KR0143491B1 - Coating method by explosion spray on the continuous mold - Google Patents

Abstract

The present invention relates to a method of coating Ni-based alloy powder and WC-based alloy powder on a continuous casting mold used in a continuous casting factory of a steel mill by an explosion spraying method. By spraying Ni- or WC-based alloy powder into the continuous casting molds in one step, it can be used for both precipitation hardening and solid-hardening copper alloy molds, and more easily form a coating layer having excellent heat resistance and abrasion resistance in the continuous casting moulds. We want to provide a way to do that, and that's the purpose.

The present invention is a method of forming an explosion spray coating layer by spraying a metal powder on the surface of the material by thermal spraying, using a copper alloy continuous casting mold as the material, and has a particle size of 40-60μm as the metal powder The main idea is to form an explosion spray coating layer having excellent heat resistance and abrasion resistance in a continuous casting mold by using a Ni-based alloy powder or a WC-based alloy powder to explode the powder into the mold at a speed of 900 m / sec or more.

Description

Formation method of blast coating layer with excellent heat resistance in continuous casting mold

Figure 1: Schematic diagram of a conventional continuous casting mold

2 is a photograph of a coating layer formed by a conventional two-stage plasma spraying method.

3 is a photograph of the sprayed coating layer formed according to the present invention

4 is a schematic diagram of a preferred thermal spray for implementing the present invention.

* Explanation of symbols for main parts of the drawings

4: Mold 5: Bond coating

6: Top coating 7: Dragon case

8: Cover connection ring 9: Flame cover

9A: Flame Hole

The present invention relates to a method of forming an explosion spray coating layer having excellent heat resistance and abrasion resistance in a continuous casting mold by explosion spraying a Ni-based alloy powder and a WC-based alloy powder on a continuous casting mold used in a continuous casting factory of a steel mill.

Recently, the continuous casting (hereinafter referred to as performance) technology of steel has been developed, and the performance ratio for steel production is rapidly increasing. As a result, the performance of speeding up the injection speed and the width changing technology during casting have been developed. Therefore, the mold used for continuous casting is gradually used in harsh conditions, and in particular, the damage occurs due to wear and corrosion at the lower end, which causes frequent repair and replacement. Therefore, the continuous casting mold is coated to improve productivity and product quality by extending the life of the mold.

As shown in FIG. 1, the continuous casting mold is assembled into a long side 1 and a short side 2, and the short side 2 is movable in operation to change the width of the cast product.

In general, since the mold is worn by the movement of the cast during operation, the wear resistant coating layer 3 is formed at the lower end of the mold.

Conventional methods for forming a wear-resistant coating layer on the lower end of a mold include a method of forming a Ni electroplating layer, a method of forming a Ni alloy plating layer (Japanese Patent Nos. 733885 and 1182099 and Japanese Patent Laid-Open No. 56-160643, 58-38637, 54-46131, 58-112633, 58-112634), and recently, a method of performing two-stage spray coating by using a plasma spray method (Japanese Patent Laid-Open Nos. 57-7360, and 57). -7361).

However, in the case of using the electroplating method, the process is complicated and there is a limit in improving the wear resistance because of limitations in the coating components.

In general, in the case of electroplating, a surface hardness of 200-300 Hz can be obtained.

On the contrary, in the case of thermal spray coating, a high hardness of 600Hz or more of surface hardness can be obtained. FIG. 2 shows a tissue photograph of the two-stage spray coating layer formed by coating the two-stage spray coating on the mold.

As can be seen from FIG. 2, the two-stage spray coating method is a one-stage coating with a two-stage coating of Ni electroplating or thermal spraying to improve adhesion to the mold 4 and to reduce thermal shock with the bond coating (5). Top coating 6 is then performed.

In addition, after plasma spray coating, heat treatment is performed to reduce porosity and improve adhesion to the coating layer.

Thus, the two-stage spray coating method has to go through a two-step process of electroplating and thermal spray coating, there is a technical difficulty to prevent the softening of the mold during the heat treatment after the plasma spray coating.

In particular, the plasma spray coating method is applicable only to precipitation hardening copper alloy molds, and in solid solution hardening copper alloy molds, the mold hardness is deteriorated to about 40-50 Hz after heat treatment at about 120 Hz.

Accordingly, the present inventors conducted research and experiments to solve the above-described problems, and based on the results, the present invention proposes the present invention. By applying one-stage explosive spray coating on a continuous casting mold to a continuous casting mold or a WC alloy powder, it is possible to form a coating layer having excellent heat resistance and wear resistance on a continuous casting mold. I want to provide a way to do that, and that's what it is.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention is a method of forming an explosion spray coating layer by spraying a metal powder on the surface of the material by thermal spraying, using a copper alloy continuous casting mold as the material, having a particle size of 40-60μm as the metal powder The present invention relates to a method of forming an explosion spray coating layer having excellent heat resistance and abrasion resistance in a continuous casting mold by spraying the powder on the mold using a Ni-based alloy powder or a WC-based alloy powder at a speed of 900 m / sec or more.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Explosive spray coating method differs from plasma or high-speed spray coating technology, which is the standard spray coating technology, by exploding acetylene, hydrogen, propane, oxygen, and nitrogen gas in a tube with one end blocked. It is a method of dissolving and scattering various powders by obtaining a flow rate.

