U.S. patent application number 13/520405 was filed with the patent office on 2012-12-20 for cold rolled electromagnetic steel sheet used for rapid cycling synchrotron and producing method thereof.
This patent application is currently assigned to BAOSHAN IRON & STEEL CO., LTD.. Invention is credited to Lingfeng Chen, Xiao Chen, Zhanyuan Hu.
Application Number | 20120318411 13/520405 |
Document ID | / |
Family ID | 45722851 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120318411 |
Kind Code |
A1 |
Chen; Lingfeng ; et
al. |
December 20, 2012 |
COLD ROLLED ELECTROMAGNETIC STEEL SHEET USED FOR RAPID CYCLING
SYNCHROTRON AND PRODUCING METHOD THEREOF
Abstract
A cold rolled electromagnetic steel sheet for rapid cycling
synchrotron, and a manufacturing method thereof, the method
includes the steps of 1) smelting and casting, the composition of
the cold rolled electromagnetic steel sheet is C 0.001-0.003 wt %,
Si 0.60%-0.90 wt %, Mn 0.40%-0.70 wt %, P.ltoreq.0.04 wt %, Al
0.60-0.80 wt %, S.ltoreq.0.0035 wt %, N.ltoreq.0.003 wt %, and the
rest is Fe; smelting and RH refining, and then casting to form
semi-finished product; 2) hot rolling; 3) normalizing, in which the
normalizing temperature is controlled between 960.degree.
C.-980.degree. C., and the normalizing time is 30-60 sec; 4)
pickling and cold rolling; 5) annealing, wherein the annealing
temperature is controlled to be between 850.degree. C.-870.degree.
C., and the annealing time is 13-15 sec; 6) obtaining non-oriented
silicon steel product after coating. The cold rolled
electromagnetic steel sheet of the present invention has low
coercivity, specifically in case that the magnetizing intense
returns to zero after reaching 10 Oersted (Oe), the coercivity of
the material is Hc.ltoreq.79.6 A/m; high magnetic induction, which
is B50.gtoreq.1.75 T; and low iron losses of P15/50.ltoreq.4.2
W/kg, and the iron losses after strain-annealing is
P15/50.ltoreq.3.5 W/kg.
Inventors: |
Chen; Lingfeng; (Shanghai,
CN) ; Chen; Xiao; (Shanghai, CN) ; Hu;
Zhanyuan; (Shanghai, CN) |
Assignee: |
BAOSHAN IRON & STEEL CO.,
LTD.
Shanghai
CN
|
Family ID: |
45722851 |
Appl. No.: |
13/520405 |
Filed: |
April 13, 2011 |
PCT Filed: |
April 13, 2011 |
PCT NO: |
PCT/CN2011/072709 |
371 Date: |
July 3, 2012 |
Current U.S.
Class: |
148/522 ;
148/307 |
Current CPC
Class: |
C22C 38/04 20130101;
C21D 8/12 20130101; C22C 38/001 20130101; C21D 8/1233 20130101;
C22C 38/004 20130101; C22C 38/02 20130101; C22C 38/002 20130101;
C22C 38/06 20130101 |
Class at
Publication: |
148/522 ;
148/307 |
International
Class: |
C21D 8/12 20060101
C21D008/12; H01F 1/01 20060101 H01F001/01 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2010 |
CN |
201010265803.1 |
Claims
1. A cold rolled electromagnetic steel sheet for a rapid cycling
synchrotron, the composition of which is C 0.001-0.003 wt %, Si
0.60%-0.90 wt %, Mn 0.40%-0.70 wt %, P.ltoreq.0.04 wt %, Al
0.60-0.80 wt %, S.ltoreq.0.0035 wt %, N.ltoreq.0.003 wt %, and the
rest are Fe and unavoidable impurities.
