Closed Forging Method for Improving the Microstructure Uniformity of Disk Forgings

Abstract

The present invention discloses a closed forging method for improving the tissue uniformity of disk-shaped forgings, which includes: designing the size drawing of the rough blank of the forging according to the specification requirements of the finished forging, selecting the forging equipment, choosing bar stock as the raw material, and designing the closed preforming process route; preparing a set of closed preforming dies; forging and forming the rough blank in the set of closed preforming dies through the forging equipment according to the closed preforming process route; and performing die forging on the rough blank to form the finished disk-shaped forging in one heat. By using the closed forging method of the present invention, the forging and forming of the rough blank of the disk-shaped forging is carried out in a closed die, and different structural shapes of dies are selected according to the ratio of the height / diameter of the blank, effectively improving the flaw detection level and the grain size grade of the forging, thereby improving the tissue uniformity of the disk-shaped forging, significantly improving the product qualification rate and quality stability; and significantly reducing the number of forging heats, greatly shortening the production cycle, saving the economic cost, and significantly improving the production efficiency and economic cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of forging, and particularly relates to a closed-die forging method for improving the tissue uniformity of disk forgings. Background Art

[0002] With the continuous development of fields such as machinery, aviation, and aerospace, the requirements for the tissue uniformity of disk forgings are getting higher and higher. The tissue uniformity is mainly characterized by the flaw detection level and the grain size grade. The rough blank of the disk forging largely determines the final tissue uniformity level of the disk forging product. Therefore, disk forgings attach more and more importance to the process design of blank making and the flaw detection tissue uniformity. The conventional forging blank making method for disk forgings with high requirements for tissue uniformity is to repeatedly upset and draw the large deformation in 10 - 15 heating passes within a certain temperature range to achieve the state of refining metal grains and uniform organization. However, during the smelting and solidification process of large-size and large-tonnage metal raw materials, local grain structures are inevitably coarsened and aggregated, and it is very difficult to completely break and refine them during subsequent blooming forging. The grains are not only coarse but also have obvious directionality, which is fatal for disk forgings as rotating workpieces. Therefore, forging manufacturers need to formulate process plans to improve the tissue uniformity of the raw materials after smelting. The existing forging process route uses the matching deformation under different temperature conditions of low-high-low to perform upsetting and drawing forging blank making. After obtaining the ideal rough blank size, machining and flaw detection are carried out. If it is unqualified, it needs to be forged and repaired again and repeat machining and flaw detection until it is qualified. After the rough blank is qualified, die forging is carried out to obtain the disk forging of the required size.

[0003] For disk forgings with high requirements for flaw detection tissue level, using the above traditional forging blank making method not only has a long production cycle, high production cost, and low material utilization rate, but also seriously affects the product qualification rate and the delivery specified node. Therefore, there is an urgent need for a new forging blank making method to improve the tissue uniformity level of disk forgings. Summary of the Invention

[0004] To at least partially solve the technical problems existing in the above-mentioned prior art, the present invention provides a closed-die forging method for improving the tissue uniformity of disk forgings, including the following steps:

[0005] S1) According to the specification requirements of the forging finished product, design the rough blank size drawing of the forging, select a forging equipment with an appropriate tonnage, select a bar stock with a specification of diameter D0 × height H0 as the raw material, and then design a closed-die blank making process route. Among them, the specification requirements of the forging finished product include the shape, size, and weight of the forging finished product, and the closed-die blank making process route includes the forging pass N, the deformation per pass ε, and the heating temperature T per pass;

[0006] S2) Prepare a closed preforming die set, which includes a first die, a second die, and a third die. The first die, the second die, and the third die all include an upper die seat, a lower cushion block, a lower die seat, a lower die, and an upper die punch. Among them, the upper die punch and the lower cushion block of the first die are of flat die structure, the upper die punch and the lower cushion block of the second die are of boss type structure, and the upper die punch and the lower cushion block of the third die are of groove type structure;

[0007] S3) According to the closed preforming process route, forge and form a rough blank in the closed preforming die set by a forging device, specifically including:

[0008] S3.1) If the ratio of the height H0 of the bar stock to the diameter D0 is between 1.0 and 1.7, the number of forging heats N = 1. After heating the bar stock at the heating temperature T, put it into the first die and forge it according to the deformation amount ε to form a rough blank that meets the rough blank size requirements;

[0009] S3.2) If the ratio of the height H0 of the bar stock to the diameter D0 is between 1.8 and 2.5, the number of forging heats N = 2. In the first heat forging, after heating the bar stock at the first heat heating temperature T1, put it into the second die and forge the intermediate blank according to the first heat deformation amount ε1; in the second heat forging, heat the intermediate blank at the second heat heating temperature T2 and then put it into the first die and forge it according to the second heat deformation amount ε2 to form a rough blank that meets the rough blank size requirements;

[0010] S3.3) If the ratio of the height H0 of the bar stock to the diameter D0 > 2.5, the number of forging heats N ≥ 3. In the first heat forging, after heating the bar stock at the first heat heating temperature T1, put it into the second die and forge the first heat intermediate blank according to the first heat deformation amount ε1; in the second heat forging, heat the first heat intermediate blank at the second heat heating temperature T2 and then put it into the third die and forge the second heat intermediate blank according to the second heat deformation amount ε2; then measure the ratio of the height H2 of the second heat intermediate blank to the diameter D2. If the ratio of the height H2 of the second heat intermediate blank to the diameter D2 is between 1.0 and 1.7, perform the third heat forging. In the third heat forging, heat the second heat intermediate blank at the third heat heating temperature T3 and then put it into the first die and forge it according to the third heat deformation amount ε3 to form a rough blank that meets the rough blank size requirements; if the ratio of the height H2 of the second heat intermediate blank to the diameter D2 is between 1.8 and 2.5, perform the third heat forging and the fourth heat forging. In the third heat forging, heat the second heat intermediate blank at the third heat heating temperature T3 and then put it into the second die and forge the third heat intermediate blank according to the third heat deformation amount ε3, and then in the fourth heat forging, heat the third heat intermediate blank at the fourth heat heating temperature T4 and then put it into the first die and forge it according to the fourth heat deformation amount ε4 to form a rough blank that meets the rough blank size requirements; if the ratio of the height H2 of the second heat intermediate blank to the diameter D2 > 2.5, repeat the above process of S3.3 until a rough blank that meets the rough blank size requirements is forged and formed;

[0011] S4) After cooling the rough blank, perform flaw detection. After passing the inspection, perform die forging on the rough blank to form the finished disk-shaped forging in one heat.

[0012] Further, in the closed-die forging method for improving the tissue uniformity of the disk-shaped forging, the material of the disk-shaped forging is alloy structural steel, high-strength structural steel, superalloy or titanium alloy.

[0013] Further, in the closed-die forging method for improving the tissue uniformity of the disk-shaped forging, the materials of the molds in the closed-die preform die set are 5CrNiMoV or 4Cr5MoSiV1.

[0014] Further, in the closed-die forging method for improving the tissue uniformity of the disk-shaped forging, the number of forging heats N is controlled to be at most no more than 6 heats.

[0015] Further, the above-mentioned closed-die forging method for improving the tissue uniformity of the disk-shaped forging further includes preheating the closed-die preform die set and spraying a lubricant in the cavities of the molds in the closed-die preform die set before step S3.

[0016] Preferably, in the above-mentioned closed-die forging method for improving the tissue uniformity of the disk-shaped forging, the preheating temperature of the closed-die preform die set is controlled to be 250°C to 450°C.

[0017] Preferably, in the above-mentioned closed-die forging method for improving the tissue uniformity of the disk-shaped forging, the lubricant is water-based graphite or oil-based graphite.

[0018] Further, in the above-mentioned closed-die forging method for improving the tissue uniformity of the disk-shaped forging, the circumferential clearance between the lower die and the upper die punch in each mold of the closed-die preform die set is controlled to be 0.5 mm to 1.2 mm.

