Method for surfacing stellite alloy on casing and application

Abstract

The method for surfacing stellite alloy on the cartridge receiver comprises the steps that a conical shape from the tail end of a tungsten electrode of an electrode part material to a round head is polished, the part is cleaned through ultrasonic waves, and then a boundary line of an area to be welded is marked out along a tool notch; pre-welding preheating is conducted on the part, meanwhile, all welding seams are grouped, and welding is conducted in a symmetrical sequence; setting a welding current, and surfacing a frame on the boundary of the delimited to-be-welded area; performing surfacing of a base layer in the frame, and performing surfacing of a filling layer and a covering layer after cooling; after surfacing, the part and the test plate are subjected to heat preservation stress relief heat treatment together, and the hardness of the workpiece is evaluated by detecting the hardness of a surfacing layer of the test plate. The process is stable, the problems of many internal defects and low hardness qualification rate after welding are solved, and the method can be applied to surfacing of stellite alloy on cases of various models.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of gas turbine and aero-engine manufacturing, and relates to a method for hardfacing Stellite on a casing and application thereof. BACKGROUND

[0002] Stellite is a kind of hard alloy capable of resisting various types of wear and corrosion at high temperature oxidation. According to different components in the alloy, welding wires and powders can be made for hardfacing processes. The main material of a certain gas turbine casing is stainless steel, and the structure is a split casing. A plurality of Stellite needs to be hardfaced on the three-layer flange edges on the outer wall of the part. After hardfacing Stellite on 1Cr18Ni9Ti, 0Cr17Ni12Mo2 and other stainless steel materials, the strength and hardness of the materials after welding increase, the plasticity and toughness decrease, the residual stress is large, cold cracks are prone to occur, a large amount of heat input is generated during welding, which easily causes serious casing welding deformation. On the other hand, the hardness of the hardfaced area has strict requirements, and the first-time qualified rate of hardness detection is too low. How to solve the problems of casing welding deformation, many internal defects of the weld, and low qualified rate of hardness detection after welding by studying the Stellite argon arc welding technology of large casing parts has become an urgent problem in the manufacturing of medium and large power gas turbines. SUMMARY

[0003] The application aims to provide a method for hardfacing Stellite on a casing and application thereof to solve the above problems.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical solutions. A method for hardfacing Stellite on a casing, comprising: Grinding the tungsten tip of the electrode part material to a conical shape of a round head, ultrasonic cleaning the part, and then drawing a boundary line of the to-be-welded area along the tool slot; Preheating the part before welding, grouping all the welds, and welding in a symmetrical sequence; Setting the welding current, hardfacing a frame on the to-be-welded area boundary, hardfacing a backing layer in the frame, and then hardfacing a filling layer and a surface layer after cooling; After hardfacing, the part is heat treated together with a test plate to eliminate stress, and the hardness of the workpiece is evaluated by testing the hardness of the hardfaced layer of the test plate.

[0005] Further, the grinding of the tungsten tip of the electrode part material to a conical shape of a round head and the ultrasonic cleaning of the part comprise: Select cerium tungsten electrode, diameter φ2 ~ φ4mm; tungsten electrode is polished into a conical round head, the angle is 30° ~ 45°; 2%-3% APC-Ⅰ water-soluble cleaning solution is used, the water temperature is heated to 40-50 degrees Celsius in the ultrasonic cleaning machine, the parts are cleaned, the cleaning time is 20-30 minutes, and the dry and clean compressed air is blown dry.

