An Adaptive Welding Method for the Wear-Resistant Layer of a Turbine Blade

Abstract

The present invention relates to the technical field of aero-engine blade welding, and particularly relates to an adaptive welding method for a wear-resistant layer of a turbine blade, which includes Step 1: pre-welding machining and positioning reference; Step 2: welding motion trajectory; Step 3: visual positioning and compensation algorithm; Step 4: wear-resistant alloy welding; Step 5: vacuum stress relief treatment; Step 6: slow-feed grinding machining; Step 7: fluorescent inspection; The present invention adopts a visual positioning and compensation algorithm, which can realize the automatic planning and compensation of the starting position, welding path and arc-ending position of the wear-resistant layer. By using a numerically controlled programmable three-axis machine tool, precise positioning can be achieved, and the starting, process edge and ending positions of welding can be accurately controlled. Through the coordination of a plasma arc welding heat source and a wire feeding system, the front wire feeding and stability of the molten pool during the welding process can be realized, ensuring the precise control forming of the wear-resistant layer.

Description

Technical Field

[0001] The present invention relates to the technical field of aeroengine blade welding, and particularly relates to an adaptive welding method for a wear-resistant layer of a turbine blade. Background Art

[0002] Turbine blades are key components of aeroengines. The thermal energy generated by high-temperature gas is used to drive the high-speed rotation of the turbine blades to do work and form power. However, during the operation of an aeroengine, vibration stress is inevitably generated, which directly affects the service life of the turbine blades. Therefore, in the design of low-pressure turbine blades with a large length-diameter ratio and a large aspect ratio, a crowned structure is adopted to reduce vibration. The crowned shoulders between adjacent blades mesh with each other to form a blade ring, and a wear-resistant layer is pre-placed by welding, which can reduce high-temperature fretting wear, reduce the crowned engagement gap, and reduce the influence of vibration stress, thereby effectively improving the service reliability of the turbine blades.

[0003] Currently, the wear-resistant layer structure of turbine blades is prepared by welding, mainly by manual tungsten inert gas welding. Since overheating easily occurs during manual welding of the wear-resistant layer, the quality is unstable, the qualified rate is low, the thickness of the wear-resistant layer is uneven, and the consistency is difficult to guarantee. As a result, the mechanisms of cracks and block shedding are unclear, and the limitations of process control measures are prominent. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides an adaptive welding method for a wear-resistant layer of a turbine blade; the specific technical solution is as follows:

[0005] An adaptive welding method for a wear-resistant layer of a turbine blade includes the following steps:

[0006] Step 1: Pre-welding processing and positioning reference;

[0007] (1) Taking the tenon of the turbine blade as the positioning reference, process the weld surface of the wear-resistant layer of the turbine blade;

[0008] (2) To ensure the stability of the wear-resistant layer welding process, it is necessary to realize the coordinated movement of the welding torch and nozzle, and the welding wire and wire feeder nozzle within a limited processing space without spatial interference;

[0009] (3) Before welding, reserve a machining allowance of 1.4 mm - 1.5 mm along the thickness direction of the weld surface of the wear-resistant layer of the turbine blade, with a root transition concave R of 1.4 mm. To ensure the smooth movement of the welding torch and wire feeding mechanism to the welding position, continue to transition a second concave R of 1.4 on the non-working surface of the wear-resistant layer, that is, form a double concave R of 1.4 mm;

[0010] (4) Use a 50um alumina grinding wheel to polish the interlocking surface part and adjacent areas to expose the metallic luster; the grinding depth perpendicular to the interlocking surface is not less than 0.1 mm, and the grinding on both sides of the interlocking surface is not less than 6 mm in range and the depth is not more than 0.05 mm;

[0011] (5) Before welding, steam degreasing and cleaning with anhydrous ethanol are carried out. Ultrasonic cleaning can also be used as an auxiliary. No oil stains or foreign matters are allowed. After cleaning, it is assembled into a special welding fixture.

[0012] Step Two: Welding movement trajectory

[0013] (1) To ensure the stability of the molten pool formed during welding and the wire feeding droplet transfer, wire feeding is carried out in the forward welding direction. Starting from the concave R position at the root of the wear-resistant layer, the arc moves outward to the convex R position to complete the entire welding trajectory, and the arc and wire feeding always maintain a fixed 45-degree angle.

