Who are they and what do they do? The hardener's job is to carry out the heat treatment of metals to achieve materials with certain desirable properties.
What are the activities of the job? The work activities include hardening metal parts, i.e. their heating in ovens as well as by direct flame, their subsequent quick cooling (this is how hard surfaces of the relevant parts are achieved), firing of metal parts, i.e. heating then slow cooling them (this is how internal toughness and strength the relevant parts are achieved), tempering treatment of metal parts, i.e. their heating with subsequent cooling in several rapid phases with interim pauses (this is how both internal toughness and hard surfaces of the relevant parts are achieved), cementation of metal parts i.e. heating them while saturating their surfaces with carbon (hard surfaces are achieved), nitriding of metal parts i.e. heating them while saturating their surfaces with nitrogen (hard and wear-resistant surfaces are achieved) and performing of other heat-treatment methods based on such individual processes controlling and operating automated process units using the processes already described singly or together.
Where is it done and under what conditions? This job is usually done in industrial plants/factories and shops, where there will be high temperatures, and the work environment can be fairly unpleasant at times with relatively hard manual labour.
What tools/equipment do they use? Typical tools and equipment include furnaces, cooling equipment, salt baths, hardening presses, electric measuring instruments, handling equipment, etc.
What do you need to succeed? You need to have done vocational training in hard treatment processes, and have overall fitness, dexterity and fast reactions.