[0019] Further, in the above-mentioned closed-die forging method for improving the tissue uniformity of the disk-shaped forging, when heating the blank before the next heat forging after each heat forging is completed, first pad up the blank and air-cool it for 5 to 10 minutes and then put it into the furnace for heating, so that the temperature difference between the inside and outside of the blank is kept below 200°C.

[0020] Further, in the above-mentioned closed-die forging method for improving the tissue uniformity of the disk-shaped forging, determine the deformation per heat ε and the heating temperature per heat T according to the following method based on the material of the disk-shaped forging:

[0021] For titanium alloy disk-shaped forgings, the die forging heating temperature range is 30°C below the phase transformation point to 50°C below the phase transformation point, and the die forging deformation is controlled within 25% to 35%;

[0022] For superalloy disk-shaped forgings, the die forging heating temperature range is 1000°C to 1150°C, and the die forging deformation is controlled within 20% to 40%;

[0023] For alloy structural steel disk forgings and high-strength structural steel disk forgings, the die forging heating range is 1140°C to 1230°C, and the die forging deformation is controlled within 35% to 50%.

[0024] The closed-die forging method for improving the microstructure uniformity of disk forgings of the present invention has the following advantages and beneficial effects:

[0025] The forging and forming of the blank of the disk forging is carried out in a closed die, and the blank is deformed under the action of triaxial compressive stress. Dies with different structural shapes are selected according to the ratio of the height / diameter of the blank, so that all surfaces of the blank are deformed as evenly as possible, avoiding the phenomena of local grass-like clutter and defective non-conformity during forging inspection and local mixed crystal in the microstructure, thereby effectively improving the forging inspection level and grain size grade, improving the microstructure uniformity of the disk forging, and significantly improving the product qualification rate and quality stability;

[0026] The closed-die forging method of the present invention significantly reduces the number of forging heats, greatly shortens the production cycle, saves economic costs, and significantly improves production efficiency and economic costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only for further understanding of the embodiments of the present invention and constitute a part of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. In the drawings:

[0028] Figure 1 is a schematic structural view of the first die in the closed-die preform die set used in the closed-die forging method for improving the microstructure uniformity of disk forgings of the present invention;

[0029] Figure 2 is a schematic structural view of the second die in the closed-die preform die set used in the closed-die forging method for improving the microstructure uniformity of disk forgings of the present invention;

[0030] Figure 3 is a schematic structural view of the third die in the closed-die preform die set used in the closed-die forging method for improving the microstructure uniformity of disk forgings of the present invention;

[0031] Figure 4 is a schematic view of the dimensions of a compressor titanium alloy disk forging forged using Embodiment 1 of the present invention;

[0032] Figure 5 is a schematic view of the dimensions of a high-temperature alloy turbine guide vane forged using Embodiment 2 of the present invention;

[0033] Figure 6 It is an optimized flaw detection diagram. Among them, (a) is a schematic diagram of partial unqualified flaw detection of a forging forged by using the existing free forging blank making plus die forging forming process, and (b) is a schematic diagram of all qualified flaw detection of a forging forged by using the closed die forging method for improving the tissue uniformity of disk-shaped forgings of the present invention;

[0034] Figure 7 It is a metallographic diagram of a forging. Among them, (a) is the metallographic diagram of a forging forged by using the existing free forging blank making plus die forging forming process, and (b) is the metallographic diagram of a forging forged by using the closed die forging method for improving the tissue uniformity of disk-shaped forgings of the present invention.

[0035] Explanation of reference numerals:

[0036] 1: upper die holder; 2: lower cushion block; 3: lower die holder; 4: lower die; 5: upper die punch. Specific implementation manners

[0037] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0038] The closed die forging method for improving the tissue uniformity of disk-shaped forgings of the present invention includes the following steps:

[0039] S1) According to the specification requirements of the forging finished product, design the size diagram of the forging rough blank, select a forging equipment with an appropriate tonnage, select a bar stock with a specification of diameter D0×height H0 as the raw material, and then design the closed die blank making process route. Among them, the specification requirements of the forging finished product include the shape, size and weight of the forging finished product, and the closed die blank making process route includes the number of forging heats N, the deformation amount ε per heat, and the heating temperature T per heat;

