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推杆套筒(图1)是柴油机里的重要零件之一。其外圆精度和光洁度要求高,内孔除底部要加工一个半球外,其余均为毛坯面。因材料为50Mn2,塑性差,变形抗力高。另外,又因为该零件断面收缩率大(零件变形程度ε=76%),如用坯料直接冷挤压成形是困难的。因此,长期来一直用热挤形式供坯,内孔不加工,外圆放较多的机加工余量,故费工费料。为使该零件能直接上无心磨床进行磨削,我们经过反复试验,终于在两种钢质桶形挤压件上成功地应用了变薄引伸工艺,使推杆套筒外圆能直接进行磨削。
Putter sleeve (Figure 1) is one of the important parts in diesel engine. The requirements of its precision and finish cylindrical high, the hole in addition to the bottom of a hemisphere to be processed, the rest are rough surface. Due to the material is 50Mn2, poor plasticity, high deformation resistance. In addition, since the part has a large reduction in area (degree of deformation of the part ε = 76%), it is difficult to perform direct cold extrusion using a billet. Therefore, for a long time has been using hot extrusion form for blanching, the hole is not machined, the outer circle put more machining allowance, so the labor costs of materials. In order to grind the part directly on the centerless grinder, we have repeatedly tried and succeeded in applying the thinning and drawing process to the two kinds of steel barrel extrudates so that the outer circumference of the push rod sleeve can be ground directly cut.