preheating liquid metals

例句：

1. 1. The oven needs to be preheated before cooking the meat.
   在烹饪肉类之前，烤箱需要预热。
2. 2. The car's engine needs to be preheated before starting.
   汽车的引擎在启动前需要预热。
3. 3. Before we start working on this project, we need to preheat the machine.
   在我们开始这个项目之前，我们需要预热机器。