JP2003033802A - Production method of cold rolled steel plate with good degreasing character and chemical conversion treatability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of cold rolled steel plate which improves a degreasing character and chemical conversion treatability without changing a coated amount of antirust oil. SOLUTION: When a skin pass rolling on a cold rolled steel plate with a surface roughness being below 1.5 μm in terms of Ra is performed after annealing, an organic material of skin pass rolling lubricant is deposited on a surface of steel plate after being rolled at a rate of 20-80 mg/m<2> by using a skin pass rolling lubricant which contains 1-15% water-soluble organic material and an antirust oil is coated. The said treatment is also applied to a cold rolled steel plate with a Ni-deposited amount <=15 mg/m<2> , or to a cold rolled steel plate which is annealed with a surface roughness of a hearth roll in the annealing furnace <=8 μ in terms of Ra.

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, the surface of which is used for plating or painting.

[0002]

2. Description of the Related Art A cold-rolled steel sheet as a steel sheet product is usually in a state in which rust-preventing oil is applied to the surface of the cold-rolled steel sheet when it is shipped from a steelmaking factory to prevent rusting. In automobile manufacturers, home appliance manufacturers, etc. who use this steel sheet, after the parts having the required shape are processed and formed, in most cases they are painted or plated to cover the surface to form the final product. When coating or plating the surface of the steel sheet, oil and fat components such as rust preventive oil are degreased so that the coating adheres to the coating as sufficiently and uniformly as possible, and in the case of coating, a chemical conversion treatment is further performed to form a base layer.

Whether or not degreasing is sufficiently performed is usually evaluated by the surface wetted area ratio. When the degreasing treatment is carried out under the same conditions, the higher the wetted area ratio, the better the degreasing property as a cold-rolled steel sheet. Is judged to have good chemical conversion treatability. When the same rust preventive oil is applied, the degreasing property is better as the application amount is smaller, but naturally the risk of rusting increases as the application amount decreases. Therefore, when shipping the steel sheet, the rust preventive oil is applied within the minimum range capable of suppressing rusting, and it is difficult to reduce the applied amount of the rust preventive oil for improving the degreasing property.

The cold rolled steel sheet is temper-rolled at the time of shipping after annealing in order to improve the shape such as correction of flatness and prevent the occurrence of stretcher strain. In many cases, temper rolling liquid is used for temper rolling, but since the rust preventive oil is applied immediately after temper rolling, the temper rolling liquid has its rust prevention property even if mixed with rust preventive oil. , Those that do not adversely affect degreasing and chemical conversion treatability are selected.

There is a dry rolling method that does not use a rolling liquid for temper rolling. In this case, only the effect of rust preventive oil needs to be considered, but the increase in roll wear and the occurrence of flaws increase the production efficiency, and thus the specific production efficiency is low. Limited to use. It has also been attempted to improve the rustproofing property by applying a tempered rolling liquid with excellent rustproofing properties, but in this case, the change in viscosity makes it easier for foreign matter to mix in and tends to increase surface defects. There is.

As described above, various studies have been conducted on the type and composition of rust preventive oils and temper rolling liquids, combinations thereof, and the like. However, there is a strong demand for improved degreasing properties from shipping destinations that use cold-rolled steel sheets, and in addition, sometimes spot-like degreasing defects may occur, and to improve degreasing properties without impairing rust prevention, More sufficient measures are needed.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a cold rolled steel sheet having improved degreasing properties and chemical conversion treatability without changing the amount of rust preventive oil applied.

[0008]

[Means for Solving the Problems] The present inventors have made it possible to improve the degreasing property and chemical conversion treatability of a cold-rolled steel sheet, that is, the water-wetted area ratio after the degreasing process, by keeping the amount of rust preventive oil applied constant. Considered. Numerous studies have already been made on the improvement of composition of temper rolling liquid and rust preventive oil and improvement by selection of additives. Therefore, the present inventor conducted an investigation mainly focusing on the method of using the temper rolling liquid.

There are almost 100% organic oil-based tempering liquids and aqueous solutions mixed with water-soluble organic substances and inorganic substances. Considering the treatment conditions, etc., we decided to use a water-soluble organic aqueous solution. As the organic matter, a surfactant such as a sulfonate and an antirust agent such as an amine salt are added to a carboxylic acid type organic substance. In many cases, in rolling using such a tempered rolling liquid, the organic matter deposited on the surface of the steel sheet immediately after rolling exceeds 100 mg / m ² .

