A vacuum heat treatment process for 00Cr25Ni6Mo3N steel impeller

Abstract

The invention provides a vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller, comprising vacuum solution treatment: under vacuum conditions, heating to 650-680°C at a speed of 1-3°C / min, keeping the temperature for 240-300min, heating to 850-880°C at a speed of 1-3°C / min, opening a pressure dividing valve, introducing 35-45Pa nitrogen to divide the furnace pressure, keeping the temperature for 120-180min, heating to 1040-1100°C at a speed of 1-3°C / min, keeping the temperature for 120-180min, cooling to 900-1100°C at a speed of 4-6°C / min, introducing 0.45-0.55MPa nitrogen into the furnace, cooling to 50-60°C and taking out of the furnace; water cooling after taking out of the furnace: after taking out of the furnace, the impeller is cooled in water, cooled to water temperature and naturally dried. The invention provides a 00Cr25Ni6Mo3N steel impeller vacuum heat treatment process, and the impeller flow channel surface quality after the treatment is high and the impeller is not easily deformed.

Description

Technical Field

[0001] The invention relates to the technical field of material heat treatment, and in particular to a vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller. Background Art

[0002] Vacuum heat treatment has the advantages of less oxidation, less decarburization and good finish on the surface of the heat-treated workpiece. It is a metal heat processing method that the heat treatment industry has long pursued. The vacuum heat treatment process of 00Cr25Ni6Mo3N steel is relatively complicated, and there is still a blank in China. Due to the complex structure of the 0Cr25Ni6Mo3N steel impeller, when the cooling speed is too fast, the impeller is very easy to deform, and when the cooling speed is too slow, the required heat treatment structure cannot be obtained, and thus the required comprehensive performance cannot be achieved.

[0003] The impeller flow channel is of precision-machined size before heat treatment. Currently, the heat treatment of impellers mainly relies on box-type resistance furnaces or pre-vacuum gas protection furnaces. However, using these heat treatment equipment to heat treat impellers has many human factors, oxidation, poor finish, low dimensional accuracy, and difficulty in ensuring mechanical properties. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller with high heat treatment quality on the surface of an impeller flow channel and impeller heat treatment that is not easily deformed.

[0005] In order to solve the above technical problems, the present invention provides a 00Cr25Ni6Mo3N steel impeller vacuum heat treatment process, comprising the following steps:

[0006] Vacuum solution treatment: under vacuum conditions, heat to 650-680°C at a rate of 1-3°C / min, keep warm for 240-300min, then heat to 850-880°C at a rate of 1-3°C / min, open the pressure divider valve, introduce 35-45Pa nitrogen to divide the furnace pressure, keep warm for 120-180min, then heat to 1040-1100°C at a rate of 1-3°C / min, keep warm for 120-180min, cool to 900-1100°C at a rate of 4-6°C / min, introduce 0.45-0.55MPa nitrogen into the furnace, cool to 50-60°C and take out of the furnace;

[0007] Water cooling after leaving the furnace: After leaving the furnace, the impeller is cooled in water, and after cooling to water temperature, it is naturally dried out of the water.

[0008] Furthermore, the vacuum solution treatment is carried out in a vacuum heat treatment integrated furnace.

[0009] Furthermore, the vacuum degree of the vacuum condition is 1.33×10 -2~1.33×10 -3 Pa.

[0010] Furthermore, the impeller after being taken out of the furnace is transferred to water for cooling within 0.5-1.5 minutes.

[0011] Furthermore, the water temperature is 20-30°C.

[0012] The present invention provides a 00Cr25Ni6Mo3N steel impeller vacuum heat treatment process, which heats up at a heating rate of 1 to 3°C / min and in a step-by-step heating manner during the solution treatment process, and can effectively control the uniformity of the furnace temperature. In addition, when the furnace temperature rises to 850 to 880°C, nitrogen is introduced into the furnace for partial pressure, which can effectively avoid the evaporation of elements of the material under vacuum and high temperature, thereby ensuring the quality and performance of the material. At the same time, the present invention cools to 1000°C at a cooling rate of 4 to 6°C / min, and then introduces 0.45 to 0.55MPa nitrogen into the furnace for cooling, and the impeller is cooled to 50 to 60°C before being taken out of the furnace, which can effectively reduce the deformation of the impeller.

[0013] Due to the fast cooling speed of the impeller, the surface temperature is low and the core temperature is high, and the structural transformation of the core is not thorough enough. Therefore, through the subsequent continued water cooling method, the core of the impeller material is further cooled to prevent the precipitation phase from occurring due to insufficient cooling speed after the impeller is taken out of the furnace, which affects the corrosion resistance of the material.

