JP2953346B2 - Rolls for supporting steel plates in hot-dip metal plating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet supporting roll used in contact with a hot gas atmosphere of a hot-dip metal plating facility,
In particular, the present invention relates to a touch roll and a pass roll for supporting a steel sheet in a cooling building for cooling a steel sheet immediately after plating in a hot-dip metal plating facility. More specifically, the present invention relates to a touch roll and a pass roll for supporting a steel sheet in a steel sheet cooling building immediately after passing through an alloying furnace of an alloying hot-dip galvanizing facility.

[0002]

2. Description of the Related Art In hot-dip galvanizing equipment, particularly a steel sheet immediately after plating is at a high temperature, and its plating film is softened in a metallurgically activated state and easily reacts with other metals. I have. Particularly, in an alloyed hot-dip galvanizing facility, an alloying furnace for reheating a steel sheet immediately after plating is vertically installed in order to alloy a plating film and a steel sheet. At this time, the furnace temperature in the alloying furnace reaches 900 ° C. or more, and the heating source is gas heating with few exceptions. Since this gas heating is performed in the atmosphere, the high-temperature exhaust gas rises together with the steel sheet due to the draft effect. The steel sheet is reheated to about 600 ° C by this gas heating.

FIG. 1 is an explanatory diagram of a cooling process after a dipping process in a hot dip galvanizing tank in an alloyed hot dip galvanizing facility. Plated steel sheet S that has passed through an annealing furnace (not shown)
Entered the plating bath (zinc pot) 1, was turned upward by the sink roll 2, and was adjusted to a predetermined plating adhesion amount by a gas wiping device (not shown) installed above the plating bath 1. Thereafter, it passes through the alloying furnace 3 and is reheated at that time. Subsequently, the alloying is completed while passing through the holding band 4. The steel sheet temperature at this time is about 450 ° C. Thereafter, the cooling process starts. The steel sheet passes through the air-cooling zone 5, the air-water-air cooling zone 6, passes through the sink roll 2, and is turned by the top roll 7, which is the first deflector roll.

[0004] The distance between the sink roll 2 and the top roll 7 varies depending on the equipment, but is as long as about 40 to 50 m. If no touch roll is provided in the middle, flapping of the steel sheet due to string vibration occurs. When the nozzle is brought close to the steel sheet for adjusting the amount of adhesion, the nozzle and the steel sheet come into contact with each other, causing abrasion and significantly deteriorating the surface quality. Therefore, touch rolls 8 to 11 are placed before and after the location where the string vibration is applied.
Has been set up to prevent this.

[0005] Atmosphere conditions of the touch roll installed in the equipment shown in FIG. 1 differ depending on the installation location. That is, since the touch roll 8 is immediately after the plating, the plating is in contact with the steel sheet in a molten state, but the atmosphere is around 80 ° C. The touch roll 9 is in a state where alloying of the steel plate heated for alloying is in progress, and the contact temperature is about 450
℃, atmosphere is about 600 temperature by the draft of the alloying furnace 3
° C, oxidizing atmosphere due to slight exhaust gas leakage. The touch roll 10 is an oxidizing humid air atmosphere having a contact temperature of about 400 ° C. and a temperature of about 150 ° C. at the boundary between the holding zone 4 and the air cooling zone 5. The touch roll 11 is used at a boundary between the air cooling zone 5 and the air / water air cooling zone 6 in a humid atmosphere with a contact temperature of about 350 ° C. and a temperature of about 150 ° C. Further, water used in the air-water air cooling zone 6 adheres.

[0006] As described above, the touch roll is exposed to ambient environmental conditions having different characteristics. Conventionally, these touch rolls are provided with hard Cr plating, WC-12Co-based material, Co-20Cr-6Mo-
Thermal spraying of 10Ni-15W material has been used. However, as shown below, it was not yet practical.

[0007] Touch Cr No. Usage conditions Service life Hard Cr plating 8 Plating peeling at non-plated part, metal corrosion about 10 days WC-12Co Bauter spraying 9 Thermal spray peeling at non-plated part, metal corrosion about 2 days WC-12Co shear coat 10 Thermal spray peeling and non-metallic corrosion in non-plated area Approx. 2 days Co-Mo-Cr thermal spraying 11 Overall thermal spray peeling and metal erosion Approx. 3 days Thus, operating conditions after touch roll 9 A poor touch roll was in a state where it could not be used with conventional surface treatment and the roll itself could not be used. Therefore, string vibration of the steel sheet is frequently generated, and the above-mentioned operation is hindered.

Further, in the surface treatment merely for improving the corrosion resistance of the roll, the plating layer of the steel sheet adheres to the roll and a flaw is transferred to the surface of the steel sheet. It becomes a defect and yield decreases. Therefore, a surface treatment method having both corrosion resistance, zinc adhesion resistance, and abrasion resistance has been required.

