Heat treatment method for wear-resistant accessory of ultra-large mining excavator

Abstract

Disclosed in the present invention is a heat treatment method for a wear-resistant accessory of an ultra-large mining excavator. The method comprises the steps of: heating a wear-resistant accessory of an ultra-large mining excavator to the austenitizing temperature thereof, and homogenizing same; quenching the homogenized wear-resistant accessory to room temperature to obtain a wear-resistant accessory having a martensitic structure; rapidly heating the wear-resistant accessory, which has been subjected to primary quenching, to the austenitizing temperature or above again, subjecting same to heat preservation for a short period of time, and performing a complete austenitizing treatment, wherein the austenite structure does not significantly grow; performing secondary quenching, involving: rapidly cooling the wear-resistant accessory, which has been subjected to a complete austenitizing treatment, such that the structure still contains a certain amount of retained austenite; subjecting the wear-resistant accessory, which has been subjected to secondary quenching, to a partitioning treatment, followed by air cooling to room temperature; subjecting the partitioned wear-resistant accessory to a cryogenic treatment, and then heating same to room temperature; and performing a tempering treatment. In the present invention, by means of a readily achievable heat treatment process, a wear-resistant accessory product having excellent performance is obtained, thereby satisfying the performance requirements of wear-resistant accessories for ultra-large excavators.

Description

A heat treatment method for wear-resistant parts of ultra-large mining excavators Technical Field

[0001] This invention relates to a heat treatment method for wear-resistant parts of ultra-large mining excavators, belonging to the field of excavator parts heat treatment technology. Background Technology

[0002] Wear-resistant parts play a crucial role in various engineering machinery, especially in high-load, high-wear working environments. These parts need to withstand prolonged friction, impact, and load, making their stable and durable performance paramount. Traditional wear-resistant parts for ultra-large mining excavators (such as bucket teeth, bucket lip sleeves, and wear caps) are mostly made of medium- and low-carbon alloy steel, using normalizing and tempering heat treatment processes to obtain a tempered martensitic structure. Carbon content is a key factor affecting the mechanical properties of materials. While high carbon content brings excellent hardness and wear resistance, it often sacrifices impact toughness, making the material prone to cracking or surface fatigue under harsh working conditions. Conversely, while low carbon content improves impact toughness, the reduction in hardness and wear resistance leads to a shorter service life. To balance these performance contradictions, the industry has attempted to improve the overall performance of materials by adding alloying elements such as Ni, Al, and rare earth elements.

[0003] The patent document describes a heat treatment process for excavator bucket teeth (CN110846474A), comprising: step 100, austenitizing the excavator bucket teeth to obtain excavator bucket teeth with an austenitic structure; step 200, quenching the excavator bucket teeth with the austenitic structure in a quenching medium below Ms and holding it at a certain temperature to obtain excavator bucket teeth with a martensitic structure; step 300, quenching the excavator bucket teeth with the martensitic structure in a quenching medium above Ms and holding it at a certain temperature to obtain excavator bucket teeth with a bainitic structure, followed by air cooling. The microstructure of the excavator bucket teeth finally obtained through this heat treatment process is martensite + bainite + a small amount of thin-film retained austenite, which significantly improves surface hardness, impact toughness, and wear resistance.

[0004] Patent document CN114182179A describes a high-strength bucket tooth steel for engineering machinery and its production method and heat treatment process, comprising the following steps: blast furnace hot metal—converter—LF refining—RH vacuum degassing—continuous casting—hot rolling, ultimately obtaining a tempered martensitic structure. In this scheme, the content of impurity elements such as P and S is controlled to be no higher than 0.02%, exhibiting good yield strength and tensile strength, and is not easily deformed or fractured under harsh working environments.

[0005] Patent document CN103498109B discloses an excavator bucket tooth and its manufacturing method, comprising a casting process and a heat treatment process. The heat treatment process involves a quenching temperature of 900–950℃, a holding time of 2.0–4.0 h after quenching, a tempering temperature of 230–260℃, and a tempering holding time of 3.0–4.0 h. This invention achieves conventional performance levels in the casting while the heat treatment process is easy to implement, the production process is relatively simple, and energy consumption is low.

