A wear-resistant and durable shot and a preparation method thereof

Abstract

This invention relates to a wear-resistant and durable shot peening agent and its preparation method. The composition of the shot peening agent, by mass percentage, is: C: 0.68-1.20%, Si: 0.32-0.74%, Mn: 4.6-8.5%, Mo: 4.2-8.7%, W: 2.7-5.7%, Cu: 1.3-3.8%, P: less than 0.05%, S: less than 0.03%, with the balance being Fe and unavoidable impurities. The shot peening agent is prepared by water atomization or gas atomization of molten steel with the above composition. The shot peening agent is then heated to 830-920℃ and held, followed by quenching to room temperature. The quenching cooling rate is V1≤V≤V2. The value is ℃ / s, where: V1=7.65*ln(151.2-3.56*[C]-2.15*[Si]-6.24*[Mn]-5.71*[Mo]-3.05*[W]-0.98*[Cu])+14.5; V2=44.2+27.4*[C]-11.2*[Si]-3.24*[Mn]+3.55*[Mo]+2.16*[W]-2.84*[Cu]; where [C], [Si], [Mn], [Mo], [W], and [Cu] represent the mass percentage content of C, Si, Mn, Mo, W, and Cu, respectively.

Description

Technical Field

[0001] This invention relates to a wear-resistant and durable shot peening device and its preparation method. The shot peening device has excellent wear resistance and the shot body will not break during long-term use, thus exhibiting good durability. This invention also provides a method for preparing the shot peening device. Background Technology

[0002] Shot peening, also known as shot blasting or shot pelleting, involves propelling shot onto the surface of a metal material using a shot peening machine. This is done for surface modification (e.g., hardening) or to remove surface scale, rust, coatings, etc. Current technologies typically impose high requirements on the strength and wear resistance (i.e., hardness) of shot peening; therefore, shot peening usually needs to maintain an austenitic structure. To obtain an austenitic structure, in addition to controlling the composition to meet certain conditions, a relatively high cooling rate is also required to ensure that the austenitic structure is maintained at room temperature.

[0003] In actual industrial production, shot peening is usually prepared by atomizing the melt with water or gas. However, the atomization process typically involves extremely high cooling rates. During shot peening, it has been found that due to the excessively high cooling rate, the shot often breaks apart during operation due to high-speed collisions between the shot and the working surface or between the shot and the workpiece. This results in damage after a short period of operation, insufficient durability, and the tendency to leave defects on the surface during surface treatment.

[0004] Based on the aforementioned problems in the existing technology, this invention proposes a shot peening method that has both excellent wear resistance and is not easily broken during use, thus possessing high durability. Summary of the Invention

[0005] This invention provides a wear-resistant and durable shot peening material. The shot peening material has excellent wear resistance and the shot body will not break during long-term use, thus exhibiting good durability.

[0006] The technical objective of this invention is achieved through the following means.

[0007] This invention provides a wear-resistant and durable shot peening material, wherein the composition of the shot peening material, by mass percentage, is: C: 0.68-1.20%, Si: 0.32-0.74%, Mn: 4.6-8.5%, Mo: 4.2-8.7%, W: 2.7-5.7%, Cu: 1.3-3.8%, P: less than 0.05%, S: less than 0.03%, with the balance being Fe and unavoidable impurities;

[0008] Shot peening is prepared by water atomization or gas atomization of molten steel with the above composition. The shot is then heated to 830-920℃ and held, followed by quenching to room temperature. The quenching cooling rate is V1≤V≤V2, in ℃ / s, where:

[0009] V1=7.65*ln(151.2-3.56*[C]-2.15*[Si]-6.24*[Mn]-5.71*[Mo]-3.05*[W]-0.98*[Cu])+14.5;

[0010] V2=44.2+27.4*[C]-11.2*[Si]-3.24*[Mn]+3.55*[Mo]+2.16*[W]-2.84*[Cu];

[0011] In the formula, [C], [Si], [Mn], [Mo], [W], and [Cu] represent the mass percentage content of C, Si, Mn, Mo, W, and Cu, respectively.

