Steel for automotive axle and method for producing the same

Abstract

The application discloses a kind of automobile axle steel and its production method. By optimizing adjustment to each element composition and content in automobile axle steel, combined with the reasonable control to heating temperature, rolling process and coiling temperature, the synergistic effect of fine-grain strengthening and precipitation strengthening can be formed, so as to obtain the excellent mechanical properties of automobile axle steel with yield strength ≥700MPa, tensile strength ≥800MPa and elongation ≥11% in hot rolling state. After hot stamping, the yield strength is still maintained ≥680MPa, the tensile strength is ≥780MPa, and the elongation is ≥13%. The steel has high strength, good hot stamping forming property and excellent welding performance, low carbon equivalent, small welding cold crack sensitivity index, and fully meets the production and use requirements of truck rear axle housing and axle.

Description

Technical Field

[0001] This application belongs to the field of metallurgical technology, and in particular relates to a steel for automobile axles and a method for producing the same. Background Technology

[0002] With the increasing size and weight reduction of heavy-duty trucks, high-strength steel with a tensile strength of 700MPa and above is now widely used for automobile beams and bodies. However, for automobile axle housings, materials with tensile strengths of 510MPa and 550MPa are still the main materials used. As a key component of the driving system, the automobile axle needs to support the weight of the assembly and protect the transmission components. With the development of manufacturing technology, hot-rolled steel plates with a thickness of 12-16mm have been used to manufacture stamped and welded axle housings to replace traditional cast axle housings. This process requires the material to have high strength, good stamping formability, and excellent welding performance. However, the existing technology has the following drawbacks: First, there is currently a lack of dedicated high-strength hot-rolled steel plates and corresponding standards for automotive stamped and welded axle housings in China, and the main reliance is on substitute materials; Second, the axle housing needs to undergo medium-frequency heating at 900℃ during hot pressing and is subjected to severe bending and bulging deformation. The existing materials experience a significant decrease in strength after hot pressing, making it difficult to meet the stringent performance requirements of yield strength ≥700MPa, tensile strength ≥800MPa, elongation ≥13%, and strength reduction ≤20MPa after hot pressing; In addition, since the axle housing needs to be assembled by welding, the strength and toughness requirements of the weld and heat-affected zone are high. The existing substitute materials are insufficient in terms of welding performance and hot working stability, making it difficult to balance formability, weldability, and performance retention after hot pressing. Summary of the Invention

[0003] This application provides a steel for automobile axles and its production method. In the hot-rolled state, the steel plate has high strength, fine grains, excellent stamping formability and weldability. During use, the steel plate is suitable for hot stamping forming process, and the strength decreases little after hot forming.

[0004] In a first aspect, embodiments of this application provide a steel for automotive axles, comprising, by mass percentage: C: 0.15–0.18%, Si: 0.10–0.4%, Mn: 1.30–1.50%, P: ≤0.015%, S: ≤0.0020%, Cr: 0.30–0.40%, Nb: 0.02–0.04%, Mo: 0.15–0.30%, Als: 0.010–0.040%, with the balance being iron and unavoidable impurities.

[0005] According to the embodiments of the first aspect of this application, the steel for automobile axles has a yield strength ≥700MPa, a tensile strength ≥800MPa, and an elongation ≥11%; and / or, the steel for automobile axles after hot forming has a yield strength ≥680MPa, a tensile strength ≥780MPa, and an elongation ≥13%.

[0006] Secondly, this application provides a production method for improving the mechanical properties of steel for automobile axles, comprising: providing molten iron; smelting the molten iron in a converter, and then blowing argon into a ladle after smelting the molten iron in the converter to obtain molten steel after converter smelting; and refining the molten steel after converter smelting by LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar flow cooling and coiling to obtain steel for automobile axles.

[0007] According to an embodiment of the second aspect of this application, heating includes heating the continuously cast slab at a temperature of 1160°C to 1200°C.

[0008] According to an embodiment of the second aspect of this application, heating includes heating up and heating up uniformly, and the temperature for both heating up and heating up uniformly is 1180°C to 1200°C.

[0009] According to an embodiment of the second aspect of this application, the final rolling temperature of the roughing roll is 1070°C to 1100°C.

