Raw Material of Seamless Pipe

1. Raw materials for seamless pipes

The raw materials of seamless pipes can be divided into carbon steel, alloy steel and stainless steel.

(1) Carbon steel seamless pipe

①Low carbon steel (carbon content less than 0.25%): Low carbon steel seamless pipes have good toughness and plasticity and are easy to process. However, low carbon steel has relatively low strength and hardness, making it unsuitable for mechanical parts.
②Medium carbon steel (carbon content between 0.25% and 0.6%): Medium carbon steel pipe has high hardness and strength and is suitable for making mechanical parts with high strength requirements.
③High carbon steel (carbon content greater than 0.6%): High carbon steel has very high hardness and strength, but its toughness and plasticity are poor, and it is easy to break.

(2)Alloy steel seamless pipe

Alloy seamless steel pipe is a kind of seamless steel pipe. Its properties are much higher than ordinary seamless steel pipes. Because this kind of seamless steel pipe contains more Cr, its heat resistance, cold resistance and corrosion resistance are unparalleled. Seamed steel pipes are not as good as steel pipes, so alloy steel pipes are widely used in fields such as crude oil, chemical plants, power engineering, and heating furnaces.

Alloy seamless steel pipes include elements such as silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, aluminum, copper, boron, rare earths, etc.

(3) Stainless steel seamless pipe

Stainless steel is the abbreviation of stainless acid-resistant steel. Steel that is resistant to weak corrosive media such as air, steam, and water or is stainless is called stainless steel; steel that is resistant to chemical corrosive media (chemical corrosion such as acids, alkalis, salts, etc.) This kind of steel is called acid-resistant steel.Stainless steel seamless pipes are widely used in petroleum, chemical, pharmaceutical, food and other industries, as well as construction, decoration and other fields.

2. Production and manufacturing methods

According to different production methods, it can be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, etc.

(1) Hot rolled seamless pipe

Hot-rolled seamless pipes are generally produced on automatic pipe rolling units. The solid tube blank is inspected and surface defects are removed, cut into the required length, centered on the perforated end of the tube blank, and then sent to the heating furnace for heating and piercing on the punching machine. It continues to rotate and advance during piercing holes. Under the influence of the rollers and the end, the tube blank is hollow gradually, which is called gross pipe. Then it is sent to the automatic pipe rolling machine to continue rolling. Finally, the wall thickness is evened by the leveling machine, and the diameter is determined by the sizing machine to meet the specification requirements. The use of continuous pipe rolling units to produce hot-rolled seamless steel pipes is a more advanced method.

(2) Cold rolled pipe or cold drawn pipe

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 composed of a variable cross-section circular groove and a fixed conical head. Cold drawing is usually performed on a 0.5~100T single-chain or double-chain cold drawing machine.

(3)Extruded tube

In the extrusion method, the heated tube blank is placed in a closed extrusion cylinder, and the perforated rod and the extrusion rod move together to cause the extruded part to be extruded from the smaller die hole. This method can produce steel pipes with smaller diameters.

3.Uses of seamless pipes

Seamless pipes are widely used. General-purpose seamless pipes are rolled from ordinary carbon structural steel, low alloy structural steel or alloy structural steel, with the largest output, and are mainly used as pipes or structural parts for conveying fluids. Special-purpose seamless pipes include seamless pipes for boilers, seamless pipes for geology, and seamless pipes for petroleum.

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