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Hot Strip Mill Model
Introduction
The American Iron and Steel Institute (AISI), in conjunction
with the Department of Energy (DOE) and several North
American steel companies, funded the development of a
microstructure evolution and mechanical properties model.
INTEG process group, inc. undertook the task of
commercializing the technology developed by the University of
British Columbia (UBC) and the National Institute of Standards
and Technology (NIST). With the support of the AISI, DOE and
five North American steel companies (Dofasco, IPSCO, Stelco,
US Steel, Weirton Steel), INTEG continues to upgrade, enhance
and validate the model referred to as the AISI Hot Strip Mill
Model (HSMM).
INTEG has evolved the HSMM into a user-friendly, accurate and valuable tool. The user can easily
set-up their mill configuration, including number of reheat furnaces, roughing mill stands, heat
retention equipment, finishing mill stands, run out table cooling system and mill exit area. The model
can handle both strip and plate and can be configured for reversing mills, continuous mills, tandem
mills or Steckel mills utilizing a coiler or cooling bed. A variety of steel grades can be handled with
the included material characteristics for basic carbon grades, HSLA grades and Interstitial Free grades.
Dual phase steels are being added.
The HSMM can be utilized for conducting what-if analysis and detailed process analysis for any of the
following parameters:
Mechanics of Rolling
o Temperatures radiation, water loss, work roll conduction, mechanical working
o Rolling Loads rolling forces (flow stress), rolling torques, motor current, motor
power
o Roll Bite Parameters draft, percent reduction, bite angle, roll bite lubrication
o Limits edger buckling, bite angle
o Quality strip profile and flatness (shape)
Microstructure/Mechanical Properties
o Transformation, grain size, precipitation
o Yield Strength, Tensile Strength, Elongation
The HSMM uses a series of physical models to calculate both thermal-mechanical and microstructure
evolution. The model can be run in both single-node and multiple-node modes. The single-node mode
is used for rapid calculation and verification with plant data. The multiple-node mode uses finite
An AISI/DOE Technology
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difference calculations for detailed analysis and study. The microstructure model calculates
metadynamic and static recrystallization, austenite grain growth, precipitation, phase transformation
and ferritic grain size. After calculating the final temperature run down for the coiler or cooling bed,
the final mechanical properties including Yield Strength (YS) and Tensile Strength (TS) are
determined.
The enhanced HSMM was validated using a variety of samples from several steel companies.Excellent agreement was obtained for YS and TS with final ferrite grain size coming in within
acceptable standards of error given the natural error induced with the measurement of grain size.
Applications
The Hot Strip Mill Model can be used for a variety of applications. Current users have utilized the
HSMM to study mill configurations, rolling schedules, and process parameters to gain detailed insight
into their operations not normally available with their current models and control systems (such as
temperature distribution, transformation start temperatures and final mechanical properties).
Applications for the model include:
Development and optimization of rolling practices
Comparative analysis of various mill configurations and upgrade programs
Overall facility production capability analysis for a given product mix
Product development
Evaluation of relationships among process variables such as speed, temperature, retained
strain, and mechanical properties
Conducting a sensitivity analysis by varying one parameter to determine its impact on other
parameters
New Features
Based upon feedback from current users and the requirements needed for the steel industry of the
future, HSMM version 6.1 was recently released and contains new features that expand its
functionality and flexibility.
The key enhancements include:
Low Coiling Temperatures the run out table model has been enhanced so that coiling
temperatures down to 150 - 200C can be accurately modeled fornext generation steels.
Grade Builder allows the user to add and configure a new grade of steel by adjusting the
model coefficients and/or selecting the algorithm to be used (including their own).
Flow Stress Tuning a built-in tool that allows the flow stress equations to be tuned to match
mill data, improving the accuracy and expanding the range of these equations.
Resistance to Deformation Method Setup a built-in tool forsimplifying the calculation
of the coefficients for the Resistance to Deformation Method using data entered in the rolling
schedules.
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Strip Profile and Flatness calculations added to increase the functionality and value of the
HSMM forvalidating the quality of the rolling schedule and the mechanics of rolling.
