Forging method for cooperatively controlling shape property of L-shaped stainless steel main pump connecting pipe large forging

Abstract

The invention provides a shape cooperative control forging method for an L-shaped stainless steel main pump connecting pipe large forging. The method comprises the steps that tool assistive devices are prepared, the tool assistive devices comprise a flat-bottom upper die, a profiling lower die, a profiling upper die and a core rod, the profiling lower die is provided with a V-shaped die cavity, and the profiling upper die is in a V shape; a square blank 1 is obtained under the forging conditions that the upsetting deformation of a steel ingot is larger than or equal to 50%, the deformation of each anvil during drawing is larger than or equal to 15%, the forging temperature of each heating number ranges from 1150 DEG C to 1240 DEG C, and the forging duration does not exceed 20 min; the blank 1 is flattened and thickened through a profiling lower die and a flat-bottom upper die, and a blank 2 with one side being a plane and the included angle between the two edges of the other side being a right angle is obtained; the upper profiling die and the lower profiling die are used for conducting stamping forming on the blank 2 to obtain a blank 3, and the blank 3 is used for providing two branch pipe transition areas and a branch pipe body; and the mold closing state of the upper profiling mold and the lower profiling mold is kept, movement of the blank 3 is limited through a core rod, the ends of the two branch pipes are subjected to flattening treatment, and the L-shaped stainless steel main pump connecting pipe large forge piece is obtained. According to the method, the profiling forming problem and the grain uniformity problem of an existing L-shaped stainless steel main pump connecting pipe large forge piece can be solved.

Description

Technical Field

[0001] The invention belongs to the field of metal material forming, and more specifically, relates to a method for forging a large L-shaped stainless steel main pump pipe forging with coordinated shape control. Background Art

[0002] The main pump take-over is the link between the nuclear reactor pressure vessel and the main pump, which forms a complete circuit in the reactor. Its main function is to transport fluid and heat. The connection between the main pump take-over and the pressure vessel cylinder is the weak link of the reactor pressure vessel and the key part of evaluating its safety. Therefore, the main pump take-over is required to have reliable safety quality.

[0003] The main pump pipe is a complex and special-shaped forging. The two branches intersect to form a right-angle transition area. The diameter of one branch exceeds 500mm and the length of the branch can reach 1000mm. In view of the structural characteristics of the L-shaped main pump pipe, the previous forging schemes mostly used drawing and splitting forming, only profiling the right-angle transition area formed by the intersection of the two branches, without forming the branch pipes. Fig.10 As shown. After the forging is drawn and divided, the weight of the forging is 8.0t, while the weight of the rough processing of the product only accounts for 31% of the weight of the forging. The material utilization rate is low and the machining workload and processing cycle are greatly increased. With the increasingly fierce market competition, the original forming scheme can no longer meet the market's requirements for the production cost and cycle control of the main pump pipe products. The use of die forging to achieve near-net forming of the main pump pipe will also become a production trend. For large main pump pipes with a single-side branch length of up to 1000mm and a branch diameter of D≥Φ500mm, the billet has great resistance in its right-angle transition area and when it flows to the ends of the two branches during the plastic deformation process, which is prone to forging defects such as missing quantity, and it is necessary to add repair and other processes to ensure the forging forming. Therefore, it is urgently necessary to develop a near-size copying forging process based on integrated special-shaped forgings for the main pump pipe forgings to achieve near-net forming and solve the technical difficulties in forging the main pump pipe forgings.

[0004] In addition, the main pump pipe forging is made of ultra-low carbon austenitic stainless steel. Due to its material characteristics, it will not undergo phase change, and it is difficult to effectively improve the product grain size through heat treatment processes such as solid solution. Grain size is one of the main factors affecting material performance. Coarse grains will drastically deteriorate material performance, causing the product to fail early and cause major safety accidents. Therefore, for the main pump pipe forging, in order to ensure product quality and performance and improve its safety and reliability, the grain size must be effectively controlled during the forging process. Summary of the invention

[0005] The invention aims to solve the problem of profiling and grain uniformity of the existing L-shaped stainless steel main pump pipe large forging (branch pipe diameter D≥Φ500mm, single-side branch pipe length≥1000mm).

