Seamless Steel Pipes；Seamless steel pipe is a round, square or rectangular steel with a hollow cross-section and no seams around it. Seamless steel pipe is made from ingots or solid billets by piercing into capillary tubes, and then hot-rolled, cold-rolled or cold-drawn. Seamless steel pipe has a hollow cross-section and is mostly used as a pipeline for transporting fluids. Compared with solid steel such as round steel, steel pipes have the same bending and torsional strength and are lighter in weight. They are economical cross-sectional steels and are widely used in the manufacture of structures. Parts such as oil drilling rods, automobile drive shafts, bicycle frames, steel scaffolding for construction and mechanical parts.
Seamless steel pipe production has a history of nearly 100 years.
The German Manisman brothers first invented the double-slant cut mirror machine in 1885. 1891 invented the cycle rolling machine. 1903 Swiss Stiefel invented the automatic tube rolling machine. Later, there were a variety of active extension machines such as continuous tube rolling machines and top tube rolling machines.And began to develop into a modern enterprise in China. Seamless steel pipe industry.
The 1930s, due to the use of three-roller rolling mill, extrusion machine and ordinary cold rolling mill.The variety and quality of steel pipe has been improved. 1960s, due to the improvement of continuous pipe making machine, the emergence of three-roller perforating machine, especially the enterprise application system tension reducer and the success of continuous casting billet, improve the efficiency of social production management, enhance the ability of seamless steel pipe and welded pipe competition. 1970s In the 1970s, seamless pipe and welded pipe side by side, the world’s steel pipe production at an annual rate of more than 5% growth.
After 1953, China began to attach importance to enterprise development, carried out preliminary research on seamless steel pipe industry, and formed a production management system for rolling various large, medium and small tubes. Generally speaking, copper tubes are also made by ingot beveling, tube rolling machine rolling, steel coil drawing and other processes.
① Main production processes (main inspection processes) for hot-rolled seamless pipes
Pipe billet preparation and inspection → pipe billet heating → piercing → pipe rolling → pipe scrap reheating → fixing (shrinking) diameter → heat treatment → finished pipe straightening → finishing → inspection (non-destructive, physical and chemical, stage inspection) → storage.
②The main production process of cold-rolled (drawn) seamless pipe
Prepared billet → pickling and lubrication → cold rolling (drawing) → heat treatment → straightening → finishing → the inspection.
Seamless Steel Pipes
Seamless steel pipe is light in weight, its weight is only 1/5 of square steel.
Seamless steel pipe is corrosion-resistant, resistant to acid, alkali, salt, and atmospheric corrosion, high temperature, good impact and fatigue resistance, no need for regular maintenance, the effective service life of 15 years or more.
The tensile strength of seamless steel pipe is more than 8-10 times that of ordinary steel, modulus of elasticity is better than that of steel, excellent creep resistance, corrosion resistance, and impact resistance.
advantages of seamless steel pipe such as excellent mechanical properties and easy processing.
Seamless steel pipe has high elasticity, can be used repeatedly in mechanical equipment, has no memory, no deformation, anti-static.
In recent years, seamless steel tubes have been widely used in various industries. The market demand is too large, and the more enterprises produce seamless steel tubes, the more uneven the quality of products.
The first thing we need to know is that the wall thickness of high-quality seamless steel will be particularly thick, because the thicker the wall thickness of the product, the more economical and practical it is, and if the wall thickness is thinner, the greater the chance of its processing cost. If this happens, the resource cost will be higher. Second, the technology of seamless steel also determines its limitations. General seamless steel has low precision, uneven wall thickness, low brightness inside and outside the tube, high sizing cost, pits, and black spots inside and outside. It is not easy to remove; again, it must be processed offline for inspection and shaping. Therefore, it embodies its superiority in high pressure, high strength, and mechanical structure material. In the process of using it, we will slowly find out.
In fact, seamless steel pipe has entered the market only in recent years. With the increase of market demand, the advantages of seamless steel pipes have been stimulated. However, there are also many counterfeit products in the market. I hope you will be selective in your choice. Must be cautious.
As seamless steel pipe works under high temperature and pressure standards for a long time, the raw material will have stress relaxation, plastic deformation, and ductility reduction, initial mechanism changes, corrosion and other phenomena.
Seamless steel tubes used as heating furnaces should have
Adequate long-term compressive strength.
Sufficient plastic deformation work.
less ageing and thermal ductility.
high oxidation resistance, resistance to fly ash, high temperature gases, steam and intergranular corrosion.
Steel grades of seamless steel pipes include carbon steel and its ferritic, ferritic and martensitic stainless wear-resistant steels. To better improve the thermal efficiency and reduce fuel consumption of thermal diesel generating sets, the trend of large space and high main parameters (high temperature, high pressure) thermal power plant generating sets (above 1000MW) is the dominant trend in all aspects. part of the world. The working pressure of steam is increased to 31.5 to 34.3 MPa, and the temperature of saturated steam is 595 to 650°C. It is moving toward high critical pressure, making higher regulations for seamless steel pipes explicitly. Therefore, the development and design of a new steel grade to consider the use of high major parameters of the power plant boiler. Table 1 shows the commonly used steel grades for seamless steel tubes; Table 2 shows the new steel grades for seamless steel tubes.