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How to Distinguish High Quality GB/T9948 Seamless Steel Pipe

Date:2019-07-15    keywords:GB/T9948,seamless steel pipe

Classification of 3087 seamless steel tubes: seamless steel tubes are divided into hot rolling and cold rolling seamless steel tubes.


Hot-rolled seamless steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes.


Cold-rolled seamless steel pipe is divided into general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe, other steel pipes, and also includes carbon thin-walled steel pipe and alloy thin-walled steel pipe. Stainless steel thin-walled steel pipe and special-shaped steel pipe. The outer diameter of the hot-rolled seamless pipe is generally larger than 32mm, the wall thickness is 2.5-75mm, the diameter of the cold-rolled seamless steel pipe can be 6mm, the wall thickness can be 0.25mm, the outer diameter of the thin-walled pipe can be 5mm, and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.

Generally used seamless steel pipe: it is made of 10, 20, 30, 35, 45 and other high-quality carbon steel 16Mn, 5MnV and other low-alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steel hot-rolled or cold-rolled. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid conveying pipes. 45, 40Cr and other medium carbon steel seamless pipes are used to make mechanical parts, such as the force parts of automobiles and tractors. Generally, seamless steel pipes are required to ensure strength and flattening test. The hot rolled steel pipe is delivered in a hot rolled state or a heat treated state; the cold rolling is delivered in a heat treated state.

Seamless steel tubes for low and medium pressure boilers: used in the manufacture of various low and medium pressure boilers, superheated steam pipes, boiling water pipes, water wall pipes and superheated steam pipes for locomotive boilers, large smoke pipes, small smoke pipes and arch brick pipes. Hot-rolled or cold-rolled seamless steel tubes are made of high-quality carbon structural steel. It is mainly made of steel No. 10 and No. 20. In addition to ensuring chemical composition and mechanical properties, it is required to carry out hydraulic test, crimping, flaring and flattening. Hot rolling is delivered in a hot rolled state, and cold rolling is delivered in a heat treated state.

High-pressure boiler steel pipe: high-quality carbon structural steel, alloy structural steel and stainless steel heat-resistant steel seamless steel pipe used for steam boiler pipes mainly used for manufacturing high pressure and above. These boiler pipes are often operated under high temperature and high pressure. The pipe will also oxidize and corrode under the action of high temperature flue gas and water vapor. Therefore, the steel pipe is required to have high durability, high oxidation resistance and good structural stability. The steel grade is: high quality carbon structure. Steel steel has 20G, 20MnG, 25MnG; alloy structural steel No. 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.; rust-resistant heat-resistant steel commonly used 1Cr18Ni9, 1Cr18Ni11Nb high-pressure boiler tube to ensure chemical composition and mechanical properties It is necessary to do the hydraulic test one by one, and to make the flaring and flattening test. The steel pipe is delivered in a heat treated state. In addition, there are certain requirements for the microstructure, grain size and decarburization layer of the finished steel pipe.

Seamless steel pipes for geological drilling and oil drilling: drilling wells for drilling underground structures, groundwater, oil, natural gas and mineral resources. Oil and natural gas mining is inseparable from drilling wells. Seamless steel pipes for oil drilling for geological drilling are the main equipment for drilling, mainly including core outer tubes, core inner tubes, casings and drill pipes. Because the drilling pipe is deep enough to work in a depth of several kilometers, the working conditions are extremely complicated, and the drill pipe is subjected to stress such as tension, pressure, bending, torsion and unbalanced impact load, and is also subject to mud and rock wear. Therefore, the pipe is required. Must have sufficient strength, hardness, wear resistance and impact toughness, steel for steel pipe with "DZ" (geological Chinese phonetic prefix) plus the number one represents the steel yield point, the commonly used steel number is DZ45 45MnB, 50Mn; 40Mn2, 40Mn2Si of DZ50; 40Mn2Mo, 40MnVB of DZ55; 40MnMoB of DZ60, 27MnMoVB of DZ65. The steel pipes are delivered in a heat treated state.

Petroleum cracking tubes: seamless tubes for furnace tubes, heat exchanger tubes and pipes used in petroleum refineries. Commonly used in high-quality carbon steel (10, 20), alloy steel (12CrMo, 15CrMo), heat-resistant steel (12Cr2Mo, 15Cr5Mo), stainless steel (1Cr18Ni9, 1Cr18Ni9Ti). In addition to the chemical composition and various mechanical properties, the steel pipe also guarantees water pressure, flattening, flaring and other tests, as well as surface quality and non-destructive testing. The steel pipe is delivered under heat treatment. Stainless steel tube: stainless steel tube with various hot-rolled and cold-rolled stainless steel, widely used in petroleum, chemical equipment pipelines and stainless steel structural parts for various purposes, except for chemical composition and mechanical properties, used as a steel tube subjected to fluid pressure. To ensure that the water pressure test is qualified. All kinds of special steel pipes must be guaranteed according to the regulations.

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