Induction Work Roll Heating Technology

for

Superior Rolling Mill Shape Control

2

13

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 aren’t

sufficient to control Flatness;

• Reduce or eliminate edge cracks

and strip breaks;

• Unnecessary slitting sheet edges

due to flawed edge profile;

Work

roll

Backup

roll

Segmented

shape meter

Sheet

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

Sheet

Automated

lubricant sprays

Center buckles & tight edges

Sheet width Sheet width

Shape

profile

Spray

outputsController

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 doesn’t work efficiently in

demanding shape profiles.

Using only cooling sprays

Segmented

Shape Meter

Automated

Induction Workcoils

Sheet

Automated

Lubricant Sprays

More uniform shape profile

Sheet width Sheet width

Shape

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

Edge-Assist

With Comaintel Induction Edge Heating

Loose edges

Compound shape

Center buckles & tight edges

Sheet width

¼-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

Automated

lubricant sprays

Sheet width Sheet width

Controller

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.

¼-buckles & tight edges

Shape

Profile

Segmented

Shape Meter

Full-range Actuator

Outputs

Automated

Induction Workcoils

The Optimal Approach

Induction Work Roll Heating Technology

High-frequency

(≈25 kHz) surface

eddy currents

OptiCoil inductor is

essentially half a

transformer

Energy transfer = f(1/g2)

g

Heats from the outside, to put the

heat on the surface where it’s

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.

OptiCoil

Concentrating the flux in the center

and using high-frequency maximizes power

transfer and reduces sensitivity to gap.

Patented OptiCoil is flat (doesn’t

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

Heating;

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

Comaintel’s 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.

Comaintel’s 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.

Comaintel’s Rolling Mill Induction Heaters