CN113231646A - Method for preparing GCr15 bearing steel and automobile parts based on electron beam 3D printing technology - Google Patents
Method for preparing GCr15 bearing steel and automobile parts based on electron beam 3D printing technology Download PDFInfo
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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
- B33Y10/00—Processes of additive manufacturing
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- 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
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- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F2003/248—Thermal after-treatment
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Abstract
The invention relates to the technical field of electron beam printing, and discloses a method for preparing GCr15 bearing steel and automobile parts based on an electron beam 3D printing technology; the method comprises the steps that a construction platform is located in a sealed space, the construction platform in the sealed space is guaranteed to be located in a gas pressure environment of 2-3 MPa, electron beam 3D printing is conducted, and a mobile heating device installed on the construction platform is used for conducting uniform dynamic preheating on a printing layer selection area where an electron beam emitting device is located before GCr15 bearing steel powder is melted by the electron beams; preheating to a temperature of 30-50 ℃ below the critical phase transition temperature t; the electron beam 3D printing is specifically: rapidly melting GCr15 bearing steel powder at 1500-2000 ℃ in a printing layer selection area by electron beams; finally, obtaining a workpiece made of GCr15 bearing steel; the method provided by the invention can ensure that the printing layer is heated uniformly, and the GCr15 bearing steel workpiece with excellent density is prepared.
Description
Technical Field
The invention relates to the technical field of electron beam printing, in particular to a method for preparing GCr15 bearing steel and automobile parts based on an electron beam 3D printing technology.
Background
The Selective Electron Beam Melting (SEBM) technique is a forming process for 3D printing of metal materials, and is a 3D printing technique very similar to SLS, and the used material is conductive metal. GCr15 is a typical representative of bearing steel, has high hardness and excellent frictional wear performance, and is widely applied to parts such as internal combustion engines, electric locomotives, steel rolling equipment, various transmission shafts, shaft sleeves and the like. EBM typically uses titanium alloys and cannot print GCr15 bearing steel parts. This is due to the charge upon which the entire process is based. EBM requires conductive metals because the technology itself is charge-based. In other words, the charge is responsible for reacting the powder with the electron beam, thereby curing the powder. The EBM3D printing process begins by filling the powder hopper with the required metal powder. After completion, the powder box was placed into the 3D printer where the heating phase was initiated. The powder needs to be heated just below its melting point before printing. The electron beam is controlled by a set of solenoids that selectively move as the powder is melted, fusing the powder particles together.
In the prior art, only a printing layer is locally heated, so that the heating is uneven and the risk of distortion exists; due to the fact that the melting point of GCr15 bearing steel is high, the phenomenon of uneven heating can be further amplified, the distortion risk is high, and the comprehensive performance of GCr15 bearing steel is reduced;
in the prior art, the printing process is carried out in vacuum, mainly for preventing the powder from being oxidized at high temperature; due to the limitation of the vacuum space, the size of the printed workpiece cannot be further increased, so that workpieces with smaller sizes are usually intelligently printed in the prior art.
Disclosure of Invention
The technical problem solved by the invention is as follows: the GCr15 bearing steel is difficult to print by the electron beam in the prior art, and the problems of nonuniform heating and low density of the obtained workpiece exist in the prior art.
The technical scheme of the invention is as follows:
a method for preparing GCr15 bearing steel and automobile parts based on an electron beam 3D printing technology comprises the following steps:
step 1: stock preparation
Selecting GCr15 bearing steel powder as a raw material for electron beam 3D printing; then testing the critical phase transition temperature t of the GCr15 bearing steel powder;
step 2: CAE treatment of workpiece models
Using Auto CAD to construct and print a three-dimensional structure model, adding support to the constructed three-dimensional structure model, and adopting CAE technology to analyze thermodynamics and statics so as to optimize the support of the three-dimensional structure model; then slicing the three-dimensional structure model by using slicing software, and guiding the sliced model into electron beam 3D printing equipment;
and step 3: electron beam 3D printing
Firstly, adding GCr15 bearing steel powder prepared in the step 1 into a powder container of an electron beam 3D printing device, and then preheating a building platform;
the construction platform is positioned in a sealed space, and high-purity argon is filled in the sealed space; ensuring that a construction platform in the sealed space is in a gas pressure environment of 2-3 MPa, and performing electron beam 3D printing to obtain a workpiece made of GCr15 bearing steel;
before the GCr15 bearing steel powder is melted by the electron beams, a mobile heating device arranged on a construction platform is used for uniformly and dynamically preheating a printing layer selection area where an electron beam emitting device is located; preheating to a temperature within a range of 30-50 ℃ below the critical phase transition temperature t;
before the GCr15 bearing steel powder is melted by the electron beam, an electron beam limiting cylinder is used for controlling the uniformity of the electron beam dose and the radiation field;
wherein, electron beam 3D prints specifically is: rapidly melting GCr15 bearing steel powder at 1500-2000 ℃ in a printing layer selection area by electron beams; molten GCr15 bearing steel powder formed a micro-melt pool; after the electron beam leaves, cooling the micro-molten pool area to be below the critical phase transition temperature t at the speed of 50-150 ℃/s;
and 4, step 4: thermal treatment
After the printing in the step 3 is finished, carrying out heat treatment on the obtained workpiece; the heat treatment comprises a first carburizing treatment and a second strengthening treatment;
and 5: determination of the Density
And (4) performing density measurement on the workpiece subjected to heat treatment in the step (4), observing the printed inner hole by using an optical microscope, and evaluating the density of the printed sample.
