JPH03207807A - Roll in furnace for heat treatment - Google Patents

Abstract

PURPOSE:To obtain a roll in a furnace for heat treatment having excellent build-up property, spalling resistance and wear resistance by arranging Mg2SiO4 thermal spraying coating layer on surface of the roll base body. CONSTITUTION:The base body of roll in the furnace for conveying the steel plate while supporting in the heat treatment in a high temp. atmosphere, is made of heat resistant steel. In order to obtain good stickness of thermal spraying coating layer to the surface of base body of roll in the furnace, the alloy having excellent stickness to the base material is thermal-sprayed and formed at about 0.03-0.5mm thickness as under-coat. On this surface, further, Mg2SiO4 (forsterite) thermal-spraying coating layer is formed. In the case of using this at high temp. of particularly >= about 1000 deg.C, cermet thermal spraying coating layer composed of >=40vol.% Mg2SiO4 and the balance heat resistant metal or alloy of Co, Cr, Ni, Al, Y, Ta, Hf, Mo, W, etc., is desirably formed. Thickness of the thermal spraying coating layer is desirable to be about 0.05-3.0mm. By this method, the roll in the furnace for heat treatment having excellent build-up property, high temp. spalling resistance and high temp. wear resistance and long service life, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an in-furnace roll for conveying high-temperature steel materials, and for example, to an in-furnace roll for conveying steel plates disposed in a heat treatment furnace. In particular, the present invention is a new proposal for coating a roll in a conveyor furnace for high-temperature steel materials, which has an excellent pill-up prevention effect, good adhesion to the roll base, and excellent wear resistance.

[Prior Art] Furnace rolls disposed in a heat treatment furnace, such as a continuous annealing furnace, are exposed to an oxidizing or reducing atmosphere at 600 to 1200°C for a long time, and the material to be annealed is Since the roll is conveyed in an atmosphere, its surface is subject to significant abrasion, and oxides and iron powder of the material to be annealed are likely to accumulate and adhere to the roll surface, forming what is called a pill stub.

As described above, when unevenness occurs on the furnace roll due to abrasion or pilt-up, the steel plate that is the material to be heat treated (hereinafter referred to as annealed material) becomes flawed during transportation. This has led to a decline in the quality of the annealed material.

Conventionally, in order to prevent such quality deterioration of annealed materials, operations were periodically interrupted and the inside of the heat treatment furnace was cooled, and then workers entered the furnace to perform grinding and maintenance on the surfaces of the rolls inside the furnace. or replacing the roll itself.

Conventional furnace rolls used under these circumstances include: (1) The material to be annealed through which the sheet is passed is supported by a roll made of a heat-resistant alloy containing high C and high Ni and water-cooled or non-water-cooled. , Metal roll used for conveyance (2) For the purpose of extending the life of the heat-resistant alloy roll mentioned in (1) above, AQ203, 2r0 is applied to the surface of the heat-resistant alloy roll.
2. Ceramic coated rolls coated with ceramics such as Sin2 by thermal spraying; cermet coated rolls coated by thermal spraying with a composite of ceramics and a heat-resistant alloy; and (3) Sleeve-shaped carphone rolls made of graphite or graphite fibers.

The above-mentioned conventionally used furnace rolls do not satisfy the characteristics desired by the present inventors.

In other words, regarding the water-cooled metal roll mentioned in (1) above, the roll surface temperature decreases and the building temperature increases. Although it is effective in preventing the occurrence of heat loss, it has the disadvantage of increasing heat loss due to water cooling.

On the other hand, in the case of non-water-cooled metal rolls, although the heat loss due to water cooling can be eliminated, the temperature in the furnace (roll speed) can reach over 800℃, which causes frequent build-up and causes scratches on the material to be annealed. This led to a decline in quality.

Next, in order to overcome the drawbacks of the heat-resistant alloy roll, a roll coated with ceramic or cermet as described in (2) above; that is, a roll made of heat-resistant alloy is coated with A
A coating layer made of ceramic or cermet such as Q■03, Zr02, Cr203 is effective in improving heat resistance and wear resistance, but it is still not sufficiently effective in terms of pill-up resistance and peeling resistance. There is a strong demand for an immediate solution. For example, JP-A-63-47379
``A hearth roll made of a cermet sprayed layer made of ZrSrQ4 and a heat-resistant alloy coated with chromium oxide for sealing,'' proposed in Japanese Patent Publication No. 1-122611, and Cr203 and MCrAiY (where M is Ni
, Go and CoN i alloys).
The cermet composite coated hearth roll made of sealed R203 has excellent abrasion resistance and heat resistance, but if used for a long time at temperatures above 950℃, a build-up phenomenon may be seen and it may not be able to withstand long-term use. found. In addition, it was found that the ^X203 coated hearth roll could not withstand long-term use, as peeling phenomenon was observed when used for a long time in a furnace at temperatures of 800° C. or higher.

