High strength steel having good toughness
First Claim
1. A method of making a steel tube, comprising:
- providing a carbon steel composition comprising;
about 0.20 wt. % to about 0.30 wt. % carbon;
about 0.30 wt. % to about 0.70 wt. % manganeseabout 0.10 wt. % to about 0.30 wt. % silicon;
about 0.90 wt. % to about 1.50 wt. % chromium;
about 0.60 wt. % to about 1.00 wt. % molybdenum;
about 0.020 wt. % to about 0.40 wt. % niobium; and
about 0.01 wt. % to about 0.04 wt. % aluminum;
forming the steel composition into a tube;
heating the formed steel tube in a heating operation to a first temperature of about 880°
C. to about 950°
C. for about 10 to 30 minutes;
quenching the formed steel tube in a quenching operation from the first temperature at a first rate such that the microstructure of the quenched steel is greater than or equal to about 95% martensite by volume; and
tempering the formed steel tube after the quenching operation by heating the formed steel tube to a second temperature less than about 550°
C.;
wherein the steel tube after tempering has a yield strength greater than about 165 ksi and wherein the Charpy V-notch energy is greater or equal to about 80 J/cm2 in the longitudinal direction and 60 J/cm2 in the transverse direction at about room temperature.
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Accused Products
Abstract
Embodiments of the present disclosure comprise carbon steels and methods of manufacture. In one embodiment, quenching and tempering procedure is performed in which a selected steel composition is formed and heat treated to yield a slightly tempered microstructure having a fine carbide distribution. In another embodiment, a double austenizing procedure is disclosed in which a selected steel composition is formed and subjected to heat treatment to refine the steel microstructure. In one embodiment, the heat treatment may comprise austenizing and quenching the formed steel composition a selected number of times (e.g., 2) prior to tempering. In another embodiment, the heat treatment may comprise subjecting the formed steel composition to austenizing, quenching, and tempering a selected number of times (e.g., 2). Steel products formed from embodiments of the steel composition in this manner (e.g., seamless tubular bars and pipes) will possess high yield strength, e.g., at least about 165 ksi, while maintaining good toughness.
111 Citations
18 Claims
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1. A method of making a steel tube, comprising:
-
providing a carbon steel composition comprising; about 0.20 wt. % to about 0.30 wt. % carbon; about 0.30 wt. % to about 0.70 wt. % manganese about 0.10 wt. % to about 0.30 wt. % silicon; about 0.90 wt. % to about 1.50 wt. % chromium; about 0.60 wt. % to about 1.00 wt. % molybdenum; about 0.020 wt. % to about 0.40 wt. % niobium; and about 0.01 wt. % to about 0.04 wt. % aluminum; forming the steel composition into a tube; heating the formed steel tube in a heating operation to a first temperature of about 880°
C. to about 950°
C. for about 10 to 30 minutes;quenching the formed steel tube in a quenching operation from the first temperature at a first rate such that the microstructure of the quenched steel is greater than or equal to about 95% martensite by volume; and tempering the formed steel tube after the quenching operation by heating the formed steel tube to a second temperature less than about 550°
C.;wherein the steel tube after tempering has a yield strength greater than about 165 ksi and wherein the Charpy V-notch energy is greater or equal to about 80 J/cm2 in the longitudinal direction and 60 J/cm2 in the transverse direction at about room temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of forming a steel tube, comprising:
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providing a steel rod comprising; about 0.20 wt. % to about 0.30 wt. % carbon; about 0.30 wt. % to about 0.70 wt. % manganese; about 0.10 wt. % to about 0.30 wt. % silicon; about 0.90 wt. % to about 1.50 wt. % chromium; about 0.60 wt. % to about 1.00 wt. % molybdenum; about 0.020 wt. % to about 0.40 wt. % niobium; and about 0.01 wt. % to about 0.04 wt. % aluminum; forming the steel rod into a tube in a hot forming operation at a temperature of about 1200°
C. to 1300°
C.;heating the formed steel tube in a first heating operation to a temperature of about 880°
C. to 950°
C. for about 10 to 30 minutes;quenching the formed steel tube in a first quenching operation after the first heating operation at a rate such that the microstructure of the quenched steel is greater than or equal to about 95% martensite by volume; and tempering the formed steel tube after the first quenching operation by heating the formed steel tube to a temperature between about 450°
C. to about 550°
C. for between about 5 minutes to about 30 minutes;wherein the steel tube after tempering has a yield strength greater than about 165 ksi and wherein the Charpy V-notch energy is greater or equal to about 80 J/cm2 in the longitudinal direction and about 60 J/cm2 in the transverse direction at about room temperature. - View Dependent Claims (15, 16, 17, 18)
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Specification