Flat shell and efficient printing method thereof

Abstract

The invention relates to a flat shell and an efficient printing method thereof, and belongs to the technical field of additive manufacturing. According to the invention, the axis of the flat shell is parallel to the substrate, and the support is arranged between the flat shell and the substrate; the substrate is divided into a region A and a region B; the area A is quadrilateral and is located in the center of the substrate, the side length of the area A is 55-65% of the side length of the substrate, and the area B is the remaining area obtained by subtracting the area A from the substrate; through analogue simulation, pre-printing and local reverse modeling, the deformation of the area A is controlled within + / -2mm; the deformation amount of the area B is controlled within + / -3 mm; the area A and the area B adopt different printing parameters, and the laser power and the scanning speed of the area A are both higher than those of the area B; and carrying out heat treatment to obtain the flat shell. And meanwhile, it is guaranteed that the deformation of the obtained flat shell is smaller than or equal to + / -0.5 mm, the tensile strength is 1000 MPa or above, and the yield strength is 800 MPa or above.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of additive manufacturing technology, in particular to a flat shell and an efficient printing method thereof. BACKGROUND

[0002] As an advanced additive manufacturing technology, laser selective printing technology has been widely used in many fields. The circular thin-walled part of the flat shell product (the outer diameter size is 360-400 mm, and the wall thickness size is 2.3-3 mm) is perpendicular to the substrate during the laser selective printing process, that is, the flat shell is placed horizontally during printing. When this printing method is used, the overall deformation of the obtained flat shell product is small, and the product quality is high.

[0003] However, there are still many problems: for example, the number of printing support structures is large, which not only increases the material consumption and time cost in the printing process, but also makes the subsequent wire cutting, heat treatment and other processes face higher cost and equipment resource waste. In addition, the most important thing is that the printing efficiency is very low, and if the flat shell product is printed along the vertical direction, the flat shells will be bonded, which will damage the flat shell itself during subsequent wire cutting, affecting the surface quality and performance.

[0004] Therefore, there is an urgent need for an efficient printing method to improve production efficiency while ensuring product quality and size requirements. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a flat shell and an efficient printing method thereof to improve production efficiency while ensuring product quality and size requirements.

[0006] In one aspect, the present application provides an efficient printing method for a flat shell, comprising the following steps:

[0007] S1: model design, the axis of the flat shell is parallel to the substrate, and a support is arranged between the flat shell and the substrate; and the substrate is divided into an A region and a B region;

[0008] The A region is a quadrilateral and is located at the center of the substrate, and the side length of the A region is 55-65% of the side length of the substrate, and the B region is the substrate region excluding the A region;

[0009] S2: model adjustment, through simulation simulation, pre-printing and local reverse modeling, the deformation of the A region is controlled within ±2mm; and the deformation amount of the B region is controlled within ±3mm;

[0010] S3: additive printing, the A region and the B region use different printing parameters, and the laser power and the scanning speed of the A region are both greater than those of the B region;

[0011] S4: obtaining the flat shell after heat treatment.

[0012] Further, in the simulation process, A area is ∑XX=-0.0035~ -0.004; ∑YY=-0.0035~ -0.004; ∑ZZ=-0.03, B area is ∑XX=-0.004~ -0.0043; ∑YY=-0.004~ -0.0043; ∑ZZ=-0.03.

[0013] Further, the laser power of A area is 320~350W, and the scanning speed is 1000~1100mm / s; the laser power of B area is 300~320W, and the scanning speed is 900~1000mm / s.

[0014] Further, the preheating temperature of the substrate is 80~100℃.

[0015] Further, the support structure comprises block-shaped supports and columnar supports.

[0016] Further, the interval between the flat shells is 10mm~15mm.

[0017] Further, the holding temperature of the heat treatment is 780~820℃, the holding time is 3~5h, and the furnace cooling is performed to 80℃ or below and then air cooling.

[0018] Further, the deformation of the flat shell is ≤±0.5mm, and the tensile strength is >980MPa and the yield strength is >800MPa.

[0019] Further, the number of each furnace is 7 times of the traditional one, the single-piece production time is shortened by nearly 60%, and the post-processing resource occupation is reduced by more than 2 times.

[0020] On the other hand, the application provides a flat shell, which is prepared by the method of the application, and the outer diameter size of the flat shell is 360~400mm, and the wall thickness size is 2.3~3mm.

