Method for regulating stress deformation of suspended structure of hot end cartridge prepared by selective laser melting

Abstract

The application discloses a method for preparing a stress deformation regulation and control of a hot end machine case suspension structure by selective laser melting, and comprises the following steps: dividing the bottom of a model suspension part into three layers of a bottom layer, a transition layer and a solid layer; slicing the bottom layer and setting a scanning mode as strip scanning; slicing the transition layer and setting a scanning mode as chessboard scanning, and remelting layer by layer; and using solid printing parameters to complete the preparation of the part. The application can realize the forming of the suspension structure under the condition of no support and reduce the stress deformation, and improve the size precision and surface quality of the suspension structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-energy beam metal additive manufacturing, and particularly relates to a stress deformation regulation and control method for preparing a hot end case overhanging structure by selective laser melting. BACKGROUND

[0002] With the development of the integration of aero-engine structures, the shapes of some parts are increasingly complex. Selective laser melting technology (SLM) mainly uses laser to scan the powder bed layer by layer, and has unique advantages in the preparation of complex parts. However, when forming an overhanging structure, the overhanging structure is prone to warping deformation due to high thermal stress accumulation, which affects the precision and forming ability of the part. At present, the preparation of overhanging structures mainly adds auxiliary supports to improve the formability of the overhanging structure and control stress deformation. After the hot end case is designed in an integrated manner, there are many overhanging structures, and a large number of supports are usually added to assist in forming during the forming process, resulting in a long post-processing time of the part, reducing the production efficiency of the part, and increasing the cost of the component. SUMMARY

[0003] The main purpose of the present application is to provide a stress deformation regulation and control method for preparing a hot end case overhanging structure by selective laser melting, which can control the deformation of the overhanging structure under the condition of no support, realize high-precision forming of the overhanging structure, reduce the processing amount of post-processing, and improve the production efficiency of the part.

[0004] To this end, the stress deformation regulation and control method for preparing a hot end case overhanging structure by selective laser melting provided by the present application comprises the following steps:

[0005] Step one, the bottom of the overhanging part of the hot end case model is divided into a bottom layer, a transition layer and a solid layer from bottom to top;

[0006] Step two, slice the bottom layer of the overhanging part, set the scanning mode to strip scanning, and use the printing equipment to print and form the bottom layer;

[0007] Step three, slice the transition layer of the overhanging part, set the scanning mode to chessboard scanning, and set the layer-by-layer remelting at the same time, the remelting scanning mode adopts strip scanning, and use the printing equipment to print and form the transition layer;

[0008] Step four, use the solid process parameters to form the solid layer of the overhanging part and the remaining parts of the hot end case model, the scanning mode is strip scanning, and the preparation of the hot end case is completed.

[0009] Specifically, the thickness of the bottom layer is 0.1-0.2mm, and the thickness of the transition layer is 0.3-0.6mm. The reason why the thickness of the bottom layer is set to 0.1-0.2mm is that when the thickness is greater than 0.2mm, warping deformation is easy to occur due to heat treatment during printing, and if it is less than 0.1mm, the transition layer cannot play a supporting role. The transition layer is the main part of the support-free forming, and if the thickness of the transition layer is too small, warping may occur in the suspended part during the forming of the entity layer, and if the thickness is too large, the forming efficiency will be reduced and the forming precision will be poor.

[0010] Specifically, when printing the bottom layer of the suspended part, the laser power is set to 200-230W, and the scanning speed is set to 1200-1500mm / s. In this parameter range, the forming precision of the bottom layer can be guaranteed and the thermal stress deformation is reduced, providing a good substrate for subsequent transition layer printing. If a smaller power or a larger speed is used, the bottom layer cannot be well formed, and there will be a large number of pores, and if a larger power or a smaller speed is used, the thermal stress accumulation will be intensified due to high energy input, causing large warping deformation of the bottom layer.

