Medium and low pressure steel pipe made in China
(1) Gb3087-82 seamless steel tubes for low and medium pressure boilers. Tensile test shall comply with GB / t228-87, hydrostatic test with GB / t241-90, flattening test with GB / t246-97, flaring test with GB / t242-97 and cold bending test with gb244-97.
(2) Gb5310-95 seamless steel tubes for high pressure boilers. Tensile test, hydraulic test and flattening test are the same as those specified in gb3087-82; Impact test according to gb229-94, flaring test according to GB / t242-97 and grain size test according to Yb / t5148-93; Microstructure inspection shall be in accordance with gb13298-91, decarburized layer inspection shall be in accordance with gb224-87, and ultrasonic inspection shall be in accordance with GB / t5777-96.
(3) The physical performance inspection and indexes of imported boiler tubes shall be carried out in accordance with the relevant standards specified in the contract（ 1) The main importing countries of boiler tubes are Japan and Germany. The specifications of frequently imported products are 15914.2mm; 2734.0mm; 219.110.0mm; 41975mm; 406.460mm, etc. The minimum specification is 31.84.5mm, and the length is generally 5 ~ 8m.
(2) In the import claim case, the ST45 seamless boiler tubes imported from Mannesmann steel pipe plant in Germany were found to have internal defects exceeding the regulations of the plant and the standards of the German iron and Steel Association.
(3) Alloy steel pipes imported from Germany are mainly 34CrMo4 and 12CrMoV. This kind of steel pipe has good high-temperature performance and is often used as steel pipe for high-temperature boiler.
(4) There are many alloy pipes imported from Japan, with specifications of 426.012mm 5 ~ 8m; 152.48.0mm12m; 89.110.0mm6m； 101.610.0mm12m; 114.38.0mm6m; 127.08.0mm9m, etc. Implement Japanese industrial standard jisg3458, and the steel grade is stpa25. This kind of steel pipe is often used as supporting superalloy pipe. High pressure seamless steel pipe is a kind of seamless pipe. The manufacturing method is the same as that of seamless pipe, but there are strict requirements for the steel grade used in the manufacture of steel pipe. According to the service temperature, it is divided into general boiler tube and high-pressure boiler tube.
① The service temperature of high-pressure seamless steel pipe is below 450 ℃, and the domestic pipe is mainly made of No. 10 and No. 20 carbon steel hot-rolled pipe or cold drawn pipe.
② High pressure seamless steel pipe is often in high temperature and high pressure conditions. The pipe will be oxidized and corroded under the action of high temperature flue gas and steam. The steel pipe is required to have high lasting strength, high anti-oxidation and corrosion performance and good structural stability.