[0040] S2) Prepare a closed die blank making die set. The closed die blank making die set includes a first die, a second die and a third die. The first die, the second die and the third die all include an upper die holder 1, a lower cushion block 2, a lower die holder 3, a lower die 4 and an upper die punch 5. Among them, as Figure 1 shown, the upper die punch 5 and the lower cushion block 2 of the first die are of a flat die structure, as Figure 2 shown, the upper die punch 5 and the lower cushion block 2 of the second die are of a boss type structure, as Figure 3 shown, the upper die punch 5 and the lower cushion block 2 of the third die are of a groove type structure;

[0041] S3) According to the closed preform forging process route, the rough blank is forged and formed within the closed preform forging die set by forging equipment, specifically including:

[0042] S3.1) If the ratio of the height H0 of the bar stock to the diameter D0 is between 1.0 and 1.7, the number of forging heats N = 1. After heating the bar stock at the heating temperature T, it is placed into the first die and forged with a deformation amount ε to form a rough blank that meets the rough blank size requirements.

[0043] S3.2) If the ratio of the height H0 of the bar stock to the diameter D0 is between 1.8 and 2.5, the number of forging heats N = 2. In the first forging heat, after heating the bar stock at the first forging heat temperature T1, it is placed into the second die and forged with a first forging heat deformation amount ε1 to form an intermediate blank. In the second forging heat, the intermediate blank is heated at the second forging heat temperature T2 and then placed into the first die and forged with a second forging heat deformation amount ε2 to form a rough blank that meets the rough blank size requirements.

[0044] S3.3) If the ratio of the height H0 of the bar stock to the diameter D0 > 2.5, the number of forging heats N ≥ 3. In the first forging heat, after heating the bar stock at the first forging heat temperature T1, it is placed into the second die and forged with a first forging heat deformation amount ε1 to form a first forging heat intermediate blank. In the second forging heat, the first forging heat intermediate blank is heated at the second forging heat temperature T2 and then placed into the third die and forged with a second forging heat deformation amount ε2 to form a second forging heat intermediate blank. Then, measure the ratio of the height H2 of the second forging heat intermediate blank to the diameter D2. If the ratio of the height H2 of the second forging heat intermediate blank to the diameter D2 is between 1.0 and 1.7, then perform the third forging heat. In the third forging heat, the second forging heat intermediate blank is heated at the third forging heat temperature T3 and then placed into the first die and forged with a third forging heat deformation amount ε3 to form a rough blank that meets the rough blank size requirements. If the ratio of the height H2 of the second forging heat intermediate blank to the diameter D2 is between 1.8 and 2.5, then perform the third forging heat and the fourth forging heat. In the third forging heat, the second forging heat intermediate blank is heated at the third forging heat temperature T3 and then placed into the second die and forged with a third forging heat deformation amount ε3 to form a third forging heat intermediate blank. Then, in the fourth forging heat, the third forging heat intermediate blank is heated at the fourth forging heat temperature T4 and then placed into the first die and forged with a fourth forging heat deformation amount ε4 to form a rough blank that meets the rough blank size requirements. If the ratio of the height H2 of the second forging heat intermediate blank to the diameter D2 > 2.5, then repeat the above process of S3.3 until a rough blank that meets the rough blank size requirements is forged and formed.

[0045] S4) After cooling the rough blank, perform flaw detection. After passing the inspection, perform die forging on the rough blank, and form the finished disk-shaped forging in one forging heat.

[0046] Furthermore, in the closed forging method for improving the tissue uniformity of the disk-shaped forging of the present invention, the material of the disk-shaped forging can be alloy structural steel, high-strength structural steel, high-temperature alloy steel, or titanium alloy.

[0047] Further, in the closed-die forging method for improving the microstructure uniformity of disk forgings according to the present invention, the materials of the molds in the closed-die preforming die set are made of 5CrNiMoV or 4Cr5MoSiV1.

[0048] Further, in the closed-die forging method for improving the microstructure uniformity of disk forgings according to the present invention, the number of forging heats N is controlled to be at most no more than 6 heats.

