Treatment method for cracks at corners of nickel-containing continuous casting slab

Abstract

The invention discloses a treatment method for cracks at corners of a nickel-containing continuous casting slab. The method comprises the following steps: (1) proportioning: uniformly mixing components of a thermit, wherein the components of the thermit comprise Al, Fe2O3, MnO2, Fe, Si and other micro component powder, the grain sizes of which are 100[mu]m; (2) feeding: calculating the amount of the thermit needed for a 10mm thick thermit covering layer, wherein the actual feeding amount is 1.2-1.5 times of the calculated amount; and (3) igniting to react: after feeding, putting a magnesium rod on the end part of the thermit as an ignition substance, approaching the end part of the thermit on the surface of the nickel-containing continuous casting slab with an ignited flue gas spray gun flame slowly step by step, and quickly combusting the magnesium rod embedded onto the end to lead to a self-maintaining reaction of the thermit. The method disclosed by the invention can optimize the treatment effect of the cracks at the corners of the slab, improves the treatment efficiency and stability, and reduces the surface defect occurrence rate of a finished product steel plate caused by thecracks at the corners on the surface of the slab.

Description

technical field [0001] The invention relates to the technical field of continuous casting and steel casting, in particular to a method for treating cracks at the edges and corners of nickel-containing continuous casting slabs. Background technique [0002] Corner cracks are common surface defects of continuous casting slabs, which mainly occur at or near the corners of the upper surface of the continuous casting slab. Since the cracks at the corners of the slab are related to the state of the mold, the quality of the mold flux, the casting speed, the secondary cooling intensity and the mode, etc. Fit or blockage of the nozzle may cause cracks at the corners of the continuous casting slab. For continuous casting slabs of medium and high alloys containing nickel alloy elements ≥ 1% (the total alloy content ranges from 5% to 10%), due to the difference in physical parameters such as latent heat and shrinkage coefficient of higher alloy elements in the cooling process, and the ...

AI Technical Summary

Problems solved by technology

However, there are many problems in the existing flame cleaning technology: 1) The cracks at the corners of the continuous casting slab are generally irregular, and the depth often fluctuates in a large range of 2-20mm, and the heat generated by flame combustion is not enough Ensure that the molten metal penetrates deep. Since the thickness of the defect layer cannot be effectively detected, if cracks are to be completely eliminated, it is necessary to remove the surface layer of the billet as thick as possible, which will cause a great waste of billets; 2) at the opposite corner In the process of deep cleaning of cracks, more molten oxides will be produced to cover the corner area, and partially oxidized metal liquid will even penetrate into the depth of micro cracks, because the metal liquid containing nickel oxide will combine with the steel base after cooling Therefore, during the heating process of the slab, these oxides further deteriorate into serious nickel-containing iron oxide scale deposits. After the slab is released from the furnace, it is difficult for general high-pressure descaling equipment to remove such thick and dense oxide scales. The iron sheet is removed cleanly, resulting in the formation of iron oxide surface defects in the subsequent rolling process, and even damage to the surface of the roll, resulting in composite surface defects, which seriously affect the quality and yield of finished products

3) Excessive temperature differences in different areas will significantly increase the crack tendency of medium and high alloy steel slabs. Therefore, the slab is generally cleaned with temperature to reduce the temperature gradient between the cleaned area and the surrounding steel base. Greatly increases the labor intensity of the operator and increases the risk of personal injury

This method is mainly used for ordinary low-carbon structural steel, micro-alloyed steel and low-alloy steel, and for medium-high alloy steel with nickel content ≥ 1%, Al+Fe 2 o 3 The heat of a single aluminothermic reaction is not enough to support the full melting and mixing of the powder with a sufficient amount of single alloy, and the high content of nickel, manganese and other components that do not participate in the aluminothermic reaction, because the melting point and enthalpy are different from those of the steel base, it is easy to Melting occurs, resulting in uneven composition of the aluminothermic reaction area (that is, the crack area), which affects the quality and performance of the steel

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