KR800000663B1 - Method for fe-cr-ni steel alloy - Google Patents

Abstract

A Cr ore melt, a high-Si low-C ferronickel obtained from a high-C ferronickel, sand and lime and a scrap iron mixture of steel and/or stainless steel are mixed with each other, and the mixture is heated to reduce Cr oxides in the Cr ore melt by si in the high-Si low-C ferronickel to obtain a low C Fe-Cr-Ni alloy without decarburization by oxygen blowing.

Description

Manufacturing method of iron-chromium-nickel alloy steel

1 is a flow chart of a manufacturing process according to one embodiment of the present invention.

The present invention relates to a method for producing iron-chromium-nickel alloy steel (hereinafter referred to as Fe-Cr-Ni alloy steel), and in particular, a melt of Cr ore incorporating a crude material such as lime as Cr source. In addition, molten or solid high Si low carbon Fe-Ni (hereinafter referred to as Si-) is obtained by adding silica or coke to the cross-carbon Fe-Ni obtained by melting and reducing Ni ore in a melting furnace by lime, cost, etc. Ni) is used as a reducing agent and a Ni source, and Si-Ni is usually mixed with Fe source of a mixed melt such as snowfall or copper and stainless snowfall, and the melt of the Cr source Of Fe-Cr-Ni alloy steel, characterized in that the mixture is stirred, mixed and agitated and immediately cast without undergoing a decarburization process by O ₂ blowing. It is a recipe.

Conventionally, various methods shown below are known as steelmaking methods of stainless steel.

(A) The most commonly used stainless snow or snow is melted by electric furnace only using ferrochrome (Fe-Cr), ferro-manganese (Fe-Mn), ferronickel (Fe-Ni), etc. The molten steel containing 0.5% to 1.5% of the obtained C was oxidized and decarburized to about 0.08% to 0.04% by introducing O ₂ for deoxidation, followed by silicochrome (Si-Cr) or silicon manganese (Si). -A method in which a solvent is prepared by operating approximately four steps in which the Mn oxide and the Cr oxide are reduced and recovered, and then the final alignment is performed in the same drying machine.

(B) Charge the melt melted by an electric furnace or a melting furnace such as Cupola using the above raw material into a converter, and blow in O ₂ or O ₂ + Ar to the converter to decarburize. Method of combining furnace-converter to be performed.

(C) A method of aligning again the degassing or vacuum melting furnace in the step (b).

(D) A method for effectively recovering Cr-Mn from slag generated by the decarburization treatment in step (b) above using a reducing system such as ferrosilicon (Fe-Si).

(E) After the converter, it is the same as the above (c), but instead of the melting furnace of (b), a combustion furnace such as a blast furnace is used, and as a raw material, a reducing agent such as coke is used for Cr ore and steel A method of producing a melt of chromium iron containing high carbon and producing stainless steel by a combination of blast furnace → electricity → degassing.

In each of these methods, the use of low-carbon alloy iron for the purpose of reducing the carbon content in stainless steel is preferred for ferroalloy as a raw material for manufacturing stainless steel, but low-carbon alloy iron has undergone a complicated process in ore. Since it is manufactured, it is expensive and inevitably increases the manufacturing cost of stainless steel. In addition, if low cost ferroalloy is used, since all of these ferroalloys contain a large amount of carbon, more than a specified amount of carbon exists in the molten stainless steel, and even in the case of the stainless steelmaking method in order to reduce the amount of carbon in the molten steel It is necessary to blow out O ₂ into the molten stainless steel to decarburize, and with the refining of O ₂ , loss due to oxidation of Cr, Mn, and Ni as an active ingredient cannot be avoided, and a large amount of equipment, a complicated process, It is difficult to say that it is a satisfactory method because it requires difficult operation and a lot of expenses.

Accordingly, an object of the present invention is to solve the problems described above, a method for producing a low-carbon Fe-Cr-Ni-based alloy steel that does not include any step of decarburizing the O ₂ in the molten steel, that is, a substantial decarburization process It is possible to manufacture Fe-Cr-Ni alloy steel of sufficiently low carbon without including, to significantly reduce the loss of Cr, Mn, Ni, and further provide a steelmaking method that can improve the work efficiency and productivity beyond the conventional method. You can do it.

That is, the steelmaking method of the present invention has a main process as shown in FIG. 1, each process is effectively reasonably coupled, and continuously and continuously processes Fe-Cr-Ni alloy steel of the final target component in ore. It can be manufactured in bulk and economically.

