1. Definition and production process
1. definitionHot rolled seamless steel pipe is made by heating the solid tube billet, punching holes with a puncher, and then hot rolling. This process allows the steel pipe to be rolled at high temperature, and can produce steel pipes of various sizes and thick walls.
2. Production process：
1. Tube preparation：Select appropriate steel billet, the quality of which (including chemical composition, impurity content, etc.) plays a key role in the performance of steel pipes. Generally, the materials of pipe billets include carbon steel, alloy steel, etc.
2. heating: Heat the tube to a high temperature of about 1100-1250℃. This temperature range can make the steel billet reach a good plastic state, which is convenient for subsequent piercing and rolling operations.
3. perforationThe most common piercing method is oblique rolling piercing. Through the action of two relatively rotating rollers and a mandrel, the metal in the center of the tube is squeezed out to form a hollow rough tube.
4. Hot Rolling：The rough tube enters the tube rolling mill for hot rolling. Through multiple passes of rolling, the wall thickness and outer diameter of the rough tube are gradually reduced to reach the specified size. There are many types of tube rolling mills, such as automatic tube rolling mills and continuous tube rolling mills. The working principles of different types of tube rolling mills are slightly different, but the purpose is to shape the steel tube and achieve the required accuracy.
5. Sizing and reducing：After hot rolling, some steel pipes need to be sized or reduced. Sizing is to accurately control the outer diameter of the steel pipe to meet the standard requirements; reducing is to reduce the outer diameter while keeping the wall thickness of the steel pipe relatively stable to meet the size requirements of different users.
6. Cooling and finishing: Finally, the steel pipe is cooled (usually air-cooled or water-cooled), and then undergoes finishing processes such as straightening, head cutting, and inspection to ensure that the straightness, dimensional accuracy, and surface quality of the steel pipe meet the requirements.
2. Performance characteristics
1. Good mechanical properties：After the hot rolling process, the hot rolled seamless steel pipe has a denser metal structure and excellent mechanical properties such as strength and toughness. For example, the hot rolled seamless steel pipe made of ordinary carbon structural steel can have a yield strength of more than 235MPa and a tensile strength of about 370-500MPa. This good mechanical property enables it to withstand higher pressures and loads, and is suitable for various engineering structures and fluid transportation applications.
2. Wide range of sizes: The outer diameter can range from tens of millimeters to hundreds of millimeters, such as common outer diameters are 76mm, 89mm, 108mm, 219mm, 325mm, etc.; the wall thickness range is also wide, ranging from 3-70mm, which can meet the diverse needs of different industries for steel pipe sizes, whether it is large oil pipelines or small mechanical structure pipes.
3. Relatively low production costs: Compared with some cold-processed seamless steel pipes, hot-rolled seamless steel pipes are rolled at high temperatures, the metal has less deformation resistance, the required rolling force is relatively low, and the production efficiency is higher, so in large-scale production, the production cost has certain advantages.
3. Application Areas
1. Oil and Gas Industry。
2. Construction Industry。
3. Mechanical manufacturing field。
4. International standards
· API SPEC 5L "Line Pipe Specification"：Used for oxygen, water and oil pipelines in the petroleum and natural gas industries, it specifies the size, material, performance, test methods, inspection rules, etc. of pipeline pipes. It is the international general standard for steel pipes used in petroleum and natural gas pipelines1.
· API SPEC 5CT "Casing and Tubing Specification"：It is the standard for oil pipes used in the petroleum industry to extract oil or natural gas from oil wells and for casing used as the well wall of oil and gas wells. It has strict regulations on the size, material, performance, connection method, etc. of casing and oil pipes1.
· ASTM A213 Standard Specification for Ferritic and Austenitic Alloy Steel Seamless Tubes for Boilers, Superheaters, and Heat Exchangers：Applicable to ferrite and austenite alloy steel seamless steel pipes used in boilers, superheaters and heat exchangers, and stipulates the chemical composition, mechanical properties, heat treatment system, test methods, etc. of the steel pipes.
· ASTM A312 Standard Specification for Seamless and Welded Austenitic Stainless Steel Pipe：Seamless and welded austenitic stainless steel pipes used in various industrial fields have requirements on the material, size, mechanical properties, corrosion resistance, processing technology, etc. of stainless steel pipes.
· DIN 17175-79 "Heat-resistant seamless steel pipe": German industrial standard, applicable to heat-resistant seamless steel pipes, has strict regulations on the chemical composition, mechanical properties, heat resistance, dimensional accuracy, etc. of steel pipes, and has a certain influence in Europe and internationally.
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