[0021] Compared with the prior art, the application can at least achieve one of the following beneficial effects:

[0022] 1. The flat shell is placed vertically during printing, that is, the axis of the flat shell is parallel to the substrate. Compared with the prior art (horizontal placement during printing, the central axis of the flat shell product is perpendicular to the substrate), the printing yield is increased by more than 7 times, for example, the number of single furnace printing is increased from 4 to more than 28. At the same time, the post-processing cost is greatly reduced: in the wire cutting process, the number of products that can be cut is increased from 4 to more than 28 for the same wire distance, and the workload is reduced by more than 7 times; the waste of equipment resources in the heat treatment process is also reduced by 7 times, and the overall post-processing cost is reduced by more than 50%.

[0023] 2. In the printing process, the flat shell is placed vertically, and the substrate is divided into A area and B area, and during subsequent model adjustment, the deformation of the A area is controlled within ±2mm by using simulation, pre-printing and local reverse modeling; the deformation of the B area is controlled within ±3mm; during printing, the laser power and scanning speed of the A area are both greater than those of the B area, so that the deformation of the obtained flat shell is ≤±0.5mm, and the tensile strength is >980MPa and the yield strength is >800MPa.

[0024] The above technical solutions can be combined with each other in the present application to realize more preferred combination schemes. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification or be understood by implementing the present application. The purpose and other advantages of the present application can be achieved and obtained from the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0026] Figure 1 The printing arrangement schematic diagram for Comparative Example 1 is shown, and the central axis of the flat shell product is perpendicular to the substrate;

[0027] Figure 2 The printing arrangement schematic diagram for Example 1 is shown, and the central axis of the flat shell product is parallel to the substrate;

[0028] Figure 3 The schematic diagram of the block-shaped support structure is shown;

[0029] Figure 4 The schematic diagram of the columnar support structure is shown;

[0030] Figure 5 The schematic diagram of the cooperation between the columnar support and the block-shaped support is shown;

[0031] Figure 6The schematic diagram is divided for the substrate A area and B area;

[0032] Reference signs:

[0033] 1, support tooth; 2, support hollow; 3, columnar unit. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of the present application and serve to explain the principles of the embodiments of the present application, but are not used to limit the scope of the present application.

[0035] As an advanced additive manufacturing technology, laser selective printing technology has been widely used in many fields. In the laser selective printing process, the center axis of the flat shell product is perpendicular to the substrate, that is, the flat shell is placed horizontally during printing. When this printing method is used, the overall deformation of the obtained flat shell product is small, and the product quality is high.

[0036] However, there are still many problems: for example, the number of printing support structures is large, which not only increases the material consumption and time cost in the printing process, but also makes the subsequent wire cutting, heat treatment and other processes face higher cost and equipment resource waste. In addition, the most important thing is that the printing efficiency is very low, and if the flat shell product is printed along the vertical direction, the flat shells will be bonded, which will damage the flat shell itself during subsequent wire cutting, affecting the surface quality and performance.

[0037] Therefore, the present application provides a high-efficiency printing method for flat shell, comprising the following steps:

[0038] S1: model design, the axis of the flat shell is parallel to the substrate, and a support is arranged between the flat shell and the substrate; and the substrate is divided into A area and B area;

[0039] The A area is a quadrilateral and is located at the center of the substrate, and the side length of the A area is 55-65% of the side length of the substrate, and the B area is the remaining part of the substrate after subtracting the A area.

[0040] S2: model adjustment, through simulation simulation, pre-printing and local reverse modeling, the deformation of the A area is controlled within ±2mm; and the deformation amount of the B area is controlled within ±3mm;

[0041] S3: additive printing, the A area and the B area use different printing parameters, and the laser power and the scanning speed of the A area are both greater than those of the B area;

[0042] S4: obtaining the flat shell after heat treatment.

[0043] It should be noted that the flat shell is vertically placed during the printing process, that is, the axis of the flat shell is parallel to the substrate, which is different from the prior art (horizontally placed during printing, and the central axis of the flat shell product is perpendicular to the substrate). When printing with the same specification equipment, the printing yield is increased by more than 7 times, for example, the number of single furnace printing is increased from 4 to more than 28. At the same time, the post-processing cost is greatly reduced: in the wire cutting process, the number of products that can be cut under the same wire distance is increased from 4 to more than 28, and the workload is reduced by more than 7 times; the waste of equipment resources in the heat treatment process is also reduced by 7 times, and the overall post-processing cost is reduced by more than 50%.

