JP5053060B2 - Cold-rolled steel sheet with excellent degreasing and chemical conversion properties - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet having stably excellent degreasability, even when a variance in a degreasing liquid occurs due to mixing of degreasability deteriorating factor components such as rust preventive oil into a degreasing liquid or reduction in pH or the like particularly with the lapse of time in a degreasing step in the side of a consumer, without being affected by them, and having excellent chemical convertibility even in a chemical conversion treatment step performed successively to the degreasing step. <P>SOLUTION: In the cold rolled steel sheet, Ni of &le;15 mg/m<SP>2</SP>is adhered to the surface of a steel sheet, and thereafter, to the surface of the steel sheet, an water soluble skinpass rolling liquid is adhered in an amount of 90 to 300 mg/m<SP>2</SP>per side in terms of the amount of remaining organic matter after skinpass rolling, the water soluble skinpass rolling liquid being mainly made up of a water soluble rust preventive and water and containing an alkali pH regulator of 2 to 4 times mol to 1 mol of acid in the water soluble rust preventive. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a cold-rolled steel sheet that is used after being subjected to a surface treatment. More specifically, in automotive parts or home appliance parts, after processing into a desired shape, welding, etc., coating oil is used to degrease the processing oil or rust preventive oil and undergo chemical conversion treatment to form the base treatment It is related with the cold-rolled steel plate suitable for.

  In general, cold-rolled and annealed steel sheets are prepared for the purpose of preventing buckling and stretcher strain, imparting the necessary mechanical properties, stabilizing the shape such as flattening the surface, and imparting surface roughness suitable for the application. It is common to perform quality rolling. In the temper rolling, a water-soluble tempered rolling liquid is used except for the tin plate and other special cases, and the water-soluble tempered rolling liquid is also used in the manufacturing process of the cold-rolled steel sheet.

  Cold-rolled steel sheets are shipped in a state in which rust-preventing oil is applied in the final process for the purpose of preventing rust generation and improving formability. For customers such as automobiles and home appliances, molding is performed on the desired part shape such as pressing, and in most cases, it is degreased with an alkaline degreasing solution or solvent, and is coated or plated, so it is good for steel sheets Degreasing properties are required.

  In particular, steel plates for automobiles are generally subjected to a chemical conversion treatment such as a phosphate treatment as a coating base treatment after forming and degreasing, and then a cationic electrodeposition coating is further performed. In order to develop an excellent appearance and post-coating corrosion resistance by electrodeposition coating, it is necessary to form a chemical conversion treatment as a base coating as a normal film. In order to form a good chemical conversion film, it is necessary to form crystal nucleation base points in the chemical conversion pretreatment, and to subsequently grow a chemical conversion film crystal in the chemical conversion process.

In the case of producing a cold-rolled steel sheet by a continuous annealing method, a trace amount Ni plating technique called flash plating has been proposed in order to develop good chemical conversion treatment properties (Patent Documents 1 and 2). In patent document 1, the technique which makes metal Ni adhere 0.3-10 mg / m < ² > on a cold-rolled steel plate is proposed. The phosphate crystal grows with the cathode part on the surface of the steel plate as the nucleus, but due to the potential difference between Ni and Fe partially deposited on the surface of the steel plate, an electrically non-uniform state is formed and Ni adheres. The part which becomes a cathode part becomes a starting point of phosphate crystal formation. And the improvement effect of chemical conversion property and corrosion resistance after coating is acquired. Further, Patent Document 2 proposes a technique in which Ni oxide and / or Ni hydroxide adhere to 1 to 150 mg / m ^{2 in} terms of Ni element weight on a cold-rolled steel sheet. By this technique, the chemical conversion treatment property that does not respond sensitively to changes with time of the chemical conversion bath components is expressed.

  Ni flash plating applied to a cold-rolled steel sheet manufactured by a continuous annealing method has an effect of improving the chemical conversion property, but a decrease in degreasing property may be pointed out. When Ni oxide or Ni hydroxide is formed on the surface, the affinity with oil is strong, so when a degreasing deterioration factor component such as rust preventive oil is mixed in the degreasing liquid with time, or in the air In some cases, such as when the pH is lowered due to the influence of carbon dioxide, the rust preventive oil is hardly removed in the degreasing step due to the influence of the degreasing liquid fluctuation in the degreasing step.

