A Magnetic Means of Monitoring Hardness Due to Heat Treatment in Steel Production

A number of researchers have reported work of varying degrees of success in determining mechanical hardness by magnetic means. The methods reported fall into the two categories of static testing (dc) or dynamic testing (ac). This paper describes a method of testing which is named the "differential" method. Since mechanical hardness is affected by many factors, several of which have no effect on magnetic properties, a universal hardness tester operating on magnetic properties would be impossible to develop; however, this paper describes how a magnetic means is employed to compare the hardness of a given material to a sample of the same material of known hardness. Test results are presented for carbon steel (AISI 1095) and alloy steel (AISI 4150).