An evaluation is presented of the microstructural characteristics and mechanical properties of welds in 20 mm thickness high strength low alloy steel HSLA 80, of Australian manufacture. In total, nine butt joints were prepared using the double tandem (four wire) submerged arc welding process in which both heat input and travel speed were varied. The inclusion size distribution was determined for selected welds and showed that heat input had a major effect. Colour etching techniques were used to reveal the solidification structure, which in turn correlated with welding parameters. As the heat input increased, the cooling rate decreased resulting in a larger cellular dendritic cell spacing, decreased acicular ferrite content, and coarser acicular ferrite laths. The effect of travel speed on delta ferrite cell spacing and prior austenite grain size was found to be co-dependent on the heat input and the thermal profile resulting from multiple electrode welding. These results show that increased deposition rates can be achieved by increasing the travel speed and current density without sacrificing joint quality.
The steady‐state creep of particle‐strengthened systems is predicted from the matrix behaviour within the framework of the threshold stress concept. A procedure is outlined for estimation of the hardening parameter σp reflecting the effect of the particles. Unlike previous suggestions neither questionable nor restrictive simplifications are assumed for σp and the stress exponent nm of the particle‐free matrix. The proposed approach is exemplified with γ’ precipitation‐strengthened Ni‐based superalloy Nimonic PE 16 crept at 810°C. The matrix creep data and, in particular, the needed nm‐values are measured on single‐phase Nichrome reference alloys.
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