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本文的目的在于,用定向凝固的方法使碳化物适当地排列起来,从而使高铬铸铁得到高的强度。 Fe—30％Cr—C合金的碳量范围为2.6—3.2％,在真空感应炉中以高纯度的材料制备而得。合金在特定装置中作定向凝固,定向凝固的速度为3—7200毫米/小时。炉子用铂绕制。利用镓—铟共晶作为冷却剂,这样,可以在液—固界面上得到陡而固定的热梯度.在试样长度上扫描检查了排列成长的区域。对这些区域做了定量金相分析.确定了排列状成长与成长速度和成分之间的关系.测量了定向凝固试样的强度,而且与定量金相分析的数据联系起来。证明了,在Fe—Cr—C系中共晶线附近成分的合金可以得到排列状的成长而没有初生的组成体。对于远离共晶线的合金,则因偏析而导致形成有初生组成体的起始区。用上述方法,对共晶线附近的合金,用低的成长速度,可以得到超过超强度材料的强度(3100Mpa)。所得到的强度水平与成长速度在600毫米/小时以下时所得到的组织有密切的关系。初生组成体的出现会显著地降低强度。碳化物的体积百分数和碳化物间距也影响性能。在类似于连续铸造所用的成长速度下,所得的强度大约在2500Mpa左右。
The purpose of this paper is to properly align carbides by directional solidification to achieve high strength in high chromium cast iron. The carbon content of the Fe-30% Cr-C alloy ranges from 2.6 to 3.2% and is prepared from a high purity material in a vacuum induction furnace. Directional solidification of the alloy in a specific device, the directional solidification speed of 3-7200 mm / hour. The stove is made of platinum. Using gallium-indium eutectic as a coolant, a steep and constant thermal gradient can be obtained at the liquid-solid interface, and the length of the alignment is examined by scanning across the length of the sample. Quantitative metallographic analysis of these regions was performed to determine the relationship between the rate of growth and the growth rate and composition of the alignment, the strength of the directional solidification specimen was measured and correlated with the data from the quantitative metallographic analysis. It was proved that the alloy in the Fe-Cr-C system in the vicinity of the eutectic line can be grown in an array without any primary composition. For the alloy away from the eutectic line, the starting region where the primary composition is formed is due to the segregation. Using the above method, the strength of the alloy exceeding the super strength (3100 Mpa) can be obtained with a low growth rate for the alloy near the eutectic line. The resulting level of strength is closely related to the microstructure obtained at growth rates below 600 mm / h. Emergence of newborn bodies will significantly reduce the intensity. The volume percentage of carbides and carbide spacing also affect performance. At similar growth rates used for continuous casting, the resulting strength is around 2500 MPa.