Integral forging method for a reactor nuclear island austenitic stainless steel hanging basket cylinder with flange

Abstract

The present invention belongs to the field of manufacturing reactor internals, and relates to an integral forging forming method for a flange-equipped austenitic stainless steel basket cylinder in the nuclear island of a reactor. The method includes heating and pressing an ingot raw material into an octagonal prism-shaped ingot; performing cutting and removing the surface oxide scale; carrying out upsetting and drawing of the ingot under a certain heating regime; performing rolling, drawing, and shoulder pressing to form a blank; punching and reaming the blank; cutting the blank to form a dividing groove between the cylinder and the flange; performing rolling and drawing on the cylinder part blank on one side of the dividing groove again; heating the cylinder part blank multiple times; pressing the flange part blank to make the strain generated in the flange blank greater than 8%; performing rough machining; carrying out solution heat treatment and aging heat treatment on the basket cylinder forging; and performing finish machining. By adopting the above method, the performance parameters of the flange-equipped austenitic stainless steel basket cylinder in the nuclear island of the reactor are improved, especially the grain size and impact performance of the flange, and the overall energy consumption of this process method is reduced.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing reactor internals, and particularly to an integral forging forming method for a flange-equipped austenitic stainless steel basket cylinder in a reactor nuclear island. Background Art

[0002] The reactor internals are installed inside the nuclear island pressure vessel. Nuclear fuel assemblies are installed inside it, and the service environment bears high temperature, high pressure, and strong irradiation. Its main functions are to provide positioning and support for nuclear fuel assemblies, provide reliable guidance for the startup of control rods, power adjustment, and reactor shutdown, absorb the impact energy when control rods drop, reasonably distribute channels for fluid media, shield neutrons and gamma rays to reduce the radiation damage of the pressure vessel, provide fixed support and guidance for neutron fluence rate and temperature measurement, and provide secondary safety support for the fall under a core meltdown accident.

[0003] The main material of the reactor internals is austenitic stainless steel, and some materials are nickel-based alloys. Among them, the basket cylinder is a 304NG austenitic stainless steel flange-equipped cylindrical forging. The new generation of mobile reactor design first integrates the flange and the cylinder body as a whole, reducing the number of welds inside the nuclear island.

[0004] The difficulty in forming large austenitic stainless steel forgings lies in the control of grain structure. The required grain size of the basket cylinder forging is ≥ grade 3, and the impact performance is ≥ 160 J. The current hot manufacturing method is difficult to meet the requirements for controlling the grain size of large austenitic stainless steel basket cylinder forgings. Especially at the cylinder flange, due to less deformation and repeated high-temperature heating, the grain size is ≤ grade 1, or even cannot be rated, and the impact performance is ≤ 80 J. In addition, even if the grain of austenitic stainless steel is refined by forging deformation and can meet the service performance requirements, new mixed grain defects are extremely likely to occur during the subsequent high-temperature solution treatment process (the solution temperature after forging of the basket cylinder is ≥ 1000 °C), resulting in serious over-standard grain size and causing the forging to be scrapped due to unqualified flaw detection, resulting in huge economic losses.

[0005] Therefore, how to make the large austenitic stainless steel blank generate the appropriate deformation amount required for grain refinement during the integral forging forming process and not accumulate excessive deformation energy storage, so as to prevent abnormal grain coarsening during the subsequent high-temperature solution treatment stage, is the key to controlling the shape and properties of the integral forging of the austenitic stainless steel basket cylinder. Summary of the Invention

[0006] In view of the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide an integral forging forming method for a flange-equipped austenitic stainless steel basket cylinder in a reactor nuclear island and a flange-equipped basket cylinder prepared by this forming method.

[0007] To achieve the above purpose and other related purposes, on the one hand, the present invention provides an integral forging forming method for a flange-equipped austenitic stainless steel basket cylinder in a reactor nuclear island, including:

[0008] 1) Provide ingot raw materials and make them into ingots;

[0009] 2) Ingot heating regime: Heat the ingot at a heating rate not higher than 42 °C / h to 510 °C - 560 °C and hold for 4 - 6 hours; then heat at a heating rate not higher than 52 °C / h to 610 °C - 660 °C and hold for 3 - 5 hours; then heat at a heating rate not higher than 62 °C / h to 810 °C - 860 °C and hold for 3 - 5 hours; then heat at a heating rate not higher than 72 °C / h to 1110 °C - 1160 °C and hold for 2 - 4 hours; then heat at a heating rate not higher than 82 °C / h to 1190 °C - 1230 °C and hold for 0.5 - 2 hours;

[0010] 3) Ingot pressing process: Press the ingot after the heating regime into an octagonal prism - shaped ingot;

[0011] 4) Cut off 23% - 25% of the volume of the ingot from the riser end and 12% - 13% of the volume of the ingot from the tail end, and remove the scale on the surface of the octagonal prism - shaped billet;

