Fluidized bed circulating boiler steel structure welding construction method

Abstract

The invention discloses a fluidized bed circulating boiler steel structure welding construction method. The construction quality is improved through pre-welding treatment, welding process optimization, deformation control and environmental protection management. The method comprises the specific steps that welding wire greasy dirt and an oxidation film are cleaned before welding, a truncated-edge single-side V-shaped groove is prepared, and during welding, structural deformation is reduced through shrinkage allowance reserving, a reversible deformation method, rigid fixing and a segmented assembly sequence; and slag is cleaned layer by layer after welding, and quality inspection is carried out in real time. The welding quality stability is improved, the welding deformation is reduced by more than 30%, the green construction requirement is met, and the method is suitable for efficient welding of large boiler steel structures.

Description

Technical Field

[0001] The present invention relates to a welding construction method for the steel structure of a fluidized bed circulating boiler. Background Art

[0002] At present, traditional manual arc welding or gas shielded welding technology is generally adopted for the welding construction of boiler steel structures. However, the existing traditional processes lack systematic management of pre-welding material treatment (such as cleaning of welding wire oil stains and preparation of bevels), resulting in defects such as porosity and slag inclusion in the welds; insufficient control of welding deformation: when welding long welds, the segmented backstep welding method or anti-deformation measures are not effectively adopted, resulting in excessive overall deformation of the steel structure and affecting the installation accuracy; environmental protection and safety risks: the spatter, dust, and oil volatilization generated during the welding process lack effective control, easily causing environmental pollution and fire hazards; low detection coverage rate: the proportion of non-destructive testing is insufficient or the standards are not unified, making it difficult to comprehensively ensure the welding quality; poor process standardization: the management of welding materials, environmental control, and personnel division of labor are not clear, resulting in great randomness in process execution. For example, a method for fabricating an H-shaped steel member erection jig and an H-shaped steel member disclosed in CN110369941A sets the angle of anti-deformation when each component is assembled to balance the deformation amount generated after welding. In addition, multiple inspection procedures are set before assembly forming, correction, and component assembly to timely correct the dimensional deviation, thereby obtaining high-quality steel structure products. However, the materials are not pretreated before welding, resulting in defects such as porosity and slag inclusion in the welds. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a welding construction method for the steel structure of a fluidized bed circulating boiler.

[0004] The present invention is achieved through the following technical solutions.

[0005] A welding construction method for the steel structure of a fluidized bed circulating boiler provided by the present invention includes the following steps:

[0006] (1) Clean the oil stains and oxide films on the surface of the welding wire;

[0007] (3) Prepare a blunt-edge single-sided V-shaped bevel for the butt weld of the steel column, and clean the oil stains and rust on the surface of the bevel and the inner and outer walls of the base material to metallic luster. The cleaning range is 10 - 20 mm on both the inner and outer sides of the base material;

[0008] (4) Set the welding parameters according to the bevel type and the thickness of the base material:

[0009] (5) Perform welding operations on the steel column, platform railing, and connecting beam. The welding method is:

[0010] For welds longer than 1 m, the step-by-step backstep welding method is adopted, and the interlayer joints are staggered by more than 30 mm; the maximum thickness of the root pass is 6 mm, and the root fillet size of the fillet weld is ≤8 mm for flat welding, ≤7 mm for horizontal welding and overhead welding, and ≤10 mm for vertical welding;

[0011] (6) After welding, the weld slag and spatter are cleaned layer by layer by the cleaning personnel, and the quality inspectors check the interlayer quality in real time;

[0012] (7) After welding is completed, the cleaning personnel remove the residues on the weld surface, the quality inspectors conduct visual inspection, and the non-destructive testing personnel extract 30% of the butt welds of the steel columns for ultrasonic non-destructive testing.

[0013] In the step (5), welding is carried out by CO₂ gas shielded welding or manual arc welding. For CO₂ gas shielded welding, a Φ1.2 welding wire is used, and the welding parameters are: current 110 - 185 A, voltage 19 - 34 V; for manual arc welding, a Φ3.2 welding electrode is used, and the welding parameters are: current 110 - 140 A, voltage 22 - 24 V.

