CN114603158A - Method for improving structure and performance of alloy steel deposit layer manufactured by laser fuse additive manufacturing - Google Patents
Method for improving structure and performance of alloy steel deposit layer manufactured by laser fuse additive manufacturing Download PDFInfo
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- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/60—Treatment of workpieces or articles after build-up
- B22F10/64—Treatment of workpieces or articles after build-up by thermal means
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/20—Direct sintering or melting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/20—Post-treatment, e.g. curing, coating or polishing
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Abstract
The invention provides a method for improving the structure and performance of an alloy steel deposit layer manufactured by laser fuse additive manufacturing, which comprises the steps of carrying out pulse current treatment on the alloy steel deposit layer manufactured by the laser fuse additive manufacturing, cutting the alloy steel deposit layer into cuboid small samples with the same volume by a wire electric discharge machine to carry out pulse current treatment, leading the thermal expansion of the materials to be far behind the temperature rise due to high energy input in a short time of the pulse current, thereby generating instant hot-pressing stress, generating crack healing effect under the combined action of the hot-pressing stress and the Joule heat effect, improving the nucleation rate by the pulse current, generating a large number of crystal nuclei in a short time, inhibiting the growth of the crystal grains, realizing the refinement of the crystal grains, reducing the processing stress and the brittleness of a metal material by the pulse current, improving the tensile strength and the elongation rate, therefore, the aims of improving the structure of alloy steel manufactured by laser fuse additive manufacturing and improving the mechanical property of the alloy steel by pulse current treatment are fulfilled.
Description
Technical Field
The invention belongs to the field of post-treatment of metal laser fuse additive manufacturing, and particularly relates to a method for improving the structure and performance of a deposition layer of alloy steel manufactured by laser fuse additive manufacturing.
Background
Additive Manufacturing (AM) is a manufacturing technology based on the principle of 'discrete-accumulation', adopts a material layer-by-layer accumulation method to manufacture a 3D metal component through a computer aided design model, and is widely applied in the fields of aerospace, energy power, national defense and military industry and the like. The AM has been developed rapidly in recent years due to the fact that the AM can be used for rapidly manufacturing parts with complex geometric shapes and structures, production time is saved, efficient material utilization rate is achieved, expensive machining tools and clamps are basically not needed, production cost is low, and the like. AM is gradually becoming an economical and efficient production method in the small-lot production of high-value parts.
The laser fuse wire additive manufacturing technology (LMD) is a process of gradually forming a three-dimensional entity by using laser as an energy source and metal wire materials as raw materials and realizing the accumulation from point to line to surface through digital automatic control. The metal wire has low use cost, high use efficiency, cleanness and no pollution. In the laser fuse wire additive manufacturing process, a metal wire is heated and melted on a substrate to form a molten pool, the substrate and a deposition layer are continuously heated, and the heat dissipation effect of the former deposition layer is weaker and weaker along with the increase of the forming height, so that the thermal conditions of each layer of a workpiece are different and the workpiece undergoes a plurality of thermal cycles. In the process, the melting, solidification and cooling of the wire are carried out in a short time, which causes a large temperature gradient between a molten pool and a substrate, generates thermal stress and residual stress, and further easily forms cracks, pores, poor interlayer bonding and other defects in a metal deposition layer, and finally causes the reduction of the mechanical property of a workpiece. Therefore, how to reduce or eliminate the defects in the laser fuse additive manufacturing process, improve the structure morphology of the alloy steel component manufactured by the laser fuse additive manufacturing process, and improve the mechanical properties of the alloy steel component is a research hotspot in the field of laser fuse additive manufacturing at present.
In order to improve the structure and the morphology of a deposited layer in the additive manufacturing process of a laser fuse and improve the mechanical property of the deposited layer, various treatment modes are proposed, such as a traditional heat treatment mode, namely a tempering treatment mode, to improve the residual stress and the like in the additive manufacturing structural part of the laser fuse. However, the conventional heat treatment method is not capable of processing large-sized structural members due to its slow heating speed and the limitation of the size of the heat treatment device during the treatment process. Based on this, a method capable of rapidly performing heat treatment, pulse current treatment, has been developed. The laser fuse additive manufacturing alloy steel is subjected to pulse current treatment, so that good effects can be obtained. The pulse current treatment is a new method for drastically changing the structure and mechanical properties of metal materials by using high-density electronic charges, and is commonly used for realizing the superplasticity of alloys, healing of internal defects of the materials, improvement of the surface properties of structural parts and the like. Pulsed current processing has found application in many materials. For example, the function of applying pulse current to the titanium alloy in the stretching process greatly improves the deformability of the titanium alloy and realizes the superplasticity of the titanium alloy. The high-energy pulse current technology has the characteristics of high heating speed, short heat preservation time, energy conservation and the like, and has better effects on the aspects of tissue improvement, recrystallization, phase transformation, material damage healing, improvement of the fatigue performance of metal materials and the like, because the pulse current treatment special electric pulse heating mode is incomparable with the traditional heat treatment method. Therefore, aiming at the problem of large and thick columnar crystals easily generated in the laser fuse additive manufacturing process, the pulse current is introduced into the laser fuse additive manufacturing field to refine the grain size of a deposition layer in the laser fuse additive manufacturing process and improve the mechanical property of the deposition layer.
