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

Abstract

The invention discloses a heat treatment method for wear-resistant accessories of an ultra-large mining excavator, which comprises the following steps: heating the wear-resistant accessories of the ultra-large mining excavator to austenitizing temperature, and homogenizing; quenching the wear-resistant accessory subjected to homogenization treatment to room temperature to obtain the wear-resistant accessory with a martensitic structure; the wear-resistant accessory subjected to primary quenching is rapidly heated again to the temperature above the austenitizing temperature, heat preservation is conducted for a short time, complete austenitizing treatment is conducted, and the austenite structure does not grow obviously; secondary quenching is conducted, specifically, the abrasion-resistant accessory subjected to complete austenitizing treatment is rapidly cooled, so that the structure further contains a certain amount of retained austenite; the wear-resistant accessory subjected to secondary quenching is subjected to partitioning treatment, and air cooling is conducted to the room temperature after partitioning; carrying out subzero treatment on the wear-resistant accessory subjected to partitioning treatment, and then heating to room temperature; and tempering. Through the heat treatment process easy to implement, the wear-resistant accessory product with excellent performance is obtained, and the performance requirement of the wear-resistant accessory of the oversized excavator is met.

Description

Technical Field

[0001] The invention relates to a heat treatment method for wear-resistant accessories of a super-large mining excavator, belonging to the technical field of heat treatment of excavator accessories. Background Art

[0002] Wear-resistant accessories play a pivotal role in all kinds of engineering machinery, especially in high-load and high-wear working environments. Such accessories need to withstand long-term friction, impact and load, so the stability and durability of their performance are particularly important. Traditional wear-resistant accessories of ultra-large mining excavators (such as bucket teeth, bucket lip sleeves and wear-resistant caps, etc.) are mostly made of medium and low carbon alloy steels, and tempered martensite structures are obtained through normalizing and tempering heat treatment processes. Carbon content is a key factor affecting the mechanical properties of materials. Although high carbon content can bring excellent hardness and wear resistance, it often sacrifices impact toughness, making the material prone to cracking or surface fatigue under harsh working conditions; on the contrary, although low carbon content improves impact toughness, the reduction in hardness and wear resistance will lead to a shortened service life. In order to balance these performance contradictions, the industry has tried to improve the comprehensive performance of materials by adding alloy components such as Ni, Al and rare earth elements.

[0003] Patent document heat treatment process method for excavator bucket teeth (CN110846474A), including: step 100, austenitizing the excavator bucket teeth to obtain an excavator bucket tooth with an austenite structure; step 200, quenching the excavator bucket teeth with an austenite structure into a quenching medium below Ms, and heat-insulating to obtain an excavator bucket tooth with a martensite structure; step 300, quenching the excavator bucket teeth with a martensite structure into a quenching medium above Ms, and heat-insulating to obtain an excavator bucket tooth with a bainite structure, and then air-cooling. The microstructure of the excavator bucket teeth finally obtained by this heat treatment process is martensite + bainite + a small amount of film-like residual austenite, which significantly improves the surface hardness, impact toughness and wear resistance.

[0004] Patent document A high-strength bucket tooth steel for engineering machinery and its production method and heat treatment process (CN114182179A), including the following steps: blast furnace molten iron - converter - LF refining - RH vacuum degassing - continuous casting - hot rolling, and finally obtaining tempered martensite structure. In this scheme, the content of impurity elements such as P and S is controlled to be no more than 0.02%, with good yield strength and tensile strength, and not easy to deform and break in harsh working environment.

[0005] Patent document A bucket tooth for excavators and its preparation method (CN103498109B) includes a casting process and a heat treatment process, wherein the heat treatment process is that the quenching temperature is 900-950°C, the holding time after quenching is 2.0-4.0h, the tempering temperature is 230-260°C, and the tempering holding time is 3.0-4.0h. This invention makes the casting reach the conventional performance level, and the heat treatment process is easy to implement, the production process is relatively simple, and the energy consumption is low.

