Determining the ferrite phase fraction after heating or cooling of a steel strip

Patent metadata

Field	Value
Publication number	US-10655197-B2
Application number	US-201414888821-A
Country	US
Kind code	B2
Filing date	Apr 4, 2014
Priority date	May 3, 2013
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

A method for determining the ferrite phase fraction x a after heating or when cooling a steel strip ( 2 ) in a metallurgic system. Also, a device for carrying out the method. A method by which the ferrite phase fraction in the steel strip ( 2 ) can be determined online, quickly and easily, includes measuring a width w 1 and a temperature T 1 of the steel strip ( 2 ), wherein the steel strip ( 2 ) comprises a ferrite phase fraction x a 1 during the measurements; heating or cooling the steel strip ( 2 ); when heating the steel strip ( 2 ) a phase conversion at least in part occurs, a→y from the ferrite state a into the austenitic state y and when cooling the steel strip a phase conversion at least in part occurs, from the austenitic state y into the ferrite state a; measuring of a width w and a temperature T of steel strip ( 2 ) converted at least in part; determining the ferrite phase fraction of the formula (I), wherein T 0 is a reference temperature and a a and a y are the linear heat expansion coefficients of ferrite and austenite.

First claim

The invention claimed is:

1. A method for determining a ferritic phase fraction x α of an at least partly converted steel strip after at least one of heating or cooling of the steel strip, comprising the following method steps in sequence:
measuring a width w 1 and a temperature T 1 of the steel strip, wherein the steel strip has a ferritic phase fraction x α1 during the measurement;
heating or cooling the steel strip, wherein at least a partial phase conversion from a ferritic state α into an austenitic state γ takes place in the steel strip during heating or at least a partial phase conversion from an austenitic state γ into a ferritic state α takes place in the steel strip during cooling;
measuring a width w and a temperature T of the at least partly converted steel strip and;
determining the ferritic phase fraction x α of the at least partly converted steel strip through

x
α

=

-
w

-

w
⁢

⁢

x
α1

⁢

α
α

⁡

(

T
1

-

T
0

)

-

w
⁢

⁢

α
γ

⁢

(

T
1

-

T
0

)

+

w
⁢

⁢

x
α1

⁢

α
γ

⁡

(

T
1

-

T
0

)

+

w
1

+

w
1

⁢

α
γ

⁡

(

T
-

T
0

)

w
1

⁡

[

-

α
α

⁡

(

T
-

T
0

)

+

α
γ

⁡

(

T
-

T
0

)

]

,

wherein
T 0 is a reference temperature and
α α and α γ are linear coefficients of thermal expansion of ferrite and austenite, respectively.

2. A method for determining a ferritic phase fraction x α of an at least partly converted steel strip after

Assignees

• Primetals Technologies Austria GmbH

Inventors

• Burger Rainer
• Linsbod Robert
• Linzer Bernd
• Mikota Josef
• Rimnac Axel

Classifications

• C21D9/54

  Furnaces for treating strips or wire · CPC title

• C21D1/00 Primary

  General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering · CPC title

• C21D1/54

  Determining when the hardening temperature has been reached by measurement of magnetic or electrical properties · CPC title

• G05D23/00

  Control of temperature · CPC title

• C21D2211/005

  Ferrite · CPC title