Flywheel rotor
A solid steel flywheel rotor having improved material properties offers improved energy storage at reduced cost. A process for manufacturing the rotor is also provided.
1. A flywheel rotor comprising a rotationally symmetric mass made of a single piece of steel having
a yield strength of at least 900 MPa,
a fracture toughness of at least 40 MPa·m 0.5 ,
a maximal intrinsic defect size that is 2 mm or smaller, and
the mass having a diameter greater along a first axis than its widest thickness along a second axis, the widest thickness being between 10 inches and 14 inches, the mass configured to rotate about the second axis.
2. The flywheel rotor of claim 1 not including a hole through a center axis of the mass.
3. The flywheel rotor of claim 1 wherein at least some portion of the mass is greater than 4 inches from an outer surface of the mass.
4. The flywheel rotor of claim 1 further comprising a plurality of journals protruding from the mass, each journal shaped to physically couple to a shaft.
5. The flywheel rotor of claim 1 wherein the rotor has a mass within a range of 2 to 5 tons.
6. The flywheel rotor of claim 1 wherein the mass has an outer diameter within a range of 36 to 72 inches.
7. The flywheel rotor of claim 1 wherein the mass is formed of through-hardened and tempered 300M steel, formed using one of
a vacuum-arc-remelting (VAR) process,
an electro-slag-remelting (ESR) process, and
a vacuum induction melting (VIM) process.
8. The flywheel rotor of claim 1 wherein the mass comprises a fishtail shape.
9. A flywheel rotor comprising
a rotationally symmetric mass made of a single piece of through-hardened and tempered steel,
the mass having a diameter greater along a first axis than its widest thickness along a second axis, wherein the widest thickness of the mass is between 10 and 14 inches,
the mass comprising a plurality of journals protruding from the mass, each journal shaped to physically couple to a shaft, and
the mass configured to rotate about the second axis.
10. The flywheel rotor of claim 9 having a yield strength of at least 900 MPa.
11. The flywheel rotor of claim 9 having a fracture toughness of at least 40 MPa·m 0.5 .
12. The flywheel rotor of claim 9 having a maximal intrinsic defect size that is equal to or smaller than 2 mm.
13. The flywheel rotor of claim 9 not including a hole through a center axis of the mass.
14. The flywheel rotor of claim 9 wherein at least some portion of the mass is greater than 4 inches from an outer surface of the mass.
15. The flywheel rotor of claim 9 wherein the rotor has a mass within a range of 2 to 5 tons.
16. The flywheel rotor of claim 9 wherein the diameter is within a range from 48 to 72 inches.
17. The flywheel rotor of claim 9 wherein the mass comprises a fishtail shape.
18. A method for manufacturing a flywheel rotor comprising:
alloying a plurality of elements to form a single mass of steel, the mass having a diameter greater along a first axis than its widest thickness along a second axis, the widest thickness being between 10 inches and 14 inches, the mass configured to rotate about the second axis;
refining the mass using one of:
a vacuum-arc-remelting (VAR) process,
an electro-slag-remelting (ESR) process, and
a vacuum induction melting (VIM) process;
performing a multi-step forging process to align grain size and direction within the mass;
heating and quenching the mass to through-harden the mass;
tempering the mass; and
machining the mass.
19. The flywheel rotor of claim 1 wherein the fracture toughness is in a range from 150 MPa·m 0.5 to 200 MPa·m 0.5 .