Two-heat forming forging process of large crankshaft

Abstract

A two-heat forming forging process for large crank throws is provided. A forging machine, an anvil mold, and an operating device are used. In the first heat, the shape and parameters of a forged preform having a protrusion base and two web bodies are set, and multiple upsetting and stretching processes are used to complete the forging of the preform. In the second heat, the shape and parameters of the intermediate forging in multiple processes are set, and a forging press that repeatedly rotates and moves left and right at different angles and repeatedly replaces the anvil mold is used, and repeated pressing and bending is performed using a covered bending mold with an arc-shaped pressing surface, and multiple compressions are performed using multiple core molds, so that the forging is gradually formed, and the forming forging of the crank throw is achieved. The present disclosure provides a forging process that accomplishes shape forging and bend forging of crank throw forgings with a relatively small force and a relatively short forging press distance, and realizes the forging of relatively large crank throw forgings by a forging machine with a relatively small pressure, and the process has the characteristics of a large forging ratio, good forming degree, short forging time, low material consumption, and low production cost.

Description

Technical Field

[0001] The present disclosure relates to crankshaft forgings, particularly to the two-heat forming forging process of large crankshafts, and belongs to the field of forging technology. In particular, the present disclosure relates to assembled crankshaft forging preforms, and particularly to the forging process of large assembled crankshaft preforms. Further, the present disclosure further relates to the forging of large crankshafts, particularly to the forging process of the journal part of large crankshafts. Also, the present disclosure relates to the forming forging process of crankshafts.

[0002] (Cross-reference to Related Applications) The present disclosure claims priority based on a Chinese application filed with the China National Intellectual Property Administration on January 20, 2022, with application number 202210066376.7 and title "Two-heat Forming Forging Process of Large Crankshafts", a Chinese application filed with the China National Intellectual Property Administration on January 20, 2022, with application number 202210065615.7 and title "Forging Process of Crankshaft Preform", a Chinese application filed with the China National Intellectual Property Administration on January 20, 2022, with application number 202210065671.0 and title "Forging Process of Journal of Large Crankshaft", and a Chinese application filed with the China National Intellectual Property Administration on January 20, 2022, with application number 202210066077.3 and title "Forming Forging Process of Crankshaft", and all of its content is incorporated herein by reference.

Background Art

[0003] The crankshaft is a major component used for converting the rotational motion and reciprocating motion of a machine, and the crank throw is an important element of the crankshaft. The crankshaft functions to convert the rotational motion and reciprocating motion of the machine. Since the crank throw of a large crankshaft is subject to large and complex forces, sufficient rigidity, strength, and impact load resistance are required. To meet the above performance requirements, it is common to select a forging as the crank throw of a large assembled crankshaft. The production process of the forged crank throw is relatively complex, requiring multiple processes, multiple heats, and multiple exchanges of anvil types. The journal is the part of the crank throw that connects to the connecting rod. The forging process is the most complex, and at one end of both webs of the crank throw, a columnar forging material close to the net shape of the journal is forged by integral forging.

[0004] Commonly used forging processes include the full mold forging method, die forging method, and bending forging method. The die forging method requires a forging machine of tens of thousands of tons and expensive dies, and the quality of the forgings is not ideal. The bending forging method has good metal flow and forming, is easy to operate, and does not have high requirements for equipment, but has a large number of heats, increased material consumption and energy consumption, and even the most advanced manufacturers at home and abroad need 5 - 7 heats to complete forging, and the cold processing allowance of the forgings is very large. The conventional methods for forging the crank throw are die forging and open die forging. In the case of these two methods, not only are the production costs high and the production efficiency low, but also a forging machine of over ten thousand tons and expensive dies are required, and the yield of the forgings is very low, unable to meet the requirements of the forging ratio, the crystal grains of the internal structure of the forgings are coarse, the quality is insufficient, and furthermore, there are defects such as chipping and folding of the forgings.

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a result of performing simulation calculations and scientific analyses on the above problems, the inventor found that the forging process of the conventional crankshaft has the drawbacks that the forging process is rather old-fashioned, the mold installation is not reasonable, and furthermore, the anvil type replacement method is not scientific. Therefore, it is necessary to scientifically design and improve the forging process.