[0010] According to an embodiment of the second aspect of this application, the final rolling temperature of the finishing mill is 865°C to 880°C.

[0011] According to an embodiment of the second aspect of this application, the cooling rate of laminar flow cooling is 43°C / s to 60°C / s.

[0012] According to an embodiment of the second aspect of this application, the winding temperature is 582°C to 620°C.

[0013] Thirdly, this application provides a use of the automotive axle steel described in the first aspect or the automotive axle steel produced by the production method described in the second aspect, wherein the automotive axle steel is used to manufacture the drive rear axle of a heavy-duty truck.

[0014] The automotive axle steel and its production method provided in this application, through the optimization and adjustment of the composition and content of each element in the automotive axle steel, combined with the reasonable control of heating temperature, rolling process and coiling temperature, form a synergistic effect of fine grain strengthening and precipitation strengthening. It can achieve excellent mechanical properties in the hot-rolled state with yield strength ≥700MPa, tensile strength ≥800MPa and elongation ≥11%, while the strength decreases by ≤20MPa after hot stamping, and the yield strength still remains ≥680MPa, tensile strength ≥780MPa and elongation ≥13%. This steel grade has high strength, good hot stamping formability and excellent weldability, low carbon equivalent and small welding cold cracking sensitivity index, which fully meets the manufacturing and use requirements of rear axle housings and axles of heavy-duty trucks. Detailed Implementation

[0015] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the implementation details described in this specification are merely for illustrative purposes and are not intended to limit the scope of this application.

[0016] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0017] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0018] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application). Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C and the test pressure is standard atmospheric pressure.

[0019] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0020] In view of the aforementioned deficiencies in the prior art, this application provides a steel for automobile axles and a method for producing the same. The hot-rolled stamped axle housing steel sheet for automobiles with a tensile strength ≥800MPa produced by the method of this application has excellent hot stamping forming performance and welding performance, and fully meets the manufacturing and use requirements of rear axle housings and axles of heavy-duty trucks.

[0021] This application provides a steel for automotive axles, comprising, by mass percentage: C: 0.15-0.18%, Si: 0.10-0.4%, Mn: 1.30-1.50%, P: ≤0.015%, S: ≤0.0020%, Cr: 0.30-0.40%, Nb: 0.02-0.04%, Mo: 0.15-0.30%, Als: 0.010-0.040%, with the balance being iron and unavoidable impurities.

[0022] This application employs a composite alloying composition design with specific components and contents of C, Si, Mn, Cr, Nb, and Mo. C element strengthens the matrix through solid solution, while Mn, Cr, and Mo synergistically enhance hardenability and promote the formation of strong and tough structures such as bainite. Nb element significantly improves the strength-toughness balance of the steel through grain refinement and precipitation strengthening. Simultaneously, the contents of impurity elements such as P and S are strictly controlled to reduce the damage of inclusions to plasticity and toughness, and Al deoxidation ensures the purity of the steel. This composition system, combined with precise control of heating, rolling, and coiling processes, enables the production of fine-grained steel in the hot-rolled state. The ferrite / bainitic microstructure gives the steel sheet both high strength (tensile strength ≥ 800 MPa), excellent stamping formability, and weldability. Furthermore, the addition of microalloying elements such as Mo and Nb effectively suppresses microstructure softening and grain coarsening during hot stamping. This results in a strength reduction of ≤ 20 MPa after hot forming at 900℃, while maintaining a good balance of yield strength ≥ 680 MPa, tensile strength ≥ 780 MPa, and elongation ≥ 13%. This fully meets the comprehensive requirements of heavy-duty truck rear axle housings and axles for high material strength, hot working stability, formability, and weldability.

[0023] In some optional embodiments, the steel for automotive axles (which can be understood as hot-rolled steel) has a yield strength ≥700MPa, a tensile strength ≥800MPa, and an elongation ≥11%.

[0024] As an example, the yield strength of steel used in automotive axles can be 700 MPa, 715 MPa, 730 MPa, 745 MPa, 760 MPa, 800 MPa, 810 MPa, 820 MPa, 830 MPa, 840 MPa, 850 MPa, or 900 MPa.