[0012] 5) Subject the ingot obtained in step 4) to the ingot heating regime in step 2) and perform upsetting and drawing of the ingot, with the total forging ratio greater than 7.2;

[0013] 6) Round, draw out, and press shoulders on the ingot processed in step 5) to make a blank;

[0014] 7) Punch and ream the blank;

[0015] 8) Cut the blank to form a parting groove for the cylinder and the flange;

[0016] 9) Round and draw out the cylinder part blank on one side of the parting groove again: Heat the cylinder part blank multiple times, and perform reaming and drawing of the cylinder part after each heating until the target size;

[0017] 10) Press the flange part blank circumferentially along the flange so that the strain generated in the flange blank is greater than 8%;

[0018] In steps 5) - 10), the temperature of the blank is greater than 860 °C, and the preferred temperature is 860 - 1230 °C;

[0019] 11) Rough machining before performance heat treatment;

[0020] 12) Solution heat treatment and aging heat treatment of the hanging basket cylinder forging: Heat the forging that has undergone rough machining in step 13) to 900°C - 940°C at a rate not exceeding 52°C / h and hold for 3 - 4 hours to consume excess deformation energy storage. Then, heat it to 1040°C - 1080°C at a rate not exceeding 72°C / h and hold for 2 - 3 hours, followed by water quenching. Then, heat it to 650°C - 690°C at a rate not exceeding 52°C / h and hold for 17 - 18 hours, followed by water cooling;

[0021] 14) Rough machining and finish machining before finish product processing.

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

[0023] The forging forming method of the present invention is suitable for the integral forging forming method of large - specification austenitic stainless steel special - shaped forgings (ingot ≥ 50 tons). Specifically:

[0024] 1) It is suitable for the forging of the austenitic stainless steel hanging basket cylinder with flanges in the nuclear island of the reactor. Through specific heating systems, forging processes, and heat treatment processes, it ensures that the key forgings in the nuclear island meet the requirements of shape accuracy and tissue performance;

[0025] 2) Compared with the traditional method of manufacturing the flange and cylinder of the hanging basket cylinder separately and then welding them, the integral forging forming maximally retains the integrity of the metal streamline of the forging, eliminates the weld along the circumferential direction of the cylinder, and increases the in - service reliability of nuclear power equipment;

[0026] 3) Adopt the method of hierarchical and zonal heating to avoid the overall forging being at a high temperature (≥ 1200°C) for too long.

[0027] 4) After pressing the flange, adopt the method of zonal local induction heating for the blank of the cylinder part, which avoids abnormal grain growth of the flange with deformation energy storage during subsequent repeated heating, and the overall energy consumption of this heating method is reduced by more than 20%.

[0028] 5) Using the present forging forming process, the grain size of the overall component reaches above grade 3, the impact performance is above 160 J, and the grain size of the flange part is increased to above grade 3. The impact performance is increased from less than 100 J to above 160 J (measured ≥ 300 J), with a large margin, improving the reliability of the in - service equipment. Description of the Drawings

[0029] Figure 1 It is the forging processing flow chart in the embodiment of the present invention;

[0030] Figure 2 The two - dimensional drawing of the forging product in Embodiment 2, where a is the cylinder and b is the flange;

[0031] Figure 3Observation results of the grain microstructure at the cylinder end of the forging product in Example 2;

[0032] Figure 4 Observation results of the grain microstructure at the flange end of the forging product in Example 2;

[0033] Figure 5 2D drawing of the forging product in Example 4;

[0034] Figure 6 Observation results of the grain microstructure at the cylinder end of the forging product in Example 4;

[0035] Figure 7 Observation results of the grain microstructure at the flange end of the forging product in Example 4. Specific implementation manners

[0036] Generally speaking, for the overall forging forming method of the reactor nuclear island austenitic stainless steel hanging basket cylinder with flange of the present invention, through specific heating systems, forging processes and heat treatment energy removal processes, the performance parameters of the reactor nuclear island austenitic stainless steel hanging basket cylinder with flange are improved, especially the grain size and impact performance of the flange, and the overall energy consumption of this process method is reduced. The specific implementation manners of the present invention are as follows:

[0037] The first aspect of the present invention provides an overall forging forming method for a reactor nuclear island austenitic stainless steel hanging basket cylinder with flange, including the following steps:

[0038] 1) Provide an ingot raw material and make it into an ingot;

[0039] Specifically, 304NG austenitic stainless steel can be used, and Si≤0.4%, P≤0.03% for the ingot raw material or the ingot. The above raw materials are prepared by the smelting method of electric furnace smelting → AOD refining method → electroslag remelting. The weight of the cast ingot is greater than 50 tons, generally 50 tons to 100 tons.

[0040] 2) Ingot heating system, the heating is carried out in a general heating furnace.

