CN112427658A

CN112427658A - Preheating and heat-insulating device for laser additive manufacturing

Info

Publication number: CN112427658A
Application number: CN202011321339.3A
Authority: CN
Inventors: 高铭余; 王宏涛; 谢宏斌; 方攸同; 刘嘉斌
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2021-03-02
Anticipated expiration: 2040-11-23
Also published as: CN112427658B

Abstract

The utility model provides a preheat heat preservation device for laser vibration material disk, should preheat the heat preservation device and set up on laser vibration material disk's cladding workstation, should preheat the heat preservation device and have the heat preservation chamber, be provided with heating accuse temperature unit and work piece clamping unit in the heat preservation chamber, heat preservation chamber open-top is equipped with the lid in order to allow laser to act on the vibration material disk on, the opening part. The invention has the advantages that: the blank of preheating-heat preservation integrated equipment for experiments in the field of laser additive manufacturing research is filled, an equipment solution is provided for controlling the critical process of working temperature in the laser additive manufacturing technology, and a foundation is laid for promoting research progress.

Description

Preheating and heat-insulating device for laser additive manufacturing

Technical Field

The invention particularly relates to a preheating and heat-preserving device for laser additive manufacturing.

Background

Copper, as the first metal material used by human, is the second most nonferrous metal in the world, and has high electrical conductivity, high thermal conductivity, high corrosion resistance, easy processability and good mechanical properties, so that copper and copper alloys are widely used in industrial sectors of mechanical manufacture, transportation, construction, electricity, electronics and the like to manufacture various electronic materials and structural components, are key materials for the power industry, the electronic information industry, aerospace engineering, aeronautical and maritime engineering, automobile industry and military industry, and are also important basic materials for national economy and scientific and technological development. The copper has the greatest characteristics of high electrical conductivity and high thermal conductivity, but the copper has low hardness and poor wear resistance, and the application range of the copper is greatly influenced.

The laser surface strengthening technology began to emerge from the high-power laser in the 70's of the 20 th century. With the progress of modern science and the development of industrial technology, high-power laser processing equipment is gradually perfected, the research of laser surface strengthening technology is also obviously improved, and the application field of the laser surface strengthening technology is continuously expanded. The research of the laser technology in the aspect of steel materials reaches a certain level, and the laser technology is practically applied in industrial production and obtains obvious economic benefits, such as die or part repair, roller laser cladding and laser additive manufacturing. Existing studies have shown that: one of the key parameters determining the quality of laser additive manufacturing is the temperature and cooling rate of the melted region on the surface of the substrate material. In order to ensure the quality uniformity of the surface coating produced by the laser additive manufacturing, the temperature of the melting zone is required to be kept stable in the laser additive manufacturing process.

However, in the copper alloy aspect, because copper has high reflectivity and good heat conduction to laser, it is difficult to ensure the temperature stability of the melting region when laser material addition is performed on the surface of the copper alloy: in the application of high-speed laser additive on the surface of copper alloy, the problem that a molten pool is not easily formed due to high reflectivity and good thermal conductivity of copper to laser still exists.

Therefore, if the technical difficulties can be solved, the overall development of the copper alloy laser additive can be greatly promoted.

Disclosure of Invention

In order to comprehensively solve the existing problems, the invention provides a preheating and heat-insulating device for laser additive manufacturing.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for laser cladding of copper alloy powder on a copper-based surface comprises the following steps:

(1) polishing the surface of the copper-based workpiece by using a polishing tool to remove a surface oxide layer; cleaning the surface of the copper-based workpiece by using a stain remover to obtain a copper-based surface with a clean surface;

(2) fixing a copper-based workpiece on a working platform;

(3) carrying out high-speed laser cladding on a copper-based workpiece by using laser cladding powder through a high-speed laser cladding fiber laser, wherein the powder feeding mode is central powder feeding, the included angle between a cladding head and the surface of a working platform is 75-86 degrees, and a cladding layer with the single-layer thickness of 0.3-1.0mm is directly obtained;

the laser cladding powder comprises the following chemical components in percentage by weight:

c: 0.01% -0.25%, B: 0.5% -3%, Si: 1% -4%, Cr: 0-12%, Fe: 0.5% -14%, Cu: 10% -50%, Ni: 30-80 percent, the size interval of the powder particles is 25-150 mu m, and the sphericity is more than or equal to 80 percent.

In the invention, the copper matrix is common copper materials such as pure copper, chromium zirconium copper, brass, bronze, cupronickel and the like. The laser cladding powder needs to be dried before cladding, the drying temperature is 80-100 ℃, and the drying time is 1-2 h.

In the step (1), the polishing tool may be a polishing machine and sandpaper. The stain remover preferably adopts acetone or absolute ethyl alcohol.

In the step (2), the temperature of the working platform is preferably controlled at 100-400 ℃ to perform preheating and heat preservation treatment on the copper-based workpiece, aiming at the problem that a molten pool is not easy to form due to good heat conductivity of the copper-based workpiece.

Preferably, the working platform is a preheating and heat-insulating device, and the preheating and heat-insulating device comprises a heating temperature control unit, a copper-based workpiece clamping unit and a preheating and heat-insulating unit; the heating temperature control unit comprises a metal electric heating rod, the preheating heat-preservation unit comprises a groove plate, the metal electric heating rod is arranged in a groove of the groove plate, the copper-based workpiece clamping unit comprises a screw nut and a pressing plate which are matched with the groove plate, the copper-based workpiece clamping unit also comprises an iron-based metal plate which is used for connecting the copper-based workpiece, and the screw nut and the pressing plate are matched to press and fix the iron-based metal plate and the copper-based workpiece on the groove plate; the preheating and heat-preserving unit further comprises an upper tank body and a lower tank body, the groove plate is arranged in the upper tank body, the upper tank body is arranged above the lower tank body, and heat-preserving materials are filled between the upper tank body and the lower tank body;

the use method of the preheating and heat-preserving device comprises the following steps: an iron-based metal plate is padded between the copper-based workpiece and the groove plate, and the copper-based workpiece and the iron-based metal plate are pressed and fixed on the groove plate through a copper-based workpiece clamping unit; heating the slot plate to a preset preheating temperature of 100-400 ℃ by a heating temperature control unit; carrying out laser cladding on the copper-based workpiece; after cladding, covering the upper groove body by using a cover plate, cooling the copper-based workpiece to the preheating temperature in the preheating and heat-preserving unit, and then closing the heating temperature control unit to naturally cool the copper-based workpiece to the room temperature.

