12-13

The aluminum brazing material consists of a thin layer of aluminum-silicon alloy wrapped on one or both sides of the core alloy (AA3003)

2022-12-13

The aluminum brazing material consists of a thin layer of aluminum-silicon alloy coated on one or both sides of the core alloy (AA3003). The low-melting aluminum-silicon alloy melts and flows during the brazing process, and after cooling, a metallurgical bond is formed between the parts to be joined. Core alloy: NOCOLOK brazing requires the solidus temperature of the base metal not lower than 615 ℃. At the same time, because the flux has certain restrictions on the dissolution of MgO on the surface of the alloy, Mg and MgO react with the flux to form MgF2, the melting point of the flux increases, and the flux loses activity, so the content of Mg should not exceed 1% (preferably 0.5). Thus, aluminum alloys suitable for NOCOLOK brazing include commercially pure aluminum and Al-Mn alloys with low Mg content (e. g., AA3003, AA3102, AA3005, AA3105, etc.). And aluminum magnesium silicon alloy (such as AA6063, AA6951, etc.). AA3003 is a conventional alloy that can be considered for automotive heat exchangers. It can be used for all brazing methods. Note: Most aluminum alloys can be brazed, but all brazing techniques cannot be used. There are mainly protective atmosphere brazing (CAB), commonly known as NB brazing, vacuum brazing (VB). For air furnace brazing, the choice of alloy may be the same as for CAB. AA3003 is a conventional alloy that can be considered for automotive heat exchangers. It can be used for all brazing methods. In order to obtain higher strength, AA3005 alloy is used for vacuum brazing, and age-strengthened alloys AA6060, AA6063 and AA6951 can also be used for vacuum brazing. In order to make it possible to age strengthen the 6000 series alloys, the cooling rate after brazing must be very fast. In order to achieve the highest strength after aging, the cooling rate must be> 1°C/SCE in the temperature range of 400°C to 200°C. 500 series alloys can also be used for VB brazing. It is difficult to solder these alloys with flux. When the magnesium content in the alloy is high, the flux cannot remove the oxide. For NB(CAB) brazing, the Mg content is objectively limited to about 0.4%. The same is true of other magnesium-containing alloys such as the 6000 series. 1000, 2000 and 7000 series alloys are rarely used for brazing. The 000 series and the other two low alloy composition series have lower post-weld strength. When the alloy composition is high, its brazing melting point is low, failing to provide good brazing.

12-12

The brazing of aluminum can be carried out by chemical and physical methods.

2022-12-12

The following chemical and physical methods can only be used for brazing aluminum. The master-slave order of the aluminum brazing method is FB → VB → NB, and the physical reduction method VB and VAW do not require flux coating. The disadvantage of the VB method is that the reduction is not thorough enough, leaving a part of the oxide, and then strengthening the magnesium added to the aluminum in the vacuum with the reduction reaction decomposition, so that it is corrosion resistant. In addition, the medium gas of the VAW method requires the use of nitrogen with a dew point of -70°C and an oxygen content of 6-8ppm, which is difficult to achieve. And after the metal surface treatment must be carried out before painting. The other is a chemical reduction method. The biggest difference between FB method and NB method lies in the different types of flux. The FB method uses a chloride flux (ZnCl2,LiCl2) base, which not only corrodes the base material (substrate) but also causes environmental pollution and other public hazards. Therefore, subsequent cleaning operations are essential. And the surface treatment must be carried out before painting. Compared with the NB method, fluoride flux (KAlF4) is used, no cleaning is required after brazing, the corrosion resistance is strong, and no surface treatment is required during coating. Although the flux will contaminate the equipment like the FB method, the corrosion of the equipment itself is less than that of chloride (furnace age FB = 1/2 year, NB = 5-6 years). However, only the fluorine (F) in the flux reacts with the magnesium (Mg) in the base metal material (base metal) to affect the brazing quality, so the Mg content in the base metal should be below 1%. Another disadvantage is the problem of flux residue. But this method has many advantages, so NB furnace is still the mainstream in brazed heat exchanger.

