Alloy workpiece heat treatment method

Abstract

The invention provides an alloy workpiece heat treatment method which comprises the following steps: providing an alloy workpiece, a vacuum furnace and carbon powder, cleaning the alloy workpiece, drying the alloy workpiece, extracting air in the vacuum furnace to enable the air pressure in the vacuum furnace to be less than 10 <-2 > Pa, and baking the carbon powder to a temperature higher than a preheating temperature; the alloy workpiece is embedded in carbon powder, then the alloy workpiece and the carbon powder are transferred into a vacuum furnace at the same time, and the vacuum furnace is heated to a first critical temperature; and after the alloy workpiece is subjected to heat preservation for at least 30 min, the alloy workpiece is cooled to the room temperature in a furnace cooling and air cooling mode. According to the technical scheme, the carbon powder is preheated, so that the activity of the carbon element is excited, an oxidation film attached to the surface of the workpiece is thoroughly removed, the porcelain boat is used for paving the carbon powder, the porcelain boat is prevented from being damaged by heating before the workpiece, and when the heat treatment process is nearly finished, the workpiece is cooled in two modes of furnace cooling and air cooling, so that the service life of the workpiece is prolonged. Oxidation discoloration of the workpiece surface is avoided, and the workpiece heat treatment effect is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment, and in particular relates to a heat treatment method for an alloy workpiece. Background Art

[0002] At present, in order to improve the strength, toughness and other performance indicators of mechanical parts, various metal components need to be heat treated after processing and forming. Common heat treatment process means mainly include annealing, normalizing, quenching, tempering, aging treatment, carburizing, carbonitriding and other methods. Among them, the general process of annealing, normalizing, quenching or tempering of metal components includes: heating the workpiece to the critical temperature, keeping the workpiece warm, and then cooling the workpiece. The cooling methods mainly include furnace cooling, air cooling, water cooling and oil cooling. Depending on the cooling method and critical temperature, the mechanical properties of the workpiece after heat treatment are also different. For alloy materials, since they contain various metal elements or non-metal elements, the melting points of these metal elements and non-metal elements are different. When the alloy workpiece is heat treated, the critical heating temperature obviously needs to be higher in order to fully adjust the crystal phase structure of the alloy material. However, in the process of heating the alloy workpiece to the critical temperature, the oxygen in the external environment can easily invade the surface of the alloy workpiece, causing the surface of the alloy workpiece to be oxidized and discolored, or even blackened, affecting the expected effect of the workpiece heat treatment.

[0003] For example, the patent document with the authorization announcement number "CN104651586B" discloses a bright heat treatment process for maraging stainless steel wire. Its steps are as follows: 1) select maraging stainless steel wire as the heat treatment material; 2) clean and dry the steel wire with a cleaning liquid; 3) put the steel wire into a sealed test tube and fill it with reducing powder; 4) place the test tube containing the steel wire in a vacuum annealing furnace for vacuumization; 5) perform bright heat treatment. By adopting this patented technical solution, the purpose of making stainless steel wire bright is achieved through vacuum heat treatment and setting reducing powder. However, when this patented technology is actually applied, on the one hand, the high temperature resistance of the sealed test tube is limited. In the vacuum furnace, the sealed test tube is often damaged by heat before the workpiece, resulting in the interruption of the entire heat treatment process; on the other hand, when the workpiece is buried in the reducing powder, since the powder is not pre-heated, the reducing activity of the powder is not fully and fully exerted, so that there are still local areas on the surface of the workpiece that are oxidized and discolored; in addition, when the heat treatment process is nearing the end, if the workpiece is immediately taken out and quickly air-cooled, the air in the external environment will still cause oxidation and discoloration on the surface of the workpiece, affecting the final heat treatment effect of the workpiece. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for heat treatment of an alloy workpiece.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention provides a method for heat treating an alloy workpiece, comprising the following steps:

[0007] Step 1: Preparatory stage: Provide alloy workpiece, vacuum furnace and carbon powder, use ultrasonic cleaning machine to clean the alloy workpiece, then dry the alloy workpiece, remove the air in the vacuum furnace, and make the air pressure in the vacuum furnace less than 10 -2 Pa, send the carbon powder into the oven and continue to bake it until the surface temperature of the carbon powder reaches above the preheating temperature;

[0008] Step 2: Pre-treatment stage: burying the alloy workpiece in the carbon powder, then transferring the alloy workpiece and the carbon powder into a vacuum furnace at the same time, and then heating the vacuum furnace until the temperature in the vacuum furnace reaches a first critical temperature before proceeding to the next step;

[0009] Step 3: Post-processing stage: After the alloy workpiece is kept warm for at least 30 minutes, the alloy workpiece is cooled to room temperature by furnace cooling and air cooling.