With a tempered rolling fluid having various concentrations of organic matter, the amount of organic matter deposited on the surface of the steel sheet after temper rolling is changed by changing the method of supplying the rolling fluid, etc. Oil was applied and the degreasing and chemical conversion treatability was investigated.
As a result, it was found that when the amount of organic substances deposited was reduced, the workability of rolling was deteriorated, such that the dull surface of the roll became more worn and dry rolling was approached, and the degreasing property was not good. However, as the amount of organic substances deposited increases, not only the degreasing property deteriorates, but also gumming of organic substances tends to occur, tending to cause indentation flaws and stains on the steel plate surface due to foreign substances adhering to the roll surface. There is. From these results, it has been clarified that there is an optimum amount of organic matter deposited in terms of rolling workability and degreasing property.

The amount of the organic matter deposited largely depends on the surface roughness of the steel sheet after temper rolling, and increases as the roughness value increases. In the case of cold-rolled steel sheet, the surface roughness of the steel sheet generally called dull finish is 0.5 to 1.5 μm in Ra and 0.1 to 0.3 μm in bright finish. In addition, the concentration of the temper rolling liquid, the supply method during rolling, and the like for obtaining the above-mentioned optimum amount of organic matter deposited were investigated.

When the cold rolled steel sheet is treated by the continuous annealing method,
In order to improve the chemical conversion treatment property and the rustproof property, a slight amount of Ni called flash plating may be attached. Since this Ni flash plating may greatly affect the water-wetted area ratio after the degreasing treatment at the shipping destination, the influence within the range of the optimum organic substance deposition amount in the above-mentioned temper rolling was investigated. As a result, it has been confirmed that by setting the upper limit of the Ni deposition amount, a steel sheet having excellent degreasing properties and chemical conversion treatability can be obtained.

Further, it has been found that controlling the amount of organic substances deposited in the temper rolling within an optimum range is effective in preventing dot-like degreasing defects. What is dot-like degreasing failure?
This is a phenomenon in which locally scattered degreasing defects are detected on the surface of a cold-rolled steel sheet product that has passed through a continuous annealing furnace after degreasing the molded product at the shipping destination.

This is because when the steel sheet passes through the continuous annealing furnace,
Small recessed flaws are made on the surface of the steel sheet, and these flaws are often smoothed by temper rolling.However, depending on the state of the flaws, temper rolling liquid enters the inside of the flaws, and this causes the flaws at the shipping destination. It is said that the dot-shaped degreasing failure of appears. As a countermeasure against this, it is effective to reduce the amount of rust preventive oil applied, but this cannot be sufficiently reduced due to rusting of the steel sheet.

Most of the dents and flaws in the steel sheet are considered to be due to protrusions called build-up on the surface of the hearth roll that accumulates with the passage of the steel sheet in the areas where the temperature of the steel sheet is highest, such as the heating zone and the soaking zone. . The build-up formation is difficult to avoid in the operation of the furnace, but it is said that the formation is changed depending on the surface roughness of the hearth roll. Therefore,
When the surface roughness of the hearth rolls in the heating zone, soaking zone and slow cooling zone was changed, the size of the dent defects detected on the surface of the steel sheet before temper rolling changed. It was also found that the dot-shaped degreasing defect decreased as the size of the dent defect decreased. From this, it was also confirmed that if the surface roughness of the hearth roll is lowered and then the amount of the organic substances deposited in the temper rolling is set in the optimum range, the above-mentioned defective spot degreasing can be significantly reduced.

As described above, the degreasing property and the chemical conversion treatability of the steel sheet are significantly improved by controlling the remaining amount of the rolling fluid by temper rolling without changing the amount of rust preventive oil applied at the time of shipping. It became clear that it could be done. Therefore, the present invention has been completed by further studying various conditions for realizing this effect with good reproducibility. The gist of the present invention is as follows.

(1) During temper rolling of a cold rolled steel sheet having a surface roughness Ra of 1.5 μm or less, after temper rolling, a temper rolling liquid containing 1 to 15% of a water-soluble organic substance is used, and the steel sheet after rolling is used. A method for producing a cold-rolled steel sheet excellent in degreasing property and chemical conversion treatment property, which comprises depositing 20-80 mg / m ² of organic matter of temper rolling liquid on the surface.