Furthermore, the frid is T type frid, and the screw nut is T type screw nut.

Furthermore, the T-shaped groove plate is made of an aluminum alloy material.

Further, the iron-based metal plate is a low carbon steel plate.

Furthermore, the heat insulation material is heat insulation ceramic fiber cotton.

In the step (3), the laser cladding process parameters are determined as follows:

determining defocus

According to the characteristics of high-speed laser cladding, the actual focus position is located on the workpiece and is positive defocusing, the defocusing amount influences the size and energy distribution of an actual light spot, and the appropriate defocusing amount is determined according to cladding material components and cladding thickness. The method specifically comprises the steps of indicating the position of a red light focus by a laser, measuring the size of a focus spot, and determining different defocusing amounts by measuring the actual spot sizes of different defocusing amounts and different laser cladding powder components. Preferably, the positive defocus amount ranges from 0.5 to 1.5 mm. Particularly, through a great deal of research and creative work, the inventor finds that for the specific laser cladding powder disclosed by the invention, positive defocusing amount and spot diameter are closely related to copper content in the used laser cladding powder, the higher the copper content in the laser cladding powder is, the smaller the defocusing amount matched with the laser cladding powder is, the smaller the spot diameter is, and the physical mechanism behind the laser cladding powder is that the higher the copper content is, the better the thermal conductivity of the laser cladding powder is, and more concentrated laser energy is needed to realize effective melting and cladding. The empirical formula summarized from the above findings is:

the positive defocusing amount is (1.5-copper mass percentage/50) mm;

the spot diameter is equal to (3.2-copper mass percent/50).

Determination of laser power and cladding scanning speed

After the spot size is determined, the appropriate laser power and cladding scanning rate are selected according to the laser scanning rate, the laser spot size and the matching relation between the laser power and the cladding powder. Specifically, repeated iteration experiments of different laser powers and different scanning rates of single-pass cladding are adopted to finally determine the process parameters matched with the components of the laser cladding powder. Preferably, the laser power 2400-.

Determination of central powder feeding parameter

The central powder feeding parameters need to be matched with the power parameters of the laser on one hand and are related to the overall movement of the cladding head on the other hand. Due to the limitations of laser power, spot size and scanning rate, the width of single-pass cladding is very limited, which limits the range of industrial application. For large-area laser cladding, a multi-pass lapping technology is adopted, and each pass of cladding is overlapped according to a certain proportion, so that the width of a cladding layer is increased. And under the condition that the laser power and the scanning rate corresponding to single-channel cladding are determined, cladding effects under different lap joint rates are compared, and a corresponding more appropriate lap joint rate, powder disc rotating speed and shielding gas (argon) flow are selected. Preferably, the scanning mode is lapping scanning, the lapping rate is 55-65%, the rotating speed of the powder disc is 0.6-0.9r/min, and the flow of argon is 1-10L/min. In particular, the inventor finds that when a certain incident angle exists between the semi-molten powder of the central powder feeding and the previous lapping, the semi-molten powder is collided, so that the power density distribution is uneven, a molten pool is influenced, and the quality of a cladding layer is finally influenced. In order to ensure proper overlapping rate and good cladding quality and better match powder with relative components, the invention provides an attempt to adjust the included angle between the cladding head and the working surface, and the angle is vertically adjusted from conventional 90 degrees to 75-86 degrees.

Compared with the prior art, the invention has the following advantages:

(1) aiming at specific laser cladding powder, a transition layer, a pre-coating layer and the like are not required to be added before cladding, the desired cladding layer is directly obtained by single-layer cladding in a mode of feeding powder in the center and controlling the working included angle of a cladding head, and the process is simplified; the cladding layer obtained by adopting a high-speed laser cladding method is reliably metallurgically bonded with the copper matrix, has good quality, does not have cracks or air holes, and improves the hardness of the surface of the copper matrix.

(2) Aiming at the laser cladding of specific laser cladding powder on a copper substrate, the invention summarizes empirical formulas of positive defocusing amount and spot diameter, and greatly reduces workload on the basis of ensuring the quality of a cladding layer.

(3) According to the invention, the copper-based workpiece is preheated and insulated to promote firm consolidation of the cladding layer and the matrix and fully release thermal stress generated in the cooling process, so that residual internal stress is remarkably reduced, and a guarantee is provided for realizing a large-area crack-free cladding layer.

In order to solve the problem that a molten pool is not easy to form due to good heat conductivity of a copper-based workpiece, the invention provides the preheating and heat-insulating device which is used for preheating additive materials during copper-based laser additive manufacturing so as to stably form the molten pool.

A preheat heat preservation device for laser vibration material disk, this heat preservation device that preheats sets up on laser vibration material disk's cladding workstation, should preheat the heat preservation device and have the heat preservation chamber, is provided with heating temperature control unit and work piece clamping unit in the heat preservation chamber, and heat preservation chamber open-top is equipped with the lid in order to allow laser to act on the vibration material disk on, the opening part.

Further, the device comprises a heating temperature control unit, a copper-based workpiece clamping unit and a preheating and heat-preserving unit; the copper-based workpiece clamping unit comprises a screw nut and a pressing plate which are matched with the groove plate, and further comprises an iron-based metal plate used for connecting the copper-based workpiece, and the screw nut and the pressing plate are matched to press and fix the iron-based metal plate and the copper-based workpiece on the groove plate.

Furthermore, the heating temperature control unit comprises a metal electric heating rod, the preheating and heat-preserving unit comprises a groove plate, and the metal electric heating rod is arranged in a groove of the groove plate; the preheating and heat-insulating unit further comprises an upper groove body and a lower groove body, the T-shaped groove plate is arranged in the upper groove body, the upper groove body is arranged on the lower groove body, and heat-insulating materials are filled between the upper groove body and the lower groove body.

Furthermore, the heating temperature control unit comprises a temperature control regulation control base and a heating flat plate, the temperature control regulation control base is connected with the heating flat plate through a support column, and a heat insulation sheet is arranged on the support column; preheat the heat preservation unit and include cell body and lower cell body, T type notch board set up last cell body in, last cell body set up lower cell body on, and the cell body intussuseption is filled with the coolant liquid down.

