U.S. patent application number 16/639746 was filed with the patent office on 2020-06-25 for method for reinforcing rail by laser and auxiliary heat source efficient hybrid cladding.
This patent application is currently assigned to Wuhan Hivalue Intelaser Ltd.. The applicant listed for this patent is Wuhan Hivalue Intelaser Ltd. Huazhong University of Science and Technology WUHAN NRD LASER ENGINEERING CO.,LTD. Invention is credited to Pinghua Guo, Qianwu HU, Li MENG, Li NIU, Dengzhi WANG, Xiaohua XU, Xiaoyan ZENG.
Application Number | 20200199698 16/639746 |
Document ID | / |
Family ID | 63238669 |
Filed Date | 2020-06-25 |
United States Patent
Application |
20200199698 |
Kind Code |
A1 |
ZENG; Xiaoyan ; et
al. |
June 25, 2020 |
METHOD FOR REINFORCING RAIL BY LASER AND AUXILIARY HEAT SOURCE
EFFICIENT HYBRID CLADDING
Abstract
The disclosure discloses a method for reinforcing a rail by
laser and auxiliary heat source efficient hybrid cladding. The
laser and the auxiliary heat source simultaneously apply on a
region to be cladded of a rail surface. The laser serves as a main
heat source to enable simultaneous and rapid fusion of an added
metal powder and partial substrate material in the rail surface to
form a molten pool. The auxiliary heat source moves with the laser
heat source in the same direction at the same speed, and performs
synchronous preheating and/or post-heating on the laser molten
pool, the heat-affected zone and the surface layer of the rail
substrate to reduce the temperature gradient, thereby reducing the
cooling rate, and avoiding martensite transformation and cracking
in the heat-affected zone.
Inventors: |
ZENG; Xiaoyan; (Hubei,
CN) ; MENG; Li; (Hubei, CN) ; WANG;
Dengzhi; (Hubei, CN) ; HU; Qianwu; (Hubei,
CN) ; Guo; Pinghua; (Hubei, CN) ; XU;
Xiaohua; (Hubei, CN) ; NIU; Li; (Hubei,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wuhan Hivalue Intelaser Ltd.
Huazhong University of Science and Technology
WUHAN NRD LASER ENGINEERING CO.,LTD |
Hubei
Hubei
Hubei |
|
CN
CN
CN |
|
|
Assignee: |
Wuhan Hivalue Intelaser
Ltd.
Hubei
CN
Huazhong University of Science and Technology
Hubei
CN
WUHAN NRD LASER ENGINEERING CO.,LTD
Hubei
CN
|
Family ID: |
63238669 |
Appl. No.: |
16/639746 |
Filed: |
January 18, 2019 |
PCT Filed: |
January 18, 2019 |
PCT NO: |
PCT/CN2019/072300 |
371 Date: |
February 18, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21D 1/09 20130101; C21D
9/04 20130101; C23C 24/106 20130101; C21D 2211/009 20130101 |
International
Class: |
C21D 1/09 20060101
C21D001/09; C21D 9/04 20060101 C21D009/04; C23C 24/10 20060101
C23C024/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 23, 2018 |
CN |
201810063575.6 |
Claims
1. A method for reinforcing a rail by laser and auxiliary heat
source efficient hybrid cladding, wherein in the method, a laser
and an auxiliary heat source are utilized to simultaneously apply
on a region to be cladded of a rail surface; the laser serves as a
main heat source to enable rapid fusion of an added powder material
and a partial substrate material on the rail surface to form a
molten pool and then to form a cladded coating; the auxiliary heat
source is located in front of or/and behind the main heat source,
moves with the main heat source in the same direction at the same
speed, and performs synchronous preheating and/or post-heating on
the molten pool, a heat-affected zone and a surface layer of a rail
substrate to reduce a temperature gradient between the molten pool
and heat-affected zone and the rail substrate, thereby reducing a
cooling rate of the molten pool and heat-affected zone, and
avoiding martensite transformation in the laser-heat-affected zone
and generation of cracks in the cladded coating and the
heat-affected zone at a high laser scanning rate.
2. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 1, wherein a
thermal cycle process of the heat-affected zone under laser action
is reasonably regulated by the combined action of the laser and the
auxiliary heat source such that a cooling time of the heat-affected
zone is larger than a critical cooling time of transformation from
austenite to pearlite in a continuous cooling transformation (CCT)
curve or a time-temperature-transformation (TTT) curve, thereby
meeting critical conditions of complete transformation from
austenite to pearlite, and allowing the heat-affected zone to be
transformed into a fine lamellar pearlite structure which has an
interlamellar spacing less than or equal to that of the rail
substrate and has a hardness between hardnesses of the cladded
coating and the rail substrate, so that mechanical properties
between the cladded coating, the heat-affected zone and the rail
substrate are reasonably matched, the hardness curve is smooth, and
the overall fatigue performance is good.
3. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 1, wherein the
auxiliary heat source adopts any one of induction heating,
oxyacetylene flame and propane torch, or any combination
thereof.
4. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 1, wherein a
preheating temperature is 100-1000.degree. C., and a post-heating
temperature is 300-700.degree. C.
5. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 1, wherein the
cladded coating obtained by single processing has a thickness of
0.1-2 mm, a width of 3-20 mm, and a hardness which is controlled
within a range of HV250 to HV500 according to specific requirements
of the rail.
6. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 1, wherein the
heat-affected zone has a width of less than 1 mm and a hardness of
HV250 to HV400, and there is no martensite transformation in the
heat-affected zone.
7. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 1, wherein the
method comprises following specific implementation steps of: (1)
polishing the region to be cladded of the rail surface first to
remove surface rust and contaminants; (2) adjusting a defocusing
distance of a laser beam to allow a laser spot to be a circular
spot with a diameter of 3-20 mm or a rectangular spot with a size
of (1-3) mm.times.(6-30) mm; (3) adjusting relative position of the
laser spot and the auxiliary heat source such that the laser spot
is in front of, in the middle of or behind the auxiliary heat
source; (4) turning on the laser and the auxiliary heat source, and
synchronously feeding or pre-placing a coating material into a
laser irradiation region of the rail surface by using an automatic
powder feeder, so that the molten pool is formed when the focused
laser beam is incident on the rail substrate, and then the cladded
coating is formed on the rail surface after the molten pool is
solidified, wherein the auxiliary heat source plays a role of
preheating and/or post-heating the rail, with a preheating
temperature of 100-1000.degree. C. and a post-heating temperature
of 300-700.degree. C.; (5) after a layer of the cladded coating is
formed, determining whether a thickness of the cladded coating
meets working conditions, and if so, ending the cladding process;
if not, repeating the above steps (2), (3) and (4) until the
thickness requirements are met; (6) after the cladding process is
finished, inspecting the surface of the corrosion-resistant cladded
coating by penetration or ultrasonic inspection, to ensure that
there are no metallurgical defects in the cladded coating; and (7)
selectively performing cleaning and profile trimming on a rail
tread to make its surface flat.
8. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 1, wherein the
method is integrated with a fixed processing platform to perform
off-line processing of the rail, or integrated with an on-line
mobile laser processing vehicle to perform on-line laser cladding
reinforcement or repair of the rail at a railway site.
9. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 3, wherein the
induction heating is implemented by an induction power supply and
an induction coil; wherein the induction coil is formed by bending
and welding a copper tube, a magnet is embedded on the copper tube
in a working area, a lower surface of the copper tube is parallel
to a cladded surface of the rail, with a gap of 0.5-15 mm; a
heating zone on the rail surface has a linear structure, which is
parallel to a longitudinal direction of the rail and has a length
of 10-500 mm.
10. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 1, wherein the
added powder material is an iron-based alloy, main chemical
compositions of which are: 0.01-0.60% C, 10-40% Cr, 5-18% Ni,
0.1-3.0% Si, 0-3% B, 0-3% Mo, 1-3% Mn and Fe balance; or the added
powder material is a nickel-based alloy or a cobalt-based alloy,
wherein main chemical compositions of the nickel-based alloy are:
0.01-0.50% C, 20-30% Cr, 5-10% W, 3-5% Si, 0-3% B, 5-10% Fe and Ni
balance; and main chemical compositions of the cobalt-based alloy
are: 0.01-0.5% C, 20-35% Cr, 1-10% Ni, 1-3% Si, 5-15% W, 0-3% B,
0.5-2% Mn and Co balance.
11. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 2, wherein the
auxiliary heat source adopts any one of induction heating,
oxyacetylene flame and propane torch, or any combination
thereof.
12. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 2, wherein a
preheating temperature is 100-1000.degree. C., and a post-heating
temperature is 300-700.degree. C.
13. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 2, wherein the
cladded coating obtained by single processing has a thickness of
0.1-2 mm, a width of 3-20 mm, and a hardness which is controlled
within a range of HV250 to HV500 according to specific requirements
of the rail.
14. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 2, wherein the
heat-affected zone has a width of less than 1 mm and a hardness of
HV250 to HV400, and there is no martensite transformation in the
heat-affected zone.
15. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 2, wherein the
method comprises following specific implementation steps of: (1)
polishing the region to be cladded of the rail surface first to
remove surface rust and contaminants; (2) adjusting a defocusing
distance of a laser beam to allow a laser spot to be a circular
spot with a diameter of 3-20 mm or a rectangular spot with a size
of (1-3) mm.times.(6-30) mm; (3) adjusting relative position of the
laser spot and the auxiliary heat source such that the laser spot
is in front of, in the middle of or behind the auxiliary heat
source; (4) turning on the laser and the auxiliary heat source, and
synchronously feeding or pre-placing a coating material into a
laser irradiation region of the rail surface by using an automatic
powder feeder, so that the molten pool is formed when the focused
laser beam is incident on the rail substrate, and then the cladded
coating is formed on the rail surface after the molten pool is
solidified, wherein the auxiliary heat source plays a role of
preheating and/or post-heating the rail, with a preheating
temperature of 100-1000.degree. C. and a post-heating temperature
of 300-700.degree. C.; (5) after a layer of the cladded coating is
formed, determining whether a thickness of the cladded coating
meets working conditions, and if so, ending the cladding process;
if not, repeating the above steps (2), (3) and (4) until the
thickness requirements are met; (6) after the cladding process is
finished, inspecting the surface of the corrosion-resistant cladded
coating by penetration or ultrasonic inspection, to ensure that
there are no metallurgical defects in the cladded coating; and (7)
selectively performing cleaning and profile trimming on a rail
tread to make its surface flat.
16. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 2, wherein the
method is integrated with a fixed processing platform to perform
off-line processing of the rail, or integrated with an on-line
mobile laser processing vehicle to perform on-line laser cladding
reinforcement or repair of the rail at a railway site.
17. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 11, wherein the
induction heating is implemented by an induction power supply and
an induction coil; wherein the induction coil is formed by bending
and welding a copper tube, a magnet is embedded on the copper tube
in a working area, a lower surface of the copper tube is parallel
to a cladded surface of the rail, with a gap of 0.5-15 mm; a
heating zone on the rail surface has a linear structure, which is
parallel to a longitudinal direction of the rail and has a length
of 10-500 mm.
18. The method for reinforcing the rail by laser and auxiliary heat
source efficient hybrid cladding according to claim 2, wherein the
added powder material is an iron-based alloy, main chemical
compositions (by weight percentage) of which are: 0.01-0.60% C,
10-40% Cr, 5-18% Ni, 0.1-3.0% Si, 0-3% B, 0-3% Mo, 1-3% Mn and Fe
balanc; or the added powder material is a nickel-based alloy or a
cobalt-based alloy, wherein main chemical compositions (by weight
percentage) of the nickel-based alloy are: 0.01-0.50% C, 20-30% Cr,
5-10% W, 3-5% Si, 0-3% B, 5-10% Fe and Ni balance; and main
chemical compositions (by weight percentage) of the cobalt-based
alloy are: 0.01-0.5% C, 20-35% Cr, 1-310% Ni, 1-3% Si, 5-15% W,
0-3% B, 0.5-2% Mn and Co balance.
Description
BACKGROUND
Technical Field
[0001] The present disclosure belongs to the field of material
processing, and particularly relates to a method for efficiently
preparing a metal cladded coating on a rail surface by laser and
auxiliary heat source hybrid cladding. The method can improve the
wear resistance and contact fatigue performance of the rail, solve
the problems of poor railway shunt, and repair the damaged
rail.
Description of Related Art
[0002] China's rail transit has developed rapidly, and by the end
of 2016, the national railway operation mileage has reached 124,000
kilometers. With the increase of railway transportation volume,
train speed and axle load, damage problems such as rail wear,
rolling contact fatigue and rail corrosion of rails are becoming
more and more prominent. The damage of the rail mainly occurs on
the surface, and thus, the preparation of the coating on the
surface of the rail is of great significance for extending its
service life.
[0003] Thermal spraying, electroplating and welding are the main
methods currently used to prepare a metal coating on a rail
surface. The thermal spray coating and the electroplating coating
are mechanically bonded with the rail substrate, and are easy to
fall off during the wheel-rail friction process due to the weak
bonding force. The welding layer and the rail substrate are
metallurgically bonded, but in this method, the heat input and
heat-affected zone are large, resulting in that the microstructure
and performance uniformity of the surfacing layer are poor, and the
martensite structure is easily induced inside the rail
substrate.
[0004] Compared with plasma arc and arc welding, laser cladding has
the advantages of high energy density, small heat-affected zone,
low heat input, low residual stress, small substrate penetration
depth and high cladding efficiency, and is widely used in the
preparation of surface strengthening coating and the additive
manufacturing of metal parts. The Chinese Patent Application
Publication No.: 107099793 discloses a method for improving the
wear resistance of the wheel and rail in heavy-haul trains by using
a laser-clad cobalt alloy coating, which uses a high-power laser to
clad a cobalt alloy powder on the surface of the wheel and rail to
reduce the surface friction coefficient thereof, thereby improving
the wear resistance of the wheel rail and extending the service
life of the wheel rail. However, with the rapid heating and rapid
cooling effect of the laser, high-carbon acicular martensite
structure may be generated in the heat-affected zone of the rail.
The martensite structure has high hardness, but low toughness,
which may easily cause the rail breakage. Therefore, the martensite
structure in the rail shall be prohibited according to the railway
industry standard TB/T2344-2003. In addition, since the cladded
coating and the heat-affected zone have a high cooling rate and a
large temperature gradient relative to the rail substrate at a high
laser scanning rate, cracks may be easily generated in the cladded
coating and the heat-affected zone, which affects the safe service
of the train.
[0005] By combining a high-energy laser beam with an auxiliary heat
source to perform hybrid processing, the above problems can be
effectively solved. The Chinese Patent Publication No.: 101125394
discloses an automatic powder feeding laser induction hybrid
cladding method and device, in which a laser and an induction heat
source are used to perform hybrid processing, so that not only can
the cladding efficiency be greatly improved, but also the problem
that the alloy material with poor weldability are easily cracked
during laser cladding can be solved. However, this method does not
consider how to reduce and avoid the martensite phase
transformation in the heat-affected zone when preparing a cladded
coating on a large high-carbon steel substrate (such as a rail), as
well as technical problems such as matching of mechanical
properties of the cladded coating, the heat-affected zone and the
substrate in a specific service environment (rolling rail
contact).
SUMMARY
[0006] The present disclosure provides a method for efficiently
preparing a high-performance cladded coating on a rail surface by
laser and auxiliary heat source hybrid cladding to achieve the
purpose of reinforcing and repairing the rail surface. A laser and
an auxiliary heat source simultaneously apply on a region to be
cladded of the rail surface, which not only avoids generation of
cracks in the cladded coating and the heat-affected zone at a high
laser scanning rate, but also avoids generation of harmful
structures such as martensite in the heat-affected zone to ensure
that mechanical properties between the cladded coating, the
heat-affected zone and the rail substrate are well matched. The
method of the present disclosure can be used for preparing a
cladded coating on a rail surface to improve the wear resistance
and contact fatigue performance of the rail, and can also solve the
problems of poor railway shunt, repair of damaged rails and the
like.
