Effects of multi-pass arc welding on mechanical properties of carbon steel C 25 plate

Abstract

The effects of multi-pass welding on mechanical properties of C25 carbon steel plate were examined. Mild steel plate workpieces of 90 x 55 mm2 area and 10 mm thickness with a 30 o vee weld-grooves were subjected to single and multi-pass welding. Toughness, hardness and tensile tests of single and multi-pass welds were cond-ucted. Toughness values of the welds under  double pass welds were higher than both single pass and unwelded alloy, at respective maximum values of 2464, 2342 and 2170 kN/m. Hardness values were reduced under do-uble pass relative to single pass welding with both being lower than the value for unwelded alloy; the values were 40.5, 43.2 and 48.5 RB respectively at 12 mm from the weld line. The tensile strength of 347 N/mm2 under multi-pass weld was higher than single pass weld with value of 314 N/mm2. Therefore, the temperature distrib-ution and apparent  pre-heating during multi-pass welding increased the toughness and tensile strength of the weldments, but reduced the hardness.