Method for improving plastic inclusions in steel for grinding balls

Abstract

The application discloses a method for improving plastic inclusions in mill ball steel and belongs to the technical field of steel metallurgy. In the method, low-alkalinity slag refining is carried out in the RH process, Ca, Si, Al and O in the molten steel can form composite inclusions through reaction, the content of B-type, D-type and Ds-type inclusions in the mill ball steel is controlled, and high-proportion retention of plastic inclusions in the mill ball steel is realized. The method solves the problem that the content of B-type, D-type and Ds-type inclusions in the steel exceeds the standard due to the fact that the alkalinity control mode of high-alkalinity refining is adopted in the refining slag, thereby affecting the quality of the steel. The method is implemented in the operation between the LF and RH processes, and does not hinder the continuity of the on-site production.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, specifically relating to a method for improving the plastic inclusions in grinding ball steel. Background Technology

[0002] The core raw material for wear-resistant steel balls is grinding ball steel, which is widely used in many industries such as metallurgy, building materials, mining, and power. Globally, the annual demand for wear-resistant steel balls has exceeded 20 million tons, while China, as the world's largest producer and consumer of grinding ball steel, consumes approximately 5 million tons annually.

[0003] With the continuous development of the mining industry, users have put forward more stringent requirements for the quality standards of grinding ball steel: it must not only have excellent wear resistance, good internal quality and uniform overall hardness, but also have excellent toughness, so as to extend the service life of wear-resistant materials in ore crushing operations.

[0004] However, in the actual production of ball steel, to ensure that the molten steel meets the low-oxygen standard, the amount of aluminum added often exceeds the standard significantly, and the entire production process adopts a high-basicity refining process. The large amount of aluminum used for deoxidation generates type B inclusions (i.e., alumina), which significantly damage the mechanical properties of the steel. More importantly, when type B inclusions react with CaO and SiO2 inclusions in the molten steel, they further form large-sized, brittle, hard calcium aluminate inclusions (corresponding to type D and Ds inclusions). This problem has a fatal impact on the quality of ball steel.

[0005] To date, research reports on methods for controlling ductile inclusions in ball steel are still relatively scarce. There is an urgent need to develop a targeted control technology that, on the one hand, increases the proportion of ductile inclusions in ball steel, and on the other hand, solves the problem of excessive levels of B-type, D-type, and Ds-type brittle inclusions in ball steel under the existing full-process high-basicity refining process. Ultimately, this will achieve a high retention rate of ductile inclusions in ball steel, significantly improving its overall quality.

[0006] Therefore, how to achieve a high retention rate of plastic inclusions in grinding ball steel has become an urgent problem to be solved. Summary of the Invention

[0007] Therefore, the purpose of this invention is to provide a method for improving the plastic inclusion content in ball steel. This method controls the content of B, D, and Ds inclusions in ball steel, achieving a high proportion of plastic inclusion retention. It solves the problem that the use of high-basicity refining in the refining slag during the smelting of ball steel leads to excessive levels of B, D, and Ds inclusions in the steel, thus affecting the quality of the steel.

[0008] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for improving the amount of plastic inclusions in grinding ball steel, comprising the following steps: S1: The steelmaking raw material of the ball steel is smelted in a converter to obtain molten steel; S2: The molten steel undergoes deoxidation, alloying, and slag washing in the ladle to obtain the molten steel leaving the station; After the converter smelting, when 2 / 3 of the steel has been tapped, 1.5-3.0 kg / t of quicklime and 3.0-5.1 kg / t of pre-melted calcium aluminate are added for slag washing. S3: After the molten steel leaving the station is uniformly mixed with the high-basicity slag-forming material, it is refined into high-basicity slag white slag using an LF furnace to obtain LF refined molten steel. The high-alkalinity slag-forming material is composed of the following components by weight percentage: The total weight of FeO and MnO is ≤1.0%, CaO: 50%-56%, SiO2: 6%-12%, Al2O3: 20%-28%, MgO: 8%-10%; the value of CaO / SiO2 is R, which is 5.0-7.0; the remainder is MnO, P2O5, TiO2 and unavoidable impurities; S4: The LF refined steel is uniformly mixed with low-alkalinity reducing slag-forming material and then refined in an RH furnace to obtain RH refined steel. The low-alkalinity reducing slag-forming material is composed of the following components by weight percentage: The total weight of FeO and MnO is ≤1.0%, CaO: 32%-40%, SiO2: 30%-38%, Al2O3: 20%-30%, MgO: 6%-10%; the value of CaO / SiO2 is R, where R is 1.0-1.3; the remainder is MnO, P2O5, TiO2 and unavoidable impurities. S5: The RH refined molten steel is continuously cast to produce ball steel.

