A method of preheating a powder bed in electron beam selective melting

Abstract

The present application relates to a kind of powder bed preheating method in electron beam selective melting, it relates to the field of additive manufacturing, it includes: after single layer powder laying, using first electron beam carries out first scanning preheating, then using first electron beam and second electron beam sequentially carries out second scanning preheating, third scanning preheating and fourth scanning preheating;The beam current of first electron beam in first scanning preheating is stepped increase;The beam current of first electron beam in third scanning preheating is less than the beam current of second electron beam.The preheating method provided by the present application, by using the mode of double electron beam cooperation, based on the preheating scanning process of specific design, can effectively control powder bed temperature fluctuation, to reduce the thermal stress in the forming process of large size workpiece, guarantee the manufacture of typical structural member without crack and warping deformation, improve the performance stability between component furnace.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of additive manufacturing, in particular to a powder bed preheating method in electron beam selective melting. BACKGROUND

[0002] At present, powder bed metal additive manufacturing has been widely used in advanced manufacturing fields such as aerospace, military equipment, automobiles and molds.

[0003] CN115592141A discloses an electron beam selective melting powder laying device and its use method, which mainly comprises a powder scraping mechanism, a pressing mechanism, a transmission device, a track and a powder storage bin. The scraper in the powder scraping mechanism is composed of rakes arranged alternately. The pressing mechanism is composed of a hydraulic oil spring and a roller to press the laid powder. The powder scraping mechanism and the pressing mechanism are controlled by the transmission mechanism. The front of the powder laying device is controlled by a lead screw, a servo motor and a shaft coupling for accurate transmission control of the running distance. The rear is controlled by a guide rail for accurate direction control. The powder storage bin is mainly used for storing powder.

[0004] However, the additive manufacturing of large-sized metal parts is still a bottleneck restricting its development, because the effective forming area of the electron beam selective melting equipment is small at high temperature, it is difficult to form large-sized difficult-to-weld and non-weldable high-temperature alloy and refractory alloy components, and it is difficult to inhibit the deformation or even cracking of large-sized complex structure components. When the temperature difference in a large area above 1000℃ is large, holes will be generated at the edge position of the large-sized part, resulting in poor part quality.

[0005] In order to meet the forming quality integration control of large-sized complex structure high-temperature alloy and refractory alloy material parts, the electron beam selective melting technology needs to realize efficient energy input control and stable thermal stress control, and ensure the uniformity in the forming space and time scale. For example, the number of electron guns is increased or additional auxiliary heating devices are added to preheat the un-melted powder.

[0006] However, when the material with extremely high crack sensitivity such as large-sized complex structure non-weldable and difficult-to-weld high-temperature alloy and refractory alloy parts is used, the problem of cracking, deformation and the like cannot be effectively avoided by only increasing the number of electron guns or adding additional auxiliary heating devices to preheat the un-melted powder. SUMMARY

[0007] In view of the problems in the prior art, the purpose of the present application is to provide a powder bed preheating method in electron beam selective melting, so as to solve the problems of product cracking, deformation and the like when the electron beam selective melting additive manufacturing is carried out on the material with extremely high crack sensitivity.

[0008] To achieve this purpose, the technical scheme adopted by the present application is as follows:

[0009] The application provides a powder bed preheating method in electron beam selective melting, and the preheating method comprises the following steps:

[0010] After the single-layer powder laying, first scanning preheating is performed by using the first electron beam, and then second scanning preheating, third scanning preheating and fourth scanning preheating are sequentially performed by using the first electron beam and the second electron beam.

[0011] In the first scanning preheating, the beam current of the first electron beam is stepwise increased, and the increasing rate is 1-10 mA / s.

[0012] In the third scanning preheating, the beam current of the first electron beam is smaller than that of the second electron beam.

[0013] The preheating method provided by the application can effectively control the powder bed temperature fluctuation by using the double-electron-beam cooperation mode based on the specifically designed preheating scanning process, thereby reducing the thermal stress in the forming process of large-size parts, ensuring the manufacturing of typical structural parts without cracks and warping deformation, and improving the performance stability between component furnace times.

[0014] As a preferred technical solution of the application, in the first scanning preheating, the beam current of the first electron beam is 40 mA-90 mA, the focusing is 50 mA-2000 mA, and the scanning speed is 15 m / s-40 m / s.

[0015] Preferably, the time of the first scanning preheating is ≤60 s.

