1989 Volume 7 Issue 4 Pages 501-506
Effect of ambient pressure on mechanical properties of mild steel welded joints obtained by gravity arc welding process was investigated. Welding was executed by low hydrogen type electrode of 4 mm in diameter under pressure range from 0.1 to 5.1 MPa (abs.). As base metals, SM41A steel plates of 6 and 9 mm in thickness were used.
Main results obtained are summarized as follows:
1) Charpy impact value of weld metal decreases considerably with an increasing pressure. The tensile strength and the elongation decrease somewhat and the average hardness increases slightly with it.
2) As the pressure increases, volume of pearlite in weld metal increases and the structure tends to be bainitic. The grain size of dendrite tends to decrease.
3) As the pressure increases, content of diffusible hydrogen in deposited metal (HD) increases up to about I MPa, however, it tends to decrease over that pressure.
4) As the pressure increases, content of Si and Mn in weld metal decreases and content of C and O increases considerably. Content of P and S is approximately constant regardless of pressure.
5) Mechanical properties of weld metal decrease with an increasing pressure, because the content of C, O and H in weld metal increases with it.