[0006] In order to achieve the above object, the present invention provides a method for forging a large L-shaped stainless steel main pump pipe forging with coordinated control of shape, the method comprising the following steps:

[0007] Prepare a tooling auxiliary tool, the tooling auxiliary tool comprises a flat bottom upper die, a contoured lower die, a contoured upper die and a core rod, the contoured lower die has a V-shaped die cavity, and the contoured upper die is V-shaped;

[0008] Obtain a square billet 1 under the forging conditions that the deformation of the steel ingot during upsetting is ≥50%, the deformation of each anvil during drawing is ≥15%, the forging temperature of each fire is 1150°C to 1240°C, and the forging time does not exceed 20 minutes;

[0009] The blank 1 is flattened and thickened by using the profiling lower die and the flat-bottom upper die to obtain a blank 2 with a flat surface on one side and right angles on the other side;

[0010] The blank 2 is punched and formed by using the profiling upper die and the profiling lower die to obtain a blank 3, wherein the blank 3 is used to provide a transition area between two branch pipes and a main body of the branch pipe;

[0011] The mold-closing state of the profiling upper die and the profiling lower die is maintained, and the movement of the blank 3 is restricted by the core rod, so that the ends of the two branch pipes are flattened respectively to obtain the L-shaped stainless steel main pump pipe large forging.

[0012] Optionally, the size of the blank 1 is determined based on the following formula:

[0013]

[0014] t1=a-(40~60) (2)

[0015]

[0016] In the above formula, L1 is the length of blank 1, V 坯料1 is the volume of billet 1, t1 is the thickness of billet 1, a is the diameter of the branch pipe of the large forging of the L-shaped stainless steel main pump, V 锻件 It is the volume of the large forging of the L-shaped stainless steel main pump.

[0017] Optionally, the process of flattening and thickening the blank 1 by using the profiling lower die and the flat-bottom upper die to obtain a blank 2 with a flat surface on one side and right angles on the other side further comprises the following steps:

[0018] The blank 1 is rotated 45° clockwise and placed in the die cavity of the profiling lower die, the thickness of the die cavity is the same as the diameter of the forging branch pipe, and the inner arc radius of the profiling lower die is the same as the arc radius of the forging;

[0019] The flat upper die covering the horizontal length direction of the blank 1 is aligned with the contoured lower die and then pressed down with a pressing amount = H1 / 3 to form a blank 2 with a length of L2, a height of H2, and a thickness of t2, wherein H1 is the length of the diagonal of the blank 1, and t2 = a.

[0020] Optionally, the blank 2 is punched and formed by using the profiling upper die and the profiling lower die to obtain the blank 3 as follows:

[0021] Keep the blank 2 in the die cavity of the profiling lower die, replace the profiling upper die, align the profiling upper die with the profiling lower die, and then punch the blank 2, with the pressing amount = H2-a-(60~70), so that the two branch pipe transition areas and the main body of the L-shaped stainless steel main pump connecting pipe large forging are formed.

[0022] Optionally, the L-shaped stainless steel main pump pipe large forging shape coordinated control forging method further includes the following steps:

[0023] After the two branch pipe ends of the blank 3 are flattened to obtain an L-shaped stainless steel main pump pipe large forging, the L-shaped stainless steel main pump pipe large forging is cooled in water, and the transfer time into water is ≤5min.

[0024] The beneficial effects of the present invention are:

[0025] The present invention provides a forging method for collaboratively controlling the shape of an L-shaped stainless steel main pump pipe large forging. Through corresponding forming schemes and tooling design schemes, a 10,000-ton press is used and equipped with corresponding tooling auxiliary tools. With the help of free forging and die forging, the grain uniformity problem and the profiling forming problem of the L-shaped stainless steel main pump pipe large forging are solved. While meeting the forging size requirements, the grain size of the entire cross-section of the forging is achieved to be ≥3 levels, thereby meeting the needs for shape and controllability of the L-shaped stainless steel main pump pipe large forging.

