JP2002226976A - Galvanized steel sheet having excellent adhesiveness, workability, chemical convertability and weldability, and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inorganic-lubrication-treated galvanized steel sheet having high adhesive strength with various adhesive including a mastic adhesive, sufficient adhesive strength even in a precured state, high adhesive strength to the T-peel test, and sufficient workability and weldability as well as chemical convertability. SOLUTION: An inorganic lubricant film has a composition which is composed essentially of zinc phosphate and in which insoluble phosphate consisting of zinc metaphosphate and/or zinc polyphosphate and soluble phosphate consisting of zinc orthophosphate are present in a mixed state, and the insoluble phosphate is concentrated in the surface layer of the film. It is desirable that, when the quantity of the insoluble phosphate, the quantity of the soluble phosphate and the total quantity of the insoluble and the soluble phosphate in the film are represented by P1, P2 and (P1+P3) expressed in terms of P quantity (mg/m2), respectively, these quantities satisfy the following inequalities (1), (2): (1) 0.10<=P1/(P1+P2)<=0.95, (2) 5 (mg/m2)<=(P1+P2)<=500 (mg/m2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to lubrication of galvanized steel sheets and galvanized steel sheets (hereinafter collectively referred to as "zinc-based steel sheets"), and more particularly, to the demand for severe workability. The present invention relates to a galvanized steel sheet provided with a lubricating film capable of ensuring excellent press workability, achieving both adhesiveness and chemical conversion property, and not deteriorating spot weldability, and a method for producing the same.

[0002] With respect to adhesiveness in particular, this lubricating film is
Stable adhesiveness can be ensured even for adhesives with low adhesive strength (for example, mastic-type adhesives such as sheet adhesives for reinforcing steel sheets, adhesives for high rust prevention spot sealers, and highly foamable filling sealants). Extremely excellent adhesive compatibility,
It is characterized in that it is possible to ensure chemical conversion treatment that is difficult to achieve compatibility with adhesiveness.

[0003]

2. Description of the Related Art Galvanized steel sheets represented by hot-dip galvanized steel sheets, galvannealed steel sheets, electro-galvanized steel sheets, and Zn-Ni alloy electro-plated steel sheets are used in automobiles, home appliances, It is widely used for building materials and the like, and its demand tends to increase further in the future.

[0004] With the increase in demand for galvanized steel sheets,
Various performances other than corrosion resistance are required. For example, in automotive body applications, in addition to press formability, chemical conversion treatment is required to ensure bondability such as spot weldability or adhesion, and paintability.

[0005] However, the zinc-based plated steel sheet has a problem that press workability is deteriorated due to exfoliation of plating and seizure of a mold due to the presence of relatively soft zinc, which is rich in reactivity, and has poor formability. It cannot be used as is for the required applications. For this reason, a method of compensating for the deterioration of workability is usually adopted by applying lubricating oil.However, lubricating oil is not sufficient because the oil film breaks when the mold and steel plate come into contact under severe workability conditions. High moldability could not be secured.

Conventional techniques for imparting lubricity to galvanized steel sheets are disclosed, for example, in JP-A-3-183797 and JP-A-3-183797.
No. 249180, each publication proposes forming an inorganic lubricating film made of Mn oxide or Mn oxide containing phosphoric acid to prevent metal contact between the plating film and the mold. .

[0007] Japanese Patent No. 2819427 proposes an inorganic lubricating film made of amorphous phosphorus oxide. In each of Japanese Patent Nos. 2,691,797 and 2,826,902, a metal oxide film is formed on a lower layer as a false adhesion preventing function film, and an oxygen oxidation such as a phosphor oxide and a borate is formed on the upper layer as a rollable lubrication function film. Salt, or Si, A
It has been proposed to form a film mainly composed of a colloidal agent such as l or Ti.

Further, Japanese Patent Application Laid-Open No. 2000-64054 discloses a coating type phosphate-treated steel sheet containing an amorphous component and a crystalline component of hopeite, and a method for producing the same. All of these conventional inorganic lubricating films are intended to improve the workability (press formability) of galvanized steel sheets and to ensure chemical conversion treatment. Sex is not considered at all.

[0009]

As the above prior art aims at, it is very important to improve the workability of the zinc-based plated steel sheet and to ensure the chemical conversion treatment when assuming an automobile body. Furthermore, since a wide variety of adhesives have come to be used in assembling automobile bodies, a wide range of adhesive compatibility can be applied to galvanized steel sheets, as with ordinary steel sheets, using various adhesives. Is also required.

Adhesives used for automobile bodies are roughly classified into two types. That is, an adhesive for a vehicle body having a relatively high adhesive strength such as a structural adhesive, and a mastic type adhesive having a relatively low adhesive strength for the purpose of reinforcing panels and improving rust resistance of welded portions. .

In general, the conventional inorganic lubricating film as described above has poor compatibility with an adhesive, and when such a zinc-coated steel sheet subjected to such inorganic lubrication treatment is applied as a steel sheet for an automobile body, Ensuring adhesion is a major problem.

For the purpose of improving the adhesiveness, for example, Japanese Patent Application Laid-Open No. Hei 8-296058 discloses that before the inorganic lubrication treatment, the plating surface is activated by alkali degreasing or the like as a pretreatment, and the inorganic lubrication film and the plating are treated. It has been proposed to improve the adhesion to the layer to ensure adhesive compatibility. However, although this activation treatment can be expected to improve the adhesiveness of vehicle body adhesives with high adhesive strength, adhesives with low adhesive strength, especially mastics mainly composed of synthetic rubber or foamed urethane resin In the case of a mold adhesive, sufficient adhesive strength cannot be secured, and it cannot be said that adhesive compatibility was sufficiently improved.

As a method of applying the adhesive in assembling an automobile body, after calcination is performed at a relatively low temperature immediately after application of the adhesive to a state where the adhesive is not sufficiently cured and the adhesive strength is weak. Two-stage baking is also employed, in which the adhesive is completely cured at the same time when the coating film is baked after painting (full cure state). In the conventional inorganic lubricated steel sheet, there is also a problem that a sufficient adhesive strength cannot be ensured in the pre-baked state.

[0014] In an evaluation method in which local stress concentration is unlikely to occur in the adhesive, such as a general shearing tension, even if a sufficiently high adhesive strength can be ensured, a T-shape is required. In the T-peel peeling test in which local stress concentration tends to occur in the adhesive due to bonding, the bonding strength may be extremely reduced. That is, it is not possible to reliably evaluate whether or not the adhesive strength of a vehicle body panel having a complicated shape is sufficient when considering the adhesiveness of a vehicle body panel having a complicated shape only by a test such as shear tension.

The present invention solves the above-mentioned problems of the conventional inorganic lubrication treatment technology for galvanized steel sheets, and can secure high adhesive strength when bonded with various adhesives including a mastic adhesive. Inorganic lubrication-treated zinc-based alloy that shows sufficient adhesive strength even in the pre-cured state and high adhesive strength in the T-type peel test, and at the same time, has sufficient chemical conversion treatment properties and sufficient workability and weldability. This is to provide a plated steel sheet.

[0016]

Means for Solving the Problems The present inventors have conducted an inorganic lubrication treatment on a zinc-based plated steel sheet without impairing the extremely excellent workability of a phosphate-based inorganic lubrication film.
We studied for the purpose of improving the adhesiveness. Regarding the improvement of adhesiveness, even under severe adhesive conditions such as the use of a mastic adhesive, a pre-cured state, and a T-shaped adhesive, where the adhesive strength is low, the same adhesive strength as an untreated steel sheet for vehicle bodies can be secured. Was targeted.

As a result, the separation between the phosphate-based inorganic lubricating film and the adhesive occurs near the interface thereof,
By controlling the composition of the phosphate-based coating, particularly the composition of the outermost surface of the coating, to a polymer state in which dehydration and condensation of phosphoric acid has progressed, it has been found that extremely excellent adhesiveness that can achieve the above-mentioned target can be secured.

However, since the phosphate-based inorganic lubricating film which is extremely excellent in adhesion compatibility is extremely dense, it is intended to improve, for example, paint adhesion and post-paint corrosion resistance to a steel sheet for an automobile body. During chemical conversion treatment (zinc phosphate treatment), which is carried out constantly, the film does not dissolve at all,
It has been found that poor chemical formation, in which zinc phosphate crystals do not precipitate, is likely to occur, which causes problems in coating adhesion and corrosion resistance after coating.

The inventors of the present invention have conducted further studies aiming at achieving both adhesion and chemical conversion treatment, and as a result, have found that a coating composition (hereinafter referred to as insoluble phosphoric acid) which is difficult to dissolve in a chemical conversion treatment suitable for adhesion. Salt) and a coating composition (hereinafter, referred to as a soluble phosphate) that easily dissolves during alkali degreasing and zinc phosphate treatment, which are the usual chemical conversion treatments, to form an adhesive coating and a chemical conversion treatment. Have been found to be compatible at a high level. More specifically, regarding the adhesiveness, since the surface state of the inorganic lubricating film has a great effect, the insoluble phosphate is concentrated on the surface, and the soluble phosphate is concentrated inside. Thus, compatibility between the adhesiveness and the chemical conversion treatment can be achieved.

