Crank near-net forming die
By combining local die forging and bending forging, and using specific molds and processes, the problems of complex forming and dimensional deviation in crank forging were solved, achieving high-quality near-net-shape forming of crank blanks and reducing costs and processing difficulty.
Patent Information
- Application Number
- CN202423247377.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2026-01-27
- Estimated Expiration
- 2034-12-27
AI Technical Summary
Existing crank forging processes suffer from problems such as high forging difficulty, complex forming, poor fiber flowability, uneven quality, large machining allowance, high equipment requirements, and high mold consumption, making it difficult to guarantee the dimensional consistency and internal and external quality of crank blanks.
A method combining local die forging and bending forging is adopted. A simple mold is used to perform local die forging by forming a cavity with four forming modules. Combined with bending forging for rapid forming, near-net-shape forming of the crankshaft bend part is achieved, reducing dimensional deviations in the free forging stage.
It improves the internal and external quality of the crankshaft bend, ensures the consistency of blank dimensions, reduces raw material and machining costs, and simplifies mold making and operation processes.
Smart Images
Figure CN223833360U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of parts manufacturing, specifically a near-net-shape mold for forging diesel engine crankshafts. Background Technology
[0002] Crankshafts are important components of large and medium-sized marine diesel engines. They are mainly used in the crankshafts of large and medium-sized marine diesel engines and low-speed diesel engines for power generation. Forging them is difficult, the forming process is complex, and the forgings are required to have good fiber flow properties.
[0003] Currently, there are three main processes for manufacturing cranks internationally: block forging, die forging, and bending forging.
[0004] The block forging method involves first forging the crankshaft into an approximately rectangular shape, and then removing excess metal from the crank pin by machining. This method results in a reduction in crankshaft quality and a shortened service life because the forging fibers at the junction of the crank pin and the inner side of the crankshaft are cut off, where stress is high. Furthermore, the presence of defects such as porosity and segregation, along with the large size making it difficult to forge through, contributes to this problem.
[0005] Die forging is a method in which a prepared rectangular billet is placed in a special extrusion die and extruded into a crank using a large-tonnage press and the die. This method has a high forming rate, is simple to operate, produces a dense structure, has a short forging process, and low machining costs. However, it has a long die manufacturing cycle, high manufacturing costs, and high die consumption, placing extremely high demands on forging equipment.
[0006] Bending forging is currently the most widely used process for manufacturing marine composite crankshafts and cranks both domestically and internationally. It involves first forging a convex billet with a boss in the middle, and then bending it into shape on a bending forging die. The size of the billet determines the size of the crank after bending and the subsequent machining allowance. Therefore, the billet preparation process is the most critical link in the crank forging process, which requires extremely high levels of skill and operational expertise from the workers. To ensure the dimensional requirements of subsequent machining, the allowance of crank forgings formed by bending forging is often larger than that of die forging, and it is also prone to uneven distribution.
[0007] The crank mainly consists of two parts: the crank head and the crank arm. The crank head includes multiple inclined surfaces on the left and right sides, as well as inclined surfaces on the top and bottom sides (see...). Figure 1a and Figure 1b It is relatively difficult to forge multiple inclined surfaces on the left and right, as well as upward and downward inclined surfaces, using the bending forging method. The bends that can be formed by bending forging are basically flat and rectangular (see...). Figure 2 The only way to remove excess material is through machining. Summary of the Invention
[0008] The purpose of this utility model is to solve the above-mentioned technical problems and provide a mold for near-net-shape crank forming that is simple in structure, makes the forming size of the crank blank closer to the finished size of the product, reduces the influence of dimensional deviations in the free forging stage on the size of the crank blank, and ensures the consistency of the crank blank size and machining allowance.
[0009] The present invention relates to a near-net-shape mold for crankshafts, comprising a base, an outer mold ring on the base, and four forming modules inside the outer mold ring. The four forming modules consist of two symmetrically arranged inclined surface forming modules and arc surface forming modules, forming a cavity with openings at the top and bottom.
