Welding tool and welding method for stainless steel filter plate of vertical filter press

Abstract

The invention discloses a welding tool and a welding method for a stainless steel filter plate of a vertical filter press, and relates to the technical field of filter press filter plate machining. The tool comprises a bedplate and a positioning frame, the specification of the bedplate is consistent with that of a stainless steel base plate, a screw hole matched with a through hole of the base plate is formed, the base plate can be pressed and fixed through a screw, and an angular seat with a caulking groove is arranged on the side edge to achieve axial positioning of a hinged shaft; the positioning frame is provided with an annular positioning plate matched with the check ring, and pre-positioning of the check ring is completed by inserting the pin into the through hole of the base plate. The method is based on the tool, and the processes of four-person opposite synchronous welding, sketch charcoal pen smearing on the to-be-welded area before welding and segmented dismounting and mounting of screws in the welding area are adopted. Welding deformation can be effectively controlled, the defect of weld joint needle holes is overcome, and welding precision and machining efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of vertical filter press filter plate processing technology, specifically to a welding fixture and welding method for stainless steel filter plates of vertical filter presses, which is applicable to high-precision welding processing of large-size austenitic stainless steel filter plates. Background Technology

[0002] Vertical filter presses are core equipment in the field of solid-liquid separation, and stainless steel filter plates are key working components of vertical filter presses. For example... Figure 1 As shown, the stainless steel filter plate 100 to be welded includes a rectangular stainless steel substrate 101. An annular stainless steel retaining ring 102 is welded to the surface of the stainless steel substrate 101. The stainless steel retaining ring 102 and the stainless steel substrate 101 enclose a filter groove for accommodating a honeycomb support plate. A pressing nozzle 103 and a hinge shaft 104 are also welded to the two long sides of the stainless steel substrate 101, respectively.

[0003] During the welding process, the inner and outer internal corners at the junction of the stainless steel retaining ring 102 and the stainless steel substrate 101 must be fully welded. However, stainless steel filter plates are typically large in size, and the stainless steel substrate 101 and stainless steel retaining ring 102 are easily subjected to welding thermal stress during welding, resulting in warping, shrinkage, and misalignment. This causes the flatness and dimensional tolerances of the filter plate to exceed design requirements, thereby affecting the sealing performance and normal use of the filter plate and significantly increasing the scrap rate. Existing welding fixtures for this type of filter plate generally suffer from low positioning accuracy, cumbersome disassembly and assembly operations, and insufficient ability to limit the deformation of the retaining ring and substrate, failing to meet the high-precision welding requirements of large-size stainless steel filter plates.

[0004] In addition, the welding of the stainless steel retaining ring to the inside corner of the substrate is a fillet weld, which is difficult to protect the molten pool and is prone to defects such as oxidation inclusions, pinholes and pores, which can lead to leakage during the use of the filter plate. Existing technologies rely on high-purity argon gas protection and special flux, which are costly and cannot completely solve the pinhole problem. Existing processes mostly use single-person segmented welding, which results in asymmetrical welding heat input and further aggravates deformation. The welding of the hinge shaft relies on manual support, which can easily cause tilting and offset along its own axis, causing subsequent jamming of the filter plate and frame assembly, requiring repeated adjustments.

[0005] There is currently no effective solution to the above problems, and there is an urgent need for a welding fixture and matching welding method that can take into account deformation control, weld quality, and welding efficiency. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects or one of the defects of the prior art and provide a welding fixture for stainless steel filter plates of vertical filter presses, which solves the technical problems of large welding deformation, high weld pinhole defect rate, low welding efficiency and insufficient positioning accuracy in the prior art, and realizes high precision, high efficiency and low defect rate welding of large-size stainless steel filter plates.