[0010] In step 1, the process parameters for cleaning the alloy workpiece with an ultrasonic cleaning machine are as follows: the specification model of the ultrasonic cleaning machine is: F-031 ultrasonic cleaning machine, the cleaning agent is acetone solution, the vibration frequency of the ultrasonic cleaning machine is 40 Hz, and the cleaning duration is more than 20 minutes.

[0011] The step 1 of drying the alloy workpiece refers to: using argon gas with a purity of 99.99% or more to dry the alloy workpiece.

[0012] The process parameters for feeding the carbon powder into the oven for continuous baking in step 1 are: the carbon powder is spread in the characteristic container, the carbon powder and the characteristic container are baked in the oven for a duration of not less than 30 minutes, and the preheating temperature is 200°C.

[0013] The process parameters for burying the alloy workpiece in the carbon powder in step 2 are: the carbon powder is spread in a characteristic container, and the relative height between the top surface of the carbon powder and the top surface of the alloy workpiece is greater than 10 mm, and the relative height between the bottom surface of the alloy workpiece and the bottom surface of the characteristic container is greater than 5 mm.

[0014] The characteristic container is a porcelain boat.

[0015] Heating the vacuum furnace in step 2 means: first raising the temperature in the vacuum furnace from room temperature to a second critical temperature, and the temperature rising rate in the vacuum furnace is less than 6°C / min, and then keeping the alloy workpiece warm for at least 30 minutes, and then raising the temperature in the vacuum furnace to the first critical temperature.

[0016] The first critical temperature is 800°C, and the second critical temperature is 400°C.

[0017] The process parameters of the post-processing stage in step three are: firstly cooling the alloy workpiece to the third critical temperature in the furnace, and then air-cooling the alloy workpiece to room temperature, and the cooling rate of the alloy workpiece in the furnace is greater than 30°C / min.

[0018] The alloy workpiece heat treatment method further includes the following steps: during the post-processing stage of step three, argon gas with a pressure not exceeding 2 Bar is continuously introduced into the vacuum furnace.

[0019] The beneficial effects of the present invention are as follows: by adopting the technical scheme of the present invention, on the one hand, due to the preheating of the carbon powder, the activity of the carbon element in the carbon powder is stimulated, and when the workpiece is buried in the carbon powder, the reducing property of the carbon element can fully play a role, thereby preventing the surface of the workpiece from being oxidized and discolored; on the other hand, a porcelain boat is used to pave the carbon powder, and the porcelain boat has a high high temperature resistance, which can prevent the porcelain boat from being damaged by heat in the vacuum furnace before the workpiece, and the porcelain boat is an open structure, which can prevent the workpiece from being damaged by the increased heat pressure in the vacuum furnace; in addition, when the heat treatment process is nearing the end, the workpiece is first cooled with the furnace and then air-cooled, which can prevent oxygen in the external environment from entering the vacuum furnace, prevent the surface of the workpiece from being oxidized and discolored, and improve the heat treatment effect and quality of the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0022] like Figure 1 As shown, the present invention provides a method for heat treatment of an alloy workpiece, comprising the following steps:

[0023] Step 1: Preparatory stage: Provide alloy workpiece, vacuum furnace and carbon powder, use ultrasonic cleaning machine to clean the alloy workpiece, then dry the alloy workpiece, remove the air in the vacuum furnace, and make the air pressure in the vacuum furnace less than 10 -2 Pa, send the carbon powder into the oven and continue baking until the surface temperature of the carbon powder reaches above the preheating temperature;

[0024] Step 2: Pre-treatment stage: burying the alloy workpiece in the carbon powder, then transferring the alloy workpiece and the carbon powder into a vacuum furnace at the same time, and then heating the vacuum furnace until the temperature in the vacuum furnace reaches a first critical temperature before proceeding to the next step;

[0025] Step 3: Post-processing stage: After the alloy workpiece is kept warm for at least 30 minutes, the alloy workpiece is cooled to room temperature by furnace cooling and air cooling.

