材料期刊网

为了研究硅钢热轧板脆性随温度的变化,测定了不同温度下材料的冲击韧性值,得出3％ Si-Fe的热轧板,存在一脆性转变温区,其上、下限温度分别约为+100°和0℃。在此范围内,冲击韧性对温度的变化极为敏感,变化量可达一个数量级以上;在此温区外,冲击韧性几乎不因温度而变化.可以解释为:3％Si-Fe的热轧板,在脆性转变温区的上限内处于塑性状态;低于下限温度时则处于脆性状态。因此,冷轧前将板卷预热到60—80℃是避免断裂的有效措施,此时,它处于塑性状态,也不致产生损坏最终磁性的时效现象。 观察3％Si-Fe热轧板断口看出:脆性断口上占绝对优势的是沿{100}面的解理断裂,介于各解理面系间较窄的过渡区的晶面多属{110},在解理面上往往可以发现(110)滑移面露头的痕迹,解理的主要走向与这些滑移痕迹几乎平行,解理面上较大的解理台阶的面多属{110}:塑性断裂时,断口上存在大量区别于{110}面系的高指数面,即使在塑性断裂时也存在少量沿{100}的解理断裂。

The impact-toughness of a hot-rolled 3％ Si-Fe sheet steel has been measured to in-vestigate its ductile-brittle transition behavior. It was found that the transition from brit-tle to ductile fracture for this steel was within the temperature range of 0 to 100℃.At this range, the impact-toughness value was very sensitive to temperature changes,variation amounted to more than one order in magnitude could happen. Beyond thisrange, however, the curve rised asymptotically to a constant value, at which tempera-ture the sheet steel became ductile. In view of this, preheating the sheet to 60-80℃prior to cold-rolling was found to be an effective way in preventing brittle-cracking,whereas any aging effect which might deteriorate the magnetic properties of the sheetwas found to be neghglble. It is convenient to define the type of deformation after the indices of crystallineplanes being pre-determined by the etch-figure method. Fractography observations bySEM showed that, the {100} planes constituted the majority of the cleavage facets onbrittle fracture, but the narrow transition zone between the different cleavage facetsappeared to be {110} planes. Traces of {110) slip planes on cleavage facets mightoften be found on the cleavage facets, with the main cleavage direction almost parallel tothese slip traces. The majority of larger cleavage steps on the cleavage facets belongedto the {110} planes. During Plastic cracking many high-index crystalline planes otherthan {110) may be observed on the fracture surface, but cleavage along the {100}planes may still occur although with much less frequencies.