2. A method for manufacturing cold rolled electromagnetic steel
sheet for rapid cycling synchrotron as in claim 1, including the
steps of: 1) smelting and casting, wherein the composition of the
cold rolled electromagnetic steel sheet is C 0.001-0.003 wt %, Si
0.60%-0.90 wt %, Mn 0.40%-0.70 wt %, P.ltoreq.0.04 wt %, Al
0.60-0.80 wt %, S.ltoreq.0.0035 wt %, N.ltoreq.0.003 wt %, and the
rest are Fe and unavoidable impurities; wherein carrying out
smelting, RH refining under the said composition, and then casting
liquid steel to form semi-finished product, wherein when the RH
refining is finished, contents of free oxygen in the liquid steel
is lower than 25 ppm; 2) hot rolling; 3) normalizing, in which
normalizing temperature is controlled between 960.degree.
C.-980.degree. C., and normalizing time is 30-60 sec; 4) pickling
and cold rolling; 5) annealing, wherein annealing temperature is
controlled to be between 850.degree. C.-870.degree. C., and the
annealing time is 13-15 sec; 6) obtaining non-oriented silicon
steel product after coating.
3. The method for manufacturing a cold rolled electromagnetic steel
sheet for rapid cycling synchrotron according to claim 2, wherein
an average size of grain in the steel sheet is more than 40
.mu.m.
4. The method for manufacturing cold rolled electromagnetic steel
sheet for rapid cycling synchrotron according to claim 2, wherein
an average size of grain in the steel sheet is controlled to be
between 40-45 .mu.m.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a cold rolled
electromagnetic steel sheet, particularly to a cold rolled
electromagnetic steel sheet for rapid cycling synchrotron, and a
manufacturing method thereof.
BACKGROUND
[0002] One of the important features of a rapid cycling synchrotron
is that the magnetizing current operates in a DC-biased sinusoidal
current state, a rapid cycling synchrotron (RCS) with relative high
energy is used to accelerate particles to increase the energy; and
when a certain requirement for beam energy is obtained, it is drawn
from a ring and scattered to a spallation target. Based on
characteristics of the device, there are relative high requirements
for the cold rolled electromagnetic steel sheets for manufacturing
the magnet:
[0003] Low coercivity: when magnetizing intense returns to zero
after reaching 10 Oersted (Oe), the coercivity of the material
Hc.ltoreq.79.6 A/m.
[0004] High electromagnetic induction: B50.gtoreq.1.74 T, with the
controlling object of 1.75-1.76 T; low iron losses:
P15/50.ltoreq.4.7 W/kg, with the controlling object of 3.8-4.2
W/kg, and the iron losses after strain-annealing is
P15/50.ltoreq.3.5 W/kg,with the controlling object of 2.8-3.2
W/kg.
[0005] Currently, in Japan, Europe and United States, the
electromagnetic steel sheets for rapid cycling synchrotron are
mainly manufactured by the following method:
[0006] 1. JP H05-247604 discloses a method of tempering (by
critical reduction rate) extra-low carbon aluminum killed steel.
The purpose of critical tempering is to coarsen the grain of the
pure iron belt when the user carries out electromagnetic annealing,
so that extra-low coercivity can be obtained. The drawbacks of the
method are that since the critical reduction rate is relative
large, which causes strain ageing, so that the hardness of the pure
iron belt increases rapidly after being delivered. Thus, it will be
difficult for the user to punch the iron belt. And, if the pure
iron belt is annealed by a bell type furnace, the performance of
the magnet will suffer fluctuation caused by the fluctuation of the
pure iron belt in lengthwise.
[0007] 2. The rapid cycling synchrotrons in United States and
Germany mainly use ordinary non-oriented electrical steel, such as
M600-50A or M470-50A and so on. The product is obtained by the
manufacturing method of smelting-continuous casting-hot
rolling-pickling-cold rolling-annealing-coating. Although the
product satisfies the requirements in terms of coercivity and iron
losses, its electromagnetic induction is relative low, with B50
actual in the range of 1.69-1.72 T, which directly effect the
capacity of the rapid cycling synchrotron.
