A valve box machining method

Abstract

The application discloses a valve box processing method, comprising the following steps: S1, rough machining of a pressure pump valve box forge blank; S2, normalizing treatment; S3, first tempering treatment; S4, carbonitriding treatment; S5, precooling quenching treatment; S6, second tempering treatment; and S7, packaging. The application simultaneously permeates carbon and nitrogen into the workpiece in the form of carbonitriding to form a carbonitriding layer, on the one hand, carbon atoms enter the metal surface and combine with metal atoms to form carbide, thereby improving the hardness and wear resistance of the workpiece surface, and wear and scratches on the metal surface can be effectively prevented; on the other hand, the permeation of nitrogen forms a dense nitride layer on the workpiece surface, improves the corrosion resistance, and enables the workpiece to be applicable to a harsh environment during oil exploitation; and on the third aspect, the residual compressive stress of the carbonitriding layer can improve the fatigue limit of the workpiece, thereby improving the fatigue strength of the workpiece and reducing brittleness.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of valve box heat treatment, in particular to a valve box machining method. BACKGROUND

[0002] The valve box is an important component of the fracturing pump and is mainly used for fracturing operation of deep and medium-deep wells in oil and gas fields. Due to the increasing number of ultra-high pressure and ultra-deep oil wells, the fracturing equipment is more widely applied, and the fracturing equipment has higher and higher requirements for the displacement and pressure of the fracturing pump. The higher the pressure is, the greater the impact on the valve box is, so it is necessary to improve the hardness, wear resistance and toughness of the valve box.

[0003] For example, a hot treatment method for a stainless steel material for a fracturing pump valve box in application No. 202111008484.0 can effectively control the microstructure transformation process of the stainless steel material and the microstructure of the material after quenching. The austenite phase rapidly transforms into quenched martensite during water quenching, and oil cooling is mainly used in the late quenching period to prevent internal stress concentration and eliminate the risk of stress cracking and uneven microstructure performance caused by rapid cooling in the water cooling process. It meets the needs of the oil drilling and fracturing industry for stainless steel fracturing equipment products, such as high pressure resistance, corrosion resistance, ability to withstand long-term alternating load environment, pitting resistance, crack resistance and long service life. SUMMARY

[0004] To solve the above technical problems, the application provides a valve box machining method.

[0005] A valve box machining method comprises the following steps:

[0006] S1, rough machining of the pressure pump valve box forging blank;

[0007] S2, normalizing treatment;

[0008] S3, first tempering treatment;

[0009] S4, carbonitriding treatment;

[0010] S5, pre-cooling quenching treatment;

[0011] S6, second tempering treatment;

[0012] S7, packaging.

[0013] As a further technical solution of the application, in the S4, the process of the carbonitriding treatment is as follows: the workpiece is heated to 820-840 DEG C in the furnace for 12-14 hours, the penetrant and the catalyst are introduced, and the penetration depth is 0.6-1 mm.

[0014] Through the technical scheme, on one hand, carbon atoms enter the metal surface and combine with metal atoms to form carbides, thereby improving the hardness and wear resistance of the workpiece surface, and effectively preventing the wear and scratch of the metal surface.

[0015] On the other hand, the penetration of nitrogen forms a dense nitride layer on the surface of the workpiece, thereby improving the corrosion resistance, and making the workpiece suitable for harsh environments in oil exploitation.

[0016] Thirdly, the residual compressive stress of the co-diffusion layer can improve the fatigue limit of the workpiece, thereby improving the fatigue strength and reducing the brittleness of the workpiece.

[0017] As a further technical scheme of the present application, in the carbon-nitrogen co-diffusion treatment, ammonia and anhydrous ethanol are used as the penetrant, and CaCl2 is used as the catalyst.

[0018] As a further technical scheme of the present application, in S5, the pre-cooling quenching process is as follows: after the workpiece is taken out of the furnace, it is cooled to room temperature by oil cooling, and then heated to 850-870 DEG C for 10-12 hours, and then cooled by air cooling.

[0019] Through the above technical scheme, by pre-cooling the workpiece, the surface residual austenite is reduced, the workpiece deformation is avoided, and the oil cooling method is used for rapid cooling, and then directly quenched after rapid cooling, which can improve the core strength of the workpiece.

[0020] As a further technical scheme of the present application, in S5, the workpiece heating rate is 50-70 DEG C / h.

[0021] Through the rapid heating rate, the thermal stress generated during heating is reduced, and the fatigue strength of the workpiece is improved.

[0022] As a further technical scheme of the present application, in S6, the process of the second tempering treatment is as follows: the workpiece is heated to 240-260 DEG C for 20-22 hours, and then cooled by air cooling.

[0023] Through the above technical scheme, by low temperature tempering, the high hardness and wear resistance of the quenched workpiece can be maintained, and the quenching residual stress and brittleness are reduced.

[0024] As a further technical scheme of the present application, in S2, the process of the normalizing treatment is as follows: the workpiece is heated to 850-870 DEG C for 10-12 hours, and then cooled by air cooling.

