Effects of Rapid Induction Heating on Transformations in 0.6% C Steels

Effect of induction heating on Vickers and Knoop hardness of 1045 steel heat treated

“…But, in addition, a considerable increase in the thickness of the layer was measured at points C and D. This variation was associated, not with heating by electromagnetic induction; which depends on the intensity of the magnetic field, the frequency of the working current, the separation between the piece and the inductor coil, as well as the magnetic characteristics of the material to be treated; if not to the geometric shape of the piece. In addition to the above, the austenitizing time is also a variable that influences the depth of penetration of the temper and showed a clear trend specifically at points C and D where it was observed that at austenitizing times of 2.0 and 2.2 s the thickness the layer was less; Cunningham et al [11] indicate that the variations in the depth of the layer are due, in the case of induction by a single shot, to the exposure time of the steel above the critical temperature A3, for which it was concluded that the geometry of the piece mainly influenced the temperature reached in the different areas of the piece, and that areas A and B were exposed to a shorter time to induction heating compared to points C and D. Figure 8 shows the results of the thermodynamic simulation with the JmatPro software, where the chemical composition of the AISI 1045 steel is considered, in addition to the ASTM grain size, whose value was determined experimentally, only for the austenitized sample for 2.4 s, and it was 9 ASTM at a temperature of 1123 K. The simulation was used in order to appreciate and confirm what was reported by Cyderman et al [4], who determined that at short heating times the grain size decreases and the surface hardness of the hardened layer decreases.…”

“…Microstructure has been reported to have a large effect on the mechanical properties of the product, ie, it is essential to control grain size growth in heat treated alloys. Due to the above, one of the microstructural advantages of induction hardening is the refinement of the austenitic grain; the temperatures used for heating conventional Jominy specimens ensure a grain size refinement of approximately 30-40 µm (ASTM 6.5-7) [4].…”

“…The standard assumes that the steels will produce an ASTM 7 grain size. Some studies have shown an inverse relationship between austenitic grain size and hardening [2][3][4], which consider austenitic grain sizes in the 4-8 range.…”

Influence of Specimen Design on Maximum Heating Rate and Temperature Variation During Induction Heating in an 805L Dilatometer

“…A solid 4 mm diameter cylinder of the 1045 steel from a hardenability study was heated at a programmed rate of 200 o C•s -1 and the time-temperature data shown in Figure 5 (a) indicate that a 200 o C•s -1 heating rate was achieved for both ferrite-pearlite and austenite except for the period where additional energy was needed for the transformation from ferrite-pearlite to austenite [3]. -1 showing an increased Ac1 temperature and an anomalous expansion at the Ac1 temperature with the faster heating rate.…”

Effect of Thermomechanical Rolling of the Induction Hardenability of a Micro-Alloyed 1045 Steel

“…This change in behavior is the result of the kinetics of dissolution of the ferrite and carbide micro-constituents in austenite as affected by both the temperature and the time at temperature. Also, it has been shown that increased heating rates increased both the Ac1 and the Ac3 temperatures for both carbon and low alloy steels [6][7][8], thus requiring higher austenitizing temperatures for full transformation to austenite before quenching. In industry, both as hot rolled (HR) ferrite-pearlite microstructures and quenched and tempered microstructures are employed to produce high strength induction hardened shafts, typically for drive axles and steering racks, used in automotive and truck applications.…”