A wear-resistant and long-life shot peening

Abstract

This invention relates to a wear-resistant, long-life shot peening agent. The shot peening agent, by mass percentage, comprises: C: 0.55-1.0%, Si: 0.25-0.65%, Mn: 5.8-10.5%, Cr: 3.0-7.0%, Ni: 5.6-8.4%, B: 0.0015-0.004%, 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 820-900℃ and held, followed by quenching to room temperature at a quenching cooling rate of V1≤V≤V2. The unit is ℃ / s, where: V1=8.58*ln(103.8-11.27*[B]-5.78*[Mn]-3.16*[Cr]-1.88*[Si]-1.05*[Ni]-2.14*[C])+13.7; V2=37.5+3018*[B]-1.5*[Mn]+5.4*[Cr]-2.1*[Ni]-6.2*[Si]+37.9*[C]; where [C], [Si], [Mn], [Cr], [Ni], and [B] represent the mass percentage content of C, Si, Mn, Cr, Ni, and B, respectively.

Description

Technical Field

[0001] This invention relates to a wear-resistant, long-life shot peening material. The shot peening material has excellent wear resistance and the shot body will not break during long-term use, thus having a long service life. 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 surface. This results in damage after a short period of operation, insufficient service life, and the easy presence of surface defects during the surface treatment process.

[0004] Based on the aforementioned problems in the existing technology, this invention proposes a shot peening material that has excellent wear resistance, is not easily broken during use, and has a long service life. Summary of the Invention

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

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

[0007] This invention provides a wear-resistant, long-life shot peening material, wherein the composition of the shot peening material, by mass percentage, is: C: 0.55-1.0%, Si: 0.25-0.65%, Mn: 5.8-10.5%, Cr: 3.0-7.0%, Ni: 5.6-8.4%, B: 0.0015-0.004%, 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 820-900℃ and held, followed by quenching to room temperature. The quenching cooling rate is V1≤V≤V2, in ℃ / s, where:

[0009] V1=8.58*ln(103.8-11.27*[B]-5.78*[Mn]-3.16*[Cr]-1.88*[Si]-1.05*[Ni]-2.14*[C])+13.7;

[0010] V2=37.5+3018*[B]-1.5*[Mn]+5.4*[Cr]-2.1*[Ni] -6.2*[Si]+37.9*[C];

[0011] In the formula, [C], [Si], [Mn], [Cr], [Ni], and [B] represent the mass percentage content of C, Si, Mn, Cr, Ni, and B, 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 0.55-1.0%.

[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 0.25-0.65%.

[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 5.8-10.5%.

[0016] Cr: Chromium is also an element that improves hardenability, and chromium dissolved in steel can significantly increase strength. The carbides formed by chromium are also crucial for ensuring wear resistance. The chromium content in this invention is set at 3.0-7.0%.

[0017] Ni: Nickel is also an element that improves hardenability, which can effectively improve the strength and wear resistance of shot peening and ensure that shot peening has a room temperature austenitic structure. The nickel content of this invention is controlled at 5.6-8.4%.

[0018] B: Boron is a powerful element that improves hardenability. Even trace amounts of boron can significantly reduce the critical cooling rate of steel, thus playing a strong role in stabilizing austenite. At the same time, boron can effectively improve the strength and wear resistance of steel. The boron content in this invention is set to 0.0015-0.004%.

[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, the shot can maintain its room-temperature austenitic structure while ensuring good integrity even during high-speed, long-term, and repeated collisions between the shot and the metal surface or between the shot and other parts of the metal. This ensures that the shot does not break after long-term use and has a satisfactory service life.

[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: V1=8.58*ln(103.8-11.27*[B]-5.78*[Mn]-3.16*[Cr]-1.88*[Si]-1.05*[Ni]-2.14*[C])+13.7; V2=37.5+3018*[B]-1.5*[Mn]+5.4*[Cr]-2.1*[Ni] -6.2*[Si]+37.9*[C]; The inventors discovered that if the quenching cooling rate V < V1, no shot peening with a fully 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 life. 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, while also ensuring that it is not prone to breakage and fracture during use, greatly improving the service life 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 life, 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] It should be noted that the quenching process of the present invention does not require tempering or annealing, and the quenched shot peening can be directly used in the corresponding working conditions.

