JPH0693472A - High strength cold rolled steel plate excellent in phosphating treatability - Google Patents

Abstract

PURPOSE:To produce a high strength cold rolled steel plate excellent in phosphating treatability by forming a specified alloy layer on the surface of a cold rolled steel plate having a specified compsn. CONSTITUTION:On the surface of a cold rolled steel plate contg., by weight, 0.001 to 0.25% C, 0.1 to 1.5% Si and 0.2 to 3.0% Mn and contg. at least one kind among 0.5 to 1.5% Cu, 0.5 to 1.5% Ni, 0.2 to 1.0% Mo, 0.1 to 2.5% Cr, 0.01 to 0.1% V, 0.0005 to 0.003% B, 0.01 to 0.20% Ti and 0.01 to 0.20% Nb, and the balance Fe with inevitable impurities, an Ni-P alloy layer in which alloy grains in a granular depositing state are precipitated at 1X10<12> to 1X10<16> pieces/m<2> distribution density is formed. The grains contain 0.01 to 16.0wt.% P, and the coating weight of the alloy layer is regulated to 5 to 60mg/m<2> per side of the steel plate as the coating weight of Ni. In this way, the high strength cold rolled steel plate excellent in phosphating treatability can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength cold-rolled steel sheet excellent in phosphatability.

[0002]

2. Description of the Related Art In recent years, in the automobile industry, social demands for reducing fuel consumption have been strengthened, and weight reduction of vehicle bodies has been progressing. As one of the methods, use of a high-strength cold-rolled steel sheet that is thinner and stronger than conventional steel sheets is promoted.
Further, due to an increasing concern about safety in a developed transportation society, high-strength cold-rolled steel sheets are positively used as a vehicle body reinforcing member equipped to ensure the safety of passengers.

Since such a high-strength cold-rolled steel sheet is thinner than the conventional steel sheet, the corrosion allowance is reduced, and therefore pitting corrosion is feared and its prevention becomes a problem. Further, when it is used as a reinforcing member, there is a concern that the plate thickness may be reduced due to corrosion, and strengthening corrosion resistance is a major issue for maintaining strength.

As a method for improving the corrosion resistance, there are methods such as electrogalvanizing and hot dip galvanizing, which actually provide an excellent rust preventive effect. On the other hand,
Due to various circumstances such as usage conditions, cold-rolled steel sheets are often used as they are without plating, and in that case, corrosion resistance is mainly improved by painting.

However, even when it is used after being coated in this way, the corrosion resistance after coating of the high-strength cold-rolled steel sheet may sometimes be inferior. There are various factors that can be considered depending on the situation in which corrosion occurs, and the reason cannot be clearly stated. However, as a result of investigations, it has been frequently observed that when a phosphate-treated film used as a coating base treatment has some problem, the corrosion resistance after coating is often inferior.

The factors affecting the phosphating property of cold-rolled steel sheets have been extensively studied so far, and the chemical composition of the steel sheet, contaminants on the steel sheet surface, oxide film properties, surface thickening elements and surface It has been pointed out that it is related to the crystal orientation. These factors are strongly related to the material design of cold-rolled steel sheets and the manufacturing method itself.When the surface state of the resulting steel sheet is not appropriate, the rate of nucleation at the initial stage of formation of phosphate coating And the distribution is greatly affected, and a coarse phosphate film is generally formed, resulting in a film with a lot of blemishes, and in many cases, poor post-coating corrosion resistance.

Further, in order to increase the strength of the steel sheet, C,
In the case of a high-strength cold-rolled steel sheet in which a large amount of elements such as Si, Mn and Cu, Ni, Mo, Cr, V, B, Ti, Nb are positively contained,
As the behavior of these elements, there are cases where the surface layer of the steel sheet is heavily concentrated due to heating during annealing, and it is exposed on the surface as a selective oxidation layer. This results in the processability being affected.

Further, the method for producing a high-strength cold-rolled steel sheet includes a method using a box-type annealing method, a method using a continuous annealing method, and a method in which rapid cooling is performed by water cooling or steam cooling during continuous annealing. Since there are various manufacturing methods as described above, and the surface conditions of the steel sheet are different in each case, the manufacturing method of the steel sheet has a great influence on the phosphatability.

