Laser cladding method based on pulse powder feeding and laser cladding head

Abstract

The present invention discloses a laser cladding method based on pulse powder feeding, comprising: step 1, clamping a workpiece to be processed and pre-processing it; step 2, adjusting the frequency and quantity of powder feeding according to the material properties of the workpiece to be processed; step 3, feeding powder using the powder feeding frequency and quantity determined in step 2, and laser cladding the workpiece to be processed; step 4, checking whether the morphology of the workpiece after cladding meets the standard, if it meets the requirements, the processing is ended, if it does not meet the requirements, return to step 2, and readjust the frequency and quantity of powder feeding; a laser cladding head is also disclosed. The beneficial effect of the present invention is that applying periodic impact force to the molten pool can effectively optimize laser cladding and achieve the effect of ultrasonic refinement.

Description

Technical Field

[0001] The invention relates to the field of composite field laser cladding, and in particular to a laser cladding method based on pulse powder feeding and a laser cladding head. Background Art

[0002] In the field of composite field laser cladding, other fields are added to make laser cladding more efficient.

[0003] The high-frequency and low-amplitude vibration of ultrasonic vibration can affect the solidification microstructure of the cladding layer, effectively reduce microscopic defects, refine the organizational structure of the cladding layer, promote crystallization and solidification nucleation, and change the preferred orientation of dendrites. The vibration does not affect the growth rate of the main dendrite arm, but has a significant effect on the width of the main dendrite arm, the formation, growth rate and competitive growth of the secondary dendrite arm. The larger the ultrasonic amplitude, the more luxuriant the dendrite arm, and the more obvious the competitive growth, which can indirectly reduce the pores and cracks of the cladding layer. The optimization effect is best when the ultrasonic amplitude is 6-8μm.

[0004] There are two common methods of ultrasonic field composite laser cladding, namely wire-guided ultrasound or adding an ultrasonic field to the entire workpiece. The former wire feeding is worse in accuracy and stability than powder feeding, and the powder feeding method can process the surface of parts more freely than the wire feeding method; for the latter, the workpiece is relatively large, and to achieve sufficient amplitude, very high power is required. In fact, only the molten pool part requires ultrasonic vibration. Changing to the pulse powder method directly applies vibration to the molten pool part, reducing energy consumption and avoiding the influence of long-term ultrasonic vibration on the workpiece. Secondly, in the ultrasonic composite field, there is not only the ultrasonic field. For other fields generated by the external ultrasonic field, their influence on laser cladding is unknown, and the laser cladding effect is not stable under this state.

[0005] Therefore, the prior art needs to develop a method for laser cladding without applying other fields, and needs to use laser cladding equipment to optimize the laser cladding based on pulsed powder feeding. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a laser cladding method and a laser cladding head based on pulsed powder feeding. The method and the device can effectively optimize the laser cladding and achieve the effect of ultrasonic refinement by applying periodic impact force to the molten pool through pulsed powder feeding. At the same time, the laser cladding will not become unstable due to the external field, which provides a new idea for the subsequent optimization of laser cladding.

[0007] The laser cladding method based on pulsed powder feeding of the present invention is characterized by comprising the following steps:

[0008] Step 1: Clamp the workpiece to be processed and perform pretreatment;

[0009] Step 2: Adjust the frequency and quantity of powder feeding according to the material properties of the workpiece being processed:

[0010] Adjust the powder feeding frequency, powder feeding amount and powder carrier gas flow rate according to the additional vibration required. The powder feeding frequency needs to be coupled with the natural frequency of the molten pool vibration, and the powder feeding amount and powder carrier gas flow rate are controlled according to the actual situation;

[0011] Step 3, feeding powder using the powder feeding frequency and quantity determined in step 2, and performing laser cladding on the workpiece being processed;

[0012] Step 4: Check whether the morphology of the workpiece after cladding meets the standard (such as using manual measurement or 3D scanning to check whether the amount of added material meets the requirements). If it meets the requirements, the processing is completed. If it does not meet the requirements, return to step 2 and readjust the frequency and amount of powder feeding.

[0013] Furthermore, pretreatment refers to the use of CNC milling or wire cutting methods to process the damaged parts of the workpiece to be processed, while removing the internal damaged area and cleaning it after cutting.

