Method of processing a multiple alloy rotor

• US 7,065,872 B2
• Filed: 12/04/2003
• Issued: 06/27/2006
• Est. Priority Date: 06/18/2003
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Schwant, Robin Carl, Ganesh, Swami, Yang, Ling, Reed, Francis Alexander, Falsetti, Robert V., Wang, John Zhiqiang
• Primary Examiner(s): Jimenez, Marc
• Assistant Examiner(s): AGRAWAL, CHRISTOPHER K
• Application Number:
  US10/707,302
• Publication Number:
  US 20050091832A1
• Time in Patent Office: 936 Days
• Field of Search: 298/89, 298/892, 298/892.3, 298/897.1, 294/070.1, 294/070.5, 723/52
• US Class Current: 29/889.2
• CPC Class Codes: B21K 1/10 of cylindrical form
• CPC Class Codes: B22D 11/126 for cutting
• CPC Class Codes: B23P 15/006 turbine wheels
• CPC Class Codes: G01N 2291/02854 Length, thickness
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/2693 Rotor or turbine parts
• CPC Class Codes: G01N 29/0618 synchronised with scanning, e.g. in real-time
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/265 by moving the sensor relative to a stationary material
• CPC Class Codes: G01N 9/24 by observing the transmission of wave or particle radiation through the material
• CPC Class Codes: Y10T 29/4932 Turbomachine making
• CPC Class Codes: Y10T 29/49337 Composite blade
• CPC Class Codes: Y10T 29/49771 Quantitative measuring or gauging
• CPC Class Codes: Y10T 29/49989 Followed by cutting or removing material

Abstract

A method of processing a rotor. The rotor is formed by casting an ingot to have first and second regions formed of different alloys that intermix during casting to define a transition zone therebetween. The ingot is forged to yield a rotor forging that contains axially-aligned first and second alloy regions and a transition zone therebetween. A three-dimensional approximation of the transition zone is generated, which can be used to predict the effects of the transition zone on the dynamic performance of a rotor machined from the forging.

Claims

1. A method for processing a rotor forging, the method comprising the steps of:

casting an ingot to have at least first and second ingot regions axially aligned within the ingot, the first and second ingot regions being formed of different alloys that intermix during casting to define a transition zone between the first and second ingot regions, the transition zone having a composition that differs from and varies between the first and second ingot regions;

forging the ingot to produce a rotor forging containing first and second forging regions and a transition zone therebetween corresponding to the first and second ingot regions and the transition zone of the ingot such that the first and second forging regions are formed of the different alloys and the transition zone of the rotor forging has a composition that differs from and varies between the first and second forging regions, the first and second forging regions and the transition zone therebetween being axially aligned along a geometric centerline of the rotor forging;

ascertaining boundary points of the transition zone within the rotor forging to define a plurality of two-dimensional cross-sectional shapes of the transition zone; and

then

using the plurality of two-dimensional cross-sectional shapes to produce a three-dimensional approximation of the shape of the transition zone within the rotor forging.

2. The method according to claim 1, wherein the transition zone of the rotor forging is asymmetrical about the geometric centerline of the rotor forging following the forging step.

3. The method according to claim 1, further comprising the steps of:

producing a rotor forging specimen in accordance with the casting and forging steps of claim 1, whereby the rotor forging specimen contains first and second specimen regions and a transition zone therebetween, the first and second specimen regions are formed of the different alloys, the transition zone of the rotor forging specimen has a composition that differs from and varies between the first and second specimen regions, and the first and second specimen regions and the transition zone therebetween are axially aligned along a geometric centerline of the rotor forging specimen;

ascertaining boundary points of the transition zone within the rotor forging specimen to define a plurality of two-dimensional cross-sectional shapes of the transition zone within the rotor forging specimen;

using the plurality of two-dimensional cross-sectional shapes of the transition zone within the rotor forging specimen to produce a three-dimensional contour of the shape of the transition zone within the rotor forging specimen; and

using the three-dimensional contour of the shape of the transition zone within the rotor forging specimen and the boundary points of the transition zone within the rotor forging to produce the three-dimensional approximation of the shape of the transition zone within the rotor forging.