[0012] The purpose of selecting the shot peening composition and quenching process parameters in this invention is explained below.

[0013] C: Carbon is an important austenite forming element and an element that improves hardenability, used to ensure the acquisition of austenite structure at room temperature. At the same time, C is also an important element for ensuring strength and wear resistance. The C content in this invention is controlled at 0.68-1.20%.

[0014] Si: Silicon is also an element that improves hardenability and ensures the stability of room temperature austenite. The Si content in this invention is controlled at 0.32-0.74%.

[0015] Mn: Manganese is a powerful element that improves hardenability and can effectively promote the formation of austenite, ensuring the stability of austenite at room temperature. At the same time, manganese can ensure that shot peening has excellent strength and wear resistance. Moreover, manganese is relatively inexpensive. Therefore, this invention adds a large amount of manganese, with an addition amount of 4.6-8.5%.

[0016] Mo: Molybdenum has the effect of improving hardenability and can also improve the strength of shot peening through solid solution strengthening. Molybdenum has an excellent effect on improving the wear resistance of shot peening. The amount of molybdenum added in this invention is 4.2-8.7%.

[0017] W: Tungsten has a similar effect to molybdenum, specifically improving hardenability. It can enhance the strength of shot peening through solid solution strengthening. Tungsten has a very significant effect on improving the wear resistance of shot peening. The amount of tungsten added in this invention is 2.7-5.7%.

[0018] Cu: Copper is also an element that improves hardenability. Copper can improve the strength and wear resistance of shot peening. The copper content in this invention is 1.3-3.8%.

[0019] P, S: Phosphorus and sulfur are unavoidable impurity elements in steel. Their presence affects the strength and wear resistance of steel. Under the condition that the cost is acceptable and the process conditions allow, the content of phosphorus and sulfur should be reduced as much as possible. Considering cost factors and manufacturing conditions, the phosphorus content of this invention is limited to below 0.05% and the sulfur content is limited to below 0.03%.

[0020] By combining the aforementioned elements and atomizing the molten steel, shot peening with high wear resistance and a room-temperature austenitic structure can be achieved. However, as mentioned earlier, the cooling rate of the atomization process is too fast, making the shot prone to breakage due to impact during subsequent use. Through continuous experimentation in actual production, the inventors of this invention discovered that by rationally controlling the cooling rate in conjunction with the specific shot peening composition, it is possible to ensure a room-temperature austenitic structure while maintaining good integrity even during high-speed, long-term, and repeated collisions between the shot and the metal surface or between the shot and other shot particles during subsequent use. This ensures that the shot does not break after long-term use and exhibits satisfactory durability.

[0021] In fact, the cooling rate is extremely high during atomization, and it is quite difficult to control the cooling rate within a suitable range during atomization. Therefore, this invention proposes to quench the shot after it has been prepared by atomization, and to control the cooling rate during the quenching stage, so as to ensure that the shot has a room temperature austenitic structure and that the shot remains intact and does not break after long-term use.

[0022] Based on repeated experiments, the inventors obtained the appropriate range of quenching cooling rates for the shot peening composition of this invention, namely V1≤V≤V2. Through experiments and induction, the inventors derived the following values: V1=7.65*ln(151.2-3.56*[C]-2.15*[Si]-6.24*[Mn]-5.71*[Mo]-3.05*[W]-0.98*[Cu])+14.5; V2=44.2+27.4*[C]-11. 2*[Si]-3.24*[Mn]+3.55*[Mo]+2.16*[W]-2.84*[Cu]; The inventors discovered that if the quenching cooling rate V < V1, no shot peening with a completely room-temperature austenitic structure is obtained after quenching, ultimately leading to insufficient wear resistance. If the quenching cooling rate V > V2, the risk and probability of shot breakage and damage increase during subsequent use, failing to meet the requirements for long-term operation and resulting in insufficient service durability. By controlling the cooling rate of the shot peening containing the composition of this invention within V1-V2 during subsequent quenching, it is possible to ensure the acquisition of a room-temperature austenitic structure, thereby giving the shot peening excellent wear resistance, and also to ensure that it is not prone to breakage and fracture during use, greatly improving the service durability of the shot peening.

