Preparation method of modified high-chromium cast iron grinding ball and high-chromium cast iron grinding ball

Abstract

The invention provides a preparation method of a modified high-chromium cast iron grinding ball and the high-chromium cast iron grinding ball, and particularly relates to the technical field of wear-resistant materials. The preparation method comprises the following steps: carrying out vacuum refining and deslagging on a first high-chromium cast iron liquid, and blowing titanium carbide into the bottom of a refining furnace to form a second high-chromium cast iron liquid; the second high-chromium cast iron liquid is poured into a pouring ladle with preset vanadium-nitrogen alloy, the vanadium-nitrogen alloy is dissolved and reacts to form third high-chromium cast iron liquid, then the third high-chromium cast iron liquid in the pouring ladle is poured into a mold to obtain a grinding ball semi-finished product, and finally the grinding ball semi-finished product is quenched and tempered to obtain the high-chromium cast iron grinding ball. Through the synergistic effect of modification treatment and heat treatment strengthening, the double effects of improving the overall hardness of the grinding ball and reducing the hardness difference between the surface layer and the core part are finally achieved, and the abrasion loss is effectively controlled while the abrasion resistance is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of wear-resistant materials, in particular to a preparation method of a modified high-chromium cast iron grinding ball and the high-chromium cast iron grinding ball. Background Art

[0002] Modification is an effective method for improving the comprehensive mechanical properties of metallic materials. In hypoeutectic high-chromium cast iron, modification primarily refines austenite grains by increasing the nucleation rate of the first precipitated austenite. In hypereutectic high-chromium cast iron, modification primarily refines carbides by increasing the nucleation rate of the first precipitated carbides. The goal of modification is to promote austenite and carbide nucleation, promote carbide spheroidization, improve carbide morphology, and improve the shape and distribution of inclusions.

[0003] Titanium carbide is a commonly used modifier in high-chromium cast iron. In hypoeutectic high-chromium cast iron, it effectively refines austenite grains; in hypereutectic high-chromium cast iron, it refines primary carbides. However, both titanium and titanium carbide additions are subject to certain limitations. If too much is added, the titanium carbide aggregates and grows, reducing the number of solid-phase particles and limiting the refining effect. If too little is added, the amount of titanium carbide is insufficient, resulting in a limited number of solid-phase particles and still no effective refining effect. The core of this dilemma lies in the high solubility of titanium carbide in molten iron. Any added titanium or titanium carbide will dissolve in the molten iron. The titanium carbide particles, acting as a modifier, precipitate first during solidification and tend to aggregate and grow. Therefore, obtaining finer and more dispersed solid-phase titanium carbide particles is key to further improving the effectiveness of the modification treatment.

[0004] To address this issue, nano-Y2O3 particles are added during the modification process, allowing the first-precipitated titanium carbide to grow by adhering to the nano-Y2O3 particles. This has a certain improvement effect. However, the dispersion of nano-Y2O3 particles in molten iron is difficult to control, making it difficult to promote its use in industrial production. Another method is to add NbC, using the first-precipitated NbC to guide the precipitation and growth of titanium carbide, which also has a certain improvement effect. However, because the solubility product of [Nb] and [C] in the molten iron is less than an order of magnitude different from the solubility product of [Ti] and [C], a large amount of NbC is still required to achieve a good refinement effect. However, adding too much NbC will cause Ostwald coagulation and growth, thereby limiting the refinement effect. Therefore, the introduction of NbC does not effectively achieve the effect of refining titanium carbide particles.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] One of the purposes of the present invention is to provide a method for preparing modified high-chromium cast iron grinding balls, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0007] A second object of the present invention is to provide a high chromium cast iron grinding ball.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: A first aspect of the present invention provides a method for preparing high-chromium cast iron grinding balls that have undergone a metamorphic treatment. After vacuum refining and slag removal of a first high-chromium cast iron liquid, titanium carbide is blown into the bottom of the refining furnace to obtain a second high-chromium cast iron liquid; the second high-chromium cast iron liquid is poured into a casting ladle pre-filled with a vanadium-nitrogen alloy, the vanadium-nitrogen alloy is dissolved to form a third high-chromium cast iron liquid, and the third high-chromium cast iron liquid is poured into a mold to obtain a semi-finished grinding ball. Finally, the semi-finished grinding ball is quenched and tempered to obtain a high-chromium cast iron grinding ball.

[0009] Furthermore, the particle size of the titanium carbide is 10-200 mesh.

[0010] Furthermore, the particle size of the vanadium-nitrogen alloy is 1 to 10 mm; Preferably, the chemical composition of the vanadium-nitrogen alloy includes: V: 80-90%, N: 10-20%.

