Brass alloys for use in turbocharger bearing applications
View Patent ↗In accordance with an exemplary embodiment, a high-strength brass alloy includes, by mass %, about 1.3% to about 2.3% of aluminum (Al), about 1.5% to about 3.0% of manganese (Mn), about 1% maximum of iron (Fe), about 1% maximum of nickel (Ni), about 0.4% maximum of tin (Sn), about 0.5% to about 2.0% of silicon (Si), about 57% to about 60% of copper (Cu), less than about 0.1% of lead (Pb), and the balance of zinc (Zn) and inevitable impurities, with the proviso that the ratio of Si/Mn is in the range of about 0.3 to about 0.7, and with the further proviso that the “zinc equivalent” content according to the following formula: ZnEq=Zn+Si*10−Mn/2+Al*5 is from about 51% to about 58%.
1. An alloy comprising, by weight:
about 57% to about 60% copper;
less than about 0.1% lead;
less than about 1% iron;
less than about 0.4% tin;
less than about 1% nickel;
about 1.5% to about 3.0% manganese;
about 0.5% to about 2.0% silicon;
about 1.3% to about 2.3% aluminum; and
a balance zinc,
with the proviso that a ratio of Si/Mn is in the range of about 0.3 to about 0.7, and with the further proviso that a zinc equivalent content according to the following formula: ZnEq=Zn +Si*10−Mn/2+Al*5 is from about 51% to about 58%, and with the further proviso that the alloy comprises beta phase in an amount from about 75% to about 90% by weight,
wherein the alloy has been thermally processed by extrusion at a rate of about 96% or greater followed by cold drawing at a rate of about 5% to about 8%, and wherein the alloy exhibits a tensile strength Rm greater than about 600 MPa, a proof strength Rp0.2 greater than about 350 MPa, and an elongation ratio greater than about 12% as a result of said thermal processing.
2. The alloy of claim 1 , comprising gamma phase in an amount less than about 0.5% by weight.
3. A turbocharger bearing formed of an alloy that comprises, by weight:
about 57% to about 60% copper;
less than about 0.1% lead;
less than about 1% iron;
less than about 0.4% tin;
less than about 1% nickel;
about 1.5% to about 3.0% manganese;
about 0.5% to about 2.0% silicon;
about 1.3% to about 2.3% aluminum; and
a balance zinc,
with the proviso that a ratio of Si/Mn is in the range of about 0.3 to about 0.7, and with the further proviso that a zinc equivalent content according to the following formula: ZnEq=Zn +Si*10−Mn/2+Al*5 is from about 51% to about 58%, and with the further proviso that the alloy comprises beta phase in an amount from about 75% to about 90% by weight, and wherein the turbocharger bearing has been thermally processed by extrusion at a rate of about 96% or greater followed by cold drawing at a rate of about 5% to about 8% and thereby exhibits a tensile strength Rm greater than about 600 MPa, a proof strength Rp0.2 greater than about 350MPa, and an elongation ratio greater than about 12%.
4. The turbocharger bearing of claim 3 , comprising gamma phase in an amount less than about 0.5% by weight.
5. A method of manufacturing a bearing for use in a gas turbine engine, the method comprising the steps of:
forming an alloy comprising by weight:
about 57% to about 60% copper;
less than 0.1%;
less than about 1% iron;
less than about 0.4% tin;
less than about 1% nickel;
about 1.5% to about 3.0% manganese;
about 0.5% to about 2.0% silicon;
about 1.3% to about 2.3% aluminum; and
a balance zinc,
with the proviso that a ratio of Si/Mn is in the range of about 0.3 to about 0.7, and with the further proviso that a zinc equivalent content according to the following formula: ZnEq=Zn+Si*10−Mn/2+Al*5 is from about 51% to about 58%, and with the further proviso that the alloy comprises beta phase in an amount from about 75% to about 90% by weight,
wherein forming the alloy comprises thermal processing by extrusion at a rate of about 96% or greater followed by cold drawing at a rate of about 5% to about 8%, such that the alloy exhibits a tensile strength Rm greater than about 600 MPa, a proof strength Rp0.2 greater than about 350 MPa, and an elongation ratio greater than about 12%; and
machining the alloy into the shape of a turbocharger bearing.
6. The method of claim 5 , wherein the alloy comprises gamma phase in an amount less than about 0.5% by weight.