Journal of Materials Processing Technology 211 (2011) 66–77 Contents lists available at ScienceDirect Journal of Materials Processing Technology journal homepage: www.elsevier.com/locate/jmatprotec Effects of continuous cast section size on torsion deformation and fatigue of induction hardened 1050 steel shafts Robert Cryderman a , Nima Shamsaei b , Ali Fatemi b,∗ a Gerdau MACSTEEL, Monroe, MI, USA b Mechanical, Industrial and Manufacturing Engineering Department, The University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA article info Article history: Received 18 December 2009 Received in revised form 25 August 2010 Accepted 27 August 2010 Keywords: Cast section size effect Cast reduction ratio Case hardening Torsion fatigue Torsion properties abstract This study investigates the influence of continuous cast section size on the mechanical performance of induction hardened parts produced from steel bars. SAE 1050 steel from commercially produced Jumbo Blooms, Blooms, Rotary Round, and Billet were hot rolled into round bars with diameters of 37–44 mm. These bars were then normalized, machined into test specimens, the gauge sections were polished, and the specimens were case-hardened by induction hardening. Torsional monotonic and fully reversed cyclic fatigue tests were conducted to study the effect of the initial continuous cast section size on deformation and fatigue behaviors. Reduction ratios in this study ranged from a low of 20.4:1 for the Billet, up to a high of 142:1 for the Jumbo Bloom. Test results indicate that the continuous cast section size has only small effects on the torsion monotonic and cyclic deformation properties and negligible effect on the torsion fatigue performance. Small differences observed in deformation and fatigue properties between the four processes are attributed mostly to the variation in case and core hardness levels caused by small differences in chemistry, particularly carbon content. Variations in sulfur content also influence ductility and fatigue behavior. At high strains, the cracks initiated in shear as longitudinal cracks for all four materials. At low strains, the cracks initiated at the surface in tension as spiral cracks due to normal tensile stresses. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Over time, in the interest of economical production, casting of steel has progressed from casting Ingots, to casting very large rect- angular (Jumbo) Blooms, to casting near square Blooms of smaller sections, to casting Billets as squares or rounds. After casting, Ingots were heated in soaking pits, rolled into Blooms, reheated and rolled into Billets, and reheated again and rolled into bars. The Jumbo Bloom process follows the same processing route. Progressing to Bloom casting eliminates the need for the initial soaking pit and Bloom rolling processes. Progression to Billet casting eliminates the Bloom reheating and rolling to Billets, only a single heating is required after casting to allow rolling into bars. Historically, highly stressed steel components such as induction-hardened drive shafts, power transmission shafts, and axles were produced from Ingots. As Ingot production ceased due to the high costs, production of axles changed to Jumbo Blooms and Blooms. With the continuing drive to reduce costs and become more energy efficient, the manufacturing process of many of these components has been changing to the Billet ∗ Corresponding author. Tel.: +1 419 530 8213; fax: +1 419 530 8213. E-mail address: afatemi@eng.utoledo.edu (A. Fatemi). cast process. However, there continues to be specifications that permit only bloom or ingot cast steel for some components, such as automotive axle shafts. It is estimated that the annual extra cost of these restrictions is in excess of $16M for automotive axle shafts based on assumption of 200,000 tons/year of consumption and a conservative cost differential of $80/ton. Therefore, the purpose of this study is to investigate the effects of cast section size (reduction ratio) on the service durability of 1050 grade axle shafts. Brunet (1985) mentioned four parameters influencing the qual- ity of the final production in continuous casting. These include the metallurgical structure as a result of melting and casting process, temperature gradient, reduction ratio for each pass in addition to total reduction ratio, and finally overall deformation in the rolling process. The effects of casting section size and casting parameters on the solidification structure and consequently on the mechani- cal properties and fatigue behavior have been topics of interest in many studies. In general, solidification structure and consequently the mechanical behavior of the continuous casting products are affected by casting velocity, additive elements, electromagnetic stirring, temperature gradient and solidification rate, and many other factors during continuous casting process. High rolling temperature and low rolling speed as well as high reduction ratios were reported by Brunet (1985) to enhance the mechanical properties. Dyck et al. (1988) investigated the effect of 0924-0136/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2010.08.026