Further, the GCr15 bearing steel powder raw material adopted in the step 1 has high sphericity and good fluidity, the specific fluidity is 13.6s/50g, and the powder particle size is as follows: 28-66 μm, chemical elements: c: 0.65-0.92%, Cr: 1.70-1.9%, Si: 0.2-0.5%, Mn: 0.25 to 0.45%, Nb: less than or equal to 0.30 percent, Sn: less than or equal to 0.30 percent, Cu: less than or equal to 0.25 percent, Mo: less than or equal to 0.10 percent, Fe: the balance, powder tap density 4.98g/cm3Apparent density of 4.5g/cm3(ii) a Compared with the GCr15 bearing steel element composition in the prior art, the comprehensive performance of the workpiece is better by adjusting the specific content of the element and adding Nb and Sn elements, and the service life and the wear resistance of the workpiece are ensured.
Further, the parameters set by the electron beam in the step 3 when the powder is melted in the selected printing layer area are as follows: the scanning speed is 8-25 m/s; scanning current: 5 mA-10 mA. Because the printing layer is fully heated by adopting the mobile heating device before the electron beam is printed, the temperature of GCr15 bearing steel powder is close to the melting temperature, and the printing speed can be greatly improved; the improvement of the printing efficiency can effectively promote the industrialization process of electron beam metal printing.
Further, the first carburizing treatment includes: heating a workpiece by adopting electromagnetic induction in a vacuum environment, carburizing the surface of the workpiece, and then tempering and quenching; wherein the strong infiltration temperature is 980 ℃ and the time is 30 min; tempering at 170 deg.C for 40 min. The hardness index of the surface of the workpiece can be greatly improved through carburizing and quenching, and the wear resistance of the workpiece is improved; the workpiece can reach the preset temperature in a short time by an electromagnetic induction heating mode, the heat loss is low, and the treatment efficiency is high; compared with the traditional furnace chamber heating, the furnace chamber heating device is beneficial to saving energy and does not cause secondary pollution to the environment.
Further, the second strengthening treatment comprises:
(1) pre-heat treatment: uniformly preheating the surface of the workpiece for 30-60 min by adopting flame;
(2) normalizing: heating the workpiece to 757-857 ℃, carrying out heat penetration on the workpiece, then carrying out heat preservation for 10-20 min, rapidly cooling by adopting water cooling, and immediately converting into spheroidizing annealing;
(3) spheroidizing annealing: the bearing steel is subjected to an isothermal spheroidizing annealing process, wherein the spheroidizing heating temperature is 650-690 ℃, the bearing steel is heated to 800-900 ℃ before annealing, and the bearing steel is subjected to normalizing after heat preservation for 20-35 min;
(4) and (3) cooling: the water-through fast cooling is carried out to 300-450 ℃, the time of the water-through fast cooling is controlled to be 20-30 s,
(5) quenching and tempering: quenching and tempering by using a resistance furnace; wherein, quenching is carried out for 30min at the temperature of 860 ℃ and oil quenching is carried out; tempering at 170 deg.C for 50 min;
(6) cryogenic treatment: and cooling the workpiece for 8-10 hours at-196 ℃ by adopting liquid nitrogen.
The organization structure of the workpiece alloy is effectively improved through the second strengthening treatment, and the hardness and the wear resistance of the workpiece alloy are effectively improved; the cryogenic treatment can improve the hardness, the wear resistance, the dimensional stability and the service life of the workpiece through phase change strengthening and precipitation strengthening; and the method is efficient and pollution-free, and the production cost is relatively low.
Further, the preheating temperature of the building platform is 710 ℃, the electron beam melting beam current is 5mA, and the speed is 1 m/s; the melting rate of the powder at the bottom layer of the construction platform can be improved through preheating, the powder is effectively prevented from splashing, and the density of the workpiece is improved.
