KR20000040949A - Method for coating casting roll of thin board caster having two rolls - Google Patents

Abstract

PURPOSE: A method for coating the casting roll of a thin board caster is provided to increase abrasion resistance of an edge dam as well as to increase durability of a casting roll. CONSTITUTION: An oxy-fuel coating layer(43) is formed in a convex unit(41a) of a casting roll side(41). The layer is coated by pouring semi-melting powder to the convex surface of the casting roll side at mach 1 to 2 of flame in a temperature of more than 10000°C. Herein, the powder has excellent abrasion resistance and durability is coated on the layer at 3000 to 1000cm/min of spraying speed in 20 to 50g/m of spraying amount and 0.1 to 0.8mm of oxy-fuel thickness.

Description

Casting roll coating method of twin roll sheet casting machine

The present invention relates to a method for coating a casting roll of a twin-roll sheet casting apparatus for producing a thin plate (hot coil) directly from molten steel without making a slab, and more specifically, two casting rolls which are water-cooled in opposite directions to each other. The present invention relates to a method of coating a material having excellent wear resistance and durability in a side part of a casting roll in a twin roll sheet casting apparatus for manufacturing cast steel (thin plate) by supplying molten steel between casting rolls while rotating in a rotary furnace.

Generally, in the sheet casting method, molten steel is accommodated in the ladle 10 as shown in FIGS. 1 and 2, the molten steel is introduced into the tundish 20 along the nozzle, and the molten steel introduced into the tundish 20 is It is supplied through the nozzle 30 between the edge dams 50 provided at both ends of the casting roll 40, that is, between the pair rolls 40, and the thin plate 60 is manufactured and wound up in a winding facility through a cooling process. , A thin plate (coil) is produced.

Therefore, an important technique in the twin roll sheet metal casting process for directly manufacturing a thin plate 60 having a thickness of 10 mm or less from molten steel is through an injection nozzle 30 between the internal water-cooled twin rolls 40 rotating in opposite directions at a high speed. By supplying molten steel to produce a thin plate 60 of a desired thickness.

In the conventional twin roll casting method, the side of the casting roll 40 and the edge dam are rotated in contact with each other while maintaining an appropriate force, and this contact portion is likely to be worn.

In general, as shown in Figure 3, the material of the casting roll is made of a copper alloy, nickel plated 42 is used to protect the casting roll made of a copper alloy.

However, when the nickel plated 42 is used as described above, the nickel plated layer is ductile, so that scratches are generated on the plated layer when friction with the refractory material, or the side of the cast roll side is deformed when the molten steel penetrates. Becomes more severe at high temperatures. In addition, when the nickel plating 42 is used as described above, the use of the material of the edge dam 50 is restricted, and there is a problem in using a hard material.

In order to solve this problem, as shown in FIG. 4, a convex portion 41a which locally protrudes the side portion 41 of the casting roll 40 is formed to minimize the area rubbed with the edge dam 50, or in FIG. 3. As shown, a complex edge dam is used by inserting a soft, abrasion-resistant (good lubricity) material such as boron nitride into the portion 51 of the edge dam 50 that contacts the casting roll 40. This improved the wear resistance and durability of the casting roll 40.

However, the nickel plated layer is scratched or damaged at high temperatures even when it is in contact with a material having good lubrication (good wear resistance) such as boron nitride, which is a problem in durability, and may cause leakage or pinching of molten steel during casting. There is a problem.

In particular, as the casting progresses at a high temperature for a long time, molten steel or cast steel is caught between the side of the casting roll and the edge dam, thereby damaging the surface of the casting roll or damaging the edge dam.

MEANS TO SOLVE THE PROBLEM The present inventors made the research in order to solve the conventional problem as mentioned above, and based on the result, this invention proposes this invention, The present invention is the cast roll side part of the twin-roll type sheet casting apparatus whose surface is plated with nickel. The purpose of the present invention is to provide a casting roll coating method of a twin-roll thin sheet casting apparatus that can not only improve durability of a casting roll but also improve edge wear resistance by thermally coating a material having excellent wear resistance and durability. .

1 is a schematic view of a general twin roll sheet casting device

Figure 2 is a schematic view of the casting roll and the edge dam in the conventional twin roll sheet casting device

Fig. 3 is a plan view showing a cast casting roll and an edge dam of a conventional twin-roll type thin plate apparatus whose surface is nickel plated according to the conventional method.

Figure 4 is a plan view showing a friction relationship between the casting roll and the edge dam in the conventional twin-roll thin plate manufacturing

FIG. 5 is a plan view of an edge dam with a spray roll coated with a material having excellent wear resistance and durability according to the present invention on a nickel-plated casting roll side part; FIG.

Explanation of symbols on the main parts of the drawings

40 ... Casting roll (twin roll) 41 ... Casting roll side part 41a ... Convex part 42 ... Nickel plated layer 43 ... Spray coating layer 50 ... Edge dam 51 ... Casting roll contact part of edge dam 60 ... cast

The present invention relates to a casting roll coating method of a twin roll sheet metal casting apparatus for coating a material having excellent wear resistance and durability in a casting roll side portion, preferably a roll side convex portion of a twin roll sheet casting apparatus whose surface is plated with nickel. will be.

