As an emerging metal processing technology, laser welding technology can realize the welding processing of various metal materials, and has a wide range of applications in the metal processing industry. Laser welding technology through the laser reaction principle to gather high energy density laser beam, with fast speed, high accuracy, has been in the precision metal processing enterprises more applications. In order to speed up the innovative development of commercial air conditioning, our company has introduced laser welding, which provides a new way for the processing and manufacturing of sheet metal parts for commercial air conditioning, and further enhances the competitiveness of product quality.
Background of laser welding
At present, the air-conditioning industry generally use gas shielded welding, arc welding, reaction welding and other welding methods to achieve the sealing of sheet metal parts of the combination, but due to the above welding methods have the energy output dispersion, diffusion and other characteristics, there are generally poor quality of weld seams, high labor intensity of the personnel, the poor operating environment and other issues, and accompanied by weld splash, need to undergo the latter part of the process of grinding and smoothing, resulting in an increase in the cost of sustained welding, is not conducive to long-term development and technological innovation of enterprises. Long-term development and technological innovation.
Experimental research on laser welding
The pilot study of laser welding in our company started in the electronic control box parts, the purpose is to replace the traditional CO2 gas shielded welding through the application of laser welding. The raw material of the electronic control box parts is hot galvanized sheet, generally between 1.0 and 3.0mm thickness, mainly considering the shape of such electronic control box parts is more regular, the weld is a spatial straight line distribution state. As a key parameter for welding quality prediction, weld depth determines the quality of the final weld. If the weld depth is too large, it may lead to the parts being welded through, increasing the additional operations such as secondary repair welding, and involving gas-tight and water-sealed parts, the quality of repair welding is extremely high; if the weld depth is too small, it may lead to too large a weld height, increasing the workload of the post-process grinding. Therefore, for the relationship between weld depth and welding speed, laser power, in the experimental study is often used to control the variable method, in different power of laser welding. Of course, the first to carry out this type of electronic control box parts of the laser welding test, but also taking into account the demand for larger batches, can be fully prepared for the late automation of laser welding technology.
Practical applications of laser welding
Commercial water tray parts in the application
Catch tray parts as a commercial water-cooled unit of key parts, its welding sealing is particularly important, the parts are mainly used for water-cooled unit circulating wastewater collection, the shell to withstand the water pressure, and need to meet the corrosion requirements, often using stainless steel materials as raw materials.
Compared with the traditional carbon steel materials, stainless steel materials, high resistivity, thermal expansion coefficient is large, combined with the welding metallurgical characteristics of the material, the current manufacturing of commercial water catchment tray parts more than resistance spot welding process plus arc welding process mode, but there are certain problems and shortcomings, mainly manifested as follows: resistance spot welding can effectively reduce the welding deformation of the parts of the catchment tray, but there are obvious indentation at the weld joints, weld joints in large numbers, affecting the quality and consistency of the parts, increasing the quality of the later stages. The consistency of the quality of the parts, increasing the workload of the later grinding process. And resistance spot welding is a discrete independent point connection form, spot welding process of the water tray parts structure sealing is poor. Although manual arc welding can achieve continuous sealing welding, as shown in Figure 4, but the stainless steel arc welding deformation, a large number of arc welding will cause thermal deformation of the parts of the catch pan, affecting the position of the lowest point of the whole part, resulting in the parts of the long time to store the water, is not conducive to the long-term stable operation of water-cooled units.
The use of laser welding on the bending articulation edge of the residual seam requirements are higher, the general 1500W laser requires a weld width of 2.5mm or less, if the weld is too wide, there may be weld penetration, empty weld, deformation and other phenomena, and the requirement of the entire weld parallelism to maintain the basic consistency; Otherwise, there will be filler instability, resulting in a small gap of a section of the weld height of the large, intermediate section just to meet the requirements, while the gap large end of the empty. The gap is large at one end of the empty weld, seriously affecting the quality of the parts, the second replenishment needs to be carried out manually, which reduces the production efficiency.
Laser welding is also conducive to reducing or eliminating the workload of post-process grinding, through the appropriate welding parameter settings, you can reduce the weld height, and even achieve a flatness of 0.1mm, which is simply a blessing for stainless steel grinding. As the hardness and strength of 304 stainless steel material for the ordinary galvanized plate more than 5 times, so grinding consumption of grinding discs and workload has increased greatly, grinding a weld height of 1.2mm, the length of 100mm stainless steel weld an average of 5min, continuous grinding work not only increases the labor intensity of the operator, but also improve the production cost of the product, which is not optimistic about the development of the enterprise. Not optimistic.