[0025] As an example, the tensile strength of steel used in automotive axles can be 800 MPa, 820 MPa, 840 MPa, 860 MPa, 880 MPa, 890 MPa, 900 MPa, 910 MPa, 920 MPa, 930 MPa, 940 MPa, or 950 MPa.

[0026] As an example, the elongation of steel for automotive axles can be 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, and 18.0%.

[0027] In some optional embodiments, the steel for automotive axles, after hot forming, meets the following properties: yield strength ≥ 680 MPa, tensile strength ≥ 780 MPa, and elongation ≥ 13%.

[0028] As an example, the yield strength of steel used in automotive axles after hot forming can be 680 MPa, 695 MPa, 710 MPa, 725 MPa, 740 MPa, 745 MPa, 760 MPa, 800 MPa, 810 MPa, 820 MPa, 830 MPa, 840 MPa, 850 MPa, and 900 MPa.

[0029] As an example, the tensile strength of steel used in automotive axles after hot forming can be 780 MPa, 800 MPa, 820 MPa, 840 MPa, 860 MPa, 880 MPa, 890 MPa, 900 MPa, 910 MPa, 920 MPa, 930 MPa, 940 MPa, and 950 MPa.

[0030] As an example, the elongation of steel for automotive axles after hot forming can be 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, and 18.0%.

[0031] This application provides a production method for improving the mechanical properties of steel for automotive axles, comprising: providing molten iron; smelting the molten iron in a converter, then blowing argon into a ladle after the molten iron has been smelted in the converter to obtain molten steel after converter smelting; and refining the molten steel after converter smelting by LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar flow cooling and coiling to obtain steel for automotive axles.

[0032] This application embodiment employs a full-process process control involving converter smelting, ladle argon blowing, LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar flow cooling, and coiling. During the LF and RH refining stages, harmful elements and inclusions are effectively removed from the steel, improving its purity and laying the foundation for subsequent microstructure refinement. In the heating, rough rolling, and finish rolling stages, precise control of heating, rough rolling, and finishing temperatures promotes repeated recrystallization and refinement of austenite grains. Combined with laminar flow cooling, rapid passage through the phase transformation zone inhibits grain growth, ultimately resulting in a fine-grained ferrite / bainite microstructure after coiling, making the steel... The steel sheet, in its hot-rolled state, possesses high strength (tensile strength ≥ 800 MPa), fine grain, excellent stamping formability, and weldability. Simultaneously, through the synergistic effect of composition design and hot-rolling parameters, this process ensures high structural stability and strong resistance to softening during hot stamping at 900℃. After hot forming, the strength decrease is ≤ 20 MPa, while maintaining a good performance match of yield strength ≥ 680 MPa, tensile strength ≥ 780 MPa, and elongation ≥ 13%. This fully meets the comprehensive requirements of heavy-duty truck rear axle housings and axles for high strength, hot working stability, formability, and weldability.

[0033] In some alternative embodiments, heating includes heating the continuously cast slab at a temperature of 1160°C to 1200°C.

[0034] For example, the heating temperature can be 1160℃, 1111℃, 1162℃, 1163℃, 1164℃, 1165℃, 1166℃, 1167℃, 1168℃, 1169℃, 1170℃, 1171℃, 1172℃, 1173℃, 1174℃, 1175℃, 1176℃, 1177℃, 1178℃, 11... 79℃, 1180℃, 1181℃, 1182℃, 1183℃, 1184℃, 1185℃, 1186℃, 1187℃, 1188℃, 1189℃, 1190℃, 1191℃, 1192℃, 1193℃, 1194℃, 1195℃, 1196℃, 1197℃, 1198℃, 1199℃, 1200℃.

