JPS59153900A - Electrocleaning of cold rolled steel tape - Google Patents

Abstract

PURPOSE:To prevent generation of an abnormal local elongation of a cold rolled steel tape in a skin-pass rolling stage by changing the polarity of >=2 pair of the electrolytic electrode in an electrocleaning bath prior to performing box annealing for each one pair of the electrode successively in order to retard in this way the decrease of the electrolytic current. CONSTITUTION:A steel tape S with has been cold-rolled is, prior to performing box annealing, treated in a cleaning bath for electrocleaning using sodium silicate as a base material in order to clean the steel tape S as well as to prevent burn by sticking SiO2 to the surface of the steel tape. Four sets of electrolytic electrode C1, C2, C3, and C4 having the same polarity wth the confronting electrode with a preceding steel tape S therebetween but a different polarity to the adjacent electrodes are provided in a cleaning bath filled with a cleaning liquid. When the polarities of these electrodes are changed in order to prevent contamination of the electrode surface, the electrode C1, for example, is first changed from +- to 00 then to -+, then, the polarities of electrodes C2, C3, C4 are similarly changed successively, thus, decrease of electrolytic current is retarded as possible, variation of the quantity of SiO2, etc., sticking to the steel tape S is also retarded. Uniform elongation in the skin-pass rolling stage after box annealing is thus secured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrolytic cleaning before box annealing of a cold rolled steel strip that has undergone cold rolling.
The present invention attempts to propose an electrolytic cleaning method for cold-rolled steel strips that can effectively prevent the occurrence of localized abnormal elongation of copper strips, which is often a problem in the rolling process.

Copper strips wound into coils after cold rolling often suffer from seizures between the plate surfaces during subsequent box annealing. For this reason, various measures have been taken in the past to prevent such seizure.In particular, electrolytic cleaning in a sodium silicate-based cleaning bath is carried out before box annealing to clean the surface of the copper strip. It is known that depositing 5iOB on the surface of the copper strip gives good results.

However, if the electrolytic cleaning treatment as described above is performed continuously for a long time with the same polarity arrangement, the electrode surface may be contaminated, temper color may occur during box annealing, and even after box annealing, There is a high risk that scratches will occur during unwinding during temper rolling, and to prevent such scratches, the polarity of the electrodes may be appropriately switched during the electrolytic treatment.

By the way, in copper strips that have been cleaned by electrolytic treatment that involves switching the m-polarity, new defects such as localized abnormal elongation often occur during iM quality rolling after box annealing. .

As a result of intensive research to elucidate the causes of the above-mentioned new defects, the inventors found that the location where localized abnormal elongation of cold rolled steel strip occurs during temper rolling is due to the polarity of the electrode during electrolytic cleaning. It was revealed that it matched the part that had been switched.

In other words, for example, as shown in Figures 1 (a) and (b), in electrolytic cleaning in which two sets of electrodes are used each with electrolysis 1 as the pole, two sets each of upper and lower electrodes are used. , lower electrode 01+02 or upper output and input sides, Tmfm0
When switching between 1, 0@, 08, and 04, conventionally they were all switched at the same time, so the electrolytic voltage becomes zero at the time of switching, and when switching the polarity, Sing and the amount of iron deposited on the surface of the cleaned copper strip decrease. As a result, (1) If there is no Sing and iron coating on the sheet surface, the smoothness will be improved and the friction coefficient will be extremely reduced during substrate rolling using tempering fluid after box annealing. 2) Also Si
If there is no ng coating, the elongation value in that area will be abnormally high due to reasons such as the case where the box 1 is blunted and seizing occurs and the rear tension becomes high during hard rolling, resulting in an abnormally high elongation value in that part, and therefore it is not uniform throughout the coil. The present invention has found that it is impossible to ensure a clear offset, and has advantageously solved the above problem.When switching the polarity of the electrode during electrolytic cleaning, the decrease in electrolytic current is suppressed as much as possible, and the current S due to a decrease in
By preventing and suppressing extreme changes in the amount of iron and iron attached to the copper strip, it is possible to ensure uniform elongation over the entire length of the coil even during temper rolling after box annealing.

That is, in this invention, prior to box annealing, a cold-rolled copper strip is subjected to electrolytic cleaning in a bath containing a sodium silicate-based cleaning bath and equipped with two or more sets of electrolytic electrodes. When switching the polarity of the electrode, the polarity is sequentially switched for each set of electrodes to continue the electrolytic treatment while suppressing a decrease in the electrolytic current, thereby solving the above problem.

