KR101135936B1 - Method for manufacturing cooling roll of strip - Google Patents

Abstract

A method of manufacturing a strip casting cooling roll is introduced to repair the joint portion of the cooling roll so that it can be reused. The method of manufacturing the strip casting cooling roll includes the steps of manufacturing a cooling roll having a cooling channel, sealing the cooling channel by covering an end plate on the cooling channel, and pure copper and a copper alloy at a joint portion of the end plate in the cooling channel. Injecting the coating material consisting of any one selected from among low temperature comprising the step of forming a coating layer of 1 ~ 10 mm thick.

Description

Manufacturing Method of Strip Casting Cooling Roll {METHOD FOR MANUFACTURING COOLING ROLL OF STRIP}

The present invention relates to a method for manufacturing a strip casting cooling roll, and relates to a method for manufacturing a strip casting cooling roll that can prevent cracking occurring during manufacture or use of the cooling roll.

In general, the strip casting process is a process for producing hot rolled strips having a thickness of 2 to 6 mm directly from molten steel. The steel rolling process can reduce manufacturing cost, equipment investment cost, energy consumption, and pollution gas emission by omitting the hot rolling process. to be.

In particular, as shown in Figure 1, the twin roll type sheet caster used in the strip casting process, the molten steel of the tundish through the cooling nozzles (10a, 10b) and the edge dam attached to both sides ( 30 is supplied to the space formed by 30, and the molten steel is solidified rapidly through contact between the cooling rolls 10a and 10b and the molten steel while rotating the two cooling rolls 10a and 10b in opposite directions. To make.

The cooling roll typically uses a copper alloy having excellent thermal conductivity and excellent high temperature strength, such as a CuCrZr alloy and a CuNiBe alloy. As shown in FIG. 2, the copper-based alloy cooling roll has a cooling channel 11 through which water is circulated for cooling in the internal structure, and covers the end plate 12 in the cooling channel 11 to weld (W). To be completely sealed. At this time, since the welding W of the end plate 12 cannot be sealed by a conventional welding method, electron beam welding is used.

However, in the case of electron beam welding, the welding cost is expensive because welding must be performed in the vacuum chamber, and there is a problem that cracks often occur at the joints when the heat shrinks after heating to about 350 degrees to fit the internal steel shaft.

In addition, the conventional strip casting process cools the molten metal, so that even when the molten metal is in contact with water, it is heated up to about 300 degrees and then cooled again. At this time, the joint is in a state of residual tensile stress. Since the hardness is in a weak state, there is a problem that cracks frequently occur in the heat cycle process at the joint portion of the copper alloy cooling roll.

An object of the present invention for solving this problem, to provide a manufacturing method of strip casting cooling roll that can form a coating layer by spraying the coating material at a low temperature on the cooling roll to prevent cracking, and reduce the manufacturing cost of the cooling roll. will be.

In order to achieve the above object, the present invention provides a method for manufacturing a cooling roll on which a cooling channel is formed, covering an end plate on the cooling channel to seal the cooling channel, and pure copper at a joint portion of the cooling channel and the end plate. And forming a coating layer having a thickness of 1 to 10 mm by spraying the coating material composed of any one selected from copper alloys at low temperature.

Here, after the forming of the coating layer, the method may further include polishing the coated surface. The powder particle size of the coating material is preferably 1 ~ 100 ㎛. Preferably, a groove having a “U” or “V” shape is formed in a joint portion between the cooling channel and the end plate. In the forming of the coating layer, it is preferable to maintain the powder preheating temperature of the coating material at 100 to 500 degrees during the low temperature spraying of the coating material. After forming the coating layer, it is preferable to further include the step of heat-treating the coating layer to 350 degrees for 2 to 24 hours after low-temperature spraying of the coating material.

According to the present invention, by forming a coating layer by spraying a coating material at a low temperature on the cooling roll, there is an advantage that it is possible to prevent cracks generated during the manufacture or use of expensive cooling rolls.

In particular, the present invention by forming a coating layer through the low-temperature spraying in the joint portion of the cooling channel and the end plate to implement a complete sealing, it is advantageous to reduce the manufacturing cost due to the use of conventional expensive electron beam welding.

