Chemical heat treatment method for skin

Abstract

The invention discloses a surface chemical heat treatment method, and relates to the technical field of pump cylinder heat treatment, the surface chemical heat treatment method comprises the following operation steps: S1, pretreatment: cleaning and drying a to-be-treated pump cylinder, removing surface oil stains and impurities, and coating the surface of the pump cylinder with a layer of high-temperature-resistant anti-oxidation coating; and S2, vacuum heat treatment is conducted, specifically, the pump cylinder coated with the coating is placed in a vacuum furnace, a vacuum pump is started to pump out air in the furnace to be in a vacuum state, and heat treatment is conducted by setting the heating temperature and the heat preservation time. According to the chemical heat treatment method for the skin, various means such as a vacuum heat treatment technology, a protective atmosphere control technology, a surface coating technology, a rapid heating technology and a rapid cooling technology are comprehensively applied, so that the defect problems of oxidation, decarburization and overheating which are easily generated in the heating process are comprehensively solved; the method can also improve the corrosion resistance, wear resistance and quality of the pump cylinder, and prolongs the service life of the pump cylinder.

Description

Technical Field

[0001] The invention relates to the technical field of pump barrel heat treatment, in particular to a surface chemical heat treatment method. Background Art

[0002] The hydraulic piston pump is one of the equipments widely used in oil field production. The pump barrel is the most important part of the hydraulic piston pump, accounting for more than 60% of the cost of the hydraulic piston pump. Chemical heat treatment must be carried out during the manufacturing process of the pump barrel to improve the surface hardness, wear resistance and corrosion resistance of its inner hole.

[0003] Traditional surface chemical heat treatment methods, such as carburizing and nitriding, mainly place the pump barrel in a specific medium for heating and insulation, so that one or more elements penetrate into the surface of the pump barrel, thereby changing its chemical composition and organizational structure, and improving surface hardness, wear resistance, fatigue strength and other properties.

[0004] However, these methods often cannot avoid oxidation and decarburization during the heating process, especially under high temperature conditions, where the oxidation problem is particularly prominent. In addition, overheating can easily lead to changes in the internal structure of the material, thereby affecting its overall performance. These problems not only seriously affect the surface quality of the material, but also significantly reduce its mechanical properties and shorten its service life. Summary of the invention

[0005] The purpose of the present invention is to provide a method for chemical heat treatment of the skin to solve the technical problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for epidermal chemical heat treatment, comprising the following steps:

[0007] S1. Pretreatment: Clean and dry the pump barrel to be treated to remove surface oil and impurities, and apply a layer of high temperature resistant anti-oxidation coating on the surface of the pump barrel;

[0008] S2. Vacuum heat treatment: put the coated pump barrel into a vacuum furnace, start the vacuum pump to extract the air in the furnace to a vacuum state, and set the heating temperature and insulation time for heat treatment;

[0009] S3, adding penetrant: after the vacuum heat treatment is completed, the pump barrel is loaded with penetrant, and then the pump barrel is placed in the pit furnace;

[0010] S4. Protective atmosphere control: Introduce inert gas into the pit furnace to form a protective atmosphere;

[0011] S5, rapid heating treatment: the pit furnace heats the pump barrel;

[0012] S6. Rapid cooling treatment: When the temperature in the pit furnace drops to 780℃-820℃, cool and keep warm for 1-2 hours, then hang the pump barrel into the cooling barrel for forced cooling to room temperature;

[0013] S7, post-processing: The cooled pump barrel is cleaned and de-coated to remove the residual coating and impurities on the surface, and subsequent processes such as machining and surface treatment are performed as needed to obtain the final product.

[0014] Preferably, the equipment required for cleaning and drying in S1 is an ultrasonic cleaning machine and a hot air dryer, which are used to separate oil stains and impurities on the surface of the pump barrel by high-frequency vibration and quickly dry the surface of the pump barrel by high-temperature hot air.

[0015] Preferably, the anti-oxidation coating in S1 adopts RLHY-33 steel heating anti-oxidation coating to ensure that the coating is uniform and dense, which is used to further prevent oxidation and decarburization.

[0016] Preferably, the penetrating agent in S3 is composed of 60-62% by weight of ferroboron, 18-20% by weight of charcoal, 16-18% by weight of potassium fluoroborate, 1.5-2.5% by weight of urea, and 0.5-1.5% by weight of rare earth.

[0017] Preferably, when preparing the penetrating agent in S3, firstly the above raw materials are crushed according to the ratio, stirred evenly, and then a proper amount of binder is added to make it into granules or small cylinders, and then dried to obtain the penetrating agent.

