Intermediate-frequency welding process method for valve lead and wiring terminal of converter transformer

Abstract

The invention belongs to the technical field of welding, and relates to an intermediate-frequency welding process method for a converter transformer valve lead and a wiring terminal, a plurality of silver-phosphorus soldering lugs are placed between the front end parts of adjacent copper woven belts, and the outer layers of the front end parts of the copper woven belts on which the silver-phosphorus soldering lugs are placed are wrapped with copper sheets; performing cold rolling and rounding on the to-be-welded part until the outer diameter of the welded part is smaller than the inner diameter of the inner hole of the wiring terminal; sleeving the induction coil of the intermediate frequency welding machine outside the copper sheet, pouring the welding fluid from the upper part of the copper sheet, and stopping heating after the welding fluid flows out from the bottom of the copper sheet; and inserting the end part of the rubbed copper woven belt into the inner hole of the wiring terminal, welding by using an intermediate frequency welding machine, enabling the copper woven belt to be always in a vertical state in the welding process, pouring welding fluid from one side of a gap between the wiring terminal and the copper woven belt, and stopping welding after the welding fluid overflows from the other side of the gap. The problems of air holes, pseudo soldering and the like in the welding part are avoided, the cost is low, and the construction period is short.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a medium-frequency welding process method for valve leads and connection terminals of a converter transformer. Background Art

[0002] In order to facilitate the installation of the valve lead of the converter transformer in the shielding tube, soft copper braided tape is often used instead of copper stranded wire as the valve lead of the converter transformer. The connection method adopts a special terminal-plug-in socket-valve sleeve structure. The plug-in part is installed at the end of the valve outlet tube. The valve lead is welded to the special terminal and then fixed to the plug-in socket with bolts.

[0003] At present, the valve leads and terminals of converter transformers are usually welded by phosphor copper welding. Because the welding parts of phosphor copper welding usually have problems such as pores and cold welding, the resistance of the valve leads of converter transformers after connection is increased, causing quality failures such as local overheating and gas production. Due to the lack of medium-frequency welding methods for soft copper braids and special terminals, converter transformer manufacturers need to purchase the entire valve lead with welded terminals from outside, which has the problems of high cost and affected construction period. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a medium frequency welding process method for valve leads and terminal blocks of a converter transformer. The technical solution adopted by the present invention is as follows: The medium frequency welding process method of the valve lead wire and the terminal of the converter transformer, wherein the valve lead wire is made of copper braided tape, comprises the following steps: Cut a number of copper braids, align the edges of the front ends of the copper braids, and stack them layer by layer. When stacking, place a number of silver-phosphorus welding sheets at a certain distance between the front ends of adjacent copper braids, and wrap copper sheets around the front ends of the copper braids where the silver-phosphorus welding sheets are placed. Processing the outer circumference of the copper sheet into a circle, and shrinking the outer diameter of the circular copper sheet to be smaller than the inner diameter of the inner hole of the terminal; Welding copper braid and copper sheet: Wrap the induction coil of the medium frequency welding machine around the outer periphery of the copper sheet, start the medium frequency welding machine to heat until the copper braid turns red, then pour the soldering liquid from the top of the copper sheet, and turn off the medium frequency welding machine to stop heating after the soldering liquid flows out from the bottom of the copper sheet; Welding copper braid / copper sheet and terminal block: make the inner hole of the terminal block be in a vertical upward position, put the induction coil of the medium frequency welding machine on the outer periphery of the terminal block, insert the front end of the copper braid wrapped with copper sheet into the inner hole of the terminal block, start the medium frequency welding machine for heating, and when the color of the terminal block changes to red, pour the welding liquid from one side of the gap between the inner hole of the terminal block and the copper braid, and turn off the medium frequency welding machine and stop heating after the welding liquid overflows from the other side of the gap. Keep the copper braid in a vertical position during the welding process.

