Forging machining method for large cylindrical nuclear power forge piece

Abstract

The invention relates to a forging processing method of a large cylindrical nuclear power forge piece, which relates to the technical field of nuclear power steel, and comprises the following steps: sequentially carrying out upsetting-drawing operation, punching, chambering, drawing to a blank size and solid solution heat treatment on a casting body to obtain the large cylindrical nuclear power forge piece; wherein the upsetting-drawing operation comprises upsetting and drawing which are sequentially carried out, the number of operation times is larger than or equal to 3, the total forging ratio is larger than or equal to 6, the initial forging temperature is 1180-1200 DEG C, and the final forging temperature is larger than or equal to 900 DEG C; and the temperature of the solid solution heat treatment is 1040-1060 DEG C. According to the forging machining method, specific upsetting-drawing operation and solid solution heat treatment are combined, the mechanical property of the obtained forge piece is improved, the use effect of the forge piece serving as a nuclear power workpiece can be improved, and for 0Cr18Ni10Ti stainless steel, the tensile strength is larger than or equal to 575 MPa at the temperature of 20 DEG C, the yield strength is larger than or equal to 250 MPa, and the ductility is larger than or equal to 50% at the temperature of 20 DEG C.

Description

Technical Field

[0001] The invention relates to the technical field of steel materials for nuclear power, and in particular to a forging method for large cylindrical forgings for nuclear power. Background Art

[0002] Nuclear power pipelines are a vital component of nuclear power plants, mainly responsible for transmitting reactor cooling, steam, auxiliary system media and other fluids and gases. Due to the particularity of nuclear power plant operating conditions, there are strict technical requirements for the design, manufacture, installation, inspection and maintenance of pipelines.

[0003] At present, nuclear power pipelines are usually prepared by forging. For example, CN102825207A discloses a forging process for a stainless steel nuclear power main pipeline, which uses 316LN electroslag ingot billet, performs heat cleaning on the surface cracks in time during the forging process, and ensures that the forging ratio is greater than 4. Its components include eleven sections, namely, hot section L001A, hot section L001B, cold section A, cold section B, cold section C, cold section D, surge tube I, surge tube II, surge tube III, surge tube IV, and surge tube V. The forging processes of the above components are grouped into hot section L001A, hot section L001B, cold section group, surge tube IIIV group, and surge tube IIIIV group.

[0004] CN102632182A discloses a hollow forging process for a nuclear power main pipeline, and the process steps are as follows: placing a TP316LN stainless steel hollow electroslag casting into a heating furnace for the first heating and heat preservation, performing a second heating after the heat preservation process, performing a third heating after the second heating, and performing a forging process after the third heating, wherein the forging process includes repeated drawing, shoulder pressing and division, and then drawing and forming 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, and the heating speed is close to the heating furnace power for heating and heat preservation.

[0005] However, the forgings currently obtained by forging still have the problem of 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 to solve the problem that the obtained forgings still have poor mechanical properties.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a forging method for a large cylindrical nuclear power forging, the forging method comprising:

[0009] The casting is subjected to upsetting-stretching operation, punching, hole expansion, stretching to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging;

[0010] Wherein, the roughing-drawing operation includes roughing and drawing performed sequentially; the number of operations of the roughing-drawing operation is ≥3 times; the total forging ratio of the roughing-drawing operation is ≥6; the initial forging temperature of the roughing-drawing operation is 1180-1200°C; the final forging temperature of the roughing-drawing operation is ≥900°C; the temperature of the solution heat treatment is 1040-1060°C.

[0011] The forging method provided by the present invention improves the mechanical properties of the obtained forgings by combining specific upsetting-drawing operations with solution heat treatment, which is beneficial to improving the use effect of the forgings as nuclear power workpieces. For 0Cr18Ni10Ti stainless steel, the tensile strength is ≥575MPa, the yield strength is ≥250MPa, and the elongation is ≥50% at 20°C; the yield strength is ≥226MPa at 100°C.

[0012] As a preferred technical solution of the present invention, the material of the casting includes 0Cr18Ni10Ti stainless steel.

