JPH0488176A - Galvanized steel sheet excellent in weldability, workability in pressing and chemical convertibility - Google Patents

Abstract

PURPOSE:To obtain a galvanized steel sheet excellent in chemical convertibility as well as weldability and workability in pressing by coating the surface of a galvanized steel sheet with an oxide layer essentially consisting of a specified amt. of ZnO and coating its upper layer with an oxide layer of specified amounts of Mn, P or the like. CONSTITUTION:As the amt. of ZnO, 30 to 3000mg/m<2> oxide is formed on the surface of a galvanized steel sheet. Its upper layer is coated with one or >= two kinds among the oxides of Mn, P, Mo, Co, Ni, Ca, W, V, etc., or boric acid by 1 to 500mg/m<2> as the amt. of metals in the oxides. If required, the oxide layer on the upper layer is furthermore incorporated with 1 to 500mg/m<2> of one or >= two kinds among SiO2, TiO2 and Al2O3. In this way, the galvanized steel sheet excellent in weldability, workability in pressing and chemical convertibility can be obtd. The above oxide film essentially consisting of ZnO can easily be formed by bringing the galvanized steel sheet into contact with an aqueous soln. of an oxidizing agent contg. acid. Moreover, the above oxide film of Mn or the like can surely be formed by immersing the galvanized steel sheet into an aqueous soln., or spraying it with an aqueous soln. or subjecting it to cathode electrolytic treatment in an aqueous soln.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a zinc-based plated steel sheet with excellent weldability, pressability, and chemical conversion treatment properties.

(Conventional technology) As a method to improve the weldability of zinc-based plated mesh plates,
For example, as shown in Japanese Unexamined Patent Publication No. 55-110783, an oxide film such as AtZ03 is formed on the surface of a plated mesh plate, and the high melting point and high electrical resistance of the oxide are used to improve weldability and to form an electrode. It has been proposed to prevent contact between the chip and plated metal to prevent chip erosion and prolong its life.

Furthermore, as shown in JP-A-59-104463, an oxide film with a ZnO/Zn ratio of 0.1 to 0.70 is generated on the surface of a plated steel sheet by heat treatment, which also improves weldability. It is proposed that

However, even with such a method, it is still difficult to obtain satisfactory results on an industrial scale, and there is a strong desire to improve the weldability of plated steel sheets.

In addition, as a method for improving the pressability of a galvanized steel sheet, for example, as described in JP-A-62-185883, the surface of the galvanized steel sheet is subjected to electrolytic chromate treatment,
As described in JP-A No. 62-192597 and the method of generating a Cr2O3 oxide film, a hard film is formed on a zinc-plated steel sheet to prevent galling of the plating and dies during pressing, thereby improving the press performance. A method for improving lubricity is disclosed.

Furthermore, as described in JP-A-1-136952, it is disclosed that the surface of a plated steel sheet is coated or coated with an organic substance such as an organic lubricating film or lubricating oil to improve pressability.

(Problems to be Solved by the Invention) However, such products have the following inadequacies when used by automobile users and the like.

The general usage process for automobile users consists of a process of cleaning steel sheets with oil, a pressing process, a degreasing process, a chemical conversion process, and a painting process. In the case of a steel plate that does not form a film or has lubricating oil or a lubricating film applied to the copper plate, sufficient lubrication performance will not be achieved because the oil will come off during the cleaning process.

Furthermore, the degreasing process before the chemical conversion treatment is burdensome and costs increase. On the other hand, zinc-plated steel sheets subjected to iron-zinc alloy flash plating have problems such as higher copper sheet costs compared to electrolytic chromate treatment, but are low cost, can be chemically treated, and can be degreased, etc. There is a desire to develop a galvanized steel sheet that does not place any stress on the process and has excellent pressability.

Furthermore, as mentioned above, there is a strong demand for zinc-based plated steel sheets that have excellent weldability, pressability, and chemical conversion treatment properties.

(Means for solving problems) The gist of the present invention is as follows.

(1) The amount of ZnO on the surface of zinc-based plated steel sheet is 30 to 300
0 mg/m2 oxide, and one or two of Mn oxide, P oxide, Mo oxide, Co oxide, Ni oxide, Ca oxide, W oxide, ■ oxide, or boric acid on the upper layer. Weldability, pressability, characterized by coating the above with 1 to 500 mg/m2 (as the amount of metal in the oxide),
Zinc-based plated steel sheet with excellent chemical conversion treatment properties.

