Copper alloys containing lead (Pb) as an alloying element were regularly used for drinking water applications. In response to the call to reduce the lead content in drinking water, the industry introduced many lead-free alloys including the bismuth-containing alloys developed in the AFS led consortium in 1990s. Since then, these alloys have evolved and replaced lead-containing copper alloys in drinking water applications all over the world. Industry has adopted new processing technologies and testing methods to make the lead-free alloys widely usable in an affordable way. This paper reviews these developments in bismuth-containing and other lead-free copper alloys since the early announcements.

Keywords: copper alloys, lead-free, castings, plumbing, corrosion testing, drinking water

INTRODUCTION

Copper and its alloys have been used for drinking water applications including pipes, valves and faucets since the early 1900s. The excellent corrosion resistance of these alloys in drinking water is the major reason for the extended use. Copper alloys develop passive surface layers when exposed to drinking water. This coating moderates the corrosion rate as well as reduces the leaching of metals into the drinking water. 

Plumbing components have traditionally been made from sand cast red and semi-red brasses (alloys C83600 and C84400) containing lead as one of the alloying elements. The lead content of these alloys varies between 4%–8%. Lead, in brasses, provides two advantages: pressure tightness and ease of machining. Lead is insoluble in solid copper and found as finely distributed globules in the inter-dendritic areas of the cast alloys contributing to the pressure tightness and machinability.  

However, the findings that lead can cause developmental challenges, especially in children, made governments introduce regulations controlling lead content in drinking water. Leaded-copper alloys used for plumbing applications, including solders and components, were identified as possible sources of lead.  

The Lead and Copper Rule (LCR) is a U.S. Environmental Protection Agency (EPA) regulation that allows a maximum 15 µg/L (15 ppb) of lead in potable water. Other jurisdictions including EU and Canada proposed limits to 5 µg/L (5 ppb). In conjunction with the Lead and Copper Rule, the EPA commissioned National Sanitation Foundation International (NSF) to develop standards for measuring, approving, and monitoring lead, copper, and many other metals and chemicals that can be introduced into potable water. In response to this, NSF has developed several standards addressing these requirements, most notably NSF Standard 61. The NSF has also established the lead action limit for point-of-use products (faucets) and in-line mechanical devices at 11 ppb. This is lower than the EPA’s 15 ppb or 15 µg/L limit because the EPA assumes that the additional 4 ppb could be contributed by other sources.  
Apart from this limit, the Safe Drinking Water Act (SDWA) by the U.S. EPA has reduced the maximum allowable lead content—that is, content that is considered “lead-free”—to be a weighted average of 0.25% calculated across the wetted surfaces of pipes, pipe fittings, plumbing fittings, and fixtures and 0.2% for solder and flux. While it is possible to surface treat the lead-containing copper alloys to reduce the lead intake by drinking water, the limits on allowable lead in alloys necessitates the development of lead-free copper alloys and solders with less than 0.2% Pb. Because of the presence of lead in brass scrap, none of the secondary casting alloys are truly lead-free. Thus, although no lead is intentionally added, a small but measurable amount of lead is typically present in many copper casting alloys.

Early on, lead-free solders were introduced for drinking water applications and the trend is continuing for solders used in other industrial applications. Attention was later focused on components such as valves and faucets which led to the development of various low-lead alloys to replace leaded-copper alloys. 

Note: Modern Casting will print this paper and the others in this summary series in their entirety in future issues this year.

Phase Change Materials (PCMs) for Thermal Management During Permanent Mold Casting 

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

Dynamic casting processes such as permanent mold and die casting require effective thermal management of molds to balance rapid heat absorption from the molten metal and immediate heat recovery to the mold for subsequent casting cycles. Existing thermal technologies like direct flame and coolants have difficulty controlling heat transfer, resulting in thermomechanical fatigue of the mold due to excessive heating and cooling. Controlling the heat transfer in molds is paramount to ensuring the production of high-quality castings and reducing production cycle times. An innovative approach to controlling thermal gradients in molds involves incorporating phase change materials (PCMs) inside the molds. With their thermal energy storage capability and high latent heat, PCMs embedded in molds facilitate mold temperature self-regulation for heating and cooling as the PCM undergoes solid-liquid phase transformations during the casting process. In this paper, the feasibility of PCMs in dynamic casting processes is presented.

Keywords: thermal management, heat transfer, phase change material (PCM), permanent mold casting, interfacial heat transfer coefficient (IHTC)

INTRODUCTION

Thermal management of permanent molds plays a crucial role in ensuring rapid solidification rates and preventing the formation of defects during solidification. Proper thermal management will also decrease casting cycle time and enhance cast product quality. The inability to control thermal conditions consistently throughout each casting cycle affects not only quality characteristics, such as porosity and shrinkage, but also results in delayed solidification. Thermal management during solidification relies on the use of thermal technologies, such as direct flame and coolants, which have been widely utilized to manipulate thermal gradients in molds. However, use of these current thermal technologies leads to excessive heating and cooling, which exacerbates thermomechanical fatigue of the molds and negatively affects product quality and productivity. For effective thermal management, it is essential to maintain a balanced control of thermal gradients during both the heating and cooling phases of the process.
Phase change material (PCM) has been proposed as a potential heating and cooling strategy to regulate thermal conditions by leveraging its latent heat thermal energy storage capability. This approach has applications in various fields, including construction, semi-conductor, and renewable power system, in response to evolving environmental standards. Essentially, PCMs possesses an intrinsic ability to absorb and release thermal energy during phase transformation cycles, leading to both heating and cooling. This latent heat storage capability allows for heat to be stored and released even with minimal temperature variation, offering a storage capacity that is 5–14 times greater than that of sensible heat storage. Consequently, the application of PCM has the potential for manipulating thermal gradients within a system, enabling efficient thermal management.

