07-29

Welding operation skills of copper and brass

2022-07-29

Copper has excellent properties such as electrical conductivity, thermal conductivity, corrosion resistance, ductility and certain strength. It is widely used in electrical, electronic, chemical, food, power, transportation and aerospace industries. In pure copper (copper) to add more than 10 kinds of alloying elements to form a solid solution of all kinds of copper alloys, such as zinc for brass; nickel for cupronickel; silicon for silicon bronze; aluminum for aluminum bronze and so on! Copper and copper alloys can be connected by brazing, resistance welding and other processes. In today's developed industry, fusion welding has occupied a dominant position. The welding of copper and copper alloy is easy to be realized by welding rod arc welding, TIG welding, MIG welding and other technological methods. There are four main elements that affect the weldability of copper and copper alloys: One is the effect of high thermal conductivity. The thermal conductivity of copper is 7 to 11 times larger than that of carbon steel. When the process parameters used are similar to those of welding carbon steel with the same thickness, the copper material is difficult to melt, and the filler metal and the base metal cannot be fused well. Second, the hot cracking tendency of welded joints is large. During welding, copper and impurities in the molten pool form a low melting point eutectic, which makes copper and copper alloys have obvious hot brittleness and produce hot cracks. Third, the defects of pores are much more serious than those of carbon steel, mainly hydrogen pores. Four is the change of welding joint performance. Grain coarsening, plasticity decreased, corrosion resistance decreased. 1. Welding of red copper Welding copper methods include gas welding, manual carbon arc welding, manual arc welding and manual argon arc welding. Large structures can also be welded automatically. (1) Gas welding of copper Butt joints are most commonly used for welding copper, and lap joints and T-joints are used as little as possible. Two kinds of welding wires can be used for gas welding, one is the welding wire containing deoxidizing elements, such as wire 201 and 202; the other is the general copper wire and the cutting strip of the base metal, using Gas agent 301 as a flux. Neutral flame shall be used for gas welding of copper. (2) Manual arc welding of copper In manual arc welding, red copper electrode copper 107 is used, and the welding core is red copper (T2, T3). The edge of the welding place shall be cleaned before welding. When the thickness of the weldment is greater than 4mm, it must be preheated before welding, and the preheating temperature is generally about 400~500 ℃. With copper 107 electrode welding, the power supply should be DC reverse connection. When welding, short arc should be used, and the welding rod should not be swung laterally. The reciprocating linear motion of the welding rod can improve the forming of the weld. Long welds shall be welded by step-back method. The welding speed should be as fast as possible. During multi-layer welding, the slag between the layers must be completely removed. Welding should be carried out in a well-ventilated place to prevent copper poisoning. After welding, flat head hammer should be used to knock the weld to eliminate stress and improve the quality of the weld. (3) Manual argon arc welding of copper When red copper manual argon arc welding, the welding wire used is wire 201 (special red copper welding wire) and wire 202, and red copper wire, such as T2. Before welding, the oxide film, oil and other dirt on the welding edge of the workpiece and the surface of the welding wire must be cleaned to avoid defects such as pores and slag inclusion. Cleaning methods are mechanical cleaning and chemical cleaning method. When the thickness of the butt joint plate is less than 3mm, no groove is opened; When the plate thickness is 3~10mm, open a V-shaped groove with a groove angle of 60~70; When the plate thickness is greater than 10mm, open an X-shaped groove with a groove angle of 60~70; In order to avoid incomplete welding, generally no blunt edge is left. According to the plate thickness and groove size, the assembly clearance of the butt joint is selected in the range of 0.5~1.5mm. Manual argon arc welding of red copper usually adopts DC positive connection, I .e. tungsten electrode is connected to negative electrode. In order to eliminate pores and ensure reliable fusion and penetration at the root of the weld, it is necessary to increase the welding speed, reduce argon consumption, and preheat the weldment. When the plate thickness is less than 3mm, the preheating temperature is 150~300 ℃; when the plate thickness is greater than 3mm, the preheating temperature is 350~500 ℃. The preheating temperature should not be too high, otherwise the mechanical properties of the welded joint will be reduced. There is also carbon arc welding of copper. The electrodes used in carbon arc welding are carbon electrodes and graphite electrodes. The welding wire used for carbon arc welding of red copper is the same as that used for gas welding. It can also be cut from the base metal and flux used for gas welding of red copper, such as gas 301, etc. 2. Welding of brass Brass welding methods are: gas welding, carbon arc welding, manual arc welding and argon arc welding. (1) gas welding of brass Due to the low temperature of the gas welding flame, the evaporation of zinc in brass during welding is less than that during electric welding, so gas welding is the most commonly used method in brass welding. The welding wire used in brass gas welding are: wire 221, wire 222 and wire 224, etc. These welding wires contain silicon, tin, iron and other elements, which can prevent and reduce the evaporation and burning of zinc in the molten pool, which is conducive to ensuring the performance of the weld and preventing pores. Gas welding brass commonly used flux of solid powder and gas flux, gas flux by boric acid methyl ester and methanol composition; flux such as gas agent 301. (2) Manual arc welding of brass In addition to copper 227 and copper 237, self-made welding rods can also be used for welding brass. When brass arc welding, DC power source should be used for positive connection, and the electrode should be connected to the negative electrode. The surface of the weldment shall be cleaned carefully before welding. Generally, the groove angle should not be less than 60~70 °. In order to improve the weld formation, the weldment should be preheated at 150~250 ℃. Short arc welding should be used during operation, not for horizontal and back and forth swing, only for linear movement, welding speed to be high. Brass weldments in contact with corrosive media such as seawater and ammonia must be annealed after welding to eliminate welding stress. (3) Manual argon arc welding of brass Brass