How is Steel Pipe Made?
Steel pipe is manufactured using a few different processes. These processes differ based primarily on the type of steel pipe and its intended uses. Below you’ll find some information about the initial stages of pipe production as well as the individual manufacturing processes for specific kinds of steel pipe.
For many types of steel pipes, the manufacturing process begins by melting iron ore and coke (a hard, porous, gray fuel that has a high carbon content). After the melting stage, the ore and coke are blasted using oxygen. This removes carbon. The product of the aforementioned processes is poured into molds, creating raw steel ingots. These ingots are rolled into blooms that become either the slabs used to create welded pipes or the billets used to create seamless pipes.
As mentioned, the production method of steel pipes differs based on their type. Below you’ll find information about the unique manufacturing methods of popular types.
Seamless Steel Pipes
During the manufacturing process for seamless steel pipes, a billet is heated and then molded into the shape of a cylinder. The cylinder, also called a round, is heated further in a furnace and then rolled. During the heating and rolling, a hole forms in the center of the cylinder, and a bullet-shaped piercer is pushed through the center. After this, the steel is rolled and stretched into the desired dimensions and lengths over the bullet-shaped piercer.
A large diameter seamless steel pipe goes through a mandrel mill process. After the piercer is pushed through, the shell of the pipe is rolled through a mandrel mill. This mandrel mill has mandrel bars inside of it. The end result of the mandrel mill process is a pipe with more controlled wall thickness and outside diameter.
Welded Steel Pipes
Steel slabs are heated and hot rolled into skelp, coiled and elongated steel ribbon, to create a welded steel pipe. Then, skelp is cut into a flat sheet of a pre-determined length. A rolling machine processes the flat sheet, forming it into a cylinder shape. This is the basic process for basic welded steel pipes. The manufacturing process for welded steel pipes differs slightly based on the type of welded steel pipe. There are three common types of welded steel pipe with different manufacturing processes: Electric-Resistance Welded Pipe, Longitudinal Welded Pipe, and Spiral Welded Pipe.
Electric-Resistance Welded Pipes (ERW)
This type of welded pipe is manufactured using a process of cold-forming a steel sheet into a cylinder shape. Electrical current is passed through the edges of the sheet so that it reaches the necessary temperature for its edges to join and bond. The seam on ERW pipe is almost undetectable, and this type of pipe is quite strong.
Longitudinal Welded Pipe (LSAW)
This type of welded pipe is created by cold-forming a heavy carbon steel plate. The LSAW pipe manufacturing process results in a straight seam that spans the entire length of a pipe on the outside.
Spiral Welded Pipe
This type of pipe is the result of winding a steel plate or HR coil into the shape of a spiral. Spiral welded pipe is easy and affordable to produce and results in a sizeable amount of pipe thickness.
All types of steel pipe are subject to quality control inspections after their production. They may also be modified according to a customer’s requirements for a particular project.
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