12-11

NOCOLOK brazing process

2022-12-11

Brazing definition: a welding method in which a metal material with a melting point lower than that of the base metal is used as a brazing material, and the base metal is wetted with a liquid brazing material, so that the interface gap between the workpiece and the base metal is filled and diffused. When brazing, only the brazing filler metal melts, while the base metal remains solid, which requires the melting point of the brazing filler metal to be lower than the base metal, and its composition is also different. The molten solder is drawn into and held in the interstices of the base metal by wetting and capillary action, and the interdiffusion between the liquid solder and the solid base metal forms a metallurgical bond. Introduction of aluminum brazing; The brazing of aluminum began in the early 1930 s. Today, many different brazing techniques have been employed. In the brazing equipment, atmosphere furnace brazing, vacuum brazing and immersion brazing accounted for a large part. The characteristics of aluminum brazing: In order to make the brazing successful, the surface of the brazed joint must be clean, and the surface must not be oxidized at the brazing temperature. Aluminum is easily oxidized in the air and during the welding process, and the aluminum oxide (Al2O3) produced has a high melting point, is very stable, and is not easy to remove. (If the temperature exceeds 250°C, high-temperature oxides will form on the surface of aluminum, which are difficult to remove by Norlock solder.) The oxide film hinders the melting and fusion of the solder, and the oxide film accounts for a large proportion, which is difficult to surface, and is prone to defects such as slag inclusion, incomplete fusion, and incomplete penetration. The oxide film on the aluminum surface and the adsorption of a large amount of water are easy to cause pores in the weld. When welding, the oxide film on the surface should be removed. (The flux reacts with the oxide and displaces the oxide, thereby preventing the weldment from contacting the furnace air, causing the solder to melt and be drawn into the weld by capillary action.) Just as oil surface watering will form water droplets due to the effect of surface tension, the brazing filler metal on the oxide film cannot be uniformly combined with the base material (base material), so a poor brazing surface will be formed.

12-11

What is brazing?

2022-12-11

12-10

常见的Welding materials

2022-12-10

Welding materials Common Welding materials Welding materials refers to the general term of materials consumed during welding, such as welding rod, welding wire, metal powder, flux, gas, etc. The welding industry is developing rapidly and is mainly divided into argon welding, CO2 welding, oxygen cutting and electric welding. The main Welding materials of oxygen cutting are: cutting nozzle, oxygen welding torch, oxygen cutting nozzle, flux, base metal (materials by Welding), welding gloves, protective mask, etc. The main application of the industry for the metal sheet metal industry, medical equipment industry, mold making, furniture factory, bicycle moped industry, mooring industry and other industries are useful. What is the role of welding materials in the welding process Welding materials for manual arc welding-Electrodes. It consists of a core and a coating. Cord-electrode (conductive) and filler metal (composed of various alloying elements). Drug skin-high temperature melting produces a large amount of gas to protect the molten droplets from hydrogen, oxygen and nitrogen in the atmosphere, and at the same time produces a large amount of slag, which is wrapped on the surface of the molten droplets and covers the surface of the molten pool to protect (called gas-slag combined protection); Sodium and potassium compounds are added to the drug skin to stabilize the arc (these compounds have low ionization potential); some alloy elements can penetrate into the molten pool by adding the coating skin. There is also a slag removal agent in the coating skin, which makes it easy to remove the welding slag covering the weld surface. The TIG electrode is a tungsten rod, which only emits electrons but does not melt during the welding process, which plays a key role in the stability of the arc. Argon-inert gas protects the molten droplets and bath from hydrogen, oxygen and nitrogen in the atmosphere during the welding process. The filling wire is composed of various alloy elements and is the main chemical composition of the weld. (The weld composition consists of a mixture of partially melted base metal and filler metal). The various welding methods, Welding materials by the different composition of the situation, on the melting arc, they play a role in roughly these aspects. Not one by one example

12-09

Types and selection principles of solder

2022-12-09

Types and selection principles of solder 1. For workpieces or structures that bear static or general loads, electrodes with equal tensile strength and base metal are usually selected, which is the principle of equal strength. For example, welding 20, such as low carbon steel or tensile strength in the left and right steel can choose a series of welding rod. And welding, such as tensile strength in the range of steel, select a series of welding rod on the line. Some people think that the choice of high tensile strength welding rod low tensile strength of the material is good, this concept is wrong, usually high tensile strength of steel plastic indicators are poor, simply the pursuit of weld metal tensile strength, reduce its plasticity, often not necessarily beneficial. 2. Welding workpieces or structures that work in special environments, such as wear resistance, corrosion resistance, and high mechanical properties at high or low temperatures, should be selected to ensure that the performance of the deposited metal is similar to or similar to the base metal Electrode, this is the principle of equivalence. For example, when welding stainless steel, stainless steel electrode should be selected; when welding heat-resistant steel, heat-resistant steel electrode should be selected. 3. The principle of equal conditions. According to the working conditions and characteristics of the workpiece or welding structure to choose the most. For example, for welding workpieces that need to withstand dynamic load or impact load tea, low-hydrogen alkaline electrodes with high impact toughness of deposited metal should be selected. On the contrary, when welding general structure, acid electrode should be selected. Although the selection of welding rod should also consider the site power supply, site equipment conditions, economy and welding efficiency, but these are relatively secondary issues, should be decided according to the actual situation. What are welding wires, electrodes, fluxes and solders? What are they used for in welding? Hope to adopt, thank you.

