JPS6052505A - Manufacture of chromium steel by refining using converter and vacuum decarburization refining furnace - Google Patents

Abstract

PURPOSE:To improve the efficiency of energy utilization by adding a substance contg. carbon to a converter as a heat source for melting a solid substance contg. Cr, burning generated gaseous CO, recovering it as steam, and using the recovered steam as a power source for an ejector in a vacuum decarburization refining equipment. CONSTITUTION:Cr steel is manufactured by refining using a converter and a vacuum decarburization refining equipment. A substance contg. carbon is added to the coverter as a heat source for melting a solid substance contg. Cr. Generated gaseous CO is burned in a flue of the converter, and it is recovered as steam. The recovered steam is used as a power source for an ejector in the vacuum decarburization refining equipment. Thus, the latent heat of the substance contg. carbon is used in the converter and the vacuum decarburization refining equipment.

Description

Detailed Description of the Invention a) Industrial Field of Application The present invention is a process for manufacturing chromium-containing steel by combining a converter and vacuum decarburization refining equipment. In addition to using a converter as a heat source for melting chromium substances, part or all of the latent heat of the carbon substances is used in a chromium-containing steel manufacturing process system using a converter and vacuum decarburization. It concerns a method of manufacturing chrome steel.

b) Prior art In general, in a converter, according to the following formula (1), [C] reacts with oxygen gas, and the reaction heat is used to increase the temperature of molten steel, melt scrap, ferroalloy, decompose iron ore, etc. ing. However, [c] is C0 as shown in equation (2)
The reaction heat of the secondary combustion (hereinafter referred to as "secondary combustion" in formula (2)) up to 2 is more than twice that of the primary combustion in formula (1) (hereinafter referred to as "primary combustion") C has a heat of reaction, and when C is used as a heat source in the steelmaking process (2
) It is important to effectively utilize the reaction heat of the equation, and conventionally I
An attempt was made to utilize the reaction heat of equation (2) in a fMh method.

C+ 40. -+ Co 2,200 kcal/kg
C-・-(t) Formula Co + Committee 02 → CO25,63
0kaa174c17c =・(2) formula is Po5t
Combustion method uses C generated by primary combustion.
OO gas, soft blowing of the converter main lance, that is, keeping the main lance as far away from the casting bath surface as possible (reducing L/Lo L: dent depth of molten steel, LO: molten steel depth) or using a special lance. By using CO gas in the furnace, we aim to increase the rate of secondary furnace sintering and increase the rate of C latent heat utilization in the converter.
Unreacted gas is mainly recovered as LDG. This method requires the use of a special lance, and also has problems such as melting of the refractories in the converter (particularly in the sloped part of the converter) due to the promotion of secondary combustion reactions in the furnace. In addition, the LDG recovery type is a method in which the secondary combustion reaction of the secondary combustion gas is prevented as much as possible, and the COO gas is recovered without reacting. Therefore, the steam required to power the ejector during vacuum decarburization and refining must be supplied from a completely separate energy system.

In the boiler-type converter including the present invention, the c
o. A method in which the gas is supplied with an oxygen source from the furnace mouth or flue to actively generate a secondary combustion reaction, and the resulting heat is exchanged with water in the pipes installed in the flue and recovered as water vapor. be.

C) Purpose of the invention The present invention provides a converter and vacuum decarburization refining equipment (for example, RH).

When melting chromium-containing steel using a combination of VOD, etc., a carbon-containing material is added to the converter as a heat source to melt the solid chromium-containing material, and the primary combustion reaction heat of C is used to melt the solid chromium-containing material. In addition to using it as a heat source for melting, the carbon-containing substance is added to the converter to increase CO generation, and an oxygen source commensurate with the COD generated from the converter mouth and/or flue is supplied to combust CO. This is a highly energy-efficient method for refining chromium-containing molten steel in which the reaction energy of perilla is recovered as steam in the flue and used as the power source for the ejector in vacuum refining equipment, which is the final decarburization furnace in the chromium-containing refining process. In the process of manufacturing chromium-containing steel by combining a converter and vacuum decarburization refining equipment, a carbon-containing substance is actively added to the converter as a CO generation source, and the heat of the next reaction is reduced by Cr in the converter. used as a heat source to melt the source,
Furthermore, the secondary reaction heat is used as steam as a power source for the vacuum NfR furnace, with the aim of effectively utilizing the latent heat of e (reaction heat up to the C-+002 reaction) within the stainless steel manufacturing process system. .

