Heat treatment method of impeller

Abstract

The invention relates to a heat treatment method of an impeller. A heat treatment method of an impeller comprises the following steps that solution treatment is conducted on the welded impeller, the impeller is heated to 1020-1060 DEG C under the vacuum condition, heat preservation is conducted, and then the impeller is cooled to 50-60 DEG C and discharged out of a furnace; the impeller subjected to solution treatment is subjected to high-temperature aging treatment, heated to 730-780 DEG C, subjected to heat preservation and then subjected to oil cooling to the room temperature; and low-temperature aging treatment is conducted on the impeller subjected to high-temperature aging treatment, after the impeller is heated to 590-635 DEG C, heat preservation is conducted, the impeller is air-cooled to the room temperature, and low-temperature aging treatment is repeatedly conducted on the treated impeller. Optimization and improvement are carried out on the basis of solution treatment and aging treatment of a traditional heat treatment process, the solution treatment is carried out under the vacuum condition, degassing treatment is carried out, gas containing hydrogen, oxygen, nitrogen and other elements at the weld joint position is effectively reduced, and the hydrogen corrosion resistance and low temperature resistance of the weld joint position are effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of material heat treatment, and in particular to a heat treatment method for an impeller. Background Art

[0002] The impeller is an important component of the centrifugal compressor. The working conditions are relatively harsh. It is not only affected by the centrifugal force, but also by the influence of the medium environment, such as corrosive media, low temperature environment, etc. Moreover, the impeller may also be affected by multiple environmental factors at the same time. Therefore, higher requirements are placed on the impeller material and heat treatment.

[0003] The existing welded impellers are subjected to solution treatment and aging treatment after welding. The weld and heat affected zone are weak links. No matter the mechanical properties, hydrogen corrosion resistance or low temperature resistance, they cannot meet the requirements similar to those of the parent material. Therefore, it is an important research direction to improve the hydrogen corrosion resistance and low temperature resistance of the weld and heat affected zone while ensuring the hydrogen corrosion resistance and low temperature resistance of the parent material through heat treatment methods. Summary of the invention

[0004] The present application improves the traditional heat treatment process and provides a heat treatment method for an impeller, which has a good solid solution treatment effect and improves the hydrogen corrosion resistance and low temperature resistance of the weld position.

[0005] A heat treatment method for an impeller of the present application comprises the following steps:

[0006] The welded impeller is subjected to a solution treatment, heated to 1020-1060°C under vacuum conditions, kept warm, and then cooled to 50-60°C before being taken out of the furnace;

[0007] The impeller after the solution treatment is subjected to high temperature aging treatment, heated to 730-780° C., kept warm, and then oil-cooled to room temperature;

[0008] The impeller after high-temperature aging treatment is subjected to low-temperature aging treatment, heated to 590-635° C. and kept warm, then air-cooled to room temperature, and the treated impeller is repeatedly subjected to low-temperature aging treatment.

[0009] Furthermore, the material of the impeller is ASTM A705-630 steel, 17-4PH steel, UNS S17400 steel, 05Cr17Ni4Cu4Nb or UNS J92180 steel.

[0010] Furthermore, the welding material is ER630 welding wire or E630 welding rod.

[0011] Furthermore, the impeller is solution treated in a step-by-step heating manner. Under vacuum conditions, it is heated to 680-700°C and kept warm for 60-90 min, then heated to 800-900°C and kept warm for 180-240 min, then heated to 1020-1060°C and kept warm for 120-180 min, and then cooled to 50-60°C and taken out of the furnace.

[0012] Furthermore, the heating rate of the solution treatment is 1-2°C / min. If the heating rate is too slow, the heating time is long, resulting in energy waste. If the heating rate is too fast, the temperature of the part will be very different from the furnace temperature, which may cause the part temperature to fail to reach the required temperature, or the mechanical properties may not meet the requirements due to insufficient heat preservation time of the part. In addition, due to the large difference between the temperature of the part and the furnace temperature, the part may bend, deform or crack.