[0041] Controlling the grain size of large-scale austenitic stainless steel is the main factor to be considered during the heating process. Since the forging has a large volume, in order to avoid the billet being in a high-temperature environment for a long time and the grains becoming abnormally coarse, a method of different temperature zones and time-sharing heat preservation is adopted to avoid grain coarsening. The specific heating system is as follows:

[0042] The ingot is heated to 510°C - 560°C at a heating rate not higher than 42°C / h and held for 4 - 6 hours; then heated to 610°C - 660°C at a heating rate not higher than 52°C / h and held for 3 - 5 hours. The purpose is to ensure that the large-volume and large-section forgings achieve uniform heating of the core at a relatively low temperature range, so as not to cause a large temperature gradient between the surface layer and the core, resulting in a tissue gradient. Then heated to 810°C - 860°C at a heating rate not higher than 62°C / h and held for 3 - 5 hours. The purpose is to fully transform ferrite and pearlite into austenite without causing a sharp growth of austenite grains. Then heated to 1110°C - 1160°C at a heating rate not higher than 72°C / h and held for 2 - 4 hours; then heated to 1190°C - 1230°C at a heating rate not higher than 82°C / h and held for 0.5 - 2 hours. The purpose is to avoid abnormal coarsening of the surface grains due to long-term stay at high temperatures.

[0043] In addition, based on the above process basis, simple adjustments can be made according to different materials. For example, when using 304NG austenitic stainless steel, the ingot heating system is as follows: The ingot is heated to 520°C - 550°C at a heating rate of 36°C / h - 42°C / h and held for 5 hours; then heated to 620°C - 650°C at a heating rate of 46°C / h - 52°C / h and held for 4.5 hours; then heated to 820°C - 850°C at a heating rate of 56°C / h - 62°C / h and held for 4 hours; then heated to 1120°C - 1150°C at a heating rate of 66°C / h - 72°C / h and held for 3 hours; then heated to 1200°C - 1220°C at a heating rate of 76°C / h - 82°C / h and held for 1 hour.

[0044] 3) Ingot pressing process: The ingot after the heating system is pressed into an octagonal prism-shaped ingot. Specifically, after the above steps of heat preservation are completed, the ingot is taken out of the heating furnace and transferred between the upper and lower flat anvils of a large forging equipment within 2 minutes, and pressed into an octagonal prism-shaped billet along the length direction of the ingot.

[0045] 4) The octagonal prism-shaped ingot is chopped and the oxide scale on the surface of the octagonal prism-shaped billet is removed. The chopped volume at the riser end of the ingot is 23% - 25% of the ingot volume to ensure the quality of the forging. The chopped volume at the tail end of the ingot is 12% - 13% of the ingot volume.

[0046] 5) The ingot obtained in step 4) is subjected to the ingot heating system in step 2) for upsetting and drawing of the ingot, and the total forging ratio is greater than 7.2, preferably the total forging ratio is greater than 7.2 - 10. Within this forging ratio range, both the requirements are met and the quality of the forging is ensured.

[0047] Specifically, such as Figure 1As shown in the figure, three upsetting and two drawing processes are adopted for large deformation of the billet to eliminate the coarse dendritic structure of the ingot. At the same time, the porosity defects existing inside the forging are compacted and welded, and the hot plastic damage of cracking of the forging is avoided. Finally, the forging blank is rolled into a short cylindrical shape, and the total forging ratio is ≥7.2.

[0048] More specifically:

[0049] The first upsetting: The initial forging temperature is ≥1200°C, and the upsetting forging ratio is ≥1.8;

[0050] The first drawing: The initial forging temperature is ≥1200°C, and the drawing forging ratio is ≥2.2;

[0051] The second upsetting: The initial forging temperature is ≥1210°C, and the upsetting forging ratio is ≥1.4;

[0052] The second drawing: The initial forging temperature is ≥1190°C, and the drawing forging ratio is ≥1.6;

[0053] The third upsetting: The initial forging temperature is ≥1160°C, and the upsetting forging ratio is ≥1.2;

[0054] For multiple upsetting and drawing processes, only the temperature at the start of deformation needs to be controlled.

[0055] 6) The steel ingot processed in step 5) is rolled, drawn, and shouldered to form a blank.

[0056] Rolling, drawing, and shouldering are all common basic or auxiliary forging processes, aiming to approach the target requirements.

[0057] 7) Punching and reaming the blank:

[0058] Specifically, the blank after rolling and drawing is punched along the direction of the initial upsetting to form a thick-walled ring blank. The thick-walled ring blank is reamed with a mandrel to the target inner diameter.

[0059] 8) Cutting the blank to form a separating groove between the cylinder and the flange:

[0060] Specifically, a separating groove between the cylinder and the flange is cut along the circumferential direction of the short cylindrical blank with a separating cutter, which serves as the identification boundary for the drawing of the cylinder section. Subsequently, the cylinder section blank after separation is rolled and drawn.

