Development of High Speed Steels with a Fine Grain Size by Carbide Dispersion Carburization (CDC) Process.

最近，人们提出了一种由超细晶粒和均匀分布的颗粒组成的高速钢的新工艺，称为碳化物弥散渗碳(CDC)工艺。在该工艺中，通过对高含量的Ti、V、Mo、W等无碳铁基合金进行渗碳处理，可以获得优异的耐磨性和优异的韧性。本研究在计算相图信息的基础上，尝试用CDC工艺生产硬度在Hv1000以上的高速钢。(1)对Fe-C和Fe-N系进行了热力学分析。(2)在热力学分析的基础上，模拟了Fe-V-Mo-C合金的组织演变(包括渗碳和热处理过程中碳化物的种类、含量和体积分数)。(3)测量了几种不同成分的Fe-V-Mo-C合金中碳化物的体积分数、尺寸和分布。检验结果表明，碳含量和V、Mo原子比是决定碳化物大小和分布的最重要因素。(4)在此基础上进行了组织控制计算和检验，得到了具有高硬度和高韧性的成分合适的合金。因此，我们可以得到硬度在Hv1000以上的优质合金。目前，与钢铁制造公司的实际应用合作项目正在进行中。

Recently, a new type of process to fabricate high speed steels consisted of hyperfine grains together with uniformly distributed particles, which is called as carbide dispersion carburization (CDC) process, is proposed. In this process, the superior resistance to wear and the outstanding toughness can be obtained by carburizing C-free Fe base alloys with high contents of Ti, V,Mo, W etc..In this study, an attempt by CDC process was made to produce high speed steels with very high hardness over Hv1000 on the basis of information of the calculated phase diagrams. The obtained results are as follows :(1) In order to establish a data base for estimating phase equilibria of the Fe-base multi-component systems, thermodynamic analysis of Fe-C and Fe-N base systems were performed.(2) On the basis of results of the thermodynamic analysis, microstructural evolution (including the kind, content and volume fraction of carbides appearing during carburizing and heat treatment) of Fe-V-Mo-C alloys was simulated.(3) Volume fraction, size and distribution of carbides in several Fe-V-Mo-C specimens with different composition produced by CDC process have been measured. The result of the examination suggests that the carbon content and the atomic ratio between V and Mo are the most important factors for determining the size and distribution of carbides.(4) On the basis of such the calculation and examination for the microstructural control, some alloys with suitable composition for obtaining both high hardness and toughness have been produced and examined. Consequently we could get some excellent alloys with hardness over Hv 1000.At the present, a cooperation project for practical applications with steel making companies is running.