As a technique for suppressing such degreasing deterioration, in Patent Document 3, a metal Ni layer is provided on the ground steel side of the steel sheet surface, a nickel hydroxide layer is provided on the outermost layer, and the Ni existing ratio in the outermost layer is 75 to 95 atm. %, And further cold-rolled steel sheet with 1 to 100 mg / m ² of Ni deposited in terms of element weight has been proposed. The metal Ni formed on the base iron side shows good reactivity in the chemical conversion treatment after degreasing, and the ratio of the metal Ni in the lower layer facing the outermost layer to 95 atm% or less is controlled by the nickel hydroxide present in the surface layer. Degreasability due to increased sensitivity to rust-preventing oil by preventing Ni from being excessively sensitive to chemical conversion solution and controlling Ni content in the surface layer to 75 atm% or more. Decline can be prevented. Moreover, in patent document 4, the roughness of a steel plate shall be 1.5 micrometers or less by Ra, and the organic substance adhesion amount to the steel plate of the temper rolling liquid containing 1-15% of water-soluble organic substance shall be 20-80 mg / m < ² >. A method for manufacturing a cold-rolled steel sheet has been proposed. If it exceeds 80 mg / m ² , not only the degreasing property is deteriorated but also organic gumming tends to occur. When it is less than 20 mg / m ² , the behavior becomes close to dry rolling, and the roll surface is abraded so that the rolling workability is greatly reduced. Examples of water-soluble organic substances having an organic adhesion amount include rust inhibitors such as carboxylic acids and amine salts, and surfactants.

  However, it is very difficult to stably control and manufacture Ni deposited on the surface of the steel sheet in the form of metal Ni, Ni oxide, and Ni hydroxide in a layered manner, and the load on the manufacturing process is large. In addition, controlling the amount of temper rolling fluid containing water-soluble organic matter to the steel sheet to be controlled within this range is a limited range of conditions, and loss when the amount of adhesion due to fluctuations in manufacturing conditions is outside the range. Have the problem of growing. Furthermore, the problem that the degreasing property is deteriorated depending on the combination of the water-soluble organic substance added to the temper rolling liquid and the rust preventive oil applied to the upper layer has not been solved.

  On the other hand, various studies have been made on water-soluble tempered rolling fluids. In Patent Document 5, an emulsion-type tempered rolling fluid containing 0.5 to 2.0% by volume of rolling oil and 0.05 to 0.5% by volume of an alkanolamine salt of a dibasic acid having 8 to 16 carbon atoms was used. A rolling method has been proposed. This is a technology that enables temper rolling at a high pressure reduction rate of 3 to 10% while having rust prevention properties, but sufficient degreasing has not been confirmed, and a degreasing liquid in the degreasing process of customers. Under the influence of fluctuation, the rust preventive oil may be difficult to remove in the degreasing process. Patent Document 6 proposes a tempered rolling fluid containing a dibasic acid having a cyclohexane ring. This has the effect of suppressing the generation of black adhesive substances that are likely to occur when passing through a tension leveler or bridal roll when the moisture of the temper rolling liquid has dried to some extent, and the occurrence of white turbidity on the steel sheet surface after the application of rust preventive oil. There is going to be. Patent Document 7 proposes a tempered rolling fluid composed of a mixed carboxylic acid composed of benzothiazolylthioalkylene carboxylic acid and aliphatic carboxylic acid and an amine, which suppresses surface scratches during rolling and disturbs dimensional accuracy. There is an effect that it does not occur. Patent Document 8 proposes a temper rolling agent composed of a specific benzotriazole compound, phenoxyalkyl carboxylic acid, aliphatic carboxylic acid, surfactant, and alkali agent. There is an effect that it can be prevented.

