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Method for refining ultra-low carbon ferritic stainless steel under vacuum

A vacuum refining, ultra-low-carbon technology, applied in the field of stainless steel smelting, can solve the problems of deoxidation and desulfurization in the reduction process, short treatment time, and carburization of molten steel, etc., achieve good deoxidation effect, appropriate vacuum treatment time, and reduce smelting cost effect

Active Publication Date: 2011-08-24
BAOSHAN IRON & STEEL CO LTD
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] Korean Patent Publication No. KR20030035078 introduces AOD (bottom-blown argon-oxygen decarburization furnace) and VOD (vacuum oxygen-blown decarburization furnace) duplex method for producing ultra-low-carbon stainless steel. The carbon content of AOD tapping is controlled at 0.0100% to 0.0300%. VOD tapping carbon can be controlled below 0.0100%. However, this patent does not involve how to deoxidize and create reducing slag, and the materials added in the reduction stage will easily cause carbon increase in molten steel;
[0010] Chinese Patent Publication No. CN101058837A proposes the step of VOD smelting ultra-pure ferritic stainless steel, which is actually a conventional VOD operation step, and does not involve how to stably control the carbon content at the end point by strengthening decarburization and preventing carburization. The processing time of the patent after the deep deoxidation of molten steel is too short, which is unfavorable to the desulfurization of molten steel;
In short, the existing technology does not involve the technology and related methods of simultaneously taking measures to strengthen decarburization and prevent carbon increase to control the carbon content at the end point, and there is no discussion on deoxidation and desulfurization in the reduction process

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  • Method for refining ultra-low carbon ferritic stainless steel under vacuum
  • Method for refining ultra-low carbon ferritic stainless steel under vacuum

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Effect test

Embodiment 1

[0042] The equipment requirements of this embodiment: 120t VOD treatment furnace, the ultimate vacuum degree is less than 100Pa, three argon blowing tuyeres at the bottom, and the total blowing capacity is higher than 60Nm 3 / h, the ladle refractory material is magnesia carbon brick (ie MgO-C brick). The initial molten steel temperature is 1610°C, the molten steel weight is 110t, and the smelted steel type is 409L. The main components before treatment are as follows:

[0043] C: 0.3%, Si: 0.03%, Cr: 11.7%, S: 0.005%, N: 0.015%, Mn: 0.22%, P: 0.015%, and the rest are Fe and trace impurity elements.

[0044] see figure 1 , combined with the VOD routine operation and this method, the implementation steps are as follows:

[0045] 1. The molten steel in the ladle is subjected to slag removal treatment (101) before entering the VOD station, and the amount of residual slag on the molten steel is less than 500kg;

[0046] 2. The ladle enters the vacuum tank, pre-vacuumizes first, a...

Embodiment 2

[0060] The equipment of this embodiment: 120t VOD treatment furnace, the ultimate vacuum degree is less than 100Pa, three argon blowing tuyeres at the bottom, and the total blowing capacity is higher than 60Nm 3 / h, the ladle refractory material is magnesia-calcium brick (that is, MgO-CaO brick). The initial molten steel temperature is 1621°C, the molten steel weight is 109.8t, and the smelted steel type is 439. The main components before treatment are as follows:

[0061] C: 0.394%, Si: 0.04%, Cr: 17.52%, S: 0.003%, N: 0.010%, Mn: 0.32%, P: 0.012%, and the rest are Fe and trace impurity elements.

[0062] Combining the VOD routine operation and this method, the implementation steps are as follows:

[0063] 1. Before the liquid steel in the ladle enters the VOD station, the slag removal treatment is carried out, and the remaining slag on the molten steel is less than 500kg;

[0064] 2. The ladle enters the vacuum tank, pre-vacuumizes first, and at the same time starts the bo...

Embodiment 3

[0078] The equipment of this embodiment: 120t VOD treatment furnace, the ultimate vacuum degree is less than 100Pa, three argon blowing tuyeres at the bottom, and the total blowing capacity is higher than 60Nm 3 / h, the ladle refractory material is magnesia-calcium brick (that is, MgO-CaO brick). The initial molten steel temperature is 1649°C, the molten steel weight is 118t, and the smelted steel type is 443. The main components before treatment are as follows:

[0079] C: 0.390%, Si: 0.05%, Cr: 20.79%, S: 0.005%, N: 0.020%, Mn: 0.22%, P: 0.010%, and the rest are Fe and trace impurity elements.

[0080] Combining the VOD routine operation and this method, the implementation steps are as follows:

[0081] 1. Before the liquid steel in the ladle enters the VOD station, the slag removal treatment is carried out, and the remaining slag on the molten steel is less than 500kg;

[0082] 2. The ladle enters the vacuum tank, pre-vacuumizes first, and at the same time starts the bott...

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Abstract

The invention discloses a method for refining ultra-low carbon ferritic stainless steel under vacuum, comprising the following steps: 1) steel ladle enters a vacuum oxygen-blowing decarburization furnace, the pressure in a vacuum is less than 100 Pa, initial chromium content of the molten steel is 10%-25%, the carbon content is 0.25%-0.60%, and the initial temperature of the molten steel is less than 1600 degrees C.; 2) oxygen-blowing decarburization processing, then main decarburization stage followed by dynamic decarburization stage; 3) free decarburization processing under high vacuum condition; 4) reducing, pre-deoxidizing, and adding active lime, ferrosilicon for pre-deoxidation and slag formation after free decarburization processing; deoxidizing, adding aluminum block, ferrosilicon, realizing final oxygen, silicon alloying, and desulphurizing strongly; 5) reducing argon-gas-blowing flow to small flow, conducting vacuum-breaking treatment, and then stirring to promote inclusion behavior to float up. The invention further reduces end-point carbon content during the ferritic stainless steel vacuum refining, meets requirements on strong desulphurization of molten steel, in order to increase the success rate of ultra-low carbon ferritic stainless steel smelting, thereby increasing the product quality and reducing the smelting cost.

Description

technical field [0001] The invention relates to the field of stainless steel smelting, in particular to a method for vacuum refining ultra-low carbon ferritic stainless steel using a vacuum blowing oxygen decarburization furnace (VOD furnace). Background technique [0002] With the tight supply of nickel resources, ferritic stainless steel, which is less dependent on nickel resources, has been paid more and more attention by the society. In order to ensure its corrosion resistance and weld ductility, ferritic stainless steel requires interstitial elements carbon and nitrogen. The lower the content, the better. When the total content of carbon and nitrogen in ferritic stainless steel is less than 0.015% (150ppm), the above-mentioned properties will be greatly improved and enhanced. Since the chromium content of ferritic stainless steel is 11% to 30%, the presence of chromium greatly reduces the activity of carbon and oxygen elements in molten steel, making it very difficult t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21C7/10C21C7/06
Inventor 徐迎铁陈兆平
Owner BAOSHAN IRON & STEEL CO LTD
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