JP3277036B2 - Chromate treated steel sheet with high corrosion resistance and excellent lubricity and conductivity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chromate-treated steel sheet mainly suitable for use in bare parts such as parts for home appliances, for example, audio and video chassis.

[0002]

2. Description of the Related Art Conventionally, zinc-coated steel sheets have generally been subjected to a chromate treatment for the purpose of rust prevention. However, the quality level at the beginning of development is the primary rust prevention from the manufacturing side to the use by home appliance manufacturers (for example, 24 to 48 in salt spray test JIS2371).
Hr rust). For this reason, in actual use, it is common to apply a rust-preventive coating after the molding process, and cannot withstand naked use.

[0003] Next, as a method for producing a chromate film that can be used naked, a technique has been developed in which an additive such as colloidal silica is contained in the chromate film or an organic resin-based film is further formed on the chromate film. Was. Thus, in recent years, unpainted naked use has become widespread. Further, in recent years, from the viewpoint of environmental protection, there has been a strong demand for a steel sheet which can be molded without oil and used without degreasing after molding for the purpose of omitting the degreasing step. Until now, various composite coated steel sheets have been proposed in which a chromate film is coated with an organic resin containing a solid lubricant. Representative examples are shown below.

[0004] Japanese Patent Application Laid-Open No. 60-103185 has a first layer usually having a chromate layer, and a second layer comprising a composite aluminum phosphate, chromic acid, rust preventive pigment, polyolefin wax, M ₀ S ₂ and silicone resin. It is a double-layer steel plate made of a urethane-modified epoxy resin layer containing the same. This is a surface-treated steel sheet comprising a chromate layer as a first layer and an acrylic resin layer having a solid lubricant as a second layer.

[0005] JP-A 61-227179 discloses a chromate layer as a first layer, a chromate salt, a silica sol, a mixture of a solid lubricant and a lubricating oil, a silane and / or titanate coupling agent and a colored layer as a second layer. This is a surface-treated steel sheet made of an acrylic resin layer containing a pigment. This is an acrylic resin composite containing a chromate layer as a first layer, 5 to 40% by weight of colloidal silica as a second layer, a solid lubricant surface-treated with a titanate coupling agent, and an epoxy resin. It is a coated steel plate.

[0006]

However, the prior art as described above has the following problems. That is, in the prior art, first, a chromate layer is formed on the first layer to ensure corrosion resistance, and then a resin-based second layer is formed to ensure lubricity. For this reason, the electric resistance is high, and there is a problem in spot weldability, projection weldability, and groundability.

[0007] Accordingly, the present invention provides a chromate having excellent long-term stability.
And formate solutions have lubricity to withstand press-molding of a non-oiling, chromate treated steel sheet having a problem-free conductive spot weldability and grounding resistance and has a high corrosion resistance to withstand the naked use The purpose is to provide.

[0008]

The present invention relates to a chromate-treated steel sheet having a chromate layer on the surface of a steel sheet, an electrogalvanized steel sheet, a hot-dip galvanized steel sheet, or the like. m ² and silica in the chromate layer in a weight ratio of SiO ₂ / Cr of 0.1 to 0.1.
Contained in a range of 6.0, and further the chromate layer in the graphite, MoS _2, BN, calcium stearate and an organic lubricating material one or 0.1 of the lubricant particles made of two or more at a weight ratio of the lubricating particles / Cr It is a chromate treated steel sheet having high corrosion resistance, excellent lubricity and conductivity, characterized by being contained in a range.

The silica used in the present invention may be either aqueous silica (colloidal silica or water-dispersible silica) or gas-phase silica, and the particle diameter is desirably 100 μm or less. Also, natural wax as an organic lubricating substance,
Lubricated particles composed of one or more of polyolefin wax, modified polyolefin wax, and fluorocarbon can be used.

