CN103602781A - Method for lowering chrome oxide in arc furnace slag in stainless steel smelting process - Google Patents

Abstract

The invention relates to a method for lowering chrome oxide in arc furnace slag in a stainless steel smelting process, which comprises the following steps: when the power supply amount reaches 53-55% of the total power supply amount, blowing oxygen for fluxing; (2) when the molten steel temperature reaches the tapping temperature after the scrap steel in the arc furnace is molten down, stopping blowing the oxygen, and blowing 100-200kg of silicon iron powder to the molten steel; blowing nitrogen at the rate of 1800 Nm<3>/h for stirring; (3) adding silicon iron and fluorite into the furnace to perform reduction while continuing blowing nitrogen at the rate of 1800 Nm<3>/h for stirring; (4) continuing power supply in the reduction process, and stopping power supply when the power supply amount reaches 2.5-3% of the total power supply amount; blowing nitrogen for stirring for more than 4 minutes, stopping the nitrogen stirring, shaking the furnace, and tapping; and (5) adding lime for slagging in the smelting process so that the alkalinity of the final arc furnace slag after reduction is 1.20-1.35. The method can lower the chrome oxide in the stainless steel arc furnace slag, enhance the recovery rate of chrome and lower the smelting cost.

Description

A kind of method that reduces chromic oxide in stainless steel smelting process electric arc slag

Technical field

The invention belongs to field of metallurgy; Be the technique in smelting stainless steel process, be specifically related to a kind of method that reduces chromic oxide in stainless steel smelting process electric arc slag.

Background technology

In full steel scrap stainless steel smelting process, electric arc furnace is allocated the raw materials such as high carbon ferro-chrome, the home scrap that contains chromium nickel, nickelalloy into, smelts the crude steel liquid that to approach stainless steel finished product.The crude molten steel of electric arc furnace output continuous casting after external refining fine setting composition becomes steel billet.

In stainless steel smelting process, characteristic due to the easy oxidation of chromium, there is high avidity with oxygen, in the situation that oxygen partial pressure is lower, also can be oxidized, therefore,, in electric arc furnace smelting, the oxidation of silicon and carbon is often accompanied by a large amount of chromium burnings, chromium burnings a large amount of in oxidising process enter in slag, cause chromium metal in stainless steel smelting to lose in a large number.In stainless steel smelting process, 97% of the loss of all chromium occurs in electric arc furnace.

Because electric arc furnace need to be pursued high efficiency production, often cannot consume the chromium metal in long period reducing slag, the dynamic conditions of adding electric arc furnace is poor, and the chromium content in slag is up to 9% left and right conventionally, and reduction effect is poor, and chromium metal loss is serious.

Summary of the invention

High for chromic oxide content in stainless steel electric arc slag, restore task weight, the difficult problem that chromium metallic reducing recovery difficult is large.The present invention proposes a kind of method that reduces chromic oxide in stainless steel smelting process electric arc slag; To drop into cheaply, significantly reduce chromic oxide in stainless steel electric arc slag, reduce the chromium loss in steelmaking process, the recycling that improves precious metal, reduces stainless smelting cost.

Technical scheme of the present invention comprises:

(1) postpone the electric arc furnace door oxygen blown time of carbon-oxygen gun, when power transmission amount is delivered to the 53%-55% of total power transmission amount, use the oxygen blast of electric arc furnace fire door carbon-oxygen gun to flux;

(2) after in electric arc furnace, steel scrap thoroughly melts clearly, blow off oxygen when liquid steel temperature reaches tapping temperature, the carbon dust pipe winding-up ferrosilicon powder of use electric arc furnace fire door carbon-oxygen gun, adjusts the interior bits mobility of stove, carries out prereduction, and ferrosilicon powder winding-up amount is 100-200kg; Utilize oxygen blast tracheae nitrogen blowing to stir, nitrogen flow is 1800Nm3/h, simultaneously low voltage, (low voltage is set to 550 volts for 90 tons of ac arc furnaces, transformer capacity 90MVA in large electric current power supply; Large electric current is set to 70 kilo-amperes).