manual argon arc welding can use standard brass welding wire: wire 221, wire 222 and wire 224, or materials with the same composition as the base metal as filling materials. Welding can be connected with DC or AC. When welding with AC, the evaporation of zinc is lighter than when DC is connected. Usually do not have to preheat before welding, only plate thickness difference is relatively large before preheating. The welding speed should be as fast as possible. After welding, the weldment should be heated to 300~400 ℃ for annealing treatment to eliminate the welding stress and prevent the weldment from cracking during use. (4) Brass Carbon Arc Welding When brass carbon arc welding, wire 221, wire 222, wire 224 and other welding wires are selected according to the composition of the base metal, and self-made brass welding wires can also be used for welding. Welding can use gas 301, etc. as a flux. Welding should be short arc operation to reduce zinc evaporation and burning loss. DC TIG welding process is widely used in copper and copper alloy welding, welding wind forming good, good quality inside and outside, under the protection of argon, the molten pool is pure, less pores, thermal cracking effect is small, easy to operate. When the thickness is ≤ 4mm, it is not necessary to preheat before welding, but directly preheat with argon gas. When the temperature of the molten pool is close to 600 ℃, filler wire can be added to melt the base metal to realize welding. For copper with a thickness greater than 4mm, pure copper should be preheated at 400-600 ℃. Copper alloy welding preheating 200-300 ℃. 300TSP,315TX DC TIG welding machine can weld pure copper, silicon bronze, phosphor bronze, brass, white copper and other copper alloys. The 300WP5 and 300/500WX4 AC/DC dual-purpose TIG welding machines can weld aluminum bronze with AC TIG (remove surface oxide film with AC square wave) and the above copper with DC TIG. In recent years, the construction of welding copper and copper alloy by MIG method is more and more, especially for aluminum bronze, silicon bronze and white copper with thickness ≥ 3mm, it is best to use MIG welding method. Thickness of 3~14mm or> 14mm copper and copper alloy almost always use MIG welding, because of high deposition efficiency, large penetration, welding speed (generally 3~4 times TIG welding), to achieve high efficiency, high quality, low cost of economic benefits requirements. Before welding, the copper material shall meet the preheating temperature requirements (pure copper 400~600 ℃, copper alloy 200~300 ℃), the welding wire and the base metal shall be sufficiently similar in chemistry, and the purity of argon shall be ≥ 99.98. • Brass is a copper-zinc alloy, because the boiling point of zinc is low, only 907 ℃, so the welding process is very easy to evaporate, which has become the biggest problem of brass welding. Under the action of high temperature, the evaporation of zinc during electrode arc welding is as high as 40%, and a large amount of zinc evaporation leads to the decrease of mechanical properties and corrosion resistance of welded joints, and also increases the sensitivity to stress corrosion. Evaporated zinc in the air is immediately oxidized into zinc oxide, the formation of white smoke, to bring great difficulties to the operation, but also affect the welder's health, therefore, welding brass places, should strengthen ventilation and other protective measures. The weldability of brass is poor, and there will be problems such as pores, cracks, evaporation and oxidation of zinc during welding. In order to solve these problems, the welding wire containing silicon is often used in welding, because silicon will form a dense silicon oxide film on the surface of the molten pool, which hinders the evaporation and oxidation of zinc and prevents the invasion of hydrogen. After welding, it can be annealed at 470~560 ℃ to eliminate stress and prevent "self cracking. 2, brass welding methods commonly used in the production of brass welding method is welding rod arc welding and argon arc welding, the process points are as follows: (1) The welding rod adopts bronze core welding rod, such as ECuSn-B(T227) and ECuAl-C(T237). Brass castings with low repair welding requirements can be used with pure copper cored electrodes, such as ECu(T107). The power supply adopts DC positive connection, and the V-groove angle shall not be less than 60 ° ~ 70 °. When the plate thickness exceeds 14mm, the surface of the weldment should be carefully cleaned before welding to remove all oil impurities that will generate hydrogen. Short arc welding should be used during operation, and the welding rod does not swing horizontally and back and forth, but only moves along the straight line of the weld. The welding speed should be fast and should not be less than 0.2~0.3 m/min. During multi-layer welding, the oxide film and slag between layers shall be removed. The copper liquid of brass has high fluidity, so the solution pool is preferably in a horizontal position. If the solution pool must be inclined, the inclination angle should not be greater than 15 degrees. (2) Argon arc welding manual tungsten argon arc welding, the welding wire adopts tin brass welding wire HSCuZ-1(HS221), iron brass welding wire HSCuZn-2(HS222), silicon brass welding wire HSCuZn-4(HS224). These wires are high in zinc and have a large amount of smoke during welding. Also available bronze wire HSCuSi(HS211), HSCuSn(HS212). Because the evaporation of zinc destroys the protective effect of argon, a larger nozzle aperture and argon flow rate should be used when welding brass. Preheating is generally not required before welding. Preheating is only required when welding joints with a thickness greater than 10mm and joints with a large difference in welding edge thickness. The latter only preheats the thicker part of the weldment edge. The power supply can be DC positive connection or AC. When welding with AC power, the evaporation of zinc is small. The welding parameters should adopt larger welding current and faster welding speed. The welding parameters of 16~20mm thick brass plate are: welding current 260 ~ 300A, tungsten electrode diameter 5mm, welding wire diameter 3.5~4.0mm, nozzle aperture 14~16mm, argon flow rate 20 ~ 25L/min. In order to reduce the evaporation of zinc, the filler wire and weldment can be "short-circuited" during operation, arc ignition and arc maintenance on the filler wire, as far as possible to avoid the arc directly acting on the base metal, the base metal is mainly heated and melted by the heat transfer of the molten pool metal. When welding, Single-layer welding should be carried out as much as possible. For joints with a plate thickness of less than 5mm, it is best to finish welding at one time. After welding, the weldment should be heated to 300~400 ℃ for annealing treatment to eliminate welding stress and prevent brass components from cracking during use.