Disclosure of Invention
The invention aims to provide a method for optimizing the structure and the performance of an alloy steel deposition layer manufactured by laser fuse additive manufacturing, which is to perform pulse current treatment on the alloy steel deposition layer manufactured by the laser fuse additive manufacturing. Due to the high energy input of the pulse current in a short time, the thermal expansion of the material is far delayed from the temperature rise, so that the instantaneous thermal compression stress is generated. The combined action of the thermal compression stress and the joule heat effect can generate the crack healing effect. And the pulse current can also improve the nucleation rate, a large number of crystal nuclei appear in a short time, and the growth of crystal grains is inhibited, so that the refinement of the crystal grains is realized. Therefore, the problems of tissue nonuniformity and poor mechanical properties in the deposited layer of the alloy steel produced by the laser fuse additive manufacturing can be improved by using a pulse current treatment method.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for improving the structure and performance of an alloy steel deposit layer manufactured by laser fuse additive manufacturing is characterized in that pulse current processing is applied to the field of alloy steel thin-walled parts manufactured by laser fuse additive manufacturing; the method comprises the following specific steps:
(1) forming an alloy steel thin-wall part by a laser fuse additive manufacturing technology;
(2) preparing a pulse current sample by using a wire cut electric discharge machine;
(3) clamping two ends of a sample on a positive electrode and a negative electrode of pulse current equipment respectively to form a closed loop;
(4) adjusting parameters of the pulse current to perform energization heating treatment on the sample;
(5) after the pulse current treatment, the sample is cooled to the ambient temperature and then is manually taken down;
high energy input in a short time of pulse current enables the thermal expansion of the material to be far delayed from temperature rise, so that instant hot-pressing stress is generated, and a crack healing effect can be generated under the combined action of the hot-pressing stress and the joule heating effect; the pulse current generates a large number of crystal nuclei in a short time to inhibit the growth of crystal grains, thereby realizing the refinement of the crystal grains.
The parameters of the electric pulse treatment applied in step (4) are: the pulse time is 40s-120s, the pulse frequency is 90Hz-200Hz, and the pulse voltage is 50V-100V.
The parameters of the electric pulse treatment applied in step (4) were: the pulse time is 90s, the pulse frequency is 200Hz, and the pulse voltage is selected from 64V, 71V and 81V.
And (5) cooling in an air cooling mode, wherein the ambient temperature is room temperature.
After the alloy steel sample manufactured by the laser fuse wire additive manufacturing is subjected to pulse current treatment, the elongation rate is more than 30% of that of the sample which is not subjected to pulse current treatment, and the microhardness, yield strength and tensile strength are improved by more than 13%.
The invention has the advantages and beneficial effects that:
(1) the alloy steel member manufactured and formed by the laser fuse wire additive manufacturing has the advantages of high deposition efficiency, high material utilization rate, low cost, short period, smooth surface of the deposition layer and few internal pore defects, and can be used as a common means for forming alloy steel.
(2) The alloy steel component manufactured by the laser fuse additive manufacturing method is heated by a pulse current technology, has the characteristics of short heating time, high cooling speed and the like, and can effectively improve the structure and the performance of the alloy steel deposited layer manufactured by the laser fuse additive manufacturing method.
