joints using welds for sealing

例句：

1. 1.The car's engine has several joints that need to be lubricated regularly.
   这辆车的引擎有几个需要定期润滑的接合部位。
2. 2. The scientist used a special tool to dismantle the joints of the robot.
   科学家使用一种特殊的工具来拆解机器人的接合部位。
3. 3.The old man had to remove the joints from his broken leg before he could walk again.
   这位老人在重新走路之前，必须先将断裂腿部的接合部位拆除。