Furthermore, the groove plate is a T-shaped groove plate, and the screw nut is a T-shaped screw nut.

Furthermore, the T-shaped groove plate is made of an aluminum alloy material.

Further, the iron-based metal plate is a low carbon steel plate.

The invention also provides a laser additive manufacturing method of the preheating and heat-insulating device for laser additive manufacturing, which comprises the following steps: the iron-based metal plate is padded between the copper-based workpiece and the trough plate, and the copper-based workpiece and the iron-based metal plate are pressed and fixed on the trough plate through the copper-based workpiece clamping unit; the groove plate is heated to a set preheating temperature through the heating temperature control unit; carrying out laser cladding on the copper-based workpiece; after cladding, covering the upper groove body with a cover plate, cooling the copper-based workpiece in the preheating and heat-preserving unit to a preheating temperature, and then closing the heating temperature control unit to naturally cool the copper-based workpiece to the room temperature.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention fills the blank of preheating-heat preservation integrated equipment for experiments in the field of laser additive manufacturing research, provides an equipment solution for controlling the critical process of working temperature in the laser additive manufacturing technology, and lays a foundation for promoting research progress.

(2) According to the invention, through the design of the groove wall which is obviously higher than the surface of the sample, basic protection measures are provided for common safety risks such as smoke dust, splashing, laser heat dissipation and the like in the laser additive manufacturing experiment process, and the personal safety of experimenters is ensured.

(3) The invention combines the design ideas of modularization and split type, depends on the design of mature modules such as heating temperature control, clamping and the like, effectively reduces the preparation difficulty of the equipment, and effectively improves the stability and reliability of the equipment; the split design not only greatly reduces the maintenance difficulty and cost of the equipment, but also provides sufficient space for the expansion and iteration of the equipment, and further improves the universality and compatibility of the equipment.

In order to solve the problem that a molten pool is not easy to form due to good heat conductivity of a copper-based workpiece, the invention provides a preheating and heat-insulating device which is used for providing necessary preheating and heat-insulating environments when the copper-based laser additive manufacturing is carried out, realizes good compatibility on axial workpieces with different sizes and can stably form the molten pool.

A heat preservation device preheats for laser vibration material disk, include with laser cladding head matched with base and preheat the heat preservation unit, should preheat the heat preservation unit and include that the component and the connecting piece are preheated in at least a set of response of locating the base both sides respectively, link to each other through the connecting piece between the adjacent response preheats the component, response preheats the component and forms work piece heating heat preservation district jointly with the base.

Further, the induction preheating element include insulation material and locate the induction coil on the insulation material, induction coil for the coiling formula link firmly on insulation material's surface, the base surface on be equipped with supervisory equipment, supervisory equipment cooperate with induction coil through high frequency power supply.

Further, the connecting piece is a bearing roller, and the heat-insulating material is provided with a through hole for inserting a shaft of the bearing roller.

Furthermore, the upper part of the base is provided with a first opening for inserting the laser cladding head, and the first opening is provided with a buckle; the lower part of the base is provided with heat-insulating ceramic, and the heat-insulating ceramic is provided with a second opening for laser to act on the additive material; the base is also provided with a fan and a temperature control probe.

Furthermore, the heat-insulating material is heat-resistant heat-insulating ceramic.

Further, the shell of the base is made of an aluminum alloy plate.

The invention also provides a laser additive manufacturing method of the preheating and heat-insulating device for laser additive manufacturing, which is characterized by comprising the following steps of: the method comprises the following steps: according to the diameter of a workpiece and the preheating requirement, installing a proper number of induction preheating elements on the base one by one in a left-right alternating manner; the workpiece is clamped and fixed on a four-jaw chuck, a base with an installed induction preheating element is sleeved in a cladding head, and the whole device is fixed on the laser cladding head through a buckle; and controlling the laser cladding head to move to drive the device to move to a workpiece processing position, starting the chuck, starting the workpiece to rotate, starting the induction coil cooling fan after the workpiece is stabilized, then starting a high-frequency power supply of the induction coil, preheating the workpiece, and starting a cladding program to carry out cladding operation after a temperature control probe integrated in the base prompts that the preheating temperature of the workpiece reaches a preset value.

Further, after preparation is finished, the high-frequency power supply of the induction coil is turned off, the cooling fan is turned off after 5min, the workpiece is slowly cooled to room temperature, the laser cladding head is lifted to be away from the device, and then the whole device is taken out.

Furthermore, the requirement on preheating and heat preservation is high, and the number of elements can be ensured to wrap the cylindrical workpiece for a complete circle

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention adopts a modularized design idea, combines the induction coil and the heat insulation material in a modularized unit form, can rapidly adjust the number, the angle and the like of the modularized units according to different preparation requirements, fundamentally solves the common problem that the traditional fixed induction heating device cannot be compatible with axial samples with different sizes, and has excellent workpiece applicability and operation flexibility;

(2) according to the invention, through distributed combination, the preheating temperatures of different areas of the workpiece can be effectively adjusted, three groups of independent induction coils can fully meet different heat preservation requirements of the front stage, the middle stage and the rear stage of laser additive manufacturing, and the processing and manufacturing requirements corresponding to different workpieces are pertinently solved, so that the material performance is further improved.

(3) According to the invention, through the totally enclosed design of the fixed base, effective protection measures are provided for common safety risks such as smoke dust, splashing, laser heat dissipation and the like in the laser additive manufacturing process, and personal safety in the research and production manufacturing processes is guaranteed. And the monitoring force in the preparation process can be effectively enhanced by combining a close-range monitoring camera, so that the safety is further improved.

(4) The heat-resistant ceramic is used as a heat-insulating material, the induction coil and the workpiece are completely isolated, potential short circuit risks are avoided, great damage to the induction coil in a traditional induction heating device caused by extreme severe environments such as laser scattering and high-temperature metal droplet splashing in the laser additive manufacturing process is avoided, cooling of equipment is achieved by combining a coil cooling fan, and the service life and the stability of the device are remarkably improved.

