Note: Descriptions are shown in the official language in which they were submitted.
METHOD FOR INTERNAL STRESS REGULATION IN SUPERALLOY DISK
FORGINGS BY PRE-SPINNING
Technical Field
The present application relates to the field of materials, in particular to a
method for internal stress
regulation in superalloy disk forgings by pre-spinning.
Background Art
The hot-end turning parts of aero-engine are mainly made of superalloy,
including high-pressure
and low-pressure turbine disks, compressor disks, middle-seal disks, etc. In
order to obtain the
predetermined mechanical properties on these superalloy disk pieces, it is
necessary to perform
organizational regulation on the forgings with a highly precisely controlled
heat treatment system.
In the heat treatment procedure, when the required mechanical properties are
obtained, certain
internal stress is inevitably introduced to the disk piece. The heat treatment
stress on the forgings
can be gradually released in the subsequent procedures of part machining,
surface treatment, and
machine service.
Excessive internal stress level can cause a relatively large deformation to a
disk piece in
machining, making it difficult to achieve a predetermined precise dimension on
the part. At the
same time, excessive and improperly distributed internal stress will degrade
the dimensional
stability of the members and parts in the service procedure, affecting the
engine efficiency or
evening causing a failure. Therefore, effective regulation of the heat
treatment internal stress on a
forgings is the premise and foundation for ensuring the dimensional stability
of rotor disks during
machining and service.
Summary
The present application proposes a method for implementing a high-speed
spinning treatment on
disk forgings, namely acquiring a predetermined micro plastic deformation on
the disk forgings by
using centrifugal force load, to effectively regulate and control the stress
distribution state in the
disk forgings on the premise of not influencing the subsequent machining and
service performance
of the disk forgings. According to the method, excessive internal stress
formed in the heat
treatment procedure can be fully released, so as to avoid the occurrence of
harmful deformation of
the disk forgings in subsequent part machining procedure. Moreover, the
internal stress
distribution can be regulated and optimized concerning the service working
conditions of the disk
forgings, so as to ensure that the disk forgings do not suffer from a harmful
deformation under
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Date Recue/Date Received 2021-07-19
115% or 120% high-stress state during a procedure of a part over-spinning
test, while having a
long-term dimensional stability in service on a machine. The method includes a
spinning operation
performed on the disk forgings after heat treatment and before part machining,
and thus is called
billet disk pre-spinning. It is a novel technology, aiming at the disk
forgings, for actively
regulating the internal stress by inducing micro plastic deformation to disk
forgings by a rotary
centrifugal force.
In order to achieve the above object, the present application provides a
method for internal stress
regulation in a superalloy disk forging by pre-spinning. The method includes:
Step 51,
determining a target revolution for regulating internal stress in the disk
forgings, and determining
a target deformation magnitude of plastic deformation required for regulating
the internal stress by
the pre-spinning of the disk forgings; and Step S2, performing the pre-
spinning of the disk
forgings by the target revolution, monitoring the deformation magnitude of the
disk forgings, and
stopping the pre-spinning when a monitored deformation magnitude of the disk
forgings reaches
the target deformation magnitude.
Preferably, Step 51 includes: Step S11, obtaining a predicted revolution for
regulating the internal
stress in the disk forgings by simulated calculation; Step S12, performing the
pre-spinning of the
disk forgings by the predicted revolution, and monitoring the deformation
magnitude of the disk
forgings; and Step S13, adjusting the predicted revolution according to a
monitored deformation
magnitude of the disk forgings to determine the target revolution.
Preferably, Step S13 includes: Step S131, determining the predicted revolution
as the target
revolution if the monitored deformation magnitude of the disk forgings reaches
the target
deformation magnitude when performing the pre-spinning of the disk forgings by
the predicted
revolution; or Step S132, if the monitored deformation magnitude of the disk
forgings is lower
than the target deformation magnitude when performing the pre-spinning of the
disk forgings by
the predicted revolution, gradually increasing the revolution of the pre-
spinning until the
monitored deformation magnitude of the disk forgings reaches the target
deformation magnitude
when performing a final revolution of pre-spinning, and determining the final
revolution as the
target revolution.
Preferably, Step S132 includes: gradually increasing the revolution of the pre-
spinning by a step of
25-100 rotations per minute if the monitored deformation magnitude of the disk
forgings is lower
than the target deformation magnitude when performing the pre-spinning of the
disk forgings by
the predicted revolution.
Preferably, Step Sll includes: Step S111, simulating heat treatment of the
disk forgings to obtain a
internal stress distribution of the disk forgings; and Step S112, simulating
the pre-spinning of the
disk forgings by different revolutions to determine the predicted revolution,
in which the
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Date Recue/Date Received 2021-07-19
pre-spinning by the predicted revolution enables the internal stress in the
disk forgings to be
regulated to be 400MPa or below and enables the residual deformation magnitude
of the disk
forgings to be 0.05%-1.95%.