[0049] Further, in the closed-die forging method for improving the microstructure uniformity of disk forgings according to the present invention, it also includes preheating the closed-die preforming die set and spraying lubricant in the cavities of the molds in the closed-die preforming die set before step S3.

[0050] Preferably, the preheating temperature of the closed-die preforming die set is controlled to be 250°C to 450°C.

[0051] Preferably, the lubricant is water-based graphite or oil-based graphite, so that the metal flow is smoother.

[0052] Further, in the closed-die forging method for improving the microstructure uniformity of disk forgings according to the present invention, the circumferential gap between the lower die and the upper die punch in each mold of the closed-die preforming die set is controlled to be 0.5 mm to 1.2 mm, so as to effectively prevent the generation of longitudinal burrs.

[0053] Further, in the closed-die forging method for improving the microstructure uniformity of disk forgings according to the present invention, after each heat of forging, observe the external shape quality of the blank. If there are cracks, stop forging to remove the defects and then proceed with the next heat of forging.

[0054] Further, in the closed-die forging method for improving the microstructure uniformity of disk forgings according to the present invention, when heating the blank before the next heat of forging after each heat of forging is completed, first pad up the blank and let it air-cool for 5 to 10 minutes and then put it into the furnace for heating, so that the temperature difference between the inside and outside of the blank is kept below 200°C, thereby making the temperature field difference between the inside and outside of the blank smaller and the overall microstructure more uniform.

[0055] Further, in the closed-die forging method for improving the microstructure uniformity of disk forgings according to the present invention, determine the deformation per heat ε and the heating temperature per heat T according to the following method based on the material of the disk forging:

[0056] For titanium alloy disk forgings, the die forging heating temperature range is 30°C below the phase transformation point to 50°C below the phase transformation point, and the die forging deformation is controlled within 25% to 35%;

[0057] For high-temperature alloy steel disk forgings, the die forging heating temperature range is 1000°C to 1150°C, and the die forging deformation is controlled within 20% to 40%;

[0058] For alloy structural steel disk forgings and high-strength structural steel disk forgings, the die forging heating range is 1140°C to 1230°C, and the die forging deformation is controlled at 35% to 50%.

[0059] The following describes in detail the closed-die forging method for improving the tissue uniformity of disk forgings of the present invention with specific embodiments.

[0060] Example 1

[0061] The closed-die forging method of Example 1 of the present invention is used to forge a titanium alloy disk forging of a compressor. The specifications of the finished forging are φ402.6×226mm, and other dimensions are as Figure 4 shown. The material of the finished forging is TC11, and the flaw detection standard requirement is φ0.8 / -12dB, and it is accepted at AAA level.

[0062] The closed-die forging method for improving the tissue uniformity of disk forgings in Example 1 of the present invention specifically includes the following steps:

[0063] S11) Select a forging equipment with a tonnage of 2500T, select a bar with a specification of φ200×520mm and a weight of 73.5kg as the raw material, and the number of forging heats in the closed-die blanking process is three heats;

[0064] S12) Prepare the first die, the second die, and the third die. Refer to Figure 1 、 Figure 2 and Figure 3 . Each die includes an upper die seat 1, a lower cushion block 2, a lower die seat 3, a lower die 4, and an upper die punch 5. Among them, Figure 1 the upper die punch 5 and the lower cushion block 2 of the first die shown in Figure 2 are of a flat die structure, Figure 3 the upper die punch 5 and the lower cushion block 2 of the second die shown in

[0065] S13) Preheat the closed-die blanking die set, with the die preheating temperature being 350 ± 50 °C. Apply a water-based graphite lubricant with a ratio of 1:4 in the cavities of each die in the closed-die blanking die set, and control the circumferential clearance between the lower die and the upper die punch in each die of the closed-die blanking die set to be between 0.5 mm and 1.2 mm. Then, forge and form a rough blank within the closed-die blanking die set through forging equipment. In a single-pass forging, forge the bar stock into an intermediate blank in the second die. In a two-pass forging, forge the intermediate blank from the single-pass into an intermediate blank for the two-pass. In a three-pass forging, forge the intermediate blank from the two-pass into a rough blank that meets the rough blank size requirements in the first die. Among them, the heating temperature T for each pass is 30 °C below the phase transformation point, the deformation amount ε1 for the single-pass is 30%, the deformation amount ε2 for the two-pass is 35%, and the deformation amount ε3 for the three-pass is 30%. Between the single-pass and the two-pass, and between the two-pass and the three-pass, first pad up the blank and air-cool it for 10 min before reheating it in the furnace;

