CN114086173B - Additive repairing method for axle - Google Patents
Additive repairing method for axle Download PDFInfo
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- CN114086173B CN114086173B CN202111302191.3A CN202111302191A CN114086173B CN 114086173 B CN114086173 B CN 114086173B CN 202111302191 A CN202111302191 A CN 202111302191A CN 114086173 B CN114086173 B CN 114086173B
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Classifications
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C24/00—Coating starting from inorganic powder
- C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
- C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
- C23C24/103—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/20—Direct sintering or melting
- B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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- Manufacturing & Machinery (AREA)
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- Mechanical Engineering (AREA)
- Metallurgy (AREA)
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- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Heat Treatment Of Articles (AREA)
- Laser Beam Processing (AREA)
Abstract
The invention relates to the technical field of axle repairing, in particular to a laser material-increasing repairing method for a rail transit train axle. The laser material-increasing repairing method for the train axle provided by the invention adopts a multi-channel multi-layer space stacking process to realize remanufacturing and forming of the damaged part. The invention obtains the repairing layer structure with refined grains by utilizing the high cooling rate of the laser material-increasing process and the repeated thermal circulation in the multi-layer space stacking process, thereby realizing the smooth transition of the structure and the performance of the combination area between the matrix and the repairing layer, eliminating the internal structural defect of the cladding layer to a certain extent, and being more beneficial to improving the fatigue performance of the repairing axle.
Description
Technical Field
The invention relates to the technical field of axle repairing, in particular to a laser material-increasing repairing method for a rail transit train axle.
Background
A large number of train axles are scrapped each year due to different degrees of damage and failure, and great economic loss is caused. Because the axle use amount is large, the replacement is frequent, the method has great remanufacturing potential, and if the damaged axle can be remanufactured and repaired by using a proper repair technology, the safe operation of a train can be effectively ensured, the production cost can be reduced, the economic benefit is improved, and a large amount of resources are saved.
However, axles are subjected to the combined action of various stresses during operation, and such complex superimposed stresses are extremely liable to cause the initiation and propagation of fatigue cracks in the repair layer, which directly jeopardize the transportation safety, and derailment caused by breakage of the axle, with the consequences of disastrous. Therefore, the repairing technology of the axle has higher requirements, and besides the excellent static mechanical property, the repairing layer of the axle also needs to have higher fatigue resistance.
The repairing layer prepared by the traditional axle repairing technology often has the problems of great thermal damage to the matrix, uneven tissue structure and unsmooth performance transition of the bonding area of the matrix and the repairing layer, poor fatigue performance caused by low plastic toughness and high content of pores and inclusion defects of the repairing layer, and the like, so that the service life of the repaired axle is shortened, and huge potential safety hazards exist.
Disclosure of Invention
The invention provides a novel laser material-increasing repairing method for a train axle, which adopts a multi-channel multi-layer space stacking process to realize the remanufacturing and forming of a damaged part;
the laser cladding path of the multi-channel multilayer space stacking process comprises transverse translation and vertical lifting:
the transverse translation adopts a spiral stepping mode; the axle always rotates at a constant rotation speed, the cladding head only moves in a translational way along the axial direction, the cladding tracks are distributed on the axle surface in a spiral line mode, the lap joint rate between cladding layer tracks is not completely constant, and the cladding layer tracks continuously and repeatedly change in a small range and are dynamic;
after one layer of cladding layer is completed, the cladding head is lifted in the radial direction, the movement is continuously repeated, and the cladding of the subsequent cladding layer is completed until the forming of a multi-lap multi-layer space stack is completed.
The invention obtains the repairing layer structure with refined grains by utilizing the high cooling rate of the laser material-increasing process and the repeated thermal circulation in the multi-layer space stacking process, thereby realizing the smooth transition of the structure and the performance of the combination area between the matrix and the repairing layer, eliminating the internal structural defect of the cladding layer to a certain extent, and being more beneficial to improving the fatigue performance of the repairing axle.
In the prior art, a cladding layer is formed by adopting an axial and radial alternate deposition mode, but the cladding layer is mainly formed by alternately carrying out axial and radial between every two layers; the working principle of the deposition mode is as follows: one way is that the cladding head moves along the axial direction during cladding, the axle is not moved, after cladding, the axle rotates a fixed angle, and cladding is repeatedly moved along the axial direction, so that a cladding layer is formed, namely, axial multi-channel deposition is realized; the other mode is that the cladding head is kept motionless during cladding, the shaft rotates for one circle, after the cladding is completed for one circle, the cladding head translates for a certain distance along the axial direction, and cladding is repeated to form a cladding layer, namely radial multilayer deposition; the two modes are alternated, usually to ensure high bond strength and low heat distortion control.
