Welding method for improving qualified rate of curve I-level fillet weld

Abstract

The invention discloses a welding method for improving the percent of pass of a curve I-level fillet weld in the field of steel structure manufacturing, which comprises the following steps of: manufacturing a backing plate by using a material which is the same as a welding base material, and mounting the backing plate at a welding part of a web plate and a bottom plate or a top plate, a gap is reserved between the side, close to the web, of the backing plate and the web by inserting the backing positioner, then fillet weld spot welding fixing is conducted on the end, tightly attached to the bottom plate or the top plate, of the backing plate, the backing positioner is taken out after fixing is conducted, and finally welding is conducted on main weld welding position areas between the backing plate and the web and between the web and the bottom plate or the top plate. According to the invention, a ceramic gasket is not adopted, but steel plate waste materials are adopted as the gasket, so that the welding cost is reduced, the adhesive force with deposited metal is very good, welding is easy, the welding difficulty is reduced, and the method has very good adaptability to the condition that the assembling clearance of a curve structure is difficult to be completely uniform and consistent; therefore, the welding qualification rate is higher and more stable than that of a ceramic gasket, and the rework rate is reduced.

Description

Technical Field

[0001] The invention relates to the field of steel structure manufacturing, and in particular to a welding method for improving the pass rate of curved grade I fillet welds. Background Art

[0002] The main welds between the web and top plate, and between the web and bottom plate of the curved steel box bridge are usually full penetration fillet welds. After welding, non-destructive testing is required to determine the weld qualification. The quality requirements of Class I welds are the highest and must be 100% inspected. Class I welds must not have defects such as cracks, weld bumps, burn-throughs, arc pits, etc., nor are surface pores, slag inclusions, arc pits, cracks, arc scratches, etc. Defects such as surface pores, slag inclusions, arc pits, cracks, arc scratches, etc. are allowed. If defects are detected, the weld needs to be planed and reworked, resulting in losses in welding auxiliary materials, welding energy, labor, construction period, etc. Due to the poor working conditions and the large safety risks of welding in closed spaces during welding in the box, the single-sided welding and double-sided forming welding process is now mostly used.

[0003] At present, the common single-sided welding and double-sided forming welding process is mainly ceramic backing welding, but this method has the following main disadvantages:

[0004] 1. The welding cost caused by the ceramic liner itself increases significantly;

[0005] 2. The ceramic liner has no adhesion to the cladding metal, and the cladding metal in the molten pool is easy to slide off, especially in horizontal welding, vertical welding, overhead welding and other welding positions;

[0006] 3. The ceramic liner needs to be attached to the surface of the base material with adhesive. The adhesive of the ceramic liner itself is easy to fall off after welding and heating, especially in the flat welding position. After heating, the liner is more likely to fall off under the action of gravity in the molten pool, which has an adverse effect on the welding process.

[0007] 4. Ceramic gaskets have certain requirements on the size of the weld gap of the base material assembly. Uneven gaps have a great impact on the welding qualification rate, and larger gaps cannot be welded. Summary of the invention

[0008] In order to overcome the above-mentioned deficiencies of the existing single-sided welding and double-sided forming process of ceramic gaskets, the technical problem to be solved by the present invention is to provide a welding method using a steel gasket to improve the pass rate of curved grade I fillet welds.

[0009] The technical solution adopted by the present invention to solve the technical problem is:

[0010] The welding method for improving the pass rate of curved grade I fillet welds comprises the following steps:

[0011] Step 1: Cut materials according to the design drawings and assemble each unit board. After the assembly dimensions are checked and qualified, each unit board is spot welded and fixed firmly;

[0012] Step 2: Use the same material as the welding base material to make the backing plate;

[0013] Step 3: Install the backing plate at the welding position between the web and the bottom plate or top plate, with one end of the backing plate close to the bottom plate or top plate, and leave a gap of 2 to 3 mm between the side of the backing plate adjacent to the web by inserting the backing locator and the web;

[0014] Step 4: Fix the end of the liner plate that is in close contact with the bottom plate or the top plate by spot welding, and remove the liner locator after fixing;

[0015] Step 5: Purge and clean the main weld areas between the liner plate and the web plate, and between the web plate and the bottom plate or top plate, and then weld the main weld according to the specified welding process and parameters.