Database Conversion Utility allows HSMM projects developed with previous versions of
the model to be converted easily and accurately for use with the latest release (now and in the
future).
Support and Future Development
The HSMM is continuously being enhanced. Work is currently in progress to expand the methods
utilized for the microstructure calculations to allow the model to handle additional grades of steel,
including Advanced High Strength Steels (dual phase, TRIP, API).
The HSMM is sold by license per PC and includes the first year of upgrades and support. After the
first year, an annual support agreement is available. Phone, e-mail and fax support is provided by
INTEGs staff in Wexford, PA USA.
A multiple day training class at INTEGs office is provided with the initial acquisition of the model.
Additional classes are available on a regular basis at INTEGs office or at the users facility for an
additional fee.
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User Inteface
Tracking
Microstructure Evolution &
Mechanical Properties
Run Out Table
Thermal-Mechanical
Rolling Mill
Thermal-Mechanical
Overview
The HSMM model performs a variety of calculations to simulate the physical process of rolling steel
in a hot strip mill. To model the various mechanical and thermodynamic processes during hot rolling,
these calculations rely on equations from the basic principles of physics and on equations developed
from theories of rolling mill researchers.
In order to properly implement the
calculations, an integrated model is
provided that includes a user-friendly
interface for set-up, configuration,
implementation and viewing results.
The HSMM contains a completely
linked model that allows the user to
simulate the processing of the steel from
reheat furnace dropout to the coiler or
cooling bed. The models trackingprogram tracks the head, middle and tail
points along the length of the piece,
modeling each point as it progresses
through the mill. The temperature
evolution, rolling forces, microstructurechanges and final mechanical properties
are all calculated for each of the three
points.
User Interface
The HSMM utilizes a user-friendly interface allowing each mill to be accurately configured, each
rolling schedule to be set-up in detail, each grade of steel to be accurately characterized and the final
results to be viewed, charted, reported and exported, as needed. The user interface can be divided into
the following main areas:
Mill Configuration
Grade Calibration Coefficients and Model Selection
Rolling Schedule Set-up and Model Results
Grade Builder
Data Exporting
Reporting
Tail Middle Head
Calculation Points
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Mill Configuration
The Mill Configuration Screen allows the user to set-up the rolling mill to be used in the modeling
process. A dynamically generated, scaled picture of the mill is displayed along the bottom while the
user configures the following stations:
Furnace Area
o Conventional Reheat Furnace
o Tunnel Furnace
Roughing Area
o Continuous Rougher
o Reversing Rougher
o Edgers, Water Sprays and Shears
Heat Retention Area
o Coil Box
o Heat Retention Covers
Finishing Area
o Tandem Millo Steckel Mill
o Edgers, Water Sprays and Shears
Runout Table Cooling Area
o Laminar Sprays
o Water Walls
Mill Exit Area
o Coiler
o Cooling Bed
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Grade Calibration Coefficients and Model Selection
The Grade Calibration Coefficients and Model Selection screen allows the user to tune the model for
each grade of steel being simulated through the rolling mill. During the overall project set-up, the user
selects a specific set of calibration coefficients to be used for the grade of steel being processed via a
specific rolling mill schedule. The user also has the option to select the force model method. A
minimal number of calibration coefficients are available for tuning the models to match mill data.