[0016] As a preferred technical solution of the application, in the second scanning preheating, the beam current of the first electron beam is 40 mA-90 mA, the focusing is 50 mA-2000 mA, and the scanning speed is 15 m / s-40 m / s.

[0017] Preferably, in the second scanning preheating, the beam current of the second electron beam is 40 mA-90 mA, the focusing is 50 mA-2000 mA, and the scanning speed is 15 m / s-40 m / s.

[0018] As a preferred technical solution of the application, in the second scanning preheating, the beam current of the first electron beam is kept constant.

[0019] Preferably, in the second scanning preheating, the beam current of the second electron beam is kept constant.

[0020] Preferably, the time of the second scanning preheating is 20-100 s.

[0021] Preferably, the beam current of the first electron beam in the second scanning preheating is equal to that of the first electron beam in the first scanning preheating.

[0022] Preferably, the beam current of the first electron beam in the third scanning preheating is kept constant.

[0023] Preferably, the beam current of the second electron beam in the third scanning preheating is kept constant.

[0024] Preferably, the time of the third scanning preheating is 10-130s.

[0025] Preferably, the beam current of the first electron beam in the third scanning preheating is kept constant.

[0026] Preferably, the beam current of the second electron beam in the third scanning preheating is kept constant.

[0027] Preferably, the beam current of the first electron beam in the fourth scanning preheating is kept constant.

[0028] Preferably, the beam current of the second electron beam in the fourth scanning preheating is kept constant.

[0029] Preferably, the time of the fourth scanning preheating is 20s-100s.

[0030] Preferably, the beam current of the first electron beam in the fourth scanning preheating is kept constant.

[0031] Preferably, the beam current of the second electron beam in the fourth scanning preheating is kept constant.

[0032] Preferably, the preheating range of the preheating method comprises one or a combination of at least two of a substrate range, a closed coordinate position range, a cross-section edge local range or a filling forming range.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] (1) The preheating method of the present application realizes that the temperature fluctuation of the web within the area of 350mmx350mm is ≤50℃, the temperature fluctuation of the part cross-section position within the range of 350mmx350mm is ≤20℃, and the temperature of the part forming cross-section position can reach ≥1100℃.

[0035] (2) The preheating method of the application makes the temperature of the forming web uniform, the forming temperature level high, and the temperature fluctuation small during the forming process by means of the double electron beam melting web technology, and successfully prints the first dense and crack-free large-size complex structure Mar-M247 high-temperature alloy part.

[0036] (3) The application not only improves the electron beam selective melting forming capacity, but also breaks through the technical problem barrier of easy cracking and deformation during printing and forming of large-size complex structure high-temperature alloy and refractory alloy. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of a local structure position of a difficult-to-weld high-temperature alloy material (Mar-M247) part in embodiment 1 of the application, the forming size is about 336mmx346mm, and the preheating outer frame range is 350mmx350mm;

[0038] Figure 2 is a forming web temperature distribution diagram of the difficult-to-weld high-temperature alloy material (Mar-M247) part in embodiment 1 of the application, corresponding to the first scanning preheating and the second scanning preheating, obtained by using a thermal imaging camera;

[0039] Figure 3 is a forming cross-section temperature distribution diagram of the difficult-to-weld high-temperature alloy material (Mar-M247) part in embodiment 1 of the application, corresponding to the third scanning preheating, obtained by using a thermal imaging camera;

[0040] Figure 4 is a forming cross-section temperature monitoring diagram of the difficult-to-weld high-temperature alloy material (Mar-M247) part in embodiment 1 of the application, obtained by using an IGAR 12-LO digital double-color IMPAC temperature meter, the accuracy is 0.5%+1℃ 500℃±3.5℃, 1000℃±6℃.

[0041] The application will be further described in detail below. However, the following examples are only simple examples of the application, and do not represent or limit the protection scope of the application, and the protection scope of the application is subject to the claims. DETAILED DESCRIPTION

[0042] In order to better illustrate the application and facilitate understanding of the technical solutions of the application, the typical but non-limiting embodiments of the application are as follows:

[0043] Currently, when electron beam selective melting additive manufacturing is carried out on materials with extremely high crack sensitivity (Al > 3% and Ti > 5% in mass percentage), it is very difficult to form large-size complex structure superalloy parts because of the high requirements on the environmental temperature and temperature fluctuation during the forming process. Mar-M247 has the characteristics of high heat-resistant strength, good high-temperature mechanical properties, good anti-creep and anti-thermal corrosion performance, and good long-term working organizational stability, so it can be used to manufacture various turbine engines and aerospace rocket engines. However, Mar-M247 is a non-weldable superalloy, and it has extremely high crack sensitivity during preparation. Therefore, the environmental temperature and temperature fluctuation during the additive manufacturing process have high requirements. Therefore, it is very difficult to form large-size complex structure superalloy parts. Based on this, the preheating process of electron beam selective melting additive manufacturing is designed in the present application, and a specific preheating process is adopted to ensure that the forming environmental temperature is uniform and consistent within the range and the temperature of the part forming cross-sectional area is at a constant level, as follows:

