钨是高速工具钢中的主要合金元素，其作用是提高热硬性。
查看答案
热作模具钢要反复锻造，锻造后的预备热处理一般是完全退火，其目的是消除锻造应力，降低硬度、便于切削加工。
A. 对
B. 错
目前，最常用的冷作模具钢属于高碳高铬模具钢，有Cr12、Cr12MoV冷作模具钢。
A. 对
B. 错
高速工具钢锻造后必须进行退火，目的在于消除应力，降低硬度，使显微组织均匀，便于淬火。
A. 对
B. 错
Listen to news report 1 and answer 2 questions.What does the news report say about Ali MacGraw and Ryan O’Neal?[音频]
A. They used to be classmates at Harvard University.
B. They became household names because of the film Love Letters.
C. They are on a national tour for their play Love Letters.
D. They are reunited to celebrate the success of their film Love Story.
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