Smelting method of ultra-low manganese steel

Abstract

The invention relates to an ultralow manganese steel smelting method which comprises the following steps: performing KR desulfurization on initial molten iron to obtain desulfurized molten iron; wherein the manganese content in the initial molten iron is less than or equal to 0.250 wt%; smelting the desulfurized molten iron in a converter by using a double-slag method, and controlling the tapping temperature and the tapping oxygen content of the converter smelting to obtain first molten steel; the first molten steel is subjected to LF refining, the LF refining temperature is controlled, and second molten steel is obtained; and the second molten steel is subjected to RH vacuum oxygen blowing refining, and the ultralow manganese steel is obtained. The content of [Mn] in the ultra-low manganese steel obtained through smelting is smaller than or equal to 0.025 wt% and is stabilized at about 99%, and low-cost stable production of the ultra-low manganese steel is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of ultra-low manganese steel preparation, and in particular to a smelting method of ultra-low manganese steel. Background Art

[0002] Ultra-low manganese steel is an important basic steel material, mainly used for smelting various high-temperature alloys, heat-resistant alloys, precision alloys and other alloys or steels. In recent years, the new energy vehicle industry, which has developed rapidly at home and abroad, also needs ultra-low manganese industrial pure iron as a raw material for the preparation of batteries.

[0003] In steel production, manganese is generally added to steel as a deoxidizer and alloying element, and is usually a beneficial element in steel. For products such as industrial pure iron, the lower the manganese content in the steel, the better. High-quality industrial pure iron requires a manganese content of less than 0.03%. When producing this type of steel, it is usually necessary to use molten iron with a manganese content of less than 0.15%, which requires separate preparation of low-manganese iron ore and separate pile construction, increasing costs; or reducing the manganese content of molten iron by pre-demanganizing the molten iron, which will also significantly increase production costs. Summary of the invention

[0004] The present application provides a smelting method of ultra-low manganese steel to solve the following technical problem: how to produce ultra-low manganese steel at low cost.

[0005] In a first aspect, the present application provides a method for smelting ultra-low manganese steel, the method comprising:

[0006] The initial molten iron is subjected to KR desulfurization to obtain desulfurized molten iron; wherein the manganese content in the initial molten iron is ≤0.250wt%;

[0007] Using a double-slag method, subjecting the desulfurized molten iron to converter smelting, and controlling the tapping temperature and oxygen content of the converter smelting, to obtain a first molten steel;

[0008] The first molten steel is subjected to LF refining, and the temperature of the LF refining is controlled to obtain a second molten steel;

[0009] The second molten steel is subjected to RH vacuum oxygen blowing refining to obtain ultra-low manganese steel.

[0010] Optionally, the steel tapping temperature is 1600°C to 1620°C.

[0011] Optionally, the oxygen content of the steel is ≥750ppm.

[0012] Optionally, the double slag method is used to smelt the desulfurized molten iron in a converter, comprising:

[0013] The desulfurized molten iron is subjected to converter smelting using a double slag method and a top-blowing oxygen and bottom-blowing argon combined blowing mode; wherein the timing of the first slag pouring in the double slag method is 3 / 10 to 4 / 10 of the total top-blowing oxygen time.

[0014] Optionally, the chemical composition of the first molten steel meets the following indicators: manganese content is ≤0.035wt%, and carbon content is ≤0.035wt%.

[0015] Optionally, the LF refining temperature T2 and the converter smelting steel tapping temperature T1 satisfy the relationship:

[0016] T2-T1=40℃~60℃.

[0017] Optionally, the manganese content in the second molten steel is ≤0.030wt%.

[0018] Optionally, the process parameters of the RH vacuum oxygen blowing refining include: oxygen blowing time is ≤10min, oxygen blowing amount is

[0019] ≤600Nm 3 .

[0020] Optionally, the manganese content in the ultra-low manganese steel is ≤0.025wt%.