(2) If the surface roughness Ra is 1.5 μm or less, Ni
The temper rolling liquid containing 1 to 15% of water-soluble organic matter is used during temper rolling of the cold rolled steel sheet with an adhesion amount of 15 mg / m ² or less, and the temper rolling liquid is applied to the surface of the steel sheet after rolling. 20 organic matter
A method for producing a cold-rolled steel sheet having excellent degreasing properties and chemical conversion treatability, which is characterized by depositing 80 mg / m ² .

(3) When performing continuous annealing of a cold rolled steel sheet having a surface roughness Ra of 1.5 μm or less, the surface roughness of the hearth roll in the annealing furnace is set to 8 μm or less Ra and the temper rolling after annealing is performed. Occasionally, a temper rolling liquid containing 1 to 15% of water-soluble organic substance is used, and 20 to 80 mg of the temper rolling liquid organic substance is applied to the surface of the steel sheet after rolling.
/ M ² It is a method for producing a cold-rolled steel sheet excellent in degreasing property and chemical conversion treatability, which is characterized in that it is attached.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The production method of the present invention is applied to a cold rolled steel sheet having a surface roughness Ra of 1.5 μm or less. The surface roughness of cold-rolled steel sheet, which is generally called dull finish, is Ra 0.5-1.5.
.mu.m, and bright finish is 0.1 to 0.3 .mu.m, because these steel sheets are targeted, but the surface roughness Ra is 1.5 .mu.m.
This is also because the amount of the temper-rolling liquid adhered increases and the degreasing property of the steel sheet tends to decrease when the value exceeds the range.

When temper rolling a product steel sheet having this surface roughness, an aqueous solution containing a water-soluble organic substance in an amount of 1 to 15% (wt%) is used as a temper rolling liquid. The organic matter contained in this temper rolling liquid was 20-80 mg / m ²
It is assumed to be attached.

The organic substances contained in the temper rolling liquid are, for example, aliphatic or aromatic carboxylic acids having a lubricating effect, surfactants such as alkylaryl sulfonic acids, and amine compounds having a rust preventive effect. If the concentration of these organic temper rolling liquids is less than 1%, there is no lubrication effect, the wear of the roll dulles increases, and re-polishing becomes necessary. However, if the content exceeds 15%, the amount of organic substances deposited on the surface of the steel sheet after rolling increases, and the degreasing property at the shipping destination deteriorates.

The organic matter adhering to the surface of the steel sheet after temper rolling is 20 to 80 mg / m ² . This is because if the amount of adhesion is less than 20 mg / m ² , the lubricity of rolling is reduced and the rust preventive property of the product steel sheet is reduced, and if it exceeds 80 mg / m ² , the degreasing property at the shipping destination is reduced. Not only that, but also because sticky substances are accumulated on the roll surface and indentation flaws increase.

MK-55 (tempered rolling agent manufactured by Idemitsu Kosan Co., Ltd.) was used as the organic substance of the tempered rolling liquid, and the concentration and the method of supply to the rolling rolls were changed to change the amount of organic substances deposited on the surface of the steel sheet after rolling. As the antirust oil, SK (rust preventive oil manufactured by Idemitsu Kosan Co., Ltd.) was used, and the degreasing property and the antirust property of the steel sheet were investigated with the coating amount being almost constant at 1.0 to 1.5 g / m ² .

Regarding degreasing property, spray cleaning was carried out for 30 seconds in an aqueous solution of 45 ° C. in which 20 g / L of a degreasing agent FC-4480 (a steel plate cleaning agent manufactured by Japan Percalize Co., Ltd.) was dissolved, and after being rinsed with water, it was left for 30 seconds The water-wetted area ratio was measured. An example of the results is shown in FIG. 1 (a). The water-wetted area ratio showed a tendency to deteriorate with the increase or decrease of the organic deposition of the temper rolling liquid.

Regarding the rust preventive property, after applying rust preventive oil, the surface is covered with C
After dripping a water drop containing 20 ppm of 1 ion, it was left indoors for 6 weeks, and from the observation of rust generated, a score of 1 to 4 was given so that the smaller the rust, the larger the value. An example of the result is shown in FIG.