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Rolling Schedule Set-up and Model Results
The Rolling Schedule Set-up and Model Results screen is used to enter the rolling schedule of the
piece being modeled and to view the results of the single node and multiple node calculations. The
screen allows the user to input and view the following:
Initial Data Pass Data
Speed/Time
Shape
Temperature Data
Rolling Parameters
Microstructure
Run Out Table
Charts
Summary Results
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Single Node
Thru Full
Slab Thickness
Multiple Node
Models
The variety of models used by the HSMM to calculate the temperatures, forces, microstructure and
final mechanical properties of the piece being modeled and can be divided into two main areas:
1. Thermal-mechanical The thermal-mechanical calculations of the rolling mill process cover
each stage of rolling from the slab dropping out of the reheat/tunnel furnace until the finished
product is coiled in the up/down coiler or delivered to the cooling bed. These calculations include
the following:
Times and speeds during material transfer and rolling
Material temperature evolution
Roll bite parameters flow stress, strain, strain rate, rolling force
Motor torques, powers, and load ratios
Production rates
Shape
2. Microstructure The microstructure evolution calculations of the rolled material start from thetime the slab drops out of the reheat/tunnel furnace and continues until the finished product
reaches its final processing temperature, at which time its final mechanical properties are
calculated. These calculations include the following:
Recrystallization
Austenite grain growth
Precipitation
Phase transformation
Ferritic grain size
Yield strength
Tensile strength
Elongation
The models can be run in single node or multiple node modes. The single node and multiple node
models are completely independent of one another and can be tuned separately.
The single node calculations look at
the steel strip as one, through-
thickness node. Mechanical property,
force and microstructure calculations
are provided for an average
calculation.
The multiple node calculationsmodel the steel strip as a series of
101 nodes through the steel thickness
and 10 nodes through each scale
layer. Mechanical property, force
and temperature calculations provide
a distribution of these values
throughout the piece.
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Thermal-Mechanical Models
To accurately calculate temperature changes, the thermal-mechanical model closely simulates the
movements of the work piece through the mill with its configured distances between mill stations
(stands or other equipment) and station speed limitations. This requires that speed profiles including
acceleration and deceleration be calculated for material movement across tables and during continuous
and reversing passes. Additionally, having these accurate time calculations provides the ability to
perform accurate production studies.
Transfer Table Times and Speeds
The travel time for the work piece across a transfer table between two mill stations depends on the
following: the speed profile as the piece leaves the first station, the top speed of the piece while free
from the two stations, and the speed profile for the piece entering the second station. The top speed of
the piece across the table depends on whether the table is long enough for the piece to accelerate to the
desired maximum table speed and decelerate in time for the next mill station. The transfer times for
the head, middle, and tail points on the work piece are calculated independently as they depend ondifferent portions of the mill station speed profiles. An example speed profile for the head, middle and
tail points of the work piece across a transfer table for the calculation of radiation time between stands
is shown below.
Rolling Pass Times and Speeds
During reversing passes for roughing stands and Steckel mill stands, each time interval of the speed
profile is calculated to determine total pass time and the total rolling time. The pass time is the time
interval from the start of the current pass at the instant the piece begins moving to the roll bite until the
piece begins moving for the start of the next pass. Pass time includes the delay time between passes.
The rolling time is the time that the material is in the roll bite.
Top Table Speed
Tail
out ofStand 1
Middle
intoStand 2
Middleout of
Stand 1
Headinto
Stand 2
Head
Out ofStand 1
Tailinto
Stand 2
Stand 1Rolling Speed
Stand 2Rolling Speed
t2 t4 t5t3t1 t6 t7
Thread Speed
Top Speed
Tailout S eed
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Temperature Evolution Calculations
To support the mechanical parameter and microstructure evolution calculations, an accurate
temperature evolution of the work piece through the rolling process is calculated and maintained using
the single node and multiple node methods. Both methods calculate and maintain temperatures for the
head, middle, and tail of the work piece.
Single Node
The single node method determines the entry and exit temperature at each equipment station location
in the hot mill. From the exit of one station to the entry of the next, the work piece experiences heat
losses due to radiation and also to water cooling if any type of descale or cooling header exists. From
the entry of the roll bite to the exit of the roll bite, the work piece deforms between the work rolls and
experiences a heat loss from contact with the water-cooled work rolls and a heat gain from the energyrequired to deform it. The resulting average temperature is then fed into the microstructure evolution
calculations.
Multiple Node
The multiple node method calculates temperature changes of the work piece by dividing all time (time
between stands, time in water header contact, and time in roll bite contact) into slices. For each time
slice, the effect of either radiation, water cooling, or roll contact is independently applied to the top
and bottom material surfaces and the temperature change by heat diffusion between layers is also
calculated. This implicit finite difference method produces a temperature distribution profile through
the layers that is input into the microstructure evolution calculations.
