Control welding deformation methods

1. Design measures

(1) Select a reasonable weld size.

Weld size increases, the deformation increases, but too small weld size will reduce the load-bearing capacity of the structure, and make the welded joint cooling speed up, heat-affected zone hardness increases, easy to produce cracks and other defects, so should meet the structural load-bearing capacity and ensure the quality of welding under the premise that with the thickness of the plate to select the process may choose the smallest weld size.

(2) Minimize the number of welds;

Appropriate selection of plate thickness, reduce the number of ribs, which can reduce the amount of weld seams and post-welding deformation correction, such as thin plate structural parts, available pressure structure instead of ribbed structure to reduce the number of welds, to prevent or reduce post-welding deformation.

(3) reasonable arrangement of the weld position.

Weld symmetry in the weld section of the neutral axis or make the weld close to the neutral axis can reduce the bending deformation.

(4) Allowance for shrinkage.

Longitudinal transverse shrinkage deformation after welding can be controlled by estimating the amount of shrinkage of the weld, leaving a shrinkage allowance in advance when designing.

(5) leave the location of the welding fixture.

The position of the welding fixture can be left on the structure so that the fixture can be used to control the technical deformation during the welding process.

2. Anti-deformation method

(1) plate thickness of 8 to 12 mm steel plate single-sided V-bevel butt welding, assembly anti-deformation 1.5 ° welding after almost no corner deformation.

(2) I-beam welding angle deformation caused by transverse shrinkage, if the use of welding before the upper and lower cover plate pressed into anti-deformation (plastic deformation), and then assembly after welding, you can eliminate the upper and lower cover plate after welding angle deformation. But the size of the upper and lower cover plate anti-deformation is mainly related to the thickness and width of the plate, but also with the thickness of the web and heat input.

(3) boilers, containers of pipe joints are concentrated in the upper part, after welding caused by bending deformation so to borrow forced anti-deformation clamping device, and with symmetrical uniform heating trace order, alternating jump welding method so that the use of the external force under the action of the elastic anti-deformation and then with a reasonable heating of the welding sequence, after welding can basically eliminate the bending deformation.

(4) the two main beams of the overhead crane is composed of left and right webs and upper and lower covers of the box structure in order to improve the rigidity of the beam, the beam is designed with large and small ribs, and most of these ribs corner welds are concentrated in the upper part of the beam, after welding will cause bending deformation under the radius. However, the technical requirements of the bridge crane stipulate that the main beam should have a certain degree of arch after welding. To solve the contradiction between the post-welding deformation and technical requirements, the method of prefabricated web arch is often used, i.e., when preparing the material, the two webs are pre-made to leave the arch.

3. Rigid fixation method

Before welding to the welded parts using an external rigid restraint, forced welding parts in the welding can not be free deformation.

(1) when welding flanges, the two flanges back-to-back fixed can effectively reduce the corner deformation.

(2) thin plate butt joint, in the he side of the surrounding with pressure iron, to prevent the thin plate after welding wave deformation.

After welding, when the applied constraint removed, the weld will still remain slightly deformed, but much less than the original, the method will make a large welding stress in the welded parts, so the weld should be used with caution for materials prone to cracking.

4. Choose a reasonable assembly welding sequence

The welding sequence has a great impact on the welded structure. Improper assembly and welding order will affect the smooth progress of the entire process. Asymmetrical welded structural parts, more attention should be paid to the reasonable arrangement of the order.

(1) Such as I-beam can be welded by two people at the same time.

(2) When the response arrangement is not symmetrical should first weld less side, because the first weld deformation, and then use the other side of the more weld-induced deformation to offset the first weld-induced deformation, can greatly reduce the overall structure of the deformation.

(3) long weld seam welding, straight through welding deformation is the largest, which is the result of continuous welding of the welded parts for a long time heating, where possible, continuous welding should be changed to intermittent welding, can reduce the weld and the base material due to the increase in the heating surface and plastic deformation.

5. Heat dissipation method

Welding with forced cooling method to dissipate the heat of the welded area (with water spray cooling method), forcing the heated area is greatly reduced, thereby reducing the deformation of the purpose.

Such as the use of heat dissipation method can reduce welding deformation, but it is not suitable for welding hardened welded parts.

6. Self-weight method

If there are more welds in the upper part of the I-beam than in the lower part, the I-beam will be bent upward after welding.

If the I-beam is turned over and set aside, the two pier points will be placed at the two end points, so that the self-weight bending tendency of the beam can be used to gradually offset the bending deformation after welding, and the beam will be flat or have only a small amount of bending deformation after being placed for a certain period of time, the key is that the distance between the two pier points must be chosen properly.