JPH0824931B2 - Cold-rolled steel sheet having excellent cleanability and a method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cold-rolled steel sheet suitable for use in applications such as press forming, bending, etc., and particularly to washing with washing oil before and after working and alkaline degreasing. The present invention relates to a cold rolled steel sheet having excellent cleaning performance during cleaning and a method for manufacturing the same.

[0002]

2. Description of the Related Art Cold rolled steel sheets are
It is widely used as a steel sheet for various press forming and bending processes. When relatively large foreign substances adhere to the surface of the steel sheet to be processed during processing, the steel sheet surface may be flawed when it comes into contact with the press-molding die, resulting in a harmful appearance defect. In automobile processing and molding, this is called a star (pimple) and is treated as an important control item for the appearance quality of a vehicle.

Further, after the press working, the parts are subjected to a rust preventive treatment, so that they are subjected to a chemical conversion treatment and electrodeposition coating. However, iron powder and dirt generated during the press working adhere to the chemical conversion treatment and coating. When it remains until time, partial coating failure occurs,
Significant problems occur in terms of appearance and rust prevention.

For this reason, it is important to improve the cleanliness of the steel sheet itself and to prevent dirt and iron powder from adhering during the press working. It has a device that cleans the surface of the steel plate with cleaning oil before and after processing, and a device that degreases the processed parts with an alkali. In these processes, iron powder and dirt adhering to the steel plate are easily cleaned. Is an important issue.

[0005]

According to the present invention, iron powder and dirt adhering to a steel sheet are particularly easily washed in the steps of washing with washing oil before and after press working and alkaline degreasing step after working. An object of the present invention is to provide a steel sheet and a manufacturing method thereof.

[0006]

Means for Solving the Problems The inventor has undertaken various investigations and experiments on the cleanability of a steel sheet, and as a result of earnest research, in particular, the surface roughness after annealing and temper rolling the steel sheet and the mineral oil to be applied after that were investigated. The inventors have found that it is extremely effective to achieve the object of the present invention by controlling the amount of oil coating of the liquid containing the main component within an appropriate range, and have completed the present invention.

That is, according to the present invention, at least one surface of the steel sheet has a center line surface roughness Ra of 0.5 to 3.0 μm.
Is a rough surface of which the viscosity at 40 ° C. is 3 cps.
Liquid of 30 cps or more is 250 × Ra to 50 per side
The present invention provides a rolled steel sheet for working, which is characterized by being coated with 00 × Ra (mg / m ² ), and which has excellent cleanability.

Further, according to the present invention, a steel plate is pressed by a working roll having regular ring-shaped irregularities (hereinafter referred to as a ring) to transfer the ring pattern to at least one surface of the steel plate to form a rough surface. As a result, the center line surface roughness Ra of the steel sheet is set to 0.5 to 3.0 μ, and the ring-to-ring spacing S _m and the ring diameter S _L of the rings formed on the steel sheet are set.
Satisfy the relationship of S _L <S _m <5S _L , and thereafter, the viscosity at 40 ° C. on the rough surface of the steel plate is 3 cps or more 3
Liquid of 0 cps or less 250 × Ra to 5000 × per side
The present invention provides a method for producing a cold-rolled steel sheet for working, which is characterized by applying Ra (mg / m ² ), and has excellent cleaning properties.

[0009]

The present invention will be described below in more detail. Detergency (easiness of cleaning) of foreign matter adhering to the surface of a solid is a very important factor in the process of cleaning, but there have been few studies in this field so far, especially the cleanliness and cleaning of cold-rolled steel sheets. Little was discussed about sex. The inventor has obtained the following findings as a result of earnest research on various factors that affect the cleanability of a cold-rolled steel sheet.

(1) Although some foreign substances adhere to the cold-rolled steel sheet by physical adsorption, for example, metallic substances such as iron flakes undergo a chemical reaction with the iron surface, resulting in deliquescent properties such as calcium. In the case of those having the above, the adsorption force is generated by the reaction with water.

(2) In the case of cold-rolled steel sheets, the steel sheets are wound into a coil shape or stacked on each other to form a product form. However, when the surfaces are held in a pressed state, the steel sheets are separated from each other. When the foreign matter is directly pressed into the steel plate by the surface pressure, the attractive force is generated by the mechanical joining (anchor effect).