Further, after the heat treatment is finished, performing sand blasting treatment on the surface of the workpiece to obtain a formed piece with good surface quality; the surface of the workpiece obtains certain cleanliness and different roughness through surface sand blasting treatment, so that the mechanical property of the surface of the workpiece is improved, and the fatigue resistance of the workpiece is improved.
The electron beam 3D printing device for printing GCr15 bearing steel powder comprises a bottom support, a high-pressure chamber arranged on the bottom support, an argon storage device arranged on the bottom support and connected with the high-pressure chamber, a pressure regulating device arranged at the joint of the high-pressure chamber and the argon storage device, a building platform arranged in the high-pressure chamber, and a printing device arranged above the building platform;
a detection assembly for detecting the pressure of the sealed cabin is arranged in the pressure regulating device; the lower end of the construction platform is provided with a fixed preheating assembly;
the printing device comprises a plurality of supports vertically arranged on a construction platform, a lifting frame movably arranged on the supports, a lifting motor arranged on the supports and used for controlling the lifting frame to lift, a movable heating device fixed on the lifting frame and used for preheating a printing layer selection area, a printer head movably arranged on the lifting frame, and a powder feeding device connected with the printer head;
the printer head comprises a central powder outlet pipe connected with the powder feeding device, two electron beam energy sources symmetrically arranged about a central powder outlet, and two electron beam light limiting cylinders respectively connected with the electron beam energy sources;
the movable heating device comprises a first heating component arranged on the central powder outlet pipe and a second heating component arranged on the lifting frame; the second heating assembly comprises two connecting rods which can be connected with the printing layer respectively, positive and negative electrode strips which are arranged on the two connecting rods respectively, and a power supply which is connected with the positive and negative electrode strips; the first heating assembly adopts an electromagnetic heating assembly.
The invention has the beneficial effects that: the invention provides a method for preparing GCr15 bearing steel and automobile parts based on an electron beam 3D printing technology, wherein a movable heating device and a printer head are positioned at a same height, and a resistance heating principle is utilized, so that a second heating assembly can heat the whole printing layer during printing, and compared with the traditional printing method of heating and melting only in a melting zone, the method can ensure that the whole printing layer is uniformly heated; the printing speed can be greatly improved by combining the first heating assembly to heat at the printer head, and the problem of slow manufacturing speed in the prior art is solved;
according to the electron beam 3D printing device provided by the invention, vacuum printing is replaced by filling argon gas into a sealed space, so that the problem that the forming size of a workpiece is limited by the size of the vacuum space can be effectively solved; the high-pressure environment can prevent oxidation, realize a protection function and improve the density of the workpiece to a certain extent. This device is heated evenly through setting up the second heating element on the crane, combines the setting of electron beam light-limiting section of thick bamboo can effectively improve the printing precision when being heated.
Drawings
FIG. 1 is a schematic structural view of embodiment 1 of the present invention;
FIG. 2 is a schematic view of the structure of a printer head according to embodiment 1 of the present invention;
FIG. 3 is a density detection diagram of a printed workpiece in embodiments 2 to 4 of the present invention;
the device comprises a bottom support 1, a 2 high-pressure cabin, a 3 argon storage device, a 4 pressure regulating device, a 40 detection assembly, a 5 construction platform, a 50 fixed preheating assembly, a 6 printing device, a 60 support, a 61 lifting frame, a 62 lifting motor, a 63 printer head, a 630 central powder outlet pipe, a 631 electron beam energy source, a 632 electron beam light limiting cylinder, a 64 powder feeding device, a 65 movable heating device, a 650 first heating assembly, a 651 connecting rod, a 652 positive and negative electrode electric sheet and a 653 power supply.