However, these are all degreased when combined with Ni adhering to the surface of the cold-rolled steel sheet to be treated for chemical conversion, especially with respect to the degreasing effect when affected by the degreasing liquid fluctuation in the degreasing process as described above. Insufficient confirmation has been made regarding the properties and chemical conversion treatment properties, and some rust preventive oil components remain because sufficient degreasing properties cannot be obtained when subjected to fluctuations in the degreasing process in the consumer. In the subsequent chemical conversion treatment step, a normal chemical conversion treatment film is not formed.
JP 56-116883 A JP 59-159989 JP-A-7-278843 JP 2003-33802 A JP-A-6-1992 JP-A-9-302368 JP 2000-87073 A JP 2001-288492 A

  The present invention solves the problems of the prior art as described above, and when a degreasing deterioration factor component such as rust-preventing oil is mixed in the degreasing liquid in the degreasing process of the customer, particularly over time, or in the air. Even when there is a degreasing liquid fluctuation, such as when the pH is lowered due to the influence of carbon, etc., it has stable good degreasing properties without being affected by those effects, and it is excellent in the chemical conversion treatment step performed subsequent to the degreasing step. It aims at providing the cold-rolled steel plate which has chemical conversion treatment property.

  In order to solve the above-mentioned problems, the present inventors diligently studied various combinations such as Ni adhesion amount on the steel sheet surface, temper rolling liquid composition, and liquid remaining amount on the steel sheet. As a result, by adding an alkaline pH adjuster that completely neutralizes the acid contained in the water-soluble anticorrosive agent, the free alkaline polar component of the alkaline pH adjuster is adsorbed with the polar component in the rust preventive oil. Prevents the strong adsorption of the polar component in the rust preventive oil and the Ni oxide or Ni hydroxide formed on the surface of the steel plate, and demonstrates the effect that the rust preventive oil is easily removed in the degreasing process. I found out.

  In order to exert this effect, the water-soluble rust inhibitor and water are the main components, and the water-soluble rust inhibitor contains an alkaline pH adjuster containing a free alkali component in a specific range that neutralizes the acid contained in the water-soluble rust inhibitor. By applying a rust preventive oil after rolling a tempered rolling fluid on a steel sheet surface to which a limited adhesion amount range Ni has been adhered and rolling it, even if there is a degreasing fluid variation, those effects are affected. It is found that a cold-rolled steel sheet having excellent degreasing properties and chemical conversion treatment properties can be obtained, having stable and good degreasing properties without being received, and imparting excellent chemical conversion treatment properties even in the chemical conversion treatment step performed following the degreasing step. I found.

The present invention has been completed based on such knowledge, and the gist of the present invention is as follows.
“(1) After 15 mg / m ² or less of Ni is adhered to the steel sheet surface, the main component is a water-soluble rust preventive agent and water, and it is at least 2 mol per mol of acid contained in the water-soluble rust preventive agent 4 that the per side 90mg / m ² ~300mg / m ² adhered to the water-soluble temper rolling liquid steel sheet surface is temper residual organic matter after rolling containing alkaline pH adjusting agent consisting of multiple mol following amines The featured cold-rolled steel sheet.
(2) The cold-rolled steel sheet according to (1), wherein the alkaline pH adjuster contained in the water-soluble tempered rolling liquid is alkanolamine.
(3) The water-soluble rust preventive contained in the water-soluble tempered rolling liquid is one or a mixture of two or more of benzoic acid derivatives, organic carboxylic acids, and organic chelate nitrogen-containing compounds. The cold rolled steel sheet according to 1) or (2) above. "
It is.

  The cold-rolled steel sheet obtained by the present invention has a stable good degreasing property without being influenced by the degreasing liquid even when there is a degreasing liquid variation, and is excellent in the chemical conversion treatment step performed subsequent to the degreasing step. Because it has processability, after processing to the desired shape and welding, etc. in parts for automobiles or home appliances, chemical treatment for degreasing the processing oil or rust preventive oil and forming the base treatment It is suitable for coating applications where