As described above, various factors affect the phosphatability of cold-rolled steel sheets, and since these factors are related to each other, the aspect is extremely complicated and good phosphatability is obtained. It has been extremely difficult to manufacture the cold-rolled steel sheet provided with it while always maintaining a stable quality level.

Particularly, in the case of a high-strength cold-rolled steel sheet which has a complicated chemical composition and is manufactured through various processes, which is the object of the present invention, a simple improvement in the manufacturing method is a fundamental improvement. Therefore, it was found that a significant improvement in phosphating property cannot be expected.

As means for overcoming the above-mentioned problems and positively controlling the phosphating property which influences the corrosion resistance after painting,
Conventionally, the following ideas have been made and proposed.

The formation of a phosphate coating on the surface of a steel sheet is generally carried out by first completely degreasing the steel sheet and then, after appropriate surface preparation, reacting the steel sheet surface with a phosphating solution. Has been done. By the way, the phosphate-treated film for obtaining good corrosion resistance after coating is a film in which phosphate crystals densely cover the surface of the steel sheet without any gaps. The conditions under which such a film is formed are largely governed by the nucleation rate and distribution of phosphate crystals at the initial stage of film formation, that is, the local cell generation rate and distribution at the interface between the phosphate treatment liquid and the steel sheet surface. . Furthermore, the conditions under which a good film can be obtained are greatly affected by the above-mentioned contaminants on the surface of the steel sheet, oxide film properties, surface thickening elements, surface crystallographic orientation, etc., resulting in fast initial nucleation and high density. The higher the value, the more dense the phosphate coating is obtained, and the corrosion resistance after coating is secured.

Therefore, from the viewpoint of smoothly promoting the initial nucleation, in the step of adjusting the surface of the steel sheet in the above-mentioned phosphate film forming step, the titanium colloid is adsorbed on the surface of the steel sheet or the phosphate is A treatment method in which heavy metal ions such as Ni and Co are added to the treatment solution to cause substitutional precipitation on the surface of the steel sheet has been widely studied and improved.

On the other hand, from the viewpoint of improving the steel plate itself, as in the above-mentioned method, there are the following means as means for smoothly proceeding the local battery generation. For example,
Japanese Examined Patent Publication No. 60-28909 discloses a steel sheet containing one or more of Si, Nb, Cr, Ti, and Al in a specified amount, and Ni.
Disclosed is a steel sheet having excellent phosphatability, which is characterized by electrolytically depositing 1 to 300 mg / m ^{2 of} other metals (hereinafter referred to as “Prior Art 1”).

In Japanese Patent Laid-Open No. 63-79996, carbon content in steel is 0.005 wt.% Or less, and Ti and / or Nb content is 0.005 wt.
To 0.15 wt.% And the balance Fe and unavoidable impurities in the surface of an ultra-low carbon steel consisting of an alloy of Ni and / or Co and P with a total amount of 10 to 500 mg / m ² . And an ultra-low carbon steel sheet excellent in phosphating property, characterized by having an alloy plating layer having a P content of 1 to 30 wt.% (Hereinafter referred to as "prior art 2").

Further, in Japanese Patent Laid-Open No. 59-159994, a Ni-P alloy layer containing 0.01 to 5.0 wt.% P is deposited on at least one surface in an amount of 1 to 100 mg / m ^2. A surface-treated steel sheet having excellent chemical conversion treatability is disclosed (hereinafter referred to as "Prior Art 3"). In prior art 3, cold-rolled steel sheet, which is water-cooled or steam-cooled at the annealing stage in the production of cold-rolled steel sheet and in which oxides formed on the surface at that time are removed by pickling treatment, has a chemical conversion treatability.
The effect of the Ni-P alloy is disclosed, and it is also disclosed that the non-plated surface of the single-sided galvanized steel sheet has the same effect.

[0017]

However, the above-mentioned method for improving the steel sheet itself has the following problems. That is, for the steel plate as in the method described above
When a Ni metal layer or a Ni-P alloy layer is attached, the phosphating property may be improved as expected, but on the other hand,
In some cases, the phosphating property rather deteriorates, and eventually the corrosion resistance after coating deteriorates.

The reason for this has not been fully clarified, but it can be considered as follows.

