Cold Rolling Mill Edge Heating for Crack-Free Low-Speed Rolling

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Solution Overview

Problem

Conventional cold rolling methods for hard-to-roll materials like silicon steel and stainless steel often result in edge cracks and sheet breakage due to inadequate heating and lubrication, especially during low-speed rolling, leading to increased energy costs and production complexities.

Innovation Solution

A tandem type cold rolling mill with an edge heater and a hybrid coolant system, where the edge portions are heated to above 60°C using an induction heating device and then jetted with a high-concentration coolant to maintain temperature and ensure proper lubrication, reducing heat loss and edge crack occurrence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the steel sheet temperature is increased to improve rolling property, then deformation resistance is decreased, but energy cost increases and production process becomes complicated

Engineering Contradiction:

Improverolling propertyVSAvoidenergy cost

Core Design Contradiction:

StrengthVSUse of energy by moving object

Solution Approach 1:

The patent applies local heating to only the edge portions of the steel sheet rather than heating the entire sheet. This localized approach raises the temperature of edge portions to above 60°C to improve ductility and prevent edge cracks, while keeping the central portion at room temperature, thus avoiding the high energy costs and process complications associated with full-sheet heating.

Inventive Principle:

Principle #3Local quality

2Temperature

If induction heating is applied to edge portions, then edge temperature increases to prevent edge crack, but lap length control becomes critical due to sheet meandering

Engineering Contradiction:

Improveedge temperatureVSAvoidlap length control

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The patent employs adjustable inductors that can be moved in the widthwise direction to dynamically adapt to sheet width variations and meandering. This dynamic adjustment capability allows the inductors to maintain optimal lap length with the edge portions despite fluctuations in sheet position, eliminating the need for complex control systems while ensuring consistent heating quality.

Inventive Principle:

Principle #15Dynamics

3Temperature

If coolant is jetted at entry side to cool the steel sheet, then rolling temperature is controlled, but heated edge portions are cooled before rolling causing increased energy consumption

Engineering Contradiction:

Improverolling temperatureVSAvoidenergy consumption

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The patent segments the coolant application into two distinct zones: high-concentration coolant is jetted only at the edge portions to maintain heating effects and prevent edge cracks, while low-concentration coolant is applied to the central portion for general temperature control. This segmented approach prevents the wasteful cooling of already-heated edge portions, thereby reducing energy consumption while maintaining effective temperature control.

Inventive Principle:

Principle #1Segmentation

4Temperature

If high-concentration coolant is jetted onto heated edge portions, then heat loss is reduced and edge temperature is maintained, but lubrication effectiveness must be ensured

Engineering Contradiction:

Improveedge temperatureVSAvoidlubrication effectiveness

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent changes the concentration parameter of the coolant by using high-concentration coolant (with higher rolling oil content) specifically for the edge portions. This parameter change serves dual purposes: the high concentration of rolling oil provides both thermal insulation to maintain edge temperature and adequate lubrication effectiveness, eliminating the need for separate heating and lubrication systems.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach prevents edge cracks and sheet breakage in low-speed rolling, stabilizes edge temperatures, and reduces energy consumption while improving product quality and productivity.

Implementation Method 1

a high-frequency current is flowed to an induction heating coil 3 to generate a high-frequency magnetic flux, whereby an induction current is generated in the edge portion of the steel sheet and the edge portion of the steel sheet is heated by Joule heat generated by the induction current

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the edge portion of the steel sheet is heated by Joule heat generated by the induction current

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS11612923B2Cold rolling mill and cold rolling method

Publication Date: 2023.03.28 JFE STEEL CORP

AI summary

In a tandem type cold rolling mill of a circulating oil-feeding system for continuously rolling a steel sheet by feeding a coolant serving as a rolling oil and a cooling water to each stand, an edge heater for heating both edge portions of the steel sheet to not lower than 60° C. as a steel sheet temperature at an entry side of a roll bite is arranged at an upstream side of the first stand in the cold rolling mill and a device for jetting a coolant having a concentration higher than that of the coolant fed to the firsts stand onto surfaces of both edge portions of the steel sheet is arranged between the edge heater and the first stand. The cold rolling mill can be used to roll a hard-to-roll material such as silicon or stainless steel sheet without causing an edge crack or sheet breakage in low-speed rolling.