JPH01123092A - Method for controlling amount of alloy in tin plating layer - Google Patents

Abstract

PURPOSE:To accurately control the amt. of alloy in a wide range, by taking a function contg. the time from the beginning of melting of plating layer to that of quenching and melting temp. as parameter, when a tin-plated sheet is treated by reflowing. CONSTITUTION:The steel sheet is plated with tin by electroplating, etc., and then the plating layer is remelted by heating the plated steel sheet to form alloy layer of iron and tin, and thereafter, cooled with water in a quenching tank. In a reflowing process of the production line of the tin-plated steel sheet above-mentioned, the amt. of alloy is controlled by taking {DELTAtXeXp[-Q/R(T +273)]}<1/2> (where, R is a gas constant and Q is activation energy) as parameter, denoting the time from the beginning of melting of the plating layer to that of quenching by DELTAt(sec) and melting temp. by T( deg.C). Thereby, the amt. of alloy is accurately controlled in the range from small to large amts. of thin in the alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for controlling the amount of alloy in a coating layer in a reflow process of a tin-plated steel sheet manufacturing line.

<Prior art> In the production of tin-plated steel sheets, generally tin is plated on the steel sheet by electroplating, and then the plated steel sheet is heated to melt the surface plating layer again to form an alloy layer of iron and tin. Next, water cooling is performed in a quench tank. Heating methods in the reflow process after plating include an induction type that uses electromagnetic induction and a conduction type that uses resistance heating.

By the way, in this reflow process, there are roughly three types of methods for controlling the amount of alloy as follows.

First, JP-A-52-95542, JP-A-55-7
As described in Japanese Patent No. 6090, there is a method of controlling the amount of alloy by controlling the maximum temperature reached by a plated steel plate by heating, that is, the temperature at the time of entry into a quench tank.

The second is JP-A-49-133229 and JP-A-50-13.
As described in Japanese Patent No. 4933, the amount of alloy is controlled by the amount of electric power input when melting tin. That is, as shown in FIG. 5, the melting temperature of tin and the quench start temperature T. , (°C) and the melting time Δt (sea). The alloy amount is controlled by controlling the area (=□ΔT·Δt) of the shaded area, which is determined by the temperature difference ΔT between , (°C) and the melting time Δt (sea).

Furthermore, there is also a method of controlling the melting time of tin, as described in Japanese Patent Application Laid-Open No. 50-68930.

<Problems to be solved by the invention> However, in the conventional method, the amount of alloy is determined with accuracy (
It is still insufficient to control. The details will be explained below.

Figure 6 shows the investigation of the relationship between the steel plate temperature and alloy content at the time of quench entry.
m
19 m, and each plot is the average value of 15 samples. It can be seen from this that there is almost no correlation between the quench entry temperature and the amount of alloy, and furthermore, the amount of alloy varies greatly due to changes in line speed.

FIG. 7 shows the results of a similar investigation of the relationship between Δt (melting time 5 ec) XΔT (quench rush temperature - 5Q melting temperature) and alloy content. According to this, between these
Although a 1:1 correspondence can be obtained with a high correlation, in reality it contains the following contradiction. That is, in the case of Δt×ΔT-0, in other words, 0.
Although an alloy of 31 g/rd would be obtained, in reality, almost no alloy would be produced without melting.

Therefore, this method cannot be applied to obtain a low alloy content, and a higher-order control equation is required.

Furthermore, the physical or chemical meaning of this Δt×ΔT is also unclear.

FIG. 8 similarly shows the investigation of the relationship between the melting time and the amount of alloy. This shows that there is almost no one-to-one correspondence between the melting time and the amount of alloy.

As described above, it is difficult to precisely control the amount of alloy over a wide range with the conventional techniques.The present invention was made in view of these problems of the conventional techniques. The object of the present invention is to provide a control method that can accurately control the appearance of a hit alloy.

Means for Solving the Problems> The present invention reduces the time from the start of melting of the plating layer to the start of quenching in the reflow process of a tin-plated steel plate manufacturing line.
This is a tin plating layer alloy and a method for controlling the amount thereof, characterized in that the amount of the alloy is controlled using the following parameters, where Δ(sec) and the melting temperature are T (° C.).

