JPH073379A - Production of low-silicon, low-sulfur and high-carbon ferrochrome - Google Patents

Abstract

PURPOSE:To produce a low-silicon, low-sulfur and high-carbon ferrochrome in a high yield with a high productivity by adding a chromium ore and a basic slag making agent to a molten high-carbon ferrochrome received in a ladle from an elctric furnace, agitating and refining the mixture. CONSTITUTION:The molten high-carbon ferrochrome produced by reducing a chromium ore with carbon in an electric furnace is tapped in a ladle from the furnace. A chromium ore and a basic slag making agent, scale and a basic slag making agent or a chromium ore, scale and a basic slag making agent are added to the molten high-carbon ferrochrome, and the mixture is agitated, desiliconized and desulfurized. The basic slag making agent contains CaO and/or MgO and about 80% of CaO, MgO or (CaO+MgO), a hammer scale produced in forging and hammering or a mill scale formed in rolling is used as the scale. A low-silicon, low-sulfur and high-carbon is obtained in this way in a high chromium yield with improved productivity.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing low silicon, low sulfur, high carbon ferrochrome, more specifically, desiliconization and desulfurization in a ladle to produce low silicon, low sulfur, high carbon ferrochrome. It is about the method.

[0002]

BACKGROUND OF THE INVENTION High carbon ferrochromium is generally produced by carbon reduction of chromium ore using an electric furnace. Its application is mainly as a chromium component additive in the production of steel, especially stainless steel. Conventionally, low-silicon / low-sulfur products have been required for high-carbon ferrochrome, which is used especially when producing stainless steel by a converter method.

The reasons are: 1) By using high carbon ferrochromium having a low silicon content as a chromium component additive in the steelmaking process by the converter method, (1) the amount of purified oxygen used for removing Si in the oxygen blowing process. Reduction of. (2) Reduction in the amount of CaO added corresponding to SiO ₂ generated by oxygen blowing. (3) Reduction of chromium loss and furnace material melting loss by reducing the amount of slag. And 2) by using high carbon ferrochrome having a low sulfur content as a chromium component additive, it is possible to reduce the desulfurization cost of the hot metal which is a raw material for steelmaking.

In general, high carbon ferrochromium is produced by reducing chromium oxide and iron oxide in chromium ore with carbon in an electric furnace using a chromium ore, a carbonaceous reducing agent such as coke and a slag-forming agent as raw materials. It Increasing the chromium yield is of paramount importance for the economical production of high carbon ferrochrome. Therefore, in this case, the carbonaceous material used as the reducing agent is added in an amount larger than the theoretical amount of carbon required to reduce the chromium oxide and iron oxide in the chromium ore.

As a result, excess carbon reduces some silicon dioxide to silicon, which is contained in high carbon ferrochromium. Typical high carbon ferrochromes usually contain 2.5% or more of silicon.

The sulfur content in the high carbon ferrochrome varies depending on the sulfur content in the raw material and the silicon content in the high carbon ferrochrome as described later, but in the usual method, the sulfur content satisfying the requirements for steelmaking is satisfied. It is not possible to produce high carbon ferrochrome with a high index.

[0007] Conventionally, when producing low-silicon, low-sulfur, high-carbon ferrochrome, compared with the case of producing high-carbon ferrochrome having a normal silicon content and sulfur content (hereinafter, referred to as a normal product), a chromium ore To produce low-silicon / high-carbon ferrochrome in an electric furnace, and desulfurize the low-silicon / high-carbon ferrochrome by adding a desulfurizing agent outside the furnace.・ Low sulfur ・
Manufactured high carbon ferrochrome.

[0008]

However, as described above, the conventional method is a method of smelting by reducing the compounding ratio of the carbonaceous material as the reducing agent to the chromium ore as compared with the case of producing a normal product. Therefore, the silicon content in the high-carbon ferrochromium is reduced, but the amount of chromium transferred to the slag without reduction is increased, and the chromium yield is reduced.