Described low voltage, large electric current is to determine according to arc furnace transformer capacity and voltage-regulation gear, the general low-grade location voltage of setting, the electric current of high tap position;

(3) by step (2), adjust slag and have after fine mobility, in stove, add ferrosilicon and fluorite to reduce, ferrosilicon and fluorite are according to weight 1:(1.5-2) proportioning adds, and add-on is determined with furnace capacity and the chromium content of smelting steel grade; (90t capacity of electric arc furnace, the steel grade that chromium content is 18% is used ferrosilicon amount 250-400kg, fluorite 500-700kg) continues to use furnace door carbon oxygen lance oxygen hose nitrogen blowing to stir simultaneously, nitrogen flow 1800Nm3/h; Low voltage, large electric current power supply;

(4), when the lasting power transmission amount of reduction process reaches the 2.5%-3% of total power transmission amount, stop power supply; Furnace door carbon oxygen lance oxygen hose nitrogen blowing churning time >=4min, stops nitrogen gas stirring, grate subsequently, the mixed steel of going out of slag;

(5) smelting process adds lime slag making, and after reduction, the basicity (CaO/SiO2) of electric furnace finishing slag is controlled at 1.20-1.35.

Embodiment

embodiment mono-:the full steel scrap stainless steel smelting of 90t, current consumption 37000kwh/ stove, implement the technical program as follows:

(1) postpone furnace door oxygen lance oxygen blown opportunity.When reaching 20000kwh, power transmission amount bring into use furnace door carbon oxygen lance oxygen blast to flux;

(2) after waste steel for electric furnace thoroughly melts clearly, blow off oxygen when temperature reaches 1620 ℃ of tapping temperatures, use the interior bits mobility of carbon dust pipe winding-up ferrosilicon powder adjustment stove of furnace door carbon oxygen lance to carry out prereduction, winding-up ferrosilicon powder amount 100-200kg ferrosilicon powder is adjusted slag and is had good mobility; Oxygen hose nitrogen blowing stirs, nitrogen flow 1800Nm3/h, simultaneously low voltage, large electric current power supply.

(3) by step (2), adjust slag and have in the backward stove of fine mobility and add ferrosilicon and fluorite to reduce, ferrosilicon and fluorite are according to weight 1:(1.5-2) proportioning adds use ferrosilicon amount 250-400kg, fluorite 500-700kg; Continue to use furnace door carbon oxygen lance oxygen hose nitrogen blowing to stir, nitrogen flow 1800Nm3/h simultaneously; Low voltage, large electric current power supply;

(4) reduction process continued power 900-1100kwh, stops power supply; Furnace door carbon oxygen lance oxygen hose nitrogen blowing churning time >=4min, stops nitrogen gas stirring, grate subsequently, the mixed steel of going out of slag;

(5) smelting process adds lime slag making, and after reduction, the basicity (CaO/SiO2) of electric furnace finishing slag is controlled at 1.20-1.35.

According to the technical program is real, implement, in electric arc slag, average chromic oxide is reduced to 2.72% by former 6.55%.

89 tons of the equal taps of stove, ton slag amount 150.9Kg, 480,000 tons of annual production, direct economic benefit: in slag, chromic oxide content is reduced to 2.72% by 6.55%, ton steel reclaims pure chromium 3.953kg, and single stove reclaims pure chromium 351.82kg.

Price=150.9Kg/ ton steel * (6.55%-2.72%) * 0.684 * 12 of the content * pure chromium of pure chromium yuan in chromic oxide content * chromic oxide=47.43 yuan/ton of steel in the slag of the ton steel economic benefit=ton steel product quantity of slag * reduction.