[0008] Thus, it can be seen that the drawbacks of the rapid cycling
synchrotron caused by the present cold rolled electromagnetic steel
sheets is that:
[0009] 1. The iron losses and the coercivity satisfy the
requirements, but the electromagnetic induction is relative
low.
[0010] The performance of the product can satisfy the requirements,
but the processing prosperities and the stability are relative
low.
SUMMARY
[0011] The purpose of the present invention is to provide a cold
rolled electromagnetic steel sheet for rapid cycling synchrotron,
and manufacturing method thereof, in order to obtain a cold rolled
electromagnetic steel sheet with low iron losses, low coercivity
and high electromagnetic induction. Namely, it has low coercivity,
specifically when the magnetizing intense returns to zero after
reaching 10 Oersted (Oe), the coercivity of the material is
Hc.ltoreq.79.6 A/m; high electromagnetic induction, which is
B50.gtoreq.1.75 T; and low iron losses of P15/50.ltoreq.4.2 W/kg,
and the iron losses after strain-annealing is P15/50.ltoreq.3.2
W/kg.
[0012] To fulfill the above purpose, technical solution of the
present invention is as follows:
[0013] a cold rolled electromagnetic steel sheet for rapid cycling
synchrotron, the composition of which is C 0.001-0.003 wt %, Si
0.60%-0.90 wt %, Mn 0.40%-0.70 wt %, P.ltoreq.0.04 wt %, Al
0.60-0.80 wt %, S.ltoreq.0.0035 wt %, N.ltoreq.0.003 wt %, and the
rest of the components are Fe and unavoidable impurities.
[0014] The method for manufacturing a cold rolled electromagnetic
steel sheet for rapid cycling synchrotron according to the present
invention includes the steps of:
[0015] 1) smelting and casting, wherein the composition of the cold
rolled electromagnetic steel sheet is C 0.001-0.003 wt %, Si
0.60%-0.90 wt %, Mn 0.40%-0.70 wt %, P.ltoreq.0.04 wt %, Al
0.60-0.80 wt %, S.ltoreq.0.0035 wt %, N.ltoreq.0.003 wt %, and the
rest components are Fe and unavoidable impurities; carrying out
smelting, RH refining according to the above mentioned components,
and then casting the liquid steel to form semi-finished product,
wherein when the RH refining is finished, the free oxygen in the
liquid steel is lower than 25 ppm;
[0016] 2) Hot rolling;
[0017] 3) Normalizing, in which the normalizing temperature is
controlled to be between 960.degree. C.-980.degree. C., and the
normalizing time is 30-60 sec;
[0018] 4) Pickling and cold rolling;
[0019] 5) Annealing, in which the annealing temperature is
controlled to be between 850.degree. C.-870.degree. C., and the
annealing time is 13-15 sec;
[0020] 6) Obtaining non-oriented silicon steel product after
coating.
[0021] Further, average grain size in the steel sheet is more than
40 .mu.m, preferably is controlled to be between 40-50 .mu.m.
[0022] The design for the composition of the present invention is
as follows:
[0023] Carbon of less than 0.003%, which is in the form of
interstitial phase atom of iron based lattice cell, and strongly
hinders the grain's growth, and in turn results in degradation of
iron losses and coercivity. If the carbon exceeds 0.005%,
decarburization will become difficult, and it will cause magnetic
ageing, which results in substantial degradation in term of iron
losses. Therefore, it is preferably to control the content of
carbon to be lower than 0.003%.
[0024] Silicon of between 0.60%-0.90%, which is a vital alloy
element of the electromagnetic steel sheet, and contributes to
improve the resistivity, reduce eddy current losses, and reduce
iron losses. If content of the silicon is too low, the iron losses
will be degraded, and if the content of the silicon is too high,
the processability of the electrical steel will be degraded, and
the electromagnetic induction will decrease.
[0025] Manganese of 0.40%-0.70%, which mainly functions to increase
resistivity, to reduce iron losses and meanwhile to change surface
condition. If the content of the manganese is too high, it will
make the following cold processes difficult, and if the content of
the manganese is too low, the iron losses will increase, which
results in hot brittle.
