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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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INTEG process group, inc.

HSMM v6.1 2 May 2004

Overview Release 2.0

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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HSMM v6.1 10 May 2004


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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HSMM v6.1 11 May 2004


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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HSMM v6.1 12 May 2004


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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HSMM v6.1 13 May 2004


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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HSMM v6.1 14 May 2004


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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HSMM v6.1 15 May 2004


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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HSMM v6.1 16 May 2004


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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HSMM v6.1 17 May 2004


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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HSMM v6.1 18 May 2004


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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HSMM v6.1 19 May 2004


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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HSMM v6.1 20 May 2004


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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HSMM v6.1 21 May 2004


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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HSMM v6.1 22 May 2004


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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HSMM v6.1 23 May 2004


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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HSMM v6.1 24 May 2004


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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HSMM v6.1 25 May 2004


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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HSMM v6.1 26 May 2004


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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HSMM v6.1 27 May 2004


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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HSMM v6.1 28 May 2004


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.

hsmm overview rel 2 0

Documents