CN111733355B - Method for producing low-nitrogen medium-low micro-carbon ferrochrome by refining electric furnace - Google Patents

Method for producing low-nitrogen medium-low micro-carbon ferrochrome by refining electric furnace Download PDF

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CN111733355B
CN111733355B CN202010628887.4A CN202010628887A CN111733355B CN 111733355 B CN111733355 B CN 111733355B CN 202010628887 A CN202010628887 A CN 202010628887A CN 111733355 B CN111733355 B CN 111733355B
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molten iron
electric furnace
low
slag
nitrogen
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CN111733355A (en
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郭军
韩永光
薛金柱
王志强
柏森
付军
刘冰
刘志杰
郑海东
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Jifei Ferroalloy Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/06—Alloys based on chromium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D35/00—Equipment for conveying molten metal into beds or moulds
    • B22D35/04—Equipment for conveying molten metal into beds or moulds into moulds, e.g. base plates, runners
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/06—Making non-ferrous alloys with the use of special agents for refining or deoxidising
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C35/00—Master alloys for iron or steel

Abstract

The invention discloses a method for producing low-nitrogen medium-low micro-carbon ferrochrome by a refining electric furnace, which comprises the following steps: step 1) raw material selection, step 2) electric furnace smelting, step 3) casting and step 4) crushing. The invention is used for generating CO by injecting sodium bicarbonate into the electric furnace in a refining period2And the contact between the alloy and air is reduced by protecting the gas, so that the nitrogen in the air is prevented from entering the molten iron to increase the nitrogen content. The invention also shortens the length and the height of the electric furnace launder, and avoids the increase of the nitrogen content in the molten iron caused by the fact that the molten iron is contacted with the air for a long time in the tapping process to cause nitrogen to enter the molten iron; in addition, after the molten iron and the slag flow into the ladle together, the molten iron and the slag are poured into the ingot mold together, and the molten iron is protected by the slag in the processes of flowing into the ladle and pouring into the ingot mold and cooling and solidifying the molten iron in the ingot mold, so that the nitrogen in the molten iron is further prevented from entering the molten iron due to the contact of the molten iron and the air, and the increase of the nitrogen content in the molten iron is further avoided.

