Heat treatment system of stainless steel for mobile phone keys

Abstract

The invention discloses a heat treatment system of stainless steel for mobile phone keys, which is characterized in that 17-4PH precipitated martensitic stainless steel is selected as a workpiece material, and is matched with the steps of solution treatment and aging treatment which are carried out in sequence, and a to-be-treated workpiece is firstly heated to a solution temperature in a graded manner, so that metal elements are uniformly dissolved in a matrix; then quickly cooling to obtain a martensite structure and form a uniform solid solution; aging treatment is carried out after solution treatment, a microstructure is optimized through staged heating of the workpiece to the aging treatment temperature, heat preservation and precipitation strengthening, the strength, toughness and corrosion resistance of the treated workpiece are improved, and the comprehensive force performance is improved. A solution is provided for producing and manufacturing high-quality mobile phone keys which need to meet the requirements of high strength, high hardness and good corrosion resistance at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment, and in particular relates to a heat treatment system for stainless steel used for mobile phone keys. Background Art

[0002] Buttons are one of the indispensable parts of a mobile phone, such as the power button on the side of the phone.

[0003] The buttons of high-end mobile phones have very high requirements on material properties, including high strength and hardness, good corrosion resistance, and excellent processing performance to facilitate precision processing and molding.

[0004] How to select stainless steel materials and how to set up the heat treatment process system is crucial to whether the mobile phone keypad can achieve comprehensive performance while meeting high strength, high hardness and good corrosion resistance. This case arises from this. Summary of the invention

[0005] The purpose of the present invention is to provide a heat treatment system for stainless steel used for mobile phone keys, which can obtain mobile phone keys with high strength, high hardness and good corrosion resistance.

[0006] To this end, the present invention adopts the following technical solutions: A heat treatment system for stainless steel for mobile phone keys, comprising the following steps: 17-4PH martensitic stainless steel is selected as the material of the workpiece to be processed, and the workpiece to be processed is subjected to heat treatment, and the heat treatment comprises the following steps: S1, solution treatment: heating the workpiece to be treated to the solution temperature in stages and then keeping the temperature to make the metal elements uniformly dissolved in the matrix, and then rapidly cooling to obtain a martensitic structure to form a uniform solid solution; S2. Aging treatment: The workpiece treated in S1 is heated to the aging treatment temperature in stages, kept at this temperature for 2h~4h and then cooled to form precipitation strengthening.

[0007] Furthermore, in step S1, the solution temperature is 1050°C.

[0008] Furthermore, in step S1, the graded heating includes five stages, the first stage is heating from room temperature to 200°C; the second stage is heating from 200°C to 300°C; the third stage is heating from 300°C to 650°C; the fourth stage is heating from 650°C to 950°C; and the fifth stage is heating from 950°C to 1050°C.

[0009] Furthermore, in step S1, the rapid cooling is to cool the workpiece after the solution treatment to 45°C~55°C within 35min~45min.

[0010] Furthermore, in step S2, the aging treatment temperature is 480°C.

[0011] Furthermore, in step S2, the aging treatment includes three stages, the first stage is heating from room temperature to 200°C, the second stage is heating from 200°C to 300°C, and the third stage is heating from 300°C to 480°C.

[0012] Furthermore, in step S2, the cooling rate is controlled to cool from 480°C for 40min to 50min to below 50°C before being taken out of the furnace.

[0013] Furthermore, after the solution treatment in step S1, the hardness of the workpiece is 260-400 HV, and the microstructure is uniform lath martensite.

[0014] Furthermore, after the aging treatment in step S2, the hardness of the workpiece is 350-480 HV, and the microstructure is fine martensite.

