Bearing Design Guide: Chapter Four: LOAD SPEED CATAGORIES AND USAGES-Day 3

 
Tin bronzes:Low-speed, High-loads

          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.

                    
                    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