Description

Method for producing low-nitrogen medium-low micro-carbon ferrochrome by refining electric furnace
The technical field is as follows:
the invention relates to a method for producing low-nitrogen medium-low micro-carbon ferrochrome by a refining electric furnace, belonging to the technical field of smelting.
Background art:
the smelting method of the medium-low micro-carbon ferrochrome mainly comprises the following steps: the high carbon ferrochromium refining process, the electric silicothermic process, the heat exchange process and the vacuum process, and the traditional production process is also the electric silicothermic process, namely, under the condition of making alkaline slag in an electric furnace, reducing the oxides of chromium and iron in chrome ore by using silicon in silicon-chromium alloy to prepare medium-low micro carbon ferrochromium from the oxides.
However, the air contains about 78% of nitrogen, the nitrogen content is not controlled in the existing production process of the medium and low carbon ferrochrome, and the nitrogen content in the medium and low carbon ferrochrome is about 0.10% due to the fact that the nitrogen in the air is absorbed by the alloy in the production process. In the industries of ferrous metallurgy, casting and the like, medium-low micro carbon ferrochrome is widely used as an important raw material, with the development of economy, the requirements of steel enterprises on the components of medium-low micro carbon ferrochrome are more and more strict, and in the production of military materials, the nitrogen content in the medium-low micro carbon ferrochrome has special requirements.
The nitrogen content in the medium-low micro carbon ferrochrome in the current production technology is relatively high, and the plasticity, particularly the toughness, of steel can be obviously reduced, the weldability is poor and the cold brittleness is aggravated along with the increase of the nitrogen content in the steelmaking process; meanwhile, the aging tendency, the cold brittleness and the hot brittleness are increased, and the welding performance and the cold bending performance of steel are damaged, so the nitrogen content of the medium-low micro-carbon ferrochrome needs to be controlled from the aspect of raw materials for producing steel.
The invention content is as follows:
in order to solve the technical problems, the invention aims to provide a method for producing low-nitrogen medium-low micro-carbon ferrochrome by using chromium ore, lime and silicon-chromium alloy as raw materials and utilizing a refining electric furnace through processes, slag control and other modes.
The invention is implemented by the following technical scheme: the method for producing the low-nitrogen medium-low micro-carbon ferrochrome by the refining electric furnace comprises the following steps:
1) selecting raw materials: taking chromium ore, silicon-chromium alloy and lime as raw materials, and calculating the weight ratio of Cr in the raw material chromium ore2O3The content is 40 to 50 percent; the Cr content in the silicon-chromium alloy is 27-33 percent, and the Si content is 37-50 percent; the CaO content in the lime is 85 to 93 percent;
2) smelting in an electric furnace: the raw materials are as follows: lime: putting the silicon-chromium alloy (75-70) and (27-35) into a refining electric furnace according to the proportion, heating to 1650-;
3) casting: pouring molten iron and slag smelted by an electric furnace into a ladle, controlling the residence time of the molten iron and the slag in a launder to be less than 1min, then pouring all the molten iron and the slag in the ladle into an ingot mould within 4min, and controlling the thickness of the slag in the ladle to be not less than 250 mm.
4) Crushing: and removing the slag on the upper part of the cooled molten iron after casting, crushing, finishing and warehousing to obtain the qualified low-nitrogen medium-low micro-carbon ferrochrome.
Further, in the step 2) of electric furnace smelting, the raw materials are as follows: lime: the silicon-chromium alloy is put into a refining electric furnace according to the proportion of 75:65: 33.
Further, during the electric furnace smelting in the step 2), adding sodium bicarbonate into the refining electric furnace in batches every 8 min.
Further, in the electric furnace smelting in the step 2), the adding amount of sodium bicarbonate is 2.5 percent of the charging amount of the chromium ore each time.
Further, in the step 3) of casting, the length of the launder is less than 800mm, and the distance between the launder outlet and the ladle is less than 800 mm.
The percentages in the patent are mass percentages.
The invention has the advantages that:
1. the invention is used for generating CO by injecting sodium bicarbonate into the electric furnace in a refining period2And the contact between the alloy and air is reduced by protecting the gas, so that the nitrogen in the air is prevented from entering the molten iron to increase the nitrogen content.
2. The invention controls the ratio of the materials fed into the furnace to lead the alkalinity of the slag to be CaO/SiO2Controlling the smelting temperature to be 1.7-1.9, pouring the slag iron into the ingot mold at the smelting end point, wherein the slag has the effect of protecting the alloy, and the slag is cooled due to 2 CaO. SiO under the alkalinity2The volume change occurs, and the slag is pulverized, so that the slag and the alloy are automatically separated.
3. The invention shortens the length and the height of the electric furnace launder, and avoids the increase of the nitrogen content in the molten iron caused by the fact that the molten iron is contacted with the air for a long time in the tapping process to cause nitrogen to enter the molten iron; in addition, after the molten iron and the slag flow into the ladle together, the molten iron and the slag are poured into the ingot mold together, and the molten iron is protected by the slag in the processes of flowing into the ladle and pouring into the ingot mold and cooling and solidifying the molten iron in the ingot mold, so that the nitrogen in the molten iron is further prevented from entering the molten iron due to the contact of the molten iron and the air, and the increase of the nitrogen content in the molten iron is further avoided.
The specific implementation mode is as follows:
the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the following embodiment, among the raw materials used, Cr ore is Cr2O3The content is 48 percent; the Cr content in the silicon-chromium alloy is 32 percent, and the Si content is 45 percent; the lime contains 88 percent of CaO. The raw materials are added into a refining electric furnace for smelting in three parts, and each part of the raw materials comprises 7500kg of chromium ore, 6600kg of lime and 3300kg of silicon-chromium alloy.
Example 1:
putting the raw materials into a refining electric furnace, heating to 1750-;
pouring the refined molten iron and the slag into a ladle, wherein the length of a launder is 700mm, the distance between an outlet of the launder and the ladle is 700mm, so that the residence time of the molten iron and the slag in the launder is less than 1min, then pouring all the molten iron and the slag in the ladle into an ingot mold within 4min, and controlling the thickness of the slag in the ladle to be kept at 250-300 mm.
And removing the slag on the upper part of the cooled molten iron after casting, crushing and finishing the molten iron, and warehousing the molten iron to obtain the ferrochrome product.
Example 2:
putting the raw materials into a refining electric furnace, heating to 1650-1750 ℃, preserving heat, smelting for 25min, adding sodium bicarbonate into the refining electric furnace by one batch every 10min, wherein the adding amount of each batch is 3% of the charging amount of the chromium ore, and putting for 6 times in total to finish refining;
pouring the refined molten iron and the slag into a ladle, wherein the length of a launder is 700mm, the distance between an outlet of the launder and the ladle is 700mm, so that the residence time of the molten iron and the slag in the launder is less than 1min, then pouring all the molten iron and the slag in the ladle into an ingot mold within 4min, and controlling the thickness of the slag in the ladle to be kept at 250-300 mm.
And removing the slag on the upper part of the cooled molten iron after casting, crushing and finishing the molten iron, and warehousing the molten iron to obtain the ferrochrome product.
Example 3:
putting the raw materials into a refining electric furnace, heating to 1800-1900 ℃, carrying out heat preservation smelting for 15min, then adding sodium bicarbonate into the refining electric furnace by one batch every 5min, wherein the adding amount of each batch is 0.5 percent of the charging amount of the chromium ore, and putting for 3 times in total to finish refining;
pouring the refined molten iron and the slag into a ladle, wherein the length of a launder is 700mm, the distance between an outlet of the launder and the ladle is 700mm, so that the residence time of the molten iron and the slag in the launder is less than 1min, then pouring all the molten iron and the slag in the ladle into an ingot mold within 4min, and controlling the thickness of the slag in the ladle to be not less than 250-300 mm.
And removing the slag on the upper part of the cooled molten iron after casting, crushing and finishing the molten iron, and warehousing the molten iron to obtain the ferrochrome product.
The ferrochrome products obtained in the examples 1 to 3 are sampled and detected by Q/TJ.J08-015.4-2020 distillation-photometry for measuring nitrogen content of medium and low carbon ferrochrome, and the detection results are listed in Table 1.
TABLE 1 compositional testing tables for ferrochrome products obtained in examples 1-3
Figure BDA0002567666910000061
As can be seen from Table 1, the ferrochrome products obtained in examples 1-3 have a carbon content of less than 0.50% and are low-carbon ferrochrome products, and a nitrogen content of less than 0.05% and are low-nitrogen ferrochrome products, so that the method of the present invention can obtain qualified low-nitrogen ferrochrome products.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (4)

