Method for directly alloying manganese ore to efficiently smelt manganese-containing stainless steel

Abstract

The application provides a method for directly alloying manganese ore to efficiently smelt Mn-containing stainless steel, which comprises the following steps: adding manganese ore before starting oxygen blowing in a converter, controlling the initial temperature of the stainless steel mother liquor in the converter to be 1450 DEG C to 1550 DEG C, and reducing part of MnO by using the residual Si element in the initial stainless steel mother liquor; meanwhile, the temperature of the converter bath and the mixing ratio of nitrogen or argon under different carbon content ranges of the converter bath are precisely controlled to reduce the oxidation of Mn element; then, the slag basicity is adjusted to be 4.0 to 5.0, so that the MnO in the slag is separated, the activity is increased, and the reduction of Mn is facilitated; and after the oxygen blowing is completed, silicon is added as a reducing agent to perform the final Mn reduction, and Cr-Mn-Ni-N series stainless steel liquid is further prepared. In the smelting of the Mn-containing stainless steel, the yield of Mn in the manganese ore can be stably reached above 90%, and the manganese alloying efficiency is higher and more economical.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of stainless steel smelting, and particularly to a method for directly alloying manganese ore to efficiently smelt Mn-containing stainless steel. BACKGROUND

[0002] Cr-Mn-Ni-N stainless steel is a relatively low-cost stainless steel product, and its use has been increasing year by year in recent years, accounting for more than one-third of the total domestic stainless steel production. The main domestic production enterprises mainly use red nickel laterite ore to smelt low-nickel molten iron in a blast furnace, and then the molten iron is fed into a GOR converter or an AOD converter to smelt molten steel with a composition meeting the requirements of the finished product, which is cast into a billet after refining. Since the Mn content in Cr-Mn-Ni-N stainless steel is generally 8%-12%, Mn element is an important alloying component in Cr-Mn-Ni-N stainless steel next to Cr content, and the cost of Cr-Mn-Ni-N stainless steel accounts for about 15%.

[0003] There are mainly two methods to increase the Mn content in the current Cr-Mn-Ni-N stainless steel smelting process: one is to directly add manganese alloy (such as high-carbon ferromanganese, silicon-manganese iron, etc.); the other is to add manganese ore and alloying during smelting (i.e. manganese ore direct alloying). Since manganese alloy is refined from manganese ore by consuming a large amount of energy, therefore, directly adding manganese alloy not only has high energy consumption and pollutes the environment, but also has high price, resulting in high smelting cost of Cr-Mn-Ni-N stainless steel. Therefore, considering the cost, the manganese ore direct alloying process is more favored by the majority of steel enterprises. However, a major problem currently faced by the manganese ore direct alloying process is that the Mn recovery rate is generally low, and the economic value is low. For example, a Chinese patent with application number CN201610305864.3 discloses a manganese ore direct alloying process applied to a converter steelmaking process. The converter steelmaking process adopts a one-time carbon removal method, and the manganese alloy ore is added into the furnace in batches within 4-10 minutes after the start of the converter steelmaking smelting, and the final carbon content is C≥0.08%. However, the Mn recovery rate of the patent is only 40%.

[0004] In addition, a Chinese patent with application number CN201510296049.0 discloses a method for improving the Mn recovery rate of molten steel in manganese ore direct alloying, which processes manganese ore, lime or light-burned dolomite, anthracite or coke through multiple processes as an outer layer of powder, and aluminum powder or silicon powder as an internal powder to make a cored wire; the cored wire is fed into the steel ladle at the refining process. Although the Mn recovery rate of the patent technology can reach more than 90%, the manufacturing process is complex, special equipment needs to be additionally purchased, and it is time-consuming and labor-intensive, which is difficult to improve production efficiency and is not conducive to popularization.

[0005] Therefore, it is necessary to develop a method for directly alloying manganese ore to efficiently smelt Mn-containing stainless steel, which has a simple manufacturing process, does not require additional purchase of equipment, and can ensure that the manganese recovery rate is above 90%. SUMMARY

[0006] The present application designs a method for directly alloying manganese ore to efficiently smelt Mn-containing stainless steel by analyzing the thermodynamic and kinetic conditions of the reduction of MnO in metallurgical slag and combining the metallurgical characteristics of the converter, so that the Mn recovery rate in the manganese ore in the smelting of the Mn-containing stainless steel can be stabilized to above 90%.

