A laser additive manufacturing method for a non-magnetic layer of a permanent magnet model core

Abstract

The present application relates to a kind of permanent magnet model core non-magnetic layer laser additive manufacturing method, comprising the following steps: S1, preparation substrate;S2, develop robot automatic walking track;S3, substrate is carried out high temperature preheating treatment;S4, substrate is carried out non-magnetic layer laser additive;S5, to the cladding non-magnetic product of manufacturing completion is carried out high temperature annealing treatment;S6, post-processing.The present application can realize the continuous automatic integrated manufacturing of high-hard wear-resistant non-magnetic layer by the coupling of the trajectory programming of robot and laser cladding technology, with hardness≥HRC40, maximum thickness≥13mm, no crack and pore defect, can greatly improve the production efficiency and quality of product.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of cemented carbide additive manufacturing, in particular to a laser additive manufacturing method for a non-magnetic layer of a permanent magnet model core. BACKGROUND

[0002] Permanent magnet material, also known as "hard magnetic material", refers to a material that can maintain constant magnetism after magnetization. Since 2000, China has become the world's largest rare earth permanent magnet material producer, exporter and consumer, and the production scale is expanding and showing a steady growth trend year by year. By 2019, the output of rare earth permanent magnet materials in China had reached 180,300 tons. After years of development, China's rare earth permanent magnet industry has formed an industrial cluster mainly in Zhejiang Dongyang and Ningbo area, Beijing-Tianjin area, Shanxi area, Baotou and Ganzhou area. However, most of the rare earth permanent magnet material enterprises in China have small production scale and low industrial concentration, and the polarization of enterprises is serious. Taking sintered neodymium-iron-boron material as an example, there are nearly 200 sintered neodymium-iron-boron production enterprises in China, and enterprises with annual output of more than 3,000 tons account for only 7.5%, while enterprises with annual output of less than 1,500 tons account for 84%. The key reason why many enterprises cannot produce more is that the production and quality of permanent magnet molds cannot keep up. Among them, the manufacturing of the non-magnetic layer on the surface of the permanent magnet model core is a key difficulty.

[0003] Due to the service environment required, the surface of the permanent magnet model core needs to have high hardness, high wear resistance and high corrosion resistance, and at the same time, due to the production of permanent magnet products, the surface also needs to have no magnetism. Therefore, the surface hardening layer of the permanent magnet model core cannot be obtained by simple induction quenching and other solid phase transformation methods, but can only be manufactured by surface hardfacing cemented carbide. At present, the industry still adopts the very backward manual hardfacing method. The production efficiency is extremely low (a skilled worker can at most hardface 8 per day), the labor intensity of workers is large, it is easy to crack, and it is greatly affected by human factors, the product quality is low and unstable, which greatly limits the production and processing of permanent magnet molds and the subsequent production of permanent magnet products, and a new technology is urgently needed to replace and upgrade. SUMMARY

[0004] In view of the above problems of the prior art, the purpose of the present application is to overcome the deficiencies in the prior art and provide a laser additive manufacturing method for a non-magnetic layer of a permanent magnet model core. Through the coupling of trajectory programming of a robot and laser cladding technology, continuous automatic integrated manufacturing of a high-hardness wear-resistant non-magnetic layer with hardness ≥HRC40, maximum thickness ≥13mm, and no crack and pore defects can be realized, which can greatly improve the production efficiency and quality of the product.

[0005] The laser additive manufacturing method for a non-magnetic layer of a permanent magnet model core provided by the present application comprises the following steps:

[0006] S1, preparing the base body: according to the product shape characteristics, the alloy base body is processed by wire cutting or numerical milling technology;

[0007] S2, developing a robot automatic walking track: according to the product shape characteristics, a robot continuous automatic walking track is developed;

[0008] S3, high temperature preheating treatment of the base body: before additive manufacturing, the base body is placed in a high temperature furnace, heated to 600-800℃, and kept for 30-40 minutes for high temperature preheating treatment;

[0009] S4, laser additive of the base body: the alloy base body 1 preheated in step S3 is taken out from the high temperature furnace and fixed on the four-jaw chuck on the two-axis turntable, and the laser additive manufacturing process is started while hot, and the laser additive walking track is used in step S2;

[0010] S5, high temperature annealing treatment of the manufactured cladding non-magnetic product: after additive manufacturing, the product is taken off from the four-jaw chuck of the two-axis turntable and quickly placed in another high temperature furnace, the furnace temperature is set to 500℃, and the stress relief annealing treatment is kept for 3-5h;

[0011] S6, post-processing: after the annealing treatment in step S5, the additive manufactured non-magnetic layer product is machined to realize forming.

