JP2707927B2 - High press formability galvanized steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrogalvanized steel sheet,
Highly oil-coated films that have both rust prevention during the storage period and press formability during processing of galvanized steel sheets such as galvannealed steel sheets, galvanized steel sheets, and galvannealed steel sheets It relates to a press-formable zinc-based galvanized steel sheet.

[0002]

2. Description of the Related Art Conventionally, the press formability of galvanized steel sheets such as electrogalvanized steel sheets, galvannealed steel sheets, galvanized steel sheets, and galvannealed steel sheets has not always been sufficient.

For example, in an electrogalvanized steel sheet or a hot-dip galvanized steel sheet, since a coating layer is composed of a soft η phase of zinc, adhesion occurs partially at a die shoulder portion where a high surface pressure is applied at the time of forming. Friction resistance increases. In this case, since the plating layer has lower shear resistance than the adhered portion, the plating film may peel off or the plate may break.

[0004] Further, in the galvannealed steel sheet, after hot-dip galvanizing, mutual diffusion of iron and zinc occurs due to heat. With this, alloying of Fe and Zn progresses.
This time, the diffusion of iron and zinc is partially inhibited, and the iron concentration is lower on the surface of the plating layer than at the interface with the base iron. Furthermore, in recent years, plating has tended to be thicker from the viewpoint of improving corrosion resistance, the difference in iron concentration at the surface and interface has been increasingly widened, and a relatively soft ζ phase (FeZn ₁₃ ) with a low iron concentration exists on the surface. Easier,
The same phenomenon as the above-described electrogalvanized steel sheet and hot-dip galvanized steel sheet may occur.

[0005] Therefore, as a measure for improving the press formability of the galvanized steel sheet, a lubricant such as an organic solid lubricant is applied (see JP-A-1-136952) or a flash coat of Fe-Zn is applied. The lubrication is improved by rubbing. However, all of these methods are not only costly, but also in the method of applying a solid lubricant, the solid lubricant itself has inferior rust-preventing ability, and when the steel sheets are stacked, the solid lubricant is applied to the steel sheets by one another. Adhere to each other to cause a problem such as blocking.

Therefore, in order to solve these problems,
Attempts have been made to apply a metal working oil having both functions of a rust preventive oil and a press working oil to a steel sheet by imparting lubricity (press workability) to the rust preventive oil, and to press work. For example, Japanese Unexamined Patent Publication (Kokai) No. 3-212495 discloses that a base oil is provided with a rust preventive additive which is an alkyl sulfonate, a carboxylic acid, or a salt thereof, a lubricating aid which is a trialkyltrithiophosphite compound, and an inert type. A rust-prevention and press working oil comprising a sulfur-based extreme pressure additive is disclosed.

As described above, the anti-rust oil has lubricating properties (pressability).
In order to impart, an extreme pressure agent is usually blended. However, in such rust-preventive oils containing extreme pressure agents,
Oil stain is generated in the overlapping part of the steel sheet and the steel sheet, and the rust inhibitor and the extreme pressure agent in the rust preventive oil have an antagonistic action, and satisfactory press forming performance is not exhibited, or even if exhibited, it is not enough There are drawbacks such as performance level.

[0008]

SUMMARY OF THE INVENTION It is a general object of the present invention to greatly improve the press-forming performance of a zinc-coated steel sheet to a performance equivalent to the case where a flash coat or an organic solid lubricant is used. Provide galvanized steel sheets that can reduce surface damage and cracking during pressing, suppress the occurrence of oil stains at the overlap between steel sheets, and do not require a new press oil application process. It is to be.

A more specific object of the present invention is to prevent antagonism between the rust preventive agent and the extreme pressure agent added to the rust preventive oil, thereby preventing rust preventive oil from exhibiting both rust preventive property and workability. An object of the present invention is to provide a press-formable galvanized steel sheet obtained by applying a rust and metal working oil composition.

