KR0160067B1 - Vapor source heated by resistance for vacuum deposited steel sheet - Google Patents

Abstract

The present invention relates to a large-scale resistive heating evaporation source for applying to a process of vacuum depositing a target material such as steel strips continuously. More specifically, the evaporation source of the present invention is used for depositing a material having low melting point and high vapor pressure even at low temperature, such as zinc (Zn) and magnesium (Mg), on a moving steel strip, and high-speed evaporation is possible even with a single evaporation source. Regardless of the position of the steel strip, there is a characteristic that a uniform adhesion amount can be obtained on the steel surface.

In the evaporation source for vacuum deposition, there are two parts that need precise control, one to precisely control the plating deposition amount, and the other to uniformly control the distribution of the plating deposition amount adhered to the material. For accurate control of the plating deposition amount, the temperature of the graphite crucible 7 is measured and controlled, and the distribution of the plating adhesion amount adhered to the material is controlled by the cover 9 of the evaporation source.

Description

Resistance heating evaporation source for vacuum deposition steel sheet production

1 is a schematic diagram of resistance heating evaporation source of the present invention.

2 is an example of a shape drawing of an evaporation source cover of the present invention.

3 is a model diagram for calculating the deposition thickness distribution.

4 is a calculation of the deposition thickness distribution when the present invention is applied.

5 is a thickness distribution of the zinc deposition layer prepared in the embodiment of the present invention.

6 is a thickness distribution of the zinc deposition layer prepared in the comparative example.

* Explanation of symbols for main parts of the drawings

1: cover for steam flow control 2: evaporate

3: thermocouple 4: PID controller

5: power supply 6: resistance heating source

7: graphite crucible 8: refractory brick

9 graphite insulation 10 ceramic insulation

11: hole

12: The steel plate surface partitioned imagining that the deposited steel plate surface is composed of n unit areas.

13: Melting surface of the evaporation source partitioned by imagining that the melting surface is divided into m unit evaporation sources

The present invention relates to a large-scale resistive heating evaporation source for applying to a process of vacuum depositing a target material such as steel strips continuously. More specifically, the evaporation source of the present invention is used for depositing a material having low melting point and high vapor pressure even at low temperature, such as zinc (Zn) and magnesium (Mg), on a moving steel strip, and high-speed evaporation is possible even with a single evaporation source. Regardless of the position of the steel strip, there is a characteristic that a uniform adhesion amount can be obtained on the steel surface.

Compared to the electroplating or hot-dip plating method, the vacuum deposition method has a wider selection range of materials and plating materials and a wider range of control of plating amount, and thus its use is gradually expanding. In particular, recently, a process of continuously depositing a target material such as steel strip, synthetic resin, paper, and the like has been attracting attention. The core technology of the vacuum deposition process is the selection or fabrication of evaporation sources for the application. The evaporation source should be capable of stable evaporation with solid stones, and the distribution of plating amount along the length and width directions of the material should be uniform.

Currently, as the evaporation source for continuous vacuum deposition, an electron beam evaporation source and a resistance heating evaporation source are mainly used. The electronic load evaporation source can evaporate almost any material and is energy efficient because it directly heats the evaporates. In electron beam vacuum deposition, it is possible to control the width distribution of the coating in the width direction of the material to be transported by controlling the beam pattern of the electron beam, and to control the distribution of the coating length in the longitudinal direction of the material by controlling the size (Power) of the injected electron beam. Can be.

In addition, since the electron beam is incident on the surface of the evaporate with a large kinetic energy (typically 4 to 50 keV), the evaporate is melted to effectively remove impurities or oxide layers formed on the surface to realize process reproducibility and obtain a clean plating layer. Can be.

However, for materials with low melting point (419 ° C) and boiling point (907 ° C), such as zinc, the output of the electron beam that is introduced to prevent boiling of the evaporation source cannot be raised above a certain threshold, so that it forms on the surface of the molten evaporate. It becomes difficult to remove the oxide film. As a result, by irradiating the oxide film with an electron beam, the oxide film partially suppresses evaporation, thereby degrading the reproducibility of the process. In addition, it is difficult to obtain a uniform deposition amount in the width direction of the material even under the control of the electron beam irradiation pattern.