Here, the present invention relates to a galvanized steel sheet having a phosphate-based inorganic lubricating film on the surface of a zinc- or zinc-alloy-plated steel sheet. And / or a mixture of an insoluble phosphate which is a polyphosphate and a soluble phosphate which is an orthophosphate. Is a zinc-based plated steel sheet characterized by the presence of a soluble phosphate.

In a preferred embodiment of the galvanized steel sheet of the present invention, the amount of the insoluble phosphate, the amount of the soluble phosphate, and the total amount of the insoluble and soluble phosphates in the inorganic lubricating film are determined by:
Assuming that P amount (mg / m ² ) is P1, P2, and (P1 + P2), these amounts satisfy the following expressions (1) and (2): 0.10 ≦ P1 / (P1 + P2) ≦ 0.95 ‥‥ (1) 5 (mg / m ² ) ≦ (P1 + P2) ≦ 500 (mg / m ² ) ‥‥ (2) and / or the element composition of Zn, P, and O on the outermost surface of the inorganic lubricating film is In the atomic ratio of Zn / P and O / P, the following (3)
It is desirable to satisfy Expression (4) and Expression (4).

(Zn / P) + 1.0 ≦ (O / P) ≦ 3 × (Zn / P) +1.5 ‥‥ (3) 0.6 ≦ (Zn / P) ≦ 1.6 ‥‥ (4) These books In the galvanized steel sheet according to the invention, it is exemplified that the metaphosphate is zinc metaphosphate and the polyphosphate is zinc polyphosphate.

From another viewpoint, the present invention relates to a method for producing orthophosphoric acid: 10 to 100 g / L on a surface of a zinc or zinc alloy plated steel sheet.
And Zn / P: 0.1 to 0.9 in weight ratio, Zn / P, and a phosphoric acid condensation aid, and have a pH of 1 to 4 and a liquid temperature of 20 to 80 ° C. and satisfy the following formula (5). A method for producing a galvanized steel sheet, comprising contacting a treatment liquid.

55 ≦ (liquid temperature) + 10 × (liquid pH) ≦ 100 (5) In the method for producing a zinc-based plated steel sheet according to the present invention, the zinc- or zinc-alloy-plated steel sheet is brought into contact with the solution before it is brought into contact with the solution. It is preferable to perform a pretreatment of alkali immersion or acid immersion, or a combination of alkali immersion and acid immersion, followed by washing with water.

The P content (P1 + P2) of the entire coating can be determined by a suitable quantitative analysis method (eg, analysis of the characteristic X-ray intensity of P by fluorescent X-rays, or dissolving only the phosphate coating with a 1% aqueous solution of dichromic acid). Weight method or chemical analysis method). On the other hand, the amount of insoluble or soluble phosphate (P1
Or P2) can be quantified from the X-ray diffraction intensity. For example, the soluble phosphate is usually only zinc orthophosphate crystals, and the amount of the whipite is quantified by X-ray diffraction intensity to be P2, and this amount is determined as the total amount of the entire film obtained as described above. By subtracting from the amount of P, the amount of insoluble phosphate (P1) can be determined.

The element composition in the surface layer of the coating is XPS
(X-ray photoelectron spectroscopy). In the present invention, the surface layer of the coating means a surface region that can be analyzed by XPS.

In the inorganic lubricating film according to the present invention, the insoluble phosphate concentrates on the surface layer of the film, and the ratio of the insoluble phosphate is higher in the surface layer of the film than in the inside of the film. The concentration of the insoluble phosphate in the surface layer of the coating means that the Zn / P ratio and the O / P ratio of the elemental composition of the surface layer depend on the amount of orthophosphate (according to the measurement conditions of XPS in the present invention, Zn / P
Ratio = 1.7-1.9 and O / P = 4.0-5.0).

The reason why the inorganic lubricating film in the galvanized steel sheet of the present invention is excellent not only in workability but also in adhesiveness, chemical conversion property and weldability is considered as follows.
Phosphoric acid is pyrophosphoric acid that has been polymerized into a linear (macromolecular) form when subjected to dehydration condensation from oritoric acid [H ₃ PO ₄ ].
(Diphosphate), becomes the polyphosphoric acids such as tripolyphosphate _{(triphosphate) [H n + 4 P n} + 2 O 3n + 7], proceeds further dehydration condensation, three-dimensionally crosslinked to a polymer phased metaphosphate [H _n P _n O
_[3n ] has a property that the bonding state is greatly changed even to an ultraphosphate having a structural unit of [ _3n ].

The present inventors treated various zinc-based plated steel sheets with various phosphoric acid aqueous solutions having different degrees of dehydration condensation,
The adhesion was investigated. As a result, the adhesion of the inorganic lubricating film formed varies greatly depending on the degree of dehydration and condensation of phosphoric acid used in the treatment. Although the adhesion is insufficient with the orthophosphoric acid treatment, pyrophosphoric acid, tripolyphosphoric acid, and metaphosphoric acid The adhesiveness was improved in this order, and the film formed by the treatment with metaphosphoric acid was particularly excellent in adhesiveness.

The reason why the inorganic lubricating film formed by the metaphosphoric acid treatment has an extremely excellent adhesive property has not been completely elucidated, but is presumed to be due to the following mechanism.

When a zinc-coated steel sheet is treated with an aqueous solution of orthophosphoric acid, the zinc in the plating film is dissolved by the etching action of phosphoric acid (Zn → Zn ²⁺ + 2e ⁻ ), and the generated zinc ion reacts with the phosphate ion. Phosphate film is formed by precipitation of insoluble zinc orthophosphate
(3Zn ²⁺ + 2PO ₄ ^3- → Zn ₃ (PO ₄ ) ₂ ). At a temperature of 100 ° C. or less, zinc orthophosphate is a tetrahydrate whipite crystal [Zn ₃
Deposited as _{(PO 4) 2 · 4H 2} O]. Since this whipite crystal is a needle-like crystal, when an inorganic lubricating film composed of whipite is formed, the surface of the film is roughened, and the slidability at the time of processing is reduced, thereby deteriorating the workability. Also, if the amount of whipite is large, since this is an insulator, resistance weldability such as spot welding is also deteriorated.

Further, when the film of whipite containing water of crystallization comes in contact with an alkaline adhesive, dissolution of the whipite crystal which is easily dissolved in the alkali region occurs, and the whipite crystal at the interface with the adhesive becomes weak, and this portion becomes weak. From the adhesive.

Further, when a zinc-based plated steel sheet is treated with phosphoric acid, particularly orthophosphoric acid having a very low pH, the zinc (Zn ²⁺ ) dissolved by the above-described etching of the plating layer becomes excessive and is consumed in the formation of Hopite. The amount of dissolved zinc increases more than the amount of dissolved zinc ions, and the dissolved zinc ions that remain without being consumed precipitate as zinc oxide such as zinc oxide and zinc hydroxide when the film is dried. The formation of the fragile layer of zinc oxide also causes deterioration of adhesiveness.

On the other hand, an inorganic lubricating film made of zinc polyphosphate or zinc metaphosphate formed by reacting polyphosphoric acid or metaphosphoric acid polymerized through a dehydration condensation reaction with zinc ions generated by its plating etching action. Is excellent in alkali resistance, and excess dissolved zinc once dissolved by etching is effectively incorporated into the film during dehydration condensation, so that zinc oxide or hydroxylation occurs at the interface between the inorganic lubricating film and the adhesive. No fragile layer of material is formed. Therefore, it is presumed that very excellent adhesiveness is exhibited.

Further, by forming a film mainly composed of polymerized zinc metaphosphate and zinc polyphosphate (hereinafter collectively referred to as "condensed zinc phosphate"), a conventional zinc phosphate mainly composed of whipite is used. Less P compared to film
Workability is improved even with the amount of adhesion. In the present invention, the film composed mainly of condensed zinc phosphate is a film that has been subjected to a treatment utilizing a deliberate dehydration condensation reaction with an additive or the like and contains 10% by volume or more of condensed zinc phosphate as an atomic equivalent. Refers to the film.

The reason why the film made mainly of condensed zinc phosphate is excellent in processability is that, as described above, as the polymerization of phosphate progresses, compared with the conventional zinc phosphate film mainly made of whipite, This is considered to be because the film is modified into a denser and harder hard film, and seizure due to metal contact between the metal mold and the plating layer during press molding is prevented.

As described above, in the zinc phosphate-based inorganic lubricating film, the film performance changes greatly depending on the progress of the polymerization of phosphoric acid, and the film of the insoluble condensed zinc phosphate which has been polymerized is converted into a film. Forming is effective for improving adhesiveness and workability.

However, the film of the condensed zinc phosphate is very difficult to dissolve in the alkaline degreasing solution used for the pretreatment or the acidic zinc phosphate treatment solution in the chemical conversion treatment (zinc phosphate treatment) step. However, zinc phosphate crystals are not easily precipitated, and the formation of the zinc phosphate is poor, and the adhesion to coating and the corrosion resistance after coating are reduced.

