Laser hardening is a technology that uses a high-energy laser beam to scan a workpiece to harden the surface of the scanned area. The basic principle is to irradiate the workpiece with a laser of a certain energy density (103~105W/cm2) so that the irradiated surface area is rapidly heated to a temperature above the phase transition point and below the melting point. At this time, the workpiece matrix is still in a cold state and the heating There is a large temperature gradient between the zone and the substrate. When the laser beam stops irradiating, due to the effect of heat conduction, the heating zone will cool rapidly (106~108℃/s) and martensitic transformation will occur, causing the surface layer of the workpiece to achieve phase transformation. hardening.
(1) Laser quenching is rapid heating and self-induced cooling. It does not require furnace insulation and coolant quenching. It is a pollution-free, green, and environmentally friendly heat treatment process that can easily quench the surface of large molds uniformly.
(2) Due to the fast laser heating speed, small heat-affected zone, and surface scanning heating and quenching, that is, instantaneous local heating and quenching, the deformation of the processed mold is very small.
(3) Because the laser beam has a small divergence angle and good directivity, it can accurately locally quench the mold surface through the light guide system.
(4) The depth of the hardened layer of laser quenching is generally 0.3~0.7mm.
Laser quenching technology is a process that uses a focused laser beam to rapidly heat the surface of steel materials, causing it to undergo phase transformation and form a martensite quenching layer. Laser quenching has high power density and fast cooling speed. It does not require cooling media such as water or oil. It is a clean and fast quenching process. Next, the editor will introduce to you the application of laser quenching technology. Compared with induction quenching, flame quenching, and carburizing quenching processes, laser quenching has a uniform hardened layer, high hardness (generally 1-3 HRC higher than induction quenching), small deformation of the workpiece, easy control of the heating layer depth and heating trajectory, and easy automation, there is no need to design corresponding induction coils according to different part sizes like induction quenching, and the processing of large parts does not need to be limited by the size of the furnace during chemical heat treatments such as carburizing and quenching. Therefore, in many industrial fields, it is gradually replacing induction. Traditional processes such as quenching and chemical heat treatment. What is particularly important is that the deformation of the workpiece before and after laser quenching is almost negligible. Therefore, it is particularly suitable for surface treatment of parts with high precision requirements. The depth of the laser-hardened layer depends on the component composition, size and shape, and laser process parameters, and is generally in the range of 0.3-2.0mm. By quenching the tooth surfaces of large gears and the journals of large shaft parts, the surface roughness remains basically unchanged and can meet the needs of actual working conditions without subsequent machining. Laser melting and quenching technology is a process that uses a laser beam to heat the surface of the substrate above the melting temperature. Due to the heat conduction cooling inside the substrate, the surface of the molten layer is rapidly cooled and solidified. The obtained melting and quenching structure is very dense, and the structure along the depth direction is the melting-solidification layer, the phase change hardening layer, the heat-affected zone, and the base material. The laser melting layer has a deeper hardening depth, higher hardness, and better wear resistance than the laser quenching layer. The disadvantage of this technology is that the roughness of the workpiece surface is damaged to a certain extent, and subsequent mechanical processing is generally required to restore it. In order to reduce the surface roughness of parts after laser melting treatment and reduce the amount of subsequent processing, special laser melting and quenching coatings can be formulated to greatly reduce the surface roughness of the melted layer. The surface roughness of rolls and other workpieces of various materials in the metallurgical industry that are currently undergoing laser melting treatment is close to the level of laser quenching.
Laser quenching is mainly used to treat iron-based materials. Its basic mechanism is to scan the surface of the workpiece with a high-energy laser beam. The surface material of the workpiece absorbs the laser radiation energy and converts it into heat energy. Then, through heat conduction, the temperature of the surrounding material increases at an extremely fast rate. Above the austenite phase transformation and below the melting point, through the self-cooling effect of the material matrix, the heated surface material is rapidly cooled at a rate exceeding the critical cooling rate of martensite phase transformation, and then phase transformation hardening is completed. Because of the large degree of superheating and undercooling during the laser quenching process, the grains of the hardened layer are extremely fine, the dislocation density is extremely high, and stress is formed on the surface, which can greatly improve the wear resistance, fatigue resistance, corrosion resistance, and corrosion resistance of the workpiece. Anti-oxidation and other functions extend the service life of the workpiece. Laser quenching has been successfully applied to the surface strengthening of wearing parts in the metallurgical industry, machinery industry, and petrochemical industry. Especially in improving the service life of wearing parts such as rollers, guides, gears, and scissors, the effect is remarkable and achievements have been made. It has achieved great economic and social benefits. In recent years, it has also been increasingly widely used in surface strengthening of parts such as molds and gears. Laser quenching technology is a process that uses a focused laser beam to rapidly heat the surface of steel materials, causing it to undergo phase transformation and form a martensite quenching layer.
