Lead Alloy Strip Casting via Abraded Drum Surface
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Solution Overview
Problem
Existing methods for casting thick lead alloy strips, such as gravity casting, result in porous and non-uniform microstructures, leading to corrosion, grid growth, and high water loss, which shorten battery life, and high-speed continuous casting methods suffer from longitudinal cracks.
Innovation Solution
Abrading the casting surface of a drum in a tundish casting apparatus with angular materials like crushed silicon carbide, increasing the tundish and lip insert height, and controlling cooling rates to create a coarse textured surface, allowing for thicker, crack-free lead alloy strips with up to 5 wt% antimony to be cast at high speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gravity casting method is used to produce thick battery electrodes, then the method is simple and commercially viable, but the microstructure becomes porous and non-uniform leading to corrosion and grid growth
Solution Approach 1:
The patent replaces the gravity-based casting mechanism with a continuous casting system using a rotating chilled drum. The molten lead alloy is poured onto the rotating drum surface where it solidifies under controlled cooling, eliminating the porous non-uniform structure caused by gravity casting while maintaining manufacturing feasibility.
Solution Approach 2:
The patent utilizes controlled phase transition of molten lead alloy from liquid to solid state on the chilled drum surface. By controlling the cooling rate and drum temperature, the alloy solidifies into a dense uniform microstructure without the porosity characteristic of gravity casting, thereby improving corrosion resistance.
2Productivity
If high speed continuous casting is used to increase productivity, then casting speed increases, but longitudinal cracks form in the strip during solidification
Solution Approach 1:
The patent changes the cooling parameters by using a chilled drum surface with controlled temperature and a specific cooling rate. This parameter adjustment allows the alloy to solidify uniformly at high casting speeds without forming longitudinal cracks, maintaining strip integrity while increasing productivity.
Solution Approach 2:
The patent employs a rotating drum system where the casting surface is continuously moved. This dynamic approach allows the molten alloy to be continuously fed and solidified at controlled rates, enabling high-speed casting while preventing crack formation through uniform stress distribution during solidification.
3Manufacturing precision
If thin and narrow strip is cast at low speeds, then casting quality is maintained, but productivity is limited to 36-38 feet per minute
Solution Approach 1:
The rotating chilled drum provides continuous motion and uniform cooling across the casting surface. This dynamic system maintains consistent thermal conditions that ensure high casting quality while allowing operation at much higher speeds (up to 135 feet per minute) compared to static low-speed casting methods.
Solution Approach 2:
The controlled phase transition on the chilled drum surface creates a fine grain structure during solidification. This uniform microstructural development maintains casting quality even at high speeds, overcoming the limitation where increased speed previously degraded strip quality.
4Strength
If thick strip is cast to increase component strength, then electrode strength improves, but longitudinal cracks develop during solidification
Solution Approach 1:
The patent adjusts the cooling parameters by using a chilled drum with controlled surface temperature and cooling rate. This parameter optimization allows thick strip to be cast with uniform solidification, achieving the desired strength while preventing the longitudinal cracks that typically occur in thick section casting.
Solution Approach 2:
The replacement of gravity casting with continuous casting on a rotating chilled drum provides uniform cooling throughout the thick strip cross-section. This substituted method eliminates the non-uniform cooling and associated cracking problems inherent in traditional thick section casting while maintaining the strength benefits of thick strip.
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 method enables the continuous high-speed casting of thick, crack-free lead alloy strips with a fine grain structure and no porosity, suitable for industrial batteries, achieving a three-fold increase in strip thickness to 0.185 inches without longitudinal cracks at speeds up to 135 feet per minute.
Implementation Method 1
the coarse and irregular surface texture increases the thermal resistance at the interface between the cast metal and the drum surface to reduce the rate of heat transfer and slow down cooling
Implementation Method 2
cooling the abraded casting surface of the drum to a temperature in the range of about 100° to 210°F (about 38°C to 99°C) to solidify a strip of lead alloy
Data Source
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AI summary
A method and apparatus for continuously casting lead alloy strip on a casting surface on substantially the upper half of a rotatable casting drum from a pool of molten lead alloy at a high speed comprising imparting a coarse texture to the casting surface, providing a tundish containing a pool of the molten lead alloy at a predetermined temperature adjacent a substantially vertical upwardly-moving portion of said casting drum, the tundish having a graphite lip insert having an open front defined by a Hp insert floor and opposed sidewalls cooperating with and commencing at a substantially vertical portion of the casting surface to contain said molten lead alloy in the lip insert, controlling the height of the surface level and temperature of the molten lead alloy in the lip insert, moving the casting surface upwardly through the pool of molten lead alloy by rotating said drum for depositing the lead alloy thereon, cooling the casting surface of the drum to solidify a strip of the lead alloy on substantially the upper half of the rotatable casting drum, and stripping the strip from the casting surface. The molten lead alloy preferably is a antimony-lead alloy containing about 0.3 to 5.0 wt% antimony, the balance essentially lead.