[0066] S14) Pad up the rough blank after forging and air-cool it. After cooling, perform contact method flaw detection using a 5 MHz probe, with the flaw detection level being φ0.8 / -12 dB and below, meeting the standard requirements;

[0067] S15) Perform die forging on the rough blank to form a finished disk-shaped forging in a single-pass. Among them, the die forging heating temperature is 30 °C below the phase transformation point, and the die forging deformation amount is between 30% and 35%.

[0068] Compared with the existing free forging process for repeatedly producing rough blanks, forging rough blanks using the closed-die forging method for improving the tissue uniformity of disk-shaped forgings in Example 1 of the present invention can reduce about 10 passes, greatly shortening the production cycle, saving economic costs, significantly improving production efficiency and product qualification rate. Moreover, by performing flaw detection on the finished disk-shaped forgings after die forging, it meets the flaw detection requirements of φ0.8 / -12 dB grade, as Figure 6 (b) shows that the pass rate of flaw detection for the closed-die forged rough blanks is as high as 99% for each batch, while there are always individual forgings with local unqualified flaw detection in the products forged by the existing free forging blanking plus die forging forming process, and the clutter is -4 dB to -6 dB, as Figure 6 (a) shows, not meeting the flaw detection requirements of φ0.8 / -12 dB grade.

[0069] Example 2

[0070] The closed-die forging method of Example 2 of the present invention is used to forge a high-temperature alloy turbine guide vane. The specification of the finished forging is φ439 × 159 mm, and other dimensions are as Figure 5 shown. The material of the finished forging is a nickel-based high-temperature alloy GH3044, with the required grain size ≥ 6 grades, and the flaw detection standard requirement is Φ1.2 flat-bottom hole, and acceptance is at AA grade.

[0071] The closed-die forging method for improving the tissue uniformity of disk-shaped forgings in Example 2 of the present invention specifically includes the following steps:

[0072] S21) Select a forging equipment with a tonnage of 10,000T, and select a bar stock with a specification of φ200×410mm and a weight of 106kg as the raw material. In the closed die preforming process, the number of forging heats is two heats;

[0073] S22) Prepare the first die and the second die, see Figure 1 、 Figure 2 , each die includes an upper die holder 1, a lower cushion block 2, a lower die holder 3, a lower die 4 and an upper die punch 5. Among them, Figure 1 the upper die punch 5 and the lower cushion block 2 of the first die shown in Figure 2 are of flat die structure, and the upper die punch 5 and the lower cushion block 2 of the second die shown in

[0074] are of convex platform type structure;

[0075] S23) Preheat the closed die preforming die set. The die preheating temperature is 350±50°C. Apply an oil-based graphite lubricant with a ratio of 1:3 to the cavities of each die in the closed die preforming die set, and control the circumferential clearance between the lower die and the upper die punch of each die in the closed die preforming die set to be between 0.5mm and 1.2mm. Then, use the forging equipment to forge and form a rough blank in the closed die preforming die set. In the first heat forging, forge the bar stock into an intermediate blank for the first heat in the second die. In the second heat forging, forge the intermediate blank for the first heat into a rough blank that meets the rough blank size requirements in the first die. Among them, the heating temperature T for each heat is 1120°C, the deformation amount ε1 for the first heat is 39%, and the deformation amount ε2 for the second heat is 34%;

[0075] S24) Pad up and air-cool the rough blank after forging. After cooling, perform contact method flaw detection using a 5MHZ probe. The flaw detection level is φ1.2 / -12dB and below, meeting the standard requirements;

[0076] S25) Perform die forging on the rough blank, and form the finished product of the disk-shaped forging in one heat of die forging. Among them, the die forging heating temperature is 1110°C, and the die forging deformation amount is between 25% and 30%.