[0026] Phosphor of lower than 0.04%, which mainly functions to
improve processability of the steel sheet. As the phosphor is a
grain boundary polyvinylidene element, if its content is too high,
the processability will be degraded, and the coercivity will rise
at the same time.
[0027] Aluminum of 0.60%-0.80%, which is mainly for increasing
resistivity, lowering iron losses, and decreasing the oxidized
impurities during steel making, and further increasing
electromagnetic induction and lowering coercivity. If the content
of aluminum is too high, it will be difficult to carry out pouring
during continuous casting, and result in decrease of
electromagnetic induction, and if the content of aluminum is too
low, the iron losses and the coercivity will be degraded.
[0028] Sulphur of less than 0.0035%. If the content of the sulphur
is more than 0.0035%, precipitation amount of manganese sulfide
will increase that intensively hinders grain growth, and the iron
losses and coercivity will be degraded.
[0029] Nitrogen of less than 0.003%. If the content of the nitrogen
is more than 0.003%, precipitation amount of aluminium nitride will
increase that intensively hinders grain growth, and the iron losses
and coercivity will be degraded.
[0030] In the manufacturing method of the present invention, when
the RH refining process is completed, content of free oxygen in
liquid steel is less than 25 ppm. Thus, generally the oxidized
impurities in the steel are reduced, and then the iron losses and
coercivity are decreased effectively.
[0031] When the RH refining is completed, if content of free oxygen
in liquid steel is more than 25 ppm, the excessive free oxygen will
act with the Si, Mn, P, Al in the steel to form a small quantity of
three composition oxidized impurity of
SiO.sub.2--Al.sub.2O.sub.3--MnO, accompanied with slight amount of
P.sub.2O.sub.5, so as to distort crystal lattice of the cured
material, which results in increase of magnetostatic energy and
magnetoelastic energy, and increase of domain wall motion
resistance.
[0032] Meanwhile, during hot rolling under 1100.degree.
C.-880.degree. C., the three composition oxidized impurity of
SiO.sub.2--Al.sub.2O.sub.3--MnO possesses sound plasticity, so as
to be rolled into chain-shape and bar-shape impurity. During cold
rolling process, the three composition oxidized impurity of
SiO.sub.2--Al.sub.2O.sub.3--MnO presents brittleness
characteristic, so that it can be easily rolled in a long string of
particle-shaped impurities, i.e. forming composite oxidized
impurities primarily of C-type impurity (chain-shape and bar shape)
and secondarily of D-type impurity (dot-shaped). This results in
difficulty of magnetizing, decrease of electromagnetic induction
intense and increase of coercivity.
[0033] Deoxidizing intensity of metal elements differs from balance
point of oxygen in steel, which in sequence shall be Al, Si, Mn.
Therefore, during smelting, by controlling total amount of Si+Al at
1.2%-1.7%, the SiO.sub.2--Al.sub.2O.sub.3 formed in the prophase of
refining can be sufficiently removed from the steel. Meanwhile,
when free oxygen is kept below 25 ppm, and Mn in the steel is
controlled to be 0.40%-0.70%, i.e. in an atmosphere of poor oxygen
and rich manganese, production of the three compositions oxidized
impurity of SiO.sub.2--Al.sub.2O.sub.3--MnO is further reduced.
Thus, the composition oxidized impurity primarily produced in the
following processes of hot rolling and cold rolling, which is of
C-type impurity (chain-shape and bar shape) and secondarily of
D-type impurity (dot-shaped), can be reduced, so the grain growth
is promoted, the electromagnetic induction is improved, and the
coercivity is lowered.