[0014] (2) A special tooling that holds the blade is driven by a numerical control slide table to achieve the welding movement trajectory along the X and Y fitting. The welding torch and wire feeding always maintain a fixed position.

[0015] Step Three: Visual positioning and compensation algorithm

[0016] (1) High-precision positioning is achieved by using a CCD industrial camera with a fixed bracket. By collecting the trajectory feature points, the coordinate points of the edges, concave R, and convex R of the wear-resistant layer are determined, and they are fitted with the theoretical coordinate points to extract the deviation and offset the coordinate system.

[0017] (2) Taking the center points of the X axes of the two edges on both sides of the concave R as the starting arc positions, and the center points of the X axes of the two edges on both sides of the convex R as the ending arc positions, the swing amplitude between them is that the coordinate points of the edges decrease by 0.3 mm along the X axis.

[0018] Step Four: Welding of wear-resistant alloy

[0019] (1) Plasma arc welding with wire filling is used to weld the wear-resistant layer. The welding area is 5 mm × 7 mm, and both the starting and ending arc positions are on the working surface of the wear-resistant layer.

[0020] (2) The movement trajectory and welding current are coordinated, that is, the welding current is at the peak when welding to the edge position.

[0021] Step Five: Vacuum stress relief treatment

[0022] After welding, it is heated to 760 °C ± 10 °C in a vacuum welding furnace, held for 1.5 h, and cooled with argon gas filling.

[0023] Step Six: Creep-feed grinding

[0024] (1) A special diamond roller is used for creep-feed grinding of the interlocking surface and the crown top of the saw teeth.

[0025] (2) After processing, the joint of the creep-feed grinding is ground to remove burrs and sharp edges.

[0026] Step Seven: Fluorescent inspection

[0027] For post - emulsification level 4 sensitivity inspection of defects and displays, determine the size, quantity, and spacing of defects according to the dedicated technical document.

[0028] For the described adaptive welding method of the wear - resistant layer of a turbine blade, in its preferred solution, in step four, the welding process parameters are: peak current 25A, duration 0.5s, base current 20A, duration 1.5s, welding speed 150mm / min, ion gas Ar flow rate 0.3L / min, shielding gas flow rate 12L / min, compression nozzle aperture 1.5mm, wire feeding speed 180mm / min, and wire feeding diameter 1.2mm.

[0029] For the described adaptive welding method of the wear - resistant layer of a turbine blade, in its preferred solution, in step six, after grinding, the wear - resistant layer alloy in the transition concave R area between the interlocking surface and the non - working surface of the serrated crown is completely removed, with a transition fillet R of 0.9, and smooth transition with both sides.

[0030] For the described adaptive welding method of the wear - resistant layer of a turbine blade, in its preferred solution, in step one, a formed diamond roller is used to process the double - concave part of the surface to be welded.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] The present invention adopts a vision - based positioning and compensation algorithm, which can realize the automatic planning and compensation of the starting position, welding path, and arc - ending position of the wear - resistant layer. Using a numerically controlled programmable three - axis machine tool can achieve precise positioning and accurate control of the starting, process edge, and ending positions of welding. Through the coordination of a plasma arc welding heat source and a wire - feeding system, it can realize pre - wire - feeding into the molten pool and stability during the welding process, ensuring the precise control forming of the wear - resistant layer. The present invention solves the problems of unstable quality, low qualified rate, uneven thickness of the wear - resistant layer, and risks of cracks and chipping caused by manual welding. The qualified rate of one - time welding can reach over 95%, the thickness of the wear - resistant layer is stable between 0.8 - 1.0, and the dilution rate of the wear - resistant layer is not more than 5%, ensuring the reliability of the turbine blade in use.

[0033] The welding method proposed by the present invention has a long design life for this type of blade stage, adding higher technical added value to interchangeability, maintainability, and quality reliability, and can meet the welding requirements of a large number of military and civilian turbine blades, with broad application prospects. Brief Description of the Drawings

[0034] Figure 1 It is a schematic structural diagram of a low - pressure turbine working blade;

[0035] Figure 2 For Figure 1 Schematic P - direction structure diagram of

[0036] Figure 3 It is the pre-welding processing drawing of the turbine blade shroud;

[0037] Figure 4 It is the schematic diagram of the welding track of the wear-resistant layer of the turbine blade.

[0038] In the figure, 1 - shroud, 2 - tenon, 3 - wear-resistant layer, 4 - transition concave R area between the interlocking surface and the non-working surface. Specific implementation manners

[0039] The present invention will be described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited by the drawings.

