After the position of the welding parts is determined, they can be fixed with a jig or location weld, and then the formal welding.The quality of the position weld directly affects the quality of the weld, which is an integral part of the formal weld.And because of its short weld pass and fast cooling, it is easy to produce welding defects. If the defects are covered by the formal weld and not found, it will cause hidden dangers.There are the following requirements for position welding.
(1) welding rod
The electrode used for positioning welding should be the same as that used for formal welding, and it should be re-dried before welding.Do not use waste electrode or unknown type electrode.
(2) location of welding
Double-sided welding and the back of the root to clear the weld, the positioning weld is best arranged on the back;For members of symmetrical shape, positioning welds should be arranged symmetrically;Where there are cross welds, no position welds should be set. At least 50mm away from the intersection.
(3) Welding process
Welding conditions should be the same as the formal weld welding, due to short weld bead, fast cooling, welding current should be greater than the normal welding current 15%~20%.For the welding parts with large stiffness or quenching tendency, preheating should be appropriate to prevent cracking of the positioning weld;When the arc is closed, the hole is filled with arc pit to prevent the cracking.In permitting conditions, can choose good plasticity and crack resistance and slightly lower strength of the welding electrode for location welding.
(4) Weld dimension
The size of the positioning weld depends on the rigidity of the structure. The principle to be mastered is to be as small as possible under the premise of meeting the requirements of assembly strength.In order to reduce the deformation and filling metal, the spacing of positioning welding can be reduced to reduce the size of positioning joint.
2021-01-08 
