SA266Gr.4 forge piece for nuclear power and manufacturing method of SA266Gr.4 forge piece

Abstract

The invention provides an SA266Gr.4 forge piece for nuclear power, which consists of the following components in percentage by weight: 0.16 to 0.20 percent of C, 0.15 to 0.35 percent of Si, 1.20 to 1.35 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.010 percent of S, less than or equal to 0.010 percent of Cr, 0.15 to 0.25 percent of Ni, less than or equal to 0.010 percent of Mo, less than or equal to 0.020 percent of V, 0.040 to 0.050 percent of Cu and the balance of iron. The invention further provides a manufacturing method of the SA266Gr.4 forge piece for nuclear power. The SA266Gr.4 forge piece for nuclear power provided by the invention has relatively high high-temperature tensile strength and relatively good toughness.

Description

Technical Field

[0001] The invention belongs to the field of alloy forging, and in particular relates to a SA266Gr.4 forging for nuclear power and a manufacturing method thereof. Background Art

[0002] At present, the technical requirements for carbon steel forgings used in steam-water separation reheaters of pressurized water reactor nuclear power units in my country are very high. The design technical specifications require high-temperature stretching at 320°C, and the acceptance value is close to the acceptance value for normal-temperature stretching. Since the weight of the forging is about 20 tons, the thickness of the forging reaches 380 mm, and the sampling position is at a deeper position of the forging, the high-temperature stretching acceptance is more difficult. SA266Gr.4 is a stainless steel with good mechanical properties, but its high-temperature tensile strength is not ideal. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a SA266Gr.4 forging for nuclear power, which has higher high-temperature tensile strength and better toughness.

[0004] In order to solve the above technical problems, the technical solution of the present invention is:

[0005] A SA266Gr.4 forging for nuclear power consists of the following components by weight: C 0.16-0.20%, Si 0.15-0.35%, Mn 1.20-1.35%, P≤0.015%, S≤0.010%, Cr≤0.010%, Ni 0.15-0.25%, Mo≤0.010%, V≤0.020%, Cu 0.040-0.050%, and the remainder is iron.

[0006] Another technical problem to be solved by the present invention is to provide a method for manufacturing the SA266Gr.4 forging for nuclear power.

[0007] To solve the above technical problems, the technical solution is:

[0008] A method for manufacturing SA266Gr.4 forgings for nuclear power, comprising the following steps:

[0009] S1. Smelting: Prepare the raw materials by weight percentage, place the raw materials in an electric furnace, and smelt until the temperature reaches 1530-1580°C to obtain molten steel;

[0010] S2 refining outside the furnace: The molten steel obtained in step S1 is placed in a LF furnace, refined for 55-75 minutes, vacuum degassed for 30-40 minutes, and then cast into an ingot;

[0011] S3 forging: The steel ingot obtained in step S2 is forged into a forging by a hydraulic press;

[0012] S4 heat treatment: The forging obtained in step S3 is subjected to preliminary heat treatment, followed by quenching, and finally tempering to obtain a SA266Gr.4 forging for nuclear power;

[0013] S5. Testing: Perform physical and chemical testing and nondestructive testing on the SA266Gr.4 forgings for nuclear power obtained in step S4.

[0014] Furthermore, in step S2 of the present invention, argon protection is used throughout the refining process outside the furnace, the vacuum degree during vacuum degassing is 50-60Pa, and the temperature of the molten steel during pouring is 1380-1420°C.

[0015] Furthermore, in step S3 of the present invention, the cutting ratio of the ingot head is 8%, the cutting ratio of the ingot tail is 4%, the initial forging temperature is 1200-1240°C, the final forging temperature is 750-800°C, and the forging ratio is ≥4.5.

[0016] Furthermore, in step S4 of the present invention, the preliminary heat treatment is carried out in an industrial resistance furnace, the heating temperature of the preliminary heat treatment is 900-920° C., and the insulation time is 1-2 hours.

[0017] Furthermore, in step S4 of the present invention, the quenching temperature is 910-930° C., the holding time is 2-3 hours, and the quenching medium is composed of the following components by weight percentage: 2-3% potassium hydroxide, 1-2% 2-methylthio-2-imidazoline hydroiodide, 6-9% tert-butyldimethylsilyl glycidyl ether, 4-5% N,N-dimethylformamide, and the rest is water.

[0018] Furthermore, the preparation steps of the quenching medium of the present invention are:

[0019] Prepare each component according to weight percentage, add potassium hydroxide into water, stir until mixed evenly, then add other components, continue stirring for 2-3 hours to obtain the quenching medium.