Time Slices
Layers
Finite Difference Nodes in Time Slices and Thickness Layers
1 2 43 5
Finite Difference Time Slices in Roll Bite
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Roll Bite Parameter Calculations
For a given rolling pass, there are several parameters that are calculated that relate to the roll bite and
its geometry: draft, percent reduction, bite angle, deformed roll radius, contact length, geometric
aspect ratio, material resistance to deformation (flow stress), and roll separating force. These
parameters apply to both horizontal and vertical (edger) stands.
The roll bite model selected by the user determines the calculated roll separating force. If a flow stress
model is selected, the material flow stress is calculated and the rolling force is then determined fromthe flow stress, material width, contact length, and a geometrical factor using Sims force model.
Adjustments are made to the force calculation for non-homogeneous compression that occurs during
rolling in the early passes when the slab is its thickest.
Calculated values for percent reduction, bite angle, and roll separating force are compared with themaximum limits for the mill stand. All over-limit conditions will be indicated to the HSMM user.
Torque, Power, and Load Ratio Calculations
The HSMM calculates motor overloading as a load ratio of the actual power required for rollingdivided by the motors rated power. Each time interval in the pass speed profile has a calculated load
ratio that is compared with the motors absolute load ratio limit. If the maximum load ratio for the
motor is exceeded, the HSMM may be able to calculate a lower acceleration rate or rolling speed that
reduces the calculated load ratio below the limit. Any power or torque calculation that exceeds the
motors limits is indicated to the HSMM user.
From the speed profile times and load ratios, an RMS cycle time is calculated for the rolling of the
work piece. If this value exceeds the value of absolute cycle time, the difference is the additional rest
time required for motor cooling
Production Rate Calculations
From the calculated rolling and pass times in the roughing mill, finishing mill, and coiler, the
production rates for each group of coupled stations is calculated. For multiple-pass stations, the
production rate calculation includes all passes. Both actual production rates and RMS production rates
are calculated. The RMS production rates include any additional delay time required for motor
cooling.
The rated production rates of the reheat furnaces are proportioned by the hearth coverage in the
furnaces (slab length over the furnace width). The mill area with the lowest RMS production rate is
the mill bottleneck that limits the overall production on the mill for the current product.
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Roll Bite Calculations
Roll Bite
The roll bite area is one of the most critical areas for
calculating proper temperatures, forces and
microstructure evolution. The piece is subjected to
various strains over a range of thicknesses and for a
variety of material types (grades of steel). The HSMMallows the user to select one of four methods for
calculating the flow stresses observed in the roll bite.
The flow stress methods available include:
Resistance to deformation
NIST Flow Stress
Shida Flow Stress
Medina Flow Stress
Resistance to Deformation
The HSMM features an enhancement that allows the user calibrate the flow stress models. The flow
stress models consist of methodologies that are based on physical principles (NIST, Shida and
Medina) or that use plant historical data (Resistance to Deformation). The tool for the Resistance to
Deformation method allows the user to utilize plant data that is entered into the rolling schedules to
calculate the required coefficients for this method. The tool for the physical based models allows the
user to calibrate these equations with the same plant data.
Select which
Schedules to Use
Plot of the
Resultant Curve
and Data
Select Method -
Resistance to
Deformation
Coefficients
Automatically
Calculated
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NIST Flow Stress Equations
Flow Stress
The following graphic displays the tool for the Flow Stress Methods that are based on physical
principles. This tool allows the user to have tuning coefficients automatically developed and utilized
based on actual plant data for temperatures and forces.
The NIST flow stress calculation utilizes
a series of equations developed by the
National Institute of Standards and
Technology. The NIST equations are
dependent on temperature, austenite grain
size, strain, and strain rate with associated
coefficients that have been developed foreach steel grade.
The Shida1 flow stress calculations define
the flow stress of steels during hot plastic
deformation as a function of carbon
content, temperature, strain and strain rate.
This method for flow stress calculation
can be used as an alternative to the NIST
method, which was provide with the
original HSMM grades, allowing the user to observer the effects of a wider range of chemical grades.