In the first place, a Ni metal layer or Ni is applied to the steel plate.
The attachment of the -P alloy layer is intended to facilitate the formation of the local battery on the surface of the steel sheet, as described above. This is a method that focuses on the fact that the phosphatization reaction proceeds with an electrochemical reaction in a local battery existing on the surface of the steel sheet as a driving force. As important in forming a local battery by the adhesion of this Ni metal layer or Ni-P alloy layer, the electrical characteristics of the local battery formed,
The distribution state is raised. And in order to improve the phosphating property, a local battery with appropriate characteristics,
It must exist in an appropriate distribution.

Regarding the electrical characteristics of the local battery referred to here, a Ni metal layer or a Ni-P alloy layer serving as the cathode portion,
The relationship between the two and the state of the surface of the steel plate that serves as the anode has a great influence. This is electrochemically clear because the local cell is formed by the combination of the cathode part and the anode part. Therefore, when trying to improve the phosphatability by depositing a Ni metal layer or a Ni-P alloy layer on the steel sheet, an appropriate combination such that an appropriate local battery is formed by both of them is formed. Is essential. If this is not appropriate, not only will it not be effective, but it may even be harmful.

That is, as often seen in the prior art, when the phosphating property is rather deteriorated by depositing the Ni metal layer or the Ni-P alloy layer, as described above, the Ni metal layer is used. It is conceivable that the combination of the layer or Ni-P alloy layer and the steel plate surface state is inappropriate, and the local battery formed by both is a detrimental condition for the phosphate treatment reaction.

In particular, in order to increase the strength of the steel sheet, C,
High-strength cold-rolled steel sheet containing elements such as Si, Mn and Cu, Ni, Mo, Cr, V, B, Ti, Nb, etc. in a large amount positively in various compositions and manufactured by various processes. In the case of, these elements have a great influence on the behavior of the surface of the steel sheet as an anode, and simply attaching a Ni metal layer or a Ni-P alloy layer improves the phosphating property. I can't say that.

On the other hand, for example, the combination of the surface states of the Ni-P alloy layer and the steel sheet is suitable, and the electrical characteristics of the formed local battery are effective for the phosphate treatment. Even if the distribution is not appropriate, the overall phosphatability will be deteriorated.

As described above, the Ni metal layer or the
In order to improve the phosphatability by depositing the Ni-P alloy layer, a combination of the Ni metal layer or the Ni-P alloy layer and the surface state of the steel sheet, and the Ni metal layer or the deposited Ni metal layer or The distribution state of the Ni-P alloy layer must be appropriate. If it is not suitable, the phosphatability may be worsened by depositing the Ni metal layer or the Ni-P alloy layer.

This makes it extremely difficult to always maintain a stable quality level for a wide variety of steel sheets manufactured by various methods.

Therefore, an object of the present invention is to solve the above-mentioned problems and to have a chemical composition necessary for obtaining a sufficiently high strength, and to manufacture the high-strength cold-rolled steel sheet through various processes. Also in, it is to provide a high-strength cold-rolled steel sheet having excellent phosphating property.

[0027]

In view of the above-mentioned circumstances, the inventors of the present invention have the chemical component composition necessary for obtaining a sufficiently high strength, and even when they are manufactured through various processes. As a result of intensive studies to develop a high-strength cold-rolled steel sheet having excellent phosphatability, the following findings have been obtained.

The phosphatability of the steel sheet is affected by the surface state of the steel sheet, such as the chemical composition of the steel sheet, contaminants on the surface of the steel sheet, oxide film properties, surface thickening elements and surface crystal orientation. In particular, high-strength cold-rolled steel sheets are positively enriched with elements such as C, Si, Mn and Cu, Ni, Mo, Cr, V, B, Ti, Nb in order to increase the strength of the steel sheet. In addition, since it is contained in and the manufacturing process is various, there are many factors involved in the surface state, and it is impossible to predict the superiority or inferiority of the phosphate treatment property. However, in the case of a high-strength cold-rolled steel sheet having a certain chemical composition, by depositing a Ni metal layer or a Ni-P alloy layer on its surface under appropriate conditions, regardless of the method for producing the steel sheet, Has excellent phosphatability,
Good film performance is demonstrated.

