JP5755155B2 - Mold repair method - Google Patents

Description

The present invention relates to a method of repairing a mold used for continuous casting of a slab, billet or bloom by using low temperature spraying (cold spray method).

2. Description of the Related Art Conventionally, when manufacturing steel sheets or the like at steel mills, for example, a mold mold 53 is used in which opposed short sides 52 are sandwiched between opposed long sides 50 as shown in FIG. As the mold 53 is used, meniscus cracks 55 and wear flaws 56 are generated on the inner surface of the mold. Further, corrosion 57 may occur at the bottom of the mold. Further, there may be a variable width rod 58 on the side surface of the short side 52 in contact with the inside of the long side 50.
When these wrinkles occur, as described in Patent Document 1, if it is the first, the mold is repaired by adding a material to the inner surface of the mold or, if necessary, the side surface by plating or high-temperature spraying. It is common.

Patent Document 2 discloses a metal having a film thickness of 3 μm to 10 mm and a porosity of 0.5% or less by low-temperature spraying on the surface of the substrate to be treated at a temperature of 300 ° C. or less and a flight speed of 500 m / second or more. It has been proposed to produce a low-temperature sprayed coating-coated member made of a nonmetal.

JP 2011-218401 A JP 2002-309364 A

However, as described in Patent Document 1, when a coating is formed on the inner surface of the mold by plating, the metal component is different from the base material made of copper or copper alloy, and of course, repair of a short life is possible. There was a problem that the base material was gradually thinned and the life was relatively short. In addition, when the mold surface is partially wrinkled, the process of filling the concave portion with plating is extremely difficult and laborious.
On the other hand, repair by high-temperature spraying can also partially repair the mold, but since the mold surface is coated with a material different from the mold body, there is a problem that the repaired sprayed coating may peel off in some cases. It was.
In addition, although the coating | coated member by low temperature spraying is proposed by patent document 2, it does not repair the continuous casting mold used in an iron mill.

The present invention has been made in view of such circumstances, and provides a mold mold repair method for repairing a mold that continuously casts a slab, billet, bloom, or the like at an ironworks to an original state or a state close to the original state. The purpose is to do.

A method of repairing a mold the mold according to the present invention along the object, a copper or Cr-Zr copper mold surface for use in continuous casting, Ri copper Tona, particle size distribution within the near-at least 80% of 5~20μm Using an inert gas as a carrier gas, low-temperature thermal spraying is performed at a temperature lower than the melting point of the metal powder to repair the overlay, and then the thermal treatment of the entire mold including the thermal spray coating or the thermal spray coating is performed. It is performed for 5 to 30 minutes at a temperature not lower than the melting point and lower than the melting point of the mold . Here, since the metal powder is an inert gas (for example, non-oxidizing gas such as argon gas) in which the carrier gas does not react with copper , the metal powder is not oxidized. Further, the metal powder made of copper undergoes plastic deformation by being sprayed at a low temperature to form a high-density sprayed coating.

Wherein at least 80% of the previous SL metal powder Ru particle size distribution in the near of 5 to 25 [mu] m. When the particle size of the metal powder is less than 5 μm, resistance is applied during spraying, the speed at the time of collision is reduced, and when the particle size of the metal powder exceeds 25 μm, a high-density sprayed coating is formed by plastic deformation after the collision. difficult. If the metal powder is allowed to fly at a higher speed, the particle size of the metal powder can be increased, but there is a problem that excessive energy is required.

The heat treatment of the mold at low temperature spraying the metal powder is at a temperature below the melting point of 900 ° C. or higher and the template, intends 5-30 minutes rows. In this case, metals (for example, Zr, Cr) other than copper contained in the base material (copper) are re-dissolved in the base material, but diffusion bonding between the metal powder and the mold further proceeds. Thereafter, when the repaired mold is rapidly cooled, a precipitation hardening type alloy is formed with a metal other than copper and copper, and the strength is increased.

In the mold mold repair method according to the present invention, the temperature of the carrier gas for low-temperature spraying is in the range of 500 to 800 ° C., and the velocity of the carrier gas is preferably 300 to 1100 m / sec. .
Here, when the speed of the carrier gas is less than 300 m / sec, the speed applied to the metal powder is insufficient, and large energy (E = 0.5 mV ² ) cannot be applied to the metal powder. Further, if the gas velocity exceeds 1100 m / sec, the nozzle configuration becomes difficult, and even if possible, excessive energy is required.

In the conventional mold, although the upper limit of the number of use was about 5 to 8 times, depending on the conditions used, by applying the method of the present invention, the surface of the mold can be used repeatedly any number of times, Actually, other parts malfunction (for example, corrosion of the cooling water groove on the back side, distortion due to thermal deformation due to use) occurs due to use, so that a mold mold having a life nearly twice that of the conventional mold can be provided.

It is a schematic explanatory drawing of the low-temperature spraying apparatus used for the mold mold repair method which concerns on one embodiment of this invention. It is explanatory drawing of the mold mold which concerns on a prior art example.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.
First, a schematic configuration of a low-temperature spraying device (cold spreader) 10 used in a mold mold repair method according to an embodiment of the present invention will be described with reference to FIG.

A low-temperature spraying device (more precisely, “low-temperature spraying device”) 10 includes an argon gas cylinder 11 which is an example of an inert gas, a regulator 12 for adjusting discharge pressure, a gas distributor 13, and a gas distributor 13. Valve adjusting mechanisms 14 and 15 for independently adjusting the pressure and flow rate of the gas. And the argon gas discharged | emitted from the valve | bulb adjustment mechanism 14 is supplied to the heater 16, and the argon gas is heated with the heater 16 to predetermined temperature (for example, 600-1000 degreeC). Heating may be performed directly by an electric heater or may be diluted with high-temperature argon gas.

The argon gas discharged from the valve adjustment mechanism 15 is supplied to the powder supply machine 18 and used as a carrier gas for the metal powder 24 supplied to the inside. The powder feeder 18 has a well-known structure and can transport a predetermined amount of metal powder 24 by gas. Reference numerals 19 and 20 are pressure gauges for measuring the pressure of each argon gas.

The heated argon gas and the metal powder 24 are supplied to the torch 21. The torch 21 receives high-temperature argon gas in the expanded chamber and ejects metal powder 24 ejected from the powder feeder 18 together with the carrier gas from the nozzle 22 on the front side. As a result, the metal powder 24 ejected from the nozzle 22 is heated with a carrier gas of 500 to 800 ° C., and a predetermined portion (for example, soot) of a copper or copper alloy mold (mold mold) 23 used for continuous casting. Sprayed on a certain surface). The nozzle 22 is a nozzle having a special structure (for example, a divergent nozzle) as is well known in the shape so that the blown gas becomes supersonic. The torch 21 is provided with a pressure gauge 25 and a thermometer 26. The speed of the carrier gas is 300 to 1100 m / sec.

The metal powder 24 supplied to the low-temperature spraying apparatus 10 is 1) pure copper (Cu ≧ 99.9 mass%), 2) Cr copper (Cr: 0.5 to 1.5 mass%, remaining Cu and inevitable impurities) ), 3) Cr—Zr copper (Cr: 0.5 to 1.5 mass%, Zr: 0.08 to 0.3 mass%, remaining Cu and unavoidable impurities), or 4) Cr—Zr—Al copper (Cr: 0.5 to 1.5 mass%, Zr: 0.08 to 0.3 mass%, Al: 0.1 to 2.0 mass%, the balance Cu and inevitable impurities). This is preferably the same as the component of the mold 23, but even when the component of the metal powder is different from the component of the mold 23, the metal powder is plastically deformed and the coating layer ( Forming a built-up part).

As for the particle size distribution of the metal powder 24, a particle size of 5 to 20 μm occupies 80% by mass. As a result, when the metal powder 24 collides with the mold 23 at supersonic speed, the metal powder 24 collides with the mold 23 and the metal powder 24 attached to the mold 23, and the metal powder 24 undergoes plastic deformation and becomes liquid. Thus, it adheres to the mold surface at a high density, and forms the above-described build-up portion (that is, build-up repair is performed). The density of the build-up portion is 90 to 98%, which is almost the same as the density (100%) of the mold 23. Therefore, when the same metal as the mold 23 is used for the metal powder 24, the build-up portion is visually observed. And the boundary between the mold 23 disappears. When the particle size of the metal powder is small, the metal powder is flowed in an air current, and a sufficient collision speed cannot be obtained.

When performing low temperature spraying (gas temperature lower than the melting point of the metal powder 24) on the surface of the mold 23, the surface of the mold is sufficiently polished with a metal brush or the like, and degreasing treatment is also performed as necessary. When thermal spraying is performed, the mold may be preheated at a temperature of 200 to 500 ° C. In this case, since it oxidizes with oxygen in the air, it is preferable to seal the whole or a necessary part with a sealed chamber or an inert gas.

