JP2576328B2 - Reflow control method for continuous tin plating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow control method for a continuous tin plating apparatus used in a tin melting apparatus of a tin plating apparatus for continuously producing tin-plated steel sheets as a material for food cans and other general cans. In particular, a conduction reflow (hereinafter, referred to as C / R) by resistance heating and an induction reflow (hereinafter, I / R) by induction heating constituting a tin melting apparatus.
(Referred to as a reflow control method) of a continuous tin plating facility for optimally controlling the output of the apparatus.

[0002]

2. Description of the Related Art It is known that tin-plated steel sheets are used as surface-treated steel sheets for food cans and other general cans. In recent years, joining using a seam welding method instead of a soldering method and an adhesion method to the joint portion has been widely spread. Although the tin-plated steel sheet is excellent in the seam welding method, it has a problem that tin as a plating material is expensive. Therefore, from the viewpoint of securing the weldability by using a small amount of tin, the following several manufacturing techniques have been proposed.

[0003] One of them is that ² to 30 mg / m ²
Of a Ni coating layer of 200 to 1000 mg /
m ² There has been proposed a surface-treated steel sheet provided with a tin (Sn) coating layer and a chromate treatment on the upper side of the tin coating layer (Japanese Patent Application Laid-Open No. 60-56074).

[0004] The other one is to set the heating rate when the temperature for tin plating exceeds the melting point of tin (232 ° C) to 40 ° C / sec or less in the tin melting step of tin plating. A method of manufacturing a thin tin-plated steel sheet by setting the final temperature of tin plating to 250 ° C. or lower and finally quenching it has been proposed (Japanese Patent Application Laid-Open No. 1-224298).

Incidentally, the former JP-A-60-56074 is disclosed.
According to the publication, after performing heat treatment at 205 ° C. for 30 minutes in an electric oven, when forming into a can body and performing a seam weldability test, the weldability was sufficiently secured with a small amount of tin. Although described, the tin of the thin plating layer applied on the Ni plating layer on the steel sheet surface is finely divided, and the adhesion of the tin is relatively weak, so that the weldability is reduced. And there is a problem that the decay resistance is reduced. Regarding such a problem, it can be said that the same applies to the latter technique disclosed in Japanese Patent Application Laid-Open No. 1-242298.

Therefore, in the case of this type of tin-plated steel sheet,
A manufacturing method in which reflow treatment is performed after tin plating on the surface of the steel sheet or tin plating on the Ni plating layer on the surface of the steel sheet is adopted. Here, the reflow treatment is a treatment in which tin is electroplated, heated to a melting point of tin by a tin melting device, and then rapidly cooled with a quench tank. By performing such a reflow treatment, an Fe—Sn alloy layer is generated on the upper side of iron, which is the steel sheet main body, and a tin plating layer can be formed on the upper side of the alloy layer. It can be manufactured using an inexpensive iron plate, has excellent corrosion resistance, and can be welded with pure tin. This is an important function of the reflow treatment.

By the way, as shown in FIG. 5, a conventional tin melting apparatus in such a continuous tin plating equipment is configured to apply a first conductor roll 2, a guide roll 3a and a guide roll 3a to a steel sheet 1 to be processed sent from, for example, a tin plating tank. 3b, and then quench tank 5 through I / R 4 for induction heating
Here, after being quenched by the cooling noise 6 and the cold water in the quench tank 5, further passed through the second conductor roll 7, and then guided to, for example, a chemical conversion treatment. Reference numeral 8 denotes a C / R for performing resistance heating control on the first conductor roll 2 and the second conductor roll 7.

In other words, the reflow control method of the tin melting apparatus considers at what speed the temperature of the tin-plated steel sheet 1 to be heated to the tin melting point is controlled. (Not shown), the total output power required to raise the temperature up to the tin melting point is determined as a function of the size of the steel sheet 1 and the line speed, and this total output power is calculated based on the size of the steel sheet 1 using the I / R4. , C / R8 and the output power ratio are determined, and I / R4 and C / R8 are determined according to this ratio.
By controlling the output power of R8, the temperature of the steel sheet is reduced as shown in FIG.
The temperature is raised with the characteristics shown in FIG.

[0009]

What is very important for the above-described reflow control method is that FIG.
As is clear from FIG. 5, the position of the melt line 9 after the steel plate 1 to be processed has passed through the I / R 4 is controlled. What the position is is the tin melting point of the steel sheet 1 to be treated (232 ° C.)
The reason for this is that the Fe—Sn alloy layer is formed at such a position in the vicinity, and the rate of temperature rise of the steel sheet 1 in the vicinity of the tin melting point has a great effect on tin adhesion and corrosion resistance.

However, in the conventional reflow control method, the total output is proportional to the line speed, and the output of the C / R 8 for controlling the temperature of the melt line position is proportional to the total output, that is, proportional to the line speed. For this reason, the heating rate of the steel sheet 1 cannot be controlled within a certain range. For this reason, there is one feeling in the adhesion and the corrosion resistance of tin.

