1. Smaller outer diameter.
2. High precision can be made in small batch production
3. Cold drawn finished products have high precision and good surface quality.
4. Steel pipe cross area is more complex.
5. Steel pipe performance is more superior, the metal is more dense. 1, production and manufacturing methods
By different production methods can be divided into hot-rolled pipe, cold-rolled pipe, cold-drawn pipe, extruded pipe and so on.
1.1, hot rolled seamless tubes are generally produced in automatic rolling unit. Solid billets are inspected and removed from surface defects, cut to the required length, centered on the perforated end face of the billet, and then sent to the heating furnace for heating, and perforated on the perforating machine. In the piercing at the same time constantly rotating and forward, under the action of the roll and the top head, the internal cavity of the billet is gradually formed, known as the rough pipe. Then sent to the automatic rolling machine to continue rolling. Finally, the wall thickness is evened out by the equalizing machine, and the diameter is set by the sizing machine to meet the specifications. The use of continuous tube rolling units to produce hot rolled seamless steel tubes is a more advanced method.
1.2, if you want to get smaller size and better quality seamless tube, must use cold rolling, cold drawing or a combination of the two methods. Cold rolling is usually carried out in a two-roll mill, the tube is rolled in a circular hole pattern consisting of variable section round hole grooves and immovable conical top head. Cold drawing is usually carried out in 0.5 to 100T single or double chain cold drawing machine.
1.3, extrusion method is to put the heated billet in a closed extrusion cylinder, perforated rod and extrusion rod together with the movement, so that the extruded parts from the smaller die hole extrusion. This method can produce smaller diameter steel pipe.
2, use
2.1, seamless pipe is widely used. General purpose seamless pipe is rolled from ordinary carbon structural steel, low alloy structural steel or alloy structural steel, the most production, mainly used as a pipeline for the transportation of fluids or structural parts.
2.2, according to the use of different three categories of supply: a, according to the chemical composition and mechanical properties of supply; b, according to the mechanical properties of supply; c, according to the hydraulic test supply. According to a, b class supply of steel pipe, such as for bearing liquid pressure, also need to carry out hydraulic test.
2.3, seamless tubes for specialized purposes include seamless tubes for boilers, seamless tubes for geological purposes and seamless tubes for petroleum purposes, among many others.
3, types
3.1, seamless steel pipe can be divided into hot-rolled pipe, cold-rolled pipe, cold-drawn pipe, extruded pipe and so on according to different production methods.
3.2, according to the shape of the classification of round tube, shaped tube. In addition to the square tube and rectangular tube, there are oval tube, semi-circular tube, triangular tube, hexagonal tube, convex tube, plum blossom-shaped tube.
3.3, according to the different materials, is divided into ordinary carbon structural pipe, low alloy structural pipe, high-quality carbon structural pipe, alloy structural pipe, stainless steel pipe and so on.
3.4, according to the specialized use, there are boiler pipe, geological pipe, petroleum pipe and so on.
4, specifications and appearance quality
Seamless pipe according to GB/T8162-87
4.1, specifications: hot rolled pipe outside diameter 32 ~ 630mm. wall thickness 2.5 ~ 75mm. cold rolled (cold drawn) pipe outside diameter 5 ~ 200mm. wall thickness 2.5 ~ 12mm.
4.2, appearance quality: the internal and external surface of the steel pipe There shall be no cracks, folding, rolling folding, delamination, hairline and scarring defects exist. These defects should be completely removed, the removal shall not make the wall thickness and outside diameter exceed the negative deviation.
4.3, the ends of the steel pipe should be cut at right angles and remove burrs. Wall thickness greater than 20mm steel pipe allows gas cutting and hot saw cutting. By agreement between the supply and demand sides can also not cut the head.
4.4, cold-drawn or cold-rolled precision seamless steel tube "surface quality" with reference to GB3639-83.
5, chemical composition test
5.1, according to the chemical composition and mechanical properties of the supply of domestic seamless steel tubes, such as 10, 15, 20, 25, 30, 35, 40, 45 and 50-gauge steel should be in accordance with the GB/T699-88 provisions. 88 of the regulations. Imported seamless pipes are tested according to the relevant standards specified in the contract. 09MnV, 16Mn, 15MnV steel chemical composition should be consistent with the provisions of GB1591-79.
5.2, the specific analysis methods refer to GB223-84 "steel and alloy chemical analysis methods" of the relevant parts.
5.3, the analysis of deviation with reference to GB222-84 "chemical analysis of steel specimens and finished products with the allowable deviation of chemical composition".
6, physical properties test
6.1, according to the institutional properties of the supply of domestic seamless pipe, ordinary carbon steel according to GB/T700-88, Class A steel manufacturing (but must ensure that the sulfur content does not exceed 0.050% and phosphorus content does not exceed 0.045%), its mechanical properties should be in line with the values set out in the table GB8162-87.
6.2, according to the hydraulic test supply of domestic seamless pipe must ensure that the standard specified in the hydraulic test.
6.3 The physical property test of imported seamless pipes shall be conducted in accordance with the relevant standards specified in the contract.
7, the main import and export
7.1, general seamless pipe imports are large. The main importing countries are Germany and Japan. European countries such as Romania, Russia, Switzerland, France, Spain, the Czech Republic, Yugoslavia, Hungary and other countries are imported. There are also a small number of imports from South America, Argentina, Mexico and other countries.
7.2, according to the different requirements of China's goods units, imported seamless pipe specifications up to more than 100 kinds of common specifications are 15922mm, 1595mm, 15918mm. 114.38mm, 114.310mm, 114.313mm. length is generally 5 ~ 8m or 4 ~ 7m ranging. Mainly hot-rolled carbon structure, and ST65. import specifications for the smallest diameter of 305mm, the largest 47813mm.
7.3, from France and Spain had imported a small number of smaller diameter and thin-walled seamless pipe, such as 183mm, 223mm, 26.93mm. Implementation of the general rules of the German Mannesmann Steel Tube Factory.
7.4, from Hungary and Japan imported seamless pipe, often refer to DIN2448, DIN1629.
7.5, in the case of import claims, the imported seamless pipe there are quality problems are: chemical composition failure, flattening test splitting, low tensile strength, the emergence of serious corrosion and pits, etc..