JPS6031884B2 - Electric furnace steel manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses steel scraps (both ordinary steel scraps and special steel scraps are referred to as steel scraps) or steel shoulders and metal oxide-containing substances (ore, ferroalloy slag, etc.) in an electric furnace. ) When the mixture is charged and melted by applying electricity, metal oxides such as iron, manganese, and chromium contained in the steel are subjected to a reduction reaction using silicon carbide to become metal, and the metal oxides contained in the steel are converted into metals. This relates to a method for recovering waste.

An electric furnace heats and melts the steel shoulder, which is the main raw material, using resistance heat and/or arc light heat, removes impurities from the molten steel,
This is a melting furnace that produces electric furnace steel by adding carbon, silicon, and necessary alloying elements to refine the steel to contain predetermined components.

The manufacturing cost of electric furnace steel is influenced by the price and yield of the main raw material, steel, as well as productivity, electricity consumption, consumption of the metal pole, consumption of furnace materials, and basic unit of auxiliary materials. Furnace capacity is becoming larger and power load is increasing. In order to further improve the dissolution rate, oxygen injection and auxiliary combustion sources such as heavy oil and kerosene have been used in combination as a dissolution heat source other than electricity. The yield of steel shoulders depends on the quality of the steel scrap, but it fluctuates greatly depending on the melting loss. Melting losses include moisture, metal oxides, and other impurities adhering to the steel shoulder, as well as dust loss during melting and/or loss due to oxidation during melting. In electric furnace melting work, metal oxides in the steel shoulder and metal oxides that are oxidized during the melting work are contained in the steel, and some of them are discarded as oxidized steel.
Most of the metal oxides contained in the reduced steel are recovered through reduction refining, but recovering them during the reduction stage leads to poor yields of ferrosilicon, ferromanganese, silicomanganese, etc., resulting in high costs. becomes a factor.

The use of auxiliary combustion chambers and the increase in the amount of oxygen used, along with the operation of devices that collect smoke emitted during operation, significantly accelerate metal oxidation during the melting process of steel shoulders, so The content of metal oxides ranges from 30 to 50%.

The oxidation loss of the steel layer is 2 to 4 in arc-light electric furnace operation.
%, which cannot be ignored in terms of manufacturing costs, and which can be solved by carrying out reduction recovery using the method of the present invention. Methods for recovering metal oxides contained in oxidized steel in electric furnace melting include using carbon materials such as coke and electrode materials, and methods using ferrosilicon as a reducing agent. In this case, the reduction reaction of the metal oxide is an endothermic reaction, resulting in an increase in power consumption.

In addition, since the specific gravity of carbonaceous material is lower than that of steel, coalwood is floating on the surface layer of steel, and there is a lot of combustion loss due to excess oxygen in the furnace, resulting in a poor yield of carbonaceous material. Furthermore, it is economically disadvantageous because the reduction reaction time is required. In the method of using ferrosilicon as a reducing agent, when comparing the cost of ferrosilicon and the cost of recovered metal, it is not used because it is not economical for reducing iron oxides, but it is not used for reducing oxides such as manganese and chromium. This has been put into practical use because it is economically viable. The present invention is a method for recovering metal oxides contained in oxidized steel during electric furnace melting using silicon carbide SIC. Silicon carbide is a compound of carbon and silicon, and it dissolves very easily in molten iron to increase the amount of carbon and silicon in molten iron, and also reacts with metal oxides such as iron, manganese, and chromium. It has the property of reducing to each metal.

Now, electric furnace steel refining generally involves the following four main processes.
) Bagging period 2) Dissolution period 3) Oxidation period 4) Reduction period 3) and 4) are called the so-called refining period.

Conventionally, in the refining of electric furnace steel using silicon carbide, silicon carbide is added to the surface of exposed molten steel immediately after the final stage of oxidation, or placed in the furnace just before tapping, or prepared in advance in a ladle. In order to increase the amount of carbon and silicon in molten steel by injecting molten steel into the steel, or to promote the production of reducing steel during reduction refining, silicon carbide powder is used by scattering on reduced steel. method is being done.

In all conventional methods, it is used in the final stage of oxidation and/or reduction stage to adjust the composition of carbon and/or silicon and to directly or indirectly deoxidize molten steel.