[0061] 9) Rolling and drawing the cylinder part blank on one side of the separating groove again: The cylinder part blank is heated multiple times, and after each heating, the cylinder part is reamed and drawn until the target size is reached.

[0062] Specifically, local induction heating is performed on the blank of the cylinder part, while the flange part is not heated to avoid secondary coarsening of grains. The mandrel expanding hole is carried out on the blank of the cylinder part. The pressing speed of the press is ≥10 mm / s. The stretching time along the axial and circumferential directions of the blank each time is ≤15 min, and the pressing rate of each anvil is ≥12%. After each complete global stretching, the blank is reheated by an intermediate frequency induction coil until it is stretched to the target size. Using intermediate frequency induction heating can achieve more than 80% of the heat accumulation on the surface layer of the forging. During the deformation process of the actual forging, due to a large amount of heat exchange with the air, the temperature decreases and heat is supplemented, and it will not cause the temperature of the core of the forging to be too high, resulting in grain coarsening or grain boundary overburning. Moreover, the local heating using the induction coil does not require the entire forging to be placed in the heating furnace, avoiding abnormal coarsening of grains in the flange section. The intermediate frequency induction coil heating method described above is known to those skilled in the art.

[0063] 10) Press the blank of the flange part along the circumferential direction of the flange so that the strain generated by the flange blank is greater than 8%, preferably 8% - 12%; specifically, make the length direction of the blank parallel to the pressing direction of the press, and use a flat anvil to press the blank along the circumferential direction of the flange so that the strain of the flange blank is ≥8%, reaching the critical strain for static recrystallization of 304NG austenitic stainless steel, and further refining the grain structure of the flange part.

[0064] The temperature of the blank in the above entire upsetting and stretching stage is ≥860 °C to avoid cracking damage caused by too low blank temperature.

[0065] 11) Rough machining before performance heat treatment;

[0066] Specifically, the shape of the forging in performance heat treatment should be as close as possible to the final delivery size. Therefore, rough machining of the forging is required before performance heat treatment. The machining size is generally a certain heat treatment allowance added to the final delivery size. At the same time, in order to avoid cracking during solution treatment caused by structures such as sharp corners and grooves. In addition, after rough machining before heat treatment, in order to pre-inspect the internal quality of the product and prevent the flow of unqualified products, UT preliminary inspection is also carried out on the forging before entering the furnace to ensure compliance with the requirements of the product non-destructive inspection standard.

[0067] 12) Solution heat treatment and aging heat treatment of the hanging basket cylinder forging: The forging after rough machining in step 13) is heated to 900°C - 940°C at a rate not exceeding 52°C / h and held for 3 - 4 hours to consume excess deformation energy storage. Then it is heated to 1040°C - 1080°C at a rate not exceeding 72°C / h and held for 2 - 3 hours, followed by water quenching. Then it is heated to 650°C - 690°C at a rate not exceeding 52°C / h and held for 17 - 18 hours, followed by water cooling. Controlling the excess deformation energy storage at 900°C - 940°C and holding for 3 - 4 hours has the best energy removal effect and will not cause rapid grain growth. The purpose of water quenching or water cooling is to retain the austenite structure formed after forging deformation. After deformation, it is desired to immerse the forging in water as soon as possible.

[0068] This solution realizes uniform heating of large-volume and large-section forgings during initial heating and minimizes the time staying at high temperatures. Among them, the time from heat treatment to the start of the water cooling process is less than 120 s, and forced cooling means are used to ensure that the water temperature increase during the cooling process does not exceed 3°C. More specifically, the holding temperature is based on the external thermocouple of the product. The loading of the forging and the arrangement of the external thermocouple are carried out according to the furnace process requirements to ensure uniform heating of the workpiece in the furnace. Shorten the time from starting the heat treatment furnace door to immersing the forging in the water tank. The actual time used in the whole process ≤ 120 seconds. Strengthen the cooling rate of the forging. In a 17.6m×7m×4m quenching water tank, 2 external circulation pumps with a flow rate of 200 cubic meters per hour are equipped, and a total of 10 internal circulation pumps are equipped on the four sides of the water tank to directly carry out forced cooling on the workpiece. The actual temperature increase value of the water temperature during the whole quenching process does not exceed 3°C. The heat treatment furnace is an electric resistance furnace, which has been verified and calibrated by the Shanghai Institute of Measurement and Testing Technology. The maximum temperature deviation of the furnace chamber is ±5°C. The temperature recording instruments and thermocouples used have all passed metrological verification and are within the validity period.

[0069] In addition, based on the above process basis, simple adjustments can be made according to different materials. For example, when using 304NG austenitic stainless steel, the forging after rough machining in step 13) is heated to 910°C - 930°C at a rate of 46°C / h - 52°C / h and held for 3 - 4 hours to consume excess deformation energy storage. Then it is heated to 1050°C - 1070°C at a rate of 66°C / h - 72°C / h and held for 2 - 3 hours, followed by water quenching. Then it is heated to 660°C - 680°C at a rate of 46°C / h - 52°C / h and held for 17 - 18 hours, followed by water cooling.

