The Effect of Trace Oxygen Addition on the Interface Behavior of Low-Alloy Steel

Abstract

This work aims to assess the effect of an oxygen content graded in minimal quantities, on the order of hundreds of ppms, on the determination of surface tension of low-alloy FeCOCr and FeCONi steels in contact with a corundum substrate. Oxygen, as a surface-active element, was segregated at the surface where it interacted with the major components of the alloys, leading to a reduction in surface tension. The sessile drop method was used for wetting tests in the temperature range from steel liquidus temperatures to 1600 °C under nonoxidizing conditions. The effect of oxygen on surface tension and wetting angles was verified by statistical analysis using the Kruskal–Wallis test, which supported the results stating that the values of these quantities decreased with increasing oxygen content. Furthermore, liquidus temperatures, which are of practical importance, were determined by the optical and DTA methods and then compared with theoretically calculated temperature values. It turned out that the increased chromium content causes difficulties in determining surface tension up to 1550 °C due to the formation of a thin Cr2O3 layer. In addition, SEM and XRD analyses accompanied by calculations in the FactSage oxide database were performed to better understand the wetting mechanism.

Laser Weld Aspect Optimization of Thin AISI 316 SS Using RSM in Relation with Welding Parameters and Sulfur Content

“…For each experiment, we compared the behavior of two casts. The inverse Marangoni convection is expected to occur in the 316 HS weld pool, but the conventional Marangoni convection is supposed to happen in the 316 LS weld pool [28]. We notice that the partially penetrated welds are obtained 17 times for both casts, wherein the inverse Marangoni convection occurs 12 times in the 316 HS cast and a conventional Marangoni occurs 5 times in the 316 LS cast; the latter convection modes phenomena especially occurred in 316 HS.…”

“…In 316 HS weld pool, the molten metal moves in inward circulation leading to deeper and narrower weld (reverse Marangoni convection). In 316 LS weld pool, the molten metal moves in outward circulation leading to wider and shallower weld bead [27][28][29]. Our study answered the following question: is the role of surfactant elements important in determining the shape of the laser weld?…”

Effect of Microchemistry Elements in Relation of Laser Welding Parameters on the Morphology 304 Stainless Steel Welds Using Response Surface Methodology

“…However, as the temperature increases, sulfur desorbs into the bulk of the liquid metal, causing an increase in surface tension. This applies to alloys with a sulfur content greater than 50 ppm [24,25]. The surface tension will be highest at the center and thus the surface flow will be radially inward, and this will induce a downward flow in the center, called inverse Marangoni convection.…”