JPH0382704A - Method for smelting stainless steel unnecessary of electric power for smelting without using electric furnace for producing raw material ferro-chromium - Google Patents

Abstract

PURPOSE:To produce a stainless steel at a low cost without using electric power by melting and perfectly reducing in a converter-type furnace after pre-reducing pellet of Cr ore and powdered coke in a rotary kiln to make high carbon ferro-chromium and executing vacuum decarbonizing refining, after adding iron scrap to this and melting. CONSTITUTION:After crashing the Cr ore, the coke powder, and pulp waste liquid and bentonite as binder is added and kneaded to make the pellet. The powdered coke as outer coating carbonaceous material, and silica and lime stone are added to the pellet and charged into the rotary kiln and heated at 1250-1400 deg.C, and after executing the pre-reduction of >=60% of Cr2O3 and FeO in the Cr ore, this is charged into the converter as tiltable. Successively, O2 gas and fuel of coal, coke, etc., are blown and the pre-reduced pellet is melted with heat generation by burning be fuel, and also by reducing the remaining Cr2O3 and FeO, the high carbon ferro-chromium is produced. The iron scrap is added to this high carbon ferro-chromium and after melting in the converter, the vacuum decarbonizing treatment is executed to produce the stainless steel at a low cost without using the electric power.

Description

[Detailed Description of the Invention] Smelting of stainless steel, for example 17C+ stainless steel, is as follows:
Generally, it has been carried out using an L-type electric furnace for smelting.
After that, the method of blowing using an L/D converter became mainstream. However, as chromium, which is the main alloying component of stainless steel, high carbon ferrochrome is still the only method used. P, which is considered the newest method
Even in the lasmach+ome method, Cl52-58%
It is said that the power consumption per charge chrome is recovered through energy recovery, but the plasma power consumption is 380 yen.
It requires 0 to 4,500 KWH and cannot be called an advanced method.

The method of the present invention substantially eliminates the use of high-carbon ferrochrome cold blocks for the production of stainless steel, and is an innovative smelting method that eliminates the use of electric furnaces at all for the production of high-carbon ferrochrome, eliminating electricity consumption for smelting. It is the law.

The smelting method for high-carbon ferrochrome is the most advanced method recently compared to the conventional method, as disclosed in Patent Publication No. 4G-34966' (Inventor:
Isao Tanabe) and patent publication 1972-37885
” (inventor: Isao Tanabe), etc., by mixing finely crushed chromium ore and finely crushed coke, and using the necessary binder, carbon-containing pellets are used, and if necessary, the required amount of exterior coke is also added. The reaction temperature was set to 12
The following results were obtained at 50 to 1400°C. That is, by setting the reduction rate of chromium to about 70% and the reduction rate of Fe to about 95%, and hot-charging the reduced pellets together with other mixtures in a closed type L-furnace, the power consumption per tonne of high carbon ferrochrome is about 1800 ~ 1700KW) I/l and the smelting power by the normal method is 400[IKWtl/+] or less.

However, the new method according to the present invention omits the electric furnace for obtaining high carbon ferrochrome and mainly uses reduced pellets. The rotary kiln descharge is temporarily held in a heat insulating furnace, then charged into a smelting reduction furnace, and either by blowing coal powder with oxygen gas or by adding coal or coke powder to oxygen gas and fuel gas such as methane, propane, butane, etc. as necessary. Fluxes such as CaF2 and CaO are added as necessary to reduce as much as possible the chromium oxide and iron oxide that were unreduced at the reduced pellet stage, and to completely melt both metal and slag. let

As a result, the metal and slag can be completely separated by the tilting operation of the smelting reduction furnace, and the resulting slag-free molten ferrochrome metal can be mixed with molten pig iron in the next process or melted and blown with steel scrap. Stainless steel can be easily blown without requiring smelting power.

By implementing the above-mentioned principle, it becomes possible to smelt stainless steel without using any smelting power, and it becomes possible to significantly reduce costs. In addition, since slag removal is complete, there is no slag-related trouble and the blowing operation is stable compared to when Cr-a'e is added directly or reduced pellets are directly added to the LID converter, and the slag loss of Cr is also reduced. It goes without saying that the recovery of this metal layer of chromium oxide by oxygen blowing is also very smooth.

Next, examples of the method according to the present invention will be explained.

Table 1 shows the composition of the raw materials used in carrying out the present invention.

(Left below) *F, C: Fixed Carbon V, M: V
olatile matte ``Next, the fineness of the chromium ore for pellets after crushing and the fineness of coke breeze is shown in Table 2, which is the standard particle size for pellets.

