07-23
→Through technology sharing, let you know the welding method of pressure welding.
2022-07-23
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. Advantages: 1) When the nugget is formed, it is always surrounded by a plastic ring, the molten metal is isolated from the air, and the metallurgical process is simple. 2) The heating time is short, the heat is concentrated, so the heat affected zone is small, and the deformation and stress are also small. Usually, it is not necessary to arrange the correction and heat treatment process after welding. 3) No filler metals such as welding wires and welding rods, as well as Welding materials such as oxygen, acetylene and argon, are required, and the welding cost is low. 4) Simple operation, easy to realize mechanization and automation, and improve working conditions. 5) high productivity, and no noise and harmful gases, in mass production, can be made with other manufacturing processes to the assembly line. However, flash butt welding requires isolation due to spark spatter. Disadvantages: 1) At present, there is still a lack of reliable non-destructive testing methods, welding quality can only be checked by destructive testing of process samples and workpieces, as well as by various monitoring technologies. 2) The lap joint of point and seam welding not only increases the weight of the component, but also causes the tensile strength and fatigue strength of the joint to be lower due to the angle formed around the nugget between the two plates. 3) The equipment has high power and high degree of mechanization and automation, which makes the equipment cost high and maintenance difficult, and the commonly used high-power single-phase AC welding machine is not conducive to the normal operation of the power grid. Scope of application: It is widely used in automobiles, aircraft, instruments, home appliances, steel bars for construction, and other industries. It is widely used in a wide range of materials, but the resistance welding of easily oxidized metals is slightly worse. 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. 2 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. A solid-phase pressure welding method that uses the heat generated by the friction of the welding contact end faces to make the end faces reach a thermoplastic state, and then quickly exerts a forging force to realize welding, Friction welding has the following advantages: (1) The welding quality is stable, the welding size accuracy is high, and the joint rejection rate is lower than that of resistance butt welding and flash butt welding. (2) Welding productivity is high, 5 to 6 times higher than flash butt welding. (3) It is suitable for welding dissimilar metals, such as carbon steel, low alloy steel and stainless steel, high-speed steel, copper-stainless steel, copper-aluminum, aluminum-steel, steel-zirconium, etc. (4) The processing cost is low, the power is saved, and the welding parts do not need special cleaning. (5) easy to realize mechanization and automation, simple operation, welding work site without sparks, arc and harmful gases. Disadvantages: it is difficult to weld non-circular section by rotating the workpiece. Disc-shaped workpieces and thin-walled pipe fittings are also difficult to weld because they are not easy to clamp. Limited by the power of the welding machine spindle motor, the maximum section that can be welded by friction welding is 20000 mm2. Friction welding machine one-time investment cost is large, suitable for mass production. Application: dissimilar metal and dissimilar steel products, such as copper-aluminum transition joints in the power industry, high-speed steel-structural steel tools for metal cutting, etc.; structural steel products, such as power station boiler serpentine tubes, valves, tractor bearings, etc. 3 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 oxide and other impurities on the surface of the workpiece, but also the surface roughness must be lower than a certain value to ensure the welding quality. Diffusion welding is under the protection of vacuum or protective atmosphere, under certain temperature (lower than the melting point of the base metal) and pressure conditions, the smooth and smooth surfaces to be welded in contact with each other are in close contact after microscopic plastic flow, and the atoms diffuse each other. After a long period of time, the original interface disappears, and the welding method of complete metallurgical combination is achieved. Diffusion welding has the following advantages: (1) can be almost no damage to the performance of the material to be welded, to achieve all kinds of the same material and different materials between the welding, can be used to manufacture double or multi-layer composite materials. (2) It can weld workpieces with complex structures and large differences in thickness. (3) The joint composition and organization are uniform, which reduces the tendency of stress corrosion. (4) The welding deformation is small and the joint precision is high, which can be used as the final assembly and connection method of the parts. (5) It can be carried out at the same time as other processing techniques (such as vacuum heat treatment, etc.), and the welding of multiple joints can be completed at the same time, thereby improving productivity. Disadvantages: Diffusion welding has high requirements for surface processing and cleaning of weldments, long welding time, low productivity, high cost, and large equipment investment. Application: welding between dissimilar metals with large melting point difference or metallurgical incompatibility, welding of metal and ceramic and welding of titanium, nickel and aluminum alloy structural parts. Not only used in atomic energy, aerospace and electronics industry and other cutting-edge technology, and has been extended to the general machinery manufacturing industry sector.