[0018] Preferably, the inert gas introduced into S4 is one of nitrogen and argon, which is used to form a protective atmosphere, isolate oxygen from direct contact with the pump barrel, and further reduce the risk of oxidation and decarburization.

[0019] Preferably, in said S5, the pump barrel is made to reach the required temperature in a short time by induction heating or laser heating.

[0020] Preferably, in S5, after heating to 600°C to 700°C and keeping warm for 0.5 to 1.5 hours, the temperature is further heated to 850°C to 950°C and kept warm for 3 to 5 hours. During the heating process, the pressure in the pump barrel is always maintained at 0.10 to 0.12 MPa.

[0021] Preferably, in S6, high-pressure air cooling or water quenching is used to quickly cool the pump barrel, which helps to refine the grains, improve the mechanical properties of the material, and reduce residual stress.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The use of vacuum environment and protective atmosphere effectively avoids the occurrence of oxidation and decarburization during heat treatment, thereby significantly improving the surface quality of the pump barrel. By reducing the occurrence of oxidation and decarburization, not only the quality of the workpiece is improved, but also the subsequent processing and treatment costs are reduced, thereby improving the overall economic benefits;

[0024] 2. Rapid heating technology and rapid cooling technology help refine the grains and improve the mechanical properties of the material such as hardness, wear resistance and fatigue strength. Rapid heating technology and rapid cooling technology shorten the heat treatment cycle and improve production efficiency.

[0025] 3. After chemical heat treatment, a hard anti-corrosion and wear-resistant layer is formed on the inner hole of the pump barrel from the surface to the inside, which improves the anti-corrosion and wear-resistant performance of the pump barrel, thereby extending the service life of the pump barrel;

[0026] In summary, the surface chemical heat treatment method of the present invention comprehensively solves the problems of oxidation, decarburization and overheating defects that are easily generated during the heating process by comprehensively utilizing multiple means such as vacuum heat treatment technology, protective atmosphere control technology, surface coating technology, rapid heating technology and rapid cooling technology. At the same time, this method can also improve the corrosion resistance and wear resistance and quality of the pump barrel and extend the service life of the pump barrel. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the process of the epidermal chemical heat treatment method of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0029] See also Figure 1 The present invention provides a technical solution: a method for epidermal chemical heat treatment, comprising the following steps:

[0030] S1. Pretreatment: Clean and dry the pump barrel to be treated to remove surface oil and impurities, and apply a layer of high temperature resistant anti-oxidation coating on the surface of the pump barrel;

[0031] S2. Vacuum heat treatment: Put the coated pump barrel into a vacuum furnace, start the vacuum pump to extract the air in the furnace to a vacuum state, and set the heating temperature and insulation time for heat treatment. The air in the furnace is extracted by the vacuum pump to form an extremely low oxygen partial pressure environment, thereby effectively avoiding the occurrence of oxidation. In addition, the vacuum environment can also reduce the decarburization tendency of the pump barrel surface and improve the surface quality;

[0032] S3, adding penetrant: after the vacuum heat treatment is completed, the pump barrel is loaded with penetrant, and then the pump barrel is placed in the pit furnace;

[0033] S4. Protective atmosphere control: Inert gas or reducing gas is introduced into the pit furnace to form a protective atmosphere. The inert gas introduced is one of nitrogen and argon, and the reducing gas is one of carbon monoxide and hydrogen. The protective atmosphere is used to isolate the pump barrel from direct contact with oxygen during the heating process, further reducing the risk of oxidation and decarburization.

[0034] S5. Rapid heating treatment: The pump barrel is heated in a pit furnace. In this process, induction heating is used to make the pump barrel reach the required temperature in a short time. When heated to 600℃~700℃, it is kept warm for 0.5~1.5 hours, and then heated to 850℃~950℃ and kept warm for 3~5 hours. During this heating process, the pressure in the pump barrel is always maintained at 0.10~0.12MPa. When induction heating is used, induction heating uses the principle of electromagnetic induction to generate a magnetic field through alternating current. The magnetic field generates eddy currents in the pump barrel, which are converted into heat energy to heat the pump barrel;

[0035] S6. Rapid cooling treatment: When the temperature in the pit furnace drops to 780℃-820℃, cool down and keep warm for 1-2 hours, then hang the pump barrel into the cooling barrel for forced cooling to room temperature. In this process, high-pressure air cooling or water quenching is used to quickly cool the pump barrel, which helps to refine the grains, improve the mechanical properties of the material, and reduce residual stress;

[0036] S7. Post-treatment: Clean and de-coat the cooled pump barrel to remove residual paint and impurities on the surface. During the operation, use professional cleaning fluid, such as acid solution and alkaline solution, mix them in proportion and add them to the pump barrel and let them stand to soften and dissolve the sediment. Then drain the cleaning fluid and rinse it with clean water. After that, carry out subsequent processes such as mechanical processing and surface treatment as needed to obtain the final product.