Although the thickness of the build-up portion depends on the depth of the wrinkles, it is usually about 0.1 to 2 mm from the surface in consideration of the final machining, assuming that the wrinkles are completely filled. Note that the thermal spray repaired mold is a) when no heat treatment is performed thereafter, b) when heat treatment is performed at 250 ° C. or higher and 500 ° C. or lower for 1 to 6 hours, c) at a temperature of 900 ° C. or higher and lower than the melting point of the mold 23 (for example, (Less than 1050 ° C.) for 5 to 30 minutes. Note that the thermal spray coating can be heat-treated without heat-treating the entire mold.

When the mold is not heat-treated as in a), the overlay is matched with the original shape to form a predetermined plane or curved surface, and the repair of the mold is completed.
Next, when the thermal spray repaired mold is subjected to heat treatment at 250 ° C. or higher and 500 ° C. or lower for 1 to 6 hours, metals and impurities other than copper contained therein are not re-dissolved in the base material (copper). . The thermally sprayed metal powder undergoes plastic deformation and is densely laminated, so it is diffusion bonded by heating at a low temperature (usually 40% or higher of the Kelvin temperature melting point, specifically about 270 ° C or higher) Form a raised layer.

Since the sprayed mold is heat treated at 500 ° C. or less, impurities and alloy metal contained in the base material do not precipitate at the grain boundaries or grains, and the properties are maintained as they are. Therefore, when the components of the mold and the metal powder are matched, the built-up portion is integrated with the mold, and peeling or the like is unlikely to occur, thus having a long life.

And as shown in c), when the heat treatment is performed at a temperature of 900 ° C. or higher and lower than the melting point of the mold 23 (for example, lower than 1050 ° C.) for 5 to 30 minutes, the diffusion bonding strength of the metal powder is further increased and the surface becomes stronger. It becomes. In addition, the alloy metal containing impurities contained in the metal is not preferable because it re-dissolves in the base material (copper), and when the cooling rate is slow, the crystal grain size becomes large and a part becomes an intermetallic compound. . When the cooling rate is high, the remaining material is cured in a solid solution state. Therefore, after the heat treatment, it is preferable to rapidly cool the heat-treated mold by spraying a non-oxidizing gas or water cooling.

Table 1 shows that when the tensile strength of the Cr—Zr copper material without heat treatment is 1, a) when heat treatment is not performed (that is, “none” ) , b) 1 to 6 hours at 250 ° C. to 500 ° C. C) heat treatment (i.e., "heat treatment 2"), c) heat treatment at 900 ° C. or more and less than the melting point of the mold 23 (eg, less than 1050 ° C.) for 5 to 30 minutes (ie, “heat treatment 2”) Show.

From Table 1, it can be seen that the cladding material (sprayed coating) has sufficient strength even without heat treatment, and when heat treatment 1 is performed, diffusion bonding develops and the strength increases. Further, even in the case of heat treatment 2, it is considered that the strength is further improved by rapid cooling.
The present invention is not limited to the above-described embodiment, and the present invention can be applied to a material change or numerical value change within a range not changing the gist of the present invention.
Moreover, in the said embodiment, although the casting_mold | template which has a long side and a short side was demonstrated, this invention is applied also to repair of the cylindrical casting_mold | template which forms a bloom and billet.
In addition, the structure of the torch may be another structure as long as it is a high-temperature inert gas that does not oxidize or combine with the metal powder and can eject the metal powder at high speed.

10: low temperature spraying device, 11: cylinder, 12: regulator, 13: gas distributor, 14, 15: valve adjusting mechanism, 16: heater, 18: powder feeder, 19, 20: pressure gauge, 21: torch , 22: nozzle, 23: mold, 24: metal powder, 25: pressure gauge, 26: thermometer

Claims (2)

Continuous copper for use in cast or Cr-Zr copper mold surface, Ri copper Tona, at least 80% of the particle size distribution in the near-Ru metal powder 5 to 20 [mu] m, using an inert gas as a carrier gas, the The low temperature thermal spraying is performed at a temperature lower than the melting point of the metal powder to repair the overlay, and then the thermal treatment of the entire mold including the thermal spray coating or the thermal spray coating is performed at a temperature of 900 ° C. or higher and lower than the melting point of the mold for 5 to 30 minutes. A method for repairing a mold, characterized in that it is performed. The method for repairing a mold according to claim 1 , wherein the temperature of the carrier gas for low-temperature spraying is in the range of 500 to 800 ° C, and the velocity of the carrier gas is 300 to 1100 m / sec. How to repair mold mold.

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