CrMn spring steel for automobile stabilizer bar and heat treatment method of CrMn spring steel

Abstract

The invention discloses a heat treatment method of CrMn spring steel for an automobile stabilizer bar, and relates to the technical field of heat treatment. Si: less than or equal to 0.40%; 0.70% to 1.00% of Mn; 0.70% to 1.00% of Cr; p: less than or equal to 0.025%; the heat treatment method sequentially comprises the following steps: heating, quenching, tempering and cooling; wherein the heating time of the heating process is the complete burning time + 20-30 min. According to the 55Cr3 stabilizer bar, heating quenching at 835 DEG C and tempering at 440 DEG C are adopted, the structure of a workpiece subjected to heat treatment is tempered troostite, no obvious tempered martensite structure exists, and the hardness is 45-48 HRC and is within the ideal hardness range of the 55Cr3 stabilizer bar.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment, in particular to a CrMn spring steel for an automobile stabilizer bar and a heat treatment method thereof. Background Art

[0002] CrMn spring steel has good comprehensive properties, and the typical grade 55Cr3 is widely used in the production of automobile stabilizer bars. In actual application, due to the chemical composition segregation inherited from the steelmaking process and the heat treatment of the stabilizer bar, brittle tempered martensite structure is easily generated after segregation after heat treatment, which affects the fatigue performance of the workpiece. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide a CrMn spring steel for automobile stabilizer bar and a heat treatment method thereof.

[0004] In order to solve the above technical problems, the technical solution of the present invention is as follows: A CrMn spring steel for automobile stabilizer bars, the chemical composition and mass percentage of which are: C: 0.52-0.64%; Si: ≤0.40%; Mn: 0.70-1.00%; Cr: 0.70-1.00%; P: ≤0.025%; S≤0.020%, and the balance is Fe and unavoidable impurities.

[0005] The present invention also provides a heat treatment method for CrMn spring steel for automobile stabilizer bar, which comprises: heating, quenching, tempering, and cooling in sequence; Among them, the heating temperature of the heating process is 830℃-840℃.

[0006] As a preferred solution of the heat treatment method of the CrMn spring steel for automobile stabilizer bar of the present invention, the heating time of the heating process is the burn-through time + 20 to 30 minutes.

[0007] As a preferred solution of the heat treatment method of the CrMn spring steel for automobile stabilizer bar of the present invention, the quenching process adopts oil quenching.

[0008] As a preferred solution of the heat treatment method of the CrMn spring steel for automobile stabilizer bar of the present invention, the tempering temperature of the tempering process is 435-445°C.

[0009] As a preferred solution of the heat treatment method of the CrMn spring steel for automobile stabilizer bar of the present invention, the tempering holding time of the tempering process is the burn-through time + 70 minutes.

[0010] The beneficial effects of the present invention are: The present invention adopts 835°C heating quenching + 440°C tempering. After heat treatment, the workpiece has a tempered troostite structure without obvious tempered martensite structure. The hardness is 45-48HRC, which is in the ideal hardness range of 55Cr3 stabilizer rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0012] Figure 1 This is a schematic diagram of the tempered martensite structure of the workpiece after the workpiece is heat treated by 890℃ heating quenching + 440℃ holding and tempering; Figure 2 This is a schematic diagram of the tempered martensite structure of the workpiece after the workpiece is heat treated by 890℃ heating quenching + 460℃ holding and tempering; Figure 3 A schematic diagram of the tempered martensite structure of a workpiece after being treated by the heat treatment method provided in the present application; Figure 4 Schematic diagram of the tempered martensite structure of the workpiece in Example 1; Figure 5 Schematic diagram of the tempered martensite structure of the workpiece in Example 2; Figure 6 Schematic diagram of the tempered martensite structure of the workpiece in Example 3. DETAILED DESCRIPTION

[0013] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific implementation modes and in combination with the accompanying drawings.

[0014] The embodiment of the present application provides a CrMn spring steel for an automobile stabilizer bar, wherein the chemical composition and mass percentage thereof are: C: 0.52-0.64%; Si: ≤0.40%; Mn: 0.70-1.00%; Cr: 0.70-1.00%; P: ≤0.025%; S≤0.020%, and the remainder is Fe and unavoidable impurities.