[0009] Based on the above technical solution, further, at the end of the converter smelting, the C content in the molten steel is ≥0.08%, and the temperature of the molten steel is 1590℃-1670℃.

[0010] Based on the above technical solution, furthermore, after the converter smelting, a double slag-blocking method is adopted for tapping; in the early stage of tapping, the converter tilt angle is 35°-75°, and a sliding plate is used to block the slag; in the later stage of tapping, when the converter tilt angle is 97°, a slag-blocking cone is used to block the slag, and the amount of slag is controlled to be ≤1.7kg / t of molten steel.

[0011] Based on the above technical solution, further, after the converter smelting, when 1 / 4 of the steel is tapped, 0.1-0.4 kg / t of aluminum ingots are added for deoxidation, followed by the addition of 16-21 kg / t of ferrosilicon, 8-15 kg / t of silicon-manganese alloy, and 8-15 kg / t of high-carbon ferrochrome for alloying.

[0012] Among them, ferrosilicon contains 72% silicon, silicon-manganese alloy contains 18% silicon and 65% manganese, and high-carbon ferrochrome contains 53% chromium.

[0013] Based on the above technical solution, further, the temperature for refining the high-alkalinity slag white residue is 1490℃-1590℃ and the time is 40min-90min; the refining temperature in S4 is 1520℃-1560℃ and the time is 40min-60min.

[0014] Based on the above technical solution, the continuous casting adopts constant casting speed control, the superheat of molten steel is 15-30℃, the electromagnetic stirring current of the crystallizer is 300-400A, the frequency is 1.0-3.0Hz, and the electromagnetic stirring current at the end is 400-500A, the frequency is 4.0-6.0Hz.

[0015] Secondly, the present invention provides a ball steel obtained by the above method, characterized in that the weight of plastic inclusions accounts for ≥80% of the total weight of all inclusions.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention conducts low-basicity slag refining in the RH process. Ca, Si, Al, and O in the molten steel will react to form composite inclusions, thereby controlling the content of B, D, and Ds inclusions in the ball steel and achieving a high proportion of plastic inclusions retained in the ball steel. This solves the problem that the use of high-basicity refining slag in the smelting of ball steel leads to excessive levels of B, D, and Ds inclusions in the steel, thus affecting the quality of the steel.

[0017] 2. The implementation of the method of the present invention is an operation performed between the LF and RH processes, and will not hinder the continuity of on-site production.

[0018] 3. This invention shortens the LF refining time through a complete coupled process of "converter slag washing + LF high-basicity white slag + RH low-basicity reduction refining". It also optimizes the characteristics of high hardness and easy formation of hard oxide inclusions in ball steel, and solves the exclusive technical problems of easy slag entanglement and insufficient inclusion refinement in ball steel slag washing. Attached Figure Description

[0019] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0020] Figure 1 The phase diagram of the CaO-SiO2-Al2O3 ternary system in the grinding ball steel obtained in this invention; Figure 2 The phase diagrams of the CaO-SiO2-Al2O3 system plastic inclusions in Example 1 and Comparative Example 1 of this invention are shown below. Figure 3 The phase diagrams of the CaO-SiO2-Al2O3 system plastic inclusions in Example 2 and Comparative Example 1 of this invention are shown below. Figure 4 The phase diagrams of the CaO-SiO2-Al2O3 system plastic inclusions in Example 3 and Comparative Example 1 of this invention are shown below. Figure 5 This is a process flow diagram of the present invention. Detailed Implementation

[0021] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0022] Using the components of the examples in Table 2 as steelmaking raw materials, and the slag-forming material components of the examples in Table 1 as low-basicity reducing slag-forming material components, the grinding ball steels of Examples 1 to 3 were obtained by using the method for improving plastic inclusions in grinding ball steel provided by the present invention.