[0006] Traditional heat treatment processes for low-carbon alloy steel, involving quenching and tempering, often result in a difficult balance between hardness, wear resistance, and impact toughness. This is particularly problematic in ultra-heavy-tonnage excavator applications, failing to meet the performance requirements of wear-resistant components such as bucket teeth, bucket lip sleeves, and wear caps. While adding high-alloy components can improve impact toughness, it increases costs and impacts market competitiveness. Therefore, there is an urgent need to develop a heat treatment process for wear-resistant components like excavator bucket teeth. This process must not only be easy to implement but, more importantly, ensure that the treated wear-resistant components achieve a new balance across the three core performance indicators of hardness, toughness, and wear resistance, thereby meeting the increasingly stringent engineering application demands. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a heat treatment method for wear-resistant parts of ultra-large mining excavators. Through an easily implemented heat treatment process, high-performance wear-resistant parts products are obtained, meeting the performance requirements of wear-resistant parts for ultra-large excavators.

[0008] To achieve the above objectives, the present invention employs a heat treatment method for wear-resistant parts of ultra-large mining excavators, comprising the following steps:

[0009] S1. Homogenization treatment: The wear-resistant parts of the ultra-large mining excavator are heated to the austenitizing temperature and then homogenized.

[0010] S2, First quenching: The wear-resistant parts after homogenization treatment are quenched to room temperature to obtain wear-resistant parts with martensitic structure;

[0011] S3. Rapid heating and microstructure refinement treatment: The wear-resistant parts that have been quenched once are rapidly reheated to above the austenitizing temperature, held for a short time, and fully austenitized, without significant growth of the austenite microstructure.

[0012] S4. Secondary quenching: The wear-resistant parts that have undergone complete austenitization are rapidly cooled so that the microstructure still contains a certain amount of residual austenite.

[0013] S5. Partitioning process: The wear-resistant parts that have undergone secondary quenching are partitioned and then air-cooled to room temperature.

[0014] S6. Cryogenic treatment: The wear-resistant parts that have undergone the fractionation treatment are subjected to cryogenic treatment and then heated to room temperature.

[0015] S7. Tempering treatment.

[0016] In some embodiments, the homogenization temperature in step S1 is 900–1200°C, and the holding time is 2.0–4.0 h.

[0017] In some embodiments, the quenching medium used in step S2 is any one of water, oil, or water-soluble quenching liquid.

[0018] In some embodiments, step S3 specifically includes: rapidly reheating the wear-resistant parts after one quenching to 870-900°C, holding for 0-30.0 min, and performing complete austenitization treatment until the austenite structure does not grow significantly and the austenite grain size is less than 20.0 μm.

[0019] In some embodiments, the rapid heating rate in step S3 is between 80 and 160 °C / s.

[0020] In some embodiments, the mixing temperature in step S5 is controlled at 360–400°C, and the mixing time is 1.0–2.0 h.

[0021] In some embodiments, the cryogenic treatment temperature in step S6 is -80 to -160°C, and the holding time is 6.0 to 12.0 hours.

[0022] In some embodiments, when the wear-resistant parts contain Si and Al elements, the microstructure of the wear-resistant parts is at least one of martensite, bainite and ferrite, and contains not less than 4.0% of residual austenite.

[0023] In some embodiments, when the wear-resistant part is a C, Cr, Ni, Mo alloy part, and the Cr content of the wear-resistant part is greater than 10%, the austenite content in the microstructure of the wear-resistant part is not less than 30%.

[0024] In some embodiments, when the carbon content of the wear-resistant parts is 0.15 to 0.25% by mass, the primary quenching temperature is controlled at 900 to 930°C, the tempering temperature is controlled at 260 to 300°C, and the tempering time is 4.0 to 8.0 h.

[0025] When the carbon content of wear-resistant parts is 0.30-0.40% by mass, the quenching temperature is controlled at 950-970℃, the tempering temperature is controlled at 180-220℃, and the tempering time is 4.0-8.0h.

[0026] In some embodiments, when the wear-resistant component is used as a bucket side guard, the yield strength is ≥1500MPa, the tensile strength is ≥1700MPa, the elongation is ≥10.0%, the Rockwell hardness is ≥42.0HRC, the impact toughness AKV is ≥40.0J, and the impact toughness AKV at -40℃ is ≥25.0J.