07-28

Detailed explanation of the welding method of copper

2022-07-28

1. Common welding methods Welding copper methods include gas welding, manual carbon arc welding, manual arc welding and manual argon arc welding. Large structures can also be welded automatically. (1) Gas welding of copper Copper is the most commonly used butt joints, lap joints and T-joints as little as possible. Two kinds of welding wires can be used for gas welding, one is the welding wire containing deoxidizing elements, such as wire 201 and 202; the other is the general copper wire and the cutting strip of the base metal, the gas agent 301 is used as the flux, and the neutral flame should be used for gas welding of copper. (2) Manual arc welding of copper. When the thickness of the weldment is greater than 4mm, it must be preheated before welding, and the preheating temperature is generally about 400-500 ℃. With copper 107 electrode welding, the power supply should be DC reverse connection. When welding, short arc should be used, and the welding rod should not be swung laterally. The reciprocating linear motion of the welding rod can improve the forming of the welding seam. The long welding seam should be gradually withdrawn and the welding speed should be as fast as possible. During multi-layer welding, the slag between the layers must be completely removed. Welding should be carried out in a well-ventilated place to prevent copper poisoning. After welding, flat head hammer should be used to knock the weld to eliminate stress and improve the quality of the weld. (3) Manual argon arc welding of copper When red copper manual argon arc welding, the welding wire used is wire 201 (special red copper welding wire) and wire 202, and red copper wire, such as T2. Before welding, the oxide film, oil and other dirt on the welding edge of the workpiece and the surface of the welding wire must be cleaned to avoid defects such as pores and slag inclusion. Cleaning methods are mechanical cleaning and chemical cleaning method. When the thickness of the butt joint plate is less than 3mm, no groove shall be opened; When the plate thickness is 3~10mm, open V-shaped groove, groove angle is 60 ° ~ 70 °; When the plate thickness is greater than 10mm, open X-shaped groove, groove angle is 60 ° ~ 70 °; In order to avoid incomplete welding, generally no blunt edge is left. According to the plate thickness and groove size, the assembly clearance of butt joint is selected in the range of 0.5~1.5mm. Manual argon arc welding of red copper usually adopts DC positive connection, I .e. tungsten electrode is connected to negative electrode. In order to eliminate pores and ensure reliable fusion and penetration at the root of the weld, it is necessary to increase the welding speed, reduce argon consumption, and preheat the weldment. When the plate thickness is less than 3mm, the preheating temperature is 150~300 ℃; when the plate thickness is greater than 3mm, the preheating temperature is 350~500 ℃. The preheating temperature should not be too high, otherwise the mechanical properties of the welded joint will be reduced. (4) Carbon arc welding of copper Carbon electrodes and graphite electrodes are used in carbon arc welding. The welding wire used for carbon arc welding of red copper is the same as that used for gas welding. It can also be cut from the base metal and flux used for gas welding of red copper, such as gas 301, etc. 2. Examples of copper welding Example 1. Manual tungsten argon arc welding of copper tubes A unit has 6 Φ180mm × 10mm copper pipe (brand T2) welding joints to be welded during equipment installation. Manual argon tungsten arc welding method has achieved good results. The welding process is as follows: Preparation before 1.1 welding 1.1.1 The welding equipment is WSE-350 AC/DC argon arc welding machine with DC connection. The Welding materials is made of copper welding wire (wire 201) with a diameter of 3mm. Argon purity ≥ 99.96%. 1.1.2 No gap shall be left when the groove is set. 1.1.3 The welding area of the copper pipe and the copper wire shall be free of oil, oxide layer, moisture, etc., and metallic luster shall be exposed. 1.1.4 Welding parameters: tungsten electrode: Φ3mm cerium tungsten electrode, nozzle: Φ14mm, welding current 160 ~ 180A, argon flow rate: 15L/min. 1.1.5 Preheating: Due to the large thermal conductivity and thermal expansion coefficient of red copper and its thermal brittleness, the groove of red copper pipe and the 60mm on both sides of the groove are preheated before welding. The preheating method adopts oxygen-acetylene flame heating, the preheating temperature is about 500 ℃, and the temperature measuring method is point contact thermometer. 1.1.6 Tack weld the pipe fittings at two places (divided into three parts according to the circumference of the pipe, two places are tack welding and one place is welding spot). The length of tack welding is ≥ 10mm and the welding height is 3mm. 1.2 welding The welding level is two layers, I .e. the bottom layer and the cover layer, which are both rotary welding. The welding position is from 10: 00 to 11: 30 on the clock, and the welding is randomly rotated up. 1.2.1 Base welding: Base welding adopts left welding method, and defects such as porosity, slag inclusion, welding flash and incomplete welding shall be prevented during welding. The angle between the welding wire and the pipe plane shall be as small as possible to enhance the argon protection effect, as shown in Fig. 7. The welding torch moves evenly, and the temperature of the molten pool should be controlled appropriately, not too high or too low, so that the welding process can proceed smoothly. The key is to pay close attention to the liquid flow of copper in the molten pool and grasp the timing of melting and penetration. When the molten pool metal slightly sinks, it indicates that the welding has been penetrated (the root forming is basically good). The "intermittent" wire feeding method is adopted for wire filling, I .e. the copper welding wire is fed and returned, which is "neat" and returned "clean". This state is always maintained for uniform forward welding. If the welding speed is slightly slow or the penetration is uneven, incomplete penetration or burn-through will occur, resulting in weld bead formation. The arc striking, joint and operation method are the same as those of the argon arc welding pipe. 1.2.2 Welding of cover surface layer: the welding torch swings left and right, and the welding wire is also fed with the movement of the welding torch. When the arc moves to both sides of the groove, it should pause for a while, and add welding wire to fill the groove and be 1.5~2mm higher than the pipe plane. Only when the welding torch and the welding wire match each other properly and swing evenly can the shape of the molten pool be controlled and the weld seam with good quality inside and outside. 1.3 considerations 1) It is strictly forbidden to "hit tungsten" (I. e. tungsten electrode and welding wire or tungsten electrode and molten pool contact) during welding. During welding, a large amount of metal fume and vapor will enter the molten pool during "tungsten beating", and a large number of honeycomb pores or cracks will be generated in the weld. In case of "tungsten beating" phenomenon, welding must be stopped, polished and welded again, and tungsten electrode shall be replaced or tungsten electrode tip shall be trimmed again until there is no copper spot metal. 2) The bonding jumper shall be firmly connected to prevent the surface of the tube from being scratched. 3) After the weld is slightly cooled, rotate the pipe fitting and pad it firmly. 4) Control the interlayer temperature. When it is found that welding is difficult to melt, it indicates that the temperature is low. It should be preheated to above 500 ℃ before welding, otherwise it is easy to produce incomplete fusion or poor fusion defects. 5) Under the condition of ensuring good fusion, the welding speed should be slightly faster, and the wire feeding is appropriate. Pay attention to the simultaneous melting and integration of the base metal and the welding wire to prevent defects such as incomplete fusion or poor fusion. 6) When the welding arc is extinguished, the welding torch cannot be lifted immediately, and the delayed gas stop protection function should be used to protect the molten pool to prevent pores. 1.4 post-weld treatment After inspection, there are no defects such as pores, cracks and slag inclusion, the welding area of the welded pipe joint is reheated to 600~700 ℃, and quenched with tap water to increase the plasticity of the welding area. Example 2. Oxygen-acetylene welding δ = 2mm thin copper plate Blast furnace circulating cooling pool water stop is made of δ = 2mm thin copper plate pair welding. During welding, because red copper has excellent thermal conductivity, or because the temperature is not enough to form a molten pool, the metal on the weld bead is not fused or not fused well. Either the temperature is too high, the welding area melts a large area, forming welding defects such as burn-through or welding flash. The welding of thin copper plate is a relatively "thorny" problem. According to the above situation, the welding method of "brass brazing" can solve this problem very well. Preparation before welding and operation process during welding are as follows: 1) 60mm on both sides of the weld shall be decontaminated and polished with a wire brush to expose metallic luster. 2) The welding parts shall not be beveled, and the clearance between the welding parts shall be less than 1mm. 3) Use Ф 3mm silicon brass welding wire (wire 224) and flux to 301 the flux. 4) Pad the welded part flat (the backing plate shall be made of flat steel plate and shall be thicker to prevent thermal deformation). 5) Preheating, two welders use medium welding guns, and the neutral flame heats the welding place at the same time, and the temperature reaches 500~600 ℃. One person welds while the other continues to heat in front of the welding position to ensure the stability of the welding process. 6) Neutral flame shall be used for preheating welders, and micro-oxidation flame shall be used for welding welders. 7) The positioning welding and formal welding shall be carried out continuously. The positioning distance shall be 60~80mm, and the positioning welding spot shall be smaller. 8) During heating and welding, pay close attention to the change of temperature in the welding area to prevent too high and too low. Generally, dark red (550~600 ℃) is appropriate for visual inspection. 9) The swing of the welding nozzle should be stable and move forward at a constant speed. The flame core (white spot) of the flame is 5~8mm higher than the melting pool. The contour of the flame should always cover the molten pool and avoid contact with air. Ensure that the brass fluid naturally and smoothly spread to both sides of the weld and dipped into the gap. 10) In order to make the structure of the welded joint crystal fine, improve the strength and toughness, after welding, use a small hammer to beat the welding meat properly. 11) Densification performance test shall be conducted after welding.