[0015] Compared with the background technology, this technical solution has at least the following advantages: The invention selects 17-4PH precipitated martensitic stainless steel as the workpiece material, cooperates with the solid solution treatment and aging treatment steps carried out in sequence, heats the workpiece to be treated to the solid solution temperature in stages, makes the metal elements uniformly dissolved in the matrix, and then quickly cools to obtain the martensitic structure to form a uniform solid solution; after the solid solution treatment, the aging treatment is carried out, heats the workpiece to the aging treatment temperature in stages, keeps the temperature, forms precipitation strengthening, and optimizes the microstructure, improves the strength, toughness and corrosion resistance of the workpiece after treatment, improves the comprehensive performance, and provides a solution for manufacturing high-quality mobile phone keys that need to meet the requirements of high strength, high hardness and good corrosion resistance at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A curve diagram of the solution treatment process in the heat treatment process provided by the present invention; Figure 2 A curve diagram of the aging treatment process in the heat treatment process provided by the present invention; Figure 3 This is a microstructure diagram of the mobile phone key workpiece after solution and aging treatment provided by the present invention. DETAILED DESCRIPTION

[0017] In the prior art, there are technical problems such as how to select stainless steel materials and how to set up the heat treatment process system to meet the high comprehensive performance requirements of mobile phone keys.

[0018] To this end, the present invention provides a new heat treatment system for stainless steel used for mobile phone keys to solve the above technical problems.

[0019] In order to make the purpose, features and advantages of the present invention clearer, the specific embodiments of the present invention are described in more detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can be implemented in many other ways different from the description. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] The present invention provides a heat treatment system for stainless steel for mobile phone keys, using 17-4PH martensitic stainless steel as the material of the workpiece to be subsequently heat treated, and the chemical composition (by mass percentage) of the 17-4PH martensitic stainless steel is as follows: C≤0.07%, Si≤1.00%, Mn≤1.00%, P≤0.04%, S≤0.03%, Ni 3~5%, Cr 15~17.5%, Cu 3~5%, Nb 0.15~0.45%, and the balance is Fe. 17-4PH steel belongs to precipitation hardening stainless steel and is widely used in aerospace, chemical equipment, energy industry, medical equipment and other fields. The heat treatment process system has a great influence on its performance, and can meet the needs of different application scenarios through precise control.

[0021] 17-4PH martensitic precipitation hardening martensitic stainless steel can meet the performance requirements of high strength and good corrosion resistance of mobile phone keys through heat treatment. The heat treatment process includes two steps: solution treatment and aging treatment. The heat treatment process is relatively difficult, and the difficulty lies in solution treatment. It is necessary to accurately select and control the heating temperature, dissolve all alloy elements into austenite, accurately select and control the cooling rate to reduce deformation, and the aging treatment requires accurate selection of the aging temperature and time to obtain the required precipitation phase, thereby obtaining the expected hardness, strength and corrosion resistance.

[0022] The heat treatment system provided by the present invention includes S1 and S2 performed sequentially, wherein: S1, solution treatment: heating the workpiece to be treated to the solution temperature in stages and then keeping the temperature to make the metal elements uniformly dissolved in the matrix, and then rapidly cooling to obtain a martensitic structure to form a uniform solid solution; Specifically, refer to Figure 1 As shown, the graded heating includes five stages. The first stage is heated from room temperature to 200°C and then kept warm for 1 minute; the second stage is heated from 200°C to 300°C and then kept warm for 1 minute; the third stage is heated from 300°C to 650°C and then kept warm for 1 minute; the fourth stage is heated from 650°C to 950°C and then kept warm for 30 minutes; the fifth stage is heated from 950°C to 1050°C and then kept warm for 90 minutes. Among them, 1050°C is the solution temperature, that is, the austenitizing temperature of 17-4PH. The above-mentioned graded heating method is used to heat to the solution temperature, and the temperature is gradually increased, which can reduce thermal stress and deformation.

[0023] In step S1, adopting an appropriate cooling rate after solutionizing can reduce residual stress and help reduce deformation. The control conditions adopted by the present invention are: cooling to 45°C~55°C within 35min~45min. In a specific embodiment, the cooling is slow cooling by air cooling for 40min until the workpiece temperature is below 50°C before being taken out of the furnace. After processing in step S1, the hardness of the workpiece is 260~400HV, and the microstructure is uniform lath martensite.