The present invention was made based on the above-mentioned findings. The cold-rolled steel sheet according to the first invention comprises carbon: 0.001 to 0.25 wt.%, Silicon: 0.1 to 1.5 wt.%, Manganese: 0.2 to 3.0 wt.%, At least one element selected from the group consisting of: copper: 0.5 to 1.5 wt.%, Nickel: 0.5 to 1.5 wt.%, Molybdenum: 0.2 to 1.0 wt.%, Chromium: 0.1 To 2.5 wt.%, Vanadium: 0.01 to 0.1 wt.%, Boron: 0.0005 to 0.003 wt.%, Titanium: 0.01 to 0.20 wt.%, Niobium: 0.01 to 0.20 wt.%, And residual iron and unavoidable impurities And a nickel metal having a distribution density of 1 × 10 ¹² pieces / m ² to 1 × 10 ¹⁶ pieces / m ² formed in a granular form on at least one surface of the cold rolled steel sheet. A nickel metal layer on which particles are deposited, and the nickel metal layer Is characterized in that it is in the range of 5 to 60 mg / m ² per one side of the cold rolled steel sheet. The cold-rolled steel sheet of the second invention comprises carbon: 0.001 to 0.25 wt.%, Silicon: 0.1 to 1.5 wt.%, Manganese: 0.2 to 3.0 wt.%, At least one element selected from the group consisting of: Copper: 0.5 to 1.5 wt.%, Nickel: 0.5 to 1.5 wt.%, Molybdenum: 0.2 to 1.0 wt.%, Chromium: 0.1 to 2.5 wt.%, Vanadium: 0.01 to 0.1 wt.%, Boron: 0.0005 to 0.003. wt.%, titanium: 0.01 to 0.20 wt.%, niobium: 0.01 to 0.20 wt.%, and the cold rolled steel sheet consisting of the balance iron and inevitable impurities, and the form of adhesion on at least one surface of the cold rolled steel sheet. And a nickel-phosphorus alloy layer in which nickel-phosphorus alloy particles are deposited at a distribution density of 1 × 10 ¹² particles / m ² to 1 × 10 ¹⁶ particles / m ^{2 in} a granular form. Phosphorus alloy particles are 0.
It contains phosphorus in the range of 01 to 16.0 wt.%, And the amount of the nickel-phosphorus alloy layer deposited is in the range of 5 to 60 mg / m ^{2 on} one side of the cold rolled steel sheet as the amount of nickel deposited. It has characteristics.

[0030]

According to the present invention, the reason why the phosphating property of the steel sheet is excellent regardless of the manufacturing process of the steel sheet has not yet been completely clarified. The combination of the Ni metal layer or the Ni-P alloy layer according to the invention and the surface state of the steel sheet inevitably formed by the chemical composition according to the present invention forms a local battery extremely smoothly on the steel sheet surface, It is presumed that this is because the state of the battery is extremely appropriate to effectively contribute to the phosphate treatment reaction.

Here, the chemical composition of the high-strength cold-rolled steel sheet of the present invention and the Ni metal layer or Ni-P deposited on the surface thereof
The reason for limiting the conditions for depositing the alloy layer as described above will be described.

Carbon has the function of improving the hardenability of the steel sheet. However, the carbon content is 0.001 wt.%
If the amount is less than the above, the desired effects cannot be obtained in the above-mentioned actions, and it takes a long time to degas the steel, which is not practical.
On the other hand, if the carbon content exceeds 0.3 wt.%, The ductility and toughness of the steel sheet deteriorate. Therefore, the carbon content of the high-strength cold-rolled steel sheet must be within the range of 0.001 to 0.3 wt.%.

Silicon has the function of improving the balance between strength and ductility of the steel sheet. Therefore, 0.1 wt.% Or more is contained for solid solution strengthening by silicon. On the other hand, if the silicon content exceeds 1.5 wt.%, The steel sheet becomes brittle. Therefore, the silicon content as a high-strength cold-rolled steel sheet is 0.1
To 1.5 wt.% Is required.

Manganese, like carbon, has the function of improving the hardenability of the steel sheet. However, if the manganese content is less than 0.1 wt.%, The desired effect cannot be obtained in the above-described action. On the other hand, if the manganese content exceeds 3.0 wt.%, The ductility of the steel sheet deteriorates. Therefore, the manganese content of the high-strength cold-rolled steel sheet must be within the range of 0.1 to 3.0 wt.%.

As described above, in the high strength cold rolled steel sheet, carbon in an amount of 0.001 to 0.3 wt.% And 0.1 to 1.5 wt.%.
Amount of silicon and manganese amount of 0.1 to 3.0 wt.% Are indispensable, but in order to further satisfy the characteristics as a high-strength cold-rolled steel sheet, precipitation strengthening, hardenability improvement and temper softening resistance are further required. It is necessary to contain a predetermined amount of at least one element selected from the group consisting of copper, nickel, molybdenum, chromium, vanadium, boron, titanium and niobium in order to improve the above.

