MIG Welding Under High Pressure Ar Arc Atmosphere

Abstract

MIG welding under high pressure Ar atmosphere (0-6 MPa) has been studied by means of welding chamber. Effects of pressure on the arc voltage, welding current and weld metal shape are studied.
MIG welding process by constant arc voltage condition and constant arc length condition are compared.
The main results are summarized as follows;
1) Increasing pressure from 0 to 6 MPa, arc became to constrictive, plural cathode spots and unstable arc were observed.
Brightness of arc column was increased. A lot of spattered droplets and fine particles were produced.
2) As welding s carried out using constant arc voltage condition, welding current was decreased above about 2 MPa.
Decreasing of heat input under high pressure was observed. Crowned weld metals, narrow bead width, weld metals which was not deep penetration were shown.
3) As welding was carried out using constant arc length condition, arc voltage was raised remarkably with pressure then also, heat input was increased.
Crowned welds were not obtained. Bead width, penetration depth were not changed remarkably in-creasing pressure from 0 MPa to 6 MPa. Area of HAZ was affected by increasing pressure. Tensile and bending test results were satisfactory under condition of this study.
4) It was estimated that constant arc length condition is good for MIG welding process under high pres-sure arc atmosphere.