JPS60187694A - Manufacture of galvanized steel sheet - Google Patents

Abstract

PURPOSE:To obtain a galvanized steel sheet having superior resistance to tension pat by carrying out electrolysis in a galvanizing bath contg. prescribed amounts of dextrin and strontium carbonate. CONSTITUTION:A galvanizing bath contg. 5-100mg/l polysaccharide or dextrin as an intermediate produced by the hydrolysis of polysaccharide and 5-500mg/l strontium carbonate is prepd. A steel sheet is galvanized in the galvanizing bath to obtain a galvanized steel sheet having superior resistance to tension pat.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a method of manufacturing an electrogalvanized steel sheet, and particularly to a method of manufacturing an electrogalvanized steel sheet with excellent tension pad resistance.

(Prior art) Electrogalvanized steel sheets have recently been used in automobiles, home appliances, audio equipment,
Electrogalvanized steel sheets are increasingly being used for parts such as office automation equipment, but the electrogalvanized steel sheets used to manufacture these parts are generally much smaller in size than those manufactured through the electrogalvanizing process in factories. Provided for use.

For this reason, it is necessary to cut slits (11) in the medium-wide electrogalvanized steel sheets manufactured in factories before use to ensure that they are suitable for press-forming the above-mentioned parts. When performing this process using a continuous press, in order for the feeding device to accurately feed the workpiece to the continuous press, the medium accuracy of the pre-slit electrogalvanized steel sheet must be maintained within a certain range. First, it is necessary to make a straight slit without any distortion.

In addition, electrolytic galvanized steel strips with narrow slits are wound around coilers, but if the coils are wound loosely, the coils become box-shaped, which is dangerous during transportation and other handling. - For this reason, in order to slit with more precision and wind up more strongly than before, a tension bat (hereinafter sometimes simply referred to as a bat) 1 is used, as shown schematically in Figure 1.
An electrogalvanized steel sheet 2 is sandwiched between upper and lower surfaces of nylon felt of a certain width, and the electrogalvanized steel sheet is passed through a slitter 4 while applying pressure to the entire inside to create tension between it and the recoiler 3. It is slit and wound.

However, the surface of electrogalvanized steel sheets usually has microcrystals of various shapes, forming microscopic irregularities.
Therefore, when slitting, when the nylon felt (tension pad) is squeezed under pressure, the soft and uneven curved parts of the surface of the electrogalvanized steel sheet are stripped off by the tension bat and attached to the pad as zinc powder. Furthermore, as the slit progresses, the zinc powder that is picked off one after another by the pads gradually accumulates on the pads, and the accumulation occurs not only between the pads and the electrogalvanized layer. The frictional force between the zinc powder and the electrogalvanized layer also increases, resulting in scratches on the slit electrogalvanized steel sheet, which significantly impairs its appearance and deteriorates its corrosion resistance, reducing its commercial value. It's going to be bad.

On the other hand, as mentioned above, electrogalvanized steel sheets, which are widely used in automobiles, home appliances, audio equipment, OA equipment, etc., are required to have excellent corrosion resistance as well as appearance. Therefore, from the viewpoint of ensuring corrosion resistance, the above-mentioned flaws must be prevented as much as possible.

(Objective of the Invention) In view of the above, the present invention provides a method for drastically reducing scratches on the electrogalvanized layer due to the tension butt during slitting and obtaining an electrogalvanized steel sheet with good appearance. That is.

(Summary of the Invention) The present inventors have arrived at the present invention as a result of various studies to achieve the above object without changing the conventional plating bath composition. Or each time a steel plate is electrogalvanized using an electrogalvanizing solution containing a combination of dextone, a hydrolysis intermediate thereof, and strontium carbonate.

Here, typical examples of the "polysaccharide" include starch and glycogen.

(Aspects of the Invention) Next, in the method for producing an electrogalvanized steel sheet with excellent tension pad resistance according to the present invention, the above-mentioned polysaccharide or dextrin, which is a hydrolysis intermediate, is added in an amount of 5 to 100 mg/
12. Strontium carbonate is added in combination at 5 to 500 mg/β, but the reason for these limitations will be explained.

First, a laboratory plating experiment conducted under the following conditions was evaluated using a simulation tester and test conditions described below.

Plating solution composition: ZnSO4・71120 400g
/ 1-Na2SO415g/E Plating solution pH: 1.8 Inter-electrode distance: 35mm The three conditions of plating solution composition, plating solution PL+, and inter-electrode distance remain unchanged, and the variable conditions include plating temperature, plating current, plating solution flow rate, etc. In addition to experimenting with the effect of small amounts of additives, we also evaluated the tension pad properties (easiness and difficulty of causing scratches due to padding) of the plated specimens using the simulation tester described below, and conducted thorough inspections. . As a result, electrogalvanized steel sheets could be obtained by simply adding a small amount of polysaccharides such as starch, glycogen, or dextrin, and a small amount of strontium carbonate to the plating solution without changing the plating bath composition or plating conditions. It was found that it had excellent tension resistance.