That is, the manufacturing method of the Fe-Cr-Ni alloy steel of this invention performs only melting | dissolving Cr ore by the melting furnace with the preparation materials, such as lime, and separates Ni ore from lime, coke etc. By adding silica and coke to the high-carbon Fe-Ni obtained by melt reduction in the melting furnace, and melting and mixing in the melting furnace to obtain Si-Ni, and the molten or solid Si- A third step of mixing Ni with a Fe source of a mixed melt such as ordinary snow or snowfall and stainless snow; a melt of Cr ore obtained in the first step and a mixed melt of Fe source and Si-Ni obtained in the third step The mixture is stirred in a molten state to reduce Cr oxide (or Cr oxide and Mn oxide) in the mixed melt, thereby obtaining a molten steel of a Fe—Cr—Ni alloy without substantially undergoing decarburization.

In such a 4th process, it is natural that necessary component adjustment is included, and you may add refining processes, such as degassing, deoxidation, temperature adjustment, and desulfurization, as needed of the said process.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, the 1st process of obtaining the melt of Cr ore performs only melting | dissolving Cr ore which mix | blended crude materials, such as lime, in the melting furnace 1, such as an electric furnace, and in the mixing process described next. The melt as a Cr source is obtained.

In the second step of obtaining a melt of Si-Ni, N ore is reduced and reduced in an electric furnace 2a with a reducing agent such as lime and coke to make high-carbon Fe-Ni once, and together with silica and coke, It melt-mixes in the melting furnace 2b, such as a furnace, and obtains the low carbon high Si-Ni alloy iron (it calls it Si-Ni in this invention). In the present invention, the melt of Si-Ni obtained in the above step is brought to the mixing step described below in a molten state, and Cr oxide is reduced by mixing with a melt of Fe source and Cr source to reduce Cr oxide. The basic principle is to make an alloy melt made of -Cr-Ni, but the solid Si-Ni cooled by cooling the melt of Si-Ni is ladleed with a melt of the Fe source by a hopper 10 or the like. In the case of injection into a ladle, both of them may be added and mixed, and the mixture may be mixed with the melt of Cr ore to effectively effect the mixing and stirring thereof to form an alloy melt made of low carbon Fe-Cr-Ni. Thereby, there is no substantial change in the melt.

rouit)식 전기로와 같은 용해로(3)에서 용해할때에는, 용해원료로서 Cr,Mn등의 산소와 친화력이 강한 원소로 포함하지 않는 보통강설을 사용하는 것이 바람직하다. 왜냐하면, 전극이 흑연전극이기 때문에, 용해시에 탄소가 불가피하게 용강속에 들어가는 것은, 피할 수 없으며, 전기로내에서의 산소에 의한 탈탄공정을 취할 필요가 생기고 그 때문에 Cr, Mn 등의 산소와 친화력이 강한 원소를 포함하는 스크랩(예컨대, 스테인레스강설을 다량으로 사용하면, 이들 유효금속의 산화손실이 발생하기 때문이다.On the other hand, in the third step, as the Fe source, ordinary snow or snow and stainless snow are melted in a melting furnace such as an electric furnace 3 or an electromagnetic induction furnace 3 ', and in this second process, The obtained Si-Ni is mixed and brought into the ladle 4a described below in a molten state, and the fluorine (H) is added to the Fe source melting furnace in the third step.

When dissolving in a melting furnace (3) such as a rouit type electric furnace, it is preferable to use ordinary snow which does not contain oxygen as an element having a strong affinity for Cr, Mn, etc. as a melting material. Because the electrode is a graphite electrode, it is unavoidable that carbon enters into the molten steel at the time of melting, and it is necessary to take a decarburization step by oxygen in the electric furnace, and therefore the affinity with oxygen such as Cr and Mn This is because when a large amount of scrap containing strong elements (for example, stainless steel is used), oxidation loss of these effective metals occurs.

However, a small amount of scrap containing Cr and Mn may be used.

In this third step, in the case where the induction furnace 3 is used as the melting source of the Fe source, since carbon entering the molten steel by the graphite electrode does not occur at all, no decarburization treatment is unnecessary, and as the Fe source Besides ordinary snow, a large amount of stainless steel scrap containing Cr, Mn, Ni, and the like can be used.

Moreover, in such a process, it is effective with respect to the steelmaking method of this invention to make slag at the time of Fe source melt | dissolution, and to remove the impurity in a steel beforehand.

In such a third step, the Fe source melt is mixed with molten or solid Si-Ni obtained in the above-described second step and poured into the lid 4a while being in a molten state.

In the third step of the present invention, the Si-Ni melt is added to the Fe source melt in a molten state and mixed with each other in terms of thermoeconomics. However, the present invention is not limited thereto, but the solid form Using Si-Ni does not depart from the spirit of the present invention.