Preferably, Step S111 includes: obtaining a internal stress distribution of
the disk forgings after
heat treatment by detecting an actual internal stress in the disk forgings and
correcting a
simulation result of the disk forgings by using the actual internal stress.
Preferably, Step S3 is further included: drawing a internal stress
distribution diagram of the disk
forgings after pre-spinning. Preferably, Step S3 includes: Step S31 simulating
the pre-spinning of
the disk forgings by the target revolution to obtain the internal stress
distribution of the disk
forgings after the pre-spinning; and Step S32: detecting an actual internal
stress at a feature site of
the disk forgings, and correcting a simulated result of the disk forgings
after pre-spinning by using
the actual internal stress to obtain the internal stress distribution of the
disk forgings after
pre-spinning;
Preferably, the target deformation magnitude is 0.05%-1.95%.
Preferably, the deformation magnitude of the disk forgings is monitored after
keeping a current
revolution for at least 30 seconds when performing the pre-spinning.
Preferably, when monitoring the deformation magnitude of the disk forgings, a
stable value is
taken as the monitored deformation magnitude of the disk forgings; and/or Step
S2 includes:
gradually decreasing the revolution of the pre-spinning to zero when it is
monitored that the
deformation magnitude of the disk forgings reaches the target deformation
magnitude.
Preferably, the superalloy is a wrought superalloy, a powder superalloy, or a
cast superalloy.
Preferably, the disk forgings is a disk structure without obvious stress
concentration before
pre-spinning, and the disk forgings includes annular disk forgings, compressor
disk forgings and
turbine disk forgings.
Preferably, the operating temperature of the pre-spinning is -50 C-750 C.
Preferably, the method performs the pre-spinning by a high-speed spinning test
platform and a
matched tool for positioning the disk forgings on the high-speed spinning test
platform.
According to the technical solution, the internal stress within the disk
forgings can be effectively
regulated, while the mechanical property of the disk forgings is maintained.
Therefore, the
deformation degree of subsequent part machining can be alleviated so as to
shorten the part
machining period and reduce the cost. No harmful deformation occurs in
subsequent overspeed
test and service life of the machined part, and thus the dimensional stability
of the part can be
guaranteed. By forming internal stress distribution beneficial to the working
condition of the disk
piece after the pre-spinning, compressive stress is placed into the hub, and
the fatigue life of the
disk piece can be effectively prolonged.
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Date Recue/Date Received 2021-07-19
Brief Description of the Drawings
FIG. la is a schematic structural diagram in which disk forgings is a turbine
disk, and FIG. lb is a
schematic structural diagram in which disk forgings is an annular disk (for
the purpose of showing
a cross section, FIG. la and FIG. lb are views with a portion removed, and the
disk forgings are
of a complete annular shape);
FIG. 2a to FIG. 2c respectively simulate internal stress distribution states
in different heat
treatment process parameters according to Example 1 of the present
application, in which: FIG. 2a
is a state in a low internal stress level: the maximum tensile stress in the
central region of the cross
section of the disk forgings is 286MPa; FIG. 2b is a state in a medium
internal stress level: the
maximum tensile stress in the central region of the cross section of the disk
forgings is 517MPa;
and FIG. 2c is a state in a low internal stress level: the maximum tensile
stress in the central region
of the cross section of the disk forgings is 681MPa;
FIG. 3a to FIG. 3d simulate distribution states of the stress and deformation
of a disk forgings
during pre-spinning under 0 internal stress condition according to a method of
the present
application, in which: FIG. 3a shows a Von mises equivalent stress
distribution state in the disk
forgings when reaching a maximum spinning speed; FIG. 3b shows a distribution
state of
chordwise internal stress in the disk forgings after the spinning is stopped;
FIG. 3c shows
Vonmises equivalent plastic strain distribution in the disk forgings after the
spinning is stopped;
and FIG. 3d shows a chordwise component of the residual plastic strain after
the spinning is
stopped;
FIG. 4a to FIG. 4f shows a stress and strain distribution of a disk forgings
during pre-spinning
under a condition of superimposed heat treatment internal stress stimulated
according to a method
of the present application, in which: FIG. 4a shows a Vonmises equivalent
stress distribution in a
disk forgings with medium heat treatment stress when reaching a maximum
spinning speed; FIG.
4b shows a chordwise stress distribution in the disk forgings with medium heat
treatment stress
when the spinning speed is maximum; FIG. 4c shows a Vonmises equivalent stress
distribution in
the disk forgings after the spinning is stopped; FIG. 4d shows a chordwise
stress component after
the spinning is stopped, transited from a compressive stress of -250MPa at an
inner diameter to a
tensile stress of 150MPa at an outer diameter; FIG. 4e shows a Vonmises
equivalent plastic strain
distribution in the disk forgings after the spinning is stopped; and FIG. 4f
shows a slight plastic
deformation of 0.05%-0.25% introduced into an actual part region of the disk
forgings by the
pre-spinning;
FIG. 5a to FIG. 5d show the variation of dimensions of a feature member of a
disk forgings during
pre-spinning according to a method of the present application, in which: FIG.
