Method for evaluating the hydrogen content in a steel sheet

Patent metadata

Field	Value
Publication number	US-2025035607-A1
Application number	US-202218716687-A
Country	US
Kind code	A1
Filing date	Dec 6, 2022
Priority date	Dec 17, 2021
Publication date	Jan 30, 2025
Grant date	—

Abstract

A method for evaluating the hydrogen content in a steel sheet while being submitted to an annealing process, including the following steps: estimating the microstructure of the steel sheet according to the temperature curve, computing the solubility of the hydrogen CH, computing the volume concentration of trapped hydrogen in dislocations CT and the volume concentration of hydrogen in interstitial sites of the crystal lattice CL, calculating the hydrogen content Ctotal=CL+CT at each time step of the annealing process and outputting the hydrogen content Ctotal at each time step to a user.

First claim

What is claimed is:

1 - 6 . (canceled)

7 . A method for evaluating hydrogen content in a steel sheet undergoing at least one annealing process following a thermal path, a temperature T measureable by sensors in a furnace having an atmosphere comprising hydrogen, the steel sheet comprising grains in which atoms are arranged in a crystal lattice, thus forming a microstructure of the steel including dislocations C T and interstitial sites C L , the method comprising the following successive steps:
determining the microstructure of the steel sheet as a function of the thermal path; computing a solubility of the hydrogen C H , at the surface of the steel sheet as a function of the microstructure, the temperature T and a hydrogen partial pressure p H2 ; computing the volume concentration of trapped hydrogen in dislocations C T and the volume concentration of hydrogen in interstitial sites C L , as a function of the temperature T, of trapping rate of hydrogen k, of detrapping rate of hydrogen p, of C H and of the microstructure; calculating the hydrogen content C total =C L +C T at any time of the annealing process; and outputting through a computer display the hydrogen content C total at any time to a user.

8 . The method as recited in claim 7 wherein C T and C L are calculated through the resolution of the following equations over at least part of the thickness of said steel sheet:

∂

C
L

∂
t

+

∂

C
T

∂
t

[
3
]

∂

C
T

∂
t

=

k

N
L

⁢

C
L

(

N
T

-

N
A

×

C
T

)

[
4
]

D L being the lattice diffusion coefficient of hydrogen in the crystal lattice,
x being the depth inside said steel sheet,
N L being the volume density of interstitial sites,
N T being the volume density of dislocations,
N A being the Avogadro constant.

9 . The method as recited in claim 7 wherein the solubility of the hydrogen C H is calculated through the following equations:
for a temperature T below or equal to Ac3,

log
⁢

(

C
H

)

=

0.5

log
⁢

(

p

H
2

)

-
3
-

1
⁢
5
⁢
0
⁢
0

T

[
1
]

for a temperature T above Ac3,

log
⁢

(

C
H

)

=

0.5

log
⁢

(

p

H
2

)

-

2
.
9

-

1
⁢
4
⁢
9
⁢
0

T

Assignees

• Arcelormittal

Inventors

• Dieudonne Thomas

Classifications

• C21D2211/008

  Martensite · CPC title

• C21D2211/005

  Ferrite · CPC title

• C21D2211/002

  Bainite · CPC title

• C21D2211/001

  Austenite · CPC title

• C21D1/74

  Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material · CPC title