First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in Figure 3, the method for manufacturing a strip casting cooling roll according to the present invention, the method for manufacturing a strip casting cooling roll according to the present invention, to produce a cooling roll formed with a cooling channel 110, the cooling channel ( An end plate 120 is covered and sealed to 110, and a coating material is formed by spraying a coating material at low temperature on the joint portions of the cooling channel 110 and the end plate 120.

That is, a cooling channel 110 capable of circulating water for cooling is formed on the cooling roll, and the end plate 120 is covered with the cooling channel 110 of the cooling roll, so that the cooling channel 110 and the end plate 120 Seal the seam. Thereafter, a coating material is sprayed at a low temperature on the joint portion of the end plate 120 in the cooling channel 110 to form a coating layer.

The coating material is preferably composed of a material of the same material as the cooling roll (base material), since the cooling roll according to the present embodiment is composed of a copper alloy, the coating material is ideally composed of a copper alloy. At this time, the powder particle size of the coating material is preferably 1 ~ 100 ㎛. Of course, as a coating material sprayed on the cooling roll (base material) of the copper alloy, a material composed of pure copper may be used.

In particular, when the coating material is sprayed at a low temperature, a coating layer having a thickness of 1 to 10 mm is formed at the joint portion of the cooling channel 110 and the end plate 120. This means that when the copper is laminated using the low temperature spraying process of the coating material, the coating thickness of the coating layer should be at least 1 mm. Therefore, if the thickness is less than 1 mm, sufficient sealing strength may not be produced. In the case of insufficient sealing, the coolant may leak, and in the case where the lamination thickness is 10 mm or more, the bonding strength with the base material is weakened due to the increase of the residual stress of the coating layer as well as the cost reduction.

In this embodiment, the configuration for forming a coating layer on the joint portion of the cooling channel 110 and the end plate 120 is described, but is not limited thereto, and the joint portion of the cooling channel 110 and the end plate 120 is described. It is also possible to form a coating layer through the low-temperature spraying of the coating material on the entire cooling roll including a.

On the other hand, as shown in Figure 4, the low temperature injector 200 of the coating material for forming a coating layer on the joint portion of the cooling roll, the gas control unit 210 for controlling the supply amount of gas, and the gas control unit ( A gas heater 220 for heating the gas supplied through the 210, a powder supply device 230 that receives a portion of the gas through the gas control unit 210, and supplies a coating powder, and a powder supply device 230. A mixing chamber 250 for mixing the coated powder supplied from the gas and the gas heated by the gas heater and a powder supplying device 230 and the mixing chamber 250, so that the coating powder is mixed from the powder supplying device 230. A powder preheater 240 for preheating the coating powder in the process of feeding to the chamber 250, a control unit 260 for controlling the temperature by controlling the powder preheater 240 and the gas heater 220, and a mixing chamber. Preheated coating powder mixed at 250, and heated gas It consists of a spray nozzle 270 for spraying. Here, the low temperature spraying device is the same configuration as the conventional low temperature spraying device which forms an excellent coating layer by preheating the coating material and spraying it at low temperature, so a detailed description thereof will be omitted.

However, the powder preheating temperature of the coating material during the low temperature spraying is preferably maintained at 100 ~ 500 degrees. When the powder preheating temperature of the coating material is 100 degrees or less, the effect of the powder preheating is insignificant, and when the powder preheating temperature of the coating material is 500 degrees or more, oxidation of the copper powder becomes severe.

After the low temperature spraying, the coating layer may be heat-treated at 350 degrees for 2 to 24 hours. At this time, since the strength of the base metal copper alloy is lowered at 350 degrees or higher, the temperature should be 350 degrees or lower. When the heat treatment time is 2 hours or less, the heat treatment effect is insignificant.

Meanwhile, as shown in FIG. 5, in the cooling roll 100 provided with the cooling channel 110 and the end plate 120, a groove portion 101 having a “U” or “V” shape is formed at a corresponding joint portion. Can be formed. The groove portion 101 is formed with a coating layer through the low-temperature spraying of the coating material, the coated surface after the low temperature spray coating is preferably polished.

