An interesting field of application in hardfacing is reconditioning of hardened tools, such as shear blades, punching dies, cutting edges, deep-drawing tools, etc. For this purpose, the so-called “step hardening weld method” has proven a success. Welding is carried out in the delayed transformation range which is situated between the perlite and bainite zones of TTT-curves of the steel in question. Thereby, the hardenability of the steel is taken into account. Generally, the temperature range in which welding shall be carried out is from 400°C to 600°C. This means, that step welding is based on the fact that in such steels the transformation of austenitic is clearly delayed within a certain temperature range. The sequence of operations is as follows:
- Slow heating of the workpiece to its hardening temperature. At this temperature the structure becomes austenitic.
- Cooling to step temperature; that is, to the range in which the delay in austenitic transformation (according to TTT-diagram) is most pronounced.
- Welding the workpiece at this temperature.
- Cooling the workpiece to room temperature in still air or better in oil (50°C to 150°C).
- Tempering to the respective temperature which in the case of high-speed steels lies in the range of 550°C to 570°C.
- Machining the weld area.
For the solution of the many hardfacing problems, D/F offers a complete line of welding Torches & consumables, for flux cored wire electrodes, solid wire electrodes for gas metal arc welding and submerged arc welding fluxes.