5a shows the
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Date Recue/Date Received 2021-07-19
relationship between the change in dimension of the disk forgings and the
maximum spinning
speed of the pre-spinning when there is no initial heat treatment stress
(3imtia1=0); FIG. 5b shows
the effect of heat treatment stress on the change in the outer diameter of the
disk forgings, in
which the greater the initial stress is, the lower the critical spinning speed
required for yielding is;
FIG. 5c shows the change in the dimension of the disk forgings during spinning
under different
initial stresses; and FIG. 5d shows that heat treatment stress has already
started to have a
significant effect on the variation of the outer diameter dimension of the
disk forgings during
increasing the spinning speed;
FIG. 6 shows a stress release curve during pre-spinning according to Example 1
of the present
application;
FIG. 7 shows a internal stress result obtained by simulating pre-spinning by a
predicted revolution
before and after pre-spinning according to Example 1 of the present
application;
FIG. 8a and FIG. 8b show a change in mechanical properties before and after
pre-spinning
according to Example 1 of the present application;
FIG. 9a to FIG. 9d show a regulation effect of the pre-spinning treatment on
the stress state of a
high scroll according to Example 2 of the present application; and
FIG. 10a and FIG. 10b show a stress release curve during pre-spinning and a
internal stress result
obtained by simulating pre-spinning by a predicted revolution before and after
pre-spinning
according to Example 2 of the present application, and FIG. 10c shows the
dimensional change in
Example 2 during an overspeed spinning test.
Detailed Description
Specific implementation modes of the present application will be described in
detail below with
reference to the accompanying drawings. It is to be understood that the
specific implementation
modes described herein is illustrative and explanatory of the present
application only and is not
restrictive of the present application.
In the present application, orientation wordings such as "upper, lower, left,
right" are generally
used to refer to upper, lower, left, and right as shown with reference to the
drawings, if they are
not described to the contrary; by "inner, outer" is meant the inner and outer
relative to the contours
of the members themselves. Hereinafter, the present application will be
described in detail with
reference to the accompanying drawings and implementation modes.
The present application provides a method for internal stress regulation in
superalloy disk forgings
by pre-spinning. The method Includes:
Step 51, determining a target revolution for regulating an internal stress in
the disk forgings, and
determining a target deformation magnitude of plastic deformation required for
regulating the
Date Recue/Date Received 2021-07-19
internal stress by the pre-spinning of the disk forgings; and
Step S2, performing the pre-spinning of the disk forgings by the target
revolution, monitoring the
deformation magnitude of the disk forgings, and stopping the pre-spinning when
the deformation
magnitude of the disk forgings reached the target deformation magnitude.
According to the method disclosed by the present application, the internal
stress in the disk
forgings can be effectively regulated, while the mechanical property of the
disk forgings is
maintained. Therefore, the deformation degree of subsequent part machining can
be alleviated so
as to shorten the part machining period and reduce the cost. There is no
harmful deformation
occurred in subsequent overspeed test and the service life of the machined
part, and thus the
dimensional stability of the part is guaranteed. By forming internal stress
distribution beneficial to
the working condition of the disk forgings after pre-spinning, compressive
stress is planted into
the hub, and the fatigue life of the disk forgings can be effectively
prolonged.
Specifically, according to the method provided by the present application, pre-
spinning can be
performed at a high-speed spinning platform so that the whole disk forgings
are subjected to
yielding, resulting in micro plastic deformation, thereby regulating the
internal internal stress in
the disk forgings.
In addition, by regulating the internal stress in the disk forgings, the
possibility of part warping
and deformation during subsequent machining is avoided, facilitating the
improvement of the
machining efficiency and dimension precision.
In addition, because the disk forgings without obvious stress concentration is
adopted for
pre-spinning, in order to achieve yielding of the whole disk, the internal
stress is regulated under a
revolution of the pre-spinning much higher than the revolution in service.
Therefore, in
subsequent overspeed strength test, it can be ensured that no harmful
deformation exceeding
design requirements occurs under 115% or 120% high-stress state. Likewise,
harmful deformation
will not occur in service so that the dimension control of the parts is
facilitated.
Moreover, by stopping the pre-spinning, the spinning speed of the disk
forgings is decreased, so
that a stress distribution of internal pressure and external tension is formed
along the radial
direction of the disk forgings, which is favorable for working conditions
during service
(compressive stress is planted in the hub of the disk piece), thereby
effectively prolonging the
fatigue life of the disk forgings.
Compared with the traditional method for decreasing the internal internal
stress in the disk
forgings merely by controlling the cooling speed of the heat treatment, the
present method can not
only solve the problem of machining deformation, but also ensure that no more
harmful
deformation exceeding a designed deformation occurs in the overspeed strength
test state and in
subsequent service life because the internal stress is regulated in advance.
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Date Recue/Date Received 2021-07-19
In the present application, the target revolution for regulating the internal
stress in the disk
forgings can be determined according to an appropriate manner, for example, a
simulation.
