CN106493364B - A kind of low activation martensitic steel precinct laser fusion increasing material manufacturing technique - Google Patents

Abstract

The invention discloses a kind of low activation martensitic steel precinct laser fusion increasing material manufacturing technique, its feature includes：Material is low activation martensitic steel microsphere powder, and fine powder (200 400 mesh) is 1~1.5 with the powder weight proportioning of meal (50 150 mesh), with preferable compactedness；Using precinct laser fusion rapid molding method, the 300W of laser power 20, the 135um of lasing beam diameter 70, the 2000mm/s of sweep speed 500, the 120um of sweep span 35, the 50um of lift height 20, powder preheats 150 300 DEG C, the 20cm of shaping speed 5³/ h, argon gas is protected and pressure maintains 10 20mbar in forming room, and part manufacture is incubated more than 48 hours, finally profiled part is heat-treated, Technology for Heating Processing after finishing at 250 400 DEG C：720 760 DEG C are warming up to stove, be incubated 60 120min, then cooling of coming out of the stove after cooling to less than 100 DEG C with the furnace, to reduce residual stress, the overall performance of raising part；Good part rapid shaping quality can be obtained under this technique.

Description

A selective laser melting additive manufacturing process for low-activation martensitic steel

technical field

The invention relates to a low-activation martensitic steel selective laser melting additive manufacturing process, which can be used for rapid prototyping of complex structural parts of advanced nuclear energy systems such as fusion reactor cladding and fission reactor.

Background technique

Additive manufacturing (that is, 3D printing) is a new rapid precision manufacturing technology that has emerged and developed rapidly in recent years. It has been widely used in the aerospace field; this technology can process parts that are difficult to manufacture by traditional methods, and has complex structural parts with high forming precision , high production efficiency and good integral molding effect of parts. Because the rapid prototyping process of different materials is quite different, the rapid prototyping process of components is the key to this technology. The fusion reactor uses low-activation martensitic steel as the structural material. The low-activation martensitic steel has excellent thermophysical properties, anti-radiation swelling performance, anti-corrosion performance of liquid metal, etc., and has been selected as the main structure of the fusion reactor cladding The material is also the main candidate structural material for the cladding of the future fusion engineering demonstration reactor; at the same time, the low-activation martensitic steel is also the main candidate structural material for key components of advanced nuclear energy systems such as lead-based reactor fuel assemblies. Fusion reactor cladding and lead-based reactor fuel assemblies and other key components of advanced nuclear energy systems have harsh service conditions and must withstand strong neutron irradiation, high surface heat flow, high nuclear thermal deposition, high pressure and complex mechanical loads, etc., and the structure of these key components Complicated, it puts forward higher requirements on the molding quality and molding accuracy of the parts.

Fusion reactor cladding and other advanced nuclear energy systems have high nuclear heat deposition, and cooling components generally have complex flow channel arrangements with high density and narrow intervals. At present, welding methods are often used for the molding of advanced nuclear energy systems with complex structures including flow channel cooling components, especially welding methods such as high-energy beams (such as electron beams and lasers) with small heat-affected zones combined with special molding processes (such as patent: CN201110250136.4), etc.; at the same time, in order to further improve the overall forming performance of complex parts, the composite welding technology of special welding methods (such as hot isostatic pressure diffusion welding, electron beam, laser, etc.) is also used (such as patent: CN200810021143.5) , but due to the dense welds, the welding is difficult and the welds are prone to cracks. In addition, the complex heat input in the welding process leads to large deformation of the parts, high forming difficulty and difficult post-orthopedics. The preparation cycle of the parts is long and the cost is high.

3D printing can form parts with complex structures at one time, with small deformation, near-net shape, no need for subsequent processing, etc., suitable for forming parts with complex structures; the precision processing technology of 3D printing rapid prototyping is applied to fusion reactor cladding and other advanced The preparation of complex structural components of nuclear energy systems has broad development and application prospects. It is necessary to carry out research on the rapid prototyping process of complex components of special structural materials for fusion reactors.

Contents of the invention

The technical problem to be solved in the present invention is to overcome the key problems such as high difficulty in welding processing of existing complex structural parts, large welding deformation, and easy occurrence of cracks after welding, and provide a selective laser melting additive manufacturing process for low-activation martensitic steel. Solve the problem of rapid prototyping of low-activation martensitic steel 3D printing for complex structural components of advanced nuclear energy systems. In the present invention, the selected area laser melting process is preferred for rapid processing and manufacturing of key complex structural components of advanced nuclear energy systems such as fusion reactor cladding, which has the advantages of one-time forming, high forming precision and good forming quality.