In order to solve the problem that a molten pool is not easy to form due to good heat conductivity of a copper-based workpiece, the invention provides the preheating and heat-insulating method for stably forming the molten pool by enabling cladding materials on the material-increasing materials to be continuously in a heat-insulating state in the laser cladding processing process through a heat-insulating device during the copper-based laser additive manufacturing.

The preheating and heat preservation method for laser additive manufacturing comprises the following steps: the cladding material on the material increase material is continuously in a heat preservation state in the laser cladding processing process through the heat preservation device; the processing position of the additive material is continuously in a heated state in the laser cladding processing process.

Furthermore, the heat preservation device adopts an electric heating mode to heat and preserve heat.

Furthermore, the heat preservation device adopts an electric heating rod or an electric heating plate to carry out heating and heat preservation.

Further, the heat preservation device adopts the mode of induction coil to heat the heat preservation.

Furthermore, the heat preservation device is also matched with cooling liquid and radiating fins for heating and heat preservation.

Furthermore, the heat preservation device comprises a heating temperature control unit, a copper-based workpiece clamping unit and a preheating heat preservation unit; the heating temperature control unit comprises a metal electric heating rod, the preheating heat-preservation unit comprises a groove plate, and the metal electric heating rod is arranged in a groove of the groove plate; the preheating and heat-preserving unit further comprises an upper tank body and a lower tank body, the groove plate is arranged in the upper tank body, the upper tank body is arranged above the lower tank body, and heat-preserving materials are filled between the upper tank body and the lower tank body; the heating and heat preservation mode is that the groove plate is heated to the set preheating temperature of 100-400 ℃ through the heating temperature control unit, and after laser cladding is carried out on the copper-based workpiece, the upper groove body is covered by the cover plate.

Furthermore, the heat preservation device comprises a heating temperature control unit, a copper-based workpiece clamping unit and a preheating heat preservation unit; the heating temperature control unit comprises a temperature control regulation control base and a heating flat plate, the temperature control regulation control base is connected with the heating flat plate through a support column, and a heat insulation sheet is arranged on the support column; the preheating and heat-preserving unit comprises an upper tank body and a lower tank body, the T-shaped trough plate is arranged in the upper tank body, the upper tank body is arranged above the lower tank body, and the lower tank body is filled with cooling liquid; the heating and heat preservation mode is that the heating flat plate is heated by starting the control heating temperature control unit, the set temperature is the boiling point of the cooling liquid, and the thickness of the low-carbon steel plate is changed after laser cladding is carried out on the copper-based workpiece.

Furthermore, the induction preheating element comprises a heat insulation material and an induction coil arranged on the heat insulation material, the induction coil is fixedly connected to the outer surface of the heat insulation material in a winding manner, monitoring equipment is arranged on the surface, and the monitoring equipment is matched with the induction coil through a high-frequency power supply; the heating and heat preservation mode is that the induction coil is heated to a set preheating temperature by starting a high-frequency power supply, and the high-frequency power supply is turned off after laser cladding is carried out on the copper-based workpiece.

Drawings

FIG. 1 is a schematic diagram of a laser cladding apparatus for manufacturing a pre-heating and heat-preserving device according to a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of a laser cladding apparatus for manufacturing a pre-heating and heat-preserving device according to a preferred embodiment of the present invention;

FIG. 3 is a sectional view of a laser cladding manufacturing preheating and heat preserving apparatus according to a preferred embodiment of the present invention;

FIG. 4 is a sectional view of a laser cladding manufacturing preheating and heat preserving apparatus in a preferred embodiment of the present invention;

FIG. 5 is a sectional view of a laser cladding apparatus for manufacturing a pre-heating and heat-preserving device according to a preferred embodiment of the present invention;

fig. 6 is an actual working diagram of the laser cladding head.

FIG. 7 is a metallographic image of the cladding layers of examples 4, 1, 5 and 6 at different working angles.

FIG. 8 is a phase diagram of the laser cladding layer obtained in example 1 at 50 times magnification.

FIG. 9 is a phase diagram of the laser cladding layer obtained in example 1 at 100 times magnification.

FIG. 10 is a graph of the microhardness profile of the cladding layer to the copper substrate of example 1.

FIG. 11 is a diagram showing a 100-fold magnified gold phase of the laser cladding layer obtained in example 2.

FIG. 12 is a diagram showing a 100-fold magnified gold phase of the laser cladding layer obtained in example 3.

FIG. 13 is a result of X-ray measurement of residual internal stress of the cladding layers of examples 1(a) and 7(b)

FIG. 14 is a metallographic image of a laser cladding layer of example 7.

FIG. 15 is a sectional view of the preheating and insulating apparatus manufactured by laser cladding in example 8;

FIG. 16 is a schematic view of the structure of a base according to embodiment 8.

FIG. 17 is a schematic view of an induction preheating element in example 8.

FIG. 18 is a sectional view of the preheating and heat retaining apparatus manufactured by laser cladding in accordance with the second embodiment of example 7;

fig. 19 is a schematic view of the structure of the upper tank of the second embodiment in example 7.

Fig. 20 is a schematic view of the lower tank structure of the second embodiment in example 7.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples, but the scope of the present invention is not limited thereto:

examples 1 to 3

1. The laser cladding apparatus used in examples 1 to 3 was a ZKZM-4000 laser cladding product manufactured by sienna zhongmei ltd, which included a light-coupled semiconductor laser, a water chiller, a cladding head, a powder feeder, and the like. The formula of the laser cladding powder is shown in the following table 1 (mass percent):

TABLE 1

The size interval of the alloy material powder particles is 25-150 mu m, and the sphericity is more than or equal to 80 percent.

2. Pretreatment of copper-based workpieces

Polishing the surface of the pure copper workpiece by using a polisher and abrasive paper to remove a surface oxide layer; cleaning the surface of the pure copper workpiece by using absolute ethyl alcohol or acetone to obtain the surface of the pure copper workpiece with a clean surface;

3. pretreatment of fusion-coated alloy powder

The laser cladding powder needs to be dried before cladding, the drying temperature is 80-100 ℃, and the drying time is 1-2 h.

4. Determination of laser cladding technological parameters

4.1 determination of defocus

According to the characteristics of high-speed laser cladding, the actual focus position is located on the workpiece and is positive defocusing, the defocusing amount influences the size and energy distribution of an actual light spot, and the appropriate defocusing amount is determined according to cladding material components and cladding thickness.

