Stainless Steel-Copper Clad Material With Controlled Grain Size
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Solution Overview
Problem
The workability of clad materials roll-bonded with stainless steel and copper or copper alloys is reduced due to grain coarsening, leading to decreased elongation and mechanical strength.
Innovation Solution
A clad material with a grain size of the copper or copper alloy layer between 0.050 mm and 0.150 mm, achieved through specific rolling and annealing processes, including temper rolling, clad rolling, and diffusion annealing under controlled temperature conditions, to prevent excessive crystal growth and ensure bonding between stainless steel and copper layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If diffusion annealing is performed after cold rolling to bond stainless steel and copper layers, then bonding strength between layers is improved, but grain coarsening occurs leading to reduced elongation and workability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the grain size of the copper layer through controlled rolling reduction ratios and annealing temperature ranges. By optimizing these parameters, the copper grain size is maintained between 0.050-0.150mm, achieving both adequate bonding strength and preserved workability with elongation of 8% or more.
Solution Approach 2:
The patent employs dynamic control of the manufacturing process by adjusting rolling reduction ratios and annealing conditions based on the specific grain size targets. The process dynamically balances the competing requirements of bonding strength development through diffusion annealing while preventing excessive grain growth that would harm workability.
2Ease of operation
If rolling reduction ratio is increased to refine copper grain size, then elongation is maintained, but bonding strength between layers is reduced
Solution Approach 1:
The patent resolves this contradiction by optimizing the rolling reduction ratio parameter within specific ranges (20-60% per pass, total reduction 40-80%). This optimized parameter range achieves grain refinement that maintains elongation while the subsequent controlled annealing process ensures adequate bonding strength develops without excessive grain growth.
Solution Approach 2:
The patent employs dynamic process control by sequencing rolling operations with intermediate annealing steps. The rolling reduction ratio is dynamically adjusted across multiple passes rather than applied in a single operation, allowing grain refinement to progress while managing the balance between elongation preservation and bonding strength development.
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 solution significantly reduces grain coarsening, maintaining the elongation and mechanical strength of the clad material, making it suitable for applications like chassis and heat sinks while preventing warpage and ensuring stable roll bonding.
Implementation Method 1
diffusion annealing after stainless steel and copper are bonded to each other by cold rolling
Implementation Method 2
roll-bonded to each other by cold rolling and diffusion annealing
Data Source
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AI summary
A clad material (30) includes a first layer (31) made of stainless steel and a second layer (32) made of Cu or a Cu alloy and roll-bonded to the first layer. In the clad material, a grain size of the second layer measured by a comparison method of JIS H 0501 is 0.150 mm or less.