[0010] Preferably, the inner surface of the outer mold ring is a conical surface with the larger opening facing upwards.
[0011] Preferably, the conical surface is an inclined surface at a 15° angle to the horizontal vertical direction.
[0012] Preferably, the outer slope of the inclined surface forming module is consistent with the slope of the inner surface of the outer mold ring, and the inner slope is consistent with the slope of the upper and lower slopes of the crank forging finished product; the outer slope of the arc surface forming module is consistent with the slope of the inner surface of the outer mold ring, and the inner arc surface is consistent with the arc contour line of the crank forging finished product.
[0013] Preferably, there is a gap between two adjacent inclined surface forming modules and arc surface forming modules.
[0014] Preferably, the gap width is +10 to +15 mm.
[0015] Preferably, the depth of the cavity is greater than the height of the boss-shaped crank blank +0 to +50 mm.
[0016] A forging method for a diesel engine crankshaft forging, comprising the following forging steps:
[0017] 1) The fully heated steel ingot is upset and drawn into shape once or multiple times to obtain a square boss crank blank composed of a platform surface in the rear section and a square boss in the front section.
[0018] 2) Place the square boss of the crank blank downward into the mold, with the width direction of the square boss preferably contacting the arc-shaped module of the mold.
[0019] 3) As the press descends, the flat anvil presses down on the platform surface of the square boss crank blank. Under the action of the arc forming module, the square boss begins to deform in the width direction, and the two arc surfaces are gradually formed. As the press continues to descend, the square boss also begins to contact the inclined forming module of the mold in the length direction. The square boss begins to deform in the length direction simultaneously, and the inclined surfaces on both sides are gradually formed. The press stops descending after the square boss is completely in contact with the arc forming module and the inclined forming module, and finally forms a blank with a bend with two arc sides and two inclined surfaces as well as a platform surface.
[0020] 4) The billet obtained in step 3) is lifted out of the mold, reheated in the furnace, and then subjected to bending forging to form a curved arm on the platform surface of the billet, thus obtaining the crank forging.
[0021] Preferably, in step 4), the bending forging method is as follows: after exiting the furnace, the billet is placed on a bending support, and a punch plate with an inner concave arc cavity is used to punch down from the axis of symmetry of the billet platform to form a bend arc surface. When the punch plate continues to descend to the process dimension, the bend is formed, and the two platform surfaces on both sides form V-shaped curved arms. Finally, an arc tongue plate is inserted into the opening, and the two curved arms on the press are flattened to finally form a crank forging.
[0022] Preferably, in step 1), the width B1 of the square boss blank is equal to the width B2 of the crank forging, the top length W1 of the square boss is equal to the height Y1 of the crank forging's bend end plus 50-100mm, the bottom length W2 is equal to the bottom height Y2 of the crank forging, the height H1 of the square boss is equal to the crank forging's bend length M1 plus 150-200mm, and the thickness H2 of the flat platform is equal to the crank arm thickness M2 of the crank forging.
[0023] The beneficial effects of this utility model are as follows: This utility model combines a two-step forming method of partial die forging and bending forging to form crank forgings. The partial die forging method achieves near-net-shape forming of the crankshaft crank part, making the shape of the crankshaft crank part closer to the shape of the finished product, which greatly improves the internal and external quality of the crankshaft crank. Combined with the bending forging method for rapid forming of the crank arm, it combines the advantages of both methods, ensuring the internal and external quality of the crankshaft crank for high-horsepower low-speed diesel engines. It can achieve the consistency of crank forging blank dimensions, while greatly reducing the rough machining allowance of the crank blank, reducing raw material costs and subsequent machining costs. Attached Figure Description
[0024] Figure 1a This is a side view of the finished crank forging.
[0025] Figure 1b This is the front view of the finished crank forging.
[0026] Figure 2 This is a schematic diagram of a crank forging blank produced by bending forging.
[0027] Figure 3 Schematic diagram of a square boss crank blank;
[0028] Figure 4a This is a cross-sectional view of the near-net-shape molding die of this utility model;
[0029] Figure 4b This is a top view of the near-net-shape molding die of this utility model.
