4Cr10Si2Mo钢气门杆表面麻坑分析

Analysis of surface pockmarks on the rod of gas valves of 4Cr10Si2Mo steel

4Cr10Si2Mo钢气门杆部在精磨后经常会出现"麻坑"。通过低倍检测、显微组织观察、SEM能谱分析等手段对"麻坑"产生的原因进行了研究。结果表明,其产生的原因与Si、Al、Ca形成的脆性夹杂物有关,在金属塑性变形及冷、热加工过程中,由于受到拉应力作用,脆性夹杂物碎裂后脱落而造成。为了防止"麻坑"的产生,必须提高气阀钢冶金质量,严格控制气门原材料表面质量及夹杂物的数量、大小、分布、形态。

Surface pockmarks on the rod of gas valve of 4Cr10Si2Mo steel frequently occur after accurate grinding. Many means such as macroscopic examination, metallographic analysis and SEM energy spectrum analysis, were used to analyze the causes of pockmarks. The results show that the reason of pockmarks is significantly related to nonmetallic inclusions of Si, Al and Ca. During metal plastic deformation, for example cold-forming, hot-forming,brittle nonmetallic inclusions pull off the surface of the rod after disintegration under tensile stress and form the pockmarks. Many effective measures can be adopted to prevent the production of pockmarks, such as, improvement of the metallurgical quality of valve steel and the surface quality of gas valve, and strictly controlling the quantity, size, shape and distribution of the inclusions of the steel.