In producing a chromate steel plate, the long-term stability of the chromate solution is also an industrially important factor.
When the same liquid is used for a long period of time, the lubricating particles need to be the following lubricating particles. In other words, in this case, the lubricating particles having a surface layer having a nonionic surface-active activity, wherein 1 to 70% of the weight of the lubricating particles are surface particles having a nonionic surface-active effect, /> Ru used.

The coverage of the lubricating particles on the steel sheet surface is preferably less than 50%. In the present invention, lubricating particles, such as graphite, MoS ₂ , and BN, having a surface layer having a surface-active action formed on lubricating particles are referred to as lubricating particles. Further, when the lubricating particles have a particle diameter of more than 20 μm, the lubricating particles are liable to fall off from the film, and therefore, it is preferable to use fine lubricating particles.

The steel sheet of the present invention can be easily obtained by applying and drying a predetermined amount of the above-mentioned silica and lubricating particles or lubricity-imparting particles to a chromate treatment solution, followed by drying. In the present invention, lubricating particles and lubricity-imparting particles may be mixed and used.

Although the chromate treatment of the present invention is desirably performed on both sides of the steel sheet, it may be performed on only one side.

[0014]

In the present invention, since an organic resin that inhibits conductivity is not applied, sufficient conductivity can be easily ensured within an appropriate range of silica and lubricating particles. According to the present invention, the amount of chromium deposited on the chromate layer is
If the conversion is less than 10 mg / m ² , high performance in corrosion resistance after press working cannot be expected. On the other hand, if the amount of chromium adhered on one side exceeds 200 mg / m ^{2 in} terms of metal Cr, the film thickness becomes excessively large, so that the possibility of peeling of the film at the time of press working increases and mold seizure easily occurs. For the above reasons, the amount of chromium deposited on one side is 10 to 200 mg in terms of metal Cr.
/ M ² .

The addition of silica has a weight ratio of SiO ₂ / Cr of 0.1
If it is less than 10%, the corrosion resistance is inferior. On the other hand, if the weight ratio of SiO ₂ / Cr exceeds 6.0, conductivity may be impaired. Therefore, the weight ratio of SiO ₂ / Cr is set in the range of 0.1 to 6.0. As lubricating particles, it can be used in combination with one or more of graphite, MoS ₂ , BN, calcium stearate and organic lubricating substances. A fine particle having a particle diameter of 20 μm or less is preferable because these particles are easily deposited on the mold and a galling phenomenon is easily generated by the particles and the film fragments.

As the organic lubricating substance, natural wax, polyolefin wax, modified polyolefin wax,
Lubricating particles composed of one or more fluorocarbons can be used. When the amount of the lubricating particles is less than 0.1 in terms of the lubricating particles / Cr weight ratio, there is no lubricity improving effect. On the other hand, when the amount exceeds 100, the adhesion of the film is deteriorated, which may cause mold seizure during pressing. The amount of the lubricating particles added was limited to the range of 0.1 to 100 by the weight ratio of the lubricating particles / Cr.

In order to disperse the lubricating particles in the aqueous solution, the surface of the particles can be charged and electric repulsion can be used, or nonionic steric hindrance can be used. However, in general, the chromate solution has a high electrolyte concentration, and in a method utilizing electric repulsion, ions are adsorbed in a direction to neutralize the surface charge, whereby the repulsion between the particles is reduced, and as a result, the particles are aggregated. Resulting in. The aggregated particles precipitate or float and separate, and the function of imparting lubricity gradually decreases.

Therefore, it is necessary that the surfaces of the lubricating particles have a nonionic surfactant. The nonionic surfactant layer can be formed by adsorbing a nonionic surfactant or a water-soluble polymer to lubricating particles. Nonionic surfactants include alkylphenol-based (R-
φ-O- (CH ₂ CH ₂ O) nH, R = C ₉ H ₁₉ , C ₈ H ₁₇ , n = 2-50), higher alcohols (RO (R'O) n (R "O) mH, HLB value = 7 to 16), polyalkylene glycols (RO (EO / PO) nH 2) and the like, and water-soluble polymers include polyethylene glycol and polyvinyl alcohol.

