The performance advantage of square tube after calcium treatment requires not only high strength， but also good machining performance. For sulfur-containing square tube， sulfur can improve the machinability of steel， so the sulfide inclusion in square tube is the key to determine the quality of steel. Sulfur mainly exists in the form of MNs in the steel. The single MNS inclusion is light black strip. The inclusion with this morphology cuts off the continuity of the steel matrix and makes great differences in the anisotropic properties of the steel. Calcium treatment of molten steel can form MNS inclusions and combine MNS with al CAS to form composite spindle inclusions. Such inclusions can improve the machinability of steel and avoid the adverse impact of MNS inclusions on the properties of steel.
5Except for the thickening of wall thickness， the corner size and edge flatness of square pipe reach or even exceed that of resistance welding cold forming
bThe appearance of fake and inferior square tubes often has pitting. Pockmarked surface is an irregular uneven defect on the surface of square lead pipe due to serious wear of rolling groove. Due to the pursuit of profit by fake and shoddy square tube manufacturers， the rolling of rolling groove often exceeds the standard.
According to the welding specification process test and process analysis，Galvanized square pipe it is determined that the butt weld of QB square pipe adopts double-layer CO gas shielded welding. HMnSiA，35 square tubeHow to solve problems mm welding wire for welding material; The shielding gas is pure CO gas. The welding current of layer weld is ~ A， and that of the second layer is ~ A; The arc voltage is ~ V. The process requirement is that the layer weld must be fully welded to ensure good back forming; The welding current， arc voltage， wire feeding speed and welding speed can be adjusted according to the equipment model.
KSukutaTwo main factors should be considered in the design of square pipe section: one is the safety of the section; the other is the economy of the section. For the safety of the section， we require that the ratio of waist thickness to height of H-section steel should not be less than . For H-section steel used as column， its economy is expressed by the ratio of torsion radius to its mass.
XxElectrochemical polishing: long specular gloss， stable process， less pollution and good durability. Suitable for mass production it is mainly applied to products， imported products and public service products. Its processing technology is stable and the operation is simple.
Elongation after square tube breaking (& sigma;): in the tensile test，Galvanized square pipe this material is ordinary. Square tube used to be called QB square tube.
fIt is beneficial to improve product quality. Seamless pipes can be divided into hot-rolled pipes， cold-rolled pipes， cold drawn pipes and pipes according to different production. Hot-rolled seamless pipes are generally produced on the automatic precision pipe rolling mill. The solid pipe blank is cut into the required length by removing surface defects， centering on the end face of the perforated end of the pipe blank and then sent to the heating furnace for heating. It is perforated on the piercer. At the same time， it rotates and advances continuously， Under the action of the roll and the plug， a cavity is gradually formed inside the pipe blank， which is called the rough pipe， and then sent to the automatic pipe mill for continuous rolling. After the wall thickness is adjusted by the equalizer and the diameter is determined by the sizing machine to meet the specification requirements. The continuous pipe mill is more advanced in producing hot-rolled seamless steel pipe. If you want to obtain seamless pipe with smaller size and better quality， Cold rolling and cold drawing must be adopted，Galvanized square pipe or the combination of cold rolling and cold drawing is usually carried out on the roll mill. The seamless pipe is rolled in the annular pass composed of variable section circular hole groove and fixed conical plug. Cold drawing is usually carried out on the single chain or double chain cold drawing machine， that is，35 square tubeHow to solve problems the heated pipe blank is placed in a closed cylinder， and the perforated rod and rod move， This method can produce steel pipe with small diameter. In the building materials industry， the development of various pipes is different. Because of their different characteristics， there is a certain distance between pipes. Square pipe is one of many pipes in the building materials industry. It is formed after strip steel treatment. We need to understand the various characteristics of steel pipes. However， in the building materials industry， the development of various pipes is different. Because of their different characteristics， due to the of steel pipe and other raw materials，Galvanized pipe_ Galvanized square pipe_ Seamless steel pipe_ Square tube - Wuxi Jiahang the storage of steel pipe needs specific conditions.
ZShot blasting is a high-speed rotating impeller that throws small steel shot or small iron shot out and hits the surface of the square tube at high speed so the oxide layer on the surface of the square tube can be removed. At the same time， the steel shot or iron shot impacts the surface of the square tube at high speed， resulting in lattice distortion and deformation on the surface of the square tube， resulting in surface hardness， which is the key to clean the surface of the square tube
UGood reputationWhen the square tube is processed， it needs to be properly polished to ensure durability， chemical polishing and electrochemical polishing.
iZSquare pipes are mainly used in engineering buildings， glass curtain walls， door and window decoration， steel structures， guardrails， machinery， automobiles， household appliances， shipbuilding， containers， electric power， bicycle frames， motorcycle frames， shelves， fitness equipment， leisure and tourism， steel furniture， various specifications of oil casing， oil pipes and pipeline pipes， water， gas， sewage， air Heating and other fluid transportation， fire fighting and support， construction and other fields.
Steel with chromium content of more than % in steel and high corrosion of external medium (acid， alkali salt) is called square pipe. According to the condition in steel， square tubes can be divided into martensite， ferrite， austenite and ferrite & mdash; Austenite type， precipitation hardening square tube， according to the standard gb & mdash; regulations， a total of regulations.
The covering shall be strong and durable to prevent decay and leakage caused by long-term sun and rain.
Quality departmentpThe disadvantage of solid bending is that it has tensile thinning effect. The actual bending will produce tension at the bending point， and the tensile effect will shorten the longitudinal length of the bending line; The metal at the real bend will become thinner due to stretching.
VSquare pipe is the name of square pipe， that is， steel pipe with equal side length. It is made of rolled strip steel after process treatment.
In the case of dynamic load， plastic design usually calculates the allowable stress according to the safety factor that the allowable stress is not less than the dynamic load and multiplied by the allowable stress. In the case of bending of an axis， it can be calculated by the formula a = W. replacing the calculated strength with plasticity can improve the bearing capacity of the member by %.
bQb square tube the die material selected， has obvious hardening in the deep drawing process， resulting in a lot of hard metal points， resulting in adhesion. It specializes in selling square tube， square rectangular tube， seamless square tube， galvanized square tube， galvanized tube and other special products. It is an old brand with advantageous price and guaranteed quality. It makes the surface of workpiece and die easy to be scratched and worn. Therefore， tool steel for general die can not be used.
kVThe advantage of empty bending is that it can bend the side length when the real bending cannot be carried out， such as synchronous bending and finishing of the upper side and side of qb square tube. Empty bending can also bend the inner corner of r.t without fracture of pipe wall. The disadvantage of empty bending is that when the upper side and side are synchronous empty bending， due to the pressure generated by the upper roll and the lower roll at the same time， the forming force is easy to exceed the critical point， resulting in edge instability and concave and will also affect the stable operation of the unit and forming quality. This is also the different characteristics of qb square tube and round tube empty bending.
Mechanical property is an important index to ensure the end use performance (mechanical property) of square pipe， which depends on the chemical composition and heat treatment of steel. In the steel pipe standard， according to different service requirements， the tensile properties (tensile strength， yield strength or yield point， elongation)， hardness and toughness indexes， as well as the high and low temperature properties required by users are specified.