JPH08176782A - Roll for transporting high-temperature steel products - Google Patents

Abstract

PURPOSE: To obtain a roll for transporting high-temp. steel products having an excellent heat insulating characteristics, machinability and heat resistance by roughening the surface of the outer periphery of a roll base, providing this surface with a ground surface layer of a thermally sprayed heat resistant alloy layer and providing the surface of this layer with a thermally sprayed cermet-resin mixture coating layer. CONSTITUTION: The outer periphery of the roll base material 1 having a cooling water flow passage 1a in a core part is subjected to a blasting, treatment and is thereby provided with the roughened surface of Rad about 2 to 4μm. This roughened surface is then provided thereon with the thermally sprayed coating layer 2 consisting of the thermally sprayed heat resistant alloy layer 2a and the thermally sprayed cermet- resin mixture coating layer 2b. The thermally sprayed heat resistant alloy layer 2a is adequately a Co-Ni-Cr-Al-Y based alloys, etc., which are strong to thermal impact, and can well follow up thermal expansion and contraction. The thermally sprayed cermet-resin mixture coating layer 2b is obtd. by thermally spraying a powder mixture composed of 4 to 10wt.% BN, cermet powder consisting of Ni, Co, Cr, Fe, Al, etc., and 15 to 30% resin powder of nylon, etc., by a gas combustion method and the layer having the excellent machinability and heat insulating characteristics are more preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conveyor roll installed in a heat treatment furnace for high temperature steel materials such as stainless steel plates that need to be treated at a high temperature, and provides heat insulation while maintaining build-up resistance. The goal is to improve productivity and achieve stable operation over a long period of time.

[0002]

2. Description of the Related Art Hearth rolls for heat treatment furnaces (hereinafter, referred to as conveyance rolls) that convey high temperature stainless steel plates and the like in a heat treatment line adversely affect the surface quality of materials to be conveyed (hereinafter referred to as conveyance materials). Since it is required that it is not given, a roll whose surface is coated with a heat resistant material is usually used.

By the way, in the case of the transfer roll installed in the latter half of the heating zone in the heat treatment furnace where the processing atmosphere of the transfer material exceeds 1200 ° C. or in the soaking zone, the transfer material is softened and the surface of the roll is Even a slight change is easily affected by it, and the material quality tends to deteriorate.

Further, when attention is paid to the transport roll itself, since such a roll is used in a high temperature atmosphere, the main body (base body) of the roll is usually an internal water cooling type. is there. Therefore, it is necessary to coat the roll surface, which is the passage surface of the conveying material, with a heat insulating material or the like in order to prevent the temperature of the conveying material from lowering. It is essential that the material does not damage the material, and conventionally asbestos, silica / alumina fiber, etc. have been used. As a prior document relating to this point, a roller-hearth type heating furnace carrying roll is disclosed in which a heat-resistant sheet material punched into a donut-shaped disc is inserted into an iron core and compression-molded.
No. 12, JP-A-1-301818, and the like.

However, the known coating roll as described above has various problems as described below. That is, in the method of using a disc-shaped heat-resistant heat-insulating sheet,
The work of inserting such a sheet into a roll requires a great deal of labor and time, and moreover, according to the results of use in an actual heat treatment furnace, deterioration and hardening of the asbestos layer and the inorganic fiber layer, which are the coating constituents, are observed. However, the sheets fell off the rolls in a short time and became unusable, and there was a case where the operation had to be stopped. Further, in this type of roll, the scale generated on the surface of the conveying material adheres to the surface of the roll, and the adhered scale damages the subsequent conveying material, so-called build-up still remains. It was

Regarding reduction of build-up, instead of the conventional structure in which sheet materials having inorganic fibers as a main material are laminated, a cermet having good machinability is spray-coated, as disclosed in JP-A-4-99813. Although the technology disclosed in the publication is known, the roll disclosed here conveys due to deformation of the core metal due to insufficient thermal insulation of the thermal spray coating layer, causing internal rotation and poor rotation. There is a problem that the material will be scratched, and the temperature of the material to be conveyed will drop.
However, there was an unavoidable disadvantage. Asbestos has a small thermal conductivity [cal / cm · s · ° C] of 0.00037, so the surface temperature of the core metal can be kept below 50 ° C, but the thermal conductivity of the thermal spray coating is 0.3 [cal]. / cm ・ s ・
Since it is as large as ℃], the surface temperature of the core metal rises to nearly 1000 ℃, and as a result, the above problems occur.