[0044] One, the embodiment provides a preheating method for a powder bed in electron beam selective melting, as follows:

[0045] After single-layer powder laying, first scanning preheating is carried out by using a first electron beam, and then second scanning preheating, third scanning preheating and fourth scanning preheating are carried out by using the first electron beam and a second electron beam in turn.

[0046] In the present application, in the preheating process, the stepwise preheating in the first scanning preheating gradually increases from low-energy preheating to high-energy preheating level. The stepwise preheating is to gradually increase the powder bed temperature and gradually increase the powder bonding strength on the powder bed, so that the powder bed has the ability to accept the demand of high beam and double-gun simultaneous beam, and avoids the powder flying due to the repulsive force of charge accumulation, which causes the printing failure. And the 1# gun stepwise preheating can freely adjust the gradient number and step length according to different working conditions, powder materials and temperature gradient requirements.

[0047] In the present application, in the second scanning preheating, after the double-electron-beam beam is lowered, the powder bed temperature will quickly rise and smoothly reach the powder bed environmental temperature of filling forming. The powder bed temperature can be raised to 1500 DEG C and above under the condition of large-area double-gun simultaneous beam.

[0048] In the present application, in the third scanning preheating, the first electron beam starts filling scanning, and the second electron beam performs single-gun synchronous preheating. The second electron beam filling process preheating is to maintain the powder bed temperature stable during the forming process. The generation of thermal cracks caused by temperature fluctuation is effectively avoided, and larger-size materials with crack sensitivity can be formed. The setting of the second electron beam synchronous preheating parameters mainly depends on the preheating range and the target temperature level.

[0049] In the present application, in the fourth scanning preheating, the first electron beam and the second electron beam are preheated synchronously.

[0050] The beam current of the first electron beam in the first scanning preheating is increased in steps, and the increasing rate is 1 mA / s-10 mA / s, for example, it can be 1 mA / s, 1.9 mA / s, 2.8 mA / s, 3.7 mA / s, 4.6 mA / s, 5.5 mA / s, 6.4 mA / s, 7.3 mA / s, 8.2 mA / s, 9.1 mA / s or 10 mA / s, etc., but not limited to the listed values, other values not listed in this range also meet the requirements.

[0051] The beam current of the first electron beam in the first scanning preheating is 40 mA-90 mA, for example, it can be 40 mA, 45 mA, 50 mA, 55 mA, 60 mA, 65 mA, 70 mA, 75 mA, 80 mA, 85 mA or 90 mA, etc., but not limited to the listed values, other values not listed in this range also meet the requirements.

[0052] The focusing of the first electron beam in the first scanning preheating is 50 mA-2000 mA, for example, it can be 50 mA, 60 mA, 70 mA, 80 mA, 90 mA, 100 mA, 200 mA, 300 mA, 400 mA, 500 mA, 600 mA, 700 mA, 800 mA, 900 mA, 1000 mA, 1100 mA, 1200 mA, 1300 mA, 1400 mA, 1500 mA, 1600 mA, 1700 mA, 1800 mA, 1900 mA or 2000 mA, etc., but not limited to the listed values, other values not listed in this range also meet the requirements.

[0053] The scanning speed of the first electron beam in the first scanning preheating is 15 m / s-40 m / s, for example, it can be 15 m / s, 16 m / s, 18 m / s, 20 m / s, 22 m / s, 24 m / s, 26 m / s, 28 m / s, 30 m / s, 32 m / s, 34 m / s, 36 m / s, 38 m / s or 40 m / s, etc., but not limited to the listed values, other values not listed in this range also meet the requirements.

[0054] The time of the first scanning preheating is ≤60 s, for example, it can be 60 s, 50 s, 40 s, 20 s, 10 s, 8 s, 6 s, 4 s, 2 s or 1 s, etc., but not limited to the listed values, other values not listed in this range also meet the requirements.

