Solute Distribution in Columnar Crystal Zone and Influences of Correlative Factors for Continuous Casting Slabs

The expression of the solute distribution in columnar crystal zone was deduced when the solid-liquid interface bended periodically, and the quantitative calculations of macrosegregation were also made in the process of the continuous casting. The solute distribution along the thickness direction of the slabs was obtained, which verified the theoretical calculation. The effect of the bulge size, solidification speed, and solidification shrinkage speed on macrosegregation of the slabs was calculated. It can be concluded that normal segregation and negative segregation alternatively appear as a result of the bulge. The normal segregation exponentially depends on the bulge size, and the negative segregation linearly depends on the bulge size. The extent of the normal segregation is greater than that of the negative segregation when the bulge size is the same. The macrosegregation of the same position along the thickness direction of the slabs changes in a sine wave with increasing the solidification rate, and the amplitude is larger at the casting blank center. The normal segregation linearly decreases with increasing the solidification shrinkage speed, and when the solidification shrinkage speed exceeds a critical value, the segregation appears negatively and increases linearly.

34CrNi3Mo钢锭锻裂原因

通过金相、低倍、断口及扫描电镜等手段,结合钢锭气体含量、化学成分及五害元素的分析检验,证实了34CrNi3Mo钢锭激冷层薄,柱状晶相当发达,并沿柱状晶晶界析出低熔点类夹杂物,削弱了晶间结合力,使其在锻造初期沿晶开裂而报废。为避免此类缺陷产生,必须保证钢锭的浇注质量。

送粉速率对铁基合金激光熔覆层组织形貌的影响

针对Q235钢表面改性、修复和再制造的需求,在其表面制备了不同送粉速率的铁基激光熔覆层。采用OM、SEM和EDS研究了材料的组织形貌。结果表明,随送粉速率的增加,基体热影响区碳化物聚齐成团,其耐蚀性下降;熔覆层由平面晶、粗大柱状晶、柱状树枝晶、树枝晶和等轴晶组成,随着送粉速率的增加,熔覆层下层粗大柱状晶所占面积减小,形状转变为柱状树枝晶和树枝晶,熔覆层中层组织发生细化,且快速向等轴晶转变,熔覆层表层等轴晶尺寸急剧变小;熔覆层组织枝晶为富集Ni元素的奥氏体,晶间为由富含Cr、Mo元素的马氏体、铁素体和碳化物组成的骨架状共晶体。研究可为该型激光熔覆层组织形貌改变原理增加资料。