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Cold Rolled Steel Coil And Hot Rolled Steel Coil
The cold-rolled steel coil is processed and rolled on the basis of the hot-rolled steel coil and is generally a hot rolling— pickling—cold rolling process.
The high quality cold rolled steel coil china uses hot-rolled steel coil as raw material and is subjected to pickling to remove scale and then cold-rolling. The finished product is rolled hard roll. The cold work hardening caused by continuous cold deformation makes the hardness and hardness of the rolled hard roll rise and tough. The plastic index is reduced, so the stamping performance will deteriorate and can only be used for parts that are simply deformed. Rolled hard rolls can be used as raw materials for hot-dip galvanizing plants because the hot-dip galvanizing units are provided with an annealing line. The rolling hard roll weight is generally 20-40 tons, and the steel coil is continuously rolled at a normal temperature for hot rolling pickling rolls. The inner diameter is 610mm.
Cold rolled steel
Disadvantages: Because it is not annealed, its hardness is very high (HRB is greater than 90), and the machining performance is extremely poor. Only a simple directional bending process of less than 90 degrees (perpendicular to the winding direction) can be performed.
Supplementary correction: Cold rolling is generally annealed.
The hot-rolled steel coil can destroy the cast structure of the steel ingot, refine the grain of the steel, and eliminate the defects of the microstructure, thereby making the steel structure compact and improving the mechanical properties. This improvement is mainly manifested in the rolling direction so that the steel is no longer isotropic; the bubbles, cracks, and looseness formed during casting can also be welded under high temperature and pressure.
Disadvantages: 1. After hot rolling, non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, and delamination (sandwich) occurs. The delamination greatly deteriorates the tensile properties of the steel in the thickness direction, and it is possible to cause interlayer tearing when the weld is shrunk. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the strain caused by the load;
2. Residual stress caused by uneven cooling. The residual stress is the internal self-phase equilibrium stress without external force. The hot-rolled steel of various sections has such residual stress. The larger the section size of the general steel, the larger the residual stress. Although the residual stress is self-phase balanced, it still has an effect on the performance of the steel member under external force. Such as deformation, stability, fatigue and other aspects may have adverse effects.
3. Hot rolled steel products are not well controlled for thickness and side width. We are familiar with thermal expansion and contraction. Since the hot rolling is started at the beginning, even if the length and thickness are up to standard, the negative difference will occur after cooling. The wider the width of the negative difference, the thicker the thickness is. Therefore, for large steel, there is no requirement for the side width, thickness, length, angle, and an edge of the steel.