[0070] 13) Rough machining and finish machining before finish product processing.

[0071] Specifically, 1) Since ultrasonic inspection cannot be performed on some areas of the hanging basket cylinder forgings after final machining, the forgings need to be rough-machined and ultrasonically inspected before finish machining. 2) After final finish machining, the forgings are ultrasonically inspected, liquid penetrant inspected and visually inspected according to the requirements of the procurement drawings and technical specifications. 3) Samples are taken from the cylinder and flange parts of the forgings respectively for macro and microstructural, room temperature tensile, yield strength, impact performance and intergranular corrosion testing and analysis.

[0072] Once again, the service environment of the in-core components is under strong irradiation, high temperature and high pressure, and higher mechanical property requirements are imposed on the forgings. For example, the impact value should be greater than 160 Akv / J (the requirement for pressure vessels is greater than 120 Akv / J). The hanging basket cylinder in this application is an in-core component, and the material is austenitic stainless steel 304NG (the required grain size is ≥3 grades). The grain structure cannot be adjusted by post-forging heat treatment. Therefore, it is necessary to explore and improve its performance from multiple aspects, such as strictly controlling the forging process, using intermediate frequency induction local heating and post-forging energy removal to control the grain structure of the forgings. During the R & D process, the applicant used the method of reheating the whole hanging basket cylinder forging at high temperature repeatedly, which led to unqualified grain flaw detection at the flange part. Then local heating at the cylinder end was adopted to solve the problem that after the flange end was divided, the deformable space was very small. If reheated at high temperature repeatedly and large deformation could not be provided, the grains could not be refined.

[0073] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0074] It should be noted that the process equipment or devices not specifically noted in the following embodiments all adopt conventional equipment or devices in the art.

[0075] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combined steps or the insertion of other method steps between the clearly mentioned steps, unless otherwise stated; it should also be understood that the combined connection relationship between one or more devices / devices mentioned in the present invention does not exclude the existence of other devices / devices before and after the combined devices / devices or the insertion of other devices / devices between the two clearly mentioned devices / devices, unless otherwise stated. Moreover, unless otherwise stated, the numbers of the method steps are only convenient tools for identifying the method steps, rather than limiting the arrangement order of the method steps or the scope in which the present invention can be implemented. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0076] Example 1

[0077] 1) Provide 304NG austenitic stainless steel. The 304NG austenitic stainless steel ingot of 50 tons is prepared by the smelting method of electric furnace smelting → AOD refining method → electroslag remelting, with Si ≤ 0.4% and P ≤ 0.03%.

[0078] 2) In the heating furnace, heat the ingot at a heating rate of 36 °C / h to 52 °C and hold for 5 hours; then heat it at a heating rate of 46 °C / h to 620 °C and hold for 4.5 hours; then heat it at a heating rate of 56 °C / h to 820 °C and hold for 4 hours; then heat it at a heating rate of 66 °C / h to 1120 °C and hold for 3 hours; then heat it at a heating rate of 76 °C / h to 1200 °C and hold for 1 hour.

[0079] 3) Take out the ingot from the heating furnace and transfer it between the upper and lower flat anvils of large forging equipment within 2 minutes, and press it into an octagonal prism billet along the length direction of the ingot.

[0080] 4) Cut off 23% of the volume of the ingot at the riser end and 12% of the volume of the ingot at the tail end, and use a steel hammer to knock to remove the oxide skin on the outer periphery of the billet to obtain an octagonal prism forging billet for forging.

[0081] 5) As Figure 1 shown, adopt large deformation of three upsetting and two drawing out to open the billet.

[0082] More specifically:

[0083] The first upsetting: The initial forging temperature is about 1210 °C, and the upsetting forging ratio is 1.8;

[0084] The first drawing out: The initial forging temperature is about 1210 °C, and the drawing out forging ratio is 2.2;

[0085] The second upsetting: The initial forging temperature is about 1210 °C, and the upsetting forging ratio is 1.4;

[0086] The second drawing out: The initial forging temperature is about 1190 °C, and the drawing out forging ratio is 1.6;

[0087] The third upsetting: The initial forging temperature is about 1160 °C, and the upsetting forging ratio is 1.2;

[0088] 6) Roll, draw out and shoulder the ingot processed in step 5) to make a blank

[0089] 7) Punch the blank of roll drawing out along the initial upsetting direction to form a thick-walled ring blank. Carry out mandrel reaming on the thick-walled ring blank and ream it to the target inner diameter of 1000 mm.

[0090] 8) Use a dividing chopping knife to chop a dividing groove between the cylinder body and the flange along the circumferential direction of the short cylindrical blank as the identification boundary for the stretching of the cylinder body section, and ensure that the length of one end after dividing is ≥400 mm.