The application of PCMs to manage thermal gradients in casting processes and systems has been studied. In particular, Noohi et al. investigated the efficiency of metallic PCMs as chills for rapid solidification for sand castings. Pure zinc (Zn) was chosen as the PCM chill material for experiments with an Al-4.5 wt.% Cu-0.2 wt.% Fe alloy. As a result, castings using a Zn PCM chill solidified in 380s, whereas those with traditional chills required 440s. The Zn PCM chill dissipated heat up to 60s faster due to its significant latent heat absorption effect. These findings validate the feasibility of metallic PCMs for static casting processes. However, the technology remains nascent for incorporation in dynamic casting processes, such as permanent mold casting and die casting. The challenge is that in dynamic casting processes, one requires not only rapid heat removal but also heat recovery for subsequent casting cycles.

Although rapid heat dissipation using PCMs has been validated in static casting processes, i.e., sand casting and investment casting, the literature for the application of PCMs for dynamic casting processes is lacking. Ideally, the reversible exothermic and endothermic phase transitions of PCMs can effectively control thermal gradients in molds, facilitating rapid solidification and heat recovery to the mold by integrating the PCM into the permanent mold casting system during cyclic casting processes. The primary objective of this study is to investigate the potential application and appropriate design of PCMs within permanent molds for thermal management, both experimentally and through finite element (FE) simulation and modeling. Specifically, this work examines the effects of geometrical variables and heat transfer characteristics of the molds incorporating PCM on the solidification process.

Foundry Safety Management System at Virginia Tech
Alan P. Druschitz, Virginia Tech, Materials Science and Engineering, Blacksburg, Virginia

ABSTRACT

 The Environmental Health and Safety Department at Virginia Tech created a safety management system for the on-campus Kroehling Advanced Materials Foundry. This system was so successful that it was rolled out to the entire University. This paper describes the safety management system and how it is used by students, faculty, and staff at the foundry.

Keywords: occupational health and safety, safety management, foundry safety

INTRODUCTION

The role of the Virginia Tech Environmental Health and Safety Department is to promote a positive, integrated safety culture for the university community, advocate safe and healthy living, learning, and working environments, and help departments comply with local, state, and federal regulations and mandates. When Virginia Tech decided to build the Kroehling Advanced Materials Foundry, the Environmental Health and Safety Department was asked to develop a comprehensive safety management system for the new facility. The system that was developed was so successful that it was eventually rolled out to the entire Virginia Tech University. The director of the Virginia Tech Foundry Institute for Research and Education, which is located at the Kroehling Advanced Materials Foundry, is responsible for maintaining the foundry safety management system.

Foundry Safety Management System

The Virginia Tech Safety Management System is online and available 24/7. To access the safety management system, faculty, staff, or students go to the Virginia Tech Environmental Health and Safety homepage and click on the Safety Management System link, Figure 1, which takes the user to the lab/workspaces that they are “associated” with, Figure 2. The user then selects the lab/workspace in which they are interested.

If the user is not familiar with the Virginia Tech (VT) EHS safety management system, a comprehensive user guide is available, Figure 3.

Influence of Ceramic Aggregate on Cast Iron Properties
Scott R. Giese and Justine Radunzel, University of Northern Iowa, Cedar Falls, Iowa

ABSTRACT

 Because of the Occupational Safety And Health Administration (OSHA) Silica Rule under enforcement in the foundry industry today, many iron foundries have or are considering changing from silica sand to a ceramic aggregate to alleviate the issue. The AFS Cast Iron Research Committee initiated a research project to understand the impact of the change in the microstructure and associated mechanical properties on cast iron that might accompany the use of these ceramic molding media. Funded by the American Foundry Society (AFS) and Ductile Iron Society (DIS), a research project was performed to assess the mechanical properties of class 40 gray iron and 80-55-06 ductile iron castings using an experimental casting matrix of the three aggregates with two sand to metal ratios. Results indicated that ceramic aggregates have a noticeable influence on the mechanical properties of gray and ductile iron but the sand to metal ratio has an influence on the degree of property variation.

Keywords: ceramic aggregates, silica sand, ductile iron, gray iron, and mechanical properties

INTRODUCTION

Due to the OSHA Silica Rule under enforcement in the foundry industry today, one scenario that many foundries are considering is a change from silica sand, used in most foundries today, to ceramic sand/media to alleviate the issue. There are many questions associated with this change, but one that is of primary importance is understanding the change, if any, in microstructure and the associated mechanical properties that might accompany the use of ceramic sand/media.

The American Foundry Society funded two research projects in the mid-2010s investigating the use of ceramic molding aggregates, mostly focused on the substitution of this aggregate in clay-bonded green sand molding operations. The primary objective of the investigations addressed foundry concerns in casting surface, surface defects (in terms of metal penetration and veining), attrition losses, and sand reclamation. The AFS Cast Iron Research Committee and Ductile Iron Society initiated a research program exploring the influence of ceramic aggregates leading to changes in solidification behaviors affecting the microstructure and mechanical properties of gray and ductile iron castings. Presently, information is not available for the foundry industry to understand how thermal physical characteristics can influence subtle casting design and metallurgical changes leading to potentially costly tooling alterations and mechanical properties specifications.