CN1009279B - Method for smelting micro-carbon chrome iron by the top-bottom compound blow converter - Google Patents

Abstract

The present invention relates to a method for smelting micro carbon ferrochromium. Carbon ferrochromium is put in a top and bottom combined blown converter, the reduction of carbon content is achieved by supplying air and dilute gas at a low molten pool temperature when a top-bottom lance supplies oxygen; when the carbon content of a fusant is reduced to a low carbon range, chromium mineral powder is added so as to further reduce the carbon content to a required micro carbon range. The method for smelting micro carbon ferrochromium has the characteristics of simple technology and low cost, and micro carbon ferrochromium with the carbon content which is 0.03 at most can be smelted with the method of the present invention.

Description

Method for smelting micro-carbon chrome iron by the top-bottom compound blow converter

The invention belongs to the technical field of producing extra low carbon ferrochromium.

Produce extra low carbon ferrochromium, the technology that adopts has electro-silicothermic process or solid carbon rejection processes at present.Electro-silicothermic process be with by refine in the hot stove in ore deposit carbon ferrochrome hot stove refines to such an extent that carbon content accounts for 0.03～0.1% ferrochrome silicon by means of silica through the ore deposit again.In three-phawse arc furnace, do chromic oxide in the reductive agent reducing chrome ore and ferric oxide then and make extra low carbon ferrochromium with ferrochrome silicon.The deficiency point of this technology is that current consumption is big, produces more than extra low carbon ferrochromium power consumption per ton 7000 degree, and be easy to carburetting near the electrode during reduction in electric arc furnace, thereby further reduce carbon content certain difficulty is arranged.The solid carbon rejection processes is that baked carbon ferrochrome powder is mixed agglomerate mutually with binding agent, and the vacuum oven internal heating, vacuumize and refine extra low carbon ferrochromium.Characteristics such as operation is simple though the solid carbon rejection processes is compared with electro-silicothermic process, the rate of recovery height of chromium, cost are low, it needs certain vacuum technique and does the basis, and the facility investment of its vacuum oven is bigger.

Based on the deficiency of above-mentioned existing technology, the invention provides that a kind of technology is simple, cost is low, and on existing top and bottom combined blown converter, produce the method for extra low carbon ferrochromium

The method that the present invention provides for achieving the above object with the top and bottom combined blown converter smelting extra low carbon ferrochromium, be with the carbon ferrochrome top and bottom combined blown converter of packing into, condition in the bath temperature≤1730 ℃ rifle of going to the bottom blows air and dilution property gas, and top rifle elder generation oxygen blast gas treat the carbon content of melt drop to≤0.3% o'clock top rifle switches to and blows air, and in the molten bath, add the chromite ore fine account for carbon ferrochrome Intake Quantity 2～3%, up to the carbon content of melt reduce to≤0.1%.

Show that according to theoretical study results the carbon in the ferrochrome melt is relevant with the dividing potential drop Pco of carbon monoxide with the balance of chromium, that is:

$\mathrm{［％C\; ］＝4}\sqrt{\frac{1}{K}{\mathrm{［Cr\%］}}^3}\mathrm{·Pco}$

In the formula, K is the equilibrium constant.According to following formula, reduce Pco and can make the oxidation of coal reaction be better than the oxidizing reaction of chromium, be beneficial to the reduction of melt carbon content.Burn out furnace lining and don't make chromium that too big loss be arranged for fear of bath temperature is too high, bath temperature controlled to when in the ferrochrome melt, spraying into oxygen in 1600～1730 ℃ the low scope by being blown into air and dilution property gas reduces Pco, promote the oxidation of carbon.In melt, be blown into air, utilize on the one hand airborne oxygen, be injected to together with dilution property gas on the other hand and play the relative dividing potential drop that reduces carbon monoxide when stirring the melt effect in the melt.Thereby dilution property gas can adopt N ₂, a kind of in the gas such as Ar, or N ₂, Ar mixed gas.Carbon content in smelting the ferrochrome melt drops to≤during 0.3% low carbon range, in melt, add a spot of chromite ore fine, utilize (C) and Cr ₂O ₃Oxidizing reaction carbon content is further dropped to≤little carbon range of 0.1%.

