Cu—Sn coexisting steel and method for manufacturing the same
A method for manufacturing Cu—Sn coexisting steel produces a good quality surface even after hot rolling. The steel is manufactured by continuous casting a molten steel that contains C: 0.04 to 0.20%, Si: 0.05 to 1.00%, Mn: 0.20 to 2.50%, P: no more than 0.05%, S: no more than 0.02%, Cu: 0.20 to 1.50%, Sn: 0.06 to 0.50%, Al: 0.06 to 1.00% and Ni: 0.05 to 1.00% by mass, and Fe and impurities as the remainder. The composition of the molten steel is defined as [Al]/(3[Si]+[Mn])≥0.050, [Ni]/([Cu]+5[Sn])≥0.10 and [Al]/[Ni]≥0.20 if the content of an element X in the molten steel is represented as [X], an internal oxidation layer is formed in a process of cooling a slab, and Al 2 O 3 is contained by the internal oxidation layer.
1. A method for manufacturing Cu—Sn coexisting steel by continuous casting of molten steel, the method comprising:
adjusting composition of molten steel so as to satisfy conditions represented by the following formulas (1) to (3), the molten steel containing, as chemical composition, C: 0.04 to 0.20%, Si: 0.05 to 1.00%, Mn: 0.20 to 2.50%, P: no more than 0.05%, S: no more than 0.02%, Cu: 0.20 to 1.50% and Sn: 0.06 to 0.50% and further containing Al: 0.06 to 0.25% and Ni: 0.05 to 1.00% by mass, and Fe and impurities as the remainder;
forming an internal oxidation layer by oxidizing a surface of a slab in a process of cooling the slab; and
making composite oxides that are generated in the internal oxidation layer, contain Al 2 O 3 :
[Al]/(3[Si]+[Mn])≥0.050 (1)
[Ni]/([Cu]+5[Sn])≥0.10 (2)
[Al]/[Ni]≥0.20 (3)
wherein [Al], [Si], [Mn], [Ni], [Cu] and [Sn] represent contents (% by mass) of Al, Si, Mn, Ni, Cu and Sn in the molten steel respectively.
2. The method for manufacturing Cu—Sn coexisting steel according to claim 1 , wherein
a content of Al 2 O 3 in the composite oxides that are generated in the internal oxidation layer is 15 to 40% by mass.
3. The method for manufacturing Cu—Sn coexisting steel according to claim 1 , wherein
the composition of the molten steel is adjusted so as to further satisfy a condition represented by the following formula (4):
1.0≤[Cu]/[Sn]≤8.0 (4).
4. Cu—Sn coexisting steel that is manufactured by the method for manufacturing Cu—Sn coexisting steel according to claim 1 .
5. The method for manufacturing Cu—Sn coexisting steel according to claim 2 , wherein:
the composition of the molten steel is adjusted so as to further satisfy a condition represented by the following formula (4):
1.0≤[Cu]/[Sn]≤8.0 (4).
6. Cu—Sn coexisting steel that is manufactured by the method for manufacturing Cu—Sn coexisting steel according to claim 2 .
7. Cu—Sn coexisting steel that is manufactured by the method for manufacturing Cu—Sn coexisting steel according to claim 3 .
8. Cu—Sn coexisting steel that is manufactured by the method for manufacturing Cu—Sn coexisting steel according to claim 5 .
9. A method for manufacturing Cu—Sn coexisting steel by continuous casting of molten steel, the method comprising:
adjusting composition of molten steel so as to satisfy conditions represented by the following formulas (1) to (3), the molten steel containing, as chemical composition, C: 0.04 to 0.20%, Si: 0.05 to 1.00%, Mn: 0.20 to 2.50%, P: no more than 0.05%, S: no more than 0.02%, Cu: 0.20 to 1.50% and Sn: 0.06 to 0.50% and further containing Al: 0.06 to 1.00% and Ni: 0.05 to 1.00% by mass, and Fe and impurities as the remainder;
forming an internal oxidation layer by oxidizing a surface of a slab in a process of cooling the slab; and
making composite oxides that are generated in the internal oxidation layer, contain Al 2 O 3 :
[Al]/(3[Si]+[Mn])≥0.050 (1)
[Ni]/([Cu]+5[Sn])≥0.10 (2)
[Al]/[Ni]≥0.20 (3)
wherein [Al], [Si], [Mn], [Ni], [Cu] and [Sn] represent contents (% by mass) of Al, Si, Mn, Ni, Cu and Sn in the molten steel respectively,
wherein a content of Al 2 O 3 in the composite oxides that are generated in the internal oxidation layer is 15 to 40% by mass.
10. The method for manufacturing Cu—Sn coexisting steel according to claim 9 , wherein
the composition of the molten steel is adjusted so as to further satisfy a condition represented by the following formula (4):
1.0≤[Cu]/[Sn]≤8.0 (4).
11. Cu—Sn coexisting steel that is manufactured by the method for manufacturing Cu—Sn coexisting steel according to claim 9 .
12. Cu—Sn coexisting steel that is manufactured by the method for manufacturing Cu—Sn coexisting steel according to claim 10 .