燃气轮机涡轮壳体铸造

Manufacturing Process of Gas Turbine Shell

涡轮壳体结构复杂,壁厚相差大,尺寸精度控制困难,并且易产生表面缺陷、缩松、裂纹等问题。通过对涡轮壳体的结构、质量要求和使用状况进行分析,从铸造工艺、浇注工艺、型砂工艺、热处理工艺等多方面提出了相应的解决方案。采用组芯结构、1.5%~1.9%的收缩率和防变形拉筋保证了气道的尺寸精度;采用底注式浇注系统、合理的液面上升速度等措施防止夹杂和缩松缺陷,保证了铸件内部质量;采用铬铁矿砂作为面砂、气道内使用铬铁矿砂的工艺保证了铸件表面质量和气道壁的补缩效果;采用专用料盘固定,控制加热和冷却速度,防止了铸件热处理变形。

Structure of turbine shell is complex,with large difference of wall thickness,and strict dimensional accuracy controlling.The surface defects,shrinkage porosity,cracks and other problems are also easy to come out.Based on the analysis of the structure,quality requirements and service conditions of the turbine shell,corresponding solutions from the aspects of casting process,pouring process,sand molding and heat treatment process were given.The adoption of the cores assembly structure,1.5%-1.9% of shrinkage ratio and antideformation tie pieces ensured the dimensional accuracy of the airway.The measures of bottom gating system,reasonable rising speed of liquid steel and so on avoided inclusion or shrinkage porosity defects and ensured the internal quality of the casting.The casting surface quality and the feeding effect of the air-pass wall were assured by using of chromite molding sand.A dedicated plate was used to fix the casting and proper heating and cooling rates were controlled,which prevented the casting from deformation during heat treatment process.