JPH0757904B2 - Heat treatment furnace roll and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a roll for a heat treatment furnace which is excellent in pick-up resistance and wear resistance, and a method for producing the roll.

(Prior Art) A heat treatment furnace roll, for example, a hearth roll disposed in a heat treatment furnace for thin steel plates, is continuously operated in a high temperature oxidizing or reducing atmosphere for a long period of time, and therefore its surface is worn. In response to this, the usable number of times is reduced, or the adhered oxide and iron powder from the heat-treated material are adhered and deposited on the roll surface to form a so-called build-up.

In this way, the scale adhered / formed on the surface of the hearth roll has a flaw called a pickup on the surface of the thin steel sheet which is the material to be heat treated, which is a main cause of deterioration of steel sheet quality and yield. The occurrence must be prevented as much as possible.

Therefore, various means have been conventionally proposed.

For example, (i) Japanese Patent Laid-Open No. 62-158586 discloses a means for nitriding the roll surface and then irradiating a laser beam to roughen the surface. Is a means for performing laser dull processing while spraying a cemented carbide powder having a specific particle diameter on the roll surface together with gas. (Iii) JP-A-62-158588 discloses a roll surface before laser dull processing. (Iv) Japanese Patent Laid-Open No. 55-154522 discloses that a chromium oxide layer is formed by thermal spraying on the surface of a base material of a roll for a heat treatment furnace. (V) Japanese Patent Publication No. 63-26183 discloses YO and ZrO _{2 having a} specific composition.
The means for forming a ceramic coating consisting of (vi) is disclosed in JP-A-60-141861, and the means for coating a Co-Al alloy is (vii) is disclosed in JP-A-57-111850. A heat treatment furnace roll having a specified surface roughness is further disclosed. (Viii) Japanese Patent Laid-Open No. 61-253385 discloses means for spraying ceramics, cermet, etc. after polishing / dulling the roll surface. ing.

(Problems to be Solved by the Invention) However, none of these known means can reliably provide a roll for a heat treatment furnace excellent in pick-up resistance and abrasion resistance at low cost.

That is, the means shown in (i), (ii), and (iii) above are all applied to cold rolling rolls, and wear resistance at high temperatures is required for use as a hearth roll for a heat treatment furnace. It lacks in nature and cannot be used.

Further, the means shown in (iv) and (v) have insufficient pick-up resistance and cannot provide a suitable hearth roll for a heat treatment furnace.

Further, in the means shown in (vi), Al diffusion and Al ₂ O ₃ are caused after coating.
The heat treatment for forming is actually required, and the cost is inevitable.

Furthermore, with the means shown in (vii) and (viii), it is necessary to adjust the surface roughness of the roll by electrical discharge dull machining, shot blasting, etc. However, if this adjustment is performed, the uniformity of the roll surface will be lost. , Wear and pickup are likely to occur.

That is, the above-mentioned known means could not reliably provide a roll for a heat treatment furnace excellent in pickup resistance and abrasion resistance at low cost.

An object of the present invention is to reliably provide a roll for a heat treatment furnace excellent in pick-up resistance and wear resistance and a method for manufacturing the roll at low cost.

(Means for Solving the Problem) As a result of various studies to solve the above problems, the present inventor has obtained the following new findings.

First, the fact that the rolls obtained by the means described in (i), (ii) and (iii) above lack high-temperature wear resistance means that Co-Cr-Al-Y + Al ₂ O ₃ excellent in high-temperature wear resistance is used. It can be solved by spraying the cermet of the system.

Further, the rolls obtained by the means shown in (iv) and (v) have insufficient pick-up resistance because the rolls are replaced by A instead of CrO and ZrO _2.
It can be solved by using l ₂ O ₃ .

Further, the cost increase in the means shown in (vi) can be offset by the fact that the annealing effect is exhibited by performing the laser irradiation and the heat treatment is unnecessary.

Further, in the means shown in (vii) and (viii), the uniformity of the roll surface is lost, but this can be solved by irradiating with a laser beam.

In other words, by integrating these findings,
A heat treatment furnace with excellent pick-up resistance and wear resistance by spraying a Co-Cr-Al-Y cermet containing Al ₂ O ₃ to form a coating and then irradiating the surface with a laser beam. The present invention has been completed, knowing that an industrial roll can be provided at low cost.

Here, the gist of the present invention is that a body for a heat treatment furnace roll, a Co-Cr-Al-Y-based cermet coating layer in which solid Al ₂ O ₃ particles formed by thermal spraying are dispersed, and the cermet. An Al ₂ O ₃ layer formed on the coating layer and engraved with a laser beam to have a surface roughness of 4 to 6 μm, and an alloy layer formed at the boundary between the heat treatment roll body and the cermet coating layer (2). A roll for a heat treatment furnace having excellent pick-up resistance, abrasion resistance, and peeling resistance.