[0014] In the step (3), after the groove preparation is completed, the hardened layer and overheated metal need to be removed;

[0015] The butt misalignment of the weldment is controlled as follows:

[0016] For Class II welds, the misalignment is ≤15% of the plate thickness and ≤3 mm, which is applicable to the welds at the connection of platform railings;

[0017] For Class III welds, the misalignment is ≤20% of the plate thickness and ≤4 mm, which is applicable to the welds of secondary support beams.

[0018] In the step (5), the following measures are taken to control welding deformation:

[0019] The steel column reserves the weld shrinkage allowance;

[0020] The connecting beam adopts the reverse deformation method to pre-adjust the assembly angle of the weldment;

[0021] The free deformation of the platform railing is restricted by the rigid fixing method;

[0022] The construction is carried out according to the segmented assembly welding sequence, and the welds of the main steel frame columns are preferentially welded.

[0023] In the step (7), the visual inspection of the weld includes the following steps:

[0024] The surface of the butt weld of the steel column has no cracks, slag inclusions or pores;

[0025] The depth of undercut of the fillet weld of the platform railing is ≤0.5 mm.

[0026] The requirements for the welding environment are:

[0027] The welds of steel columns in low-temperature environments are preheated and dehumidified by flame.

[0028] Wind and rain protection facilities are set up in the open-air operation area, and it is ensured that the grounding resistance of the welding machine ≤ 4Ω.

[0029] The gas cylinder administrator controls the distance between the oxygen cylinder and the acetylene cylinder ≥ 10m, and the acetylene cylinder needs to be installed with a flashback arrester.

[0030] It also includes a welding consumable management method:

[0031] The electrodes used for steel columns need to be dried before use.

[0032] The welding wires used for platform railings need to remove the surface oil stains and oxide films before use.

[0033] The requisition of welding consumables requires a requisition form signed by the welding technician, specifying whether it is used for the welding of steel columns or connecting beams.

[0034] It also includes the environmental cleaning after construction:

[0035] The waste recycling personnel uniformly handle the electrode stubs and slag of the steel column welds.

[0036] The isolation operator sets up an isolation area for the grinding wheel cutting operation of the platform railing to reduce dust.

[0037] The equipment maintenance personnel regularly overhaul the connecting beam welding machinery to reduce noise emissions.

[0038] The dangerous goods administrator stores the oil containers for the anti-corrosion coating of steel columns in a sealed manner to prevent leakage and volatilization.

[0039] The beneficial effects of the present invention are as follows: By optimizing the pre-welding treatment, welding parameter control, deformation prevention measures, environmental protection management and quality inspection processes, it aims to improve the quality stability of welds, reduce deformation, lower the risk of environmental pollution, and ensure process standardization and inspection coverage. Description of the Drawings

[0040] Figure 1 It is the construction flow chart of the present invention. Detailed Embodiments

[0041] The technical solutions of the present invention will be further described below, but the scope of protection claimed is not limited thereto.

[0042] A construction method for welding the steel structure of a fluidized bed circulating boiler includes the following steps:

[0043] (1) Clean the oil stains and oxide films on the surface of the welding wire; by thoroughly cleaning the impurities on the surface of the welding wire, the incidence of pores and lack of fusion defects during welding is reduced, and the weld density is improved.

[0044] (3) Prepare a blunt-edge single-sided V-groove for the butt weld of the steel column, and clean the oil stains and rust scale on the surface of the groove and the inner and outer walls of the base metal until metallic luster is achieved. The cleaning range is 10 - 20 mm on both the inner and outer sides of the base metal; reserve the margin through mechanical machining of the groove combined with flame cutting to effectively remove the hardened layer and avoid crack generation; clean the oil stains on the inner and outer walls of the base metal until metallic luster is achieved to enhance the weld bonding strength.

