CASTING STEEL STRIP
First Claim
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1. A method of casting thin steel strip comprising the steps of:
- determining a desired heat flux set point in casting thin cast strip from molten metal from a casting pool between casting rolls in a twin roll caster;
calculating the heat flux in the casting thin cast strip from molten metal from the casting pool in the twin roll caster; and
changing the nitrogen concentration in the casting pool to adjust the heat flux to the desired heat flux set point.
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Abstract
A method of controlling heat flux between the casting pool and the surfaces of the casting roll in a strip steel casting process includes controlling the concentration of nitrogen in the steel melt. The concentration of nitrogen may be controlled to achieve an operational heat transfer to the casting roll. The beat flux to the casting rolls may be controlled by maintaining the sum of partial pressures calculated from the nitrogen and hydrogen concentrations in the casting pool below 1.15 atmospheres. Decreasing the concentration of nitrogen can increase heat flux at the casting rolls.
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Citations
38 Claims
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1. A method of casting thin steel strip comprising the steps of:
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determining a desired heat flux set point in casting thin cast strip from molten metal from a casting pool between casting rolls in a twin roll caster;
calculating the heat flux in the casting thin cast strip from molten metal from the casting pool in the twin roll caster; and
changing the nitrogen concentration in the casting pool to adjust the heat flux to the desired heat flux set point. - View Dependent Claims (2, 3)
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4. A method of casting steel strip comprising:
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introducing molten plain carbon steel on casting surfaces of at least one casting roll with the molten steel having a nitrogen content below about 120 ppm and a hydrogen content below about 6.9 ppm and such that the sum of partial pressure of nitrogen and partial pressure of hydrogen is no more than 1.15 atmospheres;
forming a casting pool of molten metal adjacent the casting surfaces of the casting roll;
causing the nitrogen level in the molten metal in the casting pool to vary depending on casting speed and strip thickness to control heat flux between the casting pool and the surfaces of the casting roll to a desired value; and
solidifying the molten steel to form metal shells on the casting rolls having nitrogen and hydrogen levels reflected by the content thereof in the molten steel to form thin steel strip. - View Dependent Claims (5, 6, 7, 8)
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9. A method of casting steel strip comprising:
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assembling a pair of cooled casting rolls having a nip between them and confining end closures adjacent to ends of the casting rolls;
introducing molten plain carbon steel between the pair of casting rolls to form a casting pool on the casting rolls with the end closures confining the pool, with the molten steel having a nitrogen content below about 120 ppm and a hydrogen content below about 6.9 ppm and such that the sum of partial pressure of nitrogen and partial pressure of hydrogen is no more than 1.15 atmospheres;
causing the nitrogen level in the molten metal in the casting pool to vary depending on casting speed and strip thickness to control heat flux between the casting pool and the surfaces of the casting roll to a desired value;
counter-rotating the casting rolls and solidifying the molten steel to form metal shells on casting surfaces of the casting rolls having nitrogen and hydrogen levels reflected by the content of the molten steel to provide for the formation of thin steel strip; and
forming solidified thin steel strip through the nip between the casting rolls to produce a solidified steel strip delivered downwardly from the nip. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method of casting steel strip comprising:
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introducing molten plain carbon steel on casting surfaces of at least one casting roll with the molten steel having a nitrogen content below about 100 ppm and a hydrogen content below about 6.9 ppm and such that the sum of partial pressure of nitrogen and partial pressure of hydrogen is no more than 1.15 atmospheres;
forming a casting pool of molten metal adjacent the casting surfaces of the casting roll;
causing the nitrogen level in the molten metal in the casting pool to vary depending on casting speed and strip thickness to control heat flux between the casting pool and the surfaces of the casting roll to a desired value; and
solidifying the molten steel to form metal shells on the casting rolls having nitrogen and hydrogen levels reflected by the content thereof in the molten steel to form thin steel strip. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A method of casting steel strip comprising:
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assembling a pair of cooled casting rolls having a nip between them and confining end closures adjacent to ends of the casting rolls;
introducing molten plain carbon steel between the pair of casting rolls to form a casting pool on the casting rolls with the end closures confining the pool, with the molten steel having a nitrogen content below about 120 ppm and a hydrogen content below about 6.9 ppm and such that the sum of partial pressure of nitrogen and partial pressure of hydrogen is no more than 1.15 atmospheres;
causing the nitrogen level in the molten metal in the casting pool to vary depending on casting speed and strip thickness to control heat flux between the casting pool and the surfaces of the casting roll to a desired value;
counter-rotating the casting rolls and solidifying the molten steel to form metal shells on casting surfaces of the casting rolls having nitrogen and hydrogen levels reflected by the content of the molten steel to provide for the formation of thin steel strip; and
forming solidified thin steel strip through the nip between the casting rolls to produce a solidified steel strip delivered downwardly from the nip. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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28. A method of casting steel strip comprising:
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introducing molten plain carbon steel on casting surfaces of at least one casting roll with the molten steel having a nitrogen content below about 85 ppm and a hydrogen content below about 6.9 ppm and such that the sum of partial pressure of nitrogen and partial pressure of hydrogen is no more than 1.15 atmospheres;
forming a casting pool of molten metal adjacent the casting surfaces of the casting rolls;
causing the nitrogen level in the molten metal in the casting pool to vary depending on casting speed and strip thickness to control heat flux between the casting pool and the surfaces of the casting roll to a desired value; and
solidifying the molten steel to form metal shells on the casting rolls having nitrogen and hydrogen levels reflected by the content thereof in the molten steel to form thin steel strip. - View Dependent Claims (29, 30, 31, 32)
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33. A method of casting steel strip comprising:
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assembling a pair of cooled casting rolls having a nip between them and confining end closures adjacent to ends of the casting rolls;
introducing molten plain carbon steel between the pair of casting rolls to form a casting pool on the casting rolls with the end closures confining the pool, with the molten steel having a nitrogen content below about 120 ppm and a hydrogen content below about 6.9 ppm and such that the sum of partial pressure of nitrogen and partial pressure of hydrogen is no more than 1.15 atmospheres;
causing the nitrogen level in the molten metal in the casting pool to vary depending on casting speed and strip thickness to control heat flux between the casting pool and the surfaces of the casting roll to a desired value;
counter-rotating the casting rolls and solidifying the molten steel to form metal shells on casting surfaces of the casting rolls having nitrogen and hydrogen levels reflected by the content of the molten steel to provide for the formation of thin steel strip; and
forming solidified thin steel strip through the nip between the casting rolls to produce a solidified steel strip delivered downwardly from the nip. - View Dependent Claims (34, 35, 36, 37, 38)
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Specification