11-14

The development history of brazing and special connection technology, and the application in various fields.

2022-11-14

Brazing is one of the earliest material joining methods used by humans. Before humans began using iron, they invented brazing to join metals. Among the ancient artifacts unearthed in Egypt are tubes brazed with silver and copper solder and amulet boxes connected with gold solder. According to research, they belong to 5000 years ago and nearly 4000 years ago respectively. Remains of domestic lead water pipes with brazed connections in the ruins of Pompeii buried by a volcanic eruption in 79 AD. The composition ratio of the solder used is Sn:Pb = 1:2, similar to the solder used in modern times. Tin-lead alloy solder was also used in the early Warring States period of the 5th century BC in China, and brazing technology was also widely used in bronze carriages of Qin Shihuang's terracotta warriors. The earliest brazing in China is documented and is made by Ban Gu in the Han Dynasty. There is a sentence in "Han Shu": "Hu Tong's tears are like blind tears, and he can sweat gold and silver, which are also used by craftsmen today". In the "Ming Dynasty Science and Technology Mumbo" published in 1637 in the Song Dynasty, "Tiangong Kaiwo" recorded that "China's small drill uses white copper powder, and the big drill tries its best to hammer together". The "Knowledge of Physics" written by Fang Yizhi in the Ming Dynasty said, "The flux is a combination of borax and copper. If it is a combination of alley juice and silver, it is as solid as a rock. Today's solder such as jade handle, if add silver, never fall off. Try to spot weld the medicine on the mouth of a round basin in a corner. The medicine will go by itself and circle around. It is also amazing." The description clearly states that copper brazing should use borax as flux and silver brazing should use alley resin, and gives a wonderful description of the caulking behavior of the solder. Although brazing technology appeared relatively early, it has not been greatly developed for a long time. After entering the 20th century, its development is far behind the fusion welding technology. Until the 1930 s, on the basis of the development of metallurgical and chemical technology, brazing technology developed rapidly and gradually became an independent industrial production technology. Especially after the Second World War, due to the development of new technologies such as aviation, aerospace, nuclear energy, and electronics, the adoption of new materials and new structural forms put forward higher requirements for connection technology. Therefore, brazing technology has been paid more and more attention and developed rapidly, and many new brazing methods have emerged, and their applications have become more and more extensive. For example, brazing technology is widely used in the manufacture of cutting tools for various mechanical processes, in particular carbide cutting tools, drilling tools for drilling and mining, various conduits and containers, water tanks for automobiles and tractors, heat exchangers of different materials and structures for various applications, motor parts, blades and brackets for steam turbines, and other components. In light industrial production, from medical equipment, metal implants, musical instruments to household appliances, cooking utensils, bicycles, brazing technology is widely used. For the electronics industry and instrument manufacturing, brazing is the only feasible connection method on a large scale. For example, the production of components involves the connection of metal and ceramics, glass and other non-metals, and the wiring connection must prevent the damage to the components by heating, which all rely on brazing technology. In nuclear power plants and marine nuclear power plants, important components such as fuel element positioning frames, heat exchangers, and neutron detectors are often brazed.

11-13

Ancient and high development potential of welding technology, silver brazing introduction

2022-11-13

Brazing (including micro-joining), diffusion welding and the derived transition liquid phase diffusion welding (TLP diffusion welding) and liquid phase interface diffusion welding (LID welding) should be the main joining methods studied by our special committee I. As for the scope of special connection, there is no clear definition, such as high-temperature self-propagating synthetic connection, which belongs to the special committee I or high-energy beam and special welding special committee (Ⅵ special committee); the explosion is divided into category I, Category V or pressure welding V is reasonable. Here, I mainly want to talk about the characteristics of brazing diffusion welding, which may sometimes involve high-temperature self-propagating synthetic connection, explosive welding, etc. First of all, the heating temperature of brazing and diffusion welding is generally much lower than the melting point of the substrate, so it has little effect on the physical and chemical properties of the substrate. The entire weldment is heated evenly, the stress and deformation are small, and it is easy to ensure the dimensional accuracy of the weldment. Secondly, brazing and related special joining techniques are highly productive. Brazing can complete the connection of multiple joints and parts at once. For example, the brazing seam length of the combustion chamber of the 750N liquid rocket engine manufactured by the former Soviet Union is 750m, which can be brazed at one time. For example, the stainless steel panel/corrugated plate core thrust chamber shell of the rocket engine is connected by brazing, and hundreds of welds are brazed at a time. Diffusion welding and explosive welding can achieve large-area structural connections, such as the manufacture of large composite laminates. Third, brazing technology can be used for weldments with complex structure, high precision requirements, poor joint openness, and poor accessibility. For example, vacuum brazing technology can realize the precise brazing of multi-layer aluminum alloy radar antennas and microwave devices with complex structures. However, the working blades and guide blades of the aero-engine high-pressure turbine with complex internal cooling channels can only be connected with high quality by brazing. Fourth, brazing and related special joining techniques are particularly suitable for the combined joining of various materials. It can not only connect regular metal materials, but also other metal materials that are difficult to connect by other welding methods, as well as non-metallic materials such as ceramics, glass, graphite, and diamond. In addition, the connection of dissimilar metals, metals and non-metallic materials is also easy. Therefore, many structures or materials that are difficult or even impossible to connect by other welding methods can be solved by brazing. The self-propagating high-temperature synthesis connection is particularly suitable for the connection of new structural materials, such as the connection of ceramics and metals, and the connection of intermetallic compounds such as NiAl and TiAl. Explosive welding can be used to join almost any metal, such as metals with different melting points (such as lead and tantalum), metals with different thermal expansion coefficients (such as titanium and stainless steel), and metals with different hardness and physical and chemical properties (such as copper and titanium, copper and aluminum, Copper and molybdenum, aluminum and stainless steel, etc.).). It can also be used to join non-metals and metals (such as ceramics and steel).

11-12

According to different brazing process and temperature requirements, understand the corresponding type of silver solder paste.

2022-11-12

Silver solder paste is a uniform paste mixture of solder powder, flux and organic vehicle with a certain viscosity and thixotropy. The silver content of alloy powder is 15%, 45%, 50%, 56%, 72%, etc. No flux can be added to the silver solder paste composition; flux can be added, and flux does not need to be added separately when used. This series of solder paste is suitable for flame brazing, resistance brazing, high frequency brazing and furnace brazing of copper and copper alloys, steel and stainless steel, and can be applied to semi-automatic welding and fully automatic welding equipment. According to the needs of customers, specially allocated to meet various needs. Its main components are: (1) Fine atomization filling alloy: accurate alloy composition, composition, melting range, welding ability standard. (2) Flux: remove the oxide on the weldment and reduce the surface tension of the weldment. (3) Solder paste glue: It can provide the fluidity effect of the solder paste, ensure that the solder paste has a certain viscosity, play an anti-oxidation effect, and protect the solder. Product characteristics Compared with solid brazing materials, solder paste has the following advantages: (1) It is convenient for accurate cloth, especially suitable for welds with irregular shapes; (2) The ratio of solder to solder is accurate; (3) The feeding process is suitable for industrial automation production; (4) It can reduce welding steps, improve work efficiency and improve working environment.

11-11

What are the characteristics of ordinary low alloy steel welding?

2022-11-11

Ordinary low alloy steel is often used for replication. The main feature of this steel welding is that the heat-affected zone of the joint has a greater tendency to harden, and the hydrogen content will cause cold cracks in the joint. With the improvement of the strength grade of ordinary low alloy steel, the tendency of hardening and cold cracking is greater. 16 manganese steel welding method? 16 manganese steel welding should use alkaline welding rod such as 506 or 507,DC reverse connection. When the tendency of structural cracks is small, acid-coated electrodes can also be used, such as junction 502 or junction 503, and the welding process is similar to that of mild steel. When the weldment is rigid and the ambient temperature is lower than -10°C, heating is required before welding. Manual arc welding, submerged arc welding or electroslag welding can achieve satisfactory results. What is the welding method for 15 Mn-V and 15 Mn-Ti steel? 5 Mn-V and 15 Mn-Ti belong to 40 kg ordinary low alloy steel. Adding some vanadium or titanium can increase the strength grade of the steel. However, its weldability, Welding materials and welding process are similar to those of welded 16 manganese steel. When automatic submerged arc welding is adopted, the welding wire can weld 08 Mn high and 08 Mn 2 Si, and satisfactory results can be obtained when used in combination with flux 431, flux 350 or flux 250. 18 manganese molybdenum niobium steel welding method is what? 18 Mn-Mo-Nb steel is a 50kg high strength ordinary low alloy steel, commonly used in the manufacture of high pressure vessel, boiler drum and other important welding products. Due to its high strength and hardening tendency, local heating measures should be taken in spot welding. Pay attention to dry the electrode and clean the groove to prevent hydrogen from causing cold cracks. Manual welding adopts welding rods such as 607 junction; automatic submerged arc welding adopts 08 Mn 2 Mo high welding wire, and flux 250 or flux 350 welding can be adopted.