[0020] Furthermore, in the step of preparing the quenching medium of the present invention, the stirring speed is 200 rpm.

[0021] Furthermore, in step S4 of the present invention, the tempering temperature is 580-610° C., and the tempering time is 2-3 hours.

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

[0023] 1) The chemical composition of the forging has a great influence on the strength. In this regard, the present invention appropriately increases the content of strength elements C and Mn, which can effectively improve the high-temperature tensile strength of the forging. At the same time, the content of Ni element is appropriately increased, which can not only improve the strength but also enhance the toughness of the forging. In addition, the present invention also reduces the content of P and S elements, which can reduce the content of non-metallic inclusions in the forging.

[0024] 2) The present invention controls the forging heating temperature within an appropriate range, which can prevent the material from overheating and overburning, appropriately increases the forging ratio, improves the forging effect, forges tiny defects to make the material denser, and is beneficial to improving the comprehensive performance of the material.

[0025] 3) The present invention adds a preliminary heat treatment operation during the heat treatment process to prepare for the tempering process, which can refine the grains and reduce the quenching temperature to prevent the grains from growing.

[0026] 4) The present invention uses a quenching medium composed of potassium hydroxide, 2-methylthio-2-imidazoline hydroiodide, tert-butyldimethylsilyl glycidyl ether, N,N-dimethylformamide and water during quenching. The coolant has good wettability and stability, can effectively improve the hardenability of forgings, and can also effectively avoid brittle cracking of forgings. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below in conjunction with specific embodiments. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention but are not intended to limit the present invention.

[0028] Example 1

[0029] SA266Gr.4 forgings for nuclear power are composed of the following components in weight percentage: C 0.18%, Si 0.27%, Mn 1.30%, P 0.010%, S 0.008%, Cr 0.008%, Ni 0.20%, Mo 0.009%, V 0.015%, Cu 0.048%, and the rest is iron.

[0030] The manufacturing method of embodiment 1 comprises the following steps:

[0031] S1. Smelting: Prepare the raw materials by weight percentage, place the raw materials in an electric furnace, and smelt until the temperature reaches 1560°C to obtain molten steel;

[0032] S2 refining outside the furnace: argon protection throughout the process, the molten steel obtained in step S1 is placed in a LF furnace, refining for 65 minutes and then vacuum degassing for 35 minutes, and then cast into an ingot; the vacuum degree during vacuum degassing is 55Pa, and the temperature of the molten steel during casting is 1400 ℃;

[0033] S3. Forging: The steel ingot obtained in step S2 is forged into a forging by a hydraulic press, the cutting ratio of the ingot head is 8%, the cutting ratio of the ingot tail is 4%, the initial forging temperature is 1220°C, the final forging temperature is 770°C, and the forging ratio is 4.6;

[0034] S4. Heat treatment: The forging obtained in step S3 is subjected to preliminary heat treatment in an industrial resistance furnace, followed by quenching and finally tempering to obtain SA266Gr.4 forgings for nuclear power; the heating temperature for preliminary heat treatment is 910 ° C, the holding time is 1.5 hours, the quenching temperature is 920 ° C, the holding time is 2.5 hours, the tempering temperature is 600 ° C, and the tempering time is 2.5 hours;

[0035] S5. Testing: Perform physical and chemical testing and nondestructive testing on the SA266Gr.4 forgings for nuclear power obtained in step S4.

[0036] The quenching medium in step S4 is composed of the following components by weight percentage: 2.5% potassium hydroxide, 1.5% 2-methylthio-2-imidazoline hydroiodide, 8% tert-butyldimethylsilyl glycidyl ether, 4.5% N,N-dimethylformamide, and the rest water. The steps for preparing the quenching medium are:

[0037] Prepare each component according to weight percentage, add potassium hydroxide into water, stir until mixed evenly, then add other components, continue stirring for 2.5 hours to obtain quenching medium, and stir at a speed of 200 rpm.

[0038] Example 2

[0039] SA266Gr.4 forgings for nuclear power are composed of the following components in weight percentage: C 0.16%, Si 0.35%, Mn 1.25%, P 0.015%, S 0.009%, Cr 0.010%, Ni 0.15%, Mo 0.010%, V 0.018%, Cu 0.040%, and the rest is iron.

