A forging method and forming die for a super-large diameter thin-walled arc-shaped forging with a boss

Abstract

The present invention relates to a forging method and forming die for ultra-large diameter thin-walled arc forgings with bosses, and the method comprises the following steps: (1) a square billet making stage; (2) a square billet transformation into a triangular billet stage; (3) a trapezoidal billet forming stage; and (4) a final forming stage. The advantages are as follows: the present invention solves the difficult problem of forging and forming ultra-large diameter thin-walled arc forgings with bosses, and designs a corresponding forming die. By making square section billets, chamfering, making triangular section billets, pressing trapezoidal section billets, and pressing two isosceles corners of the trapezoid in the final forming stage, the difference in forging rheology between the upper and lower sides of the trapezoidal section billet is used to achieve the bending of the long strip, and finally the desired thin-walled arc forging is formed. The method can obtain a forging with a continuous overall forging texture while ensuring the shape and size of the forging through a series of simple free forging operations, thereby significantly improving the product quality.

Description

Technical Field

[0001] The invention relates to the technical field of forging, in particular to a forging method and a forming die for a super-large diameter thin-walled arc-shaped forging with a boss. Background Art

[0002] Arc-shaped forgings are extra-large equipment forgings with extremely large diameters, with an outer diameter of 11,000mm, a width of nearly 1,500mm, a wall thickness of only 300mm, an arc length of up to 15,000mm, and a full-section boss with an arc length of nearly 1,000mm and a wall thickness of 500mm. They have complex shapes and high requirements for flaw detection and performance. Very few domestic companies can successfully manufacture such forgings.

[0003] Due to the extremely large arc length and diameter, and insufficient forging press opening, traditional free forging companies divide the arc forgings into several sections and weld several thin plates together to form the entire arc forging. This method is easy to forge, but it seriously damages the continuity of the overall forging texture of the part, and has a great impact on the quality and performance of the forging products.

[0004] Chinese patent application: 202110007388.8 discloses a forming method and forming die for arc-shaped forgings with special cross-sections, wherein the forming method for arc-shaped forgings with special cross-sections includes in-die upsetting and blanking, wherein the stainless steel ingot is formed into a forming blank by in-die upsetting; hot extrusion forming, wherein the forming blank is hot extruded to form a rectangular cross-section forging, and the rectangular cross-section forging is taken out and water-cooled, and the hot extrusion ratio is not less than 4; die forming, wherein the water-cooled forging is die-formed at a temperature of 1030-1050°C to form a special-section forging; bending forming, wherein the special-section forging is bent and formed and post-processed in sequence to obtain the arc-shaped forging with special cross-sections. The patent adopts hot extrusion forming to improve the compactness of the forging, and the deformation amount and deformation conditions at each position are consistent. After hot extrusion forming, die forming is performed, which improves material utilization and production efficiency, retains the forging fiber streamline to the greatest extent, and improves the mechanical properties of the forging.

[0005] Chinese patent application: 201310681435.2 discloses a method for accurately controlling the bending curvature of a large arc-shaped forging blank, which cleverly combines free forging and die forging. The forging blank is placed between an upper diaphragm (1) having an arc-shaped boss and a lower die (2) having a cavity with a trapezoidal groove (4). The upper diaphragm (1) is driven by a forging hammer to press down the bending point of the forging blank (2) for bending forging. When the forging blank (2) contacts the lower surface of the trapezoidal groove 4, the bending forging is completed. The height of the short side and the long side of the trapezoidal groove (4) of the lower die (2) is determined according to the required bending curvature and length of the forging blank. The above-mentioned diaphragm is used to realize the bending forming of the arc-shaped forging; the bending curvature size of the large arc-shaped forging blank is accurately controlled, the number of forging fires is reduced, and the stability of the organizational properties of the large forging is improved.

