CADI grinding ball and preparation method thereof

Abstract

The invention relates to the technical field of wear-resistant materials, and provides a CADI grinding ball which is prepared by the following steps: regulating the element composition of base iron, reducing carbon and increasing chromium in the base iron, pretreating the base iron by using small-particle-size silicon carbide, and spheroidizing and inoculating the pretreated base iron to obtain a grinding ball casting. And finally, the CADI grinding ball is obtained after the grinding ball casting is subjected to heat treatment, the number of graphite spherical cores is large, the size is uniform, and the grinding ball is high in surface hardness and good in impact toughness.

Description

Technical Field

[0001] This invention relates to the field of wear-resistant materials technology, and in particular to a CADI grinding ball and its preparation method. Background Technology

[0002] In recent years, my country has consumed hundreds of millions of tons of metal wear-resistant materials, with grinding balls accounting for 60-70% of that. Therefore, grinding balls are a very important grinding material.

[0003] Traditional isothermal hardened ductile iron (ADI) has excellent toughness and is a preferred material for grinding balls. However, its initial hardness is relatively low, generally around 50 HRC, which cannot meet higher hardness requirements. On this basis, carbide-containing isothermal hardened ductile iron (CADI) has been developed. Compared with the former, its hardness, impact resistance and wear resistance are improved to varying degrees. The quality of its graphite spheroidization rate directly affects the quality of CADI grinding balls.

[0004] Currently, there is a need for a method that can stably produce high-quality CADI grinding balls. Summary of the Invention

[0005] To address the technical problems existing in the background art, the present invention proposes a CADI grinding ball, wherein the chemical composition of the grinding ball includes C: 2.0-3.5wt%, Si: 1.5-2.8wt%, Mn: 0.3-3wt%, Cr: 0.5-0.8wt%, Cu: 0.2-0.5wt%, Re: 0.01-0.03wt%, with the balance being Fe and unavoidable impurities.

[0006] This invention also proposes a method for preparing CADI grinding balls, comprising the following steps: S1. Melt the raw materials into molten iron, and remove the slag to obtain the original molten iron; S2. Add silicon carbide to the original molten iron to obtain pretreated molten iron; S3. The pretreated molten iron is subjected to wire feeding and balling inoculation treatment to obtain grinding ball castings; S4. After heat preservation, the grinding ball casting is isothermally quenched to obtain CADI grinding balls.

[0007] In step S1, the temperature of the original molten iron is 1450-1530℃.

[0008] In step S2, the silicon carbide particle size is 0.2-0.8 mm, and the silicon carbide content is 0.2-2.5 wt% of the original molten iron.

[0009] In this invention, if the silicon carbide particle size is too large, it will be unevenly dispersed, affecting the spherical nuclei of graphite.

[0010] In step S3, during the spheroidizing inoculation treatment, the raw materials for the spheroidized cored wire include, by weight percentage: Mg: 29.0-31.0%, RE: 1.5-2.5%, Ca: 2.0-3.0%, Si < 48.0%, Al < 1.0%, Ti ≤ 0.3%, with the balance being Fe.

[0011] In step S3, during the feeding and balling inoculation treatment, the raw materials for inoculating the cored wire include, by weight percentage: Ca: 2.5-3.5%, Ba: 2-4%, Si > 68%, Al < 1.0%, with the balance being Fe, wherein the total weight percentage of each raw material is 100%. Preferably, the diameter of the spheroidized cored wire and the inoculated cored wire is 10-15 mm.

[0012] In step S3, during the spheroidizing and inoculation treatment, the amount of spheroidizing cored wire used per ton of molten iron is 10-20m, and the amount of inoculated cored wire used is 15-30m. In step S3, the temperature of the feeding ball inoculation treatment is 1400-1450℃.

[0013] In step S4, the heat preservation temperature is 850-950℃, and the heat preservation time is 2-4h.

[0014] In step S4, the isothermal quenching temperature is 200-400℃, and the isothermal quenching time is 3-5h.

