1. The difference between appearance, seamless steel pipe and welded steel pipe is that the inner wall of the pipe is welded to reinforce, and seamless.

2. The pressure of the seamless steel pipe is relatively high, and the welded pipe is usually about 10 MPa, and the seamless processing of the welded pipe is now done.

3. One of the seamless steel tubes in roll forming. It is welded after rolling, and the requirements for welded steel pipes generally include spiral welding and welding. Seamless steel pipe is better in performance, of course, the price is also higher.

Steel pipe is a kind of hollow steel belt, which is widely used in pipelines for conveying fluids, such as oil, natural gas, water, natural gas, steam, etc. In addition, when the bending and torsional strength are the same, the weight is lighter, so it is also widely used in manufacturing Mechanical parts and engineering structures. It is also commonly used in the production of various conventional weapons, barrels, shells, etc.

Classification of steel pipes: steel pipes, seamless steel pipes and welded steel pipes (pipes). According to the cross-sectional shape, it can be divided into round pipes and special-shaped pipes. Steel pipes are widely used, but there are also some square, rectangular, semicircular, hexagonal, equilateral triangle, and octagonal special-shaped steel pipes.

Hydraulic test is carried out on the fluid pressure steel pipe to test the compressibility and quality, no leakage under the specified pressure, immersion or qualified expansion, some steel pipes are tested according to the standard or the buyer's requirements, flaring test, flattening test, etc.

Seamless steel pipe, seamless steel pipe is made of solid ingot or perforated capillary tube, and then hot rolled, cold rolled or cold drawn. *The diameter of the seamless steel pipe of the wall thickness specification is expressed in millimeters. Seamless steel pipe hot-rolled and cold-rolled (dial) seamless steel pipe.

Hot-rolled seamless steel pipes are general steel pipes, low and medium pressure boiler pipes, high pressure boiler pipes, alloy steels, stainless steel pipes, oil cracking pipes, geological steel pipes and other steel pipes, etc.

Cold-rolled (dial) seamless steel pipes include general steel pipes, low and medium pressure boiler pipes, high pressure boiler pipes, alloy steel, stainless steel pipes, petroleum cracking pipes, steel pipes, others include carbon thin-walled steel pipes, alloy thin-walled steel pipes, and thin-walled stainless steel pipes ,Steel Pipe.

Usually larger than 32mm hot-rolled seamless steel pipe diameter, wall thickness 2.5-75mm, cold-rolled seamless steel pipe diameter 6mm, wall thickness 0.25mm, 5mm diameter thin-walled pipe thickness less than 0.25mm, higher dimensional accuracy than hot-rolled cold .

Generally used seamless steel pipes are made of 10, 20, 30, 35 and 45 high quality carbon steel for guitars, 16 manganese, 5 for 40 MNV low alloy structural steel or cr, 45 for 30 crmnsi mn2 40 MNB for guitars made of hot rolled or cold rolled steel. At 10,20, such as low carbon steel seamless pipes are mainly used for fluid pipelines. 45 and 40 chrome medium carbon steel seamless pipes are used to manufacture mechanical parts, such as pressure parts for automobiles and tractors. Seamless steel pipes are generally used to ensure strength and flattening tests. Hot-rolled steel pipes are delivered in a hot-rolled or heat-treated state; cold-rolled and heat-treated state are delivered. Low and medium pressure boiler seamless steel pipes: used to manufacture various low and medium pressure boiler superheated steam pipes, water pipes, water wall pipes, locomotive boiler superheated steam pipes, pipes, small pipes and pipe arch bricks, etc.

High-quality carbon structural steel hot-rolled or cold-rolled seamless steel pipe (dial). It is mainly made of 10 and 20# steel, in addition to ensuring the chemical composition and mechanical properties to do hydrostatic test, edge, flaring, flattening test, etc. Delivery in the hot-rolled state, hot-rolled cold-rolled (dial) heat-treated state delivery.

High-pressure boiler tubes: mainly used in the manufacture of high-pressure steam boilers, pressure pipes, etc. High-quality carbon structural steel, alloy steel and stainless steel heat-resistant steel seamless steel pipe, the party of the boiler pipe will be oxidized and corroded under the action of high-temperature and high-pressure pipe and work under the action of high-temperature flue gas and steam, so the steel pipe has high fracture strength, High oxidation resistance, and good structural stability, the steel grades used are: high-quality carbon structural steel grade 20 grams, 20 Spanish mango, 25 Spanish mango; 15 withdrawal, alloy structural steel steel grade 20 crmog withdrawal, 12, 15 crmog, 12 cr2mog, 12 crmovg, 12 cr3movsitib, etc.; heat-resistant steel rust cr18ni9, 1 cr18ni11nb commonly used high-pressure boiler tubes, in addition to ensuring the chemical composition and mechanical properties of the root, flaring, flattening test of the hydraulic test. Steel pipes are delivered in the heat-treated state. In addition, the microstructure and grain size of the steel pipe are completed, and the decarburization layer also has certain requirements. Seamless steel pipes for geological drilling and oil drilling; to prove the underground stratum structure and groundwater, oil, natural gas and mineral resources, using wells for drilling. Mining more drilling, oil and gas geological drilling Oil drilling in seamless steel pipes as the main drilling equipment, mainly including core pipe, casing, casing, drill pipe, etc. Due to the work of drilling pipes deep into the formation depth of thousands of meters, the working conditions are very complicated, and the drill pipes are affected by pull-down, compression, bending, torsional load stress and unevenness, and are also subject to mud, stones and wear. Therefore, it is required that the oil pipes must have Sufficient strength, hardness, wear resistance and impact toughness, steel pipe steel with the pinyin "DZ (geology) plus a number represents the yield point of the steel, say ordinary steel DZ45 MNB 45 50 mn; DZ50 40 mn2 40 mn2si; DZ55 40 mn2mo 40 MNVB; 40 mnmob DZ60, DZ65 27 mnmovb. Steel pipe is delivered in a heat-treated state. Petroleum cracking pipe: used for refinery furnace tubes, seamless tubular heat exchanger tubes and pipes. Commonly used high-quality carbon steel (10 , 20), alloy steel (12 crmo 15 crmo), heat-resistant steel (12 cr2mo 15 cr5mo), stainless steel cr18ni9 two kinds) material (1, 1 manufacturing. In addition to the chemical composition and various mechanical properties of the steel pipe, and to ensure the water pressure , flattening, flaring test, surface quality and non-destructive inspection. Steel pipes are delivered in the heat treatment state. Stainless steel pipes: various stainless steel hot-rolled and cold-rolled stainless steel pipes, pipes are widely used in petroleum, chemical equipment and stainless steel structural parts for various purposes , in addition to guaranteeing the chemical composition and mechanical properties, all steel pipes are used as liquids to maintain hydraulic pressure tests under pressure. Various special steel pipes are guaranteed according to the specified conditions