JPH0976004A - Lubricating and rustproofing oil coated steel sheet excellent in workability in press - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain remarkable reduction effect of slide resistance by applying lubricating/rustproofing oil having a specified effective thickness of coating oil on the surface of a steel sheet having specified surface roughness. SOLUTION: As for a lubricating/rustproofing oil coated steel sheet, the lubricating/rustproofing oil of a quantity by which the effective thickness (t) of coating oil, which is expressed by a formula: effective thickness (t) of coating oil = coating quantity (g/m<2> ) of the lubricating/rustproofing oil per density (g/m<3> ) of the lubricating/rustproofing oil, becomes 0.5Ra-1.0Ra shall be applied on the surface of the steel sheet having surface roughness Ra (center-line mean roughness) of 0.3-2.0μm. A galvannealed steel sheet is better as the steel sheet. The effective thickness (t) (μm) of coating oil is specified at 0.5Ra-1.0Ra (μm), because the application effects (rustproofing and lubricating actions) is insufficient when the thickness is less than 0.5Ra and lubricating action of the film of coating oil is spoiled and satisfactory reduction effect of slide resistance is not obtained when the thickness is over 1.0Ra. In this way, the workability in press to be improved is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the press workability of a lubricating anticorrosive oil-coated steel sheet used as a steel sheet for automobiles, and more particularly to an improvement in sliding resistance due to the lubricating action of a lubricating antirust oil film.

[0002]

2. Description of the Related Art Various types of steel sheets used in the automobile industry, such as galvannealed steel sheets, are coated with a lubricating rust preventive oil having the effect of a rust preventive oil and a press lubricant when shipped from a steel plate manufacturer. This prevents the generation of rust before the customer uses it for press working, and also provides the lubricity required for press working (the effect of reducing the sliding resistance between the steel plate and the press die). I am trying to have it. Regarding the application of the above lubricating rust preventive oil, as a device for ensuring the rust prevention and the lubrication effect, for example, the applied amount is 0.5 to 5.0 g / m 2.
² , more preferably in the range of 1 to ² g / m ² (Japanese Patent Laid-Open No. 4-337090), or by forming a certain fine uneven surface on a steel plate and applying a coating of about 4 to 8 μm on the surface. Proposals have also been made such as capturing an oil film (Japanese Patent Laid-Open No. 7-9016).

[0003]

The inventors of the present invention unexpectedly adjusted the coating amount within a certain range of a relatively small amount in the course of research on the coating form and the rust-preventing / lubricating action of the lubricating rust preventive oil. As a result, compared to the conventional coating mode in which a large amount of coating is applied, the lubrication effect can be exhibited more effectively, and while maintaining the required rust prevention effect, the sliding resistance in press processing can be improved. It has been found that it can be significantly reduced.
The present invention has been made based on this finding.

[0004]

Means for Solving the Problems The lubricating rust-preventive oil-coated steel sheet of the present invention has a surface roughness Ra (center line average roughness) of 0.3 to 2.
On the surface of a steel plate having a thickness of 0 μm, the following formula [1]: effective oil thickness t = lubrication / rust prevention oil application amount (g / m ² ) / lubrication / rust prevention oil density (g / cm ³ ) ... [1] It is characterized in that the lubricating anticorrosive oil is applied in an amount such that the effective oil thickness t is 0.5 Ra to 1.0 Ra.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Comparing the coating amount of lubricating rust preventive oil of the present invention with that of the conventional one, a relatively large amount of coating has been conventionally made without consideration of the surface roughness of the steel sheet.
For example, a conventional general coating amount for a galvannealed steel sheet is about 1 to ² g / m ² regardless of the surface roughness. Ordinary surface roughness Ra of galvannealed steel sheet is about 0.6 to 1.1, and the density of lubricating rust preventive oil is generally about 0.9 g / cm 3.
Because it is ^3, Applying the coating amount of the above formula (1), the effective oiling thickness t of about 1.1 to 2.1, and the which corresponds to less certain coating amount covering the protrusion top of the uneven surface of the steel sheet . Application amount in the present invention (effective oil thickness t: 0.5 Ra
1.0 Ra) is regulated in a range of a small amount as compared with the conventional one, and no examples have been reported so far regarding sliding resistance and pressing behavior in such a small coating area.

By controlling the lubricating rust preventive oil on the surface of the steel sheet to such an amount that the effective oil thickness t of the formula [1] becomes 1.0 Ra or less according to the present invention, the lubricating function of the lubricating rust preventive oil can be improved. It is effectively expressed, and the sliding resistance drops sharply. Although the details of the mechanism of this phenomenon are not fully understood,
When considered in comparison with conventional multimeric coating form, as shown in FIG. 6, if the coating film 2 of the lubricating rust-preventive oil is a large amount applied that exceeds the convex portion of the steel sheet surface 1 _1, press working process, lubricating Due to its viscous nature, a considerable amount of rust preventive oil was wiped off from the surface of the steel sheet with the relative sliding of the press die 3, and as a result, the lubricating effect of the oil coating film at the sliding interface was impaired. On the other hand, when the application amount regulated by the present invention is applied, as shown in FIG. 5, unlike the above, there is almost no outflow of the oil coating film 2 wiped by the mold 3, and the oil coating film is enclosed in the unevenness. It is considered that the oil is stably stored in the sliding interface and contributes to the reduction of sliding resistance.

In the present invention, the surface roughness (Ra) of the steel sheet
The lower limit of 0.3 μm is specified because it is difficult to stably maintain the oil coating required to obtain the rust prevention / lubrication effect if the surface roughness is smaller than that. The upper limit of Ra is specified to be 2.0 μm. Above that, the coefficient of friction μ with the mold due to the unevenness of the surface increases, and in this case as well, the effect of improving sliding resistance must be ensured. Because it becomes difficult. The adjustment of the surface roughness of the steel sheet is performed, for example, in temper rolling by using a dull roll having a predetermined roughness on the roll surface and transferring the surface irregularities of the roll.

Effective oil thickness t (μm) according to the above formula [1]
Is specified in the range of 0.5 Ra to 1.0 Ra (μm) because if it is less than 0.5 Ra, the coating effect (anticorrosion / lubrication) is insufficient, and if it exceeds 1.0 Ra, the oil coating film This is because the lubricating effect of is impaired, and it becomes impossible to obtain a sufficient reduction effect of sliding resistance. The sliding resistance during press working of a steel plate differs depending on the oil coating thickness present at the sliding interface between the press die and the steel plate, and the oil coating thickness is the same when the amount of lubricating anticorrosive oil applied is the same. However, it varies depending on the surface roughness of the steel sheet. By controlling the coating amount within a certain range in consideration of the surface roughness of the steel plate by the above formula [1],
It becomes possible to effectively reduce the sliding resistance in press working.

FIG. 7 shows an example of a lubricating and rust preventive oil coating line used for carrying out the present invention. 11 is a surface roughness measuring device, 12 is a control device, 13 is a lubrication and rust preventive oil coating device, 1
Reference numeral 4 is a coating amount measuring device. The surface roughness of the steel plate 1 unwound from the reel R ₁ is detected by the surface roughness measuring device 11, and then transferred to the coating device 13. Control device 1
2 calculates the amount of lubricating rust preventive oil coating satisfying the above formula [1] based on the detection signal of the surface roughness measuring device 11, and the calculation result is output as a coating amount control signal of the coating device 13.
The steel plate 1 is coated with a controlled coating amount of the lubricating anticorrosive oil in the coating device 13, and after the coating amount is detected by the coating amount measuring device 14, it is wound on the reel R ₂ . The detection signal of the coating amount measuring device 14 is supplied to the control device 12 if necessary.
Be fed back to.

[0010]

【Example】

[1] Sliding friction characteristics (1) Test steel sheet Alloyed hot-dip galvanized steel sheet (double-sided plating) Base material steel sheet: Ultra-low carbon Ti-added IF steel (sheet thickness: 0.7 mm) Plating layer thickness: 8.4 μm / single-sided plating layer Surface roughness: Adjusted by temper rolling with dull roll

(2) Preparation of test piece After applying a lubricating rust preventive oil on both sides of the plate material cut out from the above steel plate, a thermo-hygrostat (temperature: 50 ° C, humidity: 10 to 20%,
Atmosphere: Atmosphere) Installed horizontally in 70-150
The oil coating film is dried while holding Hr. Lubricating rust preventive oil High lubricating rust preventive oil "NOX-RUST Mu-10" (Parker Kosan Co., Ltd.)
Density: 0.894 g / cm ³ (15 ℃) Viscosity: 13.7 CST (40 ℃) Total acid value: 0.89 (KOH mg / g) Moisture: 0.016% Extreme pressure additive: S-based ester compound, P-based ester compound

(3) Sliding test procedure As shown in FIG. 8, the pressing pieces 2 arranged to face each other on the left and right sides.
The pull-out force F is measured by a plane sliding test in which the test piece TP is sandwiched between 1 and 21 with a predetermined pressing force and pulled upward. Specimen size: Width 30 mm, length 300 mm Pressing piece: Pressing area 12 × 30, mm Surface roughness Ra 0.2 μm Steel plate pressing force: 900 kgf Drawing speed: 100 mm / min

The results of the above sliding test are shown in FIGS. 1 to 4 [FIG. 1: Surface roughness Ra of the test material is 1.08 μm, FIG.
0.91 μm, Figure 3: Same Ra 0.90 μm, Figure 4: Same Ra 0.65
μm]. As shown in the figure, by adjusting the coating amount of the lubricating rust preventive oil so that the effective coating thickness t becomes Ra or less, the pulling force is reduced as the sliding resistance reducing effect. That is, in a large amount application region where the effective oil thickness t exceeds Ra (as in conventional application), the sliding resistance is high,
The drawing force F is almost constant within the range of about 300 kgf, while the drawing force F sharply decreases when the effective oil thickness t becomes Ra or less. The inflection point at which the pulling force F sharply decreases depends on the degree of surface roughness of the steel sheet, and the smaller the Ra of the steel sheet surface, the more the inflection point moves to the smaller effective oil thickness t value. To do. That is, the proper coating amount for obtaining the effect of reducing the drawing force should be determined in consideration of the steel plate surface roughness, and the effective oil coating thickness t can be adjusted within the specified range according to the present invention. In addition, the storage property of the oil coating film on the sliding interface is improved, the lubricating action of the lubricating rust preventive oil is more effectively exhibited, and the sliding resistance improving effect which cannot be obtained by the conventional large amount coating can be obtained.