[0091] 9) Locally inductively heat the blank of the cylinder body part, and do not heat the flange part at this time to avoid secondary coarsening of grains. Carry out mandrel reaming on the blank of the cylinder body part. The pressing speed of the press is ≥10 mm / s. The stretching time along the axial and circumferential directions of the blank each time is ≤15 min, and the pressing rate of each anvil is ≥12%. After each complete global stretching, use an intermediate frequency induction coil to secondary heat the blank, and stretch it to an inner diameter ≥1200 mm, an outer diameter ≥1550 mm, and a length ≥5000 mm.

[0092] 10) Press the blank of the flange part along the circumferential direction of the flange to make the strain generated by the flange blank greater than 8%;

[0093] During the above entire upsetting and stretching stage, the temperature of the blank is ≥860 °C to avoid cracking damage due to too low blank temperature.

[0094] 11) Rough machining before performance heat treatment;

[0095] Specifically, the shape of the forgings after performance heat treatment should be as close as possible to the final delivery size. Therefore, rough machining needs to be carried out on the forgings before performance heat treatment. The machining size is generally a certain heat treatment allowance added to the final delivery size. At the same time, in order to avoid cracking during solution treatment caused by structures such as sharp corners and grooves. In addition, after rough machining before heat treatment, in order to pre-inspect the internal quality of the products and prevent the flow of unqualified products, UT preliminary inspection is also carried out on the forgings before they are put into the furnace to ensure compliance with the requirements of the product non-destructive inspection standards.

[0096] 12) Solution heat treatment and aging heat treatment of the hanging basket cylinder body forgings: Heat the forgings rough machined in step 13) to 910 °C at a rate of 46 °C / h and hold for 3 hours to consume the excess deformation energy storage, then heat to 1050 °C at a rate of 66 °C / h and hold for 2 hours and water quench, and then heat to 660 °C at a rate of 46 °C / h and hold for 17 hours and water cool. Among them, the time from after heat treatment to the start of the water cooling process is less than 120 s, and forced cooling means are used to ensure that the water temperature rise during the cooling process does not exceed 3 °C.

[0097] More specifically, the heat preservation temperature is based on the thermocouple externally connected to the product. The loading of the forgings and the arrangement of the externally connected thermocouple are carried out according to the requirements of the loading process to ensure uniform heating of the workpieces in the furnace. The time from starting the heat treatment furnace door to immersing the forgings in the water tank is shortened, and the actual time used in the whole process ≤ 120 seconds. The cooling rate of the forgings is strengthened. Two external circulation pumps with a flow rate of 200 cubic meters per hour are equipped in a quenching water tank of 17.6m×7m×4m, and a total of 10 internal circulation pumps are equipped on the four sides of the water tank to directly carry out forced cooling on the workpieces. The actual temperature rise value of the water temperature during the whole quenching process does not exceed 3°C. The heat treatment furnace is an electric resistance furnace, which is verified and calibrated by the Shanghai Institute of Measurement and Testing Technology. The maximum temperature deviation of the furnace chamber is ±5°C. The temperature recording instruments and thermocouples used have all passed the metrological verification and are within the validity period.

[0098] 13) Since there are some areas that cannot be ultrasonically inspected after the final machining of the hanging basket cylinder forgings, before the finished product machining of the forgings, rough machining is required, and ultrasonic testing is carried out, and then the final finished product machining.

[0099] The forgings are ultrasonically inspected, liquid penetrant inspected and visually inspected according to the requirements of the procurement drawings and technical specifications.

[0100] Samples are taken separately from the cylinder and flange parts of the forgings for detection and analysis of macro and microstructures, room temperature tensile strength, yield strength, impact performance and intergranular corrosion.

[0101] Example 2

[0102] The product prepared in Example 1 is used as P1, as Figure 2 shown.

[0103] Microstructure: Samples are taken separately from the end faces of the cylinder and flange of the forgings. The microstructure images observed with a Zeiss Axio Vert.A1 optical microscope at a magnification of 200 times are as follows Figure 3 and Figure 4 shown. The grain size at the cylinder end is ≥ grade 5, and the grain size at the flange end is ≥ grade 4. No abnormally large grains are found, meeting the requirements.

[0104] Impact performance: Impact specimens are taken circumferentially along the cylinder end and flange end respectively. The Charpy impact energies are 420 Akv / J and 408 Akv / J respectively, both greater than 160 Akv / J, meeting the requirements.

[0105] Example 3

[0106] The forging forming is carried out by a method similar to that in Example 1, but the differences from Example 1 are that

[0107] 1) 100 tons of 304NG austenitic stainless steel ingots, Si ≤ 0.4%, P ≤ 0.03%

[0108] 2) Heating system: Heat the ingot to 550°C at a heating rate of 42°C / h and hold for 5 hours; then heat it to 630°C at a heating rate of 50°C / h and hold for 4 hours; then heat it to 840°C at a heating rate of 62°C / h and hold for 4 hours; then heat it to 1150°C at a heating rate of 70°C / h and hold for 3 hours; then heat it to 1230°C at a heating rate of 82°C / h and hold for 1.5 hours.

