A method for forging a large cylindrical nuclear power plant forging

Abstract

The present application relates to a kind of large cylinder nuclear power forging's forging processing method, it is related to nuclear power steel technical field, including: the upsetting-elongation operation of casting body is sequentially carried out, punching, reaming, elongation to blank size and solid solution heat treatment, obtain large cylinder nuclear power forging;Wherein, upsetting-elongation operation includes sequentially carried out upsetting and elongation, operation frequency ≥3 times, total forging ratio ≥6, initial forging temperature is 1180-1200 ℃, final forging temperature is ≥900 ℃;Solid solution heat treatment temperature is 1040-1060 ℃. The forging processing method provided in the present application, by adopting specific upsetting-elongation operation and solid solution heat treatment combination, the mechanical properties of obtained forging are improved, it is favorable to improve the use effect of forging as nuclear power workpiece, for 0Cr18Ni10Ti stainless steel, 20 ℃ When tensile strength ≥575MPa, yield strength ≥250MPa, elongation ≥50%.

Description

Technical Field

[0001] This invention relates to the field of steel technology for nuclear power, and specifically to a forging method for large cylindrical nuclear power forgings. Background Technology

[0002] Nuclear power plant pipelines are a crucial component of nuclear power plants, primarily responsible for transporting reactor cooling, steam, auxiliary system media, and other fluids and gases. Due to the unique operating conditions of nuclear power plants, the design, manufacture, installation, inspection, and maintenance of pipelines are subject to stringent technical requirements.

[0003] Currently, nuclear power pipelines are usually manufactured by forging. For example, CN102825207A discloses a forging process for stainless steel nuclear power main pipelines, using 316LN electroslag ingot blanks. During the forging process, surface cracks are cleaned in time and the forging ratio is ensured to be greater than 4. The components include eleven sections: hot section L001A, hot section L001B, cold section A, cold section B, cold section C, cold section D, and wave tube I, wave tube II, wave tube III, wave tube IV, and wave tube V. The forging process of the above components is grouped into hot section L001A, hot section L001B, cold section group, wave tube IIIV group, and wave tube IIIIV group.

[0004] CN102632182A discloses a process for integral hollow forging of a nuclear power plant main pipeline. The process steps are as follows: TP316LN stainless steel hollow electroslag castings are placed in a heating furnace for the first heating and holding. After the holding process, a second heating is performed. After the second heating, a third heating is performed. After the third heating, forging is carried out. The forging process includes repeated drawing, then shouldering and dividing, then drawing again to form a tube blank, and finally drawing and punching the nozzle. During the forging process, when the temperature of the forging drops to 880°C, it needs to be returned to the furnace for heating. The heating rate is close to the heating furnace power, and the temperature is held.

[0005] However, the forgings produced by current forging still have poor mechanical properties, which is not conducive to the efficient operation of nuclear power plants. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a forging method for large cylindrical nuclear power forgings, so as to solve the problem that the resulting forgings still have poor mechanical properties.

[0007] To achieve this objective, the present invention adopts the following technical solution: This invention provides a forging method for large cylindrical nuclear power plant forgings, the forging method comprising: The casting is subjected to upsetting-drawing operations, punching, reaming, drawing to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging; The upsetting-drawing operation includes upsetting and drawing performed sequentially; the upsetting-drawing operation is performed ≥3 times; the total forging ratio of the upsetting-drawing operation is ≥6; the initial forging temperature of the upsetting-drawing operation is 1180-1200℃; the final forging temperature of the upsetting-drawing operation is ≥900℃; and the solution heat treatment temperature is 1040-1060℃.

[0008] The forging method provided by this invention improves the mechanical properties of the forgings by combining specific upsetting-drawing operations with solution heat treatment, which is beneficial to improving the performance of the forgings as nuclear power components. For 0Cr18Ni10Ti stainless steel, the tensile strength is ≥575MPa, the yield strength is ≥250MPa, and the elongation is ≥50% at 20℃; the yield strength is ≥226MPa at 100℃.

[0009] As a preferred technical solution of the present invention, the material of the casting includes 0Cr18Ni10Ti stainless steel.

[0010] As a preferred technical solution of the present invention, the heating rate of the casting to the initial forging temperature is 40-60℃ / h.

[0011] As a preferred technical solution of the present invention, the forging ratio of upsetting in the upsetting-drawing operation is ≥1.7.