Another disadvantage of the electron beam is that the electron beam must pass between the material and the evaporation source, so that a certain space must be maintained between the material and the evaporation source. Therefore, a considerable amount of vapor flow from the evaporation source is lost to the wall of the vacuum chamber by the divergence. . In a resistive heating evaporation source, this space is not required, so that the vapor deposition efficiency is much increased.

The resistive heating evaporation source is originally used for one-time deposition of small materials, but is also partially used for depositing aluminum and zinc while transferring target materials such as synthetic resin and paper. The resistance heating evaporation source mainly uses a method of evaporating the evaporate contained in the container-type resistor by directly energizing and heating it. If the resistance heating evaporation source is enlarged, there is a difficulty in overheating due to an increase in contact resistance in the electrode part, and the difficulty of uniformizing the width in the width direction of the material is problematic.

At present, for continuous vacuum deposition of aluminum, several small resistance heating sources (boron nitrogen complex heating elements) are installed in parallel. In this configuration, a problem arises in that the operation is stopped when any one of several resistance heating sources is broken, and because the evaporation sources must be controlled independently, the process becomes complicated and it is difficult to obtain reproducibility.

As a method of continuously depositing zinc on a steel strip, a method of melting zinc by induction heating outside the vacuum chamber and introducing the vapor into the vacuum chamber has been reported. In this method, the delivery pipe (Duct), which leads the zinc vapor, should be heated to prevent zinc from adhering to the delivery pipe, and the resistance heating source is installed again inside the vacuum deposition tank to control the temperature of the zinc vapor. This is a dual process that requires adjustment. In addition, the plating deposition amount distribution in the material width direction is controlled by using a shutter to control the flow of the vapor flow to the vacuum deposition tank. In order to control the distribution of the plating amount using the shield plate, an apparatus for mechanically opening and closing the shield plate is required.

The present invention relates to a resistance heating evaporation source capable of effectively evaporating a material having a low melting point and high vapor pressure, such as zinc and magnesium, in a continuous vacuum deposition of a target material. The energy efficiency is high and the process is simple. It is characterized by the fact that the distribution can be controlled uniformly.

Referring to the configuration of the present invention in detail as follows.

The resistance heating evaporation source devised in the present invention is composed of a fume source, graphite crucibles and insulation, a cover for controlling the flow of steam, and a temperature measuring and controlling device. 1 is a block diagram of the resistance heating evaporation source of the present invention. An evaporate 2 (for example, zinc) is charged into the graphite crucible 7 and the lid 1 is covered. The resistance heating source 6 is mounted around the graphite crucible 7 and the graphite crucible 7 is heated using this to heat the evaporate 2 charged therein. The outer side of the resistance heating source (6) by placing a heat insulating material in triplicate to increase the thermal efficiency, to minimize the effect on other parts of the vacuum deposition tank in which the device is installed.

In the evaporation source for vacuum deposition, there are two parts that need precise control, one to precisely control the plating deposition amount, and the other to uniformly control the distribution of the plating deposition amount adhered to the material. Under constant ambient pressure, the saturation vapor pressure of the material is determined by the temperature, so the decisive factor which determines the coating weight is the temperature of the evaporate 2. In the present invention, the temperature of the graphite crucible 7 is measured and controlled for accurate control of the plating amount. As shown in FIG. 1, the thermocouple 3 is inserted into the sidewall of the graphite crucible 7, and the temperature is maintained at a constant temperature by interlocking with a power supply source 5, which is a heating source, and controlling it with a PID (Proportional Integral Deviative) control device 4. Keep it.

The distribution of the plating adhesion amount adhered to the material is controlled by the cover 1 of the evaporation source. When the steam flow is generated with the same strength along the width direction of the material, the steam flow overlaps in the center portion, and the center portion of the material exhibits a greater amount of plating adhesion than the edge. In order to solve this problem, in the present invention, the cover 1 is put on the graphite crucible 7 to suppress the generation of steam flows and to control the flow of the steam flow by making a hole 11 of a suitable shape through theoretical examination. Figure 2 shows the three types of cover devised in the present invention.

The plating adhesion amount distribution obtained by covering the cover which has such a shape was calculated by the following method.

1) The surface of the material to be deposited is divided into n (i = 0 to n) unit elements, and m evaporation sources (depending on the presence and size of holes in the cover and whether or not the amount of vapor flow is generated) are m (j = It is considered to be divided into unit elements of 0 to m) d.

2) The density of vapors reaching the surface of the substrate at the angle of ψ with each element evaporation source can be expressed by the following equation.