[0040] The adaptive welding of the wear-resistant layer of the first-stage working blade of the low-pressure turbine includes the following steps:

[0041] Step 1: Pre-welding processing and positioning reference;

[0042] (1) Taking the tenon 2 of the turbine blade as the positioning reference, process the surface to be welded of the wear-resistant layer 3 of the turbine blade;

[0043] (2) To ensure the stability of the welding process of the wear-resistant layer, it is necessary to realize the coordinated movement of the welding torch and nozzle, and the welding wire and wire feeding nozzle within the limited processing space without spatial interference;

[0044] (3) Before welding, reserve a machining allowance of 1.5 mm on the crown top side of the shroud 1, and use a formed diamond roller to machine the root transition concave R of 1.4 mm and the non-working surface of the wear-resistant layer to continue to transition to the second concave R of 1.4, that is, form a double concave R of 1.4 mm;

[0045] (4) Use a 50um granularity alumina grinding wheel to polish the interlocking surface part and adjacent areas to expose the metallic luster; the grinding depth perpendicular to the interlocking surface is not less than 0.1 mm, and the grinding on both sides of the interlocking surface is not less than 6 mm in range and the depth is not more than 0.05 mm;

[0046] (5) Before welding, perform steam degreasing and cleaning with anhydrous ethanol, and ultrasonic cleaning can also be assisted. No oil stains and foreign matters are allowed; after cleaning, assemble it into a special welding fixture;

[0047] Step 2: Welding movement track;

[0048] (1) To ensure the stability of the molten pool and the wire feeding droplet transfer formed during the welding process, use forward wire feeding in the welding direction, start the arc from the concave R position at the root of the wear-resistant layer 3, and move outward to the convex R position to complete the entire welding track, and the arc and wire feeding always maintain a fixed angle of 45 degrees;

[0049] (2) Use a numerical control slide table to drive the tooling for holding the blade to realize the welding movement track along the X, Y fitting, and the welding torch and wire feeding always maintain a fixed position;

[0050] Step 3: Visual positioning and compensation algorithm;

[0051] (1) High-precision positioning is achieved by using a CCD industrial camera with a fixed bracket. By collecting trajectory feature points, the coordinate points of the edges, concave R, and convex R of the wear-resistant layer are determined, and then fitted with the theoretical coordinate points to extract the deviation and offset the coordinate system.

[0052] (2) Taking the X-axis center points of the two sides of the concave R as the starting arc positions and the X-axis center points of the two sides of the convex R as the ending arc positions, the swing amplitude of the trajectory in between is that the edge coordinate points decrease by 0.3 mm along the X-axis.

[0053] Step 4: Welding of wear-resistant alloy

[0054] (1) Plasma arc welding with filler wire is used to weld the wear-resistant layer. The welding surface is as small as 5 mm × 7 mm, and both the starting and ending arc positions are on the working surface of the wear-resistant layer. Welding process parameters: peak current 25 A, duration 0.5 s, base current 20 A, duration 1.5 s, welding speed 150 mm / min, ion gas Ar flow rate 0.3 L / min, shielding gas flow rate 12 L / min, compression nozzle aperture 1.5 mm, wire feeding speed 180 mm / min, wire feeding diameter 1.2 mm.

[0055] (2) The movement trajectory and welding current are coordinated, that is, the welding current is at the peak when welding to the edge position.

[0056] Step 5: Vacuum stress relief treatment

[0057] After welding, it is heated to 760 °C ± 10 °C in a vacuum welding furnace, held for 1.5 h, and cooled with argon gas.

[0058] Step 6: Creep-feed grinding

[0059] (1) A special diamond roller is used for creep-feed grinding of the interlocking surface and crown top of the sawtooth crown. After grinding, the wear-resistant layer alloy in the transition concave R area 4 between the interlocking surface and the non-working surface of the sawtooth crown is completely removed, and its transition fillet is R0.9, with smooth transition to both sides.

[0060] (2) After processing, the joint of the creep-feed grinding is ground to remove burrs and sharp edges.

[0061] Step 7: Fluorescent inspection

[0062] Check for defects and display with a post-emulsification level 4 sensitivity, and determine the size, quantity, and spacing of the defects according to the special technical document.

