覆膜砂壳型铸造FC25汽缸成分和工艺控制

Composition and Process Control of FC25 Cylinder Shell Coated Sand Casting

介绍了制冷压缩机用汽缸铸件的技术要求和工艺控制难点。从以下几方面：铁液成分控制、铁液的孕育、铸件冷却方式以及热处理等对汽缸硬度和组织的影响进行了分析。结果表明：采用覆膜砂壳型铸造壁厚26mm铸态FC25灰铸铁汽缸，须严格控制化学成分（质量分数，％）3.2～3.4C，1.6～1.8Si，0.6～0.8Mn，碳当量控制在3.7％～3.8％，适当提高Si／C比；做好炉前孕育处理并适当控制硫含量0.08％~0.1％含量，可达到事半功倍的效果；正火处理可挽救硬度较低铸件，但成本增加；浇注完毕后20min打箱振动去除余砂、增加通风冷却可代替正火处理，并可拓宽成分控制范围。

The technical requirements for refrigeration compressor cylinder and difficulties of casting technique were introduced. The hardness and microstructure of cylinder were analyzed from the following aspects： the control of the chemical composition in liquid iron, inoculation of liquid iron, cooling method of casting and heat treatment. The results show that the using coated sand shell casting wall thickness 26 mm as-cast FC25 grey cast iron cylinder, the chemical composition 3.2%- 3.4%C, 1.6%-1.8%Si, 0.6%-0.8% Mn, controlling carbon equivalent in 3.7%-3.8%, increasing of Si/C ratio properly. Must be strictly controlled. The inoculation and proper control of 0.08%-0.1% S can reach twice the result with half the effort. Normalizing treatment may save the low hardness castings but increase the cost. Shaking out after keep warm for 20 min and removing residual sand with vibration sieve to increase the ventilation cooling can broaden the composition range.