Means for Solving the Problems

[0006] The present disclosure devised a two-heat forming forging process for a large crankshaft. The two-heat forming forging process for a large crankshaft sets the shape and parameters of a two-web body having a raised base in the first heat, and sets the shape, parameters, and bending parameters of the intermediate state of the two webs and journals in the second heat, and utilizes a die forging process to achieve the purpose of forging a large crankshaft forging with two heats.

[0007] Specifically, the present disclosure provides a forging process for crankshaft reform, sets the shape and parameters of the crankshaft reform, installs an anvil type that automatically exchanges, and utilizes a forging process that repeatedly performs installation and stretching to complete forging in one hit. The present disclosure provides a forging process for the journal of a large crankshaft, uses a plurality of different special anvil types, repeatedly performs forging presses on the forging multiple times and at multiple angles by changing the anvil type multiple times to gradually form the journal part. As a result, the cold working allowance of the journal part is the smallest and the forging process is the fastest. The present disclosure provides a forming forging process for a crankshaft according to the present disclosure, sets the shape and parameters of the forging, and achieves forming of the journal, forming by process, bending, crimping, and finish forging in one hit, realizing the purpose of reducing the number of hits and increasing the forging ratio.

[0008] The present disclosure provides the following technical solutions. A two-heat forming forging process of a large crankshaft, which utilizes a forging machine, an anvil die, and operating equipment. The anvil die includes an upper anvil, a lower die, a core die, and an upper die. The lower die includes a small flat anvil, a large flat anvil, a double-edge press groove die, a convex die, a trapezoidal die, and a concave die. The upper die includes a mounting processing plate, an exchange anvil die, and a covering bending die. The operating equipment includes a workbench and a manipulator. The workbench includes a horizontal workbench and a vertical workbench. The manipulator includes a first manipulator and a second manipulator. The upper anvil is connected to the forging machine. The convex die and the double-edge press groove die respectively form a fixed hinge with the large flat anvil. The exchange anvil die includes a concave exchange anvil die and an arc-shaped exchange anvil die. There are a plurality of core dies, and different core dies have different differences in thickness at both ends. The lower die is arranged on the horizontal workbench and is movable together with the horizontal workbench. The first manipulator is configured to clamp the forging. The second manipulator is configured to clamp the core die or the upper die. The two-heat forming forging process of the large crankshaft includes the following steps: First heat: Forge a preform having a two-web body with a protrusion platform in the middle. The two-web body is set to have a length of L, a width of b, and a height of h1. If the protrusion platform has a height of h2 and a width of b, the total height of the preform: h = h1 + h2. Step 1: Select a billet according to the weight requirement of the crankshaft forging, and heat it to a predetermined forging temperature. Step 2: Place the billet heated in Step 1 between the upper anvil and the small flat anvil to stretch the billet. Step 3: Stand the forging stretched in Step 2 on the vertical workbench, clamp the mounting processing plate with the second manipulator, and place it between the forging and the upper anvil, and mount the forging to 1 / 2 of its original length. Step 4: Stretch the forging mounted in Step 3 to have a cross-section of (3b / 4) × (3b / 4). Step 5: Stand the forging stretched in Step 4 on the vertical workbench, place the forging at 1 / 2 of its original length, Step 6: Stretch the forging placed in Step 5 to have a cross-section of b×b, Step 7: Place the middle part of the forging in Step 6 above the double-edge press groove type, and forge left and right grooves that are parallel below the forging, Step 8: Flip the forging with left and right grooves in Step 7 upside down by 180°, place it on the flat anvil and forge it. Forge it into two web bodies with a width of b, a height of h1, and a length of L corresponding to the left part of the left groove and the right part of the right groove, and forge the part between the left groove and the right groove into a protruding platform with a height of h2 and a width of b, thereby manufacturing a two-web body preform. Second heat: Forging Set the transition shape, parameters, and bending parameters of the two-web body and the journal, 1. Forging of the journal Step 9: Heat the forging in Step 8 to the forging temperature, Step 10: Place the heated preform on the flat anvil, press and stretch the two webs thinly to finish the forging to the predetermined dimensions, Step 11: Clamp the preform with the first manipulator, place the middle part of the preform in Step 10 above the convex type, repeatedly invert it by 180° and forge it, forge it while moving left and right, change the position multiple times and forge it to rough forge the two sides of the journal, Step 12: Place the preform in Step 11 in a trapezoidal mold with the protruding platform facing up, clamp the concave exchange anvil mold with the second manipulator and place it on the preform, and rough forge the lower surface of the journal on the bottom surface of the two-web body facing the protruding platform, Step 13: Place the two sides and the lower surface of the journal in Step 11 and Step 12 on the convex type, repeatedly invert it, move left and right to alternately forge the two sides, the lower surface and the connection part of the journal, and forge it to be close to the journal shape, Step 14: Place the journal of the preform in Step 13 in a concave shape, repeatedly invert it to change the angle of the forging press, use the upper anvil to press down the head part of the protruding base, so that the head part of the protruding base is formed as the upper surface of a polygonal journal by the forging press, and the two side surfaces and the lower surface of the journal are formed as semi-cylindrical bodies by the forging press. Step 15: Arrange the journals forged in Step 14 alternately in convex and concave shapes, use an uneven anvil and an arc-shaped exchange anvil die as the upper anvil, forge the journals at multiple angles, and forge the cylindrical material of the journals. 2. Bending Step 16: Place the lower surface of the cylindrical journal in a concave shape, use the second manipulator to clamp the covering and bending die and cover and arrange it on the upper surfaces of the two webs of the two-web body, press it down with the upper anvil, and the preform is bent to a predetermined angle to form a "herringbone" shape. 3. Press Fitting Step 17: Place the "herringbone" preform on a large flat anvil, use the second manipulator to insert the core die with the largest difference in thickness at both ends into the opening of the preform, press it down with the upper anvil, press fit the two legs of the "herringbone" shape, make the two legs of the preform approach each other, turn it upside down and press and forge it so that the two legs of the preform contact the core die. Step 18: Exchange the core dies in the order of the largest difference in thickness at both ends, repeat the operation in Step 17, make the two webs of the two-web body contact the core die, turn the preform upside down and perform forging, and finish forging the outside of the two-web body to forge the crank handle of the crank throw. 4. Stretching the Head Part Step 19: Synchronously rotate the core die and the preform in a press-fitted state and place them on a large flat anvil, forge the head part of the protruding base, and stretch it to form a crank throw head part in the shape of a frustum of a square pyramid. 5. Finishing Step 20: Place the preform in Step 19 on a large flat anvil or a small flat anvil, and finish the crank throw to the predetermined dimensions of the finished product.