From another aspect, the present invention is, on the surface of the roll body for heat treatment furnaces, thermal spraying of Co-Cr-Al-Y cermet containing a solid Al ₂ O ₃ particles, the solid Al ₂ O ₃ particles are dispersed After forming the coating layer, the surface of the coating layer is irradiated with a laser beam to perform dulling with a surface roughness Ra of 4 to 6 μm.
On the surface layer of the coating layer, the metal Al contained in the cermet
By diffusing the metal Al and oxygen in the atmosphere to form an Al ₂ O ₃ layer, and the coating layer by diffusion of the metal component contained in the heat-treating roll body and the cermet. And a heat treatment roll main body, an alloy layer is formed at the boundary between the heat treatment roll body and the heat treatment roll main body, which is excellent in pick-up resistance, abrasion resistance and peeling resistance.

According to a preferred embodiment of the present invention, the surface of the coating layer is exposed to, for example, 4S (maximum height Rmax of 4 μm prior to laser beam irradiation).
m or less), the surface may be smoothed by polishing.

The cermet used for thermal spraying in the present invention is Al ₂ O ₃
Is a Co—Cr—Al—Y-based cermet, and specifically, 10Al ₂ O ₃ +90 (24Co-24Cr-50Al-2Y) is exemplified.

(Operation) Hereinafter, the present invention will be described in detail together with the operation and effect.

The heat treatment furnace roll according to the present invention has Al ₂ O on its surface.
_It has a coating film formed by spraying a Co-Cr-Al-Y-based cermet containing a large amount of solid solution Al containing ₃ .

Here, 10Al ₂ O ₃ +90 (24Co
-24Cr-50Al-2Y) or Co-Cr-Al containing Al ₂ O ₃
The reason why -Y type cermet is exemplified
₂ O ₃ +90 (24Co-24Cr-50Al-2Y) is subjected to heat treatment after thermal spraying to improve the adhesion between the roll surface and the thermal spray layer, or the formation of Al ₂ O ₃ on the thermal spray surface layer by diffusion of Al. This is because it has been known to be an element that greatly promotes the improvement of the wear resistance of the material. In the following description of the present invention, Al ₂ O ₃ using _{10Al 2 O 3 +90 (24Co-} 24Cr-50Al-2Y) as Co-Cr-Al-Y system cermet containing, but the present invention is to It is not limited.

The thickness of the sprayed coating does not need to be particularly limited,
It may be appropriately set according to the performance required for the roll, but according to the knowledge of the present inventor, the thickness of 100 μm or more has a great effect on the improvement of the pick-up resistance and the wear resistance. Is desirable.

Figure 1 (a) shows this 10Al ₂ O ₃ +90 (24Co-24Cr-50Al).
2-2) is a schematic cross-sectional view near the surface of the roll after thermal spraying. The surface of the roll 3 is coated with a coating layer 2 made of a Co-Cr-Al-Y-based alloy, and Co-Cr-Al It can be seen that the Al ₂ O ₃ particles 1 are dispersed and present in the coating layer 2 of the Y-based alloy.

Next, in the heat treatment furnace roll according to the present invention, the coating layer 2 on the surface of the roll 3 is irradiated with a laser beam. FIG. 1 (c) is a schematic cross-sectional view of the vicinity of the surface of the roll 3 which is being irradiated with a laser beam from a conventional laser beam oscillator 6, and is irradiated with the laser beam so that it is about 20 μm in FIG. It is shown that recesses having a depth of about 10 to 15 μ are formed on the surface of the coating layer 2 at intervals. By irradiating the surface with a laser beam, surface roughness can be imparted to the coating layer 2 and wear resistance can be improved, and at the same time, solid solution Al dispersed in the thermal spray material is diffused to the surface. , Al combined with O ₂ in the atmosphere
_{A 2} O ₃ layer 4 is formed. This Al ₂ O ₃ is shown in FIG.
The maximum thickness of layer 4 is of the order of 20 μm. Furthermore, at the interface between the thermal spray material and the roll base material by this laser beam processing, Fe-Co-
The alloy layer 5 of Cr is formed with a maximum thickness of about 20 μm,
The effect of further improving the adhesiveness of the sprayed coating is obtained.

According to the knowledge of the inventor of the present invention, as shown in FIG. 2 (a), when the surface roughness is as small as less than 4 μm, the contact surface pressure of the thin steel sheet on the roll surface is too weak, causing slip, Seizure occurs between the heat-treated material and the roll, and the heat-treated material is bonded to the roll to cause pickup. If the surface roughness exceeds 6 μm and is too high, pick-up cannot be prevented due to the adhered oxide from the heat-treated material and the adhesion / accumulation of iron powder on the roll surface. Therefore, the surface roughness of the coating layer 2 after laser beam processing is in the range of 4 to 6 μm, which is very effective in preventing pickup.

Here, the surface roughness is represented by the center line average roughness (Ra) specified in JIS B 0601.

Further, as shown in FIG. 2 (b), the unevenness of the surface is not uniform and the wear tends to progress locally due to a method other than the laser beam processing, such as shot blasting and discharge dull processing. The surface roughness decreases rapidly during use, the effect of preventing pickup is small, and the pickup cannot be practically prevented.

