Crmn series spring steel for automobile stabilizer rod and heat treatment method therefor

Abstract

The present invention relates to the technical field of heat treatment. Disclosed is a heat treatment method for a CrMn series spring steel for an automobile stabilizer bar. The steel comprises the following chemical components in percentage by mass: 0.52-0.64% of C; ≤0.40% of Si; 0.70-1.00% of Mn; 0.70-1.00% of Cr; ≤0.025% of P; ≤0.020% of S, and the balance being Fe and inevitable impurities. The heat treatment method sequentially comprises: heating, quenching, tempering and cooling, wherein the heating time of the heating process is the soaking time +20-30 min. The present invention uses heating quenching at 835°C and tempering at 440°C, the workpiece structure is tempered bainite after heat treatment, no obvious tempered martensite structure is found, and the hardness is 45-48 HRC, which falls within the ideal hardness range of 55Cr3 stabilizer rods.

Description

CrMn spring steel for automobile stabilizer and heat treatment method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of heat treatment, in particular to a CrMn spring steel for automobile stabilizer and a heat treatment method thereof. BACKGROUND

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

[0003] SUMMARY

[0004] The present application solves the technical problems of overcoming the shortcomings of the prior art and providing a CrMn spring steel for automobile stabilizer and a heat treatment method thereof.

[0005] In order to solve the above technical problems, the technical scheme of the present application is as follows:

[0006] A CrMn spring steel for automobile stabilizer, the chemical composition and mass percentage of which are as follows: C: 0.52-0.64%; Si: ≤0.40%; Mn: 0.70-1.00%; Cr: 0.70-1.00%; P: ≤0.025%; S ≤0.020%, the balance being Fe and inevitable impurities.

[0007] The present application also provides a heat treatment method for the CrMn spring steel for automobile stabilizer, which comprises the following steps in sequence: heating, quenching, tempering, cooling;

[0008] The heating temperature of the heating process is 830-840 DEG C.

[0009] As a preferred scheme of the heat treatment method for the CrMn spring steel for automobile stabilizer, the heating time of the heating process is 20-30 min longer than the soaking time.

[0010] As a preferred scheme of the heat treatment method for the CrMn spring steel for automobile stabilizer, the quenching process adopts oil quenching.

[0011] As a preferred scheme of the heat treatment method for the CrMn spring steel for automobile stabilizer, the tempering temperature of the tempering process is 435-445 DEG C.

[0012] As a preferred scheme of the heat treatment method of the CrMn spring steel for the automobile stabilizer bar, the holding time of the tempering process is the burning time + 70 min.

[0013] The present application has the following advantages:

[0014] The present application adopts 835℃ heating quenching + 440℃ tempering, and the workpiece has tempered troostite structure after heat treatment, and no obvious tempered martensite structure is observed, and the hardness is 45-48HRC, which is in the ideal hardness range of 55Cr3 stabilizer bar. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0016] Fig. 1 is a schematic diagram of the tempered martensite structure of the workpiece after heat treatment of 890℃ heating quenching + 440℃ holding tempering;

[0017] Fig. 2 is a schematic diagram of the tempered martensite structure of the workpiece after heat treatment of 890℃ heating quenching + 460℃ holding tempering;

[0018] Fig. 3 is a schematic diagram of the tempered martensite structure of the workpiece after heat treatment by the heat treatment method provided by the present application;

[0019] Fig. 4 is a schematic diagram of the tempered martensite structure of the workpiece in Example 1;

[0020] Fig. 5 is a schematic diagram of the tempered martensite structure of the workpiece in Example 2;

[0021] Fig. 6 is a schematic diagram of the tempered martensite structure of the workpiece in Example 3. DETAILED DESCRIPTION

[0022] In order to make the content of the present application more easily and clearly understood, the following will further describe the present application in detail according to the specific embodiments and in combination with the drawings.

[0023] The present application provides a CrMn spring steel for automobile stabilizer bar, and the chemical composition and mass percentage are as follows: 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 inevitable impurities.