[0005] Preferably, when several silver-phosphorus welding sheets are placed at a certain distance between the front end portions of adjacent copper braided belts, the edge of the front end portion of the copper braided belt is left with a certain length of overhang from a silver-phosphorus welding sheet at the front end; when copper sheet is wrapped around the outer periphery of the front end portion of the copper braided belt, the edge of the front end portion of the copper sheet is flush with the edge of the front end portion of the copper braided belt, and the edge of the rear end portion of the copper sheet is left with a certain length of overhang from a silver-phosphorus welding sheet at the rear end.

[0006] Preferably, before welding the copper braid and the copper sheet, an asbestos rope with water is placed around the lower part of the copper braid.

[0007] Preferably, after the copper braid and the copper sheet are welded, the welded ends of the copper braid are ground flat to remove oxides.

[0008] Preferably, before welding the copper braid / copper sheet and the terminal, the terminal is wrapped with water-containing asbestos rope in advance.

[0009] Preferably, before welding the copper braid / copper sheet and the terminal, the terminal is preheated.

[0010] Preferably, after welding the copper braid / copper sheet and the terminal block, the welding position of the terminal block is polished until the surface of the welding position is smooth, free of sharp corners and burrs, and the original color of copper is exposed. The upper surface of the terminal block is polished until there is no oxide scale, and the oxide on the surface of the polished welding area is cleaned.

[0011] Preferably, during the welding of the copper braid and the copper sheet, and during the welding of the copper braid / copper sheet and the terminal block, the medium frequency welding machine switch is intermittently and discontinuously pressed to perform welding.

[0012] Preferably, the silver-phosphorus welding sheet is in the shape of an elongated strip, and when placed, the length direction of the silver-phosphorus welding sheet is consistent with the width direction of the copper braided belt.

[0013] Preferably, after wrapping the front end of the copper braided belt with copper foil around its periphery, the total cross-sectional area of ​​the to-be-welded portion of the copper braided belt with the silver-phosphorus soldering sheet and wrapped with copper foil is calculated so that the total cross-sectional area of ​​the to-be-welded portion meets the process standards.

[0014] Beneficial effects of the present invention: The present invention wraps copper sheet around the front end of the copper braided belt, so that the front ends of several copper braided belts can be inserted into the inner hole of the terminal after cold rolling; silver-phosphorus welding sheets are filled between adjacent copper braided belts, and the copper braided belts are better fused together after the silver-phosphorus welding sheets melt during welding; during the welding process, the welding liquid is poured in from the upper part of the copper sheet and flows out from the bottom of the copper sheet, and the welding liquid is poured in from one side of the gap between the inner hole of the terminal and the copper braided belt and overflows from the other side of the gap, thereby ensuring sufficient filling of the welding liquid; during the welding process, the inner hole of the terminal is in a vertically upward state, so that the copper braided belt is always in a vertical state, thereby ensuring the overall welding quality of the valve lead and the terminal. In summary, the present invention avoids the problems of pores and cold welding in the welding parts of the valve lead and the terminal, and at the same time, there is no need to purchase the entire valve lead with the terminal welded from outside, thereby reducing costs, shortening construction period, and improving the production efficiency and product quality of the converter transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a schematic diagram of placing a silver-phosphorus solder sheet and wrapping a copper sheet according to an embodiment of the present invention; Figure 2 A schematic diagram of the welding position of the copper braided belt inserted into the wiring terminal according to an embodiment of the present invention; In the figure, 1 is a copper braided belt, 2 is a silver-phosphorus solder sheet, 3 is a copper sheet, and 4 is a terminal block. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0017] 1. Prepare the raw materials for making valve leads, as well as welding materials and welding equipment.

[0018] According to the design drawings of the converter transformer, copper braided belts 1 are used to make the valve lead of the converter transformer. Each valve lead of the converter transformer corresponds to N1 copper braided belts 1 of model TZ-05-25. In this embodiment, the cross-sectional area of ​​each copper braided belt 1 is 25mm 2 According to different rated currents of the valve leads of the converter transformer, copper braided belts 1 with different cross-sectional areas are selected, and different numbers N1 of copper braided belts 1 are determined.

