Vacuum brazing deformation control method for martensitic stainless steel stator of aero-engine

Abstract

The invention discloses a vacuum brazing deformation control method for a martensitic stainless steel stator of an aero-engine, which comprises the following steps of: S1, cleaning each single piece, combining and positioning parts by using a combined clamp, measuring the related sizes of the parts after positioning, and filling the qualified parts with brazing filler metal; s2, a brazing clamp of a graphite tray structure is designed; s3, a vertical vacuum brazing furnace is selected for conducting brazing machining on the part; s4, setting three heat preservation steps at 400 DEG C, 700 DEG C and 800 DEG C in the heating process; s5, after brazing heat preservation is completed, furnace cooling is carried out to be below 150 DEG C, then inert gas is filled, and a draught fan is started for rapid cooling; s6, after brazing is completed, the temperature is increased to 555 DEG C at the speed of 10-20 DEG C / min, heat preservation is conducted for 2-2.5 h, and then argon is filled for cooling; deformation control in the martensitic stainless steel stator brazing process is achieved, the height and uniform distribution of blades relative to an outer ring after stator brazing are guaranteed, and the airflow characteristic of stator parts is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of welding control, in particular, relates to a vacuum brazing deformation control method for aero-engine martensitic stainless steel stator. BACKGROUND

[0002] The aero-engine stator assembly is formed by vacuum brazing of the stator outer ring and the blades, and the base material of the parts is 1Cr13Ni martensitic stainless steel. Since the phase of the base body changes dramatically during the heating and cooling process of the martensitic stainless steel, and the volume difference between the phases is large, the deformation control of this type of material during hot working is extremely difficult. During the brazing heating process, the parts are deformed greatly (the deformation can reach 1mm, i.e. the roundness reaches 1mm, when the control is poor) due to factors such as uneven heating, uneven cooling, and release of mechanical machining residual stress. The roundness of the outer ring of the parts is poor, the height difference of the blades relative to the outer ring after welding is out of tolerance, and the uniformity of the blades is out of tolerance (the requirement is that the height difference of the 40 blades relative to the outer ring needs to be controlled within ±0.25, and the uniformity of the 40 blades needs to be controlled to be ≤0.35).

[0003] The traditional vacuum brazing has a holding step at about 600℃ and before the melting temperature of the filler metal during the heating process, and the heating rate is about 10℃ / min. The holding step at about 600℃ is mainly to ensure that the binder is completely volatilized, and to ensure that the vacuum degree is guaranteed during the subsequent heating process. The holding step before the melting temperature of the filler metal can also ensure that the temperature of each part of the part is uniform. However, the parts of the martensitic stainless steel stator are severely deformed according to this heating scheme. The existing process cannot meet the precision requirements of the parts.

[0004] The existing patent with the patent number CN102922230A discloses a method for vacuum brazing of a martensitic stainless steel rectifier assembly, which is characterized by: filling foil-shaped filler metal between the blades to ensure the brazing gap of the rectifier assembly. A positioning method of adding H1Cr11Ni2W2MoV welding wire is adopted, and a symmetric cross-welding is adopted, with a welding point diameter of Φ3, so that the welding stress of the part is small, the part deformation is reduced after subsequent brazing, and there is no cracking phenomenon in the argon arc welding point. A tempering process is added after vacuum brazing to improve the mechanical properties of the part. At the same time, the brazing fixture is made of graphite, and a layer of aluminum oxide is sprayed on the surface of the brazing fixture, which can avoid the adhesion of the brazing fixture and the part after brazing, and the brazing fixture does not deform at 1055℃. This patent is only applicable to parts with the structure of an inner ring fixed blade brazed into a ring and an unconstrained outer ring of the blade. The blade is relatively free during the welding process, and the size control requirement is low. The heating measures of this patent only focus on the removal of the binder and the heat penetration, and do not involve the related control of the material phase change and deformation. At the same time, the brazing process of the type of part focused on by this patent has limited means for deformation control. This patent solves the problem of uniformity of the gap between the multiple blades and the cracking of the welding point, and focuses on gap control. SUMMARY

