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Strike plate
A tool for welding welds
The arc plate is used for welding welds. At the starting point and end point of the solder joint, often due to the weldment profile of the butt weld, the types of the butt weld have straight edge seam, unilateral V-shaped seam, bilateral V-shaped seam, U-shaped seam, K-shaped seam, X-shaped seam and so on. The starting point and the end point of the weld often appear concave welding joints due to impenetrability, in order to avoid cracks after stress
Stress concentration
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Steel structure engineering construction quality acceptance code
When welding, the two ends should be welded to the arc plate, and then the excess part is cut off, so that the cross section of the weld will not be reduced.
- Chinese name
- Strike plate
- Foreign name
- Arc plate
- subject
- Mechanical engineering
- domain
- Mechanical equipment
- Van Wai
- weld
- Weld type
- Straight edge seam, unilateral V-shaped seam, bilateral V-shaped seam, etc
With the rapid development of railway modernization,
Aluminium alloy
The welded structure of car body has been widely used in the rail transit equipment manufacturing industry. Because the aluminum alloy material itself has fast thermal conductivity, large expansion coefficient, easy oxidation and other properties, it will produce a series of difficulties in the welding process, and it is easy to produce welding defects such as pores and non-fusion in the welding process, and must be repaired and welded. However, in the actual welding process, frequent welding defects result in a very high welding repair rate
Aluminum alloy welding
Repair generally can not be more than 2 times, otherwise it will be scrapped. For example, for the coupler beam, a key component in the aluminum alloy body structure of a high-speed train, the economic loss of 1 piece is as high as 150,000 yuan. However, for the butt weld of the medium and thick plate of the coupler beam, the traditional "flat" arc plate used in welding repair cannot fit closely with the surface of the weld, which affects the rapid conduction of welding heat, and it is easy to produce defects such as non-fusion at the arc end of the repaired weld, resulting in the qualification rate of welding repair only about 60%. Therefore, it is necessary to study this problem. To improve the pass rate of a welding
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1. Welding repair treatment method
(1) Grinding defects Because welding defects are mostly local problems of welds, in order to ensure the accessibility of welding, after determining the location of welding defects and removing welding defects, it is necessary to ensure that the root width of the area to be welded is not less than 5mm, and the slope roots at both ends of the area to be welded and the groove surfaces on both sides are milled to a smooth transition, so that the Angle of the groove is not less than 30°. The gradient of the longitudinal transition area from the root of the groove to the surface of the weld is not less than 1:4. Under the premise of complete removal of defects, the amount of weld removal should be minimized to reduce the amount of welding repair filling, so as to control heat input and welding deformation.
(2) Installation arc plate Because aluminum alloy MIG welding process in the base metal heat dissipation faster, melting pool cooling speed is also faster, in the weld arc end is easy to produce porosity, non-fusion welding defects, therefore, in order to avoid defects, must be installed in the weld arc and weld groove of the same form of welding arc plate. Because the starting point of the repair welding is downhill welding, the arc starting plate with the same form of the weld groove can not give full play to the role of the arc starting, so the repair arc starting plate is generally used for welding repair operation. The arc plate is a rectangular plate, one side wall of the rectangular plate is a slope, and the slope Angle between the slope and one side of the rectangular plate is a slope Angle, and the slope Angle is 30° ~ 45°.
Before welding repair, the arc guide plate is placed on the weld, so that the slope edge of the arc guide plate fits with the edge of the starting end of the area to be welded, that is, the slope of the arc guide plate is connected with the longitudinal transition area, and the arc guide plate and the base material are clamped and fixed with F-shaped clamp.
(3) If the thickness of the base metal is ≥8 mm, the oxygen-acetylene flame needs to be used to preheat the area to be welded before welding, so that the preheating temperature is controlled at 80 ~ 120 ° C, and the inter-channel temperature is controlled at 100 ~ 120 ° C when multi-layer and multi-channel welding is carried out. After the welding and repair is completed, loosen the fixture, and polish and remove the arc plate used for repair by hand milling. Retain the original weld and the repair weld, and smooth the joint between the two welds to make the height of the weld.
2. The shortcomings of the existing arc guide plate for repair
(1) Because the arc plate for repair needs to be assembled on the weld, and the weld is generally left with a residual height of about 1~2mm, resulting in a small contact area between the arc plate and the residual height of the weld. In the welding process, the heat conduction effect is poor, and the high local heat will seriously affect the welding quality in the longitudinal transition area, which is easy to produce welding non-fusion and weld porosity defects. At the same time, due to the high local temperature, the heat affected zone in the welded joint will be softened, and the strength of the base metal will be reduced.
(2) The surface tension of molten metal is small and the fluidity is very strong. The initial stage of welding repair is downhill welding, which speeds up the flow rate of molten metal, resulting in insufficient concentration of heat at the arc initiation end, which makes the longitudinal transition area of the arc initiation end and the root of the groove easy to produce welding non-fusion and weld porosity defects.
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Aluminum alloy welding
The greater the heat input, the more serious the performance degradation. However, the occurrence of defects at the arc initiation during the repair welding will increase the heat input of the weld partially due to repeated welding, thus reducing the strength of the welded joint.
