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在高铬不锈钢的生产中,影响质量最严重的是钢锭中的轴心裂纹和钢材中的髪纹。本文的研究结果指出,这两种缺陷属于同一来源,没有轴心裂纹的钢锭在锻成钢材后也没有髪纹。钢锭中轴心裂纹是在凝固过程中形成的,因而冷凝条件对它有影响。利用耐火材料做锭模可以得到内部坚实的钢锭,减小锭模模壁厚度,增大钢锭圆锥度或降低浇铸温度等只能减轻而不能完全消除裂纹。熔炼过程中的脱氧方法对钢中夹杂物的性质和形状分布有影响。改善脱氧方法并采用薄模浇铸,可以大大地减少轴心裂纹和髪纹,从而提高钢的收得率。我们认为夹杂物的性质、多寡及其形状分布可能对钢液的流动性和表面张力有影响;改善钢液的流动性或减小其表面张力可以促进钢液的充填性能,从而弥补凝固过程中由于冷凝收缩而产生的缺陷。在一定压力以下的真空中熔化和浇铸可以得到内部良好的钢锭。通过真空熔铸所得到的钢锭,其柱状晶区大小缩小,而柱状晶的缩小对避免钢锭中轴心裂纹有利。得到这种效果的原因可能是多方面的,真空有去气作用,在真空中钢锭的凝固散热与在一般情况下有所不同,真空作用使钢液的性质发生变化等等。虽然,上述几方面的理论基础还有待于进一步研究,但从目前实际效果来说,真空熔化和浇铸应该认为是提高不锈钢质量的一个重要发展方向。
In the production of high chromium stainless steel, the most serious impact on the quality of steel ingot is the axis of the heart crack and steel 髪 pattern. The research results of this paper point out that the two defects belong to the same source. The ingots without axial cracks have no streaks after they are forged into steel. Axis cracks in the ingot is formed during the solidification process, so the condensation conditions have an impact on it. The use of refractory ingot mold can get a solid ingot, reducing the mold wall thickness, increase the ingot conicity or reduce the casting temperature can only reduce and can not completely eliminate the crack. The deoxidation process in the smelting process has an effect on the nature and shape distribution of the inclusions in the steel. Improve the method of deoxidation and the use of thin-walled casting, can greatly reduce the axial cracks and stirrup, thereby enhancing the yield of steel. In our opinion, the nature and amount of inclusions and their shape distribution may have an impact on the fluidity and surface tension of the molten steel. Improving the fluidity of the molten steel or reducing its surface tension can promote the filling performance of the molten steel and make up the solidification process Defects due to condensation and shrinkage. Melting and casting in a vacuum below a certain pressure gives a good internal ingot. The obtained ingot obtained by vacuum casting has a reduced columnar grain size, and the reduction of the columnar grain is advantageous for avoiding axial cracks in the ingot. The reason for this effect may be multifaceted, the vacuum gasification effect, in the vacuum ingot solidification heat dissipation and under normal circumstances vary, the vacuum effect of the molten steel properties change and so on. Although the theoretical basis of the above aspects remains to be further studied, vacuum melting and casting should be regarded as an important development direction for improving the quality of stainless steel from the current practical results.