[0014] Therefore, the vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller provided by the present invention not only solves the problem of decreased corrosion resistance of the material caused by the formation of precipitation phases in the material due to insufficient cooling, but also ensures the mechanical properties of the material, and can also reduce the deformation of the impeller with a complex structure during the heat treatment process, by controlling the process parameters in the solution treatment and further rapid water cooling after the solution treatment.

[0015] Furthermore, the vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller provided by the present invention can complete the multi-step operation processes of heating, heat preservation and cooling in the solution treatment at one time in the furnace, and the operation process has a high degree of automation, which reduces the unqualified product quality caused by human errors of operators.

[0016] At the same time, the present invention provides a 00Cr25Ni6Mo3N steel impeller vacuum heat treatment process, in which the solid solution treatment is carried out under vacuum conditions, which can avoid oxidation of the impeller surface and avoid maintaining the original processing roughness in the flow channel, thereby improving the smoothness of the impeller surface, improving the surface quality of the impeller, and improving the high-quality product rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a process flow chart of vacuum heat treatment of a 00Cr25Ni6Mo3N steel impeller provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] See also Figure 1 The embodiment of the present invention provides a vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller, which includes two processes: vacuum solution treatment and continuous water cooling after being taken out of the furnace. Specifically, the process includes the following steps:

[0019] Step 1) Vacuum solution treatment: under vacuum conditions, heat to 650-680°C at a rate of 1-3°C / min, keep warm for 240-300min, heat to 850-880°C at a rate of 1-3°C / min, open the pressure divider valve, introduce 35-45Pa nitrogen to divide the furnace pressure, keep warm for 120-180min, heat to 1040-1100°C at a rate of 1-3°C / min, keep warm for 120-180min, cool to 900-1100°C at a rate of 4-6°C / min, introduce 0.45-0.55MPa nitrogen into the furnace, cool to 50-60°C and take out of the furnace.

[0020] The present invention heats the furnace at a heating rate of 1 to 3°C / min and in a step-by-step heating manner during solution treatment, thereby effectively controlling the uniformity of the temperature in the furnace.

[0021] In addition, when the temperature rises to the range of 850-880°C, nitrogen is introduced into the furnace for partial pressure, which can prevent the evaporation of elements in the material under vacuum and high temperature, thereby ensuring the quality and performance of the material.

[0022] In addition, since the cooling rate during the solution treatment directly affects the quality of the impeller, a too slow cooling rate will not only fail to obtain the corresponding dual-phase structure, but also have the risk of generating precipitation phases, reducing the corrosion resistance of the material. A too fast cooling rate will increase the deformation of the impeller. Therefore, the present invention cools to 1000°C at a cooling rate of 4 to 6°C / min during the solution treatment, and then introduces 0.45 to 0.55MPa of nitrogen into the furnace for further cooling, and cools to 50 to 60°C before taking out of the furnace. The deformation of the impeller can be effectively reduced.

[0023] At the same time, the present invention adopts vacuum solution treatment during the solution treatment of the impeller, which can avoid oxidation of the impeller surface and avoid maintaining the original processing roughness in the impeller flow channel, thereby improving the smoothness of the impeller surface, improving the surface quality of the impeller, and improving the high-quality product rate.

[0024] Step 2) Water cooling after leaving the furnace: After leaving the furnace, the impeller is cooled in water, and after cooling to water temperature, it is naturally dried.

[0025] Since the impeller cools down quickly, the surface temperature will be low while the core temperature will be high, which may easily cause the transformation of the core structure to be incomplete. Therefore, after the solution treatment, the core of the impeller material is further cooled by subsequent water cooling to prevent the impeller from cooling down insufficiently after being taken out of the furnace and causing precipitation phases to affect the corrosion resistance of the material.

[0026] The vacuum solution treatment is carried out in a vacuum heat treatment integrated furnace. Since the vacuum heat treatment is an integrated furnace with a high degree of automation, human errors caused by manual operation can be avoided, and the failure of mechanical properties after heat treatment due to human factors can be reduced.

[0027] The vacuum degree of the vacuum condition is 1.33×10 -2 ~1.33×10 -3 Pa.

[0028] The impeller after being taken out of the furnace is transferred to water for cooling within 0.5-1.5 minutes, and the water temperature is 20-30° C. Further water cooling of the impeller in a relatively short period of time can avoid the situation where the impeller surface temperature is low and the core temperature is high due to the impeller cooling speed being too fast, and can make the core structure of the impeller material change completely, and can prevent the precipitation phase from occurring due to insufficient cooling of the impeller after being taken out of the furnace, thereby affecting the corrosion resistance of the material.

