JPS61284512A - Production of high-chromium steel using chromium ore - Google Patents

Abstract

PURPOSE:To obtain a high-chromium steel with good efficiency at a high recovery rate by blowing a powder mixture composed of chromium ore and carboneous material to the fire point of a molten iron and melt-reducing the chromium ore at a high temp. CONSTITUTION:The molten iron 2 which is preliminarily dephosphorized is contained in an oxygen top furnace 1. The lance 3 is a composite nozzle which ejects the powder mixture composed of the chromium ore and carboneous material entrained in a carrier gas from the nozzle 31 positioned at the center and ejects gaseous oxygen from the circumferential nozzles 32. The powder mixture is thereby always blown to the fire point of the molten metal and the reduction reaction of the chromium ore progresses in the presence of the carboneous material. The chromium oxide and iron oxide in the ore are migrated as metal into the molten iron by the above-mentioned operation. The chromium- component to be migrated in the slag can be decreased by such method and the efficient production of the high-chromium steel is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing high chromium steel in an oxygen top blowing furnace.

More particularly, the present invention relates to a method for efficiently and economically producing high chromium steel by blowing chromium ore powder with an oxygen jet into an oxygen top blowing furnace.

BACKGROUND ART Conventionally, high chromium steel such as stainless steel has been produced by reducing chromium ore with coke in an electric furnace to produce high carbon ferrochrome, and using this as a raw material. In other words, in this method, high temperatures are required for the reduction of ores with high Cr% to proceed, so they are treated with an excessive amount of carbonaceous material (
This is a two-step method in which high chromium steel is produced by melting the obtained ferrochrome together with an iron source and decarburizing it again in an electric furnace in the presence of coke.

However, this method called “indirect manufacturing method” has
When viewed as a consistent flow from chrome ore to stainless steel, there are the following problems.

(1) Expensive electricity is used as the large amount of energy required to reduce chromium oxide.

(2) Since ferrochrome manufacturing plants and steelmaking plants are generally located far apart, high-carbon ferrochrome is produced as a molten product, but it is solidified once and then remelted during the steelmaking process, resulting in large energy losses.

(3) Since a large amount of slag is refined in contact with ferrochrome having a high [Cr%], the (Cr%) in the slag
It is difficult to lower the chromium loss, and the loss of chromium is large.

Therefore, in order to reduce the cost of melting high chromium steel, it is necessary to solve these problems, and the following measures have been considered. In other words, (1) use cheap primary energy instead of electricity as energy for reducing chromium ore, (2) minimize energy loss in the integrated process from chromium ore to stainless steel, (3) ) It is important to minimize the amount of slag and create a reaction or reaction environment with a high Cr recovery rate.

Based on this idea, for example, Japanese Patent Application Laid-Open No. 54-1583
No. 20 proposes a method for producing chromium steel from chromium ore using a bottom-blown converter.

However, when chromium ore is directly added to hot metal,
Since the cooling capacity of chromium ore is large, the temperature at the reduction site of the chromium ore decreases, and in order for the Cr reduction reaction to occur, it is necessary to wait for the temperature of the hot metal itself to rise to the required temperature due to the decarburization reaction.

For this reason, the time required to reduce the chromium ore becomes longer, and although carbonaceous material is added, the reduction of the chromium ore proceeds only with the beads in the hot metal, limiting the amount of reduction and producing high-chromium steel with a high yield. It was difficult to do so.

That is, in the prior art, the following problems existed in melting chromium steel from chromium ore using an oxygen converter.

(1) Since chromium ore is used as a raw material, the molten steel temperature is low and the Cr recovery rate is low.

(2) It is necessary to raise the temperature of the hot metal itself to a high temperature at which the Cr reduction reaction proceeds, and for this reason, the temperature is increased by burning carbonaceous materials, so the -9 content in the molten steel or hot metal becomes low, and the Cr
Recovery rate is low.

(3) Impurities in hot metal, especially P, are difficult to remove;
A large amount of slag is required, and Cr migrates into this slag, resulting in a low Cr recovery rate.

Problems to be Solved by the Invention An object of the present invention is to solve the above-mentioned problems of the prior art, and to process chromium ore from chromium ore with high thermal efficiency and high Cr content using an oxygen top-blowing furnace.
The object of the present invention is to provide a method for producing high chromium steel with a high recovery rate.

More specifically, the present invention makes full use of the characteristics of an oxygen top-blowing furnace to proceed with the reduction of chromium ore under the best temperature and chemical conditions, thereby producing high chromium steel efficiently and with a high Cr recovery rate. The purpose is to provide a method for

Means for Solving the Problems In order to achieve the above-mentioned object of the present invention, the present inventors have conducted many years of experiments and studies, and have discovered that high chromium steel can be produced from chromium ore in a high yield using an oxygen top-blowing furnace. found that the following is important:

(1) In order to provide the chromium ore with the highest temperature reduction site, it is effective to inject the chromium ore into the hot spot of the molten metal in the oxygen top blowing furnace. The fire point of an oxygen furnace is about 2000° C., and when chromium ore and reducing carbonaceous material are injected into the fire point, favorable conditions for the progress of the Cr reduction reaction can be obtained.

