Claims
- 1. A method for mitigating a solidification segregation of steel during a continuous casting of steel or ingot casting of steel which contains .alpha.-phase stabilizing elements and .gamma.-phase stabilizing elements other than carbon and further contains carbon from 0.005% to 0.08% inducing an Ar.sub.4 transformation, comprising the steps of:
- cooling said casting in a first temperature range where liquid and .delta. phases are present and where all of the .alpha.-phase stabilizing elements and the .gamma.-phase stabilizing elements have the highest concentrations at interdendritic liquid regions essentially coincident with one another;
- further cooling said casting from the first temperature range down to a second temperature range where the .delta. phase and a .gamma. phase coexist in a solidified shell of the casting;
- controlling a cooling rate of the region in the casting which corresponds to approximately half of the thickness of the casting and where the .delta. phase and the .gamma. phase coexist in the second temperature range to 40.degree. C./min or less thereby separating the .alpha.-phase stabilizing elements and .gamma.-phase stabilizing elements from one another at said region in said casting;
- further cooling said casting from the second temperature range down to a third temperature range where the .delta. phase disappears and only the .gamma. phase exists at said region in the solidified shell; and
- performing cooling in the third temperature range, while retaining separated .alpha.-phase stabilizing elements and .gamma.-phase stabilizing elements, the highest concentration sites of the elements being separated due to the controlled cooling rate.
- 2. A method according to claim 1, wherein the casting is cooled at a rate of 30.degree. C./minute or more at said region in the casting when the Ar.sub.4 transformation is completed.
- 3. A method according to claim 2, wherein heating and cooling of the casting is repeated at least once while the temperature of the casting is within a temperature range of the Ar.sub.4 transformation and the rate of the heating is made higher than the rate of the cooling.
- 4. A method according to claim 1, wherein heating and cooling of the casting is repeated at least once while the temperature of the casting is within a temperature range of the Ar.sub.4 transformation and the rate of the heating is made higher than the rate of the cooling.
- 5. A method according to claim 1, wherein said casting is produced by continuous casting, and said cooling at a rate of 40.degree. C./minute or less is carried out during a secondary cooling of the continuous casting.
- 6. A method according to claim 1, wherein said casting is cooled below the temperature at which the Ar.sub.4 transformation is completed and is then heated to a temperature where the .gamma. phase and .delta. phase coexist, and, thereafter said cooling at a rate of 40.degree. C./minute or less is conducted.
- 7. A method according to claim 6, wherein after heating to the temperature where the .delta. phase and .gamma. phase coexist, said casting is maintained at this temperature for a predetermined time.
- 8. A method for mitigating a solidification segregation of steel during a continuous casting of steel or ingot casting of steel which contains .alpha.-phase stabilizing elements and .gamma.-phase stabilizing elements other than carbon and further contains carbon more than 0.08% to 0.17% inducing an Ar.sub.4 transformation and a peritectic reaction, comprising the steps of:
- cooling said casting in a first temperature range where liquid and .delta. phases are present and where all of the .alpha.-phase stabilizing elements and the .gamma.-phase stabilizing elements have the highest concentrations at interdendritic liquid regions essentially coincident with one another;
- further cooling said casting from the first temperature range down to a second temperature range where the peritectic reaction is induced and then the .delta. phase and a .gamma. phase coexist at the region corresponding to approximately half the thickness of the casting;
- controlling a cooling rate of said region in the casting where the .delta. phase and the .gamma. phase coexist in the second temperature range to 40.degree. C./min or less thereby separating the .alpha.-phase stabilizing elements and .gamma.-phase stabilizing elements from one another at said region in said casting;
- further cooling said casting from the second temperature range down to a third temperature range where the .delta. phase disappears and only the .gamma. phase exists at said region in a solidified shell; and
- performing cooling in the third temperature range, while retaining separated .alpha.-phase stabilizing elements and .gamma.-phase stabilizing elements, the highest concentration sites of the elements being separated due to the controlled cooling rate.
- 9. A method according to claim 8, wherein the casting is cooled at a rate of 30.degree. C./minute or more at said region in the casting when the peritectic reaction or Ar.sub.4 transformation is completed.
- 10. A method according to claim 9, wherein heating and cooling of the casting is repeated at least once while the temperature of the casting is within a temperature range of the peritectic reaction and the Ar.sub.4 transformation and the rate of the heating is made higher than the rate of the cooling.
- 11. A method according to claim 8, wherein heating and cooling of the casting is repeated at least once while the temperature of the casting is within a temperature range of the peritectic reaction and the Ar.sub.4 transformation and the rate of the heating is made higher than the rate of the cooling.
- 12. A method according to claim 8, wherein said casting is produced by continuous casting, and said cooling at a rate of 40.degree. C./minute or less is carried out during a secondary cooling of the continuous casting.
- 13. A method according to claim 8, wherein said casting is cooled below the temperature at which the Ar4 transformation is completed and is then heated to a temperature where the .gamma. phase and .delta. phase coexist, and, thereafter said cooling at a rate of 40.degree. C./minute or less is conducted.
- 14. A method according to claim 13, wherein after heating to the temperature where the .delta. phase and .gamma. phase coexist, said casting is maintained at this temperature for a predetermined time.
Priority Claims (3)
Number |
Date |
Country |
Kind |
59-21940 |
Feb 1984 |
JPX |
|
59-21941 |
Feb 1984 |
JPX |
|
59-21942 |
Feb 1984 |
JPX |
|
Parent Case Info
This application is a continuation-in-part, of now abandoned application Ser. No. 700,675, filed Feb. 11, 1985, now abandoned.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
3771584 |
Wojcik |
Nov 1973 |
|
Foreign Referenced Citations (3)
Number |
Date |
Country |
52-77816 |
Jun 1977 |
JPX |
54-4224 |
Jan 1979 |
JPX |
261660 |
Dec 1977 |
SUX |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
700675 |
Feb 1985 |
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