Porosity caused by hydrogen in horizontal fillet welding

Abstract

In order to investigate the behavior of porosity caused by hydrogen in horizontal fillet welding, the growth and the distribution of porosity were studied using flux coated electrodes with varions water contents.
1. Growth of porosity The growth of porosity becomes most remarkable when the hydrogen content of the weld is in a certain value, i.e. 15-17 cc/ 1OOg as diffusible hydrogen content. At higher hydrogen content, the pores become Smaller and porosity formation changes to bubbling type from non bubbling type. In bubbling type, the special solidification lines appear in the solidification structure of the pheriphery of pore.
These lines may be caused by the rise of bubble from the pore to the molten pool. In consequence of this behavior, the growth of prosity becomes difficult and smaller pore are formed.
2. Distribution of porosity According to the measurements of length and diameter of pore, pores in a weld may be clasified into following 2 categories:
A. Pores with length shorter than l₁ (-1.2 mm)
B. Pores with length longer than l₂ (l₂<l₁)
And the proes with length l₁-l₂ are very few.
This tendency may depend on the movement and the hydrogen content of molten pool.
Morevoer this may be interpreted by a view of probability which is assumed to be decided by the relative position of pore-molten metal interface for solid-molten metal interface.