From the above findings, it has been found that holding foreign matter adhering to the surface of the steel sheet in a state where it does not adhere to the steel sheet is a method for improving the removability (cleanability) of the foreign matter. That is, by making the surface roughness of the cold-rolled steel sheet relatively large, it is possible to provide a situation in which foreign matter exists without being adsorbed in a holding place where it is not pushed into the steel sheet, and the foreign matter and the steel sheet surface are not affected by oxygen and moisture in the atmosphere. It is important to keep a state in which a liquid containing mineral oil as a main component is applied in an appropriate amount according to the rough surface so as not to be adsorbed by the reaction.

The reason for the manufacturing conditions regulated in the present invention will be described below.

First, when the roughness Ra of the steel sheet is less than 0.5 μm, there is no place to retain the oil content even if the steel sheet is oiled, so the oil content is superposed on the coiled steel sheet or sheet. Are extruded by the surface pressure between the steel plates,
Can't hold enough. Therefore, the foreign matter adhering to the steel sheet directly contacts the steel sheet surface and is adsorbed by various chemical reactions, or is pressed into the steel sheets by the surface pressure between the steel sheets and adsorbed by a mechanical joining force (anchor effect). For this reason, even if the steel sheet is washed, the cleaning property is significantly deteriorated.

From this point of view, it is desirable that the roughness of the steel sheet is as large as possible, and further considering that foreign matters easily flow out during cleaning, the smaller the number of peaks and valleys on the rough surface of the steel sheet, the better. The upper limit of the roughness is not restricted from the viewpoint of cleanability, but is generally 3.0 μm or less in consideration of being used for processing. Then, the surface roughness of the steel sheet is preferably adjusted by temper rolling.

Next, the liquid applied to the steel sheet will be described.
If the viscosity of this liquid is less than 3 cps (at 40 ° C), the oil content will be described later, and if the viscosity is less than 3 cps (at 40 ° C), the oil content will remain on the rough surface of the steel sheet when held in a coil shape or stacked in a sheet shape. It flows out without being held, and the cleaning property is remarkably deteriorated as described above. The viscosity of this liquid is 30
When the temperature is higher than cps (at 40 ° C), the oil content is excellently retained by the steel plate, and although foreign matter can be prevented from adsorbing to the steel plate, the viscosity is extremely high during cleaning, making it difficult to remove the oil content itself and making it easier to clean. Deteriorates.

The amount of oil applied is defined as an appropriate amount that can be held in balance with the roughness of the steel plate surface. That is, when the amount of applied oil is less than 250 × Ra (mg / m ² ), the amount of oil is too small and the number of places where foreign matters come into direct contact with the steel sheet increases.

Further, since the amount of oil applied is small, air and water are directly present at the contact interface between the foreign matter and the steel sheet to cause various chemical reactions, increasing the adsorption force of the foreign matter to the steel sheet, resulting in deterioration of the cleaning property. The upper limit of the amount of oil applied is not from the viewpoint of detergency. The reason is that even if oil is applied excessively, when it is piled up in a coil shape or a sheet shape, the liquid that cannot be retained on the rough surface will flow out from the steel plate end face and retain the maximum amount that can be retained. Because. From this point of view, the maximum amount of oil is 5000 ×
Ra (mg / m ² ), and this amount or less is sufficient.

The oil species used here are preferably those having rust preventive properties, and may be mineral oils or animal and vegetable oils (oils and fats). Mineral oil is most preferable in that it does not deteriorate on the surface of the steel sheet, but tallow oil, whale oil, vegetable oil, etc. may be used. Moreover, these aqueous solutions may be used. The liquid containing such a fat or oil as a main component may be applied to both sides or one side of the steel sheet. The coating method is arbitrary such as a roll coater method and a spray method.

The steel sheet to which the present invention can be applied may be any steel sheet as long as the rough surface satisfies the above-mentioned conditions. For example, various surface-treated steel sheets (Zn or Zn
(Alloy-plated steel sheet, Sn-plated steel sheet, Cr-plated steel sheet, etc.), and ultra-low carbon steel sheet, low carbon steel sheet, stainless steel sheet, and dissimilar metal sheet (aluminum sheet, etc.) may be used.

