What's Lead-free Brass
Leaded brass, known for its excellent cold and hot working properties, machinability, and wear resistance, is widely used in various shapes of machining components. It holds a significant share in the entire copper industry and is recognized globally as an essential basic material. Its applications range from civilian to military industries, including water supply systems, electronics, automobiles, ships, airplanes, and more. However, medical research has shown that lead (Pb) causes significant damage to the hematopoietic and nervous systems, especially to children's kidneys and other organs. With the advancement of science and the improvement of living standards, more countries and regions have started to focus on environmental and health issues. Many governments have introduced regulations limiting the use of lead-containing copper alloys. For example, the United States, the European Union, and Japan have set strict limits on the lead content in copper alloys and the leaching of lead from drinking water. In California, the AB1953 bill (also known as CA65) took effect on January 1, 2010, permanently banning leaded brass in the bathroom and plumbing markets. As a result, lead-free machinable brass, an eco-friendly alternative to traditional leaded brass, has naturally become a research and development focus.
Lead-free machinable brass, also known as environmentally friendly machinable brass, is designed by modifying the composition of brass to replace lead with non-toxic or low-toxicity materials, maintaining machinability while protecting the ecological environment. It meets industrial needs and helps protect health and the environment, making it one of the main ways to reduce lead pollution. Research on lead substitutes for making lead-free brass started internationally in the 1990s. In comparison, China's development in this area began later, but currently, Chinese companies have developed lead-free machinable brass with comparable machinability to leaded brass, meeting the latest environmental standards in Europe, the U.S., and Japan. These materials have successfully entered the bathroom and drinking water systems in markets such as Europe, the U.S., and Japan. As the overall research and development of lead-free machinable brass continue to progress, the demand for lead-free brass in society will inevitably grow.
Bismuth as a Lead Substitute in Machinable Copper Alloys:
Bismuth (Bi) is a "green" metal element, safe for use, and shares many similarities with lead in terms of properties due to their proximity on the periodic table. As a result, bismuth has been extensively studied as a substitute for lead in brass. In some countries, bismuth-containing copper alloys have already entered mass production. For example, bismuth and selenium (Se) copper alloys developed by Bell Labs (U.S.) and KITZ Corporation (Japan) are used in water faucet and valve components. Germany has developed bismuth-based copper alloys as a substitute for lead in casting alloys, and the UK has developed a low-lead casting brass alloy for water supply systems.
China is also active in developing lead substitutes using bismuth. For instance, Hailiang Group's research team, including Wang Zhijun and Zhang Tianli, has developed HB-20 lead-free brass bars with a chemical composition of 56%-62% copper (Cu), 36%-40% zinc (Zn), 0.5%-3% bismuth, and 0.01%-0.05% selenium, with the remainder being rare metals and unavoidable impurities. Ningbo Bowei Group's patent (CN1710126) has introduced an environmentally friendly, low-antimony, bismuth-based lead-free machinable brass alloy, containing 55%-65% copper, 0.3%-1.5% bismuth, 0.05%-1.0% antimony (Sb), and trace amounts of other elements.
These new materials are already in mass production, but due to price and minimum order quantity (MOQ) requirements, their use in the communications industry is limited. Since the communications industry is not in direct contact with consumers and does not typically involve water sources, the use of leaded brass is exempt from ROHS and REACH regulations.
Why Lead-Free Brass for RF Connectors is Expensive:
The high cost of lead-free bismuth brass for RF connectors can be attributed to the small volume of shipments. The minimum order quantity for a batch of copper bars is 500kg. Since each RF connector weighs only 5-10 grams, 500kg of lead-free bismuth brass can produce 50,000 to 100,000 finished products, but customers typically order only 5,000 to 10,000 units, leading to surplus materials and inventory, which ties up capital. Furthermore, the lack of an industry-wide production scale means that waste materials cannot be efficiently recycled or may have little resale value, further driving up the cost of the finished products. Additionally, the manufacturing time for lead-free brass is higher than for leaded brass, increasing labor costs.
Secondly, the minimum order quantity of 500 KGS refers to one specific type of copper rod. For example, a BNC RF connector, as shown below, is composed of five brass parts, with diameters ranging from 14.55mm to 3.18mm. Therefore, each part requires ordering the corresponding copper rod. It is also possible to machine smaller diameter parts from larger diameter rods; however, this approach generates a large amount of waste, which increases the cost of the finished product. Additionally, the machining time cost for lead-free brass is higher than for regular leaded brass.
In conclusion, the price of finished products made from lead-free brass will only approach or match the price of leaded brass when the communications industry widely adopts lead-free brass for RF connectors. However, considering that communication products rarely come into direct contact with consumers or water sources, and given the high cost of lead-free brass, it has not yet been widely adopted in the industry from a cost perspective.