[0007] A method for directly alloying manganese ore to efficiently smelt Mn-containing stainless steel, comprising the following steps:

[0008] (1) Oxygen blowing smelting is performed on the stainless steel mother liquor in the converter, and manganese ore is added into the furnace before oxygen blowing of the converter starts, the main component composition of the manganese ore is: Mn: 28%-45%, Fe: 3%-25%, Al2O3: 3%-10%, SiO2: 3%-13%, the addition amount of the manganese ore is controlled to be 20-50 kg / t of steel (amount of molten steel), and the initial temperature of the stainless steel mother liquor entering the furnace is controlled to be 1450°C-1550°C;

[0009] (2) When the carbon content in the converter bath is >1.0% after oxygen blowing of the converter, the converter bath temperature is controlled to be 1450°C-1550°C, and any one or more of nitrogen gas or argon gas is mixed according to a ratio of 5:1;

[0010] (3) When the carbon content in the converter bath is 0.35%<carbon content in the converter bath≤1.0%, the converter bath temperature is controlled to be 1600°C-1650°C, and any one or more of nitrogen gas or argon gas is mixed according to a ratio of 1:1;

[0011] (4) When the carbon content in the converter bath is 0.10%<carbon content in the converter bath≤0.35%, the converter bath temperature is controlled to be 1650°C-1700°C, and any one or more of nitrogen gas or argon gas is mixed according to a ratio of 1:2;

[0012] (5) When the carbon content in the converter bath is 0.05%<carbon content in the converter bath≤0.10%, the converter bath temperature is controlled to be 1700°C-1750°C, and any one or more of nitrogen gas or argon gas is mixed according to a ratio of 1:3;

[0013] (6) The carbon content in the converter bath at the end of oxygen blowing is ≥0.05%; lime is added during the oxygen blowing smelting process to control the slag basicity to be 4.0-5.0;

[0014] (7) After the end of oxygen blowing, the content of MnO2 in the slag is sampled and analyzed, the amount of ferrosilicon or ferromanganese silicon is calculated according to the ratio of MnO2:Si of 10:3-3.5, and is added into the converter molten pool, the stirring intensity of nitrogen or argon is controlled at 0.7-1.2 Nm 3 / min.t, the MnO2 and Si in the slag are ensured to be fully mixed and contacted, the reduction of Mn is promoted, the stirring time is controlled at 5-8 minutes, the slag is blocked and tapped, and the Cr-Mn-Ni-N series stainless steel liquid is obtained.

[0015] It can be known from the principle of metallurgy that Mn is oxidized better than Fe in the converter under the smelting condition; it can be known from the oxygen potential diagram that Mn is oxidized prior to C below 1420℃. Therefore, under the oxidizing atmosphere condition of the iron-based steel product (including the Cr-Mn-Ni-N series stainless steel), it is difficult to efficiently reduce Mn in the manganese ore for alloying. From the condition favorable to the reduction of Mn, a higher molten pool temperature, a higher slag basicity, a reduced slag oxidizing property and a small amount of slag are required.

[0016] The present inventors firstly adjust the adding time of the manganese ore, add an appropriate amount of the manganese ore into the converter before the start of oxygen blowing, fully utilize the residual Si element in the initial stainless steel mother liquor, reduce part of MnO by Si, control the temperature of the initial stainless steel mother liquor at 1450℃-1550℃, ensure that the temperature of the converter molten pool is greater than 1450℃ when the oxygen blowing starts, make the oxygen element as much as possible to react with C to reduce the oxidation of Mn element, cooperate with the accurate regulation of the C content, the converter molten pool temperature and the mixing ratio of nitrogen or argon, make the CO partial pressure in the molten pool, promote the C-O reaction and reduce the oxidation of Mn element, cooperate with the regulation of the high slag basicity, make the MnO in the slag free and increase the activity to facilitate the reduction of Mn, and after the end of oxygen blowing, supplement silicon as a reducing agent for the final strengthening of Mn reduction, so that the manganese recovery rate reaches more than 90%, the Mn element in the manganese ore is economically utilized, the manganese alloying efficiency is higher and more economical. Moreover, the method for directly alloying the manganese ore to efficiently smelt the Mn-containing stainless steel of the present application has simple steps and easy operation, does not need to purchase additional equipment, and can ensure that the manganese recovery rate is stably more than 90%.

