| Abstract |
| SM45C steel was welded by conventional CO2 arc and narrow gap welding (NGW). The fatigue strength of NGWed sample had a value about 90 MPa higher than that of the CO2 arc welded sample. The width of welding and heat affected zone in NGWed samples decreased about 40% compared to the conventional CO2 arc welded sample. The hardness value of the welding zone in the NGW sample was 33.3% higher than that of the CO2 arc welded sample. The microstructure change of the SM45C during NGW revealed that the matrix was transformed to the martensite phase. With the small width of welding and heat affected zone in the NGW, therefore, the specimen with NGW had a faster cooling rate after welding. We therefore concluded that the hardness was increased by hard martensite formation during cooling after NGW, and this increase in hardness resulted in better fatigue strength of SM45C steel compared to conventional CO2 arc welding. (Received March 13, 2014) |
|
|
| Key Words |
| SM45C, welding, fatigue, hardness, narrow gap welding |
|
|
 |
|
