检验钢材质量的指标有哪几项?
参考答案:
对于有明显屈服点的钢材其指标有:屈服强度、抗拉强度、伸长率、冷弯性能。对于无明显屈服点的钢材只测定后三项。
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She seemed ________ the book before, but she said she had never.
A.to read
B.to have read
C.to be reading
D.reading
容积式泵需要在开泵之前关闭出口阀,离心泵则相反。