JP2001149860A - Coated steel sheet excellent in self-lubricating property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive coated steel sheet excellent in a self- lubricating property, being suited for a high speed press. SOLUTION: A low-melting solid lubricant, having a melting point of 60-130 deg.C, of 15-60% based on the total solid lubricant, and the balance fluororesin powder are mixed, and added to the coating material of the uppermost layer so that their total weight is 1.0-10.0 wt.% based on a dry coating film. A microcrystalline wax is suitably used as the low-melting solid lubricant, and it is preferable that the solid lubricant has an average particle diameter of 1.0-20.0 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-lubricating coated steel sheet exhibiting stable high lubrication even when high-speed and difficult-to-form press processing is performed in deep drawing of a steel sheet or the like.

[0002]

2. Description of the Related Art It has been noted that a coated steel sheet having a lubricating film to which a solid lubricant has been added can omit a degreasing step and a coating step after press working. Its use is expanding for the purpose of maintenance and space saving.

Further, from the demand for further cost reduction,
Although application to a high-speed press is being promoted, the high-speed press is required to exhibit stable lubricating characteristics at a wide range of processing temperatures because of a large temperature fluctuation due to friction. For this reason, Japanese Unexamined Patent Publication No. 3-281578 discloses a wax (in this case, a polyolefin resin).
And a wear-resistant paint in which two kinds of solid lubricants of fluorine resin are co-dispersed. However, instead of simply using two kinds of lubricants together, a liquid obtained by dissolving the two components in a high-temperature solvent and then quenching is used as the lubricating component of the paint. It is characterized in that it is brought into a state of being covered (masked) by a film.

In Japanese Patent Application Laid-Open No. 8-134487, after mixing and stirring fine-grained fluororesin powder into a molten polyolefin-based resin, the whole is coagulated and refined to obtain a polyolefin-based resin block. Disclosed is a lubricated metal plate obtained by previously manufacturing a solid lubricant in which a fluororesin powder is dispersed and adding the solid lubricant to a coating resin.

[0005]

As described above, it is excellent in terms of performance to prepare two solid lubricants having different melting temperatures in advance by a microencapsulation technique or a pre-granulation formulation. Although lubricating properties can be obtained, it naturally leads to a significant increase in cost and work. The present invention provides a lubricated coated steel sheet that is controlled so as to be in an appropriate dispersed form by mixing a simple two-component solid lubricant without using such preliminary microencapsulation technology or pre-granulation means. Things.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a low melting point solid lubricant having a melting point of 60 to 130.degree. The remaining amount as a lubricant, a total of 1.0 to
A coated steel sheet having excellent self-lubricating properties characterized by being mixed and added at 10.0% by mass. Here, the melting point is 60 to 130.
The low-melting solid lubricant at ℃ is blended in such a manner that the low-melting solid lubricant becomes a semi-molten state when heated and dried in a coating line and bleeds out to the coating film surface side,
A part thereof is coated so as to surround the high melting point fluororesin powder, thereby controlling the dispersion form of the solid lubricant.

Solid lubricants which solidify at room temperature and have the above melting point include natural waxes such as beeswax and montan wax, paraffin wax, petroleum-based microcrystalline wax (melting point 60 to 90 ° C., average molecular weight 580 to 580). 700) and polyethylene wax (melting point 90-130 ° C., average molecular weight 5000 or less). In particular, the microcrystalline wax is preferable because it has good adhesive bonding strength to the organic film base material, and the dispersed state after bleeding is finely dispersed on the surface.

Examples of the fluororesin powder include ethylene tetrafluoride (PTFE), ethylene tetrafluoride-propylene hexafluoride copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE). They are,
Even when the temperature exceeds 300 ° C., it exhibits a stable form and properties, and does not cause physical change such as melting in the heating and baking process of the coated steel sheet in a short time.

The solid lubricant to be added preferably has an average particle size of 1.0 to 20.0 μm. When the average particle size is less than 1.0 μm, the lubricating effect is reduced, and when the average particle size exceeds 20.0 μm, the coating stability is poor,
Further, this is because a problem such as falling off of the resin powder during the processing is likely to occur.

[0010] The compounding ratio of the solid lubricant to be mixed in the uppermost coating material is 1.0 to 10% in a dry film state of the product.
It must be 0% by mass. If the amount is less than 1.0% by mass, the lubricating effect becomes insufficient, while if the amount exceeds 10.0% by mass, the effect is saturated.

As the organic film material in the paint of the uppermost layer, polyester resin, acrylic resin, epoxy resin, urethane resin, urea melamine resin,
Examples thereof include amino resins, phenolic resins, polyvinyl chloride fluororesins, etc., alone or in combination, and plastics such as polyester, polyethylene terephthalate, polyvinyl chloride, polyethylene, and polypropylene. The steel sheet serving as the base of the coating in the present invention covers ordinary steel sheets, stainless steel sheets and various types of plated steel sheets.

