Heat treatment method for improving toughness of 42CrMo bar and 42CrMo bar

Abstract

The invention provides a heat treatment method for improving the toughness of a 42CrMo bar and the 42CrMo bar, and the heat treatment method comprises the following steps: S1, carrying out preheating treatment on the 42CrMo bar with a preset mass ratio to obtain a first sample; s2, quenching the first sample to obtain a second sample; s3, the second sample is subjected to tempering treatment, and a 42CrMo bar with the material toughness improved is obtained; the quenching treatment in S2 specifically comprises the following steps: rapidly heating the first sample to 800-850 DEG C, preserving heat, and carrying out oil quenching to obtain a second sample; the tempering treatment in the step S3 specifically comprises the following steps: heating the second sample to 560-630 DEG C, preserving heat, and then carrying out water cooling or oil cooling to room temperature. On the basis of keeping good hardness and strength of the 42CrMo steel, the low-temperature toughness of the 42CrMo steel is further improved, powerful support is provided for wide application of the 42CrMo steel, and remarkable practical value and economic benefits are achieved.

Description

[Technical field]

[0001] The invention relates to the technical field of heat treatment of metal materials, and in particular to a heat treatment method for improving the toughness of a 42CrMo bar and the 42CrMo bar. [Background technology]

[0002] 42CrMo steel is an alloy structural steel in terms of material classification. It has good mechanical properties and machinability and is widely used. It mainly has two types of materials: plates and round bars. Its comprehensive performance is better than that of 40Cr. Among them, 42CrMo bar is a commonly used alloy structural steel with good strength and wear resistance. It is currently widely used in the manufacture of batons for military and police and various mechanical parts.

[0003] However, the impact toughness of 42CrMo steel is only required to be 63J at room temperature. In fact, this material is increasingly used in low-temperature environments, and its low-temperature toughness cannot meet higher usage requirements. How to further improve the low-temperature toughness of 42CrMo steel while maintaining its high hardness and strength is the biggest challenge in this field.

[0004] Therefore, it is necessary to study a heat treatment method for improving the toughness of 42CrMo rods and 42CrMo rods to cope with the deficiencies of the prior art, so as to solve or alleviate one or more of the above problems. [Summary of the invention]

[0005] In view of this, the present invention provides a heat treatment method for improving the toughness of 42CrMo rods and 42CrMo rods, which further improve the low-temperature toughness of 42CrMo steel while maintaining good hardness and strength, provide strong support for the wide application of 42CrMo steel, and have significant practical value and economic benefits.

[0006] In one aspect, the present invention provides a heat treatment method for improving the toughness of a 42CrMo bar, the heat treatment method comprising the following steps:

[0007] S1: preheating a 42CrMo bar with a preset mass ratio to obtain a first sample;

[0008] S2: performing quenching treatment on the first sample to obtain a second sample;

[0009] S3: Tempering the second sample to obtain a 42CrMo bar with improved material toughness;

[0010] The quenching treatment in S2 is specifically as follows: the first sample is rapidly heated to 800-850° C., and then oil quenched after heat preservation to obtain the second sample;

[0011] The tempering treatment in S3 is specifically as follows: heating the second sample to 560-630° C., keeping the temperature, and then water cooling or oil cooling to room temperature.

[0012] According to the above aspects and any possible implementation, an implementation is further provided, wherein the preset mass ratio of the 42CrMo rod in S1 is specifically the mass percentage:

[0013] C: 0.38-0.45%, Mn: 0.5-0.8, Si: 0.17-0.37, Cr: 0.90-1.20, P: ≤0.03, S: ≤0.03, Mo: 0.15-0.25%, the balance is Fe and unavoidable impurities.

[0014] According to the aspects and any possible implementations described above, an implementation is further provided, wherein the preheating treatment in S1 specifically comprises: vacuum sealing or coating the 42CrMo rods with a preset mass ratio to prevent high-temperature decarburization on the surface of the material.

[0015] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the insulation time in S2 is 0.5-1 hour.

[0016] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the second sample in S2 is a 42CrMo rod having a martensitic structure with fine grains.

[0017] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the insulation time in S3 is 1-3 hours.

[0018] According to the above aspects and any possible implementation, an implementation is further provided, wherein the 42CrMo rod with a preset mass ratio in S1 is a sample with a length of 100-300 mm and a size of φ20-30 mm.

[0019] According to the above aspects and any possible implementation, an implementation is further provided, wherein the structure of the 42CrMo rod with improved material toughness in S3 includes tempered troostite, ferrite and retained austenite.