[0024] The application further provides a heat treatment method of the CrMn spring steel for automobile stabilizer bars, which comprises the following treatment processes in sequence: heating, quenching, tempering, and cooling.

[0025] The heating temperature of the heating process is 830-840 DEG C, which can be adjusted according to the alloy composition.

[0026] It can be understood that the soaking time is determined according to the size of the workpiece and the number of heat treatments.

[0027] The quenching process is oil quenching.

[0028] The tempering temperature of the tempering process is 435-445 DEG C, and the tempering holding time is the soaking time + 70 min.

[0029] The 55Cr3 spring steel produced by the route of converter smelting-LF refining-RH vacuum treatment-continuous casting-hot rolling has segregation in different degrees. As shown in Fig. 1, the workpiece has white bright tempering martensite structure after heat treatment by using 890 DEG C heating quenching + 440 DEG C holding tempering. The tempering martensite structure cannot be eliminated by increasing the tempering temperature to 460 DEG C, as shown in Fig. 2. At the same time, the hardness is low, which affects the fatigue performance of the workpiece.

[0030] By using the heat treatment method provided in the embodiment, the workpiece has tempering troostite structure after heat treatment by using 835 DEG C heating quenching + 440 DEG C tempering, and no obvious tempering martensite structure is observed, as shown in Fig. 3. The hardness is 45-48 HRC, which is in the ideal hardness range of the 55Cr3 stabilizer bar (test shows that the fatigue performance is best in this hardness range).

[0031] The application is further described below by means of specific examples.

[0032] Example 1: Batch A The sample is heated in a resistance furnace, and the process is: 835 DEG C holding for 40 min, oil quenching, and 440 DEG C holding for 90 min tempering. The sample is subjected to metallographic test after heat treatment, and no obvious tempering martensite structure is observed, as shown in Fig. 4. The hardness test is performed, and the Rockwell hardness is 45-46.5 HRC; which meets the requirements.

[0033] Example 2: Batch B The sample is heated in a resistance furnace, and the process is: 830 DEG C holding for 40 min, oil quenching, and 435 DEG C holding for 90 min tempering. The sample is subjected to metallographic test after heat treatment, and no obvious tempering martensite structure is observed, as shown in Fig. 5. The hardness test is performed, and the Rockwell hardness is 46-47 HRC; which meets the requirements.

[0034] Example 3: Batch C The sample is heated in an electric resistance furnace, and the process is: 840℃ for 50min, oil quenching, 435℃ for 95min tempering. After heat treatment, the sample is subjected to metallographic test, and no obvious tempered martensite structure is observed, see Fig. 6. Hardness test is carried out, and the Rockwell hardness is 46.5-48HRC; which meets the requirements.

[0035] Therefore, the technical scheme of the present application processes the workpiece into tempered troostite with a hardness of 46-48HRC, and no tempered martensite structure is found, which meets the production requirements.

[0036] In addition to the above embodiments, the present application can have other implementation manners; any technical scheme formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A CrMn-based spring steel for a stabilizer bar of an automobile, characterized by: The 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%, the balance being Fe and inevitable impurities.

2. A heat treatment method of the CrMn-based spring steel for a vehicle stabilizer bar according to claim 1, characterized by: Comprise in turn: heating, quenching, tempering, cooling; The heating temperature of the heating process is 830-840 DEG C.

3. The heat treatment method of the CrMn-based spring steel for a vehicle stabilizer bar according to claim 2, characterized by: The heating time of the heating process is 20-30 min longer than the soaking time.

4. The heat treatment method of the CrMn-based spring steel for a vehicle stabilizer bar according to claim 2, characterized by: The quenching process adopts oil quenching.

5. The heat treatment method of the CrMn-based spring steel for a vehicle stabilizer bar according to claim 2, characterized by: The tempering temperature of the tempering process is 435-445 DEG C.

6. The heat treatment method of the CrMn-based spring steel for a vehicle stabilizer bar according to claim 2, characterized by: The holding time of the tempering process is 70 min longer than the soaking time.

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