[0007] The present disclosure provides a method for reinforcing a
rail by laser and auxiliary heat source efficient hybrid cladding,
in which a laser and an auxiliary heat source are utilized to
simultaneously apply on a region to be cladded of a rail surface;
the laser serves as a main heat source to enable rapid fusion of a
cladding material and a partial substrate material in the rail
surface to form a molten pool; and the auxiliary heat source is
located in front of or/and behind the laser heat source, moves with
the laser heat source in the same direction at the same speed, and
performs synchronous preheating and/or post-heating on the laser
molten pool, a laser heat-affected zone and a surface layer of a
rail substrate to reduce the cooling rate of the laser molten pool
and heat-affected zone and avoid martensite transformation in the
laser heat-affected zone and generation of cracks in the cladded
coating and the heat-affected zone at a high laser scanning
rate.
[0008] As an improvement of the above technical solution, a
temperature cycle curve of the heat-affected zone under laser
action is reasonably regulated by the combined action of the laser
and the auxiliary heat source such that a cooling time of the
heat-affected zone is larger than a critical cooling time of
transformation from austenite to pearlite in a continuous cooling
transformation curve (CCT curve) or a
time-temperature-transformation curve (TTT curve), thereby meeting
critical conditions of complete transformation from austenite to
pearlite, and allowing the heat-affected zone to be transformed
into a fine lamellar pearlite structure which has an interlamellar
spacing less than or equal to that of the rail substrate and has a
hardness between those of the cladded coating and the rail
substrate, so that mechanical properties between the cladded
coating, the heat-affected zone and the rail substrate are
reasonably matched, the hardness curve is smooth, and the overall
fatigue performance is good.
[0009] As a further improvement of the above technical solution,
the auxiliary heat source adopts any one of induction heating,
oxyacetylene flame and propane torch, or any combination thereof;
the preheating temperature is 100-1000.degree. C., and the
post-heating temperature is 300-700.degree. C.; a metal cladded
coating obtained by single processing has a thickness of 0.1-2 mm,
a width of 3-20 mm, and a hardness which is adjustable within a
range of HV250 to HV500 according to specific requirements of the
rail; the laser heat-affected zone has a width of less than 1 mm
and a hardness of HV250 to HV400, which can avoid martensite
transformation in the heat-affected zone; and the induction heating
is performed by an induction power supply and an induction coil.
The induction coil is manufactured by bending and welding a copper
tube, magnets are embedded on the copper tube in a working area, a
lower surface of the copper tube is parallel to a cladding surface
of the rail, with a gap of 0.5-15 mm; and a heating surface has a
linear structure along a longitudinal direction of the rail, and
has a length of 10-500 mm.
[0010] The method according to the present disclosure comprises
following specific implementation steps.
[0011] (1) Polish the region to be cladded of the rail surface
first to remove surface rust and contaminants.
[0012] (2) Adjust a defocusing distance of a laser beam to allow a
laser spot to be a circular spot with a diameter of 3-20 mm or a
rectangular spot with a size of (1-3) mm.times.(6-30) mm.
[0013] (3) Adjust relative position of the laser spot and the
auxiliary heat source such that the laser spot is in front of, in
the middle of or behind the auxiliary heat source.
[0014] (4) Turn on the laser and the auxiliary heat source, and
synchronously feed or pre-place a coating material into a laser
irradiation region of the rail surface by using an automatic powder
feeder, so that the molten pool is formed when the focused laser
beam is incident on the rail substrate, and then a metal cladded
coating is formed on the rail surface after the molten pool is
solidified, wherein the auxiliary heat source plays a role of
preheating and/or post-heating the rail, with a preheating
temperature of 100-1000.degree. C. and a post-heating temperature
of 300-700.degree. C.
[0015] (5) After a layer of the metal cladded coating is formed,
determine whether a thickness of the cladded coating meets working
conditions, and if so, end the cladding process; if not, repeat the
above steps (2), (3) and (4) until the thickness requirements are
met.
[0016] (6) After the cladding process is finished, inspect the
surface of the corrosion-resistant cladded coating by penetration
or ultrasonic inspection, to ensure that there are no metallurgical
defects in the cladded coating.
[0017] (7) Selectively perform cleaning and profile trimming on a
rail tread to make its surface flat.
[0018] The cladded coating material may be an iron-based alloy,
main chemical compositions (by weight percentage) of which are:
(0.01-0.60) C, (10-40) Cr, (5-18) Ni, (0.1-3.0) Si, (0-3) B, (0-3)
Mo, (1-3) Mn and Fe balance.
[0019] The cladded coating material may be a nickel-based alloy,
main chemical compositions (by weight percentage) of which are:
(0.01-0.50) C, (20-30) Cr, (5-10) W, (3-5) Si, (0-3) B, (5-10) Fe
and Ni balance.
[0020] The cladded coating material may be a cobalt-based alloy,
main chemical compositions (by weight percentage) of which are:
(0.01-0.5) C, (20-35) Cr, (1-10) Ni, (1-3) Si, (5-15) W, (0-3) B,
(0.5-2) Mn and Co balance.
