Quenched and tempered steel for steering knuckles and front axles of medium-heavy commercial vehicles and preparation method of quenched and tempered steel

Abstract

The invention discloses quenched and tempered steel for a steering knuckle and a front axle of a medium-heavy commercial vehicle and a preparation method of the quenched and tempered steel, and relates to the technical field of metallurgy, and the quenched and tempered steel comprises the following chemical components in percentage by mass: 0.40-0.45% of C, 0.20-0.40% of Si, 1.00-1.50% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, 0.15-0.40% of Ni, 0.20-0.60% of Cr, 0.01-0.10% of Mo, 0.020-0.040% of Al, 0.015-0.040% of Ti and 0.0005-0.0035% of B. The contents of the Mo element and the Cr element are greatly reduced in component design, the hardenability is improved through the trace element B, a small amount of other trace elements are added, the influence of all the elements on the material performance is comprehensively utilized, the product performance is guaranteed, and the manufacturing cost is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles and a preparation method thereof. Background Art

[0002] Currently, front axles and steering knuckles for medium- and heavy-duty commercial vehicles are manufactured using 42CrMo. While this material offers superior overall performance, it contains high levels of Mn, Cr, and the precious alloying element Mo, resulting in high material costs. Furthermore, significant price fluctuations in precious metals like Mo contribute significantly to material price fluctuations. Therefore, while ensuring that forgings such as front axles and steering knuckles meet product technical requirements, it is necessary to develop new materials for these materials to reduce manufacturing costs. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles and a preparation method thereof.

[0004] In order to solve the above technical problems, the technical solutions of the present invention are as follows: A quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles, the chemical composition and mass percentage of which are: C: 0.40-0.45%, Si: 0.20-0.40%, Mn: 1.00-1.50%, P≤0.020%, S≤0.010%, Ni: 0.15-0.40%, Cr: 0.20-0.60%, Mo: 0.01-0.10%, Al: 0.020-0.040%, Ti: 0.015-0.040%, and B: 0.0005-0.0035%.

[0005] As a preferred embodiment of the quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles according to the present invention, the quenched and tempered steel has a tensile strength greater than or equal to 1080 MPa and a yield strength greater than or equal to 930 MPa after quenching and tempering.

[0006] As a preferred solution of the quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles described in the present invention, the elongation of the quenched and tempered steel after tempering is greater than or equal to 12%, and the cross-sectional shrinkage is greater than or equal to 45%.

[0007] As a preferred solution of the quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles described in the present invention, the quenched and tempered steel has a room temperature impact AKU2≥63J and a -40°C low temperature impact AKV2≥27J after quenching and tempering.

[0008] As a preferred solution of the quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles described in the present invention, the quenched and tempered metallographic structure of the product made from the quenched and tempered steel is level 1 to 4.

[0009] The present invention also provides a method for preparing quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles, which comprises the following steps in sequence: electric furnace / converter → LF refining → VD / RH refining → continuous casting → walking beam heating furnace → initial rolling by large-scale initial rolling mill → finishing rolling by continuous rolling mill group → slow cooling.

[0010] As a preferred embodiment of the method for preparing quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles according to the present invention, the finishing rolling process of the continuous rolling mill comprises finishing rolling the rolled piece using a KOCKS rolling mill.

[0011] The beneficial effects of the present invention are: Compared with the original material 42CrMo steel, the present invention significantly reduces the content of the precious metal element Mo and the content of the Cr element in the composition design, utilizes the effect of trace B elements to improve the hardenability, adds a small amount of other trace elements, and comprehensively utilizes the influence of various elements on material properties to ensure product performance, meet the performance requirements of current medium and heavy-duty commercial vehicle front axles and steering knuckle products, and effectively reduce manufacturing costs. DETAILED DESCRIPTION

[0012] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific implementation methods.

[0013] The present application provides a quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles, the chemical composition and mass percentage of which are: C: 0.40-0.45%, Si: 0.20-0.40%, Mn: 1.00-1.50%, P≤0.020%, S≤0.010%, Ni: 0.15-0.40%, Cr: 0.20-0.60%, Mo: 0.01-0.10%, Al: 0.020-0.040%, Ti: 0.015-0.040%, B: 0.0005-0.0035%.

[0014] The tensile strength of the above-mentioned quenched and tempered steel after quenching and tempering is ≥1080 MPa, the yield strength is ≥930 MPa, the elongation is ≥12%, the cross-sectional shrinkage is ≥45%, the room temperature impact AKU2 is ≥63J, the -40℃ low temperature impact AKV2 is ≥27J, and the metallographic structure of the finished product after quenching and tempering is grade 1 to 4.

[0015] The present application also provides a method for preparing quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles, which comprises the following steps in sequence: electric furnace / converter → LF refining → VD / RH refining → continuous casting → walking beam heating furnace → initial rolling by large primary rolling mill → finishing rolling by continuous rolling mill group → slow cooling.