[0026] By adopting the technical solution of the present invention, on the one hand, the activity of the carbon element in the carbon powder is stimulated due to the preheating of the carbon powder. When the workpiece is buried in the carbon powder, the reducing property of the carbon element can fully play a role, thereby preventing the surface of the workpiece from being oxidized and discolored; on the other hand, a porcelain boat is used to pave the carbon powder. The porcelain boat has a high high temperature resistance, which can prevent the porcelain boat from being damaged by heat in the vacuum furnace before the workpiece, and the porcelain boat is an open structure, which can prevent the workpiece from being damaged due to increased thermal pressure in the vacuum furnace; in addition, when the heat treatment process is nearing the end, the workpiece is first cooled with the furnace and then air-cooled, which can prevent oxygen in the external environment from entering the vacuum furnace, prevent the surface of the workpiece from being oxidized and discolored, and improve the heat treatment effect and quality of the workpiece.

[0027] Specifically, the alloy workpiece includes 4% by weight of aluminum and 3% by weight of titanium. The purity of the carbon powder in step 1 is above 99.5%, and the fine particle size of the carbon powder is above 3500 mesh. The finer the fine particle size of the carbon powder, the more fully the carbon powder can cover the surface of the alloy workpiece, and after the carbon powder is preheated, the reducing activity of the carbon element is fully stimulated, and the oxide film attached to the surface of the alloy workpiece can be fully and thoroughly removed.

[0028] In addition, the process parameters for cleaning the alloy workpiece with an ultrasonic cleaner in step one are: the specification model of the ultrasonic cleaner is: F-031 ultrasonic cleaner, the cleaning agent is acetone solution, the vibration frequency of the ultrasonic cleaner is 40Hz, and the cleaning duration is more than 20 minutes. Drying the alloy workpiece in step one means: using argon gas with a purity of more than 99.99% to blow dry the alloy workpiece. The process parameters for continuously baking the carbon powder in the oven in step one are: the carbon powder is spread in the characteristic container, so that the carbon powder and the characteristic container are baked in the oven for not less than 30 minutes, and the preheating temperature is 200°C.

[0029] In addition, the process parameters for burying the alloy workpiece in the carbon powder in step 2 are: the carbon powder is spread in a characteristic container, and the relative height between the top surface of the carbon powder and the top surface of the alloy workpiece is greater than 10 mm, and the relative height between the bottom surface of the alloy workpiece and the bottom surface of the characteristic container is greater than 5 mm. Preferably, the characteristic container is a porcelain boat. The outer dimensions of the porcelain boat are: length × width = 20 mm × 15 mm. By adopting the technical solution of the present invention, a porcelain boat is used to spread the carbon powder. The porcelain boat has a high high temperature resistance, which can prevent the porcelain boat from being damaged by heat before the workpiece in the vacuum furnace, and the porcelain boat is an open structure, which can prevent the workpiece from being damaged by the increased heat pressure in the vacuum furnace.

[0030] Specifically, heating the vacuum furnace in step 2 means: first, raising the temperature in the vacuum furnace from room temperature to the second critical temperature, and the rate of increase of the temperature in the vacuum furnace is less than 6°C / min, and then keeping the alloy workpiece warm for at least 30 minutes, and then raising the temperature in the vacuum furnace to the first critical temperature. The first critical temperature is 800°C, and the second critical temperature is 400°C. By adopting the technical solution of the present invention, the alloy workpiece is first slowly heated to the second critical temperature, so that the carbon powder in the porcelain boat has enough time to fully exert its reducing effect, break the oxide film attached to the surface of the alloy workpiece, and improve the surface quality of the workpiece. In the process of performing step 2, a vacuum pump can also be set to remove the carbon oxide compounds formed by the combination of carbon and oxygen elements in the vacuum furnace, so that the air pressure in the vacuum furnace is always less than 10-2Pa.

