JPH07188884A - Parts in bath for continuous hot dipping equipment - Google Patents

Abstract

PURPOSE:To provide highly reliable parts of long service life in a bath by forming the corrosion resistant compound bonded with the element in the metal on the metal surface to coat the surface of a metallic member. CONSTITUTION:A strip 2 to be fed through a snout 1 is changed in direction by a sink roll in a hot dipping bath 3 to change the movement of the strip 2 by a support roll 5. The strip 1 is drawn out of a hot dipping bath 6 to adjust the hot dipping thickness by a wiping nozzle 7. The element which can be chemically bonded with the element contained in the metal is deposited on the surface of the strip 1 which is the metallic member, and the surface of the metallic member (the strip 1) is coated by forming the corrosion resistant compound bonded with the element in the metal on the metal surface. This treatment reduces the frequency of changing the roll, improves the productivity, and reduces defects.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous hot-dip metal plating apparatus, and more particularly to a continuous hot-dip metal plating apparatus which has excellent corrosion resistance due to surface modification of a metal member used by being immersed in a metal bath. Regarding parts in bath.

[0002]

2. Description of the Related Art Conventionally, a metal material has been used for a member for a continuous hot-dip galvanizing bath, and generally cast iron excellent in corrosion resistance,
Steel materials such as stainless steel and high chrome steel have been used. However, when these materials are used for a long period of time, corrosion action due to molten metal and wear due to friction occur. In other words, it is difficult for metal to prevent corrosion of molten metal.
Therefore, it was found that the metal member used by being immersed in the metal bath is corroded by the molten metal during operation, and the wear of the parts in the bath progresses rapidly. Therefore, various corrosion resistant metals,
Attempts have been made to improve the corrosion resistance and wear resistance by coating the surface of a metal with a thermal spraying method, a chemical vapor deposition method or a physical vapor deposition method using cermet, ceramics or the like. For example, as disclosed in JP-A-61-37955, a technique for producing a molten metal bath roll having excellent corrosion resistance, heat resistance, wear resistance and the like by spraying ceramics with water plasma, and JP-A-62-37955. No. 127457 attempts to improve the high temperature corrosion resistance of the metal base material by irradiating a coating of ceramics or cermet formed on the surface of the metal base material with a laser beam to partially melt the base material. However, in surface treatment technology, small pinholes are present in surface treatment coatings such as cermet and ceramics, so molten metal penetrates through the pinholes and corrodes the base metal, and the surface coating also peels off, which is extremely These methods have not been put to practical use because they are unstable and unreliable. Therefore, a ceramic liner may be fixedly arranged (Japanese Patent Laid-Open No. 61-159261).
Japanese Unexamined Patent Application Publication No. 62-93053), a method of attaching a ceramic segment to a segment receiving groove of a metal ring (Japanese Patent Laid-Open No. 62-93053) has been attempted. In recent years, JP-A-2-303
As seen in Japanese Patent Laid-Open No. H10-44002 and Japanese Unexamined Patent Publication No. 5-44002, attempts have been made to fit a sleeve of ceramics or cermet to a roll shaft and use it in a sliding portion. However, when the shaft of the roll is an iron-based metal and a ceramic or cermet sleeve is fitted to it for use in the sliding part, the commonly used fitting method cannot be used because the operating temperature is high. Absent. Therefore, as seen in Japanese Unexamined Patent Publication No. 3-177552, an attempt has been made for practical use by inserting and fitting a plastically deformable intermediate material between the roll shaft and the sleeve. However, these methods are not suitable for large parts such as the body of the roll and the frame, and cannot be applied.

[0003]

Since parts in a metal bath using a conventional metal material have large melting loss and wear damage, when a sink roll is taken as an example, in a hot dip aluminum plating bath, 4 days, hot dip galvanization If the roll shaft and bearing are worn continuously for about 7 days in the bath, the amount of looseness between the roll shaft and the bearing increases, and vibration occurs, making it impossible to obtain a uniform plated steel sheet. Therefore, it is necessary to stop the plating operation once and replace the roll shaft and the bearing. For this reason, the productivity is lowered, which causes the cost increase such as the increase of defective steel plates due to the line stop and the replacement cost. In addition, the same phenomenon as the sink roll is seen in other parts in the metal bath.

