STEEL PLATE THAT EXHIBITS EXCELLENT LOW-TEMPERATURE TOUGHNESS IN BASE MATERIAL AND WELD HEAT-AFFECTED ZONE AND HAS SMALL STRENGTH ANISOTROPY, AND MANUFACTURING METHOD THEREOF
First Claim
1. A steel plate that exhibits excellent low-temperature toughness in a base material and a weld heat-affected zone and has small strength anisotropy, whereinthe steel plate includes, by mass,C:
- 0.04%-0.10%;
Si;
0.02%-0.40%;
Mn;
0.5%-1.0%;
P;
0.0010%-0.0100%;
S;
0.0001%-0.0050%;
Ni;
2.0%-4.5%;
Cr;
0.1%-1.0%;
Mo;
0.1%-0.6%;
V;
0.005%-0.1%;
Al;
0.01%-0.08%; and
N;
0.0001%-0.0070%,with a balance including Fe and inevitable impurities,a Ni segregation ratio at a portion located at one-fourth of a thickness of the steel plate in a steel-plate thickness direction from a surface of the steel plate is 1.3 or lower,a degree of flatness of a prior austenite grain is in a range from 1.05 to 3.0,an effective diameter of crystal grain is 10 μ
m or lower, anda Vickers hardness number is in a range of 265 HV to 310 HV.
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Abstract
The present invention provides a steel plate that exhibits excellent low-temperature toughness in a base material and a weld heat-affected zone and has small strength anisotropy, wherein the steel includes, by mass, C: 0.04%-0.10%; Si: 0.02%-0.40%; Mn: 0.5%-1.0%; P: 0.0010%-0.0100%; S: 0.0001%-0.0050%; Ni: 2.0%-4.5%; Cr: 0.1%-1.0%; Mo: 0.1%-0.6%; V: 0.005%-0.1%; Al: 0.01%-0.08%; and N: 0.0001%-0.0070%, with the balance including Fe and inevitable impurities, a Ni segregation ratio at a portion located at one-fourth of a thickness of the steel plate in a steel-plate thickness direction from a surface of the steel plate is 1.3 or lower, a degree of flatness of a prior austenite grain is in a range from 1.05 to 3.0, an effective diameter of crystal grain is 10 μm or lower, and a Vickers hardness number is in a range of 265 HV to 310 HV.
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Citations
4 Claims
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1. A steel plate that exhibits excellent low-temperature toughness in a base material and a weld heat-affected zone and has small strength anisotropy, wherein
the steel plate includes, by mass, C: - 0.04%-0.10%;
Si;
0.02%-0.40%;Mn;
0.5%-1.0%;P;
0.0010%-0.0100%;S;
0.0001%-0.0050%;Ni;
2.0%-4.5%;Cr;
0.1%-1.0%;Mo;
0.1%-0.6%;V;
0.005%-0.1%;Al;
0.01%-0.08%; andN;
0.0001%-0.0070%,with a balance including Fe and inevitable impurities, a Ni segregation ratio at a portion located at one-fourth of a thickness of the steel plate in a steel-plate thickness direction from a surface of the steel plate is 1.3 or lower, a degree of flatness of a prior austenite grain is in a range from 1.05 to 3.0, an effective diameter of crystal grain is 10 μ
m or lower, anda Vickers hardness number is in a range of 265 HV to 310 HV. - View Dependent Claims (2)
Ti;
0.005%-0.03%;Cu;
0.01%-0.7%%;B;
0.0002%-0.05%;Ca;
0.0002%-0.0040%; andREM;
0.0002%40.0040%,with a balance including Fe and inevitable impurities.
- 0.04%-0.10%;
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3. A manufacturing method of a steel plate that exhibits excellent low-temperature toughness in a base material and a weld heat-affected zone and has small strength anisotropy, the steel plate including, by mass,
C: - 0.04%-0.10%;
Si;
0.02%-0.40%;Mn;
0.5%-1.0%;P;
0.0010%-0.0100%;S;
0.0001%-0.0050%;Ni;
2.0%-4.5%;Cr;
0.1%-1.0%;Mo;
0.1%-0.6%;V;
0.005%-0.1%;Al;
0.01%-0.08%; andN;
0.0001%-0.0070%,with a balance including Fe and inevitable impurities, wherein the method includes; heating a casting slab having a thickness 5.5 times to 50 times thicker than a final plate thickness, to a temperature ranging from 1250°
C. to 1380°
C., and maintaining the temperature for eight hours or more;applying a first hot rolling to the casting slab at a reduction ratio of 1.2 to 10.0, and a temperature before a final rolling pass of 800°
C. to 1250°
C. to obtain a steel strip;air-cooling the steel strip to 300°
C. or lower, and then heating the steel strip to a temperature ranging from 900°
C. to 1270°
C.;applying a second hot rolling to the steel strip at a reduction ratio of 2.0 to 40.0, and a temperature before a final rolling pass of 680°
C. to 1000°
C.;starting water-cooling within 100 seconds after the second hot rolling, and cooling the steel strip to a surface temperature of 200°
C. or lower; and
,applying tempering to the steel strip at a temperature of 550°
C. to 720°
C.- View Dependent Claims (4)
Ti;
0.005%-0.03%;Cu;
0.01%-0.7%%;B;
0.0002%-0.05%;Ca;
0.0002%-0.0040%; andREM;
0.0002%-0.0040%,with a balance including Fe and inevitable impurities.
- 0.04%-0.10%;
Specification