[0006] Further, the boundary line of the to-be-welded area along the tool slot is drawn, comprising: The scribing tool is used for scribing, and the scribing tool comprises a hoop, a protective pad, a quick clamp and a half-round head rivet; The hoop 1 is made of 1Cr18Ni9T stainless steel, with a width of 20-30mm, a thickness of 0.3mm and a length determined according to the actual circumference of the installation edge of the casing; a slot is opened, which is consistent with the angle and number of the weld; the slot width is the maximum value required by the weld width; the hoop has a scribe line with a width of about 0.2mm and a depth of about 0.05mm; the hoop is installed on the installation edge of the casing, and the angular positioning of the casing relative to the hoop is realized by aligning the angle scribe line on the hoop with the joint of the casing; the protective pad is installed on the hoop, which is made of nitrile rubber, with a length of 20-25mm and a thickness of 1mm; The hoop is fixed and locked on the installation edge of the casing by the quick clamp, and the half-round head rivet is used to fix and install the quick clamp and the hoop; The scribing tool is installed on the part installation edge, and the black scribe line on the clamp is aligned with the joint to determine the angle; The scribe needle is used to draw a line along the left and right boundaries of the slot on the scribing tool, and a boundary line of the to-be-welded area is drawn on the outer circle.

[0007] Further, the part is preheated before welding, comprising: The part is heated to 200-350 degrees Celsius for preheating.

[0008] Further, all the welds are grouped and welded in a symmetrical sequence, comprising: The symmetrical method is used for welding, all the welds are approximately divided into four groups, and the last group is welded if there are less than four welds; the determined welding sequence is marked with numbers; the symmetrical method is used for welding, and the welding is performed in the order of 1, 2, 3 and 4; the second group is welded in the order of 5, 6, 7 and 8, and the welding is sequentially performed according to the divided groups.

[0009] Further, the welding current is set, and a frame is built up on the boundary of the to-be-welded area, comprising: The welding current is 72-88A, and the argon flow rate is 13-15L / min, and a frame with a width of 4-5mm and a thickness of 1-2mm is built up on the boundary of the to-be-welded area.

[0010] Further, the row-in-border surfacing includes: The reserved border-in area is welded by adopting left welding method and small amplitude swing welding; the pre-pass weld is pressed by more than 1 / 3 width; the welding current is 80-90A; the welding seam adopts welding torch ventilation protection to prevent argon from disturbing the welding flow, and the argon flow is 8-10L / min.

[0011] Further, the surfacing of the filling layer and the cover layer after cooling down includes: After the temperature of the backing weld seam is reduced to the range of 160-240 DEG C, the welding of the filling layer weld seam is carried out; The thickness of each layer of the weld layer is 0.8-1.2mm, and the backing and filling need to be surfaced for not less than 4 times; after the welding of each layer is completed, the surface oxide is cleaned by using a steel wire brush; the welding current is 90-110A; the protection gas and flow: the welding seam adopts welding torch ventilation protection, and the argon flow is 13-15L / min.

[0012] Further, after the surfacing is completed, the part and the test plate are heat treated together to eliminate stress, and the hardness of the workpiece is evaluated by detecting the hardness of the surfacing layer of the test plate, which includes: The test plate after surfacing and the welded part are heat treated together, the heating temperature is increased to 820 DEG C-900 DEG C, the heat preservation time is 3.5-4.5 hours, and air cooling is carried out; Hardness detection: The weld seam end face on the milled test plate is surfaced, and the surfacing layer thickness is not less than 1.5mm; The hardness HRC of the surfacing layer of the test plate is detected, and the hardness value of the test plate after welding is used instead of the hardness value of the workpiece; the hardness detection area is the center area of the surfacing layer.

[0013] The application of a method for surfacing stellite alloy on a machine case is used for stellite alloy welding.

[0014] Compared with the prior art, the application has the following technical effects: The application aims to solve the problems of severe deformation, many internal defects of the weld seam and low qualified rate of the hardness detection after welding when surfacing stellite alloy on a machine case, and provides a welding method for realizing stellite alloy welding deformation control on the outer circle of the machine case, reducing welding defects and improving the qualified rate of the welding hardness detection by means of welding preparation, reasonable welding sequence design, design of a marking device, adoption of a backing method and reasonable welding parameters.

[0015] The application realizes the welding deformation control of the machine case. The welding sequence and path for reducing the welding deformation of the machine part are adopted, and the symmetrical and interval welding sequence is adopted to make the machine case be uniformly heated and welded in each direction.

[0016] This invention is simple and standardized to operate. It does not require a particularly high level of skill from the operators; welding can be performed by following the process flow, thus solving the drawback of relying on the individual skill of the operator to ensure welding quality in the past.