[0021] Optionally, the method further includes:

[0022] The ultra-low manganese steel is continuously cast to obtain an ultra-low manganese steel ingot; wherein the continuous casting speed is 0.8 m / min to 1.0 m / min.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] The smelting method of the ultra-low manganese steel provided in an embodiment of the present application comprises: subjecting initial molten iron to KR desulfurization to obtain desulfurized molten iron; wherein the manganese content in the initial molten iron is ≤0.250wt%; using a double slag method, subjecting the desulfurized molten iron to converter smelting, and controlling the steel-tapping temperature and the oxygen content of the converter smelting to obtain a first molten steel; subjecting the first molten steel to LF refining, and controlling the temperature of the LF refining to obtain a second molten steel; subjecting the second molten steel to RH vacuum oxygen blowing refining to obtain ultra-low manganese steel. The manganese content in the initial molten iron is ≤0.250wt%. The initial molten iron with a higher manganese content is used for smelting from the source of steelmaking to save smelting costs; the smelting of ultra-low manganese steel is achieved by demanganizing reaction. Demanganizing is mainly achieved by reacting manganese and oxygen in the molten steel to generate manganese oxide, which enters the slag. Manganese oxidation is an exothermic reaction. Controlling the tapping temperature of converter smelting can promote the demanganizing reaction. After manganese oxide enters the slag, the manganese oxide content in the slag increases, which will reduce the speed of manganese oxide entering the slag. The double slag method is used to pour out a part of the slag and re-slag. Reducing the manganese oxide content in the slag is conducive to the continued demanganizing reaction; controlling the oxygen content of the steel tapping of the converter smelting to ensure that the oxygen of the steel tapping is high enough to have a peroxide demanganizing effect, which is conducive to the subsequent process of further oxidation and removal of manganese in the steel; LF refining heats the first molten steel to achieve the purpose of adjusting the temperature; the second molten steel undergoes RH vacuum oxygen blowing refining to further remove manganese in the second molten steel, so that the manganese content reaches the target value. In summary, low-cost and stable production of ultra-low manganese steel is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 A schematic flow chart of a method for smelting ultra-low manganese steel provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0029] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0030] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the specification of this application, the terms "include", "comprise", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0031] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0032] In a first aspect, the present application provides a method for smelting molten manganese steel. Figure 1 A schematic diagram of a smelting method of ultra-low manganese steel provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0033] S1. KR desulfurization of initial molten iron to obtain desulfurized molten iron; wherein the manganese content in the initial molten iron is ≤0.250wt%;

[0034] In the embodiment of the present application, the initial molten iron is subjected to KR desulfurization to preliminarily remove the sulfur in the initial molten iron, and the manganese (Mn) content in the molten iron is ≤0.250wt%, and molten iron with a higher manganese content is used for smelting from the source of steelmaking to save smelting costs. The initial molten iron is used as a steelmaking raw material, and the steelmaking raw material can also include scrap steel, and the scrap steel can be low-manganese scrap steel such as pure iron, automobile plate, silicon steel, etc., and the Mn content of the scrap steel can be ≤0.150%.

[0035] S2, using a double slag method to subject the desulfurized molten iron to converter smelting, and controlling the tapping temperature and oxygen content of the converter smelting to obtain a first molten steel;

[0036] In the embodiment of the present application, a double slag method is used to pour out a part of the slag and then re-slag, so as to reduce the manganese oxide content in the slag, which is beneficial to the continued demanganese reaction; the oxygen content of the steel tapped from the converter smelting is controlled to ensure that the oxygen content of the steel tapped is high enough to have a peroxide demanganese effect, thereby facilitating further oxidation and removal of manganese in the steel in subsequent processes.

[0037] In some embodiments, the tapping temperature is 1600°C to 1620°C.

[0038] In the embodiment of the present application, the tapping temperature can be 1600°C to 1620°C, so that the high oxygen content in the steel is conducive to the subsequent demanganeseization, and the manganese content in the steel can be kept at a lower level. Exemplarily, the above tapping temperature can be 1600°C, 1602°C, 1604°C, 1606°C, 1608°C, 1610°C, 1612°C, 1612°C, 1614°C, 1616°C, 1618°C, 1620°C, etc.

[0039] In some embodiments, the oxygen content [O] of the steel is ≥750 ppm.