(2) SiO□, Ti0z, 8120 in the upper oxide layer
The zinc-based plated steel sheet having excellent weldability, pressability, and chemical conversion treatment properties according to item 1 above, which contains one or more of the following 1 to 500 cm/bo.

The zinc-based coated steel sheets that are the object of the present invention are produced by various manufacturing methods such as hot-dip plating, electroplating, vapor deposition plating, and thermal spraying, and the plating composition includes Zn, Fe, and Zn in addition to pure Zn. and Ni, Zn and AI.

Zn and Mn, Zn and Cr, Zn and P, etc. with Zn as the main component, type 1 or 2 to improve various functions such as corrosion resistance.
Contains more than one alloying element and impurity element.

There are also ceramic fine particles such as SiO□ and aZ2O3, oxides such as TiO□, and organic polymers dispersed in the plating layer. There are some whose composition changes. Also covered are steel sheets coated with organic coatings in which Zn-based particles are dispersed on these platings. For example, alloyed hot-dip galvanized steel sheets are made by heating and alloying the coating layer of hot-dip galvanized steel sheets with the base iron, and zinc and its alloys (for example, iron) are formed by electroplating or vapor deposition plating.

Steel sheets plated with nickel, chromium, etc.) and steel sheets that are heated to 200 to 550°C and alloyed with the base iron, and not only single alloy layers but also multi-layer alloys formed by electroplating, etc. Plated items, S in the plating layer
There are those in which ceramic particles such as iO□ and Al2O3 are dispersed, and there are those in which an organic film containing zinc particles is coated on the plated layer of these or directly on the steel plate. The forms of rust-proof steel sheets include double-sided plating, single-side plating, and dissimilarly plated steel sheets with different plating applied to the top and bottom surfaces.

The present inventors believe that regardless of the type of galvanized steel sheet,
As long as the plating is mainly composed of Zn, by forming ZnO on the surface of the plated steel sheet, an electrode protection metal mainly composed of Fe and Zn can be chemically formed at the tip of the electrode tip during spot welding, thereby extending the life of the electrode tip. was found to significantly improve.

In the above-mentioned conventional plated steel sheets, the oxide film mainly composed of ZnO has a ZnO content of 30 to 300, which is considered to be good for weldability.
It was unstable to generate 0 mg/m2 (per side). Here, the oxide film containing ZnO as a main component may include, in addition to ZnO, components contained in the plating layer, or compounds such as their oxides, etc., in the oxide. Further, in electrochemical treatment such as anodic oxidation, a component or a compound contained in a treatment liquid may be included.

In order to generate an oxide film mainly composed of ZnO on the surface of the galvanized layer, the present inventors used a first method to form an oxide film mainly composed of ZnO by bringing a steel plate into contact with an aqueous solution of an oxidizing agent containing an acid. The amount of ZnO is 30 to 3000 mg/m2 (
It has been found that it is possible to provide a zinc-based plated steel sheet that can be easily produced (per side) and has excellent weldability. The function of the acid is to dissolve some of the surface of the plating layer, supplying ions such as Zn from the plating layer, and increasing the pFl in the solution that comes into contact with the plating layer. Zn is oxidized on the surface of the plating layer by oxidizing Zn etc. in the bath.
It functions to form an oxide film mainly composed of nO.

As an oxidizing agent, for example, HNO: 110 to 100 g/42
By containing Zn, etc., it oxidizes and forms Zn on the surface of the plating layer.
An oxide film mainly composed of nO can be formed. 11
The reason why the lower limit of N O3 is set to 10 g/f is that if it is less than that, oxidation becomes difficult and an oxide film cannot be formed. In addition, the upper limit of HNOi is set to 100 g/f.
The reason for this is that even if the content exceeds this value, the effect as an oxidizing agent will be saturated, and Zn and Fe on the surface of the alloy layer will be dissolved, especially Fe.
This is because dissolving Fe oxides increases the production of Fe oxides, reducing the effect of improving the life of the spot welding tip.

Furthermore, as an oxidizing agent, KMnOa+Ca(CZO)z,
KzCrz07゜NaCZO:+, CIO□, KNO
,,NaN0. By adding the like, the formation of the back film is promoted.