12-08

What are the ways of welding?

2022-12-08

What are the ways of welding? Several Electric Welding Techniques there are several kinds of welding welding method? There are 6 kinds of welding methods, namely 1. Electrode arc welding: principle-arc welding method for welding with manual operation electrode. 2. Submerged arc welding (automatic welding): Principle-the arc burns under the flux layer. The heat generated by the arc burning between the wire and the weldment melts the wire, flux and base metal (weldment) to form a weld. 3, carbon dioxide gas shielded welding (automatic or semi-automatic welding): principle: the use of carbon dioxide as a protective gas melting electrode arc welding method. 4. MIG/MAG welding (MIG/active gas shielded welding):MIG welding principle-an arc welding method using inert gas as shielding gas and welding wire as melting electrode. 5. TIG welding (tungsten inert gas shielded welding) principle-under the protection of inert gas, the base metal and filler wire (also without filler wire) are melted by the arc generated between the tungsten electrode and the weldment to form a weld welding method. The electrode does not melt during welding. 6, the principle of plasma arc welding-with the help of water-cooled nozzle on the arc restraint effect, to obtain high energy density plasma arc welding method. What are the ways of welding? Fusion welding is a method of heating the workpiece interface to a molten state during the welding process and completing the welding without pressure. During fusion welding, the heat source will rapidly heat and melt the interface of the two workpieces to be welded to form a molten pool. molten pool... Fusion welding is a method of heating the workpiece interface to a molten state during the welding process and completing the welding without pressure. During fusion welding, the heat source will rapidly heat and melt the interface of the two workpieces to be welded to form a molten pool. The molten pool moves forward with the heat source, and after cooling, a continuous weld is formed to connect the two workpieces as a whole. In the welding process, if the atmosphere is in direct contact with the high temperature molten pool, the oxygen in the atmosphere will oxidize the metal and various alloying elements. Nitrogen and water vapor in the atmosphere enter the molten pool, and defects such as pores, slag inclusions, and cracks will be formed in the weld during the subsequent cooling process, which will deteriorate the quality and performance of the weld. In order to improve the quality of welding, people have developed a variety of protection methods. For example, gas shielded arc welding is to isolate the atmosphere with argon, carbon dioxide and other gases to protect the arc and molten pool rate during welding. Another example is that when welding steel, titanium iron powder with high oxygen affinity is added to the electrode coating for deoxidation, which can protect the beneficial elements manganese and silicon in the electrode from oxidation and enter the molten pool, and obtain high-quality weld after cooling. Pressure welding is under pressure conditions, so that the two workpieces in the solid state to achieve the combination of atoms, also known as solid-state welding. The commonly used pressure welding process is resistance butt welding. When the current passes through the connection end of the two workpieces, the temperature rises due to the large resistance. When heated to the plastic state, the connection becomes one under the action of axial pressure. The common feature of various pressure welding methods is that pressure is applied during the welding process without filling material. Most pressure welding methods such as diffusion welding, high frequency welding, cold pressure welding, etc. do not have a melting process, so there is no burning of beneficial alloy elements like fusion welding, and the problem of harmful elements invading the weld, thus simplifying the welding process and improving the welding safety and health conditions. At the same time, the heating temperature is lower than that of fusion welding and the heating time is short, so the heat affected zone is small. Many materials that are difficult to weld by fusion welding can often be welded by pressure welding to form high-quality joints with the same strength as the base metal. Brazing is the use of metal materials lower than the melting point of the workpiece as a solder, the workpiece and the solder are heated to a temperature higher than the melting point of the solder and lower than the melting point of the