[0040] The manufacturing method of embodiment 2 comprises the following steps:

[0041] S1. Smelting: Prepare the raw materials by weight percentage, place the raw materials in an electric furnace, and smelt until the temperature reaches 1570°C to obtain molten steel;

[0042] S2 refining outside the furnace: argon protection throughout the process, the molten steel obtained in step S1 is placed in a LF furnace, refining for 60 minutes and then vacuum degassing for 35 minutes, and then cast into an ingot; the vacuum degree during vacuum degassing is 60Pa, and the temperature of the molten steel during casting is 1410 ℃;

[0043] S3. Forging: The steel ingot obtained in step S2 is forged into a forging by a hydraulic press, the cutting ratio of the ingot head is 8%, the cutting ratio of the ingot tail is 4%, the initial forging temperature is 1230°C, the final forging temperature is 780°C, and the forging ratio is 4.5;

[0044] S4. Heat treatment: The forging obtained in step S3 is subjected to preliminary heat treatment in an industrial resistance furnace, followed by quenching and finally tempering to obtain SA266Gr.4 forgings for nuclear power; the heating temperature for preliminary heat treatment is 915 ° C, the holding time is 1.5 hours, the quenching temperature is 925 ° C, the holding time is 2.5 hours, the tempering temperature is 605 ° C, and the tempering time is 2.5 hours;

[0045] S5. Testing: Perform physical and chemical testing and nondestructive testing on the SA266Gr.4 forgings for nuclear power obtained in step S4.

[0046] The quenching medium in step S4 is composed of the following components by weight percentage: 2.7% potassium hydroxide, 1.2% 2-methylthio-2-imidazoline hydroiodide, 9% tert-butyldimethylsilyl glycidyl ether, 4% N,N-dimethylformamide, and the rest water. The steps for preparing the quenching medium are:

[0047] Prepare each component according to weight percentage, add potassium hydroxide into water, stir until mixed evenly, then add other components, continue stirring for 2 hours to obtain quenching medium, and stir at a speed of 200 rpm.

[0048] Example 3

[0049] SA266Gr.4 forgings for nuclear power are composed of the following components in weight percentage: C 0.19%, Si 0.15%, Mn 1.35%, P 0.014%, S 0.010%, Cr 0.008%, Ni 0.18%, Mo 0.010%, V 0.019%, Cu 0.050%, and the rest is iron.

[0050] The manufacturing method of embodiment 3 comprises the following steps:

[0051] S1. Smelting: Prepare raw materials by weight percentage, place the raw materials in an electric furnace, and smelt until the temperature reaches 1580°C to obtain molten steel;

[0052] S2. Refining outside the furnace: The whole process was protected by argon gas. The molten steel obtained in step S1 was placed in a LF furnace, refining for 55 minutes and then vacuum degassing for 30 minutes, and then cast into an ingot; the vacuum degree during vacuum degassing was 55Pa, and the temperature of the molten steel during casting was 1420 ℃;

[0053] S3. Forging: The steel ingot obtained in step S2 is forged into a forging by a hydraulic press, the cutting ratio of the ingot head is 8%, the cutting ratio of the ingot tail is 4%, the initial forging temperature is 1240°C, the final forging temperature is 800°C, and the forging ratio is 4.6;

[0054] S4. Heat treatment: The forging obtained in step S3 is subjected to preliminary heat treatment in an industrial resistance furnace, and then quenched and finally tempered to obtain SA266Gr.4 forgings for nuclear power; the heating temperature for preliminary heat treatment is 920°C, the holding time is 1 hour, the quenching temperature is 930°C, the holding time is 2 hours, the tempering temperature is 610°C, and the tempering time is 2 hours;

[0055] S5. Testing: Perform physical and chemical testing and nondestructive testing on the SA266Gr.4 forgings for nuclear power obtained in step S4.

[0056] The quenching medium in step S4 is composed of the following components by weight percentage: 3% potassium hydroxide, 1% 2-methylthio-2-imidazoline hydroiodide, 6% tert-butyldimethylsilyl glycidyl ether, 5% N,N-dimethylformamide, and the rest water. The steps for preparing the quenching medium are:

[0057] Prepare each component according to weight percentage, add potassium hydroxide into water, stir until mixed evenly, then add other components, continue stirring for 3 hours to obtain quenching medium, and stir at a speed of 200 rpm.

[0058] Example 4

[0059] SA266Gr.4 forgings for nuclear power are composed of the following components in terms of weight percentage: C 0.20%, Si 0.20%, Mn 1.20%, P 0.013%, S 0.009%, Cr 0.009%, Ni 0.25%, Mo 0.008%, V 0.020%, Cu 0.045%, and the rest is iron.

