CN113201686A - Smelting method of low manganese steel - Google Patents

Abstract

A smelting method of low manganese steel comprises the following process routes of blast furnace-converter-LF refining furnace-RH vacuum furnace-CC continuous casting-steel rolling, and adopts a quantitative charging system, wherein molten iron =70% +/-2%, and scrap steel =30% +/-2%; the mass percentage of the main components of the molten iron is C =4.5% +/-0.5%; mn =0.30% ± 0.10%; the proportion of the scrap steel adopts heavy scrap/light scrap/slag steel =6/3/1, and the adding proportion of each heat can be adjusted within the range of +/-5%; the slag-making materials adopt lime, raw burned dolomite and iron ore, the mass of the added slag-making materials is 6% +/-0.5% of the loading amount, the adding proportion is lime/raw burned dolomite/iron ore =4/1/1, and the adding proportion of each heat can be adjusted within the range of +/-10%. The invention solves the problem of steel grade with the manganese content controlled within 0.10 percent in the converter smelting production, realizes the low-manganese steel mass production with low cost, and can digest the steel slag produced by smelting.

Description

Smelting method of low manganese steel

Technical Field

The invention belongs to a steelmaking technology, and relates to a method for smelting low manganese steel by using an oxygen converter.

Background

Manganese is one of the most common beneficial elements in steel materials, can improve the strength of steel, reduce brittleness and reduce sulfur harm, and is generally reserved as much as possible in the smelting stage of a converter. However, in some steel grades, such as commercial purity iron, manganese is no longer a beneficial alloying element, but rather the lower the mass fraction of manganese in the steel the better. Along with the increase of the mass fraction of manganese, the electric conductivity of the steel is sharply reduced, the resistivity is correspondingly increased, the resistance temperature coefficient is reduced, the coercive force of the steel is increased, and the saturation magnetic induction, the residual magnetic induction and the magnetic permeability are all reduced, so that the mass fraction of manganese is generally required to be not more than 0.10%.

Manganese, as a metal element, can only be separated from molten iron or steel by means of oxidation and slagging. To achieve that the mass fraction of manganese is not more than 0.10%, the current control means mainly strictly requires the initial manganese of molten iron, for example, the initial manganese mass fraction of molten iron required by the first steel group Qian' an iron and steel company is not more than 0.15%. At present, most of steel mills do not have the condition, the silicon content of the molten iron is relatively low under the condition of low manganese content of the molten iron generally, and the metallurgical effect and the slagging condition are rapidly deteriorated under the condition that the manganese content of the molten iron is less than 0.20 percent. Some steel mills adopt a pre-demanganization mode to reduce the burden of reducing manganese of the converter.

The patent CN106811567B 'a method for producing low manganese steel' adopts two converters for smelting in a duplex way, which is not beneficial to cost control and production organization. The patent CN102925619A does not allow to add slag steel by controlling the oxygen activity, the solvent amount and the manganese content of molten iron at the smelting end point. The two methods can not realize the low-cost large-batch converter smelting production of steel grades with the manganese content controlled within 0.10 percent.

Disclosure of Invention

The invention aims to provide a method for smelting low manganese steel by using an oxygen converter, which can meet the requirements of producing low manganese steel under the condition of raw materials of most steel mills and realize the requirement of controlling the manganese content within 0.10 percent in low-cost large-batch converter smelting production.

The technical scheme of the invention is as follows:

a smelting method of low manganese steel comprises the following chemical components of, by mass, less than or equal to 0.008% of C, less than or equal to 0.01% of Si, less than or equal to 0.08% of Mn, less than or equal to 0.008% of P, less than or equal to 0.01% of S, and the balance Fe and essential impurities, and the smelting process comprises the following steps:

(1) the process route adopts a blast furnace, a converter, an LF refining furnace, an RH vacuum furnace, CC continuous casting and steel rolling;

(2) a quantitative loading system is adopted, and the proportion of main raw materials is 70 percent +/-2 percent of molten iron and 30 percent +/-2 percent of scrap steel;

(3) the main components of the molten iron C =4.5% + -0.5%, Mn =0.30% + -0.10%, and the proportion of the scrap steel is heavy scrap/light scrap/slag steel = 6/3/1;

(4) the mass of the slagging material is 6% +/-0.5% of the loading amount, and the addition ratio of lime/raw burnt dolomite/iron ore = 4/1/1.

