Lead-Free Copper Alloy Casting Grain Refinement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Copper alloy castings for water contact applications face challenges in achieving excellent machinability, strength, wear resistance, and corrosion resistance while minimizing lead content, which is harmful and environmentally detrimental, and require effective grain refinement without increasing manufacturing costs or using excessive Zr, which is expensive and prone to oxidation.
Innovation Solution
A copper alloy composition with specific ranges of Cu, Zr, P, Pb, Bi, Se, Te, and Zn, and optional additions of Sn, Al, As, Sb, Mn, Si, and Mg, refined during melt-solidification to achieve fine grain size and improved properties, with Zr added just before pouring to prevent oxidation and minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a large amount of Pb is added to secure machinability, then machinability is improved, but harmful effects on human body and environment increase
Solution Approach 1:
The patent changes the compositional parameters by strictly limiting Pb content to 0.01-4 mass% and introducing alternative elements (Bi: 0.01-3 mass%, Se: 0.03-1 mass%, Te: 0.05-1.2 mass%) to achieve machinability without excessive Pb. This parameter substitution resolves the contradiction between machinability and harmful effects.
Solution Approach 2:
The patent introduces intermediary elements (Bi, Se, Te) that mediate the machinability function previously provided solely by Pb. These elements act as substitutes that provide similar machining benefits while having reduced harmful environmental and health impacts.
2Manufacturing precision
If Zr content is increased to refine grains effectively, then grain refinement is improved, but oxidation of Zr and manufacturing cost increase
Solution Approach 1:
The patent optimizes the Zr content parameter to a precise range (0.0008-0.045 mass%) and combines it with P (0.01-0.25 mass%) to achieve effective grain refinement at low concentrations. This parameter optimization reduces Zr oxidation loss while maintaining grain refinement effectiveness.
Solution Approach 2:
The patent creates a composite grain-refining system using Zr in combination with P and controlled amounts of other elements. This composite approach enhances the grain refinement efficiency, allowing lower Zr content to achieve the same effect, thereby reducing oxidation losses.
3Manufacturing precision
If Zr is added early in melting process, then grain refinement effect is achieved, but oxidation of Zr increases and yield decreases
Solution Approach 1:
The patent applies preliminary protection measures by adding Zr at the final stage of melting (just before pouring) rather than early in the process. This timing strategy prevents Zr oxidation during the prolonged melting period while ensuring the element is present for grain refinement during solidification.
Solution Approach 2:
The patent creates a protected environment by conducting the final melting stage under conditions that minimize oxidation (using inert gas atmosphere or vacuum). This inert environment protects the Zr from oxidation while allowing it to dissolve into the molten copper alloy for effective grain refinement.
4Object-affected harmful factors
If Pb content is reduced to minimize harmful effects, then harmful effects are reduced, but machinability deteriorates
Solution Approach 1:
The patent changes the compositional parameters by introducing alternative machinability-enhancing elements (Bi, Se, Te) in controlled amounts. These elements substitute for Pb's machinability-providing function while having reduced harmful effects, thus resolving the contradiction.
Solution Approach 2:
The patent extracts the harmful Pb component to minimal levels (0.01-4 mass%) while retaining and enhancing machinability through other elements. This extraction approach removes the harmful substance while preserving the desirable machining properties through alternative mechanisms.
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 provides copper alloy castings with enhanced machinability, strength, wear resistance, and corrosion resistance, reducing lead content and manufacturing costs, while maintaining excellent mechanical properties and preventing casting defects, making them suitable for water contact and friction engaging applications.
Implementation Method 1
Zr is known as an element contributing to the grain refinement effectively
Implementation Method 2
Zr has an extremely strong affinity to oxygen, when Zr is melted and added in the air, Zr is likely to be oxidized
Data Source
AI summary
Copper alloy casting contains Cu: 58-72.5 mass %; Zr: 0.0008-0.045 mass %; P: 0.01-0.25 mass %; one or more elements selected from Pb: 0.01-4 mass %, Bi: 0.01-3 mass %, Se: 0.03-1 mass %, and Te: 0.05-1.2 mass %; and Zn: a remainder, wherein [Cu]−3[P]+0.5([Pb]+[Bi]+[Se]+[Te])=60-90, [P]/[Zr]=0.5-120, and 0.05[γ]+([Pb]+[Bi]+[Se]+[Te])=0.45-4 (the content of an element ‘a’ is denoted as [a] mass %; the content of γ phase is denoted as [γ]% by area ratio; and an element ‘a’ that is not contained is denoted as [a]=0). The total content of α phase and γ phase is 85% or more, γ phase content is 25% or less by area ratio, and mean grain size in the macrostructure during melt-solidification is 250 μm or less.