[0016] Furthermore, the thickness t of the liner plate is: 5≤t≤T min / 2, unit: mm, T min The smaller thickness of the two parent materials of the main weld.

[0017] Furthermore, the length a of the liner plate is: 300≤a≤2sqrt((R min +1) 2 -R min 2 )), unit: mm, R min It is the smaller radius of the horizontal curve and the vertical curve of the current curve segment.

[0018] Furthermore, the height h of the liner plate is: h = δ max +20 and 30≤h≤50, unit: mm, δ max is the maximum value of the weld gap.

[0019] Furthermore, the pad positioner comprises a handle, a connecting rod and an L-shaped supporting plate which are connected in sequence, and the thickness of the horizontal section of the L-shaped supporting plate is 2 to 3 mm.

[0020] Furthermore, a groove is provided on the horizontal section of the L-shaped support plate, and a permanent magnet is fixedly arranged in the groove.

[0021] Furthermore, the permanent magnet is adhered in the groove by means of silicone glue, and the silicone glue wraps the entire permanent magnet.

[0022] Furthermore, the connecting rod is in a U-shaped structure, the middle part of which is connected to the handle, and an L-shaped support plate is provided at each end, and the distance between the two L-shaped support plates is 1 / 3 of the length of the liner plate.

[0023] Furthermore, when the backing plate is spot welded to the bottom plate or top plate in step 4, the spot welding length is 20 mm ≤ L1 ≤ 40 mm, the spacing is 250 mm ≤ L ≤ 350 mm, and the weld leg size is 5 mm ≤ h f ≤t.

[0024] The beneficial effects of the present invention are:

[0025] 1. Instead of using high-cost ceramic liner, it is made of basically useless steel plate waste, which is the recycling of waste and reduces welding costs;

[0026] 2. The steel liner is first welded on the bottom plate or the top, and it will not fall off during the subsequent welding process. The deposited metal has good adhesion and is easy to weld, which reduces the difficulty of welding in various welding positions;

[0027] 3. It has low requirements for weld gap size accuracy and is well adaptable to situations where the gap of curved structure assembly is difficult to be completely uniform. Therefore, it has a higher and more stable welding qualification rate than ceramic gaskets, reduces the rework rate, thereby reducing the processing cost, welding auxiliary material cost, labor cost, and construction period caused by rework, and also reduces the increase in safety risks caused by rework and reduces the environmental pollution caused by welding smoke;

[0028] 4. This welding also belongs to the single-sided welding and double-sided forming welding process, which avoids welding inside the box, avoids an unfavorable working environment, and at the same time avoids safety risks such as suffocation caused by welding inside the box. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the welding structure of the liner plate and the bottom plate of the present invention;

[0030] Figure 2 It is a structural schematic diagram of the pad positioner of the present invention.

[0031] Marked in the figure, 1- liner plate, 2- belly plate, 3- bottom plate, 4- liner locator, 41- handle, 42- connecting rod, 43- L-shaped support plate, 44- groove, 45- permanent magnet. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings.

[0033] It should be noted that if there are directional indication terms in the present invention, such as up, down, left, right, front, and back directions and orientation terms, they are for the purpose of facilitating the description of the relative position relationship between components, and are not specific to the absolute position of the related components or the position relationship between components. They are only used to explain the relative position relationship and movement of the components in a certain posture. If the specific posture changes, the directional indication will also change accordingly. If there are terms related to quantity in the present invention, such as "multiple", "multiple", "several", etc., they specifically refer to two or more.