In the fourth step, the melt of Cr ore obtained in the first step is a mixed melt of Fe source and Si-Ni mixed in the third step, that is, a melt and ladle 4a (4b) containing a reducing agent. The mixing and stirring are carried out, for example, to effectively reduce Cr oxide in the mixed melt, and this mixing is not only the operation shown in the drawings but also mixing stirring such as a shaking ladle or electromagnetic stirring. This may be done using an apparatus.

In the reduction process, Cr oxide in the melt of Cr ore and Si powder in the molten or solid Si-Ni flux,

Expression

2Cr ₂ O ₃ (Chromium ore) + 3Si (Si-Ni state) → 4Cr + 3SiO ₂

It is considered to be due to the reduction reaction of.

After sufficient mixing and stirring, the molten steel is poured into the ladle 5, and if necessary, the component adjustment is performed by adding small amounts of low carbon Fe-Cr, low carbon Fe-Mn, low carbon Fe-Ni, and the like. Iii) Wait for this to mix and cast.

As described above, in the present invention, Si-Ni is added to the melt of the mixture of Cr ores as a reducing agent and an additional metal source, but a melt of Ni ore may be added together with Cr ore as the Ni source.

In addition, molten or solid Si-Ni is added to the ladle of the melt in the Fe source melting furnace 3 in the above-described embodiment, but this is a large amount of Si-Ni added, and thermally melting furnace. It is carried out in the case where a good result can be obtained by adding the melt to the ladle from (3), and these are added when the melt of Cr ore in the electric furnace 1 is removed. The reduction of the melt of Cr ore may be performed earlier, and these may be added when the melt of the Cr ore in the electric furnace 1 is taken out, and the reduction of the melt of the Cr ore may be performed first, and the resulting low carbon Fe- Substantial changes in the Cr—Ni alloy melt do not occur at all.

In the ladle 5, Ar gas may be blown from under the ladle 5 in order to quickly mix the baths, thereby making the mixing effect even more effective.

By the above four main steps, the Fe-Cr-Ni alloy steel in which the carbon content matches the target component of 0.08% or less is obtained. In addition, (6) in the figure is an ingot case.

In addition, according to the present invention, the degassing step is carried out with the molten steel mixed in the fourth step in the vacuum flow path 7 or the degassing apparatus 8 or the like in the ladle 5 in addition to the above four main steps. And a fifth step of carrying out degassing and component adjustment under reduced pressure, and a final step of the final refining furnace 9, and having a sixth step of performing temperature adjustment and desulfurization or fine adjustment with the final components.

These processes are carried out by the methods and target values usually used in the production of stainless steel.

An embodiment of the present invention is as follows.

Example 1

The component targets were placed in the median of the Sus27 (AISI304) steel grades as shown in the table below.

The ingot was aimed at 5 tons, and molten steel was produced from Hit No. 1 to 5.

1. Fee

(1) melting furnaces for Cr ores (1)

Eru type electric furnace (route turn top charge tilt type) (爐蓋 旋回 Top charge 傾 動 式)

(2) Fe source melting furnace (3)

Eru type electric furnace (rove turn top charge tilt type)

2. Source material and typical composition

3. Operational situation

(1) 3,285 kg of sufficiently dried Cr ore and 2,230 kg of quicklime were sufficiently mixed and charged into an electric furnace (1). In order to facilitate the energization, Cr ore and quicklime were charged, and then a small amount of these powders were placed under each electrode.

Dissolution melted for 1.5-2 hours and transferred to ladle 4b at a temperature of about 1,800 ° C after complete dissolution.

(2) In the Fe source melting furnace (3), 1,340 kg of ordinary snow was charged and immediately energized. Then, it was energized and melted for 1-2 hours to completely dissolve the scrap, and then a small amount of iron ore was added to the carbon transferred from the electrode to the molten steel. The temperature was lowered to the specified value, and the temperature of molten steel was adjusted to further add a small amount of CaO, CaF ₂ , FeSi (powder) and the like to form a complete white slag, and sufficient desulfurization and deoxidation was performed.

On the other hand, 6,000 kg of nickel ore is melt-reduced in (2a) with a dry machine with a nominal capacity of 30 tons as a reducing agent (coke, breeze) to make high-carbon Fe-Ni once. 3,240 kg of solid high Si low carbon Fe-Ni (Si-Ni) prepared by melt mixing in the electric furnace 2b as described above is charged into the molten steel of the Fe source melting furnace 3 in the hopper 10. After the Si-Ni was completely dissolved, the Si-Ni was pulled out to the ladle 4a at about 1,650-1,680 ° C in the electric furnace 3. The main components of this molten steel are as follows.