[0015] Beneficial effects of this invention: (1) The present invention uses SIC pretreatment agent to pretreat molten iron before spheroidization, thereby increasing the number of graphite spheroids in the original molten iron, thereby increasing the number of graphite spheroids and improving the growth of graphite spheroids. On this basis, the tendency of graphite spheroids to grow is reduced by reducing the C content. (2) This invention improves the effect of chemical composition segregation by increasing the Cr content. However, the addition of chromium increases the diameter of graphite spherical nuclei and reduces the number of graphite spherical nuclei. Therefore, the chromium content is controlled at 0.5-0.8wt% to balance the performance of graphite spherical nuclei and hardness. The final grinding ball has a graphite spherical number of 300-400 per mm. 2 Increase to 500-600 pieces / mm 2 The surface hardness increased from 50-52 HRC in the original process to 54-56 HRC, while the impact toughness remained at 8-15 J / cm. 2 . Attached Figure Description

[0016] Figure 1 This is an electron microscope image of the cross-section of the CADI grinding ball in Example 1; Figure 2 The image shows an electron microscope (EM) image of the cross-section of the CADI grinding ball in Comparative Example 1. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] The technical solution of the present invention will now be described more clearly and completely with reference to specific embodiments and comparative examples.

[0020] Example 1 This embodiment proposes a CADI grinding ball, the chemical composition of which, by mass percentage, is: C: 2.0wt%, Si: 2.3wt%, Mn: 2.5wt%, Cr: 0.6wt%, Cu: 0.3wt%, Re: 0.01wt%, with the balance being Fe and unavoidable impurities; This embodiment also proposes a method for preparing CADI grinding balls: (1) Preheat the vacuum induction furnace and control the preheating temperature to 200 degrees Celsius. Add the foundry pig iron, scrap steel and recycled materials into the vacuum induction furnace in proportion. After complete melting, add slag remover to the molten iron, remove slag, take samples for testing and adjust the carbon and chromium content in the molten iron. Then adjust the molten iron to 1500°C, remove the slag floating on the liquid surface, and obtain the original molten iron. (2) Add silicon carbide powder to the original molten iron to obtain pretreated molten iron, wherein the silicon carbide powder has a particle size of 0.2 mm and the silicon carbide accounts for 2 wt% of the original molten iron; (3) The pretreated molten iron is poured into the ladle and fed with wire spheroidizing and inoculation treatment at 1450℃. The diameter of the spheroidized cored wire and the inoculated cored wire is 15mm. For every ton of molten iron, the amount of spheroidized cored wire is 15m and the amount of inoculated cored wire is 20m. During the spheroidizing inoculation process, the temperature of the molten iron in the ladle is maintained at 1450℃. After spheroidizing inoculation is completed, slag is removed, and the slag-removed spheroidized molten iron is poured to obtain the grinding ball casting, wherein: The raw materials for spheroidized cored wire, by weight percentage, include: Mg: 29.0%, RE: 2.5%, Ca: 2.0%, Si < 48.0%, Al < 1.0%, Ti ≤ 0.3%, with the balance being Fe; The raw materials for producing cored wires include, by weight percentage: Ca: 2.5%, Ba: 4%, Si: 69%, Al < 1.0%, with the balance being Fe; (4) Place the grinding ball casting at 900℃ for 3 hours, then place it in a 300℃ salt bath (the salt bath is a high-temperature salt bath composed of potassium nitrate and sodium nitrite in a weight ratio of 1:1) for isothermal quenching for 4 hours, and then cool it to room temperature to obtain CADI grinding balls.