The contents of the present invention will be described in detail below.
First, the steel sheet in the present invention uses a cold-rolled steel sheet in which Ni of 15 mg / m ² or less is adhered to the steel sheet surface. The effect of improving chemical conversion properties and rust prevention properties can be obtained by attaching Ni. Even in the low adhesion amount range where the adhesion amount is approximately 0 to ² mg / m ² , the improvement effect of the chemical conversion treatment property and the rust prevention property is recognized, but the adhesion amount range of 3 to 15 mg / m ² is the chemical conversion treatment property and the rust prevention property. Desirable from a viewpoint. Even if the Ni adhesion amount exceeds 15 mg / m ² , there is an effect of improving the chemical conversion treatment property and the rust prevention property to a certain extent, but as will be described later, the polar component in the rust prevention oil and the Ni oxide or It is also not preferable from the economical viewpoint that the degreasing property considered to be due to an increase in the adsorptive power with Ni hydroxide becomes significant and the amount of Ni adhesion increases.

  The Ni adhesion method may be any method such as chemical plating, electroplating, and vapor phase plating, and is not particularly limited. For example, it can be formed by electroplating with a plating solution made of nickel sulfate hexahydrate. The amount of Ni adhesion can be easily controlled by increasing or decreasing the amount of plating energization. For example, in the case of electric Ni plating, when Ni ions are sufficiently supplied to the surface of the steel sheet to be plated, metal Ni is deposited, but when Ni ions are insufficiently diffused (or insufficiently supplied), the consumption of protons causes an interface. It is considered that Ni hydrated oxide is formed because the pH at the part increases. Therefore, it is considered that Ni formed on the surface of the steel sheet is not only metal Ni but also a mixture of oxidized Ni and oxidized hydroxide. Here, it is considered that removal of the rust preventive oil in the degreasing step becomes difficult and the degreasing property is lowered due to the adsorption force between the polar component in the rust preventive oil and Ni oxide or Ni hydroxide.

  The temper rolling liquid in the present invention contains an alkali pH adjuster containing a water-soluble rust inhibitor and water as main components and a free alkali component in a specific range with respect to the contained acid.

  The water-soluble rust preventive agent may be any one that has been developed for conventional water-soluble temper rolling liquids or wet temper rolling applications. For example, a mixture of a nitrite such as sodium nitrite and an ethanolamine derivative, benzoic acid Examples include benzoic acid derivatives such as sodium acid, nitrogen-containing compounds such as 1-hydroxybenzotriazole, methylbenzotriazole, and indazole, and organic carboxylic acids. However, when nitrite and alkanolamine coexist, it is known that nitrosamine is produced by reaction, and caution is required because it has a negative effect on the human body. Examples of organic carboxylic acids include aliphatic dibasic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, undecanoic acid, and suberic acid, and aromatic dicarboxylic acids such as p-nitrobenzoic acid and cyclohexanedicarboxylic acid. Can be mentioned. These can be used alone or in combination. Organic chelate nitrogen-containing compound rust preventives such as 1-hydroxybenzotriazole, methylbenzotriazole and indazole react with iron on the surface of the steel sheet to form an insoluble iron chelate film, and thus have a large rust preventive effect. In addition, benzoic acid derivatives and organic carboxylic acids have a large rust prevention effect because they promote the formation of oxide films and suppress the anode reaction. A mixture of a nitrite such as sodium nitrite and an ethanolamine derivative chemisorbs on the surface of the steel sheet and suppresses the anode reaction.

  Since the rust preventive agent such as aliphatic dibasic acid or aromatic dicarboxylic acid is acidic when dissolved in water, it is necessary to maintain the pH of the temper rolling solution at neutral or higher. An alkali pH adjuster is used as the neutralizer.

  Examples of the alkaline pH adjuster include ammonia, potassium hydroxide, and Na hydroxide, but these are not preferable from the viewpoint of workability and adverse effects on the steel sheet surface, and amines are generally used.

  Examples of the amines used as the alkaline pH adjuster include alkanolamines, lower alkylamines, lower alkylalkanolamines, polyamines, and cyclic amines.

  Of these, alkanolamine is particularly preferred. Examples of the alkanolamine include ethanolamine, isopropanolamine, diethanolamine, diisopropanolamine, dibutanolamine, and triethanolamine. The amino group side, which is a hydrophilic group, adsorbs to the surface of the steel sheet to have a rust prevention effect and a pH adjustment effect. However, since the tendency to emulsify in an aqueous solution is exhibited when the hydrophobicity increases, it is necessary to confirm the liquid stability when the number of carbon atoms in the hydrocarbon group exceeds 6.