The method of bringing the aqueous solution of Zn (No: I) z and HNO3 into contact with the steel plate may be any method such as dipping or spraying. In addition, after dipping or spraying, for example, by blowing dry heated gas onto the surface or heating the steel plate to about 100°C or less, even a thinner solution becomes a concentrated liquid due to evaporation of water, and is effective because it reacts at high temperatures. can be processed.

In this way, the composition of the oxide film etc. generated by performing the oxide film generation treatment is mainly ZnO, Fe oxide, Zn and Fe hydroxide, and whether these are alone or mixed, they do not contain impurities such as AI. It doesn't matter if it contains. but,
From the viewpoint of properties as a surface film, an oxide film containing a large amount of ZnO is desirable because it covers the surface uniformly and has a low film resistance.

In order to generate an oxide film mainly composed of ZnO, Zn
Zn(NO:+)z 100-6 as an ion replenisher
By setting the pH to 00 g/l, if the pH of the oxidizing agent aqueous solution is 4 or less, it contributes to activation of the surface of the plating layer and can supply Zn ions for generating ZnO.

The lower limit of Zn (NO3) z is set to 100 g/ffi because if it is less than that, Zn ions on the surface of the alloy layer will not be sufficient and it will be impossible to form an oxide film.

In addition, the upper limit was set at 600 g/f because if it exceeds it, too much film will be formed and the resistance will become thick (resistance heat generation with the electrode tip during welding will increase the diameter of the electrode tip. This is because it causes deterioration.

The treatment bath contains Fe and Zn in plating, and Mn as an impurity.
, AZ, P, Si, etc. may be dissolved. Among these, it is preferable to add Zn ions to the bath in advance because it eliminates the need to dissolve and supply Zn ions from the plating layer and allows ZnO to precipitate in a shorter time. Note that it is desirable to suppress the elution of other impurities to a small amount as much as possible. In particular, Fe is 1g/! If it is contained in excess of
Fe oxides and hydroxides form a resistance film, reducing the life of the spot welding tip. Therefore, although the present invention does not specify the Fe ion concentration, it is desirable to keep it as low as possible.

In order to generate an oxide film mainly composed of ZnO, a steel plate is soaked in an oxidizing agent aqueous solution containing 100 to 600 g/12 of Zn(NO+) and 310 to 310 of HNO/ffi at a bath temperature of 30 to 80°C. By contacting for 2 to 10 seconds, oxide film generation treatment can be performed.

The reason why the treatment bath temperature was set at 30 to 80°C and the lower limit was set at 30°C was to facilitate the oxidation of Zn ions on the back side of the plating, and if it was lower than that, the reaction rate was slow and it was difficult to obtain a surface film. be. Further, the reason why the upper limit is set to 80°C is that the reaction proceeds too much and excessively forms an oxide film, which impairs weldability.

However, even if the temperature exceeds 80"C, the contact time may be shortened, but since it is difficult to control the temperature to a high temperature when the contact time is shortened, it is desirable that the temperature is 80"C or less.

For this reason, depending on the balance with the line speed, the contact treatment time such as dipping or spraying is set to 0.2 to 10 seconds because if it is less than 0.2 seconds, the oxide film formation treatment is insufficient.
This is because weldability does not improve, and even if the treatment exceeds 10 seconds, too much oxide film is formed, which worsens weldability.

Further, as a second method, for example, Zn(NO3)z
・611□0:400g/l, FINO3: 1g
/ In an aqueous solution of 1, using a zinc-based plated steel plate as a cathode,
Current density 1-20 A/dm", processing time 0.5-1
An oxide with excellent weldability can be generated in 0 seconds.

Furthermore, as a third method, an oxide film mainly composed of ZnO can be reliably produced by performing alloying treatment and oxide film generation treatment after hot-dip plating, electroplating, or vapor deposition plating. As a specific method, for example, an alloying furnace for producing alloyed hot-dip galvanized steel sheets is heated to a temperature of 4.0.
Air water is adjusted to 0 to 800°C, passed through the furnace at a speed that completes alloying to the surface, and then water and air are injected with an air water nozzle to ensure the dew point of the atmosphere. The treatment can also effectively cause an oxide film formation reaction. Furthermore, by performing alloying treatment and oxide film generation treatment after hot-dip plating, electroplating, or vapor deposition plating outside the line, it is possible to reliably generate an oxide film mainly composed of ZnO. If a method similar to the above-mentioned method is adopted, the reaction for forming an oxide film mainly composed of ZnO can be performed reliably and effectively.

