High young's modulus steel plate and method of production of same
View Patent ↗Steel sheet having a composition of ingredients containing substantially, by mass %, C: 0.005 to 0.200%, Si: 2.50% or less, Mn: 0.10 to 3.00%, N: 0.0100% or less, Nb: 0.005 to 0.100%, and Ti: 0.002 to 0.150% and satisfying the relationship of Ti−48/14×N≧0.0005, having a sum of the X-ray random intensity ratios of the {100}<001> orientation and the {110}<001> orientation of a ⅙ sheet thickness part of 5 or less, having a sum of the maximum value of the X-ray random intensity ratios of the {110}<111> to {110}<112> orientation group and the X-ray random intensity ratios of the {211}<111> orientation of 5 or more, and having a high rolling direction Young's modulus measured by the static tension method and a method of production of the same are provided.
1. High Young's modulus steel sheet containing, by mass %,
C: 0.005 to 0.200%,
Si: 2.50% or less,
Mn: 0.10 to 3.00%,
P: 0.150% or less,
S: 0.0150% or less,
Al: 0.150% or less,
N: 0.0100% or less,
Nb: 0.005 to 0.100%, and
Ti: 0.002 to 0.150%,
satisfying the formula 1, having a balance of Fe and unavoidable impurities, having a sum of an X-ray random intensity ratio of the {100}<001> orientation and an X-ray random intensity ratio of the {110}<001> orientation of 5 or less at a position of a direction from the surface of the steel sheet in the sheet thickness direction of ⅙ of the sheet thickness, and having a sum of a maximum value of the X-ray random intensity ratios of the {110}<111> to {110}<112> orientation group and a X-ray random intensity ratio of the {211}<111> orientation of 5 or more:
Ti−48/14×N≧0.0005 formula 1
where, Ti and N are the contents (mass %) of the elements.
2. A high Young's modulus steel sheet as set forth in claim 1 characterized by further containing, by mass %, one or more of
Mo: 0.01 to 1.00%,
Cr: 0.01 to 3.00%,
W: 0.01 to 3.00%,
Cu: 0.01 to 3.00%, and
Ni: 0.01 to 3.00%.
3. A high Young's modulus steel sheet as set forth in claim 2 characterized by satisfying the following formula 2:
4≦3.2Mn+9.6Mo+4.7W+6.2Ni+18.6Cu+0.7Cr≦10 formula 2
where, Mn, Mo, W, Ni, Cu, and Cr are the contents (mass %) of the elements.
4. A high Young's modulus steel sheet as set forth in claim 1 characterized by further containing, by mass %,
B: 0.0005 to 0.0100%.
5. A high Young's modulus steel sheet as set forth in claim 1 characterized by further containing, by mass %, one or more of
Ca: 0.0005 to 0.1000%,
Rem: 0.0005 to 0.1000%, and
V: 0.001 to 0.100%.
6. A high Young's modulus steel sheet as set forth in claim 1 characterized by having an X-ray random intensity ratio of the {332}<113> orientation (A) of 15 or less and an X-ray random intensity ratio of the {225}<110> orientation (B) of 5 or more at a center part of the steel sheet in the sheet thickness direction and satisfying (A)/(B)≦1.00.
7. A high Young's modulus steel sheet as set forth in claim 1 characterized by having an X-ray random intensity ratio of the {332}<113> orientation (A) of 15 or less and a simple average of an X-ray random intensity ratio of the {001}<110> orientation and an X-ray random intensity ratio of the {112}<110> orientation (C) of 5 or more at a center part of the steel sheet in the sheet thickness direction and satisfying (A)/(C)≦1.10.
8. A high Young's modulus steel sheet as set forth in claim 1 characterized by having a rolling direction Young's modulus measured by the static tension method of 220 GPa or more.
9. A hot dip galvanized steel sheet characterized by comprising a high Young's modulus steel sheet as set forth in claim 1 which is hot dip galvanized.
10. A hot dip galvannealed steel sheet characterized by comprising a high Young's modulus steel sheet as set forth in claim 1 which is hot dip galvannealed.
11. A method of production of high Young's modulus steel sheet characterized by rolling a steel slab having the chemical ingredients as set forth in claim 1 at 1100° C. or less by a rolling rate until the final pass of 40% or more and by a shape ratio X found by the following formula 3 of 2.3 or more by two passes or more, hot rolling at a temperature of the final pass of the Ar a transformation point to 900° C., and coiling at 700° C. or less:
Shape ratio X=l d /h m formula 3
where, l d (contact arc length of rolling rolls and steel plate): √(L×(h in −h out )/2)
ld: (h in +h out )/2
L: diameter of rolling rolls
h in : sheet thickness of rolling roll entry side
h out : sheet thickness of rolling roll exit side.
12. A method of production of high Young's modulus steel sheet as set forth in claim 11 characterized by hot rolling so that the effective strain ε* calculated by the following formula 5 becomes 0.4 or more:
ɛ
*
=
∑
j
=
1
n
-
1
ɛ
j
exp
[
-
∑
i
=
j
n
-
1
(
t
i
τ
i
)
2
/
3
]
+
ɛ
n
formula
5
where, n is a number of rolling stands of final hot rolling, ε j is a strain given at a j-th stand, ε n is a strain given at an n-th stand, t, is a travel time (s) between an i-th to i+1st stands, and τ i is calculated by the following formula 6 by a gas constant R (=1.987) and a rolling temperature T i (K) of an i-th stand:
τ
i
=
8.46
×
10
-
9
exp
(
43800
R
×
Ti
)
formula
6
13. A method of production of high Young's modulus steel sheet as set forth in claim 11 characterized by making a differential peripheral speed rate of at least one pass of hot rolling 1% or more.
14. A method of production of high Young's modulus steel sheet characterized by hot dip galvanizing a surface of steel sheet produced by the method as set forth in claim 11 .
15. A method of production of hot dip galvannealized steel sheet characterized by hot dip galvanizing a surface of steel sheet produced by a method as set forth in claim 11 , then heat treating it in a temperature range from 450 to 600° C. for 10 seconds or more.