Composite heat treatment process and heat treatment device for reducing cracking tendency of component

Abstract

The invention relates to a composite heat treatment process and a heat treatment device for reducing the cracking tendency of a component, belongs to the technical field of additive manufacturing, and solves the problems that special equipment is needed and the process is tedious in the existing process. The composite heat treatment process comprises the following steps that 1, a component is placed in a furnace body of the heat treatment device; 2, setting heat treatment process parameters; 3, the heat treatment device is started, the component is heated, and the furnace body is filled with gas so as to apply pressure to the component; and 4, preserving heat and cooling. The heat treatment device comprises a furnace body, a heating unit, a pressurizing unit, a monitoring unit and a control unit.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a composite heat treatment process and a heat treatment device for reducing the cracking tendency of special-shaped large-sized components. Background Art

[0002] Laser selective melting additive manufacturing technology has the characteristics of high energy density, high manufacturing precision, and excellent comprehensive performance. It has outstanding advantages in the manufacturing of refractory metals and complex structures and has been widely used in the aerospace field. However, the high temperature gradient and residual stress accumulation during the laser selective melting process can easily lead to a significant increase in the cracking tendency of high-strength alloys, especially large and complex components, which seriously limits the widespread application of this technology.

[0003] Due to the high temperature gradient and residual stress accumulation during the laser selective melting forming process, the cracking tendency of components formed by laser selective melting additive manufacturing technology increases significantly. Therefore, it is necessary to perform annealing heat treatment on the components formed by laser selective melting to release the residual stress through deformation or even cracking. However, with the increase in component size and the stress concentration caused by the characteristic structure distribution, the existing annealing heat treatment cannot effectively release the residual stress of large and complex special-shaped components.

[0004] In order to solve the above problems, the existing technology adds additional steps after the annealing heat treatment process. For example, hot isostatic pressing technology is used to fill an inert gas into a closed container, so that the product produces a metallurgical reaction at a higher temperature (usually close to the forging temperature of the material) and a higher pressure (usually 100-140MPa), thereby changing the organizational structure of the product to eliminate defects such as pores and unfused materials and improve the density of the product.

[0005] However, hot isostatic pressing technology requires special equipment, and the equipment is expensive and the production cost is high. In addition, the high temperature and high pressure of hot isostatic pressing technology consumes a lot of energy. Summary of the invention

[0006] In view of the above analysis, the present invention aims to provide a composite heat treatment process and a heat treatment device for reducing the cracking tendency of components, which can solve at least one of the following technical problems: (1) The existing process for reducing the cracking tendency of components has high energy consumption; (2) The existing process for reducing the cracking tendency of components requires special equipment, and the equipment is expensive and the production cost is high; (3) The existing process for reducing the cracking tendency of components is an additional process after the heat treatment process, and the process is cumbersome.

[0007] The purpose of the present invention is mainly achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a composite heat treatment process, comprising the following steps:

[0009] Step 1: placing the component in the furnace of the heat treatment device;

[0010] Step 2: Set heat treatment process parameters;

[0011] Step 3: Start the heat treatment device to heat the component and fill the furnace with gas to apply pressure to the component;

[0012] Step 4: Keep warm and cool.

[0013] Optionally, in step 3, the applied pressure is 20-80 MPa.

[0014] Optionally, in step 3, the heating temperature is 200-1200°C.

[0015] Optionally, in step 3, the heating rate is 5-30°C / min.

[0016] Optionally, in step 4, the insulation time is 200-900 min.

[0017] Optionally, in step 3, the gas is an inert gas.

[0018] Optionally, the inert gas is helium and / or argon.

[0019] Optionally, in step 2, the heat treatment process parameters include heating rate, heating temperature, holding time, cooling rate and applied pressure.

[0020] Optionally, in step 1, the component is a special-shaped component.