[0010]

The present inventors have conducted intensive studies on a rust-preventing and metalworking oil composition for a galvanized steel sheet which can solve the problems described above. (B) with a specific extreme pressure enhancer and / or (C)
The inventors have found that the object can be achieved by combining and combining an oiliness improver having a specific composition, and completed the present invention.

Here, the present invention relates to (A) a base oil, (B)
At least one selected from a benzothiazole compound and a thiadiazole compound as an extreme pressure improver,
A base number of 400 to 50 in which calcium carbonate having a particle size of 0.1 μm or less is dispersed and dissolved as an oiliness improver (C) in a range of 0.4 to 3.0% by weight based on the whole amount.
A high press having an oil composition film in which at least one selected from sulfonates of 0 mgKOH / g is blended in a proportion such that the Ca content is in the range of 0.5 to 2.5% by weight based on the total amount. It is a formable galvanized steel sheet.

[0012]

Hereinafter, the present invention will be described in detail. The galvanized steel sheet to which the present invention is applied is an electrogalvanized steel sheet, an alloyed electrogalvanized steel sheet, a galvanized steel sheet, an alloyed galvanized steel sheet, and the like.

In the present invention, the base oil used as the component (A) in the oil composition to be applied to such a zinc-based plated steel sheet is a base oil conventionally used as a rust-preventive oil. Any of them can be selected and used,
The kinematic viscosity at 40 ° C. is preferably in the range of 1 to 500 cSt, for example, kerosene, light oil fraction, 60 spindle oil, 70N
, 100N, 150N, 300N, 500N, and BS mineral oils can be used. Among these, it is particularly preferable to use one or a combination of two or more kinds so that the viscosity at 40 ° C. is 5 to 30 cSt.

That is, according to a preferred embodiment of the present invention, the “base oil” is at least one selected from the group consisting of kerosene, a light oil fraction, a spindle oil and a mineral oil, and has a kinematic viscosity at 40 ° C. of 1 to 1. Adjusted to 500 cSt.

In the oil composition according to the present invention,
An extreme pressure improver is used as the component (B). As the extreme pressure improver, at least one selected from benzothiazole compounds and thiadiazole compounds is used.

Specific preferred examples thereof include benzothiazole, 2-mercaptobenzothiazole, 2- (hexyldithio) benzothiazole, 2- (octyldithio) benzothiazole, 2- (decyldithio) benzothiazole, 2- ( Dodecyldithio) benzothiazole,
2- (N, N-diethyldithiocarbamyl) benzothiazole, 2,5-dimethylcapto-1,3,4-thiadiazole, 2,5-bis (hexyldithio) -1,3,4
-Thiadiazole, 2,5-bis (octyldithio)-
1,3,4-thiadiazole, 2,5-bis (N, N-diethyldithiocarbamyl) -1,3,4-thiadiazole, 3,5-dimercapto-1,2,4-thiadiazole, 3,5- Bis (hexyldithio) -1,2,4-thiadiazole, 3,5-bis (octyldithio) -1,
2,4-thiadiazole, 3,5-bis (N, N-diethyldithiocarbamyl) -1,2,4-thiadiazole,
And the like.

The extreme pressure improver of the component (B) may be used alone or in combination of two or more. The compounding amount is usually 0.4 to 3% by weight based on the total amount of the composition.
Is selected in the range. When the amount is less than 0.4% by weight, the extreme pressure property is insufficient. When the amount exceeds 3% by weight, oil stain may be generated, which is not preferable.

In the oil composition of the present invention, an oiliness improver is used as the component (C). As the oiliness improver, at least one selected from sulfonates having a base number of 400 to 500 mgKOH / g in which calcium carbonate having a particle size of 0.1 μm or less is dispersed and dissolved is used. In the oil composition of the present invention, the component (C) is blended in such a ratio that the Ca content of the obtained oil composition is in the range of 0.5 to 2.5% by weight. If the Ca content is less than 0.5% by weight, the effect of improving lubricity is small, and if it exceeds 2.5% by weight, the degreasing property is undesirably deteriorated.