[0031] Furthermore, the process parameters of the post-processing stage in step three are: first, the alloy workpiece is cooled with the furnace to the third critical temperature, and then the alloy workpiece is air-cooled to room temperature, and the cooling rate of the alloy workpiece with the furnace is greater than 30°C / min. Preferably, the third critical temperature is 70°C. During the post-processing stage of step three, argon gas with a pressure not exceeding 2 Bar is continuously fed into the vacuum furnace. By adopting the technical solution of the present invention, when the heat treatment process is nearing the end, the workpiece is first cooled with the furnace and then air-cooled, which can prevent oxygen in the external environment from entering the vacuum furnace, prevent the surface of the workpiece from being oxidized and discolored, and improve the heat treatment effect and quality of the workpiece.

Claims

1. A method for heat treatment of an alloy workpiece, characterized in that: The following steps are involved: Step 1: Preparatory stage: Provide alloy workpiece, vacuum furnace and carbon powder, use ultrasonic cleaning machine to clean the alloy workpiece, then dry the alloy workpiece, remove the air in the vacuum furnace, and make the air pressure in the vacuum furnace less than 10 -2 Pa, send the carbon powder into the oven and continue to bake it until the surface temperature of the carbon powder reaches above the preheating temperature; Step 2: Pre-treatment stage: burying the alloy workpiece in the carbon powder, then transferring the alloy workpiece and the carbon powder into a vacuum furnace at the same time, and then heating the vacuum furnace until the temperature in the vacuum furnace reaches a first critical temperature before proceeding to the next step; Step 3: Post-processing stage: After the alloy workpiece is kept warm for at least 30 minutes, the alloy workpiece is cooled to room temperature by furnace cooling and air cooling.

2. The alloy workpiece heat treatment method according to claim 1, characterized in that: In step 1, the process parameters for cleaning the alloy workpiece with an ultrasonic cleaning machine are as follows: the specification model of the ultrasonic cleaning machine is: F-031 ultrasonic cleaning machine, the cleaning agent is acetone solution, the vibration frequency of the ultrasonic cleaning machine is 40 Hz, and the cleaning duration is more than 20 minutes.

3. The alloy workpiece heat treatment method according to claim 1, characterized in that: The step 1 of drying the alloy workpiece refers to: using argon gas with a purity of 99.99% or more to dry the alloy workpiece.

4. The alloy workpiece heat treatment method according to claim 1, characterized in that: The process parameters for feeding the carbon powder into the oven for continuous baking in step 1 are: the carbon powder is spread in the characteristic container, the carbon powder and the characteristic container are baked in the oven for a duration of not less than 30 minutes, and the preheating temperature is 200°C.

5. The alloy workpiece heat treatment method according to claim 1, characterized in that: The process parameters for burying the alloy workpiece in the carbon powder in step 2 are: the carbon powder is spread in a characteristic container, and the relative height between the top surface of the carbon powder and the top surface of the alloy workpiece is greater than 10 mm, and the relative height between the bottom surface of the alloy workpiece and the bottom surface of the characteristic container is greater than 5 mm.

6. The alloy workpiece heat treatment method according to claim 4 or 5, characterized in that: The characteristic container is a porcelain boat.

7. The alloy workpiece heat treatment method according to claim 1, characterized in that: Heating the vacuum furnace in step 2 means: first raising the temperature in the vacuum furnace from room temperature to a second critical temperature, and the temperature rising rate in the vacuum furnace is less than 6°C / min, and then keeping the alloy workpiece warm for at least 30 minutes, and then raising the temperature in the vacuum furnace to the first critical temperature.

8. The alloy workpiece heat treatment method according to claim 7, characterized in that: The first critical temperature is 800°C, and the second critical temperature is 400°C.

9. The alloy workpiece heat treatment method according to claim 1, characterized in that: The process parameters of the post-processing stage in step three are: firstly cooling the alloy workpiece to the third critical temperature in the furnace, and then air-cooling the alloy workpiece to room temperature, and the cooling rate of the alloy workpiece in the furnace is greater than 30°C / min.

10. The alloy workpiece heat treatment method according to claim 1 or 9, characterized in that: The alloy workpiece heat treatment method further includes the following steps: during the post-processing stage of step three, argon gas with a pressure not exceeding 2 Bar is continuously introduced into the vacuum furnace.

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