stud welding equipment includes welding machine, nail feeder, welding head and distributor. Automation equipment also includes fixture, positioner, PLC control system, gun changing system, etc. Because the electric cabinet industry mainly uses arc drawing process, the following mainly talks about arc drawing equipment. The pull arc welding machines in the market are divided into traditional thyristor welding machines and new inverter welding machines.
Thyristor welding machine has been widely used in the market for a long time, and its function and operation are generally simple, but its calorific value is high, and too fast welding beat will stimulate the overtemperature protection mechanism to suspend welding, which always consumes power in standby. The large volume of transformer makes the body heavy and difficult to handle. Although there are many disadvantages, due to its high cost performance, it is still very popular with the majority of manufacturers. It also has good welding effect in the environment of stable power supply, which is the choice of many small and medium-sized enterprises.
The inverter welding machine is divided into MOSFET inverter welding machine and IGBT inverter welding machine. Now IGBT is the main one. The inverter frequency is up to 30kHz, so the transformer has the advantages of small volume, light weight, small calorific value and higher welding beat. Standby consumes little power, is less affected by the fluctuation of power supply voltage, and the parameter adjustment is more detailed. It is suitable for customers with large budget, large welding volume and high requirements.
M8 stainless steel PS type studs are used most in the electrical cabinet industry. The length of this short cycle arc drawing stud with flange is generally 20-35mm. Individual manufacturers will use M8 Rd studs without flange necking. If you are welding M8 and PS type studs, it is recommended to select a welder with a maximum current of 800A. If M8 Rd studs are used, it is recommended to choose a welder that can use 500-600a welding, because excessive welding current will cause pores or lack of fusion.
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Five different methods of Fusion welding:
Gas welding is a fusion welding method that uses the heat generated by the combustion of combustible gas in oxygen to melt the weld of base metal to realize connection. The most widely used is the oxygen acetylene flame with acetylene gas as fuel.
Due to the simple equipment and convenient operation, 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 welding many ferrous metals, nonferrous metals and alloys.
Gas welding has the advantages of low flame temperature, slow heating speed, wide heating area, wide welding heat affected zone and large welding deformation. In the welding process, the protection of molten metal is poor and the welding quality is not easy to be guaranteed, so its application has been few. However, gas welding has the characteristics of no power supply, simple equipment, low cost, convenient movement and strong universality. Therefore, it has practical value in occasions without power supply and field work.
At present, it is mainly used for the welding of steel sheet (thickness 0.5 ~ 3mm), copper and copper alloy and the repair welding of cast iron.
2.Pneumatic welding
Like gas welding, gas pressure welding also takes gas flame as heat source. When welding, heat the ends of two butt jointed workpieces to a certain temperature, and then apply sufficient pressure to obtain a firm joint. It is a solid-state welding. Pneumatic welding without filler metal is often used for rail welding and reinforcement welding.
Electroslag welding is a welding method using the resistance heat of slag as energy. The welding process is carried out in the vertical welding position and in the assembly gap formed by the end faces of the two workpieces and the water-cooled copper sliding blocks on both sides. During welding, the resistance heat generated by the current through the slag is used to melt the end of the workpiece. According to the electrode shape used in welding, electroslag welding is divided into wire electroslag welding, plate electroslag welding and nozzle electroslag welding.
In the welding process of electroslag welding, except for an arc process in the initial stage, the rest are stable electroslag processes, which are essentially different from submerged arc welding.
Electroslag welding can weld workpieces with large thickness (from 30mm to more than 1000mm) and high productivity. It is mainly used for welding butt joints and T-joints on cross sections. Electroslag welding can be used for the welding of various steel structures and the assembly welding of castings. Electroslag welded joints are generally subject to normalizing treatment after welding due to slow heating and cooling, wide heat affected zone, coarse microstructure and toughness.
However, due to the large weld pool and slow heating and cooling, it is easy to overheat and form coarse structure in the weld and heat affected zone. Therefore, electroslag welding usually uses normalizing treatment to eliminate the coarse crystal in the joint after welding. Electroslag welding is always carried out by vertical welding, not flat welding. Electroslag welding is not suitable for workpieces with a thickness of less than 30mm, and the weld should not be too long.
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. During electron beam welding, the electron beam is generated and accelerated by the electron gun.
Common electron beam welding include 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 is long, and the size of the workpiece is limited by the size of the vacuum chamber.
Compared with arc welding, electron beam welding is characterized by large weld penetration, small weld width and high weld metal purity. It can be used not only in the precision welding of very thin materials, but also in the welding of very thick components.
All metals and alloys that can be melt welded by other welding methods can be welded by electron beam. It is mainly used for welding products requiring high quality. It can also solve the welding of dissimilar metals, easily oxidized metals and refractory metals. But it is not suitable for mass production.