[0040] In the embodiment of the present application, the oxygen content of the steel can be ≥750ppm. As the oxygen content increases, the distribution coefficient of manganese between slag and steel will also increase, which is beneficial to demanganese. When tapping, [O] < 750ppm requires point blowing to increase the oxidizability of the molten steel. When tapping, no deoxidation is performed to maintain the high oxidizability of the molten steel and inhibit the return of manganese. For example, the oxygen content of the steel can be 750ppm, 751ppm, 752ppm, 753ppm, 754ppm, 755ppm, etc.

[0041] In some embodiments, the double slag method is used to smelt the desulfurized molten iron in a converter, comprising:

[0042] The desulfurized molten iron is subjected to converter smelting using a double slag method and a top-blowing oxygen and bottom-blowing argon combined blowing mode; wherein the timing of the first slag pouring in the double slag method is 3 / 10 to 4 / 10 of the total top-blowing oxygen time.

[0043] In the embodiment of the present application, the converter smelting adopts the whole top oxygen blowing and bottom argon blowing mode. When the converter is blown to 3 / 10-4 / 10, double slag operation is performed. During the smelting process, 1 / 2-2 / 3 of the slag is poured out, and then re-slag is made to reduce MnO in the slag, which is beneficial to manganese removal; lime ≥5t and iron oxide scale 2t-4t are added after the double slag to control the heat balance. Exemplarily, the timing of the first slag pouring is 3 / 10, 4 / 10, 9 / 20, etc. of the total top oxygen blowing time.

[0044] In some embodiments, the chemical composition of the first molten steel meets the following indicators: manganese content is ≤0.035wt%, and carbon content is ≤0.035wt%.

[0045] In the embodiment of the present application, the manganese content can be ≤0.035wt% through the demanganese reaction of converter smelting; the carbon content can be ≤0.035wt%. The low carbon content is beneficial to increase the oxygen content in the steel.

[0046] S2, subjecting the first molten steel to LF refining, and controlling the temperature of the LF refining to obtain a second molten steel;

[0047] In some embodiments, the LF refining temperature T2 and the converter smelting tapping temperature T1 satisfy the relationship:

[0048] T2-T1=40℃~60℃.

[0049] In some embodiments, the manganese content in the second molten steel is ≤ 0.030 wt %.

[0050] In the embodiment of the present application, the main purpose of LF refining is to adjust the temperature of the first molten steel, cooperate with the end temperature of the converter, effectively prevent the return of phosphorus and manganese at the end of smelting, and achieve low phosphorus and low manganese control. The main purpose of LF refining is to adjust the temperature so that the temperature of the first molten steel meets the requirements of the subsequent process, and the manganese oxide content in the slag is low after re-slag making. Under oxidizing conditions, manganese in the steel is further oxidized and enters the slag to achieve the demanganese effect. LF refining heats the molten steel by generating an arc through the electrode, and the electrode heating mainly adjusts the heating temperature through the heating time (in order to increase the demanganese rate during converter smelting, the temperature cannot be too high, and the temperature must be increased during LF refining to make the temperature meet the requirements of the subsequent process). The LF furnace is heated for 1-2 cycles, and lime and slag-removing agent are added to make slag during heating, and demanganese is continued under oxidizing conditions. The ladle furnace is heated for an average of 20 minutes per furnace, and the total processing time is ≤40min, and the temperature is increased by 40-60℃ (T2-T1=40℃~60℃), and [Mn]≤0.030% in the steel out of the LF furnace. Illustratively, the above T2-T1 can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, etc.

[0051] S2. The second molten steel is subjected to RH vacuum oxygen blowing refining to obtain ultra-low manganese steel.

[0052] In some embodiments, the process parameters of the RH vacuum oxygen blowing refining include: oxygen blowing time ≤ 10 min, oxygen blowing volume ≤ 600 Nm 3 .

[0053] In the embodiment of the present application, the oxygen blowing time can be ≤10min, and the oxygen blowing amount can be ≤600Nm 3 RH oxygen blowing amount is determined by the amount of manganese removal required. Under the condition that [Mn]≤0.030% in the LF furnace steel in the previous process, 600Nm 3 The oxygen is sufficient to further remove the residual manganese in the second molten steel. If the oxygen blowing amount exceeds 600Nm 3 , the molten steel is too oxidizing, which will increase the subsequent deoxidation cost. The RH oxygen blowing amount can be 300M 3 For example, the oxygen blowing time can be 10min, 9min, 8min, 7min, 6min, 5min, 4min, etc.; the oxygen blowing amount can be 600Nm 3 、590Nm 3 、580Nm 3 、570Nm 3 、560Nm 3 wait.