4. The method according to claim 3, wherein the step of ascertaining the boundary points of the transition zone within the rotor forging comprises determining at an outside surface of the rotor forging the level of at least one alloying constituent of at least one of the different alloys of the first and second specimen regions.

5. The method according to claim 4, wherein the step of ascertaining the boundary points of the transition zone within the rotor forging specimen comprises:

sectioning the transition zone of the rotor forging specimen to define a sectioned surface on the rotor forging specimen; and

then

performing chemical analysis on the sectioned surface to determine levels of the alloying constituent at multiple locations on the sectioned surface.

6. The method according to claim 3, wherein the step of ascertaining the boundary points of the transition zone within the rotor forging specimen comprises:

sectioning the transition zone of the rotor forging specimen to define a sectioned surface on the rotor forging specimen; and

then

performing chemical analysis at multiple locations on the sectioned surface to determine levels of at least one alloying constituent of at least one of the different alloys of the first and second specimen regions.

7. The method according to claim 1, further comprising the step of using the three-dimensional approximation of the shape of the transition zone within the rotor forging to predict centerline deflection of a rotor machined from the rotor forging.

8. The method according to claim 1, further comprising the step of using the three-dimensional approximation of the shape of the transition zone within the rotor forging to identify an axial line through the rotor forging that is more centrally located with respect to material properties of the rotor forging than the geometric centerline of the rotor forging.

9. The method according to claim 1, wherein the step of ascertaining the boundary points of the transition zone within the rotor forging comprises ultrasonically examining the rotor forging to produce a noise pattern corresponding to variations in metallurgical characteristics within the rotor forging attributable to changes in chemistry between the transition zone and the first and second rotor regions.

10. The method according to claim 1, wherein the first rotor region is formed from an alloy chosen from the group consisting of CrMoV low alloy steels, martensitic stainless steels containing about 9 to about 14 weight percent chromium, Fe—

Ni alloys, and nickel-base alloys, and the second rotor region is formed from an alloy chosen from the group consisting of NiCrMoV low alloy steels and martensitic stainless steels containing about 11 to about 14 weight percent chromium.

11. The method according to claim 1, further comprising the steps of:

using the three-dimensional approximation of the shape of the transition zone within the rotor forging to establish a geometric centerline of the transition zone within the rotor forging; and

then

off-center machining the rotor forging to produce a machined rotor so that the geometric centerline of the transition zone is approximately the geometric centerline of the machined rotor.

12. A method for processing a rotor forging, the method comprising the steps of:

producing a rotor forging specimen by;

casting an ingot specimen to have at least first and second ingot specimen regions axially aligned within the ingot specimen, the first and second ingot specimen regions being formed of different alloys that intermix during casting to define a transition zone between the first and second ingot specimen regions, the transition zone having a composition that differs from and varies between the first and second ingot specimen regions;

forging the ingot specimen to produce a rotor forging specimen containing first and second forging specimen regions and a specimen transition zone therebetween corresponding to the first and second ingot specimen regions and the transition zone of the ingot such that the first and second forging specimen regions are formed of the different alloys and the transition zone of the rotor forging specimen has a composition that differs from and varies between the first and second forging specimen regions, the first and second forging specimen regions and the transition zone therebetween being axially aligned along a geometric centerline of the rotor forging specimen;

ascertaining boundary points of the transition zone within the rotor forging specimen to define a plurality of two-dimensional cross-sectional shapes of the transition zone within the rotor forging specimen; and

using the plurality of two-dimensional cross-sectional shapes of the transition zone within the rotor forging specimen to produce a three-dimensional contour of the shape of the transition zone within the rotor forging specimen;

producing a rotor forging in accordance with the casting and forging steps performed to produce the rotor forging specimen, whereby the rotor forging contains first and second regions and a transition zone therebetween, the first and second regions are formed of the different alloys, the transition zone of the rotor forging has a composition that differs from and varies between the first and second regions, and the first and second regions and the transition zone therebetween are axially aligned along a geometric centerline of the rotor forging;

ascertaining boundary points of the transition zone within the rotor forging to define a plurality of two-dimensional cross-sectional shapes of the transition zone;

using the three-dimensional contour of the shape of the transition zone within the rotor forging specimen and the boundary points of the transition zone within the rotor forging to produce a three-dimensional approximation of the shape of the transition zone within the rotor forging;

using the three-dimensional approximation of the shape of the transition zone within the rotor forging to establish a geometric centerline of the transition zone within the rotor forging; and

then

off-center machining the rotor forging to produce a machined rotor so that the geometric centerline of the transition zone is approximately the geometric centerline of the machined rotor.