[0006] In traditional technology, low-carbon alloy steel is treated by quenching + tempering process, and its hardness, wear resistance and impact toughness are difficult to balance. Especially in the application of ultra-large tonnage excavators, it cannot meet the performance requirements of wear-resistant accessories such as bucket teeth, bucket lip sleeves and wear-resistant caps. Although the addition of high alloy content components can improve impact toughness, it will lead to increased costs and affect market competitiveness. Therefore, for wear-resistant accessories such as excavator bucket teeth, it is urgent to develop a heat treatment process that is not only easy to implement, but more importantly, it is necessary to ensure that the treated wear-resistant accessories can achieve a new balance in the three core performance indicators of hardness, toughness and wear resistance, so as to meet the increasingly stringent engineering application needs. Summary of the invention

[0007] In view of the problems existing in the above-mentioned prior art, the present invention provides a heat treatment method for wear-resistant accessories of super-large mining excavators. Through an easy-to-implement heat treatment process, wear-resistant accessories products with excellent performance are obtained to meet the performance requirements of wear-resistant accessories of super-large excavators.

[0008] In order to achieve the above object, the present invention adopts a heat treatment method for wear-resistant accessories of a super-large mining excavator, comprising the following steps:

[0009] S1. Homogenization treatment: heating the wear-resistant parts of the super-large mining excavator to the austenitizing temperature and performing homogenization treatment;

[0010] S2, primary quenching: quenching the wear-resistant parts after homogenization to room temperature to obtain wear-resistant parts with martensitic structure;

[0011] S3, rapid heating and organization refinement treatment: the wear-resistant parts after the first quenching are quickly reheated to above the austenitizing temperature, and kept warm for a short time to perform complete austenitization treatment, and the austenite structure does not grow significantly;

[0012] S4, secondary quenching: the wear-resistant parts that have been completely austenitized are quickly cooled so that a certain amount of residual austenite is still contained in the structure;

[0013] S5, distribution treatment: the wear-resistant parts after secondary quenching are subjected to distribution treatment, and air-cooled to room temperature after distribution;

[0014] S6. Cryogenic treatment: subject the wear-resistant parts that have been subjected to the distribution treatment to cryogenic treatment, and then heat them 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 the quenching in step S2 is any one of water, oil, and water-soluble quenching liquid.

[0018] In some embodiments, step S3 specifically includes: re-heating the wear-resistant parts after the first quenching to 870-900°C quickly, keeping warm 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 80-160° C. / s.

[0020] In some embodiments, the distribution temperature in step S5 is controlled at 360-400° C., and the distribution 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 insulation time is 6.0 to 12.0 hours.

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

[0023] In some embodiments, 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 content of austenite in the structure of the wear-resistant parts is not less than 30%.

[0024] In some embodiments, when the mass percentage of carbon element in the wear-resistant fittings is 0.15-0.25%, the primary quenching temperature is controlled at 900-930°C, the tempering temperature is controlled at 260-300°C, and the tempering time is 4.0-8.0h;

[0025] When the mass percentage of carbon element in wear-resistant accessories is between 0.30 and 0.40%, the primary quenching temperature is controlled at 950 to 970°C, the tempering temperature is controlled at 180 to 220°C, and the tempering time is 4.0 to 8.0 hours.

[0026] In some embodiments, when the 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, and the impact toughness is A KV ≥40.0J, -40℃ impact toughness A KV ≥25.0J.

[0027] In some embodiments, when the wear-resistant accessories 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, and the impact toughness is A KV ≥30.0J, -40℃ impact toughness A KV ≥18.0J.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The double quenching + rapid heating technology combination is adopted. After obtaining martensite through the first quenching, the wear-resistant accessories are quickly heated to above the austenitizing temperature, and short-term heat preservation is carried out to achieve fine and uniform austenite grains. The second quenching forms a fine 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 partitioning treatment and cryogenic treatment work together. The partitioning treatment promotes the diffusion of carbon into the residual austenite, and the cryogenic treatment further stabilizes the structure and eliminates internal stress, comprehensively improving the hardness and impact resistance, so that the accessories can maintain excellent dimensional stability and mechanical properties under extreme temperature differences and complex working conditions, thereby 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 formulating specific heat treatment plans for wear-resistant accessories with different carbon contents, it is possible to achieve precise regulation of the performance of wear-resistant accessories, meet the stringent requirements of ultra-large tonnage excavators for wear-resistant accessories in terms of hardness, toughness and wear resistance, improve the overall working efficiency and service life of the excavator, and reduce the cost of maintenance and replacement at the same time, with significant economic benefits and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

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

[0034] Figure 2 This is a schematic diagram of the method flow of Example 1 of the present invention;

