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Measures To Prevent And Reduce Structural Deformation

Mar 14, 2018

1) reduce the cross-sectional area of the weld: as far as possible, the smaller groove size (Angle and clearance) should be adopted as far as possible.

2) under the yield strength of 345MPa, the hardened steel is adopted with a smaller thermal input, and the preheating and interlayer temperature is not preheated or properly reduced.Heat input is preferred for smaller welding methods such as CO2 gas shielded welding. 

3) thick plate welding shall replace single layer welding as much as possible. 

4) double-sided can welding operation, should use double-sided symmetrical groove, and multi-layer welding with welding components and axisymmetric 6) use the before welding deformation control method after welding angular distortion, which makes the production of one of the most common method, and the weldment in advance to make basic offset (compensation).

The reverse deformation after welding is used to prevent deformation after welding.Table 1 and FIG. 4 are respectively the reverse deformation of box column and h-beam welding.

7) rigid fixed method: also known as compulsory method.In the actual production, there is less deformation after welding of rigid and large components, and the rigidity of the components can be strengthened before welding, and the deformation response is reduced after welding.When using this method, must wait for cooling after welding fixture and support to be lifted up. Several common methods have a jig, support method, method of clamping fixture, temporary fixed method (such as welding nail fixed and fixed clamping method), positioning welding method. 

8) hammer weld method: this method is mainly applicable to the welding of thin plates.When the weld of the sheet and its thermal impact zone are not completely cooled, hammer the area immediately, and the thick plate is hit with the air gun.

9) the longitudinal shrinkage deformation of the welding seam is compensated by using the component reserved length method. 

10) to minimize the number and size of welds in design;Reasonable layout of the weld, in addition to avoid the weld density, should also make the weld position as close to the axis of the components as possible, and make the weld layout and components.

Relative to the axis. 

11) select the welding sequence correctly.In the steel structure, when there is a weld and fillet weld, in principle, the weld shall be welded to the weld and the arc weld.For the cruciform and t-type welds, the correct order should be taken to avoid welding stress concentration and ensure the welding quality of joints.It is advantageous to reduce deformation by adopting the welding of the neutral axis of the whole steel structure and taking the welding from the middle phase.Welding of important parts in steel structure with high strength should be free to contract and not be restrained.

Iv. Post-welding correction method of welding deformation:

In order to meet the design specification requirements, and the welding deformation of welded structures must be correct, from another Angle to explain, this correction are essentially trying to cause a new deformation to compensate for offset or has happened.In the construction and production, the most commonly used correction methods of post-weld residual deformation can be divided into the application of the combination of the applied force correction and the heating correction and the two methods. 

4.1 force correction method:

The force correction is usually done with a jack, a screw, a roller, or a large pressure machine. 

4.2 heating correction method:

In other words, the deformation of the structure is compensated or offset by uneven heating.The heating method can be divided into point heating, linear heating and triangle heating.Rectification can eliminate a lot of shi LiJiao are unable to solve the deformation, master the regular pattern of flame heating caused by the deformation is the key to make correction, decide the position of the main effect of flame correction is heating and heating temperature.

The welding structure of low carbon steel and ordinary alloy usually adopts the heating temperature of 650 ~ 8000C, which is generally not more than 9000C.