Secondary cooling method for controlling cross cracks in corner of microalloy steel slab

A technology of secondary cooling and micro-alloyed steel, which is applied in the field of continuous casting, can solve problems such as difficult implementation of continuous casting machines, achieve the effects of reducing crack sensitivity, reducing stress concentration, and enhancing the plasticity of casting slabs

Active Publication Date: 2014-09-17
BEIJING SHOUGANG CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This method requires the vertical section of the casting machine to be long enough to ensure the completion of the γ→α→γ transformation, which is difficult for domestic continuous casting machines

Method used

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  • Secondary cooling method for controlling cross cracks in corner of microalloy steel slab

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Experimental program
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Effect test

Embodiment approach 1

[0019] Such as figure 1 as shown, figure 1 It is a schematic flowchart of a secondary cooling method for controlling transverse cracks at corners of microalloyed steel slabs provided by Embodiment 1 of the present invention.

[0020] Step S100: Control the temperature of the corner of the slab through the weak cooling mode after the slab crystallizes and before it leaves the bending section, so that the temperature of the corner of the slab is not lower than the Ae3 temperature, that is, in the equilibrium state, the austenite The highest temperature for coexistence with ferrite. In this embodiment, temperature control is performed on the corners of the slab after crystallization and before leaving the bending section, so that the temperature of the corners of the slab can be obtained at a lower cooling rate under the action of the weak cooling mode. Precipitates with larger size and more diffuse distribution. Among them, the Ae3 temperature needs to be obtained according t...

Embodiment approach 2

[0028]When a steel factory was casting a 230mm slab, severe corner transverse cracks occurred on both the inner and outer arcs of the slab. The steel type used was Q345X, the cross-sectional size was 1500mm×230mm, and the casting speed was 1.3m / min. The scheme of the present invention is used to reset the secondary cooling model, and the secondary cooling model is set as follows: during the time period after the slab is crystallized and before it leaves the bending section, the specific water volume is set to 0.28L / kg until the slab is cooled The highest temperature at which austenite and ferrite coexist in an equilibrium state. It can be understood that the highest temperature at which austenite and ferrite coexist needs to be tested to obtain an accurate value for the steel used in the steel plant. And then increase the specific water amount to 1.2L / kg during the period of time reaching the end of the straightening section until the slab cools down to the temperature at whic...

Embodiment approach 3

[0031] When a steel factory was casting a 230mm slab, severe corner transverse cracks occurred on both the inner and outer arcs of the slab. The steel used was Q345R-1, the cross-sectional size was 2050mm×230mm, and the casting speed was 1.0m / min. The scheme of the present invention is used to reset the secondary cooling model, and the secondary cooling model is set as follows: during the time period after the slab is crystallized and before it leaves the bending section, the specific water volume is set to 0.24L / kg until the slab is cooled The highest temperature at which austenite and ferrite coexist in an equilibrium state. It can be understood that the highest temperature at which austenite and ferrite coexist needs to be tested to obtain an accurate value for the steel used in the steel plant. And then increase the specific water amount to 0.8L / kg during the period of time reaching the end of the straightening section, until the slab is cooled to the temperature at which ...

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Abstract

The invention belongs to the technical field of continuous casting, in particular to a secondary cooling method for controlling cross cracks in a corner of a microalloy steel slab. The method comprises the steps of controlling the temperature in the corner of a casting blank by a weak cooling mode after the crystal of the casting blank occurs and before the casting blank is separated from a bending section, so the temperature of the corner of the casting blank is not lower than Ae3 temperature which is the highest temperature at which austenite and ferrite coexist under the balance state; changing the weak cooling mode into an intensified cooling mode before the casting blank enters a straightening section, so the temperature of the corner of the casting blank achieves the Ar3 temperature, namely the temperature at which the austenite begins converting to the ferrite in the cooling process of the casting blank; after the casting blank enters the straightening section, continuously using the intensified cooling mode. The secondary cooling mode control of the continuous slab is optimized, and educts with larger dimension and more dispersed distribution are obtained by the weak cooling mode firstly, so the plasticity of the casting blank is greatly increased; then the transgranular ferrite with large proportion is obtained by the intensified cooling mode, the stress is reduced, the occurrence probability of cross cracks in the corner of the casting blank is greatly reduced, and the method is simple and easy to realize.

Description

technical field [0001] The invention belongs to the technical field of continuous casting, in particular to a secondary cooling method for controlling transverse cracks at corners of microalloy steel slabs. Background technique [0002] By adding a certain amount of microalloying elements (such as vanadium, titanium, niobium, etc.) into the steel according to a specific process flow, a microalloyed steel with special properties can be formed. Carbonitrides combined with these microalloying elements can regulate the recrystallization process of deformed austenite and prevent grain growth, indirectly play a role in refining grains, and can also produce precipitation strengthening for the matrix, ultimately improving the steel's strength. Strength and toughness. If the process of combining microalloys with steel is not well controlled, a large number of carbonitrides combined with AlN, Nb, Ti and V will precipitate at the grain boundaries, which will reduce the plasticity of t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B22D11/22
Inventor 李树森杨小刚张立峰张丽丽马威李中华倪有金张颖华
Owner BEIJING SHOUGANG CO LTD
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