On the other hand, Hopite crystal [Zn ₃ (PO ₄ ) ₂ .4H ₂ O]
Is easily dissolved in an alkaline or acidic solution, so that it is desirable to include an appropriate amount of whipite crystals in the inorganic lubricating film in order to ensure chemical conversion treatment. Zinc phosphate-based chemical conversion solutions, such as those commonly used in automobile body manufacturing processes, contain Mn, Ni
However, in the case of a zinc phosphate-based inorganic lubricating film that does not contain such a modifying additive element, the Hopite crystals are soluble, and the alkaline degreasing solution or the acidic zinc phosphate is used. Easy to dissolve in processing solution.

Therefore, in order to form an inorganic lubricating film having both adhesiveness and chemical conversion treatment properties, in the present invention, a large amount of condensed zinc phosphate, which is an insoluble phosphate, is present in the surface layer of the film, and the film is formed on the inner surface of the film. Causes a large amount of whipite crystals, which are soluble phosphates that are easily dissolved in the chemical conversion treatment.

As described above, in the adhesion test of the zinc phosphate-based inorganic lubricating film, the destruction starts from the vicinity of the interface between the adhesive and the inorganic lubricating film. The structure of the surface layer, and the structure inside the film does not significantly affect the adhesiveness. Therefore, in the present invention,
The polymerized insoluble condensed zinc phosphate, which is advantageous for adhesion, is concentrated on the surface layer of the inorganic lubricating film to enhance the adhesion. Since the surface layer mainly composed of the condensed zinc phosphate is hard and dense, it also has an advantageous effect on workability and weldability.

On the other hand, if a certain amount of soluble whipite remains inside the film, this inorganic lubricating film may be treated with an alkaline degreasing solution or a zinc phosphate treating solution in a zinc phosphate treatment step performed before coating after processing. Then, the whole film is dissolved. That is, even if the coating surface layer is insoluble, if the inside is soluble, the entire inorganic lubricating coating including the insoluble surface layer is completely dissolved and disappears in the chemical conversion treatment step. As a result, similar to the case where the zinc-based plated steel sheet is subjected to the chemical conversion treatment as it is, normal zinc phosphate crystals are precipitated by the chemical conversion treatment,
Chemical conversion treatment is ensured.

As described above, in the present invention, the surface layer of the film has a structure in which the chemical conversion property is poor but the adhesive property is improved, and the inside of the film has a structure in which the adhesive property is poor but the chemical conversion property is excellent. Thereby, both the adhesiveness and the chemical conversion treatment can be achieved at a high level, and also the workability and the weldability can be secured. For this reason, according to the present invention, an inorganic lubricating film which is excellent in adhesiveness, workability, chemical conversion treatment, and even weldability and is extremely effective as a steel sheet for an automobile body is formed on the surface of a galvanized steel sheet. it can.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a galvanized steel sheet and a method for manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings. In the following description,
Although the case where the metaphosphate is zinc metaphosphate and the polyphosphate is zinc polyphosphate is taken as an example, the present invention is not limited to such a form, and other metaphosphates and polyphosphates may be used. The present application can also be applied. Such metaphosphates and polyphosphates include, for example, Zn _n P _{2n + 4} O <sub>6n +
14. As</sub> the metaphosphate, Zn _n P _2n O _6n can be exemplified.

The zinc-coated steel sheet targeted in the present invention refers to a steel sheet having a zinc-containing plating layer formed on its surface by various methods including a hot-dip galvanizing method, an electrogalvanizing method, a vapor deposition plating method, a thermal spraying method and the like. means. The plating may be either single-sided plating or double-sided plating. The plating weight is not particularly limited, but is usually 10 g / m ² or more per side.
The range is 100 g / m ² or less.

The plating composition is not particularly limited as long as it contains zinc. Pure Zn plating, Zn alloy plating with one or more elements including Zn and Fe, Al, Ni, Co, etc., and further, Zn alloy plating, These platings include alloy plating of dispersion plating in which fine particles such as SiO ₂ and carbon are co-deposited. Plating in which Zn is a small element, such as a 55% Al-Zn hot-dip coated steel sheet, may be used. Further, the plating layer is not limited to one layer. It is also possible to have a plating film having two or more layers or a plating film whose composition continuously changes in the thickness direction. In that case, if the plating surface layer is a plating containing zinc, Good.

Typical galvanized steel sheets include electro-galvanized steel sheets, hot-dip galvanized steel sheets, electric Zn-Ni alloy-coated steel sheets, alloyed hot-dip galvanized steel sheets, and hot-dip galvanized steel sheets.
-Al alloy plated steel sheet. Of these, electrogalvanized steel sheets, electroplated Zn—Ni alloy coated steel sheets, and alloyed hot-dip galvanized steel sheets are often used for automobile bodies.

According to the invention, zinc metaphosphate and / or
Alternatively, an insoluble phosphate containing zinc polyphosphate and a soluble phosphate composed of zinc orthophosphate (hopite) are mixed, and the insoluble phosphate is concentrated on the surface layer (the surface of the film) and soluble phosphate is contained inside. A zinc phosphate-based inorganic lubricating film containing an acid salt is formed on the surface of a zinc-based plated steel sheet.

As a method for forming such an inorganic lubricating film, a layer composed of a soluble whipite crystal is first formed in a predetermined amount, and then a layer of insoluble zinc phosphate is formed on this layer. Stepwise processing is possible.

In this case, the first precipitation of the whipite crystal is as follows:
This is realized by treating a zinc-based plated steel sheet with a zinc phosphate treatment solution, similarly to the normal zinc phosphate conversion treatment. The processing solution used is an aqueous solution of orthophosphoric acid,
Zinc ions are supplied from a zinc-based plating which is an underlayer. Zinc ions may be added to accelerate the precipitation of Hopite crystals. Further, in order to enhance the etching effect, it is preferable to contain an etching agent which is hydrofluoric acid and a salt thereof. Mn for modifying Hopite crystals
A treatment liquid that does not contain an additive such as Ni is preferable because it can form a highly soluble zinc phosphate film by alkali degreasing. This treatment is preferably performed by a so-called reaction type treatment in which a zinc-based plated steel sheet is brought into contact with a zinc phosphate treatment liquid for a sufficient time to precipitate a predetermined amount of whipite, and then washed with water.

The polymerized insoluble zinc phosphate layer formed on the soluble zinc phosphate layer composed of the whipite crystals is dried by applying a treatment liquid without washing it with water. It is preferable to carry out by a coating type treatment. The treatment liquid to be used may be a solution containing metaphosphate and / or polyphosphate ions from the beginning.
Alternatively, by using a solution containing orthophosphate ions to advance the dehydration condensation of zinc orthophosphate in the film formation stage, only the surface layer can be a polymerized insoluble zinc phosphate film. Further, both of them can be used in combination. The zinc ions are supplied from the whipite because the whipite dissolves in the processing solution, but the processing solution may contain a zinc ion supply source or an etching agent.

From the beginning, the treatment solution containing metaphosphate and / or polyphosphate ions forms an insoluble zinc phosphate film directly by the reaction of these ions with zinc ions, so that film formation can be performed efficiently. Although possible, the stability of the solution is low and the service life may be shortened.

When a treatment solution containing orthophosphate ions is used, it is necessary to promote a dehydration condensation reaction at the time of film formation in order to form an insoluble zinc phosphate film. As means for that purpose, it is possible to add an oxidizing agent to the processing solution, increase the solution pH, increase the baking temperature, and appropriately combine the above operations. This means is basically the same as that described in the following one-step treatment.However, in the case of forming a surface insoluble zinc phosphate film in the two-step treatment, it is not necessary to leave a whipite. The condition may be set so that the vehicle travels at altitude or completely. For example, the amount of the oxidizing agent added may be increased, or the baking temperature may be increased.

As an alternative to the two-step treatment, the inorganic lubricating film of the present invention can be formed by a one-step treatment. That is, since both the insoluble phosphate and the soluble phosphate are basically phosphates, and the bonding state thereof is different, the soluble type of whipite crystal is obtained by a coating-type treatment in which the treatment liquid is applied and then dried immediately. , And a method of simultaneously forming a polymerized insoluble phosphate treatment. Specifically, since insoluble zinc phosphate is obtained by dehydration-condensation of soluble zinc phosphate,
By performing only the process corresponding to the second stage of the above two-stage process, the polymerization by dehydration condensation of zinc orthophosphate at the time of film formation is incompletely performed so that the whipite remains, so that the soluble whipite crystal and A film in which insoluble polymerized zinc phosphate crystals are mixed together can be formed. In this case, the supply of a large amount of Zn accompanying the dissolution of the plating film causes the growth of soluble whipite crystals from the plating surface. Since zinc concentrates on the surface layer of the coating, the inorganic lubricating coating of the present invention can be formed even by one-step treatment.

It is preferable that the treatment liquid used in this one-stage treatment contains, besides orthophosphate ions, an oxidizing agent as a means for promoting dehydration and condensation during formation of the film to polyphosphoric acid and / or metaphosphoric acid. Preferably,
Further, zinc ions and an etching agent are also contained. For example, an acidic aqueous solution in which an oxidizing agent is added to an aqueous solution containing orthophosphoric acid and zinc monophosphate [Zn (H ₂ PO ₄ ) ₂ ], together with an etching agent such as hydrofluoric acid and an accelerator such as a zinc nitrate solution. Can be used.

