Heze 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 ℃.
Heze dedicated square tube wholesale and direct production
Square pipe is a kind of name for square pipe and rectangular pipe, that is, steel pipes with equal and unequal 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. Square and rectangular tubes are also called square and rectangular cold-formed hollow steel sections, which are called square and rectangular tubes for short, and their codes are F and J.
Heze dedicated square tube wholesale and direct production
The construction process of square tube is relatively simple. If the square tube consumer manufacturer needs to add another process after using the round tube for construction, that is to change the cross section of the round tube to square, and the cross section of the square tube is square originally, so this process can be omitted, and the construction will be easier to stop. Analysis of seismic resistance and bearing capacity of square tube. After repeated experiments on square tubes and round tubes by square tube consumer manufacturers, it is found that square tubes can accept greater pressure and vibration than round tubes, which illustrates that the use of square tubes can improve the quality of buildings, so it is natural to choose square tubes.
Heze dedicated square tube wholesale and direct production
Seamless square tubes pass through the tube blank sawing section of the steel mill, and then are heated - perforated - sized - straightened - cooled - slugged - packaged in the annular furnace to become qualified waste products. Generally, it is impossible to place so many stock items in the consumer workshop when they are sent to the user, which requires dealers to place some stock items. However, dealers generally do not have large indoor warehouses, and some costs are too high, which is not cost-effective. Most of them are outdoor warehouses. If the seamless square tubes are placed outdoors, they will be exposed to the wind and the sun. The so-called floating rust literally means a layer of rust floating on the seamless square tube, which can be removed with a towel or other things. Simply speaking, floating rust is also considered as no rust, which belongs to the normal state. The rusting of seamless square tubes is a long-term problem. At least for more than one year, the seamless square tubes that have been exposed to the wind and the sun outside have large and small pits on them, which is the only difference between the floating rust and rusting of seamless square tubes.
Heze dedicated square tube wholesale and direct production
1. After hot rolling, non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, showing delamination (interlayering). Delamination greatly deteriorates the tensile properties of steel along the thickness direction, and may present interlaminar tearing when the weld shrinks. The partial strain induced by weld shrinkage often reaches several times of the strain at the yielding point, which is much larger than the strain caused by load; 2. Residual stress caused by uneven cooling. The residual stress is the internal self balanced stress without external force. Hot rolled section steel of various sections has this kind of residual stress. The larger the section size of ordinary section steel is, the greater the residual stress is. Although the residual stress is self equilibrated, it still affects the performance of steel members under external forces. For example, it may have adverse effects on deformation, stability, fatigue resistance, etc.