In addition to the above-mentioned air and water treatment, the oxide film generation process may include injecting electricity onto the plating surface to generate an oxide film mainly composed of ZnO, or using a heating furnace with the dew point adjusted to an oxidizing atmosphere outside the production line. Any method may be used, such as performing heat treatment to generate an oxide film mainly composed of ZnO.

In this way, 30 to 3,000 μg of ZnO-based oxide is applied to the surface of the zinc-based plated steel sheet as an oxide with excellent weldability.
It is possible to form an oxide and form an oxide having excellent pressability and chemical conversion treatment properties as described below in the upper layer.

In order to provide press lubricity, it is effective to form a hard film on the surface. Electrolytic chromate treatment and iron-zinc alloy plating are effective in this regard, but the former cannot form a chemical conversion film, and the latter requires a large amount of treatment and is expensive.

A hard film on the surface of a galvanized steel sheet that can solve these problems is an oxide film, which can dissolve in the chemical conversion treatment solution and form a chemical conversion film, and at the same time, the coating components can be dissolved into the chemical conversion treatment solution. However, it is necessary that the chemical conversion treatment is not adversely affected.

From this point of view, the present inventors added MnP,
1 of Mo+ Co, Ni, Ca, w, v, B
It has been found that it is sufficient to form an oxide film consisting of a species or two or more species. This oxide film becomes a glass-like film similar to the chromate film, suppresses galling of the plating to the die during pressing, and improves sliding properties. Furthermore, unlike a chromate film, it dissolves in chemical conversion treatment solutions.
Since it can form a chemical conversion coating and is also a component of the chemical conversion coating, there is no adverse effect even if it is dissolved in the chemical conversion treatment solution.

The structure of acid and compound films is not clear, but Mn-0 bonds,
Other metal-0 bond, P-0 bond, B-0 bond, 5i-
It may be an amorphous macromolecular structure mainly consisting of a network consisting of 0 bonds, Ti-0 bonds, and AI-0 bonds, partially replaced by -OH, CCh 6, etc., and further replaced by metals supplied from plating. I'm guessing.

In addition, since this film is an oxide film, it does not dissolve even during the cleaning process with oil or the deoiling process, resulting in a decrease in lubrication performance.
Do not place a burden on other processes.

Phosphoric acid or boric acid and colloidal SiO2, colloidal TiOz to improve the adhesion and film formability of the oxide film.
, 500mg of one or two types of Colloidal Hachi 1203
/m2 or less (P, 5iOz, Ti0z+ A7
Mix z (as h). In this way, the oxide film structure is made uniform, film formability is improved, press formability is improved, and chemical conversion treatment properties are also improved.

Such an oxide film can be reliably produced by immersing a zinc-based plated steel sheet in an aqueous solution, spraying the aqueous solution, or subjecting it to cathodic electrolysis treatment in an aqueous solution. At this time, in the case of zinc or zinc alloy plating of the plating metal as described above, zinc, alloying elements (metals), impurities in the aqueous solution, etc. are mixed in as other oxides.

Next, the coating cover range of the coating of the present invention will be described.

In order to obtain good pressability, the amount of the oxide film should be at least 1 cm/rT for the metal, but if the film amount is 500 μ/rT
If f is exceeded, the formation of the chemical conversion film will be insufficient. Therefore, the appropriate amount of oxide film is 1 to 500 cm for metal.
/V, preferably 1 to 200 /V.

Next, the total amount of one or more of colloidal 5in2, colloidal Ti0z, and colloidal Al2O:l is 500 ■/bo or less (as Sin2, TiO□, A7.o), preferably 200 ■/bo or less. Well, 500■
/A, chemical conversion treatment properties may deteriorate.

A lower limit of 1/bo is sufficient.

Next, as a method for producing the above oxide film, for example, Mn-based oxides include potassium permanganate, phosphoric acid, boric acid, sodium borate, ammonium molybdate, phosphomolybdic acid, ammonium tungstate, phosphoric acid, Lg/l as chlorides, sulfates, or phosphates of tungstic acid, tungstic acid, ammonium vanadate, cobalt, nickel, calcium, etc.! ~
A bath containing phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, etc. is used to limit the solubility and promote the reaction.

As Sin, Ti0z, and Al2O3, 1 to 60 gel of a solid colloidal fine particle aqueous solution, potassium silicofluoride, potassium titanium fluoride, etc. can be added.

