Machining process for valve body of stop valve

Abstract

The invention relates to the field of valve bodies, in particular to a machining process of a stop valve body, which comprises the following steps: annealing, stably putting the valve body into an annealing furnace, setting the temperature of the annealing furnace at 680-750 DEG C, keeping for 1-2 hours to ensure that the temperature is uniform, slowly cooling in the furnace or slowly cooling in slag outside the furnace, taking out the valve body after cooling, and detecting the quality of the valve body. The valve body is placed in a heating furnace, the valve body is heated to 850-950 DEG C, heated to the critical temperature interval of steel and heated to the target temperature, the temperature is kept for 15-30 min, then the valve body is taken out of the furnace and naturally cooled to the room temperature, the internal stress of the material is eliminated through annealing, and the material is prevented from deforming or cracking in subsequent machining; and the annealed material has good plasticity and toughness, subsequent secondary machining is facilitated, the strength and hardness of the material can be remarkably improved through normalizing, the mechanical performance of the material is improved, the strength and hardness of the obtained material are higher, and the normalized valve body material is more uniform in grain and more refined in structure.

Description

Technical Field

[0001] The invention discloses a processing technology for a stop valve body, belonging to the field of valve bodies. Background Art

[0002] The globe valve is a common type of valve, mainly used to control the flow of fluid in a pipeline. It raises or lowers the valve disc on the valve stem by rotating the handwheel or actuator, thereby opening or closing the channel. If the existing globe valve is not processed well and the surface hardness and wear resistance of key components are not effectively improved, the wear resistance of the valve itself will be insufficient. If no corresponding treatment is performed, the surface of the valve is easily corroded during the transportation of the corresponding corrosive medium, forming rust or electrolytic corrosion, affecting the appearance and function, and even causing structural damage. Therefore, it is necessary to improve the processing technology of the valve body to solve this problem. Summary of the invention

[0003] In view of the problems in the prior art, the present invention provides a processing technology for a stop valve body.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a processing technology for a stop valve body, comprising the following steps: S1: Annealing, put the valve body steadily into the annealing furnace, set the temperature of the annealing furnace at 680℃-750℃, keep it for 1h-2h to ensure uniform temperature, then slowly cool it in the furnace or slowly cool it in the slag outside the furnace. After cooling, take out the valve body and conduct quality inspection on it; S2: Normalizing, place the valve body in a heating furnace, heat the valve body to 850℃-950℃, heat to the critical temperature range of steel (above Ac3 temperature), after heating to the target temperature, keep it for 15-30 minutes, then take it out of the furnace and cool it naturally to room temperature; S3: Tempering, place the valve body in a tempering furnace and heat it to 850℃-900℃. After reaching the processing temperature, quickly immerse the heated valve body in the tempering medium to quickly cool the valve body to increase the hardness. Water cooling will cause greater deformation, while oil cooling is relatively slow. It is suitable for requirements of higher hardness and smaller deformation. Heat the cooled valve body to 550℃-700℃, perform tempering treatment to eliminate the internal stress and brittleness caused by heating, and then the valve body will naturally cool to room temperature; S4: Quenching: heat the valve body to 800℃-900℃ and maintain it for 30-50min, then quickly immerse the heated valve body in the quenching and tempering medium; S5: Surface hardening treatment, the valve body is placed in a carbon source atmosphere, treated at 850℃-950℃ for 5-8 hours, so that the surface absorbs carbon to form a hardened layer, and then placed in a nitrogen atmosphere for treatment at a temperature of 500℃-600℃. Nitriding can significantly improve the hardness and corrosion resistance of the valve body surface; S6: Inspection: After the above steps, the valve body is subjected to metallographic analysis and crack analysis to observe the material grain structure to ensure that the heat treatment effect is good and excessively coarse grains are avoided. Magnetic particle testing, ultrasonic testing and other means are used to check whether the valve body has defects such as cracks and pores.

[0005] Furthermore, in step S1, the quality inspection includes hardness inspection, metallographic analysis, tensile test, impact toughness test and magnetic inspection.

[0006] Furthermore, in step S4, the modulation medium includes oil, water, air, salt bath, polymer, gas and mixed medium.

[0007] Furthermore, the oil includes mineral oil, synthetic oil and vegetable oil, the water includes ordinary water and polymer aqueous solution, the salt bath includes molten nitrate and chloride salt, and the gas includes nitrogen, argon and helium.