1. The method for producing the low-nitrogen medium-low micro-carbon ferrochrome by the refining electric furnace is characterized by comprising the following steps:
1) selecting raw materials: taking chromium ore, silicon-chromium alloy and lime as raw materials, and calculating the weight ratio of Cr in the raw material chromium ore2O3The content is 40 to 50 percent; the Cr content in the silicon-chromium alloy is 27-33 percent, and the Si content is 37-50 percent; the CaO content in the lime is 85 to 93 percent;
2) smelting in an electric furnace: the raw materials are as follows: lime: putting the silicon-chromium alloy (75-70) and (27-35) into a refining electric furnace according to the proportion, heating to 1650-;
3) casting: pouring molten iron and slag smelted by an electric furnace into a ladle, wherein the length of a launder is less than 800mm, the distance between an outlet of the launder and the ladle is less than 800mm, the residence time of the molten iron and the slag in the launder is controlled to be less than 1min, then pouring all the molten iron and the slag in the ladle into an ingot mold within 4min, and the thickness of the slag in the ladle is controlled to be not less than 250 mm;
4) crushing: and removing the slag on the upper part of the cooled molten iron after casting, crushing, finishing and warehousing to obtain the qualified low-nitrogen medium-low micro-carbon ferrochrome.
2. The method for producing ferrochrome with low nitrogen content, medium low carbon content and low carbon content by the electric refining furnace according to claim 1, wherein in the step 2), the electric furnace smelting is carried out according to the following raw materials: lime: the silicon-chromium alloy is put into a refining electric furnace in a ratio of 75:65: 33.
3. The method for producing ferrochrome with low nitrogen content and low carbon content according to claim 1, wherein in the step 2), sodium bicarbonate is added into the electric refining furnace in batches every 8min during the electric furnace smelting.
4. The method for producing ferrochrome with low nitrogen content and low carbon content according to claim 1, wherein in the step 2), sodium bicarbonate is added into the electric furnace in an amount of 2.5% of the amount of the chromium ore charged into the furnace.
CN202010628887.4A 2020-07-02 2020-07-02 Method for producing low-nitrogen medium-low micro-carbon ferrochrome by refining electric furnace Active CN111733355B (en)

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CN1403596A (en) * 2001-08-24 2003-03-19 攀枝花市永禄科技开发有限责任公司 Pure iron smelting method
CN1810996A (en) * 2003-12-10 2006-08-02 蒋祖滨 Purifying agent

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CN1403596A (en) * 2001-08-24 2003-03-19 攀枝花市永禄科技开发有限责任公司 Pure iron smelting method
CN1810996A (en) * 2003-12-10 2006-08-02 蒋祖滨 Purifying agent

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