Model Training: Steel Rolling
Process Modeling and Mill Development
Introduction
This five-day, instructor-led course is designed to improve
mill related engineers the basic skills on rolling mill parameters calculation for mill design, development
and operation. The course covers metal deformation in the roll gap, force,
torque and power requirements, and temperature and microstructure evolution
during rolling and controlled cooling. Fundamentals on rolling mill design
and development are introduced. Primary focus is on the rolling
process modeling and application of the models in the design
and development. Students will perform various Lab projects on mill
parameters calculation, and run over a dozen of rolling mill design and
development programs hosted in www.Meta4-0.com, in order to enhance their
understanding on mill design fundamentals, and to improve their design and
development skills.
The training consists of twenty modules. Each module has
Lessons on fundamental topics, and a Lab for performing hands-on
excises. The work on steel rolling process modeling and mill design requires
large amount of hands-on calculation and data processing, so this type of Lab
excises
is necessary for high-quality training.
Audience
This course is designed for rolling mill design, development
and operation engineers who have basic experiences on steel rolling and
rolling mills, and want to enhance knowledge and skills on high quality mill
design, development or operation.
At Course Completion
After completing this course, students will be able to:
• |
Better understand rolling process as an integration of
mechanical, metallurgical and control engineering systems |
• |
Use models to determine major rolling
process parameters |
• |
Understand roll pass design fundamentals and
Use roll pass program to perform design and
development |
• |
Use advanced roll pass programs to design
high-quality roll pass schedules and to improve existing ones |
• |
Understand flow stress and mean flow stress, and perform basic
calculation on flow stress and mean flow stress |
• |
Manually calculate rolling force, torque and power, etc., and
use software to calculate the force, torque
and power, etc. for various groove sequences in various rolling
conditions |
• |
Know general methods for
rolling process modeling
and understand
strengths and limitations for each method |
• |
Understand that steel rolling is a dynamic metallurgical
process, with both softening and hardening mechanisms, and rolled steel
properties are affected by many process parameters |
• |
Have knowledge on numerical models (FEM, FDM) and use programs
to perform some numerical simulations |
• |
Know the temperature profile along the rolling production
line and over the stock cross-section |
• |
Simulate microstructure evolution during rolling by
applying internet-based simulation program |
• |
Understand the significance, function and development
progress of Level 2 system; know that quality of the control system is
one of the key indicators for the equipment technology level |
• |
Know Level 2 Model functions, architecture and future
development |
Prerequisites
Before attending this course, students are expected to have
basic knowledge and work experience of the rolling mills (flat, bar/rod,
section, etc.), basic college training on mechanical engineering, material
engineering or industry automation.
Students who completed basic college training in engineering
but not in the above-mentioned fields may satisfy the prerequisites for this
course by studying related technical articles such as those listed in
www.Meta4-0.com/metallmaterials,
www.Meta4-0.com/metalworking
and
www.Meta4-0.com/itautomation.
Student Materials
For the high quality of the training, a complete student
study manual of about 150 pages is created in accompany of the training slides
and Lab excises.
Equipment
In order for students to complete Lab excises with the
internet-based rolling mill programs, each student is required to have a
laptop computer (or a desktop computer pre-installed in the training room).
The computers must have internet access. The computers should have a
calculation program such as MS Excel.
A projector for computer is required in the training room for the
instructor to do the slide show.
Module 1: Rolling Process Basic Parameters and Concepts
This
module introduces basic parameters of the rolling process, such as draft
(height reduction), cross-sectional reduction, strain, strain rate,
temperature, spread, elongation, neutral angle, forward slip, friction,
interstand tension, force, forming resistance, torque, power, and so on.
The module focuses on the mechanical and rolling process
issues in the steel rolling.
Lessons
• |
Introduction of Rolling Process (Comparison w/
Other Forming Processes, Issues, Hot,
Cold, etc.) |
• |
Basic Geometry (Draft,
Cross-sectional Reduction, Strain, Spread, Elongation,
Bite angle, Contact Area, etc.) |
• |
Basic Rolling Process
(Strain Rate, Temperature, Forward
Slip, Friction, Interstand Tension, Formability, etc.) |
• |
Force, Torque and
Power (Forming Resistance, Force,
Torque, Power, etc.) |
• |
And so on |
There is no Lab for this module
After completing this module, students will be able to:
• |
Understand basic geometrical and process related parameters used
in the rolling |
• |
Understand key metal flow phenomena and deformation issues involved in
the primary parameters |
• |
Know basics on mill force, torque and power requirement
which are critical to the rolling mill design |
Module 2: Rolling Process Parameter
Influences and Prediction Models
This module provides quantitative description of each rolling
process parameters and their influence factors. Major parameters, such as
friction, are with rolling process models to predict them.