[0109] 4) The chopped volume at the riser end of the ingot is 24% of the ingot volume, and the chopped volume at the tail end of the ingot is 13% of the ingot volume. Remove the oxide scale on the surface of the octagonal prism billet.

[0110] 9) Re-roll and stretch the billet of the cylinder part on one side of the feeding chute: Heat the billet of the cylinder part multiple times, and perform hole expansion on the cylinder part after each heating until the target size of 2600 mm.

[0111] Specifically, perform local induction heating on the billet of the cylinder part. At this time, the flange part is not heated to avoid secondary coarsening of grains. Perform frame hole expansion on the billet of the cylinder part. The pressing speed of the press is ≥10 mm / s. The stretching time along the axial and circumferential directions of the billet each time is ≤15 min, and the forging reduction rate of each anvil is ≥12%. After each complete global stretching, use an induction coil to perform secondary heating on the billet and stretch it to the target size: inner diameter ≥3200 mm, outer diameter ≥3550 mm, length ≥7000 mm.

[0112] 13) Solution heat treatment and aging heat treatment of the forging of the hanging basket cylinder: Heat the forging rough-machined in step 13) to 930°C at 52°C / h and hold for 4 hours to consume excess deformation energy storage, then heat it to 1050°C at 70°C / h and hold for 2 hours for water quenching, and then heat it to 680°C at 50°C / h and hold for 17 hours for water cooling.

[0113] Example 4

[0114] Use the product prepared in Example 3 as P2, as Figure 5 shown.

[0115] Microstructure: Samples are taken separately from the end faces of the cylinder and flange of the forging. The microstructure images observed with a Zeiss Axio Vert.A1 optical microscope at a magnification of 200 times are as Figure 6 , 7 shown. The grains at the cylinder end are ≥Grade 4, and the grains at the flange end are ≥Grade 3. No abnormally coarse grains are found, meeting the requirements.

[0116] Impact performance: Impact specimens are taken circumferentially along the cylinder end and flange end respectively. The Charpy impact energies are 410 Akv / J and 390 Akv / J respectively, both greater than 160 Akv / J, meeting the requirements.

[0117] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for integral forging forming of a flange - equipped austenitic stainless steel hanging basket cylinder body in a reactor nuclear island, comprising the following steps: 1) Providing an ingot raw material to make an ingot; 2) Ingot heating regime: Heating the ingot at a heating rate not higher than 42 °C / h to 510 °C - 560 °C, and holding for 4 - 6 hours; then heating at a heating rate not higher than 52 °C / h to 610 °C - 660 °C, and holding for 3 - 5 hours; then heating at a heating rate not higher than 62 °C / h to 810 °C - 860 °C, and holding for 3 - 5 hours; then heating at a heating rate not higher than 72 °C / h to 1110 °C - 1160 °C, and holding for 2 - 4 hours; then heating at a heating rate not higher than 82 °C / h to 1190 °C - 1230 °C, and holding for 0.5 - 2 hours; 3) Pressing the ingot after the heating regime into an octagonal prism - shaped ingot; 4) Cutting and removing the oxide scale on the surface layer of the octagonal prism - shaped billet; 5) Subjecting the ingot obtained in step 4) to the heating regime in step 2), and performing upsetting and drawing of the ingot, with the total forging ratio greater than 7.2; 6) Rolling, drawing, and shoulder - pressing the ingot processed in step 5) to make a blank; 7) Punching and reaming the blank; 8) Cutting the blank to form a parting groove for the cylinder body and the flange; 9) Rolling and drawing the cylinder - part blank on one side of the parting groove: Heating the cylinder - part blank multiple times, and after each heating, performing reaming and drawing of the cylinder part until the target size; 10) Pressing the flange - part blank along the circumferential direction of the flange, so that the strain generated in the flange blank is greater than 8%; In steps 5) - 10), the temperature of the blank is greater than 860 °C; 11) Rough machining before performance heat treatment; 12) Solution heat treatment and aging heat treatment of the hanging basket cylinder body forging: Heating the forging after rough machining in step 11) at a heating rate not higher than 52 °C / h to 900 °C - 940 °C and holding for 3 - 4 hours to consume excess deformation energy storage, then heating at a heating rate not higher than 72 °C / h to 1040 °C - 1080 °C and holding for 2 - 3 hours for water quenching, and then heating at a heating rate not higher than 52 °C / h to 650 °C - 690 °C and holding for 17 - 18 hours for water cooling; 13) Rough machining before finish machining and finish machining.