13. The method according to claim 12, wherein the step of ascertaining the boundary points of the transition zone within the rotor forging comprises determining at an outside surface of the rotor forging the level of at least one alloying constituent of at least one of the different alloys of the first and second specimen regions.

14. The method according to claim 13, wherein the step of ascertaining the boundary points of the transition zone within the rotor forging specimen comprises:

sectioning the transition zone of the rotor forging specimen to define a sectioned surface on the rotor forging specimen; and

then

performing chemical analysis on the sectioned surface to determine levels of the alloying constituent at multiple locations on the sectioned surface.

15. The method according to claim 12, wherein the step of ascertaining the boundary points of the transition zone within the rotor forging specimen comprises:

sectioning the transition zone of the rotor forging specimen to define a sectioned surface on the rotor forging specimen; and

then

performing chemical analysis at multiple locations on the sectioned surface to determine levels of at least one alloying constituent of at least one of the different alloys of the first and second specimen regions.

16. The method according to claim 12, wherein the first rotor region is formed from an alloy chosen from the group consisting of CrMoV low alloy steels, martensitic stainless steels containing about 9 to about 14 weight percent chromium, Fe–

Ni alloys, and nickel-base alloys, and the second rotor region is formed from an alloy chosen from the group consisting of NiCrMoV low alloy steels and martensitic stainless steels containing about 11 to about 14 weight percent chromium.

17. The method according to claim 12, wherein the transition zone of the rotor forging is asymmetrical about the geometric centerline of the rotor forging following the step of producing a rotor forging.

18. A method for processing a rotor forging, the method comprising the steps of:

casting an ingot to have at least first and second ingot regions axially aligned within the ingot, the first and second ingot regions being formed of different alloys that intermix during casting to define a transition zone between the first and second ingot regions, the transition zone having a composition that differs from and varies between the first and second ingot regions;

forging the ingot to produce a rotor forging containing first and second forging regions and a transition zone therebetween corresponding to the first and second ingot regions and the transition zone of the ingot such that the first and second forging regions are formed of the different alloys and the transition zone of the rotor forging has a composition that differs from and varies between the first and second forging regions, the first and second forging regions and the transition zone therebetween being axially aligned along a geometric centerline of the rotor forging;

ascertaining boundary points of the transition zone within the rotor forging to define a plurality of two-dimensional cross-sectional shapes of the transition zone by ultrasonically examining the rotor forging to produce a noise pattern corresponding to variations in metallurgical characteristics within the rotor forging attributable to changes in chemistry between the transition zone and the first and second rotor regions;

using the plurality of two-dimensional cross-sectional shapes to produce a three-dimensional approximation of the shape of the transition zone within the rotor forging;

using the three-dimensional approximation to establish a geometric centerline of the transition zone within the rotor forging; and

then

off-center machining the rotor forging to produce a machined rotor so that the geometric centerline of the transition zone is approximately the geometric centerline of the machined rotor.

19. The method according to claim 18, wherein the first rotor region is formed from an alloy chosen from the group consisting of CrMoV low alloy steels, martensitic stainless steels containing about 9 to about 14 weight percent chromium, Fe—

Ni alloys, and nickel-base alloys, and the second rotor region is formed from an alloy chosen from the group consisting of NiCrMoV low alloy steels and martensitic stainless steels containing about 11 to about 14 weight percent chromium.

20. The method according to claim 18, wherein the transition zone of the rotor forging is asymmetrical about the geometric centerline of the rotor forging following the forging step.