[0007] To achieve the above objectives, the present invention provides the following technical solution: On one hand, the present invention provides a welding fixture for stainless steel filter plates of a vertical filter press, including a platform and a positioning frame. The platform has the same specifications as the stainless steel substrate of the filter plate to be welded. A ring of screw holes is formed on the platform, and the arrangement of these screw holes corresponds one-to-one with the positions of pre-set through holes on the stainless steel substrate and the outer side of the stainless steel retaining ring. The screw holes are used for fastening screws to pass through the through holes and engage with the threads to press and fix the stainless steel substrate onto the platform. The distance between adjacent through holes on the stainless steel substrate to be welded is no greater than 10 cm. The nominal diameter of the through holes is greater than the nominal diameter of the corresponding screw holes on the platform. The positioning frame includes an annular positioning plate, a transverse upright plate, and three longitudinal upright plates. The outer contour of the annular positioning plate is adapted to the inner contour of the stainless steel retaining ring. It is used to embed into the inner side of the stainless steel retaining ring before welding to pre-position the stainless steel retaining ring radially, ensuring the relative positional accuracy between the stainless steel retaining ring and the stainless steel substrate. After the outer weld of the stainless steel retaining ring and the stainless steel substrate is initially fixed, the positioning frame can be removed to perform inner weld welding. The horizontal upright plate and the three vertical upright plates are all vertically fixed to the upper surface of the annular positioning plate. The horizontal upright plate and each of the vertical upright plates are vertically and intersectingly fixed to each other to form a grid-shaped reinforcing frame. The two ends of the two vertical upright plates extend outward. The extended section leaves a gap with the outer wall of the stainless steel retaining ring and passes through the stainless steel retaining ring. The lower end is vertically fixed with a pin. The outer diameter of the pin is adapted to the inner diameter of the through hole and screw hole at the corresponding position. The pin can be inserted into the through hole at the corresponding position.

[0008] Furthermore, the platform is a solid carbon steel plate, and the flatness tolerance of the platform is no greater than 0.08 mm / m; the pin is a smooth rod structure, the length of which is adapted to the thickness of the stainless steel substrate, and the outer diameter of which is in micro-clear clearance fit with the through hole; or the outer wall of the pin is fitted with a wear-resistant nylon sleeve, and the wear-resistant nylon sleeve is in micro-clear clearance fit with the through hole.

[0009] Furthermore, the thickness of the annular positioning plate is at least 1 / 3 of the thickness of the stainless steel retaining ring.

[0010] Furthermore, the outer contour of the annular positioning plate is fitted with the inner contour of the stainless steel retaining ring with a clearance of 0.05mm-0.15mm.

[0011] Furthermore, the horizontal upright plate is arranged along the centerline of the length direction of the annular positioning plate, and the three vertical upright plates are evenly spaced along the width direction of the annular positioning plate; two lifting holes are opened in the middle of the horizontal upright plate.

[0012] Furthermore, an angled seat is fixedly connected to the side of the platform corresponding to the installation position of the hinge shaft of the stainless steel filter plate. A semi-circular arc groove adapted to the outer contour of the hinge shaft is opened on the horizontal plate of the angled seat. The depth of the groove is not less than 1 / 2 of the diameter of the hinge shaft. It is used to accommodate and position the hinge shaft and restrict the offset of the hinge shaft along its own axis to achieve axial positioning.