[0009] Preferably, the first manipulator is a left manipulator, and the second manipulator is a right manipulator.

[0010] Preferably, in step 2, the billet is stretched to 1.2 to 1.7 times its original length.

[0011] Preferably, in step 3, the rectangular forging is placed at 1 / 2 ± 20% of its original length.

[0012] Preferably, in step 4, the forging is stretched into a rectangular material with a cross-section of 3b / 4(1 ± 5%) × 3b / 4(1 ± 5%).

[0013] Preferably, in step 5, the forging is placed at 1 / 2 ± 10% of its original length.

[0014] Preferably, in step 6, the forging is stretched into one with a cross-section of b(1 + 0 to 5%) × b(1 + 0 to 5%).

[0015] Preferably, the convex shape is an arc shape.

[0016] Preferably, the diameter of the journal preform in the vertical direction is the diameter of the finished product ± 5%.

[0017] Preferably, the concave surface of the concave replacement anvil type is configured to mesh with the convex surface of the preform.

Advantages of the Invention

[0018] In the present disclosure, in the first heat treatment, the shape and parameters of a forging preform having a raised base and two web bodies are set, and a plurality of upsetting and stretching processes are utilized to complete the forging of the preform. In the second heat treatment, the shape and parameters of the forged workpiece in an intermediate state in a plurality of processes are set, and a forging press that rotates repeatedly with a changed angle and moves left and right, and a forging press that repeatedly exchanges an anvil type are utilized. Rotational pressing and bending are performed using a covering and bending die having an arcuate pressing surface, and multiple core dies are used to perform multiple press fittings, gradually forming the forged workpiece and achieving the forming forging of the crankshaft.

[0019] The forging process of the crankshaft preform according to the present disclosure utilizes a plurality of upsetting and stretching processes to increase the forging ratio, improve the internal quality of the forged workpiece, gradually form the forged workpiece, and can complete the forging of the crankshaft preform in one hit, achieving the purpose of the simplest forging process, the least material loss, and the lowest production cost.