[0014] The laser cladding head described in the present invention is characterized by comprising a nozzle body, an optical fiber device and a powder oscillator;

[0015] The nozzle body is provided with a laser passage, a powder feeding passage and an oscillation passage, wherein the laser passage is opened in the center of the nozzle body, and the powder feeding passage is opened around the central channel, and the laser passage and the powder feeding passage both penetrate the nozzle body from top to bottom; the oscillation passage is arranged on the side of the powder feeding passage, one end of which is connected with the powder feeding passage, and the other end of which is connected with the outer wall of the nozzle body;

[0016] The optical fiber device is arranged on the top of the nozzle body, and a laser channel coaxial with the laser path is arranged in the center of the optical fiber device, the upper end of the laser channel is connected with the top of the optical fiber device to form an optical fiber entrance, and the lower end is connected with the laser path;

[0017] The powder oscillator comprises a cylinder, a piston, an air intake pump and an air outlet pump, wherein the cylinder is installed in an oscillation passage; the end of the piston is sealed and slidably inserted into the cylinder, the front end of the piston is movably inserted into the powder delivery passage, and is axially retracted and extended along the oscillation passage; the air intake pump and the air outlet pump are respectively connected to the air inlet and the air outlet of the cylinder through gas pipelines.

[0018] Furthermore, a rubber mold is provided at the connection between the oscillation passage and the powder feeding passage.

[0019] A cladding device described in the present invention is characterized by comprising the pulse powder feeding laser cladding head described in the present invention.

[0020] The beneficial effects of the present invention are as follows: the present invention utilizes the principle of ultrasonic field assisted laser cladding, designs a powder oscillator, and replaces the ultrasonic field by adjusting the powder feeding frequency and powder feeding amount to achieve a similar effect of grain refinement and optimization of laser cladding, thereby improving the quality of laser cladding and optimizing the laser cladding products. In addition, uncontrollable factors are reduced, and the cost is reduced compared to ultrasonic field assisted laser cladding, while having higher cladding accuracy and more flexible cladding methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of the laser cladding method of the present invention.

[0022] Figure 2 It is a structural diagram of the pulse powder feeding laser cladding head of the present invention.

[0023] Figure 3 yes Figure 2 A partial enlarged view of .

[0024] Explanation of the reference numerals: 1. Nozzle body; 2. Optical fiber device; 3. Powder oscillator; 11. Laser passage; 12. Powder delivery passage; 13. Oscillation passage; 31. Cylinder; 32. Piston; 33. Air intake pump; 34. Air outlet pump. DETAILED DESCRIPTION

[0025] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0026] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0027] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0029] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0031] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0032] The present invention will be described in detail below in conjunction with exemplary embodiments with reference to the accompanying drawings.

[0033] The laser cladding method based on pulsed powder feeding of the present invention comprises the following steps:

[0034] Step 1: Clamp the workpiece to be processed and pre-process it:

[0035] When clamping the workpiece to be processed, it is necessary to ensure that both ends of the workpiece to be processed are in a clamped state, otherwise it will warp after processing. Pretreatment refers to the use of CNC milling or wire cutting methods to process the damaged parts of the workpiece to be processed, while removing the internal damaged areas and cleaning them after cutting;

[0036] Step 2: Adjust the powder feeding frequency, powder feeding amount and powder-carrying gas flow rate according to the additional vibration required:

[0037] Adjust the powder feeding frequency, powder feeding amount and powder carrier gas flow rate according to the additional vibration required. The powder feeding frequency needs to be coupled with the natural frequency of the molten pool vibration, and the powder feeding amount and powder carrier gas flow rate will affect the amplitude. The larger the amplitude, the better the dendrite crushing effect, and the greater the liquid level fluctuation caused. It is necessary to control it as appropriate according to the actual situation, so that the conveyed powder and the molten pool generated by the cladding of the workpiece to form vibration, so as to replace the ultrasonic field assisted laser cladding processing;

[0038] Step 3: Use the powder feeding frequency and quantity determined in step 2 to feed powder using the cladding equipment, and perform laser cladding on the workpiece to be processed:

[0039] Powder feeding laser cladding is carried out, and coaxial powder feeding is used for powder feeding. When feeding powder, attention should be paid to the generation of the molten pool. If the amount of melted powder in the molten pool is too little or too much, the process should be stopped immediately for inspection, and the cause should be identified before processing. The powder fed out is vibrated with the liquid in the molten pool by a special powder feeder to simulate the effect of ultrasonic field-assisted laser cladding, thereby achieving the purpose of refining grains and optimizing the laser cladding effect;

[0040] Step 4: Use manual measurement or 3D scanning to check whether the amount of additive meets the requirements. If it does, the processing is completed. If it does not, return to step 2 and readjust the frequency and amount of powder feeding:

[0041] Check whether the morphology after cladding meets the standards. If there is too much unclad powder or too little cladding, the parameters need to be readjusted before processing.