[0054] In addition, in the smelting of this manganese steel liquid, the ladle requirements are: use ultra-low manganese steel special tanks for circulation and self-use, the first 4 furnaces can use clean red hot tanks, and it is strictly forbidden to use the ladle with molten steel [Mn]>0.5% in the front tank.

[0055] In some embodiments, the manganese content in the ultra-low manganese steel is ≤ 0.025 wt %.

[0056] In the embodiment of the present application, through the above-mentioned KR desulfurization, converter smelting, LF refining and RH refining, the manganese content in the ultra-low manganese steel can be ≤0.025wt%. In addition, the ultra-low manganese steel product [Mn] is ≤0.025wt%, and is stable at about 99%, realizing low-cost and stable production of ultra-low manganese steel.

[0057] In some embodiments, the method further comprises:

[0058] The ultra-low manganese steel is continuously cast to obtain an ultra-low manganese steel ingot; wherein the continuous casting speed is 0.8 m / min to 1.0 m / min.

[0059] In the embodiment of the present application, the continuous casting pulling speed can be 0.8m / min to 1.0m / min, so that there is enough time to ensure the LF refining time and RH refining time of the previous process and ensure the smooth progress of the smelting process. Exemplarily, the continuous casting pulling speed can be 0.8m / min, 0.85m / min, 0.9m / min, 0.95m / min, 1.0m / min, etc.

[0060] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0061] Example 1

[0062] A smelting method for ultra-low manganese steel, comprising:

[0063] Preparation of ultra-low manganese steel raw materials: the molten iron uses blast furnace molten iron with a Mn mass percentage of 0.23%, and the scrap steel uses low-manganese scrap steel such as pure iron, automobile plates, and silicon steel, with a Mn content of 0.14%;

[0064] KR desulfurization: KR desulfurization of ultra-low manganese steel raw materials to obtain desulfurized molten iron;

[0065] Converter smelting: Desulfurized hot metal adopts the top oxygen blowing and bottom argon blowing mode. Double slag operation is carried out when the converter is blown to 35%. 50% of the slag is poured out during the smelting process, and then re-slag is made to reduce MnO in the slag, which is conducive to manganese removal. 5t of lime and 3t of iron oxide scale are added after the double slag to control the heat balance. The converter temperature endpoint is controlled at 1610℃, and the converter endpoint oxygen is 800ppm. The steel composition [Mn] is 0.033%, carbon is 0.032%, and no deoxidation is performed during steel tapping to maintain the high oxidation of the molten steel and inhibit the return of manganese. Ladle requirements: Use ultra-low manganese steel special tanks for circulation and self-use.

[0066] LF refining: The LF furnace is heated for 2 cycles. During heating, lime and slag-reducing agent are added to make slag. Manganese removal is continued under oxidizing conditions. The ladle furnace is heated for 20 minutes, the processing time is 38 minutes, the temperature is raised by 50°C, and the [Mn] content of the steel out of the LF furnace is 0.028%.

[0067] RH vacuum oxygen blowing refining: RH oxygen blowing time 6min, total oxygen content 300Nm 3 , [Mn] in RH steel is 0.023%.

[0068] Continuous casting: continuous casting speed 0.9m / min.

[0069] Example 2

[0070] A smelting method for ultra-low manganese steel, comprising:

[0071] Preparation of ultra-low manganese steel raw materials: molten iron is selected from blast furnace molten iron with a Mn mass percentage content of 0.24%, and scrap steel is low-manganese scrap steel such as pure iron, automobile plates, silicon steel, etc., with a Mn content of 0.14%;

[0072] KR desulfurization: KR desulfurization of ultra-low manganese steel raw materials to obtain desulfurized molten iron;

[0073] Converter smelting: Desulfurized hot metal adopts the top oxygen blowing and bottom argon blowing mode. Double slag operation is carried out when the converter is blown to 33%. During the smelting process, 50% of the slag is poured out and re-slag is made to reduce the MnO in the slag, which is conducive to manganese removal. 10t of lime and 6t of iron oxide scale are added after the double slag to control the heat balance. The converter temperature endpoint is controlled at 1620℃, and the converter endpoint oxygen is 770ppm. The steel composition [Mn] is 0.034%. Carbon is 0.033%. No deoxidation is performed during steel tapping to maintain the high oxidation of the molten steel and inhibit the return of manganese. Ladle requirements: Use ultra-low manganese steel special tanks for circulation and self-use.