[0035] Figure 3 This is the metallographic structure diagram of Example 1 of the present invention;

[0036] Figure 4 This is the XRD diagram of Example 1 of the present invention. DETAILED DESCRIPTION

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

[0038] like Figure 1 As shown, a heat treatment method for wear-resistant parts of a super-large mining excavator comprises the following steps:

[0039] S1. Homogenization treatment: Heat the wear-resistant parts of the super-large mining excavator to the austenitizing temperature and perform homogenization treatment. The homogenization temperature is 900-1200°C and the insulation time is 2.0-4.0h;

[0040] S2, primary quenching: quenching the wear-resistant parts after homogenization to room temperature to obtain wear-resistant parts with martensite structure, and the quenching medium used during quenching is any one of water, oil and water-soluble quenching liquid;

[0041] S3, rapid heating and organization refinement treatment: the wear-resistant parts after the primary quenching are rapidly reheated to 870-900°C at a rate of 80-160°C / s, and kept at this temperature for 0-30.0min to perform complete austenitization treatment until the austenite structure does not grow significantly and the austenite grain size is less than 20.0μm;

[0042] The inventors found that when the heating rate of the rapid heating microstructure refinement treatment is controlled at 80-160°C / s, the microstructure after subsequent quenching is more uniform; when the temperature is less than 80°C / s, incomplete austenitization results in larger grains, which affects the hardness and wear resistance of the material; when the temperature is greater than 160°C / s, the temperature distribution inside the material is uneven, resulting in internal stress; a heating rate of 80-160°C / s can ensure the uniformity of the austenitization process and avoid grain growth, thereby forming a finer and more uniform martensitic microstructure in the subsequent cooling process;

[0043] S4, secondary quenching: the wear-resistant parts that have been completely austenitized are quickly cooled so that a certain amount of residual austenite is still contained in the structure;

[0044] The inventors have found that after the first quenching, the wear-resistant parts are quickly heated to above the austenitizing temperature point for a short time insulation, and then subjected to the second quenching, which can effectively improve the uniformity of austenite, so that the material forms a finer and more uniform martensite or bainite structure during the cooling process, so that the strength and hardness of the material are improved, and the wear resistance and impact resistance of the material are increased. Especially under high-load working conditions, the refined structure can better withstand impact and wear, and significantly improve the crack resistance of the material under extreme working conditions;

[0045] S5. Partitioning treatment: The wear-resistant parts after secondary quenching are subjected to partitioning treatment, and air-cooled to room temperature after partitioning. The partitioning temperature is controlled at 360-400°C, and the partitioning time is 1.0-2.0h.

[0046] S6. Cryogenic treatment: The wear-resistant parts that have been subjected to the partitioning treatment are subjected to cryogenic treatment at a temperature of -80 to -160°C, and the holding time is 6.0 to 12.0 hours, and then the temperature is raised to room temperature; cryogenic treatment helps to homogenize the microstructure of the material, reduce the internal stress generated during the rapid cooling process, reduce the brittleness of the material, and increase its crack resistance and toughness; the material after cryogenic treatment can better maintain dimensional stability in extreme working environments, especially in extremely cold working environments, to avoid deformation or cracks caused by temperature differences;

[0047] S7. Tempering treatment.

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

[0049] In some embodiments, when the mass percentage of carbon elements in wear-resistant accessories is between 0.15% and 0.25%, 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 hours; when the mass percentage of carbon elements in wear-resistant accessories is between 0.30 and 0.40%, the primary quenching temperature is controlled at 950 to 970°C, the tempering temperature is controlled at 180 to 220°C, and the tempering time is 4.0 to 8.0 hours.

[0050] In some embodiments, when the 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, and the impact toughness is A KV ≥40.0J, -40℃ impact toughness A KV ≥25.0J.

[0051] In some embodiments, when the wear-resistant accessories 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, and the impact toughness is A KV ≥30.0J, -40℃ impact toughness A KV ≥18.0J.

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

[0053] Table 1 Heat treatment process parameters

[0054]

[0055] Table 2 Product performance of wear-resistant accessories after heat treatment

[0056]

[0057] Example 1

[0058] Refer to the process parameters shown in Table 1 for heat treatment. The specific process is as follows: Figure 2 As shown, the metallographic structure of the wear-resistant accessories is as follows Figure 3 As shown in the figure, the structure of the product of Example 1 is martensite + ferrite structure; the XRD diagram of the prepared wear-resistant accessories is as follows Figure 4 As shown in Table 2, the retained 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 with reference to the process parameters shown in Table 1, respectively, and the relevant mechanical property parameters are shown in Table 2.

