JPH0641713A - Member for hot dipping metal bath - Google Patents

Abstract

PURPOSE:To prevent erosion with molten metal by laminating a thermal spraying layer composed of a specific metallic material and a ceramic material on the surface of a member used in the molten metal and further, executing hole-sealing treatment to this surface. CONSTITUTION:As a snout 2 and a driving spindle of guide roll 3, snap rolls 4 used in a hot dip galvanizing apparatus is used in the hot-dipping zinc, these are eroded with the hot dipping zinc and also, in the case the hot-dipping zinc sticks and solidifies, the removal is difficult. In order to prevent these faults, after thermal-spraying Co base alloy on the surfaces of these members used in the hot-dipping zinc, further, the build-up thermal-sprayed layer of ZrO2 series ceramic of ZrO2-CaO, etc., is formed on this surface, and thereafter, by coating the SiO2 series ceramic on this surface, the hole-sealing treatment is executed. By the ZrO2 series ceramic having low wettability to the hot-dipping zinc, the solidified sticking material of the hot-dipping zinc is easily removed and also, the erosion with the hot-dipping zinc is prevented by the hole-sealing treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member for a molten metal bath, and more particularly to a member for constituting a continuous galvanizing apparatus such as a snout, a drive shaft of a snap roll or a dross recovery device.

[0002]

2. Description of the Related Art For continuously galvanizing steel sheets,
Put the steel plate from the snout into the molten zinc bath and convey it around the guide roll immersed in the molten zinc,
It was pulled up from the bathtub through a pair of snap rolls. The molten zinc bath member of this type requires the following performances.

(1) No corrosion by molten zinc occurs. (2) The attached zinc should be easily peeled off. (3) The erosion resistant film should not be attacked by the pickling solution during regular maintenance (pickling) of the members. Conventionally, for a member for a molten zinc bath, a Co-based alloy or a WC-Co based cermet is sprayed on the surface of a substrate to form a film, thereby preventing corrosion of the molten zinc. However, the former has an effect only on the performance (1), and the latter has an effect on the performances (1) and (2).
There were no measures to satisfy all of (2) and (3). That is,
Although the conventional ceramic coating is effective against the erosion of molten zinc, the underlying coating and the base material are eroded to cause floating and peeling of the ceramic coating, resulting in a short life of the bath member.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a molten metal bath member having excellent corrosion resistance against molten metal. In order to achieve the above object, the molten metal bath member according to the present invention has a base layer made of a Co-based alloy and a top layer made of ZrO ₂ -based ceramic formed on the surface of the base material by thermal spraying.
The thermal spraying broadly means a technique of melting a metal by a high-temperature heat source such as arc, gas, flame or plasma and fusing it to a substrate.

Here, the underlayer made of a Co-based alloy exerts a strong defense performance against erosion of molten metal. Also,
The upper layer made of ZrO ₂ -based ceramic has poor wettability with molten metal and can easily remove the adhered and solidified metal.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a continuous galvanizing apparatus for steel sheets, which is mainly composed of a molten zinc bath 1, a snout 2, a guide roll 3 and a pair of snap rolls 4, 4. The snout 2 is for continuously charging the steel sheet 10 into molten zinc, and is filled with an inert gas such as nitrogen. The guide roll 3 and the snap rolls 4 and 4 are provided with support shafts 5, 6 and 6, respectively, and are connected to a drive source (not shown), and are rotationally driven at a constant speed in the arrow direction. In addition, although not shown, the continuous galvanizing apparatus is provided with an ingot feeding device, a dross collecting device, a stand for the rolls 3, 4, 4 and the like.

By the way, the present inventors have taken a measure for preventing the adhesion and growth of molten zinc on the spindle connecting the support shafts 6 and 6 of the snap rolls 4 and 4 and the drive source as described below. . The material of the spindle is SUS-316L
(JIS standard), the diameter is 70 mm. First, a Co-based alloy (Co-Cr) was sprayed on the surface of the spindle base material by a gas plasma spraying method to form an underlayer layer having a thickness of 0.2 mm. Furthermore, ZrO ₂ system ceramic (Z
rO ₂₋ CaO) was also sprayed by a gas plasma spraying method to form a 0.3 mm thick overlay layer. Further, SiO ₂ -based ceramic (SiO ₂ ) was applied on the overlay layer to carry out a sealing treatment and finished with sandpaper.

The conventional spindle (which has not been surface-treated) has a life of 3 months of continuous use, but the spindle of the present invention is pickled after 3 months of continuous use. No damage was observed on the ceramic coating even after 3 months of use and pickling. The reason for this is that the underlayer made of a Co-based alloy originally has a strong defense performance against the erosion of molten zinc, and the upper layer made of ZrO ₂ -based ceramic has poor wettability with molten zinc. , The adhesion of molten zinc did not proceed so much,
It can be mentioned that zinc that has adhered and solidified can be easily removed. Moreover, since the upper layer is sealed with the SiO ₂ ceramic, the protective action against erosion is more effective.

The member for molten metal bath according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the gist. In particular, the present invention exhibits corrosion resistance properties not only for molten zinc but also for other types of metals, such as molten aluminum. As the member for the molten metal bath for forming the Co-based self-bathing alloy film and the ZrO ₂ -based ceramic film, various members such as a snout, a dross recovery device, a roll, a roll mount, and an ingot feeding device other than the drive spindle are used. Applicable and each exhibits good erosion resistance to molten metal.

[0010]

As is apparent from the above description, according to the present invention, the underlayer made of a Co-based alloy and the upper layer made of ZrO ₂ -based ceramic are formed on the surface of the base material of the member for molten metal bath. Since and are formed by thermal spraying respectively, corrosion by molten metal does not occur, the adhered molten metal is easily peeled off, and the ceramic coating is not attacked by the pickling solution during regular pickling, achieving a longer life. it can.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a bath member and a continuous galvanizing apparatus using a bath according to the present invention.

[Explanation of symbols]

 1 ... Molten zinc bath 2 ... Snout 3 ... Guide roll 4 ... Snap roll 10 ... Steel plate to be plated

Claims (2)

[Claims] 1. A member for a molten metal bath, characterized in that a lower layer made of a Co-based alloy and an upper layer made of a ZrO ₂ -based ceramic are formed on the surface of a base material by thermal spraying, respectively. 2. The member for a molten metal bath according to claim 1, wherein the surface of the overlay layer is sealed.