[0017] Preferably, the converter adopts a GOR furnace. Embodiment

[0018] The embodiment of the method for directly alloying the manganese ore to efficiently smelt the Mn-containing stainless steel of the present application is described in detail as follows: Embodiment 1

[0019] Furnace number: 532216

[0020] Smelting steel grade BN1D2 (Cr-Mn-Ni-N series stainless steel).

[0021] The method of high efficient smelting BN1D2 by direct alloying of manganese ore in Example 1 comprises the following steps:

[0022] Oxygen blowing smelting is performed on the stainless steel mother liquid in the converter, and manganese ore is added into the converter before the start of oxygen blowing in the converter, the main component composition of the manganese ore is: Mn: 28%-45%, Fe: 3%-25%, Al2O3: 3%-10%, SiO2: 3%-13%, the addition amount of the manganese ore is 20 kg / t of steel (amount of molten steel), and the initial temperature of the stainless steel mother liquid is controlled at 1488℃;

[0023] The component composition of the stainless steel mother liquid is shown in Table 1 as follows:

[0024] Table 1 Ingot component of stainless steel mother liquid (%)

[0025]

[0026] (2) When the carbon content in the converter bath >1% during oxygen blowing in the converter, the temperature of the converter bath is 1450℃-1550℃, and nitrogen is mixed according to 5:1, wherein the oxygen is 100m 3 / min, and the nitrogen is 20m 3 / min;

[0027] (3) When the carbon content in the converter bath is 0.35%<carbon content in the converter bath≤1.0% during oxygen blowing in the converter, the temperature of the converter bath is 1636℃, and nitrogen is mixed according to 1:1 during the oxygen blowing process, wherein the oxygen is 60m 3 / min, and the nitrogen is 60m 3 / min;

[0028] (4) When the carbon content in the converter bath is 0.10%<carbon content in the converter bath≤0.35% during oxygen blowing in the converter, the temperature of the converter bath is 1678℃, and nitrogen is mixed according to 1:2 during the oxygen blowing process, wherein the oxygen is 40m 3 / min, and the nitrogen is 80m 3 / min;

[0029] (5) When the carbon content in the converter bath is 0.05%<carbon content in the converter bath≤0.10% during oxygen blowing in the converter, the temperature of the converter bath is 1700℃, and nitrogen is mixed according to 1:3 during the oxygen blowing process, wherein the oxygen is 30m 3 / min, and the nitrogen is 90m 3 / min;

[0030] (6) The C content in the converter bath at the end of oxygen blowing is 0.050%; lime is added during the oxygen blowing smelting process, and the slag basicity is controlled at 4.3;

[0031] (7) After the end of oxygen blowing, the content of Mn02 in the slag is sampled and analyzed, and the amount of ferrosilicon or ferromanganese silicon 8600 kg is added into the converter bath according to the ratio of Mn02:Si of 10:3-3.5, the stirring intensity of bottom blowing nitrogen gas is kept at 0.7-1.2 Nm 3 / min.t (specifically 1.0 Nm 3 / min.t), the stirring time is controlled for 5 minutes, the slag is blocked and tapped, and the Cr-Mn-Ni-N series stainless steel BN1D2 is obtained.

[0032] In this furnace, the actual recovery rate of manganese in the manganese ore is 93.9%. Example 2

[0033] Furnace number: 532217

[0034] The steel BN1D2 (Cr-Mn-Ni-N series stainless steel) is smelted.

[0035] The method of Example 2 for directly alloying the manganese ore to efficiently smelt BN1D2 is different from Example 1:

[0036] (1) The amount of manganese ore added is 32 kg / t of steel, and the initial temperature of the stainless steel mother liquor is controlled at 1450℃;

[0037] (2) When the oxygen blowing of the converter is at 0.35% < carbon content in the converter bath ≤ 1.0%, the temperature of the converter bath is 1610℃;

[0038] (3) When the oxygen blowing of the converter is at 0.10% < carbon content in the converter bath ≤ 0.35%, the temperature of the converter bath is 1660℃;

[0039] (4) The C content in the converter bath at the end of oxygen blowing is 0.060%;

[0040] (5) The slag basicity is controlled at 4.1;

[0041] (6) After the end of oxygen blowing, the amount of ferrosilicon or ferromanganese silicon 9400 kg is added into the converter bath, and at the same time, the stirring intensity of bottom blowing nitrogen gas is adjusted to 0.7-1.2 Nm 3 / min.t (specifically 1.2 Nm 3 / min.t), the stirring time is controlled for 8 minutes, the slag is blocked and tapped, and the Cr-Mn-Ni-N series stainless steel BN1D2 is obtained.

