Role of Steel Plate Thickness on the Residual Stress Formation and Cracking Behavior During Flame Cutting
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, PASI PEURA
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Thick wear-resistant steel plates are utilized in challenging applications, which require a high hardness and toughness. However, utilization of the thick plates is problematic as they often have nonuniform mechanical properties along the thickness direction due to the manufacturing-induced segregations. In addition, the processing of thick plates commonly involves flame cutting, which causes several challenges. Flame cutting forms a heat-affected zone and generates high residual stresses during the cutting process. In the worst case, flame cutting causes cracking of the cut edge. The aim of this study is to investigate the role of plate thickness on the residual stress formation and cracking behavior when utilizing flame cutting. Residual stress profiles are measured by X-ray diffraction, plates and cut edges and are mechanically tested and characterized by electron microscopy. The results show that thicker plates generate more unfavorable residual stress state during flame cutting. Thick plates also contain segregations, which have decreased mechanical properties. The combination of high residual tensile stresses and segregations increase the risk of cracking during flame cutting. To prevent the cracking, the residual stresses should be lowered by lower cutting speeds and preheating. In addition, manufacturing practices should be aimed at lowering segregation formation in thick plates. https://doi.org/10.1007/s11661-019-05314-w The Author(s) 2019
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INTRODUCTION
THICK wear-resistant steel plates are utilized, for example, in the mining industry, where a high degree of hardness and toughness is required. In terms of properties and manufacturing, thick steel plates are more complex compared to thin plates. During solidification, liquid steel may cool unequally and the solidification process may proceed at different rates at different locations in the plate. The formation of segregation on the center plane of the plate is caused by the enrichment of alloying elements such as carbon, phosphorus, sulfur, and manganese near the center region of the thick steel plate. The rolling process compresses the regions enriched by alloying elements and nonmetallic inclusions into thin sheets or strips and results in a layered structure.[1,2] There have been several studies related to the mechanical properties of thick steel plates. Yang
TUOMAS JOKIAHO, SUVI SANTA-AHO, PASI PEURA, and MINNAMARI VIPPOLA are with the Materials Science and Environmental Engineering, Faculty of Engineering and Natural Sciences, Tampere University, 33014 Tampere, Finland. Contact e-mail: tuomas.jokiaho@tuni.fi Manuscript submitted November 7, 2018. Article published online June 17, 2019 4178—VOLUME 50A, SEPTEMBER 2019
et al.[1] studied 100- and 120-mm-thick steel plates and noticed that the mechanical properties of plates vary depending on the test location in the thickness direction and generally that properties deteriorate toward the center region of the plate. Wang et al.[2] investigated steel plates with thicknesses of 60, 90, 120, and
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