This method is good for plain carbon steels.
The Medina2 flow stress calculations define the flow stress curves as a function of temperature, strain,
strain rate, austenite grain size and chemical composition. This method for flow stress calculation can
be used as an alternative to the NIST method, which was provide with the original HSMM grades,
1 Shida S., Effect of Carbon Content, Temperature and Strain Rate on Compressive Flow Stress of Carbon Steel,Hitachi Res. Lab. Report, 1974, 1-92 Medina S.F. and C.A. Hernandez, General Expression of the Zener-Hollomon Parameter as a Function of the
Chemical Composition of Low Alloy and Microalloyed Steels, Acta Mater. Vol. 44, No. 1, pp. 137-148, 1996
Select Method Flow Stress
Automatically
calculates
coefficients to
im rove results
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Zone 1 Z-3Z-2 Zone 4 Zone 5
ParallelFlow
ImpingementZone
CounterCurrent
Flow
Zone 0
RadiationRadiation
allowing the user to observer the effects of a wider range of chemical grades. This method is good for
microalloyed steels.
Run Out Table
The run out table area is a critical area for calculating proper temperatures and microstructure
evolution. The ROT is the processing area where the austenite to ferrite transformation andprecipitation take place (in most cases) influencing the final microstructure and mechanical properties.
Temperatures, microstructure evolution and mechanical properties are calculated for both the singlenode and multiple node models. For the multiple node model the HSMM utilizes a method to
dynamically calculate the heat transfer coefficients for the surface nodes.
One of the most complicated areas to model is the heat transfer occurring during the time the steel
strip is moving down the run out table through the water sprays. As part of the HSMM developmentdone by UBC, a methodology was developed for automatically calculating the heat transfer
coefficients (HTC) for the strip surface, as the point being modeled moves down the run out table, and
to integrate the temperature calculation with the microstructure-property model3. This method
calculates an HTC based on being located in one of six different zones (0-5) relevant to each water
spray.
Several zones have been defined covering the time when there is no water on the strip (radiation
zones 0,5), when the strip is directly under the water spray (impingement zone zones 2,3) and when
there is water on the strip (zones 1,4). An adjustment to the HTC in zone 4 is also dynamically
calculated that takes into consideration the gradual drop off in heat transfer capabilities of the pooled
water on the strip.
3 Militzer M., Microstructure Engineering of Hot-Rolled Steel Strip, The Brimacombe Memorial Symposium,
pp. 695-705, October 2000
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Low Coiling Temperatures
The HSMM features and enhancement that allows the temperature model on the run out table (ROT)
to handle low coiling temperatures down to approximately 150-200C. These lower coiling
temperatures go well below the typical coiling temperature of 550-700C and are needed for products
such as advanced high strength steels, including dual phase steel produced on a hot mill.
The chart below shows the time-temperature path on the ROT for a coil being simulated on the
HSMM that had been coiled around 150C. This coil displays a typical path for a dual phase steel
where the strip is cooled to an intermediary temperature, held for a few seconds and then cooled
extensively to achieve the low coiling temperature.
The HSMM achieves these low coiling temperatures through the addition of the Leidenfrost effect into
the models boiling curves. A typical boiling curve indicates how water, when heated, passes through
nucleate boiling, transition boiling and finally into film boiling phases. These phases are a function of
the strip temperature and the rate of bubble creation as the water boils. At some point, the rate of
creation of bubbles is so great that an actual vapor barrier is created, slowing the transfer of heat
between the steel and cooling water. Johann Gottlob Leidenfrost did extensive investigation into how
a drop of water is long lived when deposited on metal that is much hotter than the boiling temperatureof water. This Leidenfrost effect has been integrated into the HSMM, so that at lower strip
temperatures, the rapid transfer of heat to the cooling water can be observed.
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Strip Profile and Flatness
Calculations have been added to HSMM to display approximate values for strip profile as determined
by the loaded roll gap and any applied work roll bending force. The model also calculates the
differential elongation across the strip width caused by a change in strip profile during a pass
reduction. If the differential elongation exceeds a known flatness dead band, the model indicates that
the strip has either a center buckle or wavy edges.