According to a preferred embodiment of the present application, the target
revolution can be
obtained by performing correction according to the simulation result.
Specifically, Step Si
includes: Step S11, obtaining a predicted revolution for regulating the
internal stress in the disk
forgings by simulated calculation; Step S12, performing the pre-spinning of
the disk forgings by
the predicted revolution, and monitoring the deformation magnitude of the disk
forgings; and Step
S13, adjusting the predicted revolution according to a monitored deformation
magnitude of the
disk forgings to determine the target revolution.
In other words, in the preferred implementation of the present application,
the predicted revolution
is firstly determined in Step S11, then pre-spinning is performed by the
predicted revolution in
Step S12, and finally, the revolution is adjusted in Step S13 according to the
deformation
magnitude of the disk forgings to correct the predicted revolution and obtain
the target revolution.
After the target revolution is determined by the disk forgings, a disk
forgings having the same
specification and state as those of the disk forgings can be pre-spun by the
determined target
revolution.
In Step S11, in order to obtain the predicted revolution, the internal stress
in the disk forgings can
be obtained by simulated calculation, and the target internal stress to be
regulated can be set as
required. In particular, when regulating the internal stress, it is necessary
to control the
deformation magnitude of micro plastic deformation in order to maintain the
mechanical
properties of disk forgings. To this end, Step S 1 1 may include: Step S111,
simulating heat
treatment of the disk forgings to obtain a internal stress distribution of the
disk forgings; and Step
S112, simulating the pre-spinning of the disk forgings by different
revolutions to determine the
predicted revolution; in which the pre-spinning by the predicted revolution
enables the internal
stress in the disk forgings to be regulated to be 400MPa or below and enables
the deformation
magnitude of the disk forgings to be 0.05%-1.95%.
In particular, in order to obtain a more precise internal stress distribution
of the disk forgings, the
simulation result can be corrected by the actually detected internal stress
distribution of the disk
forgings. Specifically, Step S111 may include: obtaining the internal stress
distribution by
detecting an actual internal stress in the disk forgings, and correcting a
simulation result of the
disk forgings by using the actual internal stress.
Those skilled in the art will appreciate that the heat treatment and pre-
spinning of the disk forgings
can be simulated in a variety of appropriate manners. For example, the
material, dimension, and
heat treatment process of the disk forgings can be set, and finite element
simulation (e.g., using
ansys software) can be performed to simulate the heat treatment of the disk
forgings. For example,
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Date Recue/Date Received 2021-07-19
the heat treatment can be simulated with reference to "Progresses in Research
of Numerical
Simulation of Heat treatment on Steel" (Journal of Tianjin University of
Technology and
Education, Vol. 24, No. 3, September 2014). Correspondingly, the pre-spinning
of the disk
forgings can be simulated by increasing spinning movements according to
parameters such as the
revolution of the pre-spinning and the like.
Under a condition not taking initial heat treatment stress (3i11itid=0) into
consideration, in the
whole process of simulating the pre-spinning treatment and after stopping the
spinning when the
treatment is completed, the stress-strain values at individual positions on
the disk forgings are
generally a function of the diameter of the disk forgings, independent of the
specific geometric
dimension feature of the cross section of the disk forgings, as shown in FIGs.
3A-3d. When the
pre-spinning reaches a maximum spinning speed, as shown in FIG. 3a, the yield
point has been
reached in the region between the inner diameter Din., and the contour line
numbered A (the yield
strength of the material at room temperature is set to 1150MPa). In the
process of increasing the
revolution, the plastic deformation firstly starts from the inner diameter
Dinner of the disk forgings
and gradually expands outwards radially. Accordingly, by precisely controlling
the maximum
spinning speed of the pre-spinning, the range in which the yield point is
reached on the disk
forgings can be precisely controlled, and the specific plastic deformation
magnitude can be
acquired. As can be seen from FIGs. 3c and 3d, for a low scroll with (Douter-
Dinii,)/Diinier<<1, the
plastic deformation magnitude of the disk forgings from the inner diameter
Dinner to the outer
diameter Pouter, i.e. an overall plastic deformation magnitude of the disk
forgings, can be
controlled within a small range of 0.05%-0.25%.
FIGs. 4a to 4f show the results of pre-spinning simulation in the presence of
heat treatment stress
(i.e. an actual state of the disk forgings). By comparison, it can be seen
that, in the presence of
heat treatment internal stress, the stress distribution and deformation
behavior of the disk forgings
during pre-spinning are greatly different from those in an ideal state without
initial stress given in
FIGs. 3a to 3d. The reason lies in that, due to the presence of the internal
stress of the initial heat
treatment, the initial chordwise tensile stress is superimposed with a pre-
spinning centrifugal force
at a position where the tensile stress is formed inside the disk forgings, so
that the critical
pre-spinning speed required for the corresponding region to reach the yield
point is much lower
than that for a situation where there is no initial stress, as shown in FIG.