The above-mentioned prior art does not give sufficient consideration to the selection of an appropriate material and process technology, and as a result, the required life cannot be obtained, and the corrosion resistance of ceramics and cermets is excellent. The material is not in practical use. In other words, how to utilize ceramics or cermet for parts in a metal bath without lowering the reliability is an issue. However, because these materials have a smaller coefficient of thermal expansion than metals,
It is difficult to fit and use the steel material generally used as a roll shaft. That is, in order to solve these problems, it is necessary to consider the characteristics of the material and select a manufacturing method suitable for the material.

The object of the present invention is to improve the corrosion resistance / wear resistance of parts in a metal bath, to prolong the service life of parts in a metal bath, to reduce downtime, to improve productivity and to reduce defects in steel sheets. An object of the present invention is to provide a continuous hot-dip metal plating apparatus capable of performing the above.

[0006]

Means for Solving the Problems The above-mentioned problems are, in a molten metal plating apparatus provided with a metal member used by being immersed in a metal bath, an element contained in the metal and a chemical substance on the surface of the metal member. It is achieved by coating the surface of the metal member by depositing an element capable of binding to the metal and forming a compound having corrosion resistance bonded to the element in the metal on the metal surface.

The above object can also be achieved by a component in a metal bath according to claim 2, wherein the metal member is a steel material.

The above object is also achieved by a component in a metal bath according to claim 3, wherein the compound having corrosion resistance is a boride-based ceramic.

The above object can also be achieved by a component in a metal bath according to claim 4, wherein the compound having corrosion resistance is a carbide type ceramic.

The above problem is also that the value obtained by multiplying the difference in thermal expansion coefficient between the material coating the surface of the metal member and the metal member by the temperature of the metal bath is 6 × 10 ^-3 m / m or less. It is also achieved by the parts in the metal bath described in 1.

The above object is also achieved by a component in a metal bath according to claim 6, wherein the metal member used by being immersed in the metal bath is used with movement such as rotation in the metal bath. It

The above object is also achieved by a component in a metal bath according to claim 7, characterized in that the rotating component is a sink roll, a support roll or a drawing roll.

[0013]

In general, the parts used in the metal bath are continuously used for a long time, so that melting damage due to molten metal occurs. Also,
At the bearing portion of the roll, wear due to load due to tension applied to the strip occurs along with melting loss due to molten metal. Therefore, in the configuration of FIG. 1, the support roll and sink roll bearing portions used while rotating among the components in the hot dip bath are often melted and worn. In addition, in FIG.
Of the parts in the hot dip bath, the squeeze roll and sink roll bearings that are used while rotating are often melted and worn. When the melt damage and wear of the shaft of the roll progresses, the swirling between the roll shaft and the bearing becomes large, and vibration occurs during strip running, making stable work impossible. Further, not only the shaft portion of the roll but also the body portion is melted and worn, which causes the strip to meander and have a defective shape. Therefore, prevention of melting damage and wear of parts in the bath is an important subject for continuous plating work.

In applying the method of the present invention, the material of the roll is not limited, and a generally used steel material may be used. However, if the material composition is not suitable for surface treatment, pretreatment is required. Therefore, it is desirable to select a material composition suitable for the surface treatment.

Zn, Al and alloys thereof are generally used as the plating metal, and it is necessary to coat the surface with ceramics having corrosion resistance to these metals. Among ceramics, nitride, boride and carbide are preferable.