[0020] The forging process of the journal of a large crankshaft according to the present disclosure uses a plurality of different special anvil types, repeatedly rotates with a changed angle and moves left and right for forging pressing, and repeatedly exchanges different anvil types for forging pressing to gradually form the journal. The forming degree of the journal material is good, the processing allowance is small, the forging time is short, the material consumption is small, and the purpose of low production cost can be achieved.

[0021] The forming forging process of the crankshaft according to the present disclosure uses multiple different special anvil dies, moves left and right, rotates repeatedly to change the angle, performs forging presses, repeatedly performs forging presses with different anvil dies, and gradually forms the journal. By installing a covering bending die between the forging and the upper anvil, not only can the quick replacement of the anvil die be realized, but also by using the arc-shaped pressing surface of the bending die, a rolling press is formed between the two-web body of the forging and the die during the bending process, continuously bending the crankshaft forging with a relatively small pressing force and a relatively short pressing distance, and realizing the bending of a relatively large crankshaft forging with a forging machine with a relatively small pressure, and achieving forging forming in one hit.

[0022] The present disclosure provides a forging process that achieves the forming forging and bending forging of a crankshaft forging with a relatively small force and a relatively short forging press distance, and realizes the forging of a relatively large crankshaft forging with a forging machine with a relatively small pressure. The present invention has the characteristics of a large forging ratio, good forming degree, less processing allowance, short forging time, less material consumption, and low production cost.

Brief Description of the Drawings

[0023]

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Embodiments for Carrying Out the Invention

[0024] Hereinafter, the present disclosure will be further described with reference to the drawings.

[0025] Forging in the First Heat First, place the billet in a heating furnace and heat it to the forging temperature. Use a 16-ton billet as the billet.

[0026] As shown in FIGS. 1 and 2, the forged product 4 after heating is clamped by the first manipulator 2 and placed between the upper anvil 1 and the small flat anvil 3. The length and cross-section of the forged product 4 satisfy the aspect ratio requirements. Preferably, the forged product 4 is stretched to 1.5 times its original length.

[0027] As shown in FIGS. 3 and 4, the stretched forged product 4 is erected on a vertical workbench. The positioning and processing plate 5 is clamped by the second manipulator 2' and placed between the forged product and the upper anvil 1, and the forged product 4 is positioned to half of its original length.

[0028] As shown in FIGS. 5 and 6, the forged product 4 is placed on the small flat anvil 3, and the forged product 4 is stretched so that the cross-section becomes (3b / 4)×(3b / 4). Preferably, the forged product 4 is placed on the small flat anvil 3 and stretched to a forged product 4 with a cross-section of 900 mm×900 mm and a length of 2500 mm.

[0029] As shown in FIGS. 7 and 8, repeat the operations of FIGS. 3 and 4 to position the forged product 4 to half of its original length. Preferably, the forged product 4 is placed on the small flat anvil 3 and positioned to a length of 1250 mm.

[0030] As shown in FIGS. 9 and 10, repeat the operations of FIGS. 5 and 6 to stretch the forged product 4 to a cross-section of b×b. Preferably, the forged product 4 is stretched by the upper anvil 1 and the small flat anvil 3 to a cross-section of 1200 mm×1200 mm and a length of 1400 mm.

[0031] As shown in FIG. 11, the middle part of the forged product 4 is placed above the double-edge press groove type 6, and parallel left and right grooves are forged at the lower part of the forged product 4. Preferably, use the double-edge press groove type 11 instead of the lower anvil, and forge parallel left and right grooves below the material 11.

[0032] As shown in FIGS. 12 and 13, the forging 4 having a left groove and a right groove is inverted 180° vertically and placed on the flat anvil 8, and forged so that the left part of the left groove and the right part of the right groove are formed into two webs with a width of b, a height of h1, and a length of L, and the part between the left groove and the right groove is forged into a protruding platform with a height of h2 and a width of b, thereby manufacturing a two-web preform 7.

[0033] FIGS. 14 and 15 are a front view and a plan view of the preform, respectively.

[0034] Second heat forging The second heat forging is performed based on the preform obtained in the first heat forging, and the shape of the preform is a two-web body having a protruding platform.

[0035] The preform is heated again to the forging temperature.

[0036] As shown in FIG. 16, the heated preform 7 is placed on the flat anvil 8 and pressed by the upper anvil 1 to thinly press and stretch the two webs to finish to a predetermined dimension.