  The alkaline pH adjuster needs to be added in an amount of 2 to 4 mols per mol of acid in the water-soluble rust inhibitor. By adding an alkaline pH adjusting agent that completely neutralizes the acid contained in the water-soluble anti-corrosive agent, the free alkaline polar component of the alkaline pH adjusting agent is adsorbed with the polar component in the anti-rust oil to prevent In order to prevent strong adhesion between the polar component in the rust oil and the Ni oxide or Ni hydroxide formed on the surface of the steel sheet, and to exhibit the good degreasing property of the rust preventive oil in the degreasing process. It is necessary to fold mol or more. When good degreasing property is ensured, the chemical conversion treatment processed in a subsequent process can also be stably processed. On the other hand, when an alkaline pH adjustor exceeding 4 times mol is added, good degreasing property is maintained, but the effect is saturated, so it is not preferable from an economical viewpoint, and a water-soluble rust preventive agent is applied to the steel sheet surface. Since the ability to adsorb is reduced, the rust prevention ability is lowered, which is not preferable.

  Generally, after continuous annealing, temper rolling is performed in order to give a required mechanical property and surface roughness suitable for the application and to give a flat shape. The cold-rolled steel sheet of the present invention is temper-rolled using the temper rolling liquid. Rolling conditions such as rolling load, rolling roll surface finish, and rolling speed may be selected depending on the required mechanical properties and surface roughness suitable for the application. For the temper rolling method, an existing rolling mill such as a single stand rolling mill or a two stand rolling mill can be used. A bright roll or a dull roll having a different surface roughness can be used to finish the rolling roll to the required surface roughness.

Residual organic matter of the water-soluble temper rolling solution remaining on the surface of the steel sheet after being rolled is in the range of per side ^{90mg / m 2 ~300mg / m 2} . If it is less than 90 mg / m ² per side, the rust prevention effect on the steel sheet surface will be insufficient, and the effect of preventing the polar component in the rust prevention oil and the steel sheet surface from adsorbing firmly will be insufficient, resulting in sufficient degreasing properties. It is not preferable because it is not possible.

If it is 90 mg / m ² or more, good degreasing properties are exhibited, but it is more preferably 100 mg / m ² or more from the viewpoint of stable degreasing properties that are not affected even when the degreasing process is greatly varied. It should be noted that fluctuations in the degreasing process mean that in the actual degreasing process line, unsteady degreasing performance occurs due to, for example, mixing of degreasing ability deterioration factors such as oil and solvent or a decrease in the pH of the degreasing liquid due to some cause. Refers to the case. It is more preferably 100 mg / m ² or more from the viewpoint of maintaining good degreasing properties not only under normal line conditions and degreasing liquid capacity conditions but also under conditions severe to the degreasing properties of such steel sheets. . For example, in the examples described later, the evaluation result (number 10) of 90 mg / m ² material implemented under the degreasing conditions assuming a general degreasing process indicates that the wetness is 80 to 94%. This is because when the oil is further mixed in the degreasing liquid or when the pH is further lowered, it is considered that the water wetting result is lowered.

Also, it it is a rare that residual organic material of the water-soluble temper rolling solution remaining on the surface of the steel sheet is more than 300 mg / m ² under normal operating conditions, also rust resistance improved as exceeds 300 mg / m ² Owing to saturation of the effect and a large amount of organic residue remaining on the surface of the steel sheet, operational problems such as generation of pushing scratches on the surface of the steel sheet due to build-up of the organic residue on the roll when contacting the roll after rolling occur. This is not preferable.

  To measure the amount of residual organic matter in the water-soluble tempered rolling liquid remaining on the surface of the steel sheet after being rolled, for example, a cut sheet sample is prepared from the temper-rolled steel sheet and immersed in an organic solvent such as ethanol or acetone. It is possible to extract the temper rolling liquid and then perform liquid chromatographic analysis on the extracted liquid to perform quantification of each constituent component. Alternatively, measure the absorbance of the liquid that has been washed on the surface of the steel sheet using ion-exchanged water, measure the concentration using a calibration curve prepared in advance using organic substance-containing water with a known concentration, and determine the amount from the liquid volume and the washed area. Is possible.