If the particle size of the calcium carbonate is more than 0.1 μm, the dispersion and stability in the rust preventive oil are deteriorated due to secondary aggregation, and the oiliness improver component may be separated and settled.
In the present invention, it is limited to 0.1 μm or less, preferably 0.05 μm or less. The base value is specified because if it is less than 400 mgKOH / g, there is a risk of degreasing
If the amount is too large, alkali corrosion of Zn may be caused. Therefore, it is limited to the range of 400 to 500 mg KOH / g.

The oil composition may further include, if desired,
Various additives, for example, oxidized waxes, metal soaps such as Ca salts, Ba salts, and Na salts of higher fatty acids, fatty acids such as oleic acid, stearic acid, and lauric acid, and sorbitan monooleate, as long as the objects of the present invention are not impaired. And neutral or weakly basic sulfonates having a base value of 20 mgKOH / g or less, such as carboxylic acid partial esters of polyhydric alcohols such as Ba sulfonate and Ca sulfonate, and amides and imides.

As described above, the feature of the present invention resides in a galvanized steel sheet provided with a coating made of an oil composition for rust prevention and metal working. It is sufficient and does not need to be added again. More specifically, the feature of the present invention lies in that (B) the extreme pressure improver and / or (C) the oil improver are blended with respect to the base oil, and (B) the extreme pressure improver. Although the lubricity improving effect is observed even when the improver and the (C) oiliness improver are individually compounded, the effect is further enhanced by combining them.

The mechanism of improving lubricity in the present invention is not clear, but is considered as follows. First, the extreme pressure improver can be considered as follows. Since press molding is generally performed by continuous processing,
In the case of parts with a high degree of processing, the mold temperature rises to about 120 ° C. However, the extreme pressure improver (B) described above is used as an extreme pressure additive under such conditions of high surface pressure and high temperature. It is considered that it reacts with the surface of the galvanized steel sheet and the reaction product becomes a lubricant and has a function of reducing frictional resistance.

FIG. 3 is a graph showing the results of the embodiment described later. The relationship will be described below based on the graph. That is, from the sample after performing hat forming with a bead on an EG steel sheet coated with a rust-preventive oil containing benzothiazole as an extreme pressure improver according to the present invention, (a) an unprocessed part, (b) a bead passing part, (C) FIG. 3 is a graph showing the S2p spectrum when three portions of the bead and the die passing through the shoulder were cut out, ultrasonically washed with acetone, and analyzed by XPS. As can be seen from this, although the peak temperature was weak, the presence of S was clearly recognized as compared with the normal rust preventive oil. Then, it can be seen that the peak near 169 eV is higher in (c) than in (a) and (b) as the processing proceeds.

FIG. 4 shows the peak area ratio of each of the peaks (Eb1 = 163.4 eV) and (Eb2 = 169.0 eV). The most severe processing (c) is
The ratio of the peaks is almost twice that of (a) and (b). From this, it is considered that the extreme pressure property improver reacts with zinc in boundary lubrication to form some compound.

That is, the benzothiazole compound and the thiadiazole compound used as the extreme pressure improver in the present invention have excellent reactivity with zinc under conditions of high surface pressure and high temperature, and the reaction product becomes a lubricant to produce friction. It is considered to have the function of lowering the resistance.

Next, a rust preventive oil containing a calcium carbonate dispersion used as an oiliness improver in the present invention was applied.
The same investigation was performed on EG steel sheets, and Ca was analyzed by XPS. In each case, a strong peak was observed, and no Ca peak shift due to processing was observed. From this, it is considered that the calcium carbonate dispersion as the oiliness improver was adsorbed on the steel sheet surface.

That is, (C) the oiliness improver (calcium carbonate dispersion) is adsorbed on the steel sheet surface as a friction modifier under relatively low surface pressure and low temperature conditions to prevent metal contact between the steel sheet surface and the mold. It is considered to have a function of reducing frictional resistance.