[0013] On the other hand, the present invention provides a welding method for stainless steel filter plates of a vertical filter press, based on the above-mentioned welding fixture, comprising the following steps: S1 substrate fixing: Place the stainless steel substrate flat on the upper surface of the platform, align the through holes on the substrate with the screw holes on the platform, use fastening screws to pass through the through holes from above the substrate and screw them into the screw holes on the platform, tighten all fastening screws evenly in diagonal order, and press the stainless steel substrate flat and firmly fixed on the platform. S2 retaining ring pre-positioning: Place the stainless steel retaining ring at the preset welding position on the stainless steel substrate. After initial calibration, select a free point on the platform where no fastening screws are installed. Embed the annular positioning plate of the positioning frame into the inside of the stainless steel retaining ring. Adjust the position of the positioning frame so that the pin is aligned with the through hole at the corresponding position. Insert the pin into the through hole to complete the radial pre-positioning of the stainless steel retaining ring. S3 Pre-welding treatment: At the outer corner to be welded where the stainless steel retaining ring meets the stainless steel substrate, apply a high-purity charcoal pencil evenly, with the thickness controlled between 0.05-0.1mm. S4 outer weld welding: Four welders are positioned opposite each other around the table, corresponding to the four sides of the stainless steel retaining ring, and simultaneously perform continuous welding in a clockwise direction with the same welding parameters; during the welding process, when the welding torch moves to the vicinity of a certain fastening screw, the fastening screw at that position is first removed. After the welding torch finishes welding and leaves the area of ​​the through hole and screw hole corresponding to the screw, the fastening screw is immediately re-passed through the through hole and screwed into the screw hole and tightened according to the initial torque. S5 Positioning Frame Removal: After the outer weld is completed and cooled to room temperature, lift the positioning frame upward to disengage the pin from the through hole, remove the positioning frame, and expose the inner welding area of ​​the stainless steel retaining ring. S6 Inner weld welding: At the inner corner where the stainless steel retaining ring and the stainless steel substrate meet, repeat the pretreatment operation of step S3 and use the same welding parameters as the outer side to complete the full welding of the inner weld. S7 hinge welding: Place the hinge into the groove of the angle seat to complete the axial positioning. First, spot weld the connection end between the hinge and the stainless steel substrate. After verifying that the perpendicularity is qualified, complete the full welding. Finally, weld the pressing nozzle to obtain the finished stainless steel filter plate.

[0014] Furthermore, in step S4, the number of fastening screws removed at one time shall not exceed two, and the tightening torque of the screws shall be consistent with the initial tightening torque, with a deviation not exceeding ±5 N·m. Furthermore, in step S4, the four welders use a welding current of 120-140A, a welding speed of 120-150mm / min, and control the interpass temperature within 150℃. The four welders start their welding at the same position and at the same welding speed.

[0015] Furthermore, in step S3, the high-purity charcoal pencil used is a binder-free, sulfur-free soft charcoal pencil with a carbon content ≥95%.

[0016] Compared with the prior art, the present invention has the following outstanding advantages: Excellent welding deformation control: Through the uniform pressure and fixing structure of the entire circumference of the platen, combined with the segmented removal and immediate locking process of the fastening screws during welding, the continuous and complete welding of the weld seam is ensured, while the stable pressure and limiting of the stainless steel substrate is achieved throughout the welding process. Combined with the symmetrical heat input design of four people welding in opposite positions, the welding thermal stress can be effectively offset, the warping deformation of the stainless steel substrate and the radial shrinkage and displacement of the stainless steel retaining ring can be significantly suppressed, and the shape and position accuracy of the filter plate after welding can be greatly improved.

[0017] Significantly improved weld quality and reliability: The pre-treatment process of applying high-purity charcoal pencils before welding effectively eliminates metal oxide inclusions in the molten pool by utilizing the oxidation-reduction effect of graphite. At the same time, the protective gas generated by the reduction reaction can isolate the molten pool from the oxidation attack of air, fundamentally solving the defects such as pinholes, pores, and oxide inclusions that are prone to occur in stainless steel corner welds, improving weld density and mechanical properties, eliminating the risk of leakage during the use of filter plates, and eliminating the need for additional special equipment and high-cost consumables.

[0018] Welding efficiency and positioning accuracy are greatly improved: The process design of four people welding simultaneously can significantly shorten the welding operation time of a single filter plate and improve the batch processing efficiency; by using the annular positioning plate to pre-position the stainless steel retaining ring radially and the angular seat groove to position the hinge shaft axially, the welding position accuracy of each component can be effectively guaranteed, avoiding errors caused by manual positioning, improving the product welding qualification rate, and reducing the workload of subsequent assembly and debugging.

