Carbon steel pipe starts out by arriving at the pipe mill in the form of either a billet (basically a large solid steel bar) or a coil (imagine a roll of toilet paper made out of steel). Depending on the manufacturing method used by the mill, these billets or coils will be processed to yield the finished end product. We will examine the various manufacturing methods used to make carbon steel pipe, but first let's look at how the carbon steel got here in the first place.