[0021] Example 2 This embodiment proposes a CADI grinding ball, the chemical composition of which, by mass percentage, is: C: 3.1wt%, Si: 2.5wt%, Mn: 1.5wt%, Cr: 0.8wt%, Cu: 0.2wt%, Re: 0.02wt%, with the balance being Fe and unavoidable impurities; This embodiment also proposes a method for preparing CADI grinding balls: (1) Preheat the vacuum induction furnace and control the preheating temperature to 300 degrees Celsius. Add the foundry pig iron, scrap steel and recycled material into the vacuum induction furnace in proportion. After complete melting, add slag remover to the molten iron, remove slag, take samples for testing and adjust the carbon and chromium content in the molten iron. Then adjust the molten iron to 1500°C, remove the slag floating on the liquid surface, and obtain the original molten iron. (2) Add silicon carbide powder to the original molten iron to obtain pretreated molten iron, wherein the silicon carbide powder has a particle size of 0.3 mm and the silicon carbide content is 2.5 wt% of the original molten iron; (3) The pretreated molten iron is poured into the ladle and fed with wire spheroidizing and inoculation treatment at 1450℃. The diameter of the spheroidized cored wire and the inoculated cored wire is 10mm. For every ton of molten iron, the amount of spheroidized cored wire is 20m and the amount of inoculated cored wire is 25m. During the spheroidizing inoculation process, the temperature of the molten iron in the ladle is maintained at 1450℃. After spheroidizing inoculation is completed, slag is removed, and the slag-removed spheroidized molten iron is poured to obtain the grinding ball casting, wherein: The raw materials for spheroidized cored wire, by weight percentage, include: Mg: 29.0%, RE: 2.5%, Ca: 2.0%, Si < 48.0%, Al < 1.0%, Ti ≤ 0.3%, with the balance being Fe; The raw materials for producing cored wires include, by weight percentage: Ca: 2.5%, Ba: 4%, Si: 69%, Al < 1.0%, with the balance being Fe; (4) Place the grinding ball casting at 850℃ for 4 hours, then place it in a 200℃ salt bath (a high-temperature salt bath composed of potassium nitrate and sodium nitrite in a weight ratio of 1:1) for isothermal quenching for 5 hours, and then cool it to room temperature to obtain CADI grinding balls.

[0022] Example 3 This embodiment proposes a CADI grinding ball, the chemical composition of which, by mass percentage, is: C: 3.5wt%, Si: 1.5wt%, Mn: 2.0wt%, Cr: 0.5wt%, Cu: 0.27wt%, Re: 0.03wt%, with the balance being Fe and unavoidable impurities; This embodiment also proposes a method for preparing CADI grinding balls: (1) Preheat the vacuum induction furnace and control the preheating temperature to 300 degrees Celsius. Add the foundry pig iron, scrap steel and recycled material into the vacuum induction furnace in proportion. After complete melting, add slag remover to the molten iron, remove slag, take samples for testing and adjust the carbon and chromium content in the molten iron. Then adjust the molten iron to 1500°C, remove the slag floating on the liquid surface, and obtain the original molten iron. (2) Add silicon carbide powder to the original molten iron to obtain pretreated molten iron, wherein the silicon carbide powder has a particle size of 0.3 mm and the silicon carbide content is 1.5 wt% of the original molten iron; (3) The pretreated molten iron is poured into the ladle and fed with wire spheroidizing and inoculating treatment at 1430℃. The diameter of the spheroidized cored wire and the inoculated cored wire is 15mm. For every ton of molten iron, the amount of spheroidized cored wire is 20m and the amount of inoculated cored wire is 30m. During the spheroidizing inoculation process, the temperature of the molten iron in the ladle is maintained at 1430℃. After spheroidizing inoculation is completed, slag is removed, and the slag-removed spheroidized molten iron is poured to obtain the grinding ball casting, wherein: The raw materials for spheroidized cored wire, by weight percentage, include: Mg: 29.0%, RE: 2.5%, Ca: 2.0%, Si < 48.0%, Al < 1.0%, Ti ≤ 0.3%, with the balance being Fe; The raw materials for producing cored wires include, by weight percentage: Ca: 2.5%, Ba: 4%, Si: 69%, Al < 1.0%, with the balance being Fe; (4) Place the grinding ball casting at 950℃ for 2 hours, then place it in a 400℃ salt bath (a high-temperature salt bath composed of potassium nitrate and sodium nitrite in a weight ratio of 1:1) for isothermal quenching for 3 hours, and then cool it to room temperature to obtain CADI grinding balls.