[0037] As shown in FIGS. 17 to 19, the preform 7 is clamped by the first manipulator 2 and the middle part of the preform 7 is placed above the convex die 9, and the preform 7 is repeatedly inverted 180° and forged, forged while moving left and right, and forged by changing the position a plurality of times to rough forge the two side surfaces of the journal.

[0038] As shown in FIGS. 20 and 21, the preform 7 is placed in the trapezoidal die 11 with the protruding platform facing upward, and the concave interchangeable anvil die 10 is clamped by the second manipulator 2' and placed on the preform 7 to rough forge the lower surface of the journal at the bottom surface of the two-web body facing the protruding platform.

[0039] As shown in FIGS. 22 and 23, place two side surfaces and the lower surface of the journal on the convex mold 9, clamp the preform 7 with the second manipulator 2' and repeatedly invert it, move it left and right to alternately forge the two side surfaces, the lower surface and the connecting part of the journal, and forge the two side surfaces, the lower surface and the connecting part of the journal to be close to the journal shape. Preferably, at the same time, forge and press with the upper anvil 1 to make the protruding platform polygonal.

[0040] As shown in FIG. 24, place the journal in the preform 7 on the concave mold 12, repeatedly invert the preform 7 with the second manipulator 2' to change the angle of the forging press, press down the head part of the protruding platform with the upper anvil, and forge and press to form the head part of the protruding platform as the upper surface of the polygonal journal. Forge and press to form the two side surfaces and the lower surface of the journal as semi-cylindrical bodies.

[0041] As shown in FIGS. 25 to 30, place the journal between the upper anvil 1 and the convex mold 9, between the upper anvil 1 and the concave mold 12, between the arc-shaped exchange anvil mold 13 and the convex mold 9, and between the arc-shaped exchange anvil mold 13 and the concave mold 12, and forge the journal at multiple angles to forge it into a cylindrical journal.

[0042] As shown in FIGS. 31 and 32, place the lower surface of the journal on the concave mold 12, clamp the covering and bending mold 14 with the second manipulator 2' and place it on the upper surfaces of the two webs of the two-web body, press it down with the upper anvil 1, and bend the preform 7 to a predetermined angle to form a "herringbone" shape.

[0043] As shown in FIGS. 33 and 34, place the preform 7 horizontally on the flat anvil 8 with the second manipulator 2', insert the core mold 15 with the largest difference in thickness at both ends into the opening of the preform 7 with the first manipulator 2, press the two webs together, turn it upside down and further forge and press the two webs so that the two webs are in contact with the core mold.

[0044] As shown in Fig. 35, the core die 15 is replaced by the first manipulator 2 in the order of the largest difference in thickness at both ends, and the operations in Figs. 33 and 34 are repeated so that the two webs further contact the core die, the forging is performed by inverting the forging workpiece, and the outer side of the two-web body is finish-forged to forge the crank handle of the crankshaft. Preferably, the forging is performed so as to form two parallel crank handles.

[0045] As shown in Fig. 36, the core die 15 and the preform 7 are rotated in a press-fitted state, and the head portion of the boss is placed on the flat anvil 8 for forging. The preform 7 in the state of Fig. 36 is rotated by 90° to be as shown in Fig. 37, and further forging is performed on the upper end portion of the journal and stretched to form a crankshaft head portion in the shape of a frustum of a square pyramid.

[0046] As shown in Fig. 38, the preform 7 is placed on the flat anvil 8 to finish the crank handle. Alternatively, the preform 7 is placed on the small flat anvil 3 to finish the crank handle. As shown in Fig. 39, the core die 15 and the preform 7 are inverted in a press-fitted state to finish the side surface of the crank handle.

[0047] As shown in Fig. 40, the preform 7 is rotated, the crank handle is placed on the flat anvil 8, and finish-forging is performed on the crankshaft until it reaches a predetermined dimension. Alternatively, the preform 7 is rotated, the crank handle is placed on the small flat anvil 3, and finish-finishing forging is performed on the crankshaft until it reaches a predetermined dimension. As shown in Fig. 41, the forging workpiece is rotated by 90°, the side surface of the crank handle is finished, and the forging of the crankshaft is completed.