[0021] The present disclosure has the following beneficial
effects:
[0022] {circle around (1)} The laser and the auxiliary heat source
simultaneously apply on a region to be cladded of a rail surface;
the high-energy laser beam enables rapid fusion of a cladded
coating material and a thin-layer material on the rail surface to
form a molten pool; and the auxiliary heat source performs
synchronous preheating and post-heating on the laser molten pool, a
heat-affected zone and a surface layer of the rail substrate to
reduce a temperature gradient between the laser molten pool, the
heat-affected zone and the rail substrate, thereby reducing the
cooling rate, and avoiding cracking and spalling of the metal
cladded coating and the heat-affected zone at a high laser scanning
rate.
[0023] {circle around (2)} Through adjusting the relative position
of the laser and the auxiliary heat source, the laser processing
power, the laser scanning rate, and the heating temperature of the
auxiliary heat source to the rail, a temperature cycle curve of the
heat-affected zone can be reasonably controlled such that a cooling
time of the heat-affected zone is larger than a critical cooling
time of transformation from austenite to pearlite in the CCT curve
or the TTT curve, thereby meeting critical conditions of complete
transformation from austenite to pearlite, and allowing the
heat-affected zone to be transformed into a fine lamellar pearlite
structure which has an interlamellar spacing less than or equal to
that of the rail substrate and has a hardness between those of the
cladded coating and the rail substrate, so that mechanical
properties between the cladded coating, the heat-affected zone and
the rail substrate are reasonably matched, the hardness curve is
smooth, and the overall fatigue performance is good.
[0024] {circle around (3)} Compared with other methods such as
plasma arc and electric arc, the laser energy density is high, the
heat-affected zone is small, the martensite structure in the
heat-affected zone can be eliminate while the heating width and
depth of the induction coil and other auxiliary heat sources are
just larger than the heat-affected zone width, so that the overall
heat input is small resulting in small processing residual stress
and deformation, and high stability of the rail; the device has
good flexibility and high processing precision, and can repair
rails with different degrees of damage.
[0025] {circle around (4)} The cladded coating has low dilution
rate, especially for a thinner cladded coating. When the thickness
of the cladded coating is less than 0.5 mm, the dilution rate of
the coating is less than 5%, which can ensure the wear resistance
and corrosion resistance of the cladded coating.
[0026] {circle around (5)} Due to the combination of the auxiliary
heat source, the energy required to form the molten pool is greatly
reduced. When the laser power is 1-20 kW, the deposition rate of
the cladded coating can reach 10-250 g/min, and the scanning speed
reaches 0.4-30 m/min. Compared with the pure laser cladding
process, the deposition efficiency is increased by 3-15 times.
[0027] The present disclosure has strong versatility, and can
efficiently prepare a wear-resistant, corrosion-resistant and
fatigue-resistant cladded coating with uniform composition and
matched mechanical properties directly on the rail surface, and can
also repair a locally damaged rail. The hardness distribution curve
of the reinforced or repaired rail along the depth direction is
smooth, the mechanical properties of the cladded coating, the
heat-affected zone and the substrate are matched with each other,
and the overall fatigue performance is good, so that the coating
spalling does not occur during the service. Meanwhile, various
process components used in the method in the present disclosure
have high integration degree and are easy to integrate with related
processing platforms, and the method can be used for both a fixed
laser processing machine to perform off-line processing and mobile
laser processing equipment (e.g., a mobile laser processing
vehicle) to perform on-line reinforcement or repair at the railway
site.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a top view showing laser and induction
post-heating hybrid cladding on a rail surface in a case where the
laser spot is located in front of induction heating.
[0029] FIG. 2 is a top view showing laser, induction preheating and
induction post-heating hybrid cladding on a rail surface in a case
where the laser spot is located in the middle of induction
heating.
[0030] FIG. 3 is a top view showing laser, induction heating and
oxyacetylene flame (or laser, induction heating and propane torch)
heating hybrid cladding on a rail surface.
[0031] FIG. 4 is a top view showing laser and oxyacetylene flame
(or laser and propane torch) heating hybrid cladding on a rail
surface.
[0032] FIG. 5 is a hardness distribution diagram along the depth
direction of a rail with a
[0033] Fe-based metal cladded coating prepared by laser and
induction post-heating hybrid cladding.
[0034] FIG. 6 is a hardness distribution diagram along the depth
direction of a rail with a Ni-based metal cladded coating prepared
by laser, induction preheating and induction post-heating hybrid
cladding.
[0035] FIG. 7 is a hardness distribution diagram along the depth
direction of a rail with a Co-based metal cladded coating prepared
by laser, induction heating and oxyacetylene flame (or laser,
induction heating and propane torch) heating hybrid cladding.
[0036] FIG. 8 is a hardness distribution diagram along the depth
direction of a rail with a Fe-based metal cladded coating prepared
by laser and oxyacetylene flame (or laser and propane torch)
heating hybrid cladding.
[0037] In the figures: 1, laser spot; 2, induction heating coil;
2(a), induction preheating coil; 2(b), induction post-heating coil;
and 3, oxyacetylene flame (or propane torch).
DESCRIPTION OF THE EMBODIMENTS
[0038] For clear understanding of the objectives, features and
advantages of the present disclosure, detailed description of the
present disclosure will be given below in conjunction with
accompanying drawings and specific embodiments. It should be noted
that the embodiments described herein are only meant to explain the
present disclosure, and not to limit the scope of the present
disclosure. Furthermore, the technical features related to the
embodiments of the disclosure described below can be mutually
combined if they are not found to be mutually exclusive.
