The foreign substances in the black stripe defect are mainly magnesium-alumina spinel and feldspar, and a small amount of perovskite, which comes from ladle slag.The foreign material in the gray stripe defect is mainly magnesium oxide and contains a small amount of feldspar.The foreign material in the irregular strip gap is mainly alumina, containing a small amount of zirconia.
The microscopic features of the black stripe defects on the board were observed by electron probe.High power observation, the block can distinguish a lot of broken particles, broken shape, because of its different from the steel base, and a large number, should be foreign.Further observation and analysis of the components by energy spectrometer showed that the main phase was magnesium oxide, and a small number of grains were similar to magnesium-calc-olivine.
The aggregate was magnesia.The matrix is mainly magnesia powder and flake graphite, and a small amount of silicon carbide antioxidants.Magnesia is a multi – crystalline, intercrystalline feldspar.In addition, there is a small amount of magnesium-calcium olive.
The foreign matter in the gray strip is mainly magnesium oxide, while the foreign matter in the gray strip is mainly magnesia (magnesium oxide).Magnesia itself contains a small amount of feldspar.It can be seen that the ore of foreign matter and slag line magnesium-carbon brick is in good agreement.It can be considered that the foreign matter in the gray strip comes from the broken and detached magnesium-carbon brick.It is gray due to the scattered distribution of exfoliates on the surface strip.It is understood that after the occurrence of such defects, slag line after repair, hot rolled plate surface quality will return to normal.
Inspection and analysis of irregular strip defects
The microscopic features of irregular strip defects were observed by electron probe.There is a foreign body in the skin damage, because it is far more than the number of normal inclusions, should be foreign.The foreign body was found to be alumina and a small amount of silicon, calcium, manganese and zirconium.
Analysis of the lower nozzle of steel injection most of the lower nozzle of steel injection adopts rigid jade material and contains little zirconia.For comparison, the lower nozzle before and after use was taken to make lithofacies grinding plate. The morphology of the nozzle before use was analyzed with electron probe, with dense structure, and the morphology of the intact nozzle after use, with loose structure and fragmented particles, was the state after material decomposition.
The foreign material in the irregular strip and the mineral contrast of slag line magnesium-carbon brick in the irregular strip are mainly alumina, which can correspond to corundum in the nozzle, and a small amount of zirconia can also match the material in the lower nozzle.A small amount of silicon, calcium and manganese should be the product of erosion of the nozzle.The form of alumina in the foreign material is similar to that of corundum.The coincidence of many phenomena suggests that the extraneous matter in the defects of irregular strip comes from the extraneous matter in the eroded orifice.The peeling of the defects indicates that the foreign material is originally under the surface of the casting billet and forms peeling after rolling, and the foreign material in the skin damage is exposed. Due to the different exposure of foreign material in different parts, the band width is also different.It is known that such defects disappear after the nozzle is replaced, which proves the correctness of the analysis results.