[0060] The manufacturing method of embodiment 4 comprises the following steps:

[0061] S1. Smelting: Prepare the raw materials by weight percentage, place the raw materials in an electric furnace, and smelt until the temperature reaches 1530°C to obtain molten steel;

[0062] S2 refining outside the furnace: argon protection throughout the process, the molten steel obtained in step S1 is placed in a LF furnace, refining for 75 minutes and then vacuum degassing for 40 minutes, and then cast into an ingot; the vacuum degree during vacuum degassing is 50Pa, and the temperature of the molten steel during casting is 1380 ℃;

[0063] S3. Forging: The steel ingot obtained in step S2 is forged into a forging by a hydraulic press, the cutting ratio of the ingot head is 8%, the cutting ratio of the ingot tail is 4%, the initial forging temperature is 1200°C, the final forging temperature is 750°C, and the forging ratio is 4.7;

[0064] S4. Heat treatment: The forging obtained in step S3 is subjected to preliminary heat treatment in an industrial resistance furnace, and then quenched and finally tempered to obtain SA266Gr.4 forgings for nuclear power; the heating temperature for preliminary heat treatment is 900°C, the holding time is 2 hours, the quenching temperature is 910°C, the holding time is 3 hours, the tempering temperature is 580°C, and the tempering time is 3 hours;

[0065] S5. Testing: Perform physical and chemical testing and nondestructive testing on the SA266Gr.4 forgings for nuclear power obtained in step S4.

[0066] The quenching medium in step S4 is composed of the following components by weight percentage: 2% potassium hydroxide, 2% 2-methylthio-2-imidazoline hydroiodide, 7% tert-butyldimethylsilyl glycidyl ether, 4.8% N,N-dimethylformamide, and the rest water. The steps for preparing the quenching medium are:

[0067] Prepare each component according to weight percentage, add potassium hydroxide into water, stir until mixed evenly, then add other components, continue stirring for 2.5 hours to obtain quenching medium, and stir at a speed of 200 rpm.

[0068] Comparative Example 1

[0069] The composition of the forging is: C 0.15%, Si 0.27%, Mn 1.30%, P 0.010%, S 0.008%, Cr 0.008%, Ni 0.20%, Mo 0.009%, V 0.015%, Cu 0.048%, and the rest is iron. That is, the difference between Comparative Example 1 and Example 1 is that the content of the C element is lower than the range defined by the present invention, and the other components and preparation method are the same as those of Example 1.

[0070] Comparative Example 2

[0071] The composition of the forging is: C 0.18%, Si 0.27%, Mn 1.19%, P 0.010%, S 0.008%, Cr 0.008%, Ni 0.20%, Mo 0.009%, V 0.015%, Cu 0.048%, and the rest is iron. That is, the difference between Comparative Example 2 and Example 1 is that the content of the Mn element is lower than the range defined by the present invention, and the other components and preparation method are the same as those of Example 1.

[0072] Comparative Example 3

[0073] The composition of the forging is: C 0.18%, Si 0.27%, Mn 1.19%, P 0.010%, S 0.008%, Cr 0.008%, Ni 0.14%, Mo 0.009%, V 0.015%, Cu 0.048%, and the rest is iron. That is, the difference between Comparative Example 3 and Example 1 is that the content of Ni element is lower than the range defined by the present invention, and the other components and preparation method are the same as those of Example 1.

[0074] Comparative Example 4

[0075] The composition of the forging is the same as that of Example 1. The difference from Example 1 is that the quenching medium in step S4 is replaced by water.

[0076] Experimental Example 1: High Temperature Tensile Strength Test

[0077] The SA266Gr.4 forgings for nuclear power prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to high temperature tensile strength tests according to ASTM E21-2020 "High Temperature Tensile Test Methods for Metallic Materials". The test results are as follows:

[0078] As shown in Table 1.

[0079]

[0080] Table 2

[0081] It can be seen from Table 1 that the high temperature yield strength and tensile strength of Examples 1-4 all meet the standard requirements, indicating that the SA266Gr.4 forgings for nuclear power prepared by the present invention have good high temperature tensile strength, while the content of the C element in Comparative Example 1 is lower than the range specified in the present invention, and the content of the Mn element in Comparative Example 2 is lower than the range specified in the present invention, so the yield strength and tensile strength of both are weaker than those of Example 1.

[0082] Experimental Example 2: Toughness Test

[0083] The SA266Gr.4 forgings for nuclear power prepared in Examples 1-4 and Comparative Example 3 were subjected to toughness tests (3 specimens, average value) according to ASTM A370-2015, and the test results are shown in Table 2.

