铸铁的冷焊法最容易产生白口铁、裂纹,对操作技术的要求也比较高。
参考答案:对
An unhappy childhood may have some negative effects on a person’s character;
however,they are not always ________.[ ]
A.practical
B.avoidable
C.permanent
D.beneficial
钢的含碳量越高,马氏体转变温度也越高。()