Hot-rolling composite roll produced by cetrifugal casting

Abstract

A centrifugally cast hot-rolling composite roll comprising (a) an outer layer made of cast iron having a chemical composition comprising by mass 2.5-3.5% of C, 1.3-2.4% of Si, 0.2-1.5% of Mn, 3.5-5.0% of Ni, 0.8-1.5% of Cr, 2.5-5.0% of Mo, 1.8-4.0% of V, and 0.2-1.5% of Nb, the balance being Fe and inevitable impurities, a mass ratio of Nb / V being 0.1-0.7, and a mass ratio of Mo / V being 0.7-2.5, and meeting the condition of 2.5 ‰¤ V + 1.2 Nb ‰¤ 5.5, and having a structure comprising 0.3-10% by area of a graphite phase; (b) a shaft portion made of ductile cast iron in which the area ratio of ferrite is 35% or less; and (c) an intermediate cast iron layer.

Description

technical field

[0001] The present invention relates to a composite roll for hot rolling made by centrifugal casting, in which an outer layer excellent in wear resistance, seizure resistance, and accident resistance and an axial core portion excellent in toughness are interposed and integrated by interposing an outer layer, and particularly relates to a thin steel plate Composite rolls for centrifugal casting hot rolling that are suitable for work rolls for final rolling of hot strip rolling mills. Background technique

[0002] A heated slab with a thickness of several hundreds of mm produced by continuous casting or the like is rolled into a steel plate with a thickness of several to tens of mm by a hot strip rolling mill having a roughing mill and a finishing mill. The finishing mill is usually a quadruple rolling mill with 5 to 7 stands arranged in series. In the final rolling mill with 7 racks, the first rack to the third rack is called the front rack, and the fourth ra...

Examples

Embodiment 1～7

[0146] Examples 1-7, Comparative Examples 1-5

[0147] (1) Manufacture of compound roll

[0148] Each molten solution of the composition (mass %) shown in Table 1 was cast in a centrifugal casting cylindrical mold made of ductile cast iron with an inner diameter of 400mm, a length of 1500mm and a thickness of 276mm rotating at a high speed (the inner surface is coated with zirconium with a thickness of 3mm). In the coating with stone as the main body), the outer layer is centrifugally cast. The casting temperature of the melt for the outer layer is between Ts+80° C. and Ts+100° C. (where Ts is the austenite crystallization start temperature.). The gravity multiple of the outer periphery is 120G. The resulting outer layer had an average thickness of 96 mm and a scrap diameter of 65 mm from the surface.

[0149] Before the innermost surface of the outer layer is solidified, on the inner surface of the outer layer, cast a melt for the intermediate layer having the following co...

Embodiment 8

[0211] According to the same method as in Examples 1 to 7, the melts for the outer layer and the melts for the intermediate layer having the compositions shown in Table 5 were cast into centrifugal castings made of ductile cast iron with an inner diameter of 760 mm, a length of 2700 mm, and a thickness of 320 mm. A cylindrical mold (coated with zircon-based paint with a thickness of 3 mm on the inner surface) was formed by centrifugal casting to form an outer layer with an average thickness of 91 mm, and an intermediate layer with an average thickness of 20 mm. Thereafter, the shaft core portion was formed by the same method as in Examples 1 to 7. The distribution of Cr, V, and Nb in the vicinity of the intermediate layer was measured for a test piece cut from the roll body end surface of the obtained composite roll at a position separated by about 100 mm in the roll axis direction. The results are shown in Figure 5-1 middle.

[0212] 【table 5】

[0213]

[0214] Depend ...

Embodiment 9

[0218] By the same method as in Examples 1 to 7, the melt for the outer layer and the melt for the intermediate layer having the compositions shown in Table 7 were cast into a centrifugal casting made of ductile cast iron with an inner diameter of 795 mm, a length of 2700 mm, and a thickness of 302.5 mm. The outer layer with an average thickness of 85 mm and the middle layer with an average thickness of 10 mm were formed by a centrifugal casting method using a cylindrical mold (the inner surface was coated with a coating mainly composed of zircon with a thickness of 3 mm). Thereafter, the shaft core portion was formed by the same method as in Examples 1 to 7. The distribution of Cr, V, and Nb in the vicinity of the intermediate layer was measured for a test piece cut from the roll body end surface of the obtained composite roll at a position separated by about 100 mm in the roll axis direction. The results are shown in Figure 5-2 middle.