[0074] LF refining: LF furnace is heated for 1 cycle, lime and slag-reducing agent are added during heating to make slag, and manganese removal is continued under oxidizing conditions. The ladle furnace is heated for 15 minutes, the processing time is 35 minutes, the temperature is raised to 40°C, and the [Mn] content of the steel out of the LF furnace is 0.030%.

[0075] RH vacuum oxygen blowing refining: RH oxygen blowing volume is 600M 3 Calculation for removing 5ppm manganese, based on Mn content, RH oxygen blowing time 8min, total oxygen volume 1000Nm 3 , [Mn] in RH steel is 0.022%.

[0076] Continuous casting: continuous casting speed 1.0m / min.

[0077] Example 3

[0078] A smelting method for ultra-low manganese steel, comprising:

[0079] Preparation of ultra-low manganese steel raw materials: molten iron is selected from blast furnace molten iron with a Mn mass percentage of 0.25%, and scrap steel is low-manganese scrap steel such as pure iron, automobile plates, silicon steel, etc., with a Mn content of 0.13%;

[0080] KR desulfurization: KR desulfurization of ultra-low manganese steel raw materials to obtain desulfurized molten iron;

[0081] Converter smelting: Desulfurized hot metal adopts the top oxygen blowing and bottom argon blowing mode. Double slag operation is carried out when the converter is blown to 38%. During the smelting process, 60% of the slag is poured out and then re-slag is made to reduce MnO in the slag, which is conducive to manganese removal. 3t of lime and 1.5t of iron oxide scale are added after the double slag to control the heat balance. The converter temperature endpoint is controlled at 1620℃, and the converter endpoint oxygen is 780ppm. The steel composition [Mn] is 0.032%. Carbon ≦0.033%, no deoxidation during steel tapping, maintain the high oxidation of the molten steel, and inhibit the return of manganese. Ladle requirements: Use ultra-low manganese steel special tanks for circulation and self-use.

[0082] LF refining: The LF furnace is heated for one cycle. During heating, lime and slag-reducing agent are added to form slag. Manganese removal is continued under oxidizing conditions. The ladle furnace is heated for 15 minutes. The processing time is 35 minutes. The temperature is raised to 40°C. The [Mn] content of the steel out of the LF furnace is 0.026%.

[0083] RH vacuum oxygen blowing refining: RH oxygen blowing time 3min, total oxygen content 100Nm 3 , [Mn] in RH steel is 0.022%.

[0084] Continuous casting: continuous casting speed 0.8m / min.

[0085] Example 4

[0086] A smelting method for ultra-low manganese steel, comprising:

[0087] Preparation of ultra-low manganese steel raw materials: molten iron is selected from blast furnace molten iron with a Mn mass percentage content of 0.23%, and scrap steel uses low-manganese scrap steel such as pure iron, automobile plates, and silicon steel, with a Mn content of 0.13%;

[0088] KR desulfurization: KR desulfurization of ultra-low manganese steel raw materials to obtain desulfurized molten iron;

[0089] Converter smelting: Desulfurized hot metal adopts the top oxygen blowing and bottom argon blowing mode. Double slag operation is carried out when the converter is blown to 35%. During the smelting process, 60% of the slag is poured out and then re-slag is made to reduce MnO in the slag, which is conducive to manganese removal. 12t of lime and 7t of iron oxide scale are added after the double slag to control the heat balance. The converter temperature endpoint is controlled at 1600℃, and the converter endpoint oxygen is 760ppm. The steel composition [Mn] is 0.035%. Carbon is 0.034%. No deoxidation is performed during steel tapping to maintain the high oxidation of the molten steel and inhibit the return of manganese. Ladle requirements: Use a special tank for ultra-low manganese steel for circulation and self-use.

