Residual Stress, Microstructure and Cracking Characteristics of Flame Cut Thick Steel Plates : Towards Optimized Flame Cutting Practices
|Tila||Julkaistu - 15 marraskuuta 2019|
|Nimi||Tampere University Dissertations|
The main purpose of this work is to identify the main contributors behind the
cracking phenomenon of thick plates in flame cutting. In addition, the goal is to give guidelines for a more effective flame cut process and to determine the most suitable microstructural characteristics for thick wear-resistant steel plates and flame cutting. To achieve these goals, a trial batch of thick wear-resistant steel plates was manufactured. The plates were flame cut with different cutting parameters and the residual stress state of the flame cut samples was measured by X-ray diffraction. In addition, both original and flame cut samples were characterized by electron microscopy and mechanical tests. The results of this study showed that residual stress formation during flame cutting can be controlled by choosing the right cutting parameters. Preheating and a
slow cutting speed produced the most beneficial residual stress state: higher
compressive stresses and lower tensile stresses. In addition, it was shown that
cracking increased with increasing segregations in the plate structure. Furthermore, long horizontal prior austenite grain boundaries were found to create beneficial sites for crack formation and propagation. Therefore, in plate manufacturing it is recommended to aim for a small and equiaxed prior austenite grain structure. In addition, it is advantageous to reduce the amount and severity of the segregations in the structure when possible.