高周波溶解遠心鋳造法による工具鋼と高速度鋼の機器分析用試料の検討

Abstract

The fact that samples prepared by a high frequency induction melting and centrifugal casting method is excellent in uniformity suggests that this method is adequate for the preparation of tool and high speed steel samples containing a large amount of carbide-forming elements for instrumental analysis. In this study remelted samples which were prepared from tool (JSS 600∼605) and high speed (JSS 606∼611) steels for chemical analysis by this method were analyzed in comparison with the same standared samples for instrumental analysis. The method for the assessment of the remelted samples was as follows. The equations of the working curves were derived from the data for the standard samples for instrumental analysis by curve fitting with orthogonal polynominals. The F-test was performed for comparison of the mean squares of both data. Emission spectral analysis (Cu, Ni, Cr, Mo, V, W) and X-ray fluorescence analysis (Ni, Cr, Mo, V, W) of tool steels showed that some of the standard samples gave abnormally higher values in tungusten analysis. The working curves successfully constructed from the standard samples when excluded those samples with abnormal tungsten content and included Fe-W alloy samples (JSS FXS 375∼378). In order to make clear the cause of this higher analytical value, the microstructures were investigated with an optical microscope and an electron probe X-ray microanalyzer. It was inferred as a main cause that comparatively large tungusten carbide scattered non-uniformly in one standard sample, while there was no carbide in the remelted samples. In X-ray fluorescence analysis (Co, Cr, V, Mo, W) of high speed steels, there was a discrepancy in analytical values of vanadium between the standard sample and the remelted one with a high vanadium content (V: 3.19%), and the analytical values of tungsten in the high tungsten standard samples showed considerable scattering in positive errors. Microstructure observations confirmed that the positive errors were due to the presence of coarse unmelted carbide in the standard samples.