[0011] Furthermore, the molar ratio of the vanadium nitrogen alloy to the titanium carbide is 1:(1.2-1.6).

[0012] The mass ratio of the vanadium-nitrogen alloy to the second high-chromium cast iron liquid is 0.2-0.4%.

[0013] Furthermore, the quenching temperature is 990-1010°C, and the tempering temperature is 200-300°C.

[0014] Furthermore, the preparation method also includes a process of adding raw materials and melting them before all steps to obtain the first high-chromium cast iron liquid.

[0015] The second aspect of the present invention provides a high chromium cast iron grinding ball, which is prepared by the above-mentioned preparation method.

[0016] Furthermore, the difference between the surface hardness and the core hardness of the high chromium cast iron grinding ball is ≤4.0HRC.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: In the preparation method provided by the present invention, the blown titanium carbide is completely dissolved in the first high-chromium cast iron liquid to form a second high-chromium cast iron liquid. While the vanadium-nitrogen alloy is dissolved, titanium nitride is also precipitated. The titanium nitride particles are stirred by melt convection to avoid ripening and coarsening and achieve uniform distribution, and then serve as a heterogeneous nucleation base to promote the precipitation of titanium carbide on its surface; the vanadium introduced when the vanadium-nitrogen alloy is added generates vanadium carbide during further cooling, and grows on the surface of titanium carbide, eventually forming a crystal nucleus composed of titanium nitride-titanium carbide-vanadium carbide. This multi-stage dependent growth and staged precipitation pattern effectively inhibits the ripening and coarsening of the crystal nucleus, significantly refines the proeutectoid austenite or proeutectoid carbide during solidification, and improves the size and distribution of the carbide, thereby improving the performance of the high-chromium cast iron. On this basis, the introduction of vanadium-nitrogen alloy not only participates in the modification reaction, but also produces a precipitation strengthening effect through the secondary precipitation of vanadium carbide during the subsequent heat treatment. This secondary hardening effect improves the uniformity of hardness from the surface to the core of the grinding ball, narrowing the hardness difference between the surface and the core. Through the synergistic effect of modification and heat treatment strengthening, the dual effects of increasing the overall hardness of the grinding ball and reducing the hardness difference between the surface and the core are ultimately achieved, effectively controlling wear while ensuring wear resistance.

[0018] The high-chromium cast iron grinding balls provided by the present invention, thanks to the advantages of the aforementioned preparation method, possess higher and more uniform hardness, while also exhibiting excellent impact toughness and wear resistance. These high-chromium cast iron grinding balls exhibit a longer service life under harsh operating conditions and are particularly suitable for high-impact and highly corrosive grinding environments, significantly reducing equipment maintenance costs and downtime. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0020] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0021] A first aspect of the present invention provides a method for preparing a high-chromium cast iron grinding ball that has undergone a metamorphic treatment. After vacuum refining and deslagging a first high-chromium cast iron liquid, titanium carbide is blown into the bottom of the refining furnace to form a second high-chromium cast iron liquid; the second high-chromium cast iron liquid is then poured into a casting ladle pre-filled with a vanadium-nitrogen alloy, and the vanadium-nitrogen alloy is dissolved to form a third high-chromium cast iron liquid; the third high-chromium cast iron liquid is then poured into a mold and solidified to obtain a semi-finished grinding ball; and finally, the semi-finished grinding ball is quenched and tempered to obtain a high-chromium cast iron grinding ball.

[0022] In the preparation method provided by the present invention, the blown titanium carbide can be completely dissolved in the first high-chromium cast iron liquid to form dissolved titanium [Ti] and dissolved carbon [C], that is, the titanium and carbon in the second high-chromium cast iron liquid are in a completely dissolved state. When the second high-chromium cast iron liquid is introduced into the casting ladle, the temperature of the cast iron liquid drops sharply, and the following three processes are triggered in sequence: (1) the vanadium-nitrogen alloy pre-placed in the casting ladle will dissolve into the second high-chromium cast iron liquid to form dissolved nitrogen [N] and dissolved vanadium [V]; (2) the dissolved titanium [Ti] reacts with the dissolved nitrogen [N] to form titanium nitride. The titanium nitride particles are evenly distributed under the action of convection stirring and will not mature or coarsen; (3) the unreacted dissolved titanium [Ti] reacts with the dissolved carbon [C] to form titanium carbide, which is preferentially precipitated on the surface of the titanium nitride. In the further cooling process, the dissolved vanadium continues to react with the unreacted carbon to form vanadium carbide, which is precipitated on the surface of the titanium carbide, and finally forms a crystal nucleus composed of titanium nitride-titanium carbide-vanadium carbide. This multi-stage dependent growth and phased precipitation pattern effectively inhibits the ripening and coarsening of the crystal nucleus, significantly refining the proeutectoid austenite or proeutectoid carbides during solidification and improving the size and distribution of the carbides, thereby improving the performance of high-chromium cast iron. During the subsequent heat treatment heating process, vanadium carbide can partially dissolve in the austenite. During tempering, vanadium carbide will precipitate and produce a secondary strengthening effect. This secondary strengthening effect can improve the hardness uniformity of the grinding ball from the surface to the core area, reducing the hardness difference between the surface and the core. Through the synergistic effect of metamorphic treatment and heat treatment strengthening, the dual effects of increasing the overall hardness of the grinding ball and reducing the hardness difference between the surface and the core are ultimately achieved, effectively controlling wear while ensuring wear resistance.