[0008] Furthermore, in step S5, the carbon source includes a solid carbon source, a liquid carbon source, a gaseous carbon source and a mixed carbon source. The solid carbon source includes charcoal and graphite powder. The liquid carbon source includes ethanol and methanol. After decomposition, the two provide carbon monoxide and hydrogen, which is one of the commonly used carbon sources. The gaseous carbon source includes carbon monoxide, methane and natural gas. The mixed carbon source includes drip carburizing atmosphere, endothermic gas and exothermic gas.

[0009] Beneficial effects of the present invention: 1. Annealing can eliminate the internal stress of the material to avoid deformation or cracking of the material in subsequent processing. The annealed material has good plasticity and toughness, which is convenient for subsequent secondary processing, especially excellent cutting performance. It can also refine the grain of the material, which helps to improve the mechanical properties and stability of the material. In addition, the hardness of the material is reduced, making it easier to form in subsequent hot processing (such as forging, extrusion, etc.).

[0010] 2. Normalizing can significantly improve the strength and hardness of the material and improve its mechanical properties. The obtained material has higher strength and hardness. The grains of the valve body material after normalizing are more uniform and the structure is finer, which helps to improve the overall performance, reduce the uneven structure of the material inside the valve body during the subsequent processing, and improve the deformation after quenching.

[0011] 3. The valve body after quenching and tempering has higher hardness and better strength. It is suitable for occasions with large mechanical loads and pressures. It can maintain good toughness and fatigue resistance while increasing hardness, avoiding brittleness caused by excessive hardness, improving the surface hardness of the valve body and thus improving wear resistance. It is suitable for valve bodies with high wear resistance requirements, effectively eliminating the internal stress generated during quenching, and reducing material deformation and cracks. 4. The martensitic structure of the material is formed through quenching. The valve body after quenching has excellent wear resistance, which is suitable for valves with high pressure and high sealing performance requirements, and makes the valve body show strong fatigue resistance and corrosion resistance under dynamic load. DETAILED DESCRIPTION

[0012] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0013] A process for processing a stop valve body comprises the following steps: S1: Annealing, put the valve body steadily into the annealing furnace, set the temperature of the annealing furnace at 680℃-750℃, keep it for 1h-2h to ensure uniform temperature, then slowly cool it in the furnace or slowly cool it in the slag outside the furnace. After cooling, take out the valve body and conduct quality inspection on it; S2: Normalizing, place the valve body in a heating furnace, heat the valve body to 850℃-950℃, heat to the critical temperature range of steel (above Ac3 temperature), after heating to the target temperature, keep it for 15-30 minutes, then take it out of the furnace and cool it naturally to room temperature; S3: Tempering, place the valve body in a tempering furnace and heat it to 850℃-900℃. After reaching the processing temperature, quickly immerse the heated valve body in the tempering medium to quickly cool the valve body to increase the hardness. Water cooling will cause greater deformation, while oil cooling is relatively slow. It is suitable for requirements of higher hardness and smaller deformation. Heat the cooled valve body to 550℃-700℃, perform tempering treatment to eliminate the internal stress and brittleness caused by heating, and then the valve body will naturally cool to room temperature; S4: Quenching: heat the valve body to 800℃-900℃ and maintain it for 30-50min, then quickly immerse the heated valve body in the quenching and tempering medium; S5: Surface hardening treatment, place the valve body in a carbon source atmosphere (such as methane, ethylene, etc.) and treat it at 850℃-950℃ for 5-8 hours, so that the surface absorbs carbon to form a hardened layer, and then place it in a nitrogen atmosphere for treatment at a temperature of 500℃-600℃. Nitriding can significantly improve the hardness and corrosion resistance of the valve body surface; S6: Inspection: After the above steps, the valve body is subjected to metallographic analysis and crack analysis to observe the material grain structure to ensure that the heat treatment effect is good and excessively coarse grains are avoided. Magnetic particle testing, ultrasonic testing and other means are used to check whether the valve body has defects such as cracks and pores.

[0014] In step S1, the quality inspection includes hardness inspection, metallographic analysis, tensile test, impact toughness test and magnetic inspection, wherein the hardness inspection ensures that the surface hardness of the valve body meets the design requirements, the metallographic analysis observes the grain structure of the material to ensure that the heat treatment effect is good and avoid excessively coarse grains, the tensile test measures the tensile strength, yield strength, elongation and other mechanical properties of the material to verify whether it meets the specified standards, the impact toughness test uses the Charpy impact test to evaluate the impact resistance of the material at different temperatures to ensure that it has sufficient toughness and the ability to resist brittle fracture, and the magnetic test may be required for some special applications (such as stainless steel) to confirm whether the material is completely austenitized or the degree of martensitic transformation.