The treating solution used in this case was Zn based on a solution containing an orthophosphoric acid concentration of 10 to 100 g / l.
A solution containing g / l containing phosphoric acid dehydrated and condensed, and an oxidizing agent added to make it polymerizable, the pH of the solution was adjusted to 1 to 3.5, and the solution temperature was adjusted to 20 to 90 ° C. Is preferred. Further, it is preferable to add an etching agent such as hydrofluoric acid and a salt thereof and a promoter of a zinc nitrate solution in order to promote precipitation of a whipite crystal.

First, phosphoric acid is contained as a main component.
It is desirable that orthophosphoric acid be contained as phosphoric acid at that time. The concentration of orthophosphoric acid solution is 10 g / l or more and 100 g / l
The following are preferred. If it is less than 10 g / l, it is difficult to form the inorganic lubricating film in the present invention, and it is difficult to secure good workability. On the other hand, if it exceeds 100 g / l, not only the inorganic lubricating film becomes too thick, the effect of improving the workability is saturated, but also the cohesive failure occurs in the lubricating film, deteriorating the adhesiveness, further increasing the insulation resistance and increasing the weldability. Also degrade. Furthermore, good workability,
In order to ensure adhesion, chemical conversion treatment and weldability,
20 g / l or more and 80 g / l or less are more desirable.

The concentration of zinc contained in the processing solution was 1 g / l
More than 10g / l is desirable. If it is less than 1 g / l, the formation of the soluble zinc orthophosphate in the present invention becomes insufficient, and good chemical conversion treatment properties cannot be obtained. If it exceeds 10 g / l, the zinc ion in the solution will be excessive, and the zinc amount at the time of film formation will be excessive more than it is consumed by the formation of zinc orthophosphate crystals or the generation of insoluble condensed phosphoric acid,
As described above, excessive zinc ions precipitate as zinc oxide such as zinc oxide and zinc hydroxide when the film is dried, which causes a deterioration in adhesiveness. In order to maintain better performance, 3 to 8 g / l is more preferable. As a method of supplying zinc, it is not preferable to add another anion to the processing solution. Therefore, a method of adding monobasic zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ), or a method of supplying zinc oxide or carbonate There is a method of adding zinc or the like.

Further, in order to effectively promote the dehydration condensation reaction of phosphoric acid, it is necessary to add an oxidizing agent as a phosphoric acid condensation aid. The molar ratio of orthophosphoric acid (oxidant molar ratio / orthophosphoric acid molar ratio)
Is preferably 0.01 to 1.50. The addition amount is 0.
If it is less than 01, the insoluble condensed zinc phosphate as the essence of the present invention will not be sufficiently produced, and the adhesiveness cannot be secured. On the other hand, when the ratio exceeds 1.50, the dehydration-condensation reaction becomes excessive, and soluble zinc orthophosphate crystals required for ensuring chemical conversion property are not generated. In this case, a more preferable addition amount of the oxidizing agent is 0.05 or more and 1.20 or less.

As the oxidizing agent added at this time, inorganic peroxide, hydrogen peroxide and nitric acid are suitable. As the inorganic oxide, peroxoacid or a salt thereof can be used. Examples of peroxoacids are peroxosulfuric acid, peroxoboric acid, peroxocarbonate, peroxophosphoric acid and the like.
The inclusion of other elements as impurities in the inorganic lubricating film
Peroxophosphoric acid, which is taken into the film as a constituent element of the inorganic lubricating film, hydrogen peroxide that is decomposed into water and oxygen by a redox reaction, and carbon dioxide An oxidizing agent which does not remain in the inorganic lubricating film after being gasified, such as nitric acid, nitrous acid, and salts thereof which decomposes into peroxocarbonic acid and nitrogen dioxide, which decomposes into nitrogen dioxide, is preferable. In order to promote the precipitation of soluble zinc orthophosphate crystals, it is preferable to add an etching agent such as hydrofluoric acid or a salt thereof.

The pH of the solution is desirably 1.0 to 3.5. Processing solution pH
This changes the precipitation state of soluble zinc phosphate and insoluble zinc phosphate. If the liquid pH is less than 1.0,
If the etching force is too strong and excessive zinc ions are present at the time of film formation, zinc oxide is formed in the lubricating film, resulting in poor adhesion. On the other hand, when the pH of the treatment liquid is low, crystals of soluble zinc orthophosphate are difficult to precipitate, and the chemical conversion treatment property is reduced. On the other hand, when the pH of the solution is more than 3.5, the precipitation of zinc orthophosphate is promoted, but the formation of insoluble zinc polyphosphate is insufficient, and the adhesiveness is reduced. Further, in this pH range, sludge is generated in the treatment liquid, and in a coating type treatment in which coating and drying are performed without washing with water, the sludge adheres to the surface of the steel sheet, resulting in surface defects and poor appearance. Hinders the formation of phosphate compounds. In order to form a phosphate in the present invention, a treatment solution in an acidic region is essential, but more preferably, a solution pH
Is preferably 1.5 or more and 3.0 or less. As a method of adjusting the pH of the treatment liquid, it is sufficient to add an alkaline solution such as sodium hydroxide, but it is more preferable to add ammonia water or the like in which no cation remains.

In order to effectively precipitate soluble zinc orthophosphate crystals in a short period of time and to effectively cause a dehydration-condensation reaction of the insoluble condensed phosphate, the temperature of the treatment solution must be adjusted.
It is effective to keep the temperature at 20 ° C. or higher, preferably 40 ° C. or higher. When the temperature of the treatment liquid is lower than 20 ° C., the precipitation of zinc orthophosphate is insufficient, and sufficient chemical conversion treatment property cannot be secured. However, it is effective to suppress the temperature of the solution to 90 ° C. or less, and preferably 70 ° C. or less, because the solution concentration changes due to remarkable evaporation of the solution and the oxidizing agent in the processing solution is decomposed. When the temperature exceeds 90 ° C., not only the composition of the treatment liquid becomes unstable, but also the zinc is excessively eluted from the plating film, and zinc oxide is formed on the lubricating film, thereby deteriorating the adhesiveness.

In the present invention, in order to simultaneously form insoluble zinc polyphosphate and soluble zinc orthophosphate in the inorganic lubricating film, the liquid pH and the liquid temperature are important factors. It is desirable to satisfy the following relational expression.

55 ≦ (liquid temperature) + 10 × (liquid pH) ≦ 100 5 (5) When the value of the expression (5) is less than 55, the precipitation of soluble zinc orthophosphate crystals does not occur, and In addition to the difficulty in securing the amount, insoluble condensed zinc phosphate is easily generated, and good chemical conversion property cannot be secured. On the other hand, when the value of equation (5) exceeds 100, the etching power becomes stronger, the deposition of soluble zinc orthophosphate proceeds excessively, the amount of adhesion becomes too large, and excess zinc ions dissolve during film formation. This leads to the formation of zinc oxide and deteriorates the adhesiveness. In order to obtain better performance, it is preferable that the following relationship be satisfied.

60 ≦ (liquid temperature) + 10 × (liquid pH) ≦ 95 The processing time at this time is desirably from 1 second to 15 seconds. If the processing time is less than 1 second, zinc ions are supplied along with the etching of the surface of the plated steel sheet, and the time until the zinc phosphate film formed by the reaction with the processing solution is deposited is insufficient, and a strong film is formed. Are not easily formed, the adhesiveness cannot be ensured, and the workability is also reduced. On the other hand, processing time
If it is longer than 15 seconds, the amount of etching of the plating film becomes excessive and excessive zinc ions are supplied until the film is formed, so that a thick zinc oxide layer is formed on the surface layer, and the adhesiveness is deteriorated. descend. More preferably, it is 3 seconds or more and 10 seconds or less.

After the treatment liquid is applied, it is heated and dried to form a film. In this case, the drying temperature is preferably from 60 to 200 ° C. at the maximum plate temperature. When the maximum plate temperature is less than 60 ° C., not only drying is insufficient, but also the dehydration condensation reaction does not proceed, hindering the formation of the phosphoric acid compound in the present invention, and good adhesiveness cannot be secured. . If the temperature is higher than 200 ° C., the dehydration / condensation reaction proceeds excessively, the film becomes too strong, and the chemical conversion property deteriorates. Furthermore, in order to effectively promote the dehydration condensation reaction of the insoluble condensed phosphate simultaneously with the precipitation of soluble zinc orthophosphate crystals,
Preferably, the drying temperature is between 70 and 150 ° C. The baking method at this time is not particularly limited as long as the film is dried, and may be a hot air drying blower, a regenerative oven, or high frequency induction heating.