[0025] Through the above technical scheme, by normalizing treatment, the crystalline grains in the material are refined, and the toughness is improved.

[0026] As a further technical solution of the present invention, in S3, the first tempering process is as follows: the workpiece is heated to 800℃-820℃ and held for 14h-16h, and then cooled by water cooling.

[0027] The above technical solution involves a first tempering treatment to initially stabilize the surface structure of the workpiece, followed by water cooling to rapidly reduce the workpiece temperature and prevent temper brittleness.

[0028] In summary, the present invention has at least one of the following beneficial technical effects:

[0029] This application introduces carbon and nitrogen into a workpiece simultaneously via carbonitriding to form a carbon-nitrogen co-diffusion layer. On one hand, carbon atoms enter the metal surface and combine with metal atoms to form carbides, thereby increasing the surface hardness and wear resistance of the workpiece and effectively preventing wear and scratches on the metal surface. On the other hand, the infiltration of nitrogen forms a dense nitride layer on the workpiece surface, improving corrosion resistance and enabling the workpiece to be used in the harsh environment of oil extraction. Thirdly, the residual compressive stress of the co-diffusion layer can increase the fatigue limit of the workpiece, thereby improving its fatigue strength and reducing brittleness.

[0030] Simultaneously, the carbonitrided workpiece is subjected to rapid cold treatment and quenching to obtain martensite with high wear resistance and increase surface hardness. Detailed Implementation

[0031] The present application will be further described in detail below with reference to the embodiments.

[0032] This application discloses a valve box processing method, including the following steps:

[0033] S1, the pressure pump valve box forging blank is rough-machined;

[0034] S2, normalizing treatment;

[0035] In S2, the normalizing process is as follows: the workpiece is heated to 850℃-870℃ and held for 10h-12h, followed by air cooling.

[0036] S3, First tempering treatment;

[0037] In S3, the first tempering process is as follows: the workpiece is heated to 800℃-820℃ and held for 14h-16h, followed by water cooling.

[0038] Normalizing refines the grains in the material, improving toughness. At the same time, a first tempering process initially stabilizes the surface structure of the workpiece. Water cooling is used to quickly reduce the workpiece temperature and prevent temper brittleness.

[0039] S4, carbonitriding treatment;

[0040] In step S4, the carbonitriding process is as follows: the workpiece is placed in a furnace and heated to 820℃-840℃ and kept there for 12h-14h, and a penetrating agent and a penetrating accelerator are introduced to a penetration depth of 0.6mm-1mm.

[0041] Simultaneously, carbon and nitrogen are diffused into the workpiece to form a carbon and nitrogen co-diffusion layer;

[0042] On the one hand, carbon atoms enter the metal surface and combine with metal atoms to form carbides, thereby increasing the hardness and wear resistance of the workpiece surface, which can effectively prevent wear and scratches on the metal surface;

[0043] On the other hand, the penetration of nitrogen creates a dense nitride layer on the surface of the workpiece, which improves its corrosion resistance and makes it suitable for the harsh environment of oil extraction.

[0044] Thirdly, the residual compressive stress in the co-diffusion layer can enhance the fatigue limit of the workpiece, thereby improving its fatigue resistance and reducing its brittleness.

[0045] In some specific real-time examples, ammonia and anhydrous ethanol are used as permeating agents, and CaCl2 is used as a permeation accelerator.

[0046] S5, pre-cooling and quenching treatment;

[0047] In S5, the pre-cooling quenching process is as follows: after the workpiece is taken out of the furnace, it is cooled to room temperature by oil cooling, heated to 850℃-870℃ at a heating rate of 50℃ / h-70℃ / h and held for 10h-12h, and then cooled by air cooling.

[0048] Pre-cooling the workpiece reduces residual austenite on the surface, avoids workpiece deformation, and uses oil cooling for rapid cooling. Then, quenching is performed directly after rapid cooling, which can improve the core strength of the workpiece.

[0049] S6, second tempering treatment;

[0050] In step S6, the second tempering process is as follows: the workpiece is heated to 240℃-260℃ and held for 20h-22h, followed by air cooling.

[0051] Low-temperature tempering can maintain the high hardness and wear resistance of quenched workpieces, and reduce quenching residual stress and brittleness.

[0052] S7, Packaging.

[0053] The carbonitriding furnace used in this application is a JT-25 type gas carburizing furnace. Specific Implementation

[0055] Example 1

[0056] A valve box processing method according to this embodiment includes the following steps:

[0057] 1. Rough machining of the pressure pump valve box forging blank;

[0058] 2. Normalizing treatment;

[0059] The workpiece was heated to 870℃ and held for 12 hours, followed by air cooling.

[0060] 3. First tempering treatment;

[0061] The workpiece was heated to 820°C and held for 16 hours, followed by water cooling.

[0062] 4. Carbonitriding treatment;

[0063] The workpiece was placed in a furnace and heated to 840℃ for 14 hours. Ammonia was introduced into the furnace at a rate of 500 L / h, anhydrous ethanol was introduced at a rate of 50 d / min, and 30 g of CaCl2 was added.