If the nonionic surface layer is less than 1% of the lubricity-imparting particles, the ability to disperse the particles is small, and the particles will aggregate and precipitate in the chromate solution. Of the lubricity imparting particles,
When the lubricating component is less than 30%, the contribution of lubricating properties is reduced. Therefore, the range of 30% or more and less than 99% of the weight of the lubricating particles is internal lubricating particles, and the weight of the lubricating particles is range of less than 70% 1% shall be the surface layer having a nonionic surface activity.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. As a test material, a cold-rolled steel sheet (SPCC) with a thickness of 1 mm, an electrogalvanized steel sheet (SECC) with 20 g of zinc on each of the front and back surfaces, and zinc on each of the front and back surfaces
A hot-dip galvanized steel sheet (SPGC) with a basis weight of 60 g was used.

The chromate solution has an average particle size of chromic anhydride.
14nm liquid phase silica ｛Snowtex O manufactured by Nissan Chemical Co., Ltd.
(Trade name)｝, gas-phase silica having an average particle diameter of 7 nm (manufactured by Nippon Aerosil Co., Ltd.) was arbitrarily adjusted. In addition, the chromate solution was appropriately subjected to preliminary reduction using a reducing agent. The lubricating particles had use is A. Graphite B. MoS ₂ C.I. BN D. Calcium stearate Polyolefin wax F. PTFE (polytetrafluoroethylene wax).

[0022] for the stomach nonionic surfactants W. Lion Co., Ltd. Lipponox NC-100: alkylphenol-based LEOCOL SC-90 manufactured by Lion Corporation: higher alcohol type Sanyo Chemical PEG 1500: polyethylene glycol, but is not limited thereto. A anions based and cationic active agent V. Na lauryl sulfate anion Stearyl dimethyl benzyl ammonium chloride cation system was used. Further, as a wax emulsion having a surface layer of a nonionic surfactant, a. Sanyo Chemical KUE-13 natural wax 29% wax in solids b. Sanyo Chemical KUE-8 modified polyethylene wax
86% wax in solids was used. As a wax emulsion having a surface layer of an anionic surfactant c. EMUSTAR-0001 synthetic wax made by Nippon Seisakuwa was used.

As a method for adsorbing a surfactant to lubricating particles such as MoS ₂ , BN, and polyolefin wax to obtain lubricating particles, first, an aqueous solution of a surfactant is prepared,
The mixture was aged while stirring while adding lubricating particles. Thereafter, a chromate solution was mixed to a required concentration. Lubricating particles A,
B, C, D, E, and F are each ball milled to a particle size of about 8
The one adjusted to μm was used.

After mixing the lubricating particles or lubricity-imparting particles with the prepared chromate solution, the solution was stored with stirring for one week, and then applied to a steel plate with a bar coater and dried at 150 ° C. Table 1 shows the conditions of the chromate film in this case. At this time, the amount of Cr attached to the chromate film was 50 mg / m ^{2 in} terms of metal Cr, and the weight ratio of SiO ₂ / Cr was 3.0.

The press formability was determined by a cylinder drawing test with a diameter of 33 mm in which a blank with a diameter of 73 mm was drawn through without oiling. Those that can be squeezed were marked with ○, and those that could not be drawn were marked with x. Conductivity is good if the electrode is in contact with the steel plate surface at 10mm intervals and the resistance between them is 0.5Ω or less.
Those that exceeded were evaluated as defective.

The corrosion resistance is 5% in salt spray test (JIS2371)
Those with a rusting time of less than 100 hours were rated as x, and those with a rusting time of 100 hours or more were rated as ○. The ratio of the lubricating component in the lubricating particles is
It was determined by the ratio of the weight of the added lubricating particles to the weight of the solid component after the adsorption of the surfactant. The above evaluation results are also shown in Table 1 .

