Off-highway wide-body mine car leaf spring and method of making same

Abstract

This invention discloses a non-highway wide-body mining car leaf spring and its preparation method. Its chemical composition, by mass percentage, includes: C 0.28%~0.32%, Si 1.10%~1.20%, Mn 1.20%~1.30%, P≤0.010%, S≤0.005%, Cr 1.00%~1.10%, Ti 0.010%~0.030%, Mo≤0.10%, Ni≤0.20%, Cu≤0.10%, Al 0.01%~0.04%, with the balance being Fe and unavoidable impurity elements. Matching the temperature and speed of the straightening machine during the continuous casting process helps to form a uniform and dense solidification structure, improving the internal homogeneity of the continuously cast billet. Precise control of the temperature and cooling rate at the entry and exit of the slow cooling pit during the billet slow cooling process reduces the problem of cracking in the continuously cast billet. The low-carbon design combined with the billet heating process can effectively solve the technical problem of complete decarburization of the surface of high-silicon steel. Quenching and tempering the heated variable cross-section rolled leaf springs helps to ensure the high toughness, low-temperature impact resistance and high fatigue life of the leaf springs, extending their service life to more than 180 days and reducing material and energy waste.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and in particular relates to a leaf spring for off-highway wide-body mining cars and its preparation method. Background Technology

[0002] Off-highway wide-body mining trucks are suitable for the efficient transportation needs of off-highway scenarios such as open-pit mines and large-scale earthwork projects. Its operation is characterized by extreme off-highway heavy-duty conditions, as follows: mostly unpaved dirt roads and gravel roads with many potholes, bumps and other harsh road surfaces, requiring frequent impact loads; steep slopes, requiring continuous high load output uphill and frequent braking downhill; large load fluctuations: when loading, the falling ore and rock will cause instantaneous impact on the truck bed; during driving, due to road undulations, the load fluctuates periodically, requiring high suspension load stability; extreme temperature and high-intensity continuous operation, running for 16 to 24 hours a day, with an annual mileage of 50,000 to 100,000 kilometers, the equipment needs to withstand high-frequency fatigue loads, and the leaf springs need to withstand tens of thousands of vibration cycles every day.

[0003] Therefore, leaf spring materials need to possess high strength, toughness, fatigue life, and low-temperature impact resistance. However, the service life of traditional mining truck leaf springs is currently only about 20-30 days, resulting in waste of materials and energy. In view of this, how to develop a technology that can improve the performance of leaf springs for off-highway wide-body mining trucks is the technical problem this invention aims to solve. Summary of the Invention

[0004] The purpose of this invention is to provide a leaf spring for off-highway wide-body mining cars and its manufacturing method, aiming to improve the performance of leaf springs for off-highway wide-body mining cars.

[0005] To solve the above-mentioned technical problems, the present invention is mainly achieved through the following technical solutions: In a first aspect, the present invention provides an off-highway wide-body mining car leaf spring, the chemical composition of which, by mass percentage, comprises: C 0.28%~0.32%, Si 1.10%~1.20%, Mn 1.20%~1.30%, P≤0.010%, S≤0.005%, Cr 1.00%~1.10%, Ti 0.010%~0.030%, Mo≤0.10%, Ni≤0.20%, Cu≤0.10%, Al 0.01%~0.04%, with the balance being Fe and unavoidable impurity elements.

[0006] In some embodiments of this application, the chemical composition, by mass percentage, includes: C 0.29%~0.30%, Si 1.13%~1.17%, Mn 1.23%~1.27%, P≤0.008%, S≤0.003%, Cr 1.03%~1.05%, Ti 0.018%~0.022%, Mo≤0.10%, Ni≤0.20%, Cu≤0.10%, Al 0.018%~0.022%, with the balance being Fe and unavoidable impurity elements.