[0011] Specifically, the laser power of the chessboard scanning is set to 280-290W, the scanning speed is set to 1200-1500mm / s, the number of chessboard grid vectors is 50-200, and the same laser power and scanning speed as the chessboard scanning are used during the layer-by-layer remelting. Chessboard scanning can effectively reduce the accumulation of thermal stress in the material, and in order to make the transition layer and the entity layer combine more closely, the same laser power as the entity layer is used, and the scanning speed is relatively more likely to affect the accumulation of thermal stress. When the speed is too high, the powder bed cannot be fully melted, resulting in more pores, and when the speed is too low, the stress accumulation will be intensified and warping deformation will occur. The number of chessboard grid vectors also affects stress accumulation and surface topography, and when the number of vectors is low, the surface flatness will be large, affecting the forming precision, and when the number of vectors is high, local thermal stress accumulation will be large and deformation will occur. Layer-by-layer remelting can smooth the rough surface formed by chessboard scanning, which is beneficial to the forming of subsequent layers.

[0012] Specifically, the laser power of the entity process parameters is 280-290W, and the scanning speed is 920-980mm / s.

[0013] Specifically, the thickness of the bottom layer is 0.2mm, the thickness of the transition layer is 0.5mm, the laser power is 220W when printing the bottom layer of the suspended part, the scanning speed is 1400mm / s, the laser power of the entity process parameters is 285W, the scanning speed is 960mm / s, the laser power is set to 285W when chessboard scanning, the number of chessboard grid vectors is 100, and the scanning speed is 1300mm / s.

[0014] The present application is ingenious in that the bottom of the overhanging structure of the hot end cartridge model is printed in layers when printing, and special printing parameters are matched for each layer to achieve the purpose of regulating the thermal stress distribution of the bottom of the overhanging structure, effectively reducing the stress deformation of the overhanging structure under the condition of no support. Among them, the bottom layer serves as the support base of the overhanging structure on the powder bed, by controlling the thickness of the bottom layer to be 0.1-0.2mm, setting the scanning mode to be strip-shaped scanning, and combining with special printing process parameters, the forming precision of the bottom layer can be guaranteed while reducing thermal stress deformation, providing a good base for subsequent transition layer printing. The transition layer is the main part of regulating stress distribution and reducing thermal stress deformation, by setting the thickness of the transition layer to be 0.3-0.6mm, setting the scanning mode to be chessboard-shaped scanning, and setting the layer-by-layer remelting, in addition to special printing system, the accumulation of thermal stress in the material can be effectively reduced, and the layer-by-layer remelting can make the rough surface formed by the chessboard-shaped scanning smooth, which is beneficial to the forming of the subsequent layer.

[0015] In summary, the present application successfully prepares a hot end cartridge with precision meeting the design requirements under the condition of no support by layering the overhanging structure of the hot end cartridge model and combining with special printing system, greatly reducing the post-processing process of the hot end cartridge and improving the preparation efficiency of the parts. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 The process flow diagram for forming the overhanging structure of the hot end cartridge of the present application;

[0018] Figure 2 The layering schematic diagram of the overhanging part model of the hot end cartridge. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0020] Reference Figure 1 A method for preparing an overhanging structure of a hot end cartridge by selective laser melting, stress deformation regulation and control, comprising the following steps:

[0021] Step one, the bottom of the suspended part of the hot end cartridge model is divided into three layers, namely the bottom layer, the transition layer and the entity layer, as shown in Figure 2 The bottom layer is a metal base for the forming of the transition layer to avoid the influence of the forming precision caused by the direct forming of the transition layer on the powder bed. The transition layer is the main part of the support-free forming.

[0022] The inventor further found that the bottom layer thickness is controlled in the range of 0.1-0.2mm, and the transition layer thickness is controlled in the range of 0.3-0.6mm, which is more appropriate, because if the bottom layer thickness is greater than 0.2mm, it is easy to cause warping deformation due to heat treatment, and if it is less than 0.1mm, it cannot support the transition layer. If the transition layer thickness is too small, the suspended part may also warp when forming the entity layer, and if the transition layer thickness is too large, it will cause the forming efficiency to decrease and the forming precision to deteriorate.

[0023] Step two, slice the bottom layer of the suspended part, and set the scanning mode to strip scanning, the laser power to 200-230W, and the scanning speed to 1200-1500mm / s. The reason why the parameter range is set in the above range is that it can guarantee the forming precision of the bottom layer and reduce the thermal stress deformation, and provide a good substrate for the subsequent transition layer printing. If the laser power is less than the above range or the scanning speed exceeds the above range, the bottom layer cannot be well formed, and there will be a large number of pores, and if a larger power or a smaller speed is used, the thermal stress accumulation will be intensified due to the higher energy input, causing the bottom layer to warp and deform.