Further, if a pre-treatment is carried out before the application of the treatment liquid by alkali immersion or acid immersion, or a combination of alkali immersion and acid immersion, the precipitation of the condensed zinc phosphate is promoted. Become. By immersion in an alkali solution or an acid solution, dirt on the plating surface is removed, and the plating surface is etched to promote the deposition of soluble zinc orthophosphate crystals. In addition, the oxide on the plating surface layer is removed, and with the activation of the surface, the dehydration-condensation reaction of phosphoric acid is promoted, so that the formation of condensed zinc phosphate also proceeds, and the zinc oxide hardly remains on the surface layer, An improvement in adhesion can be expected as compared with a case where the pretreatment is not performed. Also, the type of alkali or acid solution used for pretreatment,
The solution concentration, immersion time and the like are not particularly limited as long as the surface layer can be etched. However, it is effective to wash with water in order to remove dirt, sludge, liquid residue and the like after etching before applying the treatment liquid. Without washing,
An undesired pretreatment liquid forms an oxide layer thickly on the surface of the plating film and adversely inhibits the lubricating film forming reaction. The washing method, washing time, and water temperature are not particularly limited as long as the remaining alkali and acid solution during etching can be removed.

Further, after the pretreatment and before the application of the inorganic lubricating treatment liquid, the plated steel sheet is immersed in a surface conditioning liquid containing a titanium colloid or the like which is constantly performed by zinc phosphate treatment or the like to promote a whipite crystal. You may.

The method of forming the film is not particularly limited as long as the insoluble condensed zinc phosphate is concentrated in the surface layer and a zinc phosphate film in which soluble Hopite crystals remain can be formed, but there is no particular limitation. From the viewpoints of restrictions on processing and processing costs, coating-type processing is advantageous.

In this case, the treatment solution may be applied as long as the treatment solution can be uniformly applied to the galvanized steel sheet, and can be applied by a method such as dipping, spraying, or a roll coater. When the zinc-based plated steel sheet is plated on both sides, it is preferable to apply the treatment liquid on both sides, but it is also possible to treat only one side.

In the inorganic lubricating film according to the present invention, the insoluble phosphate composed of zinc metaphosphate and / or zinc polyphosphate is concentrated in the surface layer, thereby improving the workability and weldability in addition to the high adhesiveness. Secured. That the insoluble phosphate is concentrated in the surface layer means that the concentration of the insoluble phosphate is higher in the surface layer of the film than in the inside. The coating surface layer may be composed of only an insoluble phosphate or a mixture of a soluble phosphate.

It is preferable that the insoluble phosphate concentrated in the surface layer is composed of only zinc metaphosphate or a mixture of metaphosphate and polyphosphate. Most preferably, the surface layer of the coating consists essentially of zinc metaphosphate or a mixture of zinc metaphosphate and polyphosphate.

In the inside of the inorganic lubricating film, the precipitation ratio of soluble zinc orthophosphate, that is, hopeite, is higher than that of the surface layer. As a result, the film easily dissolves when treated with an alkali degreasing solution or an acidic chemical conversion treatment solution, so that the inorganic lubricating film does not impair the chemical conversion treatment properties and is similar to a zinc-based plated steel sheet having no lubricating film formed thereon. Good chemical conversion property is provided. In order to enhance the solubility, a whipite crystal containing as little Ni or Mn as possible is more effective.

To obtain the above effect sufficiently, the amount of the insoluble phosphate, the amount of the soluble phosphate, and the total amount of the insoluble and soluble phosphate in the inorganic lubricating film according to the present invention should be changed to the P amount ( mg / m ² ) as P1, P2, and (P1 +
P2), these amounts are expressed by the following formula (1) and (2)
It is preferable to satisfy the formula.

0.10 ≦ P1 / (P1 + P2) ≦ 0.95 ‥‥ (1) 5 (mg / m ² ) ≦ (P1 + P2) ≦ 500 (mg / m ² ) ‥‥ (2) That is, the adhesion amount of the inorganic lubricating film is , as shown in the above (2), as P amount is preferably set to 5 mg / m ² or more 500 mg / m ² or less. This P amount is the total P amount of both insoluble and soluble zinc phosphates in the coating (that is, P1 + P2). If the total P amount is less than 5 mg / m ² , the lubricating effect is insufficient, and the workability deteriorates. On the other hand, if the total P amount exceeds 500 mg / m ² , the lubricating film is too thick, so that cohesive failure easily occurs in the lubricating film in the adhesiveness test, which lowers the adhesiveness and deteriorates workability. Since the amount of precipitated crystals is large, the effect of improving workability is also reduced. If the amount of insulating zinc phosphate is too large, the weldability is also adversely affected. Better workability,
In order to secure the adhesiveness, the chemical conversion property, and the weldability, the total P amount is preferably in the range of 20 mg / m ^{2 to} 300 mg / m ² .

The ratio of the amount of P of the insoluble phosphate to the total amount of P in the whole film, that is, ΔP1 / (P1 + P
2) The value of｝ is preferably in the range of 0.10 or more and 0.95 or less, as shown in equation (1). If this ratio is less than 0.10, the insoluble phosphate in the surface layer will be insufficient, and it will be difficult to ensure adhesiveness. In addition, the precipitation amount of the whipite crystal increases, the surface becomes rough, and the workability also decreases. On the other hand, ｛P1 /
When the value of (P1 + P2)｝ is greater than 0.95, the amount of soluble phosphate is small, so that the film is not dissolved in the chemical conversion treatment, and it is difficult to deposit chemical conversion crystals. ｛P1 / (P1 + P
2) The more preferable range of｝ is 0.20 or more and 0.90 or less.

In order to ensure good adhesiveness in the inorganic lubricating film according to the present invention, Zn dissolved in the etching action of the treatment liquid reacts with phosphoric acid and precipitates on the surface of the steel sheet. It is also preferable that the element composition ratio (atomic ratio) of Zn, P, and O satisfy the following expressions (3) and (4).

(Zn / P) + 1.0 ≦ (O / P) ≦ 3 × (Zn / P) + 1.5 ‥‥ (3) 0.6 ≦ (Zn / P) ≦ 1.6 ‥‥ (4) This relational expression The film that satisfies is stoichiometrically in a form close to zinc metaphosphate and / or zinc polyphosphate. For zinc metaphosphate, O / P = 3.0, Zn / P = 0.5
, One of the zinc polyphosphates, zinc pyrophosphate, is O
/P=3.3, Zn / P = 1.0, and zinc orthophosphate has O / P = 4.0, Zn / P = 1.5. Further, according to the surface analysis results of XPS described later, Zn / P = 0.7 to 0.9, O / P
= 2.5-3.5, Zn / P = 1.7-1.9, O / P = 4.0-5.
It was 0. Therefore, although there is a slight difference between the stoichiometric value and the measured value, it is possible to determine the zinc phosphate composition state of the surface layer by XPS. That is, the closer to the zinc orthophosphate, the more the O / P
The ratio and Zn / P ratio increase. Therefore, in order to condense the condensed zinc phosphate in the surface layer, it is necessary to reduce the O / P and Zn / P ratio of the surface layer as compared with zinc orthophosphate.

When (O / P) <(Zn / P) +1.0, the amount of phosphate is relatively large, and needle-like brittle phosphoric acid crystals are precipitated, and the adhesiveness is deteriorated. Also, (O / P)> 3 ×
In the case of (Zn / P) +1.5, the amount of Zn is relatively large, and zinc oxide such as zinc hydroxide and zinc oxide is generated in the surface layer by excessive etching, so that the adhesiveness is deteriorated. In addition, such a film has a reduced strength of the film itself and deteriorates workability.

When the value of Zn / P is less than 0.6, the precipitation reaction between phosphoric acid and zinc is not performed normally, and the phosphoric acid crystal is deposited as it is. Are not formed, and the amount of the film becomes very small. In such a case, it cannot be said that a strong film is formed as the inorganic lubricating film, which causes problems in terms of adhesiveness and workability. On the other hand, when the value of Zn / P exceeds 1.6, the formation of a film mainly composed of condensed zinc phosphate having very excellent compatibility with the adhesiveness was not achieved, and the amount of precipitated whipite crystals having poor adhesiveness was not obtained. Increase. When the amount of precipitated whipite is large, the strength of the coating film is reduced, and the workability tends to deteriorate.

As described above, the surface layer of the inorganic lubricating film according to the present invention is preferably made of substantially only zinc metaphosphate or a mixture of zinc metaphosphate and zinc polyphosphate. , Zn / P = 0.8-1.
3, the region of O / P = 2.5-3.5 is particularly preferred.

The zinc phosphate-based film used as the inorganic lubricating film in the present invention may be used in order to further improve the processability by using a lubricating metal salt (eg, metal soap), colloidal particles (eg, colloidal silica) and other materials. Additives can also be incorporated into the film. However, the total amount should not exceed zinc phosphate. Other metal salts are preferably insoluble. If soluble in water or phosphoric acid aqueous solution, it reacts with phosphate ions during film formation, and the value of Zn / P does not accurately reflect the degree of condensed phosphoric acid chloride.

The galvanized steel sheet having a phosphate film produced by the method of the present invention was significantly improved while maintaining good weldability, adhesion and chemical conversion treatment properties of the galvanized steel sheet. It has press formability, and can perform severe press forming without generating galling or powdering. Therefore, it is particularly suitable for automobiles where press molding is frequently used, but can of course be used for home appliances and building materials.

