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Method for processing ultra-pure ferrite stainless steel by using ladle refining furnace to control carbon and nitrogen content

A ladle refining furnace and ladle refining technology, applied in the field of metallurgy, can solve the problems of product refining rate reduction, steel modification, etc., and achieve the effects of saving investment, flexible and convenient shutdown, and low maintenance costs

Active Publication Date: 2009-09-02
BAOSHAN IRON & STEEL CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This makes the production of ultra-low carbon and nitrogen ferritic stainless steel with the conventional ladle refining furnace (LF) often cause the problem of changing the steel grade due to the unqualified steel composition due to excessive carbon and nitrogen, and the product refining rate is reduced.
Since the problem of carbon and nitrogen increase in ferritic stainless steel refining in ladle refining furnace has not been solved, it is impossible to refine ultra-low carbon and nitrogen ultra-pure ferritic stainless steel in conventional ladle refining furnace (LF)

Method used

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  • Method for processing ultra-pure ferrite stainless steel by using ladle refining furnace to control carbon and nitrogen content
  • Method for processing ultra-pure ferrite stainless steel by using ladle refining furnace to control carbon and nitrogen content

Examples

Experimental program
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Effect test

Embodiment 1

[0040] When using the 30t EAF-AOD-LF-CC (electric arc furnace-argon oxygen decarburization furnace-ladle refining furnace-continuous casting) process to produce 409L ferritic stainless steel, when the electric arc furnace is smelted and passed through the argon oxygen decarburization furnace ( After AOD) refining, hoist the ladle to the LF station of the three-phase AC ladle refining furnace, and seat it on the ladle car, connect the bottom blowing pipeline and open the bottom blowing gas valve to test the gas. The ventilation brick has good air permeability, and the ladle car is driven Go to the heating station of the LF furnace and lower the ladle cover to keep a good seal between the ladle cover and the upper edge of the ladle. Then take a sample from the opening on the ladle cover, and take a sample from the temperature measurement port (T=1575°C), and send the sample to the laboratory for inspection and analysis. Add the weighed slag into the furnace from the alloy feedin...

Embodiment 2

[0043] Also adopt the technological process of embodiment 1, just change the gas ratio of blowing process into the mixed gas containing 20% ​​coke oven gas and 80% argon, gas flow rate is 78m 3 / h·t steel, other operating procedures are basically unchanged.

[0044] Spray 20% coke oven gas + 80% Ar mixed gas into the hollow electrode. Due to the increase in the proportion of coke oven gas, the blowing flow rate increases, and the arc power increases by 2.2 times. After refining for 9 minutes, the carbon content in the steel decreases from 0.02%. To 0.0079%, the nitrogen content was reduced from 164ppm to 93ppm. Continue the gas blowing treatment until the end of refining, and the nitrogen content continues to decline during the gas blowing process. At the end of the LF treatment, the nitrogen content drops to 35ppm, and the carbon content in the steel also continues to drop from 0.0079% to 0.0025%.

Embodiment 3

[0046] The smelting process flow of embodiment 3 adopts 30t EAF-AOD-VOD-LF-CC (electric arc furnace-argon oxygen decarburization furnace-vacuum oxygen blowing decarburization furnace-ladle refining furnace-continuous casting) process, and the production steel type is 409L iron Body stainless steel. After the molten steel initially smelted in the electric furnace is refined by AOD, the steel is poured into the ladle and sent to VOD for refining. At the end of VOD treatment, the carbon content in the steel reaches 29ppm and the nitrogen content is 56ppm. The molten steel after VOD refining is hoisted into the LF station for heating and composition fine-tuning.

[0047] In the LF refining process of the three-phase AC ladle refining furnace, the basic operation of this furnace is similar to the operation steps of Example 1. During the refining and electrification process of this furnace, 5% coke oven gas + 95% coke oven gas is injected from the graphite electrode hole The mixed ...

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Abstract

The invention discloses a method for controlling the carbon and nitrogen content of ultra-pure ferritic stainless steel in a ladle refining furnace. Oxygen decarburization furnace or vacuum oxygen blowing decarburization furnace to make the composition of molten steel meet the requirements of ultra-pure ferritic stainless steel; 2) ladle refining, during the electrification process, the mixed gas of coke oven gas and argon is injected through the central hole of the graphite electrode of the refining furnace , forming a hydrogen-containing plasma arc at the lower end of the electrode to achieve decarburization and denitrification of molten steel while ensuring the cleanliness of molten steel; wherein, the mixing ratio of coke oven gas and argon gas is 95:5 to 5:95, and the pressure range of the mixed gas is 0.02~10MPa, the flow rate range of the mixed gas is 0.01~50Nm3 / h; 3) When the power is off, stop blowing gas to the center hole of the graphite electrode, and lift the ladle away from the ladle refining furnace after the molten steel composition and temperature are qualified, and send it to the next step Do pouring.

Description

technical field [0001] The invention relates to the technical field of metallurgy, in particular to a method for controlling the carbon and nitrogen content of ultra-pure ferritic stainless steel in a ladle refining furnace. Background technique [0002] Ferritic stainless steel has much better resistance to stress corrosion such as chloride and caustic alkali than austenitic stainless steel, good local corrosion performance in seawater and high temperature oxidation resistance, and low price, so it is widely used in various sectors of the national economy. Fields, such as household appliances, kitchen utensils, hardware products, automotive exhaust systems, construction, and petrochemicals. The disadvantage of ordinary ferritic stainless steel is that it is sensitive to intergranular corrosion, its plasticity and toughness are very low, its ductile-brittle transition temperature is above room temperature, and its welding performance is poor. Relevant studies have shown tha...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C33/04C21C7/04
Inventor 崔健陈兆平沈建国姜周华战东平黄宗泽
Owner BAOSHAN IRON & STEEL CO LTD
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