Thursday, August 25, 2016

Bearing Design Guide: Chapter Four: LOAD SPEED CATAGORIES AND USAGES-Day 4

Aluminum Bearings: High-loads, Low-speed

          The aluminum bronze alloys are used more frequently as bushings for their wear resistance, heavy load-carrying ability, and temperature service since they retain their physical and mechanical strengths at higher temperatures than the other bronze alloys. They possess excellent corrosion resistance and are used extensively in marine service.  Because of their short freezing or solidification range in casting, they are preferred for permanent mold castings.

          The aluminum bronzes with about 8% aluminum content will not respond to heat treatment.  Above 10% aluminum content, they can be heat treated.

           The aluminum bronze alloys are considered to be non-sparking and suitable for equipment handling explosives, petroleum, chemical and gas products and in mines.
                            The average physical properties are:
                            Brinell hardness 140 to 230 BHN
                            Coefficient of friction (dry) .30
                            Minimum recommended shaft hardness 400 BHN
                            BHN with heat-treated aluminum bronzes increased to  600 BHN
                            Maximum operating temperatures 750° with intermittent service   through 1200° F.

   CDA             Tensile Strength PSI             Yield Strength PSI          Elongation %          BHN
    952                         68000                                    26000                                20                      125
    953                         70000                                    26000                                25                      140
    953HT                    80000                                    40000                                12                      175           954                         85000                                    32000                                12                      170
    954HT                    95000                                    45000                                10                      195
    955                         95000                                    42000                                10                      195
    955HT                   110000                                   62000                                 8                       230

Principle uses: Marine equipment, pump impellers, acid-resistant pumps, valve seats, guides, worm screws, nuts, gears, mine equipment, chemical, gas and petroleum-related machinery and equipment. Several of these aluminum bronze alloys are used extensively in permanent molded castings such as pole-line hardware and other products replacing sand-cast items.

 Well...that's it for our fourth section. Only one more to go!  Until next time my metal loving friends...

 Next Up: Chapter 4: Load Speed and Usages- Manganese Bronzes: High-loads, Low-speed

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