[0015] In step S4, the modulation medium includes oil, water, air, salt bath, polymer, gas and mixed medium, wherein water has a fast cooling speed, meets the needs of low carbon steel and medium carbon steel, and is suitable for the needs of high strength and simple shape valve bodies; oil has a medium cooling speed, meets the needs of low carbon steel and alloy steel, and is suitable for the needs of high strength and complex shape valve bodies; air has a slow cooling speed, meets the needs of high alloy steel and stainless steel, and is suitable for the needs of complex shape and quenching crack sensitive valve bodies; polymer coolant has a controllable cooling speed, meets the needs of various types of steel, and is suitable for the needs of valve bodies with strict requirements on cooling speed and deformation control; salt bath has a fast cooling speed, meets the needs of low carbon steel and medium carbon steel, and is suitable for the needs of high hardness and rapid cooling of valve bodies.

[0016] The oil liquid includes mineral oil, synthetic oil and vegetable oil, the water liquid includes ordinary water and polymer aqueous solution, the salt bath includes molten nitrate and chloride salt, and the gas includes nitrogen, argon and helium.

[0017] In step S5, the carbon source includes a solid carbon source, a liquid carbon source, a gaseous carbon source and a mixed carbon source. The solid carbon source includes charcoal and graphite powder, the liquid carbon source includes ethanol and methanol, the gaseous carbon source includes carbon monoxide, methane and natural gas, and the mixed carbon source includes a drip carburizing atmosphere, an endothermic gas and an exothermic gas. Example

[0018] A process for processing a stop valve body comprises the following steps: S1: Annealing. Before placing the valve body into the annealing furnace, check whether there are cracks, scale, decarburization layer and other problems on the surface of the valve body to ensure surface finish and flatness. After confirming that there are no problems, set the temperature of the annealing furnace at 680℃ and maintain it for 1 hour to ensure uniform temperature. Then slowly cool it in the furnace or slowly cool it in the slag outside the furnace. After cooling, take out the valve body and conduct quality inspection. The quality inspection includes hardness inspection, metallographic analysis, tensile test, impact toughness test and magnetic inspection. The hardness inspection ensures that the surface hardness of the valve body meets the design requirements. The metallographic analysis observes the grain structure of the material to ensure good heat treatment effect and avoid excessively coarse grains. Tensile testing measures the tensile strength, yield strength, elongation and other mechanical properties of the material to verify whether it meets the specified standards. The impact toughness test uses the Charpy impact test to evaluate the material's impact resistance at different temperatures to ensure that it has sufficient toughness and the ability to resist brittle fracture. For some special applications (such as stainless steel), magnetic testing may be required to confirm whether the material is completely austenitized or the degree of martensitic transformation. In this process, the heating rate is controlled to avoid excessive temperature differences between the surface and the inner layer due to excessive heating. The annealing temperature should be adjusted according to the specific composition of the material to achieve the best plasticity and toughness.

[0019] S2: Normalizing, place the valve body in a heating furnace, where the heating furnace can be a resistance furnace, an induction furnace or an atmosphere furnace. The resistance furnace is suitable for batch heating of small and medium-sized stop valves and has high temperature uniformity. The induction furnace has a fast heating speed and is suitable for rapid heating and high energy efficiency, but requires valve bodies with higher technical requirements. The atmosphere furnace is suitable for valve bodies that are sensitive to oxidation. The use of a protective atmosphere can avoid oxidation problems. Heat the valve body to 850°C, which is the critical temperature range of steel (above Ac3 temperature). After heating to the target temperature, keep it for 15 minutes and then take it out of the furnace to cool naturally to room temperature. S3: Quenching and tempering. The valve body is placed in a quenching and tempering furnace and heated to 850℃. During heating, the heating rate should be controlled between 50℃ / hour and 150℃ / hour. Too fast a heating rate may cause thermal stress inside the material and cause cracks. After reaching the processing temperature, the heated valve body is quickly immersed in the quenching and tempering medium to cool the valve body quickly to increase the hardness. Water cooling will cause greater deformation, while oil cooling is relatively slow and is suitable for requirements of higher hardness and smaller deformation. The cooled valve body is heated to 550℃ and tempered to eliminate the internal stress and brittleness caused by heating. The valve body is then naturally cooled to room temperature. S4: Quenching, heat the valve body to 800℃ and maintain it for 30 minutes, then quickly immerse the heated valve body in a tempering medium, which includes oil, water, air, salt bath, polymer, gas and mixed medium. The water has a fast cooling speed and meets the needs of low carbon steel and medium carbon steel, and is suitable for high strength and simple shape valve bodies. The oil has a medium cooling speed and meets the needs of low carbon steel and alloy steel, and is suitable for high strength and complex shape valve bodies. The air has a slow cooling speed and meets the needs of high alloy steel and stainless steel, and is suitable for complex shape and quenching crack sensitive valve bodies. The polymer coolant has a controllable cooling speed and meets the needs of various types of steel, and is suitable for valve bodies with strict requirements on cooling speed and deformation control. The salt bath has a fast cooling speed and meets the needs of low carbon steel and medium carbon steel, and is suitable for high hardness and rapid cooling of valve bodies. The oil includes mineral oil, synthetic oil and vegetable oil. The water includes ordinary water and polymer aqueous solution. The salt bath includes molten nitrate and chloride salt. The gas includes nitrogen, argon and helium.