[0006] However, the above-mentioned patented methods are either complicated and costly, or the quality of the products is not high. Therefore, the present invention starts from the shape characteristics of the arc forging, designs special tooling, develops an integral forming forging process, improves the forging rheology of the forging, ensures the forged texture of the product, and improves the quality of the forging product, which not only significantly improves the material utilization rate, but also ensures the continuous forged texture of the forging. There is no report on the forging method and forming die of the ultra-large diameter thin-walled arc forging with a boss of the present invention. Summary of the invention

[0007] The object of the present invention is to provide a forging method and a forming die for a super-large diameter thin-walled arc-shaped forging with a boss in view of the deficiencies in the prior art.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] The present invention provides a forging method for a super-large diameter thin-walled arc-shaped forging with a boss, comprising the following steps:

[0010] (1) Billet making stage: In this stage, the steel ingot is subjected to two large deformation rate overall upsetting and drawing, and then the upper and lower flat anvils are used to draw the stepped billet; it should be noted that in order to facilitate subsequent deformation, the edges and corners of the billet need to be chamfered, and the chamfer angle is preferably 45°, H / 2 ≥ 200mm (H is the billet thickness, and the chamfer of 200mm is based on simulation setting. When it is less than 200, when the triangular cross-section is formed from the flat square, the corners are prone to local deformation and cracking. The billet quality is calculated based on the forging product quality, and the cross-sectional size is set at the same time. The cross-sectional size of the billet is 2000×1000mm and the length is 7000mm), and it is important to control the boss area and the non-boss area The billet has a high concentricity in the length direction, and finally a shape such as Figure 2 Billet shown.

[0011] (2) The stage of transforming the square billet into a triangular billet: the square billet is placed in the special triangular upper and lower molds. The schematic diagram of the mold and the square billet position is shown in the figure. Figure 3 As shown, the square billet is drawn into a triangular billet section by section. Figure 4 The triangular blank shown in the figure has three points that require special attention in the process:

[0012] ① The problem of connecting the anvil when pulling the triangular billet. To ensure the linearity of the billet, the amount of anvil fed each time needs to be ≤2a / 3 (a is the thickness of the triangular mold);

[0013] ② In order to reduce the forming risk of subsequent processes, the triangular billet formed by the step billet and the triangular billet formed by the non-step billet should also maintain a high concentricity in the length direction, and the two triangles should have geometric similarity;

[0014] ③ The cross section of the triangular billet is an isosceles triangle, in which the non-isosceles angle α is 45°, and the corners should be rounded, with a fillet radius R of about 200mm.

[0015] (3) In the trapezoidal billet forming stage, the upper flat anvil is used to press the top angle of the isosceles triangle billet to obtain the following Figure 5 The cross section of the blank shown is an isosceles trapezoid. There are four key points when preparing the trapezoidal blank:

[0016] ① Use a flat anvil to press the cross-section triangle to the height of the trapezoid to obtain a blank with an isosceles trapezoidal cross-section. At this time, due to the rapid forging flow near the upper edge of the trapezoid, the two waistlines of the trapezoid will be locally convex near the upper edge. In order to eliminate the deformation of this area and ensure the isosceles trapezoid, the triangular die in step 2 needs to be used for local trimming;

[0017] ②Height control of the trapezoidal section of the blank, that is, the flat anvil is pressed to a trapezoidal height B4 of about 1200mm;

[0018] ③ The problem of connecting the anvils of the trapezoidal cross-section blanks. To ensure the linearity of the blanks, the amount of anvils fed each time must be ≤2b / 3 (b is the thickness of the flat anvil);

[0019] ④ In order to reduce the forming risk of subsequent processes, the trapezoidal cross-section blank in the step area and the trapezoidal cross-section blank in the non-step area should maintain a high concentricity in the length direction, and the heights of the two trapezoidal cross-sections should be the same.

[0020] (4) Final forming stage, i.e. using a flat anvil to press the two sides of the trapezoidal cross-section blank. The relative positions of the flat anvil and the blank are shown in the figure. Figure 6 As shown in the figure, during rolling deformation, due to the difference in forging flow between the upper and lower end faces of the trapezoid, the forging flow near the bottom edge of the trapezoid is larger, causing the long strip billet with a trapezoidal cross-section to bend in the length direction, and finally realize the formation of an arc forging. There are three key points in this process:

[0021] ① The upper flat anvil and the relative position relationship with the long billet. Considering the influence of the friction resistance between the upper anvil surface and the long billet on the arc deformation of the billet, the upper anvil needs to form a certain angle β with the long billet with a trapezoidal cross section during rolling, 20°≤β≤25°;