5b. The greater the initial
chordwise tensile stress introduced by heat treatment is, the lower the
critical spinning speed
required by the disk forgings for reaching the yield point during the pre-
spinning is. In addition, a
position on the disk forgings which reaches the yield point at the earliest
time is no longer at the
inner diameter Dimier, but at the position with an initial maximum tensile
stress formed in the inner
region of the cross section due to heat treatment. As the spinning speed
increases, the range in
8
Date Recue/Date Received 2021-07-19
which the yield point is reached gradually expands from the position with
maximum tensile stress
to adjacent regions. Under a constant maximum spinning speed, with the
increase of the heat
treatment internal stress, the change in the outer diameter of the disk
forgings after spinning
treatment is increased. The reason lies in that, the more the heat treatment
stress as regulated as a
whole is, the more the elastic deformation magnitude of individual positions
in the disk forgings
recovered due to the loss of stress constraint is. Specifically, along with
the heat treatment stress of
the disk forgings, the tensile stress in the tensile stress region is
regulated by generating local
plastic deformation, and the compressive stress region which is in a balanced
state with the tensile
stress region due to mutual constraint can be synchronously and elastically
stretched due to the
loss of the constraint, macroscopic manifestation of which is that, the higher
the internal stress of
the heat treatment is, the larger a permanent increase in the value of the
outer diameter Dout, of the
disk forgings after pre-spinning treatment is. FIG. 5c shows the dynamic
variation of the outer
diameter Dout, of the disk forgings vs. the spinning speed during the whole
process of loading and
unloading in pre-spinning by a maximum spinning speed of 9750 rotations
permin. For one
specific pre-spinning, the disk forgings is directly proportional to the
square of the spinning speed
in the elastic deformation stage. Comparing FIG. 5c with FIG. 5d, it can be
seen that the
increasing speed of the outer diameter of the disk forgings is accelerated
after the yielding starts,
however, in the unloading stage after reaching the maximum spinning speed, the
outer diameter of
the disk forgings remains a linear relationship with the square of the
spinning speed. With the
increase of the heat treatment internal stress, under the same pre-spinning
condition, the initial
yielding time of disk forgings becomes earlier, and the permanent deformation
magnitude of the
outer diameter after unloading becomes larger. In particular, FIG. 5d, which
is a partially enlarged
view of the spinning speed increasing stage in FIG. Sc, shows that the
magnitude of the heat
treatment internal stress has a significant influence on the deformation
behavior of the disk
forgings at the early stage of the spinning speed increase.
When the disk forgings is of the low scroll structure as shown in FIG. lb, in
which the disk
forgings has a dimension feature that the diameter Dinner of an inner hole is
close to the diameter
pouter of an outer circle and both of them are relatively large, namely
(Doutor-D 1/D
inner, ¨ inner<<1,
individual gradients of the stress-strain amounts formed on the cross section
of the disk forgings
by the pre-spinning are relatively small, and the overall distribution is
relatively even. Such a
feature of a low scroll configuration makes it possible to realize complete
yielding of the disk
forgings and acquire a trace amount of permanent plastic deformation by the
technology of
pre-spinning the disk forgings, by which the internal stress distribution
state of "internal pressure
and external tension" caused by heat treatment can be completely
reconstructed. In fact, all the
configurations of turning pieces with annular features like the low scroll are
suitable for regulating
9
Date Recue/Date Received 2021-07-19
the stress distribution state of the disk forgings by adopting a pre-spinning
method.
Compared with parts such as a low scroll, a labyrinth disk, and a baffle or
the like having small
cross sections, when the disk forgings is of the high scroll structure as
shown in FIG. la, a higher
level of internal stress is often formed in the disk forgings during heat
treatment due to features of
usually heavy weight of the high scroll and large thickness at a site such as
a hub or the like. The
overall structural features of the high scroll part are that the outer contour
is relatively thick and
large and the structure has high rigidity, therefore, the problem of affecting
the dimension of the
parts by the heat treatment internal stress in the machining process is often
not as serious as that in
other thin-wall disk pieces.
However, during the procedure of over-spinning test and service on a machine,
if the tensile stress
in the heat treatment internal stress is superimposed with a service load, it
is possible for a specific
position of the disk forgings to reach the yield point within the spinning
speed range much lower
than the nominal load. In the working process of the disk forgings, once a
local yielding
phenomenon occurs in the residual tension region, the overall regulation of
the internal stress of
the heat treatment will be resulted in, which is manifested as harmful
deformation in macroscopic
dimension of the disk forgings beyond expectation. In fact, excessive heat
treatment internal stress
is one of the leading reasons for the loss of dimensional stability for a high
scroll in service under
a working condition with a strength much lower than a designed strength.
The difference between the inner diameter and the outer diameter of the high
scroll is large,
namely (Douter-Di.)/Diimer>>1. Therefore, if a spinning speed for yielding the
whole of the high
scroll is adopted for pretreatment, the plastic deformation magnitude at the
inner diameter position
will be too large, negatively influencing the structural performance of the
material.