[0044] In the present application, the flat shell is vertically placed during the printing process, and the substrate is divided into A and B regions, and during subsequent model adjustment, the deformation of the A region is controlled within ±2mm by using a combination of simulation, pre-printing and local reverse modeling; the deformation of the B region is controlled within ±3mm; during the printing process, the laser power and scanning speed of the A region are both greater than those of the B region, ensuring that the deformation of the obtained flat shell is ≤±0.5mm, and the tensile strength is >980MPa and the yield strength is >800MPa.

[0045] Specifically, in the simulation process, different simulation coefficients are used, wherein the A region has ∑XX=-0.0035~ -0.004; ∑YY=-0.0035~ -0.004; ∑ZZ=-0.03, and the B region has ∑XX=-0.004~ -0.0043; ∑YY=-0.004~ -0.0043; ∑ZZ=-0.03.

[0046] It should be noted that in the present application, since the flat shell is formed by using a vertical placement printing method during the printing process, the heat accumulation and dissipation in the B region and the A region are different. Since the B region dissipates heat quickly, the product in this region deforms greatly. The product printed in the A region of the substrate deforms less due to slow heat dissipation. Therefore, in the simulation process, ∑XX and ∑YY of the B region are greater than those of the A region.

[0047] Since the flat shell is vertically placed during the printing process in the present application, deformation occurs in the X and Y directions, and the outer diameter of the flat shell obtained by the present application is 360-400mm, which does not exceed 1000mm, so deformation does not occur in the Z direction. Therefore, ∑ZZ of the A region and the B region is the same.

[0048] Specifically, the laser power of the A area is 320-350 W, and the scanning speed is 1000-1100 mm / s; the laser power of the B area is 300-320 W, and the scanning speed is 900-1000 mm / s. The layer thickness is 30 pm, and the scanning interval is 0.12 mm; the printing environment is argon protection (purity 99.999%), and the oxygen content is less than or equal to 50 ppm, and the cabin temperature is 60-100 DEG C.

[0049] It should be noted that the heat of the A area of the substrate is not easy to dissipate, because the heat can only be transmitted to the powder below and around, the heat dissipation path is long and slow, and the heat is easy to accumulate. The B area of the substrate edge is closer to the cooling boundary, and the heat can be more quickly conducted to the substrate support and the cabin, and the heat dissipation speed is fast.

[0050] In order to compensate for the difference in heat conduction, higher power (320-350 W) and faster scanning speed (1000-1100 mm / s) are used in the A area of the substrate, which can melt the powder while avoiding overheating, splashing or deformation of the part caused by heat accumulation. In the B area of the substrate, slightly lower power (300-320 W) and slightly slower speed (900-1000 mm / s) are used, which can ensure that there is enough energy input to completely melt the powder under the condition of faster heat dissipation, avoiding un-melted defects.

[0051] Through such differential control, the molten pool shape and cooling and solidification process of different positions on the entire printing plane tend to be consistent, so that the printed parts are relatively uniform in density, microstructure and mechanical properties.

[0052] In the present application, the laser power of the A area can be 320 W, 325 W, 330 W, 335 W, 340 W, 345 W or 350 W; the scanning speed can be 1000 mm / s, 1010 mm / s, 1020 mm / s, 1030 mm / s, 1040 mm / s, 1050 mm / s, 1060 mm / s, 1070 mm / s, 1080 mm / s, 1090 mm / s or 1100 mm / s; if the laser power and scanning speed are too high, the energy input is excessive. It will cause the molten pool temperature to be too high and unstable, and produce intense metal vapor and splashing. If the laser power and scanning speed are too low, the energy input is insufficient. It will cause the powder to be unable to completely melt, and the combination with the lower layer or the same layer material is not firm, forming interlayer or interlayer pores, which seriously reduces the density and mechanical properties of the part.