[0037] The equipment required for cleaning and drying in S1 is an ultrasonic cleaning machine and a hot air drying machine, which are used to separate the oil and impurities on the surface of the pump barrel by high-frequency vibration, and quickly dry the surface of the pump barrel by high-temperature hot air.

[0038] The anti-oxidation coating in S1 adopts RLHY-33 steel heating anti-oxidation coating to ensure that the coating is uniform and dense, which is used to further prevent oxidation and decarburization. The RLHY-33 steel heating anti-oxidation coating forms a dense protective film at high temperature, effectively reducing the generation of oxide scale and improving the utilization rate of the pump barrel; preventing the oxidation or volatilization of elements in the pump barrel, ensuring the quality and performance stability of the pump barrel; reducing the generation of oxide scale and subsequent processing procedures, and reducing production costs.

[0039] The penetrating agent in S3 is composed of 60-62% of ferroboron, 18-20% of charcoal, 16-18% of potassium fluoroborate, 1.5-2.5% of urea, and 0.5-1.5% of rare earth in weight percentage. When preparing the penetrating agent in S3, firstly, the above raw materials are crushed according to the proportion, stirred evenly, and then a proper amount of binder is added to make it into granules or small cylinders, and then dried to obtain the penetrating agent;

[0040] In the infiltrant, ferroboron is the boron supply agent and potassium fluoroborate is the activator. The chemical reaction is as follows:

[0041] 4KBF4+4B+O2=2K2O+8BF2

[0042] Among them: BF2 is an unstable gas, which decomposes and separates active boron atoms to form stable BF3

[0043] gas;

[0044] 3BF2=〔B〕+2BF3

[0045] The active [B] atoms are absorbed, diffused, and reacted by the workpiece surface to form Fe2B or FeB+Fe2B;

[0046] Urea in the penetrating agent has the function of catalyzing the penetration in boronization;

[0047] The penetration mechanism mainly includes the following three points:

[0048] First: H2 and CO produced by thermal decomposition of urea can purify the surface of the workpiece and remove the oxide film produced by chemical adsorption. According to the redox reaction equilibrium curves of the Fe-H2-H2O system and the Fe-CO-CO2 system, there are the following reactions:

[0049] 4H2+Fe3O4=3Fe+4H2O

[0050] H2+FeO=Fe+H2O

[0051] CO+Fe3O4=3FeO+CO2

[0052] CO+FeO=Fe+CO2

[0053] Second: H2 and BF3 gas generated in the infiltrant react with the workpiece (Fe) to directly generate Fe2B or FeB

[0054] 2BF3+3H2+4Fe=2Fe2B+6HF

[0055] Among them: HF gas also has a purifying effect on the surface of the workpiece;

[0056] Third: The preferential penetration of active nitrogen and carbon atoms decomposed from urea causes the lattice distortion of the workpiece surface and increases the dislocation density, thus activating the surface and accelerating the adsorption process of boron atoms. In particular, the penetration of nitrogen atoms reduces the A1 temperature of the steel and expands the γ phase region, which is equivalent to increasing the boronizing temperature. Since boron atoms can form interstitial solid solutions in γ-Fe, the diffusion rate in γ-Fe is much faster than that in α-Fe. Therefore, the expansion of the γ phase region is conducive to the diffusion of boron atoms and the formation of borides.

[0057] Since rare earth is added to the penetrant, the effects of rare earth are as follows:

[0058] First: catalyzing infiltration. After adding rare earth, the infiltration layer can be thickened.

[0059] Second: change the performance of the boronized layer. The disadvantages of traditional 45 steel solid boronizing are that the boronized layer is thin and brittle, not firmly bonded to the matrix, and easy to break and peel off. Under a microscope, the outer layer of the surface after boronization is a high-boron phase FeB, and the inner layer is a low-boron phase Fe2B. Adding rare earth elements can reduce the amount of FeB and increase the amount of Fe2B. At the same time, it can thicken the boronized layer, shrink the carbon-rich transition zone, or even make it disappear, greatly improving the supporting strength of the boronized layer and avoiding the breakage and peeling of the boronized layer.