[0034] For normalizing, the normalizing temperature is controlled
to be between 960.degree. C.-980.degree. C., and the normalizing
time is 30-60 sec. The control of the normalizing temperature
relates to Si, Mn, Al, N, C, S. The increase in the contents of Si,
Al, Mn may help in lowering the normalizing temperature, but if the
normalizing temperature is too low, and if the normalizing time is
too short, accumulation and growth of the product precipitated from
the steel will be negatively affected, which may result in decrease
of the magnetic induction and degradation of iron losses and
coercivity. If the contents of Si, Al, Mn is decreased, the
normalizing temperature will be increased, but if the normalizing
temperature is too high, and if the normalizing time is too long,
the loss on ignition of the steel will increase, part of the
precipitated products from the steel, such as Mn, AIN and the like,
are solid solved, which will result dispersion after cold rolling
and annealing, so that carbon and nitrogen deposition will be
precipitated, which will severely degrade the iron losses and
coercivity. To this end, while the normalizing temperature is
controlled, the contents of the sulphur and the nitrogen are
required to be S.ltoreq.0.0035% and N.ltoreq.0.003%.
[0035] For annealing, the annealing temperature is controlled to be
between 850.degree. C.-870.degree. C., and the annealing time is
13-15 sec. If the annealing temperature is too high, and if the
annealing time is too long, average diameter of the grain will
excessively large, thus the electromagnetic induction is lowered,
and the processability degrades; while if the annealing temperature
is too low, and if the annealing time is too short, the grain
growth will be hindered, so that the iron losses and the coercivity
are degraded, because of the presence of phosphor in the steel,
which results in grain boundary polyvinylidene. To this end, when
the annealing temperature is controlled, the content of P element
is required to be P.ltoreq.0.04%.
[0036] The average grain size in the steel sheet is more than 40
.mu.m, preferably is controlled to be between 40-50 .mu.m. The
grain size has certain relationship with the coercivity. If the
grain is too small, the iron losses will increase, and the
coercivity is relatively large. If the grain is too large, area
occupied by the gain boundary will decreases, so that the
coercivity will decreases at the same time, but the magnetic
induction will further decreases.
Beneficial Effects of the Invention
[0037] 1. The present invention reduces the contents of the impure
element and impurity, so as to further increase the magnetic
induction, and lower the coercivity, by content-optimized
proportioning and exploration on favorable elements, such as Si,
Mn, Al. By preferred design for the normalizing process and
annealing process, coarsening of the precipitated products and the
grain is facilitated, so that the iron losses and the coercivity
decreases, thus, a cold rolled electromagnetic steel sheet for
rapid cycling synchrotron with low iron losses, low coercivity and
high magnetic induction can be obtained. Provide solid guarantee in
term of raw material for improving the technical level of rapid
cycling synchrotron of our country, and broaden the way in product
development.
[0038] 2. The product cost is competitive. The present invention
carries out annealing and coating based on just one time of cold
rolling, instead of applying the method of tempering (by critical
reduction rate) extra-low carbon aluminum killed steel, such that
the operation is simplified, and the cost is competitive.
DETAILED DESCRIPTION
[0039] The present invention will be described in detail below in
reference to the embodiments.
[0040] The main composition of the steel used in the embodiments of
the present invention and those in the comparative example are
listed in table 1.
[0041] After liquid steel sequentially passes a converter, and then
is RH refined and poured to form semi-finished product, it
undergoes processes of hot rolling, normalizing, pickling, cold
rolling, annealing and coating to obtain then a non-oriented
electrical steel product. During such processes, the semi-finished
produced is hot rolled to be a steel belt of 2.6 mm, then the hot
rolled steel belt of 2.6 mm is normalized with the normalizing
temperature being controlled at 970.degree. C. and the normalizing
time being controlled to be 30-60 sec. The normalized steel belt is
cold rolled to be a steel belt of 0.5 mm, and then it is finally
annealed and coated. The final annealing temperature after cold
rolling is 850.degree. C., and the annealing time is controlled to
be 13-15 sec, and thereby a cold rolled electromagnetic steel sheet
is obtained.
[0042] The index for the electromagnetic performance of the cold
rolled electromagnetic steel sheet of the embodiments and those of
the comparative examples are listed in table 2.
