介绍了一种铸态球墨铸铁凸轮轴的技术要求:本体取样,抗拉强度≥700 MPa,屈服强度≥480 MPa,伸长率≥2％,同时铁素体体积分数≤5％,渗碳体体积分数≤3％.采用覆砂铁型工艺生产可以满足上述要求,但缺点是生产周期长,效率低,热处理耗能高,成本也高.为解决上述问题,进行了壳型工艺生产的试验.由于壳型冷却速度远比覆砂铁型慢,使凸轮轴共析转变时的珠光体体积分数降低,无法满足客户需求.通过反复调整化学成分,适当提高w(C)量,多次调整w(Si)、w(Mn)、w(Cu)、w(Sn)量,最终使力学性能达到客户要求.

By statistical analysis,the relationship between the matrix hardness of the high pearlite-containing nodular iron and its nodularity and pearlite content was investigated.The result showed that the Rockwell hardness of the high pearlite-containing nodular iron camshaft increased with increasing of its nodularity and pearlite content.

通过统计分析研究了高珠光体含量球铁的基体硬度HRC与球化率（n）/珠光体含量（P）的关系。结果表明,n和P都与基体硬度HRC正相关。P＞75%～80%,HRC≤23;P＞80%～85%,HRC≤25;P＞85%～90%,HRC＞25。利用上述关系,可以用HRC对球铁凸轮轴中的球化率和珠光体含量进行鉴别。该方法已经用于生产实践。

Sichuan V-Ti pig iron and Hebei ductile iron have been used to manufacture 491Q type hardened camshaft and the effect of both iron on the microstructure and hardness of the camshaft been researched.Studies have shown that the microstructure of Sichuan vanadium-titanium pig iron consists of as tiny dot graphite+A type graphite+carbide+ pearlite while the microstructure of Hebei ductile iron consists of A-type graphite+C-type graphite+pearlite.The microstructure in the camshaft manufactured from the group-Ⅰingredient(230 kg Sichuan V-Ti pig iron+100 kg scrap steel+220kg back charge+other alloys) consists of the 4-6 grade A-type graphite+small amount E-type graphite+95% pearlite+about 5% cementite,and his matrix hardness is 252-255HB.The microstructure in the camshaft manufactured from the group-Ⅱingredient(150 kg Sichuan V-Ti pig iron+80 kg Hebei ductile iron+100 kg scrap steel+220 kg back charge+other alloys)consists of the 4-6 grade A-type graphite+small amount E-type graphite+100% pearlite,and its matrix hardness 210-229HB.The above-mentioned phenomenon has been given preliminary analysis.

通过统计分析研究了四种灰铸铁凸轮轴硬度HB与HRB之间的关系,获得了四种灰铸铁凸轮轴HB与HRB之间回归方程。研究发现,灰铸铁凸轮轴的基体硬度HB与HRB在试验范围内正相关,并对此做了分析。

采用光学显微镜和扫描电子显微镜分析了Cu-Cr系合金铸铁凸轮轴中的初生奥氏体枝晶的形貌特征和显微组织.研究发现,该奥氏体枝晶由片间距为约100nm的层片珠光体(屈氏体)组成.作者认为,屈氏体枝晶是D型石墨合金灰铸铁凸轮轴具有较高强度的原因.

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302～327 MPa和248～263 HB;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202～238 MPa和220～237 HB;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237～273 HB和241～250 MPa.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100 nm的珠光体.这种不含石墨的珠光体的强度和硬度(高于346 HV)都较高,因而是含钛D型石墨灰铸铁具有较高强度的原因.