d) Structure and operation of the invention The present invention uses stainless steel scrap and/or ferrochrome alloy as a Cr source in a roller type converter (steam recovery unit) for the purpose of supplementing part or all of the amount of heat source for melting. Carbon-containing substances (powder or lump coke, coal,
Hydrocarbon substances such as graphite, heavy oil, propane, etc.) are added from above the steel bath surface in the converter through an above-furnace hopper, pack, lance, nozzle, etc., or added from a nozzle installed below the steel bath surface. At the same time, acid is blown from the upper main lance and/or the lower nozzle to generate COO gas. In order to proactively prevent the secondary combustion that occurs in the COO gas furnace, we aim for hard plow refining in which the main lance is placed as close to the steel bath surface as possible. ~1.50 Oram or VLO
It is necessary to perform blowing within the range of ≧0.6. 800n
If the main lance is brought closer to the steel bath surface below 17 m, there is a high possibility that the lance tip nozzle will be damaged by the shaking molten iron, which is extremely dangerous. When fc is set to 1.500 s/m or more, the secondary combustion rate increases and at the same time Cr2O in the slag at the time of blow-off increases.
3% or unmelted Cr alloy iron occurs, reducing the Cr yield in the converter.

It is well known that I and /Lo are correlated with the distance between the steel bath surfaces of the lance. (at 0.6, the secondary combustion rate tends to increase, and in addition, as with the change in the distance between the hot water levels, the slag content (%cr2o,) at the time of blow-off tends to be high, and the Cr yield tends to decrease. Regarding the amount of bottom-blown gas, no change in the secondary combustion rate was observed in the range of at least 0.05 to 0.3 ONm5/l-8-m1n, so blowing was performed under virtually the same lance conditions as in the case of blowing. When the bottom blowing gas is above 0.30 Nm, the secondary combustion rate tends to decrease as the stirring force increases in the steel bath, which is advantageous from the perspective of the present invention. However, it is better to decide based on a comprehensive consideration of metallurgical refining and dust amount, etc. In addition, in the present invention, in order to recover the generated COO gas vapor, an oxygen source (mainly 6) is used from the furnace mouth and/or flue. The CO gas is completely combusted in the flue, and the reaction heat and the sensible heat of the waste gas are used to convert the water flowing through the pipes installed on the inner wall of the flue into steam. Steam is temporarily stored in an accumulator.

After the melting of solid chromium-containing substances and decarburization of rice are completed in the converter, the final decarburization and refining is performed in a vacuum decarburization refining equipment, for example, RH, and the degree of vacuum in the RH tank is set to, for example, 1O to 150 To.
In order to perform decarburization while maintaining the vacuum within the vacuum, an ejector powered by steam is used to maintain the above degree of vacuum. At this time, the steam produced on the converter side and accumulated in the accumulator is depressurized to, for example, 10 to 15 kg7cm2 and used as ejector driving steam for RH, thereby reducing the carbon content of the carbon-containing material added in the converter. The present invention is an energy efficient method of producing chromium-containing steel in which carbonaceous material is added to the converter in an energy efficient manner since some or all of the latent heat (heat of reaction leading to CO2 evolution) can be used within the stainless steel refining process.

e) Example Preliminary hot metal 11&j, st, de-P1 de-S treated C-3, 84%, 81 = tr, Mn = 0.3
0%, P=0.028chi, S=0.006%, Tem
71.3 t'i of hot metal at p = 1328°C was charged into a converter equipped with two bottom-blowing nozzles, and the molten pig iron was blown from the upper main lance.
2 gas 16,00. As a result of decarburizing and refining for about 10 minutes while blowing Ar O, 15Nm3/l-8-m1n''fz from the lower nozzle at ONm5/hr, C=1.
．． 12%, Mn = 0.29%, P = 0.028
molten steel with S=0.005% and Temp=1580°C. Here, Cr=16.0~16.5cm SUS
Add 10t'i of 430 series scrap, and at the same time charge 3.0t of small coke (10~20+m) of C = 88%, S = 0.41% in the furnace from the upper main lance. 18.00 nNm3/hr,
Between the lance tip and the steel bath surface 1300. ,T,/Lo=
Blow under the condition of 0.8, and then blow Ar = from the lower nozzle.
As a result of carrying out scrap melting and refining for about 11 minutes while blowing 0.25 Nm/l-8-m1n, C=0
．． 89%, Mn = 0.31%, P = 0.028%
, S = 0.018%, Cr = 2.06%, temperature 15
Molten steel at 92°C was obtained. After that, approximately 55 (35.2 tons of high carbon ferrochrome preheated to 1℃, 1.5 tons of coke as a heat source for melting, 1 ton of CaO2, lightly calcined dolomite)
4.5t'fi = charged in two parts, 02 = 1 g, 00 ONm / h r from the upper main lance
1,050 to 1,250 mm between the lance tip and the steel bath surface,
Shi/L.