[0012] Preferably, the forging ratio of the upsetting-drawing operation is ≥1.7.

[0013] As a preferred technical solution of the present invention, when the upsetting-drawing operation is carried out in multiple drawing operations, the forging ratio of the first drawing is 1.7-3, the forging ratio of the intermediate drawing is 1.7-2, and the forging ratio of the last drawing is ≥1.7 under the premise of satisfying the total forging ratio.

[0014] As a preferred technical solution of the present invention, if the forging temperature is <900℃ during the forging process of the upsetting-drawing operation, the temperature is increased to the initial forging temperature at a heating rate of 40-60℃ / h.

[0015] As a preferred technical solution of the present invention, the punching operation temperature is 1140-1160℃.

[0016] As a preferred technical solution of the present invention, the working temperature for hole enlargement is 1070-1090℃.

[0017] As a preferred technical solution of the present invention, the operating temperature for drawing to the blank size is 1070-1090℃.

[0018] As a preferred embodiment of the present invention, the solution heat treatment time is 3.8-4.5 hours.

[0019] Compared with existing technical solutions, the present invention has the following beneficial effects: (1) By adopting the forging process of the present invention and controlling the forging ratio and process temperature, and combining the heat treatment cooling method, the grain size of the material can be improved, thereby ensuring the mechanical properties of the product. For 0Cr18Ni10Ti stainless steel, the tensile strength at 20℃ is ≥575MPa, the yield strength is ≥250MPa, and the elongation is ≥50%; the yield strength at 100℃ is ≥226MPa, the grain size is ≥5 grade, and the intergranular corrosion is: 180° bending occurs after 60min at 650℃±10℃, without cracks.

[0020] (2) The forging process provided by the present invention has a scientific and reasonable process and stable quality. At the same time, it can improve the first-pass inspection rate of products to 100%, avoid the energy waste caused by rework and repair, and shorten the production cycle and manufacturing cost. Attached Figure Description

[0021] Figure 1 This is a flowchart of a forging method for large cylindrical nuclear power forgings provided in an embodiment of the present invention; Figure 2 This is a sampling diagram of the performance testing and analysis of the forgings obtained in the embodiments of the present invention.

[0022] In the figure: T represents the wall thickness of the forging.

[0023] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0024] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows: This embodiment provides a forging method for large cylindrical nuclear power forgings, the process of which is as follows: Figure 1 As shown, the forging process includes: The casting is subjected to upsetting-drawing operations, punching, reaming, drawing to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging; In this invention, large cylindrical nuclear power forgings refer to hollow cylindrical forgings with dimensional parameters such as height or diameter ≥ diameter (cross-sectional) size > 450-900mm and weight ≥ 5t; wherein, the cylindrical shape refers to a hollow column that is open at one end and sealed at the other end.

[0025] In this invention, the material of the casting is preferably austenitic stainless steel, such as 0Cr18Ni10Ti stainless steel, and the exemplary composition by mass percentage is as follows: C≤0.08%, Si≤0.8%, Mn≤2.00%, S≤0.02%, P≤0.035%, 17.00%≤Cr≤19.00%, 9.00%≤Ni≤12.00%, 5C≤Ti≤0.8%, with the balance being Fe and unavoidable impurities.

[0026] In this invention, the casting refers to a product that can be forged and processed by steelmaking processes or other procedures known in the art, such as a casting obtained by casting or semi-continuous casting after smelting.

[0027] The upsetting-drawing operation includes upsetting and drawing performed sequentially.

[0028] The upsetting-drawing operation is performed ≥3 times, for example, 3, 4, 5, 6, 7 or 8 times, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0029] Wherein, the total forging ratio of the upsetting-drawing operation is ≥6, for example, it can be 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8 or 8, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0030] In this invention, the total forging ratio refers to the total forging ratio of multiple upsetting-drawing operations. For example, if the upsetting-drawing operation is performed 3 times, the total forging ratio is the total forging ratio of the 3 upsetting-drawing operations. If the upsetting-drawing operation is performed 4 times, the total forging ratio is the total forging ratio of the 4 upsetting-drawing operations, and so on.