[0035] This embodiment controls the heating temperature within the range of 1160℃ to 1200℃, enabling the continuous casting slab to achieve homogenization of the austenitic structure during heating. This avoids grain coarsening due to excessively high temperatures or insufficient dissolution of alloying elements due to excessively low temperatures. This heating regime provides fine, original austenitic grains for subsequent roughing and finishing rolling stages. Combined with deformation recrystallization during rolling, it effectively promotes grain refinement, ultimately resulting in a fine-grained ferrite / bainite structure in the hot-rolled state. This gives the steel plate high strength (tensile strength ≥ 800 MPa), excellent stamping formability, and weldability. Meanwhile, the appropriate heating temperature ensures that microalloying elements such as Nb and Mo are fully dissolved and precipitate in the form of fine carbonitrides during subsequent cooling, resulting in a significant precipitation strengthening effect and improving the thermal stability of the microstructure. This enhances the steel plate's resistance to softening during hot stamping at 900℃, and the strength decrease after hot forming is ≤20MPa, while still maintaining a good match of yield strength ≥680MPa, tensile strength ≥780MPa, and elongation ≥13%. This fully meets the comprehensive requirements of heavy-duty truck rear axle housings and axles for high strength, hot working stability, formability, and weldability.

[0036] In some optional embodiments, heating includes both heating and homogenization, with the heating and homogenization temperatures ranging from 1180°C to 1200°C.

[0037] As an example, the temperatures for heating and equalization can be 1180℃, 1181℃, 1182℃, 1183℃, 1184℃, 1185℃, 1186℃, 1187℃, 1188℃, 1189℃, 1190℃, 1191℃, 1192℃, 1193℃, 1194℃, 1195℃, 1196℃, 1197℃, 1198℃, 1199℃, and 1200℃, respectively.

[0038] In some optional embodiments, the final rolling temperature of the roughing roll is 1070°C to 1100°C.

[0039] As an example, the finishing rolling temperature of the roughing mill can be 1070℃, 1071℃, 1072℃, 1073℃, 1074℃, 1075℃, 1077℃, 1078℃, 1079℃, 1080℃, 1081℃, 1082℃, 1083℃, 1085℃, 1086℃, 1087℃, 1088℃, 1089℃, 1090℃, 1092℃, 1094℃, 1095℃, 1096℃, 1097℃, 1098℃, 1099℃, or 1100℃.

[0040] This embodiment controls the roughing and finishing rolling temperature within the range of 1070℃ to 1100℃, allowing the continuously cast slab to undergo sufficient deformation in the austenite recrystallization zone. This promotes repeated recrystallization and refinement of the austenite grains, providing a fine and uniform initial microstructure for subsequent finishing rolling. This temperature range ensures sufficient accumulated deformation during the roughing stage to break up the original as-cast microstructure and eliminate center segregation, while also preventing the formation of a mixed-grain microstructure due to excessively low temperatures entering the partial recrystallization zone. This results in a fine-grained ferrite / bainite microstructure in the hot-rolled state, giving the steel plate both high strength (tensile strength ≥ 800 MPa) and excellent stamping formability. The steel plate exhibits excellent weldability. Furthermore, the appropriate roughing and finishing rolling temperatures, combined with subsequent finishing rolling processes, facilitate strain-induced precipitation of microalloying elements such as Nb and Mo, producing fine carbonitride strengthening phases. This further enhances the matrix strength and thermal stability of the microstructure, significantly improving the steel plate's resistance to softening during hot stamping at 900℃. The strength reduction after hot forming is ≤20MPa, while maintaining a good balance of yield strength ≥680MPa, tensile strength ≥780MPa, and elongation ≥13%. This fully meets the comprehensive requirements of heavy-duty truck rear axle housings and axles for high strength, hot working stability, formability, and weldability.

[0041] In some optional embodiments, the finishing rolling temperature is 865°C to 880°C.

[0042] As an example, the finishing rolling temperature can be 865℃, 866℃, 867℃, 868℃, 869℃, 870℃, 871℃, 872℃, 873℃, 874℃, 875℃, 876℃, 877℃, 878℃, 879℃, or 880℃.