Further, since there is a negative correlation between silicon and sulfur in the high carbon ferrochrome, the sulfur content increases as the silicon content in the high carbon ferrochrome decreases. Therefore, in desulfurization, a large amount of desulfurization agent is required, which causes a remarkable decrease in the temperature of the molten metal, and there are drawbacks such as loss due to casting and deterioration of work efficiency. In the past, heat insulating equipment such as a low frequency furnace was used to prevent them.

[0010]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems by providing a high carbon ferrochromium having a low silicon and sulfur content without lowering the chromium yield and using a heat-retaining facility. A method of manufacturing is provided. That is, the present invention, produced in an electric furnace by carbon reduction of chromium ore, tapping, ladle-received high carbon ferrochrome melt, chromium ore and basic slag forming agent, or scale and basic slag forming agent, or It is a method for producing low silicon, low sulfur, and high carbon ferrochrome, which comprises adding chromium ore, scale, and a basic slag forming agent, and stirring and refining.

[0011]

The method for producing low silicon, low sulfur and high carbon ferrochrome of the present invention will be described. The ordinary molten metal discharged from the electric furnace is received by the ladle, and chromium ore, scale, or chromium ore and scale are added to this molten molten metal, and the mixture is stirred, whereby silicon in high carbon ferrochrome and chromium ore are added. Alternatively, it is reacted with chromium oxide or iron oxide in the scale to desiliconize. The reaction is shown below.

3Si + 2Cr ₂ O ₃ = 4Cr + 3SiO ₂ (1) Si + 2FeO = 2Fe + SiO ₂ (2) The reaction product SiO ₂ is a base added together with chromium ore and / or scale. A slag is formed by combining with CaO and / or MgO in a slag forming agent, and desulfurization is performed by this slag produced to produce low silicon / low sulfur / high carbon ferrochrome.

The slag formation reaction is shown below. _{SiO 2 + 2CaO = 2CaO · SiO} 2 ............... (3) When _{SiO 2 + 2MgO = 2MgO · SiO} 2 ............... to (4) addition of chromium ore, basic slag component to the chromium ore As compared with the case where only the scale is added, the amount of the basic slag-forming agent required is small.

The basic slag forming agent used in the present invention is CaO.
And / or MgO, and its content is CaO,
It means that MgO or CaO + MgO is 80% or more. As the scale used in the present invention, any of a hammer scale generated by forging and forging and a mill scale generated during rolling can be used.

Since the above equations (1) to (4) are exothermic reactions, no equipment for maintaining the temperature of the molten metal is required unlike the conventional method, but the total calorific value is to maintain the temperature of the molten metal. Not enough. Therefore chrome ore, scale,
The basic slag forming agent is preferably preheated to a temperature at which sintering is not performed or lower, before being added to the high carbon ferrochrome molten metal.

On the other hand, the respective amounts of chromium ore and / or scale and basic slag forming agent added to the molten metal of the normal product discharged from the electric furnace are as follows:
S% and target Si%, S%. Further, stirring means and time according to the present invention is not particularly limited, such as stirrer stirring, relay ring stirring, bottom blowing stirring of gas or a combination thereof, the throughput,
Depending on the conditions such as the target Si%, S%, etc., a known means may be appropriately used for the required time.

As described above, in the method for producing low silicon, low sulfur, and high carbon ferrochrome according to the present invention, a normal product is manufactured in an electric furnace, and the normal product is simultaneously desiliconized and desulfurized outside the electric furnace. It is a method of obtaining low silicon / low sulfur / high carbon ferrochrome by carrying out. Therefore, according to the present invention, it is not necessary to reduce the blending ratio of the carbonaceous material as a reducing agent to the chromium ore in order to reduce the silicon content of the high carbon ferrochrome in the electric furnace unlike the conventional method. However, it is possible to solve the drawback of the conventional method that the amount of chromium that is not reduced and that migrates to slag increases and the chromium yield decreases.