[0026] The present invention firstly breaks columnar crystals, improves macrosegregation, crushes cast structure, refines grains and obtains uniform forged structure by ensuring high temperature + large deformation forging technology. At the same time, it solves the forging problem of the right-angle transition area formed by the intersection of two branch pipes of the L-type main pump pipe forging and the difficulty of branch pipe profiling forging. The weight of the forging is only 6.9t. Compared with the previous scheme, the weight of the forging is reduced by 14%, which improves the product utilization rate, indirectly reduces the workload and cycle of the machining process, and reduces the manufacturing cost as a whole. The prefabricated square billet can effectively reduce the difficulty of forming the right-angle transition area formed by the intersection of two branch pipes of the L-type main pump pipe forging. Flattening and thickening can prepare for the subsequent branch pipe press forming and provide conditions for the profiling of the branch pipe body. By using the profiling of the upper and lower molds, the metal flow of the branch pipe body presents a streamlined curve and has better mechanical properties. Finally, by using the mandrel to flatten the end when the upper and lower molds are in the mold closing state, the margin in the length direction of the branch pipe can be effectively reduced, thereby reducing the weight of the forging and improving the profiling degree of the forging.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention may be better understood by referring to the following description taken in conjunction with the accompanying drawings, in which the same or similar reference numerals are used throughout the drawings to represent the same or similar components.

[0029] Figure 1 A flowchart of a method for forging a large forging of an L-shaped stainless steel main pump pipe in accordance with an embodiment of the present invention is shown;

[0030] Figure 2 A schematic structural diagram of an L-shaped stainless steel main pump pipe large forging according to an embodiment of the present invention is shown;

[0031] Figure 3 A schematic diagram showing the dimensions of a blank 1 according to an embodiment of the present invention is shown;

[0032] Figure 4 A schematic structural diagram of a flat-bottom upper mold according to an embodiment of the present invention is shown;

[0033] Figure 5 A schematic diagram of parts of a contoured lower die according to an embodiment of the present invention is shown;

[0034] Figure 6 A schematic diagram of assembling a contoured lower die according to an embodiment of the present invention is shown;

[0035] Figure 7 A schematic diagram showing the dimensions of a blank 2 according to an embodiment of the present invention is shown;

[0036] Figure 8 A schematic structural diagram of a contoured upper die according to an embodiment of the present invention is shown;

[0037] Fig. 9 A schematic diagram showing the dimensions of a blank 3 according to an embodiment of the present invention is shown;

[0038] Fig.10 A schematic diagram of a drawing and dividing forming scheme for a large forging of an L-shaped stainless steel main pump pipe according to the background technology of the present invention is shown;

[0039] Fig.11 A metallographic diagram of the finished grain size of an L-shaped stainless steel main pump pipe large forging according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to more fully understand the technical solution of the present invention, the exemplary embodiments of the present invention will be described in more comprehensive and detailed in conjunction with the accompanying drawings below. Obviously, the one or more embodiments of the present invention described below are only one or more of the specific ways in which the technical solution of the present invention can be implemented, and are not exhaustive. It should be understood that other ways belonging to a general inventive concept can be used to implement the technical solution of the present invention, and should not be limited by the exemplary embodiments described. Based on one or more embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work should fall within the scope of protection of the present invention.

[0041] Example: Figure 1 The flowchart of the method for forging a large forging of an L-shaped stainless steel main pump pipe of an embodiment of the present invention is shown. Figure 2 A schematic structural diagram of an L-shaped stainless steel main pump pipe large forging according to an embodiment of the present invention is shown.

[0042] Reference Figure 1 and Figure 2 The L-shaped stainless steel main pump pipe large forging shape coordinated control forging method of the embodiment of the present invention comprises the following steps:

[0043] Step S100, preparing tooling auxiliary tools, the tooling auxiliary tools including a flat-bottom upper mold, a contoured lower mold, a contoured upper mold and a core rod, the contoured lower mold has a V-shaped mold cavity, and the contoured upper mold is V-shaped;

[0044] Step S200, obtaining a square billet 1 under the forging conditions that the deformation of the steel ingot during upsetting is ≥50%, the deformation of each anvil during drawing is ≥15%, the forging temperature of each fire is 1150° C. to 1240° C., and the forging time does not exceed 20 minutes;

[0045] Step S300, using a contoured lower die and a flat upper die to flatten and thicken the blank 1, to obtain a blank 2 with a flat surface on one side and right angles on the other side;

[0046] Step S400, using a profiling upper die and a profiling lower die to stamp the blank 2 to obtain a blank 3, wherein the blank 3 is used to provide a transition area between two branch pipes and a main body of the branch pipe;

[0047] Step S500, keeping the mold-clamping state of the profiling upper die and the profiling lower die, using the mandrel to limit the movement of the blank 3, so as to flatten the ends of the two branch pipes respectively, and obtain an L-shaped stainless steel main pump pipe large forging.

