JPS59198142A - Weldable coated steel plate - 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 weldable coated steel plate coated with Zinoclinch candy, which has improved corrosion resistance and clouding resistance of the coating film.

High degree of corrosion resistance in recent years'? For applications that require IZ and require electric welding during assembly, weldability @ steel sheets painted with zinc-rich paint and chemically treated steel sheets are used.
a f (However, since the conventional zinc clinch coating on weldable painted steel sheets is a mixture of metal powder and a single layer of zinc, the corrosion resistance is not necessarily sufficient, and 7Q
Since the content of zinc powder is usually 80% by weight or more in order to provide electrical conductivity, the zinc powder tends to peel off and break up.
It had the disadvantage of poor powdering resistance. For this reason, when spot welding T and C are performed, the zinc powder adheres to the chip and builds up, making it difficult to increase the number of continuous welding points, and when press working is performed, how many zinc powders are deposited on the mold, There were patches of damage to the coating.

The present invention provides a weldable coated steel sheet that does not have such drawbacks, and by adding zinc-magnesium alloy powder and manganese powder in addition to zinc powder in the coating film.
The writing defects have been eliminated.

Uninvented weldability @ steel manufacturing, the plate is schematically shown in Figure 1 of the attached drawings, where a chemical conversion coating 2 is formed on the surface of a steel plate 1, and a chemical conversion coating 2 is formed on the surface of the steel plate 1. Zinc powder 3,
A zinc-rich coating film 6 containing three types of metal powders, zinc-magnesium alloy powder 4 and manganese powder 5, was formed.

These constituent elements will be explained in detail below.

Steel plate 1 is a common steel cold-rolled steel plate, but the surface has an average surface roughness R.
It is preferable to use 4 to 20μ roughened awns.

Does this increase the amount of chemical conversion coating 2 to improve corrosion resistance? This is because the distance between the welding tip and the steel plate 1 is shortened to improve electrical conductivity (or the awn has an anchor effect on the zinc clinch coating 6).

The chemical conversion coating 2 may be a generally known coating such as a phosphate coating, a chromate coating, or an organic silicate coating, but a chromate coating is suitable for corrosion protection. ! The octopus film may be a multi-layered film made by combining 2'Jf#i and 2'Jf#i of known materials.

Generally speaking, how to form a chromate film is by reactive chromate treatment, or by no-rinse applied chromate treatment. Call 1! Although there is a method using L-dissolved chromate treatment, in the case of the present invention, it is preferable to use a one-coat chromate treatment for corrosion prevention and coating adhesion, especially a one-coat type chromate treatment using a treatment solution such as the composition shown in Kf. Yes.

Treatment liquid 1 (10 parts by weight of chromium trioxide, 8140-50% reduced to trivalent state (b)) Phosphoric acid (100% H3po4) 3-4 parts by weight (C
) 4 to 5 N parts of polyacrylic acid (d) Acrylic emulsion heavy shore solid content 17 to 2 ON
Parts (200 to 4,000 parts by weight of water to make an EL aqueous solution) Treatment liquid 2 If the composition of the previous 6C treatment liquid I is 8, all or part of the hexavalent chromium in the chromium trioxide in (a) is A treatment liquid that is reduced to a trivalent state and has a ratio of hexavalent chromium amount/trivalent chromium amount from 0 to 2.3.

In the case of this chromate film, the amount of pressure film is controlled by the total amount of chromium contained in the film, and the total chromium amount is IO ~
Make sure you have a size 50 back. Is this I O"I/rr?
If it is less than t'1.7, the corrosion resistance will be poor, and the coating film adhesion will not be stable, and good dense layer property will always be obtained. Because it is C. -), ' 50 i When it is packed with 3R, the anti-corrosion property is the same as above, but the layer strength of the hyphenate layer becomes low and it becomes easy to peel off during press working etc.

Zinc-rich coating film 6 is made by adding a zinc-magnesium base metal powder bed and manganese powder to the conventional zinc-rich coating film containing only zinc powder to improve anti-corrosion properties, resistance to wiping,
It's been a long time since I've been in the middle of a long time.