[0023] like Figure 5 As shown, the method for increasing the plastic inclusions in grinding ball steel includes the following steps: S1: The steelmaking raw material of the ball steel is smelted in a converter. When the C in the molten steel reaches the converter endpoint of ≥0.08% and the temperature is 1650℃, the steel is tapped to obtain molten steel.

[0024] After smelting in the converter, steel is tapped using a double slag-blocking method. In the early stage of tapping, when the converter tilts at an angle of 35°-75°, a sliding plate is used to block the slag. In the later stage of tapping, when the converter tilts at an angle of 97°, a slag-blocking cone is used to block the slag, controlling the amount of slag to be ≤1.7kg / t of molten steel.

[0025] S2: Molten steel undergoes deoxidation, alloying, and slag washing in the ladle to obtain molten steel leaving the station.

[0026] In the process of smelting in the converter, when 1 / 4 of the steel is tapped, aluminum ingots are added for deoxidation, followed by alloying with ferrosilicon, ferromanganese silicomanganese alloy, and high-carbon ferrochrome. When 2 / 3 of the steel is tapped, 2.5 kg / t of quicklime and 5.0 kg / t of pre-melted calcium aluminate are added for slag washing.

[0027] S3: After the molten steel leaving the station is evenly mixed with the high-basicity slag-forming material, it is refined in an LF furnace with high-basicity slag white slag. The refining temperature is controlled at 1580℃ and the refining time is 70 minutes to obtain LF refined molten steel.

[0028] In Example 1, the high-alkalinity slag-forming material consisted of CaO: 51%, SiO2: 10%, Al2O3: 28%, MgO: 8%, and the CaO / SiO2 ratio was R, which was 5.1. The remainder consisted of MnO, P2O5, TiO2, and unavoidable impurities.

[0029] In Example 2, the high-alkalinity slag-forming material consists of CaO: 52%, SiO2: 8%, Al2O3: 28%, and MgO: 10%; the CaO / SiO2 ratio is R, which is 6.5; the remainder consists of MnO, P2O5, TiO2, and unavoidable impurities.

[0030] In Example 3, the high-alkalinity slag-forming material consists of CaO: 56%, SiO2: 11%, Al2O3: 22%, and MgO: 9%; the CaO / SiO2 ratio is R, which is 5.1; the remainder consists of MnO, P2O5, TiO2, and unavoidable impurities.

[0031] S4: After the LF refined steel is uniformly mixed with the low-alkalinity reducing slag material, it is refined in an RH furnace at a temperature of 1520-1540℃ for 50 minutes to obtain RH refined steel.

[0032] S5: RH refined molten steel is continuously cast to produce ball steel.

[0033] Comparative Example 1 Using the components of the comparative examples in Table 2 as steelmaking raw materials and the components of the high-basicity slag-forming materials of the comparative examples in Table 1 as the raw materials, the grinding ball steel of Comparative Example 1 was obtained by processing them using conventional methods.

[0034] The difference between the usual method and Example 1 is that: S3: After the molten steel leaving the station is evenly mixed with the high-basicity slag-forming material, it is refined in an LF furnace with high-basicity slag white slag. The refining temperature is controlled at 1580℃ and the refining time is 70 minutes to obtain LF refined molten steel.

[0035] S4: LF refined molten steel is refined in an RH furnace without any changes. The refining temperature is 1520-1540℃ and the refining time is 50min to obtain RH refined molten steel.

[0036] Table 1: Composition of slag-forming material.

[0037]

[0038] Table 2: Composition of steelmaking raw materials (mass percentage).

[0039]

[0040] like Figure 1 As shown, the compositional region of the plastic inclusions in the CaO-SiO2-Al2O3 ternary system is in the low-melting-point region surrounding the plagioclase (CaO·Al2O3·2SiO2) and pseudowollastonite (CaO·SiO2), with melting points below 1400℃. The content of CaO is 8-53%, the content of SiO2 is 32-70%, and the content of Al2O3 is 5-37%.

[0041] like Figure 2 As shown, the inclusion projections of the grinding ball steel of Example 1 and Comparative Example 1 in the CaO-Al2O3-SiO2 phase diagram are shown. It can be seen that the proportion of plastic inclusions in the grinding ball steel of Example 1 is 82%, while the proportion of plastic inclusions in the grinding ball steel of Comparative Example 1 is less than 20%.