[0024] S2. Aging treatment: The workpiece treated in S1 is heated to the aging treatment temperature in stages, kept at this temperature for 2h~4h and then cooled to form precipitation strengthening.

[0025] Specifically, in step S2, the aging treatment temperature is 480°C. Figure 2 As shown, in the aging treatment of the present invention, the graded heating includes three stages. The first stage is heated from room temperature to 200°C and then kept warm for 1 minute. The second stage is heated from 200°C to 300°C and then kept warm for 10 minutes. The third stage is heated from 300°C to 480°C and then kept warm for 120 minutes to 240 minutes.

[0026] In step S2, the cooling speed after heat preservation is controlled as follows: cooling from 480°C for 40min to 50min until the workpiece temperature is below 50°C, and then the workpiece is taken out of the furnace. In a specific embodiment, the cooling is performed by air blowing.

[0027] The present invention is as follows Figure 1 and Figure 2 The temperature and time control conditions in the process curve shown in the figure, after processing in step S1 and step S2, the hardness of the workpiece is measured to be 440 HV, which meets the required value of 350~480HV, and the microstructure is fine martensite. The hardness and strength are improved, the toughness is good, and the deformation is reduced. The deformation of the key is less than 6μm.

[0028] In summary, the microstructure of 17-4PH precipitated martensitic stainless steel is optimized through the above-mentioned solution treatment and aging treatment (see Figure 3 , microstructure 1000X), which improves the strength, toughness and corrosion resistance, improves the comprehensive performance, and can meet the quality requirements of mobile phone buttons.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A heat treatment system for stainless steel used for mobile phone keys, characterized in that: 17-4PH martensitic stainless steel is selected as the material of the workpiece to be processed, and the workpiece to be processed is subjected to heat treatment, and the heat treatment comprises the following steps: S1, solution treatment: heating the workpiece to be treated to the solution temperature in stages and then keeping the temperature to make the metal elements uniformly dissolved in the matrix, and then rapidly cooling to obtain a martensitic structure to form a uniform solid solution; S2. Aging treatment: The workpiece treated in S1 is heated to the aging treatment temperature in stages, kept at this temperature for 120min~240min, and then cooled to form precipitation strengthening.

2. The heat treatment system of stainless steel for mobile phone keys according to claim 1 is characterized by: In step S1, the solution temperature is 1050°C.

3. The heat treatment system of stainless steel for mobile phone keys according to claim 1 or 2, characterized in that: In step S1, the graded heating includes five stages, the first stage is heating from room temperature to 200°C; the second stage is heating from 200°C to 300°C; the third stage is heating from 300°C to 650°C; the fourth stage is heating from 650°C to 950°C; and the fifth stage is heating from 950°C to 1050°C.

4. The heat treatment system of stainless steel for mobile phone keys according to claim 1 is characterized by: In step S1, the rapid cooling is to cool the workpiece after the solution treatment to 45°C~55°C within 35min~45min.

5. The heat treatment system of stainless steel for mobile phone keys according to claim 1 is characterized by: In step S2, the aging treatment temperature is 480°C.

6. The heat treatment system of stainless steel for mobile phone keys according to claim 1 or 5, characterized in that: In step S2, the aging treatment includes three stages, the first stage is heating from room temperature to 200°C, the second stage is heating from 200°C to 300°C, and the third stage is heating from 300°C to 480°C.

7. The heat treatment system of stainless steel for mobile phone keys according to claim 1, characterized in that: In step S2, the cooling rate is controlled to cool from 480°C for 40min to 50min to below 50°C before being taken out of the furnace.

8. The heat treatment system of stainless steel for mobile phone keys according to claim 1 is characterized by: After the solution treatment in step S1, the hardness of the workpiece is 260~400HV, and the microstructure is uniform lath martensite.

9. The heat treatment system of stainless steel for mobile phone keys according to claim 1, characterized in that: After aging treatment in step S2, the hardness of the workpiece is 350~480HV, and the microstructure is fine martensite.

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