[0013] As a preferred technical solution of the present invention, the heating rate for heating the casting to the initial forging temperature is 40-60°C / h.

[0014] As a preferred technical solution of the present invention, the forging ratio of upsetting in the upsetting-stretching operation is ≥1.7.

[0015] Preferably, the forging ratio of the drawing in the upsetting-drawing operation is ≥1.7.

[0016] As a preferred technical solution of the present invention, when the upsetting-drawing operation is performed multiple times, 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 on the premise of meeting the total forging ratio.

[0017] As a preferred technical solution of the present invention, if the forging temperature during the forging process of the upsetting-stretching operation is less than 900°C, the temperature is increased to the initial forging temperature at a heating rate of 40-60°C / h.

[0018] As a preferred technical solution of the present invention, the punching operating temperature is 1140-1160°C.

[0019] As a preferred technical solution of the present invention, the operating temperature of the hole expansion is 1070-1090°C.

[0020] As a preferred technical solution of the present invention, the working temperature for drawing to the blank size is 1070-1090°C.

[0021] As a preferred technical solution of the present invention, the time of the solution heat treatment is 3.8-4.5h.

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

[0023] (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°C is ≥575MPa, the yield strength is ≥250MPa, and the elongation is ≥50%; the yield strength at 100°C is ≥226MPa, the grain size is ≥5 levels, and intergranular corrosion: 180° bending occurs after 60 minutes at 650°C±10°C, and there is no crack.

[0024] (2) The forging method provided by the present invention has a scientific and reasonable process method and stable quality. At the same time, it can increase the one-time inspection rate of products to 100%, avoid the energy waste caused by rework and repair, and shorten the production cycle and manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a forging method for a large cylindrical nuclear power forging provided by an embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of sampling for performance testing and analysis of the forgings obtained in the embodiment of the present invention.

[0027] In the figure: T is the wall thickness of the forging.

[0028] The present invention is further described in detail below. However, the following examples are only 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 shall be subject to the claims. DETAILED DESCRIPTION

[0029] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0030] This embodiment provides a forging method for a large cylindrical nuclear power forging, the process is as follows: Figure 1 As shown, the forging method comprises:

[0031] The casting is subjected to upsetting-stretching operation, punching, hole expansion, stretching to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging;

[0032] In the present invention, large cylindrical forgings for nuclear power 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 cylinder with one end open and the other end sealed.

[0033] In the present invention, the material of the casting is preferably austenitic stainless steel, such as 0Cr18Ni10Ti stainless steel, and the mass percentage composition is exemplarily as follows:

[0034] 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%, and the balance is Fe and unavoidable impurities.

[0035] In the present invention, the casting refers to a product that can be used for forging obtained through a steelmaking process or other processes known in the art, such as a casting obtained by casting or semi-continuous casting after smelting.

[0036] The upsetting-lengthening operation includes upsetting and lengthening performed sequentially.

[0037] The number of operations of the upsetting and lengthening operation is ≥ 3 times, for example, it can be 3 times, 4 times, 5 times, 6 times, 7 times or 8 times, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0038] Among them, the total forging ratio of the upsetting-lengthening 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, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0039] In the present invention, the total forging ratio refers to the total forging ratio of upsetting-lengthening operations performed multiple times. For example, when the upsetting-lengthening operation is performed three times, the total forging ratio is the total forging ratio of the three upsetting-lengthening operations. When the upsetting-lengthening operation is performed four times, the total forging ratio is the total forging ratio of the four upsetting-lengthening operations, and so on.

[0040] Among them, the forging ratio of upsetting in the upsetting-stretching operation 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, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0041] Among them, the forging ratio of the drawing in the upsetting-drawing operation 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, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0042] In the present invention, in the multiple stretching processes during the roughing-stretching operation, the forging ratio of the first stretching is 1.7-3, the forging ratio of the middle stretching is 1.7-2, and the forging ratio of the last stretching is ≥1.7 as long as the total forging ratio is met.