Next, in the case of the carbon roll mentioned in (3) above, build-up is generated relatively little even if it is used in either a high-temperature weakly oxidizing atmosphere or a high-temperature reducing atmosphere. For example, “Cr
Carbon rolls impregnated with C.203 exhibit good pill-up resistance in a weakly oxidizing atmosphere.
The operating temperature of the r203-containing carbon roll is about 900°C, and at higher temperatures, the oxidative wear and tear increases, so the wear resistance is extremely poor and it cannot be used. Furthermore, there was a problem that the strength was insufficient for large diameter rolls (φ800 or more) such as those used in continuous annealing furnaces.

[Problem to be solved by the invention] As mentioned above, in the conventional furnace roll for a heat treatment furnace, it is possible to maintain the peeling resistance and abrasion resistance of the surface film, and to maintain the build-up resistance under high-temperature operating conditions. There was nothing that satisfied me.

The present inventors have researched various coating materials that have excellent peeling resistance and have a large build-up prevention effect that can be applied to furnace rolls used in oxidizing, neutral, or reducing atmospheres. The present invention has been completed by discovering a coating material that has excellent adhesion to the roll substrate and particularly excellent pill-up resistance.

That is, an object of the present invention is to provide a furnace roll for a high-temperature heat treatment furnace that can satisfy all of pill-up resistance, wear resistance, and peeling resistance even under high-temperature operating conditions.

[Means for Solving the Problems] The present invention that achieves the above objectives is based on Mg2S
in4 (forsterite) thermal spray coating layer or Mg2
Contains 40% by volume or more of Sin4 (forsterite),
The remainder is Co. Cr, Ni, AM, Y, T.
A cermet thermal spray coating layer made of heat-resistant metals or alloys exclusively for Hf, Mo, and W. The object of the present invention is to provide a heat treatment furnace lamp i roll having excellent hilt-up resistance, peeling resistance I1 property, and abrasion resistance, which is characterized by the following properties: 4-4.

[Effect] The present invention will be explained in further detail.

In a heat treatment furnace with a high-grade atmosphere, the base of the furnace rolls that support and transport the steel plate is made of heat-resistant steel. 1. On the surface of this furnace roll base, a 0.03 mm - 0.5 alloy with excellent adhesion to R}mura metal was sprayed by a thermal spraying method.
Form mm. The purpose of forming this thermal sprayed alloy layer as an undercoat is to obtain good adhesion with the roll base, and to improve bonding with the Mg2Sin4 thermal sprayed layer of the present invention or the cermet thermal sprayed layer, so that the roll base under the usage environment is Withstands thermal shock to materials and mechanical shock from contact with steel plates,
This is a widely used technique that aims to increase the peeling resistance of the coating layer. The present invention's Mg2S+0. + (forsterite) thermal spray coating layer or Mg2Sl04 (forsterite) containing 40% by volume or more, and the balance [:o. C
A thermally sprayed coating layer of a cermet layer made of a heat-resistant metal or alloy inclusion such as Al, Mo, AfL, Ta, or Y is formed to a thickness of 0.05 mm to 3.0 tnm by a thermal spraying method.

J2SiO4 generally has poor wettability and reactivity with iron-based metals, so when used as a conveyor roll in a heat treatment furnace, Hilt-up tests have shown that it is a good material for build-up resistance. I found the result. Mg2Si
The present invention was achieved by discovering that a single thermal spray coating has excellent build-up resistance. General heat treatment is 100
Since the furnace is operated at temperatures below 0°C, is the Mg2Si04 thermal spray coated furnace roll sufficient for application?In special cases, especially in hot water above 1000°C, the Mg2SiO4 thermal spray coating layer has poor flexibility against temperature fluctuations. However, peeling from the roll base is likely to occur, so J2Si04 (forsterite) is recommended as the furnace inlet for high-temperature heat treatment furnaces.
It was discovered that thermal spray coating has a limited service temperature limit.

Therefore, in the present invention, in order to take advantage of the excellent build-up resistance effect of Mg2Sij)4, we have improved
()4 as a binder [;o, [:r, Ni, A
M. Y. Ta l i fH. ．． ．． We have discovered a cermet spray coating layer that has excellent peeling resistance and hilt-up resistance at temperatures above I000° C. by incorporating an appropriate amount of a heat-resistant metal or alloy of w'J.