(3) After laser leaves a molten pool, the alloy steel component manufactured and formed by laser fuse additive manufacturing has extremely high cooling speed, and supercooled austenite generates solid phase transformation to generate a martensite structure and present lath martensite characteristics. The heating temperature at the bottom of the deposition layer exceeds AC3Since the heat dissipation speed of the substrate is faster than that of the melt, a fine acicular martensite structure is generated, and the structure is disordered and coarse in grains. When the laser fuse additive manufacturing alloy steel deposition layer is heated to above 600 ℃ through the pulse current technology, high-temperature tempering can occur inside the deposition layer, and a typical tempering structure, namely a tempered sorbite, is generated. When the tempering is carried out at the temperature of more than 600 ℃, the characteristics of the martensite of the top and middle laths of the deposition layer are completely disappeared to form an equiaxial alpha phase, at the moment, the aggregation, the growth and the spheroidization of carbides occur, and meanwhile, obvious spherical cementite appears on the boundary of the tempered sorbite. The pulsed current treatment greatly improves the texture non-uniformity of the laser fuse additive manufacturing alloy steel deposit.
(4) After the pulse current treatment, the material can generate larger temperature rise and Joule heat, has larger hot-pressing stress, and under the double actions of temperature gradient and stress gradient, the power for driving the atom diffusion in the deposition layer is larger, so that the healing and the repairing of some local defects are extremely favorable.
Drawings
FIG. 1 is a schematic diagram of a pulsed current system apparatus; wherein 1 is a high-energy pulse power supply, 2 is a clamp, and 3 is an alloy steel component
FIGS. 2a-c illustrate a conventional laser fuse additive manufacturing alloy steel structure; wherein fig. 2a is the microstructure of the top of the sediment layer, fig. 2b is the microstructure of the middle of the sediment layer, and fig. 2c is the microstructure of the bottom of the sediment layer;
FIGS. 3a-c are laser fuse additive manufacturing alloy steel structures after pulsed current treatment; wherein fig. 3a is the microstructure of the top of the sediment layer, fig. 3b is the microstructure of the middle of the sediment layer, and fig. 3c is the microstructure of the bottom of the sediment layer.
Detailed Description
In order to make the technical solution of the present invention more clear, further detailed description is provided herein.
The invention relates to a method for manufacturing alloy steel by using pulse current processing to assist laser fuse material increase, which can effectively improve the structure and performance of alloy steel components manufactured by laser fuse material increase and solve the problems of uneven structure and relatively poorer mechanical property caused by overlarge temperature gradient and high cooling speed when the alloy steel components are manufactured by laser fuse material increase.
The method for improving the structure and the performance of the alloy steel deposition layer manufactured by the laser fuse wire additive manufacturing comprises the steps of cutting an alloy steel thin-wall piece manufactured by the laser fuse wire additive manufacturing into cuboid samples with the same volume size by using a wire cut electric discharge machine, clamping two ends of the cut samples at a positive electrode and a negative electrode of pulse current equipment respectively to form a closed loop, adjusting parameters of the pulse current to perform electrifying and heating treatment on the samples, after the treatment is completed, cooling the samples to room temperature in an air cooling mode, and manually taking down the samples. The method comprises the following specific steps:
and S1, searching and selecting appropriate laser fuse additive manufacturing alloy steel forming process parameters, and forming the alloy steel single-channel multilayer sample by using the laser fuse additive manufacturing technology.
S2, selecting a single-channel multilayer sample with good surface quality, and cutting the sample by using a wire cut electrical discharge machine, wherein the requirements on the length and the width of the sample are strict, and the thickness of the sample is unified and standardized.
S3, before pulse current treatment, the electrode clamps with two symmetrical ends are spaced at a certain distance to enable the alloy steel sample to be placed in the middle of the pulse current electrode clamps, the distance between the electrode clamps is adjusted to compact the surface of the sample, pulse current parameters are set, pulse current heating treatment is carried out, and then air cooling is carried out to room temperature.
The invention also comprises such features:
the laser fuse additive manufacturing alloy steel process parameters in the step S1 include: laser power, scanning speed, wire feeding angle, defocusing amount, spot diameter, gas flow and other parameters; the samples in the step S2 have uniform dimensions, including length, width, and thickness; the parameters of the pulse current system in step S3 include: pulse voltage, pulse time, pulse frequency.
The laser power control range of the laser fuse additive manufacturing system is 2000W-2500W.
The scanning speed control range of the laser fuse additive manufacturing system is 2.5-6.5 mm/s
The wire feeding speed control range of the laser fuse additive manufacturing system is 10mm/s-20 mm/s.
The defocusing amount of the laser fuse wire additive manufacturing system is 50mm, the diameter of a light spot is 0.75mm, and the gas flow is 25L/min.
The pulsed current samples were of the same size and had a length of 100mm, a width of 10mm and a thickness of 3 mm.
The pulse voltage control range of the pulse current system is 50V-100V.
