Solidification microstructure refinement method of steel continuous casting slab based on target equiaxed grain size and proportion

A technology of solidification structure and equiaxed crystals, which is applied in the field of iron and steel metallurgy, can solve the problems of homogeneity and density affecting the quality stability of high-end steel products, solute segregation, and severe anisotropy, so as to improve processing performance and service performance. Improve the effect of homogeneity and density, theory and process improvement

Active Publication Date: 2021-01-05
UNIV OF SCI & TECH BEIJING
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  • Abstract
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Problems solved by technology

However, the homogeneity and density problems caused by solidification structure defects are the key to the quality stability of high-end steel products!
[0004] Due to the particularity of continuous casting cooling, most steel continuous casting slabs have small proportions of equiaxed grains and large sizes, severe anisotropy, and significant solute segregation, which directly affects the processing performance and service performance of the product
The microstructure and composition defects in steel continuous casting slabs are difficult to completely eliminate in the thermal processing and heat treatment process, which affects the service life of the product

Method used

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  • Solidification microstructure refinement method of steel continuous casting slab based on target equiaxed grain size and proportion
  • Solidification microstructure refinement method of steel continuous casting slab based on target equiaxed grain size and proportion
  • Solidification microstructure refinement method of steel continuous casting slab based on target equiaxed grain size and proportion

Examples

Experimental program
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Effect test

Embodiment 1

[0075] According to the quality requirements, the target equiaxed grain size is set to 100 μm, and the area ratio of the equiaxed grain area is 36%. According to the calculation and solution of the aforementioned method, the total amount of zirconium-iron alloy that needs to be added to VD in the 100t ladle is 2.67Kg; when a gear steel After entering the VD, add 2.67Kg bulk zirconium-iron alloy, and use gas to stir until uniform; then lift the molten steel with qualified composition and temperature to the continuous casting ladle turret, and then use the same parameters as the comparative example to complete the casting and solidification. The cross-section of the slab sample was treated by a grinding machine and then etched with hot hydrochloric acid solution or electrolyte. It can be observed that the area ratio of equiaxed crystals is about 36%, and the diameter of equiaxed crystals is about 100 μm.

Embodiment 2

[0077] According to the quality requirements, the target equiaxed grain size is set to 150 μm, and the area ratio of the equiaxed grain area is 64%. According to the above method, VD+tundish double-point addition can be carried out, and the total amount of ferro-titanium alloy added to VD in the 100t ladle is calculated as 1.62Kg, the feed rate of titanium iron in the tundish is 12m / min, when a certain boiler tube steel enters the VD, add 1.62Kg bulk zirconium ferroalloy, and use gas to stir until uniform; then lift the molten steel with qualified composition and temperature To the continuous casting ladle turret, after the molten steel enters the tundish, start to feed the line at the above rate, and then use the parameters consistent with the comparative example to complete casting and solidification. The cross-section of the slab sample was treated by a grinding machine and then eroded by hot hydrochloric acid solution or electrolyte. It can be observed that the area ratio o...

Embodiment 3

[0079] According to the quality requirements, the target equiaxed crystal size is set to 120 μm, and the area ratio of the equiaxed crystal region is 50%. According to the aforementioned method, the tundish + mold double-point feeding line can be carried out, and the calculated line rate of feeding titanium iron in the tundish is: 10m / min, the crystallizer feeding cerium iron line speed is 5m / min. A certain Q345E molten steel with qualified composition and temperature after refining is hoisted to the turret of continuous casting ladle. After the molten steel enters the tundish, it starts to feed the ferro-titanium wire at the above rate, and after pouring into the crystallizer, feeds the ferro-cerium wire at the above rate. Casting and solidification were then performed using parameters consistent with those of the comparative example. The cross-section of the cast slab sample was treated by a grinding machine and then etched with hot hydrochloric acid solution or electrolyte....

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Abstract

The invention relates to the technical field of ferrous metallurgy, and provides a method for refining the solidified structure of a continuously-cast steel billet based on the dimension and proportion of a target isometric crystal. The method is applied to the ferrous metallurgy process. As for molten steel with a certain qualified element, one or more metamorphic elements of a specified quantityare added at one or more nodes of the smelting, refining and continuous casting procedure according to the proportion and dimension of the target isometric crystal corresponding to working conditionparameters in the steelmaking process to cast the molten steel containing the metamorphic elements into a billet, so that the solidified structure of the steel billet is refined. According to the improvement mechanism of the method, particles of a specific type are generated after the metamorphic elements are added, and are used as a heterogeneous nucleation matrix for steel solidification, so that the nucleation density of the core part of the cast billet is improved, and the dimension and proportion of the target isometric crystal are regulated and controlled. By the adoption of the method,quantitative adjustment of the solidified structure of the continuously-cast steel billet is fundamentally achieved, the homogeneity and compactness of the solidified structure of the continuously-cast steel billet can be improved, the defects of solidification segregation, porosity, shrinkage and the like are overcome, and the processability and usability of steel are improved.

Description

technical field [0001] The invention relates to the technical field of iron and steel metallurgy, in particular to a method for refining the solidification structure of steel continuous casting slabs based on the target equiaxed grain size and ratio. Background technique [0002] Steel is one of the most widely used materials in national life, and plays an irreplaceable role in my country's economy, military, national defense, transportation, communications, civil engineering and other aspects. my country is the country with the largest crude steel output in the world, and it is still showing an upward trend year by year. The development and preparation of high-end steel still occupies a key proportion in industrial structural materials. [0003] With the in-depth development and vigorous promotion of technologies such as secondary refining and protective casting, the purity of domestic steel products has basically reached or even exceeded the international advanced level. ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21C7/00B22D11/11C22C38/02C22C38/04C22C38/06C22C38/12C22C38/08C22C38/16C22C38/18C22C38/60C22C38/32C22C38/56C22C38/36C22C38/58C22C38/38C22C38/34C22C38/44C22C38/22C22C38/42C22C38/20C22C38/40C22C38/48C22C38/26C22C38/46C22C38/24C22C38/54C22C30/02G16C60/00G16C20/10
CPCB22D11/11C21C7/0006C22C30/02C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06C22C38/08C22C38/12C22C38/16C22C38/18C22C38/20C22C38/22C22C38/24C22C38/26C22C38/32C22C38/34C22C38/36C22C38/38C22C38/40C22C38/42C22C38/44C22C38/46C22C38/48C22C38/54C22C38/56C22C38/58C22C38/60G16C20/10G16C60/00
Inventor 兰鹏张家泉
Owner UNIV OF SCI & TECH BEIJING
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