Conventional hardening is today effected in large furnaces needing a lot of space as well as a lot of energy and usually effected in separate factories thus meaning long transports of steel parts forward and backwards. The main objective is to develop an equipment which can be used industrially for hardening, using magnetic field techniques as outlined i- the title which permits hardening in-line, little energy, smoother and repeated cuality, short heating times and little space which all give shorter through-times. However, for hardening the parts must be heated up to app. 850° - 900° C, followed by cooling and tempering. This means a new method which will save not only the environment but also costs and efficiency and through-times will be cut down from some days to just one or two hours at a maximum. The estimated cost saving is about 20.000 kECU per year for the heat treaters in all Europe.