[0021] In a second aspect, the present invention provides a heat treatment device for completing the above-mentioned composite heat treatment process, comprising a furnace body, a heating unit, a pressurizing unit, a monitoring unit and a control unit;

[0022] The heating unit is used to heat the furnace body, the pressurizing unit is used to fill the furnace body with gas, the monitoring unit is used to detect the temperature and pressure inside the furnace body, and the working states of the heating unit and the pressurizing unit are controlled by the control unit.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] (1) The process of the present invention is a new composite heat treatment system with an external energy field, that is, no additional process is added. Inert gas is filled into the device during the heat treatment process to achieve the purpose of applying a certain pressure to the component during the heat treatment process. The applied pressure resists the release of residual stress inside the component during the heat treatment process, while improving the residual stress elimination effect (manifested as lower residual stress, shortened heat treatment time, and improved efficiency), reducing the probability of component deformation and cracking, and improving the product qualification rate. Specifically, the internal residual stress of the component after being treated by the composite heat treatment process of the present invention is reduced by more than 26% compared with that after being treated by the existing heat treatment process, and the efficiency is improved by more than 10%.

[0025] (2) Compared with hot isostatic pressing technology, the composite heat treatment process of the present invention can achieve the purpose of improving the residual stress elimination effect (manifested as lower residual stress, shortened heat treatment time, and improved efficiency) and reducing the deformation and cracking probability of components at a lower temperature (lower than the melting temperature of the alloy, hot isostatic pressing technology requires a temperature close to the forging temperature of the alloy) and a lower pressure (20-80MPa, much lower than the 100-140MPa of hot isostatic pressing technology) without chemical reaction. Therefore, the composite heat treatment process of the present invention has low energy consumption.

[0026] (3) The composite heat treatment process of the present invention only requires adding a pressurizing device capable of applying pressure to the existing heat treatment device to realize a low-pressure heat treatment process. There is no need to purchase special equipment, which is beneficial to reducing production costs.

[0027] (4) The present invention controls the thermal insulation to be gradient thermal insulation, and controls the gradient temperature, gradient segmentation mode and pressure of the gradient thermal insulation, thereby further ensuring that the residual stress of the treated component is lower.

[0028] (5) The composite heat treatment process of the present invention applies pressure during the heat treatment process and does not require additional steps. Therefore, the process of the present invention is simple and is conducive to improving production efficiency.

[0029] (6) The composite heat treatment process of the present invention is applicable to the heat treatment process of alloy components manufactured by additive manufacturing of different types, and has a wide range of uses, and is particularly suitable for the heat treatment of alloy components of special shapes and large sizes (1m×1m×2m).

[0030] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can be obvious from the description or understood by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0032] Figure 1 This is a photo of the component after treatment in Comparative Example 1;

[0033] Figure 2 This is a photo of the component after treatment in Example 1. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0035] In a first aspect, the present invention provides a composite heat treatment process, comprising the following steps:

[0036] Step 1: Place the component in the furnace body of the heat treatment device, place the component in the center of the furnace body, and place it symmetrically according to the characteristic structural distribution of the component;

[0037] Step 2: Set heat treatment process parameters;

[0038] Step 3: Start the heat treatment device to heat the component and fill the furnace with gas to apply pressure to the component;

[0039] Step 4: Keep warm and cool.

[0040] The present invention utilizes the principle of hot isostatic pressing to carry out a heat treatment process on large and complex components of laser selective melting formed precipitation-strengthened high-temperature alloys, and applies a certain pressure to the components to offset the residual stress of the components, thereby preventing the components from releasing stress in the form of deformation or cracking during the heat treatment process.

[0041] In step 1, the heat treatment device includes a furnace body, a heating unit, a pressurizing unit, a monitoring unit and a control unit. The furnace body meets the pressure vessel standard. The heating unit is used to heat the furnace body, the pressurizing unit is used to fill the furnace body with inert gas, the monitoring unit is used to detect the temperature and pressure in the furnace body, and the working state of the heating unit and the pressurizing unit is controlled by the control unit. The inert gas can be, for example, helium and / or argon.

[0042] Specifically, in step 2, the heat treatment process parameters include heating rate, heating temperature, holding time, cooling rate and applied pressure.

[0043] In step 3, during the heating process, pressure is gradually applied by filling the furnace with inert gas, so that the component is subjected to pressure while being heated.