07-28

Dissimilar connection between glass and metal welding

2022-07-28

Glass materials are widely used because of high temperature wear resistance, corrosion resistance, insulation, oxidation resistance and other characteristics, but the low ductility and poor impact toughness of glass itself limit its application in engineering. Therefore, the glass-metal composite connector, which combines the excellent properties of glass and metal, has been widely used in microelectronic packaging, batteries, instruments, solar vacuum collector tubes, composite materials and other fields, so it is of great significance to study the sealing of glass and metal. There are many sealing methods for glass and metal, among which the most studied and mature theory is matching sealing. Matching sealing is to pre-oxidize the metal before sealing to generate a layer of oxide layer with appropriate thickness on the metal surface, then put the metal and glass in a furnace for heating and holding for a certain period of time and then cool to room temperature. However, matching sealing needs to be heated in the furnace and then cooled, so the production cycle is long. However, the laser has extremely high energy, can realize rapid heating and rapid cooling in non-contact local, and can also realize the sealing of devices with complex joint shape, so it is more and more widely used in the field of sealing. The welding of glass and metal belongs to different kinds of materials, so their welding belongs to dissimilar welding. This is why we introduce dissimilar welding. In subsequent articles, we will gradually introduce the matching sealing (welding) and laser welding of glass and metal.