[0019] The tooling is highly versatile and easy to operate: the positioning frame can be quickly inserted, positioned and disassembled through the pin and the through hole of the table plate, without obstructing the welding area inside the retaining ring. No special tools are required to complete the disassembly and assembly, which greatly shortens the auxiliary welding time. The tooling can be adapted to the welding and processing of stainless steel filter plates of different models and specifications of vertical filter presses by adjusting the size of the table plate, the inner contour specification of the ring positioning plate and the groove parameters, and has a wide range of applications. Attached Figure Description

[0020] Figure 1 This is a structural schematic diagram of the stainless steel filter plate of a vertical filter press to be welded. Figure 2 This is an exploded structural diagram of the welding fixture of the present invention; Figure 3 for Figure 2 A partially enlarged structural diagram; Figure 4 This is a schematic diagram showing the connection between the welding fixture of the present invention and the stainless steel filter plate. The markings in the diagram are as follows: 100-Stainless steel filter plate, 101-Stainless steel base plate, 102-Stainless steel retaining ring, 103-Pressing nozzle, 104-Hinge shaft, 105-Through hole; 200-Table plate, 201-Screw hole, 202-Angle seat, 203-Inset groove; 300-Positioning frame, 301-Annular positioning plate, 302-Horizontal vertical plate, 303-Longitudinal vertical plate, 304-Pin, 305-Lifting hole. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0022] This embodiment focuses on the welding process of austenitic stainless steel filter plates for a large-format 2620mm×1236mm vertical filter press: I. Prefabrication Parameters of Welding Fixtures Tablet 200 parameters: The table is made of solid Q235 carbon steel flat plate and its external dimensions are completely consistent with those of stainless steel substrate 101: length 2620mm, width 1236mm, thickness 60mm, and four corners are set with 4-R177mm rounded corners to match the substrate; the flatness tolerance of the upper surface of the table is 0.08mm / m, which matches the form and position tolerance requirements of the substrate.

[0023] Along the rectangular track outside the stainless steel retaining ring 102 on the plate, 42 M16 internal threaded screw holes 201 are opened. The positions of the screw holes correspond one-to-one with the 42 φ18mm through holes 105 marked on the drawing on the stainless steel substrate. The center distance between adjacent screw holes is 8cm (corresponding to the design requirement that the distance between adjacent through holes on the substrate is no more than 10cm), ensuring that the substrate is fixed with uniform force. The nominal diameter of the through hole 105 on the substrate is larger than the nominal diameter of the screw hole 201 on the plate, which facilitates the installation and positioning of the fastening screws.

[0024] On the left and right sides of the table plate along its length, corresponding to the installation positions of the press port hinge shaft marked on the drawing, two sets of 45# steel angle seats 202 are welded respectively; a semi-circular arc groove 203 is opened on the horizontal plate of the angle seat, with a groove radius of 15mm (suitable for φ30mm hinge shaft) and a depth of 18mm (greater than 1 / 2 of the hinge shaft diameter). The fit clearance between the inner wall of the groove and the outer wall of the hinge shaft is 0.05mm, so as to realize the axial positioning of the hinge shaft.

[0025] Positioning frame 300 parameters: The positioning frame is made of 304 stainless steel and welded together, including an annular positioning plate 301, one horizontal upright plate 302 and three vertical upright plates 303. Circular positioning plate 301: It is made of 20mm thick stainless steel plate, cut into shape. The outer dimensions are a rectangular ring with a length of 2380mm and a width of 1185mm. The four corners are rounded with 4-R10mm rounded corners to match the inner dimensions of the stainless steel retaining ring 102. The fit clearance is 0.1mm (within the design range of 0.05mm-0.15mm). The thickness is 1 / 2 of the thickness of the retaining ring, which meets the design requirement of not less than 1 / 3.

