Technical treatment of fully welded ball valve body

Everyone must have seen the valve body of fully welded ball valves, and it is known that welding joints are generally designed for narrow gap thick wall submerged arc welding. Additionally, fully welded valve bodies are mostly designed for ultra thick cylindrical welding joints. Everyone must want to know why?

1: Heat treatment technology treatment

The thick walled multi-layer welding process is a process of repeated heating and cooling of metal materials, resulting in uneven and inferior microstructure of welded joints, high residual stress, and even welding defects. Welding is the next process after the assembly of the product, and there are non-metallic sealing materials such as rubber and polytetrafluoroethylene plastic in the valve chamber, which cannot be subjected to post weld heat treatment.

2: Joint treatment

In the design of valve body welding joints, for alignment and positioning, there is a circular assembly gap at the root of the weld seam. This gap, under the action of internal pressure and external loads, will generate stress concentration several times the normal working stress, which also makes it difficult for engineers to handle.

The stress concentration and residual stress in the root gap of the valve body welding joint have become weak links in the valve body structure due to poor organization, which has attracted attention from the valve industry both domestically and internationally. However, there have been no relevant reports to solve this problem, which has become a hidden danger to the structural boundary integrity of this product.