JPS5952646A - Welding painted steel plate having excellent powdering-resisting property - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zinc chlorine-based melt coated copper plate that causes less powdering during processing such as press working.

In recent years, in the case of automobile bodies, areas where corrosion protection is essential such as undercarriages and doors are coated with phosphate coating II and chromate coating on cold-rolled steel plates.Weldable coating is applied by coating zinc-rich paint on top of the phosphate coating II and chromate coating. EL board is used. Conventionally, this type of coating - the zinc-rich coating film on J414 board was simply a coating containing a bed of zinc powder, but its anti-corrosion properties were improved by hot-dip galvanizing, (1. It is more ambiguous.1~ Since zinc rich coatings contain polyacid (usually 80% by weight or more) zinc powder to provide electrical conductivity, they have the disadvantage of causing powdering during press processing. there were.

The present invention provides a zinc-rich type steel sheet with improved removability [91], which improves the powdering defect of the zinc-rich coating film.

Is the present invention a zinc ridge containing high zinc powder content? h As a result of various studies to improve the rigid powdering properties of JIlJ, we found that adding zinc-magnesium alloy powder to zinc powder improves the powdering resistance and also improves the resistance. The gist of this work is to roughen the surface, form a phosphoric acid film and a chromate film sequentially on the board, and then apply zinc powder and zinc-
Formation of a zinc-rich coating film containing 60% or more of magnesium alloy powder.

The present invention will be described in detail below.

In the coated steel sheet of the present invention, as shown in the attached drawing, a phosphate film 2 and a chromate film 3 are sequentially formed on the surface of a steel sheet 1, and on top of the chromate film 3, zinc powder is further applied. 4 and zinc-magnesium alloy powder 5
A zinc-rich coating film 6 is formed thereon.

As the steel plate 1, a cold-rolled steel plate is usually used, but one with a roughened surface is used. This improves corrosion resistance by increasing the amount of phosphate film 2 and chromate film 3 deposited, improves electrical conductivity by shortening the distance between the welding machine tip and steel plate 1, and provides an anchor for the zinc-flitch coating 6. This is to measure the adhesion of the coating film due to the applied force, and the appropriate surface roughness is an average surface roughness Rz of 4 to 20 it. Usually, if it is less than 4μ, the above-mentioned effects cannot be obtained,
If it exceeds 20μ, the surface of the paint film will become rough, the corrosion resistance will decrease, and during processing, the distortion of the paint film will be concentrated on the convex parts, making it easy to cause the paint film to peel off. It improves paint film adhesion and corrosion resistance by working with the chromate-based film 3, and its phosphates include, for example, iron phosphate, zinc-iron phosphate, or mixed phosphates containing these salts. It is. In general, these phosphate films do not form a uniform film if the amount of the film is too small, and if the amount of the chromate-based film 3 is increased, the decrease in film adhesion due to the increase cannot be compensated for. On the other hand, if the amount of film is too large, the electrical conductivity between the steel plate 1 and the zinc-rich coating film 6 will be reduced, impairing weldability. Therefore, the film amount and [- are 1 to 50
Preferably it is 0 mg/m2.

The chromate-based film 3 is formed with the main goal of anti-corrosion properties, and for that purpose it is necessary to
'('';Y: It is preferable to increase the amount. However, in the case of chromate peel +, + < a, increasing the coating amount will reduce the coating density. For this reason, when forming the coating directly on the steel plate, the conventional coating Although there was a limit to the increase in the amount, when a phosphate film is present on the lower side, the film !fl: can be increased without reducing the adhesion of the film.

In the case of the present invention, the chromate-based film 3 is formed by a known chromate treatment method such as reactive chromate treatment (for example, chromic acid alone or with an etching agent added to it), no-rinse coating type chromate treatment, or electrolytic chromate treatment. The one you did is fine. However, after various studies, it is preferable to use a coating type chromate treatment liquid having the composition shown below in terms of corrosion protection and coating film adhesion.

Treatment liquid 1 (a) 10ffi parts of chromium trioxide in which 40 to 50 parts have been reduced to a trivalent state (b) Renp (100 CH IT31) 0. ) 3-4
Heavy 1 part (C) 4 to 5 parts polyacrylic acid (d)
Acrylic emulsion polymer solid content: 17 to 20 parts by weight (e) Water for making an aqueous solution: 200 to 4,000 parts All or part of the valent chromium is reduced to a state of 3 x 1, and the ratio of hexavalent chromium amount/trivalent chromium h1 is 0 to 2.
The processing liquid has become 3.

In the case of the present invention, the chromate-based coating 3 is controlled in all areas of chromium contained in the coating, so that the total chromium content is 10 to 50 mg/m2.

