protection film for heat treatment of metal

例句：

1. 1. The protection film is essential for the metal to be heat treated properly.
   保护膜对于金属正确热处理至关重要。
2. 2.The manufacturer used a special protection film to protect the product during shipping.
   制造商使用了一种特殊的保护膜来保护产品在运输过程中不受损害。
3. 3.The protection film was designed to prevent scratches and dents on the surface of the metal.
   这种保护膜设计用来防止金属表面出现划痕和凹痕。