Center
Buckle
Limit
Edge
Wave
Limit
Strip
Shape
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Microstructure Models
In combination with the temperature and deformation models, one of the main objectives of the
HSMM is to accurately predict the microstructure evolution (and subsequent mechanical properties)
for the hot rolling of steel. This is achieved by addressing the key metallurgical features affecting the
desired properties of the hot-rolled steel.
The processing of steel in a hot strip mill can be subdivided into three principle stages: reheating,
rolling (in both the roughing and finishing mill), and cooling (water cooling on the run-out table and
natural cooling after coiling). The metallurgical phenomena, which are calculated by the HSMM, are
summarized below.
Process Step Metallurgical Phenomena
RollingRecrystallization
Austenite Grain Growth
Precipitation
CoolingAustenite Decomposition
Precipitation
The HSMM is designed to model a variety of types of steel. The HSMM is broken down into thermal-
mechanical calculations and microstructure/mechanical properties calculations. For the
microstructure/mechanical properties calculations, it currently includes material characteristics for
three (3) grade families. The default grades of steel included in these families are shown below.
General Grouping of the HSMM Steels for the Microstructure Calculations
Family Grade Description
A36Plain carbon
DQSKno microalloying additions
HSLA-V singly microalloying with V
HSLA-Nb singly microalloying with Nb
HSLA-Nb/Ti 50Nb/Ti microalloying with a
substoichiometric Ti/N ratio
High Strength
Low Alloy
HSLA-Nb/Ti 80Nb/Ti microalloying with an over
overstoichiometric Ti/N ratio
IF-Nb rich
Interstitial Free IF-Nb lean ultra low carbon
Although the default grades include in the HSMM are certainly not an exhaustive list of hot rolled
steel products, they do cover a relatively wide range of chemistries relevant to the industry. Because
of the calculations within the HSMM, the user can enter the actual chemistry of the piece being
modeled to obtain some additional flexibility. Additional grades of steel can be implemented via
Grade Builder.
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Grade Builder
Grade Builder allows the user to configure, adapt and enhance the microstructure and thermal
evolution calculations to characterize the users grades of steel. Individual companies will now be
able to use the HSMM as their main process and product development tool by utilizing the Grade
Builder feature for their own proprietary development activities.
The first tab, Thermal and Grade Selection/Creation, allows the user to create his own grade of steel.
The core grades of steel provided with the HSMM are listed as read only so that the user can view
how these were created and can use these as a starting point to create his own grade. This tab allows
the user to manage (New, Duplicate or Delete) his grades of steel under the Grade Management
window or Thermal Grade Management window.
Launch Grade
Builder
Create the
Thermal Grade
Enter the
Chemistry
Create the
Microstructure
Grade
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The second tab, Grade Calc Methods / Equations, allows the user to select the method to be used for
each major algorithm utilized for the microstructure evolution, final mechanical properties and flow
stress calculations. The main areas are broken down into Recrystallization, Precipitation,
Transformation, Mechanical Properties and Flow Stress. Within each of these areas, the calculations
required are displayed from a drop down menu for selection of one of the available options, including
the ability to utilize a user-defined equation. When a specific equation is selected, a graph of the key
variable is displayed along with the coefficients for that equation. If the user changes the coefficients,the graph is updated. A help button (Show Eqn) is also available that will display the equation and
associated coefficients.
The following graphic shows a typical window displayed when the user clicks on the Show Eqn (show
equation) button.
Select the
Category
Select a Method
under each
Function
Select an
Equation foreach Method
Characteristics
of the Equation
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When the user of the HSMM selects to use his own equation, the user must then develop a software
subroutine to the requirements defined by a specific format. This subroutine can be developed in
either C or Fortran. The following graphic shows how the pull down menu next to each function
gives the user the option to enable an external (user) algorithm.
The following is a small sample of the Fortran code layout for the external routine that will be used as
the User Equation. Working examples with comments and instructions of how to format and
implement the routine in C or Fortran are provided. The user could also use this option to enter fixed
parameter values instead of equations.
