Welding process and deformation control of large cross-section thin-walled single box double chamber steel box girder.pdf

Responding to the application of technology ah I, for the white tower road pedestrian bridge of the production difficulties and quality requirements, in the past experience of the reasonable process measures taken to reach a very large cross-section thin-walled single box double chamber steel box girder welding processing technology and deformation control, Gu Biao, Ma Li, (Angang Steel Construction Group Co., Ltd., special structure plant, Anshan, Liaoning,). [Abstract] Aiming at the quality requirements and fabrication difficulties of Baita Road Pedestrian Bridge, after taking reasonable process measures. , , . The deformation condition generated by welding is restrained, the welding quality is guaranteed, and the requirements of product quality are fulfilled. Our unit has undertaken the task of steel structure production of Baita Road Pedestrian Bridge; the product involved here is a large cross-section thin-walled single-box double-cell steel box girder; the relevant process includes welding process; and there are requirements for deformation control; CCTC classification number is TG404; the document identification code is A; article number is 1009-914X(2014)16-0243-01. -0243-01. The size of its bridge hole arrangement is 7.25m, and the total length of this bridge is 176.7m,. The bridge is a single-hole span of 25m steel box continuous beam structure, the main girder of the transverse, is composed of three separated single box double chamber steel box girder together, between the box is set with a steel crossbeam, in the centre line of the steel box girder, the full height of the 1.3.4.1.5, the internal welding is completed, and after the test is qualified, the top plate and the longitudinal ribs on the top plate are assembled, and the spot weld is firmly. The longitudinal ribs of the top plate are inserted into the transverse partition plate for assembly, thus forming a box, involving 3, 4, 1, 6 steps. The key points in the assembly of the box girder are to strictly control the cross-section dimensions of the two ends of the box girder, and to add support to achieve the fixation purpose when implementing pre-welding operations at the end box joints, including the aspects of 3, 4, 2 and 1. The bridge has a total width of 23.0m, its starting measurement position is 0m, the bottom width of each single box is 4.860m, the outer cantilever is 1.6m long, and the bridge deck has a cross slope of 1.0% in the direction of the two intersecting directions. The project has a single box double chamber steel box girder, its cross-section is large, the web is thin, the top and bottom plates and the web have stiffener plates, there is a diaphragm in the box, and the steel structure production and inspection must meet the requirements of the Technical Specification for Highway Bridge Construction (JTG/T F50-2011) and the Ⅸ Code for Quality Acceptance of Construction of Steel Structural Engineering (GB50205-2001). -2001) requirements 。。。。。。。。。　。。。。。。。。。。。。 ?。。。。。。。。。。。。。。。。。。。　。。。。。。。。。。。。 Hey 。。。。。。。。。。。。。。。。。。。。 , 。。。。。。。。。。。。。。。。。。　。。。。。。。。。。。。。。。 After welding is easy to produce changes in shape, do not take industrial methods and measures to control is very difficult to achieve the quality requirements, for such a situation, to take control of the shape of the change of effective methods and measures, the development of a reasonable welding industrial process is to ensure the quality of the product is an important safeguard. 2 Pedestrian bridge of the structural form of the 3.4.2.2 to ensure that the top, bottom of the plate longitudinal ribs of the level and straightness of the degree of assembled up to dimensions meet the requirements so as to facilitate the insertion of the bulkheads and the accuracy of the holes in the bolt holes at the site interface. In the case of 3.5, adopt the welding sequence and method that makes people feel reasonable, to reduce residual stress and welding deformation. At the same time, 4 welding process, 4.1 chemical composition can be seen in Table 1. in addition, 4.2 material selection, 4.2.1 in the positioning welding selection of electrode arc welding, electrode selection, diameter is 4.0. Steel structure production is completed in the factory, steel structure pre-assembly is completed in the factory, pedestrian bridge cross-section direction is divided into false factory situation, pedestrian bridge length direction is divided into 13 sections factory. The top plate adopts 14mm steel plate is the steel box girder, the bottom plate also adopts 14mm steel plate, the web plate adopts 12mm steel plate, the cross partition plate in the span adopts 12mm steel plate, the cross partition plate at the pivot point adopts 20mm thick steel plate, the top plate is set up with longitudinal plate stiffening plate, the thickness of its steel plate is 14mm, the web plate is set up with vertical stiffening plate, the thickness of the steel plate is 8mm, the material is all Q 3 4 5 q D N H. There are 39 single box double chamber steel box girders, they are assembled in the factory, after that they are welded, and they are shipped out of the factory after completing these processes. The single box double chamber steel box girder, which has a large cross section and a thin web, is equipped with stiffeners at the top and bottom plates and the web, and there are also transverse bulkheads inside the box. Control of deformation after welding is difficult, so reasonable process measures must be taken to ensure product quality requirements. Approach three, for the control of welding deformation, first, for the top and bottom plate, web, using CNC cutting machine for cutting, but also planing bevel, and second, strictly control the processing accuracy of the cross partition plate and longitudinal ribs, so as to ensure that the combination with the top, bottom plate and web precision. The use of three-roller plate rolling machine, the top and bottom plate for calibration, to ensure its flatness and the release of residual stress, to ensure that the assembly of geometric dimensions and reduce welding deformation, the belly plate for calibration, to ensure its flatness and the release of residual stress, to ensure that the assembly of geometric dimensions and reduce welding deformation, the corner of the plate for calibration, to ensure its flatness and the release of residual stress, to ensure that the assembly of several dimensions and reduce welding deformation. Welding deformation. In order to prevent post-welding deformation, a counter-deformation of the plate splicing line is made before welding. Adopt an effective assembly sequence to reduce welding distortion. To carry out 3.4.1 assembly sequence is 4.2.2, for welding, selection of gas-shielded welding to weld, which welding with the choice of welding wire, the diameter of 1.2,. In the pre-welding preparation, about the base material on the surface to be welded and the surface on both sides, these parts should be uniform, smooth, and also no burrs, cracks and other defects that have an adverse effect on the quality of the weld. The surface to be welded. The surface to be welded, within 30mm from the edge of the weld bevel position, there can not affect the normal welding and weld quality of the oxide skin, corrosion, grease, water and other impurities. 4.3.2 Positioning weld, must be held by the appropriate qualification certificate of the welder to cast welding. Positioning weld thickness, should not be less than 3mm, the length should not be less than 40mm, and its spacing is suitable for 300mm to 600mm. 4.4 Welding sequence, 4.4.1 the cross partition plate corners with the web welded together, the length of the weld is about 100mm, so that the partition plate and the web to form a rigid fixation, and then weld the cross partition plate and the bottom plate weld, in order to avoid the component welded deflection, the bottom plate weld, the bottom plate weld, the bottom plate weld, the bottom plate weld, the bottom plate weld, the bottom plate weld, the bottom plate weld. 4.4.2 Weld the longitudinal seam between the base plate and the web, weld the longitudinal ribs on the base plate and the weld of the stiffener plate at the support, and finally weld the weld between the web and the transverse partition plate and the longitudinal ribs. The internal welds are inspected as required by 4.4.3. Then the remaining welds on the box body should be completed welding, which belongs to the content of 4.4.4. Attention should also be paid to the adoption of a reasonable welding sequence to prevent deformation of the welded steel box girder, which is emphasised in 4.5. Top and bottom plate welding longitudinal ribs, easy to produce wave deformation, welding, we must take the symmetrical welding method, but also to take the scattered welding method, and to take the sectional welding method, as far as possible to avoid heat concentration, in order to prevent welding deformation. Adopt the welding method of gas shielded welding to reduce the welding deformation. After welding inspection, the weld appearance 100% inspection should be qualified. In 3 ． 4 ． 1 ． In the operation of 3.4.1.1, choose the material is Q 2 3 5 B channel steel [3 6 a to lay and assemble the platform, with the help of levelling instrument for the assembly of the platform level to be measured, stipulate that the difference between the upper surface of the height of the difference can not be greater than l mm, and then after the measurement is completed with the ground to implement the welding of the steel to be fixed. 3. 3.4.1. 1. 2 Fix the base plate and attach it to the floor. 2.1.2 The base plate is fixed and fitted to the platform, and the longitudinal ribs and stiffeners at the supports are assembled. According to the actual position, weld the cross partitions of 3.4.1.3 to the base plate on the platform, and check the verticality of the cross partitions and the straightness of all the cross partitions' groove dimensions. The position number of the longitudinal rib on the two outer and middle webs should be marked, and the longitudinal rib should be assembled on the two outer and middle webs after assembling the webs to the bottom plate, which should be done in accordance with the requirements of 3.4.1.4.4.4 4.4.7.2 After welding, magnetic particle inspection should be applied, and all of them are qualified after inspection.5 Quality inspection, 5.1 Checking the width of the box beams, checking the heights, measuring the diagonal difference of the cross-sections, and testing the dimensions of the side bends, etc. After checking, all of them are qualified. Its side bend and other dimensions, after checking to see that all within the tolerance requirements.6 Conclusion, the implementation of the above process in the production of box beams, according to which the effective control of welding deformation, and thus ensure the quality of the product, and then by the customer's high praise. References, [1] referred to in the steel structure welding code for GB50661 to 2011, there is Figure 1 shows a single box double chamber steel box beam cross-section, there is also Table 1 lists the melting analysis of the composition of the grade for Q345qDN?H, the chemical composition for the C contained in the mass percentage in %, Mn, P, S, Cu, Ni, Cr, Nb, Ti, V, Als, CEV, si each has a Corresponding requirements, of which C requirements ≤ 0.15, Mn requirements in the 0.15 to 1.50 between, P requirements ≤ 0.025, S requirements ≤ 0.010, Cu requirements in the 0.20 to 0.50 between, Ni requirements ≤ 0.50, Cr requirements in the 0.40 to 0.70 between, Nb requirements ≤ 0.06, Ti requirements ≤ 0.03, V requirements ≤ O.08, Als Requirements ≥ O.015, CEV requirements ≤ 0.48, Note 1 states that is in accordance with CEV = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / l5 to calculate the carbon equivalent. Note 2, Atmospheric Corrosion Resistance Index (ACRI), equal to 26.0l times (%Cu), plus 3.88 times (%Ni), plus 1.20 times (%Cr), plus 1.49 times (%Si), plus 17.28 times (%P), less 7.29 times (%Cu) (%Ni), less 9.10 times (%Ni) (%P), less 3.39 times (%Cu) (%P). 3.39 (%Cu), greater than or equal to, 6.0. 　Technology Expo l 2 43

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