[0020] S5: Surface hardening treatment, the valve body is placed in a carbon source atmosphere, the carbon source includes solid carbon source, liquid carbon source, gas carbon source and mixed carbon source, the solid carbon source includes charcoal and graphite powder, the liquid carbon source includes ethanol and methanol, the gas carbon source includes carbon monoxide, methane and natural gas, the mixed carbon source includes drip carburizing atmosphere, endothermic gas and exothermic gas, and treated at 850℃ for 5 hours to make the surface absorb carbon to form a hardened layer, and then placed in a nitrogen atmosphere for treatment at a temperature of 500℃. Nitriding can significantly improve the hardness and corrosion resistance of the valve body surface; S6: Inspection: After the above steps, the valve body is subjected to metallographic analysis and crack analysis to observe the material grain structure to ensure that the heat treatment effect is good and excessively coarse grains are avoided. Magnetic particle testing, ultrasonic testing and other means are used to check whether the valve body has defects such as cracks and pores. Example

[0021] A process for processing a stop valve body comprises the following steps: S1: Annealing. Before placing the valve body into the annealing furnace, check whether there are cracks, scale, decarburization layer and other problems on the surface of the valve body to ensure surface finish and flatness. After confirming that there are no problems, set the temperature of the annealing furnace at 750℃ and maintain it for 2 hours to ensure uniform temperature. Then slowly cool it in the furnace or slowly cool it in the slag outside the furnace. After cooling, take out the valve body and conduct quality inspection. The quality inspection includes hardness inspection, metallographic analysis, tensile test, impact toughness test and magnetic inspection. The hardness inspection ensures that the surface hardness of the valve body meets the design requirements. The metallographic analysis observes the grain structure of the material to ensure good heat treatment effect and avoid excessive coarse grains. Tensile testing measures the tensile strength, yield strength, elongation and other mechanical properties of the material to verify whether it meets the specified standards. The impact toughness test uses the Charpy impact test to evaluate the material's impact resistance at different temperatures to ensure that it has sufficient toughness and the ability to resist brittle fracture. For some special applications (such as stainless steel), magnetic testing may be required to confirm whether the material is completely austenitized or the degree of martensitic transformation. In this process, the heating rate is controlled to avoid excessive temperature differences between the surface and the inner layer due to excessive heating. The annealing temperature should be adjusted according to the specific composition of the material to achieve the best plasticity and toughness.

[0022] S2: Normalizing, place the valve body in a heating furnace, where the heating furnace can be a resistance furnace, an induction furnace or an atmosphere furnace. The resistance furnace is suitable for batch heating of small and medium-sized stop valves and has high temperature uniformity. The induction furnace has a fast heating speed and is suitable for rapid heating and high energy efficiency, but requires valve bodies with higher technical requirements. The atmosphere furnace is suitable for valve bodies that are sensitive to oxidation. The use of a protective atmosphere can avoid oxidation problems. Heat the valve body to 950°C, which is the critical temperature range of steel (above Ac3 temperature). After heating to the target temperature, keep it for 30 minutes and then take it out of the furnace to cool naturally to room temperature. S3: Quenching and tempering. The valve body is placed in a quenching and tempering furnace and heated to 900℃. During heating, the heating rate should be controlled between 50℃ / hour and 150℃ / hour. Too fast a heating rate may cause thermal stress inside the material and cause cracks. After reaching the processing temperature, the heated valve body is quickly immersed in the quenching and tempering medium to cool the valve body quickly to increase the hardness. Water cooling will cause greater deformation, while oil cooling is relatively slow and is suitable for requirements of higher hardness and smaller deformation. The cooled valve body is heated to 700℃ and tempered to eliminate the internal stress and brittleness caused by heating. The valve body is then naturally cooled to room temperature. S4: Quenching, heat the valve body to 900℃ and maintain it for 50 minutes, then quickly immerse the heated valve body in a tempering medium, which includes oil, water, air, salt bath, polymer, gas and mixed medium. The water has a fast cooling speed and meets the needs of low carbon steel and medium carbon steel, and is suitable for high strength and simple shape valve bodies. The oil has a medium cooling speed and meets the needs of low carbon steel and alloy steel, and is suitable for high strength and complex shape valve bodies. The air has a slow cooling speed and meets the needs of high alloy steel and stainless steel, and is suitable for complex shape and quenching crack sensitive valve bodies. The polymer coolant has a controllable cooling speed and meets the needs of various types of steel, and is suitable for valve bodies with strict requirements on cooling speed and deformation control. The salt bath has a fast cooling speed and meets the needs of low carbon steel and medium carbon steel, and is suitable for high hardness and rapid cooling of valve bodies. The oil includes mineral oil, synthetic oil and vegetable oil. The water includes ordinary water and polymer aqueous solution. The salt bath includes molten nitrate and chloride salt. The gas includes nitrogen, argon and helium.