[0077] Compared with the existing free forging and repeated rough blank making process, forging the rough blank using the closed die forging method for improving the tissue uniformity of the disk-shaped forging in Embodiment 2 of the present invention can reduce 3 to 5 heats, greatly shorten the production cycle, save economic costs, significantly improve production efficiency and product qualification rate. Moreover, through metallographic inspection of the finished product of the disk-shaped forging after die forging, the grain size is grade 8. As shown in Figure 7 (b), the tissue uniformity of the disk-shaped forging is good, while the grain size of the product forged by the existing free forging blank making plus die forging forming process is grade 7 mixed with grade 4. As shown in Figure 7 (a), the tissue uniformity of the forging is unqualified.

[0078] In summary, compared with the prior art, the closed-die forging method for improving the microstructure uniformity of disk forgings has the following advantages and beneficial effects: The forging and forming of the blank of the disk forging is carried out in a closed die, and the blank is deformed under the action of triaxial compressive stress. Dies with different structural shapes are selected according to the ratio of the height / diameter of the blank, so that all surfaces of the blank are deformed as uniformly as possible, avoiding the phenomena of local grass-like clutter and defective non-conformity during the flaw detection of the forging and local mixed crystal in the microstructure, thereby effectively improving the flaw detection level and grain size grade of the forging, thus improving the microstructure uniformity of the disk forging, significantly improving the product qualification rate and quality stability; moreover, the closed-die forging method of the present invention significantly reduces the number of forging heats, greatly shortens the production cycle, saves economic costs, and significantly improves the production efficiency and economic costs.

[0079] It should be noted that in this article, unless otherwise clearly specified and defined, the term "connection" or its synonyms should be understood in a broad sense. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Moreover, expressions such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. At the same time, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. In addition, in this article, "front", "rear", "left", "right", "upper" and "lower" are all referenced to the placement state shown in the drawings.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A closed-die forging method for improving the microstructure uniformity of disk forgings, characterized in that, The closed-die forging method includes the following steps: S1) According to the specification requirements of the forged part finished product, design the size drawing of the rough blank of the forged part, select a forging equipment with an appropriate tonnage, select a bar stock with a specification of diameter D0×height H0 as the raw material, and then design the closed-die preforming process route. Among them, the specification requirements of the forged part finished product include the shape, size, and weight of the forged part finished product, and the closed-die preforming process route includes the number of forging heats N, the deformation per heat ε, and the heating temperature per heat T; S2) Prepare a closed-die preforming die set. The closed-die preforming die set includes a first die, a second die, and a third die. The first die, the second die, and the third die all include an upper die seat, a lower cushion block, a lower die seat, a lower die, and an upper die punch. Among them, the upper die punch and the lower cushion block of the first die are flat die structures, the upper die punch and the lower cushion block of the second die are boss-type structures, and the upper die punch and the lower cushion block of the third die are groove-type structures; S3) According to the closed-die preforming process route, forge and form the rough blank in the closed-die preforming die set through forging equipment, specifically including: S3.1) If the ratio of the height H0 of the bar stock to the diameter D0 is between 1.0 and 1.7, then the number of forging heats N = 1. After heating the bar stock according to the heating temperature T, put it into the first die and forge and form a rough blank that meets the rough blank size requirements according to the deformation amount ε; S3.2) If the ratio of the height H0 of the bar stock to the diameter D0 is between 1.8 and 2.5, then the number of forging heats N = 2. In the first forging heat, after heating the bar stock according to the first-forging heating temperature T1, put it into the second die and forge an intermediate blank according to the first-forging deformation amount ε1; in the second forging heat, heat the intermediate blank according to the second-forging heating temperature T2 and then put it into the first die and forge and form a rough blank that meets the rough blank size requirements according to the second-forging deformation amount ε2; S3.3) If the ratio of the height H0 to the diameter D0 of the bar stock > 2.5, then the number of forging heats N ≥ 3. In one heat forging, after heating the bar stock at the one-heat heating temperature T1, it is placed into the second die and forged into an intermediate blank of one heat with a one-heat deformation amount ε1; in the second heat forging, the intermediate blank of one heat is heated at the second-heat heating temperature T2 and then placed into the third die and forged into an intermediate blank of the second heat with a second-heat deformation amount ε2; then, measure the ratio of the height H2 to the diameter D2 of the intermediate blank of the second heat. If the ratio of the height H2 to the diameter D2 of the intermediate blank of the second heat is within 1.0 - 1.7, then perform the third heat forging. In the third heat forging, the intermediate blank of the second heat is heated at the third-heat heating temperature T3 and then placed into the first die and forged into a rough blank that meets the rough blank size requirements with a third-heat deformation amount ε3; if the ratio of the height H2 to the diameter D2 of the intermediate blank of the second heat is within 1.8 - 2.5, then perform the third heat forging and the fourth heat forging. In the third heat forging, the intermediate blank of the second heat is heated at the third-heat heating temperature T3 and then placed into the second die and forged into an intermediate blank of the third heat with a third-heat deformation amount ε3. Then, in the fourth heat forging, the intermediate blank of the third heat is heated at the fourth-heat heating temperature T4 and then placed into the first die and forged into a rough blank that meets the rough blank size requirements with a fourth-heat deformation amount ε4; if the ratio of the height H2 to the diameter D2 of the intermediate blank of the second heat > 2.5, then repeat the process of S3.3 above until a rough blank that meets the rough blank size requirements is forged and formed. S4) After cooling the rough blank, perform flaw detection. After passing the inspection, perform die forging on the rough blank to form a finished disk-shaped forging in one heat.

