The surface of slag pits is a kind of open hole formed on the surface of round billet with random distribution, irregular pit area and large inner size, with uneven surface and small amount of slag shell. In the event of defective billet to be concentrated grinding finishing, along with the emergence of a large number of waste billet. For this need analysis, and control.
It is concluded that a large number of high melting point inclusions in the bowl and the inner wall of the water in the bowl caused the volatility of the liquid level of the rod and the mold. Meanwhile, the molten mold powder absorbs some high melting points such as Al2O3 and MgO Material
, resulting in the flux to increase the viscosity of the performance change, the local formation of complex components of the cluster hard particles, with the liquid flux into the mold
and the shell between the shell. As the temperature decreases, the particle will be wrapped in the mold flux to further grow and harden, with the mold vibration is pressed into the surface of the shell of the shell, the mold in the second cooling water cooling and impact, part of the shell will automatically fall off , And finally the formation of slag pit defects.
Surface slag pit control measures are:
1, to strengthen the converter operation, to ensure deep dephosphorization on the basis of steel
, but strive to end oxidation.
2, the maintenance of the tapping port, tapping time shall not be less than 1'50 ".Slagging plug control of a slag and automatic control slag standard end slag, ladle slag thickness of ≤ 50mm.
3, the steel temperature control 1620 ~ 1640 ℃. Temperature is too low not only affect the slag melting, increase the ladle refining furnace heating burden, but also make the bottom blowing breathable brick block surface cold steel, deteriorating refining effect; temperature is not conducive to dephosphorization and increase the amount of phosphorus.
4, using one step deoxidation method. When tapping different requirements according to the steel used for different deoxidizer for the final deoxidation. Slag, fluorite and other slag materials, the impact of steel flow and the end of blowing, so that into the slag ahead of time, increase the reaction interface, and promote deoxidation products and slag droplets collision polymerization, can quickly float into the Slag, as far as possible to reduce the liquid steel pollution.
5, optimize the refining slag. The CaO-Al2O3-CaF2 slag system is optimized to be CaO-Al2O3-SiO2 slag system. The slag system has the advantages of low melting point, high emulsification and good submerged arc, especially for the inclusions effect.
6, inclusions denaturing treatment process optimization, to determine a reasonable amount of calcium. The CaSi content of Si-Al killed steel was 0.6kg / t, and that of Al-killed steel was 1.0kg / t.
7, the opening of the furnace filled with argon argon on the bare steel is not covered by the protection of molten steel to avoid secondary oxidation of molten steel.
8, smearing material in the package baking time control in 5 ~ 6h. And strive to constant speed casting, the normal level fluctuations in control within ± 3mm.