The laser device is used for indicating the position of a red light focus, the size of a focus spot is measured to be 2mm, and the positive defocusing amount and the diameter of the spot are determined by an empirical formula:

the positive defocusing amount is (1.5-copper mass percentage/50) mm;

the diameter of the light spot is (3.2-copper mass percent/50) mm

The specific parameters obtained are shown in table 2 below:

TABLE 2

	Example 1	Example 2	Example 3
				Positive defocus amount	1.3mm	0.765mm	1.1mm
Corresponding spot diameter	3mm	2.465mm	2.8mm

4.2 determination of laser Power and cladding Scan Rate

After the spot size is determined, the appropriate laser power and cladding scanning rate are selected according to the laser scanning rate, the laser spot size and the matching relation between the laser power and the cladding powder. In the embodiment, the process parameters matched with the alloy components are finally determined by adopting repeated iterative experiments of different laser powers and different scanning rates of single-pass cladding, and the specific parameters are shown in the following table 3:

TABLE 3

	Example 1	Example 2	Example 3
				Laser power	2400W	2600W	2800W
Scanning rate	95mm/s	85mm/s	75mm/s

5. Center powder feeding parameter

In 4.2, the laser power and the scanning rate corresponding to single-pass cladding are determined, cladding effects under different lapping rates are compared, and corresponding more appropriate lapping rate, powder tray rotating speed and argon flow are selected, wherein the specific parameters are shown in the following table 4:

TABLE 4

	Example 1	Example 2	Example 3
				Lap joint ratio	55％	55％	65％
Rotational speed of powder pan	0.9r/min	0.7r/min	0.6r/min
				Argon flow	10L/min	5L/min	1L/min

In order to ensure proper lapping rate and good cladding quality and better match powder with relative components, the included angle between the cladding head and the working surface is vertically adjusted to a certain angle from conventional 90 degrees, the actual working diagram is shown in fig. 6, and the working included angle is shown in table 5:

TABLE 5

	Example 1	Example 2	Example 3
				Working angle	75±0.5°	79±0.5°	86±0.5°

Based on the process steps and parameter settings, the metallographic phase of the cladding layers of examples 1, 2 and 3 is shown in fig. 8, 9, 11 and 12, and metallographic experiments prove that the cladding layers with good metallurgical quality and without cracks and air holes are obtained, the microhardness distribution curve of example 1 is shown in fig. 10, and the hardness of the cladding layers is obviously higher than that of the copper matrix, which shows that the laser cladding technology can improve the hardness of the surface of the copper material. The result of the X-ray test for the residual internal stress of the cladding layer of example 1 is shown in fig. 13(a), and the maximum residual internal stress is 326 MPa.

Examples 4 to 6

In order to verify the influence of the working angle of the cladding head on the cladding effect after central powder feeding, the working angle of the cladding head was changed, the cladding results obtained by comparing different working angles under the same conditions as in example 1 were obtained, the results are shown in table 6 below, and the corresponding metallographic results are shown in fig. 7.

TABLE 6

	Example 4	Example 1	Example 5	Example 6
					Working angle	90	75	60	45
Quality of cladding	With a small amount of pores	Pore-free and crack-free	Has a small amount of cracks	Has cracks

Example 7

In the embodiment, a laser cladding manufacturing preheating and heat preserving device is adopted, and the components shown in fig. 3 and 4 are combined to form a pattern shown in fig. 1 and 2.

The preheating and heat-insulating device is arranged on a cladding workbench for laser material increase and is provided with a heat-insulating cavity, a heating temperature control unit and a workpiece clamping unit are arranged in the heat-insulating cavity, the top opening of the heat-insulating cavity acts on material increase materials through allowing laser, and a cover is arranged at the opening. When laser operation is performed, the cover is opened. And (5) after the laser operation is finished, covering the cover when heat preservation is needed.

The preheating and heat-insulating device comprises a heating temperature control unit, a copper-based workpiece clamping platform, an upper tank body, a lower tank body and heat-insulating ceramic fiber cotton. The heating temperature control unit consists of a metal electric heating rod 1, a connecting wire 2 and a commercial modular control box 3; the copper-based workpiece clamping platform consists of a T-shaped groove plate 4, a standard T-shaped screw nut and pressure plate combination 5 and a low-carbon steel plate 6, and is used for effectively fixing a copper-based workpiece 7; and heat-insulating ceramic fiber cotton 9 is filled between the upper tank body 8 and the lower tank body 10. The heating temperature control unit can provide a heat source of 20-500 ℃, and the integrated temperature sensing probe is used for preheating and heating the copper-based workpiece clamping platform; the copper-based workpiece clamping platform adopts a modular design, consists of a standard T-shaped groove plate, a screw nut, a pressing plate and a low-carbon steel plate, and can clamp copper-based workpieces with different sizes; the upper and lower tank body combination plays a role in supporting the copper-based workpiece clamping platform, and the lining is filled with ceramic fiber cotton, so that the heat insulation function is considered, and the heat insulation of the whole copper-based workpiece clamping platform including the copper-based workpiece is realized. The heating temperature control unit uses a metal electric heating rod as a heating unit, integrates a temperature sensing element and ensures the safety and controllability of temperature; the control console uses the modularized temperature control unit, has a temperature display function, can obtain set temperature and actual temperature information, and is matched with a temperature setting key and an indicator lamp for prompting working conditions and a power supply main switch. The top end of the lower tank body, the joint of the upper tank body and the electric wire joint of the upper tank body are tightly sealed by high-temperature-resistant rubber rings, so that the heat insulation performance is improved.

Before laser cladding manufacturing, the metal electric heating rod 1 is controlled by the commercial modular control box 3, the T-shaped groove plate 4 is heated to a set preheating temperature, and the low-carbon steel plate 6 and the copper-based workpiece 7 are heated simultaneously under the action of heat transfer. And the preheating temperature of the copper-based workpiece 7 before additive manufacturing is accurately controlled.

