The Analysis of the Microstructure and Mechanical Properties of Low Carbon Microalloyed Steels after Ultra Fast Cooling

Abstract

In this paper, two low carbon microalloyed steels, named as steel A and steel B, were fabricated by ultra fast cooling (UFC). In both steels, the microstructures containing quasi polygonal ferrite (QF), acicular ferrite (AF) and granular bainite (GB) can be obtained by UFC process. The amount of AF in steel B is more than that in steel A. The size and distribution of precipitates (Nb/Ti carbonitrides) in steel B are finer and more dispersed than those of in steel A due to relatively low finish cooling temperature. The mechanical properties of both steels are effectively enhanced by UFC process. UFC process produces low-temperature transformation microstructures containing a significant amount of AF. The mechanical properties of steel B were more satisfactory than those of steel A due to the finer average grain size, the greater amount of the volume fractions and smaller size of secondary phases.

Experimental evidence on structural adequacy of high strength S690 steel welded joints with different heat input energy

“…Moreover, such changes in microstructures in these welded joints had been investigated systematically by Mayr,Ding et al,and Azhari et al [12~14]. These materials researchers had carried out systematic experimental and numerical investigations to correlate mechanical properties of these HAZ using high-fidelity micro-mechanical models and mesoscale mechanical analyses [15,16]. It should be noted that the primary interests of these material researchers are to understand, and then, to characterize microstructures and their recrystallization conditions so that they are able to develop a variety of high performance steels with different and probable less expensive chemicals.…”

“…In order to investigate and quantify effects of various heat input energy onto the mechanical properties of the S690-QT steel welded joints under tension, a series of carefully planned and executed standard tensile tests on cylindrical coupons of the welded joints were conducted [15,16]. Table 3 summarizes the test programme in which a total of 18 standard cylindrical coupons, i.e.…”

The Effect of Electrode Type on The Tensile Strength Characteristics of Welded Joints Between SA.240 Tp.304 Stainless Steel and SA.36 Carbon Steel Alloys through SMAW Welding Process

“…Changes in grain structure from fine-flat elongated to coarse and stress release induce a decrease in material hardness. Systematic and numerical systematic have been investigated to correlate mechanical properties in the HAZ area using high fidelity micro-mechanical models and meso-scale mechanical analysis [18,19]. The temperature and stress areas calculated using the finite element method have been studied with the welded laser process with plate area.…”

Archives of Metallurgy and Materials

“…However, AF has high-angle grain boundary and inter-locking structure. Low temperature crack resistance is better because it prevents and refracts the crack propagation [7,8]. CGHAZ is coarse because it experiences the higher heat effects.…”