Effect of various phase fraction of bainite, intercritical ferrite, retained austenite and pearlite on the corrosion behavior of multiphase steels

2021 ◽  
Vol 178 ◽  
pp. 109043
Author(s):  
Neetu ◽  
Prvan Kumar Katiyar ◽  
S. Sangal ◽  
K. Mondal
Keyword(s):  
Corrosion Behavior ◽  
Retained Austenite ◽  
Phase Fraction ◽  
Multiphase Steels

Residual Stress in Steel Fusion Welds Joined Using Low Transformation Temperature (LTT) Filler Material

2013 ◽  
Vol 768-769 ◽  
pp. 620-627 ◽  
Author(s):  
Jens Gibmeier ◽  
Esther Obelode ◽  
Jens Altenkirch ◽  
Arne Kromm ◽  
Thomas Kannengiesser
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Transformation Temperature ◽  
Retained Austenite ◽  
Welding Residual Stress ◽  
Phase Fraction ◽  
Filler Materials ◽  
Ni Content

Welding residual stress is of major concern for structural integrity assessment in industrial components. Shear and volume strains resulting from the austenite-martensite-transformation affect the development of residual stress during welding. Controlling the phase transformation allows adjustment of the welding residual stress. Low transformation temperature (LTT) weld filler materials exhibiting reduced MS-temperatures allow postponing the phase transformation. The associated strain arising from the delayed transformation compensates for the thermal contraction strains and as such may reduce tensile or even introduce compressive residual stress. In this article we discuss the tri-axial residual stress distribution in 15 mm S690Q steel plates joined with LTT filler materials with 10 wt% Cr and a Ni-content that varies from 8 to 12 wt%. Using complementary synchrotron X-ray and neutron diffraction stress analysis the macroscopic residual stress was derived from the phase specific lattice strain and phase fraction of martensite and retained austenite, respectively. The local phase specific unstrained lattice parameters were determined using stress relieved combs. The investigation revealed increasing phase fraction of retained austenite with increasing Ni-content. Further, independent of the Ni-content in each weld in the fusion zone, significant compressive residual stresses were found in the longitudinal direction, which are balanced by tensile residual stresses in the heat affected zone (HAZ). In the weld transverse and normal direction the stress distribution is qualitatively similar but less in magnitude. The increased amount of retained austenite reduces the compressive stress arising from shear and volume strains during the delayed phase transformation and therefore no significant increase in compression was observed for decreasing MS-temperatures.

scholarly journals Influence of Quenching and Partitioning Parameters on Phase Transformations and Mechanical Properties of Medium Manganese Steel for Press-Hardening Application

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1879
Author(s):  
Charline Blankart ◽  
Sebastian Wesselmecking ◽  
Ulrich Krupp
Keyword(s):  
Mechanical Properties ◽  
Phase Transformations ◽  
Retained Austenite ◽  
Phase Fraction ◽  
Manganese Steel ◽  
Process Window ◽  
Quenching And Partitioning ◽  
Press Hardening ◽  
Austenite Content ◽  
Medium Manganese Steel

It has been proven that through targeted quenching and partitioning (Q & P), medium manganese steels can exhibit excellent mechanical properties combining very high strength and ductility. In order to apply the potential of these steels in industrial press hardening and to avoid high scrap rates, it is of utmost importance to determine a robust process window for Q & P. Hence, an intensive study of dilatometry experiments was carried out to identify the influence of quenching temperature (TQ) and partitioning time (tp) on phase transformations, phase stabilities, and the mechanical properties of a lean medium manganese steel. For this purpose, additional scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and energy dispersive X-ray spectroscopy (EDX) examinations as well as tensile testing were performed. Based on the dilatometry data, an adjustment of the Koistinen–Marburger (K-M) equation for medium manganese steel was developed. The results show that a retained austenite content of 12–21% in combination with a low-phase fraction of untempered secondary martensite (max. 20%) leads to excellent mechanical properties with a tensile strength higher than 1500 MPa and a total elongation of 18%, whereas an exceeding secondary martensite phase fraction results in brittle failure. The optimum retained austenite content was adjusted for TQ between 130 °C and 150 °C by means of an adapted partitioning.

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