Claims

1. An adaptive welding method for the wear-resistant layer of a turbine blade, characterized in that: It includes the following steps: Step 1: Pre-welding processing and positioning reference; (1) Taking the tenon of the turbine blade as the positioning reference, process the surface to be welded of the wear-resistant layer of the turbine blade; (2) To ensure the stability of the welding process of the wear-resistant layer, it is necessary to realize the coordinated movement of the welding torch, nozzle, welding wire and wire feeding nozzle within the limited processing space without spatial interference; (3) Before welding, reserve a machining allowance of 1.4 mm - 1.5 mm along the thickness direction of the surface to be welded of the wear-resistant layer of the turbine blade, with a root transition concave R of 1.4 mm. To ensure the smooth movement of the welding torch and wire feeding mechanism to the welding position, continue to transition the second concave R of 1.4 on the non-working surface of the wear-resistant layer, that is, form a double concave R of 1.4 mm; (4) Use a 50um grain size alumina grinding wheel to polish the interlocking surface part and adjacent areas to expose the metallic luster; the grinding depth perpendicular to the interlocking surface is not less than 0.1 mm, and the grinding on both sides of the interlocking surface is not less than 6 mm in range and the depth is not more than 0.05 mm; (5) Before welding, perform steam degreasing and cleaning with anhydrous ethanol, and ultrasonic cleaning can also be assisted. No any oil stains and foreign matters are allowed; after cleaning, assemble it to a special welding fixture; Step 2: Welding movement trajectory; (1) To ensure the stability of the molten pool and wire feeding droplet transfer formed during the welding process, use forward wire feeding in the welding direction, start the arc from the concave R position at the root of the wear-resistant layer, move outward to the convex R position to complete the entire welding trajectory, and the arc and wire feeding always maintain a fixed 45-degree angle; (2) Use a numerically controlled slide table to drive the tooling for holding the blade to fit along X and Y to realize the welding movement trajectory, and the welding torch and wire feeding always maintain a fixed position; Step 3: Visual positioning and compensation algorithm; (1) Use a CCD industrial camera with a fixed bracket to achieve high-precision positioning. By collecting trajectory feature points, determine the coordinate points of the edges, concave R and convex R of the wear-resistant layer, fit them with the theoretical coordinate points, extract the deviation and offset the coordinate system; (2) Taking the X-axis center point of the two edges on both sides of the concave R as the starting arc position, and the X-axis center point of the two edges on both sides of the convex R as the arc ending position, the swing amplitude between them is that the edge coordinate points decrease by 0.3 mm along the X-axis; Step 4: Welding of wear-resistant alloy (1) Use plasma arc welding with filler wire to weld the wear-resistant layer, and the welding area is 5 mm × 7 mm, and both the starting and ending arc positions are on the working surface of the wear-resistant layer; (2) Coordinate the movement trajectory and welding current, that is, the welding current is at the peak value when welding to the edge position; Step 5: Vacuum stress relief treatment After welding, heat up to 760 °C ± 10 °C in a vacuum welding furnace, keep it warm for 1.5 h, and cool it with argon gas; Step 6: Creep-feed grinding (1) Use a special diamond roller to perform creep-feed grinding on the interlocking surface and crown top of the sawtooth crown; (2) After processing, grind the joint of the creep-feed grinding to remove burrs and sharp edges; Step 7: Fluorescent inspection Check for defects and displays with a post-emulsifiable 4th level sensitivity, and judge the size, quantity and spacing of the defects according to the special technical document.

2. The adaptive welding method of a wear-resistant layer of a turbine blade according to claim 1, characterized in that: In Step 4, the welding process parameters are as follows: peak current 25 A, duration 0.5 s, base current 20 A, duration 1.5 s, welding speed 150 mm / min, ion gas Ar flow rate 0.3 L / min, shielding gas flow rate 12 L / min, compression nozzle aperture 1.5 mm, wire feeding speed 180 mm / min, wire feeding diameter 1.2 mm.

3. An adaptive welding method for a wear-resistant layer of a turbine blade according to claim 1, characterized in that: In Step 6, the wear-resistant layer alloy at the transition concave R area between the interlocking surface and the non-working surface of the serrated crown is completely removed after grinding. The transition fillet is R0.9 and is smoothly transitioned with both sides.

4. An adaptive welding method for a wear-resistant layer of a turbine blade according to claim 1, characterized in that: In Step 1, a formed diamond roller is used to machine the double concave areas of the surface to be welded.

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