Study On The Evolution Rule Of Steel Plate Surface Scratches In The Rolling Process

At present, the common method of removing strip surface oxide scale is picklingmethod, but pickling method exists the serious problems of environmental pollution,hydrogen reduction method may remove the oxide scale, but the strip surface appears alarge number of microscopic cracks and holes. In addition, in the production practice, it isfound strip and roll surface often appears scratches in the high speed rolling. In order toexplore the strip surface microscopic cracks and the production scratches evolves rule inthe rolling process. The experiment uses Q215plain carbon steel as the experimentalmaterials, using self-made device to fabricate scratch on steel plate surface, making ahorizontal rolling and longitudinal rolling for it. Studying on the evolution of strip surfacescratches in the rolling process.Using the self-made device to manufacture scratches on the strip surface, byobserving the scratches surface and cross section, it is found that the strip surfacescratches are mainly composed by the center groove area, the bulged area on both sidesand the turned exhibition area on both sides. Scratches become wider and deeper with thepressure increasing.Using the four-roll mill for rolling the steel sheet with a scratch, using the scanningelectron microscope to observe the scratches change rule of steel plate surface after eachpass rolling, using the optical microscope to observe the scratches section profile changerule of steel plate surface after each pass rolling. Using the TR200-type surface roughnessmeasuring instrument to measure the roughness curve of scratches after each pass rolling.The study found that: After the steel plate horizontal rolling, the scratches extend towardthe rolling direction, scratches sidewalls are bonded to each other, the steel plate surfaceforms two creases and two creases become more and more wider with the rolling passesincreasing. when the scratch is deep, scratch is very difficult to eliminate in the last rolling.It forms a folding in the steel plate surface subcutaneous, the surface creases and thesubcutaneous folding caused the steel surface quality defects. After the steel platelongitudinal rolling, the scratches extend toward the rolling direction, scratches sidewallsgather to the center groove area, the steel plate surface forms one crease and the creasebecomes more and more narrower with the rolling passes increasing. When the scratch isdeep, scratch is very difficult to eliminate in the last rolling. The steel plate surface formsa tiny crease and it can cause the steel surface quality defects.Using self-made equipment roller-brushing the steel plate surface, the steel platesurface appears a large number of scratches, using the optical microscope to observe thesteel plate surface morphology after every time rolling, it is found that the steel platesurface appears a large number of crack after the first time rolling, cracks and scratches are vertical. After the fifth pass rolling, the steel plate surface of the deeper scratchesexists still cracks, the shallow scratches relatively almost disappear.