Porphyritic hot-rolled pickling board surface color difference mechanism and control measures
Hot-rolled pickling plate is between manufacture and hot rolled plate products, its quality requirement for higher than that of hot rolled plate, and part of the hot-rolled pickling plate production should be carried out in accordance with the requirements of the manufacture.
Found that the process of production, hot-rolled pickling surface quality defects existing in the plate are pitting, pits, oxygen spots, wounds, and fold, owe pickling and pickling and so on, these defects are clear, the reasons for the formation control is easy to be put forward. In shougang qianan region, however, the iron and steel co., LTD.
Found in large quantities of field production after acid pickling of hot rolling steel strip surface defects porphyritic chromatism, affect the apparent quality of the finished product. Such defects after rolling of cold rolled under the big pressure rate gradually disappear, smaller effects on the surface quality of the finished product; But the defects in the heat generation of cold hot-rolled pickling plate products has had a huge impact, serious influence on the performance of the product plating.
Related research at home and abroad shows that the structure of hot rolled plate surface oxidation iron and its combination with the steel substrate status is the key to the effect of acid pickling. Some scholars of stainless steel strip surface striation defects were analyzed, and the color that differs from the strip surface roughness is the main cause of the color difference defects, and the surface roughness is the main reason for the different surface of strip steel intergranular corrosion of different level. Further research: on the surface of the slab casting mold slag increases carbon and lubricant combustion increases carbon will aggravate intergranular corrosion.
Some researcher’s longitudinal chromatic aberration on the surface of cold rolled stainless steel strips are analyzed, and says the main reason for the color difference is in the process of cold rolling emulsion lubrication and nozzle clogging.
However, after the prevalence of pickling hot-rolled pickling plate porphyritic chromatism flaw, also no literature was systematically in this paper. Shougang researchers analyzed the pickling hot-rolled pickling board surface after the generating mechanism of porphyritic chromatism flaw and improvement and prevention measures are put forward at the same time.
Through the observation, can be after pickling hot-rolled pickling plate porphyritic defect according to the degree of color into light, medium and heavy level 3. Mild defect when the side sees light, blurred; Moderate when the defect is visible, plate roll surface local distribution; When severe defects visible, plate roll the entire surface are visible. Color marble stripes, no obvious feel. Pickling board surface color is different, uneven contrast, surface or there are all kinds of color piece of porphyritic, porphyritic chromatism flaw substantially along the rolling direction is outspread, some even along rolling into a strip.
SEM analysis showed that the color difference area and the normal area is mainly the surface roughness is different. Color difference areas present a pit dense, high roughness of the surface morphology, surface level off is a smooth and normal area, basic no porous morphology. EDS spectrum showed that normal regional and color differences are 100 Fe element can confirm the tin oxide has been removed.
It is not hard to see, the reason for the chromatism defect is:
(1) color area of the combination of iron oxide and matrix interface morphology is different from the normal area, pickling of strip surface roughness after causing visual contrast differences, formed the porphyritic chromatism flaw. Due to differences in the strip surface roughness, is bound to affect the subsequent plating process, a huge difference to the quality of pickling plate products.
(2) the porphyritic chromatism defect mainly with hot rolling finishing work roll surface oxidation film state. Oxide film peeling, rough, uneven roll rolling steel strip makes three tin generated and non-uniform pressure, the pressure into the place of iron and the steel substrate interface roughness, pits, after acid pickling to remove iron, the roughness of differences lead to the emergence of the color difference.
(3) through the rolling system optimization, optimization, and finishing roll used water system, the optimization of rolling lubrication technology can effectively eliminate the porphyritic chromatism defect after pickling hot-rolled pickling board.