[0015] The embodiment of the present application also provides a heat treatment method for CrMn spring steel for automobile stabilizer bars, which method includes the following treatment processes in sequence: heating, quenching, tempering, and cooling.

[0016] The heating temperature of the heating process is 830°C-840°C, which can be properly controlled and adjusted according to the alloy composition. The heating time is controlled according to the through-burning time + 20~30min.

[0017] It is understood that the burn-through time is determined according to the size of the workpiece and the number of heat treatments.

[0018] The quenching process adopted is oil quenching.

[0019] The tempering temperature of the tempering process is 435-445℃, and the tempering holding time is the burning-through time + 70min.

[0020] The 55Cr3 spring steel produced by converter smelting → LF refining → RH vacuum treatment → continuous casting → hot rolling has different degrees of segregation inside. Figure 1 As shown in the figure, the workpiece has white bright tempered martensite structure after heat treatment by 890℃ heating quenching + 440℃ holding tempering. The tempered martensite structure cannot be eliminated by increasing the tempering temperature to 460℃. Figure 2 At the same time, the hardness is low, which affects the fatigue performance of the workpiece.

[0021] However, the heat treatment method provided in this embodiment adopts 835℃ heating quenching + 440℃ tempering. After heat treatment, the workpiece has a tempered troostite structure, and no obvious tempered martensite structure is observed. Figure 3 , hardness 45-48HRC, which is in the ideal hardness range of 55Cr3 stabilizer bar (experiments show that fatigue performance is best in this hardness range).

[0022] The following is further described by means of specific examples.

[0023] Example 1: Batch A φ21mm samples were heated in a resistance furnace, process: 835℃ for 40min, oil quenching, 440℃ for 90min tempering. After heat treatment, the samples were subjected to metallographic test, and no obvious tempered martensite structure was found. Figure 4 . Carry out hardness test, Rockwell hardness 45-46.5HRC; meet the requirements.

[0024] Example 2: Batch B φ25mm samples were heated in a resistance furnace, process: 830℃ for 40min, oil quenching, 435℃ for 90min tempering. After heat treatment, the samples were subjected to metallographic tests, and no obvious tempered martensite structure was observed. Figure 5 . Carry out hardness test, Rockwell hardness 46-47 HRC; meet the requirements.

[0025] Example 3: Batch C φ28mm samples were heated in a resistance furnace, process: 840℃ for 50min, oil quenching, 435℃ for 95min tempering. After heat treatment, the samples were subjected to metallographic test, and no obvious tempered martensite structure was found. Figure 6 . Carry out hardness test, Rockwell hardness 46.5-48 HRC; meet the requirements.

[0026] Therefore, the workpiece structure after being processed by the technical solution of the present application is tempered troostite with a hardness of 46-48HRC, and no tempered martensite structure is found, which meets the production requirements.

[0027] In addition to the above embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A CrMn spring steel for automobile stabilizer bar, Features: Its chemical composition and mass percentage are: C: 0.52~0.64%; Si: ≤0.40%; Mn: 0.70~1.00%; Cr: 0.70~1.00%; P: ≤0.025%; S≤0.020%, and the balance is Fe and unavoidable impurities.

2. A heat treatment method for the CrMn spring steel for automobile stabilizer bar according to claim 1, Features: Including in order: Heating, quenching, tempering, cooling; Among them, the heating temperature of the heating process is 830℃-840℃.

3. The heat treatment method of CrMn spring steel for automobile stabilizer bar according to claim 2, Features: The heating time of the heating process is the burning-through time + 20 to 30 minutes.

4. The heat treatment method of CrMn spring steel for automobile stabilizer bar according to claim 2, Features: The quenching process adopts oil quenching.

5. The heat treatment method of CrMn spring steel for automobile stabilizer bar according to claim 2, Features: The tempering temperature of the tempering process is 435-445°C.

6. The heat treatment method of CrMn spring steel for automobile stabilizer bar according to claim 2, Features: The tempering holding time of the tempering process is the burning-through time + 70 minutes.

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