[0084]

(Example 1) This example illustrates a galvanized steel sheet having an inorganic lubricating film formed according to the present invention by a two-step processing method.

An alloyed hot-dip galvanized steel sheet made of a 0.80 mm ultra-low carbon IF steel (with a basis weight of 60 g / m2 per side)
² ) was used as a galvanized steel sheet. This plated steel sheet is first immersed in the following zinc phosphate treatment solution for 5 seconds, then washed with water and dried to form a film made of soluble Hopite crystal with a P adhesion amount of 40 mg / m ² on both surfaces. did.

Zinc phosphate treatment liquid used for formation of Hopite film Orthophosphoric acid: 16.0 g / l Zinc monophosphate: 8.0 g / l Zinc nitrate: 4.0 g / l Hydrofluoric acid: 0.5 g / l Liquid pH: 3.7 (Adjusted with NaOH) Liquid temperature: 60 ° C Separately, orthophosphoric acid, pyrophosphoric acid, and metaphosphoric acid solutions with a Zn ion source added so that the Zn / P atomic ratio becomes 1, and mixing them in various ratios The prepared mixed solution was prepared. Using each of these solutions, the zinc-coated steel sheet on which the above-mentioned whipite film is formed is immersed in the solution, and then immediately dried without being washed with water, so that the total P adhesion amount is 85 mg / m ² (insoluble 45 mg /
An inorganic lubricating film of m ² ) was formed to obtain a lubricated steel sheet for testing. The drying temperature was in the range of 70-90 ° C. for both the first reaction type treatment and the subsequent coating type treatment.

The amount of the whipite crystals in the inorganic lubricating film thus formed was converted from the diffraction intensity of the (040) plane (lattice constant = 4.57 °) of the whipite into a P adhesion amount (= P2) by X-ray diffraction. I asked. The amount of phosphate in the entire coating can be calculated from the characteristic X-ray intensity of P in fluorescent X-rays based on the amount of P attached (= P1 + P
Converted to 2). The amount of insoluble phosphate is the total P
From the attached amount (P1 + P2), the P attached amount (P
2) was subtracted.

The element composition of the surface layer of the inorganic lubricating film was examined by the XPS method. In XPS, the XPS intensity at the binding energy of each element present in the solid surface layer is measured, and the element abundance ratio of each element can be determined from the intensity. XPS analysis was performed under the following conditions.

XPS Measurement Conditions X-ray source: Mg-Kα (8 kA-30 mA) Sputtering: Ar high-speed ion etching (50 kV-0.6 A) Sputtering rate = 12-13 ° / sec.

After sputtering for 5 seconds (approximately 60 ° in the depth direction) under the above conditions, based on theoretical calculation, the element ratio of each element in the surface layer is calculated from the peak area of the XPS intensity peak at the binding energy of each element. , And the Zn / P ratio and O /
The P ratio was calculated. Before the XPS measurement, it is necessary to remove the surface layer having a thickness of about 60 ° from the surface by sputtering for 5 seconds.
This is because it is difficult to accurately determine the extremely surface layer due to contamination or the like.

Further, the adhesiveness of each lubricated plated steel sheet was investigated using a mastic type adhesive having a lower adhesive strength than the vehicle body adhesive and having a severe adhesiveness.
The evaluation of the adhesiveness was performed by a shear tensile test shown in FIG. In order to evaluate the oil surface adhesion, before applying the adhesive, apply 2 g / m ² of Idemitsu Oil Coat SK, which is a general anti-corrosion oil, to both the adhesion surfaces of the two test pieces, and humid atmosphere. (50 ℃
X95% RH) and stored for 7 days, apply an adhesive to a predetermined area of one test piece, and use a spacer to form a two-piece adhesive with a thickness of 1.0 mm. The test pieces were overlapped, baked under predetermined baking conditions to cure the adhesive, and the adhesive strength was investigated. The adhesive strength at that time is determined from the maximum strength at the time of shearing tensile strength to the adhesive area (25 × 25 mm)
Was evaluated by the value divided by. The test conditions and criteria are as follows.

Shear tensile test specimen with mastic type adhesive : 100 × 25 mm 2 pieces (general rust preventive oil 2.0 g / m ² coated) Adhesive area: 25 × 25 mm Spacer: 1.0 mm Adhesive: synthetic rubber High rust preventive spot sealer (manufactured by Iida Sangyo) Baking conditions: 180 ° C x 30 minutes Shear tensile speed: 50 mm / min (criterion) ◎: Shear strength ≧ 0.20 MPa, ○: Shear strength = 0.14 to 0.20 MPa, × : Shear strength <0.14 MPa.

The above criterion is that a non-lubricated galvannealed steel sheet (2.0 g / m ² oil coated with a general rust preventive oil)
Based on the fact that the adhesive strength at was 0.20 Mpa, it was equal to or greater than ◎, and the strength reduced by 30% (= 0.14 Mpa)
If the above is true, there is no practical problem, and the case where the adhesive strength is lower than that is judged as x.

FIG. 2 shows the relationship between the evaluation of the adhesive strength thus obtained and the element composition ratio of the surface layer of the inorganic lubricating film. From FIG. 2, the Zn / P ratio and the O / P ratio of the surface layer of the lubricating film were as described above.
It can be seen that when the expressions (3) and (4) are satisfied, good adhesiveness can be ensured. In particular, Zn / P = 0.8-1.
3. Excellent adhesiveness can be obtained in the range of O / P = 2.5-3.5.

Example 2 This example also illustrates a zinc-coated steel sheet having an inorganic lubricating film formed according to the present invention by a two-step treatment method.

An alloyed hot-dip galvanized steel sheet made of an ultra-low carbon IF steel sheet having a thickness of 0.80 mm (weight per side: 60 g / m 2)
² ) was immersed in the following zinc phosphate treatment solution, and then washed and dried to form a film composed of soluble Hopite crystals with various amounts of P attached up to 95 mg / m ² on both surfaces by a reactive treatment. The amount of soluble Hopite deposited was adjusted by changing the immersion time in the treatment solution and the pH of the treatment solution.

The zinc phosphate treatment liquid used for forming the whipite film orthophosphoric acid: 16.0 g / l zinc monophosphate: 8.0 g / l zinc nitrate: 4.0 g / l hydrofluoric acid: 0.5 g / l liquid pH: 3.5 4.54.5 (adjusted with NaOH) Liquid temperature: 60 ° C. Immersion time: 1 to 120 seconds The plated steel sheet having a whipite film obtained above was immersed in a pyrophosphoric acid aqueous solution to which a Zn ion source was added as in Example 1. after immediately by a coating-treated for drying, total P coating weight to form an inorganic lubricant coating of ^{100 mg / m 2 (5~100 mg} / m 2 as a P deposition amount of insoluble phosphate) without washing Thus, a lubricated steel sheet for a test was obtained. The drying temperature was the same as in Example 1.
Was the same as

For each of the lubricated steel sheets thus obtained, in the same manner as in Example 1, the amount of insoluble phosphate and the amount of soluble phosphate (the amount of hopite precipitation) of the inorganic lubricating film, and the elemental composition ratio of the surface layer of the film (Zn / P ratio and O / P ratio), and the adhesion by a shear tensile test using a mastic type adhesive.

In this example, the chemical conversion property of each lubricated steel sheet was further investigated. The chemical conversion treatment was performed under standard conditions using a commercially available zinc phosphate treatment liquid PB-L3020 (manufactured by Nippon Parkerizing Co., Ltd.). Evaluation of chemical conversion treatment
After the chemical conversion treatment, the area of the portion (scale) where chemical conversion crystals did not grow was determined by EM observation (× 500), and the area ratio was evaluated according to the following criteria. The area ratio of the skeleton of the chemical conversion crystal is 5
%, The corrosion resistance after painting deteriorates.
There is no problem as long as the squashed area ratio is 5% or less.

Evaluation criteria for chemical conversion treatment (A = Area of scum generation) ：: A = 0% (overall chemical conversion crystal growth) ：: 0% <A ≦ 5% (Small crystal scum generation) Δ: 5% <A ≦ 10% (slightly crystallized) ×: 10% <A ≦ 60% (crystal skeleton is remarkable) XX: A> 60% (almost entire crystallized) The amount of P adhesion of the insoluble phosphate relative to the total P adhesion Percentage
The relationship between [P1 / (P1 + P2)] and the chemical conversion property and adhesiveness is shown in FIGS. 3 (a) and (b), respectively. According to FIG. 3 (a), in order to ensure chemical conversion treatment, P1 / (P1 + P2)
Is desirably 0.95 (P2 = 5 mg / m ² ) or less, and it is found that 0.90 (P2 = 10 mg / m ² ) or less is preferable in order to obtain more favorable chemical conversion treatment properties. From FIG. 3 (b), the value of P1 / (P1 + P2) was 0.10 (P1
= 10 mg / m ² ) or more, and it is understood that 0.20 (P1 = 20 mg / m ² ) or more is suitable for obtaining even better adhesion.

Example 3 This example illustrates a galvanized steel sheet having an inorganic lubricating film according to the present invention formed by a one-step processing method.

