P280GH carbon steel forge piece for nuclear island throttle valve and manufacturing method of P280GH carbon steel forge piece

Abstract

The invention provides a P280GH carbon steel forge piece for a nuclear island throttle valve, which is prepared from the following components in percentage by weight: 0.16 to 0.20 percent of C, 0.30 to 0.40 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, 0.25 to 0.30 percent of Cr, 0.05 to 0.08 percent of Mo, 0.1 to 0.3 percent of Ni, 0.1 to 0.3 percent of Cu, less than or equal to 0.010 percent of Nb, less than or equal to 0.010 percent of V, 0.002 to 0.004 percent of Ca and the balance of iron. The invention further provides a manufacturing method of the P280GH carbon steel forge piece for the nuclear island throttling valve. The P280GH carbon steel forge piece for the nuclear island throttle valve, provided by the invention, has fewer hairlines and better mechanical properties.

Description

Technical Field

[0001] The invention belongs to the field of alloy forging, and in particular relates to a P280GH carbon steel forging for a nuclear island throttle valve and a manufacturing method thereof. Background Art

[0002] In the supply process of nuclear power forgings, more and more technical conditions require the detection of the number of hairline defects in forgings. Hairline is a fine linear defect in metal, usually formed by plastic inclusions extending along the metal flow direction during forging or rolling. Hairline has obvious directionality, which makes the metal material properties anisotropic, and also affects the continuity of the metal matrix to a certain extent, and has an adverse effect on the mechanical properties of the metal material.

[0003] P280GH is a carbon steel grade with specified high temperature characteristics, with good impact toughness and welding performance. Its uses are similar to 16Mn, such as carbon steel tube sheets and flanges for shell and tube heat exchangers. P280GH is mainly used in the field of nuclear power, mainly as rolled or forged pipe fittings for the main steam system, feedwater flow control system, and auxiliary feedwater system of steam generators, or forged or die-forged elbows for the main steam system of steam generators. The existing P280GH carbon steel forgings also have certain cracking problems. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a P280GH carbon steel forging for a nuclear island throttle valve, which has fewer hairline cracks and better mechanical properties.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] A P280GH carbon steel forging for a nuclear island throttle valve consists of the following components by weight: C 0.16-0.20%, Si 0.30-0.40%, Mn 1.20-1.35%, P≤0.015%, S≤0.010%, Cr0.25-0.30%, Mo 0.05-0.08%, Ni 0.1-0.3%, Cu 0.1-0.3%, Nb≤0.010%, V≤0.010%, Ca0.002-0.004%, and the remainder is iron.

[0007] Another technical problem to be solved by the present invention is to provide a method for manufacturing the P280GH carbon steel forging for the nuclear island throttle valve.

[0008] To solve the above technical problems, the technical solution is:

[0009] A method for manufacturing a P280GH carbon steel forging for a nuclear island throttle valve comprises the following steps:

[0010] S1. Electric furnace smelting: prepare raw materials, place the raw materials in an electric furnace, and smelt until the temperature reaches 1580-1620°C to obtain molten steel;

[0011] S2 refining outside the furnace: the molten steel obtained in step S1 is placed in a LF furnace, refined to a temperature of 1550-1600 ℃, vacuum degassing treatment for 15-25min, and then cast into an ingot;

[0012] S3 forging: The steel ingot obtained in step S2 is subjected to upsetting and drawing by a press to obtain a forging;

[0013] S4 heat treatment: The forging obtained in step S3 is normalized and then tempered to obtain a P280GH carbon steel forging for a nuclear island throttle valve;

[0014] S5. Testing: Perform physical and chemical testing and nondestructive testing on the P280GH carbon steel forgings for the nuclear island throttle valve obtained in step S4.

[0015] Furthermore, in step S3 of the present invention, the upsetting ratio is 2.2-2.5, the drawing ratio is 1.2-1.5, and the total forging ratio is ≥3.5.

[0016] Furthermore, in step S3 of the present invention, the initial forging temperature is 1205-1235°C, and the final forging temperature is 750-850°C.

[0017] Furthermore, in step S3 of the present invention, the removal ratio of the riser end of the steel ingot is 20%, and the removal ratio of the nozzle end of the steel ingot is 5%.

[0018] Furthermore, in step S4 of the present invention, the heat treatment is carried out in an industrial resistance furnace.

[0019] Furthermore, in step S4 of the present invention, the normalizing temperature is 880-920° C., and the normalizing cooling method is water cooling.