A film can be reliably formed by immersing the aforementioned zinc-based plated steel sheet in such an aqueous solution, by spraying the aqueous solution, or by electrolytically treating it in the aqueous solution.

When the oxide film is formed in this way, a part of the plating layer and the alloy metal in the plating layer is mixed into the oxide film as other oxides.

(Example) Next, examples of the present invention are shown in the table below along with comparative examples.

Note 1) Types of galvanized steel sheets: AS: Alloyed hot-dip galvanized steel sheets (Fe10%, i 10.25%, remaining Zn
) EG, ii electrogalvanized steel sheet, Gl: hot-dip galvanized steel sheet (An O, 3%, Fe O, 8%, Pb
Zn/Zn-Cr
: 12% Cr-containing electrolytic alloy plating upper layer electrogalvanized Ig/bo steel sheet Note 2) ZnO film treatment conditions/immersion: Zn(NOx)z H6FlzO: 400
g/12, HNO3 near 0 g/f at 50°C
Z
An nO film was formed.

・Electrolysis: Zn(NO+)z ・6HzO: 400
g/j! , [lNO:l :1 g/l aqueous solution with a current density of 7 A/da using a zinc-based plated conditioning plate as a cathode"
A ZnO film was produced by electrolysis for 1 to 7 seconds.

・Air/water spray: Zinc-based plated steel sheet after alloying treatment (500
°C) Z
An nO film was produced.

Note 3) Upper layer oxide film formation conditions: Mn oxide formation is potassium permanganate = 50g/l
, phosphoric acid 10 gel, sulfuric acid 3g/2, zinc carbonate: 5g
//! The steel plate to be treated is immersed in a solution (30°C) of
After performing electrolysis at dm2 for 1.5 seconds, it was washed with water and dried.

・P oxide generation is potassium phosphate 50g/Q1, phosphoric acid 10g/j! A galvanized steel plate is immersed in an aqueous solution of
5-1OA/dm2 1-1.5 seconds).

・Mo oxide generation is ammonium molybdate = 50
g/j2, phosphoric acid: 10 g, solution of #2 (30
℃) or use the steel plate as a cathode.
After electrolysis was performed for 1.5 seconds at 7 A/dm2 using the PT electrode as an anode, it was washed with water and dried. ammonium molybdate,
The solution was prepared by adjusting the concentration of phosphoric acid, adding sulfuric acid and zinc carbonate to some parts, and adjusting the temperature of the solution, immersion time, and amount of electrolysis.

・Co oxide production is cobalt nitrate = 200g/! , Zinc nitrate: 150 g/f, Concentrated nitric acid: 1 cc/f solution at 30°C, using the steel plate to be treated as the cathode and the PT electrode as the anode, 7
A/dm" for 1.5 seconds, followed by washing with water and drying. The concentrations of cobalt nitrate, zinc nitrate, and nitric acid were adjusted to and
It was created by adjusting the temperature of the solution and the amount of electrolysis.

・For Ni oxide generation, nickel nitrate: 250g/42, zinc nitrate: 150g/f, concentrated nitric acid 1cc/ffi solution 3
After treatment at 0°C, electrolysis was performed at 7A/dm for 1.5 seconds using a steel plate as a cathode and a PT electrode as an anode, followed by washing with water and drying.The concentrations of nickel nitrate, zinc nitrate, and nitric acid were adjusted. Furthermore, phosphoric acid, sulfuric acid, and zinc carbonate were added to some parts, and the temperature of the solution and the amount of electrolysis were adjusted.

・Ca oxide was generated by electrolyzing a solution of calcium nitrate: 250 g/l and concentrated nitric acid: lcc/f at 30°C at 7 A/dm2 for 1.5 seconds using the copper plate to be treated as the cathode and the PT electrode as the anode. After that, it was washed with water and dried. The concentration of calcium nitrate and nitric acid was adjusted, and phosphoric acid, sulfuric acid, and zinc carbonate were added to the negative part, and the temperature of the solution and the amount of electrolysis were adjusted.