[0039] In the present disclosure, a laser is used as a main heat
source to deposit an alloy material on a surface of a rail, and an
auxiliary heat source preheats or/and post-heats the rail to reduce
the cooling rate of the cladded coating and the heat-affected zone,
so that a functional coating with wear resistance, fatigue
resistance and corrosion resistance can be efficiently prepared on
the rail surface, or the damaged rail can be repaired. The
thickness of the cladded coating obtained in a single processing is
0.1-2 mm, and the hardness can be adjusted in a range of HV250 to
HV500 according to the specific requirements of the rail.
Meanwhile, by adopting the technical route proposed by the present
disclosure, martensite is not generated in the heat-affected zone
of the rail, and the mechanical properties of the cladded coating
and the rail substrate are reasonably matched, so that the rail has
better bending fatigue and contact fatigue performance while being
reinforced and repaired. The present disclosure will be further
described below with reference to the accompanying drawings and
embodiments.
[0040] The present disclosure provides a method for reinforcing a
rail by using laser and auxiliary heat source hybrid cladding, in
which the auxiliary heat source may adopt induction heating,
oxyacetylene flame, propane torch or a combination of induction
heating and oxyacetylene flame (or propane torch). The present
method can be integrated with fixed laser processing equipment to
perform off-line processing on a rail, or integrated with a
vehicle-mounted laser processing platform to perform on-line
reinforcement or repair on a rail at the railway site. The
implementation steps include the following.
[0041] (1) Polish a region to be cladded of a rail surface to
remove surface rust and contaminants.
[0042] (2) Adjust the defocusing distance of a laser beam to allow
a laser spot to be circular with a diameter of 3-20 mm or
rectangular with a size of (1-3) mm.times.(6-30) mm.
[0043] (3) Adjust the relative position of the laser spot and the
auxiliary heat source so that the laser spot is in front of, in the
middle of or behind the auxiliary heat source.
[0044] (4) Turn on the laser and auxiliary heat source, and
synchronously feed (or place in advance) the alloy powder material
into the laser irradiation region of the rail surface by using an
automatic powder feeder, so that a molten pool is formed when the
focused laser beam irradiates on the rail substrate, and then a
metal coating is formed on the rail surface after the molten pool
is solidified; the auxiliary heat source acts on the rail for
preheating and/or post-heating, with a preheating temperature of
100-1000.degree. C. and a post-heating temperature of
300-700.degree. C.
[0045] (5) After a layer of metal cladded coating is formed,
determine whether the thickness of the cladded coating meets
working conditions, and if so, end the cladding process; if not,
repeat the above steps (2), (3) and (4) until the thickness
requirements are met.
[0046] (6) After the cladding process is finished, inspect the
surface of the corrosion-resistant cladded coating by penetration
or ultrasonic inspection, to ensure that there are no metallurgical
defects in the cladded coating.
[0047] (7) According to application requirements, selectively
perform cleaning and profile trimming on the rail tread to make the
surface flat, thereby obtaining a finished product.
[0048] Embodiment 1: on-line laser and induction post-heating
efficient hybrid cladding at the railway site
[0049] In this embodiment, the service rail is efficiently
reinforced or repaired at the railway site, in which induction
heating acts as an auxiliary heat source, and an industrial
manipulator or a three-dimensional motion axis is used as a
machining motion and position control unit. A region to be cladded
of a rail surface is heated with the heating temperature and time
controlled by an induction heating device and a temperature control
part. The induction heating device includes an induction power
supply and an induction coil, and the temperature control part
includes an infrared thermometer and a temperature controller, in
which the induction coil is connected to the induction power
supply, the infrared thermometer is connected to the temperature
controller, and the temperature controller is connected to the
induction power supply via a data line. A detection signal of the
infrared thermometer is input to the temperature controller, and
after calculation, the temperature controller outputs a control
signal to adjust the output power of the induction heating power
supply to achieve the control of the induction heating temperature
of the rail. The laser spot is focused on the front of the
induction coil, as shown in FIG. 1. Basic implementation steps for
preparing a metal cladded coating on a rail surface by laser and
induction post-heating hybrid cladding are as follows.
[0050] (1) Select iron-based alloy powder as cladding material, the
main chemical compositions (Wt. %) of which are: (0.01-0.60) C,
(10-40) Cr, (5-18) Ni, (0.1-3.0) Si, (0-3) B, (0-3) Mo, (1-3) Mn
and Fe balance.
[0051] (2) Polish a region to be cladded of a rail surface to
remove surface rust and contaminants.
[0052] (3) Adjust the position of the induction coil such that its
lower surface is parallel to the region to be cladded of the rail
surface with a gap of 5 mm; the infrared thermometer is targeted at
the induction heating region of the rail surface, the infrared
thermometer is connected to the temperature controller and the
induction power supply to detect and control the induction heating
temperature; the induction heating temperature is set to
700.degree. C.
[0053] (4) Adjust the defocusing distance of a laser beam and the
relative position of the laser spot and the induction coil such
that the laser spot is focused on a rail surface in front of the
induction coil; the laser spot is a circular spot with a diameter
of 3 mm, the powder feed rate of a powder feeder is 10 g/min, the
laser power is 1 kW, and the laser scanning speed is 0.4 m/min.