workpiece, and the liquid solder is used to wet the workpiece, fill the interface gap and realize the interdiffusion of atoms with the workpiece, so as to realize the welding method. The joint formed during welding that connects the two connected bodies is called a weld. Both sides of the weld will be subjected to welding heat during welding, and the organization and performance changes will occur. This area is called the heat affected zone. Due to the different Welding materials of the workpiece material and welding current during welding, overheating, embrittlement, hardening or softening may occur in the weld and heat affected zone after welding, which also reduces the performance of the weldment and deteriorates the weldability. This requires adjustment of the welding conditions, pre-heating of the weldment interface before welding, and post-weld heat treatment during welding can improve the welding quality of the weldment. In addition, welding is a local rapid heating and cooling process, the welding zone due to the restraint of the workpiece body around and can not be free expansion and contraction, after cooling in the weldment will produce welding stress and deformation. Important products need to eliminate welding stress and correct welding deformation after welding. Modern welding technology has been able to weld no internal and external defects, mechanical properties are equal to or even higher than the connected body of the weld. The mutual position of the welded body in space is called the welded joint. The strength of the joint is not only affected by the quality of the weld, but also related to its geometry, size, force and working conditions. The basic forms of joints are butt joint, lap joint, T-joint (positive junction) and angle joint. The cross-sectional shape of the butt joint weld is determined by the thickness of the welded body before welding and the groove form of the two sides. When welding thicker steel plates, in order to weld through, various shapes of grooves are made at the side so that the welding rod or welding wire can be easily fed. The groove forms include one-sided welding groove and two-sided welding groove. When selecting the groove form, in addition to ensuring penetration, factors such as convenient welding, small amount of filler metal, small welding deformation and low groove processing cost should also be considered. When two steel plates with different thicknesses are butted, in order to avoid serious stress concentration caused by rapid cross-section changes, the thicker plate edges are often gradually thinned to reach the same thickness at the two joints. Butt joints have higher static strength and fatigue strength than other joints. Welding of butt joints is often preferred for connections that work under alternating, impact loads or in low-temperature and high-pressure vessels. The pre-welding preparation of lap joints is simple, easy to assemble, and the welding deformation and residual stress are small, so it is often used on site to install joints and unimportant structures. In general, lap joints are not suitable for working under alternating loads, corrosive media, high or low temperatures, etc. The use of T-joints and corner joints is usually due to structural requirements. Fillet welds with incomplete penetration on T-joints have similar operating characteristics to fillet welds of lap joints. When the weld is perpendicular to the direction of the external force, it becomes a positive fillet weld, at which time the surface shape of the weld will cause different degrees of stress concentration. The bearing capacity of the corner joint is low, and it is generally not used alone. It is only improved when the welding is through, or when there are fillet welds inside and outside. It is mostly used at the corner of the closed structure. Welded products are lighter than rivets, castings and forgings, which can reduce weight and save energy for transportation tools. Welding of good sealing, suitable for the manufacture of various types of containers. The development of joint processing technology, so that welding and forging, casting combination, can be made into large, economical and reasonable cast welding structure and forging welding structure, economic benefits are very high. The welding process can make effective use of materials, and the welding structure can use materials with different properties in different parts, giving full play to the advantages of various materials to achieve economy and high quality. Welding has become an indispensable and increasingly important processing method in modern industry.