[0005] The present application is mainly aimed at the problems in the prior art that the phase of the base body changes dramatically in the process of heating and cooling of the martensitic stainless steel, the volume difference between the phases is large, and therefore the deformation control is extremely difficult in the process of hot working of the material; the uneven heating, uneven cooling, release of residual stress caused by mechanical processing and other factors cause large deformation of the part in the process of brazing (the deformation can reach 1mm, i.e. the roundness reaches 1mm when the control is poor), the roundness of the outer ring of the part is poor, and the height difference and the uniformity of the position of the blade relative to the outer ring after brazing are out of tolerance.

[0006] An aero-engine martensitic stainless steel stator vacuum brazing deformation control method, comprising the following steps: S1, clean each single piece, use a combined clamp to combine and position the parts, measure the related dimensions of the parts after positioning, and add brazing filler metal to qualified parts; S2, design a brazing clamp with a graphite tray structure, the brazing clamp only supports the inner and outer rings of the parts, and the flatness of the clamp is ≤0.1mm; S3, select a vertical vacuum brazing furnace to braze the parts, use the heating elements with the same shape as the outer ring of the parts and consistent distances between parts in the vertical furnace structure, so that the radiation heat flux density at each position of the outer ring of the parts is the same; S4, set three holding steps at 400℃, 700℃ and 800℃ during the heating process, and slowly increase the temperature before 400℃, increase the temperature rate between 400~800℃, and quickly increase the temperature from 800℃ to the brazing temperature; wherein, increase the temperature to 400℃ at a rate of 7.5℃ / min, increase the temperature to 700℃ at a rate of 11℃ / min, increase the temperature to 800℃ at a rate of 8.5℃ / min, and increase the temperature to the brazing temperature at a rate of 12℃ / min, so that the brazing filler metal at each position melts uniformly; S5, after the brazing holding is completed, cool the furnace to below 150℃, then fill in inert gas and open the fan for rapid cooling, and take the parts out of the furnace when the temperature of the parts is below 70℃; S6, after brazing, increase the temperature to 555±25℃ at a rate of 10~20℃ / min, hold for 2~2.5h, and then cool by filling in inert gas.

[0007] Further, in the step S3, check the flatness of the graphite clamp support surface when loading the furnace, and place the parts on the graphite clamp and in the middle area of the vertical furnace.

[0008] Further, in the step S3, the vertical vacuum brazing furnace is evacuated to less than 4×10 2 Pa.

[0009] Further, in the step S2, the material of the brazing fixture is dense graphite, the linear expansion coefficient of which is less than that of the part base material, and the graphite material has good dimensional thermal stability, so that the flatness of the brazing fixture does not change after multiple furnace entries.

[0010] Further, in the step S4, the temperature is raised to 400 DEG C at a rate of 7.5 DEG C / min, and held for 20-25 min; the temperature is raised to 700 DEG C at a rate of 11 DEG C / min, and held for 10-15 min; the temperature is raised to 800 DEG C at a rate of 8.5 DEG C / min, and held for 25-30 min; and finally the temperature is raised to the brazing temperature at a rate of 12 DEG C / min.

[0011] Further, in the step S5, after the brazing holding is completed, the furnace is cooled to below 150 DEG C, and then argon is filled to cool, and the filling pressure of the argon is 1 bar.

[0012] Further, in the step S6, after the part is vacuum brazed, tempering treatment is performed, the hardness before tempering is required to be HBS≥287 (HRC≥30.5), the tempering specification is to raise the temperature to 555 DEG C at a rate of 10-20 DEG C / min, hold for 2-2.5 h, after the holding is completed, 1 bar of argon is filled and the fan is turned on to cool to 100 DEG C.

[0013] Further, after the tempering treatment, a step of inspecting the hardness of the part outer ring is further included, the hardness is required to be in the range of 287-330 (HRC in the range of 30.5-35.25), after the inspection is completed, the size of the part is inspected, and only the part that passes the hardness inspection and the size inspection is determined as a qualified part.

[0014] Further, the brazing fixture supports the end faces of the inner and outer rings of the part, and the circumference of the fixture is in a free state, so that the constraint of the inner ring and the blade and the constraint of the outer ring and the fixture are reduced.

[0015] Further, the contact area of the brazing fixture and the part is less than 20% of the total area of the part.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application is brazing processing by selecting vertical vacuum brazing furnace, setting three holding steps at 400 DEG C, 700 DEG C, 800 DEG C in the heating process, and slowly heating before 400 DEG C, increasing the heating rate between 400 DEG C and 800 DEG C, and rapidly heating from 800 DEG C to brazing temperature; after brazing is completed, the furnace is cooled to below 150 DEG C, then inert gas is filled and the fan is started to cool rapidly; the brazing fixture with graphite tray structure is designed, which only supports the inner and outer rings of the part; finally, the part is inspected. The present application selects vertical vacuum brazing furnace, according to the heat radiation heat transfer principle, the heating element is close to the outer surface of the part, which improves the uniformity of the part heating, reduces the deformation risk from the heating source. By setting the holding step and the heating rate according to the change of the thermal expansion coefficient of the material, the heating rate of the part can be effectively reduced, the production efficiency can be ensured, and the grain growth can be prevented. The present application solves the deformation control of the martensitic stainless steel stator brazing process, ensures the height and uniform distribution of the blade relative to the outer ring after the stator brazing, ensures the airflow characteristics of the stator part, and is popularized and applied in the vacuum brazing of similar materials and structure parts; by formulating a specific cooling scheme, the material performance can be ensured, the cooling speed can be reduced, and the deformation caused by uneven cooling can be prevented. The present application designs the brazing fixture with graphite tray structure, which only supports the inner and outer rings of the part, which reduces the contact and heat shielding between the brazing fixture and the part to the maximum extent compared with the full constraint fixture, effectively reduces the temperature difference between the contact surface and the remaining non-contact surface position of the part in the heating and cooling process; in addition, the linear expansion coefficient of graphite is smaller than that of steel and other materials, and the high-temperature stability is good, so that the flatness of the fixture is basically unchanged after high-temperature brazing cycle, reducing the risk of part deformation. The heating scheme designed based on the change of the thermal expansion coefficient of the material is scientific and reasonable. Slow heating before 300 DEG C reduces inconsistent deformation, appropriate speed increase between 300 DEG C and 800 DEG C ensures efficiency, and rapid heating from 800 DEG C to brazing temperature ensures the melting effect of the brazing material, which accurately controls the heating process at different stages, essentially reduces the deformation caused by material characteristics, and takes into account the production efficiency and product quality. BRIEF DESCRIPTION OF DRAWINGS Figure 1 The flowchart of the present application; Figure 2 The schematic diagram of the heating of the vertical furnace of the present application; Figure 3 The stator assembly brazing thermal cycle curve schematic diagram of the present application; Figure 4 The structure schematic diagram of the brazing fixture of the present application; Figure 5 The part and brazing fixture structure schematic diagram of the present application; Figure 6 The stator tempering thermal cycle curve schematic diagram of the present application; Figure 7This is a diagram showing the coefficient of thermal expansion of materials at various temperatures during the brazing thermal cycle of this invention. In the above figure, 1. blade; 2. stator outer ring; 3. stator inner ring; 4. heating element; 5. brazing fixture. Detailed Implementation

[0017] To clearly illustrate the technical features of the present invention, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the invention; however, the invention may be implemented in other ways different from those described herein, and therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0018] Example 1 like Figure 1 As shown, this embodiment provides a method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines, including the following steps; Pre-welding treatment: The stator outer ring 2 (outer diameter φ500mm) and 42 blades 1, made of 1Cr13Ni martensitic stainless steel, are ultrasonically cleaned to remove surface oil and oxide film; the blades 1 are positioned on the opening of the stator outer ring 2 according to the design position using a combination fixture; the initial height difference of the blades 1 relative to the stator outer ring 2 is detected by a coordinate measuring machine (controlled within ±0.15mm) and the uniformity of the position (≤0.25mm); after the parts are qualified by measurement, foil brazing filler is pre-placed at the welding interface.

[0019] like Figure 2 As shown, according to the Stefan-Boltzmann equation, in order to ensure that the radiated heat flux density is consistent, the heating element 4 needs to be close to the outer surface of the part. A vertical vacuum brazing furnace is selected for brazing to ensure that the radiated heat flux density at each position of the outer ring of the part is basically consistent during the brazing process, thereby improving the heating uniformity of the part and reducing the risk of part deformation.

[0020] Select a vertical vacuum brazing furnace (model: ZJ-1000). Check that the flatness of the graphite tray support surface is 0.08mm (≤0.1mm). Place the part stably in the center of the tray, ensuring that the part is 150mm away from the heating element on all four circumferences. Close the furnace door, start the vacuum pump, and evacuate to a vacuum level of 3×10⁻⁶. 2 Pa (<4×10~) 2 Pa).

[0021] Since the blade 1 and the outer ring cannot be fixed by mutual constraint, positioning and the brazing fixture 5 are needed for assistance to ensure the relative position of the parts. Figure 4 As shown in the figure, Figure 5 In this embodiment, a graphite tray structure brazing fixture 5 is designed, which only supports the inner and outer rings of the parts, and the height H between the two steps of the brazing fixture 5 ensures that the stator inner ring 3 does not contact the blade 1. This structure minimizes the contact and thermal shielding between the brazing fixture 5 and the parts compared to the full constraint fixture, effectively reducing the temperature difference between the contact surface and the rest of the non-contact surface of the parts during heating and cooling. Secondly, the graphite has a smaller linear expansion coefficient than other materials such as steel, and the graphite material has good dimensional thermal stability, and the flatness of the fixture is basically unchanged after high-temperature brazing cycle, reducing the risk of part deformation.

[0022] In this embodiment, according to the Stefan-Boltzmann equation:

[0023] In the above formula, is the radiant heat flux ( ); is the emissivity of the object surface, is the Stefan-Boltzmann constant; is the area of the radiation surface 1; is the shape coefficient (the proportion of the distance from the radiation surface one to the radiation surface two) from the radiation surface one (i.e. the heating element 4) to the radiation surface two (i.e. the stator outer ring 2); are the absolute temperatures of the radiation surface one and the radiation surface two respectively. As can be seen from the formula, the radiant heat flux received by the parts during brazing is greatly affected by the geometric shape and relative position of the outer surface of the parts and the surface of the furnace heating element (including the reflecting screen). The use of coaxial ring heating for the annular stator parts can better improve the uniformity of the radiation received by the parts.

[0024] The thermal expansion coefficients of 1Cr13Ni martensitic stainless steel at various temperatures during brazing heat cycle were measured and compared, and the material expansion coefficient graph was obtained. As can be seen from Figure 7 , the material thermal expansion coefficient increases rapidly before the heating temperature reaches 300℃, and the sample heating speed should be slow during this process; the material thermal expansion coefficient increases slowly between 300~800℃, and the heating speed can be appropriately increased during this process; the material thermal expansion coefficient decreases sharply between 800~840℃, and then increases slowly, and the heating speed should be appropriately slowed down to alleviate the problem of inconsistent local deformation caused by the decrease of thermal expansion coefficient.

[0025] In this embodiment, as shown in Figure 3As shown, the specific heating scheme is as follows: The parts are heated according to the thermal cycling curve. During the heating process, three holding steps are set at 400℃, 700℃, and 800℃. The heating rate is slow before reaching 400℃, the heating rate is increased between 400℃ and 800℃, and the temperature is rapidly increased between 800℃ and the brazing temperature. Specifically, the temperature is increased to 400℃ at a rate of 4.5~10.5℃ / min; to 700℃ at a rate of 8~14℃ / min; to 800℃ at a rate of 5.5~11.5℃ / min; and to the brazing temperature at a rate of 9~15℃ / min, ensuring uniform melting of the brazing filler metal in all parts.

[0026] In this embodiment, the heating scheme specifically includes four stages: Stage 1: Heating to 400℃ at a slow heating rate of 7.5℃ / min and holding for 25min to ensure adhesive evaporation and uniform part temperature, with the circumferential temperature of the part ≤5℃; Stage 2: Heating to 700℃ at a normal heating rate of 11℃ / min and holding for 15min to ensure processing efficiency and quickly equalize the internal temperature of the part, with the measured temperature difference at each point on the thermocouple ≤8℃; Stage 3: Heating to 800℃ at a rate of 8.5℃ / min and holding for 30min, confirming the temperature uniformity error of each part ≤3℃ using an in-furnace infrared thermometer, ensuring uniform part temperature before brazing; Stage 4: Heating to the brazing temperature (990℃) at a relatively rapid rate of approximately 12℃ / min to ensure complete melting of the brazing filler metal and filling of the weld.

[0027] After the brazing and heat preservation are completed, the furnace is cooled. After the heat preservation is completed, the heating power is turned off, and the furnace is cooled to 140℃ (furnace temperature monitoring accuracy ±2℃). Argon gas of 1 bar is introduced and the blower is started. The furnace is then removed after cooling to 70℃ at a rate of 20℃ / min.

[0028] Post-processing and inspection: such as Figure 6 As shown, after vacuum brazing, the parts undergo subsequent tempering. Before tempering, the hardness requirement is HBS ≥ 287 (HRC ≥ 30.5). Tempering specifications: heat to 555℃ at (10~20)℃ / min, hold for 2.5h, and after holding, purge with 1 bar of argon gas and cool to 100℃ with a blower. Finally, the hardness of the outer ring of the part is checked, requiring HBS: 287~330 (HRC: 30.5~35.25). After the check, the part dimensions are checked. The maximum height difference between the blades and the outer ring is ±0.23mm, and the maximum uniformity is 0.32mm, both meeting the technical requirements (±0.25mm and ≤0.35mm). Only parts that pass both the hardness and dimensional checks are considered qualified.

[0029] This invention, through a vertical vacuum brazing furnace and graphite fixtures, improves the circumferential heating uniformity of parts during welding by 40%, avoiding elliptical deformation of the outer ring caused by uneven heat flux density (measured roundness ≤1mm, positional accuracy ≤0.35mm), reducing deformation by 80% compared to existing technologies, and eliminating the need for post-weld correction. Slow heating up to 300℃ (7.5℃ / min) reduces stress concentration caused by martensitic phase transformation volume differences; appropriate acceleration between 300~800℃ balances efficiency and grain growth risk; rapid heating after 800℃ ensures brazing filler metal fluidity. Cooling the furnace to below 150℃ before starting the fan avoids stress concentration caused by rapid cooling to 950℃, reducing deformation by 60% compared to traditional processes (directly starting the fan at 950℃).

[0030] Example 2 like Figure 1 As shown, this embodiment provides a method for efficient brazing deformation control of small-sized stator assemblies, including the following steps: S1. For small-sized stators (outer ring diameter φ300mm, number of blades 1: 28), after cleaning, use positioning pins for quick assembly, check the initial height difference ±0.12mm, uniform distribution position accuracy ≤0.20mm, and after inspection and approval, pre-fill with powdered brazing filler metal (particle size ≤100μm). S2. Design a brazing fixture 5 with a graphite tray structure. The brazing fixture 5 only supports the inner and outer rings of the part, and the flatness of the fixture is ≤0.1mm. Specifically, a small vertical furnace (model: ZJ-500) is used, the graphite tray flatness is 0.05mm, the part is placed in the upper middle part of the furnace body (the area with dense heating elements), and a vacuum of 2×10~ is applied. 2 Pa; S3. A vertical vacuum brazing furnace is selected to braze the parts. The heating element 4 of the vertical furnace structure has the same shape as the outer ring of the parts and the same distance between each part, so that the radiant heat flux density at each position of the outer ring of the parts is the same. S4. During the heating process, three holding steps are set at 400℃, 700℃, and 800℃. The temperature is increased slowly before reaching 400℃, then the rate of increase is accelerated between 400℃ and 800℃, and finally, the temperature is rapidly increased from 800℃ to the brazing temperature. Specifically, the temperature is increased to 400℃ at a rate of 7.5℃ / min and held for 20 minutes (to improve binder evaporation efficiency); then increased to 700℃ at a rate of 11℃ / min and held for 10 minutes; then increased to 800℃ at a rate of 8.5℃ / min and held for 25 minutes; finally, the temperature is increased to the brazing temperature at a rate of 12℃ / min, ensuring uniform melting of the brazing filler metal in all parts; the measured radial temperature difference of the parts is ≤3%. S5. After brazing, the parts are cooled to below 150°C in the furnace, then inert gas is introduced and the fan is turned on for rapid cooling. The parts are taken out of the furnace when they are cooled to below 70°C. S6. After brazing, heat to 555±25℃ at a rate of 10~20℃ / min and hold for 2~2.5h, then cool with inert gas.

[0031] In this embodiment, the furnace was cooled to 130°C and then purged with argon gas for further cooling. The tempering temperature was 560°C, and the furnace was held at that temperature for 2 hours. The hardness was HBS295, and the dimensions were found to be within acceptable limits.

[0032] In this embodiment, the small-sized parts have low heat capacity. By shortening the heat preservation time (e.g., heat preservation at 700℃ for 10 minutes), the overall brazing cycle is shortened by 15% compared to Example 1, while the deformation is controlled within ±0.22mm and 0.30mm.

[0033] Example 3 like Figure 1 As shown in the figure, this embodiment provides a deformation control method for a complex structure stator (scenarios with non-uniform blade distribution). The specific steps are as follows: Pre-welding treatment: For stators with non-uniformly distributed blades (such as 12 groups of blades, with 3 blades densely arranged in each group), a laser positioning instrument is used to assist in the assembly, focusing on controlling the initial height difference (±0.20mm) in the dense area, and a pre-placed annular brazing filler strip is used.

[0034] Furnace loading and fixture optimization: An adjustable inner ring support column (height error ±0.05mm) was added to the graphite tray to ensure the stability of the planar support under non-uniform loads. Vacuum was then applied to 3.5×10⁻⁶ mm. -2 Pa.

[0035] The heating scheme is consistent with claim 1. During cooling, the furnace is cooled to below 150°C (the actual cooling rate is 5°C / min). After argon gas is added, the fan power is increased by 20% to balance the cooling rate of the complex structure.

[0036] Tempering and inspection: After tempering, the blade height difference in densely packed areas is ±0.25mm (critical acceptable value), the uniformity of the blade distribution is 0.35mm (compliant), and the hardness is HBS310, which meets the usage requirements.

[0037] This invention features an innovative fixture structure: an adjustable inner ring support column solves the problem of local deformation under non-uniform loads, avoiding the shielding effect of traditional fully constrained fixtures on heat conduction. Actual measurements show that the temperature difference between the contact and non-contact surfaces is ≤10℃, a 50% reduction compared to steel fixtures. For complex structures, increased fan power ensures uniform cooling and prevents warping deformation caused by localized cooling rate differences.

[0038] Obviously, the embodiments described above are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines, characterized in that, Includes the following steps: S1. Clean each individual piece, use a combination fixture to assemble and position the parts, measure the relevant dimensions of the parts after positioning, and fill the qualified parts with brazing filler metal. S2. Design a brazing fixture for a graphite tray structure, wherein the brazing fixture only supports the inner and outer rings of the part, and the flatness of the fixture is ≤0.1mm; S3. A vertical vacuum brazing furnace is selected to braze the parts. The heating element of the vertical furnace structure has the same shape as the outer ring of the parts and the same distance between each part, so that the radiant heat flux density at each position of the outer ring of the parts is the same. S4. During the heating process, three heat preservation steps are set at 400℃, 700℃, and 800℃. The temperature is increased to 400℃ at a rate of 7.5℃ / min. Between 400℃ and 800℃, the heating rate is increased to 11℃ / min from 400℃ to 700℃, 8.5℃ / min to 800℃, and 12℃ / min to the brazing temperature, so that the brazing filler metal melts uniformly in all parts. S5. After brazing and heat preservation, the parts are cooled to below 150°C in the furnace, then inert gas is introduced and the fan is turned on for rapid cooling. The parts are taken out of the furnace when they are cooled to below 70°C. S6. After brazing, heat to 555±25℃ at a rate of 10-20℃ / min and hold for 2-2.5 hours, then cool with inert gas.

2. The method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 1, characterized in that, In step S3, the flatness of the graphite fixture support surface is checked during furnace loading, and the parts are placed on the graphite fixture and positioned in the middle area of ​​the vertical furnace.

3. The method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 1, characterized in that, In step S3, the vertical vacuum brazing furnace is evacuated to a vacuum level of less than 4 × 10⁻⁶. -2 Pa.

4. The method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 1, characterized in that, In step S2, the brazing fixture is made of dense graphite, whose coefficient of linear expansion is less than that of the component matrix material, so that the flatness of the brazing fixture remains unchanged after multiple furnace passes.

5. The method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 1, characterized in that, In step S4, the temperature is increased to 400℃ at a rate of 7.5℃ / min and held for 20-25 minutes; then increased to 700℃ at a rate of 11℃ / min and held for 10-15 minutes; then increased to 800℃ at a rate of 8.5℃ / min and held for 25-30 minutes; finally, the temperature is increased to the brazing temperature at a rate of 12℃ / min.

6. The method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 1, characterized in that, In step S5, after the brazing and heat preservation are completed, the furnace is cooled to below 150°C and then argon gas is introduced for further cooling. The argon gas is introduced at a pressure of 1 bar.

7. The method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 1, characterized in that, In step S6, after the part is vacuum brazed, it is tempered. Before tempering, the hardness test requires HBS≥287 (HRC≥30.5). The tempering specification is to heat to 555℃ at 10~20℃ / min and hold for 2~2.5h. After the holding is completed, 1 bar of argon gas is introduced and the fan is turned on to cool to 100℃.

8. The method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 7, characterized in that, After the tempering process, an inspection step is also included: the hardness of the outer ring of the part is checked, and the HBS is required to be in the range of 287 to 330 (HRC in the range of 30.5 to 35.25). After the inspection is completed, the size of the part is checked. Only parts that pass both the hardness and size inspections are considered qualified parts.

9. A method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 1, characterized in that, The brazing fixture supports the inner and outer ring end faces of the part. The fixture is free in the circumferential direction, which reduces the constraints between the inner ring and the blade, as well as between the outer ring and the fixture.

10. A method for controlling deformation during vacuum brazing of martensitic stainless steel stators for aero-engines according to claim 9, characterized in that, The contact area between the brazing fixture and the part is less than 20% of the total area of ​​the part.

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