[0034] The present invention provides a welding method for improving the pass rate of curved grade I fillet welds, comprising the following steps:

[0035] Step 1: According to the BIM model data and the detailed design drawings, the parts are cut and blanked and the welding grooves are processed. The bottom plate unit, top plate unit, web plate unit, and diaphragm unit are assembled and welded on the ground tire. Through this step, each assembly unit has a good anti-deformation ability. After the production of each assembly unit is completed, it is necessary to ensure that the size and weld inspection are qualified; then the bottom plate unit, web plate unit, top plate unit, and diaphragm unit are assembled on the ground tire by the upright or inverted method. After the assembly size inspection is qualified, each unit is spot welded and fixed firmly, and the assembly size is checked again to confirm that it is correct;

[0036] Step 2: While assembling, make the backing plate 1, using the same material as the parent material, preferably using leftovers for processing, and preferably using laser cutting for cutting, which has a smooth cut surface and less oxide;

[0037] Step 3: Figure 1 As shown, a backing plate 1 is installed at the welding position between the web plate 2 and the bottom plate 3 or the top plate, one end of the backing plate 1 is close to the bottom plate 3 or the top plate, and a gap of 2 to 3 mm is left between the side of the backing plate 1 adjacent to the web plate 2 by inserting a backing locator 4 and the web plate 2. The gap is preferably 2 mm, which can ensure that the cladding metal liquid flows through the gap and ensure the firmness of the welding after solidification;

[0038] Step 4: Fix the liner plate 1 and the end of the bottom plate 3 or the top plate by spot welding. After fixing, take out the liner positioner 4. The optimal process parameters for spot welding are: spot welding length 20mm≤L1≤40mm, spacing 250mm≤L≤350mm, and weld foot size 5mm≤h f ≤t, the commonly used dimensions of the above-mentioned spot welding length, spacing, and weld leg are the minimum dimensions. If the dimensions are too small, the backing plate 1 may be easily deformed or fall off during the main weld welding process;

[0039] Step 5: Purge and clean the main weld areas between the liner plate 1 and the web plate 2, and between the web plate 2 and the bottom plate 3 or the top plate, and then weld the main weld according to the welding process and parameters of the welding process assessment. Solid welding wire, flux-cored welding wire, gas shielded welding, submerged arc welding, manual welding, robot welding, etc. can be used with corresponding process parameters.

[0040] Compared with the traditional ceramic liner welding process, the advantages of this process are: the liner plate 1 is fixed to the base plate 3 by spot welding, which is more convenient to operate and has a stronger connection, and will not fall off during the subsequent welding process; the ceramic liner is usually provided with a groove to form a molten pool, and the ceramic liner is not attached to the cladding metal, so the weld gap size requirements are relatively high. After the steel liner is used in this application, the liner plate 1 will be directly welded to the cladding metal, so the weld size requirements are relatively low, which can be suitable for welding welds with larger gaps and reduces the welding difficulty.

[0041] For various parameters of the liner plate 1, the present invention provides the following preferred solutions:

[0042] The thickness t of the liner plate 1: 5≤t≤T min / 2, unit: mm, T min The smaller thickness of the two parent materials of the main weld;

[0043] The length a of the liner plate 1: 300≤a≤2sqrt((R min +1) 2 -R min 2 )), unit: mm, R min The smaller radius of the horizontal curve and the vertical curve of the current curve segment;

[0044] The height h of the backing plate 1: h = δ max +20 and 30≤h≤50, unit: mm, δ max is the maximum value of the weld gap.

[0045] If the thickness of the backing plate 1 is too thin, it is easy to burn through during welding. If it is too thick, it may increase the cost and cause waste. The commonly used thickness is 5mm or 8mm. The length of the backing plate 1 is determined to control the shortest and longest values ​​of the gap distance between the backing plate 1 and the curved surface base material when the deviation range is between 0 and 1mm. The height of the backing plate 1 is mainly affected by the weld gap. If it is too high, the cladding metal liquid cannot completely fill the weld. If it is too short, it will affect the firmness of the welding. Usually, about 30mm is enough.