After laser cladding manufacturing begins, the low-carbon steel plate 6 is used for protecting the T-shaped groove plate 4 from laser ablation damage, and heat input by laser can be diffused by excellent heat conductivity of copper and copper alloy, so that the high-temperature-resistant heat-preservation ceramic fiber cotton 9 between the upper groove body 8 and the lower groove body 10 starts to play a role, and heat conducted by the copper-based workpiece 7 is concentrated in the copper-based workpiece clamping platform by means of heat preservation performance of the ceramic fiber cotton 9 and a closed space formed by combination of the upper groove body 8 and the lower groove body 10, so that effective heat preservation of the copper-based workpiece is realized.

In other embodiments, as shown in fig. 18 to 20, the heating temperature control unit includes a temperature control adjustment control base 1a and a heating flat plate 2a, the temperature control adjustment control base is connected to the heating flat plate 2a through a supporting column 3a, and a heat insulation sheet 30a is disposed on the supporting column; the preheating and heat-preserving unit comprises an upper tank body 8a and a lower tank body 10a, the upper tank body 8a is an aluminum alloy tank body, and specifically, the bottom of the upper tank body 8a is provided with aluminum alloy heat-dissipating fins 80; the lower tank body 10 is an aluminum alloy tank body, the side wall of the lower tank body 10a is provided with a pressure relief port 110 and a liquid supplementing port 111, the lower tank body 10a is placed at the top of the heating flat plate, the upper tank body 8a is placed inside the lower tank body 10a, and cooling liquid is filled inside the lower tank body 10 a; after the work is finished, the lower tank body 10a is slightly lifted, the waste powder is cleaned and recovered, the tank is cleaned and the like, and the cooling liquid used for a long time is replaced.

Before laser cladding manufacturing, the cooling liquid stored in the lower groove body 10a is heated to a boiling point, the upper groove body 8a and the sample clamping platform are heated simultaneously under the action of heat transfer, an experimental sample is preheated to a position near the boiling point of the cooling liquid, and accurate control of the preheating temperature of the copper-based workpiece before additive manufacturing is achieved.

After laser cladding manufacturing begins, due to the fact that laser heat is input rapidly, an experimental sample is heated rapidly, the low-carbon steel plate 11, the T-shaped groove plate 4 and the upper groove body 8a conduct heat gathered by the experimental sample rapidly to cooling liquid close to boiling through the heat dissipation fins 80, the cooling liquid vaporizes rapidly and absorbs a large amount of heat, steam carries heat to be discharged from the pressure relief opening 110, powerful refrigeration is achieved, and effective heat preservation of a copper-based workpiece is achieved.

The use method of the preheating and heat-insulating device manufactured by laser cladding adopts the device and comprises the following steps:

(1) before starting, whether the display screen, the button, the power supply and the like of the control box 3 operate normally or not is checked, whether the metal heating rod 1 is fixed with the T-shaped groove plate 4 tightly or not is checked, and whether the metal heating rod is connected with the power supply line 2 normally or not is checked.

(2) And clamping a copper-based workpiece 7 on a copper-based workpiece clamping platform by using a pressing plate, padding a low-carbon steel plate 6 between the copper-based workpiece and the T-shaped slot plate 4, tightly compacting and fixing the copper-based workpiece 7, the low-carbon steel plate 6 and the T-shaped slot plate 4 by using the pressing plate, opening a heating temperature control unit control box 3, adjusting the required preheating temperature to be 250 ℃, and waiting for the temperature sensing number to reach the preheating temperature.

(3) And carrying out laser cladding manufacturing on the copper-based workpiece 7 by adopting the laser cladding device and the process parameters of the embodiment 1.

(4) After cladding, the cover plate is covered, the copper-based workpiece 7 is slowly cooled to the preheating temperature in the heat preservation equipment, the power supply of the heating temperature control unit control box 3 is turned off, and the copper-based workpiece 7 is cooled to the room temperature along with the preheating device.

(5) And after the copper-based workpiece 7 is cooled to room temperature, opening the cover plate, taking out the copper-based workpiece 7, lifting the upper groove 8, and performing cleaning work such as waste residue and the like.

In another preferred embodiment, in the step 2), the copper-based workpiece is welded on the mild steel plate to prevent the copper-based workpiece from deforming due to heating, so that the copper-based workpiece cannot be tightly attached to the mild steel plate to weaken the heat preservation and conduction condition. The other steps are the same as the using method of the preheating and heat-preserving device manufactured by laser cladding.

The method can be used as the preheating method in the embodiments 1 to 6 and combined with the copper alloy laser cladding scheme in the embodiments 1 to 6.

The metallographic phase of the laser cladding layer of example 7 is shown in fig. 14, and it was confirmed by metallographic experiments that a cladding layer having good metallurgical quality and no cracks and pores was obtained. The result of the X-ray test of the residual internal stress of the cladding layer of example 7 is shown in fig. 13(b), and the maximum residual internal stress is 187 MPa. Compared with the embodiment 1, the residual internal stress is obviously reduced, mainly because the preheating and heat preservation are adopted to promote the firm bonding of the coating and the substrate and fully release the thermal stress generated in the cooling process, and the realization of the large-area crack-free cladding layer is guaranteed.

Example 8

In the embodiment, a laser additive distributed induction preheating and heat preserving device is adopted, and the laser additive distributed induction preheating and heat preserving device is combined by the parts shown in fig. 16 and 17 into a pattern shown in fig. 15.

The preheating and heat-insulating device for laser additive manufacturing comprises a base 100, wherein the base 100 is used for fixing the device and a laser cladding head, so that the device and the laser cladding head can move along with the cladding head 1 all the time, and specifically, a shell of the base 100 is welded by an aluminum alloy plate; the two sides of the base 100 are provided with at least one group of induction preheating elements 200, the induction preheating elements 200 are wrapped on the outer surface of the workpiece, and in other embodiments, the induction preheating elements 200 are arranged in one group or more than one group, the induction preheating elements and the base form a workpiece heating and heat preservation area together, the induction preheating elements 200 are main parts for preheating and heat preservation of the workpiece, the units can be connected with each other, and the number of the induction preheating elements 200 is arranged according to the difference of the size and the shape of the workpiece; the adjacent induction preheating elements are matched through the connecting piece 101, the design of the connecting piece 101 achieves the constant distance between the induction preheating elements and a workpiece, and the stability of induction heating performance is ensured, particularly, the connecting piece 101 is a bearing roller.