[0054] (5) Turn on a motion control unit, the laser and the
induction heating power supply, and synchronously feed (or
pre-place) the cladding material into the laser irradiation region
of the rail surface by using an automatic powder feeder, so that a
molten pool is formed when the focused laser beam is incident on
the rail substrate, and then a metal cladded coating is formed on
the rail surface after the molten pool is solidified.
[0055] (6) After a layer of cladded coating is formed, determine
whether the thickness of the cladded coating meets working
conditions, and if so, end the cladding process; if not, repeat the
above steps (2), (3), (4) and (5) until the thickness requirements
are met.
[0056] (7) After the cladding process is finished, inspect the
surface of the metal coating by penetration or ultrasonic
inspection, to ensure that there are no metallurgical defects in
the cladded coating.
[0057] (8) According to application requirements, selectively
perform cleaning and profile trimming on the rail tread to make the
surface flat, thereby obtaining a finished product.
[0058] In this embodiment, the thickness of the prepared iron-based
metal cladded coating is 0.1 mm, the mechanical properties between
the cladded coating, the heat-affected zone and the rail substrate
are reasonably matched, and the hardness distribution along the
rail depth direction is as shown in FIG. 5.
[0059] Embodiment 2: on-line laser, induction preheating and
induction post-heating efficient hybrid cladding at the railway
site
[0060] In this embodiment, the service rail is efficiently
reinforced or repaired at the railway site, in which induction
heating acts as an auxiliary heat source, the induction heating
control part is the same as that in Embodiment 1, and an industrial
manipulator or a three-dimensional motion axis is used as a
machining motion and position control unit. The laser spot is
focused in the middle of the induction coil, as shown in FIG. 2.
Basic implementation steps for preparing a metal cladded coating on
a rail surface by laser, induction preheating and induction
post-heating hybrid cladding are as follows.
[0061] (1) Select nickel-based alloy powder as cladding material,
the main chemical compositions (Wt. %) of which are: (0.01-0.50) C,
(20-30) Cr, (5-10) W, (3-5) Si, (0-3) B, (5-10) Fe and Ni
balance.
[0062] (2) Polish a region to be cladded of a rail surface to
remove surface rust and contaminants.
[0063] (3) Adjust the position of the induction coil such that the
lower surface is parallel to the region to be cladded of the rail
surface with a gap of 0.5 mm; the infrared thermometer is targeted
at the induction heating region of the rail surface, and the
infrared thermometer is connected to the temperature controller and
the induction power supply to detect and control the induction
heating temperature; the induction heating temperature is set to
500.degree. C.
[0064] (4) Adjust the defocusing distance of a laser beam and the
relative position of the laser spot and the induction coil such
that the laser spot is focused on a rail surface in front of the
induction coil; the laser spot is a rectangular spot with a size of
1.times.6 mm, the powder feed rate of a powder feeder is 50 g/min,
the laser power is 5 kW, and the laser scanning speed is 2
m/min.
[0065] (5) Turn on a motion control unit, the laser and the
induction heating power supply, and synchronously feed (or
pre-place) the cladding material into the laser irradiation region
of the rail surface by using an automatic powder feeder, so that a
molten pool is formed when the focused laser beam is incident on
the rail substrate, and then a metal cladded coating is formed on
the rail surface after the molten pool is solidified.
[0066] (6) After a layer of cladded coating is formed, determine
whether the thickness of the cladded coating meets working
conditions, and if so, end the cladding process; if not, repeat the
above steps (2), (3), (4) and (5) until the thickness requirements
are met.
[0067] (7) After the cladding process is finished, inspect the
surface of the metal coating by penetration or ultrasonic
inspection, to ensure that there are no metallurgical defects in
the cladded coating.
[0068] (8) According to application requirements, selectively
perform cleaning and profile trimming on the rail tread to make the
surface flat, thereby obtaining a finished product.
[0069] In this embodiment, the induction coil consists of two
parts: 4(a) and 4(b) connected by a copper tube, in which 4(a)
plays a role of preheating the rail, and 4(b) plays a role of
delaying the cooling rate of the rail. In practical applications,
under the premise of reasonable matching of mechanical properties,
the cladding efficiency can be effectively improved, which is
conducive to energy conservation. The thickness of the prepared
nickel-based metal cladded coating is 0.5 mm, the mechanical
properties between the cladded coating, the heat-affected zone and
the rail substrate are reasonably matched, and the hardness
distribution along the rail depth direction is as shown in FIG.
6.
[0070] Embodiment 3: off-line laser, induction heating and
oxyacetylene flame (or propane torch) heating efficient hybrid
cladding on a rail surface
[0071] In this embodiment, off-line reinforcement or repair is
performed on the rail, in which induction heating and oxyacetylene
flame (or propane torch) act as the auxiliary heat source. The
laser spot is focused in front of the induction coil, and the
oxyacetylene flame (or propane torch) preheats a rail surface to be
cladded, as shown in FIG. 3. The laser and the induction coil move
in the same direction at the same speed, and the induction heating
synchronously preheats the laser molten pool and the heat-affected
zone of the rail. The basic implementation steps are as
follows:
[0072] (1) Select cobalt-based alloy powder as cladding material,
the main chemical compositions (Wt. %) of which are: (0.01-0.5) C,
(20-35) Cr, (1-10) Ni, (1-3) Si, (5-15) W, (0-3) B, (0.5-2) Mn and
Co balance.