As can be seen from FIGS. 1 (a) and 1 (b), the range of the amount of organic matter deposited in the temper rolling liquid having a sufficiently high water-wetting area ratio and a high rust-prevention evaluation point is 20 to 80 mg / m 2. The range is ² .

FIG. 2 shows the results of examining the relationship between the surface roughness Ra of the product steel sheet, the concentration of the temper rolling liquid, and the amount of organic substances deposited. The larger the surface roughness Ra and the higher the concentration of the temper rolling liquid, the more the amount of organic substances deposited tends to increase. It can be seen that it is preferable that the concentration of the temper rolling liquid is 1 to 15% in order to set the adhesion amount to 20 to 80 mg / m ² in the steel sheet having the surface roughness Ra of 1.5 μm or less.

In the case of a steel sheet subjected to Ni flash plating, the amount of Ni deposited is 15 mg / m ² or less. If this is 15 mg / m ² or less, the above-mentioned surface roughness Ra is 1.
For a steel plate having a thickness of 5 μm or less, by adhering ²⁰ to 80 mg / m ² of the organic material of the temper rolling liquid on the surface of the steel plate after rolling,
This is because a steel plate having excellent degreasing property and rust preventive property can be obtained.

Ni deposited by flash plating is
When examined by fluorescent X-ray analysis (XPS), metallic Ni and Ni-O (Ni oxide or Ni hydroxide) on the surface of the steel sheet
And are in a mixed state. As a result of studying the degreasing property after applying the rust preventive oil, as shown in FIG. 3, when the atomic ratio of Ni (Ni—O) (hereinafter referred to as Ni—O ratio) is increased, the degreasing property, that is, the water wettability is improved. It turned out to drop. In order to obtain good water wettability, the Ni-O ratio is
It must be 7.5 atomic% or less.

On the other hand, when the relationship between the Ni deposition amount and the Ni-O ratio was examined, it was found that as the Ni deposition amount increased, the Ni-O ratio varied greatly as shown in FIG. It was From now on, the Ni-O ratio can be stably lowered,
And, in order to make it 7.5 atomic% or less, the amount of Ni deposited should be 1
It is clear that it should be 5 mg / m ² or less. However, the effect of improving the chemical conversion treatment property and the rust preventive property obtained by performing flash plating of Ni is recognized even when Ni is hardly detected, but it is desirable that the adhesion amount is at least 3 mg / m ² or more. The amount of Ni deposited in flash plating can be easily controlled by increasing or decreasing the plating current.

In a steel sheet having a surface roughness Ra of 1.5 μm or less, setting the adhesion amount to 20 to 80 mg / m ² is also effective for reducing spot degreasing defects. Especially the heating zone of continuous annealing furnace,
By setting the surface roughness of the hearth roll used in high temperature areas such as the soaking zone and the slow cooling zone to 8 μm or less in Ra,
This defective dot degreasing can be further suppressed.

Among the dents and flaws found on the surface of the steel sheet immediately before temper rolling in the continuous annealing equipment, the diameter is 0.1 mm or more and the depth is 1 mm.
For defects of 0 μm or more, the size is expressed as the product of the diameter and the depth, and the relationship between the size of this dent defect and the spot-like degreasing failure of the steel sheet after temper rolling and rust preventive oil application is investigated. did. The results are shown in FIG. 5, and the frequency of occurrence of defective spot degreasing increases sharply as the dent defect increases. In this case, assuming that the amount of organic matter deposited in the temper rolling liquid on the surface of the steel sheet after temper rolling is 20 to 80 mg / m ² , if the product of the diameter and the depth of the recessed flaw is 40 × 1000 μm ² or less, The occurrence rate of dot-like degreasing failure could be made almost zero.

Then, when the relation between the roughness of the hearth roll in the high temperature portion of the furnace and the product of the diameter and the depth of the recessed flaw found in the annealed steel sheet was examined, the results shown in FIG. 6 were obtained. From this figure, the product of the diameter and the depth of the dent defect is 40 × 1000 μm ²
It can be seen that the surface roughness Ra of the hearth roll may be set to 8 μm or less in order to achieve the following.

In this way, the hearth rate of the high temperature part in the furnace is
The surface roughness Ra of Ra is set to 8 μm or less, and
The amount of organic matter deposited on the surface of the steel sheet after rolling is 20 to 80 mg.
/ M ^TwoThen, the surface roughness Ra of the steel plate of 1.5 μm or less,
Poor degreasing can be almost completely suppressed.

