The present master’s thesis titled “Optimisation of solution annealing parameters of 17–4 PH steel heavy plate” addresses imprints as surface defects, specifically imprints caused by roller tables or supports in SIJ Acroni’s Wellman industrial heat-treating line furnaces. The aim of the thesis is to eliminate these imprints without deteriorating the material properties of steel specified by AMS 5604E, ASTM A693-06 and EN 10088-2 applicable standards. The imprints on the surface of the heavy steel plate are caused as a combination of the weight of the heavy steel plates and excessive soaking time on high temperature in contact surface, during solution annealing process. To validate the use of new heat treatment conditions, both laboratory and industrial level testing was conducted. Considering three temperature points and three soaking times, mechanical testing of hot–rolled heavy plate samples took place, including 1) tensile test, 2) the Charpy impact test, 3) bending test, and 4) hardness measurements. Mechanical testing was complemented by metallographic SEM analysis. Following mechanical property and microstructure analyses, novel conditions of industrial solution annealing were tested on 25 mm and 83 mm-thick 17–4 PH steel plates. Having been heat processed under these conditions in an industrial environment, the plates underwent laboratory precipitation hardening. The results of mechanical property testing, and precipitation-hardened microstructure examination show that novel conditions improve solution annealing. Examining solution annealing conditions showed that shorter soaking time inhibits surface deteriorating (imprints). The mechanical property testing results matrix represents a broad registry of 17–4 PH (SINOXX 4542) steel solution annealing conditions, as well as allows for a wide selection of these conditions for the purpose of mechanical property adaptation.
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