Lead-Tin-Silver-Bismuth Alloy for Thin Battery Grids
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Solution Overview
Problem
Lead-acid battery grids face challenges with handling and processing due to inadequate hardness, corrosion, and the formation of non-conductive oxide layers, particularly in thin grids, which leads to premature failure and increased production costs.
Innovation Solution
A lead-based alloy comprising at least 95% lead, with specific concentrations of tin (0.500% to 2.000%), silver (0.006% to 0.050%), and bismuth (0.005% to 0.050%), which allows for rapid hardening, improved mechanical properties, and resistance to corrosion and oxide layer formation, enabling the production of thin grids without artificial aging and enhanced handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thin grids are produced to meet modern battery requirements for high voltage and rapid recharge, then battery performance is improved, but handling and processing become more difficult due to inadequate hardness
Solution Approach 1:
The patent modifies the chemical composition parameters of the lead alloy by adding specific amounts of tin (0.05-2.00%), silver (0.006-0.050%), and bismuth (0.005-0.050%). These parameter changes result in rapid hardening of the alloy after casting, providing sufficient hardness for easy handling of thin grids while maintaining the thin grid design for high battery performance
Solution Approach 2:
The patent creates a composite alloy system combining lead with multiple alloying elements (tin, silver, bismuth). This composite material approach synergistically combines the benefits of each element: tin provides hardening, silver improves corrosion resistance and grain structure, and bismuth enhances hardness and reduces eutectic temperature, collectively solving both the thin grid performance and handling issues
2Reliability
If lead-calcium alloys are used to reduce corrosion compared to lead-antimony alloys, then water loss resistance is improved, but hardness and handling difficulty worsen
Solution Approach 1:
The patent adjusts the alloy composition by limiting calcium to 0.00-0.010% and adding tin (0.05-2.00%), silver (0.006-0.050%), and bismuth (0.005-0.050%). This parameter change shifts the hardening mechanism from calcium-based to tin and bismuth-based, achieving sufficient hardness while maintaining the low-corrosion advantage of low-calcium alloys
Solution Approach 2:
The patent introduces silver as an intermediary element that mediates between the conflicting requirements of low calcium content and sufficient hardness. Silver forms a eutectic structure with lead that provides grain refinement and hardening, while the low calcium content maintains corrosion resistance. The silver acts as a mediator that enables hardness without requiring high calcium levels
3Temperature
If rapid cooling is applied to harden lead-calcium alloy grids, then temperature reduction is improved, but deformation and thickness changes increase due to inadequate hardness at elevated temperatures
Solution Approach 1:
The patent modifies the alloy composition to include tin (0.05-2.00%), silver (0.006-0.050%), and bismuth (0.005-0.050%), which fundamentally changes the hardening kinetics. The alloy hardens rapidly at relatively low cooling rates, eliminating the need for aggressive rapid cooling that causes thermal shock and deformation, thus achieving both effective temperature reduction and deformation control
4Productivity
If thin grids are produced to increase the number of grids per battery, then battery voltage and amperage are improved, but corrosion resistance worsens leading to premature failure
Solution Approach 1:
The patent creates a multi-element composite alloy (lead-tin-silver-bismuth) where each element contributes specific properties. Silver provides exceptional corrosion resistance through formation of protective surface films and grain boundary strengthening, while tin and bismuth provide hardening. This composite approach allows thin grid design for high voltage/amperage while maintaining superior corrosion resistance for long service life
Solution Approach 2:
The patent optimizes the concentration parameters of alloying elements, particularly silver (0.006-0.050%), to achieve maximum corrosion resistance. The specific parameter ranges are designed to form protective surface films and refine grain structure, providing enhanced corrosion resistance that protects thin grids from premature failure while maintaining high battery performance
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 alloy enables the production of thin grids with improved mechanical properties and corrosion resistance, allowing for efficient handling and reduced premature failure, while maintaining effective charge acceptance and battery performance.
Implementation Method 1
the alloy... harden relatively rapidly
Implementation Method 2
Lead-calcium alloys... tend to form Pb 3 Ca precipitates over Sn 3 Ca precipitates
Data Source
AI summary
A lead-acid battery grid made from a lead-based alloy containing, in addition to lead, tin at a concentration that is at least about 0.500%, silver at a concentration that is greater than 0.006%, and bismuth at a concentration that is at least about 0.005%, and, if calcium is present in the lead-based alloy, the calcium is at concentration that is no greater that about 0.010%.