[0026] Reinforced frame: Both the horizontal upright plate 302 and the vertical upright plate 303 are made of 10mm thick stainless steel plate with a height of 100mm; the horizontal upright plate is set along the center line of the length direction of the annular positioning plate, and the three vertical upright plates are evenly spaced along the width direction (spacing 592.5mm). The two are welded perpendicularly to form a grid-shaped reinforced frame; two φ25mm hoisting holes 305 are symmetrically opened in the middle of the horizontal upright plate.

[0027] Positioning pins: The two ends of the two longitudinal vertical plates on both sides extend outward by 80mm, leaving a 20mm clearance with the outer wall of the retaining ring. The lower end of the extension section is vertically welded with a φ17mm smooth rod structure pin 304. The length of the pin 304 is adapted to the thickness of the stainless steel substrate 101, and its outer diameter is in micro-clear clearance fit with the through hole 105 of the substrate. The outer wall of the pin 304 is fitted with a 0.5mm thick wear-resistant nylon sleeve. The wear-resistant nylon sleeve is in micro-clear clearance fit with the through hole 105, which can protect the hole wall and ensure smooth insertion.

[0028] II. Specific Implementation Steps of Welding Method S1 Substrate Fixing: Place the stainless steel substrate 101 flat on the upper surface of the platform 200, align the through hole 105 on the substrate with the screw hole 201 on the platform, and use an M16 hexagon socket head cap screw to pass through the through hole 105 from above the substrate and screw it into the screw hole 201 on the platform. Tighten all the screws evenly in a diagonal order, with the tightening torque controlled at 35 N·m and the torque deviation not exceeding ±2 N·m, to ensure that the substrate and the upper surface of the platform are completely attached without warping or suspension.

[0029] S2 Retaining Ring Pre-positioning: Place the stainless steel retaining ring 102 at the preset welding position on the stainless steel substrate 101. Use a height gauge and right angle ruler to initially calibrate the distance between the retaining ring and the edge of the substrate to ensure uniform spacing around the perimeter. Hoist the positioning frame through the lifting hole, embed the annular positioning plate 301 of the positioning frame 300 into the inner side of the stainless steel retaining ring 102, adjust the position of the positioning frame so that the pin 304 is aligned with the corresponding position of the substrate through hole 105, insert the pin 304 into the through hole 105 without entering the screw hole 201 of the lower platform, and complete the radial pre-positioning of the stainless steel retaining ring 102.

[0030] S3 Pre-welding treatment: At the outer corner where the stainless steel retaining ring 102 and the stainless steel substrate 101 meet, apply a layer of sulfur-free and binder-free soft carbon sketching pencil with a carbon content of 98% evenly, with the coating thickness controlled at 0.08mm, covering the entire area to be welded.

[0031] The core principle behind using charcoal pencil shading in this step is as follows: Firstly, the oxidation-reduction impurity removal effect: The core component of the high-purity sketching charcoal pencil used in this embodiment is high-purity amorphous graphite, free of sulfur, organic binders, and clay impurities, thus avoiding the performance degradation caused by the introduction of harmful elements into the weld. In the high-temperature molten pool environment of the welding area, the austenitic stainless steel matrix contains alloying elements such as Fe and Cr, which easily combine with oxygen to form high-melting-point metal oxides such as FeO and Cr2O3. These oxides will remain in the molten pool to form inclusions, destroy the weld density, and at the same time consume the Cr element in the matrix, reducing the corrosion resistance of stainless steel, which is also the core cause of pinhole porosity. At high temperature, the active carbon in the graphite undergoes a directional reduction reaction with the above-mentioned metal oxides, reducing the metal oxides to pure Fe and Cr metal matrix, which is then reintegrated into the molten pool, completely eliminating oxide inclusions. At the same time, the reduced and recovered Cr element can ensure the corrosion resistance of the weld.