[0048] Specifically, in the embodiment of the present invention, the preparation of tooling and auxiliary tools includes but is not limited to the following:

[0049] The flat-bottom upper die is an upper die that cooperates with the contoured lower die to flatten and thicken the square blank 1, such as Figure 4 shown.

[0050] The combined profiling die is a die that emulates the shape of the L-shaped stainless steel main pump pipe large forging. The profiling die consists of two parts, which are mirror-symmetrical and assembled together by bolts, nuts and other fasteners. Figure 5 and Figure 6 shown.

[0051] The profiling die is a die that emulates the shape of the L-shaped stainless steel main pump pipe forging. Figure 8 shown.

[0052] The core rod is a cylindrical core rod used to flatten the end of the blank 3.

[0053] In the embodiment of the present invention, a square billet 1 is forged by step S200. Specifically, a square billet with uniform and dense structure is prefabricated by conventional forging methods such as upsetting and drawing. Figure 3 As shown. The ingot upsetting deformation is required to be ≥50%, the deformation of each anvil during drawing is ≥15%, the forging temperature of each fire is 1150℃~1240℃, and the forging time (from forging to returning to the furnace after forging) does not exceed 20min. Through upsetting, drawing and other processes, the billet has a sufficient forging ratio to ensure the overall compaction of the billet. Through high temperature + large deformation, the cast dendrites inside the steel ingot are fully and effectively compacted and broken to achieve the overall refinement of the grains inside the steel billet.

[0054] The size of blank 1 can be calculated using formula (1)(2)(3):

[0055]

[0056] t1=a-(40~60) (2)

[0057]

[0058] In the above formula, L1 is the length of blank 1, V 坯料1 is the volume of billet 1, t1 is the thickness of billet 1, a is the diameter of the branch pipe of the large forging of the L-shaped stainless steel main pump, V 锻件 It is the volume of the large forging of the L-shaped stainless steel main pump.

[0059] In the embodiment of the present invention, the flattening and thickening of the blank 1 is achieved through step S300. Specifically, the blank 1 is rotated 45° clockwise and placed in the die cavity of the assembled profiling lower die. The die cavity thickness of the profiling lower die is the same as the diameter of the forging branch pipe, and the inner arc radius of the profiling lower die is the same as the arc radius of the forging; the flat-bottomed upper die covering the horizontal length direction of the blank 1 is aligning with the profiling lower die and then pressed down, and the pressing amount ≈ H1 / 3, that is, the absolute value of the difference between the pressing amount and H1 / 3 does not exceed the set value, wherein H1 is the length of the diagonal of the blank 1. The downward pressing of the flat-bottomed upper die increases the overall thickness of the blank 1, and at the same time obtains a blank 2 with a plane on one side and right angles between the two sides on the other side, such as Figure 7 As shown, the length of the blank 2 is L2, the height is H2, and the thickness is t2, where t2=a.

[0060] In the embodiment of the present invention, the material division and profiling are realized by step S400. Specifically, after the amount of the flat-bottom upper mold is pressed down to meet the requirements, the blank 2 is kept in the mold cavity of the profiling lower mold, and the V-shaped profiling upper mold is replaced. Figure 8 After the upper and lower dies are aligned, the blank 2 is punched, and the pressing amount = H2-a-(60-70), so that the transition area of ​​the two branch pipes and the main body of the L-shaped stainless steel main pump pipe large forging are formed. The forming result is as shown in Fig. 9 The blank 3 is shown.