[0055] In the second scan preheating, the first electron beam has a beam current of 40 mA-90 mA, for example, 40 mA, 45 mA, 50 mA, 55 mA, 60 mA, 65 mA, 70 mA, 75 mA, 80 mA, 85 mA, or 90 mA, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0056] In the second scan preheating, the first electron beam has a focus of 50 mA-2000 mA, for example, 50 mA, 60 mA, 70 mA, 80 mA, 90 mA, 100 mA, 200 mA, 300 mA, 400 mA, 500 mA, 600 mA, 700 mA, 800 mA, 900 mA, 1000 mA, 1100 mA, 1200 mA, 1300 mA, 1400 mA, 1500 mA, 1600 mA, 1700 mA, 1800 mA, 1900 mA, or 2000 mA, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0057] In the second scan preheating, the first electron beam has a scanning speed of 15 m / s-40 m / s, for example, 15 m / s, 16 m / s, 18 m / s, 20 m / s, 22 m / s, 24 m / s, 26 m / s, 28 m / s, 30 m / s, 32 m / s, 34 m / s, 36 m / s, 38 m / s, or 40 m / s, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0058] In the second scan preheating, the second electron beam has a beam current of 40 mA-90 mA, for example, 40 mA, 45 mA, 50 mA, 55 mA, 60 mA, 65 mA, 70 mA, 75 mA, 80 mA, 85 mA, or 90 mA, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0059] In the second scan preheating, the second electron beam has a focus of 50 mA-2000 mA, for example, 50 mA, 60 mA, 70 mA, 80 mA, 90 mA, 100 mA, 200 mA, 300 mA, 400 mA, 500 mA, 600 mA, 700 mA, 800 mA, 900 mA, 1000 mA, 1100 mA, 1200 mA, 1300 mA, 1400 mA, 1500 mA, 1600 mA, 1700 mA, 1800 mA, 1900 mA, or 2000 mA, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0060] The scanning speed of the second electron beam in the second scanning preheating is 15 m / s-40 m / s, for example, can be 15 m / s, 16 m / s, 18 m / s, 20 m / s, 22 m / s, 24 m / s, 26 m / s, 28 m / s, 30 m / s, 32 m / s, 34 m / s, 36 m / s, 38 m / s or 40 m / s, etc., but not limited to the listed values, other values not listed in the range are also required.

[0061] The beam current of the first electron beam in the second scanning preheating is kept constant.

[0062] The beam current of the second electron beam in the second scanning preheating is kept constant.

[0063] The time of the second scanning preheating is 20 s-100 s, for example, can be 20 s, 28 s, 36 s, 44 s, 52 s, 60 s, 68 s, 76 s, 84 s, 92 s or 100 s, etc., but not limited to the listed values, other values not listed in the range are also required.

[0064] The beam current of the first electron beam in the second scanning preheating = the beam current of the first electron beam in the first scanning preheating.

[0065] The beam current of the first electron beam in the third scanning preheating < the beam current of the second electron beam.

[0066] The beam current of the first electron beam in the third scanning preheating is 4 mA-20 mA, for example, can be 4 mA, 5.6 mA, 7.2 mA, 8.8 mA, 10.4 mA, 12 mA, 13.6 mA, 15.2 mA, 16.8 mA, 18.4 mA or 20 mA, etc., but not limited to the listed values, other values not listed in the range are also required.

[0067] The focusing of the first electron beam in the third scanning preheating is 10 mA-36 mA, for example, can be 10 mA, 12.6 mA, 15.2 mA, 17.8 mA, 20.4 mA, 23 mA, 25.6 mA, 28.2 mA, 30.8 mA, 33.4 mA or 36 mA, etc., but not limited to the listed values, other values not listed in the range are also required.

[0068] In some embodiments, the first electron beam has a scan speed of 0.4 m / s to 3 m / s in the third scan preheating. For example, the first electron beam can have a scan speed of 0.4 m / s, 0.66 m / s, 0.92 m / s, 1.18 m / s, 1.44 m / s, 1.7 m / s, 1.96 m / s, 2.22 m / s, 2.48 m / s, 2.74 m / s, or 3 m / s. Other values within the range are also possible.

[0069] In some embodiments, the second electron beam has a beam current of 60 mA to 99 mA in the third scan preheating. For example, the second electron beam can have a beam current of 60 mA, 65 mA, 70 mA, 75 mA, 80 mA, 85 mA, 90 mA, 95 mA, or 99 mA. Other values within the range are also possible.

