Fine-Grained High-Tensile Brass Alloy for Cold Forming Stability
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Solution Overview
Problem
Existing special brass alloys for friction applications suffer from coarse grain size leading to grain boundary cracking during cold forming and reduced strength under thermal variations, requiring improved grain structure and thermal relaxation behavior.
Innovation Solution
A special brass alloy with a homogeneous and fine-grained microstructure, characterized by an α-β structure where the α-phase penetrates the β-matrix, resulting in enhanced thermal relaxation resistance and reduced susceptibility to grain boundary cracking, achieved through adjustments in alloy composition, particularly with Sn and Cr contributing to grain refinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional special brass alloys are used for friction applications, then the alloy provides basic friction resistance, but the coarse grain size causes grain boundary cracking during cold forming and reduces strength under thermal variations
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alloy composition parameters, specifically limiting Pb to ≤0.1 wt%, Sn to 0.18-0.4 wt%, Cr to 0.18-0.4 wt%, and Zn to 32-40 wt%, while maintaining Cu as the base metal. These compositional parameter changes result in a refined grain structure that eliminates grain boundary cracking during cold forming and improves thermal relaxation resistance, thereby resolving the contradiction between strength and reliability
Solution Approach 2:
The patent employs composite material principles by creating a multi-phase alloy system consisting of Cu matrix with dispersed Sn and Cr elements that form fine intermetallic compounds. This composite structure at the microlevel provides both the ductility needed for cold forming and the strength required under thermal variations, eliminating the grain boundary cracking issue while maintaining overall alloy strength
2Stability of the object's composition
If alloy composition is adjusted to refine grain structure, then thermal relaxation resistance improves, but alloy composition complexity increases
Solution Approach 1:
The patent resolves this contradiction through optimized parameter changes by establishing specific compositional ranges: Sn (0.18-0.4 wt%), Cr (0.18-0.4 wt%), and Zn (32-40 wt%). These controlled parameter changes achieve fine grain structure and improved thermal relaxation resistance without excessive complexity, as the ranges are precisely defined but not overly restrictive, balancing performance improvement with manufacturing feasibility
Solution Approach 2:
The patent applies local quality principles by introducing Sn and Cr elements that locally form fine intermetallic compounds and precipitates within the Cu matrix. These localized structural refinements improve thermal relaxation resistance without requiring complex overall composition, as the beneficial effects are achieved through targeted local phase formation rather than uniform complexity throughout the alloy
Data Source
AI summary
A special brass alloy containing 62.5 to 65% by weight Cu, 2.0 to 2.4% by weight Mn, 0.7 to 0.9% by weight Ni, 1.9 to 2.3% by weight Al, 0.35 to 0.65% by weight Si, 0.3 to 0.6% by weight Fe, 0.18 to 0.4% by weight Sn and Cr, either alone or in combination, ≤0.1% by weight Pb, the remainder consisting of Zn and inevitable impurities.