This is because if it is less than iomg/m, the anticorrosion property will be poor and the adhesion of the coating will not be stable, making it impossible to always obtain good adhesion. On the other hand, if it exceeds 50 mg/♂, the corrosion resistance improves, but the adhesion to the coating decreases and it becomes easy to peel off during press working.

Zinc-rich coating film 5 is a film that improves powdering resistance and corrosion resistance during processing by adding zinc-magnesium alloy powder to the conventional zinc-rich coating film that only contains zinc powder. The mixing ratio is Zn powder/Zn-
Adjust the Mg alloy powder to be 50150 to 98/2. The reason why the upper limit of the amount of zinc-magnesium alloy powder added to the zinc powder was set at 50 g is because even if the amount exceeds 50 g, no further improvement in powdering properties or corrosion resistance can be expected. On the other hand, setting the lower limit to 2 yen means that it is less than 2 yen.
This is because there is no JII effect, and the powdering resistance and anticorrosion properties are almost the same as those of zinc powder alone.

Further, if the total content of zinc powder and zinc-magnesium alloy powder in the zinc-rich coating film 6 is less than 0.001, the electrical conductivity will decrease and the electric weldability will deteriorate, so the content is made to be 60 or more. If the I-edge exceeds 91 inches, the resistance to peeling due to processing decreases, so the K is adjusted to 91 inches or less.

The resin for the coating film containing the meat powder has a molecular weight of 1 to 1.
00,000 linear epoxy resin is preferable in terms of quality and workability.

If the thickness of the coating film (dry coating film) is less than 5μ, the anticorrosion properties will be poor, so the thickness should be 5μμ or more. However, if it exceeds 50μ, the conductivity will not be improved even if the surface roughness is increased.
Make it as follows.

Regarding corrosion resistance, zinc powder and '! J! If the corrosion resistance of the lead-magmagnesium alloy powder is insufficient and a higher degree of corrosion resistance is required, it is also possible to add a rust preventive pigment. Suitable anti-rust pigments include strontium chromate, zinc chromate, calcium plumate, etc., and 0.2 to 5 tons of these are added. If more than 5q6 is added, the elution of sirovalent chromium from the coating surface becomes significant, the anticorrosive effect is saturated, and the effect of increasing the amount added is small.

In the case of the present invention, as mentioned above, when a zinc-rich coating film contains zinc powder and zinc-magnesium alloy powder, the powdering resistance and corrosion resistance during processing are improved.The reason for this is thought to be as follows. It will be done.

First, regarding the powdering resistance, this is thought to be due to the fact that the hardness of the zinc-magnesium alloy powder is significantly higher than that of zinc. In other words, in general, when the hardness of the powder increases during press processing, the amount of powder adhering to the mold decreases.
Zinc-magnesium alloy powder, which has a higher hardness than zinc powder, has less adhesion to the mold, resulting in:! iP: It is thought that powdering resistance is improved.

On the other hand, the anti-corrosion property is thought to be due to the galvanic action suppressing effect of subtik-magnesium metal on zinc.

Magnesium is electrochemically more powerful than zinc, but when placed in a corrosive environment, it produces stable corrosion and also reduces the galvanic effect against lead.1 Therefore, although the details are unknown, It is estimated that zinc-magnesium alloy also exhibits the same effects as magnesium. Therefore, when a lead-magnesium alloy is included, the self-consuming positive galvanic action of zinc is f+lU
tf (J), it is thought that the elution of 8 or more loads of zinc is suppressed and the corrosion resistance is improved.

In the case of the present invention, when the zinc-rich coating film 6 contains the scolded lead-magnesium alloy powder together with the zinc powder, the powdering resistance and corrosion resistance are improved compared to the case where only the zinc powder is used, but it is desired to further improve the corrosion resistance. In such cases, anticorrosion pigments are added as described above. The effect of adding this anti-corrosion pigment is similar to that of zinc-magnesium alloy powder, and in addition to the anti-corrosion effect of the anti-ft MrR material itself, it completely cures the effect of suppressing excessive elution of saliva buttons.

In the case of the present invention, there are no particular limitations on the magnesium content of the zinc-magnesium alloy, but one that can be produced on an industrial scale of 1 to 5 inches is preferred from the viewpoint of workability and quality. This is because, in the case of zinc, when magnesium is added, the hardness increases rapidly as shown in FIG. 2, and alloys with arbitrary components can be used in relation to corrosion resistance.

Next, the effects of the present invention will be explained with reference to Examples.

Table 1 shows the surface of a cold-rolled plate (thickness Q, 8 mm) that has been roughened to RZ-15μ by a dull skin pass.
m phosphate film and 13:jQ'74', 7
0 mg/In (all chromium needle) chromate incomplete 1! ! ,! ', and on top of that, a divine zinc clinch coating with a thickness of 15 μm was formed. The formation of the 11 phosphate coatings, romate coatings, and zinc-rich coatings was conducted under the following conditions. .

