Investigation for Quality Estimation Mechanism of Gas Pressure Welds

A Non-destructive Inspection Method of Gas Pressure Welds with Buldge Removal by Hot Shearing (Report 2)

Abstract

The previous report has clarified that the quality of gas pressure welds is influenced by local area expansion factor (α) and weld temperature (T) and that, moreover, the fracture observation helps to evaluate the quality of welds.
In this paper we report on a study about the quality estimation mechanism and the reliability of this inspection method. The conclusions are as follows;
(1) Bright or black flat fracture is found around the forced break fracture of gas pressure welds in which are observed line flaws on the surface.
(2) Line Haw, if bonding work is poor, is caused by hot shearing.
(3) The micro-observation results of bonding interface agree with the fracture form.
(4) The transition from flat fracture to crystalline fracture is influenced by α and T.
(5) It is impossible to detect light coarse welds, which present a gray flat fracture, by this inspection method. However, such welds have enough strength for practical use.