[0023] As previously described, the shot peening of the present invention produces an austenitic structure at room temperature. After atomization, the shot diameter obtained by the present invention is 0.5-6 mm. Atomization is preferably gas atomization, and the atmosphere for gas atomization should preferably be a non-oxidizing atmosphere, such as N2, Ar, or a mixture of N2 and Ar. As a further description, the holding time in the quenching treatment after atomization of the shot peening of the present invention is 5-60 min to ensure that a fully austenitic structure is obtained before quenching.

[0024] As a further option, the shot peening of the present invention exhibits excellent wear resistance and service durability, making it particularly suitable for surface modification or surface cleaning of metallic materials. Surface modification can specifically include surface hardening, and surface cleaning includes at least the following cleaning operations: removal of surface oxide scale, surface polishing, surface rust removal, and removal of surface coatings.

[0025] As another aspect of the present invention, the present invention also provides a method for preparing the aforementioned shot peening, specifically comprising melting a steel molten having the aforementioned composition, then atomizing the steel molten with water or gas to prepare shot peening, then heating the shot peening to 830-920℃ and holding it at that temperature, followed by quenching to room temperature, wherein the quenching cooling rate is V1≤V≤V2, in °C / s, wherein:

[0026] V1=7.65*ln(151.2-3.56*[C]-2.15*[Si]-6.24*[Mn]-5.71*[Mo]-3.05*[W]-0.98*[Cu])+14.5;

[0027] V2=44.2+27.4*[C]-11.2*[Si]-3.24*[Mn]+3.55*[Mo]+2.16*[W]-2.84*[Cu];

[0028] In the formula, [C], [Si], [Mn], [Mo], [W], and [Cu] represent the mass percentage content of C, Si, Mn, Mo, W, and Cu, respectively.

[0029] The preparation method of the present invention is simple and practical. No tempering or annealing process is required after the quenching process. The quenched shot peening can be used directly for the corresponding working conditions.

[0030] The beneficial effects of this invention are as follows.

[0031] This invention, through component control and the addition of a quenching process after atomization and control of the quenching cooling rate, ensures that the shot peening exhibits a room-temperature austenitic structure, resulting in excellent wear resistance. Furthermore, even after long-term use, the shot remains undamaged and does not fracture, demonstrating exceptional durability. This shot peening method is suitable for surface hardening, surface cleaning, and other similar applications. Detailed Implementation

[0032] To enable those skilled in the art to fully understand the technical solution and beneficial effects of the present invention, the following detailed explanation is provided in conjunction with specific experimental examples.

[0033] The molten steel was smelted according to the composition in Table 1. The P and S content was controlled at 0.02% ± 0.005% to be qualified. Ar atomization shot was then performed. The prepared shot was sieved, and the shot with a diameter of 3-4 mm was selected for subsequent quenching treatment (some groups did not undergo quenching treatment). Then, wear resistance simulation test and durability simulation test were performed on the shot. The relevant quenching treatment parameters and simulation test results are shown in Table 2.

[0034] (1) Wear resistance simulation test

[0035] For each sample group, 100 smooth and intact shot peening particles were taken and their initial weight W0 was measured. They were then placed together with 100 zirconia balls with a diameter of 3-4 mm in a planetary ball mill and ball-milled at 300 rpm for 5 hours. After that, the particles were taken out, washed with deionized water, dried, and the weight W1 of the shot peening particles after milling was measured. The wear resistance (i.e., weight loss) R = (W0-W1) / W0*100%. The smaller the R value, the better the wear resistance. Samples with an R value ≤5% are considered to meet the wear resistance requirements of this invention.

