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High strength, quench and tempered (Q&T) plates having yield strength of a minimum of 670 MPa and conforming to SA 517 Gr. F specification were successfully developed at Rourkela Steel Plant in plates up to 40 mm thickness. The plates are used extensively for the fabrication of impellers, penstocks, excavators, dumpers, and raw material handling devices, where welding is an important processing step. SA 517 Gr. F plates, characterized by a relatively high carbon equivalent (CE: ∼0.6) and alloyed with Ni, Cr, Mo, Cu, and V, are susceptible to a crack-sensitive microstructure and cold cracking during welding. In view of the above, the present study investigated the weldability properties of 20 mm thick plates using the shielded metal arc welding (SMAW) process. Implant and elastic restraint cracking (ERC) tests were carried out to assess the cold cracking resistance of the weld joint under different welding conditions. Preheat of 100°C, partial or full rebake, and a heat input of 14.9 to 15.4 KJ/cm resulted in static fatigue limit (SFL) values well in excess of the minimum specified yield strength (MSYS) of 670 MPa and a critical restraint intensity (K cr ) value of 34,650 MPa, indicating adequate cold cracking resistance. Lamellar tear tests conducted using full thickness plates at heat input levels ranging from 9.7 to 14.4 KJ/cm and weld restraint loads (WRL) of 510 to 685 MPa showed no incidence of lamellar tear upon visual, ultrasonic, and four-section macroexamination. The weld joint, based on optimized welding parameters, exhibited adequate tensile strength (812.4 MPa) and low temperature impact toughness 88.3 and 63.4 J (9.2 and 6.6 kg-m) at −40°C for weld metal (WM), and heat-affected zone (HAZ) properties, respectively. The crack tip opening displacement (CTOD) values of WM and HAZ (0.40 and 0.36 mm, respectively) were superior to that of the parent metal (0.29 mm), indicating adequate resistance of weld joint to brittle fracture. It was concluded that the weld joint conforms to the requirements of SA 517 Gr. F specification and ensures a high integrity of the fabricated products.

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The mean dimensions of martensitic plates formed at the burst temperature in ten iron-nickel alloys have been measured. The burst transformation proceeds predominantly by the spreading of nucleation through autocatalytic stimulation across grain boundaries rather than by filling-in of plates within partially transformed grains. The mean semithickness-to-radius ratio, [MATH], of plates is found to decrease linearly from 0.11 at 250 K to 0.04 at 80 K. Extrapolation of this linear relationship to temperatures near 0 K yields a very small [MATH] ratio, that is characteristic of the thin-plate morphology. The martensitic plates are partially twinned about the midrib, the extent of twinning increasing with decreasing burst temperature. The mean twinned semithickness-to-radius ratio, [MATH] increases with decreasing burst temperature, reaches a maximum of 0.05 at 160 K, and decreases thereafter. Extrapolation of [MATH] to zero yields 285 K as the temperature of transition from the partially-twinned plate to the fully-lath morphology

Dilation study was carried out in a thermo-mechanical simulator to understand the phase transformation behavior of a 0.15% vanadium microalloyed steel at three different cooling rates, i.e., 2, 5, and 10°C/s. Results of the study showed that the phase transformation temperatures, namely Ar 3 , Ar 1 , and B s of 0.15% vanadium microalloyed steel increased with increase in the cooling rate from 2 to 10°C/s. It was also observed that a cooling rate of 5°C/s was sufficient to form bainite microstructure in the plates while both bainite and martensite were formed when cooling rate was increased to 10°C/s. The findings of dilation study were used to design a rolling programme for commercial production of high strength steel plates of 0.15% vanadium steel chemistry.