[0027] In some embodiments, when the wear-resistant components are used as bucket teeth, bucket lip sleeves, and wear-resistant caps, the yield strength is ≥1700MPa, the tensile strength is ≥1900MPa, the elongation is ≥8.0%, the Rockwell hardness is ≥51.0HRC, the impact toughness AKV is ≥30.0J, and the impact toughness AKV at -40℃ is ≥18.0J.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The combination of double quenching and rapid heating technology is adopted. After obtaining martensite through the first quenching, the wear-resistant parts are rapidly heated to above the austenitizing temperature and held for a short time to achieve fine and uniform austenite grains. The second quenching forms a dense martensite structure and retains a certain amount of residual austenite, which greatly improves the hardness, wear resistance and impact resistance of the material, ensuring stability and reliability under high load and high wear conditions.

[0030] 2. The combination of fractionation treatment and cryogenic treatment promotes carbon diffusion into the retained austenite, while cryogenic treatment further stabilizes the microstructure and eliminates internal stress, comprehensively improving hardness and impact resistance. This allows the parts to maintain excellent dimensional stability and mechanical properties under extreme temperature differences and complex working conditions, thus extending their service life.

[0031] 3. By precisely controlling various parameters in the heat treatment process, such as homogenization temperature, quenching medium, rapid heating rate, distribution temperature, cryogenic treatment temperature and time, and by formulating specific heat treatment schemes for wear-resistant parts with different carbon contents, it is possible to achieve precise control over the performance of wear-resistant parts, meet the stringent requirements of ultra-large tonnage excavators for wear-resistant parts in terms of hardness, toughness and wear resistance, improve the overall working efficiency and service life of excavators, and reduce maintenance and replacement costs, which has significant economic benefits and practical value. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 is a schematic diagram of the method flow of the present invention;

[0034] Figure 2 is a schematic flowchart of the method in Embodiment 1 of the present invention;

[0035] Figure 3 is a metallographic diagram of Embodiment 1 of the present invention;

[0036] Figure 4 is an XRD pattern of Embodiment 1 of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0038] As shown in Figure 1, a heat treatment method for wear-resistant parts of an ultra-large mining excavator includes the following steps:

[0039] S1. Homogenization treatment: The wear-resistant parts of the ultra-large mining excavator are heated to the austenitizing temperature and homogenized. The homogenization temperature is 900-1200℃ and the holding time is 2.0-4.0h.

[0040] S2, First quenching: The wear-resistant parts after homogenization treatment are quenched to room temperature to obtain wear-resistant parts with martensitic structure. The quenching medium used during quenching is any one of water, oil, or water-soluble quenching liquid.

[0041] S3. Rapid heating and microstructure refinement treatment: The wear-resistant parts after one quenching are rapidly reheated to 870-900℃ at a rate of 80-160℃ / s and held for 0-30.0 min to carry out complete austenitization treatment until the austenite microstructure does not grow significantly and the austenite grain size is less than 20.0μm.

[0042] The inventors discovered that when the heating rate of the rapid heating microstructure refinement process is controlled between 80 and 160°C / s, the microstructure after subsequent quenching is more uniform. When the temperature is less than 80°C / s, incomplete austenitization occurs, resulting in larger grains that affect the material's hardness and wear resistance. When the temperature is greater than 160°C / s, the internal temperature distribution of the material is uneven, generating internal stress. A heating rate of 80 to 160°C / s can ensure the uniformity of the austenitization process, prevent grain growth, and thus form a finer and more uniform martensitic microstructure during the subsequent cooling process.

[0043] S4. Secondary quenching: The wear-resistant parts that have undergone complete austenitization are rapidly cooled so that the microstructure still contains a certain amount of residual austenite.

[0044] The inventors discovered that after a first quenching, the wear-resistant parts are rapidly heated to above the austenitizing temperature and held for a short time before undergoing a second quenching. This effectively improves the uniformity of austenite, allowing the material to form a finer and more uniform martensite or bainite structure during cooling. This increases the strength and hardness of the material, while also enhancing its wear resistance and impact resistance. Especially under high-load working conditions, the refined structure can better withstand impact and wear, significantly improving the material's crack resistance under extreme conditions.

[0045] S5. Partitioning treatment: The wear-resistant parts that have undergone secondary quenching are partitioned and then air-cooled to room temperature. The partitioning temperature is controlled at 360-400℃ and the partitioning time is 1.0-2.0h.