2. The overall forging forming method of the austenitic stainless steel hanging basket cylinder body with flange in the reactor nuclear island according to claim 1, characterized in that, Step 1) at least includes one of the following technical features: 1 - 1) The ingot raw material is supported by an ingot through smelting methods such as electric furnace smelting, AOD refining method, and electroslag remelting; 1 - 2) Si≤0.4% and P≤0.03% in the ingot raw material or the ingot; 1 - 3) The ingot is a 304NG austenitic stainless steel ingot; 1 - 4) The weight of the ingot is greater than 50 tons.

3. The overall forging forming method of the austenitic stainless steel hanging basket cylinder body with flange in the reactor nuclear island according to claim 1, characterized in that, The ingot heating regime in step 2) is as follows: Heat the ingot at a heating rate of 36°C / h to 42°C / h to 520°C to 550°C and hold for 5 hours; then heat at a heating rate of 46°C / h to 52°C / h to 620°C to 650°C and hold for 4.5 hours; then heat at a heating rate of 56°C / h to 62°C / h to 820°C to 850°C and hold for 4 hours; then heat at a heating rate of 66°C / h to 72°C / h to 1120°C to 1150°C and hold for 3 hours; then heat at a heating rate of 76°C / h to 82°C / h to 1200°C to 1220°C and hold for 1 hour.

4. The overall forging forming method of the austenitic stainless steel hanging basket cylinder body with flange in the reactor nuclear island according to claim 1, characterized in that Step 3) includes at least one of the following technical features: 3-1) After being processed in step 2), the ingot pressing process is carried out within 2 minutes. 3-2) The ingot pressing process uses the upper and lower flat anvils of forging equipment for pressing. 3-3) The ingot pressing process presses the ingot along its length to form an octagonal prism-shaped ingot.

5. The integral forging forming method of the austenitic stainless steel hanging basket cylinder body with flange in the reactor nuclear island according to claim 1, characterized in that, Step 5) includes at least one of the following technical features: 5-1) The specific process of upsetting and drawing: The first upsetting: The starting forging temperature ≥ 1200°C, and the upsetting forging ratio ≥ 1.

8. The first drawing: The starting forging temperature ≥ 1200°C, and the drawing forging ratio ≥ 2.

2. The second upsetting: The starting forging temperature ≥ 1210°C, and the upsetting forging ratio ≥ 1.

4. The second drawing: The starting forging temperature ≥ 1190°C, and the drawing forging ratio ≥ 1.

6. The third upsetting: The starting forging temperature ≥ 1160°C, and the upsetting forging ratio ≥ 1.

2. 5-2) The total forging ratio in the upsetting and drawing process ≥ 7.

2. 5-3) After upsetting and drawing, a rounding process is carried out.

6. The integral forging forming method of the austenitic stainless steel hanging basket cylinder body with flange in the reactor nuclear island according to claim 1, characterized in that Step 7) includes at least one of the following technical features: 7-1) Punch holes along the direction of the initial upsetting of the blank formed by round drawing and shoulder pressing to form a thick-walled ring blank. 7-2) Carry out mandrel reaming on the blank after punching to ream to the target inner diameter.

7. The integral forging forming method of the austenitic stainless steel hanging basket cylinder body with flange in the nuclear island of the reactor according to claim 1, characterized in that, Step 9) includes at least one of the following technical features: 9-1) Use the induction coil heating method to heat the blank of the cylinder part. 9-2) The temperature after multiple heating of the blank of the cylinder part is 1130°C to 1170°C. 9-3) Carry out mandrel reaming of the cylinder part, and the pressing speed of the press ≥ 10 mm / s. 9-4) Each drawing is along the axial and circumferential directions of the blank, and the drawing time ≤ 15 minutes, and the pressing rate of each anvil ≥ 12%.

8. The overall forging forming method of the austenitic stainless steel hanging basket cylinder body with flange in the reactor nuclear island according to claim 1, characterized in that, In steps 5) - 10), the temperature of the blank is 860 - 1230°C.

9. The integral forging forming method of the austenitic stainless steel basket cylinder with flange in the reactor nuclear island according to claim 1, characterized in that Step 12) is to heat the forgings rough-machined in step 11) at 46°C / h to 52°C / h to 910°C to 930°C and hold for 3 - 4 hours to consume the excess deformation energy storage, then heat at 66°C / h to 72°C / h to 1050°C to 1070°C and hold for 2 - 3 hours for water quenching, and then heat at 46°C / h to 52°C / h to 660°C to 680°C and hold for 17 - 18 hours for water cooling.

10. The overall forging forming method of the austenitic stainless steel hanging basket cylinder body with flange in the reactor nuclear island according to claim 1, characterized in that, In step 12), the time from the heat treatment to the start of the water cooling process is less than 120 s, and forced cooling means are used to ensure that the water temperature rise during the cooling process does not exceed 3°C.

11. A reactor nuclear island austenitic stainless steel basket cylinder with flange is made by using the overall forging forming method of the reactor nuclear island austenitic stainless steel basket cylinder with flange described in any one of 1-10 above.

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