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<br /><br />Hot-rolled steel: hot-rolling is relative to the cold case, the cold is below the recrystallization temperature of rolling, while the recrystallization temperature of hot rolling is carried out by rolling over.
Hot-rolled steel pipe
Benefits: You can destroy ingot casting organizations, the grain refinement of steel and to eliminate defects in the microstructure, so that the organization dense steel, mechanical properties improved. This improvement mainly reflected along the rolling direction, so that steel is no longer a certain extent, isotropic body; pouring the bubble was formed, cracks and loose, but also under high temperature and pressure have been welded together.
Disadvantages: 1. Through the hot-rolled, the steel inside the non-metallic inclusions (mainly sulfides and oxides, as well as silicate) is pressed into sheets, there stratified (laminated) phenomenon. Stratified so that along the thickness direction of steel tension performance deteriorated significantly and is likely to shrink in the weld between layers when you tear. Weld shrinkage-induced local strain to yield point strain often several times larger than the strain due to the load; 2. Uneven cooling caused by residual stress. Residual stress in the absence of external force within the self-balanced stresses under various sections of hot-rolled steel have this kind of residual stress, the general steel section size larger, the greater the residual stress. Although the residual stress is self-balanced, but the right steel members under the performance of the external force or have a certain influence. Such as deformation, stability, anti-fatigue, etc. may have an adverse effect. 3. Hot-rolled steel products, for the thickness and width in this regard while poor control. We are familiar with thermal expansion and contraction, since the beginning of the hot-rolled out of even the length, thickness of compliance, finally after cooling will still appear some negative balance, this negative differential side of the more wide-width, the thicker the more obvious manifestations. So for the large steel for the steel edge width, thickness, length, angle, and no law requires very precise edges.
Sub-hot-rolled and cold-rolled seamless steel pipe (dial) seamless steel tube types.
Hot-rolled steel sub-ordinary steel pipes, low-, medium-pressure boiler steel pipes, high-pressure boiler steel pipe, steel pipe, stainless steel pipe, oil cracking pipe, steel pipe and other pipe and so on geology.
Cold (dial) Subject to sub-normal seamless steel pipes, low and medium pressure boiler steel pipes, high-pressure boiler steel pipe, steel pipe, stainless steel pipe, petroleum cracking tubes, other steel pipes, but also includes thin-walled carbon steel, alloy thin-walled steel pipe, thin-walled stainless steel pipe, shaped steel tube. Hot-rolled seamless pipe diameter typically greater than 32mm, wall thickness 2.5-75mm, cold-rolled seamless steel pipe at Trail can go to 6mm, wall thickness can be 0.25mm, outer diameter thin-walled tube can be 5mm, wall thickness less than 0.25 mm, cold rolled size than the high accuracy.
Tends to be used seamless steel pipe: 10,20,30,35,45 and so on is high-quality carbon structural steel 16Mn, 5MnV low-alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB such as hot-rolled or cold-rolled steel made. 10,20 and other low-carbon steel seamless pipe manufacturing is mainly used for liquid pipelines. 45,40 Cr, etc. made of carbon steel seamless pipe used to make machine parts, such as cars, tractors force components. General seamless steel pipes to ensure the strength and flattening test. Hot-rolled steel with hot-rolled state or heat treatment delivery; cold-rolling to heat treatment delivery.