Profile forging method for multi-segment forge piece having special-shaped steps

Abstract

A profile forging method for a multi-segment forge piece having special-shaped steps. The method comprises the following steps: a billet making stage, involving: performing multiple instances of upsetting and drawing-out on raw-material ingots to obtain a forging billet that meets requirements; a die forging billet forming stage, involving: on the basis of the shape of a product, segmenting the forging billet to form multiple segments of plate-shaped billets of unequal heights; a loose tooling forming stage, involving: placing the plate-shaped billets into a loose tooling die, a pressing machine continuously pressing the plate-shaped billets until a die cavity is filled with special-shaped portions of the plate-shaped billets, and then performing demolding to obtain an initial forge piece; and a heat treatment stage, involving: performing overall quenching and tempering heat treatment on the initial forge piece. In the forging method, a forging process combining open-die forging and loose tooling forging is used to form an asymmetric plate-shaped structural forge piece having multiple special-shaped steps, thus improving the material utilization rate and the manufacturing efficiency, reducing the product rejection rate and cutting-machining costs, and achieving higher economic benefits.

Description

A copy forging method for multi-section special-shaped step forgings Technical Field

[0001] The invention relates to the technical field of forging in mechanical manufacturing, in particular to a contour forging method for multi-section special-shaped step forgings. Background Art

[0002] The control rod steering housing is a key functional component of a nuclear reactor. Since the control rod contacts the uranium fuel, it manages the strength of the nuclear reaction flow and is subject to severe loads. Therefore, the manufacturing requirements for the control rod component are very high. The existing forgings used in the manufacture of the reactor control rod steering housing are plate-shaped forgings with multiple steps. The shapes of the steps are inconsistent, and the shapes of the two ends and the upper and lower parts of the forging are asymmetrical, which is quite difficult to forge. Since one end of the forging is a combined structure with an upper disc shape and a lower bar shape, it is impossible to simply and efficiently complete the copy forging of this type of structure using the free forging method. In the past, the manufacturing process difficulty of the forging blank was usually simplified by increasing the forging block and simplifying the forging shape. The forgings obtained are shown in Figure (1). However, due to the increase in the size of the forging, not only the raw material consumption increases, but the forging difficulty also increases further, and the forging scrap rate increases to a certain extent. Summary of the Invention

[0003] In view of the fact that the manufacturing process difficulty of forging blanks is usually simplified by increasing forging blocks and simplifying the forging shape, the present invention provides a contour forging method for multi-stage special-shaped step forgings, which adopts a forging process combining free forging and die forging to form asymmetric plate-shaped structure forgings with multi-stage special-shaped steps, thereby improving material utilization and manufacturing efficiency, reducing product scrap rate and cutting processing costs, and having high economic benefits.

[0004] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0005] A method for forging a multi-section special-shaped step forging, comprising the following steps:

[0006] Blank making stage: The raw ingot is subjected to multiple upsetting and stretching to obtain a forging blank that meets the requirements;

[0007] Die forging blank forming stage: the forging blank is segmented and formed into multiple sections of plate-shaped blanks of different heights according to the product shape;

[0008] Tire mold forming stage: the plate-shaped blank is placed in the tire mold, and the press continuously presses the plate-shaped blank until the irregularly shaped part of the plate-shaped blank fills the mold cavity, and then demolds to obtain the initial forging;

[0009] Heat treatment stage: the initial forging is subjected to overall quenching and tempering heat treatment.

[0010] According to one aspect of the present invention, upsetting and drawing are performed at least twice from the raw material ingot.

[0011] According to one aspect of the present invention, the forging ratio in the billet making stage is ≥3.

[0012] According to one aspect of the present invention, the forging blank is segmented into three sections of plate-shaped blanks with unequal heights according to the shape of the product.

[0013] According to one aspect of the present invention, the quenching temperature of the tempering heat treatment is 935-970°C, and the tempering temperature is 635-680°C.

[0014] According to one aspect of the present invention, the rough forging is subjected to overall quenching and tempering heat treatment and then machined to obtain a finished forging.

[0015] According to one aspect of the present invention, physical and chemical tests are performed before machining to obtain the finished forging.

[0016] According to one aspect of the present invention, the finished forging is inspected, and the inspection includes: UT inspection, MT inspection, PT inspection, and dimensional inspection.

[0017] According to one aspect of the present invention, the tire mold comprises a lower cavity and an upper cavity, the lower cavity is a long strip cavity, and the upper cavity is a disc-shaped cavity.

[0018] According to one aspect of the present invention, when the plate-shaped blank is completely placed in the fetal membrane mold, the protruding end of the plate-shaped blank is aligned with the disc-shaped cavity, and the lower part of the plate-shaped blank is aligned with the elongated cavity.

