Cracking and Failure Characteristics of Flame Cut Thick Steel Plates
- PDF / 5,282,884 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 56 Downloads / 219 Views
, S. SANTA-AHO
, P. PEURA
, and M. VIPPOLA
The manufacturing of thick wear-resistant steel plates commonly leads to a layered structure and non-uniform properties in the thickness direction which makes the processing and utilization of the plates problematic. The processing steps of thick plates include flame cutting, which generates a heat-affected zone and high residual stresses into the cut edge. In the worst case, the cutting causes cracking. However, the residual stress level alone is not high enough to break a wear-resistant steel plate that behaves normally. Therefore, high-tensile stress also requires a microstructurally weak factor for crack initiation. For this reason, the main objective of this study is to reveal the main microstructural reasons behind the cracking of plates in flame cutting. To achieve this, plate samples containing cracks are mechanically tested and analyzed by electron microscopy. The results show that cracks are commonly formed horizontally into the tempered region of the heat-affected zone. Cracks initiate in the segregations, which typically have a higher amount of impurity and alloying elements. Increased impurity and alloying content in the segregations decreases the cohesion of the prior austenite grain boundaries. These weakened grain boundaries combined with high-residual tensile stress generate the cracks in the flame-cutting process. https://doi.org/10.1007/s11661-020-05639-x The Author(s) 2020
I.
INTRODUCTION
THE fabrication and solidification processes of thick wear-resistant steel plates are complex. In thick plates, cooling can occur unevenly and the solidification in continuous casting can be at different stages at different depths of the plate. This leads to the partition of solutes between liquid and solid phases because the solubility of the solutes is higher in the liquid phase than in the solid phase. As a consequence, the solid phase rejects the excess solutes at the solid–liquid interface and they are transferred into the coexisting liquid phase. This creates an enrichment of solutes in the remaining liquid during solidification and the last solidified regions have a significantly higher solute content compared to the nominal composition of the steel.[1,2] These solute-enriched regions, known as segregations, are then pressed during rolling into the form of a thin sheet or strip, thus causing a layered structure in the thick plate. Segregations are typically formed in the center region of the plate and it has been found[1] that they contain
T. JOKIAHO, S. SANTA-AHO, P. PEURA, and M. VIPPOLA are with the Materials Science and Environmental Engineering, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 589, 33014 Tampere, Finland. Contact e-mail: tuomas.jokiaho@tuni.fi Manuscript submitted 14 August, 2019. Article published online January 30, 2020 1744—VOLUME 51A, APRIL 2020
significantly higher amounts of carbon, phosphorus, and manganese compared to the nominal composition of the steel. Another study showed [3] that center segregations have el
Data Loading...
