Hearth roll and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-10088236-B2
Application number	US-201515116778-A
Country	US
Kind code	B2
Filing date	Oct 2, 2015
Priority date	Oct 2, 2014
Publication date	Oct 2, 2018
Grant date	Oct 2, 2018

Abstract

A hearth roll includes a base roll, a thermally sprayed coating formed on the base roll, and a modified coating formed on the thermally sprayed coating. The modified coating is formed by modifying a part or the whole of a surface of the thermally sprayed coating by melting and solidification of the thermally sprayed coating, by irradiating a part or the whole of the surface of the thermally sprayed coating with an energy beam. The thickness of the modified coating is from 2 to 20 μm, and the Vickers hardness HV of the modified coating is from 1.2 to 1.4 times larger than the Vickers hardness HV of the thermally sprayed coating.

First claim

The invention claimed is:

1. A hearth roll, comprising:
a base roll;
a thermally sprayed coating formed on the base roll; and
a modified coating formed on the thermally sprayed coating, the modified coating being formed by modifying a part or the whole of a surface of the thermally sprayed coating by melting and solidification of the thermally sprayed coating, by irradiating a part or the whole of the surface of the thermally sprayed coating with an energy beam,
a thickness of the modified coating being from 2 to 20 μm, and
a Vickers hardness HV of the modified coating being from 1.2 to 1.4 times larger than a Vickers hardness HV of the thermally sprayed coating.

2. The hearth roll according to claim 1 , wherein cracks are present on a surface of the modified coating, and an average spacing between adjacent cracks in a cross-section of the hearth roll cut in a thickness direction is from 10 to 100 μm, and opening widths of the cracks are less than 5 μm.

3. The hearth roll according to claim 1 , wherein the modified coating comprises from 0.5% to 2% by mass of oxygen.

4. The hearth roll according to claim 1 , wherein Al 2 O 3 is present in a dispersed state in a surface of the modified coating, and a proportion of an area of Al 2 O 3 in the surface of the modified coating is from 5% to 40%.

5. The hearth roll according to claim 1 , further comprising a chromium oxide layer formed on the modified coating, or on the modified coating and the thermally sprayed coating.

6. The hearth roll according to claim 1 , wherein the thermally sprayed coating is a cermet coating consisting of a heat-resistant alloy and a ceramic,
the ceramic including, in terms of % by volume, Cr 3 C 2 at from 50% to 90%, Al 2 O 3 at from 1% to 40%, Y 2 O 3 at from 0% to 3%, and ZrB 2 at from 0% to 40%, and the balance being composed of impurities and pores,
the heat-resistant alloy including, in terms of % by mass, Cr at from 5% to 20%, Al at from 5% to 20%, and at least one of Y or Si at from 0.1% to 6%, and the balance being composed of at least one of Co or Ni and impurities, and
from 50 to 90% by volume of the cermet coating being the ceramic, and the balance being the heat-resistant alloy.

7. The hearth roll according to claim 6 , wherein the heat-resistant alloy further includes, in terms of % by mass, at least one of Nb at from 0.1 to 10% or Ti at from 0.1 to 10%.

8. A method of producing the hearth roll according to claim 1 , comprising a step of irradiating a part or the whole of a surface of a thermally sprayed coating formed on the base roll with an energy beam, thereby modifying a part or the whole of the surface of the thermally sprayed coating by melting and solidification of the thermally sprayed coating, to form a modified coating having a thickness of from 2 to 20 μm and a Vickers hardness HV that is from 1.2 to 1.4 times larger than the Vickers hardness HV of the thermally sprayed coating.

9. The method of producing a hearth roll according to claim 8 , wherein the irradiating with the energy beam is performed in the atmosphere.

10. The method of producing a hearth roll according to claim 8 , wherein a chromate treatment is performed after the modified coating is formed.

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Tocalo Co Ltd

Inventors

• Kurisu Yasushi
• Suidzu Tatsuo

Classifications

• C21D9/563

  Rolls; Drums; Roll arrangements · CPC title

• C23C28/30

  Coatings combining at least one metallic layer and at least one inorganic non-metallic layer · CPC title

• C23C4/06

  Metallic material · CPC title

• B65H2701/173

  Metal · CPC title

• C23C4/10

  Oxides, borides, carbides, nitrides or silicides; Mixtures thereof · CPC title