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Control method for nitrogen content of molten steel of wear-resistant steel

A control method and wear-resistant steel technology, applied in the field of metallurgy, can solve problems such as poor surface quality of continuous casting slabs, failure of steel benefits to be brought into play, and decline in steel plasticity, so as to achieve the effect of improving the internal and surface quality of casting slabs

Active Publication Date: 2014-03-12
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] The nitrogen content in steel has a great influence on the mechanical properties of steel. With the increase of nitrogen content in steel, the plasticity and ductility of steel decrease; nitrogen can also increase the aging of steel, reduce the cold working performance of steel, and cause welding heat affected zone Embrittlement, slab cracking and intergranular corrosion
Therefore, reducing the nitrogen content of molten steel has always been the goal of smelting high-quality steel, especially in the smelting process of wear-resistant and abrasive tool steel. The alloying process of LF furnace is difficult and the smelting cycle is long. In order to improve the alloying efficiency and shorten the smelting cycle , to ensure the production rhythm of continuous casting. Usually, LF furnace adopts large argon gas stirring to promote alloying. This strong dynamic condition of large argon gas is in contradiction with the control of nitrogen content, resulting in high nitrogen content in smelting this series of steels, making continuous casting The internal and surface quality of the billet is poor, which affects the performance of the steel plate and subsequent processing, and ultimately prevents the benefits of steel from being brought into play

Method used

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  • Control method for nitrogen content of molten steel of wear-resistant steel
  • Control method for nitrogen content of molten steel of wear-resistant steel
  • Control method for nitrogen content of molten steel of wear-resistant steel

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Embodiment 1

[0036] In this embodiment, NM500 steel is selected, smelted in a 150-ton converter, a 150-ton ladle furnace, and cast in a slab continuous casting machine. In order to improve the surface and internal quality of the slab, the nitrogen content at the end of NM500 smelting is required to be controlled within 0.0050%.

[0037] (1) Converter blowing. The composition and temperature control at the end of blowing meet the requirements, and the converter does not carry out supplementary blowing. See Table 1.

[0038] Table 1 Composition at the end point of converter (%)

[0039]

[0040] (2) Deoxidation and slagging alloying after converter furnace. 1 minute before tapping, open the ladle bottom blowing argon flow and set the flow rate to 500NL / min, and add the auxiliary materials in the order of tapping: start tapping→refining slag, lime→aluminum block→silicomanganese, low-carbon ferromanganese.

[0041] (3) Tapping ends. After tapping and alloying, the ladle bottom blowing fl...

Embodiment 2

[0047] In this embodiment, NH1250 steel is selected, smelted in a 150-ton converter, a 150-ton ladle furnace, and cast in a slab continuous casting machine. In order to improve the surface and internal quality of the slab, the nitrogen content at the end of NH1250 smelting is required to be controlled within 0.0060%.

[0048] (1) Converter blowing. The composition and temperature control at the end of blowing meet the requirements, and the converter does not carry out supplementary blowing. See Table 2.

[0049] Table 2 Converter end point composition (%)

[0050]

[0051] (2) Deoxidation and slagging alloying after converter furnace. 1 minute before tapping, open the ladle bottom blowing argon flow and set the flow rate to 350NL / min, and add auxiliary materials in the tapping process sequence: start tapping → refining slag, lime → aluminum block → silicon manganese, low carbon ferromanganese.

[0052] (3) Tapping ends. After tapping and alloying, the ladle bottom blow...

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Abstract

The invention discloses a control method for nitrogen content of molten steel of wear-resistant steel. By virtue of optimization of a converter tapping technology, improvement of orders of deoxidizing slagging and alloying of an LF (Ladle Furnace), as well as rational control on ladle bottom argon blowing flow rate and pressure in different smelting stages, and complete protective casting of continuous casting process, the nitrogen content of the molten steel can be controlled within 0.0030% after converter tapping, nitrogen adding in molten steel during LF+RH (Ladle Furnace process +Ladle Furnace process) is steadily controlled within 0.0010%, nitrogen adding in molten steel in the continuous casting process is steadily controlled within 0.0005%, and finally, nitrogen content in a high alloy wear-resistant steel continuous casting billet is controlled within 0.0045%, therefore, internal quality and surface quality of the casting billet are improved greatly.

Description

technical field [0001] The invention relates to a steelmaking process in the field of metallurgy, and relates to a method for controlling the nitrogen content of molten steel in the wear-resistant steel smelting process. Background technique [0002] The nitrogen content in steel has a great influence on the mechanical properties of steel. With the increase of nitrogen content in steel, the plasticity and ductility of steel decrease; nitrogen can also increase the aging of steel, reduce the cold working performance of steel, and cause welding heat affected zone Embrittlement, slab cracking and intergranular corrosion. Therefore, reducing the nitrogen content of molten steel has always been the goal of smelting high-quality steel, especially in the smelting process of wear-resistant and abrasive tool steel. The alloying process of LF furnace is difficult and the smelting cycle is long. In order to improve the alloying efficiency and shorten the smelting cycle , to ensure the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21C5/30C21C7/10C21C7/072C21C7/06B22D11/18
Inventor 曹余良蔡可森周贺贺吴俊平周桂成吴伟勤吴国平孟令东朱安静王永瑞唐荆晶赵磊
Owner NANJING IRON & STEEL CO LTD
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