[0073] (2) Polish a region to be cladded of a rail surface to
remove surface rust and contaminants.
[0074] (3) Adjust the position of the induction coil such that the
lower surface is parallel to the region to be cladded of the rail
surface with a gap of 15 mm; the infrared thermometer is targeted
at the induction heating region of the rail surface, and the
infrared thermometer is connected to the temperature controller and
the induction power supply to detect and control the induction
heating temperature; the induction heating temperature is set to
300.degree. C.
[0075] (4) Adjust the defocusing distance of a laser beam and the
relative position of the laser spot and the induction coil so that
the laser spot is focused on a rail surface in front of the
induction coil; the laser spot is a rectangular spot with a size of
3.times.30 mm, the powder feed rate of a powder feeder is 250
g/min, the laser power is 20 kW, and the laser scanning speed is 30
m/min.
[0076] (5) Preheat the region to be cladded of the rail surface
with oxyacetylene flame/propane torch, in which the infrared
thermometer 6-2 is aimed at the heated region of the rail surface
to monitor the preheating temperature, and when the preheating
temperature reaches 100-200.degree. C., the oxyacetylene
flame/propane torch device is closed.
[0077] (6) Turn on the laser and the induction heating power
supply, and synchronously feed (or pre-place) the cladding material
into the laser irradiation region of the rail surface by using an
automatic powder feeder, so that a molten pool is formed when the
focused laser beam is incident on the rail substrate, and then a
metal cladded coating is formed on the rail surface after the
molten pool is solidified.
[0078] (7) After a layer of cladded coating is formed, determine
whether the thickness of the cladded coating meets working
conditions, and if so, end the cladding process; if not, repeat the
above steps (2), (3), (4), (5) and (6) until the thickness
requirements are met.
[0079] (8) After the cladding process is finished, inspect the
surface of the metal coating by penetration or ultrasonic
inspection, to ensure that there are no metallurgical defects in
the cladded coating.
[0080] (9) According to application requirements, selectively
perform cleaning and profile trimming on the rail tread to make the
surface flat, thereby obtaining a finished product.
[0081] In this embodiment, the thickness of the prepared
cobalt-based metal cladded coating is 0.2 mm, the mechanical
properties between the cladded coating, the heat-affected zone and
the rail substrate are reasonably matched, and the hardness
distribution along the rail depth direction is as shown in FIG.
7.
[0082] Embodiment 4: off-line laser and oxyacetylene flame (or
propane torch) heating efficient hybrid cladding on a rail
surface
[0083] In this embodiment, off-line reinforcement and repair is
performed on the rail, in which oxyacetylene flame (or propane
torch) is selected as an auxiliary heat source. As shown in FIG. 4,
basic implementation steps for preparing a metal cladded coating on
a rail surface by laser and oxyacetylene flame (or laser and
propane torch) hybrid cladding are as follows.
[0084] (1) Select iron-based alloy powder as cladding material, the
main chemical compositions (Wt. %) of which are: (0.01-0.60) C,
(10-40) Cr, (5-18) Ni, (0.1-3.0) Si, (0-3) B, (0-3) Mo, (1-3) Mn
and Fe balance.
[0085] (2) Polish a region to be cladded of a rail surface to
remove surface rust and contaminants.
[0086] (3) adjust parameters such that the laser beam is circular
with a diameter of 20 mm, the laser power is 15 kW, the powder feed
rate of a powder feeder is 180 g/min, and the laser scanning speed
is 10 m/min.
[0087] (4) Preheat the region to be cladded of the rail surface
with oxyacetylene flame/propane torch, in which the infrared
thermometer is aimed at the heated region of the rail surface and
monitors the preheating temperature of the rail surface to be
800-1000.degree. C.
[0088] (5) Turn on the laser, and synchronously feed (or pre-place)
the alloy powder material into the laser irradiation region of the
rail surface by using an automatic powder feeder, so that a molten
pool is formed when the focused laser beam is incident on the rail
substrate, and then a metal cladded coating is formed on the rail
surface after the molten pool is solidified; meanwhile, perform
post-heating on the cladded region of the rail surface with the
oxyacetylene flame/propane torch at a post-heating temperature of
300-400.degree. C. (monitored by the infrared thermometer), and
turn off the oxyacetylene flame/propane torch after a certain
holding time.
[0089] (6) After a layer of cladded coating is formed, determine
whether the thickness of the cladded coating meets working
conditions, and if so, end the cladding process; if not, repeat the
above steps (3), (4) and (5) until the thickness requirements are
met.
[0090] (7) After the cladding process is finished, inspect the
surface of the metal coating by penetration or ultrasonic
inspection, to ensure that there are no metallurgical defects in
the cladded coating.
[0091] (8) According to application requirements, selectively
perform cleaning and profile trimming on the rail tread to make the
surface flat, thereby obtaining a finished product.
[0092] In this embodiment, the thickness of the prepared iron-based
metal cladded coating is 2 mm, the mechanical properties between
the cladded coating, the heat-affected zone and the rail substrate
are reasonably matched, and the hardness distribution along the
rail depth direction is as shown in FIG. 8.
[0093] It should be readily understood to those skilled in the art
that the above description is only preferred embodiments of the
present disclosure, and does not limit the scope of the present
disclosure. Any change, equivalent substitution and modification
made without departing from the spirit and scope of the present
disclosure should be included within the scope of the protection of
the present disclosure.
* * * * *