The present invention is to spray the Ni-based alloy powder or WC-based alloy powder in the copper alloy continuous casting mold by the explosion spray method to form an explosion spray coating layer.

As the Ni-based alloy powder used in the present invention, it is preferable that the Ni-based alloy powder is made of wt: 72-75%, Cr: 14-17%, and the rest: Si, B, Co, C, and Fe. In the case where the Ni content is less than 72%, the thermal shock resistance is lowered, and when the Ni content is 75% or more, the hardness is lowered. Therefore, the Ni content is preferably 72-75%.

The content of Si and B is preferably 4% and 3.5%, respectively.

As the WC-based alloy powder, WC-10-20 wt% Co alloy powder is preferable.

If the Co content is less than 10% thermal shock resistance and the coating layer is hard, if the hardness is more than 20%, in the case of WC-Co alloy powder to limit the content of Co to 10-20wt% desirable.

And, it is preferable to limit the particle size of the alloy powder to 40-60μm, because the recovery rate is bad when the powder particle size is less than 40μm, there is a high risk of contaminating the coating layer and thermal spray by volatilization, 60μm or more This is because undissolved powder is present and the characteristics of the coating layer are deteriorated.

In order to form a coating layer on a continuous casting mold according to the present invention, the alloy powders must be sprayed onto the mold by thermal spraying, and the spraying speed is preferably limited to 900 m / sec or more.

This is because the adhesion of the coating layer is lowered when the spraying speed is less than 900 m / sec.

In the present invention, the explosive gas composition is not particularly limited, but the acetylene: oxygen ratio of 1: 1.1-1.3 is preferably a mixture of acetylene and oxygen.

By forming a coating layer by thermally spraying Ni-based alloy powder or WC-based alloy powder on a mold under the above conditions, an explosion spray coating layer having a hardness of 600 Hz or more, adhesion of 1300 kg / cm 2 or more, and excellent thermal shock is formed.

On the other hand, a preferred thermal spray for implementing the present invention is shown in FIG.

That is, as shown in Figure 4, the preferred thermal spray gun is provided with a flame cover (9) held in front of the conventional thermal spray gun 7 by the cover connecting ring (8), the flame cover (9) ), A flame hole 9a having the same diameter as the inner diameter (diameter of the crater) of the thermal spraying gun 7 is formed.

In the case of forming an explosion spray coating layer using the above-mentioned preferred thermal spray coating, only the high-speed melt scattering droplets are coated during the thermal spray coating, and the overall adhesion strength is not adhered to the coating portion by the low-speed or oxidative melt of the fine particles around the thermal spraying flame. Can improve.

In addition, it is possible to prevent impurities such as C, O, and H, which are generated from the thermal spray, from being adsorbed on the mold.

In the case of using the above-described preferred thermal spraying spray, the thermal spraying coating layer having superior hardness and adhesion is formed as compared with the case of not using the thermal spraying agent.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

1-stage explosion spray using Ni: 72%, Cr: 17%, Si: 4.0%, B: 3.5%, and other Ni-based alloy splits consisting of C. Fe and Co and W-10wt% Co alloy powder The coating layers were formed on the molds, respectively, and then hardness, adhesion, porosity and thermal shock were investigated. The results are shown in Table 1 below with those of the coating layer formed by a conventional two-stage plasma method (Ni-based).

In addition, the Ni-based alloy powder according to the present invention by observing the histological picture of the thermal spray coating is shown in FIG. At this time, the particle size of the powder is 40-60μm, the spraying speed is 920m / sec, the explosion gas composition was 1:12 ratio of acetylene: oxygen.

* Thermal shock represents the number of cracks in the coating when water cooled after 20 minutes at 800 ° C.

As shown in Table 1, it can be seen that the one-stage explosion spraying according to the present invention is much superior in hardness, adhesion, porosity and thermal shock than the conventional two-stage plasma method.

On the other hand, as shown in Figure 3, it can be seen that the porosity is significantly reduced when the thermal spray coating according to the present invention.

Example 2

The thermal spraying of the WC-based alloy powder in Example 1 was carried out except that the thermal spray gun was equipped with a 10 cm circular stainless steel flame cover having a flame hole of 2 cm equal to the inner diameter of the thermal spray gun. By forming an explosion spray coating layer in the same manner as the method of forming an explosion spray coating layer, and then measured the hardness, adhesion, porosity, and the results are shown in Table 2 together with the case without a cover.

As shown in Table 2, it can be seen that the use of the flame cover at the front end of the thermal spray during the thermal spray coating improves the adhesion by about 20% compared to the case where it is not.

As described above, the present invention can be applied to the continuous casting mold with excellent heat resistance and abrasion resistance only in one step, by using a cover in the front end of the coating specimen can further improve the adhesion strength between the coating layer and the base material It works.

Claims (1)

A method of forming a thermal spraying coating layer by spraying a metal powder on a surface of a material by thermal spraying, wherein a copper alloy continuous casting mold is used as the material, and the Ni-based alloy having a particle size of 40-60 μm as the metal powder. At a speed of 900 m / sec or more using powder or WC alloy powder, and using a thermal spray gun provided with a flame cover in front of which a flame hole having a diameter equal to the inner diameter of the thermal spray gun is formed. A method of forming an explosion spray coating layer having excellent heat resistance and abrasion resistance in a continuous casting mold, wherein the powder is sprayed onto the mold.