Steel plates for high-strength steel pipe piles, steel pipes for high-strength steel pipe piles, methods for manufacturing steel plates for high-strength steel pipe piles, and methods for manufacturing steel pipes for high-strength steel pipe piles.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- JFE STEEL CORP
- Filing Date
- 2023-06-27
- Publication Date
- 2026-06-09
AI Technical Summary
【0007】 以上述べたように、本発明によれば、API X100グレード以上の高強度を有し、靭性の優れた鋼板が得られる。このため、鋼管杭用鋼管への利用に好適である。
Smart Images
Figure 0007871747000001 
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Abstract
Claims
1. In mass percent, C: 0.04-0.10%, Si: 0.01 to 0.5%, Mn: 1.5-2.5%, P: 0.015% or less, S: 0.0020% or less, Al: 0.08% or less, Cr: 0.01-0.5%, Mo: 0.01-0.5%, Ti: 0.005 to 0.025%, Nb: 0.005-0.08%, N: 0.001 to 0.010%, O: 0.0050% or less It contains, The composition has the following conditions: the Ceq value expressed by equation (1) below satisfies Ceq value ≥ 0.46; the P value expressed by equation (2) below satisfies P value ≥ 0.15; and the Q value, the total mass % of Cr and Mo expressed by equation (3) below, satisfies Q value ≥ 0.50 and Cr ≤ Mo, with the remainder being Fe and unavoidable impurities. The microstructure consists of bainite or more (80%), island martensite or less (5%), and the remainder consists of one or more of the following: retained austenite, pseudo-pearlite, and ferrite, with the total area ratio of the remainder being 20% or less. Five composite carbides containing one or more of Nb, Ti, and Mo, with an equivalent circular diameter of 20 nm or less, per μm. ２ That's all. A steel plate for high-strength steel pipe piles, characterized by having a yield strength of 690 MPa or more and a tensile strength of 760 MPa or more. Ceq value=C+Mn / 6+(Cu+Ni) / 15+(Cr+Mo+V) / 5...(1) However, the element symbols in equation (1) represent the mass percentage of each contained element. P value = (Mo / 95.9+Nb / 92.91+V / 50.94+Ti / 47.9) / (100 / 55.85)×100...(2) However, the element symbols in equation (2) represent the mass percentage of each contained element. Q value = Cr + Mo ... (3) However, the element symbols in equation (3) represent the mass percentage of each contained element.
2. The aforementioned component composition is further expressed in mass%, V: 0.1% or less, Cu: 0.5% or less, Ni: 0.5% or less, Ca: 0.0005-0.0035%, REM: 0.0005-0.0100%, The steel plate for high-strength steel pipe piles according to claim 1, characterized in that it contains one or more types selected from B: 0.002% or less.
3. A method for manufacturing steel plates for high-strength steel pipe piles according to claim 1 or 2, A steel material having the above-mentioned component composition, After heating to a temperature of 1100-1300°C and hot rolling, cooling is started from Ar3 or higher, and accelerated cooling is performed at an average cooling rate of 20°C / s or higher until the cooling stop temperature is below 300°C. A method for manufacturing steel plates for high-strength steel pipe piles, characterized by subsequently reheating them to a temperature of 300°C to 500°C at an average heating rate of 0.5°C / s to 10°C / s within 300 seconds.
4. A steel pipe for high-strength steel pipe piles having a base material portion and a welded portion, The base material is, by mass%, C: 0.04-0.10%, Si: 0.01 to 0.5%, Mn: 1.5-2.5%, P: 0.015% or less, S: 0.0020% or less, Al: 0.08% or less, Cr: 0.01-0.5%, Mo: 0.01-0.5%, Ti: 0.005 to 0.025%, Nb: 0.005-0.08%, N: 0.001 to 0.010%, O: 0.0050% or less It contains, The composition has the following conditions: the Ceq value expressed by equation (1) below satisfies Ceq value ≥ 0.46; the P value expressed by equation (2) below satisfies P value ≥ 0.15; and the Q value, the total mass % of Cr and Mo expressed by equation (3) below, satisfies Q value ≥ 0.50 and Cr ≤ Mo, with the remainder being Fe and unavoidable impurities. The microstructure consists of bainite or more (80%), island martensite or less (5%), and the remainder consists of one or more of the following: retained austenite, pseudo-pearlite, and ferrite, with the total area ratio of the remainder being 20% or less. Five composite carbides containing one or more of Nb, Ti, and Mo, with an equivalent circular diameter of 20 nm or less, per μm. ２ That's all. A high-strength steel pipe for steel piles, characterized by a yield strength of 690 MPa or more, a tensile strength of 760 MPa or more, and a surface hardness of 350 HV10 or less at a position 1 mm from the surface. Ceq value=C+Mn / 6+(Cu+Ni) / 15+(Cr+Mo+V) / 5...(1) However, the element symbols in equation (1) represent the mass percentage of each contained element. P value = (Mo / 95.9+Nb / 92.91+V / 50.94+Ti / 47.9) / (100 / 55.85)×100...(2) However, the element symbols in equation (2) represent the mass percentage of each contained element. Q value = Cr + Mo ... (3) However, the element symbols in equation (3) represent the mass percentage of each contained element.
5. The aforementioned component composition is further expressed in mass%, V: 0.1% or less, Cu: 0.5% or less, Ni: 0.5% or less, Ca: 0.0005-0.0035%, REM: 0.0005-0.0100%, The steel pipe for high-strength steel pipe piles according to claim 4, characterized in that it contains one or more types selected from B: 0.002% or less.
6. A method for manufacturing a steel pipe for high-strength steel pipe piles according to claim 4 or 5, A method for manufacturing a steel pipe for high-strength steel pipe piles, characterized by using the steel plate for high-strength steel pipe piles described in claim 1 or 2 as a material, forming it into a cylindrical shape in the longitudinal direction of the steel plate, welding the butt joints where one end face of the steel plate meets the other from the inner and outer surfaces in the longitudinal direction layer by layer to form a tubular shape, and then expanding the pipe.
7. A method for manufacturing a steel pipe for high-strength steel pipe piles according to claim 6, characterized in that the pipe is reheated to a temperature of 100°C or higher and 300°C or lower after the pipe expansion.