Here, regarding the F limit of the amount of MgzSiO,
This is determined from the fact that when the body becomes 40% unrefined, the amount of pilled-up increases and becomes unusable.

In other words, even if the roll has excellent hilt-up resistance, it is meaningless if the thermally sprayed coating layer peels off from the heat-resistant steel of the roll base during high-speed operation, and adhesion strength sufficient to prevent this peeling is required. In order to ensure this adhesion, Go, Gr, Ni, A4. Y. Ta
．． }If the content of heat-resistant metals or alloys such as Mo, W, etc. increases, the adhesion improves and 5 does the peeling resistance improve?
It was confirmed that 40% by volume or more of Mg2Sin4 is required to maintain hilt-up resistance. Also, 1
In order to ensure high-temperature strength with excellent hilt-up resistance and peeling resistance in an operating environment of 000°C or higher, and to function as a furnace roll, the appropriate amount of Mg2Sin4 is 4.
It is preferable that the number of explants is 0%.

In addition, in the present invention, if the thickness of the Mg, Sin4 thermal spray coating layer or the cermet composite coating layer is thinner than 0.05 mm, if the coating is worn out, the coating layer will lose its effectiveness and will not be able to exhibit various high-temperature properties. On the other hand, if the coating layer is thicker than 3.0 mm, stress will accumulate within the layer and it will easily peel off, so the thickness of the coating layer should be 0.05111 [11 to 3.0 mm].
is within or passing through the range.

[Example] After plasma spraying CoNi (:riY) to a thickness of 0.1mm on the substrate, various thermal spray coating materials shown in Table 1 were applied to a thickness of 0.3mm by plasma spraying. A furnace roll with a sprayed coating formed thereon was subjected to a long-term actual test in a continuous annealing furnace for cold-rolled steel sheets at a working temperature of 950° C. in a non-oxidizing atmosphere.

As shown in Table 1, the Mg2Sin4 thermal spray roll of the present invention exhibits excellent hilt-up resistance and durability, while other test products did not experience build-up or
Alternatively, peeling of the sprayed coating layer occurred.

In addition, 0.0% CoNiCrA-containing Y alloy was added to the base material. After plasma spraying to a thickness of 1 mm, a cermet composite coating layer was formed by plasma spraying a thermal spray coating material consisting of Mg, Sin, and a heat-resistant alloy in the mixing ratio shown in Table 2 to a thickness of 0.3 tnm. The furnace roll was subjected to a long-term actual machine test in a non-oxidizing atmosphere in a continuous annealing furnace for cold-rolled steel sheets at a working temperature of +05°C (1°C).

As shown in Table 2, build-up occurred when the content of Mg2SiO4 was less than 40%. Further, in an atmosphere of 1050° C., it was confirmed that the peeling resistance decreased due to the decrease in the amount of alloy, and it was found that the amount of metal or alloy as a binder was required to be 10% or more, preferably 15% or more.

Table 1 Actual machine test at 950°C (Example 1) Table 2 Actual machine test at 1050°C (Example 2)? In addition, when the hearth roll according to the present invention was incorporated into the soaking zone of a continuous annealing furnace for cold-rolled steel sheets and started to be used in actual operation, the hearth roll according to the present invention showed wear, pill-up, etc. in the coating layer even after two years of use. No change was observed, and the service life was several times longer than that of conventional heat-resistant steel and rolls coated with ZrO 8% Y203, which is disclosed in Japanese Patent Application Laid-Open No. 61-124534. Ta.

The present invention is effective not only in continuous annealing furnaces for cold-rolled steel sheets, but also in continuous annealing furnaces for galvanized steel sheets, electrical steel sheets, and the like.

[Effects of the invention] As detailed above, the roll of the present invention has outstanding pill-up resistance, high-temperature peeling resistance, and high-temperature abrasion resistance, and greatly contributes to extending the life of the roll and improving the quality of threaded materials. .

Claims (2)

[Claims] 1. A heat treatment furnace roll with excellent build-up resistance, peeling resistance, and wear resistance, characterized by having a Mg_2SiO_4 (forsterite) thermal spray coating layer. 2. 40 Mg_2SiO_4 (forsterite)
Contains % by volume or more, the balance being Co, Cr, Ni, Al, Y,
An in-furnace roll for heat treatment having excellent build-up resistance, peeling resistance, and abrasion resistance, characterized by having a cermet spray coating layer made of a heat-resistant metal such as Ta, Hf, Mo, W, or an alloy.