Metallurgical Models for
Cooling Level 2
Wide range of the
metallurgical models can be applied into the various Level 2
systems, not only the rolling mill Level 2, but also the controlled cooling Level 2.
for Level 2
Application of the metallurgical models in the post-rolling
cooling Level 2 helps to find the optimal cooling schedule for
a given finish size and given steel grade. Accelerated
water-cooling or controlled air-cooling may be used to control
the cooling speed in order to achieve optimal microstructure
and thus the finish properties. There are extensive studies in this area. Several models are discussed here
Phase transformation model. Describes the progress of
various transformation reactions against time during
cooling. The kinetic equation x = 1 – exp (-k tn), together
with various extensions or modifications of it, is known to
hold for various time-dependent nucleation and growth
reactions at a constant temperature, where x is the fraction
formed, t is time and k and n are constants. These constants
should be determined for each grade and each phase, etc.
When there is sufficient number of measurement available,
the constants can be determined through system learning to
improve prediction accuracy. Further, it can be integrated
into the mechanical test laboratory that measures rolled
Grain size model at the start of the controlled cooling.
Predicts the initial grain size (grain diameter) of the
steel for controlled cooling. If the
metallurgical model is available for the rolling mill Level
2, the grain size at the entry of the controlled cooling can
be easily available; otherwise an empirical model for this
grain size could be created based on the major rolling
Precipitation model. Describe the precipitation process
for some grades such as HSLA steels that contain small
amount of carbide (or nitride) forming elements (e.g.
niobium). For those grades, the improvement of
microstructure and mechanical properties is achieved mainly
by the suppressed recrystallization of austenite, which is
considered to be due to the precipitation of carbonitrides,
especially of niobium carbide.
Controlled Cooling Level 2 Model Architecture
newly developed Level 2 model may include following modules
Thermal model including cooling-process
affected heat transfer coefficient models, and mechanical and metallurgical models to determine
various parameters, with also numerical analysis (FDM or FEM) components.
Related rolling process models and rolling
process data, with connection with rolling mill Level 2 system, etc.
Expert system, which consists of logics, data and influence factors on the mechanical, thermal and metallurgical parameters
as well as past reheating experiences.
learning techniques based on the above-mentioned process models, in which the
neural network provides the correcting factors for the model coefficients, and
fuzzy logic rules and expert system provide guidelines (upper and lower
boundaries, etc.) for the learning.
After evaluation of
nearly 10 site testing
reports, Metal Pass has developed
accurate models on heat
transfer coefficients during
controlled water cooling and
controlled air cooling.
The models can greatly
increase prediction accuracy
for the controlled cooling
We also have developed a
finite differential method (FDM) model which has great advantage over the
traditional slab element method.
Metal Pass Resources on
Level 2 Model Improvement
Work List on Level 2 and Mill Modeling
Technical papers published
in the February and March of
publications are primarily
on Level 2, Level 2 model
and process automation.
available process models for steel mill
(Dr. Benjamin Li)
See the profile for the primary consultant
Dr. Benjamin Li. You may also view our
company and personnel profiles. Please contact
us via email
firstname.lastname@example.org or by phone (001)
516 9625 for top quality consulting
Metal Pass has dozens of
research reports and some
available at no charge for the Metal Pass Consulting clients (under approval by
Dr. Benjamin Li).