[0070] In some embodiments, the second electron beam has a focus of 50 mA to 2000 mA in the third scan preheating. For example, the second electron beam can have a focus of 50 mA, 60 mA, 70 mA, 80 mA, 90 mA, 100 mA, 200 mA, 300 mA, 400 mA, 500 mA, 600 mA, 700 mA, 800 mA, 900 mA, 1000 mA, 1100 mA, 1200 mA, 1300 mA, 1400 mA, 1500 mA, 1600 mA, 1700 mA, 1800 mA, 1900 mA, or 2000 mA. Other values within the range are also possible.

[0071] In some embodiments, the second electron beam has a scan speed of 15 m / s to 40 m / s in the third scan preheating. For example, the second electron beam can have a scan speed of 15 m / s, 16 m / s, 18 m / s, 20 m / s, 22 m / s, 24 m / s, 26 m / s, 28 m / s, 30 m / s, 32 m / s, 34 m / s, 36 m / s, 38 m / s, or 40 m / s. Other values within the range are also possible.

[0072] In some embodiments, the third scan preheating has a time of 10 s to 130 s. For example, the third scan preheating can have a time of 10 s, 22 s, 34 s, 46 s, 58 s, 70 s, 82 s, 94 s, 106 s, 118 s, or 130 s. Other values within the range are also possible.

[0073] In some embodiments, the first electron beam has a constant beam current in the third scan preheating.

[0074] In some embodiments, the second electron beam has a constant beam current in the third scan preheating.

[0075] In the fourth scan preheating, the first electron beam has a beam current of 40 mA-99 mA, for example, 40 mA, 45 mA, 50 mA, 55 mA, 60 mA, 65 mA, 70 mA, 75 mA, 80 mA, 85 mA, 90 mA, 95 mA, or 99 mA, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0076] In the fourth scan preheating, the first electron beam has a focus of 50 mA-2000 mA, for example, 50 mA, 60 mA, 70 mA, 80 mA, 90 mA, 100 mA, 200 mA, 300 mA, 400 mA, 500 mA, 600 mA, 700 mA, 800 mA, 900 mA, 1000 mA, 1100 mA, 1200 mA, 1300 mA, 1400 mA, 1500 mA, 1600 mA, 1700 mA, 1800 mA, 1900 mA, or 2000 mA, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0077] In the fourth scan preheating, the first electron beam has a scanning speed of 15 m / s-40 m / s, for example, 15 m / s, 16 m / s, 18 m / s, 20 m / s, 22 m / s, 24 m / s, 26 m / s, 28 m / s, 30 m / s, 32 m / s, 34 m / s, 36 m / s, 38 m / s, or 40 m / s, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0078] In the fourth scan preheating, the second electron beam has a beam current of 40 mA-99 mA, for example, 40 mA, 45 mA, 50 mA, 55 mA, 60 mA, 65 mA, 70 mA, 75 mA, 80 mA, 85 mA, 90 mA, 95 mA, or 99 mA, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0079] In the fourth scan preheating, the second electron beam has a focus of 50 mA-2000 mA, for example, 50 mA, 60 mA, 70 mA, 80 mA, 90 mA, 100 mA, 200 mA, 300 mA, 400 mA, 500 mA, 600 mA, 700 mA, 800 mA, 900 mA, 1000 mA, 1100 mA, 1200 mA, 1300 mA, 1400 mA, 1500 mA, 1600 mA, 1700 mA, 1800 mA, 1900 mA, or 2000 mA, etc., but not limited to the listed values, and other values not listed in this range are also acceptable.

[0080] The scanning speed of the second electron beam in the fourth scanning preheating is 15 m / s-40 m / s, for example, can be 15 m / s, 16 m / s, 18 m / s, 20 m / s, 22 m / s, 24 m / s, 26 m / s, 28 m / s, 30 m / s, 32 m / s, 34 m / s, 36 m / s, 38 m / s or 40 m / s, etc., but not limited to the listed values, other unlisted values in the range also meet the requirements.

[0081] The time of the fourth scanning preheating is 20 s-100 s, for example, can be 20 s, 28 s, 36 s, 44 s, 52 s, 60 s, 68 s, 76 s, 84 s, 92 s or 100 s, etc., but not limited to the listed values, other unlisted values in the range also meet the requirements.

[0082] The beam current of the first electron beam in the fourth scanning preheating is kept constant.

[0083] The beam current of the second electron beam in the fourth scanning preheating is kept constant.

[0084] The preheating range of the preheating method includes one or a combination of at least two of the substrate range, the closed coordinate position range, the cross-sectional edge local range or the filling forming range.