Detailed Description
Example 1: an electron beam 3D printing device for printing GCr15 bearing steel powder as shown in fig. 1 and 2 comprises a bottom support 1, a high pressure chamber 2 arranged on the bottom support 1, an argon gas storage device 3 arranged on the bottom support 1 and connected with the high pressure chamber 2, a pressure regulating device 4 arranged at the joint of the high pressure chamber 2 and the argon gas storage device 3, a building platform 5 arranged in the high pressure chamber 2, and a printing device 6 arranged above the building platform 5;
a detection assembly 40 for detecting the pressure of the sealed cabin 2 is arranged in the pressure regulating device 4; the lower end of the construction platform 5 is provided with a fixed preheating assembly 50;
the printing device 6 comprises a plurality of supports 60 vertically arranged on the construction platform 5, a lifting frame 61 movably arranged on the supports 60, a lifting motor 62 arranged on the supports 60 and used for controlling the lifting frame 61 to lift, a movable heating device 65 fixed on the lifting frame 61 and used for preheating a printing layer selection area, a printer head 63 movably arranged on the lifting frame 61, and a powder feeding device 64 connected with the printer head 63;
the printer head 63 comprises a central powder outlet pipe 630 connected with the powder feeding device 64, two electron beam energy sources 631 symmetrically arranged about the central powder outlet 630, and two electron beam light limiting cylinders 632 respectively connected with the electron beam energy sources 631;
the movable heating device 65 comprises a first heating component 650 arranged on the central powder outlet pipe 630 and a second heating component arranged on the lifting frame 61; the second heating assembly includes two connection bars 651 capable of being connected to the printing layers, respectively, positive and negative electrode pads 652 provided on the two connection bars 651, respectively, and a power source 653 connected to the positive and negative electrode pads 652.
The first heating assembly 650 employs an electromagnetic heating assembly.
The electromagnetic heating assembly, the power supply 653, the electron beam limiting cylinder 632, the electron beam energy source 631, the powder feeding device 64, the lifting motor 62, the fixed preheating assembly 50 and the detection assembly 40 are commercially available products in the prior art, and specific product types can be selected by those skilled in the art according to needs.
Example 2:
the embodiment is a method for preparing GCr15 bearing steel and automobile parts by printing by adopting the device in the embodiment 1, and a specific printing sample workpiece is a crankshaft and a connecting rod; wherein the crankshaft is 120mm long and 30mm wide, and the connecting rod is 70mm long and 25mm wide;
the method specifically comprises the following steps:
step 1: stock preparation
The GCr15 bearing steel powder is used as a raw material for electron beam 3D printing; the specific flowability was 13.6s/50g, the powder particle size: 28-36 μm, chemical elements: c: 0.65%, Cr: 1.70%, Si: 0.2%, Mn: 0.25%, Nb: 0.1%, Sn: 0.1%, Cu: 0.1%, Mo: 0.08%, Fe: the balance, powder tap density 4.98g/cm3Apparent density of 4.5g/cm3(ii) a Then testing the critical phase transition temperature t of the GCr15 bearing steel powder;
step 2: CAE treatment of workpiece models
Using Auto CAD to construct and print a three-dimensional structure model, adding support to the constructed three-dimensional structure model, and adopting CAE technology to analyze thermodynamics and statics so as to optimize the support of the three-dimensional structure model; then slicing the three-dimensional structure model by using slicing software, and guiding the sliced model into electron beam 3D printing equipment;
and step 3: electron beam 3D printing
Firstly, adding GCr15 bearing steel powder prepared in the step 1 into a powder container of an electron beam 3D printing device, and then preheating a building platform 5; preheating temperature is 710 ℃, electron beam melting beam current is 5mA, and speed is 1 m/s;
the construction platform 5 is positioned in the sealed space, and the argon storage device 3 is filled with high-purity argon; ensuring that a construction platform in the sealed space is in a gaseous pressure environment of 2MPa, and performing electron beam 3D printing to obtain a workpiece made of GCr15 bearing steel;
wherein, before the GCr15 bearing steel powder is melted by the electron beam, a moving heating device 65 arranged on the construction platform 5 is used for uniformly and dynamically preheating a printing layer selection area where the printer head is positioned; preheating to 30 ℃ below the critical phase transition temperature t;
before the GCr15 bearing steel powder is melted by the electron beam, an electron beam limiting cylinder 632 is used for controlling the uniformity of the electron beam dose and the radiation field;
wherein, electron beam 3D prints specifically is: the electron beam enables GCr15 bearing steel powder to be rapidly melted at 1600 ℃ in a selected area of a printing layer; molten GCr15 bearing steel powder formed a micro-melt pool; cooling the micro molten pool area to be below the critical phase transition temperature t at the speed of 50 ℃/s after the electron beam leaves;
parameters set by the electron beam when melting the powder in the print zone selection: the scanning speed is 8 m/s; scanning current: 5 mA.
And 4, step 4: thermal treatment
After the printing in the step 3 is finished, carrying out heat treatment on the obtained workpiece; the heat treatment comprises a first carburizing treatment and a second strengthening treatment;
the first carburizing treatment includes: heating a workpiece by adopting electromagnetic induction in a vacuum environment, carburizing the surface of the workpiece, and then tempering and quenching; wherein the strong infiltration temperature is 980 ℃ and the time is 30 min; tempering at 170 deg.C for 40 min.
