Advances in Ferrous Metallurgy: Developments in Testing and Processing
Sponsored by: AIST Metallurgy—Processing, Products and Applications Technology Committee
Program Organizers: Daniel Baker, LIFT; Emmanuel De Moor, Colorado School of Mines; Kishlay Mishra, Nucor Castrip Arkansas LLC; Lijia Zhao, Northeastern University

Tuesday 2:00 PM
October 19, 2021
Room: A210
Location: Greater Columbus Convention Center

2:00 PM
Effect of Alloying Content on Fractional Softening Behavior and Microstructural Evolution During Double-twist Torsion Testing of Microalloyed Steels: Trevor Ballard¹; Emmanuel De Moor¹; ¹Advanced Steel Processing and Products Research Center, Colorado School of Mines
    The non-recrystallization temperature (T_nr) represents an important parameter in the development of controlled rolling schedules. T_nr is commonly defined as the temperature below which complete static recrystallization ceases to occur. While T_nr is defined as a single temperature, partial recrystallization occurs over a wide temperature range. The current study applies a double-twist torsion test to a set of microalloyed steels with varying titanium, niobium, and vanadium contents. The partial recrystallization temperature regime was predicted for each alloy using fractional softening calculations. Increasing niobium reduced the fractional softening, while varying titanium and vanadium had minimal effect. Interrupted double-twist torsion tests were conducted to study the microstructural evolution at temperatures above, within, and below the partial recrystallization regime. The prior austenite microstructure was evaluated to assess the correspondence between the recrystallized fraction and fractional softening. The precipitation state was evaluated to show the effect of microalloying content on recrystallization and softening behavior.

2:20 PM
The Effect of Energy-power Parameters of Hot Rolling on Structure and Properties of Low Alloyed Steels: Valeriy Mishchenko¹; Sergеy Sheyko¹; Vadim Shalomeev¹; ¹Zaporizhzhia National University
    The paper focuses on identifying temperature and level of hot deformation modes boosting mechanical properties of steel 10ХФТБч (Standard of Ukraine). The effect of energy-power parameters of hot rolling on formation of macrostructure and microstructure of duplex steel is clearly identified. The procedure described in the paper improves homogeneous structure of the designed steel, thus preventing the central part of the rolled plate from being overheated.

2:40 PM
Reducing the Effects of Texture on Phase Fraction Measurement of Retained Austenite Using X-ray Diffraction: Michael Cox¹; Adam Creuziger²; Kip Findley¹; ¹Colorado School of Mines; ²National Institute of Standards and Technology
    High error has been observed in X-ray diffraction phase fraction measurements of retained austenite in rolled sheet steel. The suspected cause of this error is the textured nature of rolled materials. A novel, hexagonal grid sampling method has been investigated via numerical simulation and experimentation. The method samples the rolling, transverse, and normal direction-containing quadrant of the pole figure to reduce texture-based bias error in the measurement. Simulated measurements used texture data from four rolled sheet steels, one of which was used for experimental trials. Single-vector based measurements present significant bias error in both simulated and experimental trials. On the other hand, the hex-scheme measurements found phase fractions comparable to neutron diffraction results using over three hundred diffraction vectors. Using a hex-scheme containing only four diffraction vectors, a retained austenite phase fraction was measured within 1 percent volume of the prior neutron diffraction data on the same duplex steel sheet.

3:00 PM
3D Non-destructive Characterization of Texture Evolution in Electrical Steels with Lab-based Diffraction Contrast Tomography: Jun Sun¹; Florian Bachmann¹; Jette Oddershede¹; Hrishikesh Bale²; William Harris³; Erik Lauridsen¹; ¹Xnovo Technology; ²Carl Zeiss X-ray Microscopy; ³Carl Zeiss Microscopy, LLC
    Electrical steels with high Si contents are widely used in electrical power transformers, motors and generators. Texture is the most important property for electrical steel as the orientations of the grains strongly influence the magnetization and electrical resistance of the materials. Lab-based diffraction contrast tomography (LabDCT) is a recently developed X-ray based technique that is able to map the grain morphologies and crystallographic orientations non-destructively in 3D. The recent advancements of LabDCT allows seamless recording and reconstructing large sample volumes that are statistically relevant. In this work, we will present examples of using LabDCT to quantitively characterize the texture of both non-oriented and oriented electrical steels, with the emphasis on tackling challenges such as addressing structural anisotropy in non-oriented electrical steels and mapping out statistically relevant sample volumes for oriented electrical steels after secondary recrystallization.

3:20 PM
Hole Expansion Performance of Three High Strength Steels: Observation of Room Temperature Strain Ageing Phenomena: Rachael Stewart¹; Mike Settle¹; ¹Cleveland-Cliffs Steel Corporation
     A delay between hole punching and expanding had a measured negative impact on the hole expansion performance (HER) of certain steels. A HSLA590GA, a Complex Phase780GI and a Dual Phase780GI steel were tested after delay times between 1 hour and 10 days. The HER of punched holes in all three steels decreased with delay time. Over the ten day study, the rate of decay followed a logarithmic trend in all three steels. The relative loss of performance after 10 days was similar across all three steels,although the measured HER was different in each. The 24-hour loss in HER was avoided by storage in freezer, and machined holes did not lose performance with time. The time and temperature dependence of the phenomena suggest a diffusion mechanism. Hydrogen diffusion was ruled out by testing hydrogen charged samples. It is therefore theorized that a room temperature ageing phenomena at the sheared edge caused the observed decrease in HER.