12-07

The update of modern welding technology is the innovation and upgrading of manufacturing process and technology

2022-12-07

What is welding Welding, also known as welding, is a manufacturing process and technique for joining metals or other thermoplastic materials such as plastics by heat, high temperature or high pressure. There are many sources of energy for modern welding, including gas flame, arc, laser, electron beam, friction and ultrasonic. In addition to being used in factories, welding can also be performed in a variety of environments, such as the field, underwater and space. No matter where, welding can bring danger to the operator, so appropriate protective measures must be taken when welding. Possible injuries caused by welding include burns, electric shock, visual impairment, inhalation of toxic gases, excessive ultraviolet radiation, etc. What is welding? Welding: Simply put, it is to connect two metal or non-metal devices after treatment. There are many methods for welding together: for example, melting both ends of the two pieces and then connecting them together; Another example is to use another The melting of the material connects the two workpieces together; There are many types of classification and equipment, for example, a brief introduction: Welding of metal pipe fittings: two welding, laser welding, electromagnetic welding, diffusion welding, etc. The equipment required for welding PCB board, semiconductor tube shell packaging, micro-assembly, microwave welding, high-power module, high-power LED, etc. includes: single vacuum reflow soldering/vacuum eutectic furnace; Vacuum reflow soldering/vacuum eutectic furnace with double bubble discharge combined with positive and negative pressure, etc. Basic knowledge of welding? 1. Fusion welding-heating the workpiece to be joined to make it partially melt to form a molten pool, which will be joined after cooling and solidification. If necessary, molten filler can be added to assist. It is a Welding processing suitable for various metals and alloys without pressure. 2, pressure welding-the welding process must apply pressure to the welding parts, which belongs to the processing of various metal materials and some metal materials. 3. Brazing-metal materials with lower melting point than the base metal are used as brazing materials, liquid brazing materials are used to wet the base metal, fill the joint gap, and diffuse with the base metal to realize the link welding parts. It is suitable for Welding processing of various materials, and also suitable for Welding processing of different metals or heterogeneous materials. There are many sources of energy for modern welding, including gas flame, arc, laser, electron beam, friction and ultrasonic. In addition to being used in factories, welding can also be performed in a variety of environments, such as the field, underwater and space. No matter where, welding can bring danger to the operator, so appropriate protective measures must be taken when welding. Possible injuries from welding include burns, electric shock, visual impairment, inhalation of toxic gases, and excessive ultraviolet radiation. Before the end of the 19th century, the only welding process was metal forging welding, which was used by blacksmiths for hundreds of years. The earliest modern welding technology appeared in the late 19th century, first arc welding and oxygen gas welding, and later resistance welding. In the early 20th century, there was a great demand for military equipment in World War I and World War II, and the corresponding cheap and reliable metal connection process was paid attention to, which promoted the development of welding technology. After the war, several modern welding techniques emerged, including the most popular manual arc welding, and automatic or semi-automatic welding techniques such as gas metal arc welding, submerged arc welding (submerged arc welding), flux cored arc welding and electroslag welding. In the second half of the 20th century, the development of welding technology was changing with each passing day, and laser welding and electron beam welding were developed. Today, welding robots are widely used in industrial production. Researchers are still deeply studying the nature of welding, continue to develop new welding methods, and further improve the quality of welding. The history of metal joining dates back thousands of years, with early welding techniques found in Bronze Age and Iron Age Europe and the Middle East. The two-river civilization of ancient Babylon thousands of years ago began to use soft brazing technology. B. C., in the manufacture of 5.4 tons of ancient India Delhi iron column, people used welding technology.

12-06

The influence of welding operation environment on welding connection

2022-12-06

Environmental factors. Environmental factors refer to the working temperature, load conditions (such as load type, mode of action, speed, etc.) and working medium of the welding structure. Welded structures are in a variety of environments. Welded structures operating at high temperatures require materials with sufficiently high high temperature strength, good chemical and structural stability, and high creep strength. The welding structure working at room temperature requires the material to have good mechanical properties in the natural environment. When the working temperature is low or subjected to impact load, special attention should be paid to the performance of the material at the lowest ambient temperature, especially the impact toughness, to prevent low temperature brittle failure. For the components bearing east load, the material is required to have good dynamic fracture toughness and shock absorption. When the working medium is corrosive, the welding area is required to have corrosion resistance. Welded structures working in a nuclear radiation environment, due to the effect of neutron radiation, will lead to an increase in the yield point of the material, a decrease in plasticity, an increase in the brittle transition temperature, a decrease in toughness, and an increase in the radiation brittleness of the material.

12-05

What is the effect of welding process on welding effect?

2022-12-05

Process factors. Process factors include welding methods used in construction, welding process specifications (such as welding heat input, preheating, welding sequence, etc.), post-weld heat treatment, etc. In the same base metal, using different welding methods and process measures, the weldability is very different. For example, aluminum and its alloys are difficult to be welded by gas welding, but good welding results can be obtained by argon arc welding. Titanium alloy for hydrogen, oxygen, N. gas welding and electrode arc welding can not be good welding, and argon arc welding or electron beam welding is easier to weld. Therefore, the development of new welding methods and new processes is an important way to improve the weldability of the process. The effect of welding method on weldability is first manifested in the energy density, temperature and heat input of the welding heat source. Secondly, it is manifested in the way to protect the molten pool and the vicinity of the joint, such as protective slag, gas protection, slag-gas joint protection, vacuum welding, etc. For high-strength steel having an overheating sensitivity, narrow-gap gas shielded welding, pulsed arc welding, plasma arc welding, or the like can be used from the viewpoint of preventing overheating. Can be used to improve its weldability. The most commonly used process measures are preheating before welding, slow cooling and post-weld heat treatment. These process measures are effective measures to prevent hardening and embrittlement of heat-affected zone, reduce welding stress and avoid hydrogen-induced cracks. Reasonable arrangement of welding sequence can also reduce stress and deformation. In principle, the workpiece to be welded should be in a state of free expansion and contraction as much as possible during the entire welding process. Post weld heat treatment can eliminate residual stress, prevent delayed cracking, and allow hydrogen to escape. In addition, the gas cutting, cold working, assembly and other processes of metal materials before welding should conform to the characteristics of the material to avoid defects such as welding cracks due to local hardening, embrittlement and stress concentration.