The method and purpose of using silicon carbide according to the present invention is completely different from that of the conventional ones. It is used in the charging stage and/or melting stage to prevent overoxidation of molten steel, and it is used as a deoxidizer in the reduction stage. This improves efficiency, facilitates reductive refining, reduces loss of valuable materials that are discarded as metal oxides, and reduces thermal energy consumption.

That is, the basic usage method according to the present invention is that silicon carbide is charged into the hearth before charging steel scraps, and/or mixed and charged together with steel scraps when additionally charging a steel layer, etc. and those used during the dissolution phase. The purpose of using the method of the present invention is to reduce and recover metal oxides such as iron, manganese, and chromium produced during the melting process from the initial stage of electric furnace melting, and to increase the amount of carbon and silicon. isn't it.

The specific gravity of silicon carbide is 3.5, which is lower than the specific gravity of molten steel and higher than the specific gravity of oxidized steel, which is 2.5 to 3.0. A portion of silicon is absorbed into the molten steel as melting progresses, and the rest is suspended between the molten steel and the oxidized steel and is not exposed on the surface of the steel.
Metal oxides in oxidized steel can be efficiently reduced and recovered. The silicon carbide used may be crude, and the same effect can be expected. This crude silicon carbide is a so-called reduced raw material that is reused as a raw material in the production of Q-crystal silicon carbide because its quality as silicon carbide is low and the crystal shape is extremely small in the silicon carbide manufacturing process. There are some types of crystals, which can be used alone or in combination with Q crystals to economically recover metals. The chemical reaction formula when metal oxides in oxidized steel are reduced and recovered using silicon carbide is as follows.

3Fe010SIC=Si02000CO+Spot e3Mn〇1S
IC=Si〇20C〇13MnCr2030SIC=S
i020CO+2CrFe2030SIC=Si020CO12Fe oxide The oxides of iron, manganese, and chromium contained in the oxidized steel
There are higher oxides such as 2Q, Nm203, C3,
In order to increase the efficiency of metal reduction by silicon carbide, it is necessary to have a small amount of higher oxides and a large activity coefficient of lower oxides, and for this purpose, basicity is adjusted.

For this purpose, Ca○ or Si02 or the like is usually used. Therefore, the use of silicon carbide mixed with lime and/or silica sand is also a means that meets the purpose of the present invention.

This will be illustrated below with examples.

Example 1 When producing electric furnace steel using ordinary steel scrap in arc-light electric furnace operation, examples of operation using silicon carbide and operation using recarburizing agent are shown, and examples of operations using silicon carbide and recarburizing agent are shown. Shows the effect of reducing oxides.

Furnace used: 10000K. V. A20Ton electric arc furnace steel shoulder tattoo: 30,000k9 Method of the present invention: SIC180k9 having the following composition was poured into a hearth just before being put into a steel shoulder bag and melted.

(Particle size distribution and main component content) (Remainder: Si02, Fe, etc.) Operation using carburizing agent: Contains 50% carbon (remaining portion: approx. 4
5% iron content) recarburizer 350k9 was added and melted at the time of additional charging.

Example 2 Using high manganese steel shoulders in lone light furnace operation,
An example will be shown in which silicon carbide is used to reduce and recover manganese oxides in oxidized steel when producing high manganese steel.

Furnace used: 2500K. V. A 5Ton arc electric furnace charging material: High manganese steel scrap 5250k
g (C: 1.1f Mn: 13.4% content) Ordinary steel scrap (C
:0.2% content) 750k9 silicon carbide usage amount
50k9 (SIC: 85%, Free carbon: 12
% content) How to use silicon carbide: Mixed with high manganese steel shoulders and ordinary steel scraps, charged and melted.

Below is a comparison of the method of the present invention and an operation that does not use silicon carbide. Example 3 When manufacturing high manganese steel in a solitary light electric furnace operation, manganese slag generated during the production of medium carbon ferromanganese is simultaneously charged into the high manganese steel layer and the steel shoulder to be oxidized during the melting process. An example will be shown in which manganese oxide and manganese oxide contained in manganese slag were reduced and recovered using silicon carbide.