(K is a constant and n is an experimental constant between 3 and 5)

3) Therefore, the vapor deposited on the steel sheet surface, i, can be expressed as the sum of the vapor densities evaporated from the m point evaporation sources. (See Figure 3)

(Si is the amount of adhesion to the steel sheet, Sj is the amount of evaporation of the evaporation source)

(Lj is the positional variable of the evaporation source: the hole size of the cover)

(Y is the width direction of evaporation source)

4) By combining the results of Si calculation, it is possible to calculate the distribution of the plating direction in the width direction of the steel sheet.

The estimated value of the plating adhesion distribution thus obtained is shown in FIG.

Another effect of putting the cover 1 on the evaporation source and allowing the vapor flow through the small hole 11 is to ensure the reproducibility of the process irrespective of the formation of the oxide film on the surface of the evaporate 2. . By covering the lid 1 on the graphite crucible 7, evaporation takes place in a nearly closed system of the evaporate 2. That is, even if an oxide film is formed on the surface of the evaporate, if the temperature of the evaporate is kept constant through sufficient preheating time, the vapor pressure of the evaporate in the graphite crucible 7 has a saturated vapor pressure at that temperature. Therefore, the amount of vapor flows through the hole 11 of the cover 1 is only affected by the temperature of the evaporate. As described above, since the temperature of the evaporate is controlled using the thermocouple 3, the amount of vapor flow can be constantly controlled, and as a result, the reproducibility of the process is improved.

Hereinafter, specific embodiments of the present invention will be described.

Example 1

Zinc was vacuum deposited using the resistance heating evaporation source of the present invention. As a material, cold rolled steel sheets of 0.45 mm thick and 300 mm wide were transferred to a speed of 5 m / min, and an evaporation source cover of the form (1) of FIG. 2 was used. The temperature of the evaporation source was kept at 600 ° C. As a result, it was confirmed that the thickness of the zinc deposition layer measured at all positions in the steel strip width direction was within an error range within 10% of the overall average value.

Example 2

Zinc was deposited under the same conditions as in Example 1, and the evaporation source cover of Form (2) of FIG. 2 was applied. As a result, it was confirmed that the thickness of the zinc deposition layer measured at all positions in the width direction of the steel strip was within an error range within 10% of the stagnant average value.

Example 3

Zinc was deposited under the same conditions as in Example 1, and the evaporation source cover of Form (3) of FIG. 2 was applied. As a result, it was confirmed that the thickness of the zinc deposition layer measured at all positions in the strip width direction was within an error range within 10% of the stagnant average value.

Comparative Example 1

Zinc was vacuum deposited using an electron beam evaporation source. The material used was 0.45mm thick and 300mm wide internal smoked steel sheets transported at a speed of 5m / min, and the electron beams were focused on both edges of the crucible, that is, at both ends in the width direction of the steel strip. As a result, it was confirmed that the thickness of the zinc deposition layer measured for each position along the width direction of the strip showed an error of 10% or more in the stagnant average value.

Comparative Example 2

Zinc was vacuum deposited as a resistive heating evaporation source. The same conditions as in Example 1 were performed, but no evaporation source cover was applied. As a result, it was confirmed that the thickness of the zinc deposition layer measured for each position along the width direction of the strip showed an error of 10% or more in the stagnant average value.

In the above results, the zinc vacuum-deposited steel sheet manufactured by the resistive heating evaporation source of the present invention exhibited a deposition thickness distribution having an error range within an average value of ± 10% depending on the width direction of the steel strip. Zinc vacuum-deposited steel sheet manufactured by resistance heating evaporation source without cover showed error range over ± 10% of average value.

The deposition thickness distribution measurement results of Examples of the present invention are shown in FIG. 5, and the deposition thickness distribution measurement results of Comparative Examples are shown in FIG. Uniformity of the deposition thickness distribution is a criterion indicating the basic quality and reliability of the product, the above results mean that the zinc-deposited steel sheet according to the present invention has a quality without problems in use.

Claims (1)

In the resistance heating evaporation source for vacuum deposition steel sheet production, a lid 1 having a plurality of widthwise deposition thickness adjusting holes 11 is mounted on the graphite crucible 7, and the power supply 5 and the side wall of the graphite crucible 7 are mounted. Resistance heating evaporation source by inserting connected thermocouple (3).