HOT WORKING AND MULTIPASS DEFORMATION OF A 41CR4 STEEL

The hot working response of a 41Cr4 steel has been investigated by means of torsion tests at temperatures of 850, 950 and 1050 ◦C, in order to simulate the rolling schedule for this material. The equivalent strain rates used in this part of the study ranged between 5 and 0.05 s−1. The peak stresses obtained from the flow curves were related to strain rate (ε) and temperature (T) by means of the well known equation ε˙ exp Q/RT = A(sinh ασ)n where Q was the activation energy for hot working, n was the stress exponent, and A and α were material parameters. A least square analysis of the data led to n = 4.3, α = 0.0096 MPa−1 and Q = 295 kJ mol−1. A subsequent analysis was aimed at simulating rolling practice; the strain and strain rate for each single pass were determined on the basis of the real rolling schedule, and a series of multi-step torsion tests with different finishing temperatures (1050, 800 and 750 ◦C) were carried out. The microstructures of the samples after deformation were then analysed by means of light microscopy, and the differences in term of morphology, distribution and amount of the various constituents are discussed.