[0013] Furthermore, the vacuum degree of solution treatment is 1.33×10 -2 ~1.33×10 -3 Pa.

[0014] Furthermore, the solution treatment is performed in a vacuum degassing device, such as a vacuum heat treatment furnace.

[0015] Furthermore, the heating rate of the high temperature aging treatment is ≤70°C / h, and the holding time is 3 to 4h.

[0016] Furthermore, the heating rate of the low-temperature aging treatment is ≤50°C / h, and the holding time is ≥5h.

[0017] Furthermore, the total number of low-temperature aging treatments is 2 to 3 times.

[0018] The beneficial effects of this application are as follows:

[0019] (1) This application optimizes and improves the traditional heat treatment process based on the solution treatment and aging treatment. The solution treatment is carried out under vacuum conditions, and degassing treatment, dehydrogenation, deoxidation, and denitrification are carried out at the same time, effectively reducing the gas containing elements such as hydrogen, oxygen, and nitrogen at the weld position, and effectively improving the hydrogen corrosion resistance and low temperature resistance of the weld position. The impeller prepared by the heat treatment process of this application has high hydrogen corrosion resistance and low temperature resistance for both the base material and the welding material. The hardness after heat treatment can be lower than HBW290, the impact toughness of the base material is higher than 100J, and the impact toughness of the weld can be higher than 30J. It can be well applied to countries in extremely cold regions such as Russia, and is suitable for media containing corrosive substances such as H2S.

[0020] (2) The present application can achieve precise temperature control, further ensuring the solution treatment effect of the impeller, making the overall properties of the impeller more stable, and the comprehensive mechanical properties of the base material, weld and heat-affected zone are good.

[0021] (3) The present application effectively increases the amount of reversed austenite in the base material and weld by increasing the number of low-temperature aging treatments, effectively reduces the hydrogen diffusion capacity, effectively improves the hydrogen corrosion resistance of the base material and weld, and reduces the possibility of hydrogen embrittlement fracture. At the same time, the increase in austenite content does not lose toughness at low temperatures, thereby improving the low-temperature resistance of the weld. DETAILED DESCRIPTION

[0022] The technical solution in the present application will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0023] A heat treatment method for an impeller of the present application comprises the following steps:

[0024] The welded impeller is subjected to solution treatment under vacuum conditions with a vacuum degree of 1.33×10 -2 ~1.33×10 -3 Pa, heated to 680-700℃ at a heating rate of 1-2℃ / min and kept for 60-90min, heated to 800-900℃ at a heating rate of 1-2℃ / min and kept for 180-240min, heated to 1020-1060℃ at a heating rate of 1-2℃ / min and kept for 120-180min, cooled to 50-60℃ and taken out of the furnace. Solution treatment is carried out in vacuum degassing equipment. Heat treatment under vacuum conditions is carried out under negative pressure, causing the gas elements in the material to move to the negative pressure side, and some gas elements overflow the surface of the material, especially the weld position. For example, the E630 electrode welding method is electrode arc welding. Welding in the air can easily cause gas elements to enter the weld. When heat treated under vacuum conditions, the gas elements in the weld under negative pressure overflow, thereby improving the impact toughness of the weld. The use of vacuum degassing equipment can continuously process metal heat treatment processes including heating, insulation and cooling. It can complete the treatment process that requires more than a dozen or even dozens of actions at one time in the vacuum degassing equipment. The operation process has a high degree of automation and accurate control, which reduces operator error.

[0025] The impeller after the solution treatment is subjected to high temperature aging treatment, heated to 730-780° C. at a heating rate of ≤70° C. / h, kept at this temperature for 3-4 hours, and then oil-cooled to room temperature.

