With the rapid development of China's automobile and home appliance industry, higher requirements are put forward for the mold industry. How to improve the processing quality and service life of molds has always been a topic that people are constantly exploring. The use of surface strengthening treatment is an important way to improve the quality and service life of the mold. It is of great significance for improving the overall performance of the mold, greatly reducing the cost and giving full play to the potential of the traditional mold. Commonly used mold surface strengthening treatment processes include chemical heat treatment (such as carburizing, carbonitriding, etc.), surface coating treatment (such as surfacing, thermal spraying, EDM surface strengthening, PVD and CVD, etc.), surface processing strengthening treatment ( Such as shot peening, etc.). Most of these methods are more complicated, the processing period is longer, and there is a large deformation after processing. In recent years, with the emergence of high-power lasers and the increasingly widespread and mature application of laser processing technology in the industry, it provides a new technical approach for the strengthening of mold surfaces. 1 Laser surface strengthening treatment method There are many methods for laser surface treatment, including laser phase transformation hardening (LTH), laser surface melting treatment (LSM), laser surface coating and alloying (LSC/LSA), and laser surface chemical vapor deposition (LCVD). Laser physical vapor deposition (LPVD), laser shock (LSH) and laser amorphization, etc., which have been studied to improve the life of the mold, laser phase transformation hardening and laser surface cladding and alloying, this paper mainly discusses the use of laser Phase change hardening technology improves the mechanism and method of mold life. Laser phase transformation hardening (laser quenching) is the use of laser irradiation to the metal surface, so that the surface rapidly reaches the phase transition temperature at a high temperature rise rate to form austenite. When the laser beam leaves, the heat conduction of the metal itself occurs. Self-quenching, causing martensite transformation on the metal surface. Compared with the traditional quenching method, laser quenching is carried out in the process of rapid heat and quenching, and the temperature gradient is high, so that a special hardened structure with extremely high hardness, such as grain refinement and high dislocation density, is formed on the surface. The hardness of the quenched layer is 15% to 20% higher than that of ordinary quenching. The depth of the hardened layer can reach 0.1 to 2.5 MM, which can greatly improve the wear resistance of the mold and prolong the service life of the mold. 2 The composition of the laser enhanced processing system It consists of three parts: the first part is the laser system, which consists of the laser head, the excitation power supply, the cooling system and the cavity parameter conversion device; the second part is the beam transmission and transformation device, which guides the laser beam to the parts to be processed according to the processing requirements. At the same time, the spatial intensity distribution of the laser beam is transformed to meet the effective strengthening treatment of different force parts on the surface of the mold. After the beam is transformed, the required strengthening unit can be generated on the surface of the mold, and the multi-axis linkage numerical control system can control, fast and effectively strengthen the three-dimensional surface of the mold; the third part is the computer numerical control system. Control the multi-axis motion of the laser working head and the numerical control table, and the trajectory of the laser beam relative to the workpiece determines the shape of the strengthened strip to realize the laser strengthening treatment of the complex mold surface. 3 laser strengthening treatment process 3.1 workpiece surface pretreatment coating When the laser is determined, the ability of the metal material to absorb the laser depends mainly on its surface state. Generally, the surface of the metal material to be laser processed is mechanically processed, and the surface roughness value is small, and the reflectance can reach 80% to 90%, so that most of the laser energy is reflected off. In order to improve the absorption rate of the laser on the metal surface, the surface of the material should be surface treated (often called blackening) before the laser heat treatment, that is, the surface of the metal that needs laser treatment is coated with a coating that has high absorption capacity for the laser. . Surface pretreatment methods include phosphating, surface roughness, oxidation, spray coating, coating, and the like, among which phosphating and spraying are commonly used. Commonly used coating aggregates are graphite, carbon black, manganese phosphate, zinc phosphate, water glass, and the like. There are also direct use of carbon inks and matt paints as pretreatment coatings. For some low carbon steel materials, the surface is treated with carbon black powder, which can be carburized during laser quenching. We use the blackening solution (type 86-1) developed by Shanghai Opto-mechanical Co., Ltd., which has a simple treatment method and can be directly sprayed on the surface of the workpiece, and the laser absorption rate is over 90%. 3.2 Process parameter optimization The laser phase transformation hardening process parameters mainly include laser output power P, spot size D and scanning speed V. Under certain conditions, the depth H of the laser hardened layer has the following relationship with P, D, V: H=P/( D.V). In order to obtain the optimal process parameters, the basic method is to determine a range of process parameters based on the existing successful data, and then take three factors of P, D, and V, each taking three levels, and making an orthogonal test table on the test piece. Conduct a pilot study. Figure 2 shows the relationship between laser power and hardened layer depth at different scanning speeds for CR-MO cast iron used in automotive taillight bracket drawing die. 4 Hardened layer residual stress and wear resistance During the laser hardening process, the change of the surface structure of the metal material and the generation and disappearance of the surface temperature difference with respect to the material will inevitably generate residual stress. The magnitude and distribution of residual stress have a great influence on the practical performance of the mold, and the residual stress generated by laser hardening is distributed along the depth of the hardened layer. The wear resistance of the mold surface is related to various factors such as the microstructure, grain size, hardness and surface state of the material, and these factors are affected by the processing parameters. Therefore, the laser-enhanced process parameters directly affect the resistance of the mold. Grinding performance. Figures 6 and 7 show the effect of laser power and scanning speed on the wear resistance of 35CRMN steel. It can be seen from the figure that within a certain range, when the scanning speed is constant, the improvement of the power wear resistance is increased; when the power is constant, the improvement of the scanning speed also contributes to the improvement of the wear resistance. 5 Summary Through the laser strengthening treatment of several different mold materials, and comparison with the actual working conditions, it shows that the laser strengthening technology can greatly improve the service life of the mold, and the strengthening effect of the cold die is more obvious. For example, the punch made of T8A steel and the die made of CR12MO steel are laser hardened, the laser hardened layer is 0.15MM, the hardness is 1200HV, the service life is obviously increased, and the punching is increased from 25,000 pieces to 100,000 pieces, that is, the life is improved. 3 to 4 times. The advantages of using laser enhancement technology are: (1) It can be carried out in a specified area according to the shape characteristics and use requirements of the mold, and there is no damage to the surface quality. The laser-treated mold can be directly put into production without subsequent processing, thereby reducing the manufacturing cost of the mold. (2) Through the preparation of special laser intensification processing software, computer automatic optimization of laser processing parameters, computer simulation and processing of real-time monitoring and computer prediction of surface structure and performance after laser processing can be realized, and complex shapes of molds can be realized. And artificially intelligent surface treatment. (3) Using laser cladding and alloying techniques, alloys of arbitrary composition and corresponding microstructures can be obtained on the surface of inexpensive metal materials to obtain good comprehensive mechanical properties, improve and improve the wear resistance and corrosion resistance of the surface of materials. Heat resistance. These technologies are used in the repair and reinforcement of scrap molds and have a broad market prospect. 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