[0061] In the embodiment of the present invention, the forming of the branch pipe end is achieved through step S500. After the material is divided and profiled, the upper and lower profile dies are kept in a closed state, and the mandrel is used to limit the movement of the blank 3, and the ends of the two branch pipes of the L-shaped stainless steel main pump pipe large forging are flattened and finished respectively. After completion, they are immediately put into water for cooling, and the transfer time into water is ≤5min, so that the forging is cooled quickly to avoid coarsening or mixed crystals due to high residual heat.

[0062] The L-shaped stainless steel main pump pipe large forging synergistic control forging method of the embodiment of the present invention adopts the grain control method of "high temperature + large deformation" and the profiling forming method of "prefabricated square billet + flattening and thickening + material profiling + branch pipe end forming", which has the following beneficial effects:

[0063] 1. If Figure 3As shown, the prefabricated square blank 1 can reduce the difficulty of forming the right-angle transition area formed by the intersection of the two branch pipes of the L-shaped stainless steel main pump connecting pipe large forging.

[0064] 2. Flattening and thickening the blank 1 can prepare for the subsequent branch pipe forming. Flattening and thickening the blank as a whole facilitates the next step of dividing the two branch pipes and forming the main body.

[0065] 3. After the profiling upper die and the combined profiling lower die are closed, the right-angle transition part of the L-shaped stainless steel main pump pipe forging and the main body of the branch pipe have been formed. By using the mandrel to level the end when the upper and lower molds are closed, the margin in the length direction of the branch pipe can be effectively reduced, thereby reducing the weight of the forging and improving the profiling degree of the forging.

[0066] 4. During the forging process, high temperature and large deformation are guaranteed, which effectively breaks the columnar grains, crushes the cast structure, improves the macro segregation, refines the grains and obtains a uniform forged structure.

[0067] 5. If Figure 8 The profiling upper die shown is used to perform profiling according to the right-angle transition area of ​​the large forging of the L-shaped stainless steel main pump pipe and the diameter of the branch pipe. In combination with the combined profiling lower die, the L-shaped main pump pipe forging can be effectively profiled.

[0068] 6. If Figure 5 and Figure 6 As shown in the profiling lower die parts drawing and assembly drawing, the combined profiling lower die is composed of two parts, which are mirror-symmetrical and assembled together by bolts, nuts and other fasteners. By placing margin profiling, the L-type main pump pipe forging can be effectively profiled. At the same time, after the end is flattened, the combined profiling lower die can be separated by removing the lower die fasteners to quickly and conveniently realize the demoulding of the forging.

[0069] The following is a specific example. For the forging schematic diagram, the length L0≈1800mm and the branch pipe diameter The forging process of the L-shaped ultra-low carbon austenitic stainless steel main pump pipe forging with a 90° angle between the two pipes is as follows:

[0070] Step 1: Prefabricate square billets. Prefabricate square billets with uniform and dense structure, length L1≈1350mm, thickness t1≈550mm and rounded corners through conventional forging methods such as upsetting and drawing, which is billet 1, and the rounded corner R≈50mm. It is required that the deformation of the steel ingot during upsetting is ≥50%, the deformation of each anvil during drawing is ≥15%, and the forging time of each fire (from the start of forging after taking out of the furnace to the end of forging and returning to the furnace) shall not exceed 20 minutes.

[0071] Step 2: Flatten and thicken. Rotate the blank 1 45° clockwise and place it in the assembled lower mold cavity. The cavity diameter Use a 2600mm long, 595mm wide flat-bottomed upper die and align it with the lower die and press down by ≈650mm to form a blank 2 with an upper length L2≈2000mm, a height H2≈1350mm, and a thickness t2≈600mm.

[0072] Step 3: Material separation and profiling. After the flat upper die is pressed down, keep the blank 2 in the profiling lower mold cavity, replace the V-shaped profiling upper die, and the upper mold cavity diameter After the V-shaped upper die and the lower die are aligned, the blank 2 is punched, and the pressing amount is ≈800mm. The transition area of ​​the two branch pipes and the main body of the branch pipe are formed. of blank 3.

[0073] Step 4: Forming the branch pipe ends. After the material is divided and profiled, the upper and lower dies are kept in the closed state, and the core rod with a diameter of ≈600mm is used to limit the movement of the blank. The ends of the two branch pipes of the L-type main pump pipe forging are leveled respectively until the branch pipe length is ≈1800mm. After the forging is completed, it is immediately cooled in water. The transfer time into water is 2 minutes, so that the forging is cooled quickly to avoid coarsening or mixed crystals due to preheating.

