Waiting for the European Parliament to announce their decision about regulating lead in metal alloys is like watching a domino teeter on its edge. If this domino falls, it will trigger a chain reaction up and down global supply chains. Parliament is considering whether to implement stringent regulations to severely reduce levels of lead in metal products, both manufactured in the European Union and imported. Metalworking and metal removal fluid suppliers and users alike are anxious about this decision because a change would mean that current formulations of fluids and alloys, machine tools and metal processing procedures may no longer be feasible.
There is no question that lead accumulates in human bones and other tissues and has serious adverse health effects, including miscarriage, anemia, hearing loss and impaired cognition. The U.S. Environmental Protection Agency reports that common routes of exposure include consuming lead-contaminated food and water, using ceramic dishes and glassware that contain lead, and inhaling or ingesting lead particles present in soil, dust and the air. Two major applications of lead compounds – as additives in paints and gasoline – were outlawed in the U.S. in the 1980s and 1990s because of this. Mining, smelting and other commercial operations release lead particles that disperse in the air, accumulate in soils and crops, and contaminate the food chain.
The tendency for lead to accumulate and its toxicity – especially brutal to children and pregnant women – continue to motivate concern and regulatory limitations. According to Bureau Veritas Consumer Products Services, many countries now regulate the use of lead in toys, paints and materials that may come in contact with food and beverages.
Falling Slowly
A decade ago, the EU Parliament issued the Restriction of Hazardous Substances Directive. Effective July 1, 2006, RoHS declared lead, cadmium, mercury, hexavalent chromium and other materials to be hazardous substances. Parliament initially proposed outlawing the use of lead in appliances, certain consumer equipment, electric tools, specific electric and electronic equipment and other products. The final version of RoHS contained an exemption that permitted the use of lead up to 0.35 percent in steel, 0.4 percent in aluminum alloys and 4 percent in copper alloys such as brasses and bronzes because of its important contribution to the machinability of these alloys.
However, in 2011, Sweden submitted a dossier to the European Chemicals Agency claiming to demonstrate that children, especially those under three years of age, may be exposed repeatedly to lead by mouthing consumer articles containing lead for alloying and other purposes. The dossier called for strict regulation of sales to reduce risks of neurological effects due to lead consumption by children, and the Committee for Risk Assessment agreed.
The draft of the next-generation legislation, RoHS 2, would have allowed the lead exemption to expire on July 21, 2016. Thereafter, use of lead would be limited to no more than 0.1 percent by weight in alloys for a much broader range of products. This would affect American machine shops that import leaded steels, aluminum alloys and brasses from Europe and those that export individual parts and components of assembled products to markets in the EU.
For over a year, Parliament has been reconsidering their decision to revoke the lead exemption. In January 2015, it received an application requesting the renewal of the original regulation. At this writing, lawmakers have missed two deadlines to respond (January and April of this year). Now it appears that the Parliament has postponed its decision indefinitely. If it rejects the application, new regulations on lead levels in alloys would go into effect between 12 and 18 months following the decision.
Heavy Hitter
One immediate effect of removing lead from alloys, according Miles Free, director of industry research and technology at the Precision Machined Products Association in Cleveland, would be an estimated 25 percent or greater reduction of machining speed efficiency and increased electricity consumption. Additionally, he said, the metalworking fluid industry would be hard pressed to reformulate metal removal fluids for low-lead alloys and scale up production of new products within the 12- to 18-month window.
The value of lead as an alloying element is due to its relatively low shear strength, which substantially reduces friction. Benefits of lower friction include less thermal stress on tools and parts, faster machining operations, shorter cycle times, reduced electric power consumption and more forgiving conditions for metal removal fluids.
In a 2007 article published in Todays Machining World, Free gave a working definition of machinability as the ability of material to travel through the shop starting as bars, ending as parts and causing the least amount of aggravation and trouble for the machine and the machine operator.
Free explained that machinability is not simply equivalent to Brinell hardness, a material characteristic measured by applying a standard test force to press a hardened steel ball on a test piece and then measuring the diameter of the permanent indentation. Rather, Free believes that machinability corresponds to the speed at which metal is processed. He cited Feeds and Speeds for Better Machining, which claimed that cutting speeds for leaded alloys are 15 to 25 percent faster than nonleaded grades.
Free detailed the scientific basis for the effect of lead on machinability: Cycle times have been improved by lead because lead allows you to run at a higher speed. It lubricates. It melts at around 621.5 Celsius…so during the cut it creates a liquid phase that can act as a lubricant in place. It reduces friction, pulls a little heat out by melting, and there is a theory that it helps to create the next chip by a process called liquid metal embrittlement.
Setting Up Alternatives
Motivated by environmental and regulatory concerns, metal suppliers are developing replacements for leaded alloys. Fortune Minerals Limited asserts that bismuth – also the active ingredient in Pepto Bismol – is an environmentally acceptable lead substitute for alloys for automotive and medical applications.
In the late 1980s and 1990s, Free told LubesnGreases, U.S. companies were melting, selling and machining bismuth treated steels. However, the yield loss in production of these steels made them more costly for the steel companies to manufacture. While bismuth created free-cutting properties at room temperature, he explained, it resulted in loss of ductility at rolling temperatures. So as long as leaded grades were permitted, the bismuth steels were too expensive to compete, Free concluded.
With todays restrictions and concerns around lead, South Korean steel producer POSCO is mass producing a free-cutting steel that substitutes bismuth for lead. In January 2012, the Korea Herald reported, The worlds fourth-largest steelmaker said it has been working on the project since 2005 in efforts to improve health conditions for workers and cope with tightening environmental regulations at home and abroad. The company told the Herald that it began supplying its latest product in August 2011 to LG Electronics for television components, has recently obtained a material certificate from Hyundai Motor Group, and has another agreement in the works with Samsung Electronics.
New alternatives are also available for C36000 brass, also known as 360 brass, a leaded alloy used widely in potable water fixtures, faucets and taps. In 2006, California Assembly Bill 1953 legislated, No person shall introduce into commerce, for use in California, any pipe, pipe or plumbing fitting, or fixture intended to convey or dispense water for human consumption through drinking water or cooking that is not lead free. This includes kitchen faucets, bathroom faucets and any other end-use devices intended to convey or dispense water for human consumption through drinking or cooking. This bill defined lead free as not more than a weighted average of 0.25 percent lead content in pipe and fittings. This law went into effect January 1, 2010.
In his 2009 article in Production Machining, Free described new alloys to replace C36000 in order to comply with AB 1953. Green Dot Eco Brass Co. developed C69300 brass, a totally lead free alloy. The metal is harder than stainless steel, but it is formulated with a proprietary copper-zinc-silicate intermetallic compound to improve machinability. Mueller Brass developed C27450 brass that substitutes zinc in place of lead to meet AB 1953, but does contain up to 0.25 weight percent lead. This material is less machinable (requires more power to remove chips) than C36000. Free observed that it is feasible for machinists to adjust their operating parameters to process these two new brasses, detailed in Figure 1.
Suppliers of metalworking and metal removal fluids may need to reformulate their products for use with these and other new alloys. Regardless of the outcome of deliberations by the EU Parliament, permitted levels of lead in alloys are falling.
Mary Moon, Ph.D., is a physical chemist with hands-on R&D and management experience in the lubricating oil and grease and specialty chemicals industries. She volunteers as treasurer of the Philadelphia section of STLE. Contact her at mmmoon@ix.netcom.com or (267) 567-7234.