A method for producing peritectic steel by a medium-thin slab continuous caster

A medium-thin slab continuous casting and production package technology, which is applied in the manufacture of converters, etc., can solve problems such as breakout, poor castability, and excessive fluctuation of mold liquid level, so as to reduce secondary oxidation and improve castability , the effect of changing the nature

Inactive Publication Date: 2017-04-19

SHANDONG IRON & STEEL CO LTD

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AI-Extracted Technical Summary

Problems solved by technology

[0003] The main problems encountered in the production of peritectic steel with low Mn/Si by medium and thin slab continuous casting machines are: 1. The crystallizer liquid level fluctuates too much, generally ±15mm; 2. Due to the low Mn/Si of this steel type , the inclusions generated in molten steel are mainly SiO 2 , poor pourability

[0004] Excessive fluctuations in the liquid level of the mold are the main causes of defects such as slag inclusions, pits, and longitudinal cracks on the surface of the slab, and even steel breakout accidents, which seriously affect the quality of peritectic steel products and the continuity of production

At present, most p...

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Method used

[0027] The present invention provides a method for producing peritectic steel with a medium-thin slab continuous caster, comprising the steps of: converter steelmaking, LF furnace refining, and medium-thin slab continuous caster continuous casting. The present invention controls the entire process of converter steelmaking-LF refining-medium-thin slab continuous casting machine continuous casting, so that the crystallizer liquid level fluctuation range is controlled within ±3mm, avoiding excessive crystallizer liquid-level fluctuations to medium and thin slabs The impact caused by the normal and stable production of peritectic steel in large quantities by continuous casting machines; further, by controlling the deoxidatio...

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Abstract

The invention discloses a method for producing peritectic steel by using a medium-thin slab continuous caster. The method comprises the following steps: converter steelmaking, external refining of an LF furnace, and continuous casting of the medium-thin slab continuous caster. According to the invention, the entire process of converter steelmaking, LF furnace refining and continuous casting of the medium-thin slab continuous caster is controlled, so that the crystallizer liquid level fluctuation range is controlled within +/-3 mm; the deoxidization and alloying of the steelmaking process are controlled to enable the steel inclusions to be mainly spessartine with low melting point and strong plasticity; in the refining process, the secondary oxidation of molten steel is reduced, and an argon system is designed reasonably to ensure the maximum flotation of the inclusions; during continuous casting, the pouring is protected, the secondary oxidation of molten steel is reduced, the properties of the inclusions in the molten steel are changed, and the pourability is improved, so that the mass normal stable production of peritectic steels by using the medium-thin slab continuous caster is realized.

Application Domain

Manufacturing converters

Technology Topic

Thin slabDeoxidization +8

Examples

Experimental program(2)

Example Embodiment

[0033] Example 1:

[0034] The 137t molten iron was sent to the 120t oxygen top-blown converter for blowing, and the feed was started at 1/3 of the converter tapping process after the converter was finished, and finished at 3/4. The order of addition was lime, fluorite, and silicon-manganese alloy. , aluminum alloy; lime 680kg, fluorite 170kg, adding a small amount of silicon-manganese alloy, aluminum alloy to reduce the oxidation of slag. When tapping, the double slag blocking process of slag blocking plug and slag blocking rod is adopted, and the thickness of the ladle slag layer is 30mm. After slag making and slag blocking, the final slag basicity is controlled at 3.0, and the endpoint components (weight percentage) are controlled at [C]: 0.08%, [S]: 0.020%, [P]: 0.01%, and the endpoint temperature is 1658°C.

[0035] Then, the molten steel enters the LF refining process. After the ladle arrives at the station, the bottom is blown, and the argon flow rate is guaranteed to be about 200NL/min according to the slag condition. Argon stirring, control the argon gas flow at about 80NL/min; add 80kg of aluminum blocks according to the secondary sampling components for deep deoxidation; then add alloying elements ferromanganese 360kg, ferrosilicon 200kg, ferrotitanium 100kg according to the tertiary sampling components, and then add argon Open the gas flow to 500NL/min, adjust the argon gas flow to 80NL/min after heating to the final temperature, and adjust the chemical composition (weight percentage) to: [C]: 0.13%, [Si]: 0.15%, [Mn]: 0.38%, [S]: 0.005%, [P]: 0.010%, Alt: 0.015%; the exit temperature is 1580℃, and the soft blowing of argon is guaranteed for 9 minutes before leaving the station;

[0036] Then the molten steel enters the continuous casting process, and a straight arc medium and thin slab continuous casting machine (section 135mm×(900-1600mm)) is used, and the dynamic secondary cooling adopts the alloy peritectic weak cooling water distribution to control the uneven growth of the billet shell. In the production of 135×1030 cross-section slabs, the wide surface water flow rate of the mold is 290L/min, and the narrow surface water flow rate is 21L/min.

[0037] The mold slag used is a special mold slag for peritectic steel, and its chemical composition (weight percentage) is: CaO: 30.1%, SiO 2 : 37.1%, MgO: 1.7%, Al 2 O 3 : 4.5%; Na 2 O: 9.2%; F: 10.6%, C: 5.4%, H 2 O: 0.31%, the rest are impurities. The mold powder has a melting point of 1090°C and a viscosity of 1.3 poise. In order to control the melting speed of the mold flux, the argon gas flow between the plates is controlled at 4NL/min, and the insertion depth of the immersion nozzle is 130mm.

[0038] In addition, the continuous casting process needs to pay attention to the protective pouring. Argon was blown into the tundish plug hole and the steel receiving hole 10 minutes before the pouring, to eliminate the weak oxidizing atmosphere remaining during the baking process in the tundish as much as possible, and reduce the inclusions caused by the oxidation of molten steel during the pouring; Flow and pour, add covering agent to prevent molten steel from being exposed in the air; after pouring, blow argon gas between the tundish plates, stopper, upper nozzle and protective casing to prevent the formation of negative pressure between plates, large ladle nozzle, etc. Air is sucked in and the molten steel is oxidized to ensure that the weight percent of T[O] in the tundish molten steel is 0-0.0035%, and the weight percent of [N] is 0-0.0050%.

[0039] The quality of the peritectic steel produced reaches the national standard at a high casting speed (above 1.8m/min), and there are no defects such as slag inclusions, pits, and longitudinal cracks on the surface of the slab, and no steel breakout accidents occur during the continuous casting process. .

Example Embodiment

[0040] Example 2:

[0041] The 132t molten iron was sent to the 120t oxygen top-blown converter for blowing, and the feed was started at 1/3 of the converter tapping process after the converter was finished, and finished at 3/4. The order of addition was lime, fluorite, and silicon-manganese alloy. , aluminum alloy; lime 650kg, fluorite 160kg, adding a small amount of silicon-manganese alloy, aluminum alloy to reduce the oxidation of slag. When tapping, the slag blocking plug and slag blocking rod double slag blocking process are adopted, and the thickness of the ladle slag layer is 25mm. After slag making and slag blocking, the final slag basicity is controlled at 2.9, and the final composition (weight percentage) is controlled at [C]: 0.085%, [S]: 0.020%, [P]: 0.01%, and the end temperature is 1665°C.

[0042] Then the molten steel enters the LF refining process, the ladle is blown at the bottom after arriving at the station, and the flow of argon gas is guaranteed to be about 200NL/min according to the slag condition; Stone 200kg), blow argon and stir, and control the flow rate at about 80NL/min; according to the secondary sampling components, add 80kg of aluminum blocks to carry out deep deoxidation, and then add alloying elements ferromanganese 360kg, ferrosilicon 200kg, ferrotitanium 100kg according to the three sampling components, and then Open the argon flow to 500NL/min, adjust the argon flow to 80NL/min after heating to the final temperature, and adjust the chemical composition (weight percentage) to: [C]: 0.13%, [Si]: 0.15%, [Mn] ]: 0.38%, [S]: 0.005%, [P]: 0.010%, Alt0.015%; the exit temperature is 1580℃, and the soft argon blowing guarantees 9min before leaving the station;

[0043] Then the molten steel enters the continuous casting process, and a straight arc medium and thin slab continuous casting machine (section 135mm×(900-1600mm)) is used, and the dynamic secondary cooling adopts the alloy peritectic weak cooling water distribution to control the uneven growth of the billet shell. In the production of 135×1030 cross-section slabs, the wide surface water flow rate of the mold is 290L/min, and the narrow surface water flow rate is 21L/min.

[0044] The mold slag used is a special mold slag for peritectic steel, and its chemical composition (weight percentage) is: CaO: 30.41%, SiO 2 : 37.04%, MgO: 1.79%, Al 2 O 3 : 4.33%; Na 2 O: 9.48%; F: 10.25%, C: 5.49%, H 2 O: 0.23%, the rest are impurities. The melting point of mold powder is 1083°C, and the viscosity is 1.32 poise. In order to control the melting speed of the mold flux, the argon gas flow between the plates is controlled at 5NL/min, and the insertion depth of the immersion nozzle is 130mm.

[0045] In addition, the continuous casting process needs to pay attention to the protective pouring. Argon was blown into the tundish plug hole and the steel receiving hole 10 minutes before the pouring, to eliminate the weak oxidizing atmosphere remaining during the baking process in the tundish as much as possible, and reduce the inclusions caused by the oxidation of molten steel during the pouring; Flow and pour, add covering agent to prevent molten steel from being exposed in the air; after pouring, blow argon gas between the tundish plates, stopper, upper nozzle and protective casing to prevent the formation of negative pressure between plates, large ladle nozzle, etc. Air is sucked in and the molten steel is oxidized to ensure that the weight percent of T[O] in the tundish molten steel is 0-0.0035%, and the weight percent of [N] is 0-0.0050%.

[0046] The quality of the peritectic steel produced reaches the national standard at a high casting speed (above 1.8m/min), and there are no defects such as slag inclusions, pits, and longitudinal cracks on the surface of the slab, and no steel breakout accidents occur during the continuous casting process. .

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Classification and recommendation of technical efficacy words

Reduce secondary oxidation
Change nature

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Aluminium Argon Manganese Molten steel

A method for producing peritectic steel by a medium-thin slab continuous caster

AI-Extracted Technical Summary

Problems solved by technology

Method used

Abstract

Examples

Example Embodiment

Example Embodiment

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Description & Claims & Application Information

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