[0046] For the liner positioner 4, a common backing plate can be used to ensure the gap between the liner plate 1 and the web 2. In order to facilitate plugging and unplugging, the preferred solution of the present invention is as follows: Figure 2As shown, the liner positioner 4 includes a handle 41, a connecting rod 42 and an L-shaped support plate 43 connected in sequence, and the horizontal section of the L-shaped support plate 43 has a thickness of 2 to 3 mm and a length not exceeding the height of the liner plate 1. The liner plate 1 is placed and abutted against the horizontal section of the L-shaped support plate 43, and is positioned by abutting the side of the liner plate 1 against the vertical section of the L-shaped support plate 43. The bottom of the L-shaped support plate 43 should be flush with the bottom of the connecting rod 42 so that the two abut against the web 2 to achieve the positioning of the liner plate 1.

[0047] Furthermore, in order to directly fix the backing plate 1 on the backing locator 4 so as to install the backing plate 1 at different angles, a groove 44 is provided on the horizontal section of the L-shaped support plate 43, and a permanent magnet 45 is fixedly provided in the groove 44. The permanent magnet 45 adopts a neodymium iron boron permanent magnet sheet to ensure that the distance from the top of the permanent magnet 45 to the bottom of the L-shaped support plate 43 is 2 to 3 mm. The backing plate 1 is fixed on the backing locator 4 by the permanent magnet 45, which is convenient for controlling the position and angle of the backing plate 1 through the backing locator 4, and the backing locator 4 can be easily removed afterwards.

[0048] As for the fixing method of the permanent magnet 45, the preferred method of the present invention is that the permanent magnet 45 is pasted in the groove 44 by silicone glue, and the silicone glue wraps the entire permanent magnet 45. The silicone glue has a certain elasticity, and wraps the permanent magnet 45 inside, which can play a buffering role, protect the permanent magnet 45, and prevent the permanent magnet 45 from being damaged due to impact or wear.

[0049] For some longer lining plates 1, an L-shaped support plate 43 and a permanent magnet 45 may not provide sufficient connection stability. Therefore, a preferred solution is that the connecting rod 42 has a U-shaped structure, the middle part of which is connected to the handle 41, and an L-shaped support plate 43 is provided at each end. The distance between the two L-shaped support plates 43 is 1 / 3 of the length of the lining plate 1, so as to provide a balancing support.

[0050] The present invention is further described below in conjunction with embodiments.

[0051] Example

[0052] Take the welding of the main weld between the web and bottom plate of a Q355C material 20mm thick curved steel box bridge as an example.

[0053] Step 1: According to the BIM model data and the detailed design drawings, carry out the cutting and welding of parts and the processing of welding grooves, and complete the assembly and welding of the stiffening ribs of the bottom plate unit, top plate unit, web plate unit, and diaphragm unit on the ground tire respectively; assemble the bottom plate unit, web plate unit, top plate unit, and diaphragm unit on the ground tire by the positive assembly method. After the assembly size inspection is qualified, each unit is spot welded and fixed firmly, and the assembly size is checked again to confirm that it is correct;

[0054] Step 2: While assembling, make the backing plate 1, use the leftover material of Q355C material for processing, and use laser cutting for cutting; determine the size of the backing plate 1 according to the commonly used steel box girder specifications: the thickness of the backing plate 1 is 8mm, the length is 500mm, and the height is 30mm. After the backing plate 1 is cut according to the controlled size, the oxides, burrs, etc. are cleaned and the surface is flat;

[0055] Step 3: Place one end of the liner plate 1 close to the bottom plate 3, leaving a 2mm gap between one side and the web plate 2, and use the liner positioner 4 to determine the gap and temporarily fix it. The distance between the two L-shaped support plates 43 is 150mm;

[0056] Step 4: Fix the liner plate 1 and the bottom plate 3 by spot welding with a fillet weld, with a spot welding length of 20 mm, a spacing of 300 mm, and a weld foot size of 5 mm. After the liner plate 1 is welded and fixed, pull out the liner positioner 4;

[0057] Step 5: Purge and clean the main weld area, and then weld the main weld according to the welding process and parameters specified in the welding process assessment.