[0031] In the upsetting-drawing operation, the forging ratio of the upsetting is ≥1.7, for example, it can be 1.7, 1.8, 1.9, 2, 2.2, 2.4, 2.6, 2.8 or 3, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0032] In the upsetting-drawing operation, the forging ratio of the drawing is ≥1.7, for example, it can be 1.7, 1.8, 1.9, 2, 2.2, 2.4, 2.6, 2.8 or 3, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0033] In this invention, during the upsetting-drawing process, the forging ratio for the first drawing is 1.7-3, the forging ratio for the intermediate drawing is 1.7-2, and the forging ratio for the last drawing is ≥1.7, provided that the total forging ratio is met.

[0034] The initial forging temperature for the upsetting-drawing operation is 1180-1200℃, for example, it can be 1180℃, 1182℃, 1184℃, 1186℃, 1188℃, 1190℃, 1192℃, 1194℃, 1196℃, 1198℃ or 1200℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0035] The heating rate of the casting to the initial forging temperature is 40-60℃ / h, for example, it can be 40℃ / h, 42℃ / h, 44℃ / h, 46℃ / h, 48℃ / h, 50℃ / h, 52℃ / h, 54℃ / h, 56℃ / h, 58℃ / h or 60℃ / h, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0036] The final forging temperature of the upsetting-drawing operation is ≥900℃, for example, it can be 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0037] In the forging process of the upsetting-drawing operation, if the forging temperature is <900℃, the temperature is increased to the initial forging temperature at a heating rate of 40-60℃ / h. For example, the heating rate can be 40℃ / h, 42℃ / h, 44℃ / h, 46℃ / h, 48℃ / h, 50℃ / h, 52℃ / h, 54℃ / h, 56℃ / h, 58℃ / h, or 60℃ / h, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0038] The operating temperature for punching is 1140-1160℃, for example, it can be 1140℃, 1142℃, 1144℃, 1146℃, 1148℃, 1150℃, 1152℃, 1154℃, 1156℃, 1158℃ or 1160℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0039] The operating temperature for hole enlargement is 1070-1090℃, for example, it can be 1070℃, 1072℃, 1074℃, 1076℃, 1078℃, 1080℃, 1082℃, 1084℃, 1086℃, 1088℃ or 1090℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0040] The operating temperature for drawing to the blank size is 1070-1090℃, for example, it can be 1070℃, 1072℃, 1074℃, 1076℃, 1078℃, 1080℃, 1082℃, 1084℃, 1086℃, 1088℃ or 1090℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0041] In this embodiment, the blank size drawn to the blank size refers to the blank size before rough machining.

[0042] The solution heat treatment temperature is 1040-1060℃, for example, it can be 1040℃, 1042℃, 1044℃, 1046℃, 1048℃, 1050℃, 1052℃, 1054℃, 1056℃, 1058℃ or 1060℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0043] The solution heat treatment time is 3.8-4.5h, for example, it can be 3.8h, 3.9h, 4h, 4.1h, 4.2h, 4.3h, 4.4h or 4.5h, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0044] In this invention, during solution heat treatment, water cooling can be selectively continued until the surface temperature of the billet measured 10 minutes after the billet leaves the quenching tank is below 60°C.

[0045] Furthermore, in order to ensure that the forgings obtained by the forging method of this invention possess good mechanical properties, the following practical examples are provided for illustrative purposes: Example 1 This embodiment provides a forging method for large cylindrical nuclear power forgings, as detailed below: The casting is subjected to upsetting-drawing operations, punching, reaming, drawing to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging; The casting is made of 0Cr18Ni10Ti stainless steel and is a hollow column with the following dimensions: outer diameter 740mm, inner diameter 520mm, and height 2980mm. The upsetting-drawing operation includes sequential upsetting and drawing; the upsetting-drawing operation is performed 3 times; the total forging ratio of the upsetting-drawing operation is 10.8; the forging ratios in the upsetting-drawing operation are sequentially: 1.7, 2, 1.7, 1.8, 1.7, 1.9; the initial forging temperature of the upsetting-drawing operation is 1190℃; the heating rate of the casting to the initial forging temperature is 50℃ / h; the final forging temperature of the upsetting-drawing operation is 900℃; if the forging temperature is <900℃ during the forging process of the upsetting-drawing operation, the temperature is increased to the initial forging temperature at a heating rate of 50℃ / h; the dimensions of the product obtained from the upsetting-drawing operation are: outer diameter 780mm, inner diameter 480mm, and height 3070mm. The punching operation temperature is 1150℃, and the dimensions of the punched product are: outer diameter 1020mm, inner diameter 380mm, and height 1300mm. The working temperature for the hole enlargement is 1080℃, and the dimensions of the product obtained by hole enlargement are: outer diameter 1070mm, inner diameter 500mm, and height 1300mm. The operating temperature for drawing to the blank size is 1080℃, and the resulting blank dimensions are: outer diameter 780mm, inner diameter 480mm, and height 3070mm. The solution heat treatment was performed at a temperature of 1050°C for 4 hours.

