304 stainless steel plate edge scale defect formation reasons and control methods

August 2, 2023
Latest company news about 304 stainless steel plate edge scale defect formation reasons and control methods


As a representative steel grade of austenitic stainless steel, 304 stainless steel plate for cold rolling production, often in the strip surface produces line-like edge scale defects, which are mostly distributed in the distance from the two sides of the unequal width of the interval, and can only be seen after pickling. About the morphology and impact of edge scale as described below.


Stainless steel plate defects


Stainless steel cold rolled plate production process of the formation of edge scale defects are mostly short needle-like lines, the length of the basic 5-8mm or so, a small number of lengths can reach 120mm or even longer. Side scales and normal rolling surface is not in the same plane, the depth is 5-251Lm, its bottom and side surface rough and uneven, the normal rolling at the relatively flat width of the narrower side scales and normal rolling surface boundaries are not obvious, the wider side scales and the boundaries of the normal rolling surface is very obvious.

As the stainless steel newspaper edge scale edge inclusions exist mainly for chromium oxide and iron oxide inclusions. So the reason for the formation of edge scale defects is mainly pressed into the iron scale on the surface of the stainless steel plate with the formation of grooves, after pickling the upper part of the grooves and the middle of the oxide skin will be removed, the edge of the grooves will still be there is no pickling clean residual oxide skin.


304 stainless steel plate


Stainless steel plate edge scale defect control methods


Control of stainless steel plate edge scale defects there are four main ways, respectively, is to optimize the quality of raw material plate bad, to ensure the quality of plate bad repair and grinding, reasonable control of plate bad out of the furnace temperature, and appropriately reduce the coiling temperature.


The first is to improve the quality of raw material stainless steel slab, raw material plate bad width fluctuation is relatively large, length direction trapezoidal and other defects will make the control of the vertical roller side pressure amount is not very stable, which leads to the width of the sideturn wider. Continuous casting plate also longitudinal side concave casting can significantly reduce the width of the stainless steel roll rollover, and with the degree of side concave is not the same, the width of the stainless steel roll rollover to reduce the amount of change, when the amount of side concave to 3mm, the stainless steel roll rollover width reduction effect is the most significant.


Secondly, to ensure that the quality of stainless steel bad grinding, because the side of the flip is mainly continuous casting billet side did not grind or grinding incomplete, but also by the heating furnace heating oxidation of stainless steel also the surface becomes rough, stainless steel plate is also rolled thin turned to the surface of the strip steel caused. So to improve the stainless steel slab grinding process, especially on the side of the plate also to do complete grinding. If the original casting bad side finish is good, in the plate bad heating, rolling process in the stainless steel strip surface rough ho and oxidation will be lighter, which can also significantly reduce or eliminate side scale defects. In addition to reasonable control of stainless steel plate also out of the temperature, if the higher the heating temperature of the stainless steel plate bad, the longer the time in the furnace, the higher the degree of oxidation on the surface of the plate will be, the thicker the iron scale will be, after the seat of the work of the scales in addition to the higher the difficulty of the work, and ultimately prone to produce the corresponding surface quality problems.


The last one is to reduce the coiling temperature moderately, which has a great influence on the effect of removing iron scale on 304 stainless steel plate. When the stainless steel strip coiling temperature increases, the iron scale structure will also be more compact, and the matrix is very tightly combined. Under the premise of ensuring that the stainless steel sheet and strip coiling is smooth and the coil shape is good, reduce the coiling temperature of the stainless steel sheet and strip in moderation, for example, to speed up the cooling rate in the laminar cooling process, which can increase the thermal stress between the oxide skin and the stainless steel substrate, in order to let the iron continue to fall off easily, which is conducive to the removal of scales in the post-processing process, and to reduce the generation of edge scale defects.


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