Unlike the deposition mode, the multi-layer and multi-layer space stacking process is a continuous forming process, the axle always rotates at a constant rotation speed, the cladding head only moves in a translation mode along the axial direction, the cladding tracks are distributed on the axial surface in a spiral line mode, and the forming paths of all layers are identical. After one layer of cladding layer is completed, the cladding head is lifted along the radial direction, and the movement is continuously repeated to complete cladding of the next layer. The overlap ratio between cladding layer tracks is not completely constant, but continuously and repeatedly changed within a small range and is dynamic; the inter-channel overlap ratio of the multi-channel stacking is not less than 50%; the number of stacking layers of the multi-layer stack is not less than 2.
Preferably, the cladding head advances by half the spot size for every 1 revolution of the axle; and each time a cladding layer is formed, the cladding head is lifted by 1mm. The cladding path is reasonably controlled, which is beneficial to grain refinement of the repair layer and eliminates the defects of the internal structure of the repair layer.
In the cladding process, internal structural defects such as voids, inclusions such as oxides, and inter-layer interfaces between internal channels of the cladding layer are often generated in the formed cladding layer due to a small amount of carry-in of the powder used for cladding, improper control of the cladding process, and the like. These structural defects in the cladding layer can lead to poor fatigue performance of the repair layer, and if no measures are taken to eliminate, the fatigue performance of the formed part is reduced. Therefore, the invention provides further optimized control for the multi-channel multi-layer space stacking process, and the method comprises the following steps:
the multi-channel multilayer space stacking process is to carry out gradient cladding on the surface of the axle to be repaired by adopting iron-based alloy powders with different carbon contents. The method comprises the following steps:
for the 1 st cladding layer, the carbon content of the iron-based alloy material is 0.06-0.07%;
for the 2 nd cladding layer, the carbon content of the iron-based alloy material is 0.08-0.09%;
for the 3 rd cladding layer and above, the carbon content of the iron-based alloy material used was 0.1%.
The invention thoroughly solves the problems of great thermal damage to the matrix and abrupt change of the tissue performance of the interface transition region inherent in the conventional axle laser cladding repair technology by a gradient cladding mode. Although the prior art also proposes to improve the hardness of the gradient cladding layer by regulating and controlling the carbon and boron element contents, when the carbon content of each layer of powder is specifically regulated and controlled, reasonable optimization design is required to be combined with the characteristics of an axle base material and an iron-based alloy material and the specific implementation of a multi-channel multi-layer space stacking process, so that the hardness increasing effect of the repairing layer caused by the dilution of the base body on the repairing layer is fully absorbed, the problems of component segregation and uneven structure of the cladding layer are solved, and the structure with excellent mechanical property is obtained; meanwhile, the method is also beneficial to reducing the content of inclusions and pores in the cladding layer, weakening the bonding surface of the matrix and the cladding layer and the inter-channel and inter-layer interface in the cladding layer, and improving the fatigue performance of the repaired axle.
In addition, the invention further optimizes the technological conditions of gradient cladding.
Preferably, the laser beam of the laser cladding is non-Gaussian distribution laser, the light spots are uniformly distributed round or rectangular light spots, and the light spot energy is uniformly distributed so as to reduce the dilution influence of the matrix on the repair layer.
Preferably, the laser power is 1600-1800W, the scanning speed is 6-8 mm/s, and the powder feeding speed is 8-15 g/min.
Preferably, the cladding head is a special structure cladding head with good atmosphere protection for the molten pool: the cladding head adopts an annular coaxial powder feeding nozzle, the composition structure of the nozzle is a multilayer concentric cone design, and a laser beam channel, a powder channel, a cooling loop and a protective gas channel are structurally arranged. The central part of the nozzle is in a taper hole shape and is used as a laser beam channel, a powder cavity is arranged outside the laser beam channel, powder enters the powder cavity under the action of carrier gas and gradually is converged and sprayed out towards the front end of the nozzle, and the converging point of the powder is overlapped with the focus of the laser beam. The distance between the outlet of the nozzle and the working surface is designed to be 15-20 mm, and the cladding head with the structure can form good atmosphere protection for the molten pool part. Because the cladding powder low alloy steel material has the characteristic of easy oxidation, the cladding head with the special structure can be matched with the laser beam to realize the application of the low alloy steel material in the aspect of axle repair.
