Preparation method of long-life elastic blade root gasket

Abstract

The invention relates to a preparation method of a long-life elastic blade root gasket, and belongs to the field of metal materials. The sandwich structure that the nickel-titanium metal cloth is clamped between the two layers of nickel-based high-temperature alloy plates is adopted, the problem that an existing blade root gasket is prone to loosening in the using process is solved, and the nickel-titanium metal cloth is woven through a Dutch twill weaving method; the manufacturing process comprises the steps of preparing the nickel-based high-temperature alloy plate, preparing the nickel-titanium alloy Dutch twill screen cloth, and performing resistance welding on the plate and the screen cloth. The structure has certain elasticity, is convenient to assemble outdoors, has certain elasticity at high temperature and can buffer stress generated by overstocked nickel-based alloy plates on the two sides, so that deformation of the alloy plates and overall deformation of the gasket can be reduced, the service life of the gasket is prolonged, the service life of the gasket is more than five times that of a conventional gasket, and the service life of the gasket is prolonged. And the requirements of the 700 DEG C grade high-pressure regulating stage blade root gasket can be well met.

Description

Technical Field

[0001] The invention belongs to the field of metal materials and relates to a method for preparing a long-life high-temperature resistant elastic blade root gasket. Background Art

[0002] Ultra-supercritical steam turbine and gas turbine blades are very important components. For blades below 650℃, they are made of heat-resistant steel. Blade assembly relies on the high dimensional accuracy of the blades themselves and on-site processing to achieve gap-free fit between the blade roots (CN201910021025.2). Considering the potential impact of expansion thermal stress on blade life, the assembly method of blades above 700℃ has changed. A certain gap is left between the blades and the blade roots. A gasket, namely the blade root gasket, is inserted into the gap to protect the blade roots from external damage and to achieve a tight fit between the blades.

[0003] The gas pressure and temperature of the blades are different, so the selected gasket materials are also different. For nickel-based alloy blades working in the high-pressure regulating stage, the blade root gasket is made of nickel-based high-temperature alloy material with high high-temperature strength and creep rupture strength.

[0004] There is usually a certain gap between the roots of steam turbine and gas turbine blades. Blade root gaskets are installed between the blade roots. Blade root gaskets are subjected to stress during service. The main failure mechanism is plastic deformation caused by stress. Under stress during operation, plastic deformation may occur after long-term use, resulting in a decrease in gasket thickness, making the original tight fit become gaps, and some are too loose, which may cause blade vibration. Therefore, the ideal gasket should always maintain an interference fit during operation to prevent the blade root from loosening. The existing gasket manufacturing method is difficult to meet the requirements, and new gaskets need to be developed. Summary of the invention

[0005] Based on the excellent oxidation resistance and high temperature performance of nickel-based alloys and the superelasticity of nickel-titanium alloys, the present invention solves the problem that the current blade root gasket is easy to loosen during use by designing a sandwich structure with a double-layer nickel-based high-temperature alloy plate sandwiched with a nickel-titanium metal cloth woven in Dutch twill. The structure is elastic at the assembly temperature and can adapt to different gap tolerances. Secondly, it has high high-temperature strength and elasticity at high temperatures, which can relieve the stress caused by the expansion of the blade root and improve the service life.

[0006] The main production processes of blade root gaskets include the preparation of nickel-based high-temperature alloy plates, the preparation of nickel-titanium alloy Dutch twill mesh, and the resistance welding of plates and meshes.

[0007] A method for preparing a long-life elastic blade root gasket, characterized in that a sandwich structure of nickel-titanium metal cloth sandwiched between double-layer nickel-based high-temperature alloy plates is adopted to solve the problem that the current blade root gasket is easy to loosen during use. The nickel-titanium metal cloth is woven using a Dutch twill weaving method; the production process includes the preparation of nickel-based high-temperature alloy plates, the preparation of nickel-titanium alloy Dutch twill mesh cloth, and the resistance welding process of the plates and the mesh cloth.