Industrial Applicability

[0048] The present disclosure relates to a two - heat forming forging process of a large crankshaft. A forging machine, an anvil type, and operating equipment are utilized. In the first heat, the shape and parameters of a forging preform having a raised base and two web bodies are set, and a plurality of processes of setting and stretching are used to complete the forging of the preform. In the second heat, the shape and parameters of the forgings in an intermediate state in a plurality of processes are set, and a forging press that rotates and moves left and right by changing the angle and repeating the rotation, and a forging press that repeatedly exchanges the anvil type are used. A covering bending die having an arc - shaped pressing surface is used to perform rotational pressing and bending, and a plurality of core dies are used to perform multiple press - fits, and the forgings are gradually formed to achieve the forming forging of the crankshaft. The present disclosure provides a forging process that can achieve the forming forging and bending forging of a crankshaft forging with a relatively small force and a relatively short forging press distance, and realizes the forging of a relatively large crankshaft forging by a forging machine with a relatively small pressure. The present invention has the characteristics of a large forging ratio, good forming degree, short forging time, low material consumption, and low production cost.

[0049] In addition, the two - heat forming forging process of the large crankshaft according to the present disclosure is feasible and can be used for various industrial applications. For example, the two - heat forming forging process of the large crankshaft according to the present disclosure can be used in the forging field and the like.

Explanation of Signs

[0050] 1 Upper anvil 2 First manipulator 2′ Second manipulator 3 Small flat anvil 4 Forging 5 Setting - in processing plate 6 Double - edge press groove die 7 Preform 8 Large flat anvil 9 Convex type 10 Concave - shaped exchange anvil type 11 Trapezoidal die 12 Concave type 13 Arc-shaped lower type 14 Laid folding type 15 Core type

Claims

1. A two - heat forming forging process of a large crankshaft, using a forging machine, an anvil type, and operating equipment, wherein the anvil type includes an upper anvil, a lower die, a core die, and an upper die; the lower die includes a small flat anvil, a large flat anvil, a double - edge press groove type, a convex type, a trapezoidal type, and a concave type; the upper die includes a mounting plate, an exchangeable anvil type, and a covering and bending type; the operating equipment includes a workbench and a manipulator; the workbench includes a horizontal workbench and a vertical workbench; the manipulator includes a first manipulator and a second manipulator; the upper anvil is connected to the forging machine; the convex type and the double - edge press groove type respectively form a fixed hinge with the large flat anvil; the exchangeable anvil type includes a concave - shaped exchangeable anvil type and an arc - shaped exchangeable anvil type; there are a plurality of core dies, and different core dies have different differences in thickness at both ends; the lower die is arranged on the horizontal workbench and is movable together with the horizontal workbench; the first manipulator is configured to clamp the forging; the second manipulator is configured to clamp the core die or the upper die, The two - heat forming forging process of the large crankshaft includes the following steps: First heat: Forging a preform having a two - web body with a protruding platform in the middle, The two - web body is set to have a length of L, a width of b, and a height of h １ such that when the protruding platform has a height of h2 and a width of b, the total height of the preform: h = h １ + h ２ and, Step 1: Select a billet according to the weight requirement of the crankshaft forging, and heat it to a predetermined forging temperature, Step 2: Place the billet heated in Step 1 between the upper anvil and the small flat anvil to stretch the billet, Step 3: Stand the forging stretched in Step 2 on the vertical workbench, clamp the mounting plate with the second manipulator, place it between the forging and the upper anvil, and mount the forging to half of its original length. Step 4: Stretch the forging mounted in Step 3 to a cross-section of (3b / 4) × (3b / 4). Step 5: Stand the forging stretched in Step 4 on the vertical workbench, and mount the forging to half of its original length. Step 6: Stretch the forging mounted in Step 5 to a cross-section of b × b. Step 7: Place the middle part of the forging stretched in Step 6 above the double-edge press groove die, and forge left and right grooves that are parallel below the forging. Step 8: Invert the forging having the left and right grooves in Step 7 180° vertically, place it on the flat anvil and forge it. Forge the left part of the left groove and the right part of the right groove so that they respectively have a width of b, a height of h １ and a length of L to form two web bodies, and forge the part between the left and right grooves into a protruding platform with a height of h ２ and a width of b, thereby manufacturing a preform of a two-web body. Second heat: Forging Set the transition shape, parameters, and bending parameters of the two-web body and the journal. Step 9: Heat the preform in Step 8 to the forging temperature. Step 10: Place the heated preform on the flat anvil, press and stretch the two-web body thinly, and finish it to the predetermined dimensions. Step 11: Clamp the preform with the first manipulator, place the middle part of the preform in Step 10 above the convex die, repeatedly invert it 180 degrees and forge it, forge it while moving left and right, change the position multiple times and forge it to roughly forge the two side surfaces of the journal. Step 12: Place the preform in the trapezoidal mold such that the raised platform of the preform in Step 11 faces upward, clamp the concave replacement anvil mold with the second manipulator and surround the preform, rough forge the lower surface of the journal on the bottom surfaces of the two web bodies facing the raised platform. Step 13: Place the two side surfaces and the lower surface of the journal in Steps 11 and 12 in the convex mold, repeatedly invert, move left and right, and alternately forge the two side surfaces, the lower surface and the connecting part of the journal to forge it to be close to the journal shape. Step 14: Place the journal of the preform in Step 13 in the concave mold, repeatedly invert and change the angle of the forging press, press down the head part of the raised platform with the upper anvil, the head part of the raised platform is formed as the upper surface of the polygonal journal by the forging press, and the two side surfaces and the lower surface of the journal are formed as semi-cylindrical bodies by the forging press. Step 15: Alternately place the journal forged in Step 14 in the convex mold and the concave mold, use a non-flat anvil and the arc-shaped replacement anvil mold as the upper anvil, forge the journal at multiple angles to forge the cylindrical material of the journal. Step 16: Place the lower surface of the cylindrical journal in the concave mold, clamp the covering and bending mold with the second manipulator and cover and place it on the upper surfaces of the two webs of the two web bodies, and the preform is bent to a predetermined angle to form a "V" shape. Step 17: Place the "V"-shaped preform on the large flat anvil, insert the core mold with the largest difference in thickness at both ends into the opening of the preform with the second manipulator, press together the two legs of the "V"-shaped one, the two legs of the preform approach each other, turn it upside down and press and forge it so that the two legs of the preform contact the core mold. Step 18: Exchange the core molds in the order of the largest difference in thickness at both ends, repeat the operation in Step 17, make the two webs of the two web bodies contact the core molds, invert the preform and perform forging, finish-forge the outer sides of the two web bodies to forge the crank handle of the crank throw, Step 19: Synchronously rotate the core mold and the preform in a press-fitting state, forge the head part of the protruding base, and stretch it into a crank throw head part in the shape of a truncated square pyramid, Step 20: Place the preform in Step 19 on the large flat anvil or the small flat anvil, and finish the crank throw to a predetermined size A two-heat forming forging process for a large crank throw, characterized by the above.

