ing. Machining is the most com- mon secondary operation. Welding is needed to repair minor defects or join several castings into a larger assembly. Surface treatments are commonly applied to decorative products, plaques and statues. Each of these processing steps contrib- utes to the cost of the fi nished component. T erefore, the ease and effi ciency with which an alloy can be processed infl uences its eco- nomic viability. As a class, cast copper-based al-
loys are easy to machine (especially when compared to stainless steels and titanium, their main com- petitors for corrosion resistance). Easiest to machine are the leaded copper-base alloys. T ese alloys are free-cutting and form small, fragmented chips while generating little heat. Next in order of machinability
are moderate to high-strength alloys with second phases in their microstructures, such as unleaded yellow brasses, manganese bronzes and silicon brasses and bronzes. These alloys form short, brittle, tightly curled chips that tend to break into manageable segments. While the surface finish on these alloys will be good, the cutting speed will be lower and tool wear will increase. The most difficult copper-
base alloys for machining are the single-phase alloys such as high conductivity copper, chromium copper, beryllium copper, alumi- num bronze and copper-nickel. Their general tendency during machining is to form long, stringy chips that interfere during high- speed machining operations. In addition, pure copper and high- nickel alloys tend to weld to the tool face, impairing surface finish. Both gas-tungsten-arc and gas-metal-arc can produce X-ray quality welds when repairing minor defects in copper castings. Shielded-metal-arc welding also can be used, but the method is more difficult to control. Oxy- acetylene welding mainly is used
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BETTER PARTS THE Applied Process Inc. clocks the competition.
With so much riding on your parts, you simply don’t have time for inferior-performing solutions. As the industry leader in providing austempered ductile iron (ADI), Applied Process develops parts that meet the most stringent industry standards…time and time again. ADI parts are stronger, lighter, quieter, more uniform and have greater wear- resistance—providing increased performance with decreased production costs. It’s time to put the power of Applied Process to work for you.
Cast copper-based alloys are easy to machine, especially when compared to stainless steels and titanium, their main competitors for corrosion resistance.”
to join thin sections. Electron beam welding produces precise welds of high quality in both oxygen free and deoxidized copper. In general, alloys containing ap-
preciable amounts of lead cannot be welded, as the lead remains liquid after the weld solidifies, forming cracks in high stress fields. All cast copper alloys can be brazed and soldered to themselves and to steel, stainless steel and nickel-base al- loys. Even leaded copper alloys can be brazed, but the conditions must be controlled. Copper phosphorous alloys,
silver-based brazing alloys and copper-zinc alloys are most often used as fi ller metals. Gold-based alloys are used for electrical applica- tions, and tin-based solders are used for household plumbing. T e heat of brazing may cause
some loss of strength in heat treated copper alloys, but special techniques have been developed to remedy the problem. When necessary, the entire brazed casting can be heat treated to produce a uniform structure. T e cor- rosion resistance of copper-base alloys is not aff ected by brazing, except in special situations.
APPLIED PROCESSINC TM
Global Leader in Austempering
www.appliedprocess.com
Mar/Apr 2015 | METAL CASTING DESIGN & PURCHASING | 35 APPL068 Brand Ad_Modern
Casting_4.5x4.875.indd 1 4/23/14 3:02 PM
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