Looking at the embodiment for more clearly explaining the above-described configuration as follows.

EXAMPLE

     As shown in Figure 6, 99% copper powder (Test Example 1) having a particle size of 5 ~ 50 ㎛ was coated on a cold roll (hydraulic specimen) by the low temperature spraying process of Table 1.

TABLE 1

Process conditions Remarks Use gas nitrogen Helium, air or mixed gas available Main gas temperature 550 degrees Powder Preheat Gas Temperature 400 degrees Powder feeding speed 2kg / hr Main gas pressure 29 kg / cm ² Distance between cryogenic injector and specimen 15 mm Specimen rotation speed 40mm / s

As a result, the pure copper-coated hydraulic specimens were heat-treated at room temperature and 350 ° C., and the results of the hydraulic test confirmed that the coolant did not leak even at a pressure of 15 bar.

In particular, Figure 7 is an enlarged cross-sectional structure of the copper coating, it can be seen that the cross-sectional structure of the copper coating shows a very excellent structure. At this time, the lamination thickness is about 4 mm.

Table 2 shows the results of measuring hardness after heat treatment at 250 ° C and 350 ° C for 4 hours at room temperature of the base material and the coating layer.

TABLE 2

Room temperature 250 degrees 350 degrees CuCrZr 140 142 141 CuNiBe 205 207 205 Cu coating 149 142 124

As shown in Table 2, it can be seen that the used copper-based alloy is hardly changed in hardness when heat-treated to 350 degrees. However, the copper coating can be seen that the hardness is lowered (annealing) the coated plastic processed tissue when the heat treatment at 350 degrees.

In other words, the coating area of the copper-based alloy is lower than the base material, but if the coating site is in direct contact with the molten metal may be a disadvantage in hardness drop, but the coating site is a side that does not directly contact the molten metal in the hardness drop As the toughness increases, the probability of cracking is significantly reduced.

Although the present invention has been described in detail using the preferred embodiments, the scope of the present invention is not limited to the specific embodiments, and should be interpreted by the appended claims. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

1 is a block diagram showing a strip casting cooling roll according to the prior art.

Figure 2 is a cross-sectional view showing a longitudinal section of the strip casting cooling roll according to the prior art.

Figure 3 is a block diagram showing a method of manufacturing a strip casting cooling roll according to the present invention.

Figure 4 is a block diagram showing a low-temperature injector for producing a strip casting cooling roll according to the present invention.

Figure 5 is a cross-sectional view showing a longitudinal section of the strip casting cooling roll according to the present invention.

Figure 6 is a photograph of the low-temperature spray coating layer on a hydraulic specimen according to an embodiment of the present invention.

Figure 7 is an enlarged photo showing the cross-sectional structure laminated to the copper coating on the CuCrZr base material according to an embodiment of the present invention.

※ Code explanation for main part of drawing ※

100: cooling roll 101: groove

200: Low temperature injection device

Claims (6)

Manufacturing a cooling roll on which a cooling channel is formed; Closing the cooling channel by covering an end plate on the cooling channel; And And forming a coating layer having a thickness of 1 to 10 mm by cold spraying a coating material formed of any one selected from pure copper and a copper alloy on the joint portion of the cooling channel and the end plate. Forming the coating layer, the method of manufacturing a strip casting cooling roll, characterized in that to maintain the powder preheating temperature of the coating material 100 ~ 500 degrees during low-temperature spraying of the coating material. The method according to claim 1, After forming the coating layer, the method of manufacturing a strip casting cooling roll, characterized in that it further comprises the step of polishing the coated surface. The method according to claim 1, Powder coating size of the coating material is a manufacturing method of the strip casting cooling roll, characterized in that 1 ~ 100 ㎛. The method according to claim 1, Method for producing a strip casting cooling roll, characterized in that the groove portion of the "U" or "V" shape is formed in the joint portion between the cooling channel and the end plate. delete The method according to claim 1, After the forming of the coating layer, after the low-temperature spraying of the coating material manufacturing method of the strip casting cooling roll further comprising the step of heat-treating the coating layer to 350 degrees for 2 to 24 hours.

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