In view of the above, the method for smelting micro-carbon chrome iron provided by the invention, both can be on the top and bottom combined blown converter of the medium-frequency induction furnace transformation of the way with the carbon ferrochrome fusing of solid state and smelt; Also can directly the carbon ferrochrome of molten be smelted in industrialness top and bottom combined blown converter of producing and the hot stove duplex in ore deposit of producing carbon ferrochrome.The carbon content of general carbon ferrochrome is 6～9% scopes, and this high carbon ferro-chrome is packed into behind the top and bottom combined blown converter, utilizes and smelts lower furnace temperature and realize that for air and dilution property gas the carbon content in the ferrochrome melt descends rapidly by top rifle oxygen supply, end rifle in early stage.To respectively account for the lime and the chromite ore fine of carbon ferrochrome Intake Quantity 0.8～1.2% in case of necessity, join top and bottom combined blown converter, guarantee the basicity in molten bath and the rate of recovery of chromium with this with carbon ferrochrome.When the carbon content of smelting the ferrochrome melt drops to low carbon range, in the molten bath, add the chromite ore fine that accounts for carbon ferrochrome Intake Quantity 2～3%, and this moment the top rifle switch to blow air, end rifle continues for air and dilution property gas, is reduced to desired little carbon range up to the carbon content of ferrochrome melt.In order to help air feed, end rifle employing is made by stainless steel or red copper material, structure is double-deck concentric tubes, and the outer shroud slit-tube feeds dilution property gas when the pipe core bubbling air, thereby this moment, dilution property gas can also play the effect of cooling off end rifle.The outer shroud slit-tube can also feed CO during rifle pipe core blowing air at the end ₂End rifle is 1 for the volume ratio of air and dilution property gas: (1～3) scope.The end, top is during the rifle air feed, in order not make the solution splash, and melt stirred, fully, and top end rifle air supply intensity press standard gas and calculated, and the scope of melt per minute air feed per ton is: the top rifle is 1.5～2.0 to mark M ³/ minute ton, end rifle are 0.01～0.20 mark M ³/ minute ton.

The extra low carbon ferrochromium that the present invention produces according to above-mentioned method can be with the further refining of extra low carbon ferrochromium melt according to desired product.Be specially: when the carbon content in the ferrochrome melt drops to the desired little carbon range of product, top rifle blow off, end rifle switches to the Ar that full blows, and air supply intensity is 0.01～0.20 mark M ³/ minute ton, and add an amount of lime and account for the reductive agent of carbon ferrochrome Intake Quantity 2～3% to the molten bath top of the slag.Add an amount of lime and make basicity of slag, add lime and be beneficial to desulfurization, protect furnace lining, also can improve the rate of recovery of chromium in 1.4～1.6 scopes.Reductive agent can adopt Fe-Si powder or Si-Ca powder, makes chromium from Cr ₂O ₃Restore in the slag and enter in the melt, with this and then improve the rate of recovery of chromium.

Method with the top and bottom combined blown converter smelting extra low carbon ferrochromium provided by the present invention, compare with existing technology, technological process is simplified greatly, saving equipment and manpower, power consumption significantly reduces, produce extra low carbon ferrochromium per ton and can economize on electricity more than 2000 degree (comparing), thereby cost reduces greatly with electro-silicothermic process.In addition, the extra low carbon ferrochromium product surface of being produced is smooth, internal structure is fine and close, the carbon content of product is reached below 0.03%, and the rate of recovery of chromium reaches more than 90%.General every stove smelting cycle is about 70 minutes.This shows, adopt the present invention can increase substantially output, produce extra low carbon ferrochromium profit per ton can get 1000 surplus yuan, thereby its economic benefit is very considerable.

Claims (7)

1, with the method for top and bottom combined blown converter smelting extra low carbon ferrochromium, it is characterized in that:

A, with the carbon ferrochrome top and bottom combined blown converter of packing into, be no more than under 1730 ℃ the bath temperature, top rifle elder generation oxygen blast gas, end rifle blow air and dilution property gas;

B, treat carbon content≤0.3% o'clock of ferrochrome melt in the molten bath, to add the chromite ore fine that accounts for carbon ferrochrome Intake Quantity 2～3%, and the top rifle switches to and blows air, up to carbon content drop to≤0.1%.

2, according to the described method of claim 1 with the top and bottom combined blown converter smelting extra low carbon ferrochromium, it is characterized in that carbon content when the ferrochrome melt drop to≤0.1% after, top rifle blow off, the end rifle Ar that full blows, and add account for the reductive agent of carbon ferrochrome Intake Quantity 2～3% and add an amount of lime so that basicity of slag in 1.4～1.6 scopes;

3, according to claim 1,2 described methods with the top and bottom combined blown converter smelting extra low carbon ferrochromium, the air supply intensity that it is characterized in that the top rifle is 1.5～2.0 mark M ³/ minute. the air supply intensity of ton, end rifle is 0.01～0.20 mark/M ³/ minute. ton;

4, according to the described method of claim 1 with the top and bottom combined blown converter smelting extra low carbon ferrochromium, it is characterized in that adopting rifle at the bottom of the double-layer sleeve structure, its pipe core blows air, the circumferential weld pipe blows dilution property gas, and the volume ratio of air and dilution property gas is 1: (1～3);

5,, it is characterized in that described dilution gas can be N according to claim 1,4 described methods with the top and bottom combined blown converter smelting extra low carbon ferrochromium ₂, a kind of in the Ar gas.

6,, it is characterized in that described reductive agent is Fe-Si powder or Si-Ca powder according to the described method of claim 2 with the top and bottom combined blown converter smelting extra low carbon ferrochromium;

7,, when it is characterized in that packing carbon ferrochrome into top and bottom combined blown converter, add lime and the chromite ore fine that respectively accounts for Intake Quantity 0.8～1.2% according to claim 1,2 or 4 described methods with the top and bottom combined blown converter smelting extra low carbon ferrochromium thereupon.