Note that the above polysaccharide and textrin may be used as a mixture.

Figure 2 of the attached drawings is a graph summarizing a series of results of the above-mentioned evaluation tests, and shows the case where the amount of strontium carbonate alone added to the basic plating composition bath was changed (in the figure,
(indicated by black circles), when the amount of dextrin alone is varied (indicated by white circles in the figure), and according to the present invention, a fixed amount of strontium carbonate (in this case, 20 mg/j!
) and the amount of dextrin added (indicated by △ in the figure) shows the effect of adding each additive without affecting the tension butt resistance. From these results, it was found that electroplating with varying amounts of strontium carbonate alone in the basic plating composition did not improve the tension butt resistance of the steel sheet, whereas when dextrin was added to the basic plating composition. for,
It can be seen that adding more than about 10 mg/ff produces some effect, but it is still insufficient.

However, when electrogalvanizing is carried out by adding 20 mg/ff of strontium carbonate to the basic plating composition and changing the amount of dextrin added according to the present invention, the effect on tension butt resistance is remarkable, and When additives are used together, the amount of dextrin added is 5mg//! Effective from] Omg/l to 100
mg/, the effect remains almost unchanged at +2. Furthermore, if the amount of dextrin added exceeds 100 mg/β, the finished appearance of the plated layer will darken, which is not desirable in terms of commercial value. Therefore, the amount of dextrin added is 5 to 1
00 mg/1.

On the other hand, regarding the amount of strontium carbonate that is added in combination, we refer back to the results of two series of evaluation tests. The effects are summarized in a graph and shown in Figure 3. According to this, the combined addition of strontium carbonate is 5 mg/β to 500 m
It can be seen that it is effective at g/ρ (addition in excess of this is not economical).

We believe that the reason why the tension pad resistance is significantly improved by adding a small amount of strontium carbonate and dextrin is that fine particles of the additives are adsorbed and dense crystals are formed during plating. but,
The mechanism has not yet been elucidated.

Here, a simulation test machine for evaluating the tension pad property, which has been explained as an index with reference to FIGS. 2 and 3, will be explained with reference to FIG. 4.

In the figure, a pad mounting jig 23.23' is fixedly attached to a pad mounting board 22.22' fixed to the inside of one of the device outer frames 21.21', and these bats are attached. A pad 24.24' is disposed on the jig 23.23', and a hydraulic jack 25 is installed inside the other device outer frame 21' facing the device outer frame 21. A bat mounting board 22° and a bat mounting jig 23'' are fixedly attached to the tip thereof, and a pad 24'' is further mounted on the pad mounting jig 23°. In this way, one pad 24'' and the other pad 24'' are connected to the electrogalvanized steel sheet specimen 26 held by the chuck 30.
are placed facing each other so that they are sandwiched between the two sides.

Further, one end of a guide pin 27 inserted into a hole formed in the bat mounting board 22'' is embedded and fixed in another bat mounting board 22, and also in another hole formed in the bat mounting board 22''. A stoppered rod 28 whose one end is embedded and fixed in the substrate 22 is inserted.

Note that the device outer frame 21, 21'' is attached to a tensile tester (simulation tester) table 32 via a mounting bracket 31.

The lower part of the device configured in this way was fixed on a tensile test table, a pad was attached, and a test piece (50am rljx
350 van length) was sandwiched between the pads, and grasped the top end of the specimen with the chuck of the tensile testing machine.Next, the hydraulic jack was operated to keep the pressure between the pads constant. While keeping the pressure of the pressure gauge constant, the test piece was pulled using a tensile tester, and then it was pressed with a blade. Using the same principle as the tension pass on an actual slit line, the electrogalvanized steel sheet was tested. Evaluate the ease with which scratches form on the plating layer and the difficulty with which scratches form.

In order to determine the evaluation conditions with this simulation test machine, samples were collected from coils that were easily damaged and coils that were difficult to scratch on an actual Surin 1 line, and tested using the simulation test machine shown in the figure. , pressurizing force 80 kg/cl, pulling speed 50 cm/min
We confirmed that it is possible to perform a simulation test of the situation on the actual line by applying the same test piece three times with the same putt. In addition, it was decided to evaluate the state of flaws on the specimen after pulling out using a 5-point method as follows.

” L Sada J Survival 5 points: 4 points if there are no flaws: 3 points if there are 5 or less fiber flaws in Pano I: 2 points if there are 10 or more fiber flaws on the pad: 2 points if there are fiber flaws in the pad 1 point if there were defects caused by zinc powder partially; If the specimen had batt defects and defects caused by zinc powder almost entirely on the entire surface, if the score was 3.5 or more, there was no problem in practical use.