[0008] Furthermore, the specific preparation steps of the sandwich structure gasket are as follows:

[0009] (1) Preparation of nickel-based alloy plates: first, the master alloy is melted according to the composition percentage, vacuum melting is used, and then the ingot is electroslag remelted to obtain electroslag ingots, and then forged, hot rolled, cold rolled, and finally annealed at 800°C to obtain nickel-based alloy plates with different thicknesses of 0.3 to 1.0 mm;

[0010] (2) Manufacturing Dutch twill mesh from nickel-titanium alloy wire: First, the nickel-titanium alloy ingot is vacuum melted, and then forged, hot rolled, and cold drawn into wires with diameters of 0.18±0.01mm and 0.15±0.01mm respectively;

[0011] (3) Using the Dutch twill weaving method to weave nickel-titanium metal cloth with a thickness of 0.48 mm ± 0.02 mm:

[0012] (4) Using the resistance spot welding method, two nickel-based high-temperature alloy plates are welded together with a nickel-titanium metal cloth sandwiched between them. The number of spot welds is determined according to the area of ​​the gasket to ensure that the shear strength of the sandwich structure gasket in the plane direction after welding is greater than 15MPa;

[0013] (5) Laser cutting: The sandwich structure gasket blank is laser cut into the required size and shape to obtain the finished blade root gasket. When it is actually used, the nickel base plate of different thicknesses and the nickel-titanium bimetallic cloth of fixed thickness are welded together according to the designed gap size between the blade roots to meet the gap size requirements.

[0014] Furthermore, the composition weight percentage of the nickel-based alloy plate in step (1) is: Ni~(20-22wt%)Co~(18-20wt%)Cr~(3.5-4wt%)W~(5-6wt%)Fe~(3-4wt%)Al.

[0015] Furthermore, the mass ratio of Ni to Ti in the nickel-titanium alloy ingot in step (2) is: Ni (55-55.3) wt%: Ti (44.7-45) wt%.

[0016] Furthermore, in step (3), the warp wires of the nickel-titanium metal cloth are 0.18±0.01 mm nickel-titanium alloy wires, and the diagonal wires are 0.15±0.01 mm nickel-titanium alloy wires.

[0017] Furthermore, the diameter of the spot welding electrode tip in step (4) is 0.5 mm.

[0018] The main advantages of using the above materials and structures are: (1) The designed nickel-based alloy plate has not only γ´ strengthening phase, but also Cr 60.8 Co 28.3 Ni 6.75 W2Al2 δ phase, the synergistic effect of the two phases makes the alloy show excellent creep resistance and compression resistance, which can reduce the deformation of the gasket caused by extrusion stress; (2) The designed nickel-titanium alloy is in R phase when it is below 50℃, the metal cloth is relatively soft, and the elastic modulus is reduced, which is conducive to the assembly of the gasket. At the working temperature, the R phase turns into austenite phase with high strength and elastic deformation of up to 8%, which can buffer the stress caused by the backlog of nickel-based alloy plates on both sides, thereby further reducing the deformation of the alloy plate and the overall deformation of the gasket. The service life of the gasket made of the above materials and structures is more than 5 times that of the conventional gasket, which can well meet the requirements of the 700℃ grade high-pressure regulating stage blade root gasket. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the sandwich structure blade root gasket.

[0020] ① and ③ are nickel-based alloy plates, ② is a nickel-titanium metal cloth woven in Dutch twill, ①,

[0021] ② and ③ are welded together by resistance welding. DETAILED DESCRIPTION

[0022] (1) The blade root gasket developed by the present invention is mainly used for a series of thicknesses between 1.0 and 2.5 mm. Therefore, three typical thicknesses of 1.0 mm, 1.5 mm and 2.5 mm are selected for implementation in the specific implementation. The manufacturing specifications are 100 gaskets with a specification of 3 cm (length) × 2 cm (width) × 2.5 ± 0.02 mm (thickness), 100 gaskets with a specification of 3.5 cm (length) × 2.5 cm (width) × 1.5 ± 0.02 mm (thickness), and 100 gaskets with a specification of 2.5 cm (length) × 1.5 cm (width) × 1.0 mm ± 0.02 mm (thickness).

[0023] The specific manufacturing steps are:

[0024] ① First, the thickness is designed. According to the three-layer structure calculation, the thickness of the nickel-titanium alloy metal cloth is fixed at 0.48±0.02mm. The thickness of the 1.0mm thick gasket nickel-based high-temperature alloy plate is 0.21mm, the thickness of the 1.5mm thick nickel-based alloy plate is 0.51mm, and the thickness of the 2.5mm thick gasket is 1.01mm.