Preferably, the present invention provides a material having excellent wear resistance and durability in the casting roll side portion, preferably the roll side convex portion, of the twin roll sheet metal casting apparatus whose surface is plated with nickel, and the spraying speed: 3,000-10,000 cm / min. The present invention relates to a casting roll coating method of a twin-roll thin plate casting apparatus for spray coating on spraying conditions: 20-50 g / min, and spray thickness: 100-800 micron.

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

Improving the durability of the casting rolls should be considered by dividing into cylindrical parts in direct contact with molten steel and side parts in contact with edge dams, which are refractory.

The cylindrical part of the cast roll should be made of a material having high temperature properties, thermal shock resistance and fatigue resistance. The side of the cast roll should be used at high temperature, but it has a high wear resistance in order to improve the durability of the edge dam since it rubs against the edge dam. It is desirable to.

Therefore, in the present invention, a coating material having excellent wear resistance and durability is coated on the side of the casting roll side, that is, the edge dam, thereby improving durability of the casting roll.

Preferably, the present invention is to improve the durability of the cast roll by forming a spray coating layer by thermally coating a material having excellent wear resistance on the cast roll side portion, preferably the roll side convex portion after nickel plating.

Materials that are excellent in wear resistance and durability that can be used in the present invention include Ni-Cr-Mo alloys, Cr ₂ C ₃ -Ni-Cr alloys, and the like, and among these alloys, Ni-Cr-Mo alloys are preferable.

As a material having excellent wear resistance and durability that can be used in the present invention, Ni: 50-70wt%, Cr: 10-25wt%, Mo: 2-5wt%, Si: 2-5wt%, Fe: 1-5wt% And Cu: Ni-Cr-Mo alloy composed of 1-5 wt%.

In the Ni-Cr-Mo alloy, when the Ni content is less than 50%, the ratio of the content of Cr and Si is increased compared to the Ni component, so that the thermal shock resistance or toughness of the material is lowered and the thermal spraying layer becomes unstable. There is a risk of breaking the thermal shock or deterioration of durability, if the Ni content is more than 70% Ni because of its soft properties of the mechanical properties are deteriorated, there is a fear that the thermal spray layer is very vulnerable to scratches.

If the Cr content is 10% or less, the mechanical properties are lowered, and if the content is 25% or more, high temperature brittleness may occur and may be easily broken.

In addition, the Mo content is closely related to the edge dam and the casting roll side durability together with the material of the edge dam, the lubricity is low when the Mo content is less than 2%, and the lubricity is increased at 2% or more. More than 5% showed no increase in lubricity, but rather reduced the toughness of the material.

The content of the other components are elements added at an appropriate ratio in consideration of the toughness, brittleness and lubricity of the coating layer.

In addition, the edge dam and the casting roll side are subjected to repeated high-temperature and low-temperature thermal shocks due to the rotation of the casting rolls in the sheet casting process. Therefore, the lubricity of the material is not only correlated with durability, but mechanically. It acts as a physical property or an important factor.

Therefore, in the present invention, the material to be coated on the casting roll side portion is preferably selected in consideration of the above-mentioned viscosity.

In the present invention, the material having excellent wear resistance and durability is preferably formed on the side of the casting roll on which the nickel plating layer is formed, preferably on the convex portion 41a of the casting roll side portion 41, as shown in FIG. By spray coating, to form a spray coating layer 43, it will be described as follows.

The spray coating method is poured on the surface of the nickel-plated casting roll side surface, preferably the casting roll side convex portion in a state in which the powder, which is the material to be sprayed, is semi-melted at the flame speed of Mach 1-2 at a high temperature of 10,000 ° C. or higher. This is how the coating is made.

The spray coating method has already been developed and used in various ways, using oxygen or acetylene as a fuel, using nitrogen or argon as an atmosphere gas, and spraying the coating material at a high speed through a fine injection nozzle.

If the spraying speed is slow or fast, the thermal shock resistance or adhesiveness is deteriorated, and even the spraying amount (spray rate) and the spraying thickness have a small effect on the wear resistance and hardness, but most of them have an important effect on the thermal shock resistance or adhesiveness.

Therefore, in the present invention, in consideration of the above-mentioned point, a material having excellent wear resistance and durability, under the conditions of injection speed: 3,000-10,000 cm / min, injection amount: 20-50 g / min, and spray thickness: 0.1-0.8 mm Spray coating is preferred.

In the above description, only the thermal spray coating of a material having excellent abrasion resistance and durability is described. However, in the case where plating is performed using a material having excellent wear resistance and durability in a side portion, preferably a side convex portion of a Ni-plated casting roll, for example, Even when Cr is plated, the effect of the present invention can be achieved.

Therefore, this invention also includes plating Cr etc. to the side part of the casting roll which is Ni-plated, preferably the side convex part.

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

Example 1

Spray coating on the convex portion (primary example) of the side of the Ni-rolled casting roll using the material, as shown in Table 1, spraying speed: 80m / min, spraying amount: 30g / min, and spraying thickness: 0.1mm The wear rate, scratches, thermal shock, and hardness were measured, and the results are shown in Table 1 below.

