Common defects of billet produced by continuous caster 1. Corner cracks. After the lower port of the copper mould tube is severely worn, a larger air gap is fo
Common defects of billet produced by continuous caster
1. Corner cracks. After the lower port of the copper mould tube is severely worn, a larger air gap is formed between copper mould tube and the casting billet, resulting in a greater thermal resistance. As a result, the lower port cooling is too weak, the billet shell becomes thinner, and at the same time, due to the lower Severe wear of the mouth causes excessive cooling at the corners of the zero section, resulting in too large a cooling gradient from weak to strong cooling, resulting in stress concentration, and due to the uneven thickness of the billet shell, the casting billet becomes rhombohedral, which is easy to produce corner cracks.
2. Billet defects: middle cracks. When the cast slab passes through the secondary cooling zone, the cooling is uneven, and the thermal stress generated by the excessive temperature rise exceeds the maximum stress borne by the columnar crystals. In addition, the development of columnar crystals increases the probability of forming intermediate cracks.
3. Depress cracks. Excessive pressure of the tensioning and correcting rolls will cause reduction cracks in the solid-liquid two-phase zone of the solidified casting slab. For the casting slab with developed columnar crystals and intermediate cracks, larger reduction cracks are often formed along the direction of the compaction.
4. Loose in center of steel billet. The columnar crystals on both sides of the cast slab grow toward the center, and when they meet together, they cause a "bridge", preventing the molten steel above the bridge from supplementing the solidification and shrinkage of the molten steel below the bridge. When the molten steel under the bridge is all solidified, many small particles are left behind. Pores.
It is particularly pointed out that the longitudinal cracks on the surface of the cast slab originate in the mold, and the thickness of the primary blank shell is uneven in the curved surface area. The tensile stress acting on the blank shell exceeds the high temperature allowable strength and strain of the steel. Stress concentration leads to longitudinal cracks, which continue to expand in the second cold zone after exiting the mold.
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Harm of too high temperature: when molten steel out of cooper mold, the billet shell is thin and easy to break out; The accelerated erosion of refractory can ea
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1. The barrier function (mainly completed by the liquid slag layer) isolates the contact between air and molten steel, blocks the secondary oxidation of molten
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In continuous casting, low corrosion resistance often occurs, which directly leads to uneven composition and will eventually affect the smelting quality. In or