[0017] The process of this invention is stable and solves the problems of numerous internal defects and low hardness qualification rate after welding. It can be applied to the surfacing welding of Stellite alloy on various types of casings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the casing structure and the location of the Stellite alloy bosses of the present invention. W1, W2, and W3 represent the three-layer Stellite alloy bosses that are welded together. Figure 2 This is a schematic diagram of the angular positions of the two Stellite alloy bosses W2 and W3 overlay welded according to the present invention; in the figure, 1, 2, 3, 4 represent the welding sequence of the first group, and 5, 6, 7, 8 represent the welding sequence of the second group.

[0019] Figure 3 This is a schematic diagram of the marking device of the present invention, wherein the band is 1, the protective pad is 2, the protective pad is 3, the quick clamp is 4, and the semi-circular head rivet is 5.

[0020] Figure 4 This is a flowchart of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings: Example 1, please refer to Figure 4 The present invention provides a method for overlaying Stellite alloy onto a casing, comprising: The tungsten electrode material of the electrode part is ground from the end of the tungsten electrode to the conical shape of the round head. The part is cleaned with ultrasonic cleaning, and then the boundary line of the area to be welded is marked along the tooling groove. The parts are preheated before welding. At the same time, all welds are grouped and welded in a symmetrical order. Set the welding current and weld a frame around the defined area to be welded; then weld the bottom layer inside the frame, and after cooling, weld the filler layer and the top layer. After the welding is completed, the parts and test plates are heat-treated together to relieve stress. The hardness of the workpiece is evaluated by testing the hardness of the weld overlay on the test plate.

[0022] The purpose of this invention is to solve the problems of severe deformation, numerous internal defects in the weld, and low pass rate of post-weld hardness testing when Stellite alloy is deposited on the casing. By means of pre-weld preparation, planning a reasonable welding sequence, setting up a planning line device, adopting the "border" base method, and reasonable welding parameters, this invention provides a welding method to control the welding deformation of Stellite alloy on the outer circle of the casing, reduce welding defects, and improve the pass rate of welding hardness testing.

[0023] Example 2: The present invention provides a method for overlaying Stellite alloy onto a casing, comprising: 1. Pre-welding preparation (1) Electrode material and specifications: Cerium-tungsten electrode with a diameter of φ2~φ4mm is selected; (2) Process two test plates identical to the parent material, with dimensions of 50mm*20mm*10mm. (3) Grind the tungsten electrode. It must be sharpened before use.

[0024] The shape of the tungsten electrode tip affects the stability of the electric arc. The degree of sharpening (cone angle) is related to the welding wire diameter and the current used. For low welding currents, a small-diameter tungsten electrode can be used with a sharper tip, which makes the arc easier to ignite and stabilize. The larger the cone angle, the greater the compressibility. However, at high currents, the cone angle burns out more, and the tip is prone to melting into a spherical shape, making the arc diffusion unstable. Usually, the tip of the tungsten electrode is intentionally ground into a hemispherical shape. The tungsten electrode of this invention is ground into a rounded cone shape with an angle of 30° to 45°.

[0025] (4) Ultrasonic cleaning Use 2%-3% APC-Ⅰ water-soluble cleaning solution, heat the water to 40-50 degrees Celsius in an ultrasonic cleaner, and clean the parts thoroughly for 20-30 minutes. Then dry them with clean compressed air.

[0026] 2. Drawing lines (1) Design and fabrication of marking fixtures The marking fixture mainly includes a hoop 1, a protective pad 2, a protective pad 3, a quick clamp 4, and a semi-circular head rivet 5.

[0027] The hoop 1 is made of 1Cr18Ni9T stainless steel, with a width of 20-30mm and a thickness of 0.3mm. The length is determined according to the actual perimeter of the casing mounting edge at the welding position. It has grooves that are consistent with the angle and number of welds, and the groove width is the maximum value required for the weld width. The clamp has one engraved line, approximately 0.2 mm wide and 0.05 mm deep, painted black for easy identification. The clamp is installed on the mounting edge of the casing, and the casing is angularly positioned relative to the clamp by aligning the angle engraving line on the clamp with the casing's joint seam.