[2] Rust resistance (1) Test steel sheet Alloyed hot-dip galvanized steel sheet (double-sided plating) Base material steel sheet: Extra-low carbon Ti-added IF steel (sheet thickness: 0.7 mm) Plating layer thickness: 8.4 μm / One side Plating layer surface roughness: Ra 0.93 μm (2) Preparation of test piece Lubricating rust preventive oil (same agent type as above) was applied to both sides of the plate material (70 × 70, mm) cut from the above steel sheet and tested Let's just cut it.

(3) Rust test (corrosion resistance promotion stack test)
Stack the test pieces in a horizontal position in a thermo-hygrostat (temperature: 50 ° C, humidity: 95%, atmosphere: atmosphere).
Do). After a lapse of a predetermined period, the corrosion resistance of the three test pieces except the uppermost layer and the lowermost layer of the stacked test pieces is visually observed to evaluate the corrosion resistance.

Table 1 shows the results of the generation test. The symbols in the table are as follows. ○: No rusting, △: Rust occurred on a part of the plate surface, ×: Rust occurred on the entire plate surface Specimen No. 1 was an invention example, No. 2 was an example in which application of lubricating anticorrosive oil was omitted No. 3 is an example in which a large amount was applied according to the conventional method. Inventive example No. 1 has a rust preventive effect that can withstand long-term storage like the conventional example, although the amount of lubricating rust preventive oil applied is significantly smaller than that of the conventional example No. 3. . In this way, even if the coating thickness of the lubricating rust preventive oil is extremely thin, the same rust resistance as the conventional large amount coating can be obtained even if the coating thickness is small, even if the coating thickness is small. This is probably because the effect of blocking the outside air required to prevent rusting is secured.

[0017]

[Table 1]

[0018]

EFFECTS OF THE INVENTION According to the present invention, by applying a small amount of lubricating rust-preventing oil specified in accordance with the surface roughness of steel sheet, the lubrication function can be more effectively exerted while maintaining the required rust-preventing effect. As a result, the sliding resistance can be significantly reduced, and improved press workability can be obtained. In addition, a significant reduction in consumption of lubricating anticorrosive oil can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between an effective oil coating thickness t of lubricating anticorrosive oil on a steel plate surface (roughness Ra: 1.08 μm) and a withdrawal amount.

FIG. 2 is a graph showing the relationship between the effective oil coating thickness t of lubricating rust preventive oil on the steel plate surface (roughness Ra: 0.91 μm) and the amount of withdrawal.

FIG. 3 is a graph showing a relationship between an effective oil coating thickness t of a lubricating rust preventive oil on a steel plate surface (roughness Ra: 0.90 μm) and a withdrawal amount.

FIG. 4 is a graph showing the relationship between the effective coating thickness t of the lubricating rust preventive oil on the surface of the steel sheet (roughness Ra: 0.65 μm) and the withdrawal amount.

FIG. 5 is a cross-sectional explanatory view schematically showing the behavior of the oil coating film during the press working process of the steel sheet coated with the lubricating anticorrosive oil.

FIG. 6 is a cross-sectional explanatory view schematically showing the behavior of the oil coating film during the press working process of the steel sheet coated with the lubricating anticorrosive oil.

FIG. 7 is a schematic explanatory diagram of a lubrication anticorrosive oil application line for a steel plate.

FIG. 8 is an explanatory diagram of a pull-out test procedure for evaluating sliding resistance of a steel sheet.

[Explanation of symbols]

1: Steel plate 1 ₁ : Steel plate surface 2: Lubrication and rust preventive oil coating film 3: Press die 11: Surface roughness measuring device 12: Control device 13: Lubrication and rust preventive oil coating device 14: Coating amount measuring device 21: Pull-out test Pressing piece of machine TP: Pull-out test plate

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Claims (2)

[Claims] 1. Surface roughness Ra (center line average roughness) 0.3
On the surface of a steel sheet having a thickness of up to 2.0 μm, the following formula [1]: effective oil thickness t = lubrication / rust-prevention oil application amount (g / m ² ) / lubrication / rust-prevention oil density (g / cm ³ ) ... [1 ] A lubricating rust preventive oil-coated steel sheet excellent in press workability, characterized in that an amount of lubricating rust preventive oil having an effective oil thickness t of 0.5 Ra to 1.0 Ra is applied. 2. The lubricated anticorrosive oil-coated steel sheet excellent in press workability according to claim 1, wherein the steel sheet is a galvannealed steel sheet.