Select a User
Defined
E uation
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The third and final tab, Thermal Grade Parameters, allows the user to edit the coefficients/curves for
the thermal properties of the steel. This includes Specific Heat, Thermal Diffusivity, Thermal
Expansion, Emissivity, Yield Strength and Density.
Once the user has completed the development/enhancement of his grade of steel using Grade Builder,
these grades are now available to the user and can be selected from the Calibration screen. The user
selects his base grade from the drop down menu and then enters the actual chemistry of the piece
being modeled. The piece being modeled should fall within an acceptable range of chemistry
deviation from the base grade. The configuration for the grade of steel as developed in Grade Builder
is summarized in the Calibration screen.
Summary of the
Methods Used
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Results
The HSMM presents the results to the user in a variety of forms. A snapshot of the final results for the
mechanical properties is available for both the single node and multiple node calculations.
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Overview Release 2.0
For production capability studies, the
HSMM provides the user with
information on cycle times, production
rates and material losses (scale).
The HSMM also provides the user with the ability to graph a variety of process parameters for both
the single node and multiple node calculations. For the product temperatures, the user can enter in
actual mill temperatures (from pyrometers or on-line models) so that this data is plotted along with theHSMM results.
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For a breakdown of the results by area, separate screens are provided that allows the user to view the
temperatures, forces and microstructure evolution at each step of the process. A pop-up window is
also available that will show through thickness calculations completed by the multiple node model.
Exporting
Additionally, the HSMM allows the user to export data to be stored in .CSV files, which can be easily
imported into software packages such as Microsoft Excel.
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Summary Results History
The Summary Results History window is used to display an historical record of the last 25 calculation
runs of the model. The user has ability to select the result parameters to be displayed in the history
list. The purpose of this tool is to allow the user to analyze the effects that changes in various inputs
have on the results. For each run in the list, the user can enter a comment to record what changes were
made before making this run. Hardcopy is available with the click of a button.
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Reports
This option allows the user to create and print reports of the various inputs and outputs of the model.
The user is able to generate reports for the Mill Configuration, the current Rolling Schedule (both
Single Node and Multiple Node), and the current Calibration / Grade summary. Once a report has
been selected and generated, the user has the option to view each page of the report, print the report,
and export the report to an Adobetm .pdf file.
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Validation
The models have been validated using data from several plants and good agreement has been achieved
for a variety of products for temperatures, forces, grain size and final mechanical properties. The
Tensile Strength is viewed as the best measure of microstructure performance since the TS test is the
most repeatable in the plant and thus has the least deviation (error) built-in on the measurement side
(in other words, the lab tests would generate nearly identical results if they were completed by a
variety of personnel for the same piece). Grain size calculations, on the other hand, can contain the
largest deviation when calculated by different people. As shown in the Excel-generated charts below,
the TS comparison contains the lowest average error.
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With a minimal number of tuning coefficients in the calibration Module, the temperature model can be
tuned to match measured or online model predicted temperatures through the mill and runout table
areas (shown as black dots on the chart below). Once tuned, the temperature model can accurately
predict temperatures under different operating conditions such as changes in speeds, reductions, or
water sprays. Accurate temperature predictions are essential input for the microstructure models.
Any of the four choices for the force model (NIST, Shida, Medina, or Resistance to Deformation) can
be automatically tuned in the Calibration Module to closely match the measured forces. The graphbelow shows how the four models compare against the measured forces after the calculated values
were exported to an Excel file
Force Model Comparison
0
500
1000
1500
2000
2500
3000
RR1
RR2
RR3
RR4
RR5
RR6
RR7
RR8
RR9 F1 F2 F3 F4 F5 F6 F7
Stand
RollingForce(tonnes)
Measured
NIST
Shida
Medina
Res-to-Def
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Database Update Utility
The HSMM now incorporates a database update utility so that projects developed by the user can
continue to be used with each enhancement of the HSMM. This provides the necessary migration path
to allow the user to grow with the HSMM.
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