JPS5816037A - Refining method for high chromium alloy - Google Patents

Abstract

PURPOSE:To save the consumption of electric power and to enhance the recovering yield of Cr by refining a solid contg. Cr as a starting material in a shaft type reaction furnace provided with a plasma torch. CONSTITUTION:A solid contg. Cr such as Cr ore pellets A, lime and coke are semicontinuously charged into a shaft type reaction furnace 1 provided with a plasma torch 2. Air or oxygen enriched air heated to a high temp. is fed from a tuyere 3, and Ar, H2, natural gas, etc. are blown from the torch 2 as working gases. The resulting plasma flame has a high temp. and reducing power, and by blowing the flame into molten slag, Cr oxide remaining in the slag is advantageously reduced to lower the Cr content of the slag. When a melt 4 gathers on the bottom of the furnace, the tap hole 5 is opened to discharge the melt.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to reduce the dependence on electric power on high chromium alloys conventionally produced in electric furnaces (arc furnaces), thereby making them economical and increasing the recovery yield of chromium. About how to get it.

In the present invention, the "chromium-containing solid raw material" refers to chromium ore, a semi-reduced product obtained by solid-phase reduction of chromium ore (
Usually referred to as semi-reduced chromium pellets), ferrochrome or stainless steel scraps, etc.

In addition, "high chromium-containing metal" refers to a material whose main components are chromium and iron, and which also contains impurities such as c, st, p, and s'e, and is mainly used for high-chromium steel such as stainless steel. The alloying agent (usually referred to as chromium) during manufacture (which means an intermediate product of high chromium steel) has a chromium content in the range of 17 to 25.

These high chromium-containing metals have conventionally been manufactured by melting and reducing using an electrician.

However, since electricity is an expensive form of energy, it is desirable to reduce the degree of dependence on electricity as much as possible, and if possible, use some of the energy directly. In the production of high PM gold, the melting point (4IK, = carbon saturated material) is high.

(1) Reduction-high temperature conditions are necessary to increase the reduction recovery rate.

The problem is the front. It is well known that shaft-type furnaces are generally suitable for using secondary energy for melting and reduction with high thermal efficiency. However, due to the above-mentioned constraints (+) and (1), r-2 has been reported only for chromium 1411 and below.

In view of the above circumstances, the present invention aims to produce a PM alloy with a higher PM content than that of Hiro, using mainly a part of the energy in a reactor. This was obtained as a result of the study, and its gist is that high chromium alloy melting is performed using a solid containing chromium as a raw material in a shaft-type reactor equipped with a plasma torch. It's a method.

The following is a detailed explanation using specific examples.The raw materials are various "solid raw materials containing lithium" as defined earlier, but the shaft type reactor used in the present invention is particularly suitable. We will mainly discuss semi-reduced pellets, which are made by solid phase reduction of chromium ore islets or pellets mixed with carbon, which are easy to carry out continuous bag charging and unloading. The size of the pellets is 7 to 15- in diameter, and the weight ratio is 709.
It is desirable to have a score of 6 or more.

FIG. 1 shows an example of equipment used for rounding in accordance with the present invention. The shaft furnace 1 is semi-continuously supplied with chromium-containing solid raw materials (for example, PM ore pellets), lime as a slag-forming agent, and carbonaceous solids (for example, coke) from the top. A tuyere 3 for blowing oxygen-containing gas (air or oxygen-enriched air) is located below the center of the furnace body. In front of this tuyere, a portion of the carbonaceous solids supplied from the top burns to a high temperature) and melts and reduces the charge. It is also possible to supply fuel, for example, fine powder, from this tuyere and use the tuyere 3 as a burner for 111.
The present invention is characterized in that a plasma torch 2 is provided at the bottom of the plasma torch 2.The plasma uses hydrogen chloride, hydrocarbons, CO gas, etc. as a working gas, and is blown into a phase mainly composed of molten slag. It will be done. As for the type of plasma torch, the non-transfer type is easier to operate, but
The transition type, in which the molten high-purity alloy accumulated at the bottom of the furnace is used as the opposite electrode, is advantageous in that it has higher thermal efficiency. f Plasma flame is blown into the molten slag with its high temperature and reducing properties, so it reduces the remaining chromium oxides in the slag in an advantageous manner both in terms of equilibrium and speed, reducing the chromium content in the slag. can be lowered. When a predetermined amount of molten material 4 (molten PM alloy and molten slag) accumulates at the bottom of the furnace, a tag hole 5 is opened and the molten slag is discharged from the furnace.

The CN in the PM alloy discharged outside the furnace can be changed from saturated to unsaturated by adjusting the coke supplied from the upper part of the furnace, the amount of oxygen supplied from the tuyere 3, the amount of fuel such as powder, etc. Even the type can be changed. Among unsaturated types,
Since the melting point of C: around 3 is particularly low, it has the advantage that the operating temperature can be lowered.

The feature of the present invention is that, in order to produce high-PM alloys, a plasma torch is installed below the tuyere for supplying oxygen-containing gas, unlike a normal shaft-type single-source furnace, to produce a high-temperature, strong reduction furnace. It is said that K created the area of .

Therefore, it can be said that the method of the present invention is suitable for producing chlorine-unsaturated alloys, which tend to have a high chromium content in slag using conventional methods.

Example In the shaft furnace shown in FIG. 1 (furnace outer diameter, Max 5.8 bait, height 15 sea bream), raw materials were charged from the top of the furnace under the following conditions.

There are 10 tuyeres 3 and 100CK preheated air 20000
The plasma torch is a non-transfer type, 1000 kW, which injects Ntm''/'kr plus 4000 kg of oxygen into the furnace.
4 pieces of wood are attached, each containing 30 pieces of natural gas.
Blow in at a speed of Nws”/by O.

Hot water is tapped once every four hours, and the composition, amount, and temperature of metal and slag are carefully monitored.

Metal: 25t/tap 1610℃ Slag: 30t/night, 7' As in the process above 1650℃, the present invention combines a shaft type reactor equipped with a good torch and melting of high chromium alloy.
By resolving the conventional contradictions and converting most of the energy into energy, we have made it possible to produce high chromium alloys with a high chromium content and, if necessary, carbon-unsaturated alloys. The industrial effects are significant.

[Brief explanation of the drawing]

FIG. 1 shows an example of a shaft-type reactor using OK for carrying out the present invention. A: 4 rets of rim ore, 4 semi-reduced mpele. Lime, Coke B: Air, Oxygen, Fine Dust Officer Procedural Amendment (Voluntary) February 10, 1980 Director General of the Patent Office Shima 1) Spring Product Number 1, Indication of Case Patent Application No. 114176 No. 114176 of 1988 2, Name of the Invention - Process for Producing Alloys 3, Relationship with the Amendment Case Patent Applicant Representative Takeshi 1) Yutaka 4, Agent 2-4-1-6 Marunouchi, Chiyoda-ku, Tokyo 100, Amended (IJ specification, page 2, line 4 "Chromium content is 17-25%")
Correct the chromium content to 17 to 65.

Claims (1)

[Claims] A high chromium alloy melting method characterized in that high chromium alloy is melted using a chromium-containing solid as a raw material in a shaft-type reactor equipped with a plasma torch.