[0060] It can be seen from Examples 1 to 9 and Comparative Examples 1 to 6 that the heat treatment method of the present invention significantly improves the performance of wear-resistant accessories for super-large mining excavators by adopting steps such as rapid heating, secondary quenching, and cryogenic treatment. Compared with the comparative example, the tensile strength, hardness, impact toughness, and -40°C impact toughness of the embodiment are significantly improved. The improvement of these properties makes the materials in the embodiment perform better in high-load, high-impact, and low-temperature working environments, meeting the stringent performance requirements of wear-resistant accessories for super-large mining excavators.

[0061] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A heat treatment method for wear-resistant accessories of super-large mining excavators, characterized in that: The following steps are involved: S1. Homogenization treatment: heating the wear-resistant parts of the super-large mining excavator to the austenitizing temperature and performing homogenization treatment; S2, primary quenching: quenching the wear-resistant parts after homogenization to room temperature to obtain wear-resistant parts with martensitic structure; S3, rapid heating and microstructure refinement treatment: the wear-resistant parts after the first quenching are quickly reheated to above the austenitizing temperature, and kept warm for a short time to perform complete austenitization treatment, and the austenite structure does not grow significantly; S4, secondary quenching: the wear-resistant parts that have been completely austenitized are quickly cooled so that a certain amount of residual austenite is still contained in the structure; S5, distribution treatment: the wear-resistant parts after secondary quenching are subjected to distribution treatment, and air-cooled to room temperature after distribution; S6. Cryogenic treatment: subject the wear-resistant parts that have been subjected to the distribution treatment to cryogenic treatment, and then heat them to room temperature; S7. Tempering treatment.

2. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1 is characterized in that: In the step S1, the homogenization temperature is 900-1200° C., and the insulation time is 2.0-4.0 h.

3. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1 is characterized in that: The quenching medium used in the quenching in step S2 is any one of water, oil, and water-soluble quenching liquid.

4. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1 is characterized in that: The step S3 specifically includes: re-heating the wear-resistant parts after the primary quenching to 870-900° C. quickly, keeping the temperature for 0-30.0 min, and performing a complete austenitization treatment until the austenite structure does not grow significantly and the austenite grain size is less than 20.0 μm.

5. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 4 is characterized in that: The rapid heating rate in step S3 is 80-160° C. / s.

6. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1 is characterized in that: In the step S5, the distribution temperature is controlled at 360-400° C., and the distribution time is 1.0-2.0 h.

7. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1 is characterized in that: In step S6, the cryogenic treatment temperature is -80 to -160°C, and the insulation time is 6.0 to 12.0 hours.

8. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1 is characterized in that: When the wear-resistant parts contain Si and Al elements, the wear-resistant parts have a structure of at least one of martensite, bainite and ferrite, and contain not less than 4.0% of retained austenite.

9. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1, characterized in that: When the wear-resistant accessories are C, Cr, Ni, or Mo alloy accessories, and the Cr content of the wear-resistant accessories is greater than 10%, the content of austenite in the wear-resistant accessory structure is not less than 30%.

10. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1, characterized in that: When the mass percentage of carbon element in wear-resistant parts is 0.15-0.25%, the primary quenching temperature is controlled at 900-930°C, the tempering temperature is controlled at 260-300°C, and the tempering time is 4.0-8.0h; When the mass percentage of carbon element in wear-resistant accessories is between 0.30 and 0.40%, the primary quenching temperature is controlled at 950 to 970°C, the tempering temperature is controlled at 180 to 220°C, and the tempering time is 4.0 to 8.0 hours.

11. The heat treatment method for wear-resistant accessories of a super-large mining excavator according to claim 1, characterized in that: When the 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, and the impact toughness is A KV ≥40.0J, -40℃ impact toughness A KV ≥25.0J.

12. The heat treatment method for wear-resistant parts of a super-large mining excavator according to claim 1, characterized in that: When the wear-resistant accessories 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, and the impact toughness is A KV ≥30.0J, -40℃ impact toughness A KV ≥18.0J.

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