(1) Lin 11;? Basic 1 conversion formation conditions commercially available phosphorus five-sankaku treatment/! (Granodine 4f3, N-1) i 1
Sprayed for 0 seconds.

(2) Chromate yarn 1i city) Formation reliability 10 tons part of chromic acid trioxide, 3 parts by weight of phosphoric acid, 5 parts by weight of polyacrylic acid
Heavy (juice j'fls % - acrylic emulsion j1
i; 1 piece of hard cedar, 18 weights, 14 pieces of water, 2000 weights of water (Shade B
A coated chromate treatment solution consisting of %Cr+6/Cr""3=,=1.4 was applied by roll coating.

(3) Forming a zinc-rich coating film by baking at 250℃ (board temperature) for 60 seconds after coating using the roll coating method.

Dimension coating film It, fit: Adjust as follows.
-It is.

(1) Coating film 2υeffect゛'i: ilyuJ IS G
A 111 bending test was conducted in accordance with the test method for colored galvanized iron sheets of No. 3312. The bending test was performed using 0 sheets (O
t), 1 piece (1t), 2 pieces (2t) T 180〉Ft Post-addition after bending ．． 11. ;i
N Paste cellophane tape on the membrane, then remove the cellophane tape and remove the cellophane tape.
I did li.

(2) Powderability test: After cutting the test piece into a blank with a diameter of 360mm, apply anti-rust lubricant (Oil Coat Z2, manufactured by Idemitsu Kosan), and use a 300 ton hydraulic press with a punch diameter of 2QQIAm and a punch R13.
rlm S die R4Jm % drawing height 65 mm,
A cylindrical deep drawing test was performed with the applied material facing outward under the conditions of a 22-ton presser. After the test, the powder that had been poured into the die mold was rubbed off with iJI4 paper, and the amount was measured at 14 locations. 1 and evaluated based on the following criteria.

(3) Cross-cut the raw test piece with a knife in advance, and
1t of 180 degree density bending of t, and r'if
r Powdering resistance (n bet- [) v The drawing test was performed in accordance with JIS Z 2371, and L is 500.
240 hours: 1 yen time test, imaginary I, rating 6■shi based on the following criteria.

Cross-cut part and 4ttr+-bending part press-processed part (chi outer peripheral surface) We investigated the incidence of

(b) It'r contact shield (cow (b) Tensile shear direct elasticity: As is clear from table 1 of the original rate of less than 350 kgf, powder content; even if A is the same, the Those containing magnesium alloy powder have better electric weldability and corrosion resistance.
Raw is resistant (・Blue, improved by adding pepper.

As described above, according to the present invention, the rigid powdering of a yosin-rich coated steel sheet is improved to i4, and the corrosion resistance is improved accordingly.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the coated steel of the present invention, Saka's horizontal hole IQi, and FIG. 2 is a graph showing the relationship between Mg leaf and hardness of Zll Mg alloy. 1... Ridge, 2... Phosphoric acid coating, 3... Chromate thread; 1 plane, 4-... 1 also lead-shaped wood, 5... A-Ling-Magyo-shisom alloy powder.・・ΦZin clip lηmil1H0 Q("r,j'l・Careful 1 person Eye view [1 Tai Komaishiki company Mitsui Kin hI4 Mining Co., Ltd. agent Mitsuru Hitomi Figure 1 Figure 2 M9°/ = Continued from page 1 0 Inventor: Katsu Suzuki Ichikawa Research Institute, 1st Shin Steel Co., Ltd., 7-7 Takaya Shinmachi, Ichikawa City 0 Inventor: Kimi Sanefuji - Funabashi Type Kaishin 2-12-17 0 Inventor: Hiroki Kuyama 628-19 Hagidai-cho, Chiba-shi 0 Inventor 1556-4 Masuo, Hakuso-shi, Narabe 0 Inventor Juntabe Kobayashi 1-1-2 Sekino-cho, Koganei-shi 0 Applicant Mitsui Kinzoku Mining Co., Ltd. Nihonbashi, Chuo-ku, Tokyo Muromachi 2-1-1

Claims (3)

[Claims] (1) A phosphate film and a chromate film are sequentially formed on the surface-treated steel sheet, and then a chromate film is formed.
A weldable coated copper plate with excellent powdering properties, characterized in that a zinc-rich coating film containing a total of 60 or more zinc powder and IF lead-magnesium metal powder is formed. (2) The ratio of zinc powder/zinc-magnesium alloy powder!
io / 50 to 98/2, and the powdering resistance as set forth in claim 1, wherein the total 1i1: of both in the coating film is 60 to 91 heavy metals.・Scattered weldable painted steel plate. (3) The weldable coated steel sheet with excellent powdering resistance as set forth in Claim 1 JLJ, characterized in that a rust preventive head is added during one change of zinc-rich coating.