The second strengthening treatment comprises the following steps:
(1) pre-heat treatment: uniformly preheating the surface of the workpiece for 30min by adopting flame;
(2) normalizing: heating the workpiece to 757 ℃, carrying out heat insulation for 10min after the workpiece is diathermal, rapidly cooling by adopting water cooling, and immediately converting into spheroidizing annealing;
(3) spheroidizing annealing: the bearing steel adopts an isothermal spheroidizing annealing process, the spheroidizing heating temperature is 650 ℃, the bearing steel needs to be heated to 800 ℃ before annealing, and the bearing steel is normalized after heat preservation for 20 min;
(4) and (3) cooling: the water penetration and quick cooling are carried out to 300 ℃, the time of the water penetration and quick cooling is controlled to be 20s,
(5) quenching and tempering: quenching and tempering by using a resistance furnace; wherein, quenching is carried out for 30min at the temperature of 860 ℃ and oil quenching is carried out; tempering at 170 deg.C for 50 min;
(6) cryogenic treatment: and cooling the workpiece for 8 hours at the temperature of-196 ℃ by adopting liquid nitrogen.
And 5: determination of the Density
And 4, performing density determination on the workpiece subjected to heat treatment in the step 4 by using an Archimedes drainage method, observing the printed inner hole by using an optical microscope, and evaluating the density of the printed sample.
The density of the GCr15 bearing steel prepared by the embodiment is 97.5% on average, and no defect is observed in the GCr15 bearing steel through an optical microscope.
Example 3:
different from the embodiment 1, the specific printing sample workpiece of the embodiment is a crankshaft and a connecting rod; wherein the crankshaft is 230mm long and 60mm wide, and the connecting rod is 100mm long and 48mm wide;
the method specifically comprises the following steps:
step 1: stock preparation
The GCr15 bearing steel powder is used as a raw material for electron beam 3D printing; the specific flowability was 13.6s/50g, the powder particle size: 40-66 μm, chemical elements: c: 0.92%, Cr: 1.9%, Si: 0.5%, Mn: 0.45%, Nb: 0.30%, Sn: 0.30%, Cu: 0.25%, Mo: 0.10%, Fe: the balance, powder tap density 4.98g/cm3Apparent density of 4.5g/cm3(ii) a Then testing the critical phase transition temperature t of the GCr15 bearing steel powder;
step 2: CAE treatment of workpiece models
Using Auto CAD to construct and print a three-dimensional structure model, adding support to the constructed three-dimensional structure model, and adopting CAE technology to analyze thermodynamics and statics so as to optimize the support of the three-dimensional structure model; then slicing the three-dimensional structure model by using slicing software, and guiding the sliced model into electron beam 3D printing equipment;
and step 3: electron beam 3D printing
Firstly, adding GCr15 bearing steel powder prepared in the step 1 into a powder container of an electron beam 3D printing device, and then preheating a building platform 5; preheating temperature is 710 ℃, electron beam melting beam current is 5mA, and speed is 1 m/s;
the construction platform 5 is positioned in the sealed space, and the argon storage device 3 is filled with high-purity argon; ensuring that a construction platform in the sealed space is in a gaseous pressure environment of 3MPa, and performing electron beam 3D printing to obtain a workpiece made of GCr15 bearing steel;
wherein, before the GCr15 bearing steel powder is melted by the electron beam, a moving heating device 65 arranged on the construction platform 5 is used for uniformly and dynamically preheating a printing layer selection area where the printer head is positioned; preheating to 50 ℃ below the critical phase transition temperature t;
before the GCr15 bearing steel powder is melted by the electron beam, an electron beam limiting cylinder 632 is used for controlling the uniformity of the electron beam dose and the radiation field;
wherein, electron beam 3D prints specifically is: the electron beam enables the GCr15 bearing steel powder temperature to be 2000 ℃ in the printing layer selection area; molten GCr15 bearing steel powder formed a micro-melt pool; after the electron beam leaves, the micro molten pool area is cooled to be below the critical phase transition temperature t at the speed of 150 ℃/s;
parameters set by the electron beam when melting the powder in the print zone selection: the scanning speed is 16 m/s; scanning current: 10 mA.
And 4, step 4: thermal treatment
After the printing in the step 3 is finished, carrying out heat treatment on the obtained workpiece; the heat treatment comprises a first carburizing treatment and a second strengthening treatment;
the first carburizing treatment includes: heating a workpiece by adopting electromagnetic induction in a vacuum environment, carburizing the surface of the workpiece, and then tempering and quenching; wherein the strong infiltration temperature is 980 ℃ and the time is 30 min; tempering at 170 deg.C for 40 min.