[0007] In a second aspect, the present invention provides a method for preparing off-highway wide-body mining car leaf springs as described in any one of the embodiments of the first aspect above, comprising the following steps: primary refining, refining, vacuum degassing, continuous casting, slow cooling of steel billet, heating of steel billet, high-pressure water descaling, rolling, cooling bed cooling, blanking, heated variable cross-section rolling, quenching, tempering, stress shot blasting and electrophoresis. In the continuous casting process, the billet temperature entering the straightening machine is ≥980℃, and the drawing speed is 0.75~0.85m / min; in the billet slow cooling process, the billet temperature entering the slow cooling pit is ≥650℃, the temperature exiting the slow cooling pit is ≤150℃, and the cooling rate is ≤0.12℃ / s; in the billet heating process, the total heating time is 170~200min, the first heating temperature is 1150~1200℃, the second heating temperature and the soaking temperature are both 1200~1250℃, and the holding time is ≥120min; in the quenching process, the quenching oil temperature is 870~900℃, and the pressure quenching time is >230s; in the tempering process, the heating temperature is 360~390℃.

[0008] In some embodiments of this application, during the continuous casting step, the temperature of the billet entering the straightening machine is 980~990℃, and the casting speed is 0.78~0.82m / min.

[0009] In some embodiments of this application, during the slow cooling step of the billet, the billet temperature is 650~680℃ when it enters the slow cooling pit, the temperature when it exits the slow cooling pit is 100~150℃, and the cooling rate is 0.09~0.11℃ / s.

[0010] In some embodiments of this application, the total heating time in the billet heating step is 180~190 min, the temperature of the first heating stage is 1180~1200℃, the temperature of the second heating stage and the soaking stage are both 1230~1250℃, and the holding time is 130~145 min.

[0011] In some embodiments of this application, the billet size is 240mm × 300mm in the billet heating step.

[0012] In some embodiments of this application, during the quenching step, the oil quenching temperature is 880~890℃ and the pressure quenching time is 234~244s.

[0013] In some embodiments of this application, the heating temperature in the tempering step is 375~385°C.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: The off-highway wide-body mining car leaf spring disclosed in this invention is manufactured through processes including primary refining, refining, vacuum degassing, continuous casting, slow cooling of billets, heating of billets, high-pressure water descaling, rolling, cooling bed cooling, blanking, heated variable cross-section rolling, quenching, tempering, stress shot blasting, and electrophoresis. In the continuous casting step, matching the temperature and speed of the straightening machine helps to form a uniform and dense solidification structure, improving the internal homogeneity of the continuously cast billet. Precise control of the temperature and cooling rate at the entry and exit of the slow cooling pit in the slow cooling step solves the problem of cracking in continuously cast billets of low-carbon, high-silicon manganese-chromium steel. By adopting a low-carbon design combined with the billet heating step, the technical challenge of complete surface decarburization of high-silicon steel can be effectively solved, while reducing total surface decarburization, effectively ensuring that the flat steel has good internal and external quality. By quenching and tempering the heated variable cross-section rolled leaf springs, it is beneficial to ensure the high toughness, low temperature impact resistance and high fatigue life of the leaf springs, extending their service life to more than 180 days and reducing material and energy waste. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] In a first aspect, embodiments of this disclosure provide an off-highway wide-body mining car leaf spring, the chemical composition of which, by mass percentage, comprises: C 0.28%~0.32%, Si 1.10%~1.20%, Mn 1.20%~1.30%, P≤0.010%, S≤0.005%, Cr 1.00%~1.10%, Ti 0.010%~0.030%, Mo≤0.10%, Ni≤0.20%, Cu≤0.10%, Al 0.01%~0.04%, with the balance being Fe and unavoidable impurity elements.

[0017] In some embodiments of this application, the chemical composition, by mass percentage, includes: C 0.29%~0.30%, Si 1.13%~1.17%, Mn 1.23%~1.27%, P≤0.008%, S≤0.003%, Cr 1.03%~1.05%, Ti 0.018%~0.022%, Mo≤0.10%, Ni≤0.20%, Cu≤0.10%, Al 0.018%~0.022%, with the balance being Fe and unavoidable impurity elements.

[0018] In a second aspect, the present disclosure provides a method for preparing off-highway wide-body mining car leaf springs as described in any of the embodiments of the first aspect above, comprising the following steps: primary refining, refining, vacuum degassing, continuous casting, slow cooling of billets, heating of billets, high-pressure water descaling, rolling, cooling bed cooling, blanking, heated variable cross-section rolling, quenching, tempering, stress shot blasting, and electrophoresis.