[0023] Specifically, the main purpose of the present invention is to form finer and more dispersed carbide particles, which serve as the core for the precipitation of austenite or M7C3 carbide, thereby refining the austenite grains or M7C3 carbides and further improving the performance of high-chromium cast iron. Under normal circumstances, the solubility product of [N] and [Ti] in high-chromium cast iron liquid is 3-4 orders of magnitude lower than the solubility product of [C] and [Ti]. This means that titanium nitride will precipitate preferentially during the condensation process. The precipitated titanium nitride particles are difficult to mature and coarsen under strong stirring, and can maintain a fine and dispersed state. When titanium nitride precipitates, part of the dissolved titanium [Ti] is consumed, and titanium carbide needs to be precipitated after appropriate cooling. The precipitated titanium carbide grows on the titanium nitride. When the titanium is completely consumed, the titanium carbide changes and stops growing; as the temperature continues to drop, vanadium carbide will precipitate, and the precipitated vanadium carbide grows on the titanium carbide.

[0024] Based on this principle, the present invention introduces nitrogen by adding a vanadium-nitrogen alloy during the production of high-chromium cast iron. This allows the titanium pre-added to the high-chromium cast iron to react with the nitrogen to form fine, dispersed titanium nitride particles. Subsequently, titanium carbide readily attaches to these titanium nitride particles for growth, thereby inhibiting the Ostwald coarsening process of the titanium carbide particles. During the subsequent condensation process, vanadium carbide continues to attach to the titanium carbide for growth, ultimately serving as a nucleation site for austenite or M7C3 carbide nucleation.

[0025] The dissolution reaction of titanium carbide and vanadium nitrogen alloy in cast iron liquid is: TiC=[Ti]+[C]; VN=[V]+[N].

[0026] The formation reaction of titanium nitride is: [Ti]+[N]=TiN.

[0027] During the gradual condensation process, the precipitation reactions of titanium carbide and vanadium carbide are as follows: [Ti]+[C]=TiC; [V]+[C]=VC.

[0028] The solubility product relationship of [V], [Ti], [C] and [N] in cast iron liquid is: [V][C]>[Ti][C]>[Ti][N].

[0029] By regulating the concentrations of vanadium, titanium, carbon, and nitrogen in the cast iron liquid, the order of precipitation of various phases during the solidification process of hypoeutectic cast iron can be changed. Specifically, titanium nitride precipitates first, and then titanium carbide grows attached to the titanium nitride particles, while the precipitated vanadium carbide coats the titanium carbide particles and eventually becomes the core for the nucleation of austenite or M7C3 carbide. Since the solubility product of titanium carbide and vanadium carbide in the cast iron liquid is much smaller than that of M7C3 carbide, in hypereutectic high-chromium cast iron, titanium carbide and vanadium carbide will precipitate before M7C3 carbide, thus becoming the core for the nucleation of M7C3 carbide.

[0030] Furthermore, the particle size of the titanium carbide is 10-200 mesh.

[0031] Furthermore, the particle size of the vanadium-nitrogen alloy is 1 to 10 mm; Preferably, the chemical composition of the vanadium-nitrogen alloy includes: V: 80-90%, N: 10-20%.

[0032] Furthermore, the molar ratio of the vanadium nitrogen alloy to the titanium carbide is 1:(1.2-1.6).

[0033] Typically, but not limiting, the molar ratio of the vanadium nitrogen alloy to titanium carbide may be, for example, 1:1.2, 1:1.3, 1:1.4, 1:1.5, or 1:1.6, or any value within the range of 1:1.2 to 1.6.

[0034] The mass ratio of the vanadium-nitrogen alloy to the second high-chromium cast iron liquid is 0.2-0.4%.

