Hearth roll and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-2016348971-A1
Application number	US-201515116778-A
Country	US
Kind code	A1
Filing date	Oct 2, 2015
Priority date	Oct 2, 2014
Publication date	Dec 1, 2016
Grant date	—

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

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 a hearth roll, comprising a step of irradiating a part or the whole of a surface of a thermally sprayed coating formed on a 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 foam 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

• C21D9/56

  Continuous furnaces for strip or wire · CPC title

• C22C29/02

  based on carbides or carbonitrides · CPC title

• F27B9/30

  Details, accessories or equipment specially adapted for furnaces of these types · CPC title

• C23C4/18 Primary

  After-treatment · CPC title

• C21D9/563

  Rolls; Drums; Roll arrangements · CPC title