[0012] Further, the laser processing head in the coaxial powder feeding laser cladding system is inclinedly arranged, so that each processing position of the base body is in a near vertical relationship with the laser processing head.

[0013] Further, the initial laser power of the coaxial powder feeding laser cladding system is 2500W, then each intermediate curved surface is cladded with a 17W drop, and the final power is stabilized at 1548W.

[0014] In summary, the present application has the following beneficial technical effects:

[0015] 1. The present application mainly faces the automatic manufacturing of permanent magnet mold core surface layer high-hardness wear-resistant non-magnetic alloy, and can obtain laser additive manufacturing core non-magnetic layer products with hardness≥HRC40 and maximum thickness≥13mm without crack and pore defects. Compared with the current widely used manual surfacing method, the production efficiency can be improved by 2-3 times, and the product performance is more excellent and the quality is more stable.

[0016] 2. Compared with traditional manual surfacing, more excellent alloy organization can be obtained, and the service life is higher. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the permanent magnet mold core non-magnetic layer;

[0018] Figure 2 Fig. 1 is a schematic diagram of the morphology of the alloy base body after processing and the positioning points and trajectories of the robot programming;

[0019] Figure 3 Fig. 2 is a schematic diagram of the positioning operation field of the mechanical arm and the two-axis turntable coupling;

[0020] Figure 4 Fig. 3 is a product of the non-magnetic layer of the permanent magnet model core obtained by laser additive manufacturing;

[0021] Figure 5 Fig. 4 is a product of the non-magnetic layer of the permanent magnet model core after subsequent mechanical processing;

[0022] Figure 6 Fig. 5 is a top view of the intermediate curved surface protrusion of the non-magnetic layer and a schematic diagram of the trajectory. Figure 2

[0023] Reference signs: 1, alloy base body; 2, non-magnetic layer. DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying Figures 1-6 Further detailed description will be made to the present application.

[0025] As Figure 1 shown, the non-magnetic layer 2 of the present application is arranged on the base body 1, and the base body 1 is 45 steel. The non-magnetic layer mainly consists of an intermediate curved surface protrusion and two edge protrusions, wherein the thickness is 5-6 mm at the lowest and more than 13 mm at the highest.

[0026] In addition, CN215749787U discloses a permanent magnet ferrite tile mold lower punch structure, and the prior art also explicitly discloses a non-magnetic layer similar to the present application, but the two ends thereof are not protruded and are flat. In the manufacturing process, since the two ends are not protruded, the highest thickness is smaller, and it is easier to manufacture. Therefore, the processing difficulty of the non-magnetic layer with the two ends protruded is greater than that of the non-magnetic layer with the two ends flat. The protection scope of the present application should cover the above two kinds, and the non-magnetic layer with the two ends protruded which is more difficult to process is selected as an example for laser additive manufacturing as follows.

[0027] The embodiment of the present application discloses a laser additive manufacturing method for a non-magnetic layer of a permanent magnet model core, which specifically comprises the following steps:

[0028] S1, preparing a base body: according to the product shape characteristics, an alloy base body is processed by using wire cutting or numerical milling technology;

[0029] It should be noted that the morphology of the base body 1 is a conventional morphology in the art. It includes but is not limited to the morphology shown in Figure 2 .

[0030] S2, developing a robot automatic walking trajectory: ​

[0031] According to the product shape characteristics, the continuous automatic walking trajectory of the robot is developed; specifically, the following development steps are further included:

[0032] S2.1: The present application adopts a "6+2" axis robot system composed of a KUKA six-axis linkage manipulator and a two-axis turntable to program the trajectory. The trajectory program is developed by using the matching Workvisual software. According to the shape characteristics of the non-magnetic layer 2, the straight line walking is adopted for the two sides of the raised part, and the continuous multi-segment line walking mode is adopted for the middle part of the curved surface to complete. The straight line walking needs to determine the starting positioning points LP1 and LP2 in advance, and the multi-segment line walking needs to determine the positioning points RP1-RP7.

[0033] Further, the initial positions of LP1 and LP2 are respectively located at the two sides of the corner of the base body 1 at one end of the non-magnetic layer to be laser additive. The positions of the positioning points RP1-RP7 are divided into 6 parts for the arc line of the middle curved surface, and the 7 points are positioned in this way. It should be noted that RP1 and RP7 are respectively located at the beginning and end of the arc line of the middle curved surface. For details, see Figure 2 . Among them, LP1-RP1 and RP7-LP2 are straight line walking. The straight line walking part of the present application has a uniform melting speed.

[0034] S2.2: Through offset and loop statements, the walking trajectory of multiple straight lines and multiple melting of the middle curve is formed.