07-23
→2022-07-23
Gas welding: A fusion welding method that uses the heat generated by the combustion of combustible gas in oxygen to melt the welding place of the base metal to realize the connection. Gas welding is a welding method using gas flame as heat source. The oxygen-acetylene flame with acetylene gas as fuel is the most widely used. Because the equipment is simple and easy to operate, 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. Combustible gas: acetylene, liquefied petroleum gas, etc. Taking acetylene as an example, its flame temperature can reach 3200 ℃ when burning in oxygen. there are three kinds of oxygen acetylene flame: ① Neutral flame: the volume mixing ratio of oxygen and acetylene is 1~1.2, acetylene is fully burned, suitable for welding carbon steel and non-ferrous alloys. ② carbon flame: oxygen and acetylene volume mixing ratio is less than 1, acetylene excess, suitable for welding high carbon steel, cast iron and high speed steel. ③ oxidation flame: oxygen and acetylene volume mixing ratio is greater than 1.2, excess oxygen, suitable for brass and bronze brazing. The gas welding flame temperature is low, the heating speed is slow, the heating area is wide, the welding heat affected zone is wide, the welding deformation is large, and the molten metal is poorly protected during the welding process, and the welding quality is not easy to guarantee, so its application has been rare. However, gas welding has the characteristics of no power supply, simple equipment, low cost, convenient movement and strong versatility, so it has practical value in the field work without power supply. At present, it is mainly used for welding of thin steel plate (thickness 0.5~3mm), copper and copper alloy and repair welding of cast iron. 2 Air 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. 3 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 characteristics of electroslag welding: in the welding process of electroslag welding, except for an arc process at the beginning, the rest are stable electroslag process, which is essentially different from submerged arc welding. The advantages of electroslag welding are: large thickness of weldable workpieces (from 30mm to more than 1000mm) and 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. the limitations of electroslag welding: (1) Due to the large welding pool, slow heating and cooling, it is easy to overheat in the weld and heat affected zone to form coarse tissue, so electroslag welding usually uses normalizing treatment to eliminate coarse grains in the joint after welding. (2) 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. Classification and application of electroslag welding Classification of electroslag welding: wire electrode electroslag welding, plate electrode electroslag welding, melting tip electroslag welding and tube electrode electroslag welding, etc. Wire electrode electroslag welding is the most commonly used electroslag welding method. It uses welding wire as electrode. According to the different thickness of weldments, one or more welding wires can be used. The thickness of weldments that can be welded by single wire welding is 40~60mm. When the thickness of weldments is greater than 60mm, the welding wire should swing laterally. Three wires can weld 450mm thick weldments. Wire electrode electroslag welding is mainly used for welding thickness of 40~450mm weldments and longer weld weldments, can also be used for large weldments of the ring weld. Application: mainly used in heavy machinery manufacturing industry, manufacturing forging-welding structure and casting-welding structure, such as heavy machine tool base, high pressure boiler, weldment thickness is generally 40~450mm, the material is carbon steel, low alloy steel, stainless steel and so on. 4 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. Electron beam welding machine: The core is the electron gun, which is a device that completes the generation of electrons, the formation and convergence of electron beams, and is mainly composed of filaments, cathodes, anodes, and focusing coils. The filament is energized to heat up and heat the cathode. When the cathode reaches 2400K, electrons are emitted. Under the action of the high voltage electric field between the cathode and the anode, the electrons are accelerated (about 1/2 of the speed of light), emitted through the anode hole, then converge into an electron beam with a diameter of 0.8~3.2mm through the focusing coil, and