Induction - Rolling Mill Sheet Flatness control

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Induction Work Roll Heating Technology for Superior Rolling Mill Shape Control

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  • Induction Work Roll Heating Technology


    Superior Rolling Mill Shape Control

  • 2


    Backup roll

    Work roll

    1) Roll separation forces can cause work rolls to bend

    around the sheet, producing loose edges.

    2) Hydraulic edge jacks and stiff backup rolls partially

    counter bending around the sheet.

    3) Eventual work roll thermal expansion can generate a

    thermal crown, producing tight edges.

    The Challenge

    Mill Speed reduced to produce

    thin gauge sheet;

    Use of conventional coolant

    sprays and actuators arent

    sufficient to control Flatness;

    Reduce or eliminate edge cracks

    and strip breaks;

    Unnecessary slitting sheet edges

    due to flawed edge profile;

  • Work





    shape meter


    Lubricant sprays are used to reduce roll separation

    forces and cool the rolls, to remove debris and

    reduce roll wear.

    Conventional Corrective Tools

  • Segmented

    shape meter



    lubricant sprays

    Center buckles & tight edges

    Sheet width Sheet width





    Target Shape

    Zone-controlled lubricant sprays were

    invented to correct the gauge, profile, and

    shape automatically, by cooling the work roll

    where the sheet is thin, overworked or loose

    however it doesnt work efficiently in

    demanding shape profiles.

    Using only cooling sprays

  • Segmented

    Shape Meter


    Induction Workcoils



    Lubricant Sprays

    More uniform shape profile

    Sheet width Sheet width


    Profile Controller

    Target Shape

    Zone-controlled lubricant sprays combined

    with induction edge-heaters correct basic

    shape variations more effectively, by

    cooling the work roll where needed and

    heating the edges.

    Spray Outputs with


    With Comaintel Induction Edge Heating

  • Loose edges

    Compound shape

    Center buckles & tight edges

    Sheet width

    -buckles & tight edges

    However, set-up variations, machine

    wear, material variations, and

    transient effects (progressive work roll

    thermal deformation) can produce

    complex shape profiles that change

    throughout the production cycle.

    Limitations and Opportunities

  • Sheet


    lubricant sprays

    Sheet width Sheet width


    Target Shape

    Zone-controlled lubricant sprays and

    induction workcoils correct even complex

    shape variations, by both heating and

    cooling the work roll to directly attack

    loose and tight regions of the profile.

    -buckles & tight edges




    Shape Meter

    Full-range Actuator



    Induction Workcoils

    The Optimal Approach

  • Induction Work Roll Heating Technology


    (25 kHz) surface

    eddy currents

    OptiCoil inductor is

    essentially half a


    Energy transfer = f(1/g2)


    Heats from the outside, to put the

    heat on the surface where its

    needed, for faster response

    Designed to optimally heat only

    ferrous materials. Electrical

    resistance must be low enough to

    permit generation of high eddy

    currents at negligible voltage

    levels, but high enough to cause

    resistive heating.


    Concentrating the flux in the center

    and using high-frequency maximizes power

    transfer and reduces sensitivity to gap.

    Patented OptiCoil is flat (doesnt

    need to match roll curvature), so it

    fits any work roll diameter and

    accommodates gaps up to 6 mm.

    Work Roll

  • A typical roll edge induction heater has

    two (2) Opticoils installed on roll edges

  • Actual heating zone width

    with Comaintel 30 mm heaters

  • Roll face temperature rise at 4 kWatts

  • Optimal Flatness Control with Full Width Induction Heating

    What: Staggered Liquid Cooled Induction Coils for Full Width Flatness Control;

    Independent Controlled Induction Coils and Power Module for more

    Efficient Flatness Control;

    Most Powerful and Efficient 12 kW Power Modules in the Industry;

    Where to use them: Pre-Heat Work Roll for Immediate Required Flatness Profile Production;

    Produce Complex Shape Profile with Independent Induction Zone


    Why: Faster Start-Ups;

    Less Waste;

    Increase Mill Speed;

    Reduce Strip Breaks;

    Full Profile Control;

    Produce Complex Profiles;

    Save Energy with highly Efficient Induction Heating (up to 95%).

  • Typical workcoil tight staggered beam

  • A typical full width beam

    using Xcore LC (Induction Coils) technology

  • A typical Off-machine Cabinet

    for 100 kW/meter power density

  • The effects of air gap on workcoil efficiency

  • Multiple heating zones across roll face

    for temperature control

  • Comaintels Edge Induction Heater Solution:

    Adding Induction heaters on tight edges helps correct the overall work

    roll nip pressure profile. This corrects tight edges problems while

    allowing cooling sprays to work more efficiently.

    Comaintels Full Width Induction Heater Solution:

    Adding narrow zone Induction heaters full width across the face of the

    work roll combined with existing cooling of loose regions significantly

    increase sheet shape control range and response.

    Both Solutions enable higher quality to be produced

    at faster speeds.

    Comaintels Rolling Mill Induction Heaters