[0028] Protective pads 2 and 3 are installed on the clamp, made of nitrile rubber, 20-25 mm in length, and 1 mm thick. These two protective pads prevent the clamp 1 from damaging the weld overlay alloy mounting edge of the housing when the quick clamp 4 is closed.

[0029] The quick clamp 4 uses the standard GH-40323 GOOD HAND. The quick clamp secures the strap to the mounting edge of the casing, enabling quick assembly and disassembly.

[0030] The semi-circular head rivet 5 is designed and manufactured according to the standard 4X4 GB / T867-1986, and is used to install and fix the quick clamp 4 and the band 1.

[0031] (2) Install the scribing fixture on the mounting side of the part. When installing, pay attention to the correspondence between the fixture and the upper and lower half of the casing. Do not install it in reverse. Use the black scribing lines on the fixture to align the joint seam to determine the angle.

[0032] (3) Use a scribing needle to scribing along the left and right boundaries of the groove on the scribing fixture, and scribing the boundary line of the area to be welded on the outer circle. The scribing lines should be clearly visible.

[0033] 3. Determine the welding sequence (1) Due to the heat input during welding, the deformation of the casing is greatly affected. In order to control the welding deformation, the symmetrical welding method is adopted. All the welds are approximately divided into groups of four, and the last group with less than four welds is welded. (2) Identify the determined welding sequence by number; (3) Use the symmetrical welding method and weld in the order of 1, 2, 3, 4; (4) Weld the second group in the order of 5, 6, 7, 8, and weld them in the order of the divided groups; 4. Preheating treatment before welding in a low-temperature furnace Because gas turbine casing parts are large, a benchtop low-temperature furnace is used to preheat the parts to 200-350 degrees Celsius. Temperature differences exist between the welded parts in the welding area, which can cause welding cracks and brittle fractures. To reduce the impact of temperature differences, the parts are preheated. A reasonable heating temperature is crucial. If the heating temperature is too high, it will affect the internal structure of the material, and if the heating temperature is too low, it will not have a preheating effect.

[0034] 5. Weld the base layer "frame" First, weld the four-sided frame, with a frame width of 4-5mm and a weld thickness of 1-2mm; use welding wire with specifications of 1.6×1.6 or diameter of φ1-φ2mm. During welding, the electrode extension length is 8-15 mm; welding current: 72-88 (A); the weld is protected by gas venting through the welding torch, and a larger argon gas flow rate of 13-15 (L / min) is used to improve welding quality. 6. Apply weld overlay to form the root layer. Weld the area within the reserved frame in step five, using the left welding method and small-amplitude swaying welding; The width of the pre-weld pass should be ≥1 / 3 (the molten pool temperature should be lower than that of the right weld) to control the molten pool temperature and reduce the base metal deposition rate.

[0035] Welding current 80-90 A; the weld seam is protected by torch gas to prevent argon gas from disturbing the weld flow, and a small argon gas flow rate of 8-10 L / min is used. 7. Weld overlay filler layer and capping layer Once the temperature of the root pass weld has dropped to within the range of 160–240°C, the filler pass weld can be performed. If the cooling temperature of the root pass is too high, it will cause solder spatter and flow; if the cooling temperature is too low, it will cause welding cracks. Therefore, the interpass temperature must be strictly controlled. Each weld layer should be 0.8–1.2 mm thick, and the root pass and filler pass should be welded at least four times. After each layer of welding is completed, use a wire brush to clean the surface oxides to avoid slag inclusions; Welding current: 90-110 A; Shielding gas and flow rate: The weld is protected by torch gas, with an argon flow rate of 13-15 L / min. 8. Welding test plate Stellite alloy was deposited onto the test plate, and the welding process was carried out according to steps 4, 5, 6, and 7 of this invention.

[0036] 9. Eliminate welding stress The test plate after welding is heat-treated together with the welded parts. The temperature is raised to 820℃~900℃ and held for 3.5~4.5 hours, followed by air cooling.