Year yuan/ton steel * 480,000, benefit=ton steel benefit * annual production=47.43 ton=2277.01 ten thousand yuan

embodiment bis-:the full steel scrap stainless steel smelting of 50t, current consumption 24000kwh/ stove, implement the technical program as follows:

(1) postpone furnace door oxygen lance oxygen blown opportunity.When reaching 14000kwh, power transmission amount bring into use furnace door carbon oxygen lance oxygen blast to flux;

(2) after waste steel for electric furnace thoroughly melts clearly, blow off oxygen when temperature reaches 1620 ℃ of tapping temperatures, use the interior bits mobility of carbon dust pipe winding-up ferrosilicon powder adjustment stove of furnace door carbon oxygen lance to carry out prereduction, winding-up ferrosilicon powder amount 100-200kg ferrosilicon powder is adjusted slag and is had good mobility; Oxygen hose nitrogen blowing stirs, nitrogen flow 1800Nm3/h, simultaneously low voltage, large electric current power supply.

(3) by step (2), adjust slag and have in the backward stove of fine mobility and add ferrosilicon and fluorite to reduce, ferrosilicon and fluorite are according to weight 1:(1.5-2) proportioning adds use ferrosilicon amount 150-200kg, fluorite 300-400kg; Continue to use furnace door carbon oxygen lance oxygen hose nitrogen blowing to stir, nitrogen flow 1800Nm3/h simultaneously; Low voltage, large electric current power supply;

(4) reduction process continued power 700kwh, stops power supply; Furnace door carbon oxygen lance oxygen hose nitrogen blowing churning time >=4min, stops nitrogen gas stirring, grate subsequently, the mixed steel of going out of slag;

(5) smelting process adds lime slag making, and after reduction, the basicity (CaO/SiO2) of electric furnace finishing slag is controlled at 1.20-1.35.

According to the technical program is real, implement, in electric arc slag, average chromic oxide is reduced to 2.87% by former 6.85%.

48 tons of the equal taps of stove, ton slag amount 163.3Kg, 250,000 tons of annual production, direct economic benefit: in slag, chromic oxide content is reduced to 2.87% by 6.85%, ton steel reclaims pure chromium 4.44kg, and single stove reclaims pure chromium 213.12kg.

Price=163.3Kg/ ton steel * (6.85%-2.87%) * 0.684 * 12 of the content * pure chromium of pure chromium yuan in chromic oxide content * chromic oxide=53.34 yuan/ton of steel in the slag of the ton steel economic benefit=ton steel product quantity of slag * reduction.

Year yuan/ton steel * 250,000, benefit=ton steel benefit * annual production=53.34 ton=1333.5 ten thousand yuan.

Claims (1)

1. a method that reduces chromic oxide in stainless steel smelting process electric arc slag, its feature comprises:

(1), when power transmission amount is delivered to the 53%-55% of total power transmission amount, use electric arc furnace fire door oxygen gun blowing to flux;

(2) after in electric arc furnace, steel scrap thoroughly melts clearly, blow off oxygen when molten steel temperature reaches tapping temperature, to the ferrosilicon powder of molten steel winding-up 100-200kg; Nitrogen blowing stirs, and nitrogen flow is 1800Nm3/h, simultaneously low voltage, large electric current power supply;

(3) in stove, add ferrosilicon and fluorite to reduce, ferrosilicon and fluorite are according to weight 1:(1.5-2) proportioning adds, and continue nitrogen blowing simultaneously and stir, nitrogen flow 1800Nm3/h;

(4), when the lasting power transmission amount of reduction process reaches the 2.5%-3% of total power transmission amount, stop power supply; Furnace door carbon oxygen lance oxygen hose nitrogen blowing churning time >=4min, stops nitrogen gas stirring, grate subsequently, the mixed steel of going out of slag;

(5) smelting process adds lime slag making, and after reduction, the basicity of electric arc furnace finishing slag is controlled at 1.20-1.35.