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W18Cr4V高速钢经锻造和轧制成榨材后,在钢棒的纵向断口上出现与基体形貌不同的长短宽窄不等的深灰色细条(简称“灰条”),如图1所示(图版13)。这种“灰条”,按其大小可分为三类:(1)肉眼看不见。用10倍以上放大镜才可看见;(2)肉眼稍微看得见,用放大镜才看得清楚;(3)肉眼可看得很清楚。可看图1上的标号。综合使用宏观断口观察、金相分析、电子探针分析、透射电子显微镜和扫描电子显微镜微观断口观察等实验手段,对断口上“灰条”的属性进行了初步研究。试验用料是碱性电炉返回法冶炼的,浇注成560公斤重的扁钢锭,经锻造开坯成140毫米方棒后,轧制成不同直径的棒材。五个炉号的化学成分均符合W18Cr4V高速钢的规定范围,即(％)C0.7—0.8,W17.5—19.0,Cr3.8—4.4,V1.0—1.4,Mo≤0.30,Mn≤0.4,Si≤0.4,S≤0.30,P≤0.30。断口试样是热轧状态,未经其它热处理。
W18Cr4V high-speed steel after forging and rolling into pressed material, the longitudinal fracture in the steel rod appeared on the substrate with different length and breadth of varying width of dark gray strip (referred to as “gray bar”), shown in Figure 1 13). This “gray bar”, according to its size can be divided into three categories: (1) the naked eye can not see. With 10 times more magnifying glass can be seen; (2) the naked eye can see a little, can only see clearly with a magnifying glass; (3) the naked eye can see very clearly. See Figure 1 on the label. Comprehensively using the macroscopic fracture observation, metallographic analysis, electron probe analysis, transmission electron microscopy and scanning electron microscopy microscopic fracture observation experimental methods, the “gray bar” properties of the fracture were studied. Test materials are alkaline furnace return smelting, pouring into 560 kg heavy flat ingot, after forging billets into 140 mm square bar, rolled into bars of different diameters. The chemical composition of the five furnaces are in line with the provisions of W18Cr4V high-speed steel, namely (%) C0.7-0.8, W17.5-19.0, Cr3.8-4.4, V1.0-1.4, Mo ≤ 0.30, Mn ≤ 0.4, Si≤0.4, S≤0.30, P≤0.30. Fracture specimens are hot rolled without any other heat treatment.