Further, in the conventional method, as a result of lowering Si in the high-carbon ferrochrome in the electric furnace, S in the high-carbon ferrochrome is higher than that of a normal product in the low-silicon / high-carbon ferrochrome outside the electric furnace. In contrast to desulfurization by adding a desulfurizing agent, in the present invention, since a normal product is manufactured in an electric furnace and the normal product is desiliconized and desulfurized outside the electric furnace, S in the high carbon ferrochrome for desulfurization is The slag, which is less in quantity than the conventional method and is SiO ₂ which is a desiliconization reaction product, and CaO and / or MgO in the added basic slag-forming agent acts as a desulfurizing agent to perform desulfurization and desulfurization simultaneously. Made to obtain low silicon, low sulfur, and high carbon ferrochrome.

Further, in the present invention, Si in a normal product is
When desiliconizing outside the furnace using chromium ore and / or scale, as shown in the above equations (1) and (2),
Since the chromium ore and / or the chromium oxide and / or iron oxide contained in the scale are reduced to form chromium and / or iron and migrate into the high carbon ferrochrome, the low silicon / low sulfur / high carbon ferrochrome of the present invention The final yield is
The amount is increased by 2 to 3% compared to the amount of the standard product that was initially received by ladle, which improves the productivity.

[0020]

【Example】

Example 1 When about 12 tons of the molten metal of the high carbon ferrochrome ordinary product manufactured in the 24000 KVA electric furnace was received by the ladle,
1270 kg of mill scale preheated to 500 ° C. and 660 kg of quick lime were added, and about 13 tons of ordinary molten metal was further received by the ladle to make a total amount of received hot water of 25 tons. After that, stir for 1.5 minutes with a stirrer to reduce low silicon, low sulfur,
A high carbon ferrochrome was produced.

Example 2 A chromium ore 2440 preheated to 500 ° C. at the time when about 12 tons of a high carbon ferrochromium standard molten metal produced in the same 24000 KVA electric furnace as in Example 1 was received by the ladle.
kg and 320 kg of quick lime were added, and about 13 tons of the normal molten metal was received by the ladle, and the total amount of hot water received was 25 tons. Then, stir for 4 minutes with a stirrer to reduce the silicon content.
Produced low sulfur and high carbon ferrochrome.

Example 3 Chromium ore 810, which was preheated to 500 ° C., when about 12 tons of a high carbon ferrochrome ordinary molten metal produced in the same 24000 KVA electric furnace as in Example 1 was received by the ladle
kg, mill scale 850 kg, quick lime 300 kg, magnesia brick waste 200 kg, and about 13 tons of normal molten metal are received by the ladle, and the total amount of molten metal received is 25
Tons. Then, the mixture was stirred with a stirrer for 3 minutes to produce low silicon / low sulfur / high carbon ferrochrome.

Table 1 shows the chromium ores used in the examples of the present invention,
The composition of mill scale, quicklime and magnesia brick waste is shown. Table 2 shows the results of Examples 1 to 3 and Table 3 shows a representative example of the conventional method as a comparative example.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

As is clear from Table 2, according to Examples 1 to 3 of the present invention, when the final target Si is 1.7 to 1.8%, slag is not reduced but reduced as compared with the conventional method. The amount of transferred chromium is reduced and the chromium yield is improved by more than 2%.

[0028]

As described above, according to the method for producing low silicon, low sulfur, and high carbon ferrochromium of the present invention, the chromium yield and productivity are improved as compared with the conventional method, and at the same time as the conventional method. In particular, it is a useful method that does not require a desulfurizing agent and does not require equipment for maintaining the molten metal temperature.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiyoaki Takai 2142-3 Doraoka, Maeda, Hachimanto-ku, Kitakyushu, Fukuoka Prefecture Nippon Kyushu Kogyo Co., Ltd. Kyushu Plant (72) Inventor, Isamu Nakata Yahatahigashi, Kitakyushu, Fukuoka 2142-3 Maeda, Maeda-ku, Tokyo Kyushu Plant of Nippon Heavy Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. A high-carbon ferrochromium melt produced by an electric furnace by carbon reduction of chromium ore and subjected to tapping and ladle, with chromium ore and a basic slag-forming agent, or scale and a basic slag-forming agent, or chromium. A method for producing low-silicon, low-sulfur, high-carbon ferrochrome, which is characterized by adding ore, scale, and a basic slag forming agent, stirring and refining.