[0020] Furthermore, in step S4 of the present invention, the tempering temperature is 600-640° C., and the tempering cooling method is air cooling.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The present invention reduces the content of elements such as C, Mn, P, S, etc., which are easy to generate plastic inclusions in the raw materials, thereby reducing the generation of hairline.

[0023] 2) The riser and nozzle of the steel ingot contain a large number of inclusions and defects. In this regard, the present invention increases the removal ratio of the riser end and the nozzle end, which is beneficial to reducing the generation of hairline.

[0024] 3) Hairline is caused by the extension of plastic inclusions along the forging streamline during forging. Therefore, the present invention reduces the drawing ratio during forging and adopts a combined upsetting and drawing process for forging, which can effectively prevent the plastic inclusions from being excessively extended and elongated during the forging process and reduce the generation of hairline.

[0025] 4) The present invention also adds a small amount of Ca to the raw materials, which is also beneficial to reducing the generation of hair lines. DETAILED DESCRIPTION

[0026] 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.

[0027] Example 1

[0028] P280GH carbon steel forgings for nuclear island throttle valves are composed of the following components in weight percentage: C 0.18%, Si 0.35%, Mn 1.20%, P 0.013%, S 0.010%, Cr 0.30%, Mo 0.06%, Ni 0.2%, Cu 0.3%, Nb 0.009%, V 0.008%, Ca 0.003%, and the rest is iron.

[0029] The manufacturing method of embodiment 1 comprises the following steps:

[0030] S1. Electric furnace smelting: prepare raw materials, place the raw materials in an electric furnace, and smelt until the temperature reaches 1600°C to obtain molten steel;

[0031] S2 refining outside the furnace: the molten steel obtained in step S1 is placed in a LF furnace, refined to a temperature of 1580 ℃, vacuum degassing treatment for 20min, and then cast into an ingot;

[0032] S3. Forging: The steel ingot obtained in step S2 is subjected to upsetting and drawing by a press to obtain a forging, the upsetting ratio is 2.4, the drawing ratio is 1.4, the total forging ratio is 3.8, the initial forging temperature is 1220°C, the final forging temperature is 800°C, the removal ratio of the riser end of the steel ingot is 20%, and the removal ratio of the nozzle end of the steel ingot is 5%;

[0033] S4. Heat treatment: The forging obtained in step S3 was normalized in an industrial resistance furnace and then tempered to obtain a P280GH carbon steel forging for a nuclear island throttle valve, the normalizing temperature was 900 ° C, the normalizing cooling method was water cooling, the tempering temperature was 620 ° C, and the tempering cooling method was air cooling;

[0034] S5. Testing: Perform physical and chemical testing and nondestructive testing on the P280GH carbon steel forgings for the nuclear island throttle valve obtained in step S4.

[0035] Example 2

[0036] P280GH carbon steel forgings for nuclear island throttle valves are composed of the following components in weight percentage: C 0.16%, Si 0.40%, Mn 1.35%, P 0.015%, S 0.009%, Cr 0.28%, Mo 0.08%, Ni 0.2%, Cu 0.1%, Nb 0.010%, V 0.009%, Ca 0.002%, and the rest is iron.

[0037] The manufacturing method of embodiment 2 comprises the following steps:

[0038] S1. Electric furnace smelting: prepare raw materials, place the raw materials in an electric furnace, and smelt until the temperature reaches 1580°C to obtain molten steel;

[0039] S2 refining outside the furnace: the molten steel obtained in step S1 is placed in a LF furnace, refined to a temperature of 1550 ℃, vacuum degassing treatment for 25min, and then cast into an ingot;

[0040] S3. Forging: The steel ingot obtained in step S2 is subjected to upsetting and drawing by a press to obtain a forging, the upsetting ratio is 2.2, the drawing ratio is 1.3, the total forging ratio is 3.5, the initial forging temperature is 1205°C, the final forging temperature is 750°C, the removal ratio of the riser end of the steel ingot is 20%, and the removal ratio of the nozzle end of the steel ingot is 5%;

[0041] S4. Heat treatment: The forging obtained in step S3 was normalized in an industrial resistance furnace and then tempered to obtain a P280GH carbon steel forging for a nuclear island throttle valve, the normalizing temperature was 880 ° C, the normalizing cooling method was water cooling, the tempering temperature was 600 ° C, and the tempering cooling method was air cooling;

[0042] S5. Testing: Perform physical and chemical testing and nondestructive testing on the P280GH carbon steel forgings for the nuclear island throttle valve obtained in step S4.

