Extrusion forming process for large-specification piston skirt of marine diesel engine

Abstract

The invention relates to the field of extrusion forming of piston skirts, in particular to an extrusion forming process of a large-size piston skirt of a marine diesel engine, which comprises the following steps of: placing a piston skirt raw material in a pre-forging annular die and a pre-forging lower die, pressing and moving downwards through a pre-forging convex die, forming a piston skirt pre-forging piece, taking out the pre-forging convex die, and replacing the pre-forging convex die with a finish-forging convex die; according to the method, the extrusion deformation process of the piston skirt is optimized, the internal metal deformation is smoother, the structure is more uniform, the metal flowing state of an area A with the most concentrated stress in the using process of the piston skirt is particularly improved, and the piston skirt forging is formed through downward pressing and movement of the finish-forging male die. And the overall quality is improved.

Description

Technical Field

[0001] The invention relates to the field of piston skirt extrusion forming, in particular to an extrusion forming process of a large-size piston skirt of a marine diesel engine. Background Art

[0002] At present, the forging process of large-size piston skirts for marine diesel engines is one-time extrusion forming. Extrusion deformation can improve the internal structure and refine the grains well, but it requires both large compressive stress and a certain amount of deformation during the deformation process. In the one-time deformation process, the piston skirt area A is open-die forged before the mold cavity is filled. After the cavity is filled, when the punch further presses downward and moves, area A is almost not deformed or slightly deformed. Therefore, this process has very little improvement on the internal structure of area A. Area A of the piston skirt with greater stress corresponds to the core of the raw material with more material defects, which poses a great risk to the subsequent use of the product.

[0003] At present, the forging process of large-size piston skirts for marine diesel engines also has secondary extrusion forming. The end of the punch used for pre-forging is semicircular, and the pressure holding effect during the extrusion process is not ideal. The internal pressure of the piston skirt pre-forging is not large enough, and the improvement of the internal structure is not obvious.

[0004] Therefore, it is necessary to provide a new fuel injector nozzle of a marine diesel engine and a processing device thereof to solve the above-mentioned technical problems. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides an extrusion forming process for a large-size piston skirt of a marine diesel engine, which ensures the forming quality and internal structure performance of the piston skirt through two stages of pre-forging and final forging.

[0006] A large-size piston skirt extrusion forming process for a marine diesel engine is characterized by comprising:

[0007] 1) Pre-forging stage:

[0008] The raw material of the piston skirt is placed between the pre-forging annular die (7) and the pre-forging lower die (8);

[0009] A pre-forging punch (6) having an inclined surface angle is used to apply pressure downward from above and move to extrude the raw material, causing the raw material to be reversely extruded and deformed to form a piston skirt pre-forging (5);

[0010] 2) Final forging stage:

[0011] Placing the pre-forged piston skirt pre-forged piece (5) between the final forging annular die (3) and the final forging lower die (4);

[0012] The piston skirt pre-forging (5) is further extruded and deformed by the final forging punch (2) exerting pressure downward from the top and moving the punch downward to form a piston skirt forging (1).

[0013] Furthermore, the pre-forging annular die (7) and the final forging annular die (3) have the same shape, and the pre-forging lower die (8) and the final forging lower die (4) have the same shape.

[0014] Furthermore, the inclined plane angle of the pre-forging punch (6) is 100° to 150°, so as to generate a more uniform stress distribution during the pre-forging process and promote the flow and deformation of the material.

[0015] Preferably, the inclined plane angle of the pre-forging punch (6) is 120°.

[0016] Preferably, the forming of the piston skirt pre-forging (5) is a reverse extrusion deformation, and the final forging of the A zone of the piston skirt forging (1) is an open die forging deformation.

[0017] Preferably, the extrusion forming process of the piston skirt preforging (5) is suitable for different types of diesel engines and piston skirts made of different materials: alloy steel, aluminum alloy, titanium alloy, etc.

[0018] Compared with the related art, the large-size piston skirt extrusion forming process for marine diesel engines provided by the present invention has the following beneficial effects:

[0019] 1) Through the two-stage forming of pre-forging and final forging, the flow and deformation process of the material can be more accurately controlled to ensure the final shape and dimensional accuracy of the piston skirt. The pre-forging stage initially forms the general shape, and the final forging stage further accurately adjusts it, reducing the problems of uneven deformation and dimensional deviation caused by one-time forming.

[0020] 2) During the extrusion process, the material undergoes plastic deformation under the action of the die, which helps to refine the grains and improve the internal structure of the material. In particular, the reverse extrusion deformation in the pre-forging stage can more effectively promote the uniform deformation of the material and the densification of the internal structure, and improve the mechanical properties and durability of the piston skirt.

[0021] 3) After the raw material undergoes initial deformation in the pre-forging stage, its internal stress state and defect distribution will change. Through further extrusion in the final forging stage, these defects can be further eliminated or alleviated, reducing the risk caused by material defects in the subsequent use of the product.

[0022] 4) Compared with the traditional single extrusion forming or complex multiple forming process, the secondary extrusion forming process simplifies the process flow and die design while maintaining high forming quality, and improves production efficiency. In addition, since the pre-forging and final forging dies have the same shape, it is also convenient to manufacture and replace the dies.