[0064] 5. Pre-cooling and quenching treatment;

[0065] After the workpiece is removed from the furnace, it is cooled to room temperature by oil cooling, heated to 870°C at a heating rate of 70°C / h and held for 12 hours, and then cooled by air cooling.

[0066] 6. Second tempering treatment;

[0067] The workpiece was heated to 260°C and held for 22 hours, followed by air cooling.

[0068] 7. Packaging.

[0069] Example 2

[0070] A valve box processing method according to this embodiment includes the following steps:

[0071] 1. Rough machining of the pressure pump valve box forging blank;

[0072] 2. Normalizing treatment;

[0073] The workpiece was heated to 850℃ and held for 10 hours, followed by air cooling.

[0074] 3. First tempering treatment;

[0075] The workpiece was heated to 800℃ and held for 14 hours, followed by water cooling.

[0076] 4. Carbonitriding treatment;

[0077] The workpiece was placed in a furnace and heated to 820℃ for 12 hours. Ammonia was introduced into the furnace at a rate of 500 L / h, anhydrous ethanol was introduced at a rate of 50 d / min, and 30 g of CaCl2 was added.

[0078] 5. Pre-cooling and quenching treatment;

[0079] After the workpiece is removed from the furnace, it is cooled to room temperature with oil cooling, heated to 850°C at a heating rate of 50°C / h and held for 10 hours, and then cooled with air cooling.

[0080] 6. Second tempering treatment;

[0081] The workpiece was heated to 240°C and held for 20 hours, followed by air cooling.

[0082] 7. Packaging.

[0083] Example 3

[0084] A valve box processing method according to this embodiment includes the following steps:

[0085] 1. Rough machining of the pressure pump valve box forging blank;

[0086] 2. Normalizing treatment;

[0087] The workpiece was heated to 860℃ and held for 11 hours, followed by air cooling.

[0088] 3. First tempering treatment;

[0089] The workpiece was heated to 810℃ and held for 15 hours, followed by water cooling.

[0090] 4. Carbonitriding treatment;

[0091] The workpiece was placed in a furnace and heated to 830℃ for 13 hours. Ammonia was introduced into the furnace at a rate of 500 L / h, anhydrous ethanol was introduced at a rate of 50 d / min, and 30 g of CaCl2 was added.

[0092] 5. Pre-cooling and quenching treatment;

[0093] After the workpiece is removed from the furnace, it is cooled to room temperature by oil cooling, heated to 860°C at a heating rate of 60°C / h and held for 11 hours, and then cooled by air cooling.

[0094] 6. Second tempering treatment;

[0095] The workpiece was heated to 250°C and held for 21 hours, followed by air cooling.

[0096] 7. Packaging.

[0097] Comparative Example

[0098] 1. Rough machining of the pressure pump valve box forging blank;

[0099] 2. Normalizing treatment;

[0100] The workpiece was heated to 860℃ and held for 11 hours, followed by air cooling.

[0101] 3. First tempering treatment;

[0102] The workpiece was heated to 810℃ and held for 15 hours, followed by water cooling.

[0103] 4. Packaging.

[0104] Performance testing

[0105] Yield strength and room temperature Charpy V-type impact test were performed according to the method described in ATMA 370.

[0106] Hardness testing was performed using a Rockwell hardness tester, with direct readings.

[0107] The workpieces prepared in Examples 1-3 and Comparative Example 1 were tested according to the above testing methods. The specific test results are shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] The test results from Examples 1-3 and Comparative Example 1 show that the toughness, hardness, and wear resistance of the workpiece are greatly improved by carbonitriding.

[0112] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A valve chest machining method characterized by, It comprises the following steps: S1, rough machining of the pressure pump valve box forge blank; S2, normalizing treatment; S3, first tempering treatment; S4, carbonitriding treatment; S5, pre-cooling quenching treatment; S6, second tempering treatment; S7, packaging; In the S4, the process of the carbonitriding treatment is: the workpiece is heated to 820-840 DEG C in the furnace for 12-14 h, the penetrant and the catalyst are introduced, and the penetration depth is 0.6-1 mm; In the carbonitriding treatment, ammonia and anhydrous ethanol are used as the penetrant, and CaCl2 is used as the catalyst; In the S5, the process of the pre-cooling quenching treatment is: the workpiece is taken out from the furnace and cooled to room temperature by oil cooling, the workpiece is heated to 850-870 DEG C for 10-12 h, and then air cooling is used; In the S5, the workpiece heating rate is 50-70 DEG C / h; In the S6, the process of the second tempering treatment is: the workpiece is heated to 240-260 DEG C for 20-22 h, and then air cooling is used; In the S2, the process of the normalizing treatment is: the workpiece is heated to 850-870 DEG C for 10-12 h, and then air cooling is used; In the S3, the process of the first tempering treatment is: the workpiece is heated to 800-820 DEG C for 14-16 h, and then water cooling is used.

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