Here, the addition of zinc-magnesium alloy powder and manganese powder improves the corrosion resistance fPjt, the long joint, the rolling resistance during processing, and the continuous dot performance of spot welding. This is because I looked up and down.

The reason for this is thought to be as follows. First, the reason for the improved durability of corrosion resistance is the magnesium in the lead-magnesium alloy (see Box 1). When manganese and manganese are exposed to a corrosive environment, stable corrosion products are formed, and when they change into corrosion products, excessive amounts of zinc may occur because both white metals and manganese are electrochemically less noble than zinc. It is presumed that this is done to alleviate the nicking effect. Next, the zinc-magnesium alloy has higher hardness than zinc as shown in Figure 2 (and manganese also has a harder hardness), so it can be used in press working dies and welding tips. I think this is because manganese has a lower melting point than zinc, so it is difficult to melt during resistance welding, so it is less likely to form an alloy in the welding tip. This improves the continuous dot performance of spot welding.

The mutual mixing ratio of these zinc powders, zinc-magnesium alloy powder S, and manganese powder is 2 to 2 when the total amount of these all-pole powders is 100%.
Make it 96% by weight.

Here, the mixing ratio of each metal powder was set to 2 to 96% by weight.In the case of zinc powder, if the amount is less than 2% by weight, the galvanic effect of zinc will not be fully exerted, and if the amount exceeds 96% by weight, other This is because even with the addition of Kinpo powder, there is no difference from conventional zinc-rich coatings. In addition, in the case of zinc-magnesium alloy powder, if the content is less than 2% by weight, the action of suppressing the excessive galling and galling action of the zinc powder will be reduced, and the durability of the corrosion protection will be reduced. In addition, the resistance to nozzle ξ during spot welding and processing does not improve, and if it exceeds 96% by weight, M1! The content of button and manganese powder is low.
7. r! II. In the case of corrosion resistance, continuous spot welding performance, etc., the objective may not be achieved. There is a problem with the durability of corrosion resistance, and there is no improvement in continuous hammering performance in spot welding. The amount decreases and corrosion protection occurs.

The three metal powders mentioned above are made to have a total amount of tifJ~91% by weight in the zinc clinch coating 6.

If the amount is less than 600% by weight, the conductivity will be low and 91
This is because if it exceeds the weight percentage, the adhesion of the coating film will decrease.

F zinc-magnesium alloy powder (d) with a magnesium content of O1 to lo, W&jt% is preferred.

, Knee, f'Lkekoyo lLc'@Kaku-zuke thing]
This is because it is manufactured by a second trader and is inexpensive.

Epoxy resin having a molecular weight of 10,000 to 100,000 is preferable as the inder for bonding each metal powder in terms of quality and workability.

The coating film thickness should be 5 to 50 μm when dried. 5
If it is less than μ, the corrosion resistance will be poor, and if it exceeds 50 μ, the surface roughness of the steel plate will increase (even if it is, the conductivity will be low).

If the zinc-rich coating film 6 contains the three types of metal powders mentioned above, its anti-corrosion property will last significantly, but if a higher degree of corrosion resistance is required, the anti-rust coating film 6 should be It is also possible to add 0.2 to 5% by weight. Suitable examples of this antirust pigment include strontium chromate, zinc chromate, and calcium plumate. Here, the amount of the anti-corrosion pigment is 02 to 5% by weight.If it is less than 0.2% by weight, no effect can be obtained, so if it is less than 5% by weight? This is because, if it exceeds the range, the elution of hexavalent chromium and the like from the second surface of the membrane becomes significant, and the anticorrosive effect becomes saturated. In addition, it is not prohibited to add colored pigments other than anti-corrosion pigments for coloring within a range that does not impair coating film performance such as weldability and anti-corrosion properties.

