BN型易切削钢中夹杂物的控制及对切削性能的影响

Control of inclusion in BN free cutting steel and its effect on machinability

汽车曲轴用钢42CrMo要求在不影响力学性能的前提下,具有较好的切削性。传统的钢种无法满足使用需求,通过在钢中添加B、N元素,并对钢中夹杂物进行控制,以满足性能要求。首先通过坩埚熔炼实验得到不同B、N含量的试样;其次利用FactSage软件计算出理想条件下不同B、N含量的钢液中各种夹杂物的析出量及析出温度;然后通过对试样设置不同的冷却方式和定向凝固实验,得到钢中BN夹杂物的形貌、尺寸及分布的影响因素;最后,通过切削实验研究了夹杂物对切削性能的影响因素,最终得到理想切削性能的BN型易切削钢。结果表明,尺寸较小而密度较大的BN夹杂物对钢的切削性能的改善作用更好。切削性较好的试样,其切削性能已达到与硫系易切削钢Y1215同等水平。

Automobile crankshaft steel 42CrMo, which needs good machinability and mechanical properties, couldn＇t he made with traditional methods. The excellent mechanical properties were satisfied by adding elements B and N in the steel and controlling the formation of inclusions. Firstly, the steels with different B and N contents were obtained through crucible melting experiments. Then, the precipitation temperatures and amounts of inclu- sions in molten steels with different B and N contents were calculated by FactSage software. The factors influen- cing the morphology, size and distribution of BN inclusions in the steels were obtained by using different cooling methods for the samples and directional solidification tests. Finally, BN free cutting steel which has good machin- ability was obtained by investigating the influence factors of machinability through cutting tests. The results show that fine and dispersedly distributed BN inclusions have much more good influence on machinahility than that of coarse and sparse BN inclusions in steel. The BN free cutting steel has the same machinability with the sulfur free cutting steel Y1215.