[0046] Example 2 This embodiment provides a forging method for large cylindrical nuclear power forgings, as detailed below: The casting is subjected to upsetting-drawing operations, punching, reaming, drawing to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging; The casting is made of 0Cr18Ni10Ti stainless steel and is a hollow column with the following dimensions: outer diameter 740mm, inner diameter 520mm, and height 2980mm. The upsetting-drawing operation includes sequential upsetting and drawing; the upsetting-drawing operation is performed 4 times; the total forging ratio of the upsetting-drawing operation is 14.9; the forging ratios in the upsetting-drawing operation are sequentially: 1.8, 2.5, 1.7, 1.7, 1.8, 1.8, 1.8, 1.8, 1.8; the initial forging temperature of the upsetting-drawing operation is 1195℃; the heating rate of the casting to the initial forging temperature is 55℃ / h; the final forging temperature of the upsetting-drawing operation is 950℃; if the forging temperature is <900℃ during the forging process of the upsetting-drawing operation, the temperature is increased to the initial forging temperature at a heating rate of 55℃ / h; the dimensions of the product obtained from the upsetting-drawing operation are: outer diameter 780mm, inner diameter 480mm, and height 3070mm. The punching operation temperature is 1145℃, and the dimensions of the punched product are: outer diameter 1020mm, inner diameter 380mm, and height 1300mm. The working temperature for the hole enlargement is 1085℃, and the dimensions of the product obtained by hole enlargement are: outer diameter 1070mm, inner diameter 500mm, and height 1300mm. The operating temperature for drawing to the blank size is 1085℃, and the resulting blank dimensions are: outer diameter 780mm, inner diameter 480mm, and height 3070mm. The solution heat treatment was performed at a temperature of 1055°C for 4.2 hours.

[0047] Example 3 This embodiment provides a forging method for large cylindrical nuclear power forgings, as detailed below: The casting is subjected to upsetting-drawing operations, punching, reaming, drawing to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging; The casting is made of 0Cr18Ni10Ti stainless steel and is a hollow column with the following dimensions: outer diameter 740mm, inner diameter 520mm, and height 2980mm. The upsetting-drawing operation includes sequential upsetting and drawing; the upsetting-drawing operation is performed 5 times; the total forging ratio of the upsetting-drawing operation is 26; the forging ratios in the upsetting-drawing operation are sequentially: 2, 3, 3, 2, 3, 2, 3, 2, 3, 3; the initial forging temperature of the upsetting-drawing operation is 1180℃; the heating rate of the casting to the initial forging temperature is 40℃ / h; the final forging temperature of the upsetting-drawing operation is 900℃; if the forging temperature is <900℃ during the forging process of the upsetting-drawing operation, the temperature is increased to the initial forging temperature at a heating rate of 40℃ / h; the dimensions of the product obtained from the upsetting-drawing operation are: outer diameter 780mm, inner diameter 480mm, and height 3070mm. The punching operation temperature is 1140℃, and the dimensions of the punched product are: outer diameter 1020mm, inner diameter 380mm, and height 1300mm. The working temperature for the hole enlargement is 1090℃, and the dimensions of the product obtained by hole enlargement are: outer diameter 1070mm, inner diameter 500mm, and height 1300mm. The operating temperature for drawing to the blank size is 1090℃, and the resulting blank dimensions are: outer diameter 780mm, inner diameter 480mm, and height 3070mm. The solution heat treatment was performed at a temperature of 1040°C for 4.5 hours.

