Continuous caster roll for a continuous casting machine

Abstract

The present invention relates to a continuous caster roll for a continuous casting machine, having; a base portion and an overlay portion made of martensitic stainless steel. The steel of the overlay portion includes 12-14% by weight Cr (chromium), and the steel further includes 0.2-0.5% by weight Nb (niobium) which is a stronger carbide former than Cr, such that Cr will be kept in solid solution in the overlay portion. The balance being Fe (iron), other alloying elements and normally occurring impurities. In addition, a method to manufacture the continuous caster roll is disclosed, wherein the overlay portion is applied by any of weld cladding or laser cladding.

Claims

1. A continuous caster roll for a continuous casting machine, comprising: an overlay portion made of martensitic stainless steel that is clad on a steel base portion, wherein the steel of the overlay portion consists of the following composition by weight percent: C 0.05-0.09, Mn 0.70-1.30, Si 0.40-0.80, Cr 12.00-14.00, Ni 2.75-3.75, Mo 0.40-0.80, Nb 0.20-0.35, Cu 1.00-2.00, and Zr 0.20-0.35, the balance being Fe and normally occurring impurities.

2. The continuous caster roll of claim 1, wherein the overlay portion contains less than 10 volume percent delta ferrite.

3. A continuous caster roll for a continuous casting machine, comprising: an overlay portion made of martensitic stainless steel that is clad on a steel base portion, wherein the steel of the overlay portion consists of the following composition by weight percent: C 0.05-0.09, Mn 0.70-1.30, Si 0.40-0.80, Cr 12.00-13.00, Ni 3.50-4.50, Mo 0.70-1.30, and Nb 0.30-0.50, the balance being Fe and normally occurring impurities.

4. The continuous caster roll of claim 3, wherein the overlay portion contains less than 10 volume percent delta ferrite.

5. A continuous caster roll for a continuous casting machine, comprising: an overlay portion made of martensitic stainless steel that is clad on a steel base portion, wherein the steel of the overlay portion consists of the following composition by weight percent: C 0.05-0.09, Mn 0.70-1.30, Si 0.40-0.80, Cr 12.00-14.00, Ni 3.00-4.50, Mo 0.70-1.30, Nb 0.30-0.50, and Cu 1.50-2.50, the balance being Fe and normally occurring impurities.

6. The continuous caster roll of claim 5, wherein the overlay portion contains less than 10 volume percent delta ferrite.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Exemplifying embodiments of the present invention will now be described in more detail, with reference to the accompanying drawings, wherein:

(2) FIG. 1 shows an example of a continuous casting machine.

(3) FIG. 2 shows an example of a roll line.

(4) FIG. 3 shows an example of a continuous caster roll for a continuous casting machine according to an embodiment of the invention.

(5) FIG. 4 shows a flow chart of a method according to an embodiment of the invention.

(6) The drawings show diagrammatic exemplifying embodiments of the present invention and are thus not necessarily drawn to scale. It shall be understood that the embodiments shown and described are exemplifying and that the invention is not limited to these embodiments. It shall also be noted that some details in the drawings may be exaggerated in order to better describe and illustrate the invention.

DETAILED DESCRIPTION

(7) FIG. 1 shows a continuous slab casting process in which molten metal 10 is tapped into a ladle 12. After undergoing any ladle treatments, such as alloying and degassing, and arriving at the correct temperature, molten metal 10 from the ladle 12 is transferred via a refractory shroud to a tundish 14. Metal is drained from the tundish 14 into the top of an open-base mould 16. The mould 16 is water-cooled to solidify the molten metal directly in contact with it. In the mould 16, a thin shell of metal next to the mould walls solidifies before the middle section, now called a slab, exits the base of the mould 16 into a cooling chamber 18; the bulk of metal within the walls of the slab is still molten. The slab is supported by closely spaced, water cooled roll lines 20 which act to support the walls of the slab against the ferrostatic pressure of the still-solidifying liquid within the slab. To increase the rate of solidification, the slab is sprayed with large amounts of water as it passes through the cooling chamber 18. Final solidification of the slab may take place after the slab has exited the cooling chamber 18.

(8) In the illustrated embodiment the slab exits the mould 16 vertically (or on a near vertical curved path) and as it travels through the cooling chamber 18, the roll lines 20 gradually curve the slab towards the horizontal plane. (In a vertical casting machine, the slab stays vertical as it passes through the cooling chamber 18).

(9) After exiting the cooling chamber 18, the slab passes through straightening roll lines (if cast on other than a vertical machine) and withdrawal roll lines. Finally, the slab is cut into predetermined lengths by mechanical shears or by travelling oxyacetylene torches 22 and either taken to a stockpile or the next forming process. In many cases the slab may continue through additional roll lines and other mechanisms which might flatten, roll or extrude the metal into its final shape.

(10) FIG. 2 shows a roll line 20 according to an embodiment of the present invention, namely a common shaft roll line 20. The roll line 20 comprises a shaft 24 having an outer diameter .sub.o and supported by bearings 26 housed in bearing housings, and a plurality of continuous caster rolls (or roll mantles) 28 for transporting a metal slab along the outer surface 34 thereof, having a corresponding inner diameter .sub.i which are arranged to be fixedly supported on the shaft 24.

(11) FIG. 3 is a cross section of a continuous caster roll 28 according to an embodiment of the invention. The roll is cylinder-shaped with an axial extension L and comprises a base portion 281 and an overlay portion 282 (corresponding to the outer surface 34 in FIG. 2). The base portion can be made of any kind of steel, preferably a high temperature construction steel. The overlay portion is made of a martensitic stainless steel, which comprises 12-14 weight % of Cr. The steel further comprises 0.2-0.5 weight % Nb which is a stronger carbide former than Cr, such that Cr will be kept in solid solution in the overlay portion. The balance being Fe, other alloying elements and normally occurring impurities.

(12) In FIG. 4 a flow chart of an embodiment according to the second aspect can be seen. In a first step A a cylinder-shaped base portion is provided, wherein the base portion is made of steel, preferably a high temperature construction steel. In a second step B, the base portion is provided with an overlay portion on its outer peripheral surface. The overlay portion is provided onto the base portion by any of weld cladding or laser cladding.