Casting

Exhibit 1 shows the performance targets defined for casting products. As shown in Exhibit 3-2, the industry has determined that additional targets need to be set in a number of casting technical areas.

Exhibit 1: Performance Targets for Casting

There are a number of technology-related barriers that prevent the immediate attainment of the casting performance targets. They may be classified into five major categories: skim and dross, casting, metal processing and treatment, melting and recycling, and crosscutting.

An ideal process would eliminate skim and dross entirely. Until such technology exists, better methods for treating/removing skim and dross will need to be developed. One barrier to making better use of skim and dross is the lack of industry coordination in developing applications for nonmetallic product (NMP).

Casting barriers encompass both process control problems and safety problems. "Bleedouts" are a problem, particularly in direct chill casting. The lack of aluminum solidification models is a major barrier to process improvements. Another problem is the lack of technology to feed molten metal without turbulence. A widespread safety concern in aluminum casting plants is aluminum-water explosions.

Several barriers related specifically to continuous casting include cooling limitations, a lack of methods for continuously casting higher content alloys, and the inability to perform in-line surface removal.

The primary concern in this category is the presence of impurities. Contaminants like iron, magnesium, lead and other elements, and nonmetallic inclusions, create a number of product quality problems.

Scrap separation and processing are key problems in the area of melting and recycling. Automatic methods that can achieve aluminum scrap separations on an alloy-by-alloy basis may need to be developed. Another problem with producing recycled metal is that, the specifications for major secondary alloys are decades old and allow products with lower amounts of impurities and thus higher quality to be produced than needed by the end-user. The furnaces currently used for melting are highly energy inefficient and are thus expensive to operate.

There are many technical areas where problems are generic and shared information could help to develop either common or proprietary solutions. However, due to competition its difficult for the industry to work cooperatively. Too often, research and problem-solving are approached on a segmented, operation-specific level, without considering how the system as a whole (from primary through finished product) could be improved. Another cross-cutting barrier is the lack of good, reliable, low-cost, real-time sensors that can be used to monitor and directly or indirectly control the quality and microstructural properties of intermediate and final products.

Casting-related research that is needed to overcome these barriers can be organized under six major categories (Exhibit 2).

Understanding process fundamentals is perhaps the most important area of research for improving casting methods. One of the highest research priorities is to develop fundamental information on the solidification of alloys in order to better predict microstructure, surface properties, and the relationship of stresses and strains at elevated temperatures. One of the ultimate goals of such research would be the development of a computer model that is capable of process control in real-time.

Exhibit 2. Major Research Needs of Aluminum Casting Processes (with priority marked)

Another high-priority in the area of process fundamentals is the creation of a cooperative continuous casting consortium. This consortium would conduct generic, precompetitive research of benefit to the industry as a whole. The consortium could be established as a "center of excellence" at a university or at a separate location. The consortium would include researchers from industry, suppliers, customers, universities, and national labs. Information developed through cooperative research would be shared.

Many research needs are considered "new manufacturing concepts." These include research that will result in fundamental changes to current manufacturing practices or processes. The highest priority in this area is to develop technologies for removing specific impurities (magnesium, iron, lead, lithium, silicon, and titanium, etc.) from the melt. Another high-priority is to develop a noncontact sensor and method for identifying and separating scrap materials.

A long-term R&D priority is to develop the ingot plant of the future to produce high quality metal on demand tailored to the customer's needs with high energy efficient and zero waste. Other important needs include the development of a low-cost process for alloy/scrap purification/upgrade and the development of processes to better separate metal from dross/salt cake. Finally, there is an important need to find a productive use for nonmetallic products. While the long term goal is to eliminate the creation of dross and salt cake entirely, there is a need in the mid-term to find ways to better separate and make use of these waste materials.

Sensor research is needed to improve both the quality and structure of cast metal. Such sensors should help either detect and remove impurities and inclusions, or monitor microstructure and uniformity. The development of a low-cost inclusion sensor is considered a high priority.

The development of a high-capacity furnace design for the future is one of the highest priority R&D needs that can reduce energy use, improve environmental performance, and lower costs.

The R&D needs have been grouped according to the time frame in which R&D results could be expected and identified the organization or group most likely to fund the research (Exhibit 3 below). They also established linkages among the R&D needs.

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Exhibit 3: Linkages among the R&D needs