Copper, vanadium, titanium and niobium have a function of promoting precipitation strengthening, and niobium, molybdenum and boron have a function of improving hardenability. Then, molybdenum and chromium have an effect of improving the temper softening resistance. Therefore, copper, nickel,
At least one element selected from molybdenum, chromium, vanadium, boron, titanium, and niobium is selectively contained in the following amount. Copper: 0.5 wt.% Or more, Nickel: 0.5 wt.% Or more, Molybdenum: 0.2 wt.% Or more, Chromium: 0.1 wt.% Or more, Vanadium: 0.01 wt.% Or more, Boron: 0.0005 wt.% Or more, Titanium: 0.01 wt.% Or more, Niobium: 0.01 wt.% Or more. If the content of each of the above-mentioned elements is less than the above-mentioned amount, the desired effect on the characteristics cannot be obtained.

On the other hand, the effects of these elements on the phosphate treatment of the steel sheet are as follows. When the content of carbon increases, carbon liberated from the steel during annealing may precipitate on the surface of the steel sheet, or carbides that are considered to be derived from such carbon may form on the surface of the steel sheet. Such substances impair the phosphating property as contaminants on the surface of the steel sheet.

Silicon and manganese are concentrated on the surface of the steel sheet during annealing to form an oxide, and this oxide acts on the iron oxide on the surface of the steel sheet to improve the phosphate treatment of the steel sheet. On the other hand, when the content of these elements increases, the amount of oxides formed on the surface of the steel sheet during annealing increases, and it takes a long time to dissolve the oxides, which impairs the phosphate treatment property.

Further, in the present invention, each selective element added in addition to carbon, silicon and manganese greatly impairs the activity of the surface of the steel sheet and generally deteriorates the phosphate treatment property.

As described above, the effect of each additive element on the phosphate treatment property is wide-ranging, and the effect of the additive element also varies depending on the manufacturing method. Therefore, the phosphate treatability of the high-strength cold-rolled steel sheet having the chemical composition as described above is dominated by bad cases in many examples, but may be good in some cases. I can't tell you. Further, when a Ni metal layer or a Ni-P alloy layer is attached to such a cold rolled steel sheet, the phosphating property may be improved, but it may be deteriorated. This makes it extremely difficult to manufacture a wide variety of high-strength cold-rolled steel sheets while always maintaining a stable quality level.

Therefore, a steel sheet having the above-described chemical composition is manufactured as a high-strength cold-rolled steel sheet in various processes, and a Ni metal layer or a Ni metal layer is formed on each of them by electroplating.
A Ni-P alloy layer was deposited, and the influence of the deposition on the phosphatability of the steel sheet was investigated. The deposition conditions were changed by variously combining the deposition amount of the Ni metal layer or the Ni-P alloy layer and the particle distribution density. In addition,
The P content of the Ni-P alloy layer was 0.01 to 16.0 wt.%. In this study, the adhesion amount of Ni metal layer or Ni-P alloy layer, Ni
The P content in the -P alloy layer was determined by a fluorescent X-ray method using a standard substance, and the particle distribution density was determined by a transmission electron microscope observation by the replica method.

FIGS. 1 and 2 show the results obtained by this investigation. Judgment of superiority or inferiority of the phosphating property was performed by using the PB3030 treatment solution manufactured by Nippon Parkerizing Co., Ltd., the initial nucleus number of the phosphite crystal after the treatment for 10 seconds, and the completed phosphite after the treatment for 2 minutes. The crystal size of the coating was determined by examining each with a scanning electron microscope. Here, an initial number of nuclei of 3 × 10 ¹⁰ to 7 × 10 ¹⁰ pieces / m ² and a crystal size of 1 to 4 μm were used as good phosphate coatings.

As shown in FIG. 1, the deposition amount of the Ni metal layer was in the range of 5 to 60 mg / m ² , and the distribution density of the Ni metal was 1 ×.
Within the range of 10 ¹² to 1 × 10 ¹⁶ pieces / m ² , the phosphate treatability was good regardless of the chemical composition of the steel sheet and the manufacturing method. On the other hand, when the adhesion state of the Ni metal layer is out of the range of the above-mentioned conditions, the phosphating property of the steel sheet may be good or bad, and the phosphate of the Ni metal layer may be good or bad. The effects on processability were mixed. In FIG. 1, the mark ● indicates good phosphatability, and the mark ◯ indicates poor phosphatability.