[0029] The vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller provided by the present invention is specifically described below through an embodiment.

[0030] Example 1 A vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller

[0031] The impeller with a diameter of Φ750mm before heat treatment is produced. The impeller heat treatment process includes solution treatment and continued water cooling treatment:

[0032] Solution treatment: Vacuum solution treatment: at 1.68×10 -3 Pa vacuum degree, heated to 650℃ at 2℃ / min and kept warm for 300 minutes, then heated to 850℃ at 2℃ / min and kept warm for 150 minutes, then heated to 1070℃ at 2℃ / min and kept warm for 120 minutes, then cooled to 1000℃ at a cooling rate of 5℃ / min, then 0.5MPa nitrogen was introduced into the furnace for cooling, and cooled to 50℃ and taken out of the furnace;

[0033] Solution treatment: Heat to 850℃ and open the partial pressure valve at the same time, and introduce 40Pa nitrogen for partial pressure.

[0034] Continue water cooling: After solution treatment, the impeller is transferred to a water tank for cooling within 30 seconds. After cooling to a water temperature of 40°C, it is placed in the air.

[0035] The mechanical properties of the impeller after heat treatment are: Rm: 792Mpa; Rp0.2: 684Mpa; A: 28%; Z: 58%; Kv2: 264 / 254 / 252J; HBW: 232, and no precipitate phase is produced in the metallographic microstructure.

[0036] Example 2 A vacuum heat treatment process for a 00Cr25Ni6Mo3N steel impeller

[0037] The impeller with a diameter of Φ450mm before heat treatment is produced. The impeller heat treatment process includes solution treatment and continued water cooling treatment:

[0038] Solution treatment: Vacuum solution treatment: at 1.93×10 -3 Pa vacuum degree, heated to 680℃ at 3℃ / min and kept warm for 240 minutes, then heated to 880℃ at 2℃ / min and kept warm for 120 minutes, then heated to 1100℃ at 3℃ / min and kept warm for 120 minutes, then cooled to 1000℃ at a cooling rate of 4℃ / min, then 0.4MPa nitrogen was introduced into the furnace for cooling, and cooled to 50℃ and taken out of the furnace;

[0039] Solution treatment: Heat to 880℃ and open the pressure relief valve at the same time, and introduce 40Pa nitrogen for pressure relief.

[0040] Continue water cooling: After solution treatment, the impeller is transferred to a water tank for cooling within 20 seconds. After cooling to a water temperature of 30°C, it is placed in the air.

[0041] Mechanical properties after heat treatment: Rm: 764Mpa; Rp0.2: 625Mpa; A: 28%; Z: 60.5%; Kv2: 252 / 254 / 254J; HBW: 242, no precipitate phase is produced in the metallographic microstructure.

[0042] It can be seen from the two embodiments of the present invention that the 00Cr25Ni6Mo3N steel impeller after heat treatment by the vacuum heat treatment process provided by the present invention not only has mechanical properties that can meet the use requirements, but also has strong corrosion resistance, and at the same time, effectively reduces the deformation of the impeller.

[0043] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A vacuum heat treatment process for 00Cr25Ni6Mo3N steel impeller, It is characterized in that The steps include: Vacuum solution treatment: under vacuum conditions, heat to 650-680°C at a rate of 1-3°C / min, keep warm for 240-300min, then heat to 850-880°C at a rate of 1-3°C / min, open the pressure divider valve, introduce 35-45Pa nitrogen to divide the furnace pressure, keep warm for 120-180min, then heat to 1040-1100°C at a rate of 1-3°C / min, keep warm for 120-180min, cool to 900-1100°C at a rate of 4-6°C / min, introduce 0.45-0.55MPa nitrogen into the furnace, cool to 50-60°C and take out of the furnace; Water cooling after leaving the furnace: After leaving the furnace, the impeller is cooled in water, and after cooling to water temperature, it is naturally dried out of the water.

2. The vacuum heat treatment process for the 00Cr25Ni6Mo3N steel impeller according to claim 1, Features: The vacuum solution treatment is carried out in a vacuum heat treatment integrated furnace.

3. The vacuum heat treatment process for the 00Cr25Ni6Mo3N steel impeller according to claim 1, Features: The vacuum degree of the vacuum condition is 1.33×10 -2 ~1.33×10 -3 Pa.

4. The vacuum heat treatment process for the 00Cr25Ni6Mo3N steel impeller according to claim 1, Features: The impeller after being taken out of the furnace is transferred to water for cooling within 0.5-1.5 minutes.

5. The vacuum heat treatment process for the 00Cr25Ni6Mo3N steel impeller according to claim 1, Features: The water temperature is 20-30°C.

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