CVN(Charpy V-notch) toughness and grain size number of J55 grade oil casings produced by Baotou Iron and Steel Company did not meet the reiative standards in the past.

本文针对包钢原来生产的J55石油套管冲击韧性不足，晶粒粗大的问题开展研究。

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The height of the Ke peak is independent of the grain size while that of this peak is proportional to the number of the bamboo boundary containing in the specimen.

例如，葛峰的高度不随晶粒尺寸而变，而竹节峰的高度则与试样中所含的竹节晶界的数目成正比。

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Then the morphology was observed by optical microscope and SEM. The grain size of austenite, the number of martensite in austenite grains and the spacing of the lath martensite were measured.

用金相显微镜和SEM观察了试样铸态微观组织形态，测定了奥氏体晶粒尺寸以及奥氏体晶粒内马氏体板条束个数和马氏体板条间距。

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