the kinetic energy is converted into heat energy on the surface of the weldment, so that the weldment joint is rapidly melted, the weld is formed after cooling crystallization. According to the vacuum degree of welding workshop (weldment placement place), the classification of electron beam welding: (1) High vacuum electron beam welding. The studio and the electron gun are in the same room, the vacuum degree is 10-2~10-1Pa, which is suitable for precision welding of refractory, active, high-purity metals and small parts. (2) Low vacuum electron beam welding. The studio and the electron gun are divided into two vacuum chambers. The vacuum degree of the studio is 10-1~15Pa, which is suitable for larger structural parts and refractory metals that are less sensitive to oxygen and nitrogen. (3) Non-vacuum electron beam welding. An inert gas protective cover or nozzle is required, and the distance between the weldment and the electron beam outlet should be controlled at about 10mm to reduce the scattering caused by the collision of the electron beam and the gas molecules. Non-vacuum electron beam welding is suitable for welding carbon steel, low alloy steel, stainless steel, refractory metal and copper, aluminum alloy, etc., and the size of the weldment is not limited. The advantages of vacuum electron beam welding: (1) The energy density of the electron beam is large, up to 5 × 108W/cm2, which is about 5000 to 10000 times that of the ordinary arc. The heat is concentrated, the thermal efficiency is high, the heat affected zone is small, the weld is narrow and deep, and the welding deformation is extremely small. (2) Welding in a vacuum environment, the metal does not interact with the gas phase, and the joint has high strength. (3) The electron beam focus radius can be adjusted in a large range, flexible control, and strong adaptability. It can weld thin parts of 0.05mm and thick plates of 200~700mm. Application: Especially suitable for welding some refractory metals, active or high purity metals and heat sensitive metals. However, the equipment is complex, the cost is high, the size of the weldment is limited by the vacuum chamber, the assembly accuracy is high, and it is easy to excite X-rays, the welding auxiliary time is long, and the productivity is low. These weaknesses limit the wide application of electron beam welding. 5 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. Laser generation: after the material is excited, the wavelength, frequency, direction is exactly the same beam. The characteristics of laser: with good monochromaticness, good direction, high energy density characteristics, laser by transmission or mirror focus, can be less than 0.01mm in diameter, power density up to 1013W/cm2 energy beam, can be used as welding, cutting, drilling and surface treatment of the heat source. The material of laser is solid, semiconductor, liquid, gas, etc., which is mainly used for welding, cutting and other industrial processing is yttrium aluminum garnet (YAG) solid laser and CO2 gas laser. The main advantages of laser welding are: (1) The laser can be bent and transmitted through optical fibers, prisms and other optical methods. It is suitable for welding parts that are difficult to reach by miniature parts and other welding methods, and can also be welded through transparent materials. (2) High energy density, high-speed welding can be realized, the heat-affected zone and welding deformation are very small, especially suitable for welding heat-sensitive materials. (3) The laser is not affected by electromagnetic fields, does not produce X-rays, does not require vacuum protection, and can be used for welding large structures. (4) can be directly welded insulated conductors, without the need to strip off the insulating layer in advance; can also be welded to different materials with different physical properties. The main disadvantages of laser welding are: expensive equipment, low energy conversion rate (5% ~ 20%), high requirements for processing, assembly and positioning of weldment interfaces. At present, it is mainly used for the welding of micro devices in the electronics industry and instrument industry, as well as the welding of silicon steel sheet and galvanized steel sheet.
07-23
→Commonly used arc welding methods, these 6 to distinguish carefully!
2022-07-23
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"
07-23
→The technology of arc welding is introduced, and the analysis of welding metallurgical process.
