Following are summaries of three research papers presented in Milwaukee this April.

Evaluation of Thermal Technologies for Thermal Management of Permanent Molds (24-027)

Cheolmin Ahn, Carl Söderhjelm, Diran Apelian, Advanced Casting Research Center (ACRC), University of California, Irvine

Research Focus

Thermal management can play a pivotal role in the production of high-quality castings and the reduction of production cycle time by ensuring desired solidification patterns during dynamic casting processes such as permanent mold and diecasting processes. These processes require rapid heat removal and careful heat recovery for subsequent casting cycles, unlike traditional batch processes. Moreover, thermal management in specific localized regions of the mold is needed due to diverse mold geometries and shapes, as well as recent applications such as gigacasting. Local control of heat transfer for thermal management can be accomplished with the application of various thermal technologies, both heating and cooling. In this work, heat transfer characteristics of various thermal technologies were evaluated quantitatively through both modeling and experimental work.

The Discovery

To efficiently compare the kinetics of heating technologies, we needed to consider the adequate heating time for permanent mold casting, as it significantly impacts the casting production time. Therefore, an efficient heating time of 90 seconds was selected. According to this critical heating time, the heating rates of the steel die model were 3.38°C/s by cartridge heating, 2.06°C/s by direct flame, 1.59°C/s by hot oil, 1.26°C/s by hot water, and infrared heating at 1.26°C/s. Consequently, cartridge heating represented the highest kinetic performance among these heating technologies. These findings open up the possibility of efficiently utilizing certain heating technologies for both the heating cycle and pre-heating applications in permanent molds.

Development of Improved Repair Welding Alloy and Process for Al-Cu Sand Castings (24-052)

David J Weiss, Eck Industries, Inc. (Retired), Gerald A Gegel, Material & Process Consultancy 

Research Focus

This project addresses important considerations in the welding of 200 series alloys, specifically castings produced from A206 alloy. This alloy is difficult to weld unless key process parameters are controlled. As the volume of the welded area increases, the difficulty is compounded. We show that control of temperature of the casting during welding is the most important process parameter for low defect welding with acceptable mechanical properties, assuming that basic good welding practices are followed. The weld filler rod is also an important consideration, with the most successful welds produced using 2319 alloy.

To mitigate the effects of weld wire chemistry and other variables on weld repair quality, a project was initiated to optimize a weld alloy chemistry and the welding parameters necessary for the successful weld repair of A206 sand castings. The key objectives are summarized as follows:

• Develop or determine the optimized weld alloy.
• Develop improved repair welding practices.
• Establish effect of welding parameters on weld quality.
• Determine the effects of homogenizing post-weld heat treats.
• Determine effect of weld repair on tensile properties of A206 sand castings.

The Discovery

1. The use of 206 welding rod yields better properties when welded correctly, but it has a narrower process window to produce sound welds than the alternative 2319 alloy.

2. 2319 welding rod is easier to use than 206 welding rod. It has a higher Cu content than 206 which reduces its liquidus making it easier to puddle in the weld. However, the higher Cu content also reduces its incipient melting temperature, making weld interfaces more prone to defects if overheated.

3. Alternate welding rods used in this study did not show useful advantages over 206 or 2319 and in many cases led to greater amounts of defects and lower mechanical properties.

4. The most important factors in welding 200 series alloys, particularly for large defects is the control of preheat and the interpass temperature during welding. This must be controlled to a greater extent than in aluminum-silicon alloys. 

5. Preheat temperatures of around 250F (121C) and interpass temperatures of no more than 550F (288C) will produce acceptable welds using 2319 filler rod.

Industry 4.0 Adoption Using AI/ML Driven Metamodels for High-Performance Ductile Iron Sand Casting Design and Manufacturing (24-114)

Jiten Shah, Product Development & Analysis (PDA) LLC, Brian Began, American Foundry Society

Research Focus

Design and manufacturing of high-performance ductile iron sand castings is a multi-variant complex process with much uncertainty involved. As a result, in spite of a well-controlled operation and an experienced workforce, iron foundries in a production environment do face sporadic shrinkage and lots with nonconforming property requirements, resulting in scrap or rework. 

A framework and methodology consisting of AI (Artificial Intelligence) and ML (Machine Learning) tools, coupled with ICME (Integrated Computational Materials Engineering) and process simulation tools will be presented to quantify uncertainty (UQ). Metamodels, both predictive and prescriptive in near real-time were developed using such AI/ML techniques using historical production and selective Design of Experiments (DOE)-generated additional data. The data will be presented including details on successful corrective action production trials. The proposed framework and approach is applicable to solve such complex problems encountered in the foundry and machining operations where there is uncertainty.

The Discovery

• The metamodels developed are indicative of the impact of some of the trace elements on as-cast properties and shrinkage tendency in 100-70-03 grade of ductile iron sand castings—Al, B, V, Zn, Zr, Pb, Ti.

• Metamodels can be used to optimize the chemical composition by reducing expensive alloying elements like Ni, Mo, and Cr; keeping them on the lower side, thereby relieving some of the supply chain strains currently being experienced in the industry.

• One of the experimentally-derived Metamodels can be used by the design engineer to predict the as-cast properties and shrinkage tendency in various areas of the casting geometry for 100-70-03 grade of sand cast ductile iron as a function of section thickness, chemical composition, orientation of the feature, mold hardness and type of mold binder intended to be used.