Lessons
• |
Basic Geometric Models (Strain, Spread,
Elongation, Bite angle, Contact Area, etc.) |
• |
Basic
Rolling Process (Strain Rate, Temperature, Forward
Slip, Friction, Interstand Tension, Formability, etc.) |
• |
Force,
Torque and Power (Forming Resistance, Force,
Torque, Power, etc.) |
• |
Some Advanced Topics,
Parameters and Models (if time allows) |
Lab 2: Rolling Process Parameter Calculation
• |
Predict friction based on rolling temperature and
speed, etc. |
• |
Calculate bite angle, maximum bite angle |
• |
Determinate strain rate, etc. |
After completing this module, students will be able to:
• |
Quantitatively describe the rolling process |
• |
Apply basic models to
predict major parameters |
Module 3: Rolling Mills for Production of Strip/Plate, Bar/Rod, and Pipes
and Sections
This module briefly introduces various rolling processes and
equipment types, with technical problems, production technologies and recent development trends covered. The
equipment includes both mechanical equipment and automation systems. For
mill equipment engineers, this module covers mill types, optimization and
modernization topics; for mill operation engineers, this module may include some shape
control issues (for gauge, width and profile/flatness, etc.).
Lessons
• |
Hot Rolling of Strip and Plate; CSP/ISP and related
Technologies |
• |
Hot Rolling of Bar,
Wire Rod and Other Simple Shapes; Finishing Blocks (NTM and
RSM, etc.) |
• |
Hot Rolling of Sections
(Angle, I-Beam and U-Section, etc.) |
• |
Production of Seamless
Pipes and Welding Pipes |
• |
Cold Rolling of Steels |
• |
Others |
Lab 3: There is no Lab in this module
• |
If time allows, certain topics could be selected for
discussion. |
After completing this module, students will be able to:
• |
Identify the differences in various rolling processes and
various rolling mill equipment (machinery and control system)
types |
• |
Understand rolling
process development progress and future trends |
• |
Understand major
technologies in each of the rolling processes |
Module 4: Flow Stress and Its Modeling
This module introduces flow stress and its application in
mill force and power calculation. Flow stress models for various application
situations will be discussed. Mean flow stress, which is directly used in
the roll separating force prediction, will be introduced. Advanced topics
such as metallurgical interaction are also covered.
Lessons
• |
Introduction to Flow Stress |
• |
Flow Stress Models
for Various Application Situations |
• |
Calculation of Flow
Stress and Mean Flow Stress |
• |
Flow Stress Advanced
Topics - Metallurgical Interaction |
Lab 4: Calculation of Flow Stress and Mean Flow Stress
• |
Calculate flow stress in various strain, strain rate and
temperature, by applying a flow stress model |
• |
Calculate mean flow
stress based on a given rolling condition |
• |
Calculate flow stress
for high speed rolling process |
After completing this module, students will be able to:
• |
Understand the nature of the flow stress as metal property
of deformation resistance. |
• |
Calculate flow stress
based on flow stress model |
• |
Calculate mean flow
stress in the case of rolling |
• |
Understand and calculate flow stress in the case of the high-speed
rolling, the common case for wire rod rolling |
• |
Understand
metallurgical effects on the flow stress |
Module 5: Mill Force, Torque and Power Calculation
Fundamentals
This module explains how to calculate roll separating force,
rolling torque and mill power. For force calculation, models for the
Projective Contact Area and for the Shape Factor, both in various groove
sequences, are discussed. Experimentally established Lever Arm Ratio for
torque calculation is introduced. Mill strength calculation and motor power
determination, etc., are also covered.