The process path, the light spot shape and the size are optimized and adjusted, so that a repairing layer tissue structure with refined grains is more facilitated to be obtained, the content of inclusions and pores in a cladding layer is reduced, the bonding surface of a matrix and the cladding layer and the inter-channel and inter-layer interface in the cladding layer are desalted, the defects of the internal structure are eliminated, and the fatigue performance of the repairing axle is improved.
The repairing method further comprises the step of carrying out interlayer laser cleaning on the surface of each formed cladding layer to remove adhesion particles and oxide scales, so that a smooth and flat pollution-free surface is obtained, the content of oxides and inclusions in the repairing layer is reduced, and the fatigue performance of the repaired axle is improved.
The repairing method also comprises the step of carrying out local heat treatment on the formed axle, reducing the content of inclusions and pores in the cladding layer by means of measures, desalting the bonding surface between the matrix and the cladding layer and the interface between the inner channels and the interlayer of the cladding layer, and improving the fatigue performance of the repaired axle.
The local heat treatment is to heat by adopting a way of winding a resistance wire ceramic sheet around asbestos cloth, the stress relief annealing temperature is not higher than the axle tempering temperature, the temperature is controlled to be 450-600 ℃, the preferable annealing temperature is 500-550 ℃, the heat preservation time is 1-2 hours, and then the heat preservation is slowly cooled in the air.
As one of the specific embodiments of the present invention, the laser additive repairing method includes:
s1, preprocessing a damaged part of an axle to be repaired; the pretreatment method comprises turning and laser cleaning;
s2, carrying out nondestructive testing on the pretreated damaged part to detect whether the part to be repaired has cracks or not;
s3, utilizing light spots with uniformly distributed beam energy, and adopting a multi-channel multi-layer space stacking process to realize remanufacturing and forming of a damaged part; the multi-channel multilayer space stacking process comprises the steps of carrying out gradient cladding on the surface of an axle to be repaired by adopting iron-based alloy powders with different carbon contents;
carrying out interlayer laser cleaning on the surface of each formed cladding layer;
s4, carrying out local heat treatment on the formed axle;
s5, performing material reduction treatment on the repaired part, and recovering the size of the damaged part;
s6, performing secondary nondestructive testing on the repaired axle; the secondary nondestructive inspection comprises magnetic powder inspection and ultrasonic inspection, wherein the magnetic powder inspection is used for detecting open cracks of surfaces, and the ultrasonic inspection comprises the detection of pores, inclusions and closed cracks.
The beneficial effects of the invention are as follows:
the invention uses the laser beam with high concentrated energy as a heat source, adopts a stacking mode of synchronous powder feeding and layer-by-layer stacking by layer to realize the size recovery of the damaged part of the axle, and combines with a material reduction technology to realize the repair of the axle. The method has high automation degree, the molten pool is quickly solidified and cooled in the processing process, the heat injection to the matrix is less, the heat affected zone can keep higher strength and toughness, satisfactory forming quality and performance are obtained, and the method is more suitable for repairing the axle with higher requirements on performance recovery and matrix heat damage control.
Compared with the traditional additive repairing method, the repairing layer of the laser additive is metallurgically bonded with the axle matrix, so that the problem that the repairing layer falls off in the using process is avoided. And the rapid melting-solidification characteristic of the molten pool under the laser additive process condition ensures that the tissue structure of the repair layer is finer, and the repair layer has better and excellent comprehensive mechanical properties. Therefore, the laser additive repairing method is more suitable for repairing the axle with high requirements on mechanical properties.
Compared with the conventional laser cladding repairing method, the method for repairing the damaged part of the axle by adopting the multi-channel multi-layer space stacking technology for the first time, refines and removes textures of solidification structures by utilizing high cooling rate and repeated thermal circulation in the stacking process, so that the deposition state organization structure and mechanical property of the repairing material reach the standard of the axle body forging. In the layer-by-layer stacking additive manufacturing process, the solidification structure of each deposition layer undergoes cyclic heating and cooling processes in the subsequent layer-by-layer lapping and layer-by-layer deposition processes, namely, materials at different positions undergo a series of cyclic solid phase change processes and micro heat treatment processes, so that the repairing material obtains a refined tissue structure and excellent mechanical properties.