[0060] Working principle: The pump barrel to be treated is cleaned and dried to remove surface oil and impurities, and a layer of high-temperature resistant anti-oxidation coating is applied on the surface of the pump barrel. Then the pump barrel with coating is placed in a vacuum furnace, and the vacuum pump is started to extract the air in the furnace to a vacuum state, and the heating temperature and insulation time are set for heat treatment. After the vacuum heat treatment is completed, the pump barrel is loaded with a penetrant, and the penetrant is composed of 61% ferroboron, 19% charcoal, 17% potassium fluoroborate, 2% urea, and 1% rare earth in weight percentage. Then the pump barrel is placed in a pit furnace, and an inert gas is introduced into the pit furnace to form a protective atmosphere. At this time, the pit furnace heats the pump barrel and heats it to 600℃~ At 700℃, keep warm for 0.5 to 1.5 hours, continue heating to 850℃ to 950℃, and keep warm for 3 to 5 hours. During the heating process, the pressure in the pump barrel is always maintained at 0.10 to 0.12MPa. When the temperature in the pit furnace drops to 780℃-820℃, cool down and keep warm for 1-2 hours, then hang the pump barrel into the cooling barrel for forced cooling to room temperature. The cooled pump barrel is cleaned and de-coated to remove residual coating and impurities on the surface, and subsequent processes such as machining and surface treatment are performed as needed to obtain the final product. The contents not described in detail in this description belong to the prior art known to professional and technical personnel in this field.

[0061] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for epidermal chemical heat treatment, characterized in that: The steps are as follows: S1. Pretreatment: Clean and dry the pump barrel to be treated to remove surface oil and impurities, and apply a layer of high temperature resistant anti-oxidation coating on the surface of the pump barrel; S2. Vacuum heat treatment: put the coated pump barrel into a vacuum furnace, start the vacuum pump to extract the air in the furnace to a vacuum state, and set the heating temperature and insulation time for heat treatment; S3, adding penetrant: after the vacuum heat treatment is completed, the pump barrel is loaded with penetrant, and then the pump barrel is placed in the pit furnace; S4. Protective atmosphere control: Introduce inert gas into the pit furnace to form a protective atmosphere; S5, rapid heating treatment: the pit furnace heats the pump barrel; S6. Rapid cooling treatment: When the temperature in the pit furnace drops to 780℃-820℃, cool and keep warm for 1-2 hours, then hang the pump barrel into the cooling barrel for forced cooling to room temperature; S7, post-processing: The cooled pump barrel is cleaned and de-coated to remove the residual coating and impurities on the surface, and subsequent processes such as machining and surface treatment are performed as needed to obtain the final product.

2. A method for epidermal chemical heat treatment according to claim 1, characterized in that: The equipment required for cleaning and drying in S1 is an ultrasonic cleaning machine and a hot air drying machine, which are used to separate the oil and impurities on the surface of the pump barrel by high-frequency vibration, and quickly dry the surface of the pump barrel by high-temperature hot air.

3. The method for epidermal chemical heat treatment according to claim 1, characterized in that: The anti-oxidation coating in S1 adopts RLHY-33 steel heating anti-oxidation coating to ensure that the coating is uniform and dense, which is used to further prevent oxidation and decarburization.

4. The method for epidermal chemical heat treatment according to claim 1, characterized in that: The penetrating agent in S3 is composed of 60-62% of ferroboron, 18-20% of charcoal, 16-18% of potassium fluoroborate, 1.5-2.5% of urea and 0.5-1.5% of rare earth in weight percentage.

5. A method for epidermal chemical heat treatment according to claim 4, characterized in that: When preparing the penetrating agent in S3, firstly, the above raw materials are crushed according to the ratio, stirred evenly, and then a proper amount of binder is added to make it into granules or small cylinders, and then dried to obtain the penetrating agent.

6. The method for epidermal chemical heat treatment according to claim 1, characterized in that: The inert gas introduced into S4 is one of nitrogen and argon, which is used to form a protective atmosphere, isolate oxygen from direct contact with the pump barrel, and further reduce the risk of oxidation and decarburization.

7. The method for epidermal chemical heat treatment according to claim 1, characterized in that: In S5, the pump barrel is made to reach the required temperature in a short time by induction heating or laser heating.

8. A method for epidermal chemical heat treatment according to claim 7, characterized in that: In the S5, after heating to 600°C to 700°C and keeping warm for 0.5 to 1.5 hours, the temperature is further heated to 850°C to 950°C and kept warm for 3 to 5 hours. During the heating process, the pressure in the pump barrel is always maintained at 0.10 to 0.12 MPa.

9. The method for epidermal chemical heat treatment according to claim 1, characterized in that: In the S6, high-pressure air cooling or water quenching is used to quickly cool the pump barrel, which helps to refine the grains, improve the mechanical properties of the material, and reduce residual stress.

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