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Large diameter seamless pipe means outside diameter more than 100MM and the wall thickness is greater 0.2 than the outer diameter of the pipe, Large-diameter seamless steel tube is made from solid tube ingot or the perforation capillary, then through hot rolling and cold rolling or cold dial.
General specifications of large-diameter seamless steel pipes:
People with an outer diameter between (89mm-1200mm) are used to calling them large-diameter seamless pipes because of their relatively large diameter.
The wall thickness (5mm-200mm) can actually be divided into: large-diameter thick-walled seamless pipe, large-diameter thin-walled seamless pipe.
Large-diameter seamless steel after hot rolling or forging a special heat treatment and no further direct delivery After cooling, the state is called hot rolling or forging, hot-rolled (wrought) termination temperature is generally 800 ~ 900 ℃, After the general natural cooling in air, so hot rolling (forging) status equivalent to normalizing. The difference is because of hot-rolled (forging) the termination of high and low temperatures, unlike normalizing strict temperature control heating and thus volatility in steel microstructure and mechanical properties than are well done. Currently many steel companies controlled rolling, because the finishing temperature control is very strict, and after finishing forced cooling measures taken thus grain refinement of steel, steel delivery have higher mechanical properties. No Twist controlled cooling of hot-rolled wire rod superior than ordinary hot-rolled wire rod performance is the truth, hot-rolled (forging) state of delivery of steel, the surface is covered with a layer of iron oxide, which has a certain degree of corrosion resistance, storage custody Unlike the strict requirements as cold drawn (rolled) state of delivery of steel, medium-sized steel, thick steel plate can be stored in the open air yard or through thatch cover. Large diameter seamless steel factory before annealing heat treatment, this condition is called annealing delivery status. Annealing main purpose is to eliminate defects and improve the organization and internal stress left before the procedure and after the procedure to prepare for the organization and performance, alloy structural steel, guaranteed hardenability structural steel, cold heading steel, bearing steel, annealed steel commonly used tool steel, turbine blade steel, heat-resistant stainless steel body cable delivery.
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