Classification of uses of seamless pipes (smls pipe):
1. Structural pipe
This standard applies to seamless steel pipes for general structures and mechanical structures, and the standard for fluid seamless steel pipes applies to general seamless steel pipes for conveying fluids. The main difference between it and the structural seamless steel pipe is that the fluid seamless steel pipe is subjected to hydraulic tests or ultrasonic, eddy current, and magnetic flux leakage inspections one by one. Therefore, in the standard selection of steel pipes for pressure pipes, it is not suitable to use fluid seamless steel pipes.
The seamless steel pipe is expressed as outer diameter * wall thickness, and the thick-walled seamless steel pipe is mainly used for machining, coal mining, hydraulic steel, and other purposes. The material of thick-walled seamless steel pipe is divided into 10#, 20#, 35#, 45#16Mn, 27SiMn, 12Cr1MoV, 10CrMo910, 15CrMo, 35CrMo and so on. Thick-walled seamless steel pipe classification: hot-rolled thick-walled seamless steel pipe, cold-rolled thick-walled seamless steel pipe, cold-drawn thick-walled seamless steel pipe, extruded thick-walled seamless steel pipe, pipe jacking. Structural stainless steel seamless steel pipes are hot-rolled (extruded, expanded) and cold-drawn (rolled) stainless steel pipes and structural parts and parts widely used in chemical, petroleum, textile, medical, food, machinery and other industries. ) seamless steel pipe.
2. Fluid pipe
Fluid pipe is a pipe specially used to transport media with fluid properties. The media with fluid properties, in addition to liquid media such as water, oil, solution, etc., solid media such as cement, grain, coal powder, etc., can also flow under certain conditions.
Fluid pipes can be made of steel, non-ferrous metals such as copper and titanium, or even non-metallic materials such as plastics.
The fluid pipe must have a hollow section, but it can also be square, triangular or any other shape. Some equipment is limited by conditions and must use a rectangular pipe, but most of them still use round pipes. The circular tube has the smallest perimeter/area ratio in all geometric sections, that is, the largest internal section can be obtained under the condition of using the same amount of material.
3. High pressure boiler tube
High-pressure boiler tubes are a type of boiler tubes and belong to the category of seamless steel tubes. The manufacturing method is the same as that of the seamless pipe, but there are strict requirements on the steel type used in the manufacture of the steel pipe. High-pressure boiler tubes are often under high temperature and high pressure conditions when used, and the tubes will be oxidized and corroded under the action of high-temperature flue gas and water vapor. Steel pipes are required to have high durability, high resistance to oxidation and corrosion, and good structural stability. High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, gas guide tubes, main steam tubes, etc. of high-pressure and ultra-high pressure boilers.
4. Alloy pipe
Alloy pipe is a kind of seamless steel pipe. Alloy pipe is divided into structural seamless pipe and high-pressure heat-resistant alloy pipe. Mainly different from the production standard of alloy pipe and its industry, the annealing and tempering of alloy pipe changes its mechanical properties. meet the required processing conditions. Its performance is higher than that of ordinary seamless steel pipes. The chemical composition of alloy pipes contains more Cr, and it has high temperature resistance, low temperature resistance and corrosion resistance. Common carbon seamless pipes do not contain alloy components or have very few alloy components. The reason why alloy pipes are widely used in petroleum, aerospace, chemical, electric power, boiler, military and other industries is because the mechanical properties of alloy pipes change and can be easily adjusted.
5. Petroleum cracking pipe
Petroleum cracking pipe is a long steel material with a hollow section and no joints around it. Petroleum cracking pipe is an economical cross-section steel material. Widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile drive shafts, bicycle frames and steel scaffolding used in construction, etc., suitable for furnace tubes, heat exchanger tubes and pipes used in petroleum and refineries Seamless steel pipe.
6. Low and medium pressure boiler tubes
It is made of steel ingot or solid tube blank by perforation, and then made by hot rolling, cold rolling or cold drawing. Mechanical properties of low and medium pressure boiler tubes: tensile strength σb (MPa): ≥ 410 (42); yield strength σs (MPa): ≥ 245 (25); elongation δ5 (%): ≥ 25; reduction of area ψ (%): ≥5, hardness: unheated ≤156HB, sample size: sample size 25mm. Heat treatment specifications and metallographic structure: Heat treatment specifications: normalizing, 910 ° C, air cooling. Metallographic structure: ferrite + pearlite.
7. Hydraulic prop pipe
Hydraulic strut pipe is based on high-quality carbon structural steel, and one or several alloying elements are properly added to improve the strength, toughness and hardenability of the steel. After this kind of steel is made, it usually needs heat treatment such as quenching and tempering, chemical heat treatment, surface quenching and so on. Compared with high-quality carbon structural steel, it has good comprehensive mechanical properties, and is mostly rolled into round, square, and flat steel materials, which are used as important structural parts in machinery or machines. The corrosion resistance of the hydraulic prop tube itself is not stainless steel, of course the corrosion resistance is not good. But the wear resistance and machinability are much better than stainless steel.
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