What Is Continuous Casting?
Continuous casting allows metals and alloys to be stretched, shaped and solidified without the need for an interruption, reducing waste while improving yield, cost efficiency, and quality. Introduced into steel manufacturing the 1950s as an alternative to ingot molds, the continuous casting machine has now become a standard in premium battery grid production. Using a series of rollers and water-cooled molds, the process lessens the chance of impurities and provides better thickness ratios. To get a better idea of the continuous casting process, let’s review the basics, from molten metal to a finished grid.
Continuous Casting: Step by Step
In continuous grid manufacturing, molten lead is ladled into the casting machine, where it is then molded, cooled and stretched into the finished product. Though different machines offer various advantages, the basic process is the same. Here is how the process unfolds, step by step:
- Liquid alloy is ladled into a tundish, which directs the flow of the material into the mold. The tundish acts as a reservoir, continuing the flow of metal while the ladle refills.
- The metal pours into a water-cooled mold, where it is partially solidified and given its basic grid shape. This is the primary cooling stage.
- The semi-solid grids are sent through the strand guide, continuing to stretch the material to the desired thickness while cooling persists in the secondary cooling stage.
- The fully solidified grids are sent through straighteners, where they achieve their final dimensions.
- The finished grids are wound into a roll, ready for storage.
Wirtz Continuous Grid Casting System
At Wirtz, we’ve created a continuous casting system that eliminates lead scrap in grid production. Safer, more cost efficient and productive, the system offers flexible grid designs and all the advantages of conventional gravity casting. The machines are capable of producing up to 120 feet per minute, depending on the grid design, thickness and alloy composition. These grids are designed for use in automotive and motorcycle batteries, industrial machinery and wound cell batteries.
Positive and Negative Plating
To manufacture both positive and negative battery plating, you need two separate machines, calibrated for the different alloys. The Wirtz Conroll GRM-150 and similar models are engineered to optimize grain structure. Increased structural stability reduces the risk of corrosion for a longer lasting positive charge. Its counterpart is the Concast CC-13200, which manufactures negative grids. Specially calibrated for calcium alloys, pure lead and antimony alloys, this continuous casting machine is engineered for precise grid manufacturing without lead waste. Features of both machines include:
- Variable grid designs
- Wet or dry grid production
- Single or double-wide configurations
The Importance of Strand Containment
In configuring your continuous casting system, pay close attention to your roller or straightening apparatus. If bending forces are applied too early or too late, you risk compromising the integrity of the metal. If roller spacing is not properly calibrated, bulging can occur, during which the molten core pools unevenly within the solidified shell. Your roller configuration must ensure consistent support and shaping throughout the process. Otherwise, weakness and ruptures are likely to manifest.
Bending and Straightening
Throughout the casting process, the metal needs to be carefully and precisely bent repeatedly. However, if not done properly, bending can cause excessive strain, weakening the metal. When semi-solid metal is bent, tension is applied to the outer shell while the molten center compresses. If the shell is put under too much tension, cracks develop. Finding the right arc to bend your grids depends on the mechanical properties of the materials used. Additionally, a multi-point unbending process can help minimize the effects of these strains. When appropriately calibrated and arranged, most imperfections and malformations are generally avoidable.
Consider Continuous Casting in Your Operation
There are many benefits to integrating continuous casting into your battery grid manufacturing process. From minimal waste to increased production yield, it allows manufacturers to increase production while minimizing costs. Despite its limitations in the containment process, it otherwise offers a seamless completion, void of imperfections and wasteful by products. At Wirtz, we’re a continuous casting machine manufacturer always seeking to improve our engineering and design. To find out more information about our continuous casting machines, furnaces or any of our other industrial equipment, please contact Wirtz to get in touch with a representative.