[0026] The impeller after high-temperature aging treatment is subjected to low-temperature aging treatment, heated to 590-635°C at a heating rate of ≤50°C / h, kept warm for ≥5h, and then air-cooled to room temperature. Wherein, the heating temperature is 590-635°C, which can be 590°C, 620°C, 635°C, etc. The impeller after high-temperature aging treatment is repeatedly subjected to low-temperature aging treatment, that is, the low-temperature aging treatment steps are repeated, including the above-mentioned heating to 590-635°C at a heating rate of ≤50°C / h, kept warm for ≥5h, and then air-cooled to room temperature. As the number of aging times increases further, the effect of increasing the content of reversed austenite decreases until it is not obvious. The increase in the content of reversed austenite can improve the low-temperature impact toughness, and due to the increase in the content of reversed austenite, the diffusion of the H element is hindered, and the hydrogen corrosion resistance is improved. The total number of low-temperature aging treatments is preferably 2 to 3 times.

[0027] The impeller is made of ASTM A705-630 steel, 17-4PH steel, UNS S17400 steel, 05Cr17Ni4Cu4Nb or UNS J92180 steel or other similar steels. The welding material is ER630 welding wire or E630 welding rod or other similar welding materials.

[0028] The following examples are used to illustrate the present application but are not used to limit the scope of the present application.

[0029] Example 1

[0030] The material of the impeller of this embodiment is ASTM A705-630 steel, and the diameter before heat treatment is Φ450mm. The heat treatment method includes the following steps:

[0031] (1) The welded impeller is subjected to solution treatment under vacuum conditions with a vacuum degree of 1.78×10 -3 Pa, heated to 700℃ at a heating rate of 1℃ / min and kept warm for 60min, then heated to 880℃ at a heating rate of 2℃ / min and kept warm for 180min, then heated to 1045℃ at a heating rate of 2℃ / min and kept warm for 120min, 1.5bar nitrogen was introduced into the furnace for cooling, and the furnace was cooled to 50℃ and taken out of the furnace.

[0032] (2) The impeller after solution treatment was subjected to high temperature aging treatment by heating to 760°C at a heating rate of 60°C / h, keeping the temperature for 3h, and then oil cooling to room temperature.

[0033] (3) The impeller after high-temperature aging treatment was subjected to low-temperature aging treatment by heating to 620°C at a heating rate of 40°C / h, keeping the temperature for 5h, and then air cooling to room temperature.

[0034] (4) The impeller treated in step (3) is subjected to low-temperature aging treatment by heating to 620° C. at a heating rate of 50° C. / h, keeping the temperature for 5 h, and then air-cooling to room temperature.

[0035] (5) The impeller treated in step (4) is subjected to low-temperature aging treatment by heating to 620° C. at a heating rate of 40° C. / h, keeping the temperature for 5 h, and then air-cooling to room temperature.

[0036] After the treatment is completed, the mechanical properties of the impeller cover, impeller disc and the simulated welding sample (test plate size is 300*300*15mm) that are heat treated together are tested. The test results are as follows.

[0037] The mechanical properties test results of the wheel cover after heat treatment are as follows: tensile strength Rm: 832Mpa; yield strength Rp0.2: 688Mpa; elongation A: 21%; cross-sectional shrinkage Z: 72%; low-temperature impact energy at -45°C: 140 / 150 / 142J; hardness: HBW288.

[0038] The mechanical properties test results of the wheel after heat treatment are: Rm: 830Mpa; Rp0.2: 658Mpa; A: 20.5%; Z: 71.5%; low-temperature impact energy at -45℃: 132 / 124 / 136J; hardness: HBW288.

[0039] The mechanical properties test results of the simulated welding specimens are shown in Tables 1 and 2.