Further, in order to uniformly and uniformly irradiate the laser beam, it is desirable that the surface of the roll having the sprayed coating be polished and smoothed before the laser beam irradiation. FIG. 1 (b) is a schematic cross-sectional view of the vicinity of the surface of the roll 3 when the surface is polished and finished before laser beam irradiation, and the degree of finishing is 4S or less according to the knowledge of the present inventor. That is, it is desirable to finish the surface so that the maximum height Rmax of the surface is 4 μm or less.

The thickness of the coating layer 2 at this time is about 60 μm.

Further, the present invention will be described in detail together with examples. Note that this is an example of the present invention, and the present invention is not unduly limited thereby.

Example The heat treatment furnace roll according to the present invention and the conventional heat treatment furnace roll were installed in a continuous annealing furnace and continuously used for 30 months, and the degree of wear was measured by measuring the surface roughness Ra.

In the production of the heat treatment furnace roll according to the present invention, as a cermet, 10Al ₂ O ₃ +90 (24Co-24Cr-50Al
-2Y), the surface roughness of the coating layer was 6 μm, and the surface of the roll, that is, the surface of the coating layer was polished to 4S with a honing grindstone before the laser beam irradiation.

In addition, as a conventional heat treatment roll, 10Al ₂ O ₃ +90 (2
4Co-24Cr-50Al-2Y) with a coating layer, the surface of which has been subjected to electric discharge dull processing and then heat treatment (Comparative Example 1), and which has been subjected to shot blast processing and then heat treatment. (Comparative example 2) was used.

Results are shown in FIG. As is clear from FIG. 2, the roll for heat treatment furnace according to the present invention shows almost no change in surface roughness even after continuous use for 30 months, and exhibits extremely excellent wear resistance.

On the other hand, the surface roughness of the heat-treating furnace roll of the comparative example was drastically lowered, and the comparative example 1 could not be used after 25 months and the comparative example 2 after 20 months. Therefore, it can be seen that the wear resistance of the heat treatment furnace roll according to the present invention is excellent. From this, it is understood that the thin steel sheet heat treatment furnace roll according to the present invention can maintain the surface roughness at an appropriate value for a long period of time even in continuous use, and can prevent the occurrence of pickup.

〔The invention's effect〕

According to the present invention described in detail above, it has become possible to inexpensively provide a roll for a heat treatment furnace having excellent wear resistance and pick-up resistance. Therefore, the maintenance cost and man-hours of the roll can be reduced, and the economical effect thereof is extremely large.

Further, by irradiating with a laser beam, heat treatment becomes unnecessary, and energy cost and cost can be significantly reduced.

The practical significance of the present invention having such effects is extremely remarkable.

[Brief description of drawings]

1 (a), 1 (b) and 1 (c) are schematic explanatory views of the surface of a roll according to the present invention; FIGS. 2 (a) and 2 (b) are respectively due to dull processing. FIG. 3 is a graph showing the influence of the surface roughness and the roughness imparting means therefor on the pickup occurrence frequency; and FIG. 3 shows the relationship between the number of months of use of the roll and the surface roughness depending on the difference in the roughness imparting means in the examples. It is a graph showing. 1: Al ₂ O ₃ particles, 2: coating layer 3: roll, 4: Al ₂ O ₃ layer 5: alloy layer, 6: laser beam oscillator

Claims (3)

[Claims] 1. A roll body for a heat treatment furnace (3), and a Co—Cr—Al—Y cermet coating layer (2) on the surface of which solid Al ₂ O ₃ particles (1) formed by thermal spraying are dispersed. An Al ₂ O ₃ layer (4) formed on the cermet coating layer (2) and engraved with a laser beam to have a surface roughness of 4 to 6 μm,
Excellent pick-up resistance, abrasion resistance, and peeling resistance, characterized by comprising an alloy layer (5) formed at the boundary between the heat treatment roll body (3) and the cermet coating layer (2). Roll for heat treatment furnace. 2. A Co—Cr—Al—Y cermet containing solid Al ₂ O ₃ particles (1) is thermally sprayed onto the surface of a heat treatment furnace roll body (3) to obtain the solid Al ₂ O ₃ particles ( After forming a coating layer (2) in which 1) is dispersed, the surface of the coating layer (2) is irradiated with a laser beam to perform dulling with a surface roughness Ra of 4 to 6 μm, whereby the coating layer (2) is formed. ) In the surface layer, the metal Al contained in the cermet is diffused, and the metal Al and oxygen in the atmosphere are combined to form an Al ₂ O ₃ layer (4), and the heat treatment roll body ( 3) and the metal component contained in the cermet are diffused to form an alloy layer (5) at the boundary between the coating layer (2) and the heat treatment roll body (3). A method for manufacturing rolls for heat treatment furnaces that has excellent heat resistance, abrasion resistance, and peel resistance. 3. The method for manufacturing a roll for a heat treatment furnace according to claim 2, wherein the surface of the coating layer (2) is polished and smoothed prior to laser beam irradiation.