The second strengthening treatment comprises the following steps:
(1) pre-heat treatment: uniformly preheating the surface of the workpiece for 60min by adopting flame;
(2) normalizing: heating the workpiece to 857 ℃, carrying out heat insulation on the workpiece for 20min after diathermy, rapidly cooling by water cooling, and immediately converting into spheroidizing annealing;
(3) spheroidizing annealing: the bearing steel adopts an isothermal spheroidizing annealing process, the spheroidizing heating temperature is 690 ℃, the bearing steel needs to be heated to 900 ℃ before annealing, and the bearing steel is normalized after heat preservation for 35 min;
(4) and (3) cooling: the water penetration and quick cooling are carried out to 450 ℃, the time of the water penetration and quick cooling is controlled to be 30s,
(5) quenching and tempering: quenching and tempering by using a resistance furnace; wherein, quenching is carried out for 30min at the temperature of 860 ℃ and oil quenching is carried out; tempering at 170 deg.C for 50 min;
(6) cryogenic treatment: and cooling the workpiece for 10 hours at the temperature of-196 ℃ by adopting liquid nitrogen.
And 5: determination of the Density
And 4, performing density determination on the workpiece subjected to heat treatment in the step 4 by using an Archimedes drainage method, observing the printed inner hole by using an optical microscope, and evaluating the density of the printed sample.
The density of the GCr15 bearing steel prepared by the embodiment is 98.6% on average, and no defect is observed in the GCr15 bearing steel through an optical microscope.
Example 4:
unlike example 1, the specific print sample workpiece of this example is a cube with dimensions 10 × 10 mm;
the method specifically comprises the following steps:
step 1: stock preparation
The GCr15 bearing steel powder is used as a raw material for electron beam 3D printing; the specific flowability was 13.6s/50g, the powder particle size: 40-50 μm, chemical elements: c: 0.75%, Cr: 1.8%, Si: 0.35%, Mn: 0.35%, Nb: 0.2%, Sn: 0.2%, Cu: 0.2%, Mo: 0.9%, Fe: the balance, powder tap density 4.98g/cm3Apparent density of 4.5g/cm3(ii) a Then testing the critical phase transition temperature t of the GCr15 bearing steel powder;
step 2: CAE treatment of workpiece models
Using Auto CAD to construct and print a three-dimensional structure model, adding support to the constructed three-dimensional structure model, and adopting CAE technology to analyze thermodynamics and statics so as to optimize the support of the three-dimensional structure model; then slicing the three-dimensional structure model by using slicing software, and guiding the sliced model into electron beam 3D printing equipment;
and step 3: electron beam 3D printing
Firstly, adding GCr15 bearing steel powder prepared in the step 1 into a powder container of an electron beam 3D printing device, and then preheating a building platform 5; preheating temperature is 710 ℃, electron beam melting beam current is 5mA, and speed is 1 m/s;
the construction platform 5 is positioned in the sealed space, and the argon storage device 3 is filled with high-purity argon; ensuring that a construction platform in the sealed space is in a gaseous pressure environment of 2.5MPa, and performing electron beam 3D printing to obtain a workpiece made of GCr15 bearing steel;
wherein, before the GCr15 bearing steel powder is melted by the electron beam, a moving heating device 65 arranged on the construction platform 5 is used for uniformly and dynamically preheating a printing layer selection area where the printer head is positioned; preheating to 40 ℃ below the critical phase transition temperature t;
before the GCr15 bearing steel powder is melted by the electron beam, an electron beam limiting cylinder 632 is used for controlling the uniformity of the electron beam dose and the radiation field;
wherein, electron beam 3D prints specifically is: the electron beam enables the temperature of GCr15 bearing steel powder to be 1800 ℃ in a printing layer selection area; molten GCr15 bearing steel powder formed a micro-melt pool; after the electron beam leaves, the micro-molten pool area is cooled to be below the critical phase transition temperature t at the speed of 100 ℃/s;
parameters set by the electron beam when melting the powder in the print zone selection: the scanning speed is 12 m/s; scanning current: 7.5 mA.
And 4, step 4: thermal treatment
After the printing in the step 3 is finished, carrying out heat treatment on the obtained workpiece; the heat treatment comprises a first carburizing treatment and a second strengthening treatment;
the first carburizing treatment includes: heating a workpiece by adopting electromagnetic induction in a vacuum environment, carburizing the surface of the workpiece, and then tempering and quenching; wherein the strong infiltration temperature is 980 ℃ and the time is 30 min; tempering at 170 deg.C for 40 min.