[0019] Corresponding to each valve lead wire, a piece of copper sheet 3 with a thickness×width×length of 0.3mm×30mm×150mm is cut, and the length of 150mm is the length of the copper sheet 3 wrapped around the part to be welded of the copper braided belt 1 for one and a half circles.

[0020] Corresponding to N1-1 copper braided belts 1, each copper braided belt 1 corresponds to two silver-phosphorus welding sheets 2 (silver content 15%) with a thickness × width × length of 1mm × 5mm × 30mm. The total number of silver-phosphorus welding sheets 2 is N2 = (N1-1) × 2 pieces.

[0021] Prepare a medium frequency welding machine for welding. In this embodiment, the medium frequency welding machine model used is MINAC25 / 40.

[0022] In this embodiment, a cold rolling and rounding device and a rounding die are prepared. 2 、400mm 2 and 300mm 2 The copper sheet 3 is processed by a rounding die. Cold rolling rounding equipment and rounding dies are commonly used in the transformer production process. Rounding is a professional term in this field. The valve lead rounding is to extrude the front end of the valve lead which is non-circular and larger than the inner diameter of the inner hole of the terminal 4 by using the cold rolling rounding equipment and rounding die, so that the outer circumference of the front end of the valve lead is circular and the outer diameter is reduced to less than the inner diameter of the inner hole of the terminal 4, and then the rounded front end of the valve lead is inserted into the inner hole of the terminal 4 for welding.

[0023] 2. Filling of the copper braided belt 1 and cold rolling of the copper braided belt 1 and the copper sheet 3.

[0024] 2.1. Cut N1 copper braids 1, align the front end edges of N1 copper braids 1 and stack them layer by layer. When stacking, place two 1×5×30mm silver-phosphorus welding sheets 2 at the front end positions between adjacent copper braids 1. The two silver-phosphorus welding sheets 2 are spaced a certain distance apart. When placed, the length direction of the silver-phosphorus welding sheets 2 is consistent with the width direction of the copper braids 1, and a gap with the same thickness as the silver-phosphorus welding sheet 2 is formed between adjacent copper braids 1. When welding, the silver-phosphorus welding sheets 2 melt, so that the N1 copper braids 1 are fused together.

[0025] When placing the silver-phosphorus welding sheet 2, the edge of the front end of the copper braided belt 1 is left with a prolongation of more than 50 mm relative to the front end silver-phosphorus welding sheet 2. The reason for leaving the prolongation is that the front end of the copper braided belt 1 will be uneven after the copper sheet 3 is rounded. Before welding the copper sheet 3 and the terminal 4, the edges of the front ends of the copper sheet 3 and the copper braided belt 1 need to be cut so that the front ends of the copper sheet 3 and the copper braided belt 1 are flush. The flushness can make the front ends of the copper sheet 3 and the copper braided belt 1 better fit the inner hole of the terminal 4, thereby improving the welding quality.

[0026] A half circle of copper sheet 3 is wrapped around the outermost layer of the front end of the copper braided belt 1 on which the silver phosphorus solder sheet 2 is placed. Figure 1 As shown, Figure 1Only a part of the copper braided belt 1 wrapped with the copper sheet 3 is drawn. The front edge of the copper sheet 3 is flush with the front edge of the copper braided belt 1, and the rear edge of the copper sheet 3 is left with a certain length of margin from a silver-phosphorus solder sheet 2 at the rear end.