[0019] Advantages of the present invention: The method for forging multi-segment, special-shaped stepped forgings employs a forging process that combines free forging with die forging. This method features a relatively simple die, high forging efficiency, controllable forging dimensions, and a batch production yield of ≥98%. Compared to conventional forging blanks manufactured using the addition of forging blocks, the weight of the forging blanks manufactured using this method is reduced by approximately 30%, and the machining cycle is reduced by approximately 30%. The pie-shaped structure on the forging is forged in a near-form using die forging, forming uniform and continuous metal fiber streamlines, significantly enhancing the strength of the metal structure. Furthermore, the structure is upset in the disc-shaped cavity of the die mold, significantly improving material compaction and reducing the risk of forging defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] FIG1 is a diagram of a forging blank formed by a conventional free forging process;

[0022] FIG2 is a schematic diagram of the overall processing flow of a contour forging method for a multi-section special-shaped step forging according to the present invention;

[0023] FIG3 is a schematic top view of a multi-section special-shaped step forging according to the present invention;

[0024] FIG4 is a cross-sectional view of FIG3;

[0025] FIG5 is a side view of a multi-section special-shaped step forging according to the present invention;

[0026] FIG6 is a schematic structural diagram of the plate blank according to the present invention;

[0027] FIG7 is a schematic top view of the fetal membrane mold according to the present invention;

[0028] FIG8 is a cross-sectional view of FIG7;

[0029] FIG9 is a side view of a fetal membrane mold according to the present invention;

[0030] FIG10 is a front view of the rough forging according to the present invention;

[0031] FIG11 is a top view of the rough forging according to the present invention;

[0032] FIG12 is a left side view of the preliminary forging according to the present invention;

[0033] FIG13 is a heat treatment process curve diagram. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] As shown in Figures 2 to 13, a method for profiling a multi-section special-shaped step forging includes the following steps:

[0036] Billet making stage: billeting of steel ingots, upsetting and stretching of billets as required to ensure the forging ratio is ≥3, and forging the billets to the die forging billet size according to the product shape and overall forging plan;

[0037] Die forging blank forming stage: the forging blank is divided into sections and formed into plate-shaped blanks of different heights according to the product shape;

[0038] Tire mold forming stage: the plate-shaped blank is placed in the tire mold, and the press continuously presses the plate-shaped blank until the irregularly shaped part of the plate-shaped blank fills the mold cavity, and then demolds to obtain the initial forging;

[0039] Heat treatment stage: the initial forging is subjected to overall quenching and tempering heat treatment.

[0040] In practical applications, pre-heat treatment surface machining is required before heat treatment of the rough forging to remove scale and minor surface defects that can easily cause cracks. The rough forging then undergoes an overall quenching and tempering heat treatment to improve the material's overall performance. Furthermore, after this overall quenching and tempering heat treatment, the rough forging is machined to produce a finished forging. This finished forging has a pie-shaped upper portion and a long, asymmetrical lower portion.

[0041] In practice, before machining heat-treated forgings to obtain finished forgings, physical and chemical testing is required to verify that all material performance indicators meet acceptance requirements. After passing these tests, the finished forgings are processed according to dimensions and undergo necessary inspections based on technical requirements. Once these inspections are complete, the finished forgings are cleaned and packaged. These inspections include UT, MT, PT, and appearance and dimensional inspections.

[0042] In actual application, the specific process flow includes the following: 1. Forging; 2. Hydrogen expansion after forging; 3. Processing before heat treatment; 4. Performance heat treatment; 5. Sample cutting (samples can be added to simulate the heat treatment process); 6. Sample processing; 7. Physical and chemical testing; 8. Rough processing; 9. UT testing; 10. Finishing; 11. Dimension inspection; 12. Surface quality inspection; 13. MT inspection; 14. PT supplementary testing.

[0043] Example 1: A method for profiling multi-stage special-shaped step forgings

[0044] Step S1: Raw material selection

[0045] Purchase steel ingots from outside. When purchasing steel ingots, the raw material smelting process and chemical element requirements must be clearly defined to ensure the comprehensive performance of the steel ingot materials.

[0046] Step S2: Forging

[0047] According to the requirements of near-form forging of products, combined with finite element simulation technology, the overall plan and process of forging are designed and verified.

[0048] Billet making stage: The steel ingot is billeted, and the billet is upset twice and stretched twice as required to ensure that the forging ratio is ≥3. The billet is forged to the die forging billet size according to the product shape and the overall forging plan;

[0049] Die forging billet forming stage: Divide the forging billet into three sections of plate-shaped billets of different heights according to the product shape. At the same time, one end of the product should be appropriately lengthened as a test material.

[0050] Tire mold forming stage: The tire mold is designed and manufactured according to the forging forming plan and the size of the forging blank. The tire mold includes a lower cavity and an upper cavity. The lower cavity is a long strip cavity 2, and the upper cavity is a disc-shaped cavity 1. The other end is an open structure. In this way, the tire mold uses less material, and the bottom width of the tire mold is slightly larger than the width of the blank. The overall width is wide at the top and narrow at the bottom, which makes it easier to demold. During use, align the protruding end of the plate-shaped blank with the end of the tire mold with the disc-shaped cavity 1, and align the lower part of the plate-shaped blank with the long strip cavity 2 of the tire mold. After the plate-shaped blank is completely placed in the tire mold, operate the flat anvil on the press to continuously press the blank down until the protruding part of the blank fills the disc-shaped cavity of the mold, and then demold it to obtain a preliminary forging.