Many surface treatment methods have been developed, including CVD, PVD and thermal spraying. As mentioned above, these surface treatment coatings have small pinholes, so the molten metal penetrates through the pinholes and corrodes the base metal. These methods have not been put to practical use because they are scarce. Therefore, it is necessary to form a surface coating that is dense and has good adhesion. For that purpose, it is desirable that the base material and the surface coating are bonded by a chemical reaction. The following methods can be used to form a nitride, boride or carbide layer based on this idea. As a method for forming the nitride layer, tufftride treatment or ion nitriding treatment is generally used. Furthermore, as a method for forming a boride layer, a powder method immersion boron treatment (for example, Komatsu et al .: 2)
0) and molten salt dipping boron treatment (eg Komatsu et al. 2
Name: The Japan Institute of Metals lecture summary 1972-4). Further, the method of forming the carbide layer includes a method of coating titanium carbide by heating in a gas containing a halide (for example,
H.Wiegand, W.Ruppert: Einige Eigenschaften der Werk
stoffkombination Stahl mit Titankarbiduberzug, Met
alloberflache 14 (1960) 229) or a molten salt bath in which a metal forming a carbide is melted, and a steel material is immersed in it, and carbon diffuses from the steel material and bonds with the metal to form a carbide (for example, Toru Arai). : Metal materials, 13, 3 (197)
3) 98) etc.

[0017]

【Example】

(Example 1) In order to confirm the effect of the present invention, evaluation was performed using test pieces subjected to various surface treatments. The method of depositing a material different from the base material on the surface by CVD, PVD, thermal spraying, etc. as the surface treatment method cannot be used as a component used in a metal bath, and thus the surface formed by bonding with the base material. The coating method was investigated.

[Experiment 1] An alloy tool steel (SKD 11) having a diameter of 10 mm and a length of 50 mm was nitrided in a salt bath containing KNC and KCNO as main components. The temperature of the salt bath is 575 ° C
After holding for 12 hours, it was cooled with water. After the treatment, X-ray diffraction was performed to know the composition of the surface. As a result, it was found that chromium and iron nitrides were present on the surface.
These test pieces were subjected to Zn bath at 460 ° C and Al at 650 ° C.
It was immersed in a bath and moved at a speed of 50 m / min for 5 hours for immersion. As a result, in both the Zn bath and the Al bath, not only the surface treatment layer but also the base metal was found to be melted, and it was found that such nitriding treatment had no effect.

[Experiment 2] Alloy tool steel (SKD 11) having a diameter of 10 mm and a length of 50 mm was immersed in a molten Na ₂ B ₄ O ₇ bath to which 20% by weight of Fe-Mn metal powder was added, and the resultant was immersed in a salt bath. Compound treatment was performed. The temperature of the salt bath is 1000 ° C and 10
After holding for a time, it was cooled with oil and tempered at a temperature of 650 ° C. After the treatment, X-ray diffraction was performed to know the composition of the surface. As a result, it was found that an iron boride layer was present on the surface. These test pieces were subjected to a Zn bath at 460 ° C. and 65
It was immersed in an Al bath at 0 ° C., moved at a speed of 50 m / min and immersed for 5 hours. As a result, the surface-treated layer is stably present in both the Zn bath and the Al bath, and the boride layer formed in this manner causes the base material to be melted and damaged in both the Zn bath and the Al bath. It has been found that such a boride treatment is effective because of the lack of protection.

[Experiment 3] Alloy tool steel (SKD 11) having a diameter of 10 mm and a length of 50 mm was immersed in a salt bath prepared by adding 20% by weight of Fe-V metal powder to a molten Na ₂ B ₄ O ₇ bath and carbide. Processed. The temperature of the salt bath was set to 1000 ° C., the temperature was kept for 10 hours, the oil bath was cooled, and the temperature was tempered at 650 ° C.
After the treatment, X-ray diffraction was performed to know the composition of the surface. As a result, the presence of a vanadium carbide layer was confirmed on the surface. These test pieces were subjected to a Zn bath at 460 ° C and 650 ° C.
It was immersed in the Al bath of No. 3 and moved at a speed of 50 m / min for immersion for 5 hours. As a result, the surface treatment layer was stably present in both the Zn bath and the Al bath, and the carbide layer thus formed did not melt the base material in both the Zn bath and the Al bath. For protection, such a carbide treatment has been found to be effective.