[0053] In the present application, the laser power of the B region can be 300 W, 305 W, 310 W, 315 W or 320 W, and the scanning speed can be 900 mm / s, 910 mm / s, 920 mm / s, 930 mm / s, 940 mm / s, 950 mm / s, 960 mm / s, 970 mm / s, 980 mm / s, 990 mm / s or 1000 mm / s. If the power is too high (>320 W) or the speed is too slow (<900 mm / s), although the edge heat dissipation is fast, the high energy input will still cause problems similar to those in the A region, such as spatter, porosity, and unique stress concentration at the edge due to the mismatch between heat input and heat dissipation. If the power is too low (<300 W) or the speed is too fast (>1000 mm / s), due to the fast heat dissipation in the B region, the insufficient energy input will easily cause serious unfused defects, resulting in a loose and porous edge of the printed part with extremely low strength, and even the part cannot be formed.

[0054] If the A region and the B region use the same printing parameters, the same energy input will be generated, but the uneven shrinkage caused by different cooling conditions (slow in the A region and fast in the B region) will generate huge internal stress in the part. This stress can easily cause the part to warp and deform from the substrate, or crack during the printing process or post-processing.

[0055] Specifically, the preheating temperature of the substrate is 80-100℃.

[0056] It should be noted that during the printing process, the laser instantaneously melts the powder and rapidly cools and solidifies, resulting in a huge temperature gradient between the substrate / powder and generating a large residual stress. Preheating the substrate to 80-100℃ reduces the temperature difference between the molten pool and the substrate, making the temperature distribution more uniform and the cooling rate relatively slow. This effectively suppresses the generation of residual stress and prevents the part from warping, cracking or peeling off the substrate.

[0057] Specifically, the support structure includes block-shaped supports and columnar supports, the block-shaped supports are 3x3mm-5x5mm, and the width of the hollowed-out support teeth is 1mm-1.5mm; the columnar support parameters are: diameter 1-1.5mm, distance 4-6mm.

[0058] It should be noted that the block-shaped support: composed of solid block units, the units are connected to each other to form a three-dimensional structure similar to a grid or a block stack, with a relatively wide support surface, the structure is relatively thick and has strong integrity, and its function is to support the suspended plane of the flat shell and assist the formation of the flat shell. The columnar support: composed of dense columnar units, in the form of vertical array, the columns have a certain height and diameter, and the structure is relatively more "point-line" distributed. Its function is to support and control the deformation trend of the flat shell. The block-shaped supports and columnar supports are uniformly distributed.

[0059] Specifically, the holding temperature of the heat treatment is 780-820 DEG C, the holding time is 3-5h, and the furnace cooling is performed until the temperature is below 80 DEG C, and then air cooling is performed.

[0060] It should be noted that after printing, the organization is a typical non-equilibrium state, and there are a large number of distortions. At 780-820 DEG C, a recovery process occurs, which reduces the distortion energy and generates new, stress-free equiaxed grains, completely replacing the original high-strain columnar crystal organization. The temperature is controlled in this range, and it will not be overburned. After holding, the furnace cooling is performed, so that the temperature difference on the cross section of the flat shell is very small, and deformation will not occur. When the part is cooled to 80 DEG C in the furnace, this temperature is much lower than the plastic-brittle transition temperature of the material, and the atomic activity is very low. At this time, air cooling is performed, and the increase in cooling speed is not enough to introduce significant new stress.

[0061] Specifically, the spacing between the flat shells is 10-15mm.

[0062] It should be noted that during printing, a certain gap is required between the flat shells. On the one hand, there is enough space and path to dissipate to the surrounding powder bed, avoiding local overheating due to heat accumulation. On the other hand, there is a spacing between the flat shells, which does not need to be line cut, ensuring the quality of the flat shell. The spacing is controlled to be 10-15mm. If the spacing is too small, it will affect heat dissipation; if the spacing is too large, it will reduce production efficiency.

[0063] Specifically, the deformation of the flat shell is ≤±0.5mm, and the tensile strength is >980MPa and the yield strength is >800MPa.

[0064] Specifically, the material of the flat shell is TA15.

[0065] It should be noted that TA15 is a near-alpha titanium alloy with excellent comprehensive performance. According to the weight percentage (wt%), the chemical composition includes: Al: 5.5-7.0%; Mo: 0.5-2.0%; Zr: 1.5-2.5%; V: 0.8-2.5%; Ti: balance.