[0035] Further, the loop statement uses for loop, for i = 1 to n (n is the number of loops), such as melting a curve, when melting the second curve, the offset statement is: XRP1.Y = XRP1.Y+spacing, XRP2.Y = XRP2.Y+spacing…….

[0036] Specifically:

[0037] XRP1.Y = XRP1.Y+spacing,

[0038] XRP2.Y = XRP2.Y+spacing,

[0039] XRP3.Y = XRP3.Y+spacing,

[0040] XRP4.Y = XRP4.Y+spacing,

[0041] XRP5.Y = XRP5.Y+spacing,

[0042] XRP6.Y = XRP6.Y+spacing,

[0043] XRP7.Y = XRP7.Y+spacing;

[0044] wherein spacing is the offset. Offset = single pass cladding width x 60%.

[0045] In this application, the determined single pass cladding width is 4mm, so the offset (spacing) is 2.4mm.

[0046] Due to the thick non-magnetic layer, it is necessary to set the offset and loop statement to form a multi-layer cladding walking track, and finally obtain a track program that can be continuously and automatically formed in multiple passes and multiple layers. Simply put, the offset and loop statement can be set to adjust and control the thickness of the non-magnetic layer.

[0047] In addition, in order to reduce the inclination between the curved edge and the laser processing head, a six-axis linkage mechanical arm plus a two-axis turntable is used for trajectory programming in this embodiment. By tilting the two-axis turntable and the laser processing head, the vertical relationship between the substrate and the processing head at each position is achieved as much as possible to improve the deposition efficiency and consistency of the cladding powder, as shown in Figure 3 .

[0048] S2.3: During the curved surface cladding process, set the cladding speed to be fast on both sides and slow in the middle to obtain a more uniform forming thickness of the curved surface. The cladding speed in the middle is 0.7-0.9m / s, and the cladding speed on both sides is 1.0-1.2m / s.

[0049] Due to the flow tendency of the molten pool metal at the two positions of the curved surface under the action of gravity, it will result in the cladding thickness being large on both sides and small in the middle. The above setting can well solve this problem.

[0050] Further, RP1-RP2 and RP5-RP6 are defined as the two sides of the middle curved surface, and RP3-RP4 are defined as the middle of the middle curved surface. In order to adjust the cladding speed during the curved surface cladding process to obtain a more uniform forming thickness of the curved surface.

[0051] S3, high temperature preheating treatment of the substrate: before additive manufacturing, the alloy substrate 1 is placed in a high temperature furnace, heated to 600-800℃, and kept for 30-40 minutes for high temperature preheating treatment.

[0052] The purpose is to increase the substrate temperature during cladding to reduce the temperature gradient of the molten pool and reduce the application of additive manufacturing alloy to inhibit the formation of cracks during the manufacturing process.

[0053] S4, laser additive manufacturing of non-magnetic layer on the substrate:

[0054] The alloy substrate 1 preheated in step S3 is taken out of the high temperature furnace and fixed on the four-jaw chuck on the two-axis turntable, and the laser additive manufacturing process is started while it is hot. In this embodiment, a coaxial powder feeding laser cladding system is used for additive manufacturing.

[0055] Further, the initial laser power is 2500W, and then decreases by 17W for each cladding, and the final power is stabilized at 1548W.

[0056] In order to improve the bonding strength between the additive manufacturing alloy and the substrate, a higher initial laser power is initially used. However, as the cladding proceeds, the heat accumulation on the surface increases, which can cause the molten pool metal to overheat, affecting the stability of manufacturing and the accuracy of forming.

[0057] If the laser power decreases too fast for each cladding, such as 30W, then the laser power is not enough later, and the powder cannot be melted, so the forming height cannot be increased. If the power decreases too small, such as 10W, then due to excessive heat accumulation of the substrate, the molten pool temperature is too high, which can cause collapse and affect the forming accuracy. At the same time, the high molten pool temperature can cause part of the molten alloy to vaporize, and the metal vapor can affect the processing stability of the laser processing head. The above technical solution selected by the present application can perfectly solve the problem of molten pool metal overheating, affecting the stability of manufacturing and the accuracy of forming.

[0058] Further, the additive manufacturing alloy powder selected by the present application is cobalt-based hard alloy powder, and the composition is (mass percent):

[0059]

[0060] The alloy hardness is HRC 40-43. The above Co balance means that the remaining mass percentage is Co.

[0061] It should be noted that the above-mentioned cobalt-based hard alloy powder ratio disclosed by the present application is not a limitation of the present application, but only to meet the requirements of patent disclosure for protection. It can be understood that any additive alloy powder used in the coaxial powder feeding laser cladding system should be within the protection scope of the present application. The laser additive manufacturing non-magnetic layer product obtained by using the present application is shown in Figure 4 The production time required by the present embodiment is about 15 minutes per product.

[0062] S5, annealing treatment of the manufactured cladding non-magnetic product at high temperature:

[0063] After the additive manufacturing is completed, the product is taken off from the four-jaw chuck of the two-axis turntable and quickly placed in another high-temperature furnace. The furnace temperature is set to 500℃, and the annealing treatment is performed for 3-5h to avoid subsequent deformation and cracking of the product.

[0064] S6, post-processing: after the annealing treatment in step S5, the additive manufacturing non-magnetic layer product is subjected to subsequent mechanical processing to meet the final forming requirements of the product, and the final product is shown in Figure 5 .

[0065] For the convenience of understanding the laser additive track of the non-magnetic layer intermediate surface, reference can be made to Figure 6 .

[0066] The above are preferred embodiments of the present application, and do not limit the protection scope of the present application, so that: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for laser additive manufacturing of a non-magnetic layer of a permanent magnet model core, characterized in that: It comprises the following steps: S1, preparing a substrate: according to the product shape characteristics, an alloy substrate is processed by wire cutting or numerical milling technology; S2, developing a robot automatic walking track: according to the product shape characteristics, a robot continuous automatic walking track is developed; S3, high-temperature preheating treatment of the substrate: before additive manufacturing, the substrate is placed in a high-temperature furnace, heated to 600-800℃, and kept for 30-40 minutes for high-temperature preheating treatment; S4, laser additive of the non-magnetic layer of the substrate: the alloy substrate preheated in step S3 is taken out of the high-temperature furnace and fixed on the chuck on the two-axis turntable, and laser additive manufacturing is started while hot, and the laser additive walking track is step S2; S5, high-temperature annealing treatment of the manufactured cladding non-magnetic product: after additive manufacturing, the product is taken off from the chuck of the two-axis turntable and quickly placed in another high-temperature furnace, the furnace temperature is set to 500℃, and the stress relief annealing treatment is kept for 3-5h; S6, post-processing: after the annealing treatment in step S5, the additive manufactured non-magnetic layer product is machined to realize forming; The step S2 further comprises the following steps: S2.1: a "6+2" axis robot system composed of a KUKA six-axis linkage mechanical arm and a two-axis turntable is used for trajectory programming, a trajectory program is developed by using a matching Workvisual software, according to the shape characteristics of the non-magnetic layer, straight line walking is used for the two side upturned parts, and continuous multi-segment line walking mode is used for the middle curved convex part; the straight line walking needs to determine the starting positioning points LP1 and LP2 in advance, the multi-segment line walking needs to determine the positioning points RP1-RP7, the initial positions of the LP1 and LP2 are respectively located at the two side corners of one end of the substrate needing laser additive non-magnetic layer, and the positions of the positioning points RP1-RP7 are that the arc of the middle curve is divided into 6 parts, and the 7 points are positioned in this way; S2.2: a plurality of straight lines and a plurality of cladding curves are constructed by offset and loop statements to form a walking track; The loop statement is a for loop, for i=1 to n, n is the number of loops, and the offset statement is: XRP1.Y=XRP1.Y+spacing, XRP2.Y=XRP2.Y+spacing, XRP3.Y=XRP3.Y+spacing, XRP4.Y=XRP4.Y+spacing, XRP5.Y=XRP5.Y+spacing, XRP6.Y=XRP6.Y+spacing, XRP7.Y=XRP7.Y+spacing; Wherein spacing is the offset amount; offset amount=single cladding width*60%; S2.3: In the curved surface cladding process, the cladding speed of two sides is set to be fast and the middle is slow to obtain more uniform forming thickness of the curved surface, the middle cladding speed is 0.7-0.9 m / s, and the two sides are 1.0-1.2 m / s; the RP1-RP2 and RP5-RP6 are defined as the two sides of the middle curved surface, and the RP3-RP4 are defined as the middle of the middle curved surface; In the step S4, additive manufacturing is performed by using a coaxial powder feeding laser cladding system; the laser processing head in the coaxial powder feeding laser cladding system is arranged obliquely, so that each processing position of the base body is in a vertical relationship with the laser processing head.

2. A method of laser additive manufacturing of a non-magnetic layer of a permanent magnet model core according to claim 1, characterized in that: The initial laser power of the coaxial powder feeding laser cladding system is 2500W, then each middle curved surface is cladded by one pass with a decrease of 17W, and finally the power is stabilized at 1548W.

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