11-10

The welding knowledge of copper and copper alloy is clearly understood in this article.

2022-11-10

How to weld copper and copper alloy? There are many difficulties in welding copper and copper alloy, because its thermal conductivity is particularly good, so it is easy to cause defects such as incomplete penetration and poor fusion. After welding, the deformation of the workpiece will be very large, and the weld and fusion zone are prone to cracks and a large number of pores. The mechanical properties of the joint, especially the plasticity and toughness, are lower than those of the base metal. Copper can be welded by gas welding, but the efficiency is too low, the deformation is large, and it must be preheated to above 400°C, and the working conditions are not good. Manual arc welding can use copper 107 or copper 227 electrode, with DC reverse connection as the power supply, the arc is as small as possible, and the straight-line round-trip transportation is adopted to improve the weld formation. Hammer the weld after welding to improve the quality of the weld. If TIG welding is used, a high-quality welded joint can be obtained and the deformation of the weldment can be reduced. The welding wire 201 for the welding wire, such as the copper wire T2, must be matched with the flux 301. The power supply adopts DC positive connection. Welding workpieces and welding wires should be carefully cleaned to reduce porosity and slag inclusions. High current and high speed should be used for welding. Gas welding is usually used for welding brass. The welding wire 221, the welding wire 222, or the welding wire 224 may be used as the welding wire. These wires contain silicon, tin, iron and other elements, which can reduce the burning loss of zinc in the molten pool. Due to the low temperature of gas welding, the burning loss of zinc in brass can be reduced; a layer of zinc oxide film is covered on the surface of the molten pool with a mild oxidation flame, which can reduce the evaporation of zinc. In addition, brass can also be welded by manual arc welding and tungsten argon arc welding.

11-09

Sharing of welding methods for titanium and titanium alloy, aluminum and aluminum alloy

2022-11-09

How to weld aluminum and aluminum alloy? Aluminum and aluminum alloys are particularly likely to produce an oxide film having a large specific gravity and a high melting point during welding. This oxide film can also absorb a large amount of water, so it is easy to produce defects such as slag inclusion, poor fusion and pores during welding. In addition, aluminum alloys are also prone to thermal cracking. Gas welding or manual arc welding can be used to weld aluminum and aluminum alloys. The heat of gas welding is not concentrated, and the heat transfer of aluminum is very fast, so the production efficiency is low and the workpiece deformation is large, so it is rarely used except for thin plates. At present, AC argon arc welding is widely used for welding aluminum and aluminum alloys. Its advantages are concentrated heat, beautiful welds, small deformation, and argon protection to prevent slag inclusion and pores. If manual arc welding is used to weld aluminum, it is suitable for thick plates above 4mm. The electrode brands used are aluminum 109, aluminum 209 and aluminum 309. They are all salt-based electrodes with poor arc stability and require a DC inverter power supply. How to weld titanium and titanium alloy? Titanium is a very active element. In the liquid state and the solid state above 600 ℃, it is easy to react with oxygen, nitrogen, hydrogen and other gases to generate harmful impurities, making titanium embrittlement. Therefore, except for oxygen-acetylene gas welding, manual arc welding or other gas shielded welding, titanium and titanium alloys can only be welded by argon arc welding, vacuum electron beam welding and contact welding. The thin plates below 3mm shall be welded by argon arc welding, the power supply shall be connected by DC positive pole, and the purity of argon shall not be less than 99.98. The nozzle is as close to the workpiece as possible, the welding current is small, and the welding speed is fast. Generally, low temperature annealing should be carried out after welding to improve the crystal structure and eliminate the welding stress.