[0085] In the present application, the substrate range preheating is determined according to the preheating substrate size, and the coordinate range preheating is performed according to the coordinate position to form a closed range of self-defined preheating range. This preheating method can better adjust the preheating range according to the structural characteristics of the formed part.

[0086] In the present application, the cross-sectional edge local range refers to a filling area preheating range formed by expanding a fixed distance outside the cross-sectional edge of the formed part, and the expansion distance is at least >1 mm.

[0087] In the present application, the preheating can select full-width preheating, local preheating, or a combination of full-width preheating and local preheating. The full-width preheating and local preheating can maintain the global range powder bed temperature, while further improving the temperature level and temperature uniformity of the forming range, and to some extent, the energy is concentrated in the forming range, which is beneficial to improve the forming efficiency.

[0088] Exemplarily, ① full-width preheating is: double electron gun full-width global preheating can select substrate range preheating or coordinate position range preheating. The substrate range preheating is determined according to the preheating substrate size, and the coordinate range preheating is performed according to the coordinate position to form a closed range of self-defined preheating range. This preheating method can better adjust the preheating range according to the structural characteristics of the formed part.

[0089] ②Global + local composite preheating: the double electron beams are optionally matched with global preheating or local preheating, wherein the local preheating range is a filling area preheating range surrounded by a fixed distance of the outer expansion of the cross-section edge of the formed part. The composite preheating strategy is to maintain the global range powder bed temperature, while further improving the temperature level and temperature uniformity of the forming range. And to a certain extent, the energy is concentrated in the forming range, which is beneficial to improve the forming efficiency.

[0090] ③Local same amplitude preheating: the first electron beam and the second electron beam simultaneously perform local preheating, which concentrates energy in the filling forming range, reduces the preheating range, improves the preheating efficiency, and meets the higher environmental temperature requirement when forming high-temperature alloy or refractory alloy materials.

[0091] II. In order to illustrate the excellent effect that the powder bed preheating method in the electron beam selective melting provided by the present application can achieve, the following actual examples are used for illustration, which are as follows:

[0092] Example 1

[0093] The embodiment provides a powder bed preheating method in electron beam selective melting, specifically using Mar-M247 material for electron beam selective melting, and the preheating process is as follows:

[0094] After single-layer powder laying, the first electron beam is used for first scanning preheating, and then the first electron beam and the second electron beam are used for second scanning preheating, third scanning preheating and fourth scanning preheating in sequence;

[0095] In the first scanning preheating, the beam current of the first electron beam is stepped up, and the increasing rate is 4.2 mA / s; the beam current of the first electron beam is 40 mA as the starting point and 90 mA as the end point to reach the scanning preheating time, the focusing is 2000 mA, and the scanning speed is 30 m / s; the time of the first scanning preheating is 12 s;

[0096] In the second scanning preheating, the beam current of the first electron beam is 90 mA, the focusing is 2000 mA, and the scanning speed is 30 m / s; the beam current of the second electron beam is 90 mA, the focusing is 2000 mA, and the scanning speed is 30 m / s; the beam current of the first electron beam is kept constant; the beam current of the second electron beam is kept constant; the time of the second scanning preheating is 44 s; the beam current of the first electron beam in the second scanning preheating is equal to the beam current of the first electron beam in the first scanning preheating.

[0097] The first electron beam in the third scanning preheating performs a shaping scan, the beam current is 8 mA, the focusing is 10 mA, and the scanning speed is 1.5 m / s; the second electron beam is preheated synchronously, the beam current is 95 mA, the focusing is 1800 mA, and the scanning speed is 30 m / s; the time of the third scanning preheating is 35 s (shaping scan time); the beam current of the first electron beam in the third scanning preheating is kept constant, and the beam current of the second electron beam is kept constant;

[0098] The beam current of the first electron beam in the fourth scanning preheating is 90 mA, the focusing is 2000 mA, and the scanning speed is 40 m / s; the beam current of the second electron beam is 90 mA, the focusing is 2000 mA, and the scanning speed is 30 m / s; the time of the fourth scanning preheating is 44 s; the beam current of the first electron beam in the fourth scanning preheating is kept constant, and the beam current of the second electron beam is kept constant.