[0020] According to the above aspects and any possible implementation, an implementation is further provided, in which the 42CrMo rod with improved material toughness in S3 is machined into a Charpy impact standard specimen before the toughness test.

[0021] According to the above aspects and any possible implementation, a 42CrMo rod is further provided. The 42CrMo rod is obtained by heat treatment by the heat treatment method, and the impact energy of the 42CrMo rod is not less than 80J at -60°C.

[0022] Compared with the prior art, the present invention can achieve the following technical effects:

[0023] The present invention improves the low-temperature toughness of 42CrMo rods by changing the heat treatment temperature and significantly improves the low-temperature toughness of 42CrMo rods by controlling the temperature and holding time of quenching and tempering, while maintaining good strength and hardness, meeting the requirements of high-end machinery manufacturing industry for material properties.

[0024] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time.

Brief Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a microstructure diagram of 42CrMo rod in Example 1 of the present invention;

[0027] Figure 2 is a microstructure diagram of 42CrMo rod in Example 2 of the present invention;

[0028] Figure 3 This is a microstructure diagram of the 42CrMo rod in Comparative Example 1 of the present invention;

[0029] Figure 4 The present invention provides a process flow chart of a heat treatment method for improving the toughness of 42CrMo bars. [Specific implementation method]

[0030] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0033] like Figure 4 As shown, the present invention provides a heat treatment method for improving the toughness of 42CrMo bars, the heat treatment method comprising the following steps:

[0034] S1: preheating a 42CrMo bar with a preset mass ratio to obtain a first sample;

[0035] S2: performing quenching treatment on the first sample to obtain a second sample;

[0036] S3: Tempering the second sample to obtain a 42CrMo bar with improved material toughness;

[0037] The quenching treatment in S2 is specifically as follows: the first sample is rapidly heated to 800-850° C., and then oil quenched after heat preservation to obtain the second sample;

[0038] The tempering treatment in S3 is specifically as follows: heating the second sample to 560-630° C., keeping the temperature, and then water cooling or oil cooling to room temperature.

[0039] In a specific embodiment, the preset mass ratio of the 42CrMo rod in S1 is specifically the mass percentage:

[0040] C: 0.38-0.45%, Mn: 0.5-0.8, Si: 0.17-0.37, Cr: 0.90-1.20, P: ≤0.03, S: ≤0.03, Mo: 0.15-0.25%, the balance is Fe and unavoidable impurities.

[0041] In a specific embodiment, the preheating treatment in S1 is specifically: vacuum sealing or coating the 42CrMo rods with a preset mass ratio to prevent high-temperature decarburization on the surface of the material.

[0042] In a specific embodiment, the insulation time in S2 is 0.5-1 hour.

[0043] In a specific embodiment, the holding time is preferably 0.5 hours.

[0044] In a specific embodiment, the second sample in S2 is a 42CrMo rod having a martensitic structure with fine grains.

[0045] In a specific embodiment, the insulation time in S3 is 1-3 hours.

[0046] In a specific embodiment, the holding time is preferably 2 hours.

[0047] In a specific embodiment, the 42CrMo rod with a preset mass ratio in S1 is a sample with a length of 100-300 mm and a diameter of 20-30 mm.

[0048] In a specific embodiment, the 42CrMo rod with a preset mass ratio in S1 is preferably a sample with a length of 200 mm and a diameter of 25 mm.

[0049] In a specific embodiment, the structure of the 42CrMo rod with improved material toughness in S3 includes tempered troostite, ferrite and retained austenite.

[0050] In a specific embodiment, the 42CrMo rod with improved material toughness in S3 is machined into a Charpy impact standard specimen before the toughness test.

[0051] The present invention also provides a 42CrMo rod, which is obtained by heat treatment by the heat treatment method, and the impact energy of the 42CrMo rod is not less than 80J under -60°C.

[0052] Embodiment 1:

[0053] In this embodiment, S2 and S3 are specifically as follows:

[0054] (1) Quenching treatment: The preheated 42CrMo bar is rapidly heated to 850°C, kept at this temperature for 0.5 hours, and then oil quenched;

[0055] (2) Tempering treatment: The quenched 42CrMo bar is heated to 630°C, kept at this temperature for 2 hours, and then water-cooled to room temperature.

[0056] like Figure 1 As shown in the figure, after the above steps, the low-temperature toughness of 42CrMo rod is significantly improved, and the impact energy is as high as 88J at -60℃, while maintaining good hardness and strength.

[0057] Embodiment 2:

[0058] In this embodiment, S2 and S3 are specifically as follows:

[0059] (1) Quenching treatment: The preheated 42CrMo bar is rapidly heated to 800°C, kept at this temperature for 0.5 hours, and then oil quenched;

[0060] (2) Tempering treatment: The quenched 42CrMo bar is heated to 630°C, kept at this temperature for 2 hours, and then water-cooled to room temperature.

