Commonly used arc welding methods, these 6 to distinguish carefully!

【Summary Description】 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 weld metal energy. 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 Submerged arc welding Submerged Metal Arc Welding (SMAW) Submerged arc welding is a kind of melting electrode welding method in which granular flux is used as the protective medium and the arc is hidden under the flux layer. The welding process of submerged arc welding consists of three links: 1. evenly pile up enough granular flux at the weldment to be welded; 2. The conductive nozzle and weldment are respectively connected to the welding power supply to generate welding arc; 3. Automatically feed the welding wire and move the arc to carry out welding. The main features of submerged arc welding are as follows: 1. Unique arc performance (1) High weld quality and good slag isolation air protection effect. The main component of the arc zone is CO2, the nitrogen content and oxygen content in the weld metal are greatly reduced, the welding parameters are automatically adjusted, the arc walking is mechanized, the molten pool exists for a long time, the metallurgical reaction is sufficient, and the wind resistance is strong, so the weld composition is stable and the mechanical performance is good. (2) Good working conditions, slag isolation arc light is conducive to welding operation; Mechanized walking, the labor intensity is low. 2, the arc column electric field strength is higher than the metal electrode gas shielded arc welding has the following characteristics:(1) the equipment adjustment performance is good, because the electric field strength is higher, the sensitivity of the automatic adjustment system is higher, so that the stability of the welding process is improved;(2) The lower limit of welding current is higher. 3, high production efficiency due to the wire conductive length is shortened, the current and current density is significantly improved, so that the arc penetration ability and the welding wire deposition rate is greatly improved; and because of the heat insulation effect of flux and slag, the total thermal efficiency is greatly increased, so that the welding speed is greatly improved. Metallurgical reaction: flux participates in metallurgical reaction, Si and Mn are reduced, part C is burned, impurities S and P are limited to H removal, and hydrogen holes are prevented. Droplet transition: slag wall transition Power supply: DC power supply is used for small current conditions, constant speed wire feeding, and its own arc adjustment; high current generally uses AC power supply, variable speed wire feeding (SAW welding wire is generally thicker), arc voltage feedback arc adjustment Welding materials: welding wire and flux. The selection of welding wire and flux must ensure that high-quality welding joints are obtained, and at the same time, the cost must be reduced as much as possible, and the applicable current type and polarity must be paid attention. Scope of application: Due to the large penetration depth of submerged arc welding, high productivity, and high degree of mechanical operation, it is suitable for welding long welds of medium and heavy plate structures. It is widely used in shipbuilding, boilers and pressure vessels, bridges, overweight machinery, nuclear power plant structures, marine structures, weapons and other manufacturing departments. It is one of the most commonly used welding methods in welding production today. In addition to the connection of components in metal structures, submerged arc welding can also be used to weld wear-resistant or corrosion-resistant alloy layers on the surface of the base metal. With the development of welding metallurgy technology and Welding materials production technology, the materials of 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-based alloys, titanium alloys, copper alloys and so on. Due to its own characteristics, its application also has certain limitations, mainly as follows:(1) the limitation of welding position, due to the reason of flux retention, if no special measures are adopted, submerged arc welding is mainly used for horizontal down position welding, but not for horizontal, vertical and vertical welding;(2)Welding to the limitation of materials, it is not possible to weld aluminum, titanium and other strong oxidizing metals and their alloys, mainly used for welding ferrous metal;(3) only suitable for long weld welding cut, and can not weld space position limited weld;(4) can not directly observe the arc;(5) does not apply to thin plate, small current welding. 3 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. 4 Gas Melt Arc Welding (GMAG) (GMAG) is a fusion welding method that uses arc as a heat source. Its arc is established between the continuously fed welding wire and the molten pool. The molten pool formed by mixing the molten wire metal and the base metal is crystallized to form a weld after the arc heat source is removed and the separated base metal is connected metallurgically. The characteristics of CO2 welding:(1) under the action of high temperature of welding arc, CO2 will decompose into CO, O2 and O, which has strong compression effect on arc, thus causing the arc form of this welding method to have the characteristics of small arc column diameter, small arc heel area and often difficult to cover all molten droplets at the end of welding wire, therefore, the droplet is subjected to a large transition resistance (spot force), which makes the droplet coarsening, the axial property of the transition path becomes poor, and the splash rate is large. (2) The welding zone is well protected, and the density of CO2 is the largest among the commonly used protective gases. After CO2 gas is decomposed by heat, the volume increases, so the protection is better. (3) The energy is relatively