Invention example (2) is Cr-plated at the convex part (conventional example) of the Ni-plated casting roll side surface.

The nickel plating was 1 mm thick.

Example Champion material chief ingredient Wear rate Scratches Thermal shock Hardness (Hv 100) Conventional example Nickel plating Ni 99.9% One Severe Good 100-300 Inventive Example 1 Chrome Carbide Spray Coating Cr ₂ C ₃ 75, Ni-Cr 25% 0.4 usually usually 500-800 Inventive Example 2 Chrome plating Cr 99.9% 0.3 usually Good 300-500 Inventive Example 3 Ni-Cr-Mo Alloy Spray Ni 50-70, Cr 10-25, Mo 1-5% 0.1 Good Good 500-700

As shown in Table 1, nickel-plated when chromium carbide was sprayed (Inventive Example 1), chromium plated (Inventive Example 2), and when Ni-Cr-Mo alloy was thermally coated (Inventive Example 3) It can be seen that it shows superior properties compared to the cast roll surface treated only (prior art), that is, the wear rate was compared relative to each material when nickel plating was set to 1 for boron nitride refractory. It can be seen that the case of -Cr-Mo alloy spraying is about 10 times better than the casting roll surface treatment by conventional nickel plating (prior example).

In addition, also in hardness, it can be seen that the casting roll surface treatment only by nickel plating (conventional example) appears to be the lowest, and both the invention examples (1-3) are twice or more than the conventional example.

In particular, it can be seen that the thermally sprayed Ni-Cr-Mo alloy (Invention Example 3) is the most excellent material.

Example 2

Thermal shock, adhesiveness, and abrasion resistance of the material shown in Table 1 of Example 1 by thermal spray coating on the convex part of the side of the cast roll plated with Ni using a Ni-Cr-Mo alloy under the thermal spraying conditions as shown in Table 2 below. And the hardness was measured, the results are shown in Table 2 below.

In Table 2 below, x denotes a defect, Δ denotes a normal value, ○ denotes a good value, and ◎ denotes an excellent value.

Thermal Spraying Condition Injection speed (m / min) Injection amount (g / min) Spray thickness (mm) 25 30 50 80 100 110 15 20 30 50 60 0.05 0.1 0.5 1.0 Thermal shock × ○ ◎ ◎ ○ △ × ◎ ◎ ◎ × × ◎ ○ × Adhesive × ○ ◎ ◎ ○ △ △ ◎ ◎ ◎ △ × ◎ ○ × Wear resistance △ ○ ○ ○ ○ △ △ ○ ○ ○ △ △ ○ ○ ○ Hardness △ △ ○ ○ ○ ○ △ ○ ○ ○ △ △ ○ ○ ○

As shown in Table 2, in the case of thermal spraying in accordance with the spray coating conditions according to the present invention it can be seen that the physical properties are superior to the case out of the scope of the present invention.

As described above, the present invention not only enables the casting for a long time by improving the durability and wear resistance of the edge dam as well as the durability of the casting roll by thermally coating a material having excellent durability and wear resistance on the side of the casting roll in contact with the edge dam. In addition, since it helps to suppress the penetration of molten steel between the edge dam and the casting roll at the time of casting, it is effective to stabilize the casting.

Claims (8)

Casting roll coating method of twin roll sheet metal casting device for coating material with excellent wear resistance and durability on the side of casting roll of twin roll sheet metal casting device whose surface is plated with nickel The cast roll coating method of a twin-roll thin sheet casting apparatus according to claim 1, wherein a material having excellent wear resistance and durability is coated on the convex portion of the cast roll side portion. The material according to claim 1 or 2, wherein the material having excellent wear resistance and durability is spray coated under conditions of spraying speed: 3,000-10,000 cm / min, spraying amount: 20-50 g / min, and spraying thickness: 0.1-0.8 mm. Casting roll coating method of twin roll sheet metal casting device The method of claim 1 or 2, wherein the material having excellent wear resistance and durability is a Ni-Cr-Mo alloy or a Cr ₂ C ₃ -Ni-Cr alloy. The method of claim 3, wherein the material having excellent wear resistance and durability is a Ni-Cr-Mo alloy or a Cr ₂ C ₃ -Ni-Cr alloy. The material having excellent wear resistance and durability is Ni 50-70wt%, Cr 10-25wt%, Mo 2-5wt%, Si 2-5wt%, Fe 1-5wt%, Cu 1- Casting roll coating method of twin roll sheet metal casting apparatus, characterized in that the Ni-Cr-Mo alloy is composed of 5wt% The material according to claim 3, wherein the material having excellent wear resistance and durability is Ni 50-70wt%, Cr 10-25wt%, Mo 2-5wt%, Si 2-5wt%, Fe 1-5wt%, Cu 1-5wt% Casting roll coating method of a twin roll sheet metal casting apparatus, characterized in that the Ni-Cr-Mo alloy The casting roll coating method of a twin roll sheet metal casting apparatus according to claim 1 or 2, wherein the plating is performed using Cr as a material having excellent wear resistance and durability.