Therefore, in a zinc-based plated steel sheet provided with an oil composition film obtained by adding these both in combination, the frictional resistance can be reduced over a wider range of surface pressure and temperature conditions. It is considered that a good sliding property is stably provided to the press forming of the present invention.

In addition, these extreme pressure improvers and oiliness improvers can be used without problems in the performance other than lubricity, such as degreasing and rust resistance, if they are blended within the range specified by the present invention.
Not only can a rust-preventing oil attain a performance equal to or higher than that of a normal rust-preventive oil, but (C) a rust-preventive oil containing an oiliness improver has better rust resistance than a normal rust-preventive oil. These are those having an excellent effect on rust because the calcium carbonate dispersion as an oiliness improver is adsorbed on the steel sheet surface as described above, thereby improving the thixotropy and improving the oil retention performance. it is conceivable that.

The film thickness of such an excellent oil composition film is not particularly limited as long as the desired effect can be obtained.
About 0.3 to 3 g / m ² is sufficient. The application form may be brush coating, spray coating, or application using a roll coater.

[0031]

Next, the present invention will be described in more detail by way of examples, which are merely examples and the present invention is not limited thereto. Table 1 shows the examples of the present invention. The galvanized steel sheet is EG: electrogalvanized steel sheet (coating weight 60/60 g /
m ^2, thickness 0.8 mm) GI: hot-dip galvanized steel sheet (coating weight 90/90 g /
m ^2, thickness 0.8 mm) GA: alloyed hot-dip galvanized steel sheet (coating weight 60
/ 60 g / m ² , thickness 0.8 mm).

The rust preventive oil is usually based on a rust preventive oil (kerosene, kinematic viscosity at 40 ° C. = 15 cSt), and contains an extreme pressure improver (2-mercaptobenzothiazole) and an oil improver (particle size:
Base number 450 with 0.03μm calcium carbonate dispersed and dissolved
mg KOH / g Ca sulfonate) in the amount shown in Table 1 was applied to each galvanized steel sheet.

Each of the test materials thus obtained was evaluated for press formability, degreasing property, rust resistance and oil stain resistance. The test at that time followed the method shown below. The results are summarized in Table 1.

1) Press Formability In the hat forming test with beads shown in FIG. 1, after applying 1.0 g / m ² of each test oil composition to one side of each zinc-based plated steel sheet of 250 × 50 mm size as a test piece. , Bead height 7m
The molding was performed under the conditions of m, molding height 43 mm and molding speed 70 mm / sec, and the molding limit range when the blank holder pressure was changed in increments of 0.1 kg / cm ² was examined. That is, the higher the molding limit pressure, the better the moldability. The numbers in the figure are dimensions
(mm).

In addition, a cylindrical deep drawing test (blank: diameter 78
mm, punch: diameter 33 mm, die: diameter 35 mm) and the maximum punch force when the blank holder force was 1 ton was measured.
That is, the lower the maximum punching force, the better the lubricity.
When a crack is seen in the test piece, it is indicated by “x”.

Next, according to the plane sliding test procedure shown in FIG. 2, the test piece pressed against both dies by hydraulic pressure is pulled,
The tensile force at that time was measured with a load cell to determine the frictional force, and the friction coefficient was measured from the pressing force and the frictional force.
The test conditions were as follows. Test material 25 × 300 mm Sliding distance 150 mm Die SKD11 Pressing area 12 × 25 (board width) Pressing force 160 kgf / cm ² Speed 200 mm / min.

2) Rust prevention and oil stain resistance (Stack test) After applying 2 g / m ² of each test oil composition to various zinc-based plated steel sheets, one drop of pure water was inserted between test pieces and tested. After stacking four pieces and fixing them with packing and clips, one was left at room temperature and the other was left in a humid environment of 50 ° C. for 30 days to examine the degree of rusting and discoloration of the overlapped portion.

◎: no discoloration, :: slight discoloration, Δ: discoloration, ×: rusting.

