The choice of electrode structure to be welded to ensure safe and feasible use of the premise, according to the chemical composition of the welded materials, mechanical properties, thickness and joint type, welding structural characteristics, stress state, with conditions on the weld structure, performance requirements , welding technology, economic conditions and the construction of comprehensive test, the targeted selection of electrodes, if necessary, need for welding test.
â‘ consider the weld metal mechanical properties and chemical composition for ordinary structural steel, usually require the base material such as metal and weld strength, weld metal tensile strength should be used is equal to or slightly higher than the base metal electrode. For alloy steel, sometimes also called the base metal alloy composition and the same or close. In welded structures rigid, high stress joints, weld cracks easily under adverse conditions, consider choosing a low intensity than the base metal electrode. When the base material of carbon, sulfur, phosphorus and other elements at high levels, prone to weld cracking, good crack resistance should be used in basic low-hydrogen electrodes.
â‘¡ consider the performance of welded components and working conditions with the loads and impact loads on the weldment, in addition to meet the strength requirements, should primarily ensure that the weld metal has a high impact toughness and plasticity, the choice of plastic, the toughness index high low hydrogen electrode. Contact with corrosive media weldment should be based on the nature of media use and corrosion characteristics of stainless steel or other corrosion-resistant type electrode welding. In the heat, cold, wear or other special work under conditions of welded parts, should use the appropriate heat-resistant steel, cold steel, welding, or other special purpose welding rod.
â‘¢ consider the structural characteristics of welding and stress conditions on the structure of complex shape, rigidity of the Heavy welded, the welding process produces a large internal stress, easy to weld cracks, good crack resistance should be used in low-alkaline hydrogen electrode. Of discontinuity large, difficult to clean up the welding parts welding parts, should be used for rust, oxide, oil is not sensitive to the acidity of electrodes. Conditions imposed can not turn on the weldment should be used for all position welding electrode.
â‘£ consider the construction and economic conditions to meet product performance requirements in the case, should be used in electrode technology and good acidity. In small or poorly ventilated situations, should be used in acidic or low dust welding electrode. The structure of the large amount of welding work, conditions should maximize the use of high efficiency electrodes, such as iron electrodes, welding and other high-efficiency gravity, or use welding vertical down welding of the underlying class-specific electrode, in order to improve welding productivity.
â‘ different intensity level + low carbon steel alloy (or low-alloy steel + low-alloy high strength steel) generally require the strength of the weld metal or joints welded metal of not less than two kinds of minimum strength, use of metal electrodes deposited strength should be able to ensure the strength of the weld and joint strength of the lower voltage of not less than the strength of base metal, and weld metal ductility and toughness should be higher but not lower than the strength of the plastic base material of poor voltage performance. Therefore, according to the two lower levels of intensity among the selected steel electrode. However, in order to prevent weld cracks, should be a higher intensity level, poor welding of steel to determine the welding process, including welding specifications, preheating temperature and post weld heat treatment and so on.
â‘¡ + austenitic stainless steel low-alloy steel weld metal should be in accordance with the chemical composition of limited value in the selection of electrodes, generally used in higher levels of chromium and nickel, plastic and cracking of the better type austenitic steels Cr25-Ni13 electrodes, in order to avoid brittle hardened tissue caused by cracks. However, poor welding of stainless steel should be determined and the welding process specification.
â‘¢ stainless steel sheet should consider the grassroots level, stratified, transition requirements of the welding electrode selection of three different properties. Of the primary (carbon steel or low alloy steel) welding, choose the appropriate intensity level of the Carbon Steel Welding Rod; stratified direct contact with corrosive media, should use the corresponding components of austenitic stainless steel electrode. The key is the transition layer (ie, cross-stratified with the primary interface) welding, must take into account the dilution of the matrix material should be used in high chromium and nickel content, good ductility and crack resistance of austenitic steels Cr25-Ni13-type electrode.
Car manufacturers increasingly rely on laser technology for processing high-strength steel. Whether it is used for Welding Electrode, cutting or surface treatment, the economic advantages of laser processing are further reflected.
High-strength steel in the automobile industry has been more widely used, which makes the car to further reduce manufacturing costs. The reason is that the use of high-strength steel to reduce the car assembly part number of parts, thus reducing production costs, reduced vehicle weight, and ultimately makes the car's fuel consumption can be reduced.
New type of steel used has not been easy, there is no obstacle. In order to obtain high strength or ultra high strength properties, usually in the auto parts molding pressure during hardening. Austria's Graz University of Technology Institute of mold and shape "CoolTool" project is carried out research in this area. The program includes a process for hardening and tempering pressure mold processing system, which use improved technology, can be more economical for the diboride hardened alloy steel for pressure. The geometry of the cooling channel filled in the same mold as the internal network to optimize the cooling and heating capabilities, shortening the processing cycle.
Mold usually made of cast iron materials, its low cost and ease of secondary processing, but there is a low surface strength, abrasion resistance and poor, it is necessary to withstand the high load region, covered by a layer of high hardness materials, laser powder welding can complete this operation. Facts have proved that the laser powder welding is a good way to complete this process. TRUMPF Laser Systems have also been studies of this process, and developed a direct metal powder deposition equipment (DirectMetalDeposition, DMD).
In this process, the metal powder to the direction coaxial with the laser beam is fed into the laser pool in the surface, without preheating of the workpiece. Metal powder together with the matrix material to form a mixture of high-strength wear-resistant metallurgy. Compared with conventional sintering, laser powder deposition has unparalleled advantages: a small amount of heat input, increased hardness and reduced surface crack; hardness of limited distribution within the coating, the friction coefficient is good; minimal deformation of the matrix material, the residual stress in the molding will not cause cracks. And laser powder deposition can be used to automate production.
3D Laser Cutting - irreplaceable method
Trimming is a high-strength steel another challenge. Three-dimensional laser cutting for sheet metal forming the cutting edge, especially for the strength of steel up to 1500MPa, because there is no other alternative processing methods. In this case, the user does not need to cut the expensive stamping equipment and equipment investment. Because in the processing of these high-hardness materials, equipment, dies or traditional tool life will be shortened, and laser cutting will not have to consider these issues, also has installed a short time, the flexibility to replace the product or sample and so on.
TRUMPF has been used in three-dimensional laser products TruLaserCell Volkswagen Passat B Side cutting, of course, including trimming. B Side from the hot molded of high strength steel, its hardness is high but also under a lot of stress. High-strength steel side panels of the system B increased resistance to impact force, improve vehicle safety. This is despite the high cost of high-strength steel, but the car manufacturers still prefer to use reason.
Laser welding - efficiency, flexibility, economy
High-strength steel can be laser cut, can also be used for welding. Mig Electrode more efficient, more economical, but also greatly enhance the quality of welding. However, higher accuracy of laser welding and laser investment cost is also relatively high.