Laser welding is a kind of welding using laser beam focused by high-power coherent monochromatic photon flow as heat source. This welding method usually includes continuous power laser welding and pulse power laser welding.
The advantage of laser welding is that it does not need to be carried out in vacuum, while the disadvantage is that the penetration is not as strong as electron beam welding. Laser welding can carry out accurate energy control, so it can realize the welding of precision micro devices. It can be applied to many metals, especially to solve the welding of some difficult to weld metals and dissimilar metals.
Laser welding is suitable for the welding of micro parts and parts that are difficult to reach by other welding methods. It can also be welded through transparent materials. The heat affected zone and welding deformation are very small. It is especially suitable for the welding of heat sensitive materials. The laser is not affected by the electromagnetic field, does not produce X-rays, and does not need vacuum protection. It can be used for the welding of large structures. Laser welding technology can directly weld insulated conductors without peeling off the insulating layer in advance; It can also weld dissimilar materials with great differences in physical properties. Laser welding equipment is expensive and the energy conversion rate is low (5% ~ 20%). It has high requirements for the interface processing, assembly and positioning of weldments. At present, it is mainly used for the welding of micro devices in electronic industry and instrument industry, as well as the welding of silicon steel sheet and galvanized steel sheet.
Welding usually refers to the welding of metal. It is a forming method to connect two separated objects into one by heating or pressurizing, or both at the same time.
Welding technology is widely used in machine manufacturing, shipbuilding industry, construction engineering, power equipment production, aviation and aerospace industry. Welding technology also has some shortcomings, such as the welding structure is not detachable, which brings inconvenience to maintenance; There will be welding stress and deformation in the welded structure; The microstructure and properties of welded joints are often uneven, and welding defects will occur.
Welding technology mainly includes fusion welding, pressure welding and brazing.
Introduction to other welding:
High frequency welding takes solid resistance heat as energy. During welding, the resistance heat generated by high-frequency current in the workpiece is used to heat the surface layer of the welding area of the workpiece to the molten or close plastic * state, and then the upsetting force is applied (or not applied) to realize the metal bonding. Therefore, it is a solid-state 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. When contacting high-frequency welding, high-frequency current is transmitted to the workpiece through mechanical contact with the workpiece. During induction high-frequency welding, the high-frequency current generates induced current in the workpiece through the coupling effect of the induction coil outside the workpiece.
High frequency welding is a highly specialized welding method, and special equipment shall be equipped according to the products. High productivity, welding speed up to 30m / min. It is mainly used for welding longitudinal seam or spiral seam when manufacturing pipes.
Explosive welding is also another solid-state welding method with chemical reaction heat as energy. But it uses the energy produced by explosive explosion to realize metal connection. Under the action of explosion wave, the two metals can be accelerated and collided in less than one second to form the combination of metals.
Among various welding methods, explosive welding has the widest range of combinations of dissimilar metals that can be welded. Explosive welding can be used to weld two metals that are incompatible in metallurgy into various transition joints. Explosive welding is often used to cover flat plates with large surface area. It is an efficient method to manufacture composite plates.
Ultrasonic welding is also a solid-state welding method with mechanical energy as energy. When ultrasonic welding is carried out, under low static pressure, the high-frequency vibration emitted by the sound pole can produce strong crack friction on the joint surface and heat it to the welding temperature to form a joint.
Ultrasonic welding can be used for the 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 joint less than 2 ~ 3mm. click here to learn more about JIATONG welding techniques.
Three Methods of Pressure Welding:
This is a kind of welding method with resistance heat as energy, including electroslag welding with slag resistance heat as energy and resistance welding with solid resistance heat as energy. Since electroslag welding has more unique characteristics, it will be introduced later. This paper mainly introduces several resistance welding with solid resistance heat as energy, mainly including 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 to realize the connection. Larger currents are usually used.
In order to prevent arcing on the contact surface and to forge the weld metal, pressure must always be applied during welding. In this kind of resistance welding, the surface of the workpiece to be welded is of primary importance to obtain stable welding quality. Therefore, the contact surface between electrode and workpiece and between workpiece and workpiece must be cleaned before welding.
It is widely used in industries such as automobiles, aircraft, instruments, household appliances, steel bars for construction, etc. it is suitable for a wide range of materials, but the resistance welding of easily oxidized metals is slightly poor. 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 and stainless steel can be welded.
Friction welding is a solid-phase welding with mechanical energy as energy. It uses the heat generated by mechanical friction between two surfaces to realize the connection of metals. 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 at the end of heating, so that the hot metal is combined by upsetting. Generally, the joint surface does 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 for the welding of dissimilar metals. It shall be applicable to workpieces with a maximum diameter of 100mm with a circular cross section.