The following double-sided zinc-coated steel sheet (having a basis weight per one side) using a very low carbon IF steel sheet having a thickness of 0.80 mm as a material to be plated was used for the treatment. Using the galvanized steel sheet symbols plating species basis weight EG electrical Zn-plated steel sheets 40 g / m ² SZ electrical Zn-13% Ni alloy plated steel sheet 30 g / m ² GA galvannealed steel sheet (Fe: 10%) 55 g / m ² The following inorganic lubricating solution based on an orthophosphoric acid aqueous solution was dip-coated on these galvanized steel sheets. This dip coating is performed by immersing the plated steel sheet in the treatment liquid for 5 seconds,
The adjustment was performed by adjusting the amount of adhesion to a predetermined amount by roll-drawing. Thereafter, without washing with water, it was immediately placed in a hot-air drying oven and baked and dried at a maximum temperature of 90 ° C. for 7 seconds to form a zinc phosphate-based inorganic lubricating film on the plating surface.

The inorganic lubricating treatment liquid may contain ammonia water as a pH adjuster and / or H ₂ O ₂ (hydrogen peroxide) or nitric acid as an oxidant, if necessary, in order to promote polymerization by dehydration condensation. Was added to precipitate insoluble phosphate. The amount of phosphate film deposited (P deposited) was adjusted by changing the concentration of orthophosphoric acid in the treatment solution.

Inorganic lubricating treatment liquid used in the one-step treatment Orthophosphoric acid: 5-150 g / l Zinc: 0-20 g / l Oxidizing agent / orthophosphoric acid molar ratio: 0-2.00 Hydrofluoric acid / orthophosphoric acid molar ratio: 0.03 liquid pH: 0.8 to 4.5 Liquid temperature: 50 ° C. For each lubricated steel sheet thus obtained, in the same manner as in Example 1, the amount of insoluble phosphate and the amount of soluble phosphate (amount of whipite) of the inorganic lubricating film and the film The element composition ratio (Zn / P ratio and O / P ratio) of the surface layer was investigated. Further, the chemical conversion property was evaluated in the same manner as in Example 2. Further, the workability, adhesiveness, and weldability of each lubricated steel sheet were investigated as described below.

[0105] workability workability, the cylindrical drawing press molding, when went increased blank holder load by 5kN pitch was evaluated by measuring the formable limit load. The processing conditions and criteria (up to ○ are acceptable) are as follows.

(Processing conditions) Blank diameter: 90 mm Punch diameter: 50 mm Molding speed: 200 mm / min Lubrication: General rust preventive oil (coating amount = 2 g / m ² ) (Judgment criteria) ◎: Limit load> 70 kN, ○: critical load = 50 to 70 kN, ×: critical load <50 kN.

In the processing of a galvanized steel sheet, it is common to use a highly lubricating rust preventive oil in order to ensure workability. For reference, Idemitsu Oil Coat, which is a highly lubricating rust preventive oil, is applied to each galvanized steel sheet of EG, SZ and GA.
When the same test was carried out with 2 g / m ^{2 of} SP2 oil applied, the forming limit load was 50 to 70 kN. From these results, the target level of workability was set at 50 kN or more, preferably more than 70 kN. In this test, 2 g / m ^{2 of} Idemitsu Oil Coat SK, which is a general rust preventive oil, was applied, and then subjected to a workability test.

Adhesive Adhesive strength was measured by using a high-rust-proof spot sealer manufactured by Iida Sangyo Co., Ltd., which was used in Example 1 as a mastic type adhesive, and an epoxy-based adhesive for an adhesive sealer, manufactured by Henkel Hakusui, as a body structure adhesive. The agent was used. For the high rust prevention spot sealer, a shear tensile test was performed in the same manner as in Example 1. For the adhesive sealer, a T-peel test, which is a stricter adhesive evaluation, was performed at 170 ° C for 30 minutes. Full cure conditions) and pre-cure conditions of baking at 160 ° C. for 10 minutes.

In order to evaluate the oil surface adhesiveness, before applying the adhesive, Idemitsu Oil Coat SK, a general rust preventive oil, was used.
g / m ² on both bonded surfaces of two test pieces with oil
(50 ℃ × 95% RH) After stacking and storing for 7 days,
An adhesive is applied to a predetermined area of one test piece, and two test pieces are superimposed using a spacer so as to have an adhesive thickness of 0.15 mm, and are baked under a predetermined baking condition and bonded. The agent was cured and the bond strength was investigated. In the method of evaluating the adhesive strength of the T-shaped peeling, the value obtained by dividing the average value of the tensile load during the tensile test by the board width (25 mm) was defined as the adhesive strength.

[0110] The T-shaped peeling criterion is based on the electro-galvanized steel sheet (2.0 g / m
^Based on an adhesive strength of 140N / 25mm with ² oil coatings, the strength was equal to or better than ◎, and the strength reduced by 30% (= 98
(N / 25 mm) or more, there is no practical problem, and the case where the adhesive strength is lower than that is judged as x.

The test conditions and the evaluation criteria (up to ○) for each adhesion test are as follows. (Conditions for shear tensile test) (See Fig. 1) Specimen: 100 × 25 mm 2 pieces (2.0 g / m ^{2 of} general rust preventive oil) Adhesive area: 25 × 25 mm Spacer: 0.15 mm Adhesive: Body structure Adhesive sealer (epoxy type, made by Henkel Hakusui) Baking conditions: 170 ° C. × 30 minutes Shear tensile speed: 50 mm / min (criterion) ◎: Shear strength ≧ 12 MPa, ○: Shear strength = 8-12 MPa X: Shear strength <8 MPa.

(T-peeling tensile test conditions) (See FIG. 4) Test piece: 200 × 25 mm, 2 pieces (2.0 g / m ^{2 of} general rust preventive oil) Adhesive area: 25 × 140 mm Spacer: 0.15 mm Adhesive: Adhesive sealer for car body structure (epoxy type, made by Henkel Hakusui) Baking condition: 170 ° C x 30 minutes (full curing condition) 160 ° C x 10 minutes (precuring condition) T-shaped pulling speed: 50 mm / min (judgment) (Standard) ◎: Peel strength ≧ 140 (N / 25mm) ○: Peel strength = 98 to 140 (N / 25mm) ×: Peel strength <98 (N / 25mm) Weldability A spot welding test was carried out, the button diameter of the welded portion was checked at every 100 spots, and the evaluation was performed by obtaining the limit number of continuous spots until a nugget could not be formed (a nugget diameter could not be obtained). When the spot weldability was tested under the same conditions by applying 2 g / m ^{2 of} Idemitsu Oil Coat SP2, which is a highly lubricating rust preventive oil, to each of the EG, SZ and GA galvanized steel sheets to be compared. Since the continuous number of hits is 2500 to 5000 hits, the target level is 2500 or more hits, preferably 4000 hits or more. Also in this test, Idemitsu Oil Coat SK, which is a general rust-preventive oil, was applied at 2 g / m ² before the test.

(Welding conditions) Electrode material: Cu-1% Cr Electrode shape: CF type (tip diameter = 5 mm) Pressure: 200 kgf Squeeze time: 15 cycles (time from pressing the steel plate to energizing) Energizing time : 10 cycles Holding time: 20 cycles (time from completion of energization to electrode release) Set current: 10.5 kA Ramping speed: 2 sec / point (Evaluation criteria) (up to ○ passed) ◎:> 4000 dots, ○ : 2500 to 4000 dots, ×: <2500 dots.

The above test results are shown in Tables 1 and 2 together with the type of zinc-based plated steel sheet, the composition of the treatment solution and the treatment conditions.

[0115]

[Table 1]

[0116]

[Table 2]

Tables 1 and 2 show that, according to the preferred embodiment of the present invention, the amount and balance of the insoluble phosphate and the soluble phosphate are optimized and the element composition ratio of the outermost layer of the lubricating film is optimized. , Workability, adhesion, chemical conversion, and weldability are all sufficiently ensured, and the adhesion is good even under severe conditions to ensure adhesion, such as using a mastic adhesive, T-shaped peel, and pre-curing conditions. It can be seen that excellent adhesion can be obtained.

As the conditions of the processing solution at that time, the lower limit of the orthophosphoric acid concentration is, for example, 10 g / l or more from the sample Nos. 1 and 12 in Table 1, and the upper limit from the sample Nos. 20 and 23 in Table 2. Is 10
It turns out that it is 0 g / l or less. For the Zn concentration, see Table 1 for sample N
From o.3 and 7, the lower limit was 1 g / l or more.
25 indicates that the upper limit is 10 g / l. From the sample Nos. 11 and 12 in Table 1, adhesiveness can be secured at a molar ratio of at least 0.01 with that of orthophosphoric acid.
From o.17 and 18, and sample No.17 in Table 2, it can be seen that chemical conversion treatment can be ensured at 1.50 or less. For liquid pH,
The lower limit pH is 1.0 from the sample Nos. 7 and 8 in Table 1, and the sample No. 2 in Table 1
8 and 29 show that the upper limit pH is 3.5.

