钒钛生铁提高Cr-Cu-Mo可淬硬铸铁凸轮轴强度和硬度的机理  

Mechanism of V-Ti Pig Iron Increasing Strength and Hardness of Quenchable Cast Iron Camshaft

作　　者：沈保罗[1] 李莉 岳昌林 徐家富 曾勇 白维军 黄勇兵 

机构地区：[1]四川大学材料科学与工程学院,四川成都610064 [2]成都金顶凸轮轴铸造有限公司,四川郫县611732 [3]镇江中船瓦锡兰螺旋桨有限公司,江苏镇江212011

出　　处：《现代铸铁》2007年第3期59-63,共5页Modern Cast Iron

摘　　要：研究钒钛生铁和球铁生铁对Cr-Cu-Mo可淬硬铸铁凸轮轴显微组织和性能的影响,讨论了D型石墨的形成机理以及D型石墨灰铸铁凸轮轴具有较高强度和较高硬度的原因。研究表明,采用74%钒钛生铁+26%球铁生铁生产的凸轮轴的显微组织由95%以上的珠光体和少量渗碳体组成,石墨形态为D型,凸轮轴的本体铸态抗拉强度和硬度分别为302～327MPa和248～263HB;全部采用球铁生铁生产的凸轮轴的显微组织也由95%以上的珠光体和少量渗碳体组成,石墨形态为较粗大的A型,凸轮轴的本体铸态抗拉强度和硬度分别为202～238MPa和220～237HB;采用77%球铁生铁+23%钒钛生铁时,凸轮轴的显微组织仍然由95%以上的珠光体和少量渗碳体组成,石墨形态为较细小的A型,凸轮轴的本体铸态硬度和抗拉强度分别为237～273HB和241～250MPa。扫描电镜分析发现,含钛D型石墨灰铸铁的显微组织中有20%～30%的初生奥氏体,这些初生奥氏体与一般的D型石墨灰铸铁中的初生奥氏体不一样,它们在随后的固态相变过程中全部转变成了片间距约为100nm的珠光体。这种不含石墨的珠光体的强度和硬度(高于346HV)都较高,因而是含钛D型石墨灰铸铁具有较高强度的原因。Investigation showed that when 74% V -Ti containing pig iron plus 26% N.I. pig iron （ a sort of pig iron produced specially for nodular iron production） was utilized as the melting metallic charge, the microstructure of the alloyed cast iron camshaft consisted of more than 95% pearlite, a little amount of cementite and the type-D graphite, and the tensile strength and hardness in the base （chill-free） part of the camshaft were of 302-327 MPa and 248-263 HB, respectively; when the metallic charge was of 100% N.I.pig iron, the matrix consisted of more than 95% pearlite and a little amount of cementite also, whereas the graphite was of larger type-A, and the tensile strength and the hardness were of 202-238 MPa and 220-237 HB, respectively; when the metallic charge was 23% V-Ti pig iron plus 77% N.I. pig iron, the matrix consisted of more 95% of pearlite and a little amount of cementite also, whereas graphite is of smaller type-A , and the tensile strength and the hardness were of 241-250 MPa and 237-273 HB, respectively. It was found by SEM observation that in the microstructure of the titanium-containing type D graphite gray cast iron camshaft, there is 20%-30% primary austenite which is different from that primary austenite in the ordinary D-type graphite gray cast iron by that it has transformed into pearlite with layer distance of 100 nm during following solid transformation. Such graphite-free pearlite has higher strength and hardness（higher than 346 HV）, that just is the reason why the D-type graphite gray cast iron has higher strength and hardness.

关 键 词：可淬硬铸铁凸轮轴 钒钛生铁 硬度 抗拉强度 

分 类 号：TG143.9[一般工业技术—材料科学与工程]