Further, as shown in FIG. 2, the P content is
In the Ni-P alloy layer in the range of 0.01 to 16.0 wt.%, The deposition amount of the Ni-P alloy layer is in the range of 5 to 60 mg / m ² as the Ni deposition amount,
If the distribution density of Ni-P alloy particles is in the range of 1 × 10 ¹² 1 × 10 ¹⁶ particles / m ² , regardless of the chemical composition of the steel sheet and the manufacturing method,
Phosphate treatability was good. On the other hand, when the adhered state of the Ni-P alloy layer is out of the range of the above-mentioned conditions, the phosphatability of the steel sheet may be good or bad, and the Ni-P alloy layer The effect of phosphatase on phosphate treatment was mixed. In FIG. 2, ● indicates good phosphatability, and ◯ indicates poor phosphatability.

Here, the P content in the Ni-P alloy layer is set to 0.01 to 16.0 wt.% Mainly from the viewpoint of controlling the content. Since the amount of Ni-P alloy layer deposited is 5 to 60 mg / m ² , the absolute amount of P is small when the P content is 0.01 wt.% Or less,
Its control is difficult. For example, when the electroplating method is used to obtain the Ni-P alloy layer according to the present invention, phosphorous acid or phosphite should be used as a P source to control the concentration in the plating bath. To control the P content in the Ni-P alloy layer. Even if the content is less than 0.01 wt.%, The effect of the present invention can be expected, but on the other hand, it becomes extremely difficult to control the content, and a stable content cannot be obtained. Further, even if the content exceeds 16.0 wt.%, The effect of the present invention can be expected. However, when using the electroplating method to obtain the Ni-P coating of the present invention, it is usually 16.0 w
It is known that the content of t.% or more cannot be obtained. Therefore, the P content in the Ni-P alloy layer in the present invention is set to 0.01 to 16.0 wt.%.

Next, on the basis of this result, the effect of the Ni metal layer or the Ni-P alloy layer on the phosphating property is outside the range of the above-mentioned conditions for depositing the Ni metal layer or the Ni-P alloy layer. When the steel sheets which were mixed with each other were investigated, the chemical composition of these steel sheets was in the following range regardless of the manufacturing method. Carbon: over 0.25 wt.% Silicon: 1.5 wt.% Over Manganese: less than 0.2 wt.% 3.0 wt.% Over Copper: 1.5 wt.% Over Nickel: 1.5 wt.% Over molybdenum: 1.0 wt.% Over chromium: 2.5 wt.% over Vanadium: 0.1 wt.% over Boron: 0.003 wt.% over Titanium: 0.20 wt.% over Niobium: over 0.20 wt.%.

That is, when the content of each element added for strengthening the steel sheet is as described above, a Ni metal layer having a Ni deposition of 5 to 60 mg / m ² is formed, and The adhered form of Ni metal is granular, and the distribution density of the particles is 1 × 10 ¹² /
Even in the range of m ² to 1 × 10 ¹⁶ pieces / m ² , the phosphating property cannot always be improved. When the content of each element added for strengthening the steel sheet is as described above, the Ni content is 5 to 60 mg / m ² , and the P content is 0.01 to 16.0 wt.%. The Ni-P alloy layer is formed, and the adhesion form of the Ni-P alloy is granular, and the distribution density of the particles is in the range of 1 × 10 ¹² particles / m ² to 1 × 10 ¹⁶ particles / m ^2. However, it is not always possible to improve the phosphate treatability. However, excluding it, the following chemical composition,
That is, carbon: 0.001 to 0.25 wt.%, Silicon: 0.1 to 1.5 wt.%, And manganese: 0.2 to 3.0 wt.% Are essential, and at least one element selected from the group consisting of Copper: 0.5 to 1.5 wt.%, Nickel: 0.5 to 1.5 wt.%, Molybdenum: 0.2 to 1.0 wt.%, Chromium: 0.1 to 2.5 wt.%, Vanadium: 0.01 to 0.1 wt.%, Boron: 0.0005 to 0.003. wt.%, titanium: 0.01 to 0.20 wt.%, niobium: 0.01 to 0.20 wt.%, regardless of the manufacturing method, the Ni metal layer under the above conditions Or Ni-P
By attaching the alloy layer, the phosphate treatment of the high-strength cold-rolled steel sheet is surely improved.