As described above, in the phosphate film, the zinc insoluble and the phosphoric acid insoluble vary depending on the Zn concentration, the oxidizing agent concentration and the pH of the solution during the treatment. Although the element composition of the surface layer also changes, under the treatment solution conditions of the present invention, the balance between the insoluble phosphate and the soluble phosphate, which are the essence of the present invention, is optimized, and the element of the outermost surface layer of the lubricating film is adjusted. Since the composition can be optimized, it is possible to achieve both the adhesiveness and the chemical conversion treatment.

(Embodiment 4) In this embodiment, the effects of the processing time and the drying temperature when forming a lubricating film by one-step processing will be described.

Plate thickness: Alloyed hot-dip galvanized steel sheet made of 0.80 mm ultra-low carbon IF steel (weight per one side: 55 g /
m ² is immersed in one or both of the following alkali or acid immersion for 6 seconds, immediately subjected to a pretreatment of washing with water, applied with a phosphating solution described below by spraying for a predetermined time, and then roll squeezed. And immediately baked in a hot-air drying oven until the surface was completely dried without performing water washing.

(Content of alkali treatment) Type: Sodium hydroxide Liquid temperature: 100 g / l Liquid temperature: 60 ° C. Immersion time: 6 seconds (Content of treatment) Type: sulfuric acid Solution concentration: 10 wt% Liquid temperature: 60 ° C. Immersion time: 6 Seconds (inorganic lubrication treatment conditions used for the one-stage treatment) Orthophosphoric acid: 50 g / l Zinc: 6 g / l Oxidizing agent / orthophosphoric acid molar ratio: 0.20 (oxidizing agent uses nitric acid) Hydrofluoric acid: 0.3 g / l Liquid pH : 0.8 to 4.5 (pH adjustment is used with sodium hydroxide) For each of the lubricated steel sheets thus obtained, the amount of insoluble phosphate and soluble phosphate in the inorganic lubricating film was determined in the same manner as in Example 1 (hopite precipitation). ) And the processability, adhesiveness and chemical conversion treatment properties were investigated in the same manner as in Example 3.

Table 3 and Table 4 collectively show the processing conditions and the results of the investigation.

[0124]

[Table 3]

[0125]

[Table 4]

As shown in Table 3, as the temperature of the processing solution was increased,
From the sample Nos. 22, 23 and 24, the lower limit liquid temperature at which the workability can be ensured is 20 ° C. or higher, as the amount of the lubricating film increases. On the other hand, if the amount of the lubricating film is too large, the adhesiveness is deteriorated, and the upper limit is 90 ° C. from Sample Nos. 5 and 6. In addition, the amount of the lubricating film varies with the liquid temperature as well as the liquid pH. If the liquid temperature + 10 × the liquid pH (hereinafter, referred to as formula (5)) is small, a sufficient amount of the lubricating film cannot be secured. It can be seen that the amount of the lubricating film becomes excessive. In this case, the upper limit is 100% from Sample Nos. 19, 20, and 21.
It is.

The processing time also has a large effect on the amount of the lubricating film, and the amount of the lubricating film increases as the processing time increases. The processing time for obtaining an appropriate amount of lubricating film
o More than 1 second from 27 and 28 and less than 15 seconds from sample Nos. 33 and 34.

The drying temperature affects the amount of insoluble condensed zinc phosphate produced. By increasing the drying temperature, the production of insoluble condensed zinc phosphate is promoted and the adhesion is improved. From the sample Nos. 1 and 2, the lower limit is 60 ° C. or higher. However, if the drying temperature is too high as compared with Samples Nos. 10 and 11, the amount of soluble riorttonate precipitated will decrease, making it impossible to ensure chemical conversion treatment. Therefore, the upper limit is 200 ° C.

The influence of the pretreatment is, for example, that the sample No. 1
2 and sample Nos. 13, 14 and 15, the pH and temperature of
Even if it is out of the preferred range, it is possible to secure suitable performance by increasing the amount of the lubricating film and accelerating the precipitation of soluble zinc orthophosphate. Similarly, sample No. 20 and sample No. 21
, 22, 23, the target performance can be ensured by performing the pretreatment even under the processing conditions where it is difficult to secure the amount of the lubricating film unless the pretreatment is performed. It can be seen that it becomes possible to secure the lubricating film performance.

[0130]

According to the present invention, a zinc phosphate-based inorganic lubricating film in which the ratio of insoluble phosphate to soluble phosphate is adjusted to a zinc-based plated steel sheet and the insoluble phosphate is concentrated on the surface of the film. By forming, the workability can be remarkably improved without impairing the good chemical conversion property, adhesiveness, and weldability of the zinc-based plated steel sheet.

In particular, the galvanized steel sheet having the inorganic lubricating film is excellent in adhesive compatibility, and is suitable for various adhesives used for automobile bodies (in addition to body adhesives,
Adhesives are used in the same way as conventional lubricating films, including mastic type adhesives with low strength), adhesive strength under temporary baking conditions (pre-cure conditions), adhesive strength in various shapes, etc. This makes it possible to maintain good chemical conversion property even in the subsequent chemical conversion treatment step. Since the workability of the galvanized steel sheet is remarkably improved by the lubricating film and welding is possible as before, the inorganic lubrication-coated steel sheet of the present invention has properties that are particularly suitable as a material such as a steel sheet for an automobile body. Have.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a shear tensile test method used for evaluation of adhesiveness.

FIG. 2 is a diagram showing the relationship between the element abundance ratio in the surface layer of a zinc phosphate-based inorganic lubricating film and the adhesive strength of a mastic adhesive.

FIG. 3 (a) is a diagram showing the relationship between the ratio of insoluble phosphate in a zinc phosphate-based inorganic lubricating film and the chemical conversion property, and FIG. 3 (b) shows the ratio of insoluble phosphate. FIG. 4 is a diagram showing a relationship between and adhesiveness.

FIG. 4 is an explanatory view showing a T-shaped peeling (peel) test method used for evaluation of adhesiveness.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C23C 28/00 C23C 28/00 C (72) Inventor Masahiro Morikawa 3rd, Oaza Hikari, Kashima-shi, Ibaraki Prefecture Sumitomo Metal Industries Kashima Co., Ltd. F term in the steelworks (reference) 4K026 AA02 AA07 AA12 AA13 AA22 CA13 CA23 CA25 CA26 CA32 CA35 CA39 CA41 DA03 EA08 EB11 4K044 AA03 AB02 BA17 BB03 BC03 BC04 BC05 CA11 CA16 CA18 CA53

Claims (6)

[Claims] Claims: 1. A zinc or zinc alloy-plated steel sheet surface,
A zinc-based plated steel sheet having a phosphate-based inorganic lubricating film, wherein the inorganic lubricating film is composed of an insoluble phosphate which is a metaphosphate and / or a polyphosphate as a whole, and an orthophosphate. Zinc-based plating, wherein the zinc-based plating is in a mixed state with a soluble phosphate, and wherein an insoluble phosphate is present in a surface layer of the inorganic lubricating film and a soluble phosphate is present inside the surface layer. steel sheet. 2. The amount of insoluble phosphate, the amount of soluble phosphate, and the total amount of insoluble and soluble phosphate in the inorganic lubricating film are represented by P1 (mg / m ² ), respectively, P1, P
2. The galvanized steel sheet according to claim 1, wherein the amounts satisfy the following expressions (1) and (2) when (P1 + P2) and (P1 + P2) are satisfied. 0.10 ≦ P1 / (P1 + P2) ≦ 0.95 ‥‥ (1) 5 (mg / m ² ) ≦ (P1 + P2) ≦ 500 (mg / m ² ) ‥‥ (2) 3. Zn, P, O on the outermost surface of the inorganic lubricating film.
Has an atomic composition of Zn / P and O / P,
Claim 1 or Claim 2 which satisfies the equations (3) and (4).
The galvanized steel sheet as described. (Zn / P) + 1.0 ≦ (O / P) ≦ 3 × (Zn / P) +1.5 ‥‥ (3) 0.6 ≦ (Zn / P) ≦ 1.6 ‥‥ (4) 4. A solution containing 10 to 100 g / L of orthophosphoric acid and 1 to 10 g / L of zinc and containing an oxidizing agent as a phosphoric acid condensation aid at a molar concentration ratio of orthophosphoric acid of 0.01 to 1.50, pH: 1.0 to 3.5, and liquid temperature: 20 to 90 ° C, contact the surface of zinc or zinc-based alloy coated steel sheet with the adjusted solution for 1 to 15 seconds, and reach the maximum without washing with water A method for producing a galvanized steel sheet, comprising baking and drying at a temperature of 60 to 200 ° C. 5. The adjusted solution pH and solution temperature are as follows:
The method for producing a galvanized steel sheet according to claim 4, wherein the relation of the expression (5) is satisfied. 55 ≦ (liquid temperature) + 10 × (liquid pH) ≦ 100 ‥‥ (5) 6. An alkali immersion or an acid immersion in the zinc or zinc alloy plated steel sheet before contacting with the solution.
The method for producing a galvanized steel sheet according to claim 4 or 5, wherein a pretreatment in which alkali immersion and acid immersion are combined is performed, followed by washing with water.