The primary heat treatment for thick steel plates is defined by the UNS S17400 standard, or according to the ASTM A693 17-4-4 / 17-4 PH standard is precipitation hardening, which involves solution annealing at temperature of 1050 °C followed by quenching. Depending on the required final mechanical properties, this is followed by aging at an appropriate temperature.
Due to the increasing customer demand for thick 17-4 PH steel plates treated with double precipitation hardening and previously conducted investigations of double – stage aging and examinations of mechanical properties and microstructure was conducted on pre-industrially solution-annealed samples. Precipitation hardening of 17-4PH steel is defined by ASME SA 693 and ASTM A693 standards. In this study, we focused on the condition H1150M.
Double-stage aging, as described by the condition H1150M, was conducted on previously industrially solution-annealed and quenched samples under laboratory conditions in the first phase. The samples were aged at 760 °C for 2 hours, according to condition H1400. After appropriate cooling, the samples were aged again at 621 °C for 4 hours, according to condition H1150. In the second phase, industrial two-stage aging was carried out using a five-zone chamber furnace under conditions identical to those in the laboratory trials. Subsequently, the prescribed mechanical properties were tested.
The primary goal of this master’s thesis was to ensure the achievement of the prescribed mechanical characteristics in the double-aged condition in accordance with the ASTM A693 standard, to establish the heat treatment technology, and to expand the range of final delivery conditions for customers according to their demands.
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