JPS5837386B2 - Molten metal bath immersion parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a member immersed in a molten metal bath having excellent hot corrosion resistance against molten metal for plating, particularly molten aluminum and molten zinc.

For example, when performing molten aluminum plating on a steel plate, many molten aluminum bath immersion members such as pot rolls, pinch rolls, etc., as well as a bathtub, which come into direct contact with the plating bath are installed.

However, the rolls or aluminum bath containers that come into contact with the molten aluminum bath are subject to severe corrosion, causing problems such as the formation of scratches on plated products and a decrease in productivity.

For example, pot rolls that are immersed in an aluminizing bath are generally made of ductile cast iron.

This roll rotates a steel strip, which is a material to be plated, in a molten aluminum bath, starting from a guide 1.

However, this roll is eroded by the high-temperature molten aluminum, making the roll surface uneven and causing flaws on the surface of the thin plate material.

For this reason, attempts have been made to change the material of the roll or to thermally spray coat the roll surface with zirconia, alumina, or the like.

However, many of these known attempts have not resulted in fully satisfactory corrosion resistance or adhesion of the coating layer.

The present inventors have conducted various studies on coating materials with excellent corrosion resistance and coating adhesion that should be applied to parts immersed in molten aluminum baths or molten zinc baths. We have discovered a coating material that does not cause corrosion and has excellent corrosion resistance, and completed the present invention.

That is, an object of the present invention is to provide a molten metal bath immersion member having a coating layer formed on its surface that has excellent corrosion resistance and coating adhesion when used while being immersed in a molten aluminum bath or a molten zinc bath. The present invention will be described in further detail below.

The member immersed in a molten metal bath in the present invention is a member that comes into direct contact with molten aluminum, such as a pot roll, a metal roll, or a mounting member thereof, which is immersed in a plating bath when performing molten aluminum plating on a steel plate.

These base bodies are made of cast iron or steel.

The surface of these substrates contains 10 or more WC (by weight) or one or more of CrC and TiC, and the remainder is a hot corrosion-resistant metal, its oxide, two or more of these, or unavoidable impurities. A corrosion-resistant coating layer consisting of

This corrosion-resistant coating layer may have a composition consisting of one or more of WC, CrC, TiC and unavoidable impurities,
Alternatively, heat-resistant metals such as Co, Ni, and Si, or AI
203, Ti02, St02, etc. may be used, but the coating layer should contain WC, CrC, and TiC depending on the type of molten metal, and in the case of Zn. It is necessary to contain at least xo%, and in the case of A1 bath, it is necessary to contain 30% or more.
If C 2 , CrC 2 , and TiC are below this level, the corrosion rate by molten metal will be high and the object of the present invention cannot be achieved.

Figure 1 shows the relationship between the content of WC and the corrosion rate for molten AI and molten zinc. WC is less than 30% for molten AI and less than 10φ for molten Zn. rate is rapidly increasing.

Also, the thickness of the coating layer should be in the range of 0.1 to 2.4 mm; if it is less than 0.1 mm, it will be too thin and the coating will not be effective, and the coating layer will peel off. .

On the other hand, if the coating thickness exceeds 2.4 mm, the releasability deteriorates.

Figure 2 shows the relationship between coating thickness and peelability.
．． When the value is outside the range of 1 to 2.4, the releasability deteriorates rapidly.

The peeling index indicates whether the film peeled off after repeated heating to 1000°C and cooling with water.

Table 1 also shows that a test rod was coated with the coating material of the present invention to a thickness of 1 mm, and this was placed in a molten AI bath and a molten Zn bath for 12 hours.
This shows the corrosion rate and crack occurrence of the coating layer after being immersed for several days.Even after a long period of 12 days, no erosion due to the molten bath was observed, and although no cracks did occur, they were extremely slight. It was something.

In the present invention, the means for forming the coating layer is not particularly limited, but coating formation by thermal spraying is generally preferred.

The present invention is as described above, but WC is sprayed onto the surface of the pot roll at 0.00%. A coating was formed to a thickness of 5 mm and this was used in a molten aluminizing bath, but no change was observed even after 20 days of long-term use, and the long-term durability was more than 10 times that of conventional rolls. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the amount of WC in the coating layer and the corrosion rate due to aluminum-zinc, and FIG. 2 is a diagram showing the relationship between the coating thickness and peeling index.

Claims (1)

[Claims] 1 1 to 2. WC of 10% or higher, or one or more of CrC, TiC, and the remainder consisting of a hot corrosion resistant metal, its oxide, two or more of these, or inevitable impurities.
Molten metal bath immersion part with a surface coating layer 4 mm thick.