The prior art and its problems will be summarized below. Steel rolls The rolls are composed of corrosion-resistant materials (e.g., SUS316 or SCM440), but zinc reacts with the roll surface to form, for example, an Fe-Zn alloy with iron contained in the steel. Deterioration is remarkable. Also, the wear of the steel part is severe.

[0010] The coating of the roll surface with a ceramic nonwoven fabric has the effect of preventing the transfer of zinc, but the ceramic nonwoven fabric itself has a low mechanical strength and is liable to wear, so that its service life is short. Ceramic nonwoven fabrics are very expensive.

[0011] Ceramic spray coating on the roll surface Transfer of zinc can be almost completely prevented. However, the presence of fine cracks or through-holes in the ceramic spray coating is inevitable. There is a high risk that corrosive combustion products mainly composed of oxides such as sulfur and phosphorus penetrate into the roll base material, erode the interface between the base material and the coating layer, and peel off the coating layer.

WC-Co sprayed on the roll surface The WC-Co sprayed layer is dense and does not peel off the coating due to the occurrence of corrosion at the interface of the base material. Also, the wear resistance is sufficient. However, the metal binder such as Co and zinc are reactive and easily alloyed, so that zinc is easily picked up on the roll surface. Further, the corrosion resistance of the film itself is poor, and it is difficult to use the film for a long time.

Other prior art methods for spraying ceramics as a surface treatment method for preventing zinc from adhering to the roll surface are disclosed in JP-A-3-27807, JP-A-3-53055, and JP-A-5-195185. Proposed.

First, in Japanese Patent Application Laid-Open No. Hei 3-27807, ceramics are sprayed and the surface is sprayed with a resin. However, many resins melt or deteriorate at high temperatures, and are inferior in heat resistance and wear resistance.

In Japanese Patent Application Laid-Open No. Hei 3-53055, thermal spraying including a metal bonding material having good adhesion to ceramics is performed. Specifically, this is a cermet sprayed layer of WC-Co or the like. However, the mere inclusion of a metal binder is not corrosive. The purpose is a kind of insert material because it has a composition that can ensure the adhesion between the lower layer and the ceramic layer.

Japanese Unexamined Patent Publication No. 5-195185 discloses that multi-layer spraying is performed by changing the composition ratio of ceramics and metal, but the number of working steps is increased and the manufacturing cost is increased.

[0017]

SUMMARY OF THE INVENTION To summarize the above problems, rolls supporting a steel sheet in a high-temperature oxidizing wet atmosphere have corrosion resistance, zinc (foreign matter) adhesion, abrasion resistance, and the like. High film adhesion strength is required, and the condition that it can be manufactured at low cost is required.

Accordingly, an object of the present invention is to provide a roll for supporting a steel sheet of a hot-dip metal plating facility used in contact with a high-temperature gas atmosphere, which can solve these problems of the prior art at once.

[0019]

In order to solve such a problem, even if an alloy having high corrosion resistance at high temperature is simply coated by surface treatment, the metal is a substance having a high alloying reactivity with a metal plated on a steel sheet. The occurrence of burn-in is inevitable.

A substance having low reactivity with the plating metal;
For example, even if ceramics, etc. are coated by surface treatment, the presence of pores is unavoidable in such a surface coating layer, and corrosive substances enter through the pores, eroding the roll base material and causing peeling. Become.

Therefore, the present inventor has proposed that in the case of hot-dip galvanizing,
Preventing zinc from adhering to the roll surface from the coated steel sheet in high temperature condition, and conducting a detailed investigation and experiment on sprayed coating materials that are resistant to high-temperature corrosive atmosphere, dampness of cooling water dripping, and thermal shock. On the other hand, it has been found that by spraying ceramics containing no metal binder, it is possible to prevent the zinc adhesion while improving the film strength.

In the case of thermal spraying of ceramics alone, not a few pores are present, and corrosive substances, for example, sulfur dioxide, carbon dioxide, or water in which these are dissolved penetrate through these pores, erode the base material and form a coating film. By discovering that poling has occurred, it is possible to protect the roll base from these corrosive substances by spraying a corrosion-resistant alloy that is resistant to corrosion to the lower layer, and maintain adhesion with the ceramic sprayed layer I found something.

Further, by paying attention to the thermal expansion coefficient of the material to be sprayed and the roll base material in order to improve the adhesion and spalling resistance of each sprayed coating, heat spraying is performed by spraying a specific sprayed material as an underlayer. It was found that cracks and spalling due to differences in thermal expansion coefficient and thermal expansion can be prevented.