[0035] Typically, but not limitatively, the mass ratio of the vanadium-nitrogen alloy to the second high-chromium cast iron liquid may be, for example, 0.2%, 0.25%, 0.3%, 0.35% or 0.4%, or any value within the range of 0.2% to 0.4%.

[0036] Furthermore, the quenching temperature is 990-1010°C, and the tempering temperature is 200-300°C.

[0037] Typically, but not limiting, the quenching temperature may be, for example, 990° C., 995° C., 1000° C., 1005° C., or 1010° C., or any value within the range of 990° C. to 1010° C. The tempering temperature may be, for example, 200° C., 220° C., 240° C., 260° C., 280° C., or 300° C., or any value within the range of 200° C. to 300° C.

[0038] Furthermore, the preparation method also includes a process of adding raw materials and melting them before all steps to obtain the first high-chromium cast iron liquid.

[0039] The second aspect of the present invention provides a high chromium cast iron grinding ball, which is prepared by the above-mentioned preparation method.

[0040] Furthermore, the difference between the surface hardness and the core hardness of the high-chromium cast iron grinding balls is ≤4.0 HRC. Due to the advantages of the aforementioned preparation method, the high-chromium cast iron grinding balls provided by the present invention exhibit higher and more uniform hardness values, while also possessing excellent impact toughness and wear resistance. These high-chromium cast iron grinding balls exhibit a longer service life under harsh operating conditions and are particularly suitable for high-impact and highly corrosive wet grinding environments, significantly reducing equipment maintenance costs and downtime.

[0041] The present invention is further illustrated below by specific examples and comparative examples. However, it should be understood that these examples are merely for the purpose of further explanation and should not be construed as limiting the present invention in any form. The raw materials used in the examples and comparative examples of the present invention, unless otherwise specified, were prepared under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0042] Example 1 This embodiment provides a high-chromium wear-resistant white cast iron KmTB Cr18 grinding ball with a diameter of 80 mm, and the preparation method is as follows: 1. Melt the raw materials to obtain 40 tons of the first high-chromium cast iron liquid.

[0043] 2. The first high-chromium cast iron liquid is transferred to the LF furnace for refining and slag removal. While performing vacuum treatment, 118 kg of titanium carbide powder (particle size 10-200 mesh) is blown into the furnace from the bottom with argon gas to dissolve the titanium carbide in the high-chromium cast iron liquid.

[0044] 3. Then, pre-place 20 kg of vanadium-nitrogen alloy particles (composition: 80% V, 19% N; particle size 1-10 mm) in four 10-ton casting ladles, pour 40 tons of high-chromium cast iron liquid into the four casting ladles respectively, and gradually cast them into semi-finished grinding balls.

[0045] 4. Finally, the semi-finished grinding ball is quenched at 990℃ and tempered at 250℃ to obtain high chromium wear-resistant white cast iron KmTB Cr18 grinding ball.

[0046] Example 2 This embodiment provides a high-chromium wear-resistant white cast iron KmTB Cr15 grinding ball with a diameter of 100 mm, and the preparation method is as follows: 1. Melt the raw materials to obtain 40 tons of the first high-chromium cast iron liquid.

[0047] 2. The first high-chromium cast iron liquid is transferred to the LF furnace for refining and slag removal. While performing vacuum treatment, 155 kg of titanium carbide powder (particle size 10-200 mesh) is blown into the furnace from the bottom with argon gas to dissolve the titanium carbide in the high-chromium cast iron liquid.

[0048] 3. Then, pre-place 30 kg of vanadium-nitrogen alloy particles (composition: 80% V, 16% N; particle size 1-10 mm) in four 10-ton casting ladles, pour 40 tons of high-chromium cast iron liquid into the four casting ladles respectively, and gradually cast them into semi-finished grinding balls.

[0049] 4. Finally, the semi-finished grinding ball is quenched at 1000℃ and tempered at 250℃ to obtain high chromium wear-resistant white cast iron KmTB Cr15 grinding ball.

[0050] Example 3 This embodiment provides a high-chromium wear-resistant white cast iron KmTB Cr12 grinding ball with a diameter of 120 mm, and the preparation method is as follows: 1. Melt the raw materials to obtain 30 tons of the first high-chromium cast iron liquid.

[0051] 2. The first high-chromium cast iron liquid is transferred to the LF furnace for refining and slag removal. While performing vacuum treatment, 133 kg of titanium carbide powder (particle size 10-200 mesh) is blown into the furnace from the bottom with argon gas to dissolve the titanium carbide in the high-chromium cast iron liquid.