[0030] Figure 5 This is a schematic diagram of the arc surface forming module of the special near-net-shape forming mold of this utility model;
[0031] Figure 6 This is a schematic diagram of the inclined surface forming module of the special near-net-shape forming mold of this utility model;
[0032] Figure 7a This is a schematic diagram of a partial forging process;
[0033] Figure 7b This is a schematic diagram of the local forging state from another view direction.
[0034] Figure 8 This is a schematic diagram of the blank obtained after die forging, showing the bend with two circular arc sides and two inclined surfaces, as well as the platform surface.
[0035] Figure 9 This is a schematic diagram of the bending forging state;
[0036] Figure 10 This is a schematic diagram of a formed crank forging.
[0037] Among them, the components are: base 1, outer mold ring 2, gap 3, positioning block 4, inclined surface forming module 5, inner inclined surface 5.1, arc surface forming module 6, inner arc surface 6.1, connecting bolt 7, positioning pin 8, positioning pin 9, cavity 10; crank forging finished product 11, bend 12, crank arm 13, upper inclined surface 14, lower inclined surface 15, arc contour line 16; boss-shaped crank blank 21, platform surface 22, square boss 23; crank forging 31, bend 32, inclined surface 32.1, arc surface 32.2, crank arm 33; flat anvil 41, blank 42, bending bracket 43, punch plate 44, with concave arc cavity 44.1. Detailed Implementation
[0038] The present invention will be further explained below with reference to the accompanying drawings:
[0039] See Figure 4a and Figure 4b The near-net-shape forming mold of the crankshaft of this utility model includes a base 1, an outer mold ring 2 on the base 1, and four forming modules inside the outer mold ring 2. The four forming modules are composed of two symmetrically arranged inclined forming modules 5 (see...). Figure 5) and arc-shaped surface forming module 6 (see Figure 6 The outer mold ring 2 consists of several parts that together form a cavity 10 with openings at the top and bottom. The larger opening at the top allows for the insertion of a workpiece for localized forging, while the smaller opening at the bottom collects falling oxide scale and releases air pressure generated during press operation. The depth of the cavity 10 is greater than the height of the boss-shaped crank blank +0 to +50 mm to ensure sufficient stroke. The inner surface of the outer mold ring 2 is a tapered surface with the larger opening facing upwards, and this tapered surface is an inclined surface at a 15° angle to the horizontal vertical direction. The outer slope of the inclined forming module 5 is consistent with the inner slope of the outer mold ring 2, and the inner slope 5.1 is consistent with the slope of the upper and lower slopes of the bend 12 part of the crank forging. The outer slope of the arc forming module 6 is consistent with the inner slope of the outer mold ring 2, and the inner arc surface 6.1 is consistent with the arc contour line 16 of the bend 2 part of the crank forging. Under the action of the press, after the workpiece enters the cavity 10, it will form the shape of the bend 2 under the action of the four forming modules. There is a gap 3 between two adjacent inclined forming modules 5 and arc forming modules 6 to reduce the forming resistance of the forging at the corner. The width of the gap 3 is +10 to +15 mm. The oxide scale that falls off during forging can be collected through the cavity 10 and discharged from the bottom opening of the cavity 10, reducing the surface damage caused by the oxide scale to the crank forging blank.
[0040] During installation, the base 1 and the outer mold ring 2 are connected and fixed by connecting bolts 7; a positioning block 4 is provided between the outer mold ring 2 and the inclined surface forming module 5, and the inclined surface forming module 5 and the positioning block 4 are connected and fixed by fastening bolts 3; the inclined surface forming module 5 and the base 1 are positioned and assembled by positioning pins 9; the arc surface forming module 6 and the base 1 are positioned and assembled by positioning pins 8. Through the detachable connection between the components, when it is necessary to produce cranks of different specifications, it is only necessary to change the forming module of different size or shape to achieve near-net-shape forming, thereby reducing the mold cost.