[0043] Among them, the initial forging temperature of the roughening and 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, and other unlisted values ​​within the range also meet the requirements.

[0044] Among them, the heating rate of heating 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, and other values ​​not listed in this range also meet the requirements.

[0045] Among them, the final forging temperature of the upsetting-stretching operation is ≥900°C, for example, it can be 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C or 1000°C, but is not limited to the listed values, and other values ​​not listed in this range also meet the requirements.

[0046] Wherein, if the forging temperature during the forging process of the upsetting-stretching operation is less than 900°C, the temperature is increased to the initial forging temperature at a heating rate of 40-60°C / h, for example, it can be 40°C / h, 42°C / h, 44°C / h, 46°C / h, 48°C / h, 50°C / h, 52°C / h, 54°C / h, 56°C / h, 58°C / h or 60°C / h, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0047] Among them, the operating temperature of the 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, and other unlisted values ​​within the range also meet the requirements.

[0048] Among them, the operating temperature of the hole expansion 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, and other unlisted values ​​within the range also meet the requirements.

[0049] Among them, 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, and other unlisted values ​​within the range also meet the requirements.

[0050] In this embodiment, the blank size in the process of drawing to blank size refers to the blank size before rough machining.

[0051] Among them, the temperature of the solution heat treatment 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, and other unlisted values ​​within the range also meet the requirements.

[0052] Among them, the time of the solution heat treatment 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, and other unlisted values ​​within the range also meet the requirements.

[0053] In the present invention, when the solution heat treatment is carried out, water cooling can be optionally continued until the surface temperature of the billet measured 10 minutes after the billet leaves the quenching tank is lower than 60°C.

[0054] Furthermore, in order to provide a forging having good mechanical properties, the forging obtained by the forging method provided by the present invention is exemplified by the following actual examples, as follows:

[0055] Example 1

[0056] This embodiment provides a forging method for a large cylindrical nuclear power forging, which is as follows:

[0057] The casting is subjected to upsetting-stretching operation, punching, hole expansion, stretching to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging;

[0058] The casting is made of 0Cr18Ni10Ti stainless steel, and is a hollow cylinder with dimensions of 740 mm in outer diameter, 520 mm in inner diameter, and 2980 mm in height;

[0059] The upsetting-stretching operation includes upsetting and stretching performed sequentially; the upsetting-stretching operation is performed three times; the total forging ratio of the upsetting-stretching operation is 10.8; the forging ratios in the upsetting-stretching operation are: 1.7, 2, 1.7, 1.8, 1.7, 1.9; the initial forging temperature of the upsetting-stretching operation is 1190°C; the heating rate of heating the casting to the initial forging temperature is 50°C / h; the final forging temperature of the upsetting-stretching operation is 900°C; if the forging temperature is less than 900°C during the forging process of the upsetting-stretching operation, the temperature is increased to the initial forging temperature at a heating rate of 50°C / h; the size of the product obtained by the upsetting-stretching operation is: the outer diameter is 780mm, the inner diameter is 480mm, and the height is 3070mm;

[0060] The punching operation temperature is 1150°C, and the dimensions of the punched product are: outer diameter 1020mm, inner diameter 380mm, height 1300mm;

[0061] The operating temperature of the hole expansion is 1080°C, and the dimensions of the product obtained by hole expansion are: outer diameter is 1070mm, inner diameter is 500mm, and height is 1300mm;

[0062] The working temperature of the drawing to the blank size is 1080°C, and the size of the blank obtained is: outer diameter 780mm, inner diameter 480mm, height 3070mm;

[0063] The temperature of the solution heat treatment is 1050° C. and the time is 4 hours.

