What is a seamless tube? It is a type of boiler tube and belongs to the category of seamless steel tubes. The manufacturing method is the same as that of seamless steel pipes, but there are certain strict requirements for the steel grades used to manufacture steel pipes. Since seamless pipes are often used in high temperature and high pressure conditions, seamless pipes are mainly used to manufacture superheater pipes, reheater pipes, steam guide pipes, and main steam seamless pipes for high-pressure and ultra-high pressure boilers.
The production method of seamless tubes can be divided into general boiler tubes and high-pressure boiler tubes according to the temperature of use. The use temperature of seamless pipes is below 450 ℃, and domestic pipes are mainly made of 10#, 20# carbon steel hot-rolled pipes or cold-drawn pipes. Seamless pipes are often used in high temperature and high pressure conditions. Under the action of high temperature flue gas and water vapor, the pipe will be oxidized and corroded. The steel pipe is required to have high lasting strength, high oxidation corrosion resistance, and good microstructure stability.
Seamless pipes are widely used, mainly used to manufacture water wall pipes, boiling water pipes, superheated steam pipes, superheated steam pipes for locomotive boilers, large and small smoke pipes and arch brick pipes. And it can also be used in superheater tubes, reheater tubes, gas guide tubes, main steam tubes, etc.
Basic knowledge of seamless pipes
Under normal circumstances, the seamless steel pipes used in daily life are of normal diameter, and seamless pipes are only used in some special places. Today, I will introduce the relevant knowledge of seamless pipes to you, which will help to better use this kind of pipes in the future. In general, seamless steel pipes with small outer diameters are collectively referred to as seamless pipes, but there is still a specific range. Generally, steel diameters below 89mm and above 4mm can be called seamless pipes.
In most cases, seamless pipes are also used as pipelines for conveying fluids. Compared with solid steels such as round steel, the weight is lighter when the bending and torsional strength is the same. It is an economical section steel and is widely used in the manufacture of structures. Parts and mechanical parts, such as oil drill pipe, automobile transmission shaft, bicycle frame, steel scaffolding used in construction, etc.
The general specification of seamless pipe is between 6-89mm in outer diameter, and its diameter is relatively small. The wall thickness of 1-12mm can also be divided into small-diameter thick-walled seamless pipes and small-diameter thin-walled seamless pipes. Its weight calculation formula: [(outer diameter-wall thickness)*wall thickness]*0.02466 = kg/meter (weight per meter)
In order to make seamless pipes with smaller size and better quality, cold rolling, cold drawing or a combination of the two methods must be used. 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-section circular hole groove and a stationary conical head. Cold drawing is usually carried out on a single-chain or double-chain cold drawing machine, that is, the hot tube blank is placed in a closed extrusion cylinder. Extruded into the die hole so that seamless pipes can be produced.