Continuous casting is just maintenance, and it is impossible to correct the problems of steelmaking and equipment. During the whole operation, there will be some defects in the slab, which will affect the normal production. This is what we need to pay attention to. Only by understanding the specific types can we better operate.
Slab Defects:
1. Corner crack
After the lower mouth of the crystallizer parts is seriously worn, a large air gap is generated between the copper tube of the crystallizer and the casting blank, forming a large thermal resistance. As a result, the cooling of the lower mouth is too weak, and the shell becomes thinner. At the same time, due to the severe wear of the lower mouth, the cooling gradient from weak to strong is too large, resulting in stress concentration. In addition, due to the uneven thickness of the shell, the casting blank becomes rhombic, which is very easy to produce corner cracks.
2. Slab defects: intermediate cracks
When the slab passes through the secondary cooling zone, the cooling is uneven, and the thermal stress generated by excessive temperature rise exceeds the maximum stress borne by the columnar crystals. In addition, the developed columnar crystals increase the probability of forming intermediate cracks.
3. Press down the crack
The excessive pressure of the tension straightening roll causes the solid-liquid two-phase zone of the solidified slab to produce a reduction crack. The slab with developed columnar crystals and intermediate cracks, often forms a large reduction crack along the direction of the slab.
4. Loose center
The columnar crystals on both sides of the slab grow towards the center, which together creates a "bridging", preventing the molten steel above the bridge from supplementing the solidification shrinkage of the molten steel below the bridge. When all the molten steel below the bridge solidifies, many small pores are left.
in particular, it is pointed out that the longitudinal crack on the surface of the billet originates from the inside of the crystallizer fittings. The thickness of the primary billet shell in the meniscus area is uneven. The tensile stress acting on the billet shell exceeds the high-temperature allowable strength and strain of the steel, and the stress concentration is generated at the weak part of the billet shell, resulting in the longitudinal crack. After the crystallizer comes out, it continues to expand in the secondary cooling zone.
If you are interested in the continuous casting machine, please contact me freely.
Email: [email protected]; [email protected].
Website: www.hanrm.com; www.hanmetallurgy.com.
评论
发表评论