A picture shows difference from seamless and straight seam and spiral seam pipe

Steel pipe is grouped into two main types. They are welded steel pipe like ERW steel pipe, galvanized steel pipe and so on and seamless steel pipe. However, with different methods of producing metal pipe, we shall classify them with more detailed methods.

The four types of methods for steel pipe's making:

Furnace Weld (FW). Also called Continuous Weld;

Electric Resistance Weld (ERW);

Submerged Arc Weld (SAW), also DSAW;

Seamless (SMLS) method;

And the difference about their production process can be described in a simple picture below: