Novel method for preparing metal product by additive
Technical Field
The invention belongs to the field of metal additive manufacturing, and relates to a novel method for preparing a metal product by additive manufacturing.
Background
The additive manufacturing technology is also called as 3D printing technology, and adopts a discrete accumulation principle, according to a three-dimensional digital model of a part to be manufactured, the part is layered according to a certain thickness, sheets are continuously processed in a planar mode, and finally the sheets are superposed to form the final three-dimensional part. Compared with other traditional manufacturing technologies, the method has the characteristics of novel forming concept, strong technical adaptability, realization of function-first design and the like.
At present, 3D printing products are mainly divided into the following five types:
1. appearance piece and scaling show piece only have the show function, do not possess actual operation function.
2. Non-load bearing members, such as metal jewelry, can be used but do not bear load.
3. Weak load-bearing parts such as metal implants for medical applications, medical splints, etc.
4. The secondary bearing part is a part which bears force but does not have extra strength. Such as aluminum alloy die casting dies, and 3D printing hatches, seats, etc. used on airplanes.
5. The main bearing part is divided into two parts (1) which bear large force in the use process, for example, a landing frame (2) of an airplane is a key part regardless of the bearing force in the use process, and the key part is also called as a key part.
The first four types of metal 3D printed products enter a substantial use stage at present, but the metal 3D printed main force-bearing part product still stays in an experimental stage. This is because the metal 3D printing and forming process is a complex physical and chemical metallurgical process. The defects of overlarge or undersize dilution rate of a molten layer, holes, cracks, rough surface, coarse grains, poor compactness of a formed part and the like often occur in the forming process. Due to the frequent occurrence of the defects, the metal 3D printing main bearing part can only stay in the experimental stage.
The laser shock peening technology (laser shot peening technology) is a technology for irradiating a metal surface coating by using a high-intensity laser beam, wherein the laser plasma impacts the metal surface, and the excited plasma is used as a shot peening medium to strengthen the laser shock peening (laser shot peening) on the metal surface.
At present, the metal 3D printed matter is subjected to post-treatment strengthening by a laser shock strengthening technology (laser shot blasting technology), but the strengthening depth is limited due to the limited penetration capability of laser, and only the surface strengthening can be realized for parts with large processing depth. Secondly, the printed and formed part is in a complete solidification state, the laser shock peening technology (laser shot blasting technology) belongs to a plastic processing mode, and the phenomenon that the strengthening performance is not obvious when the printed and formed part is strengthened by adopting the laser shock peening technology (laser shot blasting) can occur.
Disclosure of Invention
The invention aims to provide a novel method for eliminating the defects of cracks, pores, coarse grains and the like generated in the 3D printing and forming process of metal and obtaining a metal product with high strength and high hardness.
The novel method for preparing the metal product in the additive mode, which is provided by the invention, prepares the metal product by combining metal 3D printing and laser shot blasting, introduces laser shot blasting treatment in the printing and forming process and comprises the following steps:
(1) drawing the design drawing into a three-dimensional model by using drawing software according to the product design drawing;
(2) carrying the three-dimensional model drawn in the step (1) into slicing software, setting printing parameters and generating a corresponding G code;
(3) and (3) substituting the G code generated in the step (2) into an upper computer, and controlling 3D printing and forming equipment to print and form a product.
In one embodiment of the method, the metal 3D printing and forming device is a laser near-net forming device, the laser of the laser near-net forming device is a continuous laser, and the continuous laser is used for printing, forming and shot blasting, the laser of the laser near-net forming device includes a continuous laser and a pulse laser, and the continuous laser is used for printing, forming and the pulse laser is used for laser shot blasting.
In one embodiment of the method, the laser has an external control function, the diameter of a light spot of the laser is 1-3 mm adjustable, and the laser power is 0-5 kw and is continuously adjustable.
In one embodiment of the above method, the laser cladding head of the laser is three-channel or four-channel, wherein two channels of the three channels send powder and one channel sends shielding gas, and two channels of the four channels send powder and two channels send shielding gas.
In one implementation mode of the method, the powder feeder of the metal 3D printing and forming equipment is a single-cylinder or double-cylinder powder feeder, the powder feeding amount is adjustable within 0-10 r/min, and the powder feeder has an external control function.
In one embodiment of the method, the shielding gas used by the metal 3D printing and forming equipment is argon gas which is mainly used for feeding powder, generating plasma and preventing molten pool oxidation.
In one embodiment of the above method, the method is directed to a thickness of the print substrate of not less than 10 mm.
In one embodiment of the above method, the printing parameters in step (2) include printing power, printing spot diameter, scanning power, powder feeding amount, layer thickness, laser peening mode, laser peening power level, and laser peening spot size.
In one embodiment of the above method, when the laser of the laser near-net forming device is a continuous laser, the laser peening mode is to perform laser peening once after each layer is printed and formed, and when the laser adopts a laser and a pulse laser, the laser peening mode is to perform laser peening on the cladding body by the pulse laser while printing and forming by the continuous laser.
The invention combines the metal 3D printing technology with the laser shock peening (laser shot peening) technology, and introduces the laser shot peening treatment in the printing and forming process. After each layer of metal cladding body is stacked, the metal cladding body is subjected to laser shock strengthening, namely, the laser shock strengthening is carried out in the state that each layer of forming layer is not completely solidified, or the laser shock strengthening is carried out while printing and forming are carried out, so that the organization structure of the metal cladding body is tighter, crystal grains are further refined, the problems of holes, cracks, surface spheroidization, coarse crystal grains and the like in the conventional metal 3D printing forming part are solved, a high-strength high-hardness metal product with excellent performance is obtained, and the 3D metal printing main bearing part can enter a substantial use stage.
Drawings
FIG. 1 is a schematic representation of a three-dimensional model of the product to be prepared in example 1.
FIG. 2 is a morphology chart of printing material GH4169 powder used in example 1.
FIG. 3 is a macro topography of the laser shock peening (laser peening) forming die used in example 1.
FIG. 4 is a macro topography of a forming die without laser shock peening (laser peening) used in example 1.
FIG. 5 is a cross-sectional profile view of FIG. 3.
FIG. 6 is a cross-sectional profile view of FIG. 4.
FIG. 7 is a microstructure topography of the forming blade die of FIG. 3.
FIG. 8 is a microstructure topography of the forming blade die of FIG. 4.
Fig. 9 is a schematic three-dimensional model of another cutting die to be prepared in example 2.
FIG. 10 is a graph showing the morphology of the stainless steel powder used as the printing material 420 in example 2.
Fig. 11 is a printed molding of example 2.
Fig. 12 is a die product of the molded article of fig. 11 with a final cut blade.
Detailed Description
The novel method for preparing the metal product in the additive mode, which is provided by the invention, adopts a mode of combining metal 3D printing and laser shock peening (laser shot peening) to prepare the metal product, and introduces laser shot peening treatment in the printing and forming process, and comprises the following steps:
(1) drawing the design drawing into a three-dimensional model by using drawing software according to the product design drawing;
(2) carrying the three-dimensional model drawn in the step (1) into slicing software, setting printing parameters and generating a corresponding G code;
(3) and (3) substituting the G code generated in the step (2) into an upper computer, and controlling 3D printing and forming equipment to print and form a product.
Example 1, this example prepares a cutting die according to the present invention by the method provided, and the specific steps are as follows:
step 1, drawing a three-dimensional model:
drawing a corresponding three-dimensional model by utilizing drawing software such as Solidworks and the like according to a two-dimensional drawing of a cutting die, and generating a file in stl format as shown in figure 1;
step 2, material selection:
according to the material pressed and cut by the cutter, the corresponding material is selected, GH4169 spherical powder is selected in the example, the particle size is 75-150 μm, the microscopic structure of the raw material is shown in figure 2, 316L stainless steel is selected as the base material, and the thickness of the base is 10 mm.
Step 3, setting parameters:
importing the stl file into slicing software, setting laser power to be 600W, scanning speed to be 600 mm/min, powder feeding amount to be 0.3r/min and layer thickness to be 0.3mm, carrying out laser shock peening (laser shot peening) once for each formed layer in a laser shock peening (laser shot peening) mode, adopting a single laser cladding head, setting the laser shock peening (laser shot peening) power to be 200W, switching-off time of laser to be 50 femtoseconds, and carrying out shot peening once to generate a corresponding G code;
step 4, printing and forming:
the 3D printing forming equipment adopts conventional laser near-net forming equipment comprising a laser, a laser cladding head, a numerical control machine tool, a powder feeder, a water cooler and a shielding gas cylinder, wherein the laser adopts a continuous laser, corresponding modification of the step 3 needs to be carried out on control software after the continuous laser is purchased, the laser cladding head of the laser can adopt three channels or four channels, the three channels can be used for feeding powder, one channel can be used for feeding shielding gas, and the four channels can be used for feeding powder, and the two channels can be used for feeding shielding gas. The powder feeder is a single-cylinder or double-cylinder powder feeder, the powder feeding amount is adjustable within 0-10 r/min, and the powder feeder has an external control function. The protective gas adopts argon gas, and is mainly used for powder feeding, generating plasma and preventing the molten pool from being oxidized.
And (4) introducing the G code generated in the step (3) into an upper computer, setting the flow rate of the protective gas to be 15L/min, and starting printing until forming, wherein the forming cutter die is shown in figure 3.
FIG. 3 is a macroscopic view of the molded article strengthened by laser shock peening (laser peening) according to the present embodiment, and it can be seen that the surface of the molded article is smooth and exhibits good metallic luster.
Fig. 4 is a macro-topography of a formed part without laser shock peening (laser peening), which shows that the surface is spheroidized and does not show good metallic luster.
FIG. 5 is a cross-sectional view of a laser shock peening (laser peening) formed part, showing the absence of voids, sand inclusion, and other defects in the cladding layer.
FIG. 6 is a cross-sectional view of a formed part without laser shock peening (laser peening), which shows the occurrence of voids, sand-containing defects in the cladding layer.
FIG. 7 is a microstructure diagram of a laser shock peening (laser peening) molded part, which shows the defects of fine grains, compact structure, no holes, etc.
FIG. 8 is a microstructure pattern of a molded article without laser shock peening (laser peening), and it can be seen that the crystal grains are coarse and have defects such as voids.
As is clear from the comparison, in the present embodiment, after each metal layer is printed, laser shock peening (laser shot peening) is performed once, and the obtained formed part has a smooth surface, exhibits good metal luster, and has defects of no holes, sand content and the like in the cladding layer, and defects of fine microstructure grains, compact structure, no holes and the like. Meets the requirements of high strength and high hardness.
Example 2
This embodiment prepares a cutting die product, and the preparation process includes following steps:
step 1, drawing a three-dimensional model:
drawing a corresponding three-dimensional model by utilizing drawing software such as Solidworks and the like according to a two-dimensional drawing of a cutting die, and generating a file in stl format as shown in FIG. 9;
step 2, material selection:
selecting corresponding materials according to the material of the cutter, wherein 420 stainless steel spherical powder with the particle size of 75-150 μm is selected in the example, the microcosmic raw material is shown in figure 10, 316L stainless steel is selected as the base material, and the thickness of the base is 10 mm;
step 3, setting parameters:
importing an stl file into slicing software, setting the laser power to be 450W, setting the scanning speed to be 400 mm/min, setting the powder feeding amount to be 0.2r/min, setting the layer thickness to be 0.2mm, and generating a corresponding G code by performing laser shock peening (laser peening) in a laser shock peening (laser peening) mode in such a way that the laser shock peening (laser peening) is performed while forming, wherein the laser shock peening (laser peening) energy is 20 joules, the laser pulse time is 25 nanoseconds, and the peening times are once;
step 4, printing and forming:
the 3D printing and forming apparatus of this embodiment differs from embodiment 1 in that the laser employs a continuous laser for printing and forming and a pulsed laser for simultaneously performing laser shock peening (laser peening) on the clad body. Namely, a single cladding head is adopted in the embodiment 1, a double cladding head is adopted in the embodiment, and other configurations and operations of the equipment are the same as those of the embodiment 1. The print forming blade die is shown in fig. 11.
Step 5, cutting blade
The formed cutting die is processed, that is, the cutting edge is cut by a machine tool, and finally the finished cutting die shown in fig. 12 is obtained.
Step 6, performance test
The punching test of the finished product of the cutting die shows that the cutting die is not deformed and the blade edge has no notch after 10 ten thousand times of punching. The product prepared by the process of printing and forming and laser shock peening (laser shot peening) in the embodiment has the advantages of high strength and high hardness, and can be used as a main bearing part.
In summary, the feasibility of the scheme disclosed by the invention is verified from two aspects by two embodiments, and the embodiment 1 verifies that the product obtained by performing sequential laser shock peening (laser shot peening) treatment after each layer is printed has a smooth surface, presents good metal luster, has no defects such as holes and sand in a cladding layer, has fine microstructure grains, a compact structure and no defects such as holes, so that the product has the requirements of high strength and high hardness and excellent performance. Example 2 demonstrates that the product obtained by performing the laser shock peening (laser peening) while printing and molding has excellent properties of high strength and high hardness. Therefore, the scheme disclosed by the invention can enable the 3D response metal product to enter a substantial use stage as a main bearing part.