[0027]

As is apparent from the above, any of the present inventions
Shows excellent press formability (lubricity), conductivity, and corrosion resistance
However, when the chromate treatment solution was stored for 7 days, No. 34,
Since No. 57 used no surfactant, lubricating particles aggregated and did not enter the chromate film, resulting in poor workability.

In Nos. 35 and 58, the nonionic surfactant was insufficient, and the lubricity-imparting particles aggregated and did not enter the chromate film, resulting in poor workability. Nos. 36, 37, 38, 49, and 59 are ionic surface layers, so that lubricity-imparting particles aggregate, do not enter the chromate film, and have poor workability. Nos. 39, 40, 50, and 51 have poor workability due to excessive surface active layer and insufficient lubricating components.

[0030]

[0031]

[0032]

[0033]

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

However, the symbols of the lubricating particles in each table indicate the following. A Graphite B MoS ₂ CBN D Calcium stearate E Polyolefin wax F PTFE (polytetrafluoroethylene wax) The nonionic surfactant used in Table 2 is W Lion Co., Ltd. Liponox NC-100: alkylphenol-based X Lion Co., Ltd. Leocol SC-90: Higher alcohol Y Y Sanyo Chemical's PEG 1500: Polyethylene glycol Anionic and cationic surfactants are V Lauryl sulfate Na Anion Z Stearyl dimethylbenzyl ammonium chloride Cationic Nonionic surfactant As a wax emulsion with a a Sanyo Kasei KUE-13 natural wax 29% wax in solids b Sanyo Chemical KUE-8 modified polyethylene wax
C Wax in solid content 86% An EMUSTAR-0001 synthetic wax manufactured by Nippon Seiwa Co., Ltd. is shown as a wax emulsion having a surface layer of an anionic surfactant.

[0038]

According to the present invention, one or more of graphite, MoS ₂ , BN, calcium stearate, and an organic lubricating substance are added as lubricating particles in an appropriate amount to a chromate film containing SiO ₂ , In addition, lubricating particles
Has a nonionic surface active surface, lubricity
Particles, and 1 to 70% of the weight of the lubricity-imparting particles.
The surface layer has a nonionic surface-active effect, making it a chromate solution with excellent long-term stability.It can be pressed without oil coating and has high corrosion resistance.The surface electrical resistance is 0.5Ω or less. Made it possible to obtain a steel plate.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaki Mabuchi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (72) Inventor Keizo Okuno 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba No. Kawasaki Steel Engineering Co., Ltd. (72) Inventor Nobuo Totsuka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Headquarters (56) References JP-A-2-34792 JP-A-3-219086 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86

Claims (4)

(57) [Claims] 1. In a chromate-treated steel sheet having a chromate layer on the surface of the steel sheet, the amount of chromium adhered is calculated in terms of metal Cr.
10 to 200 mg / m ² , and silica in the chromate layer in a weight ratio of SiO ₂ / Cr in the range of 0.1 to 6.0, and further, graphite, Mo S ₂ , BN, calcium stearate in the chromate layer. And lubricating particles consisting of one or more of organic lubricating substances in a lubricating particle / Cr weight ratio
0.1 to 100 , and the lubricating particles further contain
Lubricated with a nonionic surface active surface
And lubricating particles in a range of 1 to 70% by weight of the lubricating particles.
Chromate treated steel sheet enclosed and excellent lubricity and conductivity has a high corrosion resistance, wherein the surface layer der Rukoto with nonionic surface active agent. 2. The highly corrosion-resistant lubricating material according to claim 1, wherein the organic lubricating substance is lubricating particles composed of one or more of natural wax, polyolefin wax, modified polyolefin wax and fluorocarbon. Chromate treated steel sheet with excellent conductivity. 3. A steel sheet according to claim 1 or 2 excellent chromated steel lubricity and conductivity has a high corrosion resistance, wherein it is a galvanized steel sheet. 4. A steel sheet a chromate-treated steel sheet excellent in claim 1 or 2 lubricity and conductivity has a high corrosion resistance, wherein it is a galvanized steel sheet.