[0037] 10. Hardness Testing (1.) Mill the weld end face on the test plate to ensure that the thickness of the weld overlay is not less than 1.5mm.

[0038] (2.) The hardness (HRC) of the weld overlay layer processed on the test plate is tested. The hardness value of the test plate after welding is used to replace the hardness value of the workpiece to solve the problem that the hardness test on the workpiece directly will cause damage. The hardness test area is the central area of ​​the weld overlay layer.

[0039] Example 3: The present invention is described below with reference to a specific embodiment of the welding of a split-type casing: 1. Pre-welding preparation (1) Select a tungsten electrode with a diameter of φ2mm; (2) Grind the tungsten electrode before welding and make it into a cone shape with a rounded head and an angle of 30°. (3) Prepare two test boards with dimensions of 50mm*20mm*10mm.

[0040] 2. Draw lines Install the scribing fixture on the outer circle of the casing, and use a scribing needle to scribing along the left and right boundaries of the groove on the scribing fixture. Draw the boundary line of the area to be welded on the outer circle. The scribing line should be clearly visible.

[0041] 3. All welds are approximately divided into groups of four, with the remaining welds in groups of less than four being the last group to be welded; a symmetrical welding method is used.

[0042] 4. Preheat the parts to 200 degrees Celsius in a low-temperature heating furnace.

[0043] 5. For the base layer "border" overlay, first overlay a border of 70-80mm, extending 1-2mm beyond the surface of the overlay side. The base layer overlay width is 17mm, the overlay layer width is 20mm, and the four corners are spot welded to increase the overlay height; the electrode extension length is 10mm; welding current: 130A. 6. Perform overlay welding to form the base layer. Weld the area within the frame reserved in step 5 using the left welding method and small-amplitude swaying welding; press the previous weld seam ≥ 1 / 3 of its width; welding current 100 (A). 7. Weld the filler layer. After the temperature of the root pass weld has dropped to within 200℃, weld the filler layer. Each weld layer should be 1mm thick, and the root pass + filler layer should be welded 4 times. After each layer is welded, clean the surface oxides with a wire brush to avoid slag inclusions. Welding current: 100A. The weld should be protected with argon gas at a flow rate of 10L / min. 8. Welding test plate: Stellite alloy is deposited on the test plate. The welding process is carried out according to steps 4, 5, 6, and 7.

[0044] 9. Eliminate welding stress The test plate after welding was heat-treated together with the welded parts. The temperature was raised to 860℃, held for 4 hours, and then air-cooled.

[0045] 10. Hardness testing: The hardness (HRC) of the weld overlay on the test plate is tested. The hardness value of the test plate after welding is used to replace the hardness value of the workpiece, thus avoiding damage to the workpiece caused by directly performing hardness testing on it. The hardness testing area is the central region of the weld overlay.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method of hardfacing Stellite alloy on a cartridge, characterized in that, It comprises: Polish electrode parts material tungsten tip to the conical shape of the round head, using ultrasonic cleaning parts, and then along the tool slot to draw the boundary line of the welding area to be welded; The parts are preheated before welding, and all the welds are grouped and welded in a symmetrical sequence; Set the welding current, and weld the frame in the designated welding area boundary; Weld the backing layer in the frame, and then weld the filling layer and the surface layer after cooling; After the surfacing is completed, the parts are heat treated together with the test plate to eliminate stress, and the hardness of the workpiece is evaluated by testing the hardness of the surfacing layer of the test plate.

2. A method of hardfacing Stellite on a casing according to claim 1, characterized in that, The polishing electrode part material tungsten tip is tapered to the round head, and the parts are cleaned by ultrasonic cleaning, which comprises: Select cerium tungsten electrode, diameter φ2-φ4mm; Tungsten electrode is polished into a conical shape of round head, angle is 30°-45°; 2%-3% APC-Ⅰ water-soluble cleaning solution is used, water temperature is heated to 40-50 degrees Celsius in the ultrasonic cleaning machine, the parts are cleaned, cleaning time is 20-30 minutes, and dry and clean compressed air is used for drying.

