Quality Control of Cold-rolled Stainless Steel Sheet

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Quality Control of Cold-rolled Stainless Steel Sheet

Post  landoo on Wed Mar 06, 2013 1:56 am

The surface quality defects is pressed into the raw materials are cracks and pad of paper. In general, the number of raw materials are cracks mainly with the chemical composition of the material that steelmaking hot rolling process. The differences of the content of alloying elements not only affects the crack extent also affect the quality of the surface of the strip after pickling. Poor quality mat paper easier to produce a pad of paper pressed into the defect, sometimes the defect rate of about 10%, quality pad of paper pressed into the pad of paper can not be avoided, the defect rate of about 1.0%. Practice shows that, without liners better, because without coil pad of paper, even though some friction marks, the subsequent cold rolling process, the a conventional reduction rate pressure, most will be eliminated, not on the surface The quality of a large impact and expensive quality pad of paper. Padded paper friction marks defect ratio than defects padded paper not only affects the surface quality of the strip, but also adversely affect the surface of the work roll, reduce low hot rolled strip surface contamination dirty residue life.
With regard to the chemical composition of the stainless steel sheet, nickel is an important alloying element of the SUS304 steel, expensive, and therefore some manufacturers to reduce cost, to take to add other elements to replace the portion of the nickel, to maintain the austenite structure of the collective. However, with the decrease of nickel content, deformation martensite transformation temperature rise, prone to aging crack, detrimental to product deep processing, while the manganese content increased, the material hardening index increased, also affect the processing properties of the products.
The hot rolled steel strip coiling tension also affect the quality of its surface, such as the tension is too small, in the case of steel coils are not padded paper, cold rolled easily produce friction marks. During cold rolling speed, the rolling passes, the reduction ratio, rolling oil, roll material, and surface accuracy will be generated on the strip surface quality. Rolling the higher the speed, the higher the surface roughness of the strip after rolling. At the same time because of the high speed, sometimes after annealing the material surface oil spot, so under normal circumstances, this last rolling speed is generally 200r/min.
Stainless steel sheet cold rolling work roll is generally alloy steel and high speed steel, high speed steel rolls surface roughness of less than alloy steel rolls, the lower, the more smooth the surface roughness of the work roll steel surface roughness lower, thus requiring work roll grinding unit in good condition and stable work.
The annealing temperature is set with the stainless steel sheet, SUS304 steel generally soaking zone temperature was 1100 °C, a relatively high temperature can improve the production efficiency, but requires a high operating speed, high equipment requirements. How much of the oxygen within the lehr to have a greater impact on the composition of the oxide scale, thus affecting the effect of the pickling, the data indicate that for SUS304 steel, the residual oxygen concentration should be controlled at 3.5% -4%, the oxide scale generation amount at least, the most vulnerable pickling. And soaking temperature capabilities of the device different the annealing speed the generally higher annealing speed requires a higher line speed.

landoo

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