[0032] Secondly, the in-situ protection of the molten pool: CO and CO2 gases are continuously generated during the reduction reaction process. These gases overflow from the inside of the molten pool and form a continuous in-situ gas protection layer on the surface of the molten pool of the corner weld. This isolates oxygen and nitrogen in the air from contact with the high-temperature molten pool, solving the industry pain point that argon protection at the corner weld is prone to turbulence and inadequate protection of dead angles. It also avoids pinhole and porosity defects caused by secondary oxidation of the molten pool and nitrogen dissolution.

[0033] Third, the effect of improving weld wettability: the uniformly applied graphite layer can reduce the surface tension of molten stainless steel, significantly improve the spreading wettability of the molten pool metal at the inside corner, reduce welding defects such as undercut and incomplete penetration, and make the weld formation more uniform and full.

[0034] This step strictly controls the coating thickness because an excessively thin coating layer cannot provide enough activated carbon to achieve the above-mentioned effect, while an excessively thick coating layer will cause excessive carbon to penetrate into the molten pool, triggering the risk of intergranular corrosion of austenitic stainless steel. Therefore, the coating thickness is controlled within the optimal range of 0.05-0.1 mm.

[0035] S4 outer weld seam welding: Four welders are positioned at the top, bottom, left, and right of the worktable, corresponding to the four sides of the stainless steel retaining ring 102. They use pulsed argon arc welding with a welding current of 130A and a welding speed of 130mm / min. They start simultaneously from the four corners of the retaining ring and weld continuously in a clockwise direction. The starting position and welding speed of the four welders are completely synchronized. During the welding process, when the welding torch moves to within 50mm of the fastening screw, the assistant removes the fastening screw at that position. After the welding torch finishes welding and moves 50mm away from the area of ​​the through hole 105 and screw hole 201 corresponding to the screw, the assistant immediately puts the fastening screw back through the through hole 105 and screws it into the screw hole 201 and tightens it with an initial torque of 35N·m. Only one fastening screw is removed at a time (not exceeding the design requirement of 2). The interpass temperature is controlled below 120℃ during the welding process. The welding is paused every 300mm to cool to room temperature.

[0036] S5 Positioning Frame Removal: After the outer weld is completed and cooled to room temperature, the positioning frame is hoisted through the hoisting hole. The positioning frame 300 is lifted vertically upward to disengage the pin 304 from the through hole 105 of the substrate. The positioning frame 300 is then removed to expose the inner welding area of ​​the stainless steel retaining ring 102.

[0037] S6 Inner weld welding: At the inner corner where the stainless steel retaining ring 102 and the stainless steel substrate 101 meet, repeat the charcoal sketching operation of step S3, and use the same welding parameters as the outer side to complete the full welding of the inner weld. After welding, perform penetration testing on the inner and outer welds to ensure that there are no cracks, pores, or pinhole defects.

[0038] S7 Hinge Shaft Welding to Press Nozzle: Place the four sets of hinge shafts 104 into the grooves 203 of the corresponding angle seats 202. The inner wall of the groove is in contact with the outer wall of the hinge shaft, which restricts the tilting offset of the hinge shaft along its own axis and achieves axial positioning. First, fix the connection end between the hinge shaft and the stainless steel substrate 101 with spot welding. Use a right angle ruler to check the perpendicularity between the hinge shaft and the substrate. After the error is ≤0.5°, perform full welding. Finally, complete the welding of the press nozzle 103 to obtain the finished stainless steel filter plate.

[0039] S8 Material Inspection: After all welding processes are completed and cooled to room temperature, loosen the fastening screws diagonally, lift the filter plate off the platform, and inspect the flatness, form and position tolerances, and weld quality of the filter plate. After all meet the requirements of the drawings, it is put into storage.

