目前国内外均采用组合凹模解决凹模径向开裂的问题。在冷挤压中采用预应力圈的组合凹模与同样尺寸的整体凹模相比,其强度可提高1.4～1.8倍。在我们的实践中,两层或三层组合凹模在预应力圈选材合理、热处理恰当时,除了正常的磨损和疲劳损坏外,还未出现过径向开裂。 At present, both domestic and abroad adopt the combined concave die to solve the problem of the radial crack of the concave die. In the cold extrusion using the pre-stress ring combination die with the same size compared to the overall die, the intensity can be increased 1.4 to 1.8 times. In our practice, the two-layer or three-layer composite die have not appeared radial cracking except for the normal wear and fatigue damage when the prestressing ring is properly selected and the heat treatment is proper.