However, R: Gas constant Q: Activation energy action〉 Unsteady diffusion in a semi-infinite body is applied to the reflow treatment of tin-plated steel sheets. That is, as shown in FIG. 2, the initial iron concentration in the base material and tin plating layer before melting treatment is Cs,
Assuming Go, after the start of melting and after Δ, the concentration distribution will be as shown in FIG. Now, if the melting temperature is T (℃),
The amount S of solute that diffuses in time Δt is given by the following equation.

x (Cs-Co) Here, Do: diffusion constant Q: Activation energy R: gas constant Therefore, if the alloy amount is W, Here, k: constant of proportionality The relationship holds true.

That is, the alloy amount can be accurately controlled by controlling based on Equation 0.

<Embodiments> Hereinafter, embodiments of the present invention will be described using a conduction type as an example. In the case of the conduction type, the steel plate temperature changes as shown in FIG. 5, so the melting temperature T in equation 0 is replaced with the following Tav.

232 +Tsax Tav=□　　　　■ The results were obtained.

It can be seen that each measurement point lies well on a straight line, and that this straight line passes near the origin. In other words, it can be seen that it matches well with the above equation 0. This is linearly regressed to obtain the following equation.

Therefore, the alloy amount is controlled based on the 0 formula, but in this case, it is necessary to constantly grasp Δt and Tmax in the 0 formula and reflect this in the input power. Δt, Tm
There are two ways to determine ax: directly measuring the plate temperature @ calculating the plate temperature from input power, below:
Let's talk about.

Input power P and effective power Pi to actually raise the plate temperature
There is a relationship between the following equation.

P - P t + P t + P w where, PL
: Power loss P in reflow @ : Power loss PL between the quench tank outlet conductor and the roll. Calculate the effective power PE by considering heat dissipation and radiation during the reflow process. Taking into account the temperature of the plate at the entrance of the reflow process, we were able to obtain the following relational expression between the plate temperature T wax after quenching and the melting time Δt.

Here, To: Inlet temperature V Line speed (m/+*1n) P: Input power (K) d: Plate thickness (a) b: Plate width (W) σ: Specific gravity (g/proof) C: Specific heat (J/g −K) K, ~KS: Constant K, : 0.02 K, : 3498K
:l: 30240 K-: 5.3178
X 10hKs: 1309 Also, input power P (KW) and reflow current 1 (A).

The reflow voltage V (V) has the following relationship.

P-I-V/1000 ■
Therefore, the alloy amount is estimated from the reflow voltage ■, reflow current I, and line speed V based on formulas ■, ■, ■, ■, and the voltage is fed back based on the deviation between this estimated value and the target value. Figure 4 shows a control system for this.

In the figure, 1.2 is a conductor roll, 3 is a quench tank, 4 is a thyristor, 5 is a power source, and 6 is a voltage controller. Also, 7 is a computing unit, where ■, ■, ■, ■
Calculations are performed according to the formula, and the results are output to the voltage controller 6 for voltage feedback control. Note that S is a tin-plated steel plate. When the reflow treatment was performed in this manner, it became possible to control the alloy amount with an accuracy of ±0.1 g/ITf. In the above embodiment, the explanation was given for the conduction type, but it can also be applied to the induction type, and in this case, T of the 0 type is not Tav of the 0 type (Tmax can be used as is).

<Effects of the Invention> According to the present invention, in the reflow treatment of tin-plated steel sheets, it is possible to accurately control the amount of tin alloyed from a small range to a large range.

[Brief explanation of the drawing]

FIG. 1 is a measurement diagram of the parameters of the present invention, FIGS. 2 and 3 are explanatory diagrams showing the state of diffusion of iron into the plating layer, and FIG. 4 is a conceptual diagram showing an example of the control system of the present invention. Fig. 5 is an explanatory diagram showing the steel plate temperature during heating of the conduction type, and Figs. 6, 7, and 8 respectively show the plate temperature at the time of quench entry, Δt×ΔT and ΔT, and the amount of alloyed tin. It is a measurement diagram showing the relationship. Patent Applicant: Kawasame Steel Co., Ltd. Figure 1 Figure 2 Temperature Figure 3 Temperature

Claims (1)

[Claims] In the reflow process of a tin-plated steel sheet production line, the time from the start of melting of the plating layer to the start of quenching is Δt (se
c), When the melting temperature is T (℃), Δt×exp[-
Q/R(T+273)] A method for controlling the amount of alloy in a tin plating layer, the method comprising controlling the amount of alloy using Q/R(T+273) as a parameter. However, R: gas constant Q: activation energy