In recent years, it has been some discussions about reducing cost and labor in bridge fabrication. As the way of reducing this cost, automatic welding or high efficiency welding will be increasingly used Automation has recently extensively developed in many factories, however, it is only few case using high efficiency welding. For this reason. Specifications for Highway Bridge regulates limited heat input considering embrittlement and softening (maximum heat input is 70KJ/cm on SM570). The authors investigated charpy absorbed energy on the basis of many technical reports by using high heat input welding in order to examine the effect of embrittlement. In this paper, it is investigated Vickes hardness and tensile strength to examine the effect of softening. From the results of their investigations, the authors propose limited heat input considering both embrittlement and softening.