11-08

Welding knowledge sharing, welding process of low carbon steel or medium carbon steel

2022-11-08

Low carbon steel how to weld? Low carbon steel has low carbon content and good plasticity, and can be made into various joints and components. In the welding process, it is not easy to produce hardened tissue, crack tendency is small. At the same time, it is not easy to produce pores. It is the best Welding materials. Low carbon steel can be welded by gas welding, manual arc welding, automatic submerged arc welding, gas shielded welding and other methods, and good welded joints can be obtained. When using gas welding, do not heat for a long time, otherwise the grains in the heat-affected zone will easily become larger. When the joint stiffness is high and the ambient temperature is low, the workpiece should be preheated to 100~150 ℃ to avoid cracking. How to weld medium carbon steel? Due to the high carbon content of medium carbon steel, the weld and its heat affected zone are prone to hardening and cracking, so it should be preheated to about 300 ℃ before welding and slowly cooled after welding. Gas welding, manual arc welding and gas shielded welding can be used for welding. Welding should be used with good crack resistance, such as 506 joints and 507 joints.

11-07

Common brass welding methods, gas welding, carbon arc welding, manual arc welding and argon arc welding

2022-11-07

Brass welding methods include gas welding, carbon arc welding, manual arc welding and argon arc welding. (1) Brass gas welding Due to the low flame temperature of gas welding, 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 wires for brass gas welding are No. 221, No. 222, No. 224, etc. These wires contain silicon, tin, iron and other elements, which can prevent and reduce the evaporation and burning of zinc in the molten pool, help to ensure the performance of the weld and prevent the generation of pores. The commonly used flux for welding gas brass is solid powder and gas flux, and the gas flux is composed of methyl borate and methanol. For example, flux 301. (2) Brass manual arc welding In addition to copper 227 and copper 237, homemade welding rods can also be used for brass welding. When brass arc welding, the DC power supply should be connected to the positive pole and the electrode should be connected to the negative pole. Before welding, the surface of the weldment shall be carefully cleaned. In general, the groove angle should not be less than 60 °-70 °. In order to improve the weld formation, the weldment should be preheated 150-250 ℃. The operation should be short arc welding, no horizontal and back and forth swing, only linear motion, 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: No. 221, No. 222, No. 224, or use the same material as the base metal as the filling material. DC connection or AC connection can be used for welding. When AC welding is used, the evaporation of zinc is lighter than when DC welding is used. Usually do not need to preheat before welding, only when the thickness difference is large. The welding speed should be as fast as possible. After welding, the weldment should be heated to 300-400 ℃ for annealing treatment to eliminate welding stress and prevent the weldment from cracking during use. (4) Brass Carbon Arc Welding In the carbon arc welding process of brass, welding wire 221, welding wire 222, welding wire 224, etc. Depending on the composition of the base material, it is also possible to use a self-made brass wire for welding. A gas reagent 301 or the like may be used as a flux for soldering. Short arc welding should be used to reduce zinc evaporation and burning. DC TIG welding process is widely used in the welding of copper and copper alloys. Welding wind forming good, good quality inside and outside. Under the protection of argon, the molten pool is pure, the pores are few, the thermal cracking effect is small, and it is easy to operate. When the thickness is less than or equal to 4mm, preheating before welding is not required and can be directly preheated with argon. 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 of more than 4mm, pure copper should be preheated at 400-600 ℃. The copper alloy is preheated by welding at 200-300 ℃. 300TSP, 315TX DC TIG welding machine can weld pure copper, silicon bronze, phosphor bronze, brass, cupronickel and other copper alloys. The 300WP5 and 300/500WX4 AC/DC TIG welding machines can use AC TIG to weld aluminum bronze (use AC square wave to remove surface oxide film), and DC TIG to weld the above copper. In recent years, MIG welding of copper and copper alloys has become more and more popular, especially aluminum bronze, silicon bronze and cupronickel with a thickness of ≥ 3mm. MIG welding is almost always used for copper and copper alloys with a thickness of 3~14mm and above because of its high deposition efficiency, large penetration depth and fast welding speed (usually 3~4 times that of TIG welding), which meets the requirements of high efficiency, high quality and low cost. Before welding, all copper materials shall meet the requirements of preheating temperature (pure copper 400~600 ℃, copper alloy 200~300 ℃). The chemical composition of the welding wire is completely similar to that of the base metal, and the purity of argon is ≥ 99.98%.