[0040] Table 1

[0041]

[0042] Table 2

[0043] Weld Heat affected zone -45℃ impact energy (J) 30-36-36 80-80-78 Hardness(HBW) 284 286

[0044] The hardness of the base material, weld and heat-affected zone is less than HBW311 (HRC34), which meets the requirements of API 617 centrifugal compressors for petroleum, chemical and gas industries and NACE MR0175 metal materials for oilfield equipment resistant to hydrogen sulfide stress cracking. Among them, the minimum impact energy of the weld is 30J, which is 27J higher than the required value.

[0045] Example 2

[0046] The material of the impeller in this embodiment is UNS S17400 steel, and the diameter before heat treatment is Φ900 mm. The heat treatment method includes the following steps:

[0047] (1) The welded impeller is subjected to solution treatment under vacuum conditions with a vacuum degree of 1.75×10 -3Pa, heated to 680℃ at a heating rate of 1℃ / min and kept warm for 90min, then heated to 850℃ at a heating rate of 1℃ / min and kept warm for 240min, then heated to 1040℃ at a heating rate of 2℃ / min and kept warm for 180min, 1.5bar nitrogen was introduced into the furnace for cooling, and the furnace was cooled to 50℃ and taken out of the furnace.

[0048] (2) The impeller after solution treatment was subjected to high temperature aging treatment by heating to 750°C at a heating rate of 40°C / h, keeping the temperature for 4h, and then oil cooling to room temperature.

[0049] (3) The impeller after high-temperature aging treatment was subjected to low-temperature aging treatment by heating to 635°C at a heating rate of 50°C / h, keeping the temperature for 9h, and then air cooling to room temperature.

[0050] (4) The impeller treated in step (3) is subjected to low-temperature aging treatment by heating to 635° C. at a heating rate of 40° C. / h, keeping the temperature for 9 h, and then air-cooling to room temperature.

[0051] After the treatment is completed, the mechanical properties of the impeller cover, impeller disc and the simulated welding sample that were heat treated together were tested. The test results are as follows.

[0052] The mechanical properties test results of the wheel cover after heat treatment are: Rm: 802Mpa; Rp0.2: 635Mpa; A: 23%; Z: 75%; low-temperature impact energy at -40℃: 150 / 156 / 148J; hardness: HBW282.

[0053] The mechanical properties test results of the wheel after heat treatment are: Rm: 810Mpa; Rp0.2: 628Mpa; A: 22.5%; Z: 76.8%; low-temperature impact energy at -40℃: 148 / 166 / 168J; hardness: HBW276.

[0054] The mechanical properties test results of the simulated welding specimens are shown in Tables 3 and 4.

[0055] Table 3

[0056]

[0057] Table 4

[0058] Weld Heat affected zone -40℃ impact energy(J) 36-40-42 90-90-84 Hardness(HBW) 280 278

[0059] The hardness of the base material, weld and heat-affected zone is less than HBW311 (HRC34), which meets the requirements of API 617 centrifugal compressors for petroleum, chemical and gas industries and NACE MR0175 metal materials for oilfield equipment resistant to hydrogen sulfide stress cracking. Among them, the minimum impact energy of the weld is 36J, which is 27J higher than the required value.

[0060] Comparative Example

[0061] The material of the impeller of this comparative example is ASTM A705-630 steel, and the diameter before heat treatment is Φ450mm. The heat treatment method includes the following steps:

[0062] (1) The welded impeller is subjected to solution treatment under vacuum conditions with a vacuum degree of 1.78×10 -3 Pa, heated to 1060℃ at a heating rate of 2℃ / min, and kept warm for 120min. Then, 1.5bar nitrogen was introduced into the furnace for cooling, and the furnace was cooled to 50℃ and then taken out of the furnace.

[0063] Step (2) is the same as step (2) of Example 1.

[0064] (3) The impeller after high-temperature aging treatment was subjected to low-temperature aging treatment by heating to 635°C at a heating rate of 40°C / h, keeping the temperature for 6h, and then air cooling to room temperature.

[0065] After the treatment is completed, the mechanical properties of the impeller cover, impeller disc and the simulated welding sample that were heat treated together were tested. The test results are as follows.