[0042] In this furnace, the actual recovery rate of manganese in the manganese ore is 96.3%. Example 3

[0043] Furnace number: 532218

[0044] Smelting steel grade BN1D2 (Cr-Mn-Ni-N series stainless steel).

[0045] The method of Example 3 for high efficiency smelting BN1D2 by direct alloying of manganese ore is different from that of Example 1 in that:

[0046] (1) The dosage of manganese ore is 50 kg / t of steel, and the initial temperature of the stainless steel mother liquor is controlled at 1548°C;

[0047] (2) When the converter blows oxygen at 0.35% < carbon content in the converter bath ≤ 1.0%, the temperature of the converter bath is 1610°C;

[0048] (3) When the converter blows oxygen at 0.10% < carbon content in the converter bath ≤ 0.35%, the temperature of the converter bath is 1660°C;

[0049] (4) When the converter blows oxygen at 0.05% < carbon content in the converter bath ≤ 0.10%, the temperature of the converter bath is 1718°C;

[0050] (5) The C content in the converter bath at the end of oxygen blowing is 0.072%;

[0051] (6) The slag basicity is controlled at 4.8;

[0052] (7) After oxygen blowing is completed, 8400 kg of ferrosilicon or ferromanganese silicon is added into the converter bath, and the stirring intensity of the bottom blowing nitrogen gas is adjusted to 0.7-1.2 Nm 3 / min.t (specifically 1.2 Nm 3 / min.t), the stirring time is controlled at 6 minutes, the slag is blocked, and the steel grade BN1D2 Cr-Mn-Ni-N series stainless steel molten steel is obtained.

[0053] In this heat, the actual recovery rate of manganese in the manganese ore is 91.1%.

[0054] Comparative Example 1

[0055] Heat No.: 532185

[0056] Smelting steel grade BN1D2 (Cr-Mn-Ni-N series stainless steel).

[0057] The method of Example 3 for high efficiency smelting BN1D2 by direct alloying of manganese ore is different from that of Example 1 in that:

[0058] (1) Manganese ore is added to the furnace in the middle and late stages of converter oxygen blowing, and the dosage of manganese ore is 21 kg / t of steel, and the initial temperature of the stainless steel mother liquor is controlled at 1461°C;

[0059] (2) When the converter is blown with oxygen and the carbon content in the converter bath is greater than 1%, 10:1 nitrogen is mixed, wherein the oxygen is 100 m 3 / min, and the nitrogen is 10 m 3 / min;

[0060] (3) When the converter is blown with oxygen and the carbon content in the converter bath is 0.35% < carbon content in the converter bath ≤ 1.0%, the converter bath temperature is 1610℃, and 3:2 nitrogen is mixed during the oxygen blowing process, wherein the oxygen is 80 m 3 / min, and the nitrogen is 60 m 3 / min;

[0061] (4) When the converter is blown with oxygen and the carbon content in the converter bath is 0.10% < carbon content in the converter bath ≤ 0.35%, the converter bath temperature is 1650℃, and 5:8 nitrogen is mixed during the oxygen blowing process, wherein the oxygen is 50 m 3 / min, and the nitrogen is 80 m 3 / min;

[0062] (5) When the converter is blown with oxygen and the carbon content in the converter bath is 0.05% < carbon content in the converter bath ≤ 0.10%, the converter bath temperature is 1708℃;

[0063] (6) The C content in the converter bath at the end of the oxygen blowing is 0.053%; lime is added during the oxygen blowing smelting process, and the slag basicity is controlled at 3.8;

[0064] (7) After the oxygen blowing is completed, the content of MnO2 in the slag is analyzed by sampling, and the amount of ferrosilicon or ferromanganese silicon is added to the converter bath according to the ratio of MnO2:Si of 10:3-3.5, that is, 10300 kg, and the stirring intensity of the bottom blowing nitrogen is adjusted to 0.7-1.2 Nm 3 / min.t (specifically 1.0 Nm 3 / min.t), the stirring time is 5 minutes, the slag is blocked, and the steel grade is BN1D2 Cr-Mn-Ni-N series stainless steel molten steel.