2022-07-23
Arc: A strong and long-lasting gas discharge phenomenon, positive and negative electrodes have a certain voltage, and the gas between the two electrodes should be in the state of ionization medium. When igniting a welding arc, the two electrodes (one pole is the workpiece, the other pole is filled with metal wire or welding rod) are usually connected to the power supply, short contact and rapid separation, short circuit occurs when the two poles contact each other, forming an arc. This is called contact arcing. After the arc is formed, as long as the power supply maintains a certain potential difference between the two poles, the arc can be maintained. Arc features: low voltage, high current, high temperature, high energy density, good mobility, etc. Generally, the voltage of 20~30V can maintain the stable combustion of the arc, and the current in the arc can be from tens of amperes to thousands of amperes. To meet the welding requirements of different workpieces, the temperature of the arc can reach more than 5000K, which can melt various metals. Arc composition: cathode area, anode area, arc column area three parts, Arc welding power source: The power source used for welding arc is called arc welding power source, which can be divided into four categories: AC arc welding power source, DC arc welding power source, pulse arc welding power source and inverter arc welding power source. DC positive connection: when the workpiece is connected to the anode and the welding rod is connected to the cathode, it is called DC positive connection. At this time, the workpiece is heated greatly and is suitable for welding thick and large workpieces; DC reverse connection: when the workpiece is connected to the cathode and the electrode is connected to the anode, it is called DC reverse connection. At this time, the workpiece is heated less and is suitable for welding thin and small workpieces. When using AC welding machine for welding, there is no positive or negative connection problem because the polarity of the two poles changes alternately. welding metallurgical process In the process of arc welding, the interaction of liquid metal, slag and gas is the process of metal re-smelting. However, due to the particularity of welding conditions, the welding chemical metallurgy process has different characteristics from the general smelting process. First of all, the welding metallurgy temperature is high, the phase boundary is large, and the reaction speed is fast. When air intrudes in the arc, the liquid metal will undergo strong oxidation and nitridation reactions, and a large amount of metal will evaporate. However, the water in the air and the hydrogen atoms decomposed from the oil, rust and water in the workpiece and Welding materials can dissolve into the liquid metal at the high temperature of the arc, resulting in reduced plasticity and toughness (hydrogen embrittlement) and cracks. Secondly, the welding pool is small and the cooling is fast, which makes it difficult for various metallurgical reactions to reach a balanced state, the chemical composition in the weld is uneven, and the gas and oxides in the molten pool are too late to surface, which is easy to form defects such as pores and slag inclusions, and even cracks. In order to ensure the quality of the weld, the following measures are usually taken in the arc welding process: (1) During the welding process, the molten metal is mechanically protected from the air. There are three protection methods: gas protection, slag protection and gas-slag joint protection. (2) metallurgical treatment of the welding pool, mainly by adding a certain amount of deoxidizer (mainly ferromanganese and ferrosilicon) and a certain amount of alloying elements in the Welding materials (welding rod, welding wire, flux), FeO in the molten pool is excluded in the welding process, and the burning loss of alloying elements is compensated.
07-23
→20 minutes to learn welding knowledge, understand these explanations useful!
2022-07-23
Welding: Usually refers to the welding of metal. It is a forming method that makes two separated objects produce interatomic binding force and connect them into one by heating or pressurizing, or both at the same time. Classification: According to the different heating degree and process characteristics in the welding process, welding methods can be divided into three categories. (1) Fusion welding. The welding part of the workpiece is locally heated to a molten state to form a molten pool (usually with filler metal), which is cooled and crystallized to form a weld, which is combined into an inseparable whole by the welding workpiece. Common fusion welding methods include gas welding, arc welding, electroslag welding, plasma arc welding, electron beam welding, laser welding, etc. (2) Pressure welding. In the welding process, regardless of heating or not, all need pressure welding method. Common pressure welding are resistance welding, friction welding, cold pressure welding, diffusion welding, explosive welding, etc. (3) Brazing. After the brazing filler metal (filler metal) with a melting point lower than that of the metal to be welded is melted, the joint gap is filled, and the metal to be welded is interdiffused to realize the connection. The welding workpiece does not melt during the brazing process and generally has no plastic deformation. Characteristics of welding production: (1) Save metal materials and light structure. (2) To make heavy and complex machine parts, simplify casting, forging and cutting processes, and obtain the best technical and economic results. (3) The welded joint has good mechanical properties and sealing performance. (4) It is possible to manufacture a bimetal structure so that the performance of the material can be fully utilized. Application: Welding technology is widely used in machine manufacturing, shipbuilding industry, construction engineering, power equipment production, aviation and aerospace industry. Deficiencies: welding technology also has some shortcomings, such as welding structure can not be disassembled, to the maintenance of inconvenience; welding structure will exist in the welding stress and deformation; welding joints of the organization and properties are often uneven, and will produce welding defects.