Lessons
• |
Roll Separating Force Calculation |
• |
Projective Contact Area and Its Modeling |
• |
Shape Factor (Q-Factor) and Its Modeling |
• |
Torque Calculation,
Lever Arm Ratio Modeling |
• |
Rolling Power, Mill
Power, Motor Power, etc. |
Lab 5: Mill Force, Torque and Power Calculation
• |
Calculate Mean Flow Stress, Projective Contact Area, Shape
Factor and Roll Separating Force |
• |
Calculate Mill Torque and
Power Requirements |
After completing this module, students will be able to:
• |
Understand rolling mill force and power calculation and
modeling related issues |
• |
Calculate
mill force, torque and power for a given rolling process |
Module 6: Temperature Calculation During Rolling and
Controlled Cooling
This module explains energy balance with heat generation and
heat losses during rolling and cooling, and on this basis, the temperature
prediction. Heat transfer coefficients during rolling, controlled water
cooling and controlled air cooling, etc. are discussed.
Lessons
• |
Energy Balance with Heat Generation and Heat Losses during
Rolling |
• | Heat Transfer
Coefficients during Rolling, Controlled Water Cooling and Controlled Air
Cooling |
• | Methods for
Temperature Calculation During Rolling and Controlled Cooling |
• |
Others |
Lab 6: Temperature Calculation During Rolling and
Controlled Cooling
• |
Temperature Calculation During Rolling |
• |
Temperature Calculation
During Water-Box Cooling |
After completing this module, students will be able to:
• |
Understand energy balance and temperature process during
rolling and controlled cooling |
• |
Calculate temperature for
the rolling and controlled cooling processes |
• |
Understand major
temperature calculation methods available (empirical, numerical) |
Module 7: Metallurgical Fundamentals of Steel Rolling
This module explains metallurgical phenomena and practices as
applied to the steel rolling process. Metallurgical characteristics such as
phases, grains, grain size, microstructure transformation, and their effects
on the steel properties are covered.
Macroscopic and microscopic natures of plasticity are briefly introduced. On
the basis, microstructure evolution during rolling and controlled cooling,
and thermoechanical rolling and physical metallurgy, etc. are discussed.
Lessons
• |
Metallurgical Characteristics and their Effects on Steel
Properties |
• |
Macroscopic and Microscopic Natures of
Plasticity |
• |
Microstructural Evolution during Rolling and Controlled Cooling |
• |
Thermal Mechanical Rolling and Physical Metallurgy |
• |
Modeling of Metallurgical Processes during Rolling |
Lab 7: There is no Lab in this module
• |
Certain Topics May Be Selected for Discussion (If Time Allows) |
After completing this module, students will be able to:
• |
Know basic metallurgical phenomena such as phase transformation
and microstructure evolution |
• |
Better understand steel rolling as both mechanical and
metallurgical processes |
• |
Gain better understanding
on those rolling practices which improve rolled steel properties |
• |
Gain basic
knowledge on modeling of metallurgical processes during rolling |
• |
Consider metallurgical factors in
rolling mill design/operation |
Module 8: Roll Pass Design
Fundamentals
This module covers roll pass design fundamentals in rolling simple
shapes (round, square, flat, etc.) and complicated sections (angle, I-beam, Rail
and U-Sections, etc.). Related topics are such as spread determination, pass
sequence (RD-OV, SQ-DI and BX-BX, etc.), rolling trains (roughing, intermediate and finishing trains,
etc.) are discussed.
Lessons
• |
Purpose of Roll Pass Design |
• |
Issues in the Roll Pass
Design (Fill Ratio, Aspect Ratio, Bite Angle, Spread, Formability, etc.) |
• |
Roll Layout and Pass
sequences (Selection, Reduction Capacity; RD-OV, SQ-DI, SQ-OV, BX-BX,
etc.) |
• |
Roughing, Intermediate
and Finishing Trains; Continuous Mill, High-Speed Mill, etc. |
• |
Other topics |
Lab 8: Groove Selection and Roll Pass Design
• |
Selecting Groove Shapes for various Rolling Processes;
Matching Groove Sequences |
• |
Performing a
Diamond-Square Roll Pass Design with Simplified Spread Estimation |
After completing this module, students will be able to:
• |
Understand fundamentals on roll pass design (purpose,
issues, etc.) |
• |
Understand features
in different rolling trains and different groove sequences |
• |
Know basic roll pass
design methods and procedures |
Module 9: Spread and Forward Slip Models
This module introduces major modeling procedures to predict
spread and forward slip. Spread and forward slip are among the most
significant phenomena, and are among the most difficult parameters to
predict in rolling process design and development.
Lessons
• |
Influence Factors on Spread |
• |
Spread Models |
• |
Influence Factors on
Forward Slip |
• |
Forward Slip Models |
• |
Tension and Tension Correction on
Spread and Forward Slip |
Lab 9: Spread and Forward Slip Prediction
• |
Predicting Spread based on Existing Rolling Process
Parameters |
• |
Predicting
Forward Slip based on Existing Rolling Process Parameters |
• |
Applying Tension
Correction on Spread and Forward Slip |
After completing this module, students will be able to:
• |
Understand major influences on spread and forward slip |
• |
Perform basic
prediction of the spread and forward slip |
• |
Understand and apply
tension effects on spread and forward slip |
Module 10: Methods for Rolling Process Modeling
This module briefly introduces major methods on rolling
process modeling. Empirical models require large number of testing results
to justify their quality. Analytical methods (Slab Method, Slip-Line Method,
Upper/Lower Boundary Method, etc.) used to be important additions to the
empirical models. With the advancement of computing power, numerical
solutions such as finite-element method and finite-differential method are
popular
today. Online model, based on industrial control theory and
feedback, is among the fastest and also most accurate models. In the final
lesson, the focus is on the introduction of finite-element method,
especially its application in the rolling process parameters determination.
Lessons
• |
Empirical Method |
• |
Analytical Method
(Slab Method, Slip-Line Method, Upper/Lower Boundary Method, etc.) |
• |
Numerical Method (Finite-Element Method, Finite-Differential
Method) |
• |
Self-Improvement Method
(Or Online Method, e.g. Adaptive Learning, Neural Network, Fuzzy Logic) |
• |
Application of
Finite-Element Method in Steel Rolling |
Lab 10: Preparation for an FEM Simulation of Steel Rolling
(Instructor Led)
• |
Material Data (Flow Stress, Physical, Mechanical, Thermal,
etc.) |
• |
Boundary Conditions
(Friction Coefficient, Heat Transfer Coefficient) |
• |
Grid Generation |
After completing this module, students will be able to:
• |
Have general knowledge of various methods for steel rolling process
modeling, and strength and limitation of each method |
• |
Understand the possible application of FEM in steel
rolling, and basic knowledge on how to perform FEM simulation for rolling
process |
Module
11: Introduction to Online Model - Level 2
System
Today the quality of control system is one of the key indicators for the
equipment technology level. Level 2 system is the production execution
system, which is one of the most critical systems in the rolling mill
operation. While flat rolling uses Level 2 to perform instant draft schedule
generation, other rolling process mainly stay in the stage that Level 2 is
used for data collection and data communication.
Lessons
• | Overview of
Level 2 System |
• |
Data Collection and
Data Management |
• |
Data Populating and Data
Storage |
• |
Level 2 Systems for EAF, LMF, Caster and Rolling Mill |
• |
Next-Generation Level
2 System |
Lab 11: Discussion on the Functions of Level 2 System
(Instructor Led)
• |
Level 2 System for Flat Rolling |
• |
Level 2 System for Rod, Bar and Section
Rolling |
After completing this module, students will be able to:
• |
Understand the significance of Level 2 System |
• |
Understand the function of Level 2 System |
• |
Understand the development progress of Level 2 System |
Module 12: Introduction to Online Model - Level 2
Model
This module explains Level 2 Model, a collection of online
models used in the Level 2 system. Force prediction is improved through adaptive
learning or other advanced learning processes (e.g. Neural Network). For high
accuracy, temperature is calculated based on the force prediction. Various roll
deformations are determined. Based on principles of equal deformation targets,
metallurgical temperature targets and maximum productivity targets, etc., the
draft schedule is created pass by pass by the Level 2 model. This module also
cover some topics such as model quality and its significance, and next
generation Level 2 models, etc.
Lessons
• |
Online Model Force Prediction - Adaptive Learning |
• |
Online Model Force
Prediction - Neural Network Learning |
• |
Online Model
Temperature Prediction |
• |
Draft Scheduling and
Production Execution |
• |
Significance of Level 2
Model Quality |
• |
Next-Generation Level
2 Model (Rolling, Reheating and Controlled Cooling) |
Lab 12: Discussion on Level 2 Model Quality
(Instructor Led)
• |
Level 2 System for Flat Rolling |
• |
Level 2 System for Shape Rolling |
After completing this module, students will be able to:
• |
Understand Level 2
Model functions and significance |
• |
Understand Level 2
Model design and general architecture |
• |
Understand Level 2
Model current weaknesses and future potential |
Module 13: Roll Pass Design with AutoForm Series (I)
This module guides students to perform roll pass design
by applying internet roll
pass programs RD-OV-RD and SQ-DI-SQ.