[0066] The mechanical properties test results of the wheel cover after heat treatment are: Rm: 877Mpa; Rp0.2: 609Mpa; A: 23.5%; Z: 60%; low-temperature impact energy at -45℃: 115 / 114 / 112J; hardness: HBW297.

[0067] The mechanical properties test results of the wheel after heat treatment are: Rm: 890Mpa; Rp0.2: 622Mpa; A: 25%; Z: 64%; low-temperature impact energy at -45℃: 110 / 110 / 118J; hardness: HBW294.

[0068] The mechanical properties test results of the simulated welding specimens are shown in Tables 5 and 6.

[0069] Table 5

[0070]

[0071] Table 6

[0072] Weld Heat affected zone -45℃ impact energy (J) 20-18-18 60-68-80 Hardness(HBW) 312 300

[0073] It can be seen from the comparative examples that the hardness values ​​of the weld and heat-affected zone of ASTM A705-630 steel after primary aging treatment meet the requirements of API 617 centrifugal compressors for petroleum, chemical and gas industries and NACE MR0175 oilfield equipment metal materials for hydrogen sulfide stress cracking, but the hardness value tends to the upper limit, which is higher than that of Example 1 and Example 2. As the hardness value increases, the hydrogen corrosion resistance decreases. In addition, the impact energy of the weld in Example 3 has been reduced to 18J, which is far lower than the required value of 27J and cannot meet the design requirements.

[0074] Although the present application has been described in detail above with general descriptions and specific implementation methods, it is obvious to those skilled in the art that some modifications or improvements can be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope of protection claimed in the present application.

Claims

1. A heat treatment method for an impeller, characterized in that: The steps include: The welded impeller is subjected to a solution treatment, heated to 1020-1060°C under vacuum conditions, kept warm, and then cooled to 50-60°C before being taken out of the furnace; The impeller after the solution treatment is subjected to high temperature aging treatment, heated to 730-780° C., kept warm, and then oil-cooled to room temperature; The impeller after high-temperature aging treatment is subjected to low-temperature aging treatment, heated to 590-635° C. and kept warm, then air-cooled to room temperature, and the treated impeller is repeatedly subjected to low-temperature aging treatment.

2. A heat treatment method for an impeller according to claim 1, characterized in that: The material of the impeller is ASTMA705-630 steel, 17-4PH steel, UNS S17400 steel, 05Cr17Ni4Cu4Nb or UNS J92180 steel.

3. The heat treatment method of an impeller according to claim 1, characterized in that: The welding material is ER630 welding wire or E630 welding rod.

4. The heat treatment method of an impeller according to claim 1, characterized in that: The impeller is solution treated in a step-by-step heating manner. Under vacuum conditions, it is heated to 680-700°C and kept warm for 60-90 minutes, then heated to 800-900°C and kept warm for 180-240 minutes, then heated to 1020-1060°C and kept warm for 120-180 minutes, and then cooled to 50-60°C and taken out of the furnace.

5. A heat treatment method for an impeller according to claim 1 or 4, characterized in that: The heating rate of the solution treatment is 1 to 2°C / min.

6. The heat treatment method of an impeller according to claim 1, characterized in that: The vacuum degree of solution treatment is 1.33×10 -2 ~1.33×10 -3 Pa.

7. The heat treatment method of an impeller according to claim 1, characterized in that: Solution treatment is carried out in a vacuum degassing device.

8. The heat treatment method of an impeller according to claim 1, characterized in that: The heating rate of high temperature aging treatment is ≤70℃ / h, and the holding time is 3 to 4h.

9. The heat treatment method of an impeller according to claim 1, characterized in that: The heating rate of low-temperature aging treatment is ≤50℃ / h, and the holding time is ≥5h.

10. The heat treatment method of an impeller according to claim 1, characterized in that: The total number of low-temperature aging treatments is 2 to 3 times.

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