The second strengthening treatment comprises the following steps:
(1) pre-heat treatment: uniformly preheating the surface of the workpiece for 45min by adopting flame;
(2) normalizing: heating the workpiece to 807 ℃, carrying out heat transmission on the workpiece, then carrying out heat preservation for 15min, rapidly cooling by water cooling, and immediately converting into spheroidizing annealing;
(3) spheroidizing annealing: the bearing steel adopts an isothermal spheroidizing annealing process, the spheroidizing heating temperature is 670 ℃, the bearing steel needs to be heated to 850 ℃ before annealing, and the bearing steel is normalized after heat preservation for 28 min;
(4) and (3) cooling: water-through fast cooling is carried out to 400 ℃, the time of water-through fast cooling is controlled to be 25s,
(5) quenching and tempering: quenching and tempering by using a resistance furnace; wherein, quenching is carried out for 30min at the temperature of 860 ℃ and oil quenching is carried out; tempering at 170 deg.C for 50 min;
(6) cryogenic treatment: and cooling the workpiece for 9 hours at the temperature of-196 ℃ by adopting liquid nitrogen.
And 5: determination of the Density
And 4, performing density determination on the workpiece subjected to heat treatment in the step 4 by using an Archimedes drainage method, observing the printed inner hole by using an optical microscope, and evaluating the density of the printed sample.
The density of the GCr15 bearing steel prepared by the embodiment is 99.6% on average, and no defect is found in the interior of the GCr15 bearing steel observed by an optical microscope;
the comparison shows that the printing layer is dynamically heated, so that the whole printing layer is uniformly heated, GCr15 bearing steel powder is melted when the temperature of the whole printing layer is 100 ℃ above the phase change temperature, the compactness can be ensured to be more than 99%, and a GCr15 bearing steel workpiece with excellent performance is obtained.
Claims (10)
1. A method for preparing GCr15 bearing steel and automobile parts based on an electron beam 3D printing technology is characterized by comprising the following steps:
step 1: stock preparation
Selecting GCr15 bearing steel powder as a raw material for electron beam 3D printing; then testing the critical phase transition temperature t of the GCr15 bearing steel powder;
step 2: CAE treatment of workpiece models
Using Auto CAD to construct and print a three-dimensional structure model, adding support to the constructed three-dimensional structure model, and adopting CAE technology to analyze thermodynamics and statics so as to optimize the support of the three-dimensional structure model; then slicing the three-dimensional structure model by using slicing software, and guiding the sliced model into electron beam 3D printing equipment;
and step 3: electron beam 3D printing
Firstly, adding GCr15 bearing steel powder prepared in the step 1 into a powder container of an electron beam 3D printing device, and then preheating a building platform;
the construction platform is positioned in a sealed space, and high-purity argon is filled in the sealed space; ensuring that a construction platform in the sealed space is in a gaseous pressure environment of 2-3 MPa; performing electron beam 3D printing to obtain a workpiece made of GCr15 bearing steel;
before the GCr15 bearing steel powder is melted by the electron beams, a mobile heating device arranged on a construction platform is used for uniformly and dynamically preheating a printing layer selection area where an electron beam emitting device is located; preheating to a temperature within a range of 30-50 ℃ below the critical phase transition temperature t;
before the GCr15 bearing steel powder is melted by the electron beam, an electron beam limiting cylinder is used for controlling the uniformity of the electron beam dose and the radiation field;
wherein, electron beam 3D prints specifically is: rapidly melting GCr15 bearing steel powder at 1500-2000 ℃ in a printing layer selection area by electron beams; molten GCr15 bearing steel powder formed a micro-melt pool; after the electron beam leaves, cooling the micro-molten pool area to be below the critical phase transition temperature t at the speed of 50-150 ℃/s;
and 4, step 4: thermal treatment
After the printing in the step 3 is finished, carrying out heat treatment on the obtained workpiece; the heat treatment comprises a first carburizing treatment and a second strengthening treatment;
and 5: determination of the Density
And (4) performing density measurement on the workpiece subjected to heat treatment in the step (4), observing the printed inner hole by using an optical microscope, and evaluating the density of the printed sample.
2. The method for preparing GCr15 bearing steel and automobile parts based on the electron beam 3D printing technology as claimed in claim 1, wherein the GCr15 bearing steel powder used in step 1 has high sphericity and good fluiditySpecific flowability of 13.6s/50g, powder particle size: 28-66 μm, chemical elements: c: 0.65-0.92%, Cr: 1.70-1.9%, Si: 0.2-0.5%, Mn: 0.25 to 0.45%, Nb: less than or equal to 0.30 percent, Sn: less than or equal to 0.30 percent, Cu: less than or equal to 0.25 percent, Mo: less than or equal to 0.10 percent, Fe: the balance, powder tap density 4.98g/cm3Apparent density of 4.5g/cm3。
3. The method for preparing GCr15 bearing steel and automobile parts based on the electron beam 3D printing technology as claimed in claim 1, wherein the parameters set by the electron beam in the step 3 when melting the powder in the printing layer selection are as follows: the scanning speed is 8-16 m/s; scanning current: 5 mA-10 mA.