The method is not particularly limited as long as the organic content adhesion amount of the temper rolling liquid on the surface of the steel sheet after temper rolling can be set to 20 to 80 mg / m ² .
As shown schematically in Fig. 3, if the tempering rolling liquid is supplied from the exit side of the rolling roll to the rolling liquid pool receiver, the tempering rolling liquid adhering to the surface of the work roll is squeezed by contact with the backup roll, It is possible to control the amount of organic components attached to the surface within the above range.

[0037]

[Example] [Example 1]
Change the presence or absence of plating, surface roughness of the product, temper rolling liquid, etc.
The cold-rolled steel sheet product was manufactured. In this case, the temper rolling pressure
The bottom ratio is fixed at 0.6% and the rust preventive oil after rolling is SK (Idemitsu
Kosan Co., Ltd.) coating amount is 1.0-1.5g / m ^TwoAlmost constant
did. The surface roughness of the product is adjusted with temper rolling rolls and adjusted.
MK-55 (made by Idemitsu Kosan Co., Ltd.)
RS210 (manufactured by Idemitsu Kosan Co., Ltd.) was used in the case of the mechanical tempering liquid.
The tempered rolling fluid is fed from the exit side of the rolling roll shown in FIG.
Change the concentration of the rolling fluid by supplying it to the pool receiver
As a result, the amount of organic substances deposited on the surface of the steel sheet was changed.

[0038]

[Table 1]

The amount of organic substances deposited on the surface of the steel sheet was compared with a calibration curve prepared in advance by measuring the absorbance of a cleaning liquid obtained by washing the surface of the steel sheet with ion-exchanged water and filter paper and removing dust. Then, the concentration of the cleaning liquid was measured, and the adhesion amount was obtained from the amount of the cleaning liquid and the surface area of the steel sheet to be measured.

The degreasing property after applying rust preventive oil is the degreasing agent FC-4480.
(Nihon Parkerizing Co., Ltd. steel plate cleaning agent) was dissolved in 20 g / L of an aqueous solution at 45 ° C. for 30 seconds, spray-washed for 30 seconds, washed with water, and allowed to stand for 30 seconds. Regarding the chemical conversion treatability, PBL3020 (a chemical conversion treater manufactured by Nippon Parkerizing Co., Ltd.) was used for treatment at a predetermined temperature for a predetermined time, and the quality was judged based on the SEM observation of the chemical conversion crystal state and the amount of coating adhered.

The results of the investigation are shown in Table 1 together. If the steel plate surface roughness defined by the present invention is Ra of 1.5 μm or less,
It is clear that trial No. 2 and trial No. 12 having the organic deposition amount of the temper rolling liquid of 20 to 80 mg / m ² have excellent degreasing properties. Trial No. 5 is within the scope of the present invention, but Ni
The degreasing property was slightly inferior, probably because there was too much of the adhered amount. Regarding the chemical conversion treatability, when the degreasing property was good, all showed good results.

[Example 2] The surface roughness of the heating zone, the soaking zone and the slow cooling zone of the continuous annealing furnace was changed at the same time, and the dent defects of the steel sheet immediately before temper rolling were observed. Then, the amount of organic matter deposited in the temper rolling liquid on the surface of the steel sheet after temper rolling and the degreasing property after application of rust preventive oil were evaluated.
In this case, the surface roughness of the hearth roll was set to Ra of 0.1, 2, 8 and 10 μm. For dent defects, 100 mm square specimens were cut out from the steel sheet before temper rolling, and after confirming the existence of dent defects, the size and depth of the dent defects were measured using SEM observation and a three-dimensional roughness meter. did.

The surface roughness Ra of the product was 1.0 μm, the temper rolling conditions were the same as in Example 1, and the amount of organic substances deposited on the surface after rolling was the same as in Example 1 by changing the organic concentration of the rolling fluid. Instead, the other temper rolling conditions, the rust preventive oil coating method, the degreasing property evaluation method, and the like were all the same as in Example 1.