Here, the sodium silicate is sodium orthosilicate (1
alOsi02), sodium metasilicate (Nag-8
Although any of sodium disilicate (Na2S1g05) and sodium silicate (NaB51409) can be used, sodium orthosilicate is particularly advantageous.

The present invention will be specifically described below with reference to the drawings.

Generally, in the electrolytic cleaning treatment of cold rolled steel strip, the number of electrodes used is 4 to 8, and the polar arrangement is, for example, 4 on each side. As shown in (b), two pairs of electrode cells sandwich the steel strip S and have the same polarity, and have different polarities in the direction of threading, so that the adjacent polarities are aligned, They are arranged like +10-. In addition to the above, the polar arrangement of the electrodes is −+−
10, +=10-, etc. are possible, but such a polar arrangement is rarely used because reactive current tends to flow.

Now, when switching the polarity of the electrodes in the above-mentioned predetermined arrangement, for example, when switching the polarity of the final electrode, conventionally,
The voltages of the upper and lower electrodes were set to zero at the same time, and then a reverse voltage was applied at the same time.

In contrast, in the present invention, the above method is modified, and the polarity of the upper and lower electrodes is individually switched, for example, as described below. The specific steps are shown in Figure 2 (A) to (E).
I will explain based on.

(1) The state shown in FIG. 2(a) is the initial polar arrangement of the electrolytic electrodes, with the top and bottom both arranged in a 1-10 row arrangement.

(2) When switching the polarity of the electrodes, first set the voltage of one of the electrodes K to zero, for example, C1, as shown in (0) of the same figure.

(3) Next, as shown in the same figure (c), apply a voltage to C1 with the polarity arrangement and column reversed.

(4) Next, as shown in (e) of the same figure, the voltage of the electrode C8 is made zero, and then a reverse voltage is applied as in the case of the electrode al (see (e) of the same figure).

This completes the switching of the polarity of the upper and lower sets of electrodes.

(5) Subsequently, the polarity arrangement of the remaining electrodes is sequentially switched in the same manner as described above, and the polarity arrangement switching of all electrodes is completed.

Note that the order in which the polarities are switched is not particularly defined, and any order may be used as long as the polarities are switched sequentially for each set of electrodes.

In addition, when switching the polarity, the winding diameter is determined by a coil diameter calculator, and when the winding diameter reaches a predetermined value, a switching signal is sent to the electrolytic current polarity switch, making it easy to switch. can.

Next, the steel strip subjected to electrolytic cleaning according to the present invention was subjected to box annealing. The results of an investigation of the roughness rate over the entire length of the coil when subjected to PI quality rolling are shown in FIGS. 8(a) and 8(b), respectively, in comparison with the case of an area treated by the conventional method.

The electrolytic treatment conditions are as follows.

0 Material to be treated Mild steel strip l! l1j11200", thickness 0 #8" %0 Cleaning bath Based on sodium orthosilicate 0 Electrolytic current 2000AX 4 poles o [Decompression pressure 25V O electrode number Upper, lower Raku 2 sets 0 polar arrangement 8 stages, first - + ten - middle Department
10 - (per 14 pieces per piece) 10 Last - 10 - O switching timing and number of times When electrolytic cleaning is performed according to the conventional method of switching twice on the top side and bottom side of the copper strip, as shown in Figure 8 ( +=) As shown in Figure (A), the groaning rate was abnormally high at tl and tg when switching the electrode polarity. Even when the polarity is switched as described above, no abnormal elongation occurs and there is almost no difference from the steady electrolytic section.

As described above, according to the present invention, even if the polarity of the electrode is switched during electrolytic cleaning before box annealing, abnormal elongation does not occur during the subsequent temper-rolling process.
Uniform elongation can be ensured over the entire length of the coil.

[Brief explanation of drawings]

Figures 1 (a) and (b) are diagrams showing typical polarity arrangements, respectively; Figures 2 (a) to (e) are explanatory diagrams of how to switch the polarity arrangement of electrolytic electrodes according to the present invention; Figures 8 (a) and (b) are graphs showing the changes in the offing ratio over the entire length of the steel strip when the area subjected to electrolytic cleaning according to the present invention method and the conventional method was subjected to high quality rolling after box annealing, respectively. It is. Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] L. Prior to box annealing, a cold-rolled copper strip is subjected to electrolytic cleaning in a bath containing a sodium silicate-based cleaning bath and equipped with two or more sets of electrolytic electrodes, during which the polarity of the electrodes is switched. A method for electrolytic cleaning of a cold rolled steel strip, characterized in that the electrolytic treatment is continued while suppressing a drop in electrolytic current by sequentially switching the polarity of each set of electrodes.