Technical characteristics, principle and application of laser heat treatment

Technical characteristics, principles and applications of laser heat treatment:

1. Features: high-speed heating, high-speed cooling, fine structure, high hardness and good wear resistance; residual compressive stress greater than 400kgf/mm2 can be obtained in the quenching part, which can improve fatigue performance; local selective quenching can also be performed. By controlling the size of multiple spots, it is more suitable for hardening of local areas such as pipe holes, deep grooves, micro-zones, angles and cutting edges that other heat treatment methods cannot. Laser can be transmitted over long distances, and one laser can be realized. The workbench is used at the same time, and the computer control is used to realize the control and management of the laser heat treatment process to realize the automation of the production process.

2. Principle: The penetration ability of the laser is extremely strong. When the metal surface is heated to a critical transition temperature lower than the melting point, the surface is rapidly austenitized, and then rapidly quenched and quenched, the metal surface is quickly strengthened, that is, the laser Phase change hardening. Laser heat treatment is a method of surface treatment of metal by using a high power density laser beam to achieve surface modification treatment such as phase transformation hardening and surface alloying, and to produce surface composition, structure and properties which cannot be achieved by other surface quenching. change.

3. Application: With the development of high-power CO2 lasers, various forms of surface treatment can be realized with lasers. Many key components of automobiles, such as cylinders, cylinder liners, crankshafts, camshafts, exhaust valves, valve seats, Laser heat treatment can be almost performed on rocker arms, aluminum piston ring grooves, and the like. US General Motors uses a dozen kilowatt-class CO2 lasers to partially harden the inner wall of the steering gear casing, with a daily output of 30,000 sets, which improves the efficiency by four times. China uses a high-power CO2 laser to strengthen the inner wall of the engine cylinder bore to extend the engine. The overhaul mileage is more than 150,000 kilometers; the wear resistance of the laser-heated cylinder block and cylinder liner hardened belt is greatly improved, and the unhardened belt can increase oil storage and improve lubrication performance.

The laser heat treatment equipment and laser line of the cylinder body are similar to the laser alloying process, but the difference is that no additional alloy is added, so that the metal surface melts and then cools and solidifies, thereby obtaining a fine near uniform surface structure for some eutectic alloys. An amorphous surface layer is also obtained which has excellent corrosion resistance, for example, a chromium-based surface coating on a diesel engine cast iron seat to obtain a good stainless steel surface.

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