[0007]

DISCLOSURE OF THE INVENTION The present invention is to propose a roll surface structure capable of solving the above-mentioned problems, and particularly for conveying a high temperature steel material excellent in heat insulation, machinability and heat resistance. To propose a role.

[0008]

DISCLOSURE OF THE INVENTION The present invention, which was developed to achieve the above object, is a roll for conveying high temperature steel having a thermal spray coating layer on the outer periphery of the roll. For providing high-temperature steel material, which is provided with an underlayer of the heat-resistant alloy sprayed layer on the roughened surface, and a mixed sprayed coating layer of cermet powder and resin powder is provided on the underlayer. It is a roll. In the present invention, the content of the resin powder in the mixed powder of cermet and resin is preferably 15 to 30%. The cermet powder contains 4 to 10 wt% of BN, and the balance is Ni,
It is preferable to use at least one metal selected from Co, Cr, Fe and Al or a mixture thereof with an alloy thereof and having excellent machinability.

[0009]

The present invention will be described in detail below with reference to the drawings.
FIG. 1 shows the structure of a roll for conveying high-temperature steel material according to the present invention, where 1 is a base that constitutes a roll main body having a cooling water flow path 1a in its core, and 2 is a roughened surface of the base 1. It is a heat-resistant and heat-insulating thermal spray coating layer. This thermal spray coating layer 2 is directly formed on the outer peripheral surface of the substrate 1 by Co-Ni.
-Cr-Al-Y-based heat-resistant alloy sprayed layer 2a, sprayed by mixing cermet powder and resin powder formed on this heat-resistant alloy sprayed layer 2a and sprayed with excellent machinability and heat insulation It is composed of layer 2b (which becomes a porous coating layer).

In the present invention, as shown in FIG. 1, the surface (roughened surface) of the substrate 1 constituting the roll body is first resistant to thermal shock as an underlayer and can well follow thermal expansion and contraction. A cermet / resin mixture which forms a Co-Ni-Cr-Al-Y-based heat-resistant alloy sprayed coating layer 2a exhibiting characteristics and which has machinability and excellent heat insulation properties on the sprayed coating 2a. A two-layer thermal spray coating structure in which the thermal spray coating layer 2b is laminated is adopted. With such a thermal spray coating structure, the roll only has improved heat resistance, machinability and build-up resistance. Not only that, but it also has excellent heat insulation.

Regarding the mixed spray coating layer 2b for spraying the mixture of cermet and resin powder, the content of the resin powder was limited to the range of 15 to 30 wt% for the following reason. That is, by containing the resin powder in an amount of 15 wt% or more, it is possible to obtain a thermal sprayed layer having sufficient heat insulation while ensuring a certain level of wear resistance (machinability),
This is because it is possible to prevent deformation of the core metal of the roll. On the other hand, if the content of this resin powder exceeds 30%, no further effect can be expected. This is because, even if the content of resin powder is increased, the thermal conductivity of the coating layer is almost the same because the resin (nylon, polyester, polypropylene, etc. is used as the resin) remains in the places where pores should originally be formed. There is no change, on the other hand, the wear ratio sharply increases due to the decrease in the bonding force between the coating layers, and in particular, peeling occurs when the content of the resin powder exceeds 40%,
Therefore, it can be said that the most preferable resin powder content is 15 to 30%.

By the way, FIG. 2 shows the results of investigating the influence of the resin powder in the case of using a roll having a 100% cermet spray coating layer as a base, with respect to the thermal conductivity and wear ratio of the roll. As you can see in this figure,
It can be seen that when the content of the resin powder is 15 to 30 wt%, that is, when the content of the cermet powder is 70 to 85 wt%, both the thermal conductivity and the wear coverage are low.