However, due to the high heat treatment tensile stress present in a specific
region of the hub
position of the high scroll, a maximum tensile stress position on the disk
forgings reaches the yield
point in a low spinning speed range, even at a spinning speed lower than that
required for the
yielding at the inner hole Dinner, SO that the heat treatment internal stress
is effectively regulated.
As can be seen from FIGs. 9a and 9b, the heat-treated high scroll has very
high internal stress, the
maximum tensile stress therein appears in the inner region of the hub, the
maximum tensile stress
reaches up to 700-900MPa, and accordingly, the maximum compressive stress on
the surface of
the disk forgings can reach 1000MPa or higher. If the yield strength of the
material is 1200MPa at
room temperatureõthe hub position will actually enter a yielding state when
the working load at
the hub position in service reaches 500MPa or higher, so that the internal
stress on the disk
forgings is regulated. At this time, a harmful deformation beyond expectation
will be generated in
the disk forgings under a working condition with a yield strength much lower
than the nominal
yield strength.
Date Recue/Date Received 2021-07-19
Different from a pre-spinning of a low stroll which can achieve a yielding for
the whole disk
forgings, for the purpose of preventing excessive plastic deformation
magnitude, a plastic
deformation will be usually introduced to the high scroll only at the hub
position at the highest
pre-spinning speed so as to ensure that the tensile stress of the hub region
is sufficiently regulated.
The web and the rim region will not be subjected to plastic deformation at all
during pre-spinning,
therefore, the microstructure states such as dislocation density and the like
at the rim position will
be not influenced. As such, it is ensured that the yield strength and the
fatigue performance of the
hub position are improved, and the high-temperature creep endurance
performance of the rim
position is not attenuated.
By implementing the pre-spinning, as shown in FIGs. 9c and 9d, the chordwise
tensile stress
region in the inner region of the hub is substantially eliminated, the heat
treatment internal stress
in the disk forgings is effectively regulated, and meanwhile, the compressive
stress which is
distributed in gradients from the inner hole along the diameter direction
covers a region
corresponding to the web of the disk forgings. The internal stress
distribution state adjusted by the
pre-spinning, particularly the chordwise compressive stress implanted in the
hub region, can
significantly improve the fatigue performance of the disk forgings. More
importantly, due to the
elimination of excessive chordwise tensile stress in the hub, the disk
forgings can be prevented
from reaching the yield point too early in subsequent service due to the
residual tension
superposed with a working stress, which otherwise would lead to harmful
deformation of the disk
forgings due to internal stress regulation. Therefore, the pre-spinning
treatment of the disk
forgings is an effective stress regulation means, and has very important
engineering application
value for ensuring dimensional stability of a high scroll in subsequent
service life.
In addition, in Step S112, in order to properly set the predicted revolution,
the required degree of
regulation can be set according to the internal stress distribution obtained
by simulation, that is,
the internal stress of the pre-spun disk forgings is regulated to be 400MPa or
below. Specifically,
different pre-spinning revolutions can be set for simulating the pre-spinning,
and a finally
determined predicted revolution shall be the one enabling the internal stress
of the pre-spun disk
forgings to be regulated to be 400MPa or below. In particular, the predicted
revolution determined
by the simulated pre-spinning further entails a deformation magnitude of the
disk forgings of
0.05%-1.95%, so that the disk forgings is prevented from generating excessive
plastic deformation
and influencing the mechanical properties of the disk forgings.
In the above Step S13, the revolution of the pre-spinning can be adjusted
adaptively according to
comparison result between the monitored deformation magnitude of the disk
forgings and the
target deformation magnitude. Specifically, Step S13 includes: S131
determining the predicted
revolution as the target revolution if the monitored deformation magnitude of
the disk forgings
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Date Recue/Date Received 2021-07-19
reaches the target deformation magnitude when performing the pre-spinning of
the disk forgings
by the predicted revolution; or Step S132, if the monitored deformation
magnitude of the disk
forgings is lower than the target deformation magnitude when performing the
pre-spinning of the
disk forgings by the predicted revolution, gradually increasing the revolution
of the pre-spinning
until the monitored deformation magnitude of the disk forgings reaches the
target deformation
magnitude when performing the pre-spinning by a final revolution, and
determining the final
revolution as the target revolution.
Step S131 is applicable to a case where the predicted revolution is relatively
precise, i.e., a
required target deformation magnitude can be reached by pre-spinning by the
predicted revolution.
Step S132 is applicable to a case where the predicted revolution is not
precise enough (i.e.,
pre-spun by the predicted revolution can not reach the target deformation
magnitude) and the
modification is required, in which a specific modification is to gradually
increase the revolution of
the pre-spinning. In order to precisely determine the target revolution, it is
possible to properly set
the revolutions increased each time. Preferably, Step S132 includes: gradually
increasing the
revolution of the pre-spinning by a step of 25-100 rotations per minute if the
monitored
deformation magnitude of the disk forgings is lower than the target
deformation magnitude when
performing the pre-spinning of the disk forgings by the predicted revolution.