[0043] Example 3

[0044] P280GH carbon steel forgings for nuclear island throttle valves are composed of the following components by weight: C 0.19%, Si 0.30%, Mn 1.25%, P 0.014%, S 0.008%, Cr 0.25%, Mo 0.07%, Ni 0.1%, Cu 0.3%, Nb 0.010%, V 0.009%, Ca 0.004%, and the rest is iron.

[0045] The manufacturing method of embodiment 3 comprises the following steps:

[0046] S1. Electric furnace smelting: prepare raw materials, place the raw materials in an electric furnace, and smelt until the temperature reaches 1610°C to obtain molten steel;

[0047] S2 refining outside the furnace: the molten steel obtained in step S1 is placed in a LF furnace, refined to a temperature of 1590 ℃, vacuum degassing treatment for 24min, and then cast into an ingot;

[0048] S3. Forging: The steel ingot obtained in step S2 is subjected to upsetting and drawing by a press to obtain a forging, the upsetting ratio is 2.5, the drawing ratio is 1.2, the total forging ratio is 3.7, the initial forging temperature is 1230°C, the final forging temperature is 810°C, the removal ratio of the riser end of the steel ingot is 20%, and the removal ratio of the nozzle end of the steel ingot is 5%;

[0049] S4. Heat treatment: The forging obtained in step S3 was normalized in an industrial resistance furnace and then tempered to obtain a P280GH carbon steel forging for a nuclear island throttle valve, the normalizing temperature was 910 ° C, the normalizing cooling method was water cooling, the tempering temperature was 630 ° C, and the tempering cooling method was air cooling;

[0050] S5. Testing: Perform physical and chemical testing and nondestructive testing on the P280GH carbon steel forgings for the nuclear island throttle valve obtained in step S4.

[0051] Example 4

[0052] P280GH carbon steel forgings for nuclear island throttle valves are composed of the following components in weight percentage: C 0.20%, Si 0.32%, Mn 1.28%, P 0.015%, S 0.009%, Cr 0.27%, Mo 0.05%, Ni 0.3%, Cu 0.2%, Nb 0.008%, V 0.010%, Ca 0.003%, and the rest is iron.

[0053] The manufacturing method of embodiment 4 comprises the following steps:

[0054] S1. Electric furnace smelting: prepare raw materials, place the raw materials in an electric furnace, and smelt until the temperature reaches 1620°C to obtain molten steel;

[0055] S2 refining outside the furnace: the molten steel obtained in step S1 is placed in a LF furnace, refined to a temperature of 1600 ℃, vacuum degassing treatment for 15min, and then cast into an ingot;

[0056] S3. Forging: The steel ingot obtained in step S2 is subjected to upsetting and drawing by a press to obtain a forging, the upsetting ratio is 2.3, the drawing ratio is 1.5, the total forging ratio is 3.8, the initial forging temperature is 1235°C, the final forging temperature is 850°C, the removal ratio of the riser end of the steel ingot is 20%, and the removal ratio of the nozzle end of the steel ingot is 5%;

[0057] S4. Heat treatment: The forging obtained in step S3 was normalized in an industrial resistance furnace and then tempered to obtain a P280GH carbon steel forging for a nuclear island throttle valve, the normalizing temperature was 920 ° C, the normalizing cooling method was water cooling, the tempering temperature was 640 ° C, and the tempering cooling method was air cooling;

[0058] S5. Testing: Perform physical and chemical testing and nondestructive testing on the P280GH carbon steel forgings for the nuclear island throttle valve obtained in step S4.

[0059] Comparative Example 1

[0060] The composition of the forging is: C 0.21%, Si 0.35%, Mn 1.36%, P 0.016%, S 0.011%, Cr 0.30%, Mo 0.06%, Ni 0.2%, Cu 0.3%, Nb 0.009%, V 0.008%, Ca 0.003%, and the rest is iron; the manufacturing method is the same as that of Example 1. The difference from Example 1 is that the contents of C, Mn, P and S elements in Comparative Example 1 are all higher than the range defined by the present invention.

[0061] Comparative Example 2

[0062] The difference from Example 1 is that the removal ratio of the riser end of the steel ingot is 19%, and the removal ratio of the nozzle end is 4%.

[0063] Comparative Example 3

[0064] The composition of the forging is: C 0.21%, Si 0.35%, Mn 1.36%, P 0.016%, S 0.011%, Cr 0.30%, Mo 0.06%, Ni 0.2%, Cu 0.3%, Nb 0.009%, V 0.008%, and the rest is iron; the manufacturing method is the same as that of Example 1. The difference from Example 1 is that the composition of Comparative Example 3 does not contain Ca.