[0026] The beneficial effects of this invention are as follows.

[0027] 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, extending its service life. This shot peening method is suitable for surface hardening, surface cleaning, and other similar applications. Detailed Implementation

[0028] 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.

[0029] 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 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 life simulation test were performed on the shot. The relevant quenching treatment parameters and simulation test results are shown in Table 2.

[0030] (1) Wear resistance simulation test

[0031] 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 post-milling weight W1 of the shot peening particles 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.

[0032] (2) Life simulation test

[0033] 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. The smaller N is, the longer the shot peening life. Samples with N value ≤ 5 are considered to meet the life requirements of this invention.

[0034] Table 1. Composition of each shot peening element (by mass percentage, %).

[0035]

[0036] Table 2 Quenching parameters and performance test results for each shot peening process.

[0037]

[0038] The following analysis will be conducted in conjunction with Tables 1 and 2.

[0039] First, we analyze the effects of the quenching process after atomized shot formation and the quenching cooling rate on shot peening performance.

[0040] 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.

[0041] 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 life 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.

[0042] 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 life simulation test, which does not meet the requirements of the invention.

[0043] Comparative Examples 3-2 and 4-2 have the same composition as Examples 3-1 and 4-1, respectively. However, neither of them underwent quenching after atomization and shot blasting. Although the shot blasting has good wear resistance, the number of damaged or broken shot pieces was relatively large in the life simulation test, which could not meet the requirements of the invention.

[0044] 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 shot peening life simulation test results can meet the requirements of the invention, their wear resistance is poor and cannot meet the requirements of the invention.

[0045] 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 shot peening has better wear resistance, a large number of shot fragments are damaged or broken in the life simulation test, which does not meet the requirements of the invention.

[0046] 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 life.

[0047] Secondly, the important influence of matching the shot peening composition and quenching cooling rate of the present invention on obtaining wear-resistant and long-life shot peening is analyzed and explained.

[0048] 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, Cr, Ni, and B compared 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.

[0049] 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, Cr, Ni, and B compared to the corresponding examples. The range of the above-mentioned element contents after the change is higher than the requirements of the invention, and its 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 life simulation test is large, which cannot meet the requirements of the invention.

[0050] 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 life requirements of the invention. Even if the composition outside the scope of the present invention is quenched and cooled in accordance with the requirements of the present invention, it will still be impossible to obtain shot peening that has both wear resistance and life.

[0051] 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 material that has both wear resistance and service life.

[0052] 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.

[0053] 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, long-life shot peening agent, characterized in that, The composition of the shot peening agent, by mass percentage, is as follows: C: 0.55-1.0%, Si: 0.25-0.65%, Mn: 5.8-10.5%, Cr: 3.0-7.0%, Ni: 5.6-8.4%, B: 0.0015-0.004%, 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 820-900℃ and held, followed by quenching to room temperature. The quenching cooling rate is V1≤V≤V2, in ℃ / s, where: V1=8.58*ln(103.8-11.27*[B]-5.78*[Mn]-3.16*[Cr]-1.88*[Si]-1.05*[Ni]-2.14*[C])+13.7; V2=37.5+3018*[B]-1.5*[Mn]+5.4*[Cr]-2.1*[Ni] -6.2*[Si]+37.9*[C]; In the formula, [C], [Si], [Mn], [Cr], [Ni], and [B] represent the mass percentage content of C, Si, Mn, Cr, Ni, and B, respectively.

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

3. The wear-resistant, long-life 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, long-life shot peening according to claim 1, characterized in that, The heat preservation time is 5-60 minutes.

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

6. The wear-resistant, long-life shot peening 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, long-life shot peening according to claim 1, characterized in that, The wear-resistant, long-life shot peening is used for surface hardening or surface cleaning of metallic materials.

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

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