The following is the related content of welding deformation and flame correction construction method of steel structure brought by Zhong Da Consulting for your reference.

At present, steel structures have been widely used in factory buildings. The main components of steel structure workshop are welded H-beam columns, beams and supports. These parts have welding deformation problems in the manufacturing process. If the welding deformation is not corrected, it will not only affect the overall installation of the structure, but also reduce the safety and reliability of the project.

The deformation of welded steel structure exceeds the allowable deformation range of technical design and should be corrected to meet the product quality requirements. Practice has proved that most deformed members can be corrected. The correction method is to try to create a new deformation to offset the existing deformation.

The commonly used correction methods in the production process mainly include mechanical correction, flame correction and comprehensive correction. Flame correction is a difficult process to operate, and improper method control and temperature control will cause new and greater deformation of parts. Therefore, flame correction should have rich practical experience. In this paper, the types and correction methods of welding deformation of steel structure are roughly analyzed.

1. Types of welding deformation of steel structure and flame correction

The main components of steel structure are welded H-beam columns, beams and braces.

Welding deformation often adopts the following three flame correction methods:

1) linear heating method;

2) point heating method;

3) Triangle heating method. The heating temperature of flame correction (low carbon steel) is: low temperature correction 500 ~ 600 degrees, and the cooling mode is water; The medium temperature is corrected to 600 ~ 700 degrees, and the cooling mode is air and water; High temperature correction 700 ~ 800 degrees, cooling mode: air. Attention: The heating temperature should not be too high during flame straightening, which will cause the metal to become brittle and affect the impact toughness. 16Mn cannot be cooled by water during high temperature correction, including steel with large thickness or hardening tendency.

Second, the measures taken against all kinds of deformation

1. Angular deformation of flange plate

Correct the deformation of H-beam columns, beams and supports. Longitudinal linear heating (the heating temperature is controlled below 650 degrees) is carried out on the flange (outside the alignment weld), and the heating range cannot exceed the control range of two welding legs, so water is not used for cooling.

Attention should be paid to linear heating:

1) should not be heated repeatedly in the same position;

2) Do not water when heating. These two points are the general principles of flame correction.

2. Upward arching, downward deflection and bending of columns, beams and supports

1) On the flange plate, the bending deformation can be corrected by linearly heating the longitudinal weld from the middle to both ends. In order to avoid bending and deformation, the two heating belts should be synchronized. Low temperature correction or medium temperature correction can be adopted. This method is beneficial to reduce welding internal stress, but it is difficult to master because it shrinks longitudinally and laterally at the same time.

2) Flange plate is heated linearly and web plate is heated triangularly.

This method is effective for correcting the bending deformation of columns, beams and braces. Generally, the transverse linear heating width is 20 ~ 90 mm When the thickness of the plate is small, the heating width should be narrow, and the heating process should extend from the middle of the width to both sides. Linear heating is best done by two people at the same time, and then the triangles are heated separately. The width of the triangle should not exceed twice the thickness of the plate, and the bottom of the triangle is equal to the linear heating width of the corresponding wing plate. The heating triangle starts from the top, then expands from the center to both sides, and is heated layer by layer until the bottom of the triangle. When heating the web, the temperature should not be too high, otherwise it will cause depression and deformation, which is difficult to repair.

Thirdly, the angle heating method is also suitable for the lateral bending correction of components. Proper temperature correction should be adopted when heating, and less water should be used.

3. Wave deformation of columns, beams and supporting webs

To correct the wave deformation, we must first find the convex peak, use the point heating method and correct it with a hammer. The diameter of heating spot is generally 50 ~ 90 mm, and the diameter should be increased when the thickness of steel plate or corrugated area is large, and d=(4δ 10) mm (d is the diameter of heating spot; Delta is the plate thickness). The heating and roasting nozzle moves spirally from the highest point and adopts medium temperature correction. When the temperature reaches 600 ~ 700 degrees, put a hammer on the edge of the heating area, then squeeze the metal in the heating area with a sledgehammer, and then flatten it after cooling and shrinking. Excessive shrinkage stress should be avoided during calibration. After correcting one point, heat the second peak point, as described above. In order to speed up the cooling rate, Q235 steel can be cooled by adding water. This correction method belongs to point heating method, and the distribution of heating points can be plum blossom or chain dense points. Be careful not to exceed 750 degrees.

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The stress produced by flame correction is internal stress and welding internal stress. Improper correction, superposition of internal stress caused by welding internal stress and load stress will make the longitudinal stress of columns, beams and supports exceed the allowable stress, which will lead to the reduction of the safety factor of bearings. Therefore, the fabrication of steel structures must be cautious, reasonable technological measures should be adopted as far as possible to reduce deformation, and mechanical correction should be adopted as much as possible.

When flame correction must be used, the following points should be noted:

1) The baking position shall not be close to the maximum stress section of the main girder;

2) The fire area of the correction site should not be too large on one section, and several sections should be selected;

3) Point heating should be used to improve the stress state in the heating zone;

4) The heating temperature shall not exceed 700 degrees.

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