[0066] Aluminum Al: As the main alpha stabilizing element, Al can significantly improve the strength, elastic modulus and heat resistance of the alloy. It is a key element to ensure that TA15 has high strength and good thermal strength.

[0067] Molybdenum Mo and Vanadium V: These two are beta stabilizing elements. Their addition is controlled at a medium level, so that the microstructure of the alloy is in a "near-alpha" state. This not only ensures that the alloy has good organizational and performance stability at high temperatures, but also has certain heat treatment strengthening potential.

[0068] Zr: a neutral element, can solid solution strengthening alpha phase and beta phase, improve the room temperature strength and high temperature performance of the alloy, while the plasticity is less affected.

[0069] A flat shell is prepared by the method, the outer diameter size of the flat shell is 360-400 mm, and the wall thickness size is 2.3-3 mm.

[0070] In order to more clearly describe the present application, the following examples and comparative examples are further illustrated.

[0071] Example 1

[0072] S1: model design, the axis of the flat shell is parallel to the substrate (800 mm x 800 mm), and a support is arranged between the flat shell and the substrate; and the substrate is divided into an A area and a B area;

[0073] The A area is a quadrilateral and is located at the center of the substrate, and the side length of the A area is 60% of the side length of the substrate, that is, 480 mm x 480 mm, and the B area is the remaining area of the substrate after the A area is subtracted;

[0074] The support structure is a block support and a columnar support, the block support parameters are 3 x 3 mm grid, hollow, and the support tooth width is 1 mm; the columnar support parameters are: diameter 1.5 mm, distance 4 mm;

[0075] S2: model adjustment, simulation is carried out by a finite element software (SimufactAdditive), different simulation coefficients are adopted, the A area is ∑XX=-0.0035~ -0.004; ∑YY=-0.0035~ -0.004; ∑ZZ=-0.03, and the B area is ∑XX=-0.004~ -0.0043; ∑YY=-0.004~ -0.0043; ∑ZZ=-0.03. After simulation, pre-printing and local reverse modeling, the model is exported for printing. The deformation of the A area is controlled within ±2 mm; and the deformation of the B area is controlled within ±3 mm;

[0076] S3: additive printing, different printing parameters are adopted for the A area and the B area, the laser power and the scanning speed of the A area are both greater than those of the B area; the preheating temperature of the substrate is 80 DEG C, the laser power of the A area is 350 W, and the scanning speed is 1100 mm / s; the laser power of the B area is 320 W, and the scanning speed is 1000 mm / s; the layer thickness is 30 mu m, the scanning interval is 0.12 mm, argon protection (purity 99.999%) is adopted, the oxygen content is less than or equal to 50 ppm, and the cabin temperature is 80 DEG C.

[0077] S4: After heat treatment, a flat shell is obtained, the material of the flat shell is TA15, and the chemical composition is: Al: 6.0%; Mo: 1.5%; Zr: 2.0%; V: 1.5%; Ti: balance.

[0078] Example 2

[0079] Example 2 is substantially the same as the preparation process of Example 1, except that the substrate preheating temperature in Example 2 is 100 DEG C, the laser power of the A area is 320 W, and the scanning speed is 1000 mm / s; the laser power of the B area is 300 W, and the scanning speed is 900 mm / s.

[0080] Comparative Example 1

[0081] Comparative Example 1 is substantially the same as the preparation process of Example 1, except that Comparative Example 1 uses the existing printing method, and the flat shell is placed horizontally, i.e. the central axis of the flat shell is perpendicular to the substrate, and four pieces are printed at a time.

[0082] Comparative Example 2

[0083] Comparative Example 2 is substantially the same as the preparation process of Example 1, except that Comparative Example 2 does not divide the area, and the same printing parameters are used, the laser power is 350 W, and the scanning speed is 1100 mm / s.

[0084] Comparative Example 3

[0085] Comparative Example 3 is substantially the same as the preparation process of Example 1, except that the printing parameters of the A area and the B area are exchanged in Comparative Example 3, the laser power of the A area is 320 W, and the scanning speed is 1000 mm / s; the laser power of the B area is 350 W, and the scanning speed is 1100 mm / s.

