Several no-lead copper alloy options for water components: metalcasters have a variety of no-lead copper alloys to choose from to make cast components for potable water systems, and each alloy requires specific practices when converting from leaded alloys.
The current regulations require all products contacting potable water must be lead-free (as defined by the law). The metalcasting industry began the conversion to lead-free alloys in the 1990s in anticipation of the new regulations. The conversion accelerated from 2006-2013 as the new rules began taking effect. The first laws started in California and Vermont (as of 1/1/2010), followed by similar regulations in Maryland (2012) and Louisiana (2013). The laws became effective nationally with the passage of U.S. Public Law 111-380 (effective 1/4/2014). The federal directive mandates the use of 0.25% maximum lead content for products used in the installation or repair of water systems and plumbing providing water for human consumption. The lead percentage is determined by a weighted average lead content formula (based on the original California law), and supersedes the previous EPA Safe Drinking Water Act, Section 1417. The rules exempt material used for water not anticipated for human consumption, such as non-potable services, service saddles, distribution main gate valves, and fire hydrants. However, many of those components have been converted to no-lead casting alloys as well.
Copper alloy castings are part of water distribution for industry and homeowners in four primary areas: hydrants, the water delivery system (the water main to the in-house meter), water meters, and in-home plumbing components (water meter to the faucet). More than 30 copper alloys are listed in the ASTM standards as containing a maximum of 0.1% lead, and several more are listed that contain a maximum of 0.25% lead, the limit set in the new regulations. In addition, research is ongoing and new alloys continue to be developed and enter the marketplace. The following is a review of common alloys, current applications and relevant industry specifications. The alloys are listed using the industry standard Unified Numbering System (UNS).
Fire Hydrants--Historically, hydrants have been cast in a several different ASTM bronzes and brasses. Although exempted from the new regulations, hydrants are currently made in a variety of lead-free ASTM bronzes, brasses, and stainless steel. Hydrants are manufactured to meet American Water Works Association (AWWA) Fire Hydrant Standards.
Waterworks Products (water main to the residence)--Previously cast in leaded brass alloy C83600, commonly known as 85-5-5-5 (containing 4.0-6.0 % lead), these components have been converted and are now cast in lead-free copper alloys. The primary alloys used are C89520 (bismuth selenium), C89833 (bismuth-brass) and C89836 (bismuth-bronze). Components are manufactured to AWWA Standard C800 for underground service.
Water Meters--Traditionally produced in lead containing alloys C83600 and C84400, meters are now manufactured in a number of lead-free cast and forged copper alloys, as well as stainless steel, and plastic/composite materials to adhere to AWWA Water Meter Standards.
Plumbing Products (in-home devices, faucets etc.)--Formerly produced as copper alloy castings, brass forgings, die castings and bar stock, most are now made in a variety of lead-free cast copper alloys, stainless steel, and plastic/composite materials to meet various plumbing codes, standards, and certifications.
While metalcasters have many no-lead alloy choices that meet current government regulations, some alloys are more suitable for certain types of applications. Each alloy has properties that make it unique and provide specific benefits. And, each alloy also has melting and casting production challenges. Materials are generally selected to provide the optimum component performance at the lowest cost to the consumer. Relevant specifications and standards provide guidance for material selection. Some of the factors to consider when selecting an alloy include:
* Castability, including fluidity to fill the mold cavity, pouring temperatures, melting concerns (gas pick up, etc.).
* Mechanical properties reflecting casting integrity and microstructure.
* Chemical composition.
* Pressure tightness,
* Machinability and related issues.
* Soldering and brazing capability.
* Recycling--both in house recycling and external scrap stream.
* Component specifications and requirements. What performance standard does the component need to meet?
* Corrosion protection.
* Alloy cost and availability. Who makes it and how much is available? How available is the alloy in the scrap stream? How abundant are the alloying elements?
Among the number of no-lead casting alloys available today, the most common alloys being used for water components are bismuth brass and bronze, silicon brass and bronze, and low lead sulfur tin bronze. The following provides some guidelines for using these alloys.
While no single alloy will work best for every application, the wide variety of alternatives for lead-free copper alloys provides the opportunity to select the best possible lead-free alloy for each specific component.