  In addition, the temper rolling liquid may contain various organic or inorganic additives in addition to the water-soluble rust preventive and alkaline pH adjuster as long as the purpose and effect thereof are not impaired. There is no problem. Examples of such additives include bactericides to prevent mold and corrosion due to contact with air during long-term storage and storage in tanks, extreme pressure additives to prevent seizure during rolling, There are viscosity modifiers for controlling liquid properties. In addition, surfactants improve the uniform application of the liquid on the steel sheet surface, improve the lubricity by reducing the friction coefficient during rolling, improve the cleanability to keep the steel sheet surface clean, and suppress the foaming during liquid handling and application. It is added for the purpose of improving foamability, improving gum-up resistance, and improving direct paintability. Gum-up is a phenomenon in which an adhesive substance composed of a temper rolling liquid component and an antirust oil component is generated, and the adhesive substance entraps and deposits foreign matters such as iron powder.

  There are various types of surfactants such as cationic surfactants, anionic surfactants, and nonionic surfactants, but they are uniform without reducing the effects of water-soluble rust preventives and alkaline pH adjusters. A nonionic surfactant having both a lipophilic group and a hydrophilic group structure is desirable from the viewpoint that coating properties, lubricity, detergency, antifoaming properties, and gum-up resistance can be improved. Nonionic surface activity includes polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyalkylene alkyl ether, polyoxyethylene glycol, polyoxyethylene polyoxypropylene glycol block copolymer and the like. The surfactant can be added as a single type or a mixture of two or more types. The amount of the surfactant is added within a range in which the desired effect can be expressed, but is desirably 0.005 to 1% by mass of the total amount of the temper rolling liquid. When the amount is less than 0.005% by mass of the total amount of liquid, the effect is insufficient.

  The cold-rolled steel sheet of the present invention is coated with a rust preventive oil after temper rolling. As the rust preventive oil to be applied, known rust preventive oils conventionally used are used. Examples thereof include those containing a mineral oil composed of petroleum hydrocarbons as a main component and containing rust preventive additives such as petroleum sulfonic acid sodium salt, petroleum sulfonic acid barium salt, petroleum sulfonic acid calcium salt, and fatty acid barium salt.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

[1] Specimen (1) Cold rolled steel plate Aluminum killed steel with a thickness of 0.8 mm was pickled with 3% hydrochloric acid at 70 ° C. for 30 seconds, then washed with water, and then nickel sulfate hexahydrate 15 g / Ni plating was performed at a current density of 5 A / dm 2 in a 1 Ni plating bath (plating bath temperature 40 ° C.). The amount of Ni adhesion was controlled by changing the energization time.

(2) Water-soluble tempered rolling fluid
In order to clarify the effect of the added amount of the pH adjuster on the acid contained in the water-soluble rust preventive agent, a salt and a surfactant comprising an amine-based pH adjuster in an amount equivalent to the mol amount of the acid contained in the water-soluble rust preventive agent Based on tempered rolling fluid A dissolved in water, fluids B to E were prepared by adding an excessive amount of amine-based pH adjuster. Each temper rolling liquid was prepared by adding each component to 70 ° C. water while stirring and dissolving the mixture uniformly, and then cooling to room temperature. Each component used a commercially available reagent, and Lion Polycor SCI was used for the polyoxyethylene alkyl ether surfactant.

