Tianjin dedicated square tube wholesale and direct production
（1） Slender pipes shall be vertically hung and heated in salt bath furnace or well furnace as far as possible to reduce deformation caused by self weight. （2） When pipe fittings with different section sizes are heated in the same furnace, small pieces shall be placed at the outer end of the furnace, and small pieces shall be taken out of the furnace first. （3） Each charging amount shall be consistent with the power of the furnace. When the charging amount is large, the temperature is easy to be pressed, and the heating time needs to be extended. （4） For square tube quenched with water or salt water, the quenching temperature is taken as the lower limit, and for quenched oil or molten salt, the quenching temperature is taken as the upper limit. （5） During dual medium quenching, the time of staying in one quenching medium shall be controlled according to the above three methods. The time of moving from one quenching medium to the second quenching medium shall be as short as possible, and 0.5-2s is appropriate. （6） Pipes that are not allowed to be oxidized or decarburized on the external surface shall be heated in calibrated salt bath furnace or maintenance atmosphere furnace. If conditions are not available, it can be heated in the air resistance furnace, but protective measures shall be taken. （7） After the square tube is vertically immersed in the quenching medium, it does not swing, but moves up and down, and stops stirring the quenching medium. （8） When there is a lack of cooling ability in the part with high pipe hardness requirements, the part can be sprayed with liquid cooling while immersed in the quenching medium as a whole to improve the cooling speed. （9） It must be placed in the effective heating area. The charging amount, charging method and stacking method shall ensure that the heating temperature is evenly divided, without distortion and other defects. （10） When heating in the salt furnace, do not get too close to the electrode to prevent partial overheating, and the interval should be more than 30mm. The distance from the furnace wall and the immersion depth below the liquid level shall be more than 30mm. （11） During step quenching, the quenching temperature can be properly increased to increase the stability of austenite in rectangular tube and avoid its formation into pearlite. （12） Structural steel and carbon steel can be directly put into the furnace with quenching temperature or 20-30 ℃ higher than quenching temperature for heating. High carbon and high alloy steel shall be preheated at about 600 ℃ before rising to quenching temperature. （13） The quenching temperature can be improved properly for pipes with deeper quenching layer, and lower quenching temperature can be selected for those with shallower quenching layer. （14） The cooling water of rectangular tube shall be free of oil, soap liquid and other dirt. Under normal conditions, the water temperature shall not exceed 40 ℃, and the oil temperature shall not exceed 80 ℃.
Tianjin dedicated square tube wholesale and direct production
The standards of square tubes are divided into ministerial standards and national standards. The ministerial spiral welded square tubes are divided into SY/T5037-1999 spiral welded square tubes, GB/T9711.1-1999 spiral welded square tubes GB/T9711.2-1999 and other executive standards for square tube and square tube executive standards and size tendency GB/T9711-1997 API Spec 5L SY/T5037-2000 pipe end outer diameter tendency+2.38mm - 0.79mm D<508 ± 0.75% DD ≥ 508 ± 1.00% D ± 1.25% D wall thickness tendency 50815.0% t12.5% tD ≥ 508 ＋ 17.5% t-10.5% t D<508 ± 12.5% tDC508 ± 10.0% t ± 12.5% tweld reinforcement ≤ 3.18mm 0.5-3.0mm inside ≤ 2.0mm outside ≤ 2.5mm straightness ≤ 0.2% L ≤ 0.2% L ≤ 0.25% L pipe end status bevel angle 30 ° -- 35 ° edge clipping 1.59 ± 0.79mm bevel angle ≤ 1.59mm bevel angle 30 ° -- 35 ° edge clipping 1.59 ± 0.79mm bevel angle ≤ 1.59mm bevel angle 30 ° -- 35 °
Tianjin dedicated square tube wholesale and direct production
Wall thickness grading of rectangular pipes - extra thick rectangular pipes, thick rectangular pipes, thin rectangular pipes. The thick wall rectangular pipe is a galvanized welded square pipe used for low pressure fluid escort, which is only used for ordinary low pressure fluid, mainly used for water, gas, oil, hot water or steam escort; Galvanized welded thick wall rectangular pipe for low pressure escort is mainly used to escort ordinary low pressure fluids such as water, gas, oil, hot water or steam. The surface of the square pipe adopts hot galvanizing or cold galvanizing anti-corrosion process. The rectangular thick wall mining infusion welding square tube is mainly used for mining air pressure welding, row welding, shaft drop welding, etc.
Tianjin dedicated square tube wholesale and direct production
The square tube is a square tube type. Many materials can form a square tube. It is used in, for, and where. Most square tubes are made of steel tubes, mostly for construction, decoration, and construction. Square pipe (Fangtong) is a kind of square pipe, that is, steel pipes with equal side lengths. It is rolled from strip steel after processing. Generally, the strip steel is unpacked, leveled, curled and welded to form a round pipe, which is then rolled into a square pipe and cut to the required length. Usually 50 pieces per pack. Square tube (Fangtong) is also called rectangular tube, and the algorithm is (a+a) * 2/3.14 or (a+b) * 2/3.14