In addition, in order to avoid the influence of excessive plastic deformation
of the disk forgings
caused by pre-spinning on mechanical properties, the target deformation
magnitude can be
properly set such that only slight plastic deformation of the disk forgings
occurs, and preferably,
the target deformation magnitude is 0.05%-1.95%. When monitoring the
deformation magnitude
of the disk forgings, the deformation magnitude of a specific position (for
example, at the outer
diameter) on the disk forgings is often monitored. However, the deformation
magnitudes varies at
different positions on the overall disk forgings. For example, the deformation
magnitude at the
inner diameter is larger than that at the outer diameter. Therefore, the range
of the deformation
magnitude at individual positions shall be guaranteed to be within the range
of the target
deformation magnitude.
Further, in order to precisely monitor the deformation magnitude of the disk
forgings, it is
preferable to monitor the deformation magnitude of the disk forgings after
keeping the current
revolution of the pre-spinning for at least 30 seconds so as to ensure that
the monitoring is
performed while the plastic deformation generated by the pre-spinning has been
stabilized.
In addition, during the plastic deformation of the disk forgings due to pre-
spinning, the disk
forgings is subject to a change from elastic deformation to plastic
deformation, therefore, the
deformation magnitude of the disk forgings will be continuously changed until
reaching a stable
value. In order to precisely monitor the deformation magnitude, preferably,
when monitoring the
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Date Recue/Date Received 2021-07-19
deformation magnitude of the disk forgings, a stable value is taken as the
monitored deformation
magnitude of the disk forgings. In particular, when the monitored deformation
magnitude
fluctuates in the range of 0.01mm within 15s, it could be considered that a
stable value is
reached.
According to the method of the present application, in order to finally form a
stress distribution
state of internal pressure and external tension beneficial to a working
condition during service
along the radial direction of the disk forgings, Step S2 includes: gradually
decreasing the
revolution of the pre-spinning to zero when it is monitored that the
deformation magnitude of the
disk forgings reaches the target deformation magnitude. Specifically, the
revolution may be
gradually decreased by 1-200 rotations per second until the pre-spinning
stops.
The method of the present application is applicable to various superalloy disk
forgings with high
internal stress. In particular, the superalloy includes a wrought superalloy,
a powder superalloy, or
a cast superalloy.
In addition, in order to verify the effect of the method provided by the
present application, step S3
is included: drawing a internal stress distribution diagram of the disk
forgings after pre-spinning.
By drawing a internal stress distribution diagram after pre-spinning, the
technical effect of the
present application can be more visually seen. In particular, the internal
stress distribution diagram
after pre-spinning can be drawn in a variety of suitable manners, for example
drawing by
simulation. To improve the efficiency, preferably, step S3 includes: S31,
simulating the
pre-spinning of the disk forgings by the target revolution to obtain the
internal stress distribution
of the disk forgings after the pre-spinning; and S32, detecting the actual
internal stress at a feature
site of the disk forgings (for example, a position with small fluctuation of
the stress distribution
selected according to a simulated result), and correcting the simulated result
of the disk forgings
after pre-spinning by using the actual internal stress so as to obtain the
internal stress distribution
of the disk forgings after pre-spinning.
In the present application, the actual internal stress of the feature position
of the disk forgings can
be detected in an appropriate manner. For example, 0.2mm or more below the
surface of the
feature site of the disk forgings can be measured by an X-ray diffraction
method.
In order to ensure the final effect, the disk forgings applicable to the
present application is a disk
structure without obvious stress concentration before pre-spinning, including,
but not being
limited to, annular disk forgings, compressor disk forgings, turbine disk
forgings and the like.
Further, the pre-spinning operating temperature suitable for the present
application is
-50 C-750 C, in particular, room temperature. Particular operating
temperature depends primarily
on the ratio of the tensile strength of the material to the yield strength of
the material.
In the present application, various suitable high-speed spinning equipment can
be adopted for
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Date Recue/Date Received 2021-07-19
pre-spinning as long as the conditions of spinning speed control, temperature,
and the like required
by pre-spinning the disk forgings can be met. The deformation magnitude in the
pre-spinning
process can be monitored by using suitable equipment, for example, by infrared
displacement
detection.
The method of the present application will be illustrated by the following
Examples.
Example 1
An annular low-pressure turbine disk forgings of GI14065 alloy was used, and
the structure
thereof was as shown in FIG. lb. The inner diameter was 0618mm, the outer
diameter was
0829mm, the height was 85mm, and the weight was 130kg. After standard heat
treatment, the
chordwise internal stress in the disk forgings was the main stress. The X-ray
diffraction method
was adopted to detect 0.2 mm or more below the feature site. The chordwise
internal stress at the
hub was -384MPa, the chordwise internal stress at the web was -641MPa, and the
chordwise
internal stress at the rim was -740MPa, showing a high-stress level.