[0052] 3. Then, pre-place 40 kg of vanadium-nitrogen alloy particles (composition: 81% V, 14% N; particle size 1-10 mm) in three 10-ton casting ladles, pour 30 tons of high-chromium cast iron liquid into the three casting ladles respectively, and gradually cast them into semi-finished grinding balls.

[0053] 4. Finally, the semi-finished grinding ball is quenched at 1010℃ and tempered at 250℃ to obtain high chromium wear-resistant white cast iron KmTB Cr12 grinding ball.

[0054] Comparative Example 1 This comparative example provides a high-chromium wear-resistant white cast iron KmTB Cr18 grinding ball. The difference from Example 1 is that no vanadium-nitrogen alloy particles are added during the pouring process in step 3. The remaining steps are the same as those in Example 1 and are not repeated here.

[0055] Comparative Example 2 This comparative example provides a high-chromium wear-resistant white cast iron KmTB Cr18 grinding ball. The difference from Example 1 is that titanium carbide powder is not added during the refining and slag removal process in step 2. The remaining steps are the same as those in Example 1 and are not repeated here.

[0056] Comparative Example 3 This comparative example provides a high-chromium wear-resistant white cast iron KmTB Cr18 grinding ball. The difference from Example 1 is that 118 kg of titanium carbide powder is replaced by 94.27 kg of titanium powder. The remaining steps are the same as those in Example 1 and are not repeated here.

[0057] Comparative Example 4 This comparative example provides a high-chromium wear-resistant white cast iron KmTB Cr18 grinding ball. The difference from Example 1 is that in step 3, an equal weight of Y2O3 particles (particle size of 200 nm) are used to replace the vanadium-nitrogen alloy particles. The remaining steps are the same as those in Example 1 and are not repeated here.

[0058] Comparative Example 5 This comparative example provides a high-chromium wear-resistant white cast iron KmTB Cr18 grinding ball. The difference from Example 1 is that in step 3, an equal weight of NbC particles (particle size of 1-5 mm) are used to replace the vanadium-nitrogen alloy particles. The remaining steps are the same as those in Example 1 and are not repeated here.

[0059] Test Example 1 The grinding balls of the embodiment and the comparative example were subjected to hardness test and impact value test. The hardness test method was carried out according to the provisions of GB / T230.1 standard.

[0060] The impact value test method is based on the V-notch specimen specified in GB / T229 standard.

[0061] The obtained data are recorded in Table 1.

[0062] Table 1

[0063] As can be seen from Table 1, the synergistic effect of the modification treatment and heat treatment strengthening provided by the present invention achieves the dual effects of increasing the overall hardness of the grinding balls and reducing the hardness difference between the surface and the core, which is beneficial to effectively reduce the wear while ensuring wear resistance.

[0064] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing modified high chromium cast iron grinding balls, characterized in that: After vacuum refining and deslagging the first high-chromium cast iron liquid, titanium carbide is blown into the bottom of the refining furnace to obtain a second high-chromium cast iron liquid; the second high-chromium cast iron liquid is poured into a casting ladle pre-filled with a vanadium-nitrogen alloy, the vanadium-nitrogen alloy is dissolved to form a third high-chromium cast iron liquid, and the third high-chromium cast iron liquid is poured into a mold to obtain a semi-finished grinding ball. Finally, the semi-finished grinding ball is quenched and tempered to obtain a high-chromium cast iron grinding ball.

2. The preparation method according to claim 1, characterized in that The particle size of the titanium carbide is 10-200 meshes.

3. The preparation method according to claim 1, characterized in that The particle size of the vanadium-nitrogen alloy is 1 to 10 mm; Preferably, the chemical composition of the vanadium-nitrogen alloy includes: V: 80-90%, N: 10-20%.

4. The preparation method according to any one of claims 1 to 3, characterized in that The molar ratio of the vanadium nitrogen alloy to the titanium carbide is 1:(1.2-1.6); The mass ratio of the vanadium-nitrogen alloy to the second high-chromium cast iron liquid is 0.2-0.4%.

5. The preparation method according to any one of claims 1 to 3, characterized in that The quenching temperature is 990-1010°C, and the tempering temperature is 200-300°C.

6. The preparation method according to any one of claims 1 to 3, characterized in that The method also includes adding raw materials to melt and obtain the first high-chromium cast iron liquid before all steps.

7. A high chromium cast iron grinding ball, characterized in that: The preparation method according to any one of claims 1 to 6 is used to prepare the compound.

8. The high chromium cast iron grinding ball according to claim 7, characterized in that: The difference between the surface hardness and the core hardness of the high chromium cast iron grinding ball is ≤4.0HRC.

Images