After melting and decarburizing refining for about 15 minutes while blowing Ar 0.25 Nm/l-8-m1nf from the lower nozzle under the conditions of = 0.85 to 0.95, the 02 supply from the upper lance was carried out. At the same time as the converter is finished, the reduction fee is removed from the top of the converter.
Add 150 yu of l, and also add Ar = from the lower nozzle.
0.35Nm3/l-8-m1nf Blow reduction refining was carried out for 3 minutes, C=0.6 2%, 81 =0.0 6
%, Mn = 0.24%, P = 0.030%, S
=0.0 2 3 俤, Cr= 1 6.5 8th section, T
emp = 108.2 tons of chromium-containing crude molten steel at 1740℃
I got it. During the stainless steel scrap melting period and high carbon ferrochrome melting period, υCOCO gas was fired by natural air suction from the furnace mouth and forced air supply from the flue, resulting in 38 tons.
of vapor (351 klil/1-8) was collected. Compared to the case where no coke was used, the amount of recovered steam increased by about 9 t (83 kg/1-8) (9). In other words, the amount of CO generated increases due to the addition of coke, and as a result, the steam recovery 1 increases, and the effect of the addition of coke is significant.

After that, decarburization was carried out for about 40 minutes while blowing gaseous oxygen at a vacuum level of 10 to 100 Torr using RH, and C = 0.05%, 51 = 0.04%, Cr = 16
．． 38 units, P = 0.030 units, S = 0.020 units, Ta
mp=1.630°C. After that, Feel,
Deoxidation was carried out using At, and further RH scouring was performed for a total of 83 minutes, including deoxidation and S refining using CaO-based flux and component adjustment.

As a result, C=0.05%, 5i=0.41%, Mn=
0.42%, P=0.030%, S=0.011%, C
Molten stainless steel with r=16.38% and Temp=1585°C was obtained. The amount of steam used in 83 minutes of RH refining is 3
The amount was 4.5 t (32 ok/1-s), which was almost the same amount as the steam recovered in the converter, and as a result, all the latent heat of C could be used for refining in the converter and RH.

According to the present invention, a carbon-containing substance is added to the furnace to serve as a heat source for melting the solid (10) chromium-containing substance, and the CO generated
Gas is combusted in the flue at the top of the converter, C sensible heat is recovered as steam, and the recovered steam is used as a power source for the ejector in the vacuum decarburization refining equipment, thereby removing some or all of the latent heat of the carbon-containing material. It becomes possible to produce chromium-containing steel with high energy efficiency that can be used in converters and vacuum decarburization refining processes.

f) Effects of the Invention According to the present invention, in a method for melting chromium-containing steel by charging a carbon-containing material into a converter as a heat source for melting a solid chromium-containing material and combining it with vacuum decarburization refining equipment, C latent heat (C
-+CO2 heat of reaction), Po5t
Unlike the Combustron method, there is no melting of converter refractories, and unlike the LDG recovery type, there is no need for steam supply equipment from a separate system to the vacuum decarburization refining vessel, and within the chromium-containing molten steel refining process system. It has become possible to easily utilize all the energy required for the reaction of C to produce CO2.

(11) 22-

Claims (1)

[Claims] In a method of manufacturing chromium-containing steel using a converter and vacuum decarburization refining equipment, carbon-containing substances are added to the furnace during converter refining to serve as a heat source for melting solid chromium-containing substances, and are used for reactions in the furnace. By burning the generated CO gas and recovering it as steam, and using the recovered steam as a power source for the ejector in the vacuum decarburization and refining equipment, the latent heat of the carbon-containing material is used in the converter and the vacuum decarburization and refining process. A method for producing chromium-containing steel using a converter and a vacuum decarburization refining furnace.