Fatigue properties of welded joints of high-carbon steels

The typical too] steels of the wood-cutting industry are the unalloyed and chromium and nickel containing, low-alloyed eutectoid steels. These materials, in tempered condition have a very high, 1200-1400 MPa tensile strength. One of the major failure forms of these tools is the fatigue fracture of the tool. The high pretension and the cyclic load, caused by the cutting and the bending of the tool, easily can cause high-cycle fatigue fracture, especially at the welded area and at the heat affected zone. Thus, one of the most critical part in the manufacturing process of the handsaw blade is the welding. We have examined the fatigue properties of three types of joints: conventional and cold wire TIG welding, MIG welding, and resistance-butt welded joints. The structure at the weld and at the heat affected zone could highly affect the life-span of the tool. Therefore the welding parameters (preheat, post welding heat treatment (PWHT), shield gas, backing gas), affecting the microstructure of the weld, also have serious affects on the fatigue properties. The influence of welding parameters on the fatigue properties were examined by low-cycle fatigue test.