[0022] ② Final forming process: rolling along the length direction of the forging blank for 3 times, the first and second rolling reductions are 300mm each, and the third rolling reduction is 270mm. After the measurement meets the arc forging size requirements, the process is completed, thus achieving the overall forming of the thin-walled arc forging ( Figure 7The setting of the reduction here takes into account the forging deformation that can be achieved in each fire. The actual manufacturing can be carried out in three fires, so as to change the trapezoidal cross-section of the straight section into the arc-shaped flat square cross-section. The height of the boss and non-boss is the size requirement of the forging product itself. The triangular mold is a special mold designed to realize the forming from flat square to triangle. The key parameters are the triangle vertex angle α of 45°±3° and the thickness of 1000~1600mm. Other dimensions can be enlarged or reduced. It only needs to wrap the 2000×1000mm flat square to form a triangle with a height of 1500mm.

[0023] ③ For the rolling forming of the step area of ​​the arc forging, first of all, it is necessary to roll one anvil after another from one end of the trapezoidal cross-section blank according to the order of connecting the anvils, and when it reaches the step area, roll the trapezoidal cross-section at the step; when rolling, pay attention to control the contact area between the boss and the upper anvil in the center of the upper anvil to ensure that one anvil completes the current rolling.

[0024] The triangular die mentioned above is a square forging blank obtained by forging a blank, and then prepared by machining.

[0025] The advantages of the present invention are:

[0026] The present invention solves the difficult problem of forging and forming thin-walled arc-shaped forgings with super-large diameter and bosses, and designs corresponding forming dies. By making square-section billets (square billets), chamfering, making triangular-section billets, pressing trapezoidal-section billets, and pressing two isosceles corners of the trapezoid in the final forming stage, the bending of the long strip is achieved through the difference in forging rheology between the upper and lower sides of the trapezoidal-section billet, and finally forming the desired thin-walled arc-shaped forgings. The most obvious technical effect of this method is that through a series of simple free forging operations, on the basis of ensuring the shape and size of the forgings, forgings with continuous overall forging texture can be obtained, which significantly improves product quality.

[0027] The core of the present invention is to solve the manufacturing problem of a super-large diameter thin-walled arc forging with a boss. The biggest difficulty of this forging lies in the arc shape. Because the arc diameter is very large (generally greater than 15000mm), very thin (not exceeding 300mm), and relatively wide (15000-20000mm), it is impossible to directly use stamping to form it, and it also exceeds the working size of a general free forging press. Instead, it is designed to roll the trapezoidal cross-section. Since the forging deformation of the upper and lower bottoms of the trapezoid is different, the deformation of the lower bottom is large, and the forging rheology is large, the straight trapezoid will become an arc. After rolling back and forth 3 times, it basically becomes a semicircle.

[0028] Generally speaking, free forging can easily produce square-section billets, but it is difficult to directly produce trapezoidal-section billets. Therefore, the billet preparation method from square section to triangle and then from triangle to trapezoid is adopted, which can obtain arc forgings while ensuring excellent product performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Attached Figure 1 This is a schematic diagram of the dimensions of a 120-ton electroslag ingot.

[0030] Attached Figure 2 It is a schematic diagram of the dimensions of a square cross-section billet with steps.

[0031] Attached Figure 3 It is a schematic diagram of the relative positions of the triangular cross-section forming die and the square billet.

[0032] Attached Figure 4 It is a schematic diagram of the dimensions of a triangular cross-section billet with steps.

[0033] Attached Figure 5 It is a schematic diagram of the size of an isosceles trapezoidal cross-section billet with steps.

[0034] Attached Figure 6 This is a schematic diagram of the relative positions of the upper anvil, trapezoidal cross-section blank and lower anvil during the final forming stage.

[0035] Attached Figure 7 It is a schematic diagram of the forging after final forming.

