The tin bronzes are hard bronzes that offer increased load-carrying capacities. They are capable in accepting shock and impact loads but with reduced surface speeds. They possess excellent corrosion resistance but require mating with hard shafts, good surface finishes and good lubrication since they are more prone to seizure and cold-welding than the bronzes containing lead.
The working load can be taken at 5000 PSI but with reduced speeds. Surface speeds should not exceed 250 fpm unless positive and ideal lubrication are available. The permissible static load can be taken at 10,000 PSI. These alloys require accurate alignment and
hardened polished shafts.
hardened polished shafts.
The average physical properties are:
Brinell hardness 60 to 80 BHN
Coefficient of friction (dry) .25 to .30
Minimum recommended shaft hardness 350 BHN
Maximum operating temperature 550 ° F
CDA Tensile Strength PSI Yield Strength PSI Elongation % BHN
905 44000 25000 10 75
907 40000 25000 10 80
927 38000 20000 8 77
Principle uses: Pump impellers, valve components, wrist-pin bushings, bridge bearings and wear plates, coal-crushing machinery, press bearings, pump and paper mill bearings, worm wheels and gears.
Well...that's it for our third section. Until next time my metal loving friends...
Next Up: Chapter 4: Load Speed and Usages-Aluminum Bearings: High-loads, Low-speed
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