07-12
→Soldering Process of Solder Attachable Connectors
2022-07-12
Soldering reliability of solder mounted connectors is higher than that of traditional surface mount BGA and CGA devices. This type of connector structure has been widely used by many connector manufacturers.
07-12
→Solder application: How many cattle are filled with metal materials
2022-07-12
A solder (or brazing filler metal) is a material that is used as a filler metal at the time of brazing. After heating and melting, the solder infiltrates the base metal, fills the joint gap, and diffuses with the base metal to realize the brazing connection. Solder, as an interconnection material in electronic packaging technology, mainly undertakes the functions of mechanical connection, electrical connection and heat dissipation, and is used in all levels of electronic packaging. Solder is mainly used for lead welding, chip welding, shell sealing, etc. 1. Solder performance requirements for integrated circuit packaging In order to meet the requirements of brazing process and brazing joint performance, the solder used as the connecting material should generally meet the following basic requirements. (1) It has a suitable melting point, which must be lower than the melting temperature of the base material to be welded. (2) It has good wetting characteristics and spreading characteristics for the base metal, and can achieve proper dissolution and diffusion with the base metal. (3) The welding interface should have certain mechanical strength and stable physical and chemical properties. (4) The price is moderate, and the content of rare metals and precious metals is low. 2. Material system of solder The traditional solder is lead-tin (Sn-Pb) solder, its material system is stable, low melting point (63Sn-37Pb eutectic solder melting point of 183 degrees), with excellent welding performance, processing performance and low price, so it has been widely used.
07-12
→Brazing, a solid phase and liquid phase welding method!
2022-07-12
The energy source for brazing can be chemical reaction heat or indirect heat energy. It is the use of lower than the melting point of the melting point of the material to be welded metal as solder, after heating the solder melting, capillary action will be the solder and into the gap between the contact surface of the joint, wetting the surface of the metal to be welded, so that the liquid phase and the solid phase between the diffusion and the formation of brazing joints. Therefore, brazing is a solid phase and liquid phase welding method. Characteristics and application of brazing Brazing uses an alloy with a melting point lower than that of the base metal as a brazing filler metal. When heated, the brazing filler metal melts and fills and remains in the joint gap by wetting and capillary action. The base metal is in a solid state and relies on the mutual diffusion between the liquid brazing filler metal and the solid base metal to form a brazing joint. Brazing has little effect on the physical and chemical properties of the base metal, the welding stress and deformation are small, and the dissimilar metals with large differences in welding performance can be welded at the same time. The joint appearance is beautiful and neat, the equipment is simple, and the production investment is small. However, the strength of the brazed joint is low and the heat resistance is poor. Applications: Carbide cutting tools, drill bits, bicycle frames, heat exchangers, conduits and various containers; in the manufacture of microwave waveguides, electronic tubes and electronic vacuum devices, brazing is even the only possible connection method. The brazing filler metal is the filler metal that forms the brazed joint, and the quality of the brazed joint depends to a large extent on the brazing filler metal. The brazing filler metal should have suitable melting point, good wettability and caulking ability, can diffuse with the base metal, and should also have certain mechanical properties and physical and chemical properties to meet the performance requirements of the joint.
07-11
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