Further, the upper part of the base is provided with a first opening 110 for inserting the laser cladding head 1, and the first opening is provided with a buckle 107; the lower part of the base 100 is provided with a heat-insulating ceramic, and the heat-insulating ceramic is provided with a second opening for laser to act on the additive material.

Further, the induction preheating element 200 comprises a heat insulating material 201 and induction coils 202 arranged on the heat insulating material 201, the rated conservative setting of each group of induction coils 202 is 150W, namely the maximum heating power of each unit is limited within 450W, the heat insulating material 201 is made of heat-resistant heat-insulating ceramic, through holes 203 for inserting shafts of bearing rollers are formed in the heat insulating material, the problem that a conventional induction heating device lacks large-area heat insulation is solved due to the introduction of the high-temperature ceramic, the induction preheating element has the functions of heat insulation of workpieces, heat insulation of the coils and supporting, meanwhile, the sealing performance of the whole device is effectively improved, and the induction coils 202 are fixedly connected to the outer surface of the heat insulating material 201 in a winding mode.

Further, a monitoring device is arranged on the outer surface of the base 100, the monitoring device is matched with the induction coil 202 through a high-frequency power supply, and specifically, the base 100 connects a plurality of groups of induction preheating elements 200 through a steel module connecting piece 101; the positions of each group of induction preheating elements 200 and the induction preheating elements can be fixed through the steel module connecting piece 101, so that the induction preheating elements are not supported on the surface of a workpiece any more, and the preparation of complex special-shaped parts is supported.

Furthermore, the base 100 is also provided with 2 fans 105 and temperature control probes 106, wherein the fans 105 are arranged on the left side and the right side of the base 100; the temperature control probe 106 is used for sensing the temperature value.

(1) before starting, determining the diameter and the preheating requirement of a workpiece, installing the quantity of the induction preheating elements 200 according to the determined diameter and the preheating requirement, and installing a certain quantity of induction preheating elements 200 on the base 100 in a left-right alternating mode, wherein for the workpiece with high preheating requirement, the induction preheating elements 200 can be ensured to wrap the cylindrical workpiece for a complete circle;

(2) then, clamping the workpiece by using a four-jaw chuck, sleeving the installed induction preheating element 200 on the cladding head, rotating a buckle 107 at the top end of the base, and fixing the whole device on the laser cladding head;

(3) and then, starting the laser cladding head to slowly move to the initial position of preparation, and after the workpiece is fixed, enabling the induction preheating element 200 to be close to the outer surface of the workpiece.

(4) Starting the four-jaw chuck, rotating the workpiece, then starting the fan 105 and the high-frequency power supply, firstly setting preheating temperatures of regions corresponding to the three groups of coils to start preheating, and starting a cladding program to carry out laser cladding after the temperature control probe 106 prompts that the preheating temperature of the workpiece reaches a preset value;

(5) after laser cladding is finished, firstly turning off the high-frequency power supply, turning off the fan 105 after 5min, lifting up the laser cladding head after the workpiece slowly reaches room temperature, separating the laser cladding head from the device, and then removing the whole device;

(6) and removing impurities such as waste powder and the like remained in the device, and placing the workpiece in a dry environment for storage.

When a cylindrical workpiece is processed, the preheating and heat-preserving device for laser additive manufacturing specifically operates in the step (3) as follows: slowly moving the laser cladding head to the initial position of preparation, and loosening the buckle 107 on the top of the base 100, so that the base 100 and the induction preheating element 200 are supported on the outer surface of the workpiece by virtue of the roller; if the induction preheating elements 200 can wrap the cylindrical workpiece for a complete circle, the lowest two induction preheating elements 200 are connected and fixed at the moment, so that the workpiece is wrapped completely;

the specific detailed operation in (4) above is: the four-jaw chuck is started, the workpiece rotates, then the fan 105 and the high-frequency power supply are started, the preheating temperatures of the corresponding areas of the three groups of coils are set to start preheating, when the temperature control probe 106 prompts that the preheating temperature of the workpiece reaches a preset value, a cladding program is started, the induction preheating element 200 moves in the XY direction along with the cladding head, and the area of the induction preheating element 200 is always synchronous with the machining area.

When the preheating and heat-preserving device for laser additive manufacturing is used for a method for machining a special-shaped piece, the specific detailed operation in the step (3) is as follows: then, starting the laser cladding head to slowly move to the initial position of preparation, finely adjusting the included angle between each group of induction preheating elements 200 after the workpiece is fixed, ensuring that each group of induction preheating elements 200 are close to the outer surface of the workpiece as much as possible, and then fixing each group of induction preheating elements 200 through a steel connecting piece 101;

the specific detailed operation in (4) above is: the four-jaw chuck is started, the workpiece rotates, then the fan 105 and the high-frequency power supply are started, the preheating temperatures of the corresponding areas of the three groups of coils are set to start preheating, when the temperature control probe 106 prompts that the preheating temperature of the workpiece reaches the preset value, a cladding program is started, and the induction preheating element 200 moves along with the cladding head 1 in the XYZ direction.

Example 9

Specifically, the heat preservation device adopts an electric heating mode to heat and preserve heat.

The heat preservation device comprises a heating temperature control unit, a copper-based workpiece clamping unit and a preheating heat preservation unit; the heating temperature control unit comprises a metal electric heating rod, the preheating heat-preservation unit comprises a groove plate, and the metal electric heating rod is arranged in a groove of the groove plate; the preheating and heat-preserving unit further comprises an upper tank body and a lower tank body, the groove plate is arranged in the upper tank body, the upper tank body is arranged above the lower tank body, and heat-preserving materials are filled between the upper tank body and the lower tank body; the specific structure of the heat preservation device is the same as that in the embodiment 7; the heating and heat preservation mode is that the groove plate is heated to the set preheating temperature of 100-400 ℃ through the heating temperature control unit, and after laser cladding is carried out on the copper-based workpiece, the upper groove body is covered by the cover plate; the concrete mode is as follows: the method comprises the steps of clamping a copper-based workpiece 7 on a copper-based workpiece clamping platform by using a pressing plate, padding a low-carbon steel plate 6 between the copper-based workpiece and a T-shaped groove plate 4, tightly compacting and fixing the copper-based workpiece 7, the low-carbon steel plate 6 and the T-shaped groove plate 4 by using the pressing plate, opening a heating temperature control unit control box 3, adjusting the required preheating temperature to be 250 ℃, and carrying out laser cladding manufacturing on the copper-based workpiece 7 by using the laser cladding device and the process parameters of the embodiment 1 after the temperature sensing number reaches the preheating temperature.

