What are the control measures for welding deformation of sheet metal?


1. Design measures

(1) Choosing reasonable weld size:

With the increase of weld size, the deformation will increase, but too small weld size will reduce the load-bearing capacity of the structure, and make the cooling rate of the welded joint increase, and the hardness of haz will increase, it is easy to produce cracks and other defects, so the minimum weld size should be selected with the thickness of the plate, which can satisfy the load-bearing capacity of the structure and ensure the welding quality.

(2) To reduce the number of welds as much as possible:

To reduce the number of ribbed plates by choosing the appropriate thickness of plates, so as to reduce the correction amount of welds and post-weld deformation, such as thin-plate structural members, which can be replaced by a press-type structure, to reduce the number of weld to prevent or reduce post-weld deformation.

(3) Reasonable arrangement of weld position:

The bending deformation can be reduced when the weld is symmetrical to the neutral axis of the weld section or if the weld is close to the neutral axis.

(4) Setting aside shrinkage allowance:

The longitudinal and transverse shrinkage deformation after welding can be controlled by estimating the weld shrinkage allowance.

(5) Leaving the position of the welding fixture:

The position of the welding fixture can be left on the structure, so that the technical deformation can be controlled by using the fixture during the welding process.

2. Anti-deformation method

(1) Single-side V-groove butt welding of plate thickness 8-12mm, with 1.5°reverse deformation during assembly and almost no angular deformation after welding.

(2) The angle deformation caused by transverse contraction of i-beam after welding, if the upper and lower cover plates are pressed into reverse deformation (plastic deformation) before welding, and then welded after assembly, the welding fillet deformation of the upper and lower cover plates can be eliminated. However, the magnitude of the reverse deformation of the upper and lower cover plates is mainly related to the thickness and width of the plate, as well as the web thickness and heat input.

(3) The tube joints of boiler and container are all concentrated on the upper part, which cause bending deformation after welding, so the forced anti-deformation clamping device should be used, and the trace sequence of symmetrical and even heating should be matched, in this way, the elastic back deformation under external force is combined with a reasonable heating sequence, and the bending deformation can be basically eliminated after welding.

(4) The two main beams of the bridge crane are box-shaped structures composed of the left and right webs and the upper and lower cover plates, and the fillet welds of these ribs are mostly concentrated on the upper part of the beam, which will cause the bending deformation of the lower radius after welding. In order to solve the contradiction between the deformation after welding and the technical requirements, the method of precast web camber is often used, that is, when the material is prepared, the two webs are pre-cambered.

3. Rigid fixation

The external rigid restraint is applied to the welding parts before welding, and the welding parts can not deform freely during welding.

(1) When welding flanges, fixing the two flanges back to back can effectively reduce the angular deformation.

(2) When the thin plate is butt-jointed, the press iron is used around it to prevent the wave deformation after the thin plate is welded. After welding, when the restraint is removed, there will still be a little deformation on the weldment, but it is much less than the original.

4. Choose reasonable welding sequence

The welding sequence has great influence on the welding structure. Improper welding sequence will affect the smooth progress of the whole process. More attention should be paid to the reasonable arrangement order for the asymmetrical welded structural parts.

(1) If i-beam can be two people at the same time welding.

(2) When the recovery arrangement is not symmetrical, the less side of the weld should be welded first, because the deformation of the welding seam is large at first, and then the deformation caused by the more welding seam on the other side should be compensated for the deformation caused by the welding seam at first, the deformation of the whole structure can be greatly reduced.

(3) The deformation of straight-through welding is the largest when the long weld is welded, which is the result of the long-time heating of the butt welding part by continuous welding, and the continuous welding should be changed to discontinuous welding when possible, it can reduce the plastic deformation of weld and base metal due to the increase of heating surface.

5. Heat dissipation

During welding, the heat in the welding area is dispersed by forced cooling method (water-jet cooling method) , and the heated area is reduced greatly, so as to reduce the deformation. Such as the use of heat dissipation method can reduce welding deformation, but it is not suitable for welding hardened higher parts.

6. The self-weight method

If there are more upper welds than lower welds, the i-beam will bend upward after welding. If the i-beam is turned over and placed at two end points, the bending deformation after welding can be gradually offset by the bending trend of the beam's self-weight. After a certain time, the beam will be flat or have only a small amount of bending deformation, the key is that the distance between the two piers must be selected properly.


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Post time: Nov-16-2022