Study On Technique Of Laser Transition Hardening For Valve Core With 4Cr13 Stainless Steel

Having analysed synthetically the history, characteristics, interaction between the laser and material and technological procedure, it is put forward that poor technological repetition and transplantation exist when laser transition hardening technique (LTHT) is applied, especially that 4Cr13 stainless steel can not be pretreated with regular method. Therefore, it has been study on pretreatment method, prescription, effect of additive and properties of oxide film for 4Cr13 stainless steel, then the techniques of LTHT on single lane and whole surface, while strengthening mechanism is explored through analyzing the microstructure. Technological verification has also been conducted on the product simulation. Results have been achieved as follow:4Cr13 stainless steel manages to be pretreated before laser transition hardening with chromate-vitriol or dichromate. Within chromate-vitriol prescription, GW-1 additive can raise pretreatment velocity obviously and improve density, combining strength and uniform appearance, as well as stabilize the blacking chemical composition.The dense uniform black oxide film on the surface of material improves the attractive ratio to the laser energy greatly with better corrupt resistance, combining strength and wear resistance, which can totally meet the requirements of LTHT.When appropriate parameters are adopted, a uniform hardened case on ? 10mmx8mm rub part of valve core can be acquired with depth about0.62mm-0.86mm and hardness about 41.3 HRC-44HRC,which meets the perform requirements.The microstructures can be divided into three layers, with the hardening case having finer grains, high carbon martensite with dense dislocation, which can promote wear resistance and perform span.The technological parameters of LTHT can affect the characteristics of hardening case, so verification must be conducted before applying the product. Refining microstructures remarkably, yielding martensites with high carbon, proliferating dislocations greatly are the main causes of surface hardening.