[0086] Comparative Example 4

[0087] Comparative Example 4 is substantially the same as the preparation process of Example 1, except that the simulation coefficients of the A area and the B area are exchanged in Comparative Example 4, wherein the A area is ∑XX=-0.004~ -0.0043; ∑YY=-0.004~ -0.0043; ∑ZZ=-0.03, and the B area is ∑XX=-0.0035~ -0.004; ∑YY=-0.0035~ -0.004; ∑ZZ=-0.03.

[0088] Comparative Example 5

[0089] Comparative Example 5 is substantially the same as the preparation process of Example 1, except that step S2 is not used in Comparative Example 5, and direct modeling is used for printing and heat treatment.

[0090] Performance detection

[0091] The above examples and comparative examples are subjected to performance detection, mainly detecting the deformation amount and mechanical properties after printing, and the detection results are shown in Table 1.

[0092] Table 1 detection results

[0093]

[0094]

[0095] It can be seen from the combination of examples 1-2 and comparative examples 1-5 and reference to Table 1 that the flat shell is vertically placed during printing, i.e. the axis of the flat shell is parallel to the substrate, compared with the prior art method (horizontally placed during printing, the central axis of the flat shell product is perpendicular to the substrate). When printing with the same specification equipment, the printing yield is increased by more than 7 times, for example, the number of single furnace printing is increased from 4 to more than 28. The flat shell is vertically placed during printing, and the substrate is divided into A area and B area, and during subsequent model adjustment, the deformation of the A area is controlled within ±2mm by using the cooperation of simulation simulation, pre-printing and local reverse modeling; the deformation of the B area is controlled within ±3mm; during printing, the laser power and scanning speed of the A area are both greater than those of the B area, so as to ensure that the deformation of the obtained flat shell is ≤±0.5mm, and the tensile strength is more than 1000MPa and the yield strength is 800MPa.

[0096] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements easily thought of by those skilled in the art within the technical range disclosed by the present application should be covered within the protection scope of the present application.

Claims

1. A high-efficiency printing method for a flat shell, characterized in that, Includes the following steps: S1: Model design, the axis of the flat shell is parallel to the substrate, and a support is set between the flat shell and the substrate; and the substrate is divided into region A and region B; Region A is a quadrilateral located at the center of the substrate, and the side length of Region A is 55-65% of the side length of the substrate. Region B is the remaining area of ​​the substrate after subtracting Region A. S2: Model adjustment, through simulation, pre-printing, and local reverse modeling, controls the deformation of region A to within ±2mm; controls the deformation of region B to within ±3mm; S3: Additive printing, with different printing parameters for areas A and B. The laser power and scanning speed of area A are greater than those of area B. S4: A flat shell is obtained after heat treatment.

2. The efficient printing method for a flat shell according to claim 1, characterized in that, During the simulation, region A has ∑XX=-0.0035~-0.004; ∑YY=-0.0035~-0.004; ∑ZZ=-0.03, and region B has ∑XX=-0.004~-0.0043; ∑YY=-0.004~-0.0043; ∑ZZ=-0.

03.

3. The efficient printing method for a flat shell according to claim 2, characterized in that, The laser power in area A is 320–350 W, and the scanning speed is 1000–1100 mm / s; The laser power in region B is 300–320 W, and the scanning speed is 900–1000 mm / s.

4. The efficient printing method for a flat shell according to claim 1, characterized in that, The preheating temperature of the substrate is 80-100℃.

5. The efficient printing method for a flat shell according to claim 1, characterized in that, The support structure includes block supports and column supports.

6. The efficient printing method for a flat shell according to claim 1, characterized in that, The spacing between the flat shells is 10mm to 15mm.

7. The efficient printing method for a flat shell according to claim 1, characterized in that, The heat treatment is held at a temperature of 780–820°C for 3–5 hours, and then cooled in the furnace to below 80°C by air cooling.

8. The efficient printing method for a flat shell according to claim 1, characterized in that, The deformation of the flat shell is ≤ ±0.5 mm, and the tensile strength is > 980 MPa, and the yield strength is > 800 MPa.

9. The efficient printing method for a flat shell according to claim 1, characterized in that, The number of furnaces per batch is seven times that of the traditional batch, the production time per unit is reduced by nearly 60%, and the post-processing resource consumption is reduced by more than 2 times.

10. A flat shell, characterized in that, The flat shell is prepared by the method described in any one of claims 1-9, wherein the outer diameter of the flat shell is 360-400 mm and the wall thickness is 2.3-3 mm.

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