[0040] III. Implementation Results Verification Using the tooling and welding method of this embodiment, a large-size stainless steel filter plate of 2620mm×1236mm was welded. After welding, the flatness error of the substrate was ≤0.09mm, the positional dimension error of the retaining ring was ≤0.18mm, and the perpendicularity error of the hinge shaft was ≤0.4°, which fully met the design requirements. The weld was free of pinholes and porosity defects, with a 100% first-pass yield. The total welding time for a single filter plate was 55 minutes, which is 330% more efficient than the existing process and is fully adaptable to the batch welding processing needs of large-size filter plates.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A welding fixture for stainless steel filter plates in a vertical filter press, comprising a table (200) and a positioning frame (300), characterized in that, The specifications of the platform (200) are consistent with those of the stainless steel substrate (101) of the stainless steel filter plate (100) to be welded; a ring of screw holes (201) is opened on the platform (200), and the arrangement of the screw holes (201) corresponds one-to-one with the positions of the through holes (105) on the stainless steel substrate (101) to be welded and the outer side of the stainless steel retaining ring (102). The screw holes (201) are used to allow the fastening screws to pass through the through holes (105) and engage with the threads to press and fix the stainless steel substrate (101) on the platform (200); the distance between adjacent through holes (105) on the stainless steel substrate (101) to be welded is not greater than 10cm; the nominal diameter of the through hole (105) is greater than the nominal diameter of the corresponding screw hole (201) on the platform (200). The positioning frame (300) includes an annular positioning plate (301), a transverse upright plate (302), and three longitudinal upright plates (303). The outer contour of the annular positioning plate (301) is adapted to the inner contour size of the stainless steel retaining ring (102) and is used to embed into the inner side of the stainless steel retaining ring (102) before welding to pre-position the stainless steel retaining ring (102) radially and ensure the relative position accuracy between the stainless steel retaining ring (102) and the stainless steel substrate (101). After the outer weld of the stainless steel retaining ring (102) and the stainless steel substrate (101) is initially fixed, the positioning frame (300) can be removed to perform inner weld welding. The horizontal upright plate (302) and the three vertical upright plates (303) are all vertically fixed to the upper surface of the annular positioning plate (301). The horizontal upright plate (302) and each of the vertical upright plates (303) are vertically and intersectingly fixed to each other to form a grid-shaped reinforcing frame. The two ends of the two vertical upright plates (303) extend outward. The extended section leaves a gap with the outer wall of the stainless steel retaining ring (102) and passes through the stainless steel retaining ring (102). The lower end is vertically fixed with a pin (304). The outer diameter of the pin (304) is adapted to the inner diameter of the corresponding through hole (105) and screw hole (201). The pin (304) can be inserted into the corresponding through hole (105).

2. The welding fixture for the stainless steel filter plate of the vertical filter press according to claim 1, characterized in that, The platform (200) is a solid carbon steel plate, and the flatness tolerance of the platform (200) is no greater than 0.08 mm / m; the pin (304) is a smooth rod structure, the length of which is adapted to the thickness of the stainless steel substrate (101), and its outer diameter is in micro-clear clearance fit with the through hole (105); or the outer wall of the pin (304) is fitted with a wear-resistant nylon sleeve, and the wear-resistant nylon sleeve is in micro-clear clearance fit with the through hole (105).

3. The welding fixture for the stainless steel filter plate of the vertical filter press according to claim 1, characterized in that, The thickness of the annular positioning plate (301) is at least 1 / 3 of the thickness of the stainless steel retaining ring (102).

4. The welding fixture for the stainless steel filter plate of the vertical filter press according to claim 1, characterized in that, The outer contour of the annular positioning plate (301) is fitted with the inner contour of the stainless steel retaining ring (102) with a clearance of 0.05mm-0.15mm.

5. The welding fixture for the stainless steel filter plate of the vertical filter press according to claim 1, characterized in that, The horizontal upright plate (302) is arranged along the centerline of the length direction of the annular positioning plate (301), and the three vertical upright plates (303) are evenly spaced along the width direction of the annular positioning plate (301); two lifting holes (305) are opened in the middle of the horizontal upright plate (302).

