scholarly journals Effects of Laser Beam Parameters on Bendability and Microstructure of Stainless Steel in Three-Dimensional Laser Forming

2019 ◽  
Vol 9 (20) ◽  
pp. 4463 ◽  
Author(s):  
Daniyal Abolhasani ◽  
Seyed Mohammad Hossein Seyedkashi ◽  
Mohammad Hoseinpour Gollo ◽  
Young Hoon Moon

In this study, the effects of beam diameter and hatch spacing between the scanning paths on the bendability and microstructural behavior of an AISI 316 stainless-steel sheet in three-dimensional laser forming were investigated. The strain on the heating lines and that between the scanning tracks were numerically investigated to elucidate the effects of process parameters. The strain on heating lines and that between scanning tracks were numerically investigated. The increase in hatch spacing caused a larger amount of counter bending to be retained in the unaffected areas between the tracks through a process dominated by a temperature gradient mechanism (TGM), and also caused a lower deformation. The formation of small equiaxed dendrite grains instead of coarse and inhomogeneous austenite grains occurred during the process at a larger beam diameter and smaller hatch spacing, which increased the bendability of the material, owing to the decrease in anisotropy in the microstructure. Moreover, the increase in the grain size of the reheated overlap region of the deformed sample led to a higher bendability. Under these conditions, the microhardness was also increased owing to the grain boundary strengthening effect.

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
K. A. Habib ◽  
M. S. Damra ◽  
J. J. Saura ◽  
I. Cervera ◽  
J. Bellés

The failure of the protective oxide scales of AISI 304 and AISI 316 stainless steels has been studied and compared at 1,000°C in synthetic air. First, the isothermal thermogravimetric curves of both stainless steels were plotted to determine the time needed to reach the breakdown point. The different resistance of each stainless steel was interpreted on the basis of the nature of the crystalline phases formed, the morphology, and the surface structure as well as the cross-section structure of the oxidation products. The weight gain of AISI 304 stainless steel was about 8 times greater than that of AISI 316 stainless steel, and AISI 316 stainless steel reached the breakdown point about 40 times more slowly than AISI 304 stainless steel. In both stainless steels, reaching the breakdown point meant the loss of the protective oxide scale of Cr2O3, but whereas in AISI 304 stainless steel the Cr2O3scale totally disappeared and exclusively Fe2O3was formed, in AISI 316 stainless steel some Cr2O3persisted and Fe3O4was mainly formed, which means that AISI 316 stainless steel is more resistant to oxidation after the breakdown.


Author(s):  
M. S. Che Jamil ◽  
M. A. Sheikh ◽  
L. Li

Laser beam forming has emerged as a viable technique to form sheet metal by thermal residual stresses. Although it has been a subject of many studies, its full industrial application is not yet established. This article aims to complement the existing research in the area of laser forming in order to gain a better understanding of the process. A numerical investigation of laser forming of stainless steel sheets has been carried out and validated experimentally using a High Power Diode Laser (HPDL). Three processing parameters are tested; laser power, beam diameter and plate thickness. Also, laser bending of stainless steel tube is simulated and compared against the published experimental data. The main underlying mechanisms of laser forming are demonstrated through the simulations.


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