2. The closed die forging method for improving the microstructure uniformity of disk forgings according to claim 1, characterized in that, The material of the said disk-shaped forging is alloy structural steel, high-strength structural steel, high-temperature alloy steel or titanium alloy.

3. The closed-die forging method for improving the microstructure uniformity of disk forgings according to claim 1, characterized in that, The materials of each die of the said closed-die preforming die set adopt 5CrNiMoV or 4Cr5MoSiV1.

4. The closed-die forging method for improving the microstructure uniformity of disk forgings according to claim 1, characterized in that, The number of forging heats N is controlled to be at most no more than 6 heats.

5. The closed die forging method for improving the tissue uniformity of disk forgings according to claim 1, characterized in that, It also includes preheating the closed-die preforming die set and spraying lubricant in the cavities of each die of the closed-die preforming die set before step S3.

6. The closed die forging method for improving the microstructure uniformity of disk forgings according to claim 5, characterized in that, The preheating temperature of the closed-die preforming die set is controlled at 250°C - 450°C.

7. The closed-die forging method for improving the tissue uniformity of disk forgings according to claim 5, characterized in that The lubricant adopts water-based graphite or oil-based graphite.

8. The closed die forging method for improving the tissue uniformity of disk forgings according to claim 1, characterized in that, The circumferential clearance between the lower die and the upper die punch of each die of the closed-die preforming die set is controlled at 0.5 mm - 1.2 mm.

9. The closed-die forging method for improving the tissue uniformity of disk forgings according to claim 1, wherein, When heating the blank before the next heat forging after each heat forging is completed, first pad up the blank and let it air-cool for 5 - 10 min and then put it into the furnace for heating, so that the temperature difference between the inside and outside of the blank is kept below 200°C.

10. The closed die forging method for improving the microstructure uniformity of disk forgings according to claim 1, characterized in that, Determine the said deformation amount ε of each heat and the heating temperature T of each heat according to the following method based on the material of the disk-shaped forging: For titanium alloy disk-shaped forgings, the die forging heating temperature range is 30°C below the phase transformation point to 50°C below the phase transformation point, and the die forging deformation amount is controlled within 25% - 35%; For high-temperature alloy steel disk-shaped forgings, the die forging heating temperature range is 1000°C - 1150°C, and the die forging deformation amount is controlled within 20% - 40%; For alloy structural steel disk-shaped forgings and high-strength structural steel disk-shaped forgings, the die forging heating range is 1140°C - 1230°C, and the die forging deformation amount is controlled within 35% - 50%.

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