[0043] This embodiment controls the finishing rolling temperature within the range of 865℃ to 880℃, allowing rolling deformation to accumulate in the non-recrystallized austenite region. This introduces numerous deformation bands and dislocation defects within the austenite grains, providing a high density of nucleation sites for subsequent phase transformations. This promotes ferrite grain refinement during subsequent laminar cooling, ultimately resulting in a fine-grained ferrite / bainite microstructure. This allows the steel sheet to possess high strength (tensile strength ≥ 800 MPa), excellent stamping formability, and weldability in the hot-rolled state. This temperature range also considers the effects of microalloying elements such as Nb and Mo. The strain-induced precipitation effect allows fine carbonitrides to disperse and precipitate in the deformed austenite, which not only strengthens the matrix through precipitation but also inhibits grain growth through pinning, significantly improving the thermal stability of the microstructure. This enhances the steel plate's resistance to softening during hot stamping at 900℃, with a strength reduction of ≤20MPa after hot forming, while maintaining a good match of yield strength ≥680MPa, tensile strength ≥780MPa, and elongation ≥13%. This fully meets the comprehensive requirements of heavy-duty truck rear axle housings and axles for high strength, hot working stability, formability, and weldability.

[0044] In some optional embodiments, the laminar flow cooling rate is 43°C / s to 60°C / s.

[0045] As an example, the cooling rate of laminar flow cooling can be 43℃ / s, 44℃ / s, 45℃ / s, 46℃ / s, 47℃ / s, 48℃ / s, 49℃ / s, 50℃ / s, 51℃ / s, 52℃ / s, 53℃ / s, 54℃ / s, 55℃ / s, 56℃ / s, 57℃ / s, 58℃ / s, 59℃ / s, or 60℃ / s.

[0046] This embodiment controls the laminar cooling rate within the range of 43℃ / s to 60℃ / s, enabling rapid cooling of the finished rolled steel sheet in the austenitic transformation region. This effectively inhibits ferrite grain growth and promotes the formation of fine-grained ferrite and bainite structures, thereby achieving a good balance of high strength (tensile strength ≥ 800MPa), fine grains, excellent stamping formability, and weldability in the hot-rolled state. This cooling rate range ensures sufficient undercooling to increase the phase deformation nucleation rate and refine the grains, while avoiding the formation of hard and brittle structures such as martensite due to excessively rapid cooling, which would deteriorate formability and weldability. The coiling process causes microalloying elements to precipitate in the form of fine carbonitrides, resulting in a significant precipitation strengthening effect and improving the thermal stability of the matrix. The synergistic effect of fine grain strengthening and precipitation strengthening obtained by this process results in a small tendency for microstructure coarsening and strong resistance to softening during hot stamping at 900℃. The strength decrease after hot forming is ≤20MPa, while still maintaining a good match of yield strength ≥680MPa, tensile strength ≥780MPa, and elongation ≥13%. This fully meets the comprehensive requirements of high strength, hot working stability, formability, and weldability for the rear axle housing and axle of heavy-duty trucks.

[0047] In some optional embodiments, the winding temperature is 582°C to 620°C.

[0048] As an example, the winding temperature can be 582℃, 583℃, 584℃, 585℃, 586℃, 587℃, 588℃, 589℃, 590℃, 591℃, 592℃, 593℃, 594℃, 595℃, 596℃, 597℃, 598℃, 599℃, 600℃, 601℃, 602℃, 603℃, 604℃, 605℃, 606℃, 607℃, 608℃, 609℃, 610℃, 611℃, 612℃, 613℃, 614℃, 615℃, 616℃, 617℃, 618℃, 619℃, or 620℃.

[0049] This embodiment controls the coiling temperature within the range of 582℃ to 620℃, allowing the laminar-cooled steel sheet to complete phase transformation and be coiled within this temperature range. This ensures that austenite fully transforms into fine-grained ferrite / bainite, achieving a balance between high strength (tensile strength ≥ 800 MPa) and good plasticity. Furthermore, it allows microalloying elements such as Nb and Mo to precipitate as fine carbonitrides within the ferrite matrix, resulting in significant precipitation strengthening and further enhancing matrix strength and thermal stability. This coiling temperature range avoids grain coarsening and coarse precipitates caused by excessively high temperatures. This also avoids hardening of the structure and increase of residual stress due to excessively low temperature, thus obtaining fine grains, excellent stamping formability and weldability in the hot-rolled state; the synergistic effect of fine grain strengthening and precipitation strengthening obtained thereby makes the steel plate have a small tendency to coarsen during hot stamping at 900℃, strong resistance to softening, and a strength reduction of ≤20MPa after hot forming, while still maintaining a good match of yield strength ≥680MPa, tensile strength ≥780MPa and elongation ≥13%, thus fully meeting the comprehensive requirements of high strength, hot working stability, formability and weldability for the rear axle housing and axle of heavy-duty trucks.

