An investigation is made on the hydrogen absorption in a molten pool of weld metal.
JIS hydrogen test has been commonly used for the quantitative analysis of diffusible hydrogen content in weld metal. It is found that the estimation of hydrogen content in a molten pool from this method is incorrect due to the dependency of the results on test conditions.
The causes are;
1) It must take more than 5 sec after an arc off up to quenching a specimen in water.
2) The hydrogen diffused from deposited to the base metal during welding is accounted for the greater part of hydrogen collected by this method.
From these resaons the new technique is devloped, which can measure the hydrogen content in a molten metal immediately after an arc off.
A specimen is melted by a tungsten electrode in Ar-H₂ mixture in a copper crucibles and tightly closed in it immediately after an arc off.
Hydrogen evolved from the specimen is laed to an oxidising furnace and accumlated in a cold trap as ice. The stored ice is determined by the volumetric analysis after its conversion to vapor.
The relation between hydrogen partial pressure in the arc atmosphere and absorbed hydrogen in a molten pool obeyed a law of square root within PH₂<0.2 atm. in pure irons, low carbon steels, 1.7%Mn steels, 18-8 and 15-35 stainless steels. Hydrogen absorption in the arc melting, if it corrected using activity coefficients of C, Si, Mn, Ni and Cr on hydrogen, is nearly alike in every material and yield to Sievert's law in the temperature range of 2000-2200°C, taking into account the acivities and steel making data.