In other embodiments, the heat preservation device adopts an induction coil mode for heating and heat preservation; the induction preheating element comprises a heat insulation material and an induction coil arranged on the heat insulation material, the induction coil is fixedly connected to the outer surface of the heat insulation material in a winding mode, monitoring equipment is arranged on the surface, and the monitoring equipment is matched with the induction coil through a high-frequency power supply; the specific structure of the heat preservation device is the same as that of the embodiment 8; the heating and heat preservation mode is that the induction coil is heated to a set preheating temperature by starting a high-frequency power supply, and after laser cladding is carried out on the copper-based workpiece, the high-frequency power supply is turned off: the method specifically comprises the following steps: and starting the fan 105 and the high-frequency power supply, setting the preheating temperatures of the corresponding areas of the three groups of coils to start preheating, and starting a cladding program to perform laser cladding after the temperature control probe 106 prompts that the preheating temperature of the workpiece reaches a preset value.

In other embodiments, the heat preservation device is also matched with cooling liquid and radiating fins for heating and heat preservation; the heat preservation device comprises a heating temperature control unit, a copper-based workpiece clamping unit and a preheating heat preservation unit; the heating temperature control unit comprises a temperature control regulation control base and a heating flat plate, the temperature control regulation control base is connected with the heating flat plate through a support column, and a heat insulation sheet is arranged on the support column; the preheating and heat-preserving unit comprises an upper tank body and a lower tank body, the T-shaped trough plate is arranged in the upper tank body, the upper tank body is arranged above the lower tank body, and the lower tank body is filled with cooling liquid; the specific structure of the heat preservation device is the same as that of the other embodiment in the embodiment 7; the heating and heat preservation mode is that the heating flat plate is heated by starting the control heating temperature control unit, the set temperature is the boiling point of the cooling liquid, and after laser cladding is carried out on the copper-based workpiece, the thickness of the low-carbon steel plate is changed: the method specifically comprises the following steps: the method specifically comprises the following steps: before laser cladding manufacturing, the cooling liquid stored in the lower groove body 10a is heated to a boiling point, the upper groove body 8a and the sample clamping platform are heated simultaneously under the action of heat transfer, an experimental sample is preheated to be close to the boiling point of the cooling liquid, and accurate control of the preheating temperature of the copper-based workpiece before additive manufacturing is realized; after laser cladding manufacturing begins, due to the fact that laser heat is input rapidly, an experimental sample is heated rapidly, the low-carbon steel plate 11, the T-shaped groove plate 4 and the upper groove body 8a conduct heat gathered by the experimental sample rapidly to cooling liquid close to boiling through the heat dissipation fins 80, the cooling liquid vaporizes rapidly and absorbs a large amount of heat, steam carries heat to be discharged from the pressure relief opening 110, powerful refrigeration is achieved, and effective heat preservation of a copper-based workpiece is achieved.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. A preheat heat preservation device for laser vibration material disk, its characterized in that: the preheating and heat-insulating device is arranged on a cladding workbench for laser material increase and is provided with a heat-insulating cavity, a heating temperature control unit and a workpiece clamping unit are arranged in the heat-insulating cavity, the top opening of the heat-insulating cavity acts on material increase materials through allowing laser, and a cover is arranged at the opening.

2. The pre-heating and insulating device for laser additive manufacturing according to claim 1, wherein: the device comprises a heating temperature control unit, a copper-based workpiece clamping unit and a preheating heat-preservation unit; the copper-based workpiece clamping unit comprises a screw nut and a pressing plate which are matched with the groove plate, and further comprises an iron-based metal plate used for connecting the copper-based workpiece, and the screw nut and the pressing plate are matched to press and fix the iron-based metal plate and the copper-based workpiece on the groove plate.

3. The preheating and heat-preserving device for laser additive manufacturing according to claim 2, wherein the heating and temperature control unit comprises a metal electric heating rod, the preheating and heat-preserving unit comprises a groove plate, and the metal electric heating rod is arranged in a groove of the groove plate; the preheating and heat-insulating unit further comprises an upper groove body and a lower groove body, the T-shaped groove plate is arranged in the upper groove body, the upper groove body is arranged on the lower groove body, and heat-insulating materials are filled between the upper groove body and the lower groove body.

4. The preheating and heat-preserving device for laser additive manufacturing according to claim 2, wherein the heating temperature control unit comprises a temperature control adjustment control base and a heating flat plate, the temperature control adjustment control base is connected with the heating flat plate through a support column, and a heat insulation sheet is arranged on the support column; preheat the heat preservation unit and include cell body and lower cell body, T type notch board set up last cell body in, last cell body set up lower cell body on, and the cell body intussuseption is filled with the coolant liquid down.

5. The pre-heating and heat-preserving device for laser additive manufacturing according to claim 2, wherein the groove plate is a T-shaped groove plate, and the screw nut is a T-shaped screw nut.

6. The pre-heating and heat-preserving device for laser additive manufacturing according to claim 5, wherein the T-shaped groove plate is made of an aluminum alloy material.

7. The preheating and heat-insulating device for laser additive manufacturing according to claim 2, wherein the iron-based metal plate is a low-carbon steel plate.

8. The pre-heating insulation device for laser additive manufacturing according to claim 3, wherein the insulation material is insulation ceramic fiber cotton.

9. A laser additive manufacturing method using the pre-heating and temperature-keeping apparatus for laser additive manufacturing according to any one of claims 1 to 8, comprising the steps of: the iron-based metal plate is padded between the copper-based workpiece and the trough plate, and the copper-based workpiece and the iron-based metal plate are pressed and fixed on the trough plate through the copper-based workpiece clamping unit; the groove plate is heated to a set preheating temperature through the heating temperature control unit; carrying out laser cladding on the copper-based workpiece; after cladding, covering the upper groove body with a cover plate, cooling the copper-based workpiece in the preheating and heat-preserving unit to a preheating temperature, and then closing the heating temperature control unit to naturally cool the copper-based workpiece to the room temperature.