The upper surface of the steel casting is easy to produce defects such as sand holes, air holes and slag inclusions, so the processing amount of the upper surface is generally larger. According to the process specification, the processing allowance of the steel casting is determined to be 40 mm above, 35 mm at the side and 30 mm below. In addition, in order to prevent the opening deformation of the saddle groove when the flesh is subsequently cut, a special processing amount of 40 mm is set on the processing surface at the inner side of the saddle groove to ensure that the steel casting has sufficient processing amount and overall quality.

The linear shrinkage rate of steel casting mainly depends on the material, structure, size, molding materials and process methods, the compactness of sand mold, pouring temperature, etc., and is closely related to the obstacles encountered in the shrinkage process of each part of the steel casting. The scale of the steel casting in the length and width directions is set to 2.0%, and the height scale is 2.2%