[0019] Specifically, primary refining mainly involves melting scrap steel / molten iron, dephosphorizing, and decarburizing to adjust the chemical composition to a general range and raising the temperature of the molten steel to meet refining requirements. Refining mainly involves deoxidation and desulfurization, precisely adjusting alloying elements to the target range, and modifying harmful inclusions to make them easier to deform during later rolling rather than becoming crack sources. Vacuum degassing can remove gases from the molten steel, thereby achieving deep purification and precise tempering of the molten steel.

[0020] Specifically, in the continuous casting process, the temperature of the billet entering the straightening machine is ≥980℃, and the casting speed is 0.75~0.85m / min. The matching of temperature and casting speed in the continuous casting process helps to form a uniform and dense solidification structure, improve the internal homogeneity of the continuously cast billet, reduce center segregation and porosity, and avoid internal cracks and fractures.

[0021] Specifically, in the slow cooling process of the billet, the billet temperature is ≥650℃ when entering the slow cooling pit, and ≤150℃ when exiting the slow cooling pit, with a cooling rate ≤0.12℃ / s. Through precise control of the temperature and cooling rate when entering and exiting the slow cooling pit, the problem of cracking in low-carbon, high-silicon manganese-chromium steel is solved.

[0022] Specifically, in the billet heating process, the total heating time is 170~200min, the temperature of the first heating stage is 1150~1200℃, the temperature of the second heating stage and the soaking stage are both 1200~1250℃, and the holding time is ≥120min. By adopting a low-carbon design and combining it with the billet heating process, the technical problem of complete decarburization of the surface of high silicon steel can be effectively solved, while reducing the total surface decarburization and effectively ensuring that the flat steel has good internal and external quality.

[0023] Specifically, after the steel billet is heated, a layer of iron oxide scale composed of ferrous oxide, ferric oxide, and magnetite will form on its surface. The iron oxide scale has a different coefficient of thermal expansion than the steel billet substrate, which will affect the surface quality. High-pressure water descaling is used to remove scale. When the high-temperature steel billet comes into contact with water, a large amount of steam is generated instantly. The steam expands rapidly under the iron oxide scale, forming local high pressure, which accelerates the separation of the iron oxide scale from the steel billet substrate. High-pressure water descaling has no chemical pollution, low energy consumption, and minimal damage to the surface of the steel billet.

[0024] Specifically, in actual operation, the high-pressure water descaling system is synchronized with the rolling line, completing descaling instantly before the billet enters the rolling mill to avoid secondary oxidation.

[0025] In some embodiments of this application, the method for preparing off-highway wide-body mining car leaf springs further includes: cutting to length and packaging, wherein cutting to length and packaging are performed after the cooling bed cooling process and before the unloading process.

[0026] In some embodiments of this application, heated variable cross-section rolling includes heating at one end, rolling with variable cross-section at one end, heating at the other end, and rolling with variable cross-section at the other end.

[0027] Specifically, in the quenching step, the oil immersion temperature is 870~900℃, and the quenching time is >230s; in the tempering step, the heating temperature is 360~390℃. By quenching and tempering the heated variable cross-section rolled mine car leaf springs, it is beneficial to ensure the high toughness, low-temperature impact resistance, and high fatigue life of the mine car leaf springs, extending their service life to more than 180 days and reducing material and energy waste.

[0028] Specifically, stress shot blasting helps remove surface iron scale, increases residual stress on the leaf spring surface, and helps maintain the service life of the leaf spring.

[0029] Specifically, electrophoresis can form a protective film on the surface of the leaf spring to prevent corrosion during use.

[0030] In some embodiments of this application, during the continuous casting step, the temperature of the billet entering the straightening machine is 980~990℃, and the casting speed is 0.78~0.82m / min.

[0031] Specifically, matching the temperature and speed of the straightening machine helps prevent the formation of billet cracks during continuous casting.

[0032] In some embodiments of this application, during the slow cooling step of the billet, the billet temperature is 650~680℃ when it enters the slow cooling pit, the temperature when it exits the slow cooling pit is 100~150℃, and the cooling rate is 0.09~0.11℃ / s.

[0033] Specifically, slow cooling in a slow cooling pit helps to prevent the formation of cracks in the steel billet during the cooling process.

[0034] In some embodiments of this application, the billet size is 240mm × 300mm in the billet heating step.