[0025] ② The second step is to prepare the nickel-based alloy plate: first, the master alloy is smelted according to the composition of Ni~(20-22wt%)Co~(18-20wt%)Cr~(3.5-4wt%)W~(5-6wt%)Fe~(3-4wt%)Al, and then the ingot is electroslag remelted to obtain electroslag ingots, and then forged, hot rolled, cold rolled, and finally annealed at 800℃ to obtain plates with three thicknesses of 0.21mm, 0.51mm and 1.01mm;

[0026] ③ The third step is to prepare nickel-titanium alloy metal cloth: first, Ni and Ti are vacuum melted into alloy ingots according to the mass ratio of (55-55.3) wt%: (44.7-45) wt%, and then forged, hot-rolled, and cold-drawn into wires with diameters of 0.18±0.01mm and 0.15±0.01mm, respectively; the nickel-titanium metal cloth is woven by the Dutch twill weaving method: 0.18±0.01mm wire is used as the warp, 0.15±0.01mm wire is used as the diagonal, and the Dutch twill weave is used to form a metal cloth with a thickness of 0.48±0.02mm;

[0027] ④ The fourth step is the welding of the gasket: two nickel-based alloy plates with a thickness of 0.21 mm are sandwiched with a nickel-titanium alloy metal cloth with a thickness of 0.48 mm for resistance welding to obtain a blade root gasket with a thickness of 1.0 mm, and conventional parameters can be used for welding parameters; then two nickel-based alloy plates with a thickness of 0.51 mm are resistance welded with a nickel-titanium alloy cloth with a thickness of 0.48 mm in the same way to obtain a blade root gasket with a thickness of 1.5 mm; finally, two nickel-based alloy plates with a thickness of 1.01 mm are resistance welded with a nickel-titanium alloy cloth with a thickness of 0.48 mm in the same way to obtain a blade root gasket with a thickness of 2.5 mm;

[0028] ⑤ In the fifth step, the three specifications of plates are laser cut according to the size requirements to obtain finished blade root gaskets.

Claims

1. A method for preparing a long-life elastic blade root gasket, characterized in that: A sandwich structure with nickel-titanium metal cloth sandwiched between double-layer nickel-based high-temperature alloy plates is adopted to solve the problem that the current blade root gasket is easy to loosen during use. The nickel-titanium metal cloth is woven using the Dutch twill weaving method; the production process includes the preparation of nickel-based high-temperature alloy plates, the preparation of nickel-titanium alloy Dutch twill mesh, and the resistance welding process of the plates and the mesh.

2. The method for preparing the long-life elastic blade root gasket according to claim 1, characterized in that: The specific preparation steps of the sandwich structure gasket are as follows: (1) preparing a nickel-based alloy plate: firstly, melting a master alloy according to the composition percentage, using vacuum melting, then electroslag remelting the ingot to obtain an electroslag ingot, then forging, hot rolling, cold rolling, and finally annealing at 800°C to obtain a nickel-based alloy plate with different thicknesses of 0.3 to 1.0 mm; (2) Manufacturing Dutch twill mesh from nickel-titanium alloy wire: First, the nickel-titanium alloy ingot is vacuum melted, and then forged, hot rolled, and cold drawn into wires with diameters of 0.18±0.01mm and 0.15±0.01mm respectively; (3) Using the Dutch twill weaving method to weave nickel-titanium metal cloth with a thickness of 0.48 mm ± 0.02 mm: (4) Using the resistance spot welding method, two nickel-based high-temperature alloy plates are welded together with a nickel-titanium metal cloth sandwiched between them. The number of spot welds is determined according to the area of ​​the gasket to ensure that the shear strength of the sandwich structure gasket in the plane direction after welding is greater than 15MPa; (5) Laser cutting: The sandwich structure gasket blank is laser cut into the required size and shape to obtain the finished blade root gasket. When it is actually used, the nickel base plate of different thicknesses and the nickel-titanium bimetallic cloth of fixed thickness are welded together according to the designed gap size between the blade roots to meet the gap size requirements.

3. The method for preparing the long-life elastic blade root gasket according to claim 2, characterized in that: The composition weight percentage of the nickel-based alloy plate in step (1) is: Ni~(20-22wt%)Co~(18-20wt%)Cr~(3.5-4wt%)W~(5-6wt%)Fe~(3-4wt%)Al.

4. The method for preparing the long-life elastic blade root gasket according to claim 2, characterized in that: The mass ratio of Ni to Ti in the nickel-titanium alloy ingot in step (2) is: Ni (55-55.3) wt%: Ti (44.7-45) wt%.

5. The method for preparing the long-life elastic blade root gasket according to claim 2, characterized in that: The nickel-titanium metal cloth in step (3) has a warp thread of 0.18±0.01 mm nickel-titanium alloy wire and a diagonal thread of 0.15±0.01 mm nickel-titanium alloy wire.

6. The method for preparing the long-life elastic blade root gasket according to claim 2, characterized in that: The diameter of the spot welding electrode tip in step (4) is 0.5 mm.

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