A large marine crankshaft bending forging device and its process

Abstract

This invention belongs to the field of bending technology in large-scale forging, specifically relating to a bending forging device and process for large marine crankshafts. This process combines computer control technology and linkage force-enhancing technology to achieve conformal bending of the billet, reducing the occurrence of undercut and out-of-tolerance phenomena caused by billet shrinkage and stretching; it completely solves the problem of high friction between the die and the billet, allowing the billet to conform closely to the die shape during bending, ensuring precise control of billet dimensions, preventing wrinkles, and meeting the requirements of the bending forging process.

Description

Technical Field

[0001] This invention belongs to the field of bending technology in large-scale forging, specifically relating to a large marine crankshaft bending forging device and its process. Background Technology

[0002] The diesel engine is the heart of a ship, and its lifespan is essentially the lifespan of the ship. The low-speed crankshaft is a core component of the diesel engine, irreplaceable and unrepairable throughout the ship's lifespan. Marine crankshafts are extremely important components, accompanying the ship for its entire existence. Furthermore, a country's shipbuilding capacity and number of ships built depend entirely on the quantity of low-speed crankshafts its shipbuilding enterprises possess. Currently, the top three countries in terms of shipbuilding quantity and capacity are China, South Korea, and Japan. At present, my country relies entirely on imports of large marine crankshaft forgings (grades 70-92) from South Korea, spending as much as 500 million RMB annually, with frequent delays and a significant dependence on foreign suppliers.

[0003] Traditional bending forging processes for large crankshafts utilize a U-shaped lower die and upper tongue plate tooling. However, in actual operation, due to bending limit differences, dimensional control is inaccurate. During bending forging, the high frictional force between the lower die and the billet causes billet shrinkage, often resulting in insufficient dimensions and undersized billets. Therefore, to solve core technical problems, achieve large-scale production, resolve localization issues, and establish stable production capacity to meet the demand for marine crankshafts in Chinese shipyards, the localization of large, low-speed crankshaft forgings is urgently needed. Summary of the Invention

[0004] To address the problems of the existing technology, this invention provides a large marine crankshaft bending forging device and its process, namely, a large crankshaft conformal bending forging method. This process combines computer control technology and linkage force-enhancing technology to achieve conformal bending of the billet, reducing the occurrence of material shortage and out-of-tolerance phenomena caused by billet shrinkage and stretching; it completely solves the problem of high friction between the mold and the billet, allowing the billet to conform to the shape of the mold during bending, ensuring precise control of billet dimensions, preventing wrinkles, and meeting the requirements of the bending forging process.

[0005] The objective of this invention is achieved through the following technical solution.

[0006] A large marine crankshaft bending forging device includes an upper mold system 1, a lower mold system 2, and a locking block 3. The locking block 3 is disposed on the lower mold system 2, and the upper mold system 1 is disposed above the lower mold system 2.

[0007] Furthermore, the upper mold system 1 is hinged at both ends with upper mold connecting rods 4, and a hydraulic cylinder 6 is provided in the middle of the upper mold system 1. The piston rods at both ends of the hydraulic cylinder 6 are connected to the middle of the upper mold connecting rod 4. A pressure roller 5 is provided at the end of the upper mold connecting rod 4, and the pressure roller 5 corresponds to the locking block 3.

[0008] Furthermore, the lower mold system 2 includes a tongue plate 7 and a limiting side plate 8; the tongue plate 7 is located between the two limiting side plates 8, and the tongue plate 7 is connected to the locking block 3.

[0009] A bending forging process for large marine crankshafts specifically includes the following steps:

[0010] Step 1: First, perform a crank-cutting process on the press to control the billet size as much as possible;

[0011] Step 2: Heat the billet, and control the heating temperature to ensure uniform heating of the billet;

[0012] Step 3: Install the large marine crankshaft bending and forging device;

[0013] Step 4: Place the billet on the lower die system 2 of the large marine crankshaft bending forging device, and lock the workpiece to be processed on the tongue plate 7 of the lower die system 2 with the locking block 3.

[0014] Step 5: The upper mold system 1 is connected to the press. When the press applies downward force, the entire upper mold system 1 moves downward accordingly. The upper mold connecting rod 4 is connected to the hydraulic cylinder 6. The position of the cylinder is controlled by the computer, and the mold is pressed down according to the shape.

[0015] Step 6: After pressing down to the correct position, lift the press, open locking block 3, remove the blank, and the bending is complete.

[0016] Compared with the prior art, the advantages of this invention are as follows.

[0017] This invention features a novel design concept. Traditional bending and forging methods involve placing the workpiece on a mold with a downward-facing groove, and then pressing the workpiece into the groove using a press to complete the bending and forging process. This invention, however, reverses this approach: the groove is positioned at the top, and the press presses it downwards, allowing the workpiece to enter the mold groove from below, thus achieving the desired bending and forging shape.

[0018] Another advantage of this invention is that it abandons the existing approach of controlling the shape of the workpiece by the shape of the groove. Instead, this invention uses a pressure roller to control the bending and forging shape of the workpiece. Specifically, the principle is as follows: the position of the hydraulic cylinder is controlled by a computer to control the opening and closing angle of the upper die connecting rod. The connecting rod is connected to the pressure roller, which directly contacts the workpiece, thus bending the workpiece into the desired shape. Compared to traditional bending and forging methods, during the press's downward movement, the contact between the workpiece and the pressure roller is not sliding friction. The pressure roller rotates during contact, reducing friction and also smoothing the workpiece surface. This solves the problem of shrinkage and material shortage caused by friction between the die and the blank, improving the yield rate. Because the pressing speed and pressure roller distance are controlled by the computer, the bending dimensions of the blank are controlled by the computer, meaning it bends according to the curve shape, resulting in more precise control and easier operation. Furthermore, a single die set can process workpieces of multiple sizes by controlling the opening and closing angle of the upper die connecting rod, saving the cost of manufacturing multi-size dies and significantly improving production efficiency.