W oxide generation is ammonium tungstate: 20 g
#! , IJ 7 acid: 10 g/j2 of i-liquid (30°C) or by immersing the steel plate to be treated in the i-liquid (30°C) or using the steel plate as a cathode, p
The t-electrode was used as an anode, and electrolysis was performed at 7 A/dm2 for 1.5 seconds, followed by washing with water and drying. ammonium tungstate,
The solution was prepared by adjusting the concentration of phosphoric acid, adding sulfuric acid and zinc carbonate to some parts, and adjusting the temperature of the solution, immersion time, and amount of electrolysis.

・■ Oxide formation is ammonium vanadate: 30g/l
, Phosphoric acid: 10g/f aqueous solution (30°C) with the steel plate to be treated as the cathode and the PT electrode as the anode, 7A/d''
After performing electrolysis for 1.5 seconds, it was washed with water and dried. The solution was prepared by adjusting the concentrations of ammonium vanadate and phosphoric acid, as well as adding sulfuric acid and zinc carbonate to some parts, and adjusting the solution temperature, electrolysis time, and amount of electrolysis.

・Boron oxide is generated using boric acid: 7A/dm using a zinc-plated steel plate as a cathode in an aqueous solution containing 50 g/l.
” Electrolysis was carried out under electrolytic conditions of 1.5 to 7 seconds.

In the production of the mixed oxide film, a bath was prepared in which the respective metal salts or acids mentioned above were added and mixed.

All film amounts are measured element amounts Note 4) Chemical conversion treatment test conditions Chemical conversion treatment solution (zinc-phosphoric acid-fluorine treatment bath) contains 5D5.
000 (manufactured by Nippon Paint Co., Ltd.), degreasing and surface conditioning were performed according to the prescription, followed by chemical conversion treatment. Chemical conversion treatment films are judged by SEM (secondary electron beam image): ○ if the film is uniformly formed, Δ if the film is partially formed, and × if no film is formed. It was determined that

Note 5) Pressability test conditions and evaluation method: Sample size: 17mmX 300++m+, tensile speed: 5
00 an/ll1in, corner beat shoulder R:1. O/3
, Om+, sliding length: 200 hours, oiling: Nox last 5
30F (Parker Kosan Co., Ltd.) 40.1g/nr (
7) A test was conducted at several points with a surface pressure between 100 and 6ookgr, the pull-out load was measured, and the friction coefficient was determined from the slope of the surface pressure and the pull-out load.

Note 6: Weldability The welding conditions are as follows.

1) Pressure crab 250kgf 2) Initial pressurization time: 40Hr 3) Current application time: 12Hr 4) Holding time: 5) 1r 5) Welding current: 11kA 6) Tip tip diameter = 5.0φ (cone-shaped) 7) Electrode life end point determination: Nagent diameter at 85% of welding current is 3.6
8) Electrode material W: Cu-Cr (commonly used) Welding was performed by overlapping two plated steel plates with one side up and the other side down to determine the number of consecutive dots. .

Note 7: Measurement of ZnO film Only the plating layer was dissolved with a 5% iodine methyl alcohol solution, and the extraction residue was melted with a mixed flux (boric acid: 1: sodium carbonate: 3:3), then dissolved with hydrochloric acid, and zinc analyzed by ICP. Convert the amount to ZnO amount.

(Effects of the Invention) By doing so, the number of consecutive welding points can be increased in spot welding, welding can be performed for a long time without replacing the tip, and the durability of the tip can be improved. In addition, welding productivity can be improved, the suitable welding current range is the same as that of conventional materials, and weldability is also good.

Furthermore, the sliding properties in the press have been improved to a level higher than that of cold-rolled steel sheets,
Moreover, a chemical conversion treatment film can also be formed. As a result, it is possible to obtain excellent effects such as being able to reduce the cost in comparison with the conventional method, reduce the burden on the user in the process, and improve the productivity of the press.

Claims (2)

[Claims] (1) The amount of ZnO on the surface of zinc-based plated steel sheet is 30 to 300
0 mg/m^2 oxide, and one type of Mn oxide, P oxide, Mo oxide, Co oxide, Ni oxide, Ca oxide, W oxide, V oxide, or boric acid on the upper layer. 2
A zinc-based plated steel sheet having excellent weldability, pressability, and chemical conversion treatment properties, characterized by being coated with 1 to 500 mg/m^2 (as the amount of metal in the oxide). (2) SiO_2, TiO_2, Al in the upper oxide layer
1 to 500 mg/m of one or more of _2O_3
Weldability and pressability according to claim 1, which contains ^2,
Zinc-based plated steel sheet with excellent chemical conversion treatment properties.