4. The method for preparing GCr15 bearing steel and automobile parts based on the electron beam 3D printing technology according to claim 1, wherein the first carburization process comprises: heating a workpiece by adopting electromagnetic induction in a vacuum environment, carburizing the surface of the workpiece, and then tempering and quenching; wherein the strong infiltration temperature is 980 ℃ and the time is 30 min; tempering at 170 deg.C for 40 min.
5. The method for preparing GCr15 bearing steel and automobile parts based on the electron beam 3D printing technology as claimed in claim 1, wherein the second strengthening treatment comprises:
(1) pre-heat treatment: uniformly preheating the surface of the workpiece for 30-60 min by adopting flame;
(2) normalizing: heating the workpiece to 757-857 ℃, carrying out heat penetration on the workpiece, then carrying out heat preservation for 10-20 min, rapidly cooling by adopting water cooling, and immediately converting into spheroidizing annealing;
(3) spheroidizing annealing: the bearing steel is subjected to an isothermal spheroidizing annealing process, wherein the spheroidizing heating temperature is 650-690 ℃, the bearing steel is heated to 800-900 ℃ before annealing, and the bearing steel is subjected to normalizing after heat preservation for 20-35 min;
(4) and (3) cooling: the water-through fast cooling is carried out to 300-450 ℃, the time of the water-through fast cooling is controlled to be 20-30 s,
(5) quenching and tempering: quenching and tempering by using a resistance furnace; wherein, quenching is carried out for 30min at the temperature of 860 ℃ and oil quenching is carried out; tempering at 170 deg.C for 50 min;
(6) cryogenic treatment: and cooling the workpiece for 8-10 hours at-196 ℃ by adopting liquid nitrogen.
6. The method for preparing GCr15 bearing steel and automobile parts based on the electron beam 3D printing technology as claimed in claim 1, wherein the pre-heating temperature of the construction platform is 710 ℃, the electron beam melting beam current is 5mA, and the speed is 1 m/s.
7. The method for preparing GCr15 bearing steel and automobile parts based on electron beam 3D printing technology according to claim 1, wherein the workpiece surface is sand blasted after the heat treatment is completed.
8. The method for preparing GCr15 bearing steel and automobile parts based on electron beam 3D printing technology according to claim 1, wherein the three-dimensional model is sliced with 50 μm thickness of each layer using slicing software.
9. A method for preparing GCr15 bearing steel and automobile parts based on electron beam 3D printing technology, characterized in that, the method uses an electron beam 3D printing device for printing GCr15 bearing steel powder, comprising a bottom support (1), a high pressure chamber (2) arranged on the bottom support (1), an argon gas storage device (3) arranged on the bottom support (1) and connected with the high pressure chamber (2), a pressure regulating device (4) arranged at the connection of the high pressure chamber (2) and the argon gas storage device (3), a building platform (5) arranged in the high pressure chamber (2), a printing device (6) arranged above the building platform (5);
a detection assembly (40) for detecting the pressure of the sealed cabin (2) is arranged in the pressure regulating device (4); the lower end of the construction platform (5) is provided with a fixed preheating assembly (50);
the printing device (6) comprises a plurality of supports (60) vertically arranged on a building platform (5), a lifting frame (61) movably arranged on the supports (60), a lifting motor (62) arranged on the supports (60) and used for controlling the lifting frame (61) to lift, a mobile heating device (65) fixed on the lifting frame (61) and used for preheating a printing layer selection area, a printing machine head (63) movably arranged on the lifting frame (61), and a powder feeding device (64) connected with the printing machine head (63);
the printer head (63) comprises a central powder outlet pipe (630) connected with the powder feeding device (64), two electron beam energy sources (631) symmetrically arranged relative to the central powder outlet (630), and two electron beam light limiting cylinders (632) respectively connected with the electron beam energy sources (631);
the mobile heating device (65) comprises a first heating component (650) arranged on the central powder outlet pipe (630) and a second heating component arranged on the lifting frame (61); the second heating assembly comprises two connecting rods (651) which can be connected with the printing layer respectively, positive and negative electric sheets (652) which are arranged on the two connecting rods (651) respectively, and a power supply (653) which is connected with the positive and negative electric sheets (652).
10. The electron beam 3D printing device for printing GCr15 bearing steel powder according to claim 9, wherein the first heating assembly (650) employs an electromagnetic heating assembly.
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