[0074] After forging and forming according to the above steps, the L-type ultra-low carbon austenitic stainless steel main pump pipe large forgings are measured and sampled for grain size detection. The L-type main pump pipe forgings with a branch pipe diameter of Φ600mm and a branch pipe length of 1800mm meet the size requirements, and the grain size reaches above level 3. Fig.11 The grain morphology distribution is generally uniform.

[0075] Although one or more embodiments of the present invention are described above, it should be known to those skilled in the art that the present invention can be implemented in any other form without departing from its subject matter and scope. Therefore, the embodiments described above are illustrative rather than restrictive, and many modifications and substitutions are obvious to those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for forging a large L-shaped stainless steel main pump pipe with coordinated control of shape, characterized in that: include: Prepare a tooling auxiliary tool, the tooling auxiliary tool comprises a flat bottom upper die, a contoured lower die, a contoured upper die and a core rod, the contoured lower die has a V-shaped die cavity, and the contoured upper die is V-shaped; Obtain a square billet 1 under the forging conditions that the deformation of the steel ingot during upsetting is ≥50%, the deformation of each anvil during drawing is ≥15%, the forging temperature of each fire is 1150°C to 1240°C, and the forging time does not exceed 20 minutes; The blank 1 is flattened and thickened by using the profiling lower die and the flat-bottom upper die to obtain a blank 2 with a flat surface on one side and right angles on the other side; The blank 2 is punched and formed by using the profiling upper die and the profiling lower die to obtain a blank 3, wherein the blank 3 is used to provide a transition area between two branch pipes and a branch pipe main body; The mold-closing state of the profiling upper die and the profiling lower die is maintained, and the movement of the blank 3 is restricted by the core rod, so that the ends of the two branch pipes are flattened respectively to obtain the L-shaped stainless steel main pump pipe large forging.

2. The method for forging a large L-shaped stainless steel main pump pipe with coordinated control of shape according to claim 1 is characterized in that: The size of the blank 1 is determined based on the following formula: t1=a-(40~60)(2) In the above formula, L1 is the length of blank 1, V 坯料1 is the volume of billet 1, t1 is the thickness of billet 1, a is the diameter of the branch pipe of the large forging of the L-shaped stainless steel main pump, V 锻件 The volume of the large forging for the L-shaped stainless steel main pump.

3. The method for forging a large L-shaped stainless steel main pump pipe with coordinated control of shape according to claim 2 is characterized in that: The method of flattening and thickening the blank 1 by using the profiling lower die and the flat-bottom upper die to obtain a blank 2 with a plane on one side and right angles between two sides on the other side comprises: The blank 1 is rotated 45° clockwise and placed in the die cavity of the profiling lower die, the thickness of the die cavity is the same as the diameter of the forging branch pipe, and the inner arc radius of the profiling lower die is the same as the arc radius of the forging; The flat upper die covering the horizontal length direction of the blank 1 is aligned with the contoured lower die and then pressed down with a pressing amount = H1 / 3 to form a blank 2 with a length of L2, a height of H2, and a thickness of t2, wherein H1 is the length of the diagonal of the blank 1, and t2 = a.

4. The method for forging a large L-shaped stainless steel main pump pipe with coordinated control of shape according to claim 3 is characterized in that: The method of using the profiling upper die and the profiling lower die to stamp the blank 2 to obtain the blank 3 is specifically as follows: Keep the blank 2 in the die cavity of the profiling lower die, replace the profiling upper die, align the profiling upper die with the profiling lower die, and then punch the blank 2, with the pressing amount = H2-a-(60~70), so that the two branch pipe transition areas and the main body of the L-shaped stainless steel main pump connecting pipe large forging are formed.

5. The method for forging a large L-shaped stainless steel main pump pipe with coordinated control of shape according to claim 4 is characterized in that: Also includes: After the two branch pipe ends of the blank 3 are flattened to obtain an L-shaped stainless steel main pump pipe large forging, the L-shaped stainless steel main pump pipe large forging is cooled in water, and the transfer time into water is ≤5min.

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