[0219] 【Table 7】

[0220]

[0...

technical field

[0001] The present invention relates to a composite roll for hot rolling made by centrifugal casting, in which an outer layer excellent in wear resistance, seizure resistance, and accident resistance and an axial core portion excellent in toughness are interposed and integrated by interposing an outer layer, and particularly relates to a thin steel plate Composite rolls for centrifugal casting hot rolling that are suitable for work rolls for final rolling of hot strip rolling mills. Background technique

[0002] A heated slab with a thickness of several hundreds of mm produced by continuous casting or the like is rolled into a steel plate with a thickness of several to tens of mm by a hot strip rolling mill having a roughing mill and a finishing mill. The finishing mill is usually a quadruple rolling mill with 5 to 7 stands arranged in series. In the final rolling mill with 7 racks, the first rack to the third rack is called the front rack, and the fourth ra...

Examples

Embodiment 1～7

[0146] Examples 1-7, Comparative Examples 1-5

[0147] (1) Manufacture of compound roll

[0148] Each molten solution of the composition (mass %) shown in Table 1 was cast in a centrifugal casting cylindrical mold made of ductile cast iron with an inner diameter of 400mm, a length of 1500mm and a thickness of 276mm rotating at a high speed (the inner surface is coated with zirconium with a thickness of 3mm). In the coating with stone as the main body), the outer layer is centrifugally cast. The casting temperature of the melt for the outer layer is between Ts+80° C. and Ts+100° C. (where Ts is the austenite crystallization start temperature.). The gravity multiple of the outer periphery is 120G. The resulting outer layer had an average thickness of 96 mm and a scrap diameter of 65 mm from the surface.

[0149] Before the innermost surface of the outer layer is solidified, on the inner surface of the outer layer, cast a melt for the intermediate layer having the following co...

Embodiment 8

[0211] According to the same method as in Examples 1 to 7, the melts for the outer layer and the melts for the intermediate layer having the compositions shown in Table 5 were cast into centrifugal castings made of ductile cast iron with an inner diameter of 760 mm, a length of 2700 mm, and a thickness of 320 mm. A cylindrical mold (coated with zircon-based paint with a thickness of 3 mm on the inner surface) was formed by centrifugal casting to form an outer layer with an average thickness of 91 mm, and an intermediate layer with an average thickness of 20 mm. Thereafter, the shaft core portion was formed by the same method as in Examples 1 to 7. The distribution of Cr, V, and Nb in the vicinity of the intermediate layer was measured for a test piece cut from the roll body end surface of the obtained composite roll at a position separated by about 100 mm in the roll axis direction. The results are shown in Figure 5-1 middle.

[0212] 【table 5】

[0213]

[0214] Depend ...

Embodiment 9

[0218] By the same method as in Examples 1 to 7, the melt for the outer layer and the melt for the intermediate layer having the compositions shown in Table 7 were cast into a centrifugal casting made of ductile cast iron with an inner diameter of 795 mm, a length of 2700 mm, and a thickness of 302.5 mm. The outer layer with an average thickness of 85 mm and the middle layer with an average thickness of 10 mm were formed by a centrifugal casting method using a cylindrical mold (the inner surface was coated with a coating mainly composed of zircon with a thickness of 3 mm). Thereafter, the shaft core portion was formed by the same method as in Examples 1 to 7. The distribution of Cr, V, and Nb in the vicinity of the intermediate layer was measured for a test piece cut from the roll body end surface of the obtained composite roll at a position separated by about 100 mm in the roll axis direction. The results are shown in Figure 5-2 middle.

[0219] 【Table 7】

[0220]

[0...

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