Next, a preferred example of the method for producing a cold rolled steel sheet for processing which is excellent in cleanability of the present invention will be described. The surface roughening of the steel sheet is performed by the laser beam method in the following method, but the method is not limited to this, and any method such as the shot blast method and the grindstone method may be used.

First, the temper rolling roll 1 is irradiated with a laser beam as shown in FIG. Then, the laser beam irradiation portion is melted to form the valley portion 2, and the molten metal is bulged to the side thereof to form the ring-shaped mountain portion 3. The ring composed of such peaks and valleys is preferably regularly formed on the entire circumference of the rolling roll 1.

When the steel sheet 4 is rolled using the roll 1 having a large number of rings formed in this way, the state shown in FIG. 1 (c) is obtained. That is, the ring ridges 5 are formed on the steel plate 4 corresponding to the valleys 2 of the roll 1, the ring valleys 6 are formed on the steel plate 4 corresponding to the ridges 3 of the roll 1, and the other parts are the original. The flat portion 7 between the rings is formed on the surface of the steel sheet. The steel plate on which the ring pattern portion 8 is formed in this manner is schematically shown in FIG. In FIG. 2, (a)
Is a plan view and (b) is a sectional view thereof. These ring pattern portions 8 create a surface roughness between the ring flat portion 5 and the liquid containing the above-mentioned oil and fat is retained between them to prevent foreign matters from being adsorbed and improve the cleaning performance. Of.

The ring pattern on roll 1, ie,
By appropriately creating the ring pattern portion on the steel sheet transferred from the roll 1, that is, by appropriately adjusting the height difference between the ridge portion 5 and the valley portion 6 of the ring pattern portion 8 and the density of the ring pattern portion 8. Surface roughness of steel sheet R
a is 0.5 μ or more as described above.

When the surface roughness Ra is adjusted by the ring pattern, it is necessary to add the following restrictions in addition to the restriction of the surface roughness. That is, when the spacing S _m between the rings, which is schematically shown in FIG. 2, is equal to or smaller than the size (diameter) S _L of the rings, the rings overlap each other, so that there is no path for washing foreign substances during washing, and the washability is remarkable. to degrade. Also S
_{When m} is 5.0 × S _L or more, there is a large number of flat surfaces having no roughness in the intermediate portion between the rings and oil cannot be retained in those portions, so that foreign matter is adsorbed and the cleaning performance deteriorates. Therefore, it is necessary to satisfy the relationship of S _L <S _m <5S _L.

A steel plate on which the ring pattern portion 8 satisfying the above-mentioned conditions is formed, and at least one surface of the steel plate is coated with a liquid containing a fat and oil satisfying the above-mentioned conditions as a main component.

[0027]

EXAMPLES The present invention will be specifically described below based on examples.

(Example 1) First, a method of evaluating the cleaning property will be described. The cleaning test method is shown in FIG. Apply a certain amount of mineral oil of various viscosities to a well-washed steel plate of a certain area, sprinkle a certain amount of dust, stack 10 steel plates with each other and apply a constant surface pressure for 240 hours, then dismantle them, and then use cleaning oil To wash the steel sheet by spraying under certain conditions.
The washed steel plate was thoroughly washed with a solvent, dust in the solvent was collected with a Millipore filter, and the weight was measured. The residual dust ratio (amount of dust after cleaning / amount of dust adhesion × 100) was used as a parameter representing the cleaning property.

Ultra low carbon steel sheets were used for this test. After annealing this steel plate, the pattern is made by rolling the steel plate using a rolling roll with various roughness only on the work roll in the temper rolling mill by the shot blast method, the laser beam processing method and the grindstone. And the rough surface of the steel plate was finished in a dull and bright shape.

A liquid containing a rust preventive mineral oil as a main component was applied to the steel plate roughened as described above by a roll coater. The composition of this coating solution is the addition of metal sulfonate to oxidized wax, and the viscosity is from 2 cps to 36 c
The above dust residual rate was examined by changing to ps (at 40 ° C.).