[0027] Before welding the copper braid 1 and the copper sheet 3, calculate the total cross-sectional area S of the part to be welded after the silver-phosphorus welding sheet 2 is filled between the copper braid 1 and the copper sheet 3 is wrapped around it, S=25×N1+1×5×N2+0.3×150. The purpose of calculating the total cross-sectional area of ​​the part to be welded is to verify whether the total cross-sectional area of ​​the part to be welded after the silver-phosphorus welding sheet 2 is filled between the copper braid 1 and the copper sheet 3 is wrapped around it is between the maximum and minimum cross-sectional areas specified in the table below, otherwise it does not meet the process standards. In this embodiment, if there are ten copper braids 1 on the drawing, the nominal cross-sectional area is 300mm 2 If there are eight copper braids 1, the nominal cross-sectional area is 240mm 2 Select.

[0028] Nominal cross-sectional area Minimum cross-sectional area Maximum cross-sectional area 50mm² 69mm² 103mm² 95 mm² 113mm² 161mm² 150 mm² 180mm² 220mm² 240 mm² 302mm² 343mm² 300 mm² 340mm² 400mm² 400 mm² 412mm² 500mm² 500 mm² 500mm² 580mm² 2.2. After the adjacent copper braids 1 are filled with silver-phosphorus solder sheets 2 and wrapped with copper sheets 3, cold rolling equipment is used, and 500mm is used in sequence. 2 , 400mm 2 and 300mm 2 The rounding die is gradually cold-rolled and rounded until the copper sheet 3 and the copper braided belt 1 to be welded are round, and the outer diameter of the copper sheet 3 and the copper braided belt 1 to be welded is smaller than the inner diameter of the inner hole of the terminal 4, such as Figure 2 shown.

[0029] After N1 copper braided belts 1 are stacked together, their front ends are roughly square. After the front ends of the copper braided belts 1 are wrapped with copper sheet 3, the copper sheet 3 is close to the copper braided belt 1 and the whole is still square, while the inner hole of the terminal 4 is round. Therefore, before welding, the front ends of the N1 copper braided belts 1 wrapped with copper sheet 3 must be cold rolled and stamped to be rounded.

[0030] 3. The outer circumference of the copper sheet 3 is processed into a circle, and the outer diameter of the copper sheet 3 is shrunk.

[0031] The outer periphery of the copper sheet 3 and the front end portions of N1 copper braided belts 1 are processed into a circle by a cold rolling and stamping process, and the outer diameter of the copper sheet 3 is shrunk to a value smaller than the inner diameter of the inner hole of the terminal 4 by the cold rolling and stamping process. The cold rolling and stamping process can enable the copper sheet 3 and the front end portions of the copper braided belt 1 to be smoothly inserted into the inner hole of the terminal 4 without affecting the material properties of the copper braided belt 1, the silver-phosphorus welding sheet 2 and the copper sheet 3 themselves.

[0032] Use hydraulic wire cutters to cut off the overgrown copper sheet 3 and copper braided belt 1 so that the front ends of the copper sheet 3 and the copper braided belt 1 are flush, which is convenient for the fusion of solder liquid when welding the copper braided belt 1 later.

[0033] 4. Weld the copper braid 1 and the copper sheet 3.

[0034] In order to make the front end of the copper braided belt 1 and the upper part of the inner hole of the terminal 4 fit closely, it is necessary to ensure that the front end of the copper braided belt 1 is well flush, such as Figure 2 The upper thick black line shown must be flat, so firstly weld the end of the copper braided belt 1 and the copper sheet 3, and then grind the front end of the copper braided belt 1 flat. The specific steps are as follows: 4.1. Clamp the copper braided belt 1 after the part to be welded is rounded, and the lower part of the copper braided belt 1 is surrounded by asbestos rope with water. The asbestos rope with water can properly cool the copper braided belt 1 to prevent the copper braided belt 1 from deforming due to overheating. Wrap the induction coil of the medium frequency welding machine around the outer periphery of the copper skin 3, heat the copper braided belt 1 until it turns red, and then pour the soldering liquid from the upper part of the copper skin 3. During the heating process, press the switch of the medium frequency welding machine intermittently and discontinuously. Pressing the switch of the medium frequency welding machine intermittently and discontinuously can better control the temperature and prevent the external copper skin 3 from melting due to overheating. After the soldering liquid flows out from the bottom of the copper skin 3, turn off the medium frequency welding machine and stop heating. Red means that the copper of the copper braided belt 1 is in a high-temperature softening state, which is easy to fuse with the soldering liquid.