[0035] In some embodiments of this application, the total heating time in the billet heating step is 180~190 min, the temperature of the first heating stage is 1180~1200℃, the temperature of the second heating stage and the soaking stage are both 1230~1250℃, and the holding time is 130~145 min.

[0036] Specifically, it helps reduce carbon diffusion loss on the surface of the billet, making the decarburized layer on the billet surface as thin as possible, and ensuring that the total decarburization is ≤0.15mm.

[0037] In some embodiments of this application, during the quenching step, the oil quenching temperature is 880~890℃ and the pressure quenching time is 234~244s.

[0038] Specifically, through quenching, the carbon and alloying elements inside are frozen in a supersaturated solid solution, forming a metastable structure of high-strength martensite, which can effectively prevent the initiation and propagation of fatigue cracks and help extend service life.

[0039] In some embodiments of this application, the heating temperature in the tempering step is 375~385°C.

[0040] Specifically, tempering can eliminate or significantly reduce internal stress, thereby reducing the risk of deformation and cracking during subsequent use.

[0041] Example 1: This example provides a non-highway wide-body mining car leaf spring, whose chemical composition by mass percentage includes: C: 0.29%, Si: 1.15%, Mn: 1.24%, P: 0.008%, S: 0.003%, Cr: 1.03%, Ti: 0.020%, Mo: 0.02%, Ni: 0.01%, Cu: 0.01%, Al: 0.022%, with the balance being Fe and unavoidable impurity elements.

[0042] The above-mentioned method for preparing off-highway wide-body mining car leaf springs includes the following steps: primary refining → refining → vacuum degassing → continuous casting → slow cooling of billets → heating of billets → high-pressure water descaling → rolling → cooling bed cooling → cutting to length and packaging → blanking → heating at one end → rolling with variable cross-section at one end → heating at the other end → rolling with variable cross-section at the other end → quenching → tempering → stress shot blasting → electrophoresis. Some specific steps are as follows: (1) Continuous casting: The billet temperature is 982℃ when it enters the straightening machine and the casting speed is 0.79m / min, resulting in a billet with no cracks on the surface.

[0043] (2) Slow cooling of billet: The billet temperature is 657℃ when it enters the slow cooling pit and 144℃ when it exits the slow cooling pit. The cooling rate is 0.11℃ / s, and the surface of the billet crack is free of cracks.

[0044] (3) Steel billet heating: The steel billet size is 240mm×300mm, the total heating time is 182min, the temperature of the first heating stage is 1188℃, the temperature of the second heating stage and the soaking stage are both 1248℃, and the holding time is 133min, so that the surface of the flat steel raw material is not completely decarburized, and the total decarburization is 0.15mm.

[0045] (4) Quenching and tempering: The quenching temperature is 885℃ and the quenching time is 238s; the heating temperature in the tempering step is 380℃.

[0046] Example 2: This example provides a non-highway wide-body mining car leaf spring, whose chemical composition by mass percentage includes: C: 0.30%, Si: 1.16%, Mn: 1.27%, P: 0.005%, S: 0.003%, Cr: 1.04%, Ti: 0.022%, Mo: 0.01%, Ni: 0.02%, Cu: 0.02%, Al: 0.022%, with the balance being Fe and unavoidable impurity elements.

[0047] The above-mentioned method for preparing off-highway wide-body mining car leaf springs includes the following steps: primary refining → refining → vacuum degassing → continuous casting → slow cooling of billets → heating of billets → high-pressure water descaling → rolling → cooling bed cooling → cutting to length and packaging → blanking → heating at one end → rolling with variable cross-section at one end → heating at the other end → rolling with variable cross-section at the other end → quenching → tempering → stress shot blasting → electrophoresis. Some specific steps are as follows: (1) Continuous casting: The billet temperature is 987℃ when it enters the straightening machine and the casting speed is 0.80m / min, resulting in a billet with no cracks on the surface.

[0048] (2) Slow cooling of billet: The billet temperature is 676℃ when it enters the slow cooling pit and 120℃ when it exits the slow cooling pit. The cooling rate is 0.10℃ / s, and the surface of the billet crack is free of cracks.