[0090] LF refining: The LF furnace is heated for 2 cycles. During heating, lime and slag-reducing agent are added to make slag. Manganese removal is continued under oxidizing conditions. The ladle furnace is heated for 20 minutes, the processing time is 40 minutes, the temperature is raised to 60°C, and the [Mn] content of the steel out of the LF furnace is 0.029%.

[0091] RH vacuum oxygen blowing refining: RH oxygen blowing time is 6 minutes, the total oxygen content is 800Nm3, and the [Mn] content in the RH steel is 0.024%.

[0092] Continuous casting: continuous casting speed 1.0m / min.

[0093] Comparative Example 1

[0094] A smelting method for ultra-low manganese steel, comprising:

[0095] Preparation of ultra-low manganese steel raw materials: ironmaking uses a separate low-manganese iron ore and a separate pile to produce special low-manganese iron water, so that the Mn content of the iron water is 0.14% by mass. Scrap steel uses low-manganese scrap steel such as pure iron, automobile plates, and silicon steel, and the Mn content of the scrap steel is 0.14%;

[0096] KR desulfurization: KR desulfurization of ultra-low manganese steel raw materials to obtain desulfurized molten iron;

[0097] Converter smelting: Desulfurized hot metal adopts the top oxygen blowing and bottom argon blowing mode. Double slag operation is carried out when the converter is blown to 35%. 50% of the slag is poured out during the smelting process, and then re-slag is made to reduce MnO in the slag, which is conducive to manganese removal. The converter temperature endpoint is controlled at 1660℃, and the converter endpoint oxygen is 510ppm. The steel composition [Mn] is 0.023%. Carbon is 0.034%, and deoxidizer is added during steel tapping. Ladle requirements: Use ultra-low manganese steel special tanks for circulation and self-use.

[0098] Continuous casting: continuous casting speed 1.0m / min.

[0099] Comparative Example 2

[0100] A smelting method for ultra-low manganese steel, comprising:

[0101] Preparation of ultra-low manganese steel raw materials: molten iron is selected from blast furnace molten iron with a Mn mass percentage of 0.20%, and scrap steel is low-manganese scrap steel such as pure iron, automobile plates, silicon steel, etc., with a Mn content of 0.15%;

[0102] KR desulfurization: Desulfurization of ultra-low manganese steel raw material KR, and adding 10t of iron oxide scale for pre-demanganization. At the end of the molten iron pretreatment, the Mn content is 0.15%, and desulfurized and demanganized molten iron is obtained;

[0103] Converter smelting: Desulfurization and demanganese hot metal adopts the whole process of top oxygen blowing and bottom argon blowing mode. Double slag operation is carried out when the converter is blown to 35%. 50% of the slag is poured out during the smelting process, and then re-slag is made to reduce MnO in the slag, which is conducive to demanganese. Converter endpoint control: The converter temperature endpoint is controlled at 1670℃, and the converter endpoint oxygen is 500ppm. The steel composition [Mn] is 0.024%. Carbon is 0.033%, and deoxidizer is added for deoxidation during steel tapping. Ladle requirements: Use ultra-low manganese steel special tanks for circulation and self-use.

[0104] Continuous casting: continuous casting speed 1.0m / min.

[0105] Comparative Example 3

[0106] Based on the disclosure of Example 1, Comparative Example 3 differs from Example 1 in that the end point of the converter temperature is controlled at 1630°C.

[0107] Comparative Example 4

[0108] Based on the disclosure of Example 1, Comparative Example 3 differs from Example 1 in that the converter end point oxygen is 740 ppm.

[0109] Table 1 Manganese content of ultra-low manganese steel

[0110] Serial number Manganese content / wt% Example 1 0.023 Example 2 0.022 Example 3 0.022 Example 4 0.024 Comparative Example 1 0.023 Comparative Example 2 0.024 Comparative Example 3 0.030 Comparative Example 4 0.027

[0111] As can be seen from Table 1, through the smelting method of ultra-low manganese steel provided in the embodiment of the present application, ultra-low manganese steel (manganese content is ≤0.025wt%) can be obtained at low cost. Comparative Examples 1 and 2 adopt different raw material conditions and smelting processes, and the manganese content in the final steel can also obtain the ultra-low manganese steel of the present application, but the cost of obtaining low-manganese molten iron in the early stage is high; and the converter tapping temperature in Comparative Example 3 is high, and the oxygen content of the converter tapping in Comparative Example 4 is low, and the ultra-low manganese steel of the present application is not obtained.