Next, the material of the heat-resistant alloy sprayed layer 2a is not limited to the exemplified Co-Ni-Cr-Al-Y alloy, but other materials such as Ni-Cr-Al-Y alloy and Co-Cr- are also available. Al-Y alloys and the like are also effective, any of which are well suited to the present invention.

Further, in order to form a sprayed coating having excellent machinability, the cermet powder as the sprayed material contains BN of 4
It is preferable to use a mixture containing 10 to 10 wt% and the balance being a mixture of various heat resistant alloys made of at least one metal or alloy of Ni, Co, Cr, Fe and Al.

As a method for forming a mixed spray coating layer of cermet powder and resin powder, it is preferable to apply a spray coating method by a gas combustion method.

In forming the heat-resistant alloy sprayed coating layer 2a on the surface of the substrate 1, the surface of the substrate 1 is roughened by blasting or the like in advance in order to enhance the adhesion of the layer due to the projection effect of the sprayed coating. It is desirable to set the surface (Rad: about 2 to 4 μm). Further, it is desirable that the surface roughness of the sprayed coating layer be polished so that Ra: 10 μm or less. The thickness of the thermal spray coating layer is preferably about 200 μm for the underlayer and about 1.0 mm for the thermal spray coating layer of the mixed powder of cermet powder and resin powder.

[0017]

[Example] In a stainless steel plate heat treatment furnace having a production capacity of 30,000 tons / month, a roll for conveyance as shown in Fig. 1 was arranged, and the usage of the roll was investigated. Table 1 shows the results.

[Table 1]

In the conventional roll using asbestos and silica / alumina fiber as the coating material, when the production amount reaches 6000 tons, the coating material comes off and build-up occurs. deterioration
Concerned about the occurrence of flaws, he was forced to replace the roll. On the other hand, in the case of using a spray-coated roll of 100% cermet powder, when the production amount reaches 12000 tons, rotation failure due to bending of the core metal occurs, and there is concern that the quality of the stainless steel plate deteriorates (scratches occur). I was forced to replace the roll.

On the other hand, in a roll having a thermal spray coating layer in which 16% of resin powder is added to cermet powder,
Eventually, the core metal deformed and caused rotation failure, but it can be used until the production volume increases by about 2.2 times.
Further, when the content of the resin powder was 20%, the core metal did not bend and could be used (wear limit) until the production amount reached 42000 tons. Furthermore, we also investigated the roll having a thermal spray coating layer whose content of the resin powder is higher than the value specified in the present invention, but the wear of the thermal spray coating layer is rather fast, and especially at a mixing ratio of 28%, the production amount is increased. However, at the stage of 15,000 tons, peeling of the coating layer occurred and forced to replace the roll.

As described above, the resin powder is added to the cermet powder.
It was confirmed that by mixing in the range of 15 to 30%, it is possible to extend the life significantly compared to the conventional roll.

[0021]

As described above, according to the present invention,
Since sufficient heat insulation can be obtained even under relatively high temperature conditions, it has become possible to avoid rotation failure due to bending of the core metal of the roll. Also, since it has machinability, build-up does not occur and the roll life can be extended. In addition, the extended service life of the rolls can extend the regular repairs and improve the operating rate of the equipment.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of a transport roll according to the invention.

FIG. 2 is a diagram showing the relationship between the amount of mixed powder of cermet resin and thermal conductivity.

[Explanation of symbols]

 1 Substrate 2 Thermal Spray Coating Layer 2a Heat Resistant Alloy Thermal Spray Layer 2b Thermal Spray Coating Layer

Claims (3)

[Claims] 1. A roll for transporting high-temperature steel material having a thermal spray coating layer on the outer circumference of the roll, wherein a roughened surface is provided on the outer circumference of a roll base material, and a base layer of a heat-resistant alloy sprayed layer is provided on the roughened surface. A roll for conveying high-temperature steel, comprising a mixed spray coating layer made of cermet powder and resin powder on the underlayer. 2. The roll according to claim 1, wherein the content of the resin powder in the mixed powder of cermet and resin is 15 to 30 wt%. 3. The cermet powder contains 4 to 10 wt% of BN, and the balance is at least one metal selected from Ni, Co, Cr, Fe and Al, or a mixture thereof with an alloy thereof. The roll according to claim 1 or 2, which has excellent properties.