2. The first manipulator is a left manipulator, and the second manipulator is a right manipulator The two-heat forming forging process for a large crank throw according to Claim 1, characterized by the above.

3. In Step 2, stretch the billet to 1.2 to 1.7 times its original length The two-heat forming forging process for a large crank throw according to Claim 1 or 2, characterized by the above.

4. In Step 3, place the rectangular forging at 1 / 2 ± 20% of its original length The two-heat forming forging process for a large crank throw according to any one of Claims 1 to 3, characterized by the above.

5. In Step 4, stretch the forging into a rectangular material with a cross-section of 3b / 4(1 ± 5%) × 3b / 4(1 ± 5%) The two-heat forming forging process for a large crank throw according to any one of Claims 1 to 4, characterized by the above.

6. In Step 5, place the forging at 1 / 2 ± 10% of its original length The forging process of the crankshaft reform according to any one of claims 1 to 5, characterized by the above.

7. In step 6, the forging is stretched to have a cross-section of b(1 + 0 to 5%) × b(1 + 0 to 5%). The forging process of the crankshaft reform according to any one of claims 1 to 6, characterized by the above.

8. The convex shape is an arc shape. The two-heat forming forging process of the large crankshaft according to any one of claims 1 to 7, characterized by the above.

9. The diameter of the preform of the journal in the vertical direction is the diameter of the finished product ± 5%. The two-heat forming forging process of the large crankshaft according to any one of claims 1 to 8, characterized by the above.

10. The concave surface of the concave exchange anvil type is configured to mesh with the convex surface of the preform. The two-heat forming forging process of the large crankshaft according to any one of claims 1 to 9, characterized by the above.

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