The invention principle is as follows:

1. regarding the process route. The method adopts a blast furnace, a converter, an LF refining furnace, an RH vacuum furnace, CC continuous casting and steel rolling, and can be suitable for the configuration of tool equipment of most steel plants. The method is different from the schemes of molten iron pretreatment manganese reduction, converter duplex smelting and the like adopted by most of steel mills at present, and is simple and easy to operate.

2. The quantitative loading regime is referred to. The advantage of adopting quantitative loading is that the production organization and process are stable, which is beneficial to other operations and is the basis for realizing industrialized mass production. The molten iron is 70% +/-2% and the scrap steel is 30% +/-2%, so that the temperature in the converter smelting process is favorably reduced. The chemical equation of manganese oxidation reaction in converter blowing is [ Mn ] + (FeO) → (MnO) < [ Fe ] (1), and its basic thermodynamic parameter is lgKMn 6440/T-2.95 (2). It can be seen that the demanganization reaction is an exothermic reaction, and that the whole demanganization reaction is carried out at a relatively low temperature, which is advantageous for demanganization. The invention adopts the process route of increasing the adding amount of the scrap steel and reducing the consumption of the molten iron to accord with the thermodynamic conditions of converter smelting. The low-temperature molten pool is created by utilizing the inhibiting effect of increasing the charging amount of the scrap steel on the temperature rise of the molten pool, so that the demanganization reaction is more favorably carried out.

3. Regarding the raw material requirements. The main component C =4.5% +/-0.5% of the molten iron; mn =0.30% ± 0.10%; the proportion of the scrap steel adopts heavy scrap/light scrap/slag steel =6/3/1, the requirements of the raw materials meet more than two levels of the national people's republic of China ferrous metallurgy industry standard, and the adding proportion of each heat can be adjusted within the range of +/-5%. The invention discloses a method for preparing slag steel, which is characterized in that the proportion of adding slag steel into raw materials is determined, and most of the prior schemes clearly stipulate that the slag steel is not used. The slag steel is added to adapt to a process route, and early-stage slag is strived for by utilizing the characteristic that the slag steel contains high FeO, so that partial early-stage slag can be poured out and secondary slagging can be realized.

4. As regards the slag-forming material. Lime, raw burned dolomite and iron ore are adopted. The mass of the added slagging material is 6% + -0.5% of the loading amount, and the adding proportion is lime/raw burned dolomite/iron ore = 4/1/1. From the formula [ Mn ] + (FeO) → (MnO). sup. + Fe (1), it is found that the use of a large amount of slag is advantageous for demanganization. The manganese mass fraction of a molten pool at the initial stage of blowing appears at a low point, and according to the mass conservation law, the MnO mass fraction in slag is high, and the manganese mass fraction of molten steel is low. The method comprises pouring off a part of steel slag, adding a second batch of slag to make new slag, and adding MnO in the rest slag₂It is advantageous for removing Mn. Therefore, the invention adopts the method of secondary slagging and enlarging slagging materials, and determines the addition amount of slag charge.

The invention has the beneficial effects that: solves the problem of controlling the manganese content within 0.10 percent in the steel grade produced by converter smelting. By adopting the technical scheme of large slag amount and low iron consumption, the low-manganese steel can be produced in large batch at low cost. On the premise of not changing the conditions of the existing production equipment, the method has stable smelting process, meets the requirement of converter smelting on slagging, has obvious smelting cost, and can create greater economic benefit for enterprises. Meanwhile, the steel slag generated by smelting can be digested, and the method has positive significance for energy conservation and emission reduction of steel-making production.