<Tempered rolling fluid A1: Equivalent molar amount of acid and amine>
Water 81.5%
p-nitrobenzoic acid / isopropanolamine equivalent salt 15%
1-hydroxybenzotriazole 3%
Polyoxyethylene alkyl ether surfactant 0.5%

<Tempered rolling fluid A2: 1.5 times mol of amine with respect to acid>
Addition of 0.5 times mol of isopropanolamine (per acid component) to temper rolling fluid A1

<Tempered rolling liquid A3: Amount of amine 2 times mol to acid>
Addition of 1 mol of isopropanolamine (per acid component) to temper rolling fluid A1

<Tempered rolling liquid A4: 4 times mol of amine with respect to acid>
Addition of 3 times mol of isopropanolamine (per acid component) to temper rolling fluid A1

<Tempered rolling liquid A5: 4.5 times mol of amine with respect to acid>
Addition of 3.5 times mol of isopropanolamine (per acid component) to temper rolling fluid A1

<Tempered rolling fluid B1: equimolar amount of acid and amine>
Water 81.5%
15% equivalent salt of dodecanoic acid / diisopropanolamine
Sodium benzoate 3%
Polyoxyethylene alkyl ether surfactant 0.5%

<Tempered rolling fluid B2: 1.5 times mol of amine with respect to acid>
Addition of 0.5 times mol of diisopropanolamine (per acid component) to temper rolling fluid B1

<Tempered rolling fluid B3: Amount of amine 2 times mol to acid>
Addition of 1 mol of diisopropanolamine (per acid component) to temper rolling fluid B1

<Tempered rolling fluid B4: 4 times mol of amine with respect to acid>
Addition of 3 times mol of diisopropanolamine (per acid component) to temper rolling fluid B1

<Tempered rolling liquid B5: 4.5 times mol of amine with respect to acid>
Addition of 3.5 times mol of diisopropanolamine (per acid component) to temper rolling fluid B1

[2] Temper rolling (1) Temper rolling with a small rolling mill Using a dilution of the temper rolling liquid, temper rolling with a small rolling mill equipped with a dull roll (surface roughness Ra = 3 μm, diameter 150 mm). Rolled. The rolling conditions were a rolling speed of 10 m / min and a reduction rate of 1%.

(2) Measurement of amount of residual organic matter in temper rolling liquid remaining on steel sheet surface after rolling Prepare a cut sheet sample with a size of 100 mm x 100 mm from the temper rolled steel sheet and immerse it in 1000 cc of ethanol for 30 minutes. After extracting the remaining organic matter amount, the extract was concentrated to 5 ml with an evaporator and subjected to liquid chromatography analysis. The amount of residual organic matter per side was calculated by the weight of the residual organic matter extracted (mg) / half the cut plate sample area (m ² ).

[3] Application of rust preventive oil after temper rolling A rust preventive oil (Parker Kosan Knoxlast 530F) was applied to the temper rolled sample using a lab roll coater (urethane rubber roll, diameter 150 mm). The amount of oil coating was almost constant in the range of 1.0 to 1.5 g / m ² . The amount of oil was controlled by the number of roll rotations and roll rolling force.

[4] Performance Evaluation The following performance evaluation was performed on the steel sheet samples prepared under the various conditions. Table 1 summarizes sample levels and performance evaluation results.

(1) Degreasing evaluation Degreasing was evaluated by the surface water wetted area ratio when washed with water after alkaline degreasing and taken out after washing with water. As the alkaline degreasing solution, 20 g / L of FC-4460A manufactured by Nippon Parkerizing Co., Ltd. and 12 g / L of FC-4460B dissolved in 40 ° C. aqueous solution (pH 12.1) were used. The main components are sodium carbonate, phosphate, sodium hydroxide, and a surfactant. Considering process fluctuations such as liquid deterioration and pH change due to contamination of degreased rust preventive oil during continuous operation in the consumer, evaluation with the new liquid is insufficient, so 20 g of Nippon Parkerizing FC-4460 10 g / L of rust-preventive oil (Parker Kosan's Knoxlast 530F) was added in advance to a 40 ° C. alkaline degreasing solution dissolved in / L, and after sufficient stirring, the pH was lowered to 10.5 by including carbon dioxide. 20 L of simulated deterioration liquid was created. The simulated deterioration solution was placed in a stainless steel container, and the steel plate sample was immersed for 1 minute and 2 minutes using a 10 mmφ blade-type stirring blade and stirred for 500 minutes to perform alkaline degreasing. After degreasing, spray water washing was performed for 30 seconds, and the water wetted area ratio on the steel sheet surface after 30 seconds after water washing was visually evaluated. Evaluation was according to the following criteria.