[0036] Attached Figure 8 This is a scanning electron microscope image of the grain size of the product of Example 1. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0038] Example 1

[0039] Using a 10,000-ton press, special triangular blank upper and lower dies and upper and lower flat anvils, forging is carried out in different processes to achieve the forming of thin-walled arc forgings. The steps are as follows:

[0040] Step 1: making billets. Figure 1 After the steel ingot has been subjected to two large deformation rate overall upsetting and stretching compaction operations, it is put into the furnace and kept at 1180℃~1220℃ for 20±2h. It is then taken out of the furnace and stretched into a square section of 2000×1000mm with a chamfer of 200mm. Figure 2 The square cross-section step blank is shown.

[0041] Step 2: Place the square-section step billet in the furnace and keep it at 1180℃~1220℃ for 10±2h. Place the square billet in the special triangular upper and lower molds. Press down 200mm per anvil and advance 500mm. Press 3 times until the billet reaches the required height. Figure 4The height of B2 is 1500mm, which can realize the pulling of square billets into triangular billets. Figure 4 shown.

[0042] Step 3: After the triangular section step billet is put into the furnace and kept at 1180℃~1220℃ for 9±2h, the top angle of the isosceles triangle billet is pressed by the upper flat anvil until the trapezoid height B4 is 1200mm, and the following is obtained: Figure 5 The cross section of the blank shown is an isosceles trapezoid.

[0043] Step 4: After the trapezoidal section step billet is put into the furnace and kept at 1180℃~1220℃ for 11±2h, the two sides of the trapezoidal section billet are pressed by a flat anvil. The relative position diagram of the flat anvil and the billet is as follows: Figure 6 As shown; during rolling, the angle β between the upper anvil and the trapezoidal cross-section long billet is 20°, and the billet is rolled three times along the length direction of the forging billet. The first and second rolling amounts are 300mm each, and the third rolling amount is 270mm. When pressing the step area, the center of the anvil in the top view is controlled to be consistent with the center of the boss to ensure that only one anvil is required for each rolling of the boss. After the three rollings are completed, the size of the arc forging is measured to see if it meets the requirements. If it does, the overall forming of the thin-walled arc forging is achieved ( Figure 7 shown).

[0044] Results Figure 8 The product grain size is greater than level 5, and the room temperature yield strength and tensile strength exceed the assessment value by 50%.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the principle of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A forging method for a thin-walled arc-shaped forging with an ultra-large diameter and a boss, characterized in that: The following steps are involved: (1) Billet making stage; (2) Stage of transformation of square billet into triangular billet; (3) Trapezoidal billet forming stage; (4) Final forming stage; Step (1) specifically comprises: firstly, the steel ingot is subjected to two large deformation rate upsetting and elongation processes as a whole, then the upper and lower flat anvils are used to elongate the steel ingot to obtain a stepped square billet, and finally the edges and corners of the stepped square billet are chamfered to obtain a square billet; The chamfer angle is 45°, H / 2≥200mm, where H is the thickness of the stepped square billet, the cross-sectional dimensions of the square billet are 2000mm×1000mm, and the length is 7000mm; Step (2) specifically comprises: placing a square billet between a triangular upper and lower die, and pulling the square billet into a triangular billet section by section, wherein the triangular die is a square forging billet obtained by forging the billet, and then prepared by machining; In the process of pulling the square billet into a triangular billet section by section, the amount of each anvil advance is ≤2a / 3, where a is the thickness of the triangular die; The process of drawing the square billet into a triangular billet in sections also includes rounding the corners, wherein the cross section of the triangular billet is an isosceles triangle, wherein the vertex angle of the isosceles triangle is 42° to 48°, and the height of the triangle is 1500 mm; Step (3) specifically comprises: using an upper flat anvil to press the vertex angle of the isosceles triangle blank to obtain a trapezoidal blank; The height of the trapezoidal blank cross section is 1200mm, the triangle pressing amount is 300mm, and the upper base length of the obtained trapezoid is 300mm; the angle between the two sides of the trapezoid is 42° to 48°, wherein the amount of each anvil feed is ≤2b / 3, and b is the thickness of the flat anvil; Step (4) specifically comprises: using a flat anvil to press the two sides of the trapezoidal cross-section blank to finally form an arc-shaped forging; In the final forming stage, the forging billet is rolled three times along its length, with the reduction amounts being 300mm, 300mm, and 270mm respectively. During rolling, the upper anvil forms an angle β with the trapezoidal cross-section long billet, wherein 20°≤β≤25°.

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