材料期刊网

本文通过对冷拉Si-Cr气阀钢的断裂力学分析,将各种影响冷拉劈裂的因素归结为对钢的断裂韧度K_(Ic)、切向冷拉残余应力峰值σ_(tm)和表面缺陷深度α这三个方面。应用如下公式判断冷拉钢棒和钢丝是否可能发生冷拉劈裂破坏: K_(Ic)≈σ_(tm)((πα)~(1/2))(K_1/K_0) 冷变形后较精确的K_(Ic)值系由冷镦试样测得。 据此制定了控制缺陷深度的冷拉工艺,使Si-Cr钢在室温能够经受的一次冷拉压缩率达20—30％或更高,大大超过了以往规定的压缩率限度,达到了热拉才能容许的压缩率,避免了劈裂和再结晶粗晶,取得了高产优质的效果。

A fracture-mechanics approach was used in studying the cold-drawn splitting in Si-Cr valve steel. It seems that the cold deformation fracture toughness, K_(Ic),the peak value of cold-drawn tangential residual tensile stress, σ_(tm), and the depth of surface blemish, α, are the three main factors affected the splitting. An expression to determine the growth of split in cold-drawn rod may be as follows:K_(Ic)=σ_(tm)(πα)~(1/2)(K_I/K_0)The exact value of K_(Ic) is easily given by cold-heading specimen after cold deformation. Thus, the cold-drawing process makes possible to control the blemish depth. This process allows the steel to withstand a single cold drawing reduction of 20—30% or more at room temperature without splitting or recrystallized granular fracture and to give superior performance that can ever be obtained previously by hot drawing.