[Experiment 4] Low thermal expansion cast iron having a diameter of 100 mm and a length of 100 mm, alloy tool steel (SKD 11) and stainless steel (SUS 440) were placed in a molten Na ₂ B ₄ O ₇ bath 20 times.
Carbide treatment was carried out by immersing in a salt bath to which a metal powder of Fe-V of weight% was added. The temperature of the salt bath was set to 1000 ° C., and the temperature was maintained for 10 hours, followed by oil cooling and tempering at a temperature of 650 ° C.

These samples were tested at 450 ° C., 500 ° C., 55 ° C.
It was immersed in a Zn bath at 0 ° C., 600 ° C. and 650 ° C. for 2 hours. As a result, low thermal expansion cast iron, alloy tool steel (SKD 1
No change was observed in the VC film formed on the surface of 1), but when the bath temperature increased, stainless steel (SUS 44
Cracks were observed in the VC coating formed on the surface of (0).
The results are summarized in Table 1. However, in the table, ◯ indicates that no change was observed in the VC coating, and X indicates that cracks were observed in the VC coating. The values in parentheses are the product of the difference between the coefficient of thermal expansion of the coating and the base material multiplied by the bath temperature (×
10 ⁻³ m / m).

[0023]

[Table 1]

As can be seen from the results in Table 1, the value obtained by multiplying the difference in thermal expansion coefficient between the VC coating and the base material by the bath temperature is 5.8 × 10.
^No cracks were found in the VC coating at ^-3 m / m, but cracks were found at the VC coating at 6.3 x 10 ^-3 m / m. This shows the limit that the VC film can withstand thermal stress. Further, an experiment was conducted also in the case where a boride layer (Fe ₂ B coating) was formed, but almost the same result was obtained. Therefore, the limit of the strength of the coating film thus formed is 6 when the difference between the thermal expansion coefficient of the coating film and the base material is multiplied by the bath temperature.
It is considered to be about × 10 ⁻³ m / m.

(Embodiment 2) FIG. 1 shows an outline of products and parts in contact with molten metal. That is, the strip 2 supplied through the snout 1 in a facility for continuously performing molten metal plating on the strip is changed in direction by the sink roll 4 in the plating tank 3, and the movement of the strip is stabilized by the support roll 5. . Further, the strip pulled out from the plating bath 6 has its plating thickness adjusted by the wiping nozzle 7.

FIG. 2 also shows a schematic of the products and parts in contact with the molten metal. In FIG. 2, the plating thickness is adjusted by the squeeze roll 8 instead of the wiping nozzle of FIG. Further, the squeezing roll also has a function of stabilizing the movement of the strip, so that a support roll is not required.

The results of applying the results of the present invention to the bearings of sink rolls and support rolls for continuous galvanizing will be described below.

The sink roll has a body diameter of 650 mm and a shaft diameter of 1
50mm, support roll diameter is 200mm, shaft diameter is 80
mm, and alloy tool steel (SKD 11) was used as the material.
The sink roll and support roll have a body length of 150
Since it is as long as 0 mm, in this embodiment, the shape of the shaft portion was processed into a flange shape as shown in FIG. 3, and a salt bath was prepared by adding 20% by weight of Fe-V metal powder to a molten Na ₂ B ₄ O ₇ bath. Carbide treatment was performed by immersion. The temperature of the salt bath is 1000 ° C and 10
After holding for a while, cool with oil and temper at 650 ° C,
A VC film of about 10 μm was formed on the surface. Then, the sink roll was fixed to the body portion by using eight bolts 11 having a diameter of 25 mm. For support rolls, 8
It was fixed to the body using bolts 11 having a diameter of 10 mm.
A carbon / carbon fiber composite material was used together with both rolls for the bearing. These were installed in a continuous galvanizing machine at 460 ° C,
It was used continuously for 56 hours. As a result, no wear was observed on the shafts of both rolls. Therefore, it was confirmed that the VC film thus formed not only has excellent corrosion resistance and wear resistance in a zinc bath, but also has excellent reliability without cracking or peeling.