The selection lies within the prerogative of the component manufacturers to decide which alloy will assure the production of the highest quality products at the best possible price. Although component application and relevant specifications will be the major driving factors when selecting a no-lead alloy, manufacturers and designers also will consider the total cost of the final component.
The alloy material cost is a part of the equation, but the total overall component cost also includes the impact of the full manufacturing, finishing and recycling processes. Current market availability and long-term sustainability of the alloy are also factors to consider.
Popular Sulfur Tin Bronze
* C83470 Copper Tin Zinc Alloy
This newer sulfur containing alloy has been available in the U.S. for several years and is being used in no-lead water applications.
C83470 Copper Tin Zinc Alloy (U.S. EPA registered antimicrobial) Cu Pb Sn Zn Fe P Ni Al S Sb Si Min (%) 90.0 3.0 1.0 0.20 Max (%) 96.0 0.09 5.0 3.0 0.50 0.10 1.0 0.01 0.6 0.20 0.01 In determining Cu min, Cu may be calculated as Cu = Ni Copper + sum of named elements 99.5% min Ni value includes Co Sand Cast Tensile Strength: 28 ksi minimum Yield Strength: 14 ksi minimum % Elongation: 15 minimum Note: All properties from ASTM 13584-14 unless otherwise noted.
In most cases, few pattern changes are required when switching from leaded alloys. Melting and pouring procedures will not vary greatly from the leaded alloys. Cross contamination is not a concern with this alloy as casting returns can mix with the other alloy groups without causing a problem. The narrow freezing range of this alloy makes for a better casting microstructure, especially noticeable on large cross sections and heavy walls. The alloy is not quite as strong as the silicon alloys, but comparable to bismuth alloys. This alloy machines easier than the other popular options. This alloy is not brittle and will not crack during soldering or brazing. It is highly recyclable and does not depend on rare or uncommon elements. If proper de-oxidation procedures are not followed, SO2 bubbles can form in the castings. Cleaning room and machining processes may need to be adjusted. Specifically, the use of gang tooling creates problems evacuating chips and the design and operation of this type of tooling needs to be evaluated.
Popular Copper Bismuth Alloys
* C89833 copper bismuth alloy
* C89836 copper bismuth alloy
* C89520 copper bismuth selenium alloy (SeBiLOY II, EnviroBrass II)
C89833 Copper Bismuth Alloy (U.S. EPA registered antimicrobial) Cu Pb Sn Zn Fe P Ni Al Bi Min (%) 86.0 4.0 2.0 1.7 Max (%) 91.0 0.09 6.0 6.0 0.30 0.050 1.0 0.005 2.7 S Sb Si Min (%) Max (%) 0.08 0.25 0.005 Copper + sum of named elements 99.3% min Ni value included Co Sand Cast Tensile Strength: 30 ksi minimum Yield Strength: 14 ksi minimum % Elongation: 16 minimum Note: All properties from ASTM 13584-14 unless otherwise noted. C89836 Copper Bismuth Alloy (U.S. EPA registered antimicrobial) Cu Pb Sn Zn Fe P Ni Min (%) 87.0 4.0 2.0 Max (%) 91.0 0.25 7.0 4.0 0.35 0.06 0.90 Al Bi S Sb Si Min (%) 1.5 Max (%) 0.005 3.5 0.08 0.25 0.005 Copper + sum of named elements 99.5% min Ni value included Co Sand Cast Tensile Strength: 33 ksi minimum Yield Strength: 14 ksi minimum % Elongation: 20 minimum C89520 SeBiLOY II (EnviroBrass II) (U.S. EPA registered antimicrobial) Cu Pb Sn Zn Fe Ni Min (%) 85.0 5.0 4.0 Max (%) 87.0 0.09 6.0 6.0 0.20 0.90 Al Bi S Sb Si Min (%) 1.6 0.8 Max (%) 0.005 2.2 0.08 0.25 1.1 Copper + sum of named elements 99.5% min Ni value included Co Bi:Se >= 2:1 Sand Cast Tensile Strength: 25 ksi minimum Yield Strength: 17 ksi minimum % Elongation: 6 typical
In most cases, very few gating modifications will be required when changing from leaded brass patterns. The melting and pouring is very similar to the leaded brasses, but a slight increase in pour temperature is typical. Chips and returns are highly recyclable as long as the chips are dry enough to safely melt, and sound housekeeping practices are maintained to avoid cross-contamination with leaded alloys. These alloys are more gas prone than the leaded brasses. They are also more brittle, so new casting processes may need to be implemented to avoid cracking during shakeout and finishing. Contamination with leaded material is detrimental and metalcasting facilities pouring both bismuth and lead containing alloys need to be very careful to avoid cross contamination. This is also a major concern if bismuth alloys get into leaded alloys. Bismuth alloys are more difficult to machine compared to the leaded brasses. If overheated during machining or soldering, bismuth alloys have a potential to crack.