(3) The molten steel containing Si-Ni of the ladle 4a was transferred to a ladle 4b containing a melt of Cr ore by a crane. In addition, the molten ladle 4b of which transfer was completed was immediately transferred to the other ladle 4a of the empty ladle 4a.

This operation was repeated 4-5 times to obtain a target Cr reduction. The ladle 4b was then tilted with a crane and the slag of reducing agent was discharged. In addition, the drop in temperature was stopped around 100 ° C by the exothermic reaction when Si in the Si-Ni phase reduced Cr ore.

After the mixing was completed, the molten steel was poured from ladle 4b to ladle 5. At this time, 75 kg of low carbon Fe-Mn is added to the ladle 5 separately, and after the transfer from the ladle 4b is finished, the net Ar in the porous plug previously attached to the ladle 5 is finished. The gas was blown in, the molten steel was sufficiently stirred, the components were uniformized, the temperature was uniformed, dehydrogenation and the inclusions were removed, and the sample was sampled to check and adjust the components. When the molten steel temperature reached 1,530 ° C. ± 10 ° C., the blowing of Ar gas was stopped, the stopper of the ladle 5 was opened and closed, and the molten steel was poured into the ingot case 6.

The main components of the ingot were as follows.

Example 2

In the same manner as in Example 1, molten steel of each hit was made, and each was transferred to a vacuum degassing process with a ladle 5, using a vacuum degassing apparatus 8 (reel degassing equipment), It was held for about 30 minutes under a strong pressure of about 8.0-0.5 mmHg, and degassed.

Since each molten steel had a high temperature of about 1,700-1,750 ° C., the ladle degassing apparatus does not have to use a facility equipped with a heating means for thermal compensation, such as the heating device 9, in the degassing process. (8) fully achieved the objective.

As a result of the aforementioned degassing treatment, the respective molten steels decreased the amount of oxygen in the molten steels from 98 ppm to 38 ppm.

Although this invention manufactures desired low carbon Fe-Cr-Ni alloy steel through the process mentioned above, the effect obtained by this invention is summarized as follows.

(1) The decarburization process by oxygen injection as a state containing elements having a high affinity for oxygen such as Cr is not employed through the whole process from obtaining the Fe-Cr-Ni alloy steel from Cr ore.

(A) The oxidation loss of the useful metal of Cr is small compared with the conventional method.

In the conventional method, the loss of Cr from the raw ore to the ingot and the total Cr reaches 1.5-25%. However, as is clear from the embodiment of the present invention, the amount of Cr is reduced to 10-15% in Cr. Less waste. Therefore, the reduction of raw materials can be avoided.

(B) The problem of pollution such as air pollution caused by exhaust gas generated by the O ₂ injection occurs in the conventional method does not occur.

(C) In recent years, a method by a converter has been considered in place of the electric furnace method. However, the enormous equipment cost in such a case is also unnecessary.

(2) The present invention mixes and stirs a molten steel containing Cr ore obtained in the first step and a reducing steel obtained in the third step in a molten state to obtain a Fe-Cr-Ni alloy steel as a final target component. As in the conventional method, it is not necessary at all in the present invention that a large amount of electric power is consumed when the ferroalloy is purchased in the solid phase and dissolved together with cold materials (stainless snow, snow, etc.).

(3) In recent years, the depletion of Ni resources and the rise of Ni prices, in particular, the use of a large amount of low carbon Fe-Ni as a raw material, has been problematic in view of the manufacturing cost of steel. In order to make high Si low carbon Fe-Ni out of Ni ore or high carbon Fe-Ni by silica, etc., and use it as a reducing agent and Ni source, the desired Fe-Cr-Ni alloy steel can be used at a relatively low price. You can get

(4) Throughout the entire process, large-scale equipment is not required, work can be easily performed at inexpensive facilities and simple processes, and manufacturing costs can be greatly reduced because of high productivity.

Claims (1)

In the process of dissolving Cr ore in the melting furnace as a crude material of lime and obtaining a melt of Cr ore, separately in high carbon Fe-Ni obtained by melting and reducing Ni ore in the melting furnace with lime, coke, etc. To obtain high Si low carbon Fe-Ni by melting and mixing in a melting furnace by adding coke, etc., obtaining a Fe source which is a mixed melt of ordinary snow or snow and stainless steel, and Cr obtained in the above three steps. Mixing or stirring the melt of the ore, the high Si low carbon Fe-Ni and the Fe source to reduce Cr oxide in the melt of the Cr ore by Si in the high Si low carbon Fe-Ni. _2. A method for producing an iron-chromium-nickel alloy steel, which is cast directly without passing through a decarburization process by blowing.

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