[0061] like Figure 2 As shown in the figure, after the above steps, the toughness of 42CrMo rod is significantly improved, and the impact energy is as high as 101J at -60℃, while maintaining good hardness and strength.

[0062] Comparative Example 1:

[0063] In this embodiment, S2 and S3 are specifically as follows:

[0064] (1) Quenching treatment: The preheated 42CrMo bar is rapidly heated to 850°C, kept warm, and then oil quenched;

[0065] (2) Tempering treatment: The quenched 42CrMo bar is heated to 560°C, kept warm, and then water-cooled to room temperature.

[0066] like Figure 3 As shown, after the above steps, the impact energy of the 42CrMo rod at -60°C is extremely low, less than 10J.

[0067] The national standard for impact toughness of 42CrMo steel only requires 63J at room temperature. In fact, this material is increasingly used in low-temperature environments, and its low-temperature toughness cannot meet higher usage requirements. The specific process and toughness requirements recommended by the national standard for 42CrMo are shown in Table 1:

[0068] Brand Quenching temperature / ℃ Insulation time / h Tempering temperature / ℃ Insulation time / h Impact energy / J(room temperature) 42CrMo 850 - 560 - 63

[0069] Table 1

[0070] The present invention provides a heat treatment process for improving the toughness of 42CrMo bars by changing the heat treatment temperature. The specific embodiment shows that the process can further improve the low-temperature toughness of 42CrMo steel while maintaining the good hardness and strength. The present invention provides strong support for the wide application of 42CrMo steel and has significant practical value and economic benefits. The present invention has the advantages of simple process, convenient operation, and significant effect. The practicality and feasibility of the process are proved by the verification of specific embodiments 1-2 and comparative example 1. The present invention provides technical support for the wide application of 42CrMo steel and helps to improve the quality and performance of related products.

[0071] The above is a detailed introduction to a heat treatment method for improving the toughness of 42CrMo rods and 42CrMo rods provided in the embodiments of the present application. The description of the above embodiments is only used to help understand the method and its core idea of ​​the present application; at the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present application.

[0072] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0073] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0074] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0075] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A heat treatment method for improving the toughness of 42CrMo bars, characterized in that: The heat treatment method comprises the following steps: S1: preheating a 42CrMo bar with a preset mass ratio to obtain a first sample; S2: performing quenching treatment on the first sample to obtain a second sample; S3: Tempering the second sample to obtain a 42CrMo bar with improved material toughness; The quenching treatment in S2 is specifically as follows: the first sample is rapidly heated to 800-850° C., and then oil quenched after heat preservation to obtain the second sample; The tempering treatment in S3 is specifically as follows: heating the second sample to 560-630° C., keeping the temperature, and then water cooling or oil cooling to room temperature.

2. The heat treatment method according to claim 1, characterized in that The 42CrMo rod material with the preset mass ratio in S1 is specifically the mass percentage: C: 0.38-0.45%, Mn: 0.5-0.8, Si: 0.17-0.37, Cr: 0.90-1.20, P: ≤0.03, S: ≤0.03, Mo: 0.15-0.25%, the balance is Fe and unavoidable impurities.

3. The heat treatment method according to claim 1, characterized in that The preheating treatment in S1 is specifically: vacuum sealing or coating the 42CrMo rods with a preset mass ratio to prevent high-temperature decarburization on the surface of the material.

4. The heat treatment method according to claim 1, characterized in that: The insulation time in S2 is 0.5-1 hour.

5. The heat treatment method according to claim 1, characterized in that: The second sample in S2 is a 42CrMo rod having a fine-grained martensitic structure.

6. The heat treatment method according to claim 1, characterized in that: The insulation time in S3 is 1-3 hours.

7. The heat treatment method according to claim 1, characterized in that: The 42CrMo rods with a preset mass ratio in S1 are samples with a length of 100-300 mm and a diameter of 20-30 mm.

8. The heat treatment method according to claim 1, characterized in that: The microstructure of the 42CrMo rod with improved material toughness in S3 includes tempered troostite, ferrite and retained austenite.

9. The heat treatment method according to claim 1, characterized in that: The 42CrMo rod with improved material toughness in S3 is machined into a Charpy impact standard specimen before toughness testing.

10. A 42CrMo bar, characterized in that: The 42CrMo rod is obtained by heat treatment according to any one of claims 1 to 9, and the impact energy of the 42CrMo rod is not less than 80J at -60°C.

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