[0099] Embodiment 2

[0100] The embodiment provides a preheating method for a powder bed in electron beam selective melting, in particular, electron beam selective melting of IN738 material, and the preheating process is as follows:

[0101] After single-layer powder laying, first scanning preheating is performed by using the first electron beam, and then second scanning preheating, third scanning preheating and fourth scanning preheating are sequentially performed by using the first electron beam and the second electron beam;

[0102] The beam current of the first electron beam in the first scanning preheating is increased in steps, and the increasing rate is 3.75 mA / s; the beam current of the first electron beam is started at 40 mA and ended at 85 mA to reach the scanning preheating time, the focusing is 1800 mA, and the scanning speed is 15 m / s-30 m / s; the time of the first scanning preheating is 10 s;

[0103] The beam current of the first electron beam in the second scanning preheating is 85 mA, the focusing is 1800 mA, and the scanning speed is 30 m / s; the beam current of the second electron beam is 85 mA, the focusing is 1800 mA, and the scanning speed is 30 m / s; the beam current of the first electron beam is kept constant; the beam current of the second electron beam is kept constant; the time of the second scanning preheating is 36 s; the beam current of the first electron beam in the second scanning preheating = the beam current of the first electron beam in the first scanning preheating; the beam current of the first electron beam in the second scanning preheating > the beam current of the second electron beam;

[0104] The beam current of the first electron beam in the third scanning preheating is 4 mA, the focus is 20 mA, and the scanning speed is 0.5 m / s; the beam current of the second electron beam is 90 mA, the focus is 1900 mA, and the scanning speed is 30 m / s; the time of the third scanning preheating is 35 s (the forming scanning time); the beam current of the first electron beam in the third scanning preheating is kept constant, and the beam current of the second electron beam is kept constant;

[0105] The beam current of the first electron beam in the fourth scanning preheating is 85 mA, the focus is 1800 mA, and the scanning speed is 30 m / s; the beam current of the second electron beam is 85 mA, the focus is 1800 mA, and the scanning speed is 30 m / s; the time of the fourth scanning preheating is 35 s; the beam current of the first electron beam in the fourth scanning preheating is kept constant, and the beam current of the second electron beam is kept constant; the beam current of the first electron beam in the fourth scanning preheating > the beam current of the second electron beam.

[0106] Embodiment 3

[0107] The embodiment provides a preheating method for a powder bed in electron beam selective melting, in particular, the electron beam selective melting is performed by using GH3536 material, and the preheating process is as follows:

[0108] After the single-layer powder is laid, the first scanning preheating is performed by using the first electron beam, and then the second scanning preheating, the third scanning preheating and the fourth scanning preheating are sequentially performed by using the first electron beam and the second electron beam;

[0109] The beam current of the first electron beam in the first scanning preheating is increased in steps, and the increasing rate is 3.6 mA / s; the beam current of the first electron beam is 40 mA as the start and 79.6 mA as the end to reach the scanning preheating time, the focus is 1800 mA, and the scanning speed is 31 m / s; the time of the first scanning preheating is 11 s;

[0110] The beam current of the first electron beam in the second scanning preheating is 82 mA, the focus is 1800 mA, and the scanning speed is 31 m / s; the beam current of the second electron beam is 82 mA, the focus is 1800 mA, and the scanning speed is 31 m / s; the beam current of the first electron beam is kept constant; the beam current of the second electron beam is kept constant; the time of the second scanning preheating is 27 s; the beam current of the first electron beam in the second scanning preheating = the beam current of the first electron beam in the first scanning preheating;

[0111] The beam current of the first electron beam in the third scanning preheating is 20 mA, the focus is 36 mA, and the scanning speed is 3 m / s; the beam current of the second electron beam is 85 mA, the focus is 1800 mA, and the scanning speed is 3 m / s; the time of the third scanning preheating is 35 s (the filling forming time); the beam current of the first electron beam in the third scanning preheating is kept constant, and the beam current of the second electron beam is kept constant;

[0112] The beam current of the first electron beam in the fourth scanning preheating is 82 mA, the focus is 1800 mA, and the scanning speed is 31 m / s; the beam current of the second electron beam is 82 mA, the focus is 1800 mA, and the scanning speed is 31 m / s; the time of the fourth scanning preheating is 27 s; the beam current of the first electron beam in the fourth scanning preheating is kept constant, and the beam current of the second electron beam is kept constant; the beam current of the first electron beam in the fourth scanning preheating > the beam current of the second electron beam.

[0113] Comparative Example 1

[0114] The difference from Example 1 is only that the first scanning preheating is not performed, that is, the second scanning preheating is directly performed.

[0115] Comparative Example 2

[0116] The difference from Example 1 is only that the second scanning preheating is not performed.

[0117] Comparative Example 3

[0118] The difference from Example 1 is only that the third scanning preheating is not performed.