[0048] Example 4 This embodiment provides a forging method for large cylindrical nuclear power forgings, as detailed below: The casting is subjected to upsetting-drawing operations, punching, reaming, drawing to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging; The casting is made of 0Cr18Ni10Ti stainless steel and is a hollow column with the following dimensions: outer diameter 740mm, inner diameter 520mm, and height 2980mm. The upsetting-drawing operation includes sequential upsetting and drawing; the upsetting-drawing operation is performed 4 times; the total forging ratio of the upsetting-drawing operation is 16; the forging ratios in the upsetting-drawing operation are sequentially: 2.5, 1.8, 2, 1.9, 2, 1.9, 2, 1.9; the initial forging temperature of the upsetting-drawing operation is 1200℃; the heating rate of the casting to the initial forging temperature is 60℃ / h; the final forging temperature of the upsetting-drawing operation is 1000℃; if the forging temperature is <900℃ during the forging process of the upsetting-drawing operation, the temperature is increased to the initial forging temperature at a heating rate of 60℃ / h; the dimensions of the product obtained from the upsetting-drawing operation are: outer diameter 780mm, inner diameter 480mm, and height 3070mm. The punching operation temperature is 1160℃, and the dimensions of the punched product are: outer diameter 1020mm, inner diameter 380mm, and height 1300mm. The working temperature for the hole enlargement is 1070℃, and the dimensions of the product obtained by hole enlargement are: outer diameter 1070mm, inner diameter 500mm, and height 1300mm. The operating temperature for drawing to the blank size is 1070℃, and the dimensions of the resulting blank are: outer diameter 780mm, inner diameter 480mm, and height 3070mm. The solution heat treatment was performed at a temperature of 1060°C for 3.8 hours.

[0049] The forgings obtained in the above examples were subjected to mechanical property testing according to GOST 5632, intergranular corrosion testing according to GOST 6032-2017, and grain size testing according to GOST 5639-82. The sampling of the forgings was conducted in accordance with... Figure 2 The wall thickness T of the specific forging is determined according to the example, and the specific test results are shown in Table 1 below.

[0050] Table 1 As shown in Table 1, the solution provided by this invention improves the mechanical properties of the forgings by combining specific upsetting-drawing operations with solution heat treatment, which is beneficial to improving the performance of the forgings as nuclear power components. For 0Cr18Ni10Ti stainless steel, the tensile strength is ≥575MPa, the yield strength is ≥250MPa, and the elongation is ≥50% at 20℃; the yield strength is ≥226MPa at 100℃.

[0051] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0052] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0053] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A forging method for a large cylindrical nuclear power forging, characterized in that, The forging process includes: The casting is subjected to upsetting-drawing operations, punching, reaming, drawing to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging; The upsetting-drawing operation includes sequential upsetting and drawing; the upsetting-drawing operation is performed ≥3 times; the total forging ratio of the upsetting-drawing operation is ≥6; the initial forging temperature of the upsetting-drawing operation is 1180-1200℃; the final forging temperature of the upsetting-drawing operation is ≥900℃; and the solution heat treatment temperature is 1040-1060℃. The material of the casting is 0Cr18Ni10Ti stainless steel; The operating temperature for drawing to the blank size is 1070-1090℃; The large cylindrical nuclear power forging refers to a hollow cylindrical forging; the cylindrical shape refers to a hollow column that is open at one end and sealed at the other end; the punching operation temperature is 1140-1160℃; the reaming operation temperature is 1070-1090℃. The grain size of the large cylindrical nuclear power forging is ≥5.

2. The forging method as described in claim 1, characterized in that, The heating rate of the casting to the initial forging temperature is 40-60℃ / h.

3. The forging method as described in claim 1, characterized in that, In the upsetting-drawing operation, the forging ratio of upsetting is ≥1.

7.

4. The forging method as described in claim 1, characterized in that, In the upsetting-drawing operation, the forging ratio of the drawing process is ≥1.

7.

5. The forging method as described in claim 4, characterized in that, When the upsetting-drawing operation involves multiple drawing operations, the forging ratio for the first drawing is 1.7-3, the forging ratio for the intermediate drawing is 1.7-2, and the forging ratio for the last drawing is ≥1.7, provided that the total forging ratio is met.

6. The forging method as described in claim 1, characterized in that, If the forging temperature is <900℃ during the upsetting-drawing forging process, the temperature is increased to the initial forging temperature at a heating rate of 40-60℃ / h.

7. The forging method as described in claim 1, characterized in that, The solution heat treatment time is 3.8-4.5 hours.

Images