[0035] 4.2. After welding the copper braid 1 and the copper sheet 3, immerse the welded end of the copper braid 1 in distilled water and cool it to room temperature. Take out the copper braid 1 and wipe it clean. Use a grinder to grind the welded front end of the copper braid 1 and remove the oxide, because the oxide needs to be completely removed before inserting the welded front end of the copper braid 1 into the welding area of ​​the terminal 4.

[0036] 5. Weld the copper braid 1 / copper sheet 3 and the terminal 4.

[0037] 5.1. Before welding the copper braid 1 / copper sheet 3 and the terminal 4, wrap the terminal 4 with asbestos rope with water in advance to reduce the temperature and prevent the terminal 4 from deforming due to overheating. Make the inner hole of the terminal 4 face vertically upward, put the induction coil of the medium frequency welding machine on the outer periphery of the terminal 4, and press the switch of the medium frequency welding machine intermittently and discontinuously to preheat the terminal 4.

[0038] 5.2. Insert the front end of the copper braided belt 1 wrapped with copper sheet 3 after grinding into the inner hole of the terminal 4, so that the front end of the copper braided belt 1 is inserted to the bottom of the inner hole of the terminal 4, and the relative positions of the notches of the copper braided belt 1 and the terminal 4 are as shown in the attached figure. Figure 2 shown.

[0039] 5.3. Make the inner hole of the terminal 4 face vertically upwards, check that the copper braided belt 1 is perpendicular to the terminal 4, and then use the medium frequency welding machine to weld. During the heating process, press the switch of the medium frequency welding machine intermittently and discontinuously. When the color of the terminal 4 turns red, pour the soldering liquid into the gap between the terminal 4 and the copper braided belt 1. When the soldering liquid is poured into one side of the gap and overflows from the other side of the gap, it means that the soldering liquid has been filled, and then turn off the medium frequency welding machine to stop heating. During the welding process, keep the copper braided belt 1 in a vertical state at all times and do not tilt it.

[0040] 6. Post-weld treatment.

[0041] 6.1. After welding the copper braid 1 / copper sheet 3 and the terminal 4, grind the welding position of the terminal 4 until the surface of the welding position is smooth, without sharp corners and burrs, and the original color of copper is exposed. Grind the upper surface of the terminal 4 until there is no oxide scale to ensure that the welding quality of the valve lead and the terminal 4 meets the process requirements.

[0042] 6.2. Clean the oxide on the surface of the polished welding area of ​​terminal 4.

[0043] In the embodiment of the present invention, through the medium frequency welding process method, the difference between the inner hole diameter of the terminal 4 and the outer diameter of the copper sheet 3 after the copper braided belt 1 is welded inside is controlled between 0.5mm and 1mm, the depth of the copper braided belt 1 and the copper sheet 3 inserted into the inner hole of the terminal 4 is 6mm, and the tolerance is controlled at 0~+0.5mm, which ensures the welding area between the copper braided belt 1 and the copper sheet 3 and the inner hole of the terminal 4, thereby improving the welding quality between the valve lead of the converter transformer and the terminal 4.

[0044] In the embodiments of the present invention, technical features that are not described in detail are all existing technologies or conventional technical means and will not be described in detail here.

[0045] Finally, it should be noted that the above embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them, and the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any technician familiar with the technical field can modify the technical solutions recorded in the above embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be covered within the protection scope of the present invention.