[0064] Example 2

[0065] This embodiment provides a forging method for a large cylindrical nuclear power forging, which is as follows:

[0066] The casting is subjected to upsetting-stretching operation, punching, hole expansion, stretching to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging;

[0067] The casting is made of 0Cr18Ni10Ti stainless steel, and is a hollow cylinder with dimensions of 740 mm in outer diameter, 520 mm in inner diameter, and 2980 mm in height;

[0068] The upsetting-stretching operation includes upsetting and stretching performed sequentially; the upsetting-stretching operation is performed 4 times; the total forging ratio of the upsetting-stretching operation is 14.9; the forging ratios in the upsetting-stretching operation are: 1.8, 2.5, 1.7, 1.7, 1.8, 1.8, 1.8, 1.8; the initial forging temperature of the upsetting-stretching operation is 1195°C; the heating rate of heating the casting to the initial forging temperature is 55°C / h; the final forging temperature of the upsetting-stretching operation is 950°C; if the forging temperature is less than 900°C during the forging process of the upsetting-stretching operation, the temperature is increased to the initial forging temperature at a heating rate of 55°C / h; the size of the product obtained by the upsetting-stretching operation is: the outer diameter is 780mm, the inner diameter is 480mm, and the height is 3070mm;

[0069] The punching operation temperature is 1145°C, and the dimensions of the punched product are: outer diameter 1020mm, inner diameter 380mm, height 1300mm;

[0070] The operating temperature of the hole expansion is 1085°C, and the dimensions of the product obtained by hole expansion are: outer diameter is 1070mm, inner diameter is 500mm, and height is 1300mm;

[0071] The working temperature of the drawing to the blank size is 1085°C, and the size of the blank obtained is: outer diameter 780mm, inner diameter 480mm, height 3070mm;

[0072] The temperature of the solution heat treatment is 1055° C. and the time is 4.2 h.

[0073] Example 3

[0074] This embodiment provides a forging method for a large cylindrical nuclear power forging, which is as follows:

[0075] The casting is subjected to upsetting-stretching operation, punching, hole expansion, stretching to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging;

[0076] The casting is made of 0Cr18Ni10Ti stainless steel, and is a hollow cylinder with dimensions of 740 mm in outer diameter, 520 mm in inner diameter, and 2980 mm in height;

[0077] The roughing-stretching operation includes roughing and stretching performed sequentially; the number of operations of the roughing-stretching operation is 5 times; the total forging ratio of the roughing-stretching operation is 26; the forging ratios in the roughing-stretching operation are: 2, 3, 3, 2, 3, 2, 3, 2, 3, 3; the initial forging temperature of the roughing-stretching operation is 1180°C; the heating rate of heating the casting to the initial forging temperature is 40°C / h; the final forging temperature of the roughing-stretching operation is 900°C; if the forging temperature during the forging process of the roughing-stretching operation is less than 900°C, the temperature is increased to the initial forging temperature at a heating rate of 40°C / h; the size of the product obtained by the roughing-stretching operation is: outer diameter is 780mm, inner diameter is 480mm, height is 3070mm;

[0078] The punching operation temperature is 1140°C, and the dimensions of the punched product are: outer diameter 1020mm, inner diameter 380mm, height 1300mm;

[0079] The operating temperature of the hole expansion is 1090°C, and the dimensions of the product obtained by hole expansion are: outer diameter is 1070mm, inner diameter is 500mm, and height is 1300mm;

[0080] The working temperature of the drawing to the blank size is 1090°C, and the size of the blank obtained is: outer diameter 780mm, inner diameter 480mm, height 3070mm;

[0081] The temperature of the solution heat treatment is 1040° C. and the time is 4.5 hours.

[0082] Example 4

[0083] This embodiment provides a forging method for a large cylindrical nuclear power forging, which is as follows:

[0084] The casting is subjected to upsetting-stretching operation, punching, hole expansion, stretching to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging;

[0085] The casting is made of 0Cr18Ni10Ti stainless steel, and is a hollow cylinder with dimensions of 740 mm in outer diameter, 520 mm in inner diameter, and 2980 mm in height;

