What are the technical requirements for laser quenching?

Laser quenching is a quenching technology that uses laser to heat the surface of the material above the phase transition point, and with the cooling of the material itself, austenite transforms into martensite, thus hardening the surface of the material. The tooth surface is quenched by laser, which has the unique advantages of fast heating and cooling speed, short process cycle, no need for additional quenching medium, small workpiece deformation, clean working environment, no need for finishing such as grinding teeth after treatment, and the size of the treated gear is not limited by the size of heat treatment equipment.

1, quality advantage

Laser quenching is a clean and rapid quenching process with high power density and fast cooling speed, and it does not need cooling media such as water and oil. Compared with induction quenching, flame quenching and carburizing quenching, laser quenching has the advantages of uniform hardened layer, high hardness (generally higher than induction quenching 1-3HRC), small deformation of workpiece, easy control of heating layer depth and heating trajectory, easy automation, no need to design corresponding induction coils according to different parts sizes like induction quenching, and no limitation of furnace size in chemical heat treatment processes such as carburizing quenching for large parts, so it is being applied in many fields. It is particularly important that the deformation of the workpiece before and after laser quenching can be almost ignored, so it is especially suitable for surface treatment of parts with high precision requirements.

2. Technical characteristics

According to the composition, size and shape of the parts and laser process parameters, the depth of laser hardened layer is generally in the range of 0.3 ~ 2.0 mm. The surface roughness of gear tooth surface and journal of large shaft parts is basically unchanged after quenching, which can meet the needs of actual working conditions without subsequent processing.

Laser melting quenching technology is a technological process in which the surface of the substrate is heated to above the melting temperature by using a laser beam, and the surface of the molten layer is rapidly cooled, solidified and crystallized due to heat conduction and cooling inside the substrate. The obtained melt hardening structure is very dense, and the structure along the depth direction is melt solidification layer, phase transformation hardening layer, heat affected zone and substrate in turn. Laser melting layer has deeper hardening depth, higher hardness and better wear resistance than laser quenching layer. The disadvantage of this technology is that it destroys the roughness of the workpiece surface to a certain extent, and generally needs subsequent mechanical processing to restore it. In order to reduce the surface roughness of parts after laser melting treatment and reduce the amount of subsequent processing, Huazhong University of Science and Technology has developed a special laser melting quenching coating, which can greatly reduce the surface roughness of the fused layer. At present, the surface roughness of various materials in metallurgical industry, such as rollers and guide rails, is close to the level of laser quenching.

3. Applicable materials

Laser quenching has been successfully applied to the surface strengthening of vulnerable parts in metallurgy, machinery, petrochemical industry and other industries, especially in improving the service life of vulnerable parts such as rollers, guide rails, gears and shearing machines, with remarkable effects and huge economic and social benefits. In recent years, it has been more and more widely used in surface strengthening of die, gear and other parts.