[0046] S6. Cryogenic Treatment: The wear-resistant parts that have undergone fractionation treatment are subjected to cryogenic treatment at a temperature of -80 to -160°C for 6.0 to 12.0 hours, followed by heating to room temperature. Cryogenic treatment helps to homogenize the microstructure of the material, reduce internal stress generated during rapid cooling, reduce the brittleness of the material, and increase its crack resistance and toughness. Materials that have undergone cryogenic treatment can better maintain dimensional stability under extreme working environments, especially in extremely cold working environments, avoiding deformation or cracks caused by temperature differences.

[0047] S7. Tempering treatment.

[0048] In some embodiments, when the wear-resistant parts contain Si and Al elements, the microstructure of the wear-resistant parts is at least one of martensite, bainite, and ferrite, and contains not less than 4.0% (volume fraction) of retained austenite. When the wear-resistant parts are C, Cr, Ni, and Mo alloy parts, and the Cr content of the wear-resistant parts is greater than 10%, the austenite content in the microstructure of the wear-resistant parts is not less than 30%. This invention controls austenitization and cooling rate through secondary quenching to ensure that the microstructure contains a certain amount of retained austenite. During use, the retained austenite transforms into martensite, producing a self-sharpening effect, further improving surface hardness and wear resistance.

[0049] In some embodiments, when the carbon content of the wear-resistant parts is 0.15–0.25% by mass, the primary quenching temperature is controlled at 900–930°C, the tempering temperature is controlled at 260–300°C, and the tempering time is 4.0–8.0 h; when the carbon content of the wear-resistant parts is 0.30–0.40% by mass, the primary quenching temperature is controlled at 950–970°C, the tempering temperature is controlled at 180–220°C, and the tempering time is 4.0–8.0 h.

[0050] In some embodiments, when the wear-resistant component is used as a bucket side guard, the yield strength is ≥1500MPa, the tensile strength is ≥1700MPa, the elongation is ≥10.0%, the Rockwell hardness is ≥42.0HRC, the impact toughness AKV is ≥40.0J, and the impact toughness AKV at -40℃ is ≥25.0J.

[0051] In some embodiments, when the wear-resistant components are used as bucket teeth, bucket lip sleeves, and wear-resistant caps, the yield strength is ≥1700MPa, the tensile strength is ≥1900MPa, the elongation is ≥8.0%, the Rockwell hardness is ≥51.0HRC, the impact toughness AKV is ≥30.0J, and the impact toughness AKV at -40℃ is ≥18.0J.

[0052] The heat treatment methods for wear-resistant parts of ultra-large mining excavators in Examples 1-9 and Comparative Examples 1-6 are shown in Table 1, and the relevant parameters are shown in Table 2. The carbon content of the wear-resistant parts (bucket side guards) in Examples 1-5 and Comparative Examples 1-3 is 0.15-0.25%; the carbon content of the wear-resistant parts (bucket teeth, bucket lip sleeves, and wear caps) in Examples 6-9 and Comparative Examples 4-6 is 0.30-0.40%.

[0053] Table 1 Heat treatment process parameters

[0054]

[0055] Table 2 Performance of Wear-Resistant Parts After Heat Treatment

[0056]

[0057] Example 1

[0058] The heat treatment was performed according to the process parameters shown in Table 1. The specific process is shown in Figure 2. The metallographic structure of the obtained wear-resistant parts is shown in Figure 3. From the figure, it can be seen that the microstructure of the product of Example 1 is martensite + ferrite. The XRD pattern of the obtained wear-resistant parts is shown in Figure 4. By calculation, the residual austenite content of Example 1 is 8.42%. Other mechanical property parameters are shown in Table 2.

[0059] Examples 2 to 9 and Comparative Examples 1 to 6 were heat-treated according to the process parameters shown in Table 1, and the relevant mechanical performance parameters are shown in Table 2.