[0049] (3) Steel billet heating: The steel billet size is 240mm×300mm, the total heating time is 188min, the temperature of the first heating stage is 1200℃, the temperature of the second heating stage and the soaking stage are both 1250℃, the temperature ≥1200℃ is held for 142min, so that the surface of the flat steel raw material is not completely decarburized, and the total decarburization is 0.13mm.

[0050] (4) Quenching and tempering: The quenching temperature is 885℃ and the quenching time is 240s; the heating temperature in the tempering step is 375℃.

[0051] Comparative Example 1: A traditional mining car leaf spring, whose chemical composition by mass percentage includes: C: 0.51%, Si: 0.25%, Mn: 1.02%, P: 0.007%, S: 0.005%, Cr: 1.12%, V: 0.16%, Ti: 0.005%, Mo: 0.01%, Ni: 0.01%, Cu: 0.01%, Al: 0.014%, with the balance being Fe and unavoidable impurity elements.

[0052] The traditional method for preparing mine car leaf springs includes the following steps: primary refining → refining → vacuum degassing → continuous casting → slow cooling of billet → heating of billet → high-pressure water descaling → rolling → cooling bed cooling → cutting to length and packaging → blanking → heating at one end → rolling with variable cross-section at one end → heating at the other end → rolling with variable cross-section at the other end → quenching → tempering → stress shot blasting → electrophoresis.

[0053] (1) Continuous casting: The billet temperature is 964℃ when it enters the straightening machine and the casting speed is 0.72m / min.

[0054] (2) Slow cooling of billet: The billet temperature is 650℃ when it enters the slow cooling pit and 90℃ when it exits the slow cooling pit. The cooling rate is 0.19℃ / s.

[0055] (3) Steel billet heating: The steel billet size is 240mm×300mm, the total heating time is 243min, the temperature of the first heating stage is 1021℃, the temperature of the second heating stage and the soaking stage are both 1131℃, and the holding time is 122min, so that the surface of the flat steel raw material is not completely decarburized, and the total decarburization is 0.21mm.

[0056] (4) Quenching and tempering: The quenching temperature is 862℃ and the quenching time is 253s; the heating temperature in the tempering step is 455℃.

[0057] Performance Test 1: According to the provisions of GB / T 228.1-2021, the mechanical properties of the mine car leaf springs prepared in Example 1, Example 2 and Comparative Example 1 were tested. The test results are shown in Table 1.

[0058] As shown in Table 1, the tensile strength Rm of Example 1 is 1653 MPa, the tensile strength of Example 2 is 1661 MPa, and the tensile strength of Comparative Example 1 is 1664 MPa. The tensile strengths of the three are basically consistent and are all greater than 1650 MPa. The elongation at break A of Examples 1 and 2 is higher than 12%, and the reduction of area Z value is higher than 55%. The elongation at break A and reduction of area Z of Examples 1 and 2 are higher than those of Comparative Example 1, indicating that the leaf springs of Examples 1 and 2 have stronger plastic deformation capacity than Comparative Example 1, and the mine car leaf springs prepared by the method of this application have better toughness.

[0059] Performance Test 2: According to the provisions of GB / T 229-2020, impact tests were conducted on the mine car leaf springs prepared in Example 1, Example 2, and Comparative Example 1. The test results are shown in Table 2.

[0060] As can be seen from Table 2, the mine car leaf springs prepared in Examples 1 and 2 have a U-shaped impact energy of over 55 J at -40℃, while the mine car leaf spring of Comparative Example 1 has a U-shaped impact energy of only 20.4 J at -40℃. The mine car leaf springs prepared in Examples 1 and 2 have a V-shaped impact energy of over 35 J at -40℃, while the mine car leaf spring of Comparative Example 1 has a V-shaped impact energy of only 14.2 J at -40℃. Furthermore, the U-shaped and V-shaped notch impact energies at 23℃ and -20℃ are also higher than those of Comparative Example 1. It can be concluded that the impact performance of the mine car leaf springs prepared by the method of this application is superior to that of traditional mine car leaf springs.

