某一中载齿轮决定用45钢制造,其最终热处理采用下列哪种方案最佳
A. 淬火+低温回火
B. 渗碳+淬火+低温回火
C. 调质+表面淬火
D. 正火
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1.make great efforts to achieve or obtain (sth.) 努力,力求2. be satisfied with (sth.), not wishing for more 对…满意;对…感到满足3. move or progress at the same rate (as sb./sth.) 跟上4.have (sth.) as a starting-point, source or origin; come from 源自;源于5. make fun of 嘲弄,开玩笑6. vi. pass out of sight, especially quickly; disappear 消失;突然不见7.n. one of a series of scenes or stories constituting a literary work 片段,插曲
主销内倾的主要作用是()
A. 自动回正
B. 减少燃料的消耗
C. 提高前轮工作的安全性
D. 减少轮胎的磨损