[0119] Example 4

[0120] The difference from Example 1 is only that the beam current of the first electron beam in the third scanning preheating is a constant value, which is 70 mA / s.

[0121] Example 5

[0122] The difference from Example 1 is only that the beam current of the first electron beam in the third scanning preheating is a constant value, which is 50 mA / s.

[0123] The preheating process temperature and the forming temperature of the above examples and comparative examples are detected, and the results are as shown in Table 1.

[0124] Table 1

[0125]

[0126] As can be seen from Table 1, the scheme provided by the present application realizes effective distribution of high energy input through the double electron beam same amplitude melting forming technology, not only makes up for the temperature fluctuation problem caused by the change of energy input in the 3D printing process, but also improves the forming efficiency while guaranteeing the forming process parameter window of large-size high-temperature alloy parts.

[0127] Further, as can be seen from the temperature detection results of Example 1, Figure 1 and Figure 2 it can be seen that the double electron beam preheating can guarantee that the forming environment temperature range of about 336 mm x 346 mm is uniform and consistent, and Figure 3 andFigure 4 It is shown that the double electron beam preheating can ensure that the temperature of the part forming cross section area is stable at about 1100℃.

[0128] The above describes the preferred embodiments of the present application, but the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0129] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0130] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the idea of the present application, and it should also be considered as disclosed by the present application.

Claims

1. A method for preheating a powder bed in electron beam selective melting, characterized in that, The preheating method includes: After single-layer powder coating, a first scan preheating is performed using a first electron beam, followed by a second scan preheating, a third scan preheating, and a fourth scan preheating in sequence. The second scan preheating, the third scan preheating, and the fourth scan preheating are all performed using the first electron beam and the second electron beam; The second scanning preheating process employs a dual electron beam downbeam technique; During the third scanning preheating, the first electron beam begins to perform a filling scan, and the second electron beam performs single-gun synchronous preheating. The fourth scanning preheating is performed by synchronizing the first electron beam and the second electron beam for preheating. In the first scanning preheating, the beam current of the first electron beam increases in a stepwise manner, with an increase rate of 1-10 mA / s; In the third scan preheating, the beam current of the first electron beam is less than that of the second electron beam; in the third scan preheating, the beam current of the first electron beam is 4mA-20mA, the focusing is 10mA-36mA, and the scanning speed is 0.4m / s-3m / s; in the third scan preheating, the beam current of the second electron beam is 60mA-99mA, the focusing is 50mA-2000mA, and the scanning speed is 15m / s-40m / s.

2. The preheating method as described in claim 1, characterized in that, In the first scanning preheating, the beam current of the first electron beam is 40mA-90mA, the focusing is 50mA-2000mA, and the scanning speed is 15m / s-40m / s; The warm-up time for the first scan is ≤60s.

3. The preheating method as described in claim 1, characterized in that, In the second scanning preheating, the beam current of the first electron beam is 40mA-90mA, the focusing is 50mA-2000mA, and the scanning speed is 15m / s-40m / s; In the second scanning preheating, the beam current of the second electron beam is 40mA-90mA, the focusing is 50mA-2000mA, and the scanning speed is 15m / s-40m / s.

4. The preheating method as described in claim 1, characterized in that, During the second scanning preheating, the beam current of the first electron beam is kept constant; During the second scanning preheating, the beam current of the second electron beam is kept constant; The warm-up time for the second scan is 20-100 seconds.

5. The preheating method as described in claim 1, characterized in that, The preheating time for the third scan is 10-130 seconds; During the third scanning preheating, the beam current of the first electron beam is kept constant; During the third scanning preheating, the beam current of the second electron beam is kept constant.

6. The preheating method as described in claim 1, characterized in that, In the fourth scanning preheating, the beam current of the first electron beam is 40mA-99mA, the focusing is 50mA-2000mA, and the scanning speed is 15m / s-40m / s.

7. The preheating method as described in claim 1, characterized in that, In the fourth scanning preheating, the beam current of the second electron beam is 40mA-99mA, the focusing is 50mA-2000mA, and the scanning speed is 15m / s-40m / s.

8. The preheating method as described in claim 1, characterized in that, The preheating time for the fourth scan is 20s-100s; During the fourth scan preheating, the beam current of the first electron beam is kept constant; During the fourth scan preheating, the beam current of the second electron beam is kept constant.

9. The preheating method according to any one of claims 1-8, characterized in that, The preheating range of the preheating method includes one or a combination of at least two of the following: substrate range, closed coordinate position range, local range of cross-sectional edge, or filling forming range.

Images