Casting steel strip
View Patent ↗In twin roll casting of steel strip, molten steel is introduced into the nip between parallel casting rolls to create a casting pool supported on casting surfaces of the rolls and the rolls are rotated to deliver solidified strip downwardly from the nip. Casting surfaces are textured by a random pattern of discrete projections, which may have an average surface distribution of between 5 and 200 peaks per mm 2 and an average height of at least 10 microns. In order to suppress chatter defects, the molten steel also has manganese content of at least 0.55% by weight and a silicon content in the range of 0.1 to 0.35% by weight. The strip is thus capable of moving away from the casting pool at a speed of more than 60 meters per minute without substantial high speed chattering defects.
1. A casting roll for continuous casting of steel strip comprised of casting surfaces textured by a random distribution of discrete projections having an average surface distribution of between 5 and 200 peaks per mm 2 and an average height of at least 10 microns.
2. A casting roll as claimed in claim 1 where each casting surface is defined by a grit blasted substrate covered by a protective coating.
3. A casting roll as claimed in claim 2 where the protective coating is an electroplated metal coating.
4. A casting roll as claimed in claim 3 where the substrate is copper and the plated coating is of chromium.
5. A casting roll as claimed in claim 2 where the protective coating is an alloy of nickel, molybdenum and cobalt.
6. A casting roll as claimed in claim 2 where the protective coating is an alloy of nickel, chromium and molybdenum.
7. A casting roll as claimed in claim 1 where each casting surface is a grit blasted surface.
8. A casting roll as claimed in claim 7 where the grit blasted surface is formed of nickel.
9. A casting roll as claimed in claim 1 where each casting surface is defined by a coating deposited onto a substrate to produce the random distribution of discrete projections on that surface.
10. A casting roll as claimed in claim 9 where the coating is formed by chemical deposition.
11. A casting roll as claimed in claim 9 where the coating is formed by electro-deposition.
12. A casting roll as claimed in claim 9 where the coating is formed of a material which has a low affinity for oxidation products in molten steel such that molten steel has greater affinity for the coating material and wets the coating in preference to said oxidation products.
13. A casting roll as claimed in claim 1 where the random distribution of discrete projections comprises a random height distribution of discrete projections.
14. A casting roll as claimed in claim 1 where the discrete projections have flat areas at the peaks.
15. A casting roll as claimed in claim 14 where the discrete projection flat areas are between about 100 square microns and about 400 square microns.