[0042] like Figure 3 As shown, the inclusion projections of the grinding ball steel of Example 2 and Comparative Example 1 in the CaO-Al2O3-SiO2 phase diagram are shown. It can be seen that the proportion of plastic inclusions in the grinding ball steel of Example 2 is 83%, while the proportion of plastic inclusions in the grinding ball steel of Comparative Example 1 is less than 20%.

[0043] like Figure 4 As shown, the inclusion projections of the grinding ball steel of Example 3 and Comparative Example 1 in the CaO-Al2O3-SiO2 phase diagram are shown. It can be seen that the proportion of plastic inclusions in the grinding ball steel of Example 3 is 81%, while the proportion of plastic inclusions in the grinding ball steel of Comparative Example 1 is less than 20%.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the plastic inclusions in grinding ball steel, characterized in that, The steps include the following: S1: The steelmaking raw material of the ball steel is smelted in a converter to obtain molten steel; S2: The molten steel undergoes deoxidation, alloying, and slag washing in the ladle to obtain the molten steel leaving the station; After the converter smelting, when 2 / 3 of the steel has been tapped, 1.5-3.0 kg / t of quicklime and 3.0-5.1 kg / t of pre-melted calcium aluminate are added for slag washing. S3: After the molten steel leaving the station is uniformly mixed with the high-basicity slag-forming material, it is refined into high-basicity slag white slag using an LF furnace to obtain LF refined molten steel. The high-alkalinity slag-forming material is composed of the following components by weight percentage: The total weight of FeO and MnO is ≤1.0%, CaO: 50%-56%, SiO2: 6%-12%, Al2O3: 20%-28%, MgO: 8%-10%; the value of CaO / SiO2 is R, which is 5.0-7.0; the remainder is MnO, P2O5, TiO2 and unavoidable impurities; S4: The LF refined steel is uniformly mixed with low-alkalinity reducing slag-forming material and then refined in an RH furnace to obtain RH refined steel. The low-alkalinity reducing slag-forming material is composed of the following components by weight percentage: The total weight of FeO and MnO is ≤1.0%, CaO: 32%-40%, SiO2: 30%-38%, Al2O3: 20%-30%, MgO: 6%-10%; the value of CaO / SiO2 is R, where R is 1.0-1.3; the remainder is MnO, P2O5, TiO2 and unavoidable impurities. S5: The RH refined molten steel is continuously cast to produce ball steel.

2. The method for improving the plastic inclusions in grinding ball steel according to claim 1, characterized in that, At the end of the converter smelting process, the C content in the molten steel is ≥0.08%, and the temperature of the molten steel is 1590℃-1670℃.

3. The method for improving the plastic inclusions in grinding ball steel according to claim 1, characterized in that, After the converter smelting, steel is tapped using a double slag-blocking method. In the early stage of tapping, when the converter tilt angle is 35°-75°, a sliding plate is used to block the slag. In the later stage of tapping, when the converter tilt angle is 97°, a slag-blocking cone is used to block the slag, controlling the amount of slag to be ≤1.7kg / t of molten steel.

4. The method for improving the plastic inclusions in grinding ball steel according to claim 1, characterized in that, After the converter smelting, when 1 / 4 of the steel is tapped, 0.1-0.4 kg / t of aluminum ingots are added for deoxidation, followed by the addition of 16-21 kg / t of ferrosilicon, 8-15 kg / t of silicon-manganese alloy, and 8-15 kg / t of high-carbon ferrochrome for alloying.

5. The method for improving the plastic inclusions in grinding ball steel according to claim 1, characterized in that, The high-alkalinity slag white residue refining temperature is 1490℃-1590℃ and the time is 40min-90min; the refining temperature in S4 is 1520℃-1560℃ and the time is 40min-60min.

6. The method for improving the plastic inclusions in grinding ball steel according to claim 1, characterized in that, The continuous casting adopts constant casting speed control, molten steel superheat: 15-30℃, crystallizer electromagnetic stirring current 300-400A, frequency 1.0-3.0Hz, end electromagnetic stirring current 400-500A, frequency 4.0-6.0Hz.

7. The grinding ball steel obtained by the method according to any one of claims 1 to 6, characterized in that, The weight of plastic inclusions accounts for ≥80% of the total weight of all inclusions.

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