Thus, the present invention has been made based on several findings as described above and found that the following combinations exhibit excellent synergistic effects. Dense corrosion-resistant iron-based alloy with high temperature corrosion resistance and low pores, Inconel, W-Co-Cr-C-based material, W-Ni
A corrosion-resistant alloy sprayed layer made of one of Cr-C material or CrC + NiCr-based material, and Zr formed on the sprayed layer.
Equipped with a coating layer of a two-layer structure with a thermal spray layer made of one of O ₂ , Al ₂ O ₃ or Cr ₂ O ₃ ceramics, prevents foreign matter adhesion on the roll surface and corrosion delamination in high temperature oxidizing atmosphere It is a roll for supporting a steel plate of a hot-dip metal plating facility, which is used in contact with a high-temperature gas atmosphere, characterized by being prevented.

According to a preferred embodiment of the present invention, the thermal expansion coefficient of the corrosion-resistant alloy sprayed layer is specified to be in the range of 18 × 10 ⁻⁶ / ° C. or less, and the difference from that of the upper ceramic sprayed layer is 7 × 10 ^−6. / ℃
The following is assumed.

[0026]

FIG. 2 is a schematic diagram of a roll for supporting a steel sheet having a two-layer sprayed layer structure according to the present invention. In the figure, a corrosion resistant alloy sprayed layer 22 is provided on the surface of a roll base material 20, and a ceramic sprayed layer 24 is provided on the uppermost layer. The numbers in parentheses indicate the layer thickness.

Conventionally, inexpensive cast steel rolls have often been used as touch rolls according to the present invention. In the present invention, such an inexpensive cast steel roll may be used as the roll base material.

The roll made of cast steel is inexpensive but easily rusts as it is, and some surface treatment is indispensable for use. However, in the conventional surface treatment method, for example, in a hot metal plating facility, a hot gas atmosphere is used. Therefore, the roll itself cannot be used in a corrosive environment as described above, and the roll itself must be made of an expensive corrosion-resistant material. It was thought that this would increase the cost and affect the surface treatment method.

In the present invention, a cast steel roll can be used as a roll that satisfies all of these required properties, has a long service life, and can be manufactured at low cost. That is, according to the present invention, with such a roll surface as a base, a corrosion-resistant iron-based alloy, Inconel, W-Co-Cr-C-based material, W-Ni- Cr−
A corrosion-resistant alloy sprayed layer made of one of C material and CrC + NiCr-based material is provided as a lower sprayed layer.

The purpose of providing such a sprayed layer is to prevent corrosion of the roll surface and to prevent corrosion components from entering from an upper ceramic layer described later.

Here, stainless steel (SUS310, SUS316, etc.) is exemplified as the corrosion-resistant iron-based alloy, and austenitic stainless steel is particularly preferable. Inconel
Nickel-based alloy. W-Co-Cr-C material is
It is a corrosion resistant cemented carbide cermet. W-Ni-Cr-C material is also a corrosion resistant cemented carbide cermet. The CrC + NiCr-based material is a chromium carbide cermet.

According to the present invention, one of these thermal spraying materials is used to perform thermal spraying with the roll surface as a base, thereby forming a corrosion resistant alloy thermal spraying layer which is a lower layer of the ceramic thermal spraying layer.

The thickness of the thermal spray coating of a material satisfying the corrosion resistance of the lower layer can be generally from 50 to 500 μm. The thicker the coating, the stronger the corrosion and wear resistance, but at the expense of cost.

Therefore, according to a preferred embodiment of the present invention, the thickness of the film having sufficient corrosion resistance and not deteriorating the film strength is 70 to 200 μm to meet the cost. More preferably 70-120 μm
It is.

On such a sprayed layer, a ZrO ₂ system, Al ₂ O
_A thermal spray layer made of one of the ₃ type or Cr ₂ O ₃ type ceramics is further provided, but this ceramic type thermal spray layer is provided for the adhesion of foreign matter to the roll surface, especially for the hot dip galvanizing roll. And to prevent corrosion under high temperature oxidizing corrosive gas atmosphere. Basic ceramics such as CaO—SiO ₂ are unsuitable due to poor adhesion.

Here, ZrO ₂ ceramics include ZrO ₂ ceramics.
O ₂ -CaO, ZrO ₂ -Y ₂ O ₃ , ZrSiO _{4 and the} like are exemplified, and in particular, ZrO ₂ -C
aO and ZrO ₂ —Y ₂ O ₃ are preferred. Examples of the Al ₂ O ₃ ceramics include Al ₂ O ₃ , MgAl ₂ O ₄ , and SiO ₂ —Al ₂ O ₃ , with Al ₂ O ₃ being particularly preferred. Further, as the Cr ₂ O ₃ based ceramics, such as _{Cr 2 O 3, Cr 2 O} 3 -Al 2 O 3 is exemplified, in particular Cr ₂ O
₃ is preferred.