The pulse time control range of the pulse current system is 40-120 s.
The pulse frequency control range of the pulse current system is 90Hz-200 Hz.
Example 1:
first, preparation for laser fuse additive manufacturing. Before the laser fuse wire additive manufacturing, an angle grinder is needed to polish the substrate, then medical cotton wetted by alcohol is used for cleaning the substrate of the alloy steel member, oil stains on the surface of the substrate are removed, and the alcohol used by matching with the medical cotton is absolute ethyl alcohol with the content of not less than 99.7%. The angle grinder and alcohol cotton are used for grinding and cleaning the surface of the substrate on which the alloy steel component is deposited, so that the influence of other factors on the laser fuse additive manufacturing of the formed alloy steel component can be reduced to the greatest extent.
And secondly, performing laser fuse additive manufacturing on the formed alloy steel component. The experimental substrate is a Q235 carbon steel plate, and the diameter of the GHS785L alloy steel wire is 1.2 mm. Reasonably planning the path of the workpiece according to the shape of the workpiece and setting related laser fuse additive manufacturing process parameters, wherein the specific process parameters are 2500W of laser power, 4.5mm/s of scanning speed and 20mm/s of wire feeding speed. The final laser fuse additive manufacturing thin-walled part has the forming height of 60mm and 70 layers.
And thirdly, preparing for pulse current processing. The clamps 2 at two ends of the alloy steel component 3 are respectively connected with the high-energy pulse power supply 1, and the pulse current is sent out from the positive pole of the high-energy pulse power supply 1 and returns to the negative pole of the high-energy pulse power supply 1 through the clamps 2 and the alloy steel component 3 to form a complete current loop.
And fourthly, switching on the pulse power supply. And (3) switching on a high-energy pulse power supply 1, passing current through the clamp 2 and the alloy steel component 3, and selecting a pulse frequency of 200Hz, a pulse time of 90s and a pulse voltage of 64V. The high-energy pulse power supply 1 enables stable current to pass through the interior of the alloy steel component 3 all the time in the whole processing process, and the pulse current can effectively improve the movement of dislocation in the alloy steel component, so that the plastic deformation capacity of the alloy steel component is enhanced.
Example 2:
first, preparation for laser fuse additive manufacturing. Before the laser fuse wire additive manufacturing, an angle grinder is needed to polish the substrate, then medical cotton wetted by alcohol is used for cleaning the substrate of the alloy steel member, oil stains on the surface of the substrate are removed, and the alcohol used by matching with the medical cotton is absolute ethyl alcohol with the content of not less than 99.7%. The angle grinder and alcohol cotton are used for grinding and cleaning the surface of the substrate on which the alloy steel component is deposited, so that the influence of other factors on the laser fuse additive manufacturing of the formed alloy steel component can be reduced to the greatest extent.
And secondly, performing laser fuse additive manufacturing on the formed alloy steel component. The experimental substrate is a Q235 carbon steel plate, and the diameter of the GHS785L alloy steel wire is 1.2 mm. Reasonably planning the path of the workpiece according to the shape of the workpiece and setting related laser fuse additive manufacturing process parameters, wherein the specific process parameters are 2500W of laser power, 4.5mm/s of scanning speed and 20mm/s of wire feeding speed. The final laser fuse additive manufacturing thin-walled part has the forming height of 60mm and 70 layers.
And thirdly, preparing for pulse current processing. The clamps 2 at two ends of the alloy steel component 3 are respectively connected with the high-energy pulse power supply 1, and the pulse current is sent out from the positive pole of the high-energy pulse power supply 1 and returns to the negative pole of the high-energy pulse power supply 1 through the clamps 2 and the alloy steel component 3 to form a complete current loop.
And fourthly, switching on the pulse power supply. And (3) switching on a high-energy pulse power supply 1, passing current through the clamp 2 and the alloy steel component 3, and selecting a pulse frequency of 200Hz, a pulse time of 60s and a pulse voltage of 78V. The high-energy pulse power supply 1 enables stable current to pass through the interior of the alloy steel component 3 all the time in the whole processing process, and the pulse current can effectively improve the movement of dislocation in the alloy steel component, so that the plastic deformation capacity of the alloy steel component is enhanced.
After the alloy steel sample manufactured by the laser fuse wire additive manufacturing is subjected to pulse current treatment, the elongation rate is more than 30% of that of the sample which is not subjected to pulse current treatment, and the microhardness, yield strength and tensile strength are improved by more than 13%.