Lessons
• |
Features, Internal Logics and Application Considerations
|
• |
Input and Output
Parameters of Each Roll Pass Design Programs |
• |
Roll Pass Design Demo
by Running the Programs |
Lab 13:
Roll Pass Design with AutoForm Series (I)
• |
Roll Pass Design for Round-Oval Pass Sequence by Running
AutoForm Program RD-OV-RD |
• |
Roll Pass Design for Square-Diamond Sequence by Running
AutoForm Program SQ-DI-SQ. |
After completing this module, students will be able to:
• |
Understand basics on roll pass design and roll pass design
programs |
• |
Gain basic skills to perform roll pass design with
easy-to-use roll pass programs |
Module 14: Roll Pass Design with AutoForm Series (II)
This module guides students to perform roughing train roll pass design
by applying internet roll pass programs Box-Square-Oval-Round (4-pass train
to roll from square to round), Box-Oval-Round (3-pass train to roll from
square to round) and Box-Box (2 passes).
Lessons
• |
Features, Internal Logics and Application
Considerations, Input and Output Parameters |
• |
Box-Square-Oval-Round
(4-pass train to roll from square to round) |
• |
Box-Oval-Round
(3-pass train to roll from square to round) |
• |
Box-Box (2 box passes) |
• |
Others |
Lab 14: Roll Pass Design with AutoForm Series (II)
• |
Box-Square-Oval-Round (4-pass train to roll from square to
round) |
• |
Box-Oval-Round (3-pass
train to roll from square to round) |
• |
Box-Box (2 Passes, Two
Box passes) |
• |
Other Passes, if Time
Allows |
After completing this module, students will be able to:
• |
Have basic skills to perform roughing train (or break-down
mill) pass design with easy-to-use roll pass design programs |
• |
Further understand the issues
and deformation processes involved in the roughing train or breakdown mills |
Module 15: Roll Pass Design with FreeForm Series (I)
This module guides students to perform high-quality,
multiple-pass roll pass design for Round-Oval pass sequence, by applying a
high-quality roll pass design software. Students are also welcome to analyze
existing pass schedules to find out potential improvement opportunities.
Lessons
• |
Metal Deformation Pattern in the Continuous Mill and in
Tied Wire Block (NTM) |
• |
High-Quality Roll
Pass Design with Real-World Metal Deformation Pattern |
• |
Features, Internal
Logics and Application Considerations |
• |
Input and Output
Parameters of Each Roll Pass Design Programs |
• |
Roll Pass Design Demo
by Running the Program Pass By Pass |
Lab 15: Roll Pass Design with FreeForm Series RD-OV
• |
Perform Multiple Pass Roll Pass Design for Round-Oval Pass
Sequence (with or without considering tension effects on metal deformation) |
• |
Save A Designed Pass
Sequences to a File, and Reload the Saved Data (for further design or for
modification in order to create a new pass sequence) |
After completing this module, students will be able to:
• |
Design high-quality pass sequence schedules by fully
considering the real deformation pattern of the metal during rolling |
• |
Modify existing pass
schedule to create a new one, or to analyze a pass schedule to find out
potential weaknesses |
Module 16: Roll Pass Design with FreeForm Series (II)
This module further improve students' roll pass design skills
by continued design of high-quality, multiple-pass schedule, for
Square-Diamond (SQ-DI) pass sequence. The work will be done by applying a
high-quality roll pass design software FreeForm Series Square-Diamond.
Students are also welcome to analyze existing pass schedules to find out
potential improvement opportunities.