11-06

Common methods of welding copper, gas welding, arc welding, brazing, etc.

2022-11-06

Copper welding methods include gas welding, manual carbon arc welding, manual arc welding and manual argon arc welding. Automatic welding is also available for large structures. (1) The most commonly used method of copper gas welding is butt joint, and overlap and T-joint are used as little as possible. Two kinds of welding wires can be used for gas welding, one is welding wires containing deoxidizing elements, such as welding wire 201 and 202; the other is ordinary cutting of copper wire and base metal, using gas agent 301 as a flux. Neutral flame shall be used when welding copper. (2) red copper manual arc welding edge. 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 ℃. The welding adopts copper 107 electrode, and the power supply adopts DC reverse connection. When welding, short arc should be used, and the welding rod should not swing laterally. Reciprocating linear motion of the electrode can improve weld formation. Long welds shall be welded with a gradual retreat. The welding speed should be as fast as possible. For multi-layer welding, the interlayer slag must be thoroughly removed. Welding should be done in a well-ventilated place to prevent copper poisoning. After welding, a flat head hammer should be used to strike the weld to eliminate stress and improve the quality of the weld. (3) red copper manual argon arc welding In the manual argon arc welding of red copper, 201 wire (special red copper wire) and 202 wire are used, and T2 and other red copper wires are also used. 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 inclusions. Cleaning methods include mechanical cleaning and chemical cleaning. When the thickness of the butt plate is less than 3mm, no groove shall be opened; When the thickness of the plate is 3-10mm, a V-shaped groove is formed, and the angle of the groove is 60-70 degrees; When the thickness of the plate is greater than 10mm, open an X-shaped groove with an 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 within the range of 0.5~1.5mm. Manual argon arc welding of copper usually uses DC positive connection, that is, the tungsten electrode is connected to the 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 thickness of the plate is less than 3mm, the preheating temperature is 150-300 ℃; when the thickness of the plate is greater than 3mm, the preheating temperature is 350-500 ℃. The preheating temperature should not be too high, otherwise it will reduce the mechanical properties of the welded joint. And carbon arc welding of copper. Carbon arc welding uses carbon electrodes and graphite electrodes. The welding wire used for copper carbon arc welding is the same as the welding wire used for gas welding, and the base metal can also be cut. The gas welding flux of copper, such as gas agent 301, can be used.

11-05

Different welding methods and performance characteristics of copper-copper alloy

2022-11-05

Copper-copper alloys can be joined by processes such as brazing, resistance welding, etc. With the development of industry, the welding application of copper is more and more frequent, and the welding method has occupied a dominant position. Copper and copper alloys are easily welded by electrode arc welding, TIG welding and MIG welding. Copper has excellent electrical conductivity, thermal conductivity, corrosion resistance, ductility and certain strength. Widely used in electrical, electronics, chemical, food, electricity, transportation and aerospace industries. More than 10 kinds of alloying elements are added to pure copper (copper) to form various copper alloys with solid solutions, such as adding zinc to brass; Nickel is added in the form of white copper; Silicon is added to silicon bronze; Aluminum is aluminum bronze and so on. There are four main technical difficulties affecting the weldability of copper and copper alloys: first, the effect of high thermal conductivity. The thermal conductivity of copper is 7-11 times higher 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. Two is the welding joint hot cracking tendency. During welding, copper and impurities in the molten pool form a low melting point eutectic, which makes copper and copper alloys have obvious thermal brittleness, resulting in thermal cracking. Third, the defects that produce pores are much more serious than carbon steel, mainly hydrogen pores. Fourth, the change of welded joint performance. Grain coarsening, plasticity reduction, corrosion resistance reduction, etc.