Therefore, a thermal radiation thermometer and an ITV camera are installed near the melt line, and the operator manually adjusts the output voltage of the C / R 8 while visually checking the position of the melt line. In particular, when the line is changed, such as a change in line speed or a change in plate thickness, the operator cannot sufficiently cope with the change, and the temperature of the steel sheet 1 to be processed cannot be raised to the melting point of tin. There is a problem of tin repelling and a problem of difficulty in forming an Fe-Sn alloy layer. Further, the operator makes various setting changes in accordance with the line change, but there is a problem that the quality becomes unstable during the change of the setting.

The present invention has been made in view of the above-mentioned circumstances, and reliably controls the heating rate within a predetermined range in a heating zone of a treated steel sheet by C / R to improve tin adhesion and corrosion resistance. It is an object of the present invention to provide a method for controlling reflow of a continuous tin plating facility for achieving the above object.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to control a tin-plated steel sheet to be continuously fed while controlling output power of I / R and C / R. In the reflow control method of the continuous tin plating equipment which performs reflow control for heating and raising the temperature and further performing a quenching process, after determining the total output power of the two reflows using the line speed and the steel sheet size, the target temperature rise The output power of the C / R with respect to the total output power is determined based on the speed, and the remaining output power obtained by subtracting the output power of the C / R from the total output power is used as the output power of the I / R. This is a reflow control method for a continuous tin plating facility that controls the rate of temperature rise of a steel sheet near a point.

[0014]

Therefore, the present invention can control the output power of the C / R, which affects the temperature rise rate near the melt line position, that is, the tin melting point, by taking the above measures. And the rate of temperature rise in the vicinity of the tin melting point can be reliably controlled within a predetermined range, so that a repelling phenomenon can be avoided, and the formation of the Fe—Sn alloy layer can be reliably performed.
Tin adhesion and corrosion resistance can be improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a reflow control method applied to a tin melting device of a continuous tin plating facility. In the figure, the same parts as those of the conventional device (see FIG. 5) are denoted by the same reference numerals, and detailed description thereof will be omitted.

The method of the present invention is particularly different from the conventional method, focusing on the fact that the vicinity of the tin melting point is a heating zone by C / R, and the conventional method of determining the reflow output power depending on the line speed. Instead of the above, the output power of the C / R is determined based on the heating rate.

That is, in this reflow control,
In terms of hardware, as shown in FIG. 1, a reflow control power determination calculation unit 10 for determining the C / R output power and the I / R output power from the line speed, the steel sheet size and the target heating rate, and the reflow control power A C / R power control unit 21 that controls the output power of the C / Rs 2 and 7 based on the output power determined by the determination calculation unit 10, and a C / R power control unit 21 based on the output power determined by the reflow control power determination calculation unit 10. I / R
8 and an I / R power control unit 22 for controlling the output power.

The reflow control power determining operation unit 10 comprises:
Functionally, as shown in FIG. 2, a total output power calculating means 11 for receiving the same steel sheet size and line speed set from the outside to obtain a total output power Pt in proportion to the target heating rate α C / R output power calculating means 12 for determining the C / R output power Pc with the following relationship, and the C / R determined by the C / R output power calculating means 12
A C / R input power calculation means 13 for dividing the output power Pc by the C / R efficiency ηc to determine the C / R input power Pco is provided.

Here, the heating rate of the steel sheet 1 is changed in proportion to the line speed within a certain speed range as shown in FIG.

The reflow control power determining operation unit 10 outputs the I / R output power obtained by subtracting the C / R output power Pc determined by the C / R output power calculating means 12 from the total output power Pt. I / R output power calculating means 14 for determining as power Pi, and I / R output power Pi determined by I / R output power calculating means 14 as I
There is provided an I / R input power calculating means 15 for determining the I / R input power Pio by dividing by the / R efficiency ηi. Next, the operation of the reflow control method having the above functions will be described.

As a result of repeated experiments and studies, the present inventors have found that the temperature rise rate α ° c / sec near the tin melting point, that is, near the melt line 9, indicates that the rejection of pure tin and the Fe—Sn alloy layer I came to know that it had a great influence on generation,
The vicinity of the melt line 9 is exclusively controlled by the C / R 8 power control. Therefore, in the method of the present invention, first, the total output power Pt is obtained based on the following formula based on the steel sheet size and the line speed. Pt = d · Cp · (S · 60) · (t · 10 ⁻³ ) · (W · 10 ⁻³ ) · ΔT (1)

However, in the above equation, d: specific gravity of iron (7.8
5TON / m ³ ), Cp: specific heat (0.107KW / ° CTON)
), S: line speed mpm, t: thickness, W: width, △
T: Temperature rising temperature of the steel sheet 1 (the melting point of tin is 232 ° C.).

When the total output power Pt is obtained as described above, the power ratio distribution of each C / R and I / R is performed from the total output power Pt.
The output power Pc of C / R which affects the position of the melt line 9 will be determined. The C / R output power Pc is determined based on the temperature rise rate α ° c / sec which greatly contributes to the repelling of pure tin and the formation of the Fe—Sn alloy layer.

