Metallic Pipe Joint Structure with Tapered Intermetallic Layer
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Solution Overview
Problem
Existing joint structures for metallic pipes, such as copper and aluminum, face challenges in pressure resistance and thermal shock resistance due to small joint areas and the formation of fragile intermetallic compound layers, which decrease strength and increase costs with the use of stainless-steel joints and plating.
Innovation Solution
A joint structure featuring an expanded-diameter connecting part on one pipe and a brazing filler metal between the pipes, with an intermetallic compound layer thickness that decreases from the open end to the base end, reducing stress concentration and eliminating the need for stainless-steel joints, thereby maintaining reliability while controlling costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stainless-steel joints and plating are used to improve joint strength, then reliability increases, but manufacturing cost increases
Solution Approach 1:
The invention changes the geometric parameter of the joint structure by forming an expanded-diameter connecting part with a specific shape. This structural parameter change allows the joint to achieve sufficient strength through the brazing process alone, eliminating the need for additional stainless-steel joints and plating, thereby reducing manufacturing cost while maintaining reliability
Solution Approach 2:
The invention extracts and removes the unnecessary stainless-steel joint and plating components from the joint structure. By designing the expanded-diameter connecting part that provides adequate strength on its own, the patent eliminates these additional components, simplifying the structure and reducing manufacturing cost while maintaining the required joint strength
2Area of stationary object
If intermetallic compound layer thickness is increased to improve bonding, then joint area increases, but strength decreases due to fragile intermetallic compounds
Solution Approach 1:
The invention applies local quality control by creating a non-uniform intermetallic compound layer thickness distribution. The layer is thinner at the base end where stress concentration occurs and can be thicker at other areas, optimizing both bonding area and strength by placing material where it is most needed for structural integrity
Solution Approach 2:
The invention changes the thickness parameter of the intermetallic compound layer from a uniform distribution to a controlled non-uniform distribution. By making the layer thinner at the base end through controlled brazing parameters and the expanded-diameter geometry, the patent reduces the harmful effects of fragile intermetallic compounds while maintaining adequate bonding area
3Ease of manufacture
If uniform intermetallic compound layer thickness is formed, then bonding is simplified, but stress concentration occurs at the base end
Solution Approach 1:
The invention implements local quality optimization by creating a position-dependent intermetallic compound layer thickness. The layer is deliberately made thinner at the base end where stress concentration occurs during brazing and service, while other areas can have adequate thickness for bonding, thus improving stress resistance without significantly complicating the manufacturing process
Solution Approach 2:
The invention inverts the conventional approach of forming a uniform or thicker intermetallic layer for maximum bonding area. Instead, it deliberately creates a thinner layer at the critical base end region, reversing the typical design assumption that more material always equals better performance, and achieving improved stress resistance
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
The joint structure enhances pressure resistance and durability by minimizing the intermetallic compound layer thickness at the base end, suppressing stress-related deterioration and avoiding the use of costly stainless-steel joints, thus maintaining reliability and reducing costs.
Implementation Method 1
a brazing filler metal (14) containing the first metal (M1) or the second metal (M2) as a main component is interposed between an outer surface of the other metallic pipe and an inner surface of the expanded-diameter connecting part (13)
Implementation Method 2
An intermetallic compound layer (15) of the first metal (M1) and the second metal (M2) is present at an interface of the first metal (M1) and the second metal (M2)
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
In order to realize a joint structure for metallic pipes which is capable of suppressing cost increase while suppressing a deterioration in reliability of a joint portion between metallic pipes, the present invention provides a joint structure for metallic pipes in which: one of a first metallic pipe (11) containing a first metal (M1) as a main component and a second metallic pipe (12) containing a second metal (M2) as a main component includes an expanded-diameter connecting part (13) which is formed at an end part of the one metallic pipe, an inner diameter of the end part is greater than an inner diameter of an adjacent part (16) that is adjacent to the end part; an intermetallic compound layer (15) of the first metal (M1) and the second metal (M2) is present at an interface of the first metal (M1) and the second metal (M2) located between a brazing filler metal (14) and the one or the other of the metallic pipes; and a thickness of the intermetallic compound layer (15) is configured such that the thickness of an end portion (15b) on the side of a base end (13b) is smaller than the thickness of an end portion (15a) on the side of an open end (13a).