(Embodiment 3) In this embodiment, the result of the present invention applied to a squeezing roll for continuous aluminum plating will be described. The diameter of the squeezing roll is 150 mm and the length is 110
The shaft diameter was 0 mm, the shaft diameter was 70 mm, and low thermal expansion cast iron was used as the material. This roll was placed in a molten Na ₂ B ₄ O ₇ bath containing 20% by weight of Fe.
It was dipped in a salt bath to which a metal powder of -Mn was added to perform boride treatment. The temperature of the salt bath was set to 1000 ° C., the temperature was kept for 10 hours, the oil was cooled, and a tempered boride coating was formed at a temperature of 650 ° C. A carbon / carbon fiber composite material was used for the bearing. These were installed in a continuous aluminum plating machine at 630 ° C for 24 hours.
Used continuously for hours. As a result, no wear was observed on the body and shaft of the squeezing roll. Therefore, it was confirmed that the boride coating thus formed is not only excellent in corrosion resistance and wear resistance in an aluminum bath, but also excellent in reliability without cracking or peeling.

[0030]

According to the present invention, it is possible to form a ceramic coating having corrosion resistance on the surface of a bath component such as a roll used in a molten metal plating bath. The coating film obtained by the present invention is very dense and has good adhesion to the steel material which is the base material, so that a highly reliable long-life bath component can be obtained. According to the present invention, the use of a sink roll, a support roll, and a squeezing roll in which the surface of a steel roll is coated with ceramics can reduce the frequency of roll replacement, improve productivity, and reduce defects.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of a product and a part that come into contact with molten metal according to the present invention.

FIG. 2 is an explanatory view of another embodiment of products and parts in contact with molten metal of the present invention.

FIG. 3 is a partial perspective view of a roll showing the present invention.

[Explanation of symbols]

4 ... Sync roll, 5 ... Support roll, 8 ... Drawing roll, 9 ... Roll shaft part, 10 ... Roll body part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohito Oyagi 7-1 Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory, Ltd. (72) Inventor ▲ Taka ▼ Yoshio Kura Saiwaicho, Hitachi City, Ibaraki Prefecture 3-1-1, Hitachi Ltd., Hitachi Works (72) Inventor Masatoshi Seki, 832, Horiguchi, Katsuta City, Katsuta City, Ibaraki Prefecture 2) Hitachi, Ltd., Raw Materials Division (72) Inventor, Takahiko Okochi Katsuta City, Ibaraki Prefecture 832 Horiguchi No. 2 Inside Hitachi Molding Materials Division, Hitachi, Ltd.

Claims (7)

[Claims] 1. A hot-dip galvanizing apparatus equipped with a metal member used by being immersed in a metal bath, wherein an element chemically bound to an element contained in the metal is deposited on the surface of the metal member, A component in a bath for a continuous hot-dip metal plating apparatus, characterized in that the surface of the metal member is coated by forming a compound having corrosion resistance, which is combined with an element in the metal, on the metal surface. 2. A component in a bath for a continuous molten metal plating apparatus according to claim 1, wherein the metal portion is a steel material. 3. A component in a bath for a continuous hot-dip metal plating apparatus according to claim 1, wherein the compound having corrosion resistance is a boride-based ceramics. 4. The continuous bath metal plating device bath component according to claim 1, wherein the compound having corrosion resistance is a carbide-based ceramics. 5. The value obtained by multiplying the difference in thermal expansion coefficient between the material coating the surface of the metal member and the metal member by the temperature of the plating bath is 6 × 1.
A component in a bath for a continuous hot-dip metal plating apparatus, which is characterized in that it is 0 ^-3 m / m or less. 6. A component in a bath for a continuous hot-dip metal plating apparatus, wherein the metal member used by being immersed in the metal bath is a rotating component used in the metal bath with movement such as rotation. . 7. The in-bath component for a continuous molten metal plating apparatus according to claim 6, wherein the rotating component is a sink roll, a support roll or a drawing roll.