[0012]

EXAMPLE A coated steel sheet of the present invention was produced in a continuous coating line using a non-aging deep drawing steel sheet having a thickness of 0.6 mm which had been previously zinc-plated in a continuous hot-dip galvanizing line. The coated steel sheet is manufactured by applying a coating amount of 40 mg / m2 on the front and back surfaces of the coated steel sheet at a pretreatment facility of a continuous coating line, and then applying a coating of a high-molecular polyester component of the undercoat film on the front side by roll coating to a thickness of 7 μm.
m, and fired in a firing furnace at 215 ° C. for 30 seconds to form an undercoat film. Further, the mixing ratio of the low-melting wax solid lubricant (A) and the fluororesin powder solid lubricant (B) to the top coating film was changed as shown in Table 1 to the coating material containing polyester as the top coating film. , (A), and (B) were added to the coating material as a total of 5.0% by mass.

Here, a low melting point wax solid lubricant (A)
Is a microcrystalline wax having an average particle size of 7.0 μm and a melting temperature of 70 ° C., and a fluororesin powder solid lubricant (B)
PTFE particles having the same average particle size of 7.0 μm were used. On the baked undercoat film, each was coated with a thickness of 15 μm by a roll coat, and then 230
It was baked under the conditions of ° C × 40 seconds to form a top coat.

The quality of the lubricity was evaluated at a test temperature of 40 to 1
The judgment was made based on the value of the dynamic friction coefficient at each temperature at 20 ° C. Among them, those having a test temperature of 100 ° C. or higher were evaluated as corresponding to the processing conditions of the high-speed press. The measurement of the coefficient of kinetic friction was carried out using a Bowden tester.
The measurement was performed using a steel ball having a diameter of 5 mm under a load of 500 g.
Here, the value of the dynamic friction coefficient was set as a target (pass) to be less than 0.10. Table 1 shows the measurement results of the dynamic friction coefficient at each temperature.

[0015]

[Table 1]

[Table 1, Test No. 1 (Comparative Example 1)] When the total amount of the solid lubricant to be added is a fluororesin powder, the temperature dependence of the dynamic friction coefficient is small, and a stable value up to a high temperature is obtained. Show. However, the value of the dynamic friction coefficient is
It is at a high level of 0.12 or more. This is presumably because, when the high melting point fluororesin powder alone is used, the viscosity as a lubricant is maintained up to a high temperature range, but the level is higher than that of a low melting point wax.

[Test No. 2 (Example 1) in Table 1] The compounding ratio of the low melting point wax (microcrystalline wax) was 15
%, The value of the coefficient of dynamic friction is as low as less than 0.10, and shows a stable temperature dependence up to a high temperature of 120 ° C. This is because the molten bleed on the surface of the microcrystalline wax at the time of manufacturing and heating the coated steel sheet disperses and distributes the microcrystalline wax finely on the painted surface, and the mutual effect that the microcrystalline wax adheres to the fluororesin powder in the form of a film. Probably due to action. The blending ratio of low melting point wax (microcrystalline wax) is 60
As in Example 1, Test No. 3 (Example 2) in which the dynamic friction coefficient was less than 0.10 and showed stable temperature dependency up to a high temperature of 120 ° C.

In Table 1, Test Nos. 4 to 5 (Comparative Examples 2 to 5)
Regarding 3)] When the blending ratio of the low melting point wax (microcrystalline wax) is 75% or more, the value of the kinetic friction coefficient at less than 60 ° C. shows an extremely good low value, but the relative value of the fluororesin powder is relatively low. Since the amount of addition was small, the value of the dynamic friction coefficient in a high temperature region of 100 ° C. or more rapidly increased, and the lubricity was reduced. Therefore, as specified in the present invention, the optimal addition amount of the low melting point wax is 15 to 60.
It can be seen that the content is mass%.

[0019]

As described above, according to the present invention, it is possible to obtain a coated steel sheet which is extremely excellent in terms of die galling resistance, drawing workability, and stretchability in press working even under conditions of high-speed pressing. Therefore, the coated steel sheet according to the present invention can be used for a coated steel sheet subjected to severe processing, and its characteristics can be effectively utilized.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C10M 107/38 C10M 107/38 109/00 109/00 // B21D 22/20 B21D 22/20 E C10N 40:24 C10N 40:24 Z 50:08 50:08 F-term (reference) 4D075 AE03 CA09 DA06 DB02 EA02 EA37 EB13 EB16 EB56 4F100 AB03A AB18A AJ11B AK17B AK18B AK41B AK41C BA02 BA03 BA07 BA10A BA10B BA13 CA19B CC00B DE01 E19BCC00B DE01 CD02A DA05A EA04A PA23 PA31 PA34 QA12 4J038 BA212 CB021 CB081 CD021 CD091 CD092 DA041 DA141 DA161 DB001 DD001 DD071 DG001 EA011 MA13 PC02

Claims (2)

[Claims] 1. A low-melting solid lubricant having a melting point of 60 to 130 ° C. in a total amount of 15 to 60% of a solid lubricant in a top raw material of a coated steel sheet for forming an organic film on a surface of a steel sheet, and a fluororesin. A coated steel sheet having excellent self-lubricating properties, characterized in that 1.0 to 10.0% by mass of a total amount of powder is mixed and added to a dry coating film with the remaining amount being powder. 2. The coated steel sheet having excellent self-lubricating properties according to claim 1, wherein the low melting point solid lubricant is a microcrystalline wax.