[0112] When producing ultra-low manganese steel, it is usually necessary to use molten iron with a manganese content of less than 0.15%, which requires separate preparation of low-manganese iron ore and separate construction of a pile, increasing costs; or reducing the manganese content of molten iron by pre-demanganizing molten iron, which will also significantly increase production costs. In order to develop industrial pure iron products, the basic theories of metallurgical thermodynamics and kinetics of steelmaking demanganization reactions were analyzed for molten iron with high manganese content (the manganese content in the molten iron is ≤0.250wt%), and the converter smelting process, LF refining process and RH oxygen blowing demanganization process were optimized to achieve low-cost mass production of ultra-low manganese steel.

[0113] Please refer to Table 2 for the manganese removal cost of each process of different technologies. Compared with other manganese removal technologies, this application has obvious cost advantages. Unit: Yuan / ton.

[0114] Table 2 Demanganeseization cost

[0115]

[0116] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0117] (1) By adopting double slag + low temperature + peroxide demanganese converter smelting measures, coordinated with LF refining temperature adjustment and vacuum oxygen blowing demanganese smelting, the ultra-low manganese steel product [Mn] ≤ 0.025wt%, and stabilized at around 99%, achieving low-cost and stable production of ultra-low manganese steel.

[0118] (2) In order to develop industrial pure iron products, the embodiments of the present application analyze the basic theories of metallurgical thermodynamics and kinetics of steelmaking demanganese reaction for molten iron with high manganese content (the manganese content in the molten iron is ≤0.250wt%), optimize the converter smelting process, LF refining process and RH oxygen blowing demanganese process, and realize low-cost mass production of ultra-low manganese steel.

[0119] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for smelting ultra-low manganese steel, characterized in that: The method comprises: The initial molten iron is subjected to KR desulfurization to obtain desulfurized molten iron; wherein the manganese content in the initial molten iron is ≤0.250wt%; Using a double-slag method, subjecting the desulfurized molten iron to converter smelting, and controlling the tapping temperature and oxygen content of the converter smelting, to obtain a first molten steel; The first molten steel is subjected to LF refining, and the temperature of the LF refining is controlled to obtain a second molten steel; The second molten steel is subjected to RH vacuum oxygen blowing refining to obtain ultra-low manganese steel.

2. The method according to claim 1, characterized in that The steel tapping temperature is 1600°C to 1620°C.

3. The method according to claim 1, characterized in that The oxygen content of the steel is ≥750ppm.

4. The method according to claim 1, characterized in that: The double slag method is used to smelt the desulfurized molten iron in a converter, comprising: The desulfurized molten iron is subjected to converter smelting using a double slag method and a top-blowing oxygen and bottom-blowing argon combined blowing mode; wherein the timing of the first slag pouring in the double slag method is 3 / 10 to 4 / 10 of the total top-blowing oxygen time.

5. The method according to claims 1 to 4, characterized in that: The chemical composition of the first molten steel meets the following indicators: manganese content is ≤0.035wt%, and carbon content is ≤0.035wt%.

6. The method according to claim 1, characterized in that The temperature T2 of the LF refining and the steel tapping temperature T1 of the converter smelting satisfy the relationship: T2-T1=40℃~60℃.

7. The method according to claim 1 or 6, characterized in that: The manganese content in the second molten steel is ≤0.030wt%.

8. The method according to claim 1, characterized in that The process parameters of the RH vacuum oxygen blowing refining include: oxygen blowing time ≤10min, oxygen blowing volume ≤600Nm 3 .

9. The method according to claim 1, characterized in that: The manganese content in the ultra-low manganese steel is ≤0.025wt%.

10. The method according to claim 1, characterized in that The method further comprises: The ultra-low manganese steel is continuously cast to obtain an ultra-low manganese steel ingot; wherein the continuous casting speed is 0.8 m / min to 1.0 m / min.

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