Lessons
• |
Features, Internal Logics and Application Considerations |
• |
Input and Output Parameters of Each Roll Pass Design
Programs |
• |
Roll Pass Design Demo by Running the Programs |
Lab 16: Roll Pass Design with FreeForm Series SQ-DI
• |
Perform Multiple Pass Roll Pass Design for Round-Oval Pass
Sequence (with or without considering tension effects on metal deformation) |
• |
Save A Designed Pass Sequences to a File, and Reload the
Saved Data (for further design or for modification in order to create a
new pass sequence) |
• |
Others, If Time Allows |
After completing this module, students will be able to:
• |
Design high-quality pass sequence schedules by fully
considering the real deformation pattern of the metal during rolling |
• |
Deeply understand metal deformation pattern in continuous
mills or tied rolling block |
• |
Modify existing pass schedule to create a new one, or to
analyze a pass schedule to find out potential weaknesses |
Module 17: Calculation of Force, Torque and Power
during Rolling
This module guides students to perform rolling mill
force, torque and power calculation, for various pass sequences, by applying
a suite of internet-based mill programs.
Lessons
• |
Features, Internal Logics and Application Considerations of
the Programs |
• |
Input and Output Parameters of Each Programs, and
Involved Technical Issues |
• |
Calculation Demo for Various Grades and Various Pass
Sequences, etc. |
Lab 17: Calculation of Force, Torque and Power during Rolling
• |
Work on Three of the Nine Pass Sequence Cases in the
Force/Torque/Power Calculation (different students may work on different
pass sequences) |
• |
Others If Time Allows |
After completing this module, students will be able to:
• |
Further improve the understanding in the rolling mill
force, torque and power calculation |
• |
Have skills to calculate rolling mill force, torque and
power |
• |
And so on |
Module 18: Temperature Prediction During Rolling
and Controlled Cooling
This module guides students to perform numerical simulation
of the temperature profile over the stock cross-section along the rolling
production line (including the controlled cooling line), using
internet-based Finite-Differential Method (FDM) program. Students will gain
deep understanding on the temperature profiles during rolling and controlled
cooling.
Lessons
• |
Features, Internal Logics and Application Considerations |
• |
Input and Output
Parameters of the Programs |
• |
Finite-Differential
Method in Prediction of Temperature during Rolling and Controlled
Cooling |
• |
Application of FDM
Program for Temperature Prediction |
Lab 18: Use of Web-based FDM Program for Temperature
Prediction during Rolling and Controlled Cooling
• |
Data Input Pass by Pass and Data Calculation |
• |
Output Result and
Analysis |
After completing this module, students will be able to:
• |
Understand temperature process from furnace dropout, air
cooling, rolling, interpass cooling, water-box cooling and free and forced
air cooling, and so on |
• |
Understand temperature distribution over the
cross-section from stock center to the surface |
• |
Perform temperature calculation for temperature progress
throughout the rolling and cooling processes, and in each time point, the
temperature distribution over the stock cross-section |
• |
Understand heat generation through deformation, and the
heat transfer coefficients through heat transfers |
Module 19: Microstructure Prediction with
Web-based Program
This module first covers microstructure evolution during
rolling, such as dynamic and static recrystallization and grain growth, on
the basis of the metallurgical fundamentals discussed in module 7. Then, it
particularly guides the students to perform microstructure simulation for
the steel rolling process pass by pass. Students are asked to do analysis
of the output data in order to deeply understand the microstructural
processes.
Lessons
• |
Microstructure Evolution during Rolling and Interpass Cooling |
• |
Microstructure Models |
• |
Microstructure
Prediction Program Development |
• |
Microstructure
Prediction Program Application |
Lab 19: Microstructure Prediction with Web-based
Microstructure Simulation Program
• |
Microstructure Evolution during Rolling and Interpass Cooling |
• |
Output Results Analysis
in Order to Understand the Evolution Process |
After completing this module, students will be able to:
• |
Understand microstructure evolution during rolling process
pass by pass |
• |
Perform microstructure simulation by applying easy-to-use
simulation software available through internet |
• |
And so on |
Module 20: Review
This
module reinforces the concepts, models and calculation methods that the
students have learned throughout the course. The time may also be used for
covering special topics requested by students, or for students to perform a
small design project.
Lessons
• | Review of Material Covered |
• |
Discuss on the requested topics |
Lab 20: Review
• |
A Simplified Design Project (Optional) |
After completing this module, students will be able to:
• |
Do the rolling process related mill design or mill
improvement |
• |
Calculate rolling process parameters with empirical,
numerical and online methods |
• |
Leave the classroom with smile and confidence |
Metal Pass Consulting
|