[0016] Among them, the finishing rolling process of the continuous rolling mill includes using a KOCKS rolling mill to finish roll the rolled pieces.

[0017] The above technical solution is further illustrated below through specific embodiments and comparative examples.

[0018] Example: This embodiment provides a quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles, the chemical composition and mass percentage of which are: C: 0.40-0.45%, Si: 0.20-0.40%, Mn: 1.00-1.50%, P≤0.020%, S≤0.010%, Ni: 0.15-0.40%, Cr: 0.20-0.60%, Mo: 0.01-0.10%, Al: 0.020-0.040%, Ti: 0.015-0.040%, B: 0.0008-0.0035%.

[0019] Comparative Example 1: This comparative example uses 42CrMo tempered steel, whose chemical composition and mass percentage are: C: 0.39-0.43%, Mn: 0.70-0.90%, Si: 0.17-0.37%, P≤0.025%, S≤0.010%, Cr: 1.05-1.20%, Ni≤0.30%, Cu≤0.15%, Mo: 0.20-0.25%.

[0020] Comparative Example 2: This comparative example uses 40MnBH (GB / T5216), and its chemical composition and mass percentage are: C: 0.37-0.44%, Si: 0.17-0.37%, Mn: 1.00-1.40%, P≤0.030%, S≤0.035%, Ni≤0.30%, Cr≤0.30, B: 0.0008-0.0035%.

[0021] It can be seen from the above-mentioned embodiment, comparative example 1 and comparative example 2 that the embodiment of the present application and comparative example 2 significantly reduce the content of the precious metal element Mo and significantly reduce the content of the Cr element in the composition design.

[0022] The performance indicators achieved in the embodiment are: hardenability J9-52~57HRC; hardenability J11-50~56HRC; hardenability J13-49~56HRC, hardenability J15-46~55HRC, hardenability J20-42~53HRC, hardenability J25-39~50HRC, hardenability J30-37~48HRC, tensile strength: ≥1080Mpa, yield strength: ≥930MPa, elongation: ≥12%, reduction of area: ≥45%, normal temperature impact AKU2: ≥63J, -40℃ low temperature impact AKV2: ≥27J, metallographic structure (quenched and tempered): grades 1 to 4.

[0023] The performance indicators achieved in Comparative Example 2 are: hardenability J9-42~55HRC, hardenability J11-33~52HRC, hardenability J13-27~49HRC, hardenability J15-24~45HRC, hardenability J20-20~37HRC, hardenability J25-0~33HRC, hardenability J30-0~31 HRC, tensile strength: ≥980Mpa, yield strength: ≥785MPa, elongation: ≥10%, reduction of area: ≥45%, room temperature impact AKU2: ≥47J.

[0024] It can be seen from this that the performance of the quenched and tempered steel produced in this embodiment is significantly better than the national standard 40MnBH quenched and tempered steel, and meets the performance requirements of current medium and heavy-duty commercial vehicle front axles and steering knuckle products.

[0025] In addition to the above embodiments, the present invention may also have other implementation methods; any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles, characterized by: Its chemical composition and mass percentage are: C: 0.40~0.45%, Si: 0.20~0.40%, Mn: 1.00~1.50%, P≤0.020%, S≤0.010%, Ni: 0.15~0.40%, Cr: 0.20~0.60%, Mo: 0.01~0.10%, Al: 0.020~0.040%, Ti: 0.015~0.040%, B: 0.0005~0.0035%.

2. The quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles according to claim 1, characterized in that: The tensile strength of the quenched and tempered steel after quenching and tempering is greater than or equal to 1080 MPa, and the yield strength is greater than or equal to 930 MPa.

3. The quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles according to claim 1, characterized in that: The elongation of the quenched and tempered steel after quenching and tempering is greater than or equal to 12%, and the cross-sectional shrinkage is greater than or equal to 45%.

4. The quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles according to claim 1, characterized in that: The room temperature impact AKU2 of the quenched and tempered steel after quenching and tempering is ≥63J, and the low temperature impact AKV2 of -40°C is ≥27J.

5. The quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles according to claim 1, characterized in that: The quenched and tempered metallographic structure of the product made from the quenched and tempered steel is level 1 to 4.

6. A method for preparing the quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles according to any one of claims 1 to 5, characterized in that: The process includes the following steps in sequence: electric furnace / converter → LF refining → VD / RH refining → continuous casting → walking beam heating furnace → initial rolling on large-scale initial rolling mill → finishing rolling on continuous rolling mill → slow cooling.

7. The method for preparing quenched and tempered steel for steering knuckles and front axles of medium and heavy-duty commercial vehicles according to claim 6, characterized in that: The finishing rolling process of the continuous rolling mill group includes using a KOCKS rolling mill to perform finish rolling on the rolled piece.