下列钢淬火后硬度最低的是
A. Q235
B. 40Cr
C. GCr15
D. 45钢
滚动轴承钢GCr15的最终热处理应该是
A. 淬火+低温回火
B. 渗碳+淬火+低温回火
C. 渗碳+淬火+中温回火
D. 渗碳+淬火+高温回火
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
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