Claims

1. A medium frequency welding process for valve leads and terminal blocks of converter transformers, wherein the valve leads are made of copper braided tape, characterized in that: The following steps are involved: Cut a number of copper braids, align the edges of the front ends of the copper braids, and stack them layer by layer. When stacking, place a number of silver-phosphorus welding sheets at a certain distance between the front ends of adjacent copper braids, and wrap copper sheets around the front ends of the copper braids where the silver-phosphorus welding sheets are placed. Processing the outer circumference of the copper sheet into a circle, and shrinking the outer diameter of the circular copper sheet to be smaller than the inner diameter of the inner hole of the terminal; Welding copper braid and copper sheet: Wrap the induction coil of the medium frequency welding machine around the outer periphery of the copper sheet, start the medium frequency welding machine to heat until the copper braid turns red, then pour the soldering liquid from the top of the copper sheet, and turn off the medium frequency welding machine to stop heating after the soldering liquid flows out from the bottom of the copper sheet; Welding copper braid / copper sheet and terminal block: make the inner hole of the terminal block be in a vertical upward position, put the induction coil of the medium frequency welding machine on the outer periphery of the terminal block, insert the front end of the copper braid wrapped with copper sheet into the inner hole of the terminal block, start the medium frequency welding machine for heating, and when the color of the terminal block changes to red, pour the welding liquid from one side of the gap between the inner hole of the terminal block and the copper braid, and turn off the medium frequency welding machine and stop heating after the welding liquid overflows from the other side of the gap. Keep the copper braid in a vertical position during the welding process.

2. The medium frequency welding process for the valve lead wire and the terminal of the converter transformer according to claim 1 is characterized in that: When placing several silver-phosphorus welding sheets at a certain distance between the front end portions of adjacent copper braided belts, a certain length of overhang is left at the edge of the front end portion of the copper braided belt from a silver-phosphorus welding sheet at the front end; when wrapping copper sheet around the outer periphery of the front end portion of the copper braided belt, the front end edge of the copper sheet is flush with the front end edge of the copper braided belt, and a certain length of overhang is left at the rear end edge of the copper sheet from a silver-phosphorus welding sheet at the rear end.

3. The medium frequency welding process for the valve lead wire and the terminal of the converter transformer according to claim 1 is characterized in that: Before welding the copper braid and copper sheet, place an asbestos rope with water around the bottom of the copper braid.

4. The medium frequency welding process for the valve lead wire and the terminal of the converter transformer according to claim 3 is characterized in that: After welding the copper braid and copper sheet, grind the welded ends of the copper braid to remove the oxide.

5. The medium frequency welding process for the valve lead wire and the terminal of the converter transformer according to claim 1 is characterized in that: Before welding the copper braid / copper sheet and the terminal, wrap the terminal with water-containing asbestos rope in advance.

6. The medium frequency welding process for the valve lead wire and the terminal of the converter transformer according to claim 5 is characterized in that: Before soldering the copper braid / sheet to the terminal block, preheat the terminal block.

7. The medium frequency welding process for the valve lead wire and the terminal of the converter transformer according to claim 6 is characterized in that: After welding the copper braid / copper sheet and the terminal block, grind the welding position of the terminal block until the surface of the welding position is smooth, without sharp corners and burrs, and the original color of copper is exposed. Grind the upper surface of the terminal block until there is no oxide scale, and clean the oxide on the surface of the polished welding area.

8. The medium frequency welding process for converter transformer valve leads and terminal blocks according to claim 1, characterized in that: During the welding of copper braid and copper sheet, and during the welding of copper braid / copper sheet and terminal block, the medium frequency welding machine switch is pressed intermittently and discontinuously to perform welding.

9. The medium frequency welding process for converter transformer valve leads and terminal blocks according to claim 1, characterized in that: The silver-phosphorus welding sheet is in the shape of a long strip, and when placed, the length direction of the silver-phosphorus welding sheet is consistent with the width direction of the copper braided belt.

10. The medium frequency welding process for converter transformer valve leads and terminal blocks according to claim 1, characterized in that: After the front end of the copper braid is wrapped with copper sheet, the total cross-sectional area of ​​the portion to be welded of the copper braid with the silver-phosphorus solder sheet placed thereon and wrapped with copper sheet is calculated.

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