[0036] (2) Durability simulation test

[0037] For each sample group, 100 smooth and intact shot peening particles were placed in a vibratory ball mill and vibrated at a frequency of 800 rpm for 90 minutes without inserting grinding balls. After that, the shot peening particles were removed, and the number N of shot peening particles with surface defects or damage was observed and counted by the naked eye. The smaller N is, the better the durability of the shot peening particles. Samples with N value ≤ 5 are considered to meet the durability requirements of this invention.

[0038] Table 1. Composition of each shot peening element (by mass percentage, %).

[0039]

[0040] Table 2 Quenching parameters and performance test results for each shot peening process.

[0041]

[0042] The following analysis will be conducted in conjunction with Tables 1 and 2.

[0043] First, we analyze the effects of the quenching process after atomized shot formation and the quenching cooling rate on shot peening performance.

[0044] The shot peening components of test numbers 1-8 all meet the component requirements of this invention, but the subsequent processing technology is different, resulting in differences in the final shot peening performance.

[0045] Comparative Examples 1-2 and 2-2 have the same composition, quenching temperature, and holding time as Examples 1-1 and 2-1, respectively. However, because their cooling rate after quenching is lower than V1 required by the invention, although the durability simulation test results of shot peening can meet the requirements of the invention, their wear resistance is poor and cannot meet the requirements of the invention.

[0046] Comparative Examples 1-3 and 2-3 have the same composition, quenching temperature, and holding time as Examples 1-1 and 2-1, respectively. However, because their cooling rate after quenching is higher than V2 required by the invention, although the shot peening has better wear resistance, a large number of shot fragments are damaged or broken in the durability simulation test, which does not meet the requirements of the invention.

[0047] Comparative Examples 5-2 and 6-2 have the same composition as Examples 5-1 and 6-1, respectively. However, neither of them underwent quenching after atomization. Although the shot peening has good wear resistance, the number of broken or shattered shot pieces was relatively large in the durability simulation test, which did not meet the requirements of the invention.

[0048] Comparative Examples 7-1 and 8-1 have the same composition, quenching temperature and holding time as Examples 7-2 (7-3) and 8-2 (8-3), respectively. However, since their cooling rate after quenching is lower than V1 required by the invention, although the durability simulation test results of shot peening can meet the requirements of the invention, their wear resistance is poor and cannot meet the requirements of the invention.

[0049] Comparative Examples 7-4 and 8-4 have the same composition, quenching temperature, and holding time as Examples 7-2 (7-3) and 8-2 (8-3), respectively. However, because their cooling rate after quenching is higher than V2 required by the invention, although the wear resistance of the shot peening is better, the number of broken or fragmented shot pieces in the durability simulation test is large, which does not meet the requirements of the invention.

[0050] Therefore, quenching after atomized shot formation and controlling the quenching cooling rate within a reasonable range can ensure that shot peening has excellent wear resistance and service durability.

[0051] Secondly, the important influence of matching the shot peening composition and quenching cooling rate of the present invention on obtaining wear-resistant and durable shot peening is analyzed and explained.

[0052] Comparative Examples 9, 11, 13, 15, 17, and 19 are comparative examples of Examples 1, 2, 3, 4, 5, and 6, respectively. Each comparative example changed the content of C, Si, Mn, Mo, W, and Cu relative to the corresponding examples. The content range of the above elements after the change is lower than the requirements of the invention, and their quenching cooling rate can still meet the range of V1-V2 calculated according to the invention. However, even if the quenching cooling rate range proposed by the invention is followed, satisfactory wear resistance cannot be obtained in the end.

[0053] Comparative Examples 10, 12, 14, 16, 18, and 20 are comparative examples of Examples 1, 2, 3, 4, 5, and 6, respectively. Each comparative example changed the content of C, Si, Mn, Mo, W, and Cu compared to the corresponding examples. The content range of the above elements after the change is higher than the requirements of the invention, and their quenching cooling rate can still meet the range of V1-V2 calculated according to the invention. However, even if the cooling is carried out according to the quenching cooling rate range proposed by the invention, the number of broken or fragmented pellets in the final durability simulation test is large, which cannot meet the requirements of the invention.

