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From a ferrite/martensite cold-rolled microstructure, the interaction between ferrite
recrystallization and austenite formation is investigated. It is observed that a slow
heating rate promotes the ferrite recrystallization and a homogeneous microstructure,
whereas a fast heating rate delays the recrystallization and leads to heterogeneously
distributed austenite islands.
The nature of the intermetallic layer which forms on the steel surface during immersion
in typical galvanizing baths for galvannealed (GA) sheets production has been investigated
on two commercial Titanium-stabilized Interstitial-Free (Ti-IF) steel substrates
galvanized in baths with different Al contents. Results from this study show that in both
cases the inhibition layer is biphasic and composed of a very thin Al-rich phase layer,
identified as Fe2Al5Znx, and a thicker Zn-rich phase layer
on top of it, identified as δ. Experimental results also show that the
Fe2Al5Znx phase layer becomes discontinuous
when decreasing the bath Al content. Discussions about the mechanisms of formation and the
final microstructure of this inhibiting layer are also tackled in this paper by means of
the Al-Fe-Zn ternary phase diagram at 460 °C and assumptions to justify any deviation from
thermodynamic equilibrium are as well proposed.
The influence of variable Manganese content (2.4−4.6 wt%), while keeping constant Silicon
(1.5 wt%) and Chromium (0.3 wt%) levels, and variable oxidation potential of the annealing
atmosphere on hot dip galvanizability was investigated. Surface oxides prior to hot dip
galvanizing were analyzed and coating quality assessed. The increasing oxidation potential
of the annealing atmosphere led to a transition from external to internal selective
oxidation of Mn, Si and Cr; their enrichment at the surface could be reduced and the
metallic iron at the surface was increased. Hot dip galvanizability could thus be obtained
up to 2.9%Mn. With increasing Mn content, the surface was covered by a rising amount of
Mn-oxides. By exceeding a critical amount of Manganese, reactivity in the Zinc bath was
deteriorated. This amount was found to be between 2.9 and 3.8 wt% for Si content of 1.5
In this work, direct potential measurements during cold rolling of zinc and X20Cr13
stainless steel were carried out in the rolling slit to follow the tribologic and galvanic
mechanisms of hydrogen formation and absorption on the surface of the working rolls made
of DHQ1 grade steel. An Ag/AgCl in 3.5 M KCl reference microelectrode was used to record
the open circuit potential of the electrochemical system roller-product immersed into
commercially relevant electrolyte (rolling emulsion) with a pH value of 4.5 and an
electric conductivity 46 mS cm-1. The potential shift into either negative or positive
direction of the rolls-product system gives information on the processes taking place at
the surface in the course of the friction. A detailed discussion of the in-situ
potentiometry experiments reveals a stationary situation established between the
destruction and repassivation of the surface structures during continuous cold rolling
accompanied with intensive hydrogen evolution. Galvanic coupling of the working rolls with
the product significantly intensifies the hydrogen embrittlement related problems of the
rolls. Atomic hydrogen is adsorbed on the surface and exhibits a pressure supported
absorption into the rolls during their whole lifetime.
In order to obtain the dynamic variation rule of the sulfur content of liquid steel in
the LF refining process, a complete mathematical model including a desulfurization kinetic
model and temperature model in the deep desulfurization process is presented, based on the
practical production and reaction mechanism of ultra-low-sulfur steel in a LF. The results
show that the calculated values of the sulfur content in liquid steel using the model fit
the experimental values well, and the relative error is less than 8%. The effects of
refining slag on the desulfurization process are analyzed in this paper, which shows that
slag basicity is most important at the early and middle stages of the process, while slag
weight is most important at the middle and late stages. The effect of the above factors on
the final sulfur content of liquid steel is further analyzed quantitatively. The simulated
results provide a theoretical basis to segment control the refining process in order to
achieve the maximum effect, improving efficiency, saving energy and reducing
The paper reports the results of studies on the validation of a numerical model of the
flow of liquid steel through the tundish used for continuous casting of steel. The
facility under investigation is a single-nozzle tundish designed for casting concast
slabs. For the description of the turbulence of steel flow through the tundish, the
k-ε, RNG k-ε and Realizable k-ε turbulence model were
adopted. Computer simulations of liquid steel flow were performed using the commercial
For the validation of the numerical model and verification of the hydrodynamic conditions
occurring in the examined tundish furniture variants, obtained from the computer
simulations, a physical model of the tundish was employed. During laboratory tests
simulating the process of steel flowing through the tundish, E and F-type RTD (Residence
Time Distribution) curves were recorded, which were then juxtaposed with results obtained
from computer simulations. In order to obtain a complete hydrodynamic picture in the
tundish furniture variants tested, the computer simulations were performed for both
isothermal and non-isothermal conditions.
Low temperature degradation (LTD) of iron oxides was investigated with the aim of
understanding how natural iron ores degrade under different conditions. Minimisation of
this degradation would increase the acceptance level of natural iron ores as feed
materials without prior beneficiation. In addition to temperature and reduction gas
composition, sample positioning in the reduction furnace and sample’s original weight were
also found to influence LTD. Samples placed in the top reaction zone of the furnace, which
have the first contact with the reducing gas, were found to degrade 1.5 times more than
those in the middle and bottom reaction zones. In addition, they presented a wide range of
size in the disintegrated particles than those in the middle and bottom reaction zones.
Furthermore, the samples with an original weight equal to or greater than 5 g, had a
disintegration extent of less than 10%. Therefore, if the reduction gas comes into contact
with a certain material first, before contacting the iron oxide, it may serve to reduce on
LTD during reduction. Furthermore, in laboratory conditions, the occurrence of low
temperature breakdown of the natural iron oxides can be minimised by using samples with an
original weight equal to or greater than 5 g.