[0023] S5: Surface hardening treatment, the valve body is placed in a carbon source atmosphere, the carbon source includes solid carbon source, liquid carbon source, gas carbon source and mixed carbon source, the solid carbon source includes charcoal and graphite powder, the liquid carbon source includes ethanol and methanol, the gas carbon source includes carbon monoxide, methane and natural gas, the mixed carbon source includes drip carburizing atmosphere, endothermic gas and exothermic gas, and treated at 950℃ for 8 hours to make the surface absorb carbon to form a hardened layer, and then placed in a nitrogen atmosphere for treatment at a temperature of 600℃. Nitriding can significantly improve the hardness and corrosion resistance of the valve body surface; S6: Inspection: After the above steps, the valve body is subjected to metallographic analysis and crack analysis to observe the material grain structure to ensure that the heat treatment effect is good and excessively coarse grains are avoided. Magnetic particle testing, ultrasonic testing and other means are used to check whether the valve body has defects such as cracks and pores.

[0024] Although this specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A processing technology for a stop valve body, characterized in that The following steps are involved: S1: Annealing, put the valve body steadily into the annealing furnace, set the temperature of the annealing furnace at 680℃-750℃, keep it for 1h-2h to ensure uniform temperature, then slowly cool it in the furnace or slowly cool it in the slag outside the furnace. After cooling, take out the valve body and conduct quality inspection on it; S2: Normalizing: Place the valve body in a heating furnace and heat it to 850℃-950℃, which is the critical temperature range of steel. After heating to the target temperature, keep it for 15-30 minutes and then take it out of the furnace and cool it naturally to room temperature. S3: Quenching and tempering, the valve body is placed in a conditioning furnace and heated to 850℃-900℃. After reaching the processing temperature, the heated valve body is quickly immersed in the quenching and tempering medium to cool the valve body rapidly to increase the hardness. The cooled valve body is heated to 550℃-700℃, and tempering treatment is performed to eliminate the internal stress and brittleness caused by heating. After that, the valve body is naturally cooled to room temperature. S4: Quenching: heat the valve body to 800℃-900℃ and maintain it for 30-50min, then quickly immerse the heated valve body in the quenching and tempering medium; S5: Surface hardening treatment, placing the valve body in a carbon source atmosphere, treating it at 850℃-950℃ for 5-8 hours, so that the surface absorbs carbon to form a hardened layer, and then placing it in a nitrogen atmosphere, the temperature is controlled at 500℃-600℃; S6: Inspection: metallographic analysis and crack analysis are performed on the valve body after the above steps to observe the material grain structure and ensure that the heat treatment effect is good.

2. The process for processing the stop valve body according to claim 1 is characterized in that: In step S1, the quality inspection includes hardness inspection, metallographic analysis, tensile test, impact toughness test and magnetic inspection.

3. The processing technology of the stop valve body according to claim 1 is characterized in that: In step S4, the modulation medium includes oil, water, air, salt bath, polymer, gas and mixed medium.

4. The processing technology of the stop valve body according to claim 3 is characterized in that: The oil liquid includes mineral oil, synthetic oil and vegetable oil, the water liquid includes ordinary water and polymer aqueous solution, the salt bath includes molten nitrate and chloride salt, and the gas includes nitrogen, argon and helium.

5. The processing technology of the stop valve body according to claim 1 is characterized in that: In step S5, the carbon source includes a solid carbon source, a liquid carbon source, a gaseous carbon source and a mixed carbon source. The solid carbon source includes charcoal and graphite powder, the liquid carbon source includes ethanol and methanol, the gaseous carbon source includes carbon monoxide, methane and natural gas, and the mixed carbon source includes a drip carburizing atmosphere, an endothermic gas and an exothermic gas.