[0023] 5) The present invention optimizes the extrusion deformation process of the piston skirt, so that the internal metal deformation is smoother and the structure is more uniform. In particular, the metal flow state in the A zone where the stress is most concentrated during the use of the piston skirt is improved, and the overall quality is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the final forging structure of a large-size piston skirt for a marine diesel engine provided by the present invention through extrusion forming;

[0025] Figure 2 A schematic diagram of the extrusion-molding pre-forging structure of a large-size piston skirt for a marine diesel engine provided by the present invention.

[0026] Numbers in the figure: 1. Piston skirt forging; 2. Final forging punch; 3. Final forging ring die; 4. Final forging lower die; 5. Piston skirt pre-forging; 6. Pre-forging punch; 7. Pre-forging ring die; 8. Pre-forging lower die. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0029] See also Figure 1 to Figure 2 , a large-size piston skirt extrusion forming process for a marine diesel engine, comprising:

[0030] 1) Pre-forging stage:

[0031] Raw material placement: The raw material of the piston skirt is placed between the pre-forging annular die (7) and the pre-forging lower die (8) to form a closed space.

[0032] Pre-forging punch pressure: The pre-forging punch (6) applies pressure downward from the top and moves to extrude the raw material. Since the end of the pre-forging punch (6) is designed with a slope angle of 120°, this design helps to produce a more uniform stress distribution during the extrusion process and may promote the flow and deformation of the material.

[0033] Pre-forging forming: After being extruded by the pre-forging punch (6), the raw material is deformed into a piston skirt pre-forging (5). The main purpose of this stage is to initially shape the raw material and improve its internal structure.

[0034] Removing the pre-forging punch: After the pre-forging is completed, the pre-forging punch (6) is removed to prepare for the final forging stage.

[0035] 2) Final forging stage:

[0036] Pre-forging placement: The pre-forged piston skirt pre-forging (5) is placed between the final forging annular die (3) and the final forging lower die (4). It is worth noting that the two dies are the same in shape as the dies in the pre-forging stage, which helps to maintain the stability of the pre-forging during the final forging process.

[0037] Final forging punch pressure: Replace the final forging punch (2) and apply pressure and move it downward from the top to further extrude and deform the pre-forged piece.

[0038] Final forging forming: During the final forging process, the piston skirt forging (1) is gradually formed. In particular, the A area (such as Figure 1 The deformation of the final forging stage belongs to open die forging, which means that in this area, after the material is filled in the die cavity, as the punch is further pressed down, its deformation is relatively small or almost non-deformed. However, since the raw material has been initially deformed and the internal structure has been improved in the pre-forging stage, the main task of the final forging stage is to complete the final shape and size requirements.

[0039] Tests have shown that the present invention achieves preliminary forming and final forming respectively through two steps, namely pre-forging and final forging, which helps to better control the deformation and internal structure properties of the material. The dies used in the pre-forging and final forging stages are the same in shape, which helps to maintain the stability of the pre-forged parts during the final forging process; the bevel angle design of the pre-forging punch helps to produce a more uniform stress distribution. The pre-forging stage is a reverse extrusion deformation, which helps to improve the internal structure of the material; the final forging stage A area is an open die forging deformation, and special attention should be paid to the deformation amount and internal structure improvement of this area. This secondary extrusion forming process combines the advantages of pre-forging and final forging, and aims to improve the forming quality and internal structure properties of the piston skirt through step-by-step forming, while reducing product risks caused by material defects.

[0040] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A large-size piston skirt extrusion forming process for a marine diesel engine, characterized in that: include: 1) Pre-forging stage: The raw material of the piston skirt is placed in the space formed by the pre-forging annular die (7) and the pre-forging lower die (8); A pre-forging punch (6) having an inclined surface angle is used to apply pressure downward from above and move to extrude the raw material, causing the raw material to be reversely extruded and deformed to form a piston skirt pre-forging (5); 2) Final forging stage: Placing the pre-forged piston skirt pre-forged piece (5) in a space formed by the final forging annular die (3) and the final forging lower die (4); The piston skirt pre-forging (5) is further extruded and deformed by the final forging punch (2) exerting pressure downward from the top and moving the punch downward to form a piston skirt forging (1).

2. The extrusion forming process of a large-size piston skirt for a marine diesel engine according to claim 1, characterized in that: The pre-forging annular die (7) and the final forging annular die (3) have the same shape, and the pre-forging lower die (8) and the final forging lower die (4) have the same shape.

3. The extrusion forming process of a large-size piston skirt for a marine diesel engine according to claim 1 or 2, characterized in that: The inclined plane angle of the pre-forging punch (6) is 100° to 150°, so as to generate a more uniform stress distribution during the pre-forging process and promote the flow and deformation of the material.

4. The extrusion forming process of a large-size piston skirt for a marine diesel engine according to claim 3 is characterized in that: The inclined plane angle of the pre-forging punch (6) is 120°.

5. The extrusion forming process of a large-size piston skirt for a marine diesel engine according to claim 1, characterized in that: The forming of the piston skirt pre-forging (5) is reverse extrusion deformation, and the final forging of the A zone of the piston skirt forging (1) is open die forging deformation.

6. The large-size piston skirt extrusion forming process for marine diesel engines according to any one of claims 1 to 5, characterized in that: The extrusion forming process of the piston skirt preforging (5) is applicable to different types of diesel engines and piston skirts made of different materials, including alloy steel, aluminum alloy and titanium alloy.

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