US 2010/0300583 A1Published application

Process for the production of a grain oriented magnetic strip

AssigneeCentro Sviluppo Materiali S.p.A.

InventorsGiuseppe Abbruzzese, Stefano Cicale', Stefano Fortunati

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Abstract

A process for the production of a grain oriented magnetic strip, made of steel containing 2.3 to 5.0% of silicon, obtained by producing a hot-rolled sheet containing a distribution of second phases capable of controlling the secondary recrystallization by means of a two-step hot-rolling with an intermediate annealing, and by changing it into the final product.

Claims9

Dependent claims

A process for the production of grain oriented magnetic strip wherein a silicon steel is continuously cast, solidified and subjected to the following operations in sequence:

hot-rolling of the slab;
cooling of the hot-rolled sheet and coiling thereof;
optional annealing of the hot-rolled sheet;
cold-rolling until obtaining a strip;
decarburization annealing and primary recrystallization of the strip;
applying of an annealing separator onto the strip surface;
secondary recrystallization annealing of the strip,
and wherein the sheet and/or the strip is optionally nitrided,
characterised in that:
the steel comprises the following components, expressed in weight concentration:
Si comprised between 2.3% and 5.0%,
N comprised in the range of 20-200 ppm,
S and/or Se so that (S+(32/79)Se) be comprised in the range of between 30 and 350 ppm,
at least two elements of the series B, Al, Cr, V, Ti, W, Nb, Zr and at least one of the elements of the series Mn, Cu, such that the two quantities:
F
N
=
[
B
]
M
B
+
[
Al
]
M
Al
+
[
Cr
]
M
Cr
+
[
V
]
M
V
+
[
Ti
]
M
Ti
+
[
W
]
M
W
+
[
Nb
]
M
Nb
+
[
Zr
]
M
Zr
F
S
=
[
Mn
]
M
Mn
+
[
Cu
]
M
Cu
where [X] represents the weight concentration of element X expressed in ppm and Mx the related atomic weight, be such as to satisfy the following relationships:
1.5
·
(
[
N
]
M
N
)
<
F
N
<
40
[
S
]
+
32
79

[
Se
]
M
S
<
F
S
<
100
;
optionally C up to 800 ppm, Sn, Sb, As in concentrations such that their sum does not exceed 1500 ppm and/or P, Bi, in concentrations such that their sum does not exceed 300 ppm,
the remaining part being iron and unavoidable impurities,
and in that the resulting slab, solidified in a time lower than 6 minutes, is subjected, in the absence of a heating prior to the hot-rolling, to the following operations in sequence:
first step of the hot-rolling to a thickness of 15-30 mm, with a reduction ratio of at least 50%;
said rolling being carried out in a time interval lower than 100 s after complete solidification of the steel at a surface temperature (Tsur), before the start of said rolling, comprised between 1050° C. and 1300° C. and a core temperature (Tcore) comprised between 1100° C. and 1400° C., as well as a difference (Tcore−Tsur) greater than 30° C. (with Tcore always greater than Tsur), being the surface temperature Tsur the temperature of the slab section at a depth equal to 20% of the thickness and the core temperature Tcore the temperature of the section at the core of the slab thickness;
normalizing annealing of the rolled slab at a temperature of 900-1150° C. for a time of 1-30 min;
second step of the hot-rolling at rolling starting temperatures comprised between 880° C.-1150° C., until obtaining a sheet of <5-mm thickness.

115 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/595,659Filed 18 Apr 2008
Priority: IT RM2007A00021818 Apr 2007
Published: 2 Dec 2010
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

C21D 8/12
Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment: during…
C21D 8/1255
Characterised by the heat treatment: with diffusion of elements, e.g. decarburising, nitriding
C21D 8/1272
Characterised by the heat treatment: final recrystallisation annealing
C21D 8/1283
Involving a particular surface treatment: application of a separating or insulating coating

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US 8,277,573 B2Related patent
US 2010/0300583 A1This patent

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Abstract

A process for the production of grain oriented magnetic strip wherein a silicon steel is continuously cast, solidified and subjected to the following operations in sequence:

hot-rolling of the slab;
cooling of the hot-rolled sheet and coiling thereof;
optional annealing of the hot-rolled sheet;
cold-rolling until obtaining a strip;
decarburization annealing and primary recrystallization of the strip;
applying of an annealing separator onto the strip surface;
secondary recrystallization annealing of the strip,
and wherein the sheet and/or the strip is optionally nitrided,
characterised in that:
the steel comprises the following components, expressed in weight concentration:
Si comprised between 2.3% and 5.0%,
N comprised in the range of 20-200 ppm,
S and/or Se so that (S+(32/79)Se) be comprised in the range of between 30 and 350 ppm,
at least two elements of the series B, Al, Cr, V, Ti, W, Nb, Zr and at least one of the elements of the series Mn, Cu, such that the two quantities:
F
N
=
[
B
]
M
B
+
[
Al
]
M
Al
+
[
Cr
]
M
Cr
+
[
V
]
M
V
+
[
Ti
]
M
Ti
+
[
W
]
M
W
+
[
Nb
]
M
Nb
+
[
Zr
]
M
Zr
F
S
=
[
Mn
]
M
Mn
+
[
Cu
]
M
Cu
where [X] represents the weight concentration of element X expressed in ppm and Mx the related atomic weight, be such as to satisfy the following relationships:
1.5
·
(
[
N
]
M
N
)
<
F
N
<
40
[
S
]
+
32
79

[
Se
]
M
S
<
F
S
<
100
;
optionally C up to 800 ppm, Sn, Sb, As in concentrations such that their sum does not exceed 1500 ppm and/or P, Bi, in concentrations such that their sum does not exceed 300 ppm,
the remaining part being iron and unavoidable impurities,
and in that the resulting slab, solidified in a time lower than 6 minutes, is subjected, in the absence of a heating prior to the hot-rolling, to the following operations in sequence:
first step of the hot-rolling to a thickness of 15-30 mm, with a reduction ratio of at least 50%;
said rolling being carried out in a time interval lower than 100 s after complete solidification of the steel at a surface temperature (Tsur), before the start of said rolling, comprised between 1050° C. and 1300° C. and a core temperature (Tcore) comprised between 1100° C. and 1400° C., as well as a difference (Tcore−Tsur) greater than 30° C. (with Tcore always greater than Tsur), being the surface temperature Tsur the temperature of the slab section at a depth equal to 20% of the thickness and the core temperature Tcore the temperature of the section at the core of the slab thickness;
normalizing annealing of the rolled slab at a temperature of 900-1150° C. for a time of 1-30 min;
second step of the hot-rolling at rolling starting temperatures comprised between 880° C.-1150° C., until obtaining a sheet of <5-mm thickness.

115 more elements

Facts

Application

12/595,659Filed 18 Apr 2008

Priority

IT RM2007A00021818 Apr 2007

Published

2 Dec 2010

Term ends

Not estimatedThe source records don’t support an estimate.

Classification9 codes

C21D 8/12
Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment: during…
C21D 8/1255
Characterised by the heat treatment: with diffusion of elements, e.g. decarburising, nitriding
C21D 8/1272
Characterised by the heat treatment: final recrystallisation annealing
C21D 8/1283
Involving a particular surface treatment: application of a separating or insulating coating