6. The welding fixture for the stainless steel filter plate of the vertical filter press according to claim 1, characterized in that, An angled seat (202) is fixedly connected to the side of the platform (200) corresponding to the installation position of the hinge shaft (104) of the stainless steel filter plate (100). A semi-circular arc groove (203) adapted to the outer contour of the hinge shaft (104) is opened on the horizontal plate of the angled seat (202). The depth of the groove (203) is not less than 1 / 2 of the diameter of the hinge shaft (104). It is used to accommodate and position the hinge shaft (104) and restrict the offset of the hinge shaft (104) along its own axis to achieve axial positioning.

7. A welding method for stainless steel filter plates of a vertical filter press, implemented using the welding fixture described in any one of claims 1-6, characterized in that, Includes the following steps: S1 Substrate Fixing: Place the stainless steel substrate (101) flat on the upper surface of the platform (200), align the through hole (105) on the substrate with the screw hole (201) on the platform, use a fastening screw to pass through the through hole (105) from above the substrate and screw it into the screw hole (201) on the platform, tighten all the fastening screws evenly in diagonal order, and flatten and fix the stainless steel substrate (101) on the platform (200). S2 retaining ring pre-positioning: Place the stainless steel retaining ring (102) at the preset welding position on the stainless steel substrate (101). After preliminary calibration, select the empty point on the platform where no fastening screws are installed, embed the annular positioning plate (301) of the positioning frame (300) into the inner side of the stainless steel retaining ring (102), adjust the position of the positioning frame so that the pin (304) is aligned with the corresponding through hole (105), insert the pin (304) into the through hole (105) to complete the radial pre-positioning of the stainless steel retaining ring (102). S3 Pre-welding treatment: At the outer corner to be welded where the stainless steel retaining ring (102) and the stainless steel substrate (101) meet, apply a high-purity sketching charcoal pencil evenly, with the coating thickness controlled at 0.05-0.1mm. S4 outer weld welding: Four welders are positioned opposite each other around the table plate (200), corresponding to the four sides of the stainless steel retaining ring (102), and simultaneously perform continuous welding in a clockwise direction with the same welding parameters; during the welding process, when the welding torch moves to the vicinity of a certain fastening screw, the fastening screw at that position is first removed. After the welding torch finishes welding and leaves the area of ​​the through hole (105) and screw hole (201) corresponding to the screw, the fastening screw is immediately re-passed through the through hole (105) and screwed into the screw hole (201) and locked with the initial torque; S5 Positioning Frame Removal: After the outer weld is completed and cooled to room temperature, lift the positioning frame (300) upwards to disengage the pin (304) from the through hole (105), remove the positioning frame (300), and expose the inner welding area of ​​the stainless steel retaining ring (102). S6 Inner weld welding: At the inner corner where the stainless steel retaining ring (102) and the stainless steel substrate (101) meet, repeat the pretreatment operation of step S3 and use the same welding parameters as the outer side to complete the full welding of the inner weld. S7 Hinge Shaft Welding: Place the hinge shaft (104) into the groove (203) of the angle seat (202) to complete the axial positioning. First, spot weld the connection end between the hinge shaft and the stainless steel substrate (101). After verifying that the perpendicularity is qualified, complete the full welding. Finally, weld the pressing nozzle (103) to obtain the finished stainless steel filter plate.

8. The welding method for stainless steel filter plates in a vertical filter press according to claim 7, characterized in that, In step S4, the number of fastening screws removed at one time shall not exceed 2, and the torque for tightening the screws shall be consistent with the initial tightening torque, with a deviation of no more than ±5 N·m.

9. The welding method for stainless steel filter plates in a vertical filter press according to claim 7, characterized in that, In step S4, the four welders use a welding current of 120-140A, a welding speed of 120-150mm / min, and control the interpass temperature within 150℃. The four welders start their welding at the same position and at the same welding speed.

10. The welding method for stainless steel filter plates of a vertical filter press according to claim 7, characterized in that, In step S3, the high-purity charcoal pencil used is a binder-free, sulfur-free soft charcoal pencil with a carbon content ≥95%.

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