Views: 3 Author: Site Editor Publish Time: 2016-11-25 Origin: Site
You must have seen all welded ball valve body, all know welding joint are generally designed for thick wall narrow gap submerged arc welding, and all welded body mostly large thickness tubular welded joint.You must want to know is this why?
1: heat treatment technology
Thick wall multi-layer welding process is the process of metal material repeated heating and cooling, leading to the nonuniformity of welding joint organization and inferior, produce the high residual stress, and even produce welding defects.Welding is a process with the final after the product assembly, the valve cavity with nonmetal sealing material rubber and ptfe plastics, cannot undertake heat treatment after welding.
2: tapping processing
The body in the design of welding joint for alignment and positioning, in the presence of a ring of the weld root assembly gap, the gap under internal pressure and external load, will produce a few times the normal job stress of stress concentration, also make the engineers are difficult to deal with.
Fully welded ball valve body welding joint the root of the gap of stress concentration, residual stress, the organization of inferior become weak link in the body structure, is attention at home and abroad, but did not see any reports related to solve the problem, become a hidden danger of the boundary of this product structure integrity.