The influence of buffer layer on the properties of surface welded joint of high-carbon steel

Abstract

Surface welding with buffer layer is often in use because of its well-known properties of plasticity, or ability to slow crack growth initiated. However, in modern surface welding technologies, buffer layer is rarely used. New classes of flux-cored and self-shielded wires are recently developed and it is possible to achieve the requested properties of welded joints without buffer layer. In this paper, for comparison, the high-carbon steel surface was welded with and without buffer layer. In both cases, it has been used same surface process, but with different filler materials and equal heat input. The mechanical properties, total impact energy, as its components, the fatigue threshold value of Delta K-th, and the crack growth rate da/dN were determined. The results obtained at room temperature show better properties of the sample surface welded with the buffer layer, but, with temperature decrease a sharp decrease of toughness of the sample welded with buffer layer occured. Also, buffer layer didn't change the property of initiated crack in terms of crack growth rate. The construction from high-carbon steel are exposed to low exploitation temperature and are used for prolong working time, thus the use of buffer layer in modern surface welding technologies is not recommended.