3) Degreasing property After applying 2 g / m ² of each test oil composition to various types of galvanized steel sheets, four test pieces were piled up, fixed with packing and clips, and then placed in a moist environment at 50 ° C. After leaving for 20 days and using the open test piece, alkaline degreasing solution (manufactured by Nippon Parkerizing Co., Ltd.)
Spray degreasing with FC-4326TA) was performed at 40 ° C. for 30 seconds, and the degreasing area was measured from the water wetted area ratio after washing with water.

[0040]

[Table 1]

As is evident from Table 1, the zinc-coated steel sheet provided with the film made of the oil composition for rust prevention and metal working according to the present invention was coated with a Fe-Zn flash coat and a solid lubricant in press working. It has excellent moldability comparable to that of rust-proofing, rust resistance and oil stain properties higher than those of ordinary rust-preventive oils, and good degreasing in the pretreatment step of coating.

FIG. 3 shows three places of (a) an unprocessed part, (b) a bead passing part, (c) a bead and a die shoulder passing part after performing hat forming with a bead of the test material of test No. 20. Is a spectrum of S2p when a sample was cut out, ultrasonically washed with acetone, and analyzed by XPS (X-ray photoelectron spectroscopy). The relative comparison is made with the maximum peak taken as 100%. Although the peak intensity was weak, the presence of S was clearly recognized as compared with the ordinary rust preventive oil. Then, it can be seen that the peak near 169 eV is higher in (c) as processing proceeds, that is, as compared to (a) and (b).

FIG. 4 shows the peak area ratio of each of the peaks (Eb1 = 163.4 eV) and (Eb2 = 169.0 eV) in FIG. Peak area ratio = / +
× 100 (%). The most severe processing (c) is (a), (b)
The ratio of the peak is almost twice as large as that of. This is probably because the extreme pressure property improver reacts with zinc in boundary lubrication to form some compound. In addition,
The same evaluation as in this example was obtained for an example using thiadiazole as an extreme pressure improver.

[0044]

As is clear from the above, according to the present invention, the oil composition for rust prevention and metal working is simply applied in advance,
Excellent press formability is ensured, and a satisfactory rust-preventing effect is exhibited, and its significance is significant because of its remarkable practical effects.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram of a point of a hat forming test method with a bead.

FIG. 2 is an explanatory view of a procedure of a plane sliding test method.

FIG. 3 is a graph of an XPS spectrum (S2p) showing a result of an example using an EG steel sheet.

FIG. 4 is a graph of a peak area ratio showing a result of the same example.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location C10M 135: 36 125: 10) C10N 10:04 20:06 30:00 30:06 30:12 40 : 24 50:02 80:00 (72) Inventor Taihei Okada 24-4 Anesaki Kaigan, Ichihara-shi Idemitsu Kosan Co., Ltd. Sales Research Laboratory (56) References JP-A-3-47898 (JP, A) JP-A-3-3 106993 (JP, A)

Claims (2)

(57) [Claims] 1. A sulfonate having a base number of 400 to 500 mg KOH / g in which calcium carbonate having a particle size of 0.1 μm or less is dispersed and dissolved as an oiliness improver (C) with respect to (A) a base oil. A highly press-formable zinc-based material having an applied film composed of an oil composition in which at least one kind is blended based on the total amount so that the Ca content is in the range of 0.5 to 2.5% by weight. Plated steel sheet. 2. An amount of at least one selected from a benzothiazole compound and a thiadiazole compound as an extreme pressure improver (B) based on the total amount of (A) a base oil and 0.4 to 3. 0% by weight, and (C) a base number of 400 to 500 mg KO in which calcium carbonate having a particle size of 0.1 μm or less is dispersed and dissolved as an oiliness improver.
At least one selected from H / g sulfonates
Based on the total amount of the seed, the Ca content is 0.5 to 2.5% by weight.
Coating consisting of oil composition in proportions such that a range of
High press formability galvanized steel sheet with cloth coating.