07-27

Summary of welding methods for brass and copper

2022-07-27

Brass and copper are widely used in life and production, so what are their differences and their respective welding methods? First of all, let's talk about the difference between brass and copper. Brass is an alloy of copper and zinc, named for its yellow color. Brass with a copper content of 62% to 68% has a melting point of 934 to 967 degrees. If only composed of copper, zinc brass is called ordinary brass. If it is composed of more than two kinds of elements of a variety of alloys called special brass. Such as copper alloy composed of lead, tin, manganese, nickel, lead, iron, silicon. Brass has strong wear resistance. Special brass is also called special brass. It has high strength, high hardness and strong chemical resistance. And the mechanical properties of cutting processing is also more prominent. Seamless copper tube made of brass, soft and strong wear resistance. Brass seamless tubes can be used for heat exchangers and condensers, cryogenic pipelines, and subsea transportation pipes. Manufacture of sheet metal, bars, bars, pipes, cast parts, etc. Copper in 62% ~ 68%, strong plasticity, manufacturing pressure-resistant equipment, etc. Copper is copper simple substance, because of its color is purple red and named. Copper is industrial pure copper, its melting point is 1083 ℃, no isomeric transition, the relative density is 8.9, five times that of magnesium. It is about 15% heavier than ordinary steel. It has a rose red, purple after the formation of oxide film on the surface, so it is generally called copper. It is copper containing a certain amount of oxygen, so it is also called copper containing oxygen. Brass welding method Brass welding methods are: gas welding, carbon arc welding, manual arc welding and argon arc welding. 1. Gas welding of brass Due to the low temperature of the gas welding flame, the evaporation of zinc in brass during welding is less than that during electric welding, so gas welding is the most commonly used method in brass welding. The welding wire used in brass gas welding are: wire 221, wire 222 and wire 224, etc. These welding wires contain silicon, tin, iron and other elements, which can prevent and reduce the evaporation and burning of zinc in the molten pool, which is conducive to ensuring the performance of the weld and preventing pores. Gas welding brass commonly used flux of solid powder and gas flux, gas flux by boric acid methyl ester and methanol composition; flux such as gas agent 301. 2. Manual arc welding of brass In addition to copper 227 and copper 237, self-made welding rods can also be used for welding brass. When brass arc welding, DC power source should be used for positive connection, and the electrode should be connected to the negative electrode. The surface of the weldment shall be cleaned carefully before welding. Generally, the groove angle should not be less than 60 ~ 70o. In order to improve the weld formation, the weldment should be preheated at 150~250 ℃. Short arc welding should be used during operation, not for horizontal and back and forth swing, only for linear movement, welding speed to be high. Brass weldments in contact with corrosive media such as seawater and ammonia must be annealed after welding to eliminate welding stress. 3. Manual argon arc welding of brass Brass manual argon arc welding can use standard brass welding wire: wire 221, wire 222 and wire 224, or materials with the same composition as the base metal as filling materials. Welding can be connected with DC or AC. When welding with AC, the evaporation of zinc is lighter than when DC is connected. Usually do not have to preheat before welding, only plate thickness difference is relatively large before preheating. The welding speed should be as fast as possible. After welding, the weldment should be heated to 300~400 ℃ for annealing treatment to eliminate the welding stress and prevent the weldment from cracking during use. 4. Brass carbon arc welding When brass carbon arc welding, wire 221, wire 222, wire 224 and other welding wires are selected according to the composition of the base metal, and self-made brass welding wires can also be used for welding. Welding can use gas 301, etc. as a flux. Welding should be short arc operation to reduce zinc evaporation and burning loss. red copper welding method Welding copper (commonly known as industrial pure copper) methods include gas welding, manual carbon arc welding, manual arc welding and manual argon arc welding, and automatic welding can also be used for large structures. 1. Gas welding of copper Butt joints are most commonly used for welding copper, and lap joints and T-joints are used as little as possible. Two kinds of welding wires can be used for gas welding, one is the welding wire containing deoxidizing elements, such as wire 201 and 202, and the other is the general copper wire and the cutting strip of the base metal, using the gas agent 301 as the flux. Neutral flame shall be used for gas welding of copper. 2. Manual arc welding of copper In manual arc welding, red copper electrode copper 107 is used, and the welding core is red copper (T2, T3). The edge of the welding place shall be cleaned before welding. When the thickness of the weldment is greater than 4mm, it must be preheated before welding, and the preheating temperature is generally about 400~500 ℃. With copper 107 electrode welding, the power supply should be DC reverse connection. When welding, short arc should be used, and the welding rod should not be swung laterally. The reciprocating linear motion of the welding rod can improve the forming of the weld. Long welds shall be welded by step-back method. The welding speed should be as fast as possible. During multi-layer welding, the slag between the layers must be completely removed. Welding should be carried out in a well-ventilated place to prevent copper poisoning. After welding, flat head hammer should be used to knock the weld to eliminate stress and improve the quality of the weld. 3. Manual argon arc welding of copper When red copper manual argon arc welding, the welding wire used is wire 201 (special red copper welding wire) and wire 202, and red copper wire, such as T2. Before welding, the oxide film, oil and other dirt on the welding edge of the workpiece and the surface of the welding wire must be cleaned to avoid defects such as pores and slag inclusion. Cleaning methods are mechanical cleaning and chemical cleaning method. When the thickness of the butt joint plate is less than 3mm, no groove is opened; When the plate thickness is 3~10mm, open a V-shaped groove with a groove angle of 60 ~ 70o; When the plate thickness is more than 10mm, open an X-shaped groove with a groove angle of 60 ~ 70o; In order to avoid incomplete welding, generally no blunt edge is left. According to the plate thickness and groove size, the assembly clearance of the butt joint is selected in the range of 0.5~1.5mm. Manual argon arc welding of red copper usually adopts DC positive connection, I .e. tungsten electrode is connected to negative electrode. In order to eliminate pores and ensure reliable fusion and penetration at the root of the weld, it is necessary to increase the welding speed, reduce argon consumption, and preheat the weldment. When the plate thickness is less than 3mm, the preheating temperature is 150~300 ℃; when the plate thickness is greater than 3mm, the preheating temperature is 350~500 ℃. The preheating temperature should not be too high, otherwise the mechanical properties of the welded joint will be reduced. There is also carbon arc welding of copper. The electrodes used in carbon arc welding are carbon electrodes and graphite electrodes. The welding wire used for carbon arc welding of red copper is the same as that used for gas welding. It can also be cut from the base metal and flux used for gas welding of red copper, such as gas 301, etc.