TABLE-US-00001 TABLE 1 (in wt %) C Si Mn Al S N P Fe Embodiment 1
0.003 0.750 0.550 0.71 0.0030 0.0015 0.04 rest Embodiment 2 0.001
0.760 0.600 0.72 0.0019 0.0017 0.01 rest Embodiment 3 0.001 0.620
0.410 0.61 0.0028 0.0016 0.03 rest Embodiment 4 0.002 0.860 0.690
0.78 0.0026 0.0018 0.02 rest Embodiment 5 0.003 0.620 0.670 0.79
0.0029 0.0019 0.03 rest Embodiment 6 0.003 0.860 0.420 0.62 0.0031
0.0023 0.01 rest Embodiment 7 0.001 0.760 0.430 0.72 0.0029 0.0017
0.02 rest Embodiment 8 0.002 0.760 0.680 0.61 0.0031 0.0016 0.04
rest Comparative example 1 0.001 1.450 0.250 0.35 0.0031 0.0016
0.03 rest Comparative example 2 0.005 1.040 0.300 0.25 0.0029
0.0018 0.01 rest Comparative example 3 0.002 0.750 0.250 0.25
0.0019 0.0015 0.02 rest Comparative example 4 0.003 0.350 0.270
0.20 0.0034 0.0019 0.04 rest Comparative example 5 0.003 0.760
0.600 0.72 0.0045 0.0017 0.05 rest Comparative example 6 0.001
0.750 0.620 0.71 0.0041 0.0037 0.02 rest
TABLE-US-00002 TABLE 2 Whether meet the Diameter requirement of the
Electromagnetic Iron of using for grain coercivity Induction Losses
rapid cycling No. (.mu.m) (A/M) (T) (W/kg) synchrotron Embodiments
1 46 69.4 1.755 4.03 yes 2 48 61.5 1.757 3.92 yes 3 43 72.6 1.754
4.12 yes 4 49 60.7 1.758 3.86 yes 5 45 68.7 1.756 3.98 yes 6 44
71.6 1.752 4.06 yes 7 43 73.8 1.753 4.13 yes 8 42 75.3 1.752 4.15
yes Comparative 1 58 47.8 1.689 3.81 no examples 2 52 71.9 1.732
4.72 no 3 41 83.6 1.735 5.21 no 4 27 91.3 1.761 6.35 no 5 39 79.8
1.739 4.57 no 6 37 81.4 1.737 4.82 no
[0043] It can be seen from tables 1 and 2 that the index for the
electromagnetic performance of the steel sheets obtained by the
embodiments are significantly advantageous over those for the
electromagnetic performance of the steel sheets obtained by the
comparative examples, and the steel sheets of the embodiments
completely satisfy requirements for usage in rapid cycling
synchrotron.
[0044] In summary, based on the mechanism of the effects of various
factors on the coercivity, iron losses, magnetic induction of the
cold rolled electromagnetic steel sheet, the present invention
discovers and optimizes the blending ratio of beneficial elements
of Si, Mn, Al, and the like to reduce the contents of the
impurities, on the basis of one time cold rolling, so that the
magnetic induction is further improved. By preferred design for the
normalizing process and annealing process, the coarsening of the
precipitated products and the grain is facilitated, so that the
iron losses and the coercivity decreases, thus, a cold rolled
electromagnetic steel sheet for rapid cycling synchrotron with low
iron losses, low coercivity and high magnetic induction is
obtained.
[0045] The non-oriented electrical steel is applied in a device
called China Spallation Neutron Source Rapid Cycling Synchrotron
(CSNS/RCS), which belongs to The Institute of Modern Physics of
Chinese Academy of Sciences. The product has the characteristic of
low iron losses and high magnetic induction. The successful
applying of the present invention will provide solid guarantee in
term of raw material for improving the technical level of rapid
cycling synchrotron of our country, and broaden the way in product
development.
* * * * *