The internal stress distribution of the disk forgings was obtained by
simulating the heat treatment
of the disk forgings, and as shown in FIG. 2c, the simulated result was
consistent with the
detection result.
The pre-spinning was then simulated. For a low scroll with (Douter-
Dittller)/Dittller<<1, the plastic
deformation magnitude of the disk forgings from the inner diameter antler to
the outer diameter
Douter, i.e. the overall plastic deformation magnitude of the disk forgings,
was controlled within a
small range of 0.05%-0.25%.
As shown in FIGs. 4a to 4f, the stress-strain distribution of the disk
forgings during the
pre-spinning by different revolutions in the presence of heat treatment stress
was simulated, the
maximum chordwise tensile stress in the disk forgings was regulated to be
400MPa or below, and
the predicted revolution corresponding to an overall deformation of 0.15%-
0.25% is 9400
rotations per minute.
The pre-spinning was performed on the disk forgings at 9400 rotations per
minute for 60 seconds.
As shown in FIG. 6, the deformation magnitude of the disk forgings was
monitored, the residual
deformation at the outer diameter was detected to be 0.75mm, and the overall
deformation
magnitude corresponding to the disk forgings is 0.18-0.24%, reaching the
target deformation
magnitude, therefore, the predicted revolution was determined as the target
revolution. The
internal stress can be regulated by the pre-spinning of 9400 rotations per
minute for a batch of disk
forgings with the same specification.
In order to verify the effect of the present application, the X-ray
diffraction method was adopted to
measure internal stress (the result was shown in FIG. 7) 0.2 mm or more below
the surface of a
feature site (for example, a region with small fluctuation of stress
distribution selected according
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Date Recue/Date Received 2021-07-19
to a simulated result) of the disk forgings before and after the pre-spinning.
The test result was
substantially consistent with the simulated result. Finally, the internal
stress distribution diagram
after the pre-spinning was drawn, ready for a subsequent disk piece machining
process.
No abnormality was found in the pre-spun disk forgings by ultrasonic
inspection. Further
dissection was carried out on the disk piece, showing that the microstructure
of the disk piece and
mechanical properties at various positions (results shown in FIGs. 8a and 8b)
were not
significantly different from those of a disk piece without subjecting to the
pre-spinning.
Example 2
A typical alloy turbine disk forgings of powder superalloy FGH96 (hereinafter
also referred to as a
high scroll) was treated using the method of Example 1. The structure was
shown in FIG. la, with
an inner diameter of 0125mm, an outer diameter of 0550mm, a hub height of
215mm, and a rim
height of 60mm. The disk forgings was subjected to standard heat treatment.
The internal stress
distribution of the disk forgings was obtained by simulating the heat
treatment of the disk forgings.
The result was shown in FIGs. 9a and 9b, in which the maximum chordwise
tensile stress in the
disk piece reached above 700MPa, which was relatively high.
The pre-spinning of the disk forgings by different revolutions was simulated,
the maximum
chordwise tensile stress in the disk forgings was reduced to 400MPa or below,
and the predicted
revolution corresponding to the overall deformation of 0.15-1.0% was 23500
rotations per minute.
The test piece of the disk forgings was pre-spun at 23500 rotations per minute
for 60 seconds. The
deformation magnitude of the test piece was monitored. The residual
deformation was measured
to be 0.70mm, and the corresponding deformation magnitude was 0.12-0.88%,
therefore, the
target deformation magnitude cannot be reached. The revolution was increased
by 50 rotations
each time. When a final revolution was 23550 rotations per minute, the
residual deformation
reached 0.82mm, reaching a target deformation magnitude of 0.15-0.98%,
therefore, the final
revolution was determined as the target revolution. The internal stress can be
regulated by the
pre-spinning of 23550 rotations per minute for a batch of disk pieces with the
same specification.
In order to verify the effect of the present application, the internal stress
was measured 0.2mm or
more below the surface of a feature site of the disk forgings before and after
the pre-spinning (the
result was shown in FIG. 10b). The test result was consistent with the
simulated result. By
ultrasonic inspection to the pre-spun disk piece and an overall dissection
performance test to the
disk forgings, no significant change was found.
In addition, in order to verify the effect of the present application in terms
of dimensional stability,
an overspeed test was performed for the pre-spun piece and the non-pre-spun
piece. The test result
was shown in FIG. 10c. The dimension of the pre-spun disk piece was
substantially unchanged in
122% overspeed test.
Date Recue/Date Received 2021-07-19
The preferred implementation modes of the present application are described in
detail above with
reference to the accompanying drawings, but the present application is not
limited thereto. Many
simple variations of the technical scheme of the present application are
possible within the scope
of the technical idea of the present application. The present application
includes the combination
of various specific technical features in any suitable manner. In order to
avoid unnecessary
repetition, the present application will not be further described with respect
to various possible
combinations. However, such simple variations and combinations should also be
considered as the
disclosed content of the present application, falling within the scope of the
present application.
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Date Recue/Date Received 2021-07-19