Popular Silicon Alloys
* C87300 Silicon Bronze
* C87500 Copper Silicon Alloy
* C87600 Copper Silicon Alloy
* C87800 Cast Silicon Bronze Alloy
* C87850 Copper Silicon Alloy
Note: All properties from ASTM 13584-14 unless otherwise noted.
C87300 Silicon Bronze (U.S. EPA registered antimicrobial) Cu Pb Zn Fe Mn Si Min (%) 94.0 0.8 3.5 Max (%) 0.09 0.25 0.20 1.5 4.5 Copper + sum of named elements 99.5% min Ni value included Co Sand Cast Tensile Strength: 45 ksi minimum Yield Strength: 18 ksi minimum % Elongation: 20 minimum C87500 Copper Silicon Alloy (U.S. EPA registered antimicrobial) Cu Pb Zn Al Si Min (%) 79.0 12.0 3.0 Max (%) 0.09 16.0 0.50 5.0 Copper + sum of named elements 99.5% min Sand Cast Tensile Strength: 60 ksi minimum Yield Strength: 24 ksi minimum % Elongation: 16 minimum C87600 Copper Silicon Alloy (U.S. EPA registered antimicrobial) Cu Pb Zn Fe Mn Si Min (%) 88.0 4.0 3.5 Max (%) 0.09 7.0 0.20 0.25 5.5 Copper + sum of named elements 99.5% min Ni value included Co Sand Cast Tensile Strength: 60 ksi minimum Yield Strength: 30 ksi minimum % Elongation: 16 minimum C87800 Cast Silicon Bronze (U.S. EPA registered antimicrobial) Cu Pb Sn Zn Fe P Ni Al Min (%) 80.0 12.0 Max (%) 0.09 0.25 16.0 0.15 0.01 0.20 0.15 As Mg Mn S Sb Si Min (%) 3.8 Max (%) 0.05 0.01 0.15 0.05 0.05 4.2 Copper + sum of named elements 99.5% min Ni value included Co Permanent Mold Tensile Strength: 80 ksi minimum Yield Strength: 30 ksi minimum % Elongation: 15 minimum Note: Properties from the Copper Development Association. There is no established ASTM data yet.) C87850 Copper Silicon Alloy (U.S. EPA registered antimicrobial) Cu Pb Sn Zn Fe Min (%) 74.0 Max (%) 78.0 0.09 0.30 Rem 0.10 P Ni Mn Sb Si Min (%) 0.05 2.7 Max (%) 0.20 0.20 0.10 0.10 3.4 Copper + sum of named elements 99.5% min Ni value included Co Sand Cast Tensile Strength: 59 ksi minimum Yield Strength: 22 ksi minimum % Elongation: 16 minimum
No furnace or ladle additions are required when pouring the silicon alloys, and the alloys melt and pour at lower temperatures than other lead-free alloys. These alloys are typically much stronger and have a significant increase in fluidity over the other lead-free alloys, so they are capable of filling thinner sections. Silicon alloys contain no rare or uncommon elements. Cross contamination with any of the other alloy groups is a major problem due to the higher silicon content. When switching to silicon alloys, most of the tooling used for leaded alloys will need to be reworked. These alloys are gas prone if good melt practices are not followed. If a good quality charge material is not used, casting defects will occur in the form of misruns, oxide laps and white textured spots on the casting surface. A significant reduction in casting yield is common due to increases in gating and risers which may increase part cost. Recycling of machining chips is difficult. Silicon alloys are the most difficult to machine compared to the other popular options.
AMERICAN FOUNDRY SOCIETY COPPER ALLOY DIVISION 3, MARK ANDERSON, FORD METER BOX, MIKE BUYARSKI, FEDERAL METALS, GREGORY SVOBODA, | SCHUMANN & COMPANY.