According to the invention, by means of gradient cladding, smooth transition of the tissue structure and performance from the matrix to the repair layer is realized, and potential safety hazards caused by weak performance of a bonding area in axle operation are eliminated. Meanwhile, the substrate can fully absorb the influence of component change caused by dilution of the cladding layer, the problems of component segregation and uneven tissue structure of the cladding layer are solved, and the tissue structure with excellent mechanical properties is obtained.
According to the invention, a laser cleaning technology is introduced for the first time in the interlayer lapping process, and compared with a repairing axle formed by continuous stacking, the method has the advantages that the contents of pores and inclusion defects in the repairing material are greatly reduced, and the fatigue performance of the repairing axle is remarkably improved.
The invention adopts the low alloy steel material as the laser cladding powder, so that the obtained repairing layer has higher hardness and good plasticity and toughness. The special structure cladding head with good atmosphere protection for the molten pool is utilized, so that the problem of laser additive forming of the easily oxidized material is solved, and the application of the easily oxidized material in the aspect of axle laser cladding repair is realized.
Drawings
Fig. 1 is a schematic flow chart of the laser additive repairing method of the present invention.
FIG. 2 is a graph showing the comparison of the transition smoothness of the hardness distribution curve of the transition region in the laser additive repair method according to example 1 of the present invention and the hardness distribution curve of the conventional non-gradient laser additive repair transition region; as can be seen from the graph, the hardness distribution curve of the transition region after the gradient cladding and the local tempering heat treatment has little overall change from the matrix, the heat affected zone, the bonding surface to the cladding layer, and the transition is smooth.
Detailed Description
The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
The invention provides a laser material-increasing repairing method of an axle, which adopts a multi-channel multi-layer space stacking process, as shown in figure 1, and comprises the following steps:
s10, preprocessing the axle to be repaired, and thoroughly removing the oxide skin and the fatigue layer of the axle repairing part and the surface greasy dirt;
s20, carrying out primary nondestructive testing on the axle subjected to pretreatment processing, wherein the nondestructive testing method can comprise ultrasonic flaw detection and coloring penetration detection so as to ensure that no crack exists at the repairing part of the axle before repairing;
s30, remanufacturing and shaping a damaged part on the surface of the part to be repaired through a gradient cladding multi-layer space stacking laser material adding process; wherein:
the 1 st layer adopts iron-based alloy powder with carbon content of 0.06-0.07%, and fully absorbs the hardness rise of the repair layer caused by dilution of the matrix to the repair layer;
the 2 nd layer adopts iron-based alloy powder with carbon content of 0.08-0.09%;
layer 3 and above adopts iron-based alloy powder with carbon content of 0.1%;
the specific cladding process is as follows: the single-layer cladding layer is formed in a way of overlapping among channels and transversely spiral stepping; after the axle at the initial position rotates for 1 circle, the laser cladding head advances by half the light spot size; the cladding head at the end position is not moved, and the axle stops light after rotating for 1 circle; lifting the thickness of 1 cladding layer by 1 laser cladding head per cladding, and controlling the thickness to be about 1mm generally, so that the focus of light and powder is always on the processing surface; repeating the steps until the size of the damaged part of the vehicle suction reaches the processing requirement, and finally, additionally cladding a layer to enable the use layer to be positioned on the secondary outer layer. After each forming of 1 repair layer, before the subsequent cladding, the front cladding layer is subjected to laser cleaning to remove adhesive particles and oxide scales, so that a smooth and flat pollution-free surface is obtained.
The light beam used for laser cladding is non-Gaussian distribution laser; the light spots are uniformly distributed round or rectangular light spots, and the energy of the light spots is uniformly distributed; the cladding head is a cladding head with a special structure and good atmosphere protection for a molten pool.
S40, carrying out local heat treatment on the formed axle, heating by adopting a resistance wire ceramic sheet winding asbestos cloth wrapping mode, setting the temperature to be between 450 and 600 ℃ for stress relief annealing, preferably between 500 and 550 ℃, keeping the temperature for 1 to 2 hours, and then slowly cooling in air.
S50, performing material reduction processing on the formed axle to reach the standard size;
s60, carrying out secondary nondestructive testing on the axle subjected to the material reduction processing, wherein the secondary nondestructive testing comprises surface hardness testing so as to ensure that the hardness meets the press-fit requirement.
The invention repairs the damaged axle by adopting a laser material-increasing forming mode of overlapping multi-layer stacking of round or rectangular light spots with non-Gaussian light beams and uniform distribution, and the repairing material is low alloy steel powder with higher strength and good plasticity. The grains of the repairing material are thinned at a high cooling rate, and the repairing material obtains a tempered tissue structure by repeated thermal circulation in the stacking process, so that the repairing axle is technically ensured to have good comprehensive mechanical properties.
Compared with the high alloy material for repairing the common axle, the low alloy steel material reduces segregation in the solidification process and avoids a coarse epitaxial dendrite structure. In addition, the low alloy steel material is in a ferrite structure after solidification, in the solidification process of a molten pool generated by laser, the repairing layer undergoes solid phase transformation from austenite to ferrite, and ferrite is randomly and nondirectionally separated out in austenite crystal, so that the epitaxial growth directionality of the solidification structure of the repairing layer caused by a temperature field in the material adding process is weakened. The epitaxial directional precipitation of the solidification structure can lead to anisotropy of internal mechanical properties, residual stress caused by thermal processing can lead to cracking of stress concentration parts, and cracks can be expanded along dendrites growing epitaxially, so that macroscopic cracks of a repair layer are caused. The crack sensitivity of the repair layer is effectively reduced by adopting the low alloy steel material, the method is particularly suitable for repairing the damaged part with large thickness and concentrated stress, and the application range of the laser additive repair technology on axle repair is expanded.
The invention adopts the laser facula with even energy distribution and the gradient material-increasing repairing method, and thoroughly solves the problems of great heat damage to the matrix and abrupt change of the tissue performance of the interface transition area inherent in the common axle laser cladding repairing technology.
The hardness of the laser cladding layer is sensitive to the content of carbon element. Although carbon can increase the strength of the repair layer, it can reduce the plasticity and toughness of the repair layer. The repairing part of the axle needs to press the wheel, the higher hardness can cause the press mounting failure, and the capability of the repairing layer for resisting fatigue cracks can be reduced under the action of complex stress load in the running process of the vehicle. Compared with the laser material for material addition, the carbon content of the axle body is generally higher, and the dilution of the body to the repair layer can lead to the increase of the carbon content of the 1 st and 2 nd repair layers on the near surface. In order to ensure that the carbon content of the repairing layer is stable, the 1 st layer is made of a low-carbon-content material, so that the influence of the matrix on the performance dilution of the additive layer can be effectively reduced, and the carbon content of the subsequent additive layer is gradually increased to ensure the smooth transition from the matrix to the performance of the additive layer. In addition, the laser spots with non-Gaussian and uniformly distributed light beams can also effectively reduce the dilution of the matrix to the repair layer, and further improve the performance smoothness of the transition region.
In step S10, in an embodiment, a method for preprocessing an axle to be repaired may include: and removing surface damage by means of laser cleaning, grinding, turning and the like. However, after machining, the damaged part is cleaned by acetone or absolute alcohol cleaning agent, so that the greasy dirt on the surface is removed, and if the laser cleaning is adopted, the damaged part can be directly repaired after cleaning. In another embodiment, the pretreatment of the axle to be repaired may further include: the laser repairing part needs to adopt inclined plane transition at the beginning and ending parts, the included angle between the transition surface and the axis is not more than 45 degrees, and if the size allows the proposal of adopting 30-degree transition.
In step S20, performing non-destructive inspection on the pretreated axle may include: penetration flaw detection, ultrasonic flaw detection and CT flaw detection.
In step S30, the laser repair material is selected in such a manner that the mechanical performance index is not lower than the performance index of the manufacturing material of the axle to be repaired, and the performance of the laser repair material should be superior to the manufacturing material of the component for the performance index causing failure.
The tensile strength of the repairing layer is larger than or equal to 650MPa under the premise of ensuring the forming performance of the laser additive; and/or the yield strength of the laser additive repairing layer is greater than or equal to 500MPa; and/or the elongation value range of the laser additive repairing layer is more than or equal to 19%; and/or the impact energy value range of the laser additive repairing layer is more than or equal to 42J; and/or the hardness of the laser additive repair layer is less than or equal to 260HV 0.3 。
In step S40, the overlap ratio is ensured to be generally not lower than 50%.
In step S50, unlike the conventional additive method, since the repairing material of the present invention is low alloy steel, the repairing material has low alloy element content, high melting point, and poor high-temperature oxidation resistance, unmelted particles adhere to the surface of the additive layer, and oxide scale is formed, and accumulation between the adhering particles and oxide scale increases inclusion defects in the subsequent additive layer, the additive layer is subjected to laser cleaning after each layer of additive.
The laser cleaning is to irradiate the laser beam with high energy density onto the surface of the cleaned repairing layer, and to make the adhesive particles and oxide scale on the surface of the repairing layer fall off through vibration, decomposition, gasification and other effects to achieve the cleaning effect. The laser cleaning is a green cleaning method, does not need to use chemical agents and cleaning liquid, and can directly carry out subsequent cladding after cleaning. The laser cleaning device adopting the scanning technology can convert the point light source into a line or a surface light source, and the cleaning efficiency is greatly higher than the cleaning speed of the traditional cleaning technology. The power of the pulse laser for cleaning can be 500-1000W, the cleaning depth can reach 200-500 mu m, the cleaning effect of removing adhesive particles and oxide skin can be achieved, the subsequent continuous cladding is needed, and the excessive damage of the laser cleaning to the formed repair layer is acceptable.
In step S60, an additional cladding is performed in order to obtain a refined tempered microstructure in the minor outer layer.
In step S70, the stress relief annealing may remove the local residual stress caused by the thermal processing, temper and soften the hardened structure of the heat affected zone of the substrate, and recombine the structure of the bonding region of the additive layer and the substrate, thereby performing the functions of stress relief and reduction of the hardness of the interface region. In one embodiment, the annealing temperature is selected to be 530 ℃.
In step S80, excess additive material is removed by a mechanical subtractive process to obtain a complete axle shape. In one implementation, the axle repair portion is machined by a lathe or grinding machine to meet the size and roughness requirements, and the surface spiral trace can be removed by ultrasonic finishing or sanding.
In step S90, the repaired axle is secondarily detected, and whether the repaired axle can meet the use requirement is detected. In one embodiment, the quality detection of the repaired axle may include: size detection, form and position tolerance detection and nondestructive detection. In another embodiment, a method of inspecting a remanufactured axle includes inspecting one or more of room temperature pull-up, fatigue, impact, and microhardness of the remanufactured axle.
Example 1
The embodiment provides a laser cladding repairing method of an axle, which comprises the following specific operations:
s10, preprocessing the axle to be repaired, removing the surface defects of the axle by adopting a turning mode, and removing oil stains on the surface of the axle to be repaired by adopting absolute ethyl alcohol.
S20, carrying out primary nondestructive testing on the axle subjected to pretreatment processing;
s30, remanufacturing and shaping a damaged part on the surface of the part to be repaired through a gradient cladding multi-layer space stacking laser material adding process; wherein:
laser process parameters: the laser power is 1600-1800W, the scanning speed is 6-8 mm/min, the diameter of a light spot is 2.8mm, the defocusing amount is 20-30 mm, the powder feeding speed is 8-15 g/min, and the powder feeding mode is synchronous;
the gradient cladding repair process comprises the following steps:
the carbon content of the iron-based alloy materials used for the 1 st layer and the 2 nd layer is 0.06C and 0.08C respectively;
layer 3 and subsequent repair layers were carbon content of 0.1C.
After each layer of material is added, the repairing layer is subjected to laser cleaning, the laser power is 200W, and the scanning width of the vibrating mirror is 50mm.
S40, carrying out local heat treatment on the formed axle, carrying out stress relief annealing on the additive layer at 530 ℃, keeping the temperature for 2 hours, and carrying out air cooling.
S50, carrying out mechanical material reduction processing on the annealed material-increasing layer, and recovering the size of the damaged axle to obtain the remanufactured axle.
S60, carrying out secondary nondestructive testing on the axle subjected to the material reduction processing.
Comparative example 1: the only difference from example 1 is that: the laser cladding is non-gradient cladding, and no interlayer laser cleaning measure is carried out on the cladding layer.
The mechanical properties of the remanufactured axles obtained in example 1 and comparative example 1 were compared as follows:
TABLE 1 mechanical Properties of the remanufactured axle
From the test results in the above table, it can be seen that:
(1) The tensile strength and the yield strength of the remanufactured axle repairing layer obtained by the repairing method disclosed by the embodiment of the invention are similar to the axle requirement, and meanwhile, the remanufactured axle repairing layer has higher elongation after break and impact power, which indicates that the remanufactured axle repairing layer has higher strength and good plasticity and toughness.
(2) The microhardness of the remanufactured axle repairing layer obtained by the repairing method is lower than the axle requirement, which shows that the gradient laser cladding mode can effectively reduce the influence of the matrix on the hardness of the repairing layer so as to ensure the smooth transition from the matrix to the performance of the additive layer.
FIG. 2 is a graph showing the transition smoothness of the hardness distribution curve of the transition region in the laser additive repair method according to example 1 of the present invention compared with the hardness distribution curve of the conventional non-gradient laser additive repair transition region according to comparative example 1.
(3) The remanufactured axle repairing layer obtained by the repairing method provided by the embodiment of the invention has a higher spin-bending fatigue life.
In summary, the mechanical properties of the remanufactured axle obtained by the axle repairing method provided by the embodiment of the invention are equivalent to those of the new factory axle, and the standard and the overall performance requirements of the new factory axle are met.
While the invention has been described in detail in the foregoing general description and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the invention and are intended to be within the scope of the invention as claimed.
Claims (6)
1. A laser material-increasing repairing method for an axle is characterized in that a multi-channel multi-layer space stacking process is adopted to realize remanufacturing and forming of a damaged part;
the laser cladding path of the multi-channel multilayer space stacking process comprises transverse translation and vertical lifting:
the transverse translation adopts a spiral stepping mode, an axle always rotates at a constant rotating speed, a cladding head axially moves in a translation mode, and cladding tracks are distributed on an axle surface in a spiral line mode;
after each cladding layer is completed, the cladding head is lifted along the radial direction of the axle, and the transverse translational movement is repeated to complete the next cladding layer;
repeating the transverse translation and the vertical lifting until forming of a multi-lap multi-layer space stack;
the multi-channel multilayer space stacking process comprises the steps of carrying out gradient cladding on the surface of an axle to be repaired by adopting iron-based alloy powders with different carbon contents;
in the gradient cladding:
for the 1 st cladding layer, the carbon content of the iron-based alloy material is 0.06-0.07%;
for the 2 nd cladding layer, the carbon content of the iron-based alloy material is 0.08-0.09%;
for the 3 rd cladding layer and above, the carbon content of the iron-based alloy material used is 0.1%;
the laser beam is non-Gaussian distribution laser, the light spots are uniformly distributed round or rectangular light spots, and the light spot energy is uniformly distributed; the laser power is 1600-1800W, the scanning speed is 6-8 mm/s, and the powder feeding speed is 8-15 g/min.
2. The method of claim 1, wherein the cladding head is advanced by half a spot size for each 1 revolution of the axle; and each time a cladding layer is formed, the cladding head is lifted by 1mm.
3. The method of claim 1, wherein the multi-channel multi-layer spatial stacking process has an inter-channel overlap ratio of not less than 50% and a stacking layer number of not less than 2.
4. The method of laser additive repair of an axle of claim 3 further comprising: and carrying out interlayer laser cleaning on the surface of each formed cladding layer.
5. The method of laser additive repair of an axle of claim 4 wherein the shaped axle is subjected to a localized heat treatment;
the local heat treatment is heating by adopting a way of winding a resistance wire ceramic sheet around asbestos cloth; the temperature is set to be the stress relief annealing temperature of 450-600 ℃ and the heat preservation time is 1-2 hours.
6. The method of laser additive repair of an axle of claim 1, comprising:
s1, preprocessing a damaged part of an axle to be repaired; the pretreatment method comprises turning and laser cleaning;
s2, carrying out nondestructive testing on the pretreated damaged part to detect whether the part to be repaired has cracks or not;
s3, utilizing light spots with uniformly distributed beam energy, and adopting a multi-channel multi-layer space stacking process to realize remanufacturing and forming of a damaged part; the multi-channel multilayer space stacking process comprises the steps of carrying out gradient cladding on the surface of an axle to be repaired by adopting iron-based alloy powders with different carbon contents;
carrying out interlayer laser cleaning on the surface of each formed cladding layer;
s4, carrying out local heat treatment on the formed axle;
s5, performing material reduction treatment on the repaired part, and recovering the size of the damaged part;
s6, performing secondary nondestructive testing on the repaired axle.
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