The technical solution of the present invention is as follows: a low-activation martensitic steel selective laser melting additive manufacturing process, the realization steps are as follows:

(1) The raw material is low-activation martensitic steel microsphere powder, and the fine powder and coarse powder are proportioned in a certain proportion to increase the packing density;

(2) Graphical computer description of the complex structural parts to be formed, input the three-dimensional drawings of the complex structural parts to be formed into the control computer, mainly including the structure of the three-dimensional model, and select the forming direction according to whether support needs to be added, and select according to the size of the parts The thickness and number of layers of layered slices, the extraction and filling of section outlines, etc., the setting of slice thickness and total number of layers, etc.;

(3) Set the selective laser melting process, laser power 20-300W, beam diameter 70-135um, scanning speed 500-2000mm/s, scanning distance 35-120um, layer thickness 20-50um, powder preheating 150-300℃ , the molding speed is 5-20cm ³ /h, the molding chamber is protected by argon and the pressure is maintained at 10-20mbar;

(4) Powder ratio, the powder weight ratio of fine powder (200-400 mesh) and coarse powder (50-150 mesh) is 1 to 1.5, mixed evenly under vacuum conditions to prevent powder oxidation;

(5) Powder spreading and melting, a layer of low-activation martensitic (CLAM) steel powder with a thickness of 0.2-1mm is evenly laid on the substrate through the powder feeding mechanism, and the powder is rapidly formed by laser beam according to the shape of the computer graphic slice, Subsequent powder spreading and laser beam melting and rapid prototyping are carried out in sequence until the complex structural parts are formed;

(6) After the parts are manufactured, they are kept at 300-400°C for more than 48 hours, and finally heat-treated the formed parts. The heat treatment process: heat up to 720-760°C with the furnace, keep the temperature for 60-120min, and then cool with the furnace to below 100°C After being out of the furnace, it is cooled to reduce residual stress and improve the overall performance of molded parts;

Advantage of the present invention compared with prior art:

(1) The present invention can perform near-net molding of complex structural parts at one time, the dimensional accuracy can reach within +0.5mm, the surface quality is high, and generally no subsequent machining is required;

(2) The microstructure and mechanical properties of the material after the complex structural parts are formed and heat-treated are isotropic and homogeneous;

(3) Molding is carried out in an argon-protected environment. The oxygen content of the molded parts (less than 100ppm) meets the standard, avoiding material oxidation, high-quality molded parts, uniform structure, and no defects such as pores, cracks, and unmelted particles;

(4) The remaining powder after molding can be recycled and reused, the material utilization rate is close to 100%, and the molding speed is high (up to about 80cm ³ /h).

Description of drawings

Figure 1 is the first wall part of the Chinese liquid DFLL cladding;

Figure 2 is a Chinese liquid DFLL cladding cooling plate component;

Figure 3 shows the upper and lower nozzle parts of the Chinese lead-based reactor fuel assembly cladding tube.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. But the following embodiments are only limited to explain the present invention, and the protection scope of the present invention should include the entire content of the claims, not only limited to the present embodiment.

Embodiment 1, taking the rapid prototyping of the first wall part of the fusion reactor's liquid DFLL cladding as an example, as shown in Figure 1, the structural material is China's low-activation martensitic (CLAM) steel;

(1) The material is microsphere powder of low-activation martensitic (CLAM) steel, and the fine powder (200-350 mesh) and coarse powder (50-100 mesh) are mixed according to the weight ratio of 1:1.5 and loaded In the powder feeding mechanism, the powder is preheated to 300°C;

(2) Vacuumize the selected area laser melting equipment, fill the vacuum chamber with high-purity Ar ₂ after the vacuum degree reaches 10 ^-3 Pa level, and then evacuate again and fill it with high-purity Ar ₂ after the vacuum degree reaches 1MPa, so Repeatedly wash the furnace more than 2 times;

(3) First spread a layer of CLAM steel fine powder and coarse powder mixed proportioning powder with a thickness of 0.5mm on the powder spreading plane through the powder feeding mechanism;

(4) Input the STL format drawings of the rapidly prototyping parts into the computer, and carry out computer-aided graphics processing; according to the size of the parts: length*width*height=161mm*155mm*205mm, the layer thickness is selected to be 0.5mm, considering the parts After molding, it is separated from the processing of the substrate, and the total number of layers is 4120 layers;