Detailed Description

Example 1: smelting method of low manganese steel

(1) The process route is as follows: blast furnace-converter-LF refining furnace-RH vacuum furnace-CC continuous casting-steel rolling.

(2) A quantitative charging system is adopted, and the total charging amount is 152t, wherein 106t of molten iron and 46t of scrap steel are included.

(3) The main raw material molten iron comprises the main component C = 4.6%; mn = 0.32%; the steel scrap ratio is heavy scrap/light scrap/slag steel =6/3/1, and is respectively 27t of heavy scrap, 14.5t of light scrap and 4.5t of slag steel.

(4) The slag-making material adopts lime, raw burned dolomite and iron ore. The mass of the added slagging material is 6% + -0.5% of the loading amount, and the adding proportion is lime/raw burnt dolomite/iron ore = 4/1/1. The added slagging materials are 9.2t, 6.0t of lime, 1.7t of raw burned dolomite and 1.5t of iron ore.

The steel type smelted by the furnace is industrial pure iron M6, the chemical composition mass percent of the steel is that C is less than or equal to 0.008 percent, Si is less than or equal to 0.01 percent, Mn is less than or equal to 0.08 percent, P is less than or equal to 0.008 percent, S is less than or equal to 0.01 percent, the detection values of the end point components of the smelted steel, such as carbon, manganese, phosphorus and sulfur, are shown in table 1, and the smelting requirements of the steel type are met.

Example 2: smelting method of low manganese steel

(1) The process route is as follows: blast furnace-converter-LF refining furnace-RH vacuum furnace-CC continuous casting-steel rolling.

(2) A quantitative charging system is adopted, and the total charging amount is 153t, wherein 107t of molten iron and 46t of scrap steel are adopted.

(3) The main raw material molten iron comprises the main component C = 4.6%; mn = 0.32%; the proportion of the waste steel adopts heavy waste/light waste/slag steel =6/3/1, which is respectively 27.5t of heavy waste, 14t of light waste and 4.5t of slag steel.

(4) The slag-making material adopts lime, raw burned dolomite and iron ore. The mass of the added slagging material is 6% + -0.5% of the loading amount, and the adding proportion is lime/raw burnt dolomite/iron ore = 4/1/1. The added slagging materials are 9.4 tons of lime 6.2 tons, raw burned dolomite 1.7 tons and iron ore 1.5 tons respectively.

The steel type smelted by the furnace is industrial pure iron M6, the chemical composition mass percent of the steel is that C is less than or equal to 0.008 percent, Si is less than or equal to 0.01 percent, Mn is less than or equal to 0.08 percent, P is less than or equal to 0.008 percent, S is less than or equal to 0.01 percent, the detection values of the end point components of the smelted steel, such as carbon, manganese, phosphorus and sulfur, are shown in table 1, and the smelting requirements of the steel type are met.

TABLE 1 EXAMPLES endpoint chemical composition table (%)

。

Claims (1)

1. A smelting method of low manganese steel is characterized by comprising the following steps: the chemical composition mass percentage of the steel is less than or equal to 0.008 percent of C, less than or equal to 0.01 percent of Si, less than or equal to 0.08 percent of Mn, less than or equal to 0.008 percent of P, less than or equal to 0.01 percent of S, and the balance of Fe and essential impurities, and the smelting process comprises the following steps:

(1) the process route adopts a blast furnace, a converter, an LF refining furnace, an RH vacuum furnace, CC continuous casting and steel rolling;

(2) a quantitative loading system is adopted, and the proportion of main raw materials is 70 percent +/-2 percent of molten iron and 30 percent +/-2 percent of scrap steel;

(3) the main components of the molten iron C =4.5% + -0.5%, Mn =0.30% + -0.10%, and the proportion of the scrap steel is heavy scrap/light scrap/slag steel = 6/3/1;

(4) the mass of the slagging material is 6% +/-0.5% of the loading amount, and the addition ratio of lime/raw burnt dolomite/iron ore = 4/1/1.