[0065] In this furnace, the actual recovery rate of manganese in the manganese ore is 82.7%.

[0066] From the comparison of Comparative Example 1 and Examples 1-3, it can be seen that the addition time of the manganese ore, the converter bath temperature in the same carbon content range, the nitrogen mixing ratio in the same carbon content range, and the slag basicity of Comparative Example 1 do not meet the requirements of the present application, and the corresponding recovery rate of manganese in the manganese ore is significantly lower than that of Examples 1-3 of the present application.

[0067] In addition, the present inventors have also tested that when the stirring intensity of the bottom blowing nitrogen in step (6) of the present application is less than 0.7 Nm 3At a stirring intensity of / min.t, the stirring of the converter molten pool weakened, and the mixing of MnO2 and Si in the slag was insufficient, with the stirring intensity in the test furnace decreasing to 0.65 Nm. 3 At a stirring time of 6 minutes per minute, the yield of Mn was only 81%. When the capacity of the test equipment (converter) was 100 tons, the stirring intensity of the bottom-blown nitrogen in step (6) of this application exceeded 1.2 Nm. 3 Splashing is likely to occur when running / min.t, so it is not recommended.

[0068] The converters in Examples 1-3 and Comparative Example 1 of this application are all GOR furnaces.

[0069] Of course, the nitrogen gas mixed in steps (2) to (5) of Examples 1 to 3 and Comparative Example 1 of this application can be replaced with argon gas, or it can be replaced with a mixture of nitrogen and argon gas.

[0070] For those skilled in the art, without departing from the concept of this invention, several simple deductions or substitutions can be made, and all such deductions or substitutions should be considered to fall within the scope of protection of this invention.

Claims

1. A method for efficient smelting of Mn-containing stainless steel by direct alloying of manganese ore, characterized in that, Includes the following steps: (1) Oxygen blowing is carried out on the stainless steel mother liquor in the converter. Before the oxygen blowing starts, manganese ore is added to the furnace. The main components of the manganese ore are: Mn: 28%-45%, Fe: 3%-25%, Al2O3: 3%-10%, SiO2: 3%-13%. The amount of manganese ore added is controlled at 20-50 kg / t according to the amount of molten steel. The initial temperature of the stainless steel mother liquor entering the furnace is controlled at 1450°C-1550°C. (2) When oxygen is blown into the converter and the carbon content in the converter molten pool is >1.0%, the temperature of the converter molten pool is controlled at 1450°C-1550°C, and nitrogen or argon is mixed in at a ratio of 5:

1. (3) When the oxygen blown into the converter is 0.35% < the carbon content of the converter molten pool is ≤1.0%, the temperature of the converter molten pool is controlled at 1600°C-1650°C, and nitrogen or argon gas is mixed in at a ratio of 1:

1. (4) When the oxygen blown into the converter is 0.10% < the carbon content of the converter molten pool is ≤0.35%, the temperature of the converter molten pool is controlled at 1650°C-1700°C, and nitrogen or argon is mixed in at a ratio of 1:

2. (5) When the oxygen blown into the converter is 0.05% < the carbon content of the converter molten pool is ≤0.10%, the temperature of the converter molten pool is controlled at 1700°C-1750°C, and nitrogen or argon is mixed in at a ratio of 1:

3. (6) The carbon content in the converter molten pool at the end of oxygen blowing is ≥0.05%; lime is added during oxygen blowing smelting to control the slag basicity at 4.0-5.0; (7) After oxygen blowing is completed, sample and analyze the MnO2 content in the slag. Calculate the amount of ferrosilicon or ferromanganese to be added according to the MnO2:Si ratio of 10:3~3.5, and add it to the converter molten pool. Control the stirring intensity of bottom blowing with either nitrogen or argon at 0.7-1.2 Nm. 3 The stirring time is controlled at 5-8 minutes per minute to ensure that MnO2 and Si in the slag are fully mixed and in contact, promoting Mn reduction. The slag is then blocked and the steel is tapped to obtain Cr-Mn-Ni-N stainless steel molten steel.

2. The method for efficient smelting of Mn-containing stainless steel by direct alloying of manganese ore according to claim 1, characterized in that: The converter used is a GOR furnace.

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