[0041] Process:
[0042] The forging method for diesel engine crank forgings adopts the following forging steps:
[0043] 1) The fully heated steel ingot is upset and drawn into shape once or multiple times to obtain a square boss crank blank 21 composed of a platform surface 22 in the rear section and a square boss 23 in the front section.
[0044] See Figure 3The specific dimensions are set as follows: the length and width B1 of the square boss blank are equal to the width B2 of the crank forging; the top surface length W1 of the square boss is equal to the height Y1 of the crank forging's bend end plus 50-100mm; the bottom surface length W2 is equal to the bottom height Y2 of the crank forging; the height H1 of the square boss is equal to the crank forging's bend length M1 plus 150-200mm; the thickness H2 of the flat platform is equal to the crank arm thickness M2 of the crank forging.
[0045] 2) See Figure 7a and 7b The square boss 23 of the square boss crank blank 21 is placed downward into the mold, and the width direction of the square boss 23 is preferably in contact with the inner arc surface 6.1 of the arc surface forming module 6 of the mold.
[0046] 3) As the press descends, the flat anvil 41 presses down on the platform surface 22 of the square boss crank blank 21. With the cooperation of the arc forming module 6, the square boss 23 begins to deform in the width direction, and the two arc surfaces gradually take shape. As the press continues to descend, the length direction of the square boss 23 also begins to contact the inner inclined surface 5.1 of the inclined surface forming module 5 of the mold. The length direction of the square boss 23 begins to deform synchronously, and the inclined surfaces on both sides gradually take shape. Until the square boss 23 is completely in contact with the arc forming module and the inclined surface forming module, the press stops descending, finally forming the blank 42 with two arc sides and two inclined surfaces, as well as the platform surface (see...). Figure 8 );
[0047] 4) Remove the billet 42 obtained in step 3) from the mold, reheat it in the furnace, and then perform bending forging. See [link to relevant documentation]. Figure 9 The bending forging process is as follows: After exiting the furnace, the billet 42 is placed on the bending support 43. A punch plate 44 with an inner concave arc cavity 44.1 is used to punch down from the axis of symmetry of the platform surface of the billet 42 to form a bend arc surface. The punch plate 44 continues to descend to the process dimension to form the bend, and the two platform surfaces form V-shaped curved arms on both sides. Finally, an arc tongue plate is inserted into the opening, and the two curved arms are flattened on the press to finally form the crank forging 31 (see Figure 10 ).
[0048] The crank forging 31 then undergoes subsequent roughing, semi-finishing, and finishing processes to finally obtain the finished crank forging 11 (see Figure 1). This process is existing technology and will not be described in detail here.
Claims
1. A near-net-shape mold for a crankshaft, comprising a base, characterized in that, The base is provided with an outer mold ring, and four forming modules are provided inside the outer mold ring. The four forming modules are composed of two symmetrically arranged inclined surface forming modules and arc surface forming modules, forming a cavity with openings at the top and bottom.
2. The near-net-shape forming mold for cranks as described in claim 1, characterized in that, The inner surface of the outer mold ring is a conical surface with the larger opening facing upwards.
3. The near-net-shape forming mold for cranks as described in claim 2, characterized in that, The conical surface is an inclined plane at a 15° angle to the horizontal vertical direction.
4. The near-net-shape crank mold as described in any one of claims 1-3, characterized in that, The outer slope of the inclined surface forming module is consistent with the slope of the inner surface of the outer mold ring, and the inner slope is consistent with the slope of the upper and lower slopes of the crank forging part. The outer slope of the arc surface forming module is consistent with the slope of the inner surface of the outer mold ring, and the inner arc surface is consistent with the arc contour line of the crank forging part.
5. The near-net-shape mold for crankshafts as described in any one of claims 1-3, characterized in that, There is a gap between two adjacent inclined surface forming modules and arc surface forming modules.
6. The near-net-shape forming mold for cranks as described in claim 5, characterized in that, The gap width is +10 to +15 mm.
7. The near-net-shape crank mold as described in any one of claims 1-3, characterized in that, The depth of the cavity is greater than the height of the boss-shaped crank blank +0 to +50 mm.