BOOM/ARM MEMBER FOR CONSTRUCTION MACHINE, HAVING HIGH WELDED PORTION FATIGUE STRENGTH, AND METHOD OF IMPROVING THE FATIGUE STRENGTH

摘要

A boom/arm member for a construction machine, having high welded portion fatigue strength, and a method of increasing the fatigue strength. An end part of a fully penetrated welded section of the boom/arm member has a struck mark by vibration. Preferably, a residual stress in the bottom surface of the struck mark is a compression residual stress of not less than 10 Mpa.