[0019] Traditional methods may result in defects such as a flared mouth and a narrow waist (e.g.) Figure 4 (as shown), but this situation will not occur when using the process of the present invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the large marine crankshaft bending and forging device of the present invention.

[0021] Figure 2 This is a diagram of the forming process in step 1 of Example 1.

[0022] Figure 3 This is a diagram of the pressing process of the molding device in Example 1.

[0023] Figure 4 This is a workpiece defect diagram obtained using traditional methods.

[0024] Among them, 1 is the upper mold system; 2 is the lower mold system; 3 is the locking block; 4 is the upper mold connecting rod; 5 is the pressure roller; 6 is the hydraulic cylinder; 7 is the tongue plate; and 8 is the limiting side plate. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of the present invention. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0026] like Figure 1As shown, a large marine crankshaft bending forging device includes an upper mold system 1, a lower mold system 2, and a locking block 3. The locking block 3 is disposed on the lower mold system 2, and the upper mold system 1 is disposed above the lower mold system 2. Upper mold connecting rods 4 are hinged at both ends of the upper mold system 1. A hydraulic cylinder 6 is disposed in the middle of the upper mold system 1, and the piston rods at both ends of the hydraulic cylinder 6 are connected to the middle of the upper mold connecting rod 4. A pressure roller 5 is disposed at the end of the upper mold connecting rod 4, and the pressure roller 5 corresponds to the locking block 3. A tongue plate 7 is disposed between two restricting side plates 8, and the tongue plate 7 is connected to the locking block 3. The locking block 3 locks the workpiece to be processed onto the tongue plate 7 of the lower mold system 2, and the restricting side plates 8 are connected to the tongue plate 7, thus limiting the deformation of the workpiece.

[0027] A bending forging process for large marine crankshafts specifically includes the following steps:

[0028] Step 1: First, perform a crank-cutting process on the press to control the billet size as much as possible;

[0029] Step 2: Heat the billet, and control the heating temperature to ensure uniform heating of the billet;

[0030] Step 3: Install the large marine crankshaft bending and forging device;

[0031] Step 4: Place the billet on the lower mold system 2 of the large marine crankshaft bending forging device. The locking block 3 locks the workpiece to be processed on the tongue plate 7 of the lower mold system 2. The side plate 8 is connected to the tongue plate 7 to limit the deformation of the workpiece.

[0032] Step 5: The upper mold system 1 is connected to the press. When the press applies downward force, the entire upper mold system 1 moves downward accordingly. The upper mold connecting rod 4 is connected to the hydraulic cylinder 6. The computer controls the position of the cylinder, thereby controlling the opening and closing angle of the upper mold connecting rod 4, so as to control the shape of the pressed part and press it down according to the shape.

[0033] Step 6: After pressing down to the correct position, lift the press, open locking block 3, remove the blank, and the bending is complete.

[0034] Example 1.

[0035] Step 1: First, the billet is prepared by cranking on the press. After upsetting and drawing pre-forming operations, the billet is pre-formed. The forming process is as follows: Figure 2 As shown, try to control the size of the blank;

[0036] Step 2: Heat the billet at 1200℃ to ensure uniform heating.

[0037] Step 3: Install the upper and lower molds and align them.

[0038] Step 4: Quickly place the heated billet onto the lower mold and lock the locking block to fix the billet on the tongue plate;

[0039] Step 5: The press moves downward at a speed of 50 mm / s. The position of the hydraulic cylinder is controlled by a computer, causing the pressure roller to press down in a conforming manner. The pressing process is as follows: Figure 3 As shown;

[0040] Step 6: After pressing down to the correct position, lift the press, open the locking block, remove the blank, and the bending process is complete.

Claims

1. A large marine crankshaft bending and forging device, characterized in that, It includes an upper mold system (1), a lower mold system (2), and a locking block (3); the locking block (3) is disposed on the lower mold system (2), and the upper mold system (1) is disposed above the lower mold system (2); The upper mold system (1) is hinged at both ends with upper mold connecting rods (4), and a hydraulic cylinder (6) is provided in the middle of the upper mold system (1). The piston rods at both ends of the hydraulic cylinder (6) are connected to the middle of the upper mold connecting rod (4). A pressure roller (5) is provided at the end of the upper mold connecting rod (4), and the pressure roller (5) corresponds to the locking block (3). The lower mold system (2) includes a tongue plate (7) and a limiting side plate (8); the tongue plate (7) is located between the two limiting side plates (8), and the tongue plate (7) is connected to the locking block (3).

2. A bending forging process for large marine crankshafts, characterized in that, Specifically, the steps include the following: Step 1: First, perform a crank-cutting process on the press to control the billet size as much as possible; Step 2: Heat the billet, and control the heating temperature to ensure uniform heating of the billet; Step 3: Install the large marine crankshaft bending and forging device as described in claim 1; Step 4: Place the billet on the lower die system (2) of the large marine crankshaft bending forging device, and lock the workpiece to be processed on the tongue plate (7) of the lower die system (2); Step 5: The upper mold system (1) is connected to the press. When the press applies downward force, the entire upper mold system (1) moves downward accordingly. The upper mold connecting rod (4) is connected to the hydraulic cylinder (6). The position of the hydraulic cylinder is controlled by the computer, and the mold is pressed down according to the shape. Step 6: After pressing down to the correct position, lift the press, open the locking block (3), remove the blank, and the bending is complete.

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