Black Copper Oxide Coating on Cu-Zn Alloy Fasteners
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Solution Overview
Problem
There is a demand for metal fastener members with various color tones at a lower cost, but existing technologies lack a cost-effective method to produce black metal fastener members using Cu-Zn-based alloys with high zinc concentrations.
Innovation Solution
A fastener member is created using a copper alloy with a zinc concentration of 30% by mass or more, which is then coated with a black copper oxide layer. The porosity of the coating is controlled to achieve both high adhesion and deep blackness, with the upper layer having a higher porosity than the lower layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Cu-Zn-based alloy with high zinc concentration (30% or more) is used to reduce cost, then material cost is reduced, but the surface blackening treatment becomes difficult to perform effectively
Solution Approach 1:
The invention changes the chemical composition parameters of the alloy by specifying a zinc concentration range of 30-43% and controlling other elements (Al, Si, Fe, Ni, Mn, Mg, Pb) within specific limits. This parameter optimization enables effective surface blackening while maintaining cost benefits from high zinc content
Solution Approach 2:
The invention creates a composite structure with a Cu-Zn-based alloy base material and a copper oxide coating layer formed on its surface. The specific alloy composition serves as an optimal substrate for the copper oxide coating, resolving the contradiction between cost reduction and blackening treatability
2Illumination intensity
If a copper oxide coating is formed to achieve deep black coloration, then color depth is improved, but adhesion between the coating and base material may be compromised
Solution Approach 1:
The invention creates a gradient in porosity within the copper oxide coating layer, with the lower layer having lower porosity (5-20%) for strong adhesion to the base material and the upper layer having higher porosity (20-40%) for deep black coloration. This local quality differentiation resolves the contradiction between adhesion and color depth
3Illumination intensity
If the porosity of the copper oxide coating is increased to enhance blackness, then color depth is improved, but coating adhesion to the base material deteriorates
Solution Approach 1:
The invention divides the copper oxide coating into two distinct layers with different porosity characteristics: a lower layer with 5-20% porosity for adhesion and an upper layer with 20-40% porosity for blackness. This segmentation allows each layer to optimize its function without compromising the other
Solution Approach 2:
The invention creates a gradient in porosity within the copper oxide coating layer, with the lower layer having lower porosity (5-20%) for strong adhesion to the base material and the upper layer having higher porosity (20-40%) for deep black coloration. This local quality differentiation resolves the contradiction between adhesion and color depth
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 allows for the production of black metal fastener members at a lower cost while maintaining excellent adhesion and deep black coloration, addressing the need for cost-effective color variation in fastener members.
Implementation Method 1
a black copper oxide coating covering at least a part of the base material
Implementation Method 2
The porosity of the coating is controlled to achieve both high adhesion and deep blackness
Data Source
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AI summary
There is provided is a black metal fastener member that can be manufactured at low cost. A fastener member comprises a base material made of a copper alloy containing zinc at a concentration of 30% by mass or more and 43% by mass or less, and a black copper oxide coating covering at least a part of the base material.