[0050] This application provides an application for the aforementioned automotive axle steel or automotive axle steel produced by the aforementioned production method, wherein the automotive axle steel is used to manufacture the drive rear axle of a heavy-duty truck.

[0051] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0052] Examples 1-5 The present invention comprises preparing automotive axle steel with good hot working properties according to the following steps: Converter—Argon Station—LF Furnace—RH (Si-Ca Treatment)—Continuous Casting (Electromagnetic Stirring)—Slab Inspection—Heating—Rough Rolling—Finish Rolling—Laminar Flow Cooling—Coiling Process.

[0053] Comparative Examples 1-3 Automotive axle steel was prepared using a similar process to that in Example 1, except that the chemical composition and processing parameters were adjusted.

[0054] The chemical composition of the automotive axle steel obtained in the various embodiments and comparative examples of the present invention is shown in Table 1 below.

[0055] The main process parameters of each embodiment of the present invention are shown in Table 2 below.

[0056] The performance test results of the steel plates obtained in each embodiment of the present invention are shown in Table 3 below.

[0057] Performance testing Yield strength, tensile strength, elongation after fracture: According to GB / T228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature", steel plates from the examples or comparative examples were prepared and tensile tests were conducted using a German Zwick tensile testing machine with a load of 50 to 1500 kN and a displacement speed of 2 mm / min. The test data, such as yield strength, tensile strength, elongation, and impact absorption energy at -196℃, were obtained by computer plotting.

[0058] Table 1. Mass percentage of chemical composition of easily formable automotive axle steel described in each embodiment and comparative example. Table 2. Main process parameters of the preparation methods for each embodiment and comparative example. Table 3 Performance test results of the products prepared in each embodiment and comparative example As can be seen from the data in Table 3, the automotive axle steel obtained by this invention has good hot working properties.

[0059] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A type of steel for automobile axles, characterized in that, In terms of mass percentage, including: C: 0.15-0.18%, Si: 0.10-0.4%, Mn: 1.30-1.50%, P: ≤0.015%, S: ≤0.0020%, Cr: 0.30-0.40%, Nb: 0.02-0.04%, Mo: 0.15-0.30%, Als: 0.010-0.040%, with the balance being iron and unavoidable impurities.

2. The steel for automobile axles according to claim 1, characterized in that, The steel used in the automotive axle has a yield strength ≥700MPa, a tensile strength ≥800MPa, and an elongation ≥11%; and / or, The steel used for automotive axles, after hot forming, meets the following performance requirements: yield strength ≥ 680 MPa, tensile strength ≥ 780 MPa, and elongation ≥ 13%.

3. A method for improving the mechanical properties of steel used in automobile axles, characterized in that, include: Provide molten iron; The molten iron is smelted in a converter, and then argon is blown into a ladle after the molten iron is smelted in the converter to obtain molten steel after converter smelting. The molten steel after converter smelting is subjected to LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar flow cooling and coiling to obtain steel for automobile axles.

4. The production method according to claim 1, characterized in that, The heating includes heating the continuously cast slab at a temperature of 1160℃~1200℃.

5. The production method according to claim 1, characterized in that, The heating includes both heating and homogenization, and the temperatures for both heating and homogenization are 1180℃~1200℃.

6. The production method according to claim 1, characterized in that, The final rolling temperature of the roughing mill is 1070℃~1100℃.

7. The production method according to claim 1, characterized in that, The finishing rolling temperature is 865℃~880℃.

8. The production method according to claim 1, characterized in that, The cooling rate of the laminar flow cooling is 43℃ / s to 60℃ / s.

9. The production method according to claim 1, characterized in that, The winding temperature is 582℃~620℃.

10. The use of automotive axle steel according to any one of claims 1-2 or automotive axle steel produced by the production method according to any one of claims 3-9, characterized in that, The steel used for automobile axles is used to manufacture the rear drive axle of heavy-duty trucks.

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