Next, an example in which the present invention was implemented on an actual operation line will be specifically described.

N-side stopping plating solution composition: Zn5O< ・71h0 400g/
nNa2 S04 75g / 1 plating liquid pu: 1.8 Distance between electrodes: 35 mm Plating temperature: 60°C Current density: 50A/dm2 20g/n on a cold rolled steel plate with a plate thickness of 1.0 Dragon X9141ml1 under the above plating conditions An electrogalvanized steel sheet, which is generally referred to as an untreated product without any post-treatment, was produced by galvanizing the steel sheets.
and strontium carbonate at a rate of 10 mg/β.'' Electrogalvanized steel sheets plated with a basis weight of 20 g/rrr were manufactured under the same conditions as described in Section 2, and samples from these coils were used in the simulation test machine described above. In addition, the ease and difficulty of forming flaws due to tension pads on an actual slitting line was evaluated for the coils actually obtained. As a result, the plated layer with no additives had significant tension pad flaws, whereas the plated layer with both additives had no flaws and was in good condition.

Actual 1''1 Illusion After electrolytic galvanizing was performed using a plating solution with and without the addition of dextrin and strontium carbonate under the same conditions as in Example 1, chromate treatment was performed as a post-treatment to produce electrolytic zinc with a chromate deposition amount of 30 mg/m. A plated steel plate was manufactured, and its tension pad resistance was evaluated using the same simulation test machine as in Example 1 and an actual operating slitting line, but the results were the same as in Example 1.
g/j! The plating solution in which 10 mg of strontium carbonate was added to the plating solution had no flaws due to the tension pad, whereas the plating solution without the addition caused significant flaws.

Slong body 1 Additive-free plating solution and dextrin 60mg/j under the same plating conditions as Example 1! strondium carbonate 400mg
Electrolytic galvanized steel sheets with a zinc coating weight of 40 g/rr+ were manufactured on an actual production line using a plating solution containing 1.5 g/l of added plating solution, and a so-called non-treated product without post-treatment and a chromate treatment were applied in post-treatment.
An electrogalvanized steel sheet with a chromate coating amount of 2 Qmg/m was manufactured and evaluated using the same simulation test machine as in Example 1, as well as an evaluation using an actual slitting line. As a result, in the case of an additive-free plating solution, scratches due to padding were significant. The electrogalvanized steel sheet produced using the combined additive plating solution was in good condition with no scratches caused by padding.

Copper was electrogalvanized with a basis weight of 30 g/rrl by adding starch 30 mg/42 and strontium carbonate 20 mg/l- as additives to the plating solution under the same plating conditions as in Example 1. The tension pad resistance was evaluated using the above-mentioned simulation test machine on steel sheets electrogalvanized with the same coating weight without adding any additives as the strip, and the occurrence of defects in the steel sheet plating layer during slitting on an actual slitting line. The degree was evaluated.

As a result, when the above-mentioned additives were added to the plating solution, the plated steel strip was in good condition with no scratches, but when no additives were added, there were significant scratches.

The tension pad resistance of Examples 1 to 4 is summarized in the table below together with the plating conditions.

-Table 1 (7, l *:

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the slit line; 2nd FI! J is the effect of additives on tension padding resistance when electroplating is performed with a single addition of strontium carbonate or dextrin and a Me. Graph showing; Figure 3 shows the amount of dextrin added to the plating solution at 20 m
A graph showing the effect on tension padding resistance when changing the amount of strontium carbonate added together with g/n constant; and Figure 4 is a schematic diagram showing the configuration of a simulation test device for evaluating tension padding resistance. It is a diagram. 1: Tension pad 2: Electrogalvanized steel sheet 3: Recoiler - 4 Nisrisoku 1 Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Akira Hirose - 1 Fig. 4 = 2 Fig. #3 Fig. KJ amount ("12/l) procedure - series official book (method) % formula % 1. Indication of the incident 1982 Patent Application No. 041237 2. Name of the invention Method for manufacturing electrogalvanized steel sheet 3. Amendment Relationship with the case filed by the person applying for the patent Patent applicant Address: 5-15 Kitahama, Higashi-ku, Osaka Name (211”) Sumitomo Metal Industries, Ltd. 4, Agent Å

Claims (1)

[Claims] 5 to 100 mg/71 of dextrin, which is a polyyM compound or its hydrolysis intermediate, and 5 to 71 mg of strontium carbonate.
~500 mg/j! Electrolytic zinc metal added in combination with
A method for producing electrogalvanized steel sheets with excellent tension pad resistance, which is characterized by applying electrogalvanization to steel sheets using a coating solution.