[0045] (4) Set the welding parameters according to the groove type and the thickness of the base metal:

[0046] (5) Perform welding operations on the steel column, platform railing, and connecting beam. The welding method is:

[0047] For welds longer than 1 m, use the segmented backstep welding method, and stagger the layer joints by more than 30 mm; the maximum thickness of the root pass is 6 mm, and the root fillet size of the fillet weld is ≤8 mm for flat welding, ≤7 mm for horizontal welding and overhead welding, and ≤10 mm for vertical welding; the segmented backstep welding method reduces the linear shrinkage stress of long welds. Combined with the reverse deformation method and rigid fixation measures, the welding deformation of the steel column and platform railing is reduced by more than 30%, ensuring the structural installation accuracy.

[0048] (6) After welding, the cleaning personnel clean the weld slag and spatter layer by layer, and the quality inspection personnel check the interlayer quality in real time;

[0049] (7) After welding is completed, the cleaning personnel remove the residues on the weld surface, the quality inspection personnel conduct visual inspection, and the non-destructive testing personnel extract 30% of the butt welds of the steel column for ultrasonic non-destructive testing. Conduct ultrasonic testing on 30% of the butt welds of the steel column. Combined with the DL / T5210.5 - 2018 standard, ensure that the defect detection rate of key parts is ≥95% to avoid the risk of missed detection.

[0050] In the step (5), welding is carried out by carbon dioxide gas shielded arc welding or manual arc welding. For carbon dioxide gas shielded arc welding, use Φ1.2 welding wire, and the welding parameters are: current 110 - 185 A, voltage 19 - 34 V; for manual arc welding, use Φ3.2 welding electrode, and the welding parameters are: current 110 - 140 A, voltage 22 - 24 V.

[0051] In the step (3), after the groove preparation is completed, the hardened layer and overheated metal need to be removed;

[0052] The butt joint misalignment control of the welded parts is:

[0053] For class II welds, the misalignment is ≤15% of the plate thickness and ≤3 mm, applicable to the welds at the connection of the platform railing;

[0054] For class III welds, the misalignment is ≤20% of the plate thickness and ≤4 mm, applicable to the welds of secondary support beams.

[0055] In step (5), welding deformation is controlled by the following measures:

[0056] Steel columns are provided with a reserve weld shrinkage allowance;

[0057] The connecting beam uses the reverse deformation method to pre-adjust the weldment assembly angle;

[0058] The free deformation of the platform railing is limited by the rigid fixing method;

[0059] The construction shall be carried out in the sequence of segmented assembly and welding, with priority given to welding the main steel frame column welds.

[0060] In the step (7), the weld appearance inspection comprises the following steps:

[0061] There are no cracks, slag inclusions or pores on the surface of the butt weld of the steel column;

[0062] The undercut depth of the platform railing corner weld is ≤0.5mm.

[0063] The requirements for the welding environment are:

[0064] The welds of steel columns in low temperature environments are flame preheated and dehumidified;

[0065] Wind and rain protection facilities shall be set up in the open-air working area, and the grounding resistance of the welding machine shall be ensured to be ≤4Ω;

[0066] The cylinder manager shall control the distance between oxygen cylinders and acetylene cylinders to be ≥10m, and acetylene cylinders shall be equipped with backfire preventers.

[0067] Also includes welding material management methods:

[0068] Welding rods for steel columns need to be dried before use;

[0069] The welding wire for platform railings needs to be cleaned of surface oil and oxide film;

[0070] The welding technician must issue a receipt for welding materials, clearly stating that they are used for welding of steel columns or connecting beams.

[0071] It also includes post-construction environmental cleanup:

[0072] Scrap recycling personnel uniformly handle the welding rod heads and slag of the steel column welds;

[0073] Isolate operators to set up isolation areas for platform railing grinding wheel cutting operations to reduce dust;

[0074] Equipment maintenance personnel regularly inspect and repair the connecting beam welding machinery to reduce noise emissions;

[0075] The hazardous materials manager seals the oil containers used for anti-corrosion coating of steel columns to prevent leakage and evaporation.