Score ◎: 95-100% wet
○: Water wet 80-94%
Δ: 50-79% wet
X: Less than 50% wet

(2) Chemical conversion treatment evaluation A steel sheet sample after degreasing and washing was sprayed with a surface conditioner (preparene 40404, manufactured by Nihon Parkerizing, temperature 23 ° C.) for 20 seconds, and a chemical conversion solution (Palbond 3020, manufactured by Nihon Parkerizing, phosphoric acid). A chemical conversion film was formed by immersing in a zinc chemical conversion treatment agent at a temperature of 42 ° C. for 2 minutes, followed by spray water washing for 30 seconds and drying. About the sample which performed the chemical conversion treatment, the visual evaluation of the external appearance, SEM observation of the chemical conversion crystal form was performed, and the chemical conversion treatment film adhesion amount was measured. SEM observation was performed at an acceleration voltage of 20 kV and a magnification of 3000 times. The quality as a chemical conversion film was judged comprehensively from the appearance and crystal form and size of SEM observation such as unevenness that can be visually confirmed. Judgment of pass / fail was described as ◯: good, x: defective, and the content was described when defective. Moreover, the amount of chemical conversion film was measured by the weight method from the weight difference before and after chemical film peeling. The chemical conversion film was peeled off by immersing the steel sheet in a 5 wt% chromic anhydride aqueous solution at 70 ° C. for 15 minutes. The 5 wt% chromic anhydride aqueous solution was prepared by adding chromic anhydride (Wako Standard Grade 1 product) manufactured by Wako Pure Chemical Industries to ion-exchanged water.

(3) Rust prevention test (3-1) Indoor exposure test Rust on the surface of a 100 x 100 mm steel plate coated with antirust oil, standing on a sample stand one by one in a sample storage warehouse for 14 days We evaluated the occurrence of discoloration. Evaluation was according to the following criteria.

Rating ◎: No rust or discoloration ○: Less than 3% rust or discoloration △: 3 to 30% rust or discoloration
×: Rust and discoloration occurred over 30%

(3-2) Stack Rust Prevention Test A set of five 100 × 100 mm steel plate samples coated with rust preventive oil was taken as one set, and the stacked steel plate samples were sandwiched between Teflon (registered trademark) sheets, and then the end 4 A test that was sandwiched between 150 x 150 x 4 mm thick stainless steel plates with bolt holes at the location, bolted with a torque of 2 Nm, left in a wet test device at 50 ° C x 95% humidity for 14 days, then taken out and stacked The surface of the sample was visually observed. Evaluation was according to the following criteria.

Rating ◎: No rust or discoloration ○: Less than 3% rust or discoloration △: 3 to 30% rust or discoloration
×: Rust and discoloration occurred over 30%

(4) Build-up resistance test Rubber roll squeezing is performed on a steel plate sample (without rust-prevention oil coating, 100 × 100 mm size) immediately after temper rolling. After squeezing 100 samples, the roll surface is dried with hot air of 50 ° C. while rotating the roll, and the state of occurrence of deposits on the roll surface is visually confirmed. Evaluation was according to the following criteria.

Grade ◎: No deposit ○: Very little deposit is observed on part of roll △: Very little deposit is observed on the entire roll surface ×: Deposit is observed on the entire roll surface

Claims (3)

After adhering 15 mg / m ² or less of Ni to the steel sheet surface, the main component is a water-soluble rust preventive agent and water, and it is 2 to 4 mol per mol of acid contained in the water-soluble rust inhibitor. cold was characterized by water-soluble temper rolling fluid is adhered per one side 90mg / m ² ~300mg / m ² on the surface of the steel sheet in the residual organic matter after temper rolling containing an alkaline pH adjusting agent consisting of amines Rolled steel sheet.   The cold-rolled steel sheet according to claim 1, wherein the alkaline pH adjuster contained in the water-soluble tempered rolling liquid is alkanolamine.   The water-soluble rust preventive contained in the water-soluble tempered rolling liquid is one or a mixture of two or more of benzoic acid derivatives, organic carboxylic acids, and organic chelate nitrogen-containing compounds. Item 3. The cold-rolled steel sheet according to Item 2.