JPS59118887A - Chemical conversion treatment of steel strip - Google Patents

Abstract

PURPOSE:To improve operability and to permit easy adjustment and maintenance by passing horizontally a strip through plural bath tanks disposed in series, and operating the treatment section of the length satisfying the necessary bathing time in accordance with the speed at which the strip is passed. CONSTITUTION:The treatment times T1, T2, T3 in bath tanks 11, 21, 31 are expressed by the equation if the lengths of the respective tanks are designated as L1, L2, L3 and the speed at which a strip S is passed through the same is designated as V1. The treatment time T is therefore determined if the kind of treatment is determined. If the feed speed of the strip S is determined, the length of the bath tanks satisfying the necessary treatment time meeting said speed is calculated by the equation L=VT. The treatment section provided with the bath tanks of the required length among the 1st-3rd treatment sections 10, 20, 30 is thus operated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for chemical conversion treatment of steel plate strip.

Prior to the coating process, the steel plate strip (hereinafter referred to as strip) is subjected to a so-called chemical conversion treatment in which it is washed with phosphate. This chemical conversion treatment has traditionally been carried out by spraying a phosphate solution onto the surface of the passing strip. According to this spray method, many adjustment functions such as opening/closing of the spray nozzle and turning on and off of the pump are required in order to adjust the treatment time and amount of treatment. These adjustment functions are not only difficult and time-consuming to adjust, but also cause the nozzle to dry during outage, solidify sludge in the processing liquid, and clog the nozzle, reducing work efficiency and preventing the target from being achieved. There were drawbacks such as the lack of processing time.

An object of the present invention is to provide a chemical conversion treatment method that eliminates the above-mentioned drawbacks, improves workability, and requires less time and effort for adjustment and maintenance.

In order to achieve the above object, the present invention eliminates the nozzle method and adopts a dip method, and automatically controls the operation of the processing section according to the situation such as the quality of the strip to be processed and the passing speed. This is a chemical conversion treatment method in which the treatment time is adjusted by increasing or decreasing the number of operations.
The gist is that a plurality of baths are arranged in series, the strip is passed horizontally through these baths, and a processing section is operated whose length corresponds to the feed rate of the strip and satisfies the required bathing time. It is characterized by

The present invention will be explained below based on an example of an actual plant shown in the drawings.

In the figure, a first processing section 10, a second processing section 20, and a third processing section 30 are arranged horizontally.

These processing units 10, 20, and 30 include chemical baths 11 and 2, respectively.
1 and 31 are provided. And these bathtubs 11, 21
, 31 horizontally and the strip S is passed through the roller 3. The bathtubs 11, 21, and 31 each have a forced circulation pipe system 1 equipped with pumps 13, 23, and 33 on the suction side, and flow control valves 14, 24, and 34 on the delivery side, respectively.
2, 22, and 23. Both ends of the forced circulation pipe systems 12, 22, and 23 on the suction side and the delivery side are opened to the chemical liquid tank 1 in which the phosphate solution M is accommodated.

The bathtubs 11, 21, and 31 are housed in one tray 2 provided below these bathtubs.

The respective lengths L_1, L_2, and L_3 of the bathtubs 11, 21, and 31 along the strip passing direction are determined by the following relationship.

L_1<L_2<L_3 Next, the chemical conversion treatment mode will be explained.

When the pumps 13, 23, and 33 are started, the chemical solution M flows into each bathtub 1.
1, 21, 31 and the chemical tank 1. The level of the medicinal solution in the bathtub is kept constant to some extent, and the strip S penetrates the side wall of the bathtub so as to pass below the level of the liquid. A part of the chemical solution M is discharged from the cracks that the strip S passes through, but this chemical solution temporarily accumulates at the bottom of the tray 2.
From there, it is returned to the chemical solution tank 1.

If the passing speed of the strip S is V_1 for the lengths L_1, L_2, and L_3 of each bath, the processing time T in each bath is expressed by the following formula.

T_1=L_1/V_1, T_2=L_2/V_1, T
_3=L_3/V_1 Therefore, once the type of processing is determined, the processing time T is determined. Still, the feed speed V of the strip S
Once determined, the length of the bathtub that satisfies the required processing time corresponding to this is calculated using the equation L=VT. As a result, the processing section provided with a bathtub of the required length among the first to third processing sections is operated.

The combination of lengths due to changes in the bathtub operated here is L_
1, L_2, L_3, L_1+L_2, L_1+L_3
, L_2+L_3, L_1+L_2L_3. Therefore, if these are input into the computer's storage section, the target processing time will be constant regardless of changes in line speed.

It is now assumed that the strip S is being fed at a constant speed V_1 and the bathtubs 11 and 12 are being operated. Here, when it becomes necessary to change the traveling speed of the strip S from the point P on the strip S to V_2, when the point P comes to a position a distance D on the upstream side from the first bathtub. ,D
/V_2 and V_2T are calculated by the calculation unit of the computer, and after the calculated D/V_2 time, a bathtub corresponding to the length of V_2T is selected and only that bathtub starts operating. The flow control valves in the other bathtubs are automatically opened to drain the chemical solution and empty the bathtubs.

The number of processing units is not limited to the above, and the length of each bathtub is also determined as appropriate.

Since the present invention is constructed as described above, it is possible to prevent deterioration in work efficiency due to sludge clogging, and to automate the adjustment, which saves time and facilitates maintenance.

[Brief explanation of drawings]

The figure is a process diagram showing one embodiment of the present invention. S... Strip, M... Chemical solution, 10... First processing section 20... Second processing section, 30... Third processing section, 1
1, 21, 31... Bathtub, 12, 22, 32... Forced circulation pipe system, 13, 23, 33... Pump, 14, 2
4, 34,...flow control valve, 1...chemical tank, 2
...Tray 3...Roller

Claims (1)

[Claims] A processing section is operated in which a plurality of bathtubs are arranged in series and the length of the bathtubs is such that the strip is passed horizontally through the bathtubs, and the length of the bathtubs corresponds to the feed rate of the strip and satisfies the required bathing time. A method for chemical conversion treatment of steel plate strip, characterized by: