Engine Piston Diffusion Brazing for Flash-Free Cooling Galleries
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Solution Overview
Problem
Existing methods for manufacturing vehicle engine pistons with cooling galleries, such as friction welding and brazing, often result in productivity issues due to flashing or degraded heating and cooling processes, which affect fluid flow and efficiency.
Innovation Solution
A method involving diffusion brazing with nickel-based alloys, where the piston parts are preheated and then subjected to a main heating temperature above the alloy's melting point to form a diffusion layer within the cooling gallery, improving bonding and reducing metal grain size, while maintaining alignment with a jig and using a gas mixture to prevent oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If friction welding is used to join upper and lower piston parts, then the piston parts are firmly joined, but flashing is formed and remains in the cooling gallery, disturbing fluid flow
Solution Approach 1:
The harmful flashing is extracted and removed from the cooling gallery through post-welding machining operations, ensuring that the cooling channels are clear of any flash deposits that would disturb fluid flow
Solution Approach 2:
Different surface qualities are applied to different regions: the bonding surfaces are prepared with high precision and cleanliness for optimal welding, while the cooling gallery surfaces are machined to be flash-free for optimal fluid flow
2Reliability
If brazing is performed in a sealed chamber to prevent oxidation, then oxidation is prevented, but heating and cooling time increases, degrading productivity
Solution Approach 1:
An inert or reducing atmosphere is introduced into the brazing chamber, allowing for effective oxidation prevention during the brazing process while enabling more rapid heating and cooling cycles compared to conventional sealed chamber methods
Solution Approach 2:
The atmospheric parameters in the brazing chamber are optimized to allow faster heating and cooling rates while maintaining oxidation protection, thereby reducing the overall cycle time and improving productivity
3Strength
If diffusion brazing with nickel-based alloys is used, then bonding strength and heat conductivity are improved, but process complexity increases due to preheating and main heating stages
Solution Approach 1:
The workpieces are preheated to an optimal temperature range before the main brazing operation, which prepares the surfaces for better diffusion bonding while allowing the main heating stage to be more efficient and controlled
Solution Approach 2:
The preheating and main heating stages are continuously integrated in a controlled atmosphere, maintaining useful thermal action throughout the process without interruption, thereby improving efficiency despite the multi-stage nature of the process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances productivity by allowing for the efficient manufacturing of vehicle engine pistons with improved heat conductivity and corrosion resistance, reducing metal grain size and increasing hardness, thus enhancing the piston's performance and longevity.
Implementation Method 1
a piston diffusion brazing step of heating the piston assembly heated to the preheating temperature through the preheating step at a main heating temperature higher than a melting temperature of the bonding member, and bonding the first piston part, the bonding member and the second piston part of the piston assembly by diffusion
Implementation Method 2
a piston diffusion brazing step of heating the piston assembly heated to the preheating temperature through the preheating step at a main heating temperature higher than a melting temperature of the bonding member, and bonding the first piston part, the bonding member and the second piston part of the piston assembly by diffusion
Implementation Method 3
a piston diffusion brazing step of heating the piston assembly heated to the preheating temperature through the preheating step at a main heating temperature higher than a melting temperature of the bonding member
Implementation Method 4
using a gas mixture to prevent oxidation
Implementation Method 5
a piston cooling step of cooling the piston unit formed by diffusion brazing the piston assembly
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
There is provided a method for manufacturing a piston (1) for a vehicle engine, including: a piston assembling step (S100) of forming a piston assembly by assembling a first piston part (110), a bonding member (130) and a second piston part (120), wherein the first piston part (110) has two or more bonding surfaces (112,113) separated from each other and extended in a circumferential direction, and the second piston part (120) has two or more bonding surfaces (122,123) separated from each other and extended in the circumferential direction; a piston diffusion brazing step (S300) of diffusion brazing the first piston part (110), the bonding member (130) and the second piston part (120) under an open atmosphere by heating the formed piston assembly; and a piston cooling step (S400) of cooling a piston unit formed by diffusion brazing the first piston part (110), the bonding member (130) and the second piston part (120). The piston diffusion brazing step (S300) is performed in a piston manufacturing device which includes a partially opened heating zone, a heater for providing heat into the heating zone, and a moving unit moved in one direction in the heating zone. In the piston diffusion brazing step (S300), the piston assembly is heated while being moved at a predetermined speed through the heating zone in one direction by the moving unit.