concentrated and the penetration ability is large;(4) Low production cost and energy saving. (5) The process and technology also have good visibility of the welding area, easy to observe and operate; welding heat affected zone and welding deformation are small; the molten pool volume is small, the crystallization speed is fast, and the all-position welding performance is good; The advantages of low sensitivity to rust. Metallurgical characteristics:(1) oxidation of alloying elements during CO2 welding, CO2 will decompose into CO, O2 and O under the action of arc high temperature. Under welding conditions, CO is insoluble in metal and does not participate in reaction, while CO2 and O have strong oxidation, which oxidizes Fe and other alloying elements. (2) Deoxidation and alloying of weld metal? Usually, a certain amount of deoxidizer is added to the welding wire for deoxidation. In addition, the remaining deoxidizer remains in the weld as an alloying element to make up for oxidation loss and ensure the chemical composition requirements of the weld. Droplet transition:(1), short circuit transition (short arc, filament, small current) is suitable for all-position welding of thin plates;(2), fine particle transition, thick wire, long arc, high current welding;(3), latent arc drop transition (rarely used). Power supply: flat characteristic power supply (single knob adjustment), DC reverse connection, constant speed wire feeding Welding materials:CO2 gas and welding wire Scope of application: At present, CO2 gas shielded welding is widely used in locomotive manufacturing, shipbuilding, automobile manufacturing, coal mining machinery manufacturing and other fields. Suitable for welding low carbon steel, low alloy steel, low alloy high strength steel, but not suitable for welding non-ferrous metals, stainless steel. Although there is information that CO2 gas shielded welding can be used for welding stainless steel, it is not the first choice for welding stainless steel. 5 Plasma Arc Welding Measures such as water-cooled nozzles can reduce the cross-sectional area of the arc column area of the arc, and significantly increase the temperature, energy density and plasma flow rate of the arc. This kind of arc that compresses the arc column by external restraint is called plasma arc. Plasma arc is a special form of arc, which is an arc with high energy density and is still a gas conduction phenomenon. Plasma arc welding is the use of plasma arc heat heating & melting workpiece and base metal welding method. Classification: Perforated plasma arc welding and micro plasma arc welding. Perforated plasma arc: the welding current is 100 ~ 300A, the joint does not need to open the groove, do not leave a gap. During welding, the plasma arc can completely penetrate the weldment and form a small through hole. The molten metal is squeezed around the small hole, the arc moves, the small hole moves, and the weld is formed at the rear, thus realizing one-sided welding and two-sided forming. The upper limit of plate thickness that can be welded by this method is: carbon steel 7mm, stainless steel 10mm. Micro-beam plasma arc: welding current is 0.1 ~ 30A, welding thickness is 0.025~2.5mm. In addition, there are molten plasma arc welding suitable for copper and copper alloy welding, which can be used for deep penetration welding of thick plates or high-speed welding of thin plates and melting pole plasma arc welding of surfacing welding, and can solve the AC (variable polarity) plasma arc welding and other process methods of aluminum alloy plasma arc welding. The main process parameters of plasma arc welding are welding current, welding speed, shielding gas flow, ion gas flow, torch nozzle structure and aperture. Plasma arc cutting: the use of plasma arc high-temperature high-speed arc flow to make the incision of the metal local melting so as to evaporate, and with the help of high-speed gas flow or water flow will melt the material away from the substrate to form a cutting method. Features: (1) plasma arc energy density, high arc column temperature, strong penetrating ability, 10~12mm thickness of steel can not open groove, can be a penetration double-sided forming, welding speed, high productivity, small stress deformation. (2) The section of the weld is in the shape of a wine glass, and there is no finger penetration problem. (3) The arc straightness is good, and the fluctuation of the molten pool is small due to the influence of the arc length fluctuation. (4) arc stability 0.1A, still has a relatively flat static characteristics, with a constant current source, can be very good for thin plate welding (0.1mm). (5) Tungsten electrode shrinks to prevent welding seam from clamping tungsten (6) Using small hole welding technology to realize single-sided welding and double-sided forming. (7) the equipment is more complex, the gas consumption is large, only suitable for indoor welding. The gun is less reachable than TIG. (8) The arc diameter is small, and it is necessary to more accurately center the axis of the welding torch and the centerline of the weld. Metallurgical reaction: single, only evaporation Power supply: steep drop power supply, DC positive connection; AC, steep drop power supply, arc ignition and arc stabilization measures are required when welding aluminum and magnesium. Welding materials: protective gas, tungsten electrode Scope of application: It is widely used in industrial production, especially in the welding of copper and copper alloys, titanium and titanium alloys, alloy steels, stainless steel, molybdenum and other metals used in military and cutting-edge industrial technologies such as titanium alloy missile shells, Some thin-walled containers on aircraft, etc. 6 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 wire" is now known as "flux-cored wire"

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