[0084]

[0085] Table 2

[0086] It can be seen from Table 2 that the -20°C impact absorption energy of Examples 1-4 all meet the standard requirements, indicating that the SA266Gr.4 forgings for nuclear power produced by the present invention have good toughness, while the -20°C impact absorption energy of Comparative Example 3 is weaker than that of Example 1 because the content of Ni element is lower than the range specified by the present invention.

[0087] Experimental Example 3: Hardenability Test

[0088] The SA266Gr.4 forgings for nuclear power prepared in Examples 1-4 and Comparative Example 4 were respectively tested for terminal hardenability with reference to GB / T225-2006 “Terminal quenching test method for hardenability of steel (Jominy test)”. The test results are shown in Table 3.

[0089]

[0090] Table 3

[0091] As can be seen from Table 3, the hardness of Examples 1-4 at a distance of 15 mm from the quenching end is relatively high, indicating that the SA266Gr.4 forgings for nuclear power prepared by the present invention have good hardenability. Compared with Example 1, the hardness of Comparative Example 4 at a distance of 15 mm from the quenching end is reduced, indicating that the quenching medium used in the present invention can effectively improve the hardenability of the forging.

[0092] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A SA266Gr.4 forging for nuclear power, characterized in that: Calculated by weight percentage, it is composed of the following components: C 0.16-0.20%, Si 0.15-0.35%, Mn 1.20-1.35%, P≤0.015%, S≤0.010%, Cr≤0.010%, Ni0.15-0.25%, Mo≤0.010%, V≤0.020%, Cu 0.040-0.050%, and the rest is iron.

2. The method for manufacturing a SA266Gr.4 forging for nuclear power according to claim 1, characterized in that: The following steps are involved: S1. Smelting: Prepare the raw materials by weight percentage, place the raw materials in an electric furnace, and smelt until the temperature reaches 1530-1580°C to obtain molten steel; S2 refining outside the furnace: The molten steel obtained in step S1 is placed in a LF furnace, refined for 55-75 minutes, vacuum degassed for 30-40 minutes, and then cast into an ingot; S3 forging: The steel ingot obtained in step S2 is forged into a forging by a hydraulic press; S4 heat treatment: The forging obtained in step S3 is subjected to preliminary heat treatment, followed by quenching, and finally tempering to obtain a SA266Gr.4 forging for nuclear power; S5. Testing: Perform physical and chemical testing and nondestructive testing on the SA266Gr.4 forgings for nuclear power obtained in step S4.

3. The method for manufacturing a SA266Gr.4 forging for nuclear power according to claim 2, characterized in that: In step S2, the whole refining process outside the furnace is protected by argon, the vacuum degree during vacuum degassing is 50-60Pa, and the temperature of the molten steel during pouring is 1380-1420°C.

4. The method for manufacturing a SA266Gr.4 forging for nuclear power according to claim 2, characterized in that: In the step S3, the cutting ratio of the ingot head is 8%, the cutting ratio of the ingot tail is 4%, the initial forging temperature is 1200-1240°C, the final forging temperature is 750-800°C, and the forging ratio is ≥4.

5.

5. The method for manufacturing a SA266Gr.4 forging for nuclear power according to claim 2, characterized in that: In step S4, the preliminary heat treatment is performed in an industrial resistance furnace, the heating temperature of the preliminary heat treatment is 900-920° C., and the insulation time is 1-2 hours.

6. The method for manufacturing a SA266Gr.4 forging for nuclear power according to claim 2, characterized in that: In the step S4, the quenching temperature is 910-930° C., the holding time is 2-3 hours, and the quenching medium is composed of the following components by weight percentage: 2-3% potassium hydroxide, 1-2% 2-methylthio-2-imidazoline hydroiodide, 6-9% tert-butyldimethylsilyl glycidyl ether, 4-5% N,N-dimethylformamide, and the rest is water.

7. The method for manufacturing a SA266Gr.4 forging for nuclear power according to claim 6, characterized in that: The preparation steps of the quenching medium are: Prepare each component according to weight percentage, add potassium hydroxide into water, stir until mixed evenly, then add other components, continue stirring for 2-3 hours to obtain quenching medium.

8. The method for manufacturing a SA266Gr.4 forging for nuclear power according to claim 7, characterized in that: In the step of preparing the quenching medium, the stirring speed is 200 rpm.

9. The method for manufacturing a SA266Gr.4 forging for nuclear power according to claim 2, characterized in that: In step S4, the tempering temperature is 580-610° C., and the tempering time is 2-3 hours.

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