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

Example 1 A cold-rolled steel plate with a thickness of 0.8rrtn was subjected to a dull skin pass and roughened to a surface rIfIinRz = 20tt, and then degreased.
A coating type chromate treatment with a certain composition is applied to the roughened surface, and after application, it dries without washing with water to completely remove chromium and
20 w'rr? A chromate film was formed. Thereafter, an epoxy paint containing zinc powder, zinc-magnetic alloy powder, and manganese powder was coated on the chromate film, and this was baked at 250°C for 60 seconds to form a zinc clinch coating with a dry film thickness of I5μ. . Table 1 shows the performance of the weldable coated steel sheet obtained here, together with the mixing ratio 8 and content of residual disease powder in the coating film.

Composition of coating type chromate treatment liquid Chromium trioxide 10 parts by weight/acid
3.5 parts by weight polyacrylic acid
4 parts by weight of acrylic emulsion 1 part of combined solids 2 parts of water
2.000 parts by weight Cr+6/Cr+3-L
5. Coating-type chromate treatment liquid/The coating film performance was investigated in the following manner.

(1) Paint film adhesion A bending test was conducted according to the test method for colored lead iron plates of JIS-G 3312. The bending test was performed using 180 degree dense new bending with 0 sheets (Ol), 1 sheet (1 t), and 2 sheets (2 t) at intervals on the inside of the bend, and then applying Cellotape to the processed part coating. If fL was suddenly scratched, cellophane tape was peeled off, and the damage was evaluated according to the following criteria.

(2) Rust-preventing lubricating oil (
OilCo) Z2, made by Izumoto Kosan) was coated and punched with a 300 ton hydraulic press machine with a punch diameter of 2ooa and a punch Ro of 3m.
, die R4mx, aperture 9 height 65■, full crease presser 22
A cylindrical deep drawing test was conducted with the coating on the outside under the following conditions, and after the test, the die mold Kf7 was rubbed off with abrasive paper, and the amount was visually evaluated and evaluated using the following criteria. .

(3) Cross-cut the anti-corrosion test piece with a knife in advance, and
The one tested with 180 degree new bending and the one tested with deep drawing for front-end resistance and bending/grinding resistance -> JIS-Z
・Based on 237I, 7 tL each 1000 hours and 24
The test was conducted for 0 hours and evaluated based on the following criteria.

Cross-cut parts 2 and 4 are bent and press-processed part (deep-cut outer circumferential surface) (4) Weldability After performing spot welding under the above-mentioned welding conditions, a tensile test was conducted, and the tensile shear strength was 350, but less than 9f occurred. At a certain rate and constant welding condition, the number of consecutive hits was eclipsed.

The welding conditions for tensile shear strength were the following three conditions, and the welding conditions for the number of continuous welding points were: using a 4.5Ω-CF electrode, applying force 250 Kp, current application time (cycle) 12, and current 7.
It was performed at 500 A. In the latter case, the tensile shear strength was determined at the point of Vjtoo, and the life of the Chemi electrode was determined when the strength was lower than the allowable upper limit shown in LWMA.

(a) Medium welding conditions) Tensile shear wT bending degree 35 (first occurrence rate of less than lyf)
As is clear from the coating, when the coating film contains zinc-magnesium alloy powder and 17 ng powder, the corrosion resistance and powdering resistance of the zinc powder alone are improved.

[Brief explanation of drawings]

Fig. 1 is a schematic vB side view of the weldable coated steel plate of the present invention, Fig. 2
The figure is a graph showing the relationship between the amount of magnesium and hardness of a zinc-magnesium alloy. 1. Steel plate, 2. Chemical conversion coating, 3. Zinc powder bed, 4.
・・Zinc-magnesium base metal powder bed, 5.・Ma/gan powder, 6.・Ginoclinch coating film patent applicant Mitsuru Susumu Fuji (16), representative of Nissin Steel Co., Ltd. No.] Figure 2

Claims (2)

[Claims] (1) Chemical conversion coating on the steel plate surface? A coating film containing zinc powder, zinc-magnesium alloy powder, and manganese powder in total of 60 to 91% by weight is formed, and each metal powder in the coating film A weldable coated steel sheet characterized in that the mutual mixing ratio is 2 to 98% by weight. (2) Zinc-magnesium alloy powder contains magnesium i0. The weldable coated steel sheet according to claim 1, characterized in that the weldable coated steel sheet has a content of I to IO.