The steels for application in plastics with loads, compression moulds and large-production moulds must combine great ductility and high hardness, in order to confer greater durability and resistance to wear. These characteristics make them ideal for dealing with the processes that cause greater wear on the moulds, as in the case of complex mouldings and with reinforced plastics. The large moulds require high toughness and scratch resistance throughout their section. To maximize these characteristics it is necessary to resort to a steel suitable for thermal treatment (good hardenability), which is why the excellent hardenability is also a characteristic of relief in these applications.