[0060] As can be seen from Examples 1-9 and Comparative Examples 1-6, the heat treatment method of the present invention significantly improves the performance of wear-resistant parts for ultra-large mining excavators by employing steps such as rapid heating, secondary quenching, and deep cryogenic treatment. Compared with the comparative examples, the tensile strength, hardness, impact toughness, and -40℃ impact toughness of the examples are all significantly improved. These performance improvements enable the materials in the examples to perform better in high-load, high-impact, and low-temperature working environments, meeting the stringent performance requirements of wear-resistant parts for ultra-large mining excavators.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method of heat treating a wear part for an ultra-class mining shovel, the method comprising: Includes the following steps: ​ S1. Homogenization treatment: The wear-resistant parts of the ultra-large mining excavator are heated to the austenitizing temperature and then homogenized. S2, First quenching: The wear-resistant parts after homogenization treatment are quenched to room temperature to obtain wear-resistant parts with martensitic structure; S3. Rapid heating and microstructure refinement treatment: The wear-resistant parts that have been quenched once are rapidly reheated to above the austenitizing temperature, held for a short time, and fully austenitized, without significant growth of the austenite microstructure. S4. Secondary quenching: The wear-resistant parts that have undergone complete austenitization are rapidly cooled so that the microstructure still contains a certain amount of residual austenite. S5. Partitioning process: The wear-resistant parts that have undergone secondary quenching are partitioned and then air-cooled to room temperature. S6. Cryogenic treatment: The wear-resistant parts that have undergone the fractionation treatment are subjected to cryogenic treatment and then heated to room temperature. S7. Tempering treatment.

2. A heat treatment method of a wear part of an ultra-class mining excavator according to claim 1, characterized in that, In step S1, the homogenization temperature is 900–1200℃ and the holding time is 2.0–4.0 h.

3. The heat treatment method of a wear part for super large mining excavators according to claim 1, characterized in that, The quenching medium used in step S2 is any one of water, oil, or water-soluble quenching liquid.

4. The method of claim 1, wherein the super large mining shovel wear part is a bucket lip. Step S3 specifically includes: rapidly reheating the wear-resistant parts after one quenching to 870-900℃, holding for 0-30.0 min, and performing complete austenitization treatment until the austenite structure does not grow significantly and the austenite grain size is less than 20.0 μm.

5. A heat treatment method of a wear part of an ultra-class mining shovel according to claim 4, characterized in that, The rapid heating rate in step S3 is 80–160 °C / s.

6. The method of heat treating a wear part for an ultra-class mining shovel according to claim 1, wherein, In step S5, the mixing temperature is controlled at 360–400℃, and the mixing time is 1.0–2.0 h.

7. The method of heat treating a wear part for an ultra-class mining shovel according to claim 1, wherein, In step S6, the cryogenic treatment temperature is -80 to -160°C, and the holding time is 6.0 to 12.0 hours.

8. The method of heat treating a wear part for an ultra-class mining shovel according to claim 1, wherein, When wear-resistant parts contain Si and Al elements, the microstructure of the wear-resistant parts is at least one of martensite, bainite and ferrite, and contains not less than 4.0% of residual austenite.

9. The method of heat treating a wear part for an ultra-class mining shovel according to claim 1, wherein, When the wear-resistant parts are C, Cr, Ni, Mo alloy parts, and the Cr content of the wear-resistant parts is greater than 10%, the austenite content in the microstructure of the wear-resistant parts shall not be less than 30%.

10. The method of claim 1, wherein the method is used for a wear part of an ultra-class mining shovel, and wherein the wear part is a bucket lip. When the carbon content of wear-resistant parts is between 0.15% and 0.25%, the quenching temperature should be controlled at 900 to 930℃, the tempering temperature at 260 to 300℃, and the tempering time at 4.0 to 8.0 hours. When the carbon content of wear-resistant parts is 0.30-0.40% by mass, the quenching temperature should be controlled at 950-970℃, the tempering temperature at 180-220℃, and the tempering time at 4.0-8.0h.

11. The method of heat treating a wear part for an ultra-class mining shovel according to claim 1, wherein, When wear-resistant parts are used as bucket side guards, the yield strength is ≥1500MPa, the tensile strength is ≥1700MPa, the elongation is ≥10.0%, the Rockwell hardness is ≥42.0HRC, the impact toughness AKV is ≥40.0J, and the impact toughness AKV at -40℃ is ≥25.0J.

12. The method of heat treating a super large mining shovel wear part according to claim 1, wherein, When the wear-resistant parts are used as bucket teeth, bucket lip sheaths and wear caps, the yield strength is ≥ 1700 MPa, the tensile strength is ≥ 1900 MPa, the elongation is ≥ 8.0%, the Rockwell hardness is ≥ 51.0 HRC, the impact toughness AKV is ≥ 30.0 J, and the impact toughness AKV at -40℃ is ≥ 18.0 J.

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