[0042] The pulsed powder feeding laser cladding head of the present invention comprises a nozzle body 1, an optical fiber device 2 and a powder oscillator 3;

[0043] The nozzle body 1 is provided with a laser passage 11, a powder feeding passage 12 and an oscillation passage 13. The laser passage 11 is opened in the center of the nozzle body 1, and the powder feeding passage 12 is opened around the central channel. The laser passage 11 and the powder feeding passage 12 both penetrate the nozzle body 1 from top to bottom. The oscillation passage 13 is arranged on the side of the powder feeding passage 12, one end of which is connected to the powder feeding passage 12, and the other end of which is connected to the outer wall of the nozzle body 1.

[0044] The optical fiber device 2 is arranged on the top of the nozzle body 1, and a laser channel coaxial with the laser passage 11 is arranged in the center of the optical fiber device 2, the upper end of the laser channel is connected with the top of the optical fiber device to form an optical fiber entrance 21, and the lower end is connected with the laser passage 11;

[0045] The powder oscillator 3 comprises a cylinder 31, a piston 32, an air intake pump 33 and an air outlet pump 34. The cylinder 31 is installed in the oscillation passage 13. The end of the piston 32 is sealed and slidably inserted in the cylinder 31. The front end of the piston 32 is movably inserted in the powder delivery passage 12 and axially extends and retracts along the oscillation passage 13. The air intake pump 33 and the air outlet pump 34 are respectively connected to the air inlet and the air outlet of the cylinder 31 through gas pipelines. The air intake pump 33 and the air outlet pump 34 control the inlet and outlet of the piston 32 by filling the cylinder 31 with gas and evacuating the gas. When the powder passes through the powder delivery passage 12, the piston 32 opens and closes with frequency, so the powder in the powder delivery passage 12 will be blocked with frequency, so that the powder finally outputted presents a specific frequency, thereby achieving the function of controlling the frequency and quantity of powder delivery.

[0046] In some embodiments of the present invention, a layer of rubber mold is provided at the connection between the oscillation passage 13 and the powder delivery passage 12 , and the rubber mold can prevent powder from overflowing from the powder delivery passage 12 .

[0047] The cladding equipment described in the present invention comprises the pulse powder feeding type laser cladding head described above.

[0048] The cladding equipment of the present invention adopts a coaxial powder feeding method to feed powder. When in use, the optical fiber inlet is connected to the laser, and the powder feeding passage 12 of the pulse powder feeding laser cladding head is connected to the powder feeding equipment. The powder is blown out from the powder feeding equipment through the powder feeding passage 12. When passing through the powder path, the powder oscillator 3 matched with the powder feeding passage 12 is used to make the axial concentration of the powder change periodically, thereby controlling the powder delivery amount and delivery frequency, and then the powder is transported into the molten pool in the form of pulses, so that the powder and the liquid in the molten pool formed by the cladding form vibration, thereby simulating the effect of ultrasonic field-assisted laser cladding, thereby achieving the purpose of refining the grains and optimizing the laser cladding effect.

[0049] In actual cladding, the laser is transmitted by optical fiber, and finally the laser is output by the laser passage 11. The powder is blown into the powder feeding passage 12 by the powder feeding device under the action of the powder carrier gas. At the end of the powder feeding passage 12, there is a powder oscillator 3 for powder intervention. The cylinder 31 is inflated and exhausted by the air inlet pump 33 and the air outlet pump 34 to control the frequency movement of the piston 32. When the piston 32 is closed, the powder can be prevented from being blown out of the powder feeding passage 12. When the piston 32 is opened, it does not affect the blowing of the powder, thereby achieving the purpose of controlling the frequency and quantity of powder delivery. The powder is transported into the molten pool to form pulses. The pulsed powder is essentially a periodic change of the powder concentration in the axial direction of the powder feeding passage 12, which is different from the common sound waves and water waves. The pulsed powder enters the molten pool at a preset frequency and vibrates the molten pool, thereby achieving better cladding deposition.

[0050] Example 1

[0051] Shaft repair requires that the shaft be restored to its original length by laser cladding.

[0052] After the laser processing system and fixture are installed, the relevant procedures for laser repair are compiled according to the specific material properties of the shaft. At the same time, the damaged area of ​​the shaft is cut off, the laser and powder feeding equipment are started, and repair is carried out.