The thickness of such an upper ceramics sprayed layer can be up to 50 to 300 μm. However, as the thickness is increased, the heat shock resistance is lowered in addition to the cost, and the chipping resistance is reduced. It tends to be weak. Therefore,
The preferred thickness of the upper sprayed layer is 70 for the same reason as the lower layer.
150150 μm, more preferably 70-120 μm.

Thus, according to the present invention, there is obtained a roll for supporting a steel sheet of a hot-dip metal plating facility, which is provided with a coating layer having a two-layer structure, which prevents foreign substances from adhering to the roll surface and corrosion peeling in a high-temperature oxidizing atmosphere. Can be

Although the thermal spraying means for providing the thermal spray layer in the present invention is not particularly limited, the explosive thermal spraying method and the high-speed gas Thermal spraying and plasma spraying are preferred.

[0040]

EXAMPLE In order to examine the material of a two-layer sprayed layer that satisfies the condition that it has excellent corrosion resistance and does not easily adhere zinc in consideration of the use environment and the effect on the steel sheet, the roll surface is applied as shown in Table 1 below. And a practical performance test was conducted.

Tables 2 and 3 collectively show the physical properties of the upper and lower thermal spray layers. The rolls provided with the two-layer thermal spray coating layer thus obtained were evaluated for characteristics, and the results are summarized in Table 4.

[0042]

[Table 1] Thickness of lower thermal spray layer (corrosion resistant alloy) (μm) Thermal spraying method Inconel 625 (Ni-Cr-Mo-Fe, SNCM625 or equivalent) 70-150 Explosive thermal spraying SUS316 70-150 Explosive thermal spraying 84W-8Co- 3Cr-5C 70 to 150 detonation spraying method 70W-9Cr-5Ni-6C 70~150 detonation spraying method 80 (92Cr-8C) -20 ( 80Ni-20Cr) 70~150 detonation spraying method upper sprayed layer (ceramic) thick ( μm) Thermal spraying method (I) ZrO ₂ ceramic 50 (ZrO ₂・ CaO) + 50 ZrSiO ₄ 70-120 Explosive spraying method (II) Al ₂ O ₃ 70-120 Explosive spraying method (III) Cr ₂ O ₃ 70-120 Roll base material using plasma spraying method: Roller diameter: 120 x length 12120 (mm) STKM (Carbon steel pipe for machine structure) Operating environment : Continuous hot-dip galvanizing equipment Intermediate point between the exit of the alloying furnace and the cooling zone Maximum steel sheet contact temperature 400 ℃ Maximum ambient temperature 150 ℃ Humidity 80% or more

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Comparative Example] A ceramic having low reactivity with a lower coating composed of a corrosion-resistant plating layer or a corrosion-resistant alloy sprayed layer outside the scope of the present invention, and a plating metal similar to the present invention, on the same roll base material as in the example. A two-layer coating consisting of a thermal spray layer was applied, and the obtained two-layer coating roll was evaluated for durability and adhesion resistance under the same use conditions as in Table 1. The results are shown in Table 5 below.

[0047]

[Table 5]

As can be seen from Table 4, according to the present invention,
The life of the touch roll is at least about 3 from the conventional 2-10 days.
It has improved dramatically over the course of a month, and there has been no downgrade of products due to zinc powder adhesion and the transfer of steel sheets. On the other hand, in Comparative Example 2 in which an upper ceramic coating was applied to a conventional touch roll,
With the layer-coated roll, the life of the touch roll was only 10 to 15 days, and the life extension of the two-layer coating was slight.

[0049]

As described above, according to the present invention,
Instead of a roll that used to withstand heavy corrosion,
Practical use of a steel sheet support roll of a hot-dip metal plating facility that has dramatically improved the ability to prevent zinc adhesion and the service life. In addition, equipment replacement costs and roll production costs are significantly reduced. In addition, by selectively spraying a corrosion-resistant alloy on a roll that has not been subjected to such a surface treatment, the roll can be used without newly manufacturing a roll.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a hot-dip metal plating apparatus using a roll according to the present invention.

FIG. 2 is a schematic explanatory view of a roll having a two-layer coating structure according to the present invention.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 4/06

Claims (1)

(57) [Claims] 1. A dense, corrosion-resistant iron-based alloy having high temperature corrosion resistance and low porosity, inconel, W-Co-Cr-C-based material, W-Ni-Cr provided on a steel roll surface as a base.
-C material or a CrC + NiCr-based material, a corrosion-resistant alloy sprayed layer, and ZrO formed on the sprayed layer.
Prevention ₂ system, with a coating layer of 2-layer structure of a sprayed layer made of one of Al ₂ O ₃ system also Cr ₂ O ₃ based ceramics, corrosion peeling in foreign matter adhesion and high temperature oxidizing atmosphere on the roll surface A roll for supporting a steel sheet of a hot-dip metal plating facility used in contact with a high-temperature gas atmosphere.