Claims

1. A fluidized bed circulating boiler steel structure welding construction method, characterized in that: The following steps are involved: (1) Clean the oil and oxide film on the surface of the welding wire; (3) Prepare a blunt-edged single-sided V-shaped groove for the butt weld of the steel column, and clean the oil and rust on the groove surface and the inner and outer walls of the parent material until the metallic luster is achieved. The cleaning range is 10-20 mm on both the inner and outer sides of the parent material; (4) Set welding parameters according to groove type and base material thickness: (5) Perform welding operations on steel columns, platform railings and connecting beams. The welding method is: For welds longer than 1m, the segmented back-welding method is adopted, and the joints between layers are staggered by more than 30mm; the maximum thickness of the root weld is 6mm, and the root leg size of the fillet weld is ≤8mm for flat welding, ≤7mm for horizontal welding and overhead welding, and ≤10mm for vertical welding; (6) After welding, the cleaning personnel clean the weld slag and spatter layer by layer, and the quality inspection personnel check the interlayer quality in real time; (7) After welding is completed, the post-weld cleaning personnel remove the residue on the weld surface, the quality inspection personnel conduct an appearance inspection, and the non-destructive testing personnel select 30% of the steel column butt welds for ultrasonic non-destructive testing.

2. The method for welding the steel structure of a fluidized bed circulating boiler according to claim 1, characterized in that: In the step (5), welding is performed by carbon dioxide gas shielded welding or manual arc welding. The carbon dioxide gas shielded welding uses a Φ1.2 welding wire with welding parameters of current 110-185A and voltage 19-34V; the manual arc welding uses a Φ3.2 welding rod with welding parameters of current 110-140A and voltage 22-24V.

3. The method for welding the steel structure of a fluidized bed circulating boiler according to claim 1, characterized in that: In the step (3), after the groove preparation is completed, the hardened layer and overheated metal need to be removed; The control of weldment misalignment is as follows: Class II weld misalignment ≤15% plate thickness and ≤3mm, applicable to the welds at the platform railing joints; Class III weld misalignment is ≤20% of plate thickness and ≤4mm and is applicable to secondary support beam welds.

4. The method for welding the steel structure of a fluidized bed circulating boiler according to claim 1, characterized in that: In step (5), welding deformation is controlled by the following measures: Steel columns are provided with a reserve weld shrinkage allowance; The connecting beam uses the reverse deformation method to pre-adjust the weldment assembly angle; The free deformation of the platform railing is limited by the rigid fixing method; The construction shall be carried out in the sequence of segmented assembly and welding, with priority given to welding the main steel frame column welds.

5. The method for welding the steel structure of a fluidized bed circulating boiler according to claim 1, characterized in that: In the step (7), the weld appearance inspection comprises the following steps: There are no cracks, slag inclusions or pores on the surface of the butt weld of the steel column; The undercut depth of the platform railing corner weld is ≤0.5mm.

6. The method for welding the steel structure of a fluidized bed circulating boiler according to claim 1, characterized in that: The requirements for the welding environment are: The welds of steel columns in low temperature environments are flame preheated and dehumidified; Wind and rain protection facilities shall be set up in the open-air working area, and the grounding resistance of the welding machine shall be ensured to be ≤4Ω; The cylinder manager shall control the distance between oxygen cylinders and acetylene cylinders to be ≥10m, and acetylene cylinders shall be equipped with backfire preventers.

7. The method for welding the steel structure of a fluidized bed circulating boiler according to claim 1, characterized in that: Also includes welding material management methods: Welding rods for steel columns need to be dried before use; The welding wire for platform railings needs to be cleaned of surface oil and oxide film; The welding technician must issue a receipt for welding materials, clearly stating that they are used for welding of steel columns or connecting beams.

8. The method for welding construction of a fluidized bed circulating boiler steel structure according to claim 1, characterized in that: It also includes post-construction environmental cleanup: Scrap recycling personnel uniformly handle the welding rod heads and slag of the steel column welds; Isolate operators to set up isolation areas for platform railing grinding wheel cutting operations to reduce dust; Equipment maintenance personnel regularly inspect and repair the connecting beam welding machinery to reduce noise emissions; The hazardous materials manager seals the oil containers used for anti-corrosion coating of steel columns to prevent leakage and evaporation.

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