Welding in modern industrial production, has become an important method of metal processing technology, widely used in shipbuilding, aviation, aerospace, automotive and machinery manufacturing, and many other modern industrial sector, with the scientific and technological development, dissimilar metal faster development of welding technology, and quality requirements have become more sophisticated. In order to meet the needs of welding technology, welding of dissimilar metal welding technology has become a growing trend in the field [1].
1 Research of welding dissimilar metals
1.1 Dissimilar metal welding steel aluminum Research
In recent years, more and more attention to environmental issues, the automotive industry in order to save fuel, protect the environment, continued efforts to reduce vehicle weight, so the car with a higher material requirements. Increased use of aluminum is one of the important measures, so in the automotive industry production, the use of "steel + aluminum" double welded metal of choice for automotive lightweight program, which necessarily involves the two materials, aluminum and steel inter-connection.
Currently, aluminum and steel connections used welding methods are: pressure welding (roll welding and explosion welding, friction welding, friction stir welding), brazing, welding, diffusion welding, arc welding, laser welding and magnetic pulse welding, etc. [2].
Between aluminum steel welding, welding area has been difficult and hot issues, including the formation of brittle intermetallic compounds are the main factors affecting joint performance. Since pressure Welding Electrode Suppliers and brazing the substrate can be maintained in the solid state welding process, while easy to control heat input, so the performance of joint intermetallic compounds generally are not limited to the thickness, better suited to the welding between aluminum and steel, but the welding inefficient method, the size and shape of the workpiece have special requirements, not suitable for mass production. The welding method more flexible, more efficient, but intermetallic compounds has become an inevitable additional product. Although the method of combining the use of molten solder has obtained good results, but the growth kinetics of intermetallic compounds and how to promote the wetting of Al alloy melt the steel surface and so no systematic studies to address these issues for the promotion of efficient welding aluminum and steel welding method in the application of great significance [3].
Copper-steel dissimilar metal welding 1.2 Research
With the rapid economic development and scientific and technological advances, new materials, new processes, new equipment continue to emerge, the parts of a higher performance requirements. With steel and copper composite parts, due to the performance and economic strengths, and has broad application prospects.
Researchers around the world for copper and steel welding carried out experimental and theoretical analysis of the commonly used welding methods are welding, pressure welding, brazing and welding - brazing [4].
Each method has its own characteristics and applications. One cold metal transfer welding is a relatively new welding method, a bright future. In the copper - steel welded joints with the mechanism of research, mostly focused on the bronze and steel welded joints organization, for copper and steel welding require further study [5].
1.3 dissimilar metal welding titanium Research
With the welding of steel and titanium and titanium alloy welding, weld produced TiFe, TiFe2 and TiC brittle compounds, prone to cracking after welding, it is generally not used welding methods (refer to electrode arc welding, submerged arc welding and CO2 gas shielded arc welding .) In the welding production, the use of vacuum diffusion welding, vacuum electron beam welding, brazing and welding methods such as availability of good steel and titanium and titanium alloy welded joints
Titanium and high strength steel is widely used in aerospace, space technology, nuclear energy, ships and other important areas of weapons materials, titanium and stainless steel can be used to connect the vacuum brazing, diffusion welding, friction welding and other methods to obtain performance good joints. There is an aviation parts and TC4 titanium alloy steel 42CrMo connection between the use of diffusion bonding and brazing method to obtain high-quality connectors.
Spacecraft propulsion system in a large number of dissimilar metal pipe structure with a titanium and stainless steel, they are still mechanical connection between the sealant resin plus a combination of methods for connecting, sealing of low, joint performance is poor, and the sealing material once the invasion of catheter within the structure, will lead to serious consequences. High frequency induction brazing method, to obtain high sealing performance, high mechanical properties of brazed joints to eliminate the impurities in the possibility of invasive ductal structures, and can greatly enhance the success of a connection and productivity [7].
1.4 Mg / Al dissimilar metal Stainless Steel Welding Electrodes Research
Current research and development of magnesium alloy materials should focus on enhancing the strength, ductility, toughness, resistance to corrosion and fatigue properties to carry out comprehensive, new alloy development through the introduction of new alloying elements, the new anti-corrosion treatment process and other ways to achieve . In addition to equipment, development of magnesium alloys, alloy development, melting, the magnesium alloy research is a key issue of magnesium alloy and other metals welding problems. Mg and Al oxide film formed on the surface easily (MgO, Al2O3), commonly used in the welding process is difficult to get a good welded joints, and in the weld can easily form a large number of Mg-Al system brittle intermetallic compounds. Therefore, the use of advanced methods of connecting Mg / Al dissimilar metal welding is the field of non-ferrous metal welding topics at the forefront.
Mg / Al dissimilar metal welding research is currently focused on the welding method selection, welding parameters, filler material and the welded joint and several aspects of organizational performance. Welding methods currently used mainly welding and solid-phase welding, for example, TIG welding, electron beam welding, friction stir welding, resistance spot welding and diffusion welding and so on.
Mg, Al belong to the light non-ferrous metal materials, widely used in aerospace, automotive, electronics and other high-tech fields, Mg and Al welding problem is as practical engineering materials must involve a problem. The current study, binding easy to form a joint high-hardness brittle phase Mg-Al system, it will seriously reduce the joint organization of plastic, so the base material and welding method selected will become the focus of Mg and Al welding. Further development of Mg and Al welding process and fundamental research, the promotion of Mg / Al dissimilar metal welded joints have important applications [8].
1.5 Ti / Al dissimilar metal welding Research
Can be used to melt aluminum and titanium alloy brazing, vacuum brazing, high-frequency induction brazing, friction welding, diffusion bonding and superplastic forming / diffusion bonding and other methods to connect, aluminum and titanium alloys are easily oxidized metal, mutual solubility is very small, high inspiratory large, easy to form brittle compounds the problem, so there is still some connection difficulties. Melting brazing methods and the connection between aluminum and steel are similar by connector type restrictions. Friction welding aluminum and aluminum alloy as a middle layer needs to be added, can get very good shaping of welded joints. Diffusion bonding method requires the application of aluminum and titanium alloys formed between the wedge-shaped groove, deformation and diffusion through the aluminum to form joints. Between aluminum and stainless steel with the same brazing, vacuum brazing method as welding a long time, prone to intermetallic compounds, which affect the joint performance, it is best to Ni and then plated in titanium welding, can be a good joint performance. High frequency induction brazing method, the heating time is very short, had a chance to produce intermetallic compounds, and thus to obtain the mechanical properties and sealing properties are very good connection.