(5) Selective laser melting process: laser power 250W, laser diameter 80um, scanning speed 2000mm/s, scanning distance 90um, layer thickness 50um, powder preheating 300°C, argon protection in the molding chamber, argon pressure 17mbar, throughout the process During the molding process, ensure that the temperature in the molding room is around 350°C;

(6) The laser beam is selectively sintered according to the information of the cross-sectional profile under the control of the computer. The metal powder is sintered together under the bombardment of the laser beam and bonded with the formed part below. The first layer of powder is melted Finally, lay the second layer of powder through the powder feeding mechanism, the thickness of the powder is uniform and the same as the thickness of the first layer, so that the layers are piled up until the entire part is sintered;

(7) After the parts are sintered, keep them warm in the molding room at 350°C for 72 hours to prevent cracks in the parts. After the heat preservation is over, start to cool down to room temperature, turn on the furnace and recover the excess filling powder, and then take out the parts;

(8) Heat treatment of parts: Vacuum heat treatment is carried out after the parts are taken out to reduce the residual stress during the forming process of the parts and improve the overall performance of the parts. Heat treatment process: heat up to 740°C with the furnace, keep warm for 120min, and cool down to below 100°C with the furnace After taking out the oven to cool down;

(9) After calculation and measurement, the molding speed of the first wall part is 50cm ³ /h, the molding accuracy reaches +0.3mm, the metallographic observation structure is uniform, and there are no defects such as pores, cracks and unmelted particles.

Embodiment 2: Taking the rapid prototyping of the Chinese liquid DFLL cladding cooling plate parts of the fusion reactor as an example, as shown in Figure 2, the structural material is Chinese low-activation martensitic (CLAM) steel;

(1) The material is microsphere powder of low-activation martensitic (CLAM) steel, and the fine powder (200-350 mesh) and coarse powder (50-150 mesh) are mixed according to the weight ratio of 1:1.5 and loaded In the powder feeding mechanism, the powder is preheated at 250°C;

(2) Vacuumize the selected area laser melting equipment, fill the vacuum chamber with high-purity Ar ₂ after the vacuum degree reaches 10 ^-3 Pa level, and then evacuate again and fill it with high-purity Ar ₂ after the vacuum degree reaches 1MPa, so Repeatedly wash the furnace more than 2 times;

(3) First spread a layer of CLAM steel fine powder and coarse powder mixed ratio powder with a thickness of 0.3mm on the powder spreading plane through the powder feeding mechanism;

(4) Input the STL format drawings of the rapidly prototyping parts into the computer for computer-aided graphics processing; according to the size of the parts: length*width*height=200mm*101mm*10mm, the layer thickness is selected to be 0.3mm, considering the parts After molding, it is separated from the processing of the substrate, and the total number of layers is 40 layers;

(5) Selected area laser melting process: laser power 150W, laser diameter 90um, scanning speed 1000mm/s, scanning distance 100um, layer thickness 30um, powder preheating 250°C, argon protection in the molding chamber, argon pressure 13mbar, in the whole During the molding process, ensure that the temperature in the molding room is around 300°C;

(6) The laser beam is selectively sintered according to the information of the cross-sectional profile under the control of the computer. The metal powder is sintered together under the bombardment of the laser beam and bonded with the formed part below. The first layer of powder is melted Finally, lay the second layer of powder through the powder feeding mechanism, the thickness of the powder is uniform and the same as the thickness of the first layer, so that the layers are piled up until the entire part is sintered;

(7) After the parts are sintered, keep them warm in the molding room at 300°C for 60 hours to prevent cracks in the parts. After the heat preservation is over, start to cool down to room temperature, turn on the furnace and recover the excess filling powder, and then take out the parts;

(8) Heat treatment of parts: Vacuum heat treatment is carried out after the parts are taken out to reduce the residual stress in the forming process of the parts and improve the overall performance of the parts. Heat treatment process: heat up to 760°C with the furnace, keep the temperature for 120min, and cool with the furnace to below 100°C Then take it out of the oven to cool.

(9) After calculation and measurement, the forming speed of the cooling plate part is about 60cm ³ /h, the forming precision reaches +0.4mm, the metallographic observation structure is uniform, and no defects such as pores, cracks and unmelted particles are found.