[0024] Step three, slice the transition layer of the suspended part, and set the scanning mode to chessboard scanning, and set the layer-by-layer remelting. The reason why the transition layer scanning mode is set to chessboard scanning is that strip scanning will form continuous stress accumulation on the forming surface, and multi-layer strip scanning will cause excessive stress accumulation and warping. Chessboard scanning can make the stress relatively dispersed and uniform on the surface, eliminating the warping deformation caused by continuous stress accumulation. In addition, the laser power is consistent with the subsequent entity layer, which can make the transition layer and the entity layer more firmly combined, and the layer-by-layer remelting can flatten the rough surface formed by the chessboard scanning, which is beneficial to the subsequent layer forming.

[0025] The inventor further found that when the laser power of the chessboard scanning is set to 285 W, the scanning speed is set to 1200-1500 mm / s, and the number of chessboard vectors is 50-200, a better stress-strain regulation effect can be achieved. When the scanning speed exceeds the above range, the powder bed cannot be fully melted, and more pores are formed. When the speed is too low, stress accumulation is intensified, and warping deformation occurs. The inventor found in the experiment that the number of chessboard vectors simultaneously affects stress accumulation and surface morphology. When the number of vectors is low, the surface flatness is poor, affecting the forming precision. When the number of vectors is high, local thermal stress accumulation is large, and deformation occurs.

[0026] Step four, the remaining parts of the part are formed by using the solid process parameters (laser power 285 W, scanning speed 920-980 mm / s). Embodiment

[0027] The bottom of the suspended part of the model is divided into 3 layers, the bottom layer thickness is 0.2 mm, the transition layer thickness is 0.6 mm, and the slice thickness is 0.04 mm.

[0028] GH4169 alloy powder is used as raw material, the bottom layer process parameter adopts laser power 220 W, scanning speed 1400 mm / s, and scanning interval 0.1 mm.

[0029] The transition layer adopts chessboard scanning, the number of vectors is 100, the process parameter is laser power 285 W, scanning speed 1300 mm / s, and scanning interval 0.1 mm. The strip-shaped scanning mode is used for layer-by-layer remelting, the remelting process parameter is laser power 285 W, scanning speed 1300 mm / s, and scanning interval 0.1 mm.

[0030] The process parameters of the remaining parts of the part and the solid layer are power 285 W, scanning speed 960 mm / s, scanning interval 0.1 mm, and scanning mode is strip-shaped scanning.

[0031] After forming, the suspended part has no warping deformation, and the surface morphology is very flat. Embodiment

[0032] The bottom of the suspended part of the model is divided into 3 layers, the bottom layer thickness is 0.2 mm, the transition layer thickness is 0.6 mm, and the slice thickness is 0.04 mm.

[0033] GH4169 alloy powder is used as raw material, the bottom layer process parameter adopts laser power 200 W, scanning speed 1500 mm / s, and scanning interval 0.1 mm.

[0034] The transition layer adopts a chessboard scanning, the vector number is 50, the process parameter is a laser power 285 W, a scanning speed 1500 mm / s, and a scanning interval 0.1 mm. The strip scanning mode is adopted for layer-by-layer remelting, the remelting process parameter is a laser power 285 W, a scanning speed 1500 mm / s, and a scanning interval 0.1 mm.

[0035] The process parameter of the entity layer is 285 W, the scanning speed is 960 mm / s, and the scanning interval is 0.1 mm.

[0036] After forming, the overhanging part has no warping deformation, and the surface morphology is relatively flat.

[0037] Comparative Example 1

[0038] The bottom of the overhanging part of the model is divided into two layers, the thickness of the bottom layer is 0.2 mm, the rest is an entity layer, and no transition layer is provided, and the slice thickness is 0.04 mm.

[0039] The GH4169 alloy powder is used as raw material, the process parameter of the bottom layer adopts a laser power 200 W, a scanning speed 1500 mm / s, and a scanning interval 0.1 mm.

[0040] The process parameter of the entity layer is 285 W, the scanning speed is 960 mm / s, and the scanning interval is 0.1 mm, and the scanning mode is a strip scanning.

[0041] When the initial 2-3 layers of the forming entity layer are formed, the overhanging part is obviously warped, directly affecting the scraper powder laying process, causing the forming process to stop, which is because the bottom layer and the entity layer are both strip scanning, which will form continuous stress accumulation on the forming surface, and multi-layer strip scanning will cause excessive stress accumulation and warping, and with the increase of the number of forming layers, the stress accumulation gradually increases, and finally causes warping deformation.

