welding rules

例句：

1. 1. The engineerused a special welding machine tojoin the metal parts together.
   工程师使用一种特殊的焊接机器将金属部件连接在一起。
2. 2. Welding is a skill that requires yearsof practice and training.
   焊接是一项需要多年实践和培训的技能。
3. 3. The weldingprocess involves heating the metal together until itbecomes molten and then cooling it quickly.
   焊接过程涉及将金属加热至熔融状态，然后迅速冷却。