H-section steel and method of producing the same

Patent metadata

Field	Value
Publication number	US-10280476-B2
Application number	US-201515129518-A
Country	US
Kind code	B2
Filing date	Apr 9, 2015
Priority date	Apr 15, 2014
Publication date	May 7, 2019
Grant date	May 7, 2019

Abstract

An H-section steel has a predetermined chemical composition, in which a Mg-containing oxide having an equivalent circle diameter of 0.005 μm to 0.5 μm is contained at a total number density of 100 pieces/mm 2 to 5000 pieces/mm 2 , a thickness of a flange is 100 mm to 150 mm, at a strength evaluation portion which is at a ⅙ position from a surface of the flange in a length direction and at a ¼ position from the surface in a thickness direction, a fraction of bainite in a steel structure is 80% or more, and the average prior austenite grain size is 70 μm or more, and at a toughness evaluation portion which is at a ½ position from the surface of the flange in the length direction and at a ¾ position from the surface of the flange in the thickness direction, the average prior austenite grain size in a steel structure is 200 μm or less.

First claim

What is claimed is:

1. An H-section steel comprising, as a chemical composition, by mass %:
C: 0.05% to 0.16%;
Si: 0.01% to 0.50%;
Mn: 0.70% to 2.00%;
V: 0.01% to 0.20%;
Al: 0.0001% to 0.10%;
Ti: 0.003% to 0.030%;
N: 0.0010% to 0.0200%;
O: 0.0001% to 0.0100%;
Mg: 0.0003% to 0.0050%;
Ni: 0% to 0.50%;
Cr: 0% to 0.50%;
Cu: 0% to 0.50%;
Mo: 0% to 0.30%;
Nb: 0% to 0.010%;
B: 0% to 0.0020%;
Ca: 0% to 0.0050%; and
a remainder of Fe and impurities,
wherein a carbon equivalent C eq obtained by the following Equation 1 is 0.30% to 0.50%;
a Mg-containing oxide having an equivalent circle diameter of 0.005 μm to 0.5 μm at a total number density of 100 pieces/mm 2 to 5000 pieces/mm 2 ;
a thickness of a flange is 100 mm to 150 mm;
at a strength evaluation portion which is at a ⅙ position from a surface of the flange in a length direction and at a ¼ position from the surface in a thickness direction, a fraction of bainite in a steel structure is 80% or more, and an average prior austenite grain size is 70 μm or more; and
at a toughness evaluation portion which is at a ½ position from the surface of the flange in the length direction and at a ¾ position from the surface of the flange in the thickness direction, the average prior austenite grain size in a steel structure is 200 μm or less,
C eq =C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15  Equation (1),

wherein C, Mn, Cr, Mo, V, Ni, and Cu represent the amount of each element contained by mass % and the amount of an element not contained is 0.

2. The H-section steel according to claim 1 ,
wherein the H-section steel includes, as the chemical composition, by mass %, one or more of
Ni: 0.01% to 0.50%,
Cr: 0.01% to 0.50%,
Cu: 0.01% to 0.50%,
Mo: 0.001% to 0.30%,
Nb: 0.001% to 0.010%,
B: 0.0001% to 0.0020%, and
Ca: 0.0001% to 0.0050%.

3. The H-section steel according to claim 1 ,
wherein, at the strength evaluation portion at room temperature, a yield strength or 0.2% proof stress is 450 MPa or more, and a tensile strength is 550 MPa or more; and
at the toughness evaluation portion, a Charpy absorbed energy at a test temperature of 21° C. is 100 J or more.

4. A method of producing an H-section steel, the method comprising:
a refining step which performs deoxidizing to cause a concentration of oxygen in a molten steel to be 0.0020% to 0.0100%, then sequentially adding Ti, Al, and Mg, and adjusting a chemical composition of the molten steel to include by mass %, C: 0.05% to 0.16%, Si: 0.01% to 0.50%, Mn: 0.70% to 2.00%, V: 0.01% to 0.20%, Al: 0.0001% to 0.10%, Ti: 0.003% to 0.030%, N: 0.0010% to 0.0200%, O: 0.0001% to 0.0100%, Mg: 0.0003% to 0.0050%, Ni: 0% to 0.50%, Cr: 0% to 0.50%, Cu: 0% to 0.50%, Mo: 0% to 0.30%, Nb: 0% to 0.010%, B: 0% to 0.0020%, Ca: 0% to 0.0050%, and a remainder of Fe and impurities, and to have a carbon equivalent C eq obtained by the following Equation 2 of 0.30% to 0.50%;
a casting step which casts the molten steel to obtain a steel piece;
a heating step which heats the steel piece to 1100° C. to 1350° C.;
a hot-rolling step which performs rolling on the heated steel piece such that a surface temperature of 850° C. or higher when the rolling is finished, thereby obtaining the H-section steel; and
a cooling step which performs water-cooling the H-section steel after the hot-rolling step;
wherein Al and Mg are added after 1 minute or longer has passed from the addition of the previous element;
wherein in the cooling step, water cooling conditions are controlled so that a cooling rate in a range from 800° C. to 600° C. at a ⅙ position from a surface of a flange in a length direction and at a ¼ position from the surface of the flange in a thickness direction is 2.2° C./s or more and the surface temperature after stopping the water-cooling is recuperated within a temperature range of 300° C. to 700° C.,
C eq =C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15  Equation 2,

wherein C, Mn, Cr, Mo, V, Ni, and Cu represent the amount of each element contained by mass % and the amount of an element not contained is 0.

5. The method of producing an H-section steel according to claim 4 ,
wherein the H-section steel includes, as the chemical composition, by mass %, one or more of
Ni: 0.01% to 0.50%,
Cr: 0.01% to 0.50%,
Cu: 0.01% to 0.50%,
Mo: 0.001% to 0.30%,
Nb: 0.001% to 0.010%,
B: 0.0001% to 0.0020%, and
Ca: 0.0001% to 0.0050%.

6. The H-section steel according to claim 2 ,
wherein, at the strength evaluation portion at room temperature, a yield strength or 0.2% proof stress is 450 MPa or more, and a tensile strength is 550 MPa or more; and
at the toughness evaluation portion, a Charpy absorbed energy at a test temperature of 21° C. is 100 J or more.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Mizoguchi Masaki
• Ichikawa Kazutoshi
• MITSUYASU Kazuaki
• Sugiyama Hirokazu

Classifications

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/02

  containing silicon · CPC title

• B22D25/02

  by its peculiarity of shape; of works of art {(cylinders, pistons B22D15/02)} · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/58

  with more than 1.5% by weight of manganese · CPC title