[0042] Comparative Example 2

[0043] Different from Example 1, the scanning speed of the bottom layer process parameter is 1600 mm / s, and the overhanging part is obviously warped when the entity layer is formed, directly affecting the scraper powder laying process, causing the above results, which is because the bottom layer cannot form a relatively dense base at a too high scanning speed in the forming process, so that the transition layer is formed at a low density of the bottom layer, causing local collapse or deformation, affecting the forming precision.

[0044] Comparative Example 3

[0045] Different from the embodiment 1, when the chessboard scanning is performed, the scanning speed is 1000 mm / s, the chessboard grid vector number is 45, the surface precision of the suspended part after the forming is poor and a certain deformation occurs, because the stress accumulation is intensified and the warping deformation occurs in the forming process of the transition layer, the low vector number causes the irregular protrusions to exist on the formed surface, and the surface protrusions cannot be eliminated by the remelting, which affects the surface forming precision.

[0046] The above embodiments are only examples for clearly illustrating the present application, but not limitation to the embodiments. Other different forms of changes or variations can be made by those skilled in the art on the basis of the above description. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for regulating stress deformation of a hot end cartridge suspension structure prepared by selective laser melting, characterized in that, Comprising the following steps: Step one, the hot end machine case model of the suspended part bottom from bottom to top is divided into bottom layer, transition layer and entity layer; Step two, the bottom layer of the suspended part is sliced, and the scanning mode is set to strip scanning, and the bottom layer is printed and formed by using the printing equipment; Step three, the transition layer of the suspended part is sliced, and the scanning mode is set to chessboard scanning, and the layer-by-layer remelting is set, the remelting scanning mode adopts strip scanning, and the transition layer is printed and formed by using the printing equipment; Step four, the entity layer of the suspended part and the remaining part of the hot end machine case model are formed by using the entity process parameters, and the scanning mode is strip scanning, and the preparation of the hot end machine case is completed; The bottom layer thickness is 0.2mm, the transition layer thickness is 0.6mm, and the slicing thickness is 0.04mm; The hot end machine case takes GH4169 alloy powder as raw material, the bottom layer process parameter adopts laser power 220W, scanning speed 1400mm / s, and scanning interval 0.1mm; The transition layer adopts chessboard scanning, the vector number is 100, the process parameter is laser power 285W, scanning speed 1300mm / s, and scanning interval 0.1mm; the layer-by-layer remelting adopts strip scanning mode, and the remelting process parameter is laser power 285W, scanning speed 1300mm / s, and scanning interval 0.1mm; 2. A method for regulating stress deformation of a hot end cartridge suspension structure prepared by selective laser melting, characterized in that, The process parameter of the remaining part and the entity layer of the part is power 285W, scanning speed 960mm / s, scanning interval 0.1mm, and scanning mode is strip scanning. Comprising the following steps: Step one, the hot end machine case model of the suspended part bottom from bottom to top is divided into bottom layer, transition layer and entity layer; Step two, the bottom layer of the suspended part is sliced, and the scanning mode is set to strip scanning, and the bottom layer is printed and formed by using the printing equipment; Step three, the transition layer of the suspended part is sliced, and the scanning mode is set to chessboard scanning, and the layer-by-layer remelting is set, the remelting scanning mode adopts strip scanning, and the transition layer is printed and formed by using the printing equipment; Step four, the entity layer of the suspended part and the remaining part of the hot end machine case model are formed by using the entity process parameters, and the scanning mode is strip scanning, and the preparation of the hot end machine case is completed; The bottom layer thickness is 0.2mm, the transition layer thickness is 0.6mm, and the slicing thickness is 0.04mm; The hot end machine case takes GH4169 alloy powder as raw material, the bottom layer process parameter adopts laser power 200W, scanning speed 1500mm / s, and scanning interval 0.1mm; The transition layer adopts chessboard scanning, the vector number is 50, the process parameter is laser power 285W, scanning speed 1500mm / s, and scanning interval 0.1mm, the layer-by-layer remelting adopts strip scanning mode, and the remelting process parameter is laser power 285W, scanning speed 1500mm / s, and scanning interval 0.1mm; The entity layer process parameter is 285W, scanning speed 960mm / s, and scanning interval 0.1mm.

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