[0058] According to experimental tests, under the same welding conditions, the technical solution is used to perform single-sided welding and double-sided forming process welding in horizontal welding, vertical welding, and overhead welding positions, and the average one-time welding pass rate is 98%, which is 11 percentage points higher than the average pass rate of 87% of conventional welding methods, and the pass rate deviation is smaller and the pass rate is more stable. The increase in the pass rate means the reduction in the rework rate. In addition to consuming the same welding auxiliary materials and working hours during rework, the carbon rod, electricity, and labor costs consumed by carbon arc gouging are also increased. The increased carbon arc gouging working hours are about 1 / 3 of the welding working hours. Therefore, the reduction in the rework rate also reduces the pollution of carbon arc gouging and welding to the environment. In summary, the welding method of the present invention is practical and has a high application value.

Claims

1. A welding method for improving the pass rate of curved grade I fillet welds, characterized in that: The following steps are involved: Step 1: Cut materials according to the design drawings and assemble each unit board. After the assembly dimensions are checked and qualified, each unit board is spot welded and fixed firmly; Step 2: Select the same material as the welding base material to make the backing plate (1); Step 3: Install the backing plate (1) at the welding position between the web (2) and the bottom plate (3) or the top plate, with one end of the backing plate (1) close to the bottom plate (3) or the top plate, and leave a gap of 2 to 3 mm between the side of the backing plate (1) adjacent to the web (2) by inserting the backing locator (4) and the web (2); Step 4: Fix the liner plate (1) and the end of the bottom plate (3) or the top plate by spot welding, and remove the liner positioner (4) after fixation; Step 5: Purge and clean the main weld areas between the backing plate (1) and the web plate (2), and between the web plate (2) and the bottom plate (3) or the top plate, and then weld the main welds according to the specified welding process and parameters.

2. The welding method for improving the pass rate of curved grade I fillet welds according to claim 1, characterized in that: The thickness t of the liner plate (1): 5≤t≤T min / 2, unit: mm, T min The smaller thickness of the two parent materials of the main weld.

3. The welding method for improving the pass rate of curved grade I fillet welds according to claim 1, characterized in that: The length a of the liner plate (1): 300≤a≤2sqrt((R min +1) 2 -R min 2 )), unit: mm, R min It is the smaller radius of the horizontal curve and the vertical curve of the current curve segment.

4. The welding method for improving the pass rate of curved grade I fillet welds according to claim 1, characterized in that: The height h of the liner plate (1): h = δ max +20 and 30≤h≤50, unit: mm, δ max is the maximum value of the weld gap.

5. The welding method for improving the pass rate of curved grade I fillet welds according to claim 1, characterized in that: The pad positioner (4) comprises a handle (41), a connecting rod (42) and an L-shaped support plate (43) which are connected in sequence, and the thickness of the horizontal section of the L-shaped support plate (43) is 2 to 3 mm.

6. The welding method for improving the pass rate of curved grade I fillet welds according to claim 5, characterized in that: A groove (44) is provided on the horizontal section of the L-shaped supporting plate (43), and a permanent magnet (45) is fixedly arranged in the groove (44).

7. The welding method for improving the pass rate of curved grade I fillet welds according to claim 6, characterized in that: The permanent magnet (45) is adhered in the groove (44) by means of silicone glue, and the silicone glue wraps the entire permanent magnet (45).

8. The welding method for improving the pass rate of curved grade I fillet welds according to claim 7, characterized in that: The connecting rod (42) is in a U-shaped structure, the middle part of which is connected to the handle (41), and an L-shaped support plate (43) is provided at each end, and the distance between the two L-shaped support plates (43) is 1 / 3 of the length of the lining plate (1).

9. The welding method for improving the pass rate of curved grade I fillet welds according to claim 1, characterized in that: When the liner plate (1) is spot welded to the bottom plate (3) or the top plate in step 4, the spot welding length is 20mm≤L1≤40mm, the spacing is 250mm≤L≤350mm, and the weld leg size is 5mm≤h f ≤t.

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