(2) It is preferable to make the chromium ore and carbonaceous material into powder in advance and mix this mixed powder with a carrier gas or alone into an oxygen jet and blow it into the fire point to accelerate the reduction rate and achieve a high Cr recovery rate. Obtainable.

(3) Mixing slag-forming agents such as quicklime and silica stone into the above mixed powder to lower and sweeten the melting temperature of chromium ore,
It is extremely effective in improving the Cr reduction reaction rate.

(4) Preliminary dephosphorization of hot metal to, for example, p<0.040% is advantageous for reducing the amount of slag in the oxygen top blowing furnace and for forming a Cr reducing atmosphere. That is, the dephosphorization reaction proceeds in an oxidizing atmosphere, and therefore, the dephosphorization reaction has a property that is contradictory to the reduction reaction of Cr ore, and if it is carried out in a furnace, a large amount of slag is required. Cr loss increases.

The present invention has been completed based on the above knowledge, and according to the present invention, there is a method for manufacturing high chromium steel using chromium ore in a melting furnace equipped with an oxygen top blowing lance and containing hot metal inside. In this method, a mixed powder of chromium ore powder and carbonaceous material powder in an amount necessary for reducing the chromium ore is mixed into an oxygen jet at the outlet of an oxygen nozzle, blown into the hot metal hot point, and then A method for producing high chromium steel is provided, which comprises melting and reducing chromium ore at high temperatures and transferring chromium oxides and iron oxides in the ore as metals into hot metal.

According to a preferred embodiment of the invention, the hot metal is heated outside the furnace with P<0
．． 0.04%, preferably P<0.03%.

Furthermore, according to a preferred embodiment of the present invention, powder of a slag-forming agent such as quicklime or serpentine is mixed into the mixed powder of chromium ore and carbonaceous material, and the mixture is blown into the ignition point of the molten metal in the furnace.

Function The present invention actively utilizes the fact that the fire point of the molten metal in the oxygen top-blowing furnace is about 2000°C, and blows mixed powder of chromium ore, carbonaceous material, and more preferably a slag-forming agent into the fire point, The purpose of this invention is to promote the reduction reaction of chromium oxide at high speed and with good yield.

Expressing these reactions in chemical formulas, the heat and reducing atmosphere generated by the combustion of the carbonaceous material shown in equation (1) are used to promote the Cr reduction reaction shown in equation (2).

2C+0□-2CO・・・・・・・(1)7Cr20
i+27C→2Cr, C3+21CO-...-(2)
In the method of the present invention, the chromium ore is blown into a boiling point of about 2000° C., so as shown in FIG. 1, the Cr recovery rate is much higher than in the conventional method.

That is, FIG. 1 is a graph showing the difference in Cr recovery rate between the conventional method and the method of the present invention in reducing chromium ore in an oxygen top-blowing furnace.

As shown in FIG. 1, in the method of the present invention, the chromium ore is reduced at a boiling point maintained at about 2000°C.
Stable with high recovery rate.

On the other hand, in the conventional method, the Cr recovery rate is unstable, and in order to obtain a high recovery rate, an excessive amount of heat source, that is, a carbonaceous material, and an excessive amount of oxygen blowing are required, and the result is a high C steel. Since extra decarburization treatment is required, the treatment takes a long time. Furthermore, if the temperature of the molten metal itself is raised using the conventional method, the refractories on the inner wall of the converter will be severely worn out, and the unit consumption of the refractories will significantly increase.

Furthermore, in the method of the present invention, the CrR source location is limited to the fire point, and there is no need to raise the temperature of the entire steel bath as high as in the prior art.
Since the carbonaceous material can be used effectively, the amount of [03%] in the steel bath required for Cr reduction can be maintained at a high level. In other words, in the conventional technology, even if carbonaceous material is added, it is not consumed as it is for Cr reduction, but is consumed for raising the temperature of the molten metal by combustion, so the [03%] in the steel bath does not increase, and the Cr recovery rate remains low. was.

FIG. 2 is a graph showing the relationship between [03% in the steel bath and the Cr recovery rate. As shown in FIG. 2, the higher the 03%, the higher the Cr recovery rate, and it can be seen that the method of the present invention is advantageous.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to examples, but these examples are merely illustrative of the present invention, and it goes without saying that they do not limit the technical scope of the present invention in any way.

FIG. 3 is a schematic diagram of the apparatus used to carry out the method of the invention.

As shown in the figure, in the oxygen top-blowing furnace 1 there is pre-dephosphorized hot metal 2.
is accommodated. According to an aspect of the present invention, the hot metal 2 is:
Pro, pre-dephosphorized ex-furnace to 0.04%, preferably to P<0.030%.

A lance 3 hangs down from above the top blowing furnace 1.