07-26

Welding defects and causes of experience sharing

2022-07-26

Welding is a key work in the construction of large-scale installation projects, and its quality and efficiency directly affect the safe operation of the project and the manufacturing period. Due to the different level of skilled workers, the welding process is uneven, and there are many defects. The types and causes of defects are sorted out to reduce or prevent the generation of welding defects and improve the quality of the project. 1. weld size is not required The welding wave is thick, the shape is uneven, the weld reinforcement height is too low or too high, and the welding wave width is different. Fillet weld unilateral or excessive sag is the weld size does not meet the requirements, the reason is: 1. The weld groove angle is improper or the assembly clearance is uneven. 2. The welding current is too large or too small, and the welding specification is improperly selected. 3. The speed of the strip is uneven, and the angle of the welding rod (or welding rod) is improper. 2. crack The shape of the crack end is sharp, the stress concentration is serious, and it has a great influence on the alternating and impact load and static tension, which is the most dangerous defect in the weld. According to the causes can be divided into cold cracks, hot cracks and reheat cracks. (Cold crack) refers to the crack produced below 200 ℃, which is closely related to hydrogen, and its main causes are: 1. It is inappropriate to select preheating temperature and slow cooling measures after welding for large and thick workpieces. 2. The selection of welding materials is not appropriate. 3. The welding joint is rigid and the process is unreasonable. 4. The weld and its vicinity produce brittle and hard tissue. 5. improper selection of welding specifications. (Hot crack) refers to the crack (mainly solidification crack) generated above 300 ℃, which is mainly caused: 1. Influence of ingredients. It is easy to appear when welding pure austenitic steel, some high nickel alloy steel and non-ferrous metals. 2. The weld contains more harmful impurity elements such as sulfur. 3. Improper selection of welding conditions and joint forms. (reheat crack) stress relief annealing crack. Refers to the high-strength welding zone, due to post-weld heat treatment or high temperature use, in the heat affected zone produced intergranular cracks, the main reason is: 1. Improper heat treatment conditions for stress relief annealing. 2. The influence of alloy composition. Elements such as chromium molybdenum vanadium boron have a tendency to increase reheat cracking. 3. Improper selection of welding materials and welding specifications. 4. Unreasonable structural design causes large stress concentration. 3. stomata During the welding process, the cavity formed in the weld metal or on the surface due to the gas not being able to escape in time is caused: 1. Welding rod, flux drying is not enough. 2. The welding process is not stable enough, the arc voltage is too high, the arc is too long, the welding speed is too fast and the current is too small. 3. The oil and rust on the surface of filler metal and base metal are not removed. 4. The arc striking point is not melted by the backward method. 5. The preheating temperature is too low. 6. The positions of arc striking and arc extinguishing are not staggered. 7. The welding zone is poorly protected and the molten pool area is too large. 8. The AC power source is prone to stomata, and the stomata tendency of DC reverse connection is the smallest. 4. weld bead During the welding process, the molten metal flows to the weld outside the unmelted base metal to form a metal tumor, which changes the cross-sectional area of the weld and is detrimental to the dynamic load. Its causes are: 1. The arc is too long and the bottom welding current is too large. 2. The current is too large during vertical welding, and the strip is not properly swung. 3. The weld assembly gap is too large. 5. crater There is obvious lack of meat and depression in the end of the weld. Its causes are: 1. The welding arc closing operation is improper, and the arc extinguishing time is too short. 2. During automatic welding, the wire feeding and the power supply are cut off at the same time, without stopping the wire first and then cutting off the power. 6. undercut After the arc melts the base metal at the edge of the weld, there is no replenishment of the weld metal and the gap is left. The undercut weakens the stress section of the joint, reduces the strength of the joint, causes stress concentration, and may cause damage at the undercut. Its causes are: 1. The current is too large, the arc is too long, the speed of the strip is improper, and the arc heat is too high. 2. Submerged arc welding voltage is too low, welding speed is too high. 3. The inclination angle of welding rod and welding wire is incorrect. 7. slag inclusion Non-metallic inclusions are present within the weld metal or at the fusion line. Slag inclusions have an effect on mechanical properties, and the degree of influence is related to the number and shape of inclusions. Its causes are: 1. Each layer of welding slag is not cleaned during multi-layer welding. 2. There is thick rust on the weldment. 3. improper physical properties of electrode skin. 4. The shape of the welding layer is poor, and the groove angle design is improper. 5. The ratio of weld width to weld depth is too small, and the undercut is too deep. 6. The current is too small, the welding speed is too fast, and the slag is too late to surface. 8. incomplete penetration There is local incomplete fusion between the base metal or between the base metal and the deposited metal. It generally exists in the weld root of single-sided welding, which is very sensitive to stress concentration and has a great influence on the performance of strength fatigue. Its causes are: 1. Poor groove design, small angle, large blunt edge and small gap. 2. The angle of welding rod and welding wire is incorrect. 3. The current is too small, the voltage is too low, the welding speed is too fast, the arc is too long, and there is magnetic bias blowing. 4. There is thick rust on the weldment and it is not cleaned up. 5. Welding deviation during submerged arc welding.

07-26

Fish scale welding VS chicken excrement welding, the perfect embodiment of welding technology

2022-07-26

What is the highest level of welding technology? Is the beauty, is the parts sexy beauty, beauty a mess! TIG Welding is a kind of welding method. Pipe to pipe is directly welded, and its welding into fish scale shape is also referred to as fish scale welding. The welding method is mainly to select the welding point, energize it, knock out the arc with the welding rod head to melt the flux in the welding rod, and then swing the welding tongs left and right to make the welding core melt evenly at the welding position. It should be called fish scale welding because the welding effect is good. Welding skills 1.TIG welding itself belongs to open arc operation, which can well observe the shape and flow of molten pool, which is much superior to electrode arc welding. Welding skills 2. Controlling the stability of the hand during welding is the biggest key to avoid shaking and burning the dock pole to cause the molten pool to clamp tungsten. The control method can only be supported on the welded pipe or plate by the index finger holding the welding gun. Tungsten pole extension length can be selected according to the depth of the break, generally 3-5mm. The wire feeding method can be selected according to the size of the break. When the break angle is small, the welding wire can be placed in the middle of the molten pool and fed continuously. When the break is large, the wire can be fed at both sides (to be quite skilled and avoid touching the dock pole), and the welding torch can be moved left and right to make the edge fuse well. Regarding the full fish scale pattern on the surface, according to the scoring standard of the examination competition, the TIG weld surplus height is generally 0~2MM, and the surface is smooth and free of undercut. A blowhole. A crack. Not fusion can be. If beauty is not good enough, then there is another extreme, that is, chicken excrement welding that people can't stop.

07-26

Introduction of the advantages of laser welding technology compared with traditional welding methods

2022-07-26

Compared with other traditional welding techniques, the main advantages of laser welding are: 1. Fast speed, large depth and small deformation. It can be welded at room temperature or under special conditions, and the welding equipment is simple. For example, a laser passes through an electromagnetic field and the beam does not shift; the laser can be welded in vacuum, air, and certain gas environments, and can be welded through glass or materials that are transparent to the beam. 3, can be welded refractory materials such as titanium, quartz, etc., and can be welded to the opposite material, the effect is good. 4. After the laser is focused, the power density is high. When welding high-power devices, the aspect ratio can reach 5:1 and the highest can reach 10:1. 5, can be micro welding. The laser beam can be focused to obtain a small spot, and can be accurately positioned, can be used in mass automation production of micro, small workpiece group welding. 6, can be welded to the inaccessible parts, the implementation of non-contact distance welding, with great flexibility. Especially in recent years, optical fiber transmission technology has been used in YAG laser processing technology, so that laser welding technology has been more widely promoted and applied. 7. The laser beam is easy to realize the beam splitting according to time and space, and can carry out multi-beam processing and multi-station processing at the same time, which provides conditions for more precise welding. However, laser welding also has some limitations: 1. The assembly precision of the weldment is required to be high, and the position of the beam on the workpiece cannot be significantly offset. This is due to the fact that the laser focused light spot is small in size and the weld is narrow, which is filled with metal materials. If the workpiece assembly accuracy or beam positioning accuracy can not meet the requirements, it is easy to cause welding defects. The cost of lasers and related systems is high, and the one-time investment is large. laser welding technology

07-25

13 true sutra to prevent welding deformation, 20 minutes to learn welding knowledge.