[0061] In summary, the off-highway wide-body mining car leaf spring disclosed in this invention is prepared through processes including primary refining, refining, vacuum degassing, continuous casting, slow cooling of steel billets, heating of steel billets, high-pressure water descaling, rolling, cooling bed cooling, blanking, heated variable cross-section rolling, quenching, tempering, stress shot blasting, and electrophoresis. In the continuous casting step, matching the temperature and speed of the straightening machine helps to form a uniform and dense solidification structure, improving the internal homogeneity of the continuously cast billet. Precise control of the temperature and cooling rate at the entry and exit of the slow cooling pit in the slow cooling step solves the problem of cracking in continuously cast billets of low-carbon, high-silicon manganese-chromium steel. By adopting a low-carbon design combined with the steel billet heating step, the technical challenge of complete surface decarburization of high-silicon steel can be effectively solved, while reducing total surface decarburization, effectively ensuring that the flat steel has good internal and external quality. By quenching and tempering the heated variable cross-section rolled leaf springs, it is beneficial to ensure the high toughness, low temperature impact resistance and high fatigue life of the leaf springs, extending their service life from 20-30 days for traditional mining car leaf springs to more than 180 days, thus reducing material and energy waste.

[0062] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0063] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A leaf spring for off-highway wide-body mining cars, characterized in that, Its chemical composition, by mass percentage, includes: C 0.28%~0.32%, Si 1.10%~1.20%, Mn 1.20%~1.30%, P≤0.010%, S≤0.005%, Cr 1.00%~1.10%, Ti 0.010%~0.030%, Mo≤0.10%, Ni≤0.20%, Cu≤0.10%, Al 0.01%~0.04%, with the balance being Fe and unavoidable impurity elements.

2. The off-highway wide-body mining car leaf spring according to claim 1, characterized in that, Its chemical composition, by mass percentage, includes: C 0.29%~0.30%, Si 1.13%~1.17%, Mn 1.23%~1.27%, P≤0.008%, S≤0.003%, Cr 1.03%~1.05%, Ti 0.018%~0.022%, Mo≤0.10%, Ni≤0.20%, Cu≤0.10%, Al 0.018%~0.022%, with the balance being Fe and unavoidable impurity elements.

3. A method for manufacturing a non-highway wide-body mining car leaf spring as described in any one of claims 1 to 2, characterized in that, Includes the following steps: Primary refining, refining, vacuum degassing, continuous casting, slow cooling of billets, heating of billets, high-pressure water descaling, rolling, cooling bed cooling, blanking, heated variable cross-section rolling, quenching, tempering, stress shot blasting and electrophoresis; In the continuous casting process, the billet temperature entering the straightening machine is ≥980℃, and the drawing speed is 0.75~0.85m / min; in the billet slow cooling process, the billet temperature entering the slow cooling pit is ≥650℃, the temperature exiting the slow cooling pit is ≤150℃, and the cooling rate is ≤0.12℃ / s; in the billet heating process, the total heating time is 170~200min, the first heating temperature is 1150~1200℃, the second heating temperature and the soaking temperature are both 1200~1250℃, and the holding time is ≥120min; in the quenching process, the quenching oil temperature is 870~900℃, and the pressure quenching time is >230s; in the tempering process, the heating temperature is 360~390℃.

4. The method for preparing off-highway wide-body mining car leaf springs according to claim 3, characterized in that, During the continuous casting process, the billet temperature entering the straightening machine is 980~990℃, and the casting speed is 0.78~0.82m / min.

5. The method for preparing off-highway wide-body mining car leaf springs according to claim 3, characterized in that, In the slow cooling step of the billet, the billet temperature is 650~680℃ when it enters the slow cooling pit, and the temperature when it exits the slow cooling pit is 100~150℃, with a cooling rate of 0.09~0.11℃ / s.

6. The method for preparing off-highway wide-body mining car leaf springs according to claim 3, characterized in that, In the billet heating process, the total heating time is 180~190min, the temperature of the first heating stage is 1180~1200℃, the temperature of the second heating stage and the soaking stage are both 1230~1250℃, and the holding time is 130~145min.

7. The method for preparing off-highway wide-body mining car leaf springs according to claim 3, characterized in that, In the billet heating process, the billet size is 240mm×300mm.

8. The method for preparing off-highway wide-body mining car leaf springs according to claim 3, characterized in that, In the quenching process, the oil immersion temperature is 880~890℃, and the quenching time is 234~244s.

9. The method for preparing off-highway wide-body mining car leaf springs according to claim 3, characterized in that, During the tempering process, the heating temperature is 375~385℃.

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