[0051] Step S3: Heat treatment

[0052] Before heat treatment, the surface is machined to remove scale and surface defects. The initial forgings then undergo overall quenching and tempering heat treatment, with a quenching temperature of 935-970°C, followed by water cooling to room temperature after holding for at least 1 hour / 100 mm, and a tempering temperature of 635-680°C, followed by holding for at least 1 hour / 50 mm, and cooling to room temperature. Due to the stringent performance requirements for finished forgings, multiple simulation tests of production conditions were conducted in the laboratory to verify and ultimately determine the optimal process parameters. Contact thermocouples are also used to strictly control the surface temperature of the forgings during heat treatment to ensure uniform microstructure after heat treatment.

[0053] Step S4: physical and chemical testing

[0054] After heat treatment, samples were cut to conduct necessary mechanical property tests. The test results are shown in Table 1:

[0055] Table 1

[0056]

[0057] It can be seen that all performance indicators meet the acceptance requirements.

[0058] Step S5: Machining

[0059] During the machining process of the finished product, gantry milling machines, CNC machine tools, vertical drilling and boring machines are used to ensure that the dimensional accuracy and finish meet the requirements.

[0060] Step S6: Finished product inspection

[0061] After machining, the finished product undergoes necessary inspections according to technical requirements. Once all defects are verified, it is cleaned and packaged. Specifically, these inspections include UT, MT, PT, and appearance and dimensional inspections. The batch production yield rate is ≥98%. Furthermore, compared to conventional forging blanks manufactured with additional forging blocks, the weight of the forging blanks produced using this method is approximately 30% less.

[0062] It can be seen that the multi-segment special-shaped step forgings manufactured using this method meet the tensile strength requirements at both room temperature and 350°C, while also meeting the impact toughness requirements and satisfying quality requirements. Inspections have shown that the batch production yield rate is ≥98%. Compared to traditional forging structures manufactured by adding forging blocks, the forgings manufactured using this method are approximately 30% lighter, improving material utilization and manufacturing efficiency, reducing product scrap rates and cutting costs, and achieving high economic benefits.

[0063] Advantages of the present invention: The method for forging multi-segment, special-shaped stepped forgings employs a forging process that combines free forging with die forging. This method features a relatively simple die, high forging efficiency, controllable forging dimensions, and a batch production yield of ≥98%. Compared to conventional forging blanks manufactured using the addition of forging blocks, the weight of the forging blanks manufactured using this method is reduced by approximately 30%, and the machining cycle is reduced by approximately 30%. The pie-shaped structure on the forging is forged in a near-form using die forging, forming uniform and continuous metal fiber streamlines, significantly enhancing the strength of the metal structure. Furthermore, the structure is upset in the disc-shaped cavity of the die mold, significantly improving material compaction and reducing the risk of forging defects.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for profiling a multi-stage special-shaped step forging, characterized in that: The steps include: Billet making stage: the raw ingot is subjected to multiple upsetting and stretching to obtain a forging billet that meets the requirements; Die forging blank forming stage: the forging blank is formed into multiple sections of plate-shaped blanks of different heights according to the product shape; Tire mold forming stage: the plate-shaped blank is placed in a tire mold, and the press machine continuously presses the plate-shaped blank until the irregularly shaped part of the plate-shaped blank fills the mold cavity, and then demolds to obtain a preliminary forging; Heat treatment stage: the initial forging is subjected to overall tempering heat treatment.

2. The method for profiling a multi-stage special-shaped step forging according to claim 1, characterized in that: The raw ingot is roughened and stretched at least twice.

3. The method for profiling a multi-stage special-shaped step forging according to claim 1, characterized in that: The forging ratio in the billet making stage is ≥3.

4. The method for forging a multi-stage special-shaped step forging according to claim 1, characterized in that: The forging blank is formed into three sections of plate-shaped blanks with different heights according to the shape of the product.

5. The method for profiling a multi-stage special-shaped step forging according to claim 1, characterized in that: The quenching temperature of the quenching and tempering heat treatment is 935-970°C, and the tempering temperature is 635-680°C.

6. The method for profiling a multi-stage special-shaped step forging according to claim 1, characterized in that: The rough forging is subjected to overall tempering heat treatment and then machined to obtain a finished forging.

7. The method for profiling a multi-stage special-shaped step forging according to claim 6, characterized in that: Before machining to obtain the finished forgings, physical and chemical tests are required.

8. The method for profiling a multi-stage special-shaped step forging according to claim 6, characterized in that: The finished forgings are inspected, and the inspection includes: UT inspection, MT inspection, PT inspection, and dimension inspection.

9. A method for profiling a multi-stage special-shaped step forging according to any one of claims 1 to 8, characterized in that: The tire mold comprises a lower cavity and an upper cavity, wherein the lower cavity is a long strip cavity and the upper cavity is a disc-shaped cavity.

10. The method for profiling a multi-stage special-shaped step forging according to claim 9, characterized in that: When the plate-shaped blank is placed in the fetal membrane mold, the protruding end of the plate-shaped blank is aligned with the disc-shaped cavity, and the lower part of the plate-shaped blank is aligned with the elongated cavity.

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