The invention provides a method for improving the structure and the performance of an alloy steel deposition layer manufactured by laser fuse additive manufacturing. The invention belongs to the field of post-treatment of metal laser fuse wire additive manufacturing. After the alloy steel deposition layer is manufactured by laser fuse wire additive manufacturing, cuboid small samples with the same volume are cut by a wire-electrode cutting machine and are subjected to pulse current processing. Due to the high energy input of the pulse current in a short time, the thermal expansion of the material is far delayed from the temperature rise, so that the instantaneous thermal compression stress is generated. The combined action of the thermal compression stress and the joule heat effect can generate the crack healing effect. And the pulse current can also improve the nucleation rate, a large number of crystal nuclei appear in a short time, the growth of crystal grains is inhibited, and the refinement of the crystal grains is realized. The pulse current can also reduce the processing stress and brittleness of the metal material and improve the tensile strength and the elongation rate of the metal material. Therefore, the aims of improving the structure of alloy steel manufactured by laser fuse additive manufacturing and improving the mechanical property of the alloy steel by pulse current treatment are fulfilled.
Claims (5)
1. A method for improving the structure and the performance of a deposited layer of alloy steel manufactured by laser fuse additive manufacturing is characterized in that: applying pulse current treatment to the field of manufacturing alloy steel thin-walled parts by laser fuse wire additive manufacturing; the method comprises the following specific steps:
(1) forming an alloy steel thin-wall part by a laser fuse additive manufacturing technology;
(2) preparing a pulse current sample by using a wire cut electric discharge machine;
(3) clamping two ends of a sample on a positive electrode and a negative electrode of pulse current equipment respectively to form a closed loop;
(4) adjusting parameters of the pulse current to perform energization heating treatment on the sample;
(5) after the pulse current treatment, the sample is cooled to the ambient temperature and then is manually taken down;
high energy input in a short time of pulse current enables the thermal expansion of the material to be far delayed from temperature rise, so that instant hot-pressing stress is generated, and a crack healing effect can be generated under the combined action of the hot-pressing stress and the joule heating effect; the pulse current generates a large number of crystal nuclei in a short time to inhibit the growth of crystal grains, thereby realizing the refinement of the crystal grains.
2. The method for improving the structure and the performance of a laser fuse additive manufacturing alloy steel deposition layer as claimed in claim 1, wherein: the parameters of the electric pulse treatment applied in step (4) are: the pulse time is 40s-120s, the pulse frequency is 90Hz-200Hz, and the pulse voltage is 50V-100V.
3. The method for improving the structure and the performance of the alloy steel deposition layer manufactured by the laser fuse additive manufacturing method according to claim 2, wherein the method comprises the following steps: the parameters of the electric pulse treatment applied in step (4) are: the pulse time is 90s, the pulse frequency is 200Hz, and the pulse voltage is selected from 64V, 71V and 81V.
4. The method for improving the structure and the performance of a laser fuse additive manufacturing alloy steel deposition layer as claimed in claim 1, wherein: and (5) cooling in an air cooling mode, wherein the ambient temperature is room temperature.
5. The method for improving the structure and the performance of a laser fuse additive manufacturing alloy steel deposition layer as claimed in claim 1, wherein: after the alloy steel sample manufactured by the laser fuse wire additive manufacturing is subjected to pulse current treatment, the elongation rate is more than 30% of that of the sample which is not subjected to pulse current treatment, and the microhardness, yield strength and tensile strength are improved by more than 13%.
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| CN115386845A (en) * | 2022-08-30 | 2022-11-25 | 江苏大学 | Device and method for pulse current assisted laser directional energy deposition |
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| CN113249668A (en) * | 2021-04-30 | 2021-08-13 | 哈尔滨工程大学 | Method for improving anisotropy of additive manufacturing titanium alloy by using pulse current |
| GB202107880D0 (en) * | 2021-06-02 | 2021-07-14 | Rolls Royce Plc | Method |
| CN113579251A (en) * | 2021-07-26 | 2021-11-02 | 南京工业大学 | Treatment method for improving tissue performance on line based on electric pulse auxiliary material increase manufacturing aluminum and aluminum-lithium alloy |
| CN113667915A (en) * | 2021-07-27 | 2021-11-19 | 四川大学 | Treatment method for improving fatigue life of titanium alloy by using pulsed magnetic field treatment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115386845A (en) * | 2022-08-30 | 2022-11-25 | 江苏大学 | Device and method for pulse current assisted laser directional energy deposition |
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