[0044] Specifically, the heating rate is 5-30°C / min, for example, 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, 30°C / min.

[0045] The heating temperature is 200-1200°C, for example, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C.

[0046] The applied pressure is 20-80 MPa, for example, 20 MPa, 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa, 80 MPa.

[0047] In step 4, the insulation time is 200-900 min, for example, 200 min, 300 min, 400 min, 500 min, 600 min, 700 min, 800 min, 900 min.

[0048] It should be noted that in step 4, the heat preservation is a gradient heat preservation, including:

[0049] 400°C for 60-120 min (e.g., 60 min, 80 min, 100 min, 120 min), pressure 60 MPa;

[0050] 600-650° C. (e.g., 600° C., 610° C., 620° C., 630° C., 640° C., 650° C.), insulation for 60-200 min (e.g., 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min, 200 min), pressure 60 MPa;

[0051] 600-850°C (e.g., 600°C, 650°C, 700°C, 750°C, 800°C, 850°C), insulation for 60-120min (e.g., 60min, 80min, 100min, 120min), pressure 60MPa;

[0052] Alternatively, in step 4, the heat preservation is a gradient heat preservation, comprising:

[0053] 400°C for 60-120 min (e.g., 60 min, 80 min, 100 min, 120 min), pressure 60 MPa;

[0054] 600-650℃ (e.g., 600℃, 610℃, 620℃, 630℃, 640℃, 650℃), insulation for 60-200min (e.g., 60min, 80min, 100min, 120min, 140min, 160min, 180min, 200min), pressure 60MPa

[0055] 600-850°C (e.g., 600°C, 650°C, 700°C, 750°C, 800°C, 850°C), insulation for 60-120min (e.g., 60min, 80min, 100min, 120min), pressure 80MPa;

[0056] 800-850°C (e.g., 800°C, 810°C, 820°C, 830°C, 840°C, 850°C), insulation for 60-80min (e.g., 60min, 70min, 80min), pressure 80MPa;

[0057] 1000-1200°C (e.g., 1000°C, 1100°C, 1200°C), insulation for 80-120min (e.g., 80min, 90min, 100min, 120min), pressure 80MPa;

[0058] 600-650°C (e.g., 600°C, 610°C, 620°C, 630°C, 640°C, 650°C), insulation for 60-80min (e.g., 60min, 70min, 80min), pressure 80MPa;

[0059] 800-850°C (e.g., 800°C, 810°C, 820°C, 830°C, 840°C, 850°C), keep warm for 200 min, pressure 80 MPa.

[0060] In step 4, the application of pressure is stopped during the cooling process until the component cools to room temperature, and the cooling rate is determined according to the heat treatment system. For example, it can be furnace cooling.

[0061] The process of the present invention is a new composite heat treatment system with an external energy field, that is, no additional process is added. In the heat treatment process, an inert gas is filled into the device to achieve the purpose of applying a certain pressure to the component during the heat treatment process. The applied pressure resists the release of residual stress inside the component during the heat treatment process, while improving the residual stress elimination effect (manifested as lower residual stress, shortened heat treatment time, and improved efficiency), reducing the probability of component deformation and cracking, and improving the product qualification rate. Specifically, the internal residual stress of the component after being treated by the composite heat treatment process of the present invention is reduced by more than 26% compared with that after being treated by the existing heat treatment process, and the efficiency is improved by more than 10%.

[0062] Compared with the hot isostatic pressing technology, the composite heat treatment process of the present invention can achieve the purpose of improving the residual stress elimination effect (manifested as lower residual stress, shortened heat treatment time, and improved efficiency) and reducing the deformation and cracking probability of components at a lower temperature (lower than the melting temperature of the alloy, and the hot isostatic pressing technology needs to be close to the forging temperature of the alloy) and a lower pressure (20-80MPa, much lower than the 100-140MPa of the hot isostatic pressing technology) without chemical reaction. Therefore, the composite heat treatment process of the present invention has low energy consumption.

[0063] The composite heat treatment process of the present invention only requires adding a pressurizing device capable of applying pressure to the existing heat treatment device to realize a heat treatment process in a low-pressure state, and does not require the purchase of special equipment, which is beneficial to reducing production costs.

[0064] The present invention controls the thermal insulation to be gradient thermal insulation, and controls the gradient temperature, gradient segmentation mode and pressure of the gradient thermal insulation, thereby further ensuring that the residual stress of the treated component is lower.

[0065] The composite heat treatment process of the present invention is to apply pressure during the heat treatment process without requiring additional steps. Therefore, the process of the present invention is simple and is conducive to improving production efficiency.

[0066] The composite heat treatment process of the present invention is applicable to heat treatment processes of alloy components manufactured by additive manufacturing of different types, and has wide applicability, and is particularly suitable for heat treatment of alloy components of special shapes and large sizes (1m×1m×2m).

[0067] The composite heat treatment process of the present invention is described below with reference to specific embodiments.

[0068] Example 1

[0069] This embodiment is to perform heat treatment on a Ti-based alloy TA15 additively manufactured component, comprising the following steps:

[0070] Step 1: Place the component in the furnace body of the heat treatment device, place the component in the center of the furnace body, and place it symmetrically according to the characteristic structural distribution of the component;

[0071] Step 2: Setting heat treatment process parameters; wherein the heating rate is 5°C / min, the heating temperature is 850°C, and the applied pressure is 60MPa;

[0072] Step 3: Start the heat treatment device to heat and apply pressure to the component;

[0073] Step 4: Keep at 400℃ for 60min and pressure 60MPa, keep at 600℃ for 60min and pressure 60MPa, keep at 850℃ for 120min and pressure 60MPa, then cool in the furnace.

[0074] Example 2

[0075] This embodiment is to perform heat treatment on a Ni-based high-temperature alloy GH4099 additively manufactured component, comprising the following steps:

[0076] Step 1: Place the component in the furnace body of the heat treatment device, place the component in the center of the furnace body, and place it symmetrically according to the characteristic structural distribution of the component;

[0077] Step 2: Set the heat treatment process parameters; among which, the heating rate is 10℃ / min, the annealing temperature is 650℃, and the applied pressure is 60MPa; the solid solution temperature is 1200℃, and the applied pressure is 80MPa; the aging temperature is 850℃, and the applied pressure is 50MPa.

[0078] Step 3: Start the heat treatment device to heat and apply pressure to the component;

[0079] Step 4: Keep at 400℃ for 60min and pressure 60MPa, keep at 650℃ for 80min and pressure 60MPa; keep at 600℃ for 60min and pressure 80MPa, keep at 850℃ for 60min and pressure 80MPa, keep at 1200℃ for 100min and pressure 80MPa; keep at 600℃ for 60min and pressure 80MPa, keep at 850℃ for 200min and pressure 80MPa; then cool with the furnace.

[0080] Comparative Example 1

[0081] This comparative example is substantially the same as Example 1, except that no pressure is applied to the component during the heat treatment process, and the heat preservation is not gradient heat preservation, but heat preservation at 800° C. for 4 hours.

[0082] Comparative Example 2

[0083] This comparative example is basically the same as Example 1, except that in step 4, instead of gradient insulation, the temperature is kept at 800° C. for 4 h.

[0084] Comparative Example 3

[0085] This comparative example is basically the same as Example 1, except that the temperature of the gradient insulation is different, namely, insulation at 300°C for 60 min and pressure of 60 MPa, insulation at 700°C for 60 min and pressure of 60 MPa, and insulation at 900°C for 120 min and pressure of 60 MPa.

[0086] Comparative Example 4

[0087] This comparative example is basically the same as Example 1, except that the gradient segmentation method is different, namely, keeping warm at 400°C for 60 min and pressure of 60 MPa, keeping warm at 600°C for 60 min and pressure of 60 MPa, keeping warm at 700°C for 60 min and pressure of 60 MPa, and keeping warm at 850°C for 60 min and pressure of 60 MPa.

[0088] Comparative Example 5

[0089] This comparative example is basically the same as Example 1, except that the pressure of the gradient insulation is different, namely, 400°C insulation for 60 min at a pressure of 100 MPa, 600°C insulation for 60 min at a pressure of 100 MPa, and 850°C insulation for 120 min at a pressure of 100 MPa.

[0090] Under the same conditions, residual stress tests were performed on the components treated in the embodiment and the comparative example using the GB / T7704-2017 non-destructive testing X-ray stress measurement method. The results are listed in Table 1.

[0091] Table 1 Residual stress test results

[0092]

[0093]

[0094] It can be seen from Table 1 that when the composite heat treatment process of the present invention is not adopted (Comparative Example 1), the residual stress of the component is 33.00 MPa, while when the composite heat treatment process of the present invention is adopted (Example 1), the residual stress of the component is only 24.23 MPa, and the residual stress is reduced by 26.6%.

[0095] It can be seen from the data of Example 1, Comparative Examples 1 and 2 that when gradient thermal insulation is not adopted (Comparative Example 2), compared with the process of not applying pressure during the heat treatment process (Comparative Example 1), although the residual stress of the component can be reduced to a certain extent, the residual stress is still higher than the process of applying pressure during the heat treatment process + gradient thermal insulation (Example 1). This proves that the use of gradient thermal insulation can further reduce the residual stress of the component, and further ensure that the residual stress of the component after treatment is lower.

[0096] In addition, it can be seen from the data of Comparative Examples 3-5 in Table 1 that when gradient temperatures, gradient segmentation methods and pressures other than 400°C insulation for 60-120 min, 60 MPa pressure, 600-650°C insulation for 60-200 min, 60 MPa pressure, and 600-850°C insulation for 60-120 min, 60 MPa pressure are used, the residual stress of the component after treatment is equivalent to that of Comparative Example 2 (without gradient insulation), but is higher than the residual stress of the component after treatment in Example 1, which proves that the use of the above-mentioned gradient temperature, gradient segmentation method and pressure is beneficial to further reduce the residual stress of the component after treatment.

[0097] Figure 1 This is a photo of the component after treatment in Comparative Example 1. Figure 1 It can be seen that there are obvious cracks in the components and the product is unqualified.

[0098] Figure 2 This is a photo of the component after treatment in Example 1. Figure 2 It can be seen that there are no cracks in the component and no deformation, and the product is qualified.

[0099] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A composite heat treatment process, characterized in that: The steps include: Step 1: placing the component in the furnace of the heat treatment device; Step 2: Set heat treatment process parameters; Step 3: Start the heat treatment device to heat the component and fill the furnace with gas to apply pressure to the component; Step 4: Keep warm and cool.

2. The composite heat treatment process according to claim 1, characterized in that: In step 3, the applied pressure is 20-80 MPa.

3. The composite heat treatment process according to claim 1, characterized in that: In step 3, the heating temperature is 200-1200°C.

4. The composite heat treatment process according to claim 1, characterized in that: In step 3, the heating rate is 5-30°C / min.

5. The composite heat treatment process according to claim 1, characterized in that: In step 4, the insulation time is 200-900 minutes.

6. The composite heat treatment process according to claim 1, characterized in that: In step 3, the gas is an inert gas.

7. The composite heat treatment process according to claim 6, characterized in that: The inert gas is helium and / or argon.

8. The composite heat treatment process according to claim 1, characterized in that: In step 2, the heat treatment process parameters include heating rate, heating temperature, holding time, cooling rate and applied pressure.

9. The composite heat treatment process according to claim 1, characterized in that: In step 1, the component is a special-shaped component.

10. A heat treatment device, characterized in that: Used to complete the composite heat treatment process according to any one of claims 1 to 9, characterized in that it includes a furnace body, a heating unit, a pressurizing unit, a monitoring unit and a control unit; The heating unit is used to heat the furnace body, the pressurizing unit is used to fill the furnace body with gas, the monitoring unit is used to detect the temperature and pressure inside the furnace body, and the working states of the heating unit and the pressurizing unit are controlled by the control unit.

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