Embodiment 3: Taking the rapid prototyping of the upper and lower tube seat parts of the cladding tube of the Chinese lead-based reactor fuel assembly as an example, as shown in Figure 3, the structural material is Chinese low-activation martensitic steel;

(1) The material is the microsphere powder of low-activation martensitic steel (CLAM), and the fine powder (200-300 mesh) and the coarse powder (80-150 mesh) are mixed according to the weight ratio of 1:1.5 and loaded In the powder feeding mechanism, the powder is preheated at 250°C;

(2) Vacuumize the selected area laser melting equipment, fill the vacuum chamber with high-purity Ar ₂ after the vacuum degree reaches 10 ^-3 Pa level, and then evacuate again and fill it with high-purity Ar ₂ after the vacuum degree reaches 1MPa, so Repeatedly wash the furnace more than 2 times;

(3) First spread a layer of CLAM steel fine powder and coarse powder mixed proportioning powder with a thickness of 0.5mm on the powder spreading plane through the powder feeding mechanism;

(4) Input the STL format drawings of the rapidly prototyping parts into the computer for computer-aided graphics processing; according to the size of the parts: length*width*height=117mm*130mm*10mm, the layer thickness is selected to be 0.2mm, considering the parts After molding, it is separated from the processing of the substrate, and the total number of layers is 80 layers;

(5) Selective laser melting process: laser power 80W, laser diameter 70um, scanning speed 700mm/s, scanning distance 80um, layer thickness 20um, powder preheating 250°C, argon protection in the molding chamber, argon pressure 15mbar, throughout the process During the molding process, ensure that the temperature in the molding room is around 350°C;

(6) The laser beam is selectively sintered according to the information of the cross-sectional profile under the control of the computer. The metal powder is sintered together under the bombardment of the laser beam and bonded with the formed part below. The first layer of powder is melted Finally, lay the second layer of powder through the powder feeding mechanism, the thickness of the powder is uniform and the same as the thickness of the first layer, so that the layers are piled up until the entire part is sintered;

(7) After the parts are sintered, keep them warm in the molding room at 350°C for 48 hours to prevent cracks in the parts. After the heat preservation is over, start to cool down to room temperature, turn on the furnace and recover the excess filling powder, and then take out the parts;

(8) Heat treatment of parts: Vacuum heat treatment is carried out after the parts are taken out to reduce the residual stress during the forming process of the parts and improve the overall performance of the parts. Heat treatment process: heat up to 720°C with the furnace, keep the temperature for 90min, and cool with the furnace to below 100°C After taking out the oven to cool down;

(9) After calculation and measurement, the molding speed of the pipe seat part is 75cm ³ /h, the molding accuracy reaches +0.2mm, the metallographic observation structure is uniform, and there are no defects such as pores, cracks and unmelted particles.

It should be noted that, according to the above-mentioned embodiments of the present invention, those skilled in the art can fully realize the full scope of claim 1 and the dependent rights of the present invention, and the implementation process and method are the same as the above-mentioned embodiments; and the present invention is not elaborated Some of them belong to well-known technologies in the art.

The above are only some specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims (3)

1. a kind of low activation martensitic steel precinct laser fusion increasing material manufacturing technique, it is characterised in that：It is low activation including material Martensite steel microsphere powder, fine powder 200-400 mesh is 1~1.5 with the powder weight proportioning of meal 50-150 mesh, with preferable Compactedness；Using precinct laser fusion rapid molding method, laser power 20-300W, lasing beam diameter 70-135um, scanning speed Degree 500-2000mm/s, sweep span 35-120um, lift height 20-50um, powder preheat 150-300 DEG C, shaping speed 5- 20cm³/ h, argon gas is protected and pressure maintains 10-20mbar in forming room, and profiled part is manufactured after finishing in 250-400 DEG C of temperature The lower insulation of degree, to prevent from cracking, is finally heat-treated to the part for manufacturing, and to reduce residual stress, improves forming part The overall performance of part.

2. a kind of low activation martensitic steel precinct laser fusion increasing material manufacturing technique according to claim 1, its feature exists In：The profiled part manufacture is incubated more than 48 hours after finishing at 250-400 DEG C, prevents crackle.

3. a kind of low activation martensitic steel precinct laser fusion increasing material manufacturing technique according to claim 1, its feature exists In：The process of thermal treatment：720-760 DEG C is warming up to stove, be incubated 60-120min, then after cooling to less than 100 DEG C with the furnace Come out of the stove cooling, to reduce residual stress, improve the overall performance of profiled part.