气缸盖壳型铸型和石子造型的凝固技术

Solidification Technology for Shell Mold & Quartz Pebble Molding of Cylinder Head

以整体式直列四缸水冷式柴油发动机气缸盖为研究对象,采用单一石英石子作为造型材料,铸型由单面覆膜砂壳型、壳芯和实心砂芯组装而成,在单体直壁砂箱内进行造型紧实,用砂箱顶部锁紧压板压实铸型,将孕育铸铁HT250金属液在重力铸造下浇注成形,浇注系统采取底注开放式,实现了铸件分型面上无披缝和铸型型腔无气眼桩、无冒口的均衡凝固。结果表明,铸件的面粗糙度Sa为11.89μm,抗拉强度为265.2MPa,硬度(HB)为209;基体组织中的石墨形态为片状A型,石墨大小等级为3~4级,珠光体及索氏体数量大于98%;铸件成品率达到95%,铸造工艺出品率大于85%,砂铁比达到1∶1,石英石子和铸型覆膜砂的回收再利用率均达到90%以上。

Aiming at one-piece inline four-cylinder water-cooling diesel engine cylinder head,quartz pebble was chosen as molding material.The casting mould is made of resin coated sand shell,shell core and hot corebox sand.Mold compaction has been processed in a single flask with straight wall and with the aid of clamping plate on the top of the opening flask.HT250 inoculated cast iron was poured in gravity casting with bottom and open gating system,which realized non-joint flash non-fins in mold parting and non-air vent riser in mold cavity.The practical production reveals that roughness of casting surface feature reaches Sa=11.89μm,and tensile strength and hardness of the castings reach 265.2 MPa and209 HB,respectively.Graphite morphology and graphite size grade in the casting matrix structure belong to A type and 3-4 grade,respectively,and the content of pearlite and sorbate are more than 98%.In addition,product yield and overall yield reach 95%and 85%,respectively.Sand metal ratio may be 1∶1,and recycling ratio of quartz pebble and shell core precoated sand are more than 90%.