Molten metal rotor with hardened blade tips
Embodiments of the invention are directed to a rotor for use in molten metal and devices including the rotor. The rotor has a rotor body and blades, wherein each blade includes a tip that is at least twice as hard as the rotor body.
1. A rotor for use in molten metal, the rotor comprising a top surface and:
(a) a graphite body portion that includes a plurality of rotor blade portions, wherein each rotor blade portion has (i) an upper surface that forms part of the top surface of the rotor, (ii) a leading face, (iii) a recess, and (iv) a back channel, wherein the back channel: (A) is behind the recess, (B) is in communication with the recess, and (C) extends to the top surface of the rotor; and
(b) a hardened tip on a leading edge of each rotor blade, wherein the hardened tip has an extension that is positioned in the recess and that is also positioned in the back channel, and the hardened tip forms part of the top surface of the rotor and part of the leading face, and the hardened tip comprises material at least twice as hard as the graphite body portion.
2. The rotor of claim 1 , wherein each hardened tip is comprised of material between 2-3 times, 2-4 times, or 2-5 times as hard as the body portion.
3. The rotor of claim 1 , wherein each hardened tip is cemented to the body portion.
4. The rotor of claim 1 , wherein each hardened tip is comprised of silicon carbide and the body portion is comprised of graphite.
5. The rotor of claim 1 , wherein each blade has a first portion and a second portion, and the first portion pushes molten metal towards the second portion, and the second portion pushes molten metal outward, wherein the first portion comprises the leading edge.
6. The rotor of claim 5 , wherein each hardened tip further forms at least part of the first portion other than the leading edge.
7. The rotor of claim 6 , wherein each hardened tip further forms at least part of the second portion.
8. The rotor of claim 5 , wherein each rotor blade has an angled trailing portion that enlarges the space between each rotor blade to allow more molten metal to pass through the space.
9. The rotor of claim 1 , wherein there are three rotor blades.
10. The rotor of claim 1 , that further includes a connective portion for connecting to a rotor shaft.
11. The rotor of claim 1 that comprises a bottom, and wherein there is a flow-blocking plate at the bottom.
12. The rotor of claim 1 that further includes a bearing surface comprised of ceramic.
13. The rotor of claim 11 , wherein the flow blocking plate includes an annular bearing on its outer surface.
14. The rotor of claim 5 , wherein the first portion of each rotor blade has a horizontally-extending projection with a top surface and a bottom surface, wherein the bottom surface is angled to move molten metal into a pump chamber in which the rotor is configured to be positioned.
15. The rotor of claim 14 , wherein the second portion of each rotor blade is vertical.
16. The rotor of claim 14 , wherein the bottom surface of each horizontally-extending projection is formed at a 10°-60° downward angle relative to a horizontal axis.
17. The rotor of claim 1 that has a horizontal top surface.
18. The rotor of claim 14 , wherein the leading edge is at least ⅛″ thick.
19. The rotor of claim 1 that has a top surface and the hardened tip on each rotor blade extends along at least part of the top surface.
20. The rotor of claim 1 , wherein the hardened tip on each rotor blade comprises all of the leading edge.
21. The rotor of claim 1 , wherein each rotor blade has a height and a leading surface, the hardened tip extends along the leading surface by at least 10%, or at least 20%, or at least 30% of the height.
22. The rotor of claim 1 , wherein each rotor blade has an outermost edge that includes a height, and the hardened tip extends along the outermost edge by at least 10%, or at least 20%, or at least 30% of the height.
23. A molten metal pump including the rotor of claim 1 .
24. The pump of claim 23 that includes: a superstructure on which a motor is supported, a pump base including a pump chamber in which the rotor is received, and a plurality of support posts connecting the superstructure to the pump base.
25. The pump of claim 24 that includes a and a drive shaft having a first end and a second end, wherein the first end of the drive shaft is connected to the motor and the second end of the drive shaft is connected to the rotor.