[0065] Experimental Example 1: Hairline Test

[0066] The forgings prepared in Example 1 and Comparative Examples 1-3 were subjected to the graining test according to GB / T 15711-2018 “Tower-shaped graining acid leaching method for testing non-metallic inclusions in steel”, and the test results are shown in Table 1.

[0067] Number of hair lines Total length of hairline (mm) Example 1 0 0 Comparative Example 1 4 23 Comparative Example 2 3 18 Comparative Example 3 3 15

[0068] Table 1

[0069] As can be seen from Table 1, the number of hairline lines and the total length of hairline lines in Example 1 are both 0, indicating that the P280GH carbon steel forging for nuclear island throttle valves prepared by the present invention has fewer hairline lines. Compared with Example 1, the number of hairline lines and the total length of hairline lines in Comparative Examples 1-3 are increased, indicating that the three measures of reducing the content of C, Mn, P, and S, increasing the removal ratio of the riser end and the nozzle end of the steel ingot, and adding the Ca element can effectively remove inclusions and reduce hairline lines.

[0070] Experimental Example 2: Mechanical Properties Test

[0071] The P280GH carbon steel forgings for the nuclear island throttle valves prepared in Examples 1-4 (the thickness of each forging is 35 mm) were respectively subjected to mechanical property tests, wherein the room temperature tensile property test was carried out in accordance with ENISO6892-1:2016 (1 specimen), and the KV impact property test was carried out in accordance with ENISO148-1:2016 (3 specimens, taking the average value), and the test results are shown in Table 2.

[0072]

[0073] Table 2

[0074] It can be seen from Table 2 that the room temperature tensile upper yield strength, room temperature tensile tensile strength, and 0°C longitudinal impact absorption energy of Examples 1-4 can all meet the standard requirements, indicating that the P280GH carbon steel forgings for nuclear island throttle valves prepared in the present invention have good mechanical properties.

[0075] 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 P280GH carbon steel forging for a nuclear island throttle valve, characterized in that: Calculated by weight percentage, it is composed of the following components: C 0.16-0.20%, Si 0.30-0.40%, Mn 1.20-1.35%, P≤0.015%, S≤0.010%, Cr 0.25-0.30%, Mo 0.05-0.08%, Ni 0.1-0.3%, Cu 0.1-0.3%, Nb≤0.010%, V≤0.010%, Ca0.002-0.004%, and the rest is iron.

2. The method for manufacturing a P280GH carbon steel forging for a nuclear island throttle valve according to claim 1, characterized in that: The following steps are involved: S1. Electric furnace smelting: prepare raw materials, place the raw materials in an electric furnace, and smelt until the temperature reaches 1580-1620°C to obtain molten steel; S2 refining outside the furnace: the molten steel obtained in step S1 is placed in a LF furnace, refined to a temperature of 1550-1600 ℃, vacuum degassing treatment for 15-25min, and then cast into an ingot; S3 forging: The steel ingot obtained in step S2 is subjected to upsetting and drawing by a press to obtain a forging; S4 heat treatment: The forging obtained in step S3 is normalized and then tempered to obtain a P280GH carbon steel forging for a nuclear island throttle valve; S5. Testing: Perform physical and chemical testing and nondestructive testing on the P280GH carbon steel forgings for the nuclear island throttle valve obtained in step S4.

3. The method for manufacturing a P280GH carbon steel forging for a nuclear island throttle valve according to claim 2, characterized in that: In the step S3, the upsetting ratio is 2.2-2.5, the drawing ratio is 1.2-1.5, and the total forging ratio is ≥3.

5.

4. The method for manufacturing a P280GH carbon steel forging for a nuclear island throttle valve according to claim 2, characterized in that: In step S3, the initial forging temperature is 1205-1235°C, and the final forging temperature is 750-850°C.

5. The method for manufacturing a P280GH carbon steel forging for a nuclear island throttle valve according to claim 2, characterized in that: In the step S3, the removal ratio of the riser end of the steel ingot is 20%, and the removal ratio of the nozzle end of the steel ingot is 5%.

6. The method for manufacturing a P280GH carbon steel forging for a nuclear island throttle valve according to claim 2, characterized in that: In step S4, the heat treatment is performed in an industrial resistance furnace.

7. The method for manufacturing a P280GH carbon steel forging for a nuclear island throttle valve according to claim 2, characterized in that: In step S4, the normalizing temperature is 880-920° C., and the normalizing cooling method is water cooling.

8. The method for manufacturing a P280GH carbon steel forging for a nuclear island throttle valve according to claim 2, characterized in that: In step S4, the tempering temperature is 600-640° C., and the tempering cooling method is air cooling.

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