For this purpose, it is necessary to determine a heating rate α (° C / sec) in the vicinity of the melt line 9, and this heating rate α (° C / sec) is described below with reference to FIG. 2) It can be obtained from the equation. α = {T _c / L transit time = L T _c · {S / (60 · L)} (2) where S is the line speed (mpm) and ΔT _c (° C) is C /
R is the temperature rise temperature. On the other hand, the temperature rise temperature ΔT _c by the C / R is represented by ΔT _c = {Pc / (5.05 · 10 ⁻⁵ · tWS)} (3) In the above equation, Pc: C / R active power (output power), S: line speed, t: plate thickness, W: plate width. Therefore, when the above equation (3) is substituted into the equation (2), α = {Pc / (6.45 · 10 ⁻⁵ · tW)} (4) Therefore, the C / R output power calculating means 12 calculates the C / R output power Pc such that Pc = 6.45 · 10 ⁻⁵ · tWα (5) based on the equation (4). Therefore, this (5)
As is apparent from the equation, the C / R output power Pc can be determined from the heating rate α (° C / sec) regardless of the line speed. Conversely, if the C / R output power Pc is determined in advance, the heating rate α (° C./sec) can be determined from the above equation (5). The heating rate α (° c / sec)
) Was found to be good at 30 to 40 ° C./sec. Therefore, once the C / R output power Pc is determined as described above, the I / R output power calculation means 1
At 4, Pi = total output power Pt-C / R output power Pc (6)

The following calculations are performed to determine the I / R output power Pi, and the C / R input power calculation means 13 and I / R input power
Considering the efficiency in the R input power calculating means 15, the power is transmitted to the C / R power control unit 22 and the I / R power control unit 21,
Controls the output power of R and I / R.

In the reflow control method described above, even if the line speed is accelerated or decelerated, the C / R output power is constant regardless of the line speed, and the C / R output power Pc is calculated from the total output power Pt. The remaining power is compensated by the I / R. However, in this case, I /
There is a problem that the line speed cannot be increased due to the limit of the output of R. Therefore, as for the temperature rise rate α of the melt line 9, the inclination between the line speed and the temperature rise rate is varied as shown in FIG. 4 and the C / R is burdened to emphasize the I / R. And the rate of temperature rise of the steel sheet 1 can be controlled in an arbitrary range. The inclination of the heating rate is set, for example, by setting A, B, etc. in advance by the operator.

Therefore, according to the method of the embodiment described above, after calculating the total output power based on the steel sheet size, the line speed, and the like, the C output is determined based on the heating rate that affects the position of the melt line 9. / R output power is obtained to control the C / R output power, so that the temperature rise rate in the vicinity of the tin melting point can be controlled within a predetermined range, the rejection of pure tin can be prevented, and the Fe—Sn alloy layer can be prevented. Can be reliably generated,
Tin adhesion and corrosion resistance can be greatly improved.

The present invention is not limited to the above embodiment. For example, a radiation thermometer may be installed at a required location and a process of correcting the C / R output power or the I / R output power using the detected temperature as a feedback signal may be performed. In addition, the present invention can be implemented with various modifications without departing from the scope of the invention.

[0029]

As described above, according to the present invention, C
By reliably controlling the heating rate within a predetermined range in the heating zone of the steel sheet treated by / R, it is possible to provide a reflow control method for a continuous tin plating facility that can significantly improve tin adhesion and corrosion resistance.

[Brief description of the drawings]

FIG. 1 is a hardware configuration diagram showing one embodiment of a reflow control method according to the present invention applied to a tin melting device in a continuous tin plating facility.

FIG. 2 is a functional block diagram of a reflow control power determination calculation unit shown in FIG.

FIG. 3 is an explanatory diagram for obtaining a heating rate and the like from a relationship between a steel sheet position and a steel sheet temperature.

FIG. 4 is a view for explaining a setting example of a heating rate.

FIG. 5 is a configuration diagram showing a tin melting device in a conventional continuous tin plating facility.

FIG. 6 is a view showing a heating curve of a steel sheet in FIG. 5;

[Explanation of symbols]

2, 7: conductor roll, 4: induction reflow (I / R), 5: quenching, 6: cooling noise, 8: conduction reflow (C / R), 9: melt line, 10: reflow control power determination calculation Part, 11 ...
Total output power calculation means, 12 ... C / R output power calculation means, 14 ... I / R output power calculation means, 21 ... I / R power control unit, 22 ... C / R power control unit.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Inoue 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-50-134933 (JP, A) JP-A Sho 55-76090 (JP, A)

Claims (1)

(57) [Claims] 1. A continuous tin plating for controlling the output power of an induction reflow and a conduction reflow while heating and raising the temperature of a tin-plated steel sheet to be continuously fed and further performing a quenching process. In the equipment reflow control method, after determining the total output power of the two reflows using a line speed and a steel sheet size, determine the output power of the conduction reflow based on a target heating rate, and Determine the output power of the induction reflow by subtracting the output power of the conduction reflow from the total output power, to control the rate of temperature rise of the steel plate to be treated near the tin melting point of the continuous tin plating equipment Reflow control method.