In this test, the final cleaning was carried out only by spraying cleaning oil (spraying the above coating solution diluted with a solvent) by spraying, but in addition to this, mechanical scraping (brushing) was also used. Or alkaline degreasing or electrolysis,
Although it is possible to further reduce the dust residual rate by performing ultrasonic cleaning, the tendency of the residual rate is the same in this case as well, and the economic and time waste of adding these cleaning methods is taken into consideration. Needless to say, it is important to improve the cleanability of the steel sheet for foreign substances.

FIG. 4 shows the results of measuring the dust residual ratio according to the present test method in various combinations of roughness and oil coating amount. As is clear from FIG. 4, roughness Ra ≧ 0.5
(250 × Ra ≧ 125) and the amount of oil applied is 250 × R
In the area of a (mg / m ² ) or more (hatched area), the residual dust rate is 50% or less, and the cleaning property is excellent as compared with other areas.

FIG. 5 shows the dust residual ratio when the viscosity of the oiled liquid was changed from 2 cps to 36 cps (at 40 ° C.) in the range of the present invention. Even within this range, if the viscosity of the liquid is not 3 cps to 30 cps (at 40 ° C.), the detergency is deteriorated, and therefore, the liquid having the viscosity in the above range must be used.

Further, within the range of the present invention of the above-mentioned roughness, amount of oil, and oil solution, a ring system (S
FIG. 6 shows the dust residual rate when the ratio of _L ) to the ring spacing (S _m ) was changed from 0.5 to 7.0. Even in this region, if the value of S _m / S _L is not 1 to 5, the cleaning property will be deteriorated. Therefore, when using a rough surface of the laser pattern, the ratio of the ring diameter and the ring interval must be within the above range. I understand that it will not happen.

[0035]

As described above, according to the present invention, it is possible to manufacture a steel plate having excellent cleaning performance particularly in cleaning before and after working and cleaning by alkaline degreasing, and a metal plate including the manufactured steel plate can be manufactured. It is suitable for use in press forming, bending, etc.

[Brief description of drawings]

FIG. 1 is a step (a) of a method for roughening a steel sheet using a roll having ring-shaped irregularities formed by a laser beam method.
It is explanatory drawing shown in order of (b) and (c).

FIG. 2 is a schematic view of a steel sheet roughened by the method of FIG. (A) is a top view of a steel plate, (b) is the sectional view.

FIG. 3 is a flowchart of a detergency test method.

FIG. 4 is a diagram showing a dust residual ratio by a cleaning test conducted in Examples in various combinations of roughness and oil amount. The number attached to each symbol indicates the residual dust rate.

FIG. 5 is a diagram showing the relationship between the viscosity of an oil coating liquid (rust preventive liquid) and the dust residual rate.

[Fig. 6] Ring diameter (S _L ) and ring interval (S
It is a figure which shows the change of dust residual rate when changing the ratio of _m ).

[Explanation of symbols]

 1 processing roll 2 valley part 3 crest part 4 steel plate 5 ring crest part 6 ring trough part 7 flat part between rings 8 ring pattern part

Claims (2)

[Claims] 1. At least one surface of a steel sheet is a rough surface having a centerline surface roughness Ra of 0.5 to 3.0 μ, and a viscosity at 40 ° C. of 3 cps or more and 30 cps or less on the rough surface. Is 250 × Ra to 5000 × Ra (mg /
m ² ) A cold-rolled steel sheet for working, which has excellent cleanability and is characterized by being applied. 2. A roughening surface is formed by transferring the ring pattern onto at least one surface of the steel sheet by rolling the steel sheet with a working roll having regular ring-shaped irregularities (hereinafter referred to as “ring”). The center line surface roughness Ra of the steel sheet is 0.5 to 3.0.
μ, and the ring-to-ring spacing S _m of the rings formed on the steel plate and the ring diameter S _L satisfy the relationship of S _L <S _m <5S _L , and thereafter at 40 ° C. on the rough surface of the steel plate. A liquid having a viscosity of 3 cps or more and 30 cps or less is 250 × Ra to 500 per side.
A method for producing a cold-rolled steel sheet for working, which is excellent in cleanability, characterized by applying 0 × Ra (mg / m ² ).