The lance 3, as shown in its lower end face in FIG. 4, is equipped with a composite nozzle for blowing oxygen and mixed powder. That is, the mixed powder contained in the carrier gas is ejected from the nozzle 31 located at the center, and the oxygen gas is ejected from the surrounding nozzles 32. The carrier gas is an inert gas such as nitrogen or argon, or CD or CD□. The mixed powder is mixed into the supersonic oxygen jet due to the dynamic pressure difference caused by the difference between the jetting speed of oxygen and the jetting speed of the mixed powder, and the mixed powder is blown into the hot spot of the molten metal together with the oxygen jet.

Note that the nozzle arrangement shown in FIG. 4 is just an example, and
Other types may be used as long as they have a structure in which the oxygen jet and mixed powder are mixed on the nozzle exit side.

For example, a carrier gas may not be used to deliver the mixed powder, and the outlet of the mixed powder may be located near the oxygen nozzle outlet, and the mixed powder may be drawn into the oxygen jet by the reduced pressure created by the high velocity of the oxygen jet. It may also be a structure.

Referring again to FIG. 3, the central nozzle 31 of the lance 3 is connected to the dispenser 4. Pressurized chamber S sources are connected to the dispenser 4 at two locations, upper and lower, and feed the mixed powder of chromium ore, quicklime, recarburized material (coke), silica stone, etc. in the dispenser 4 to the center nozzle 31 .

Meanwhile, the peripheral nozzle 32 is connected to a pressurized oxygen source.

In this way, the oxygen jet and the mixed powder are blown onto the molten metal in the top blowing furnace 1. In other words, when using a composite nozzle with such a structure, the mixed powder is always blown into the molten metal at the ignition point, and the mixture is kept at the ignition point temperature.

Immediately, the reduction reaction of Cr ore proceeds in the presence of carbonaceous material.

EXPERIMENTAL EXAMPLE Using the apparatus shown in FIGS. 3 and 4, high chromium steel was produced from chromium ore under the following conditions.

Hot metal components C: 4.50% P: 0.024% S: 0.010% Mn: 0.43% S] 20.01% Oxygen flow rate: 2.5Nm’/min/T chrome ore ingredients Child, Cr: 31.2% Other ingredients Child, Fe: 20.4% 5102:2.0% 8X2O3: 13.6% MgO: 10.0% Hot metal processing amount: 95 tons Chrome ore: 57 tons Quicklime: 93kg/T Silica stone: 12kg/T Coke: 53kg/T After blowing, a high chromium steel with the following composition was obtained.

Chrome steel component Cr: 13. Q% Mn: OJ1% P: 0.034% S: 0,020% Fe: Remaining Effects of the Invention As described above, the present invention has an advantage that the molten metal in the oxygen top-blowing furnace has a fire point of about 2
Taking advantage of the fact that the temperature is 000°C, a mixed powder of chromium ore, carbonaceous material, and more preferably a slag-forming agent is blown into the fire point.
It is characterized by promoting the reduction reaction of chromium oxide at high speed and with good yield.

Therefore, chromium ore is constantly blown into the molten metal's fire point, and immediately reaches a high temperature suitable for the reduction reaction, and the reduced Cr migrates into the molten metal.

Furthermore, in the method of the present invention, there is no need to raise the temperature of the entire molten metal to the Cr reduction temperature (the added carbonaceous material can be effectively consumed to raise [03%] in the molten metal, and an environment suitable for Cr recovery is created). can be formed.

Furthermore, since there is no need to raise the temperature of the entire molten metal, the unit consumption of refractories in the furnace can be improved.

Furthermore, according to a preferred embodiment of the present invention, the hot metal is pre-dephosphorized outside the furnace, so that the amount of slag generated inside the furnace is minimized;
The Cr content transferred into the slag can be reduced and the Cr recovery rate can be improved.

As described above, according to the method of the present invention, high chromium steel can be produced efficiently and economically from chromium ore, and has great industrial significance.

[Brief explanation of drawings]

FIG. 1 is a graph showing the Cr recovery rate of the conventional method and the present invention in reducing chromium ore in an oxygen top blowing furnace. FIG. 2 is a graph showing the relationship between 63% and Cr recovery rate in the steel bath. FIG. 3 is a schematic diagram of the apparatus used to carry out the method of the invention. FIG. 4 is a diagram showing the arrangement of nozzles at the tip of a lance preferably used in the method of the present invention. (main reference number)

Claims (3)

[Claims] (1) A method for manufacturing high chromium steel using chromium ore in a melting furnace equipped with an oxygen top-blowing lance and containing hot metal, in which chromium ore powder and the amount necessary for reducing the chromium ore are used. The mixed powder with carbonaceous material powder is mixed into the oxygen jet at the outlet of the oxygen nozzle and blown into the hot spot of the hot metal, and the high temperature at the hot spot melts and reduces the chromium ore, reducing the chromium oxide and iron in the ore. A method for producing high chromium steel, characterized by transferring oxides as metals into hot metal. (2) The method for producing high chromium steel according to claim 1, wherein the hot metal charged into the melting furnace is pre-dephosphorized. (3) The high chromium steel according to claim 1 or 2, characterized in that a slag-forming agent is mixed into the mixed powder to lower the melting temperature of the chromium ore. Production method.