[0053] The laser uses a 700W fiber-coupled semiconductor laser and a self-developed coaxial powder feeding device (four-beam powder feeding tube), in which the diameter of the powder-carrying gas nozzle is 1.5mm, the diameter of the protective gas nozzle is 8mm, and the diameter of the powder path is 6mm.

[0054] Laser cladding repair process parameters are as follows:

[0055] Power: 700w; spot diameter: 2mm; powder-carrying gas flow rate: 6.5L / min; powder feeding amount 2.4g / min; scanning speed 15mm / s; powder feeding speed 2m / s; powder particle size is 200 mesh ~ 300 mesh; defocus amount is +2mm; laser cladding head inclination angle is 90 degrees.

[0056] Cladding thickness: Determined according to demand, the size after repair is required to be about 1mm longer than the original base length.

[0057] like Figure 2 The powder feeding device shown in the figure feeds powder at a certain frequency. The powder is ejected from the laser cladding head through the powder oscillator 3 at the end of the powder feeding passage 12. The air outlet pump 34 and the air inlet pump 33 in the powder oscillator 3 cooperate with each other to make the piston 32 vibrate at a high frequency. The vibration of the piston 32 changes the axial powder concentration in the powder feeding passage 12 to control the powder feeding to reach the corresponding frequency and powder feeding amount, so as to form high-frequency pulse powder so as to vibrate the molten pool in the laser cladding area, thereby achieving the effect of refining the grains and optimizing the cladding effect.

[0058] After the laser cladding finished product test meets the requirements, the fixture is removed for secondary processing. The performance of the thin plate after repair is significantly improved compared with that before repair.

[0059] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A laser cladding method based on pulsed powder feeding, characterized in that: The following steps are involved: Step 1: Clamp the workpiece to be processed and perform pretreatment; Step 2: Adjust the frequency and quantity of powder feeding according to the material properties of the workpiece being processed: Adjust the powder feeding frequency, powder feeding amount and powder carrier gas flow rate according to the additional vibration required; the powder feeding frequency needs to be coupled with the natural frequency of the molten pool vibration, and the powder feeding amount and powder carrier gas flow rate are controlled according to the actual situation; Step 3, feeding powder using the powder feeding frequency and quantity determined in step 2, and performing laser cladding on the workpiece being processed; Step 4: Check whether the morphology of the workpiece after cladding meets the standard. Specifically, use manual measurement or 3D scanning to check whether the amount of added material meets the requirements. If it meets the requirements, the processing is completed. If it does not meet the requirements, return to step 2 and readjust the frequency and amount of powder feeding; The laser cladding head used comprises a nozzle body (1), an optical fiber device (2) and a powder oscillator (3); The nozzle body (1) is provided with a laser passage (11), a powder delivery passage (12) and an oscillation passage (13); the laser passage (11) is opened in the center of the nozzle body (1), and the powder delivery passage (12) is opened around the central channel; the laser passage (11) and the powder delivery passage (12) both penetrate the nozzle body (1) from top to bottom; the oscillation passage (13) is arranged on the side of the powder delivery passage (12), one end of which is connected to the powder delivery passage (12) and the other end of which is connected to the outer wall of the nozzle body (1); The optical fiber device (2) is arranged on the top of the nozzle body (1), and a laser channel coaxial with the laser passage (11) is arranged in the center of the optical fiber device (2). The upper end of the laser channel is connected to the top of the optical fiber device to form an optical fiber entrance (21), and the lower end is connected to the laser passage (11); The powder oscillator (3) comprises a cylinder (31), a piston (32), an air intake pump (33) and an air outlet pump (34); the cylinder (31) is installed in the oscillation passage (13); the end of the piston (32) is sealed and slidably inserted into the cylinder (31); the front end of the piston (32) is movably inserted into the powder delivery passage (12) and axially extends and retracts along the oscillation passage (13); the air intake pump (33) and the air outlet pump (34) are respectively connected to the air inlet and the air outlet of the cylinder (31) through gas pipelines; a rubber mold (14) is provided at the connection between the oscillation passage (13) and the powder delivery passage (12).

2. The laser cladding method based on pulsed powder feeding according to claim 1, characterized in that: Pretreatment refers to the use of CNC milling or wire cutting methods to process the damaged parts of the workpiece to be processed, while removing the internal damaged area and cleaning it after cutting.

Images