From a technological point of view, the decisive phase during the manufacturing process of a forged, cast or rolled special steel component which is necessary to achieve the required characteristics of use, is the heat treatment: in fact, to reveal the maximum qualities required from a steel, a specific heat treatment must be carried out, in compliance with the main, very selective parameters set by the design engineer and the manufacturer of the component itself. The aspects relating to the continual improvement of the product and the heat treatment process must be tackled safely and with respect for the environment. These aspects represent a cultural and ethical question that: should not be considered just a theory but must become a working knowledge of the hazards and measures to be implemented on the plants to prevent risks. Information should be provided on the measures that must be monitored constantly. The paper compares the advantages and disadvantages from the point of view of quality, the environment and safety, of managing a hardening process using different quench media such as water, oil based whole fluids and synthetic polymer solutions. A summary then follows of the experiments carried out by Lucchini RS in the application of heat treatment technologies using polymer solutions Houghton (Aqua-Quench), "spray cooling" and "rim chilling", carried out safely and with respect for the environment. Given the vastness of the matter, a decision has been made to focus the paper only on the hardening quenching phases using different media and systems. Starting from the medium that was most widely used in the past, i.e., oil, with all the intrinsic risk factors for the environment (fumes) and for safety (fire hazards), the paper proceeds to describe polymer solutions with all their consequent advantages. Consideration is then given to the ecological fluid "par excellence", in other words water used as a total or differential quench media in a tank or combined with air (Spray Cooling). The comparison between oil and polymer solutions with a water matrix has shown how the level of safety of polymer solutions is higher compared with that of oil during the product handling phase, when using the product in sound conditions, while handling the product in the event of spillage, as well as during the hardening phases. In particular, in the event of an emergency involving a fire on other plants, use of the new product offers a greater safeguard. The results in terms of quality recorded on the department plants, after the setting up of a pilot plant in the laboratory, have been satisfactory. In any case, once the metallurgical feasibility has been ascertained, companies are duty-bound to use water either directly or combined with air in order to show greater respect for the environment and to guarantee higher levels of safety for the workers involved with the heat treatments. It is not always possible to use water directly, but it can be facilitated by the following techniques or measures: "suitable hardenability", "delayed hardening", "interrupted hardening", "thermostatting the temperature", "controlling the agitation of the bath", use of alternative techniques compared with total immersion based, for example, on the concept of differential quenching or (Rim Chilling) or the calibrated use of water and air (Spray Cooling), the degree of surface finish suitable for the type of steel. Finally, it has been underlined that the heat treatments carried out on automated plants, in other words plants normally dedicated to a well-defined type of product (axles, railway solid wheels and tyres) are safe, whereas in the case of heat treatment plants with manual handling, typical of forged parts made to specifications and of castings, each case is different and great importance must be given to the layout and the definition of the product handling procedures from the austenitization furnaces to the tanks and from the tanks to the tempering furnaces.