3. A method of hardfacing Stellite on a casing as defined in claim 1, wherein The boundary line of the welding area to be welded along the tool slot comprises: Use a scribe tool to draw a line, the scribe tool includes a hoop, a protective pad, a quick clamp and a half-round head rivet; The hoop 1 is made of 1Cr18Ni9T stainless steel material, with a width of 20-30mm, a thickness of 0.3mm and a length determined according to the actual circumference of the welding position case mounting edge; It is provided with grooves consistent with the angle and number of the weld; The groove width is the maximum value required by the weld width; The hoop has a line, the line width is about 0.2mm, and the line depth is about 0.05mm; The hoop is installed on the case mounting edge, and the angle line on the hoop is aligned with the joint of the case to realize the angular positioning of the case relative to the hoop; The protective pad is installed on the hoop, which is made of nitrile rubber, with a length of 20-25mm and a thickness of 1mm; The hoop is fixed and locked on the case mounting edge by the quick clamp, and the half-round head rivet is used to fix and install the quick clamp and the hoop; Install the scribe tool on the part mounting edge, and align the joint with the black line on the clamp to determine the angle; Draw a line along the left and right boundaries of the slot on the scribe tool, and draw the boundary line of the welding area on the outer circle.

4. A method of hardfacing Stellite on a casing as defined in claim 1, wherein The preheating of the parts before welding comprises: Preheat the parts to 200-350 degrees Celsius.

5. A method of hardfacing Stellite alloy on a casing as set forth in claim 1, wherein The grouping of all welds and the welding in a symmetrical sequence comprises: Using the symmetrical method, all welds are approximately divided into four groups, and the last group is welded if there are less than four welds; The determined welding sequence is marked with numbers; Using the symmetrical method, weld in the order of 1, 2, 3, 4; Weld in the order of 5, 6, 7, 8 for the second group, and weld in turn according to the divided groups.

6. A method of hardfacing Stellite alloy on a casing as set forth in claim 1, wherein The setting of the welding current and the welding of the frame in the designated welding area boundary comprises: Using the parameters of welding current 72-88A and argon flow rate 13-15L / min, weld the frame with a width of 4-5mm and a thickness of 1-2mm in the designated welding area boundary.

7. A method of hardfacing Stellite alloy on a casing as set forth in claim 1, wherein The backing layer welding in the frame comprises: The reserved frame inner area is welded by left welding method and small amplitude swing welding; the pre-pass welding seam is pressed to be greater than or equal to 1 / 3 of the width; the welding current is 80-90 A; the welding seam is protected by welding torch ventilation to prevent argon from disturbing the welding flow, and the argon flow is 8-10 L / min.

8. A method of hardfacing Stellite on a casing as defined in claim 1, wherein The post-cooling filling layer and cover layer surfacing are performed, including: After the base welding seam temperature is reduced to 160-240 ℃, the filling layer welding is performed; The thickness of each layer of welding layer is 0.8-1.2 mm, and the base + filling needs to be surfacing for not less than 4 times; after each layer of welding is finished, the surface oxide is cleaned by using a steel wire brush; the welding current is 90-110 A; the protective gas and flow: the welding seam is protected by welding torch ventilation, and the argon flow is 13-15 L / min.

9. A method of hardfacing Stellite alloy on a casing as set forth in claim 1, wherein After the surfacing is completed, the part and the test plate are heat treated together to eliminate stress, and the workpiece hardness is evaluated by detecting the hardness of the surfacing layer of the test plate, including: The surfacing test plate and the welded part are heat treated together, the heating temperature is increased to 820-900 ℃, the holding time is 3.5-4.5 hours, and air cooling is performed; Hardness detection: The welding seam end face on the milled test plate is processed, and the surfacing layer thickness is not less than 1.5 mm; The hardness HRC of the surfacing layer processed by the test plate is detected, and the hardness value of the test plate after welding is used instead of the hardness value of the workpiece; the hardness detection area is the center area of the surfacing layer.

10. Use of a method of hardfacing Stellite alloys on a cartridge as claimed in any one of claims 1 to 9, characterized in that, For welding of Stellite alloy.

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