Now, the formulation for the implementation was to thoroughly mix 1000 parts of chromium ore, 234 parts of coke powder (approximately 135% of the theoretical reduction amount), 30 parts of pulp waste liquid, and 30 parts of bentonite, adjust the moisture well, and use a rotary pelletizer. , average about 151
nl pellets, dried to a moisture content of 6.5%, and then added 30 parts of coke powder of 10 mm or less as exterior carbon material, 105 parts of silica stone of 5 to 2 Q mm size, and coal stone (Ca0
55.6%) Lining 75 parts Inner diameter 2.50m Length 6
The maximum temperature of the reaction zone charged into a rotary kiln at 0 m is 1.
The temperature was set at 400° C., and reduction was carried out using a rotary kiln, and while 15 parts of coke powder was being projected from the burner side, the reduced Pelle Soto and its accessories were once introduced into a heat-insulating holder. The average composition of the discharge material mainly consisting of reduced pellets after three months of continuous operation was as shown in Table 3.

Table 3 Rotary kiln, average composition of descharged material (v1%) Also, the weight of the descharged material during the average time aiming at a reaction temperature of 1400°C was 19.3 on average, and its volume was approximately 7.5 m', keeping it warm. The cage used had an internal volume of 10 m3. An average of approximately 1.5 from the start of charging the heat-retaining container to the discontinuation of charging and the charging of the melting reduction process
Despite the time, the average temperature was around 1360°C.

For the smelting reduction furnace, refer to the Pored Process in Figure 2A.
We mainly investigated the SS type (3), and for the P and C types, the smelting reduction process was performed using a combination of oxygen, coal powder, and natural gas, and the basic unit of the smelting reduction process was the average result of 20 charges, as shown in Table 4. Met.

The average composition of the obtained high carbon ferrochrome is as shown in Table 5, and the Cr yield based on this is 94.2%, which is a good value. It was concluded that the cost was considerably lower than that using a furnace.

High carbon ferrochrome melt and hot pig iron or steel,
It is well known that it is easy to smelt 17% stainless steel from scrap, and there are many different examples, so it is not considered necessary and will therefore be omitted.

Cited document 1) Patent publication No. 34966 filed in 1972, No. 1 in 1962
May 17th Inventor: Isao Tanabe 2) Patent Publication: 1971 371185 Filed: December 4, 1962 Inventor: Isao Tanabe 3) Nao Hamada; Iron and steel? 2 (1986) 1991~
2000 “Current status and future of smelting reduction technology development” 4) Miki Kai, Kio Hoshi, Yoshioki Kamidate, Tetsuya Sanno; Tetsu to Hagane 70
(19841680-686 “Metallurgical properties of converter combined blowing process in stainless steel”)

[Brief explanation of drawings]

Figure 1 shows a rotary kiln, which is a reduction furnace for carbon-containing pellets of chromium ore.Charcoal-containing chromium ore pellets are heated and reacted to form reduced pellets, which are held in a heat-insulating holding container, and the reduced pellets are charged into the melting and reduction furnace using fluorocarbons. . Figure 2A,
B and C are diagrams of the reduced pellet melting and reduction equipment, which performs the final reduction of unreduced chromium oxide and melts and separates all produced metal and slag.The slag is separated by tilting, and the molten metal is transferred to the molten liquid. It can be used as

Claims (1)

[Claims] 1. Grind chromium ore, add the required amount of binder, make it into carbon-containing pellets, add the required amount of exterior charcoal, add the required amount of silica stone and some coal, and use a rotary kiln.
A first step in which the reaction temperature is set in the range of 1250 to 1400°C, the reduction rate of chromium oxide is set to 60% or more (substantially 70 to 95%), and the reactant mainly consisting of the generated reduced pellets is kept in a heat insulating container. Implement. 2.Then, in the second step, the heat-retained product processed by the rotary kiln in the first step is charged into a melting reduction furnace, and coal or coke powder is fed into the melting reduction furnace with oxygen gas, and in some cases, hydrocarbon gas is also fed at the same time. metal and slag due to the heat generation and reduction of residual chromium oxide by the fixed carbon contained in the pellets and the fixed carbon from the carbon material charged together with the oxygen gas and the progress of melting of the reactants. By completely melting and separating the slag, adding slag-forming agents as needed to assist in this, and tilting the smelting reduction furnace, slag can be almost completely removed, and high carbon ferrochrome can be melted without slag. A method for smelting stainless steel, which is obtained as a metal and melted or mixed with steel scrap and blown into stainless steel in an L/D converter or a composite blowing L/D converter.