Table 2 collectively shows the surface roughness of the hearth roll, the amount of organic substances deposited after temper rolling, the dent defect, and the degreasing property evaluation of the product. Here, the size of the recessed flaws is about 0.1 mm to 1.5 mm, and some of them do not show a clear shape, but in that case, the diameter was approximated to a circle. Depth is 10-50 μm
Most of them were. Regarding the dent defects, the size of the largest dent defects observed in the sample specimen and the number of those having a size of 0.1 mm or more and a depth of 10 μm or more are shown. Regarding the degreasing property evaluation, evaluation of dot-like degreasing failure was shown.

[0045]

[Table 2]

From the results shown in Table 2, when the surface roughness Ra of the hearth roll is 8 μm or less, both the size and the number of the dents are relatively small, and if the dents have the same size and number, The organic deposition amount of the temper rolling liquid is 30 to 30 in the range of the present invention.
It can be seen that the sample Nos. 15, 18 and 21 having 50 mg / m ² suppress the dot-like degreasing failure. However, although the sample No. 24 is an example within the scope of the present invention, the point-like degreasing failure could not be sufficiently suppressed because the surface roughness of the hearth roll was rough.

[0047]

EFFECTS OF THE INVENTION According to the present invention, a cooling agent that improves the degreasing property of a molded part without reducing the rust preventive oil for suppressing rusting from the time of shipment from the factory to the molding and use of the part. A rolled steel sheet can be manufactured. In this way, achieving both rust prevention and degreasing has the effect of greatly improving the reliability of quality when using cold-rolled steel sheet products.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an amount of an organic steel sheet adhered to a temper rolling liquid, a surface area of a steel sheet after application of rust-preventing oil after degreasing with water, and a rust preventive property.

FIG. 2 is a diagram showing the relationship between the surface roughness of a steel sheet and the concentration of a temper rolling liquid, and the amount of organic steel sheet adhered to the surface.

FIG. 3 is a diagram showing a relationship between a Ni—O ratio during Ni flash plating and a water wetting rate of a steel plate after temper rolling and coated with rust preventive oil.

FIG. 4 is a diagram showing a relationship between a Ni deposition amount and a Ni—O ratio.

FIG. 5 is a diagram showing the relationship between the size of a dent defect on the surface of a steel sheet and the incidence rate of defective spot degreasing on a steel sheet that has been temper-rolled and then coated with rust-preventing oil.

FIG. 6 is a diagram showing a relationship between the surface roughness of a hearth roll of a continuous annealing furnace and the size of a dent defect.

FIG. 7 is a schematic diagram showing an example of a method of supplying a rolling liquid during temper rolling.

[Explanation of symbols]

1 steel plate 2 work rolls 3 backup roll 4 Rolling liquid 5 Rolling liquid supply pump

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koichi Taya             Sumitomo Metal Industry Co., Ltd.             Ceremony Company Kashima Steel Works (72) Inventor Akihiro Misawa             Sumitomo Metal Industry Co., Ltd.             Ceremony Company Kashima Steel Works F-term (reference) 4E002 AD06 BC08 BD09 CB03

Claims (3)

[Claims] 1. A temper rolling liquid containing 1 to 15% of a water-soluble organic substance is used for temper rolling after annealing of a cold rolled steel sheet having a surface roughness Ra of 1.5 μm or less, and the steel sheet surface after rolling is used. A method for producing a cold-rolled steel sheet excellent in degreasing property and chemical conversion treatment property, which comprises depositing a temper rolling liquid in an amount of 20 to 80 mg / m ² on. ^2. A cold-rolled steel sheet having a surface roughness Ra of 1.5 μm or less and a Ni deposition amount of 15 mg / m ² or less contains 1 to 15% of a water-soluble organic substance during temper rolling after annealing. A method for producing a cold-rolled steel sheet having excellent degreasing properties and chemical conversion treatment properties, which comprises applying a tempering rolling liquid to a surface of a steel sheet after rolling in an amount of ²⁰ to 80 mg / m ² using the tempering rolling liquid. 3. When continuously annealing a cold-rolled steel sheet having a surface roughness Ra of 1.5 μm or less, the hearth roll in the annealing furnace has a surface roughness Ra of 8 μm or less, and is subjected to temper rolling after annealing. , Using a tempered rolling liquid containing 1 to 15% of water-soluble organic matter,
A method for producing a cold-rolled steel sheet excellent in degreasing property and chemical conversion treatment property, which comprises applying a tempering rolling liquid to a surface of a steel sheet after rolling in an amount of ²⁰ to 80 mg / m ² .