1. Manufacturing method
Seamless steel pipes can be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, etc. according to different production methods.
1.1. Hot-rolled seamless pipes are generally produced on automatic pipe rolling units. After checking and removing surface defects, the solid tube blank is cut into the required length, centered on the perforated end face of the tube blank, then sent to the heating furnace for heating, and pierced on the piercing machine. Spin and advance the solid blank inside the process of piercing holes under the influence with the roller as well as the end. Then the solid blank is hollow finally, which is called gross pipe. Then send it to the automatic pipe rolling machine to continue rolling. Finally, the wall thickness is adjusted by the equalizing machine, and the size is sized by the sizing machine to meet the specification requirements. It is a more advanced method to produce hot-rolled seamless steel pipes by using continuous rolling mills.
1.2. If you want to obtain seamless pipes with smaller size and better quality, you must use cold rolling, cold drawing or a combination of the two. Cold rolling is usually carried out on a two-roll mill, and the steel pipe is rolled in an annular pass formed by a circular hole groove with variable cross-section and a stationary tapered plug. Cold drawing is usually carried out on a single-chain or double-chain cold drawing machine of 0.5-100T.
1.3. Extrusion method The heated tube is placed in a closed extrusion cylinder, and the perforated rod and the extrusion rod move together to make the extruded part extrude from the smaller die hole. This method can produce steel pipes with smaller diameters.
2. Type
2.1. According to different production methods, seamless steel pipes can be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, etc.
2.2. According to the shape classification, there are round tubes and special-shaped tubes. In addition to square tubes and rectangular tubes, special-shaped tubes also include oval tubes, semicircular tubes, triangular tubes, hexagonal tubes, convex-shaped tubes, and plum-shaped tubes.
2.3. According to different materials, it can be divided into ordinary carbon structural tubes, low alloy structural tubes, high-quality carbon structural tubes, alloy structural tubes, stainless steel tubes, etc.
2.4. According to special purposes, there are boiler tubes, geological tubes, oil tubes, etc.
3. Purpose
3.1. Seamless pipes are widely used. General-purpose seamless pipes are rolled from ordinary carbon structural steels, low-alloy structural steels or alloy structural steels with the largest output, and are mainly used as pipes or structural parts for conveying fluids.
3.2. There are three types of supplies according to different uses: a. Supply according to chemical composition and mechanical properties; b. Supply according to mechanical properties; c. Supply according to hydraulic test. Steel pipes supplied by Types a and b, if used to withstand liquid pressure, are also subject to hydrostatic testing.
3.3. There are many kinds of seamless pipes for special purposes, such as seamless pipes for boilers, seamless pipes for geological use and seamless pipes for petroleum.