[0086] The upsetting-stretching operation includes upsetting and stretching performed sequentially; the number of operations of the upsetting-stretching operation is 4 times; the total forging ratio of the upsetting-stretching operation is 16; the forging ratios in the upsetting-stretching operation are: 2.5, 1.8, 2, 1.9, 2, 1.9, 2, 1.9; the initial forging temperature of the upsetting-stretching operation is 1200°C; the heating rate of heating the casting to the initial forging temperature is 60°C / h; the final forging temperature of the upsetting-stretching operation is 1000°C; if the forging temperature during the forging process of the upsetting-stretching operation is less than 900°C, the temperature is increased to the initial forging temperature at a heating rate of 60°C / h; the size of the product obtained by the upsetting-stretching operation is: the outer diameter is 780mm, the inner diameter is 480mm, and the height is 3070mm;

[0087] The punching operation temperature is 1160°C, and the dimensions of the punched product are: outer diameter 1020mm, inner diameter 380mm, height 1300mm;

[0088] The operating temperature of the hole expansion is 1070°C, and the dimensions of the product obtained by hole expansion are: outer diameter is 1070mm, inner diameter is 500mm, and height is 1300mm;

[0089] The working temperature of the drawing to the blank size is 1070°C, and the size of the blank obtained is: outer diameter 780mm, inner diameter 480mm, height 3070mm;

[0090] The temperature of the solution heat treatment is 1060° C. and the time is 3.8 hours.

[0091] The forgings obtained in the above examples were tested for mechanical properties according to GOST 5632.

[0092] 6032-2017 for intergranular corrosion testing and GOST 5639-82 for grain size testing, where forging sampling is based on Figure 2 The wall thickness T of the specific forging is determined based on the example, and the specific test results are shown in Table 1 below.

[0093] Table 1

[0094]

[0095]

[0096] As can be seen from Table 1, the solution provided by the present invention improves the mechanical properties of the obtained forgings by combining specific upsetting-drawing operations with solution heat treatment, which is beneficial to improving the use effect of the forgings as nuclear power workpieces. For 0Cr18Ni10Ti stainless steel, the tensile strength is ≥575MPa, the yield strength is ≥250MPa, and the elongation is ≥50% at 20°C; the yield strength is ≥226MPa at 100°C.

[0097] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0098] 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 further describe various possible combinations.

[0099] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A forging method for large cylindrical nuclear power forgings, characterized in that: The forging method comprises: The casting is subjected to upsetting-stretching operation, punching, hole expansion, stretching to the blank size and solution heat treatment in sequence to obtain a large cylindrical nuclear power forging; Wherein, the roughing-drawing operation includes roughing and drawing performed sequentially; the number of operations of the roughing-drawing operation is ≥3 times; the total forging ratio of the roughing-drawing operation is ≥6; the initial forging temperature of the roughing-drawing operation is 1180-1200°C; the final forging temperature of the roughing-drawing operation is ≥900°C; the temperature of the solution heat treatment is 1040-1060°C.

2. The forging method according to claim 1, characterized in that: The material of the casting includes 0Cr18Ni10Ti stainless steel.

3. The forging method according to claim 1, characterized in that: The heating rate of heating the casting to the initial forging temperature is 40-60°C / h.

4. The forging method according to claim 1, characterized in that: The forging ratio of upsetting in the upsetting-stretching operation is ≥1.7; Preferably, the forging ratio of the drawing in the upsetting-drawing operation is ≥1.

7.

5. The forging method according to claim 4, characterized in that: When the upsetting-stretching operation is performed multiple times, the forging ratio of the first stretching is 1.7-3, the forging ratio of the intermediate stretching is 1.7-2, and the forging ratio of the last stretching is ≥1.7 on the premise of meeting the total forging ratio.

6. The forging method according to claim 1, characterized in that: If the forging temperature is less than 900° C. during the forging process of the upsetting-stretching operation, the temperature is raised to the initial forging temperature at a heating rate of 40-60° C. / h.

7. The forging method according to claim 1, characterized in that: The punching operation temperature is 1140-1160°C.

8. The forging method according to claim 1, characterized in that: The operating temperature of the hole expansion is 1070-1090°C.

9. The forging method according to claim 1, characterized in that: The working temperature for drawing to the blank size is 1070-1090°C.

10. The forging method according to claim 1, characterized in that: The time of the solution heat treatment is 3.8-4.5h.

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