[0054] It can be seen that the quenching and cooling rate of the present invention needs to be matched with the composition in order to obtain shot peening that meets the wear resistance and durability requirements of the invention. Even if the composition outside the scope of the present invention is quenched and cooled to meet the requirements of the present invention, it will still be impossible to obtain shot peening that has both wear resistance and service durability.

[0055] The inventors of this invention optimized the shot peening composition, added a quenching process after atomization and controlled the quenching cooling rate, and summarized the quenching cooling rate suitable for the composition of this invention. By combining composition optimization and adjustment with process step parameter control, they finally obtained shot peening with both wear resistance and service durability.

[0056] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wear-resistant and durable shot peening agent, characterized in that, The composition of the shot peening agent, by mass percentage, is: C: 0.68-1.20%, Si: 0.32-0.74%, Mn: 4.6-8.5%, Mo: 4.2-8.7%, W: 2.7-5.7%, Cu: 1.3-3.8%, P: less than 0.05%, S: less than 0.03%, with the balance being Fe and unavoidable impurities; Shot peening is prepared by water atomization or gas atomization of molten steel with the above composition. The shot is then heated to 830-920℃ and held, followed by quenching to room temperature. The quenching cooling rate is V1≤V≤V2, in ℃ / s, where: V1=7.65*ln(151.2-3.56*[C]-2.15*[Si]-6.24*[Mn]-5.71*[Mo]-3.05*[W]-0.98*[Cu])+14.5; V2=44.2+27.4*[C]-11.2*[Si]-3.24*[Mn]+3.55*[Mo]+2.16*[W]-2.84*[Cu]; In the formula, [C], [Si], [Mn], [Mo], [W], and [Cu] represent the mass percentage content of C, Si, Mn, Mo, W, and Cu, respectively.

2. The wear-resistant and durable shot peening method according to claim 1, characterized in that, The shot peening has an austenitic structure at room temperature.

3. The wear-resistant and durable shot peening method according to claim 1, characterized in that, The diameter of the shot peening is 0.5-6 mm.

4. The wear-resistant and durable shot peening method according to claim 1, characterized in that, The heat preservation time is 5-60 minutes.

5. The wear-resistant and durable shot peening method according to claim 1, characterized in that, The gas atomization uses a non-oxidizing gas.

6. The wear-resistant and durable shot peening method according to claim 5, characterized in that, The non-oxidizing gas is N2, Ar, or a mixture of N2 and Ar.

7. The wear-resistant and durable shot peening method according to claim 1, characterized in that, The wear-resistant and durable shot peening is used for surface hardening or surface cleaning of metallic materials.

8. The wear-resistant and durable shot peening method according to claim 7, characterized in that, The surface cleaning includes removing surface oxide scale, surface polishing, surface rust removal, and removing surface coatings.

9. The method for preparing wear-resistant and durable shot peening according to any one of claims 1-8, characterized in that, Shot peening is prepared by melting molten steel with the appropriate composition, followed by water atomization or gas atomization. The shot is then heated to 830-920℃ and held, and subsequently quenched to room temperature. The quenching cooling rate is V1≤V≤V2, in ℃ / s. V1=7.65*ln(151.2-3.56*[C]-2.15*[Si]-6.24*[Mn]-5.71*[Mo]-3.05*[W]-0.98*[Cu])+14.5; V2=44.2+27.4*[C]-11.2*[Si]-3.24*[Mn]+3.55*[Mo]+2.16*[W]-2.84*[Cu]; In the formula, [C], [Si], [Mn], [Mo], [W], and [Cu] represent the mass percentage content of C, Si, Mn, Mo, W, and Cu, respectively.

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