[0023] Comparative Example 1 This comparative example proposes a CADI grinding ball, which is prepared in the same way as in Example 1, except that "the particle size of silicon carbide powder is 0.2 mm" in step (2) is replaced with "the particle size of silicon carbide powder is 1.0 mm". Comparative Example 2 This comparative example proposes a CADI grinding ball, the chemical composition of which, by mass percentage, is: C: 5.0 wt%, Si: 2.3 wt%, Mn: 2.5 wt%, Cr: 0.6 wt%, Cu: 0.3 wt%, Re: 0.01 wt%, with the balance being Fe and unavoidable impurities; its preparation method is the same as that of Example 1, except that the carbon content is increased in step (1). Comparative Example 3 This comparative example proposes a CADI grinding ball, the chemical composition of which, by mass percentage, is: C: 2.0wt%, Si: 2.3wt%, Mn: 2.5wt%, Cr: 0.3wt%, Cu: 0.3wt%, Re: 0.01wt%, with the balance being Fe and unavoidable impurities; its preparation method is the same as that of Example 1, by reducing the chromium content in step (1).

[0024] The grinding balls prepared in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 1: Table 1 Performance data of grinding balls in each embodiment and comparative example

[0025] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A CADI grinding ball, characterized in that, The chemical composition of the grinding ball includes C: 2.0-3.5wt%, Si: 1.5-2.8wt%, Mn: 0.3-3wt%, Cr: 0.5-0.8wt%, Cu: 0.2-0.5wt%, Re: 0.01-0.03wt%, with the balance being Fe and unavoidable impurities.

2. A method for preparing the CADI grinding ball according to claim 1, characterized in that, Includes the following steps: S1. Melt the raw materials into molten iron, and remove the slag to obtain the original molten iron; S2. Add silicon carbide to the original molten iron to obtain pretreated molten iron; S3. The pretreated molten iron is subjected to wire feeding and balling inoculation treatment to obtain grinding ball castings; S4. After heat preservation, the grinding ball casting is isothermally quenched to obtain CADI grinding balls.

3. The method for preparing CADI grinding balls according to claim 2, characterized in that, In step S1, the temperature of the original molten iron is 1450-1530℃.

4. The method for preparing CADI grinding balls according to claim 2 or 3, characterized in that, In step S2, the silicon carbide particle size is 0.2-0.8 mm, and the silicon carbide content is 0.2-2.5 wt% of the original molten iron.

5. The method for preparing CADI grinding balls according to any one of claims 2-4, characterized in that, In step S3, during the spheroidizing inoculation treatment, the raw materials for the spheroidized cored wire include, by weight percentage: Mg: 29.0-31.0%, RE: 1.5-2.5%, Ca: 2.0-3.0%, Si < 48.0%, Al < 1.0%, Ti ≤ 0.3%, with the balance being Fe.

6. The method for preparing CADI grinding balls according to claim 5, characterized in that, In step S3, during the feeding ball-forming inoculation treatment, the raw materials for inoculating the cored wire include, by weight percentage: Ca: 2.5-3.5%, Ba: 2-4%, Si > 68%, Al < 1.0%, with the balance being Fe, wherein the total weight percentage of each raw material is 100%.

7. The method for preparing CADI grinding balls according to claim 5 or 6, characterized in that, In step S3, the diameters of the spheroidized cored wire and the inoculated cored wire are both 10-15 mm; During the spheroidizing inoculation treatment, the amount of spheroidizing cored wire used per ton of molten iron is 10-20m, and the amount of inoculated cored wire used is 15-30m.

8. The method for preparing CADI grinding balls according to any one of claims 2-7, characterized in that, In step S3, the temperature of the feeding ball inoculation treatment is 1400-1450℃.

9. The method for preparing CADI grinding balls according to any one of claims 2-8, characterized in that, In step S4, the heat preservation temperature is 850-950℃, and the heat preservation time is 2-4h.

10. The method for preparing CADI grinding balls according to any one of claims 2-9, characterized in that, In step S4, the isothermal quenching temperature is 200-400℃, and the isothermal quenching time is 3-5h.

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