To solve the problem of small contact area between the existing repair arc plate and the weld and the base material, the author invented a new type of repair arc plate.
1. Design method of the new arc guide plate for repair
(1) Design ideas
By analyzing the non-fusion defect of groove root caused by welding repair, it can be inferred that the flow speed of molten metal is ahead of the welding pool, so that the two sides of filler metal and base metal groove root do not form an effective connection, resulting in non-fusion of weld and base metal. The fast flow speed of molten metal is due to the lack of good heat transfer between the arc plate and the base metal weld, and the poor thermal conductivity of the arc plate used for repair. Try to design the surface of the arc plate into a concave arc shape to match the convex arc of the base material's weld residual height, increase the contact area between the arc plate for repair and the base material, and increase the heat conduction rate.
(2) Design method of structural shape
The shape is that one side of the arc plate body has a groove matching with the residual height of the weld, and at least one side wall of the plate body through the groove is the slope, and the Angle between the slope and the surface of the groove on the plate body is 30° ~ 45°, that is, the slope Angle is 30° ~ 45°. The thickness of the plate body is the same as that of the welded base material. The thickness refers to the thickness of the groove and slope on the plate body.
Taking the 10V groove butt weld of coupler beam, a key component of high-speed aluminum alloy car body, as an example, the arc starter plate body used in the repair is an aluminum alloy material of the same material as the welding base material, and the thickness is the same. The plate body specification is 10 mm×50mm×50mm, and one side of the plate body is processed into a groove matching with the residual height of the weld. The section shape of the groove should be able to accommodate the residual height of the weld protruding from the surface of the base material, and the groove can be processed by hand milling. A side wall on the plate body through the groove is a slope, and the Angle (slope Angle) between the slope and the surface of the groove on the plate body is 40°. In the process of repair welding, the edge of the slope of the arc drawing plate is fitted with the upper edge of the area to be welded. The incline Angle reduces the difference of the surface groove Angle of the longitudinal transition area between the slope of the reworking arc plate and the area to be welded, and realizes the straight line connection, so as to facilitate the reworking welding.
2. The use of the new arc plate for repair
(1) After the removal of welding defects, the arc starter plate and the base material are clamped and fixed with F-shaped clamp, and the F-shaped clamp is clamped on the side of the arc starter plate used for repair away from the base material to achieve the clamping and fixing between the arc starter plate used for repair and the base material. Ensure that the arc plate and the surface of the workpiece are closely fitted, ensure that the slope of the arc plate and the upper edge of the area to be welded are evenly fitted, and achieve a straight line connection to facilitate repair welding.
(2) The oxygen-acetylene flame is used to preheat the welding area before welding, and the flame should be adjusted to the carbonization flame during the preheating process, and the flame should be able to move freely above the preheating area, but direct heating of the arc plate for repair should be avoided. The contact thermometer is used for temperature measurement, and the preheating temperature is controlled at about 100℃. The welding process adopts multi-layer and multi-pass welding, and the temperature between the welding channels is controlled at about 110℃.
(3) Weld the welding area. After the repair welding is completed, remove the F-shaped fixture when the base metal weld cools to room temperature or 25℃. The reworking arc guide plate was removed by milling with a pneumatic straight mill, and the joint between the reworking arc guide plate and the weld was polished smooth.
(4) Use the pneumatic straight mill to remove the arc guide plate, after removal, the longitudinal grinding is carried out, and the joint is polished until the smooth transition, and the repaired weld is in the same height as the original weld.
3. The application effect and advantages of the new repair arc plate
Through the practical application in the coupler beam repair, it is proved that the welding operation skill requirements are reduced, the probability of defects is significantly reduced, the qualified rate of weld repair is increased from 60% to 100%, and the manufacturing cycle of coupler beam is shortened by more than 40%. Through verification, this new type of repair arc plate has the following advantages:
(1) The structure is simple and easy to process: just measure 4 values (base metal thickness, welding groove Angle, groove root clearance, weld residual height) to determine the groove size, and can be processed in batches.
(2) Easy installation and removal: F-shaped clamp is used for clamping and fixing, reliable and firm, convenient disassembly and installation
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This new type of arc starting plate for repair is suitable for the butt weld repair of the medium thick plate of aluminum alloy material above 8mm. Since the welded aluminum alloy car body plate and profile are mostly 8mm and above size, the butt weld welding repair mostly adopts multi-layer and multi-pass welding, and the flame preheating is required before welding. The new arc guide plate can accelerate the heat conduction rate of the weld arc end, and avoid the strength softening of the joint between the arc guide plate and the weld caused by the overheating of the arc guide plate.
This new type of arc plate for repair is also suitable for welding of long welds. Long weld welding will inevitably leave joints. The good thermal conductivity between the new arc plate and the base material can reduce the probability of welding failure and porosity defects at the joint, and ensure the welding quality of the joint.
The application of the new groove type arc guide plate for repair increases the contact area between arc guide plate and weld and base material, speeds up the heat conduction rate between base material and arc guide plate, reduces the occurrence of repair welding defects, and achieves good repair welding effect. This new type of welding arc plate has been declared a national patent
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