In order to change the existing process, through exchanges and cooperation with advanced laser equipment manufacturers at home and abroad, the development of six-axis industrial robots, automatic laser welding torch and wire feed control system, flexible fixture workbench integrated programmable teaching laser automatic welding program, the program through the design of flexible fixtures, different series of parts for rapid clamping and positioning, and synchronization to achieve rapid switching of parts. Through the handheld robot end torch, the welding path for teaching, so can greatly reduce the difficulty of automated welding operations, reduce the investment of professional welding operators.
The current use of six-axis robot laser welding system welding water catch pan parts, its welding power of 1500W, the average welding speed of 1.4m/min, the entire clamping and positioning spend 5min, manual teach programming spend 10min, welding process 2min, other adjustments took 8min, a single water catch pan parts initial welding took 25min, due to the reweld The parts do not need to teach and other adjustments, so the average time for mass production of a single water dish parts for 7min, and the after-process without grinding, without professional welding operators, the entire process of processing costs reduced by more than 25%.
Application of commercial support frame parts
As a commercial machine structure skeleton, support frame class parts with more, the design structure of such parts for the long box, is conducive to the assembly and load-bearing, due to this type of parts in the box mainly play a role in supporting the framework, it does not directly contact with the external environment, so the corrosion resistance requirements are not high, the general use of hot galvanized sheet thickness of 4.0mm as raw materials, galvanized sheet of galvanized sheet of galvanized sheet not only has a physical shielding effect, but also on the steel substrate also plays a role in the corrosion resistance of the steel substrate. And the steel matrix also plays a role in electrochemical protection, is a cost-effective steel materials.
However, the presence of the galvanized layer in the galvanized steel sheet adversely affects the welding process and the quality of the support parts. The reason is that during the welding process of galvanized steel, the great difference between the physical properties of the zinc plating layer and the base carbon steel (the melting point of the zinc plating layer is 420℃ and the boiling point is 908℃, while the melting point of the base steel is 1300℃ and the boiling point is 2861℃), so the vaporization of the zinc plating layer is prior to the melting of the base steel, and this phenomenon has a great impact on the welding process and weld quality of the galvanized steel plate.
At present, the factory for the support frame parts of the main welding process resistance spot welding, arc welding and laser welding three. For resistance spot welding, due to the existence of galvanized layer, the electrode is easy to alloy with the zinc layer during welding, which accelerates the oxidation process of the copper electrode surface, and the operator needs to polish the electrode head constantly, thus reducing the service life of the copper electrode. The use of manual arc welding, due to the low boiling point of zinc, in the arc just touching the galvanized layer, zinc quickly vaporized, resulting in zinc vapor sprayed outward, it is easy to weld slag particles, pores, spatter, resulting in a large difference in the flatness of the weld surface, increasing the workload of the post-process grinding, and for the need to ensure the airtightness of the waterproof parts have a major quality risk. Manual arc welding parts weld there is a more obvious phenomenon of zinc layer volatilization, especially near the middle and back end of the larger melt pool spray phenomenon, resulting in weld tumor, porosity and other quality problems.
The application of laser welding not only improves the strength and stiffness of the weld, but also solves the problems of large welding distortion, low flatness of weld joints, easy to produce gaps, and reduced strength of the base material when welding galvanized steel and high-strength steel plates with traditional resistance spot welding. Commercial support frame parts in the use of laser welding process, because the laser can be a greater energy density in the small gap to penetrate the weld, so that the weld in the form of intermittent welding, from the mechanical properties of the test data, the use of laser welding after the strength of the weld can be compared with the resistance spot welding to enhance the 30% or so.
At present, our company is gradually carrying out the innovation application of laser welding in the way of experimental research, from the electronic control box to the water catching tray, support frame and other different materials, different types of parts for experimental application, to achieve the parts of the cost reduction, quality improvement goals. The development of laser welding application of our company can not be separated from the hardware and software technical support of advanced laser welding equipment manufacturers at home and abroad, and in the future will continue to maintain exchanges and cooperation with external excellent manufacturers, to achieve win-win enterprise development.