2022-07-25

Due to the occurrence of welding deformation is mostly due to the asymmetry of the heat generated by welding, resulting in uneven expansion. Several methods to prevent welding deformation are sorted out as follows for reference: 1. Reduce the cross-sectional area of the weld, under the premise of obtaining a complete weld with no over-standard defects, as far as possible to take a smaller groove size (angle and gap). 2. The welding method with small heat input is adopted. Such as: CO2 gas shielded welding. 3. Multi-layer welding shall be used instead of single-layer welding for thick plate welding as much as possible. 4. In the case of meeting the design requirements, the longitudinal reinforcing ribs and transverse reinforcing ribs can be welded by intermittent welding. 5. When both sides can be welded, double-sided symmetrical groove shall be adopted, and the welding sequence of neutral axis symmetry with components shall be adopted in multi-layer welding. 6. When the thickness of the T-joint plate is large, the open groove angle butt weld is adopted. 7. The angular deformation after welding is controlled by the anti-deformation method before welding. 8. The rigid fixture fixing method is used to control the deformation after welding. 9. The longitudinal shrinkage deformation of the weld is compensated by the reserved length method of the component. Such as: H-shaped longitudinal weld per meter can be reserved 0.5~0.7mm. 10. For the distortion of long members. Mainly by improving the flatness of the plate and component assembly accuracy, so that the groove angle and gap accuracy. The direction or centering of the arc is accurate, so that the angular deformation of the weld and the longitudinal deformation of the wing plate and web are consistent with the length of the component. 11. In the assembly welding or structural installation of components with more welds, a reasonable welding sequence shall be adopted. 12. When welding thin plates, the water welding method is adopted. That is, the molten pool is surrounded by a protective gas in the water, and the water nearby is completely eliminated by the gas to ensure the normal welding. With this method, the metal around the solid molten pool is cooled by water in time, and the deformation is controlled to a small extent (circulating coolant is added on the opposite side of the welding side to take away the heat generated by welding). 13. Multi-section symmetrical welding, I .e. welding one section, stopping for a while, welding to the opposite side, stopping for a while.

07-24

The highest level of welding is "fish scale welding", which is very difficult for ordinary people to do. The boss's salary can reach tens of thousands.

2022-07-24

Generally speaking, such work as electric welding is not very popular in modern times, but it has to be said that this industry is actually quite profitable, but it is not easy to learn a good welding technology. Then the editor began to enter the topic and told everyone: "The highest level of" welding "is" fish scale welding ", which is difficult for ordinary people to do, and the boss's salary is tens of thousands". There may be a lot of people do not know, welding such work is actually very affect their own body, and serious circumstances may lead to the future can not have children, of course, not all welding is hurt. Then again, we can see from the picture that this work is a very interesting welding product, which must also require very high technology, should be done for many years of welding work to have such a foundation. There may be a lot of people do not know, welding such work is actually very affect their own body, and serious circumstances may lead to the future can not have children, of course, not all welding is hurt. Then again, we can see from the picture that this work is a very interesting welding product, which must also require very high technology, should be done for many years of welding work to have such a foundation. Just like these fish scale welding products in the picture, one by one contains very superb skills and workmanship, and the salary of such welding masters is more than 10,000 yuan. Some netizens said: "The materials used are thick. If you can weld this effect with 08 materials, I will call you a teacher after ten years of argon welding experience". I want the master who welded this fish scale welding artwork to study it. May it really be possible?

07-23

The characteristics and application of brazing, the common method of metal alloy welding.

2022-07-23

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. 1. 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. 2. Solder and flux 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. According to the melting point of the solder, brazing is divided into two categories: soft brazing and brazing. (1) Soldering. The melting point of the solder is lower than 450 ℃, which is called soldering. The commonly used solder is tin-lead solder, which has good wettability and electrical conductivity, and is widely used in electronic products, electrical appliances and auto parts. The joint strength of soldering is generally 60 to 140MPa. (2) Brazing. The melting point of the brazing filler metal is higher than 450 ℃, which is called hard brazing, and the commonly used brazing filler metal is brass brazing filler metal and silver-based brazing filler metal. The joint with silver-based solder has high strength, electrical conductivity and corrosion resistance, the melting point of the solder is low, the process is good, but the price of the solder is high, and it is mostly used for welding parts with higher requirements. Brazing is mostly used for the brazing of steel and copper alloy workpieces with large forces and tools. The joint strength of brazing is 200 ~ 490MPa, Note: the contact surface of the base metal should be very clean, so use flux. The function of flux is to remove the oxide and oil impurities on the surface of the base metal and the brazing material, protect the contact surface of the brazing material and the base metal from oxidation, and increase the wettability and capillary fluidity of the brazing material. The melting point of the flux should be lower than that of the solder, and the flux residue should be less corrosive to the base metal and the joint. The flux commonly used in soldering is rosin or zinc chloride solution, and the flux commonly used in brazing is a mixture of borax, boric acid and alkaline fluoride. According to the heat source or heating method, brazing can be divided into: flame brazing, induction brazing, furnace brazing, dip brazing, resistance brazing and so on. Due to the low heating temperature during brazing, the performance of the workpiece material is less affected, and the stress deformation of the weldment is also small. However, the strength of the brazed joint is generally low and the heat resistance is poor. Brazing heating method: almost all heating heat sources can be used as brazing heat sources, and according to this will be brazed. Classification. Flame brazing: heating with gas flame, used for brazing of carbon steel, stainless steel, hard alloy, cast iron, copper and copper alloy, aluminum and aluminum alloy. Induction brazing: The use of alternating magnetic field in the parts of the induction current of resistance heat heating weldments, used for welding parts with a symmetrical shape, especially the tube shaft type of brazing. Dip brazing: the weldment is partially or entirely immersed in molten salt mixture or solder melt, and the brazing process is realized by the heat of these liquid media, which is characterized by rapid heating, uniform temperature and small deformation of the weldment. Furnace brazing: the use of resistance furnace heating weldments, resistance furnace by vacuum or the use of reducing gas or inert gas to protect the weldments. In addition, there are soldering iron brazing, resistance brazing, diffusion brazing, infrared brazing, reaction brazing, electron beam brazing, laser brazing, etc. Brazing can be used for welding carbon steel, stainless steel, high temperature alloy, aluminum, copper and other metal materials, but also can connect dissimilar metal, metal and non-metal. Suitable for welding joints with little load or working at room temperature, especially for precision, miniature and complex multi-brazed weldments.