Furnace used: 2500K. V. A. Arc-light electric furnace material: high manganese steel shoulder 4800k9
(Contains C: 1.15%, Mn: 12.4%) Ordinary steel calendar (
C: 0.2% content) 1000k9 manganese slag (Mn
0:32%) 900k9 Amount of silicon carbide used 140k9 (Contains 58% SIC, 26% FreeC) How to use silicon carbide: Mix manganese slag and silicon carbide, charge into the hearth, and charge manganese steel shoulders and ordinary steel scraps. Dissolved.

Next, the Mn○ in the molten steel at the time of burn-through, the molten steel composition at the end of acid, and the composition of molten steel at the end of acid in the method of the present invention are shown. Example 4 An example is shown in which a 13% stainless steel shoulder was melted in a lOTon arc-type electric furnace, and chromium oxide contained in the oxidized steel was reduced and recovered using silicon carbide.

Furnace used: 3500K. V. Almon Arc light electric furnace charging material: 13% stainless steel shoulder 8500k
9 (Contains Cr: 13.5%, C: 0.1%) 13% stainless steel powder 3500k9 (Cr: 13.5%,
C: 0.1% content) 65% silicon carbide 25
0k9 (S; C: 65%, free carbon content 25%) Coke grains (fixed carbon content 82%) 60k9 Quicklime 540k9. How to use silicon carbide: Before charging the steel shoulder, silicon carbide was mixed with coke grains and quicklime, charged into the hearth, and then melted using the usual method.

The composition of oxidized steel C203 and beach steel is shown when silicon carbide is used.

In the conventional method of oxidized steel when silicon carbide is not used, a mixture of coke grains and ferrosilicon pongee grains (4:1) is used.
300k9 and quicklime 100k9 were similarly placed on the hearth, stainless steel scraps were charged, and electric melting was performed.

Cr203 content of oxidized steel by conventional method 32.6
% Cr amount in steel construction 154 kg Chromium yield 90.5% Example 5 In a one-dish arc-light electric furnace, a 13% stainless steel shoulder, chromium ore, and silicon carbide were used to produce oxidized steel. An example is shown in which 18% chromium stainless steel was produced by reducing and recovering chromium oxide.

Furnace used: 350 dishes. V. A loTon Arc light electric furnace Materials used: 13% stainless steel shoulder 8000k
9 (Contains Cr: 13.5%, C: 0.1%) 13% stainless steel powder 2000k9 (Cr: 13.2%,
C: 0.1% content) Chromium ore 180
0k9 (Cr203: 50.9%, Fe0: 13.8%
Contains) silicon carbide 450k9 (SIC
: 60%, FreeC 28% included) 50% Ferrosilicon 100k9 quicklime
How to use 940k9: A mixture of chromium ore, silicon carbide, fluorosilicone, and quicklime was poured into a hearth and melted before charging 13% stainless steel scraps and 13% stainless steel powder.

The Cr203 and melt components of the steel at the end of acid treatment are shown below.

Effect of the invention The effects of the present invention are listed below.

1. Since the metal in the metal oxide is reduced and recovered, the amount of molten steel increases and the yield of the product improves.

2. The generation of heat from the oxidation reaction of silicon carbide reduces power consumption and operation time.

3. The concentration of metal oxides in oxidized steel during the final stage of oxidation is reduced, so the amount of deoxidizing agent used during the reduction stage can be reduced.

4. In the production of manganese steel and chromium steel, it is possible not only to reduce the loss of manganese and chromium in steel scrap, but also to actively and economically recover high-value metals from ores and ferroalloy slag. Become.

Claims (1)

[Claims] 1. A mixture of steel scrap or steel scrap and one or more substances containing metals necessary for the product in the form of oxides, such as ferromanganese slag, manganese ore, ferrochrome slag, and chromium ore, is melted and heated with electricity. When producing furnace steel, before steel scrap is melted, silicon carbide or, if necessary, one or more of slag-forming agents such as quicklime and silica sand, carbonaceous materials, and reducing agents such as ferrosilicon are added to it. is charged into a furnace and subjected to a heating reaction to reduce and recover the respective metals from metal oxides such as iron, manganese, and chromium in the oxidized steel slag that is generated during the melting of steel scraps and/or metal oxide-containing substances. A method for producing electric furnace steel characterized by: