A method for interlayer prepositioning of a microstructure with close-packed array features

Abstract

The application relates to a method for prepositioning an intermediate layer of a microstructure-to-be-welded sample with a close-packed array feature, which comprises the following steps: air hole processing; thin plate preparation; air pipe processing and welding; processing a gap at the end of the air pipe, penetrating the air pipe through the air hole of the thin plate, and adopting argon arc welding and plasma welding to weld the thin plate and the air pipe, so that the end surface of the air pipe protrudes from the surface to be welded; cleaning the thin plate to be welded and the intermediate layer alloy; assembling and positionally welding the intermediate layer alloy and the thin plate; sealing and degassing; pressure diffusion welding, and prepositioning the intermediate layer alloy; and preparing a layer plate cooling structure to-be-welded sample. The prepositioning process of the intermediate layer alloy is advanced to before the formation of the feature microstructure, the intermediate layer alloy is prepositioned through a large-area foil-thin plate solid-phase diffusion welding process, the excess intermediate layer is removed after the feature microstructure processing, and thus the prepositioning difficulty of the intermediate layer of the microstructure-to-be-welded sample with the close-packed array feature is reduced, and the operability of the prepositioning of the intermediate layer alloy is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of aero-engine manufacturing, and particularly relates to an intermediate layer presetting method for a microstructure-to-be-welded blank with a close-packed array feature, for the diffusion welding manufacturing of a laminate cooling structural part. BACKGROUND

[0002] With the urgent demand for performance improvement of engines in the fields of aviation, aerospace, and gas turbines, higher requirements are put forward for the high-temperature resistance and structure weight reduction of hot-end components. Laminate cooling is a new type of composite cooling method, which integrates impingement cooling, convection cooling, and gas film cooling methods, and is also known as quasi-divergent cooling. It has many advantages such as reducing part wall temperature gradient, reducing structural thermal stress, saving cooling air consumption, and reducing structure weight, and can effectively improve the structural strength and service life of hot-end components. It has obvious application advantages in hot-end components such as combustion chamber liners, nozzles, and stabilizers.

[0003] At present, the process flow of a laminate cooling structure is generally laminate single piece preparation → diffusion linking → blank forming → tailor welding → shape correction. A typical laminate structure includes a to-be-welded blank I1, a to-be-welded blank II 2, a diffusion weld 4, and a close-packed array hole 5 as shown in Figure 1 The laminate structure part is a typical internal topological optimization feature, thin-walled weak rigid complex structural part. The raw material is mostly high-temperature alloy sheet. The close-packed array feature microstructure 3 is prepared on the sheet by using precise mechanical machining, electric spark machining, laser machining, electrolysis, photochemical machining, and LIGA microstructure machining methods. A semi-closed laminate structure is formed by welding (diffusion welding, pressurized brazing, etc.). Then, through multiple processes such as blank forming, tailor welding, and shape correction, a complex functional structural part such as a liner, a nozzle, and a stabilizer is finally formed. The traditional brazing method has the disadvantages of hard and brittle weld, difficult deformation, easy cracking during forming process, low service temperature, and poor fatigue resistance. Therefore, the diffusion welding method is mostly used for laminate cooling structural parts. The traditional solid-phase diffusion welding requires high roughness, cleanliness, flatness, and parallelism of the to-be-welded surface, as well as high control of diffusion welding tooling and process. Otherwise, the diffusion welded joint will have problems such as incomplete welding defects or abnormal phase aggregation, which will easily cause cracking failure during use, thereby affecting the use reliability of the structure. In academic research and engineering fields, TLP diffusion welding or pressurized brazing is mostly used to reduce the requirements for the preparation quality of the to-be-welded blank, and to realize higher welding rate and more reliable connection through the flow of liquid phase welding metal and the diffusion homogenization of atoms.

[0004] When the TLP diffusion welding or pressure brazing is used to weld the panel structure parts, the welding material (commonly referred to as the intermediate alloy) needs to be pre-placed on the welding surface. The intermediate alloy contains Si, B, P and other melting elements. The excessive amount of the intermediate alloy will cause the corrosion of the welding material and the damage to the performance. In order to reduce the damage to the panel microstructure and the structure and performance of the original material, the pre-placing of the intermediate alloy must follow the principle of small amount and applicability. The intermediate alloy is generally pre-placed on the welding surface of the characteristic microstructure of the welding blank I. The accuracy, firmness and non-pollution of the pre-placing of the intermediate alloy are the technical difficulties of the panel connection. The characteristic microstructure 3 has the characteristics of mass, dense array, array and small size. The traditional pre-placing method of the intermediate layer is to pre-place the intermediate alloy on the welding surface 4 of the dense array characteristic microstructure 3 by the manual coating or the method of energy storage micro spot welding. The work load is large, the precision is poor, the intermediate alloy is easy to fall off, the actual operation is difficult, and the demand of the subsequent assembly and diffusion connection of the panel cooling structure cannot be met. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides an intermediate layer pre-placing method for a welding blank with a dense array characteristic microstructure. Based on the analysis of the panel cooling structure welding blank preparation method and the overall manufacturing process of the assembly, the intermediate alloy pre-placing process is moved to before the formation of the characteristic microstructure. The foil intermediate alloy is pre-placed by the large-area foil-thin plate solid-phase diffusion welding process. The excess intermediate layer is removed after the characteristic microstructure processing. Therefore, the pre-placing difficulty of the intermediate layer of the welding blank with the dense array characteristic microstructure is reduced, and the operability of the intermediate alloy pre-placing is improved.

[0006] An intermediate layer pre-placing method for a welding blank with a dense array characteristic microstructure, specifically comprising the following steps:

[0007] Step one: air hole processing: a plurality of air holes are processed around the welding thin plate;

[0008] Step two: thin plate preparation;

[0009] Step three: air pipe processing and welding: a notch is processed at the end of the air pipe, the air pipe is inserted through the air hole of the thin plate, and the thin plate and the air pipe are welded by using argon arc welding and plasma welding, so that the end surface of the air pipe protrudes from the welding surface.

[0010] Step four: cleaning the welding thin plate and the intermediate alloy;

[0011] Step five: assembling and positioning the intermediate alloy and the thin plate;

[0012] Step six: sealing and degassing;

[0013] Step seven: gas pressure diffusion welding, completing the pre-placing of the intermediate alloy;

[0014] Step eight: the preparation of the plate cooling structure to be welded blank, obtaining the to-be-welded blank I with the intermediate layer alloy;

[0015] The center distance of the vent hole from the edge of the sheet is 20-30 mm.

[0016] In step two, the sheet is pretreated by plane grinding to make the flatness of the to-be-welded surface of the sheet less than or equal to 0.03 mm; and the to-be-welded surface of the sheet is cleaned and the roughness value is reduced by surface grinding or polishing to make the roughness value of the to-be-welded surface less than or equal to 0.2 μm.

[0017] In step three, the width of the gap is not greater than 1 / 2 of the pipe diameter, and the depth is not more than 1.2 mm.

[0018] The distance from the protruding to-be-welded surface of the end face of the vent pipe is 0.6-1.2 mm.

[0019] In step four, the to-be-welded sheet and the intermediate layer alloy are cleaned by using anhydrous ethanol, acetone, deionized water, and demineralized water, or ultrasonic cleaning; and the to-be-welded surfaces of the sheet and the intermediate layer alloy are not allowed to contact hard objects during cleaning.

[0020] In step five, the specific operation of assembly and positioning welding is as follows: the to-be-welded surfaces of the intermediate layer alloy and the sheet are placed opposite to each other, one short edge of the intermediate layer alloy and the sheet is aligned, the positioning welding of the short edge is completed by using energy storage spot welding along the short edge, and the interval between the positioning welding spots is not greater than 20 mm; the short edge of the sheet after the positioning welding is pressed tightly, the intermediate layer alloy is laid along the sheet, the intermediate layer alloy is not wrinkled, protruded, or damaged, and the positioning welding of the other short edge is completed; and finally, the positioning welding of the two long edges is completed.

[0021] In step six, vacuum electron beam welding, laser welding, or argon arc welding is used to seal the edge of the blank after assembly and positioning welding; then, a vacuum device is used to perform degassing treatment through the vent pipe, so that the vacuum degree is better than 4×10 -2 Pa; after the vacuum degree meets the requirement, the vacuum is continuously maintained, and the outer part of the vent pipe body is preliminarily welded by resistance welding, the number of resistance welding spots is not less than 3; then, the vacuum device is removed, and finally, the end of the pipe is further sealed by argon arc welding.

[0022] In step seven, the blank after the edge sealing welding in step six is sent into a diffusion welding device or a hot isostatic pressing device that can be filled with high-pressure argon gas, the gas pressure is 20-50 MPa, the welding temperature is 900-1090℃, and the holding time is 15-60 min.

[0023] The beneficial effects of the present application are as follows:

[0024] (1) The present application solves the problems of large workload, poor precision, easy to fall off and difficult to operate in the intermediate layer preposition of the microstructure to be welded with dense array characteristics by adopting the intermediate alloy preposition process in advance.

[0025] (2) The present application can realize uniform pressure fitting and solid-phase diffusion welding of the intermediate alloy and the thin plate without complex cladding system through air hole processing, thin plate preparation, air pipe welding, cleaning, assembly and positioning welding, edge welding and degassing and gas pressure diffusion welding, and the performance of the intermediate alloy is not changed.

[0026] (3) The present application not only can be used for the intermediate layer preposition of the microstructure to be welded with dense array characteristics, but also is suitable for the preposition of the intermediate alloy foil in the brazing or diffusion welding of large area, curved surface and honeycomb sandwich, and has excellent generalizability. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a schematic diagram of a typical laminate structure;

[0028] Figure 2 It is a schematic diagram of the air pipe welding process in the present application;

[0029] Figure 3 It is a schematic diagram of the edge welding process in the present application;

[0030] Figure 4 It is a schematic diagram of the microstructure to be welded with dense array characteristics with intermediate alloy;

[0031] wherein,

[0032] 1-welding blank I, 2-welding blank II, 3-microstructure with dense array characteristics, 4-diffusion weld, 5-dense array hole, 6-air pipe, 7-welding surface, 8-weld, 9-resistance welding area, 10-pipe end, 11-intermediate alloy, 12-welding blank I with intermediate alloy, 13-thin plate. DETAILED DESCRIPTION

[0033] In order to better explain the present application, the technical solutions and effects of the present application are described in detail in combination with the drawings and specific embodiments.

[0034] Example 1

[0035] An intermediate layer preposition method of a microstructure to be welded with dense array characteristics, specifically comprising the following steps:

[0036] Step one: air hole processing

[0037] The to-be-welded sheet 13 to be pre-positioned with the intermediate alloy 11 in this embodiment is GH5188 alloy. A plurality of vent holes are processed around the to-be-welded sheet 13. The vent holes are processed according to the diameter of the vent pipe 6 selected according to the specific situation. The diameter of the vent hole is greater than the diameter of the vent pipe 6, so that the vent pipe 6 can pass through the vent hole, and the gap between the vent hole and the vent pipe 6 is kept at a circumferential gap of 0-0.1 mm. In this embodiment, the diameter of the vent hole is Ф8.2 mm, and the center distance of the vent hole from the edge of the sheet 13 is 25 mm.

[0038] Step two: sheet 13 preparation

[0039] The sheet 13 is pre-processed by plane grinding to make the flatness of the to-be-welded surface 7 of the sheet 13 ≤0.03 mm. Surface grinding is used to clean and reduce the roughness value of the to-be-welded surface of the sheet 13, so that the roughness value of the to-be-welded surface 7 is ≤0.2 μmm.

[0040] Step three: vent pipe 6 processing and welding

[0041] The vent pipe 6 is a thin-walled pipe of high-temperature alloy or stainless steel with a diameter of Ф8 mm. An opening with a width of 3.5 mm and a depth of not more than 1.2 mm is processed at the end of the vent pipe 6. The vent pipe 6 is inserted through the vent hole of the sheet 13, and the sheet 13 and the vent pipe 6 are welded by argon arc welding, so that the end face of the vent pipe 6 protrudes from the to-be-welded surface 7 by 0.6 mm, and the weld 8 is as shown in Figure 2

[0042] Since the to-be-welded intermediate alloy 11 and the sheet 13 need to be sealed and degassed subsequently to form a vacuum and a sealed blank, an opening is designed on the vent pipe 6, and the vent pipe 6 protrudes from the to-be-welded surface 7 of the sheet 13, so as to prevent the vent pipe 6 from being blocked due to the deformation of the intermediate alloy 11, thereby ensuring more thorough degassing.

[0043] Step four: cleaning the to-be-welded sheet 13 and the intermediate alloy 11

[0044] The intermediate alloy 11 in this embodiment is BNi2 alloy foil tape. The to-be-welded sheet 13 and the intermediate alloy 11 are cleaned by using anhydrous ethanol, acetone, deionized water, and demineralized water for flushing or ultrasonic cleaning. The to-be-welded surfaces 7 of the sheet 13 and the intermediate alloy 11 are not allowed to contact hard objects during cleaning.

[0045] Step five: assembling and positioning the intermediate alloy 11 and the sheet 13

[0046] As shown in Figure 3 ​As shown in the figure, the to-be-welded intermediate layer alloy 11 and the to-be-welded surface 7 of the sheet 13 are placed oppositely, the intermediate layer alloy 11 is aligned with one short edge of the sheet 13, and the positioning welding of the short edge is completed by using energy storage spot welding to uniformly position along the short edge, and the interval of the positioning welding spots is not greater than 20 mm; the short edge positioned by spot welding is pressed tightly, the intermediate layer alloy 11 is laid along the sheet 13, the intermediate layer alloy 11 is free of wrinkles, protrusions or damages, and the positioning welding of the other short edge is completed; finally, the positioning welding of the two long edges is completed, and the positioning welding method of the other short edge and the two long edges is the same as that of the first short edge.

[0047] Step six: sealing and degassing

[0048] The sealing welding of the blank after assembly and positioning welding is completed by using argon arc welding; then the degassing treatment is performed by using the vacuumizing device through the breather pipe 6, so that the vacuum degree is better than 4x10 -2 Pa; after the vacuum degree requirement is met, the vacuumizing is continuously maintained, and the resistance welding is performed on the outside of the breather pipe 6, and the resistance welding area 9 is shown in the figure, and the number of resistance welding spots 3 is three; then the vacuumizing device is removed, and finally the argon arc welding is used to further seal the pipe end 10, and if the argon arc welding is directly used to seal the pipe end 10, the gas leakage may occur due to improper operation, resulting in the failure of sealing welding. Figure 2

[0049] Step seven: gas pressure diffusion welding

[0050] The blank after the sealing welding in step six is sent into the diffusion welding equipment or the hot isostatic pressing equipment which can be filled with high-pressure argon, so that the gas pressure is 50 MPa, the welding temperature is 900 DEG C, and the holding time is 60 min, and the presetting of the intermediate layer alloy 11 is completed.

[0051] Step eight: preparation of the to-be-welded blank of the layer plate cooling structure

[0052] By using the existing microstructure processing methods including precision machining, electric spark machining, laser machining, electrolysis, photochemical machining and LIGA, the dense array feature microstructure 3 is prepared on the sheet 13 in which the intermediate layer alloy 11 is pre-set, and the excess intermediate layer alloy 11 is removed, so that the to-be-welded blank I12 with the intermediate layer alloy is obtained, as shown in the figure. Figure 4

[0053] Example 2

[0054] ​​The difference between the embodiment and the embodiment 1 is that the sheet 13 to be welded in the embodiment is GH3230 alloy, the intermediate layer alloy 11 is B-Ni55NbCoWCrAlSiMoTi alloy, the surface of the sheet 13 to be welded is cleaned and the roughness is reduced by polishing in the step two, the gas pressure for the gas pressure diffusion welding in the step seven is 50 MPa, the welding temperature is 1090℃, and the holding time is 15 min. The rest of the settings and steps are completely same as the embodiment 1.

[0055] Embodiment 3

[0056] The difference between the embodiment and the embodiment 1 is that the intermediate layer alloy 11 in the embodiment is B-Ni65CoCrWBMoAlNb, the gas pressure for the gas pressure diffusion welding in the step seven is 30 MPa, the welding temperature is 1000℃, and the holding time is 45 min. The rest of the settings and steps are completely same as the embodiment 1.

[0057] Embodiment 4

[0058] The difference between the embodiment and the embodiment 1 is that the intermediate layer alloy 11 in the embodiment is BCo50CrNiSiWB, the gas pressure for the gas pressure diffusion welding in the step seven is 40 MPa, the welding temperature is 1030℃, and the holding time is 25 min. The rest of the settings and steps are completely same as the embodiment 1.

[0059] In order not to affect the subsequent diffusion welding of the layer plate cooling structure, the pre-set diffusion welding of the intermediate layer is particularly crucial. Too high welding temperature will melt the intermediate layer alloy 11 or make the melting reducing elements in the intermediate layer alloy 11 excessively diffuse into the sheet 13, so that the intermediate layer alloy 11 is invalid or the liquidus temperature is increased, and neither of the results is conducive to the subsequent diffusion welding of the layer plate cooling structure.

[0060] The present application sets the temperature of the gas pressure diffusion welding to be lower than the solidus temperature of the intermediate layer alloy 11 by 50-100℃, and uses relatively larger diffusion welding pressure 20-50MPa, so that the intermediate layer alloy 11 is fully deformed plastically, the alloy plastic deformation is used as the driving force to promote the intermediate layer alloy 11 and the sheet 13 to form good interface physical contact, the deformation energy is used to promote element diffusion and interface recrystallization, and relatively short diffusion welding holding time 15-60min is used to avoid excessive diffusion of the melting reducing elements.

Claims

1. A method for pre-setting an intermediate layer in a preform of a weld blank with a closely packed array microstructure, characterized in that, Specifically, the following steps are included: Step 1: Ventilation hole processing: Process several ventilation holes around the perimeter of the thin plate to be welded; Step 2: Thin plate preparation; Step 3: Vent pipe processing and welding: Process a notch at the end of the vent pipe, pass the vent pipe through the vent hole of the thin plate, and weld the thin plate to the vent pipe using argon arc welding or plasma welding methods, so that the end face of the vent pipe protrudes from the surface to be welded; Step 4: Clean the thin plate to be welded and the intermediate layer alloy; Step 5: Assemble and position the intermediate alloy layer and the thin plate; Step Six: Sealing and Degassing; Step 7: Gas pressure diffusion welding to complete the pre-placement of the intermediate layer alloy; Step 8: Preparation of the blank to be welded for the layered cooling structure, obtaining blank I with intermediate alloy layer.

2. The method for pre-setting an intermediate layer of a microstructure blank with closely packed array characteristics according to claim 1, characterized in that: In step one, the distance between the center of the vent hole and the edge of the thin plate is 20-30 mm.

3. The method for pre-setting an intermediate layer of a microstructure blank with closely packed array characteristics according to claim 1, characterized in that: In step two, during the preparation of the thin plate, a surface grinding process is used to pre-treat the thin plate so that the flatness of the surface to be welded is ≤0.03mm; then, surface grinding or polishing is used to clean the surface to be welded and reduce the roughness value so that the roughness value of the surface to be welded is ≤0.2μmm.

4. The method for pre-setting an intermediate layer of a blank to be welded with a closely packed array microstructure according to claim 1, characterized in that: The width of the notch in step three shall not exceed 1 / 2 of the pipe diameter, and the depth shall not exceed 1.2 mm.

5. The method for pre-setting an intermediate layer of a blank to be welded with a closely packed array microstructure according to claim 4, characterized in that: The distance between the end face of the vent pipe and the surface to be welded is 0.6 to 1.2 mm.

6. The method for pre-setting an intermediate layer of a microstructure blank with closely packed array characteristics according to claim 1, characterized in that: In step four, anhydrous ethanol, acetone, deionized water, and demineralized water are used to rinse or ultrasonically clean the thin plate and intermediate alloy to be welded. During cleaning, the surfaces of the thin plate and intermediate alloy to be welded are not allowed to come into contact with hard objects.

7. The method for pre-setting an intermediate layer of a microstructure blank with closely packed array characteristics according to claim 1, characterized in that: The specific operations for assembly and tack welding in step five are as follows: Place the intermediate layer alloy to be welded and the welding surfaces of the thin plate opposite each other, aligning the intermediate layer alloy with one short side of the thin plate. Use energy storage spot welding to uniformly position and complete the tack welding of the short side, with a tack welding point spacing of no more than 20mm. Press the short side that has been spot welded and positioned, and lay the intermediate layer alloy flat along the thin plate, ensuring that the intermediate layer alloy is free of wrinkles, protrusions, or damage, to complete the tack welding of the other short side. Finally, complete the tack welding of the two long sides.

8. The method for pre-setting an intermediate layer of a microstructure blank with closely packed array characteristics according to claim 1, characterized in that: In step six, vacuum electron beam welding, laser welding, and argon arc welding are used to seal the edges of the assembled and tack welded blanks; subsequently, a vacuum pump is used to remove gas through a vent pipe, achieving a vacuum level better than 4×10⁻⁶. -2 Pa; After the vacuum requirement is met, continue to maintain the vacuum and simultaneously use resistance welding to perform preliminary welding on the outside of the vent pipe body, with no less than 3 resistance welding points; then remove the vacuum device, and finally use argon arc welding to further seal the pipe end.

9. The method for pre-setting an intermediate layer of a microstructure blank with closely packed array characteristics according to claim 1, characterized in that: In step seven, the blank that has been sealed by edge welding in step six is ​​sent into a diffusion welding device or a hot isostatic pressing device that can be filled with high-pressure argon gas, so that the gas pressure is 20-50 MPa, the welding temperature is 900-1090℃, and the holding time is 15-60 min.

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