ADI拨叉的壳型铸造和等温淬火工艺

Shell Mold Casting and Iso-Thermal Quenching Process of ADI Shifting Fork

介绍了拨叉铸件的结构和技术要求.铸件采用无冒口铸造工艺生产,原铁液化学成分控制范围为：w（C）3.75％～3.98％、w（Si）1.2％～1.7％、w（S）≤0.08％、w（Mn）≤0.3、w（P）≤0.04,w（Si终）为2.5％～2.8％;出铁温度控制在1 520℃,采用喂丝法进行球化、孕育处理;采用盐浴等温淬火,奥氏体化温度为900℃,保温时间75 min,等淬温度为300～350℃,等淬时间为60 min.最终生产的铸件经过X光检测后可以达到2级甚至1级,铸态金相组织为：球径大小16～60 μm,基体组织为铁素体＋珠光体;淬火后的金相组织为致密的下贝氏体和20％的残余奥氏体组织,淬火后硬度为302～375 HB.

The construction and technical requirements of the shifting fork casting were introduced. The casting was produced by using riser-less casting method. The chemical composition of the base iron melt was controlled in the range of w（C） 3.75%- 3.98%,w（Si） 1.2%-1.7%,w（S） ≤0.08% ,w（Mn） ≤0.3,w（P） ≤0.04,the final Si content was of 2.5%~2.8% ;tapping temperature was controlled at 1 520℃;cored-wire injection process was adopted for both the nodularizing and the inoculating treatments;salt bath iso-thermal quenching process was adopted：austeniting temperature was of 900 ℃ ,holding duration was of 75 min,iso- thermal quenching temperature was of 300-350 ℃,iso-holding duration was of 60 min. The X-ray detection result of the casting reached class 2,and even class 1 ;as-cast microstructure was：nodule size of 16-60 μm;matrix microstructure was consisted of dense low bainite ＋ 20% residual austenite;the hardness after iso-thermal quenching was of 302-375 HB.