From the above, the high-strength cold-rolled steel sheet according to the present invention requires carbon: 0.001 to 0.25 wt.%, Silicon: 0.1 to 1.5 wt.%, And manganese: 0.2 to 3.0 wt.%. , At least one element selected from the group consisting of: copper: 0.5 to 1.5 wt.%, Nickel: 0.5 to 1.5 wt.%, Molybdenum: 0.2 to 1.0 wt.%, Chromium: 0.1 to 2.5 wt.%. %, Vanadium: 0.01 to 0.1 wt.%, Boron: 0.0005 to 0.003 wt.%, Titanium: 0.01 to 0.20 wt.%, Niobium: 0.01 to 0.20 wt.%. The deposition amount of the Ni metal layer formed on at least one surface of the steel plate is 5 to 60.
mg / m ² and the deposition form of the Ni metal layer is granular, and the distribution density of the particles is limited to 1 × 10 ¹² particles / m ² to 1 × 10 ¹⁶ particles / m ² . Further, the deposition amount of the Ni-P alloy layer formed on at least one surface of the cold rolled steel sheet is limited to 5 to 60 mg / m ² as the Ni deposition amount, and the P content is limited to 0.01 to 16.0 wt.%, In addition, the adhesion form of the Ni-P alloy layer is granular, and the distribution density of the particles is limited to 1 × 10 ¹² particles / m ² to 1 × 10 ¹⁶ particles / m ² .

If the cold-rolled steel sheet has the above-mentioned chemical composition and has the Ni metal layer or Ni-P alloy layer formed on the surface under the above-mentioned conditions, it has sufficient strength characteristics regardless of the production method of the steel sheet. It is possible to obtain a high-strength cold-rolled steel sheet having excellent phosphating property while maintaining the following.

Even if the steel sheet is a single-sided zinc-based plated steel sheet, the chemical composition of the steel sheet is within the scope of the present invention, and the Ni metal layer or Ni according to the conditions of the present invention is applied to the non-plated surface. If the -P alloy layer is formed, the effect of the present invention can be sufficiently obtained.

The Ni metal layer or the surface of the steel plate
The means for forming the Ni-P alloy layer may be PVD, CVD, electroless plating, or electroplating, and any of these methods does not affect the effect. Of these, the electroplating method is most advantageous in view of economy.

[0052]

EXAMPLES Next, the high-strength cold-rolled steel sheet of the present invention will be further described by comparing Examples with Comparative Examples. After cold rolling the steel sheets A to N having the chemical composition shown in Table 1,
It was processed by the representative heat treatment steps a to d shown in FIG. Further, a Ni metal layer was adhered to the surfaces of these steel plates under the conditions shown in Table 2. Also, a Ni-P alloy layer was deposited under the conditions shown in Table 3. Here, cold-rolled steel sheets A to H in Table 1 are steel sheets that are the subject of the present invention, and cold-rolled steel sheets I to N are not the subject of the present invention in terms of composition. Further, the conditions α to δ in Table 2 are the adhesion conditions of the Ni metal layer which is the object of the present invention,
The conditions ε and ζ are conditions outside the scope of the present invention. The conditions η to κ in Table 3 are the conditions for depositing the Ni—P alloy layer that is the subject of the present invention, and the conditions λ to ν in Table 3 are the conditions that are outside the subject of the present invention. An electroplating method was used as a method for attaching the Ni metal layer or the Ni-P alloy layer to the steel sheet. The plating conditions in that case are shown below. Ni plating Nickel sulfate: 120 to 240 g / l Nickel chloride: 23 to 45 g / l Boric acid: 15 to 30 g / l pH: 2.5 to 3.5 Bath temperature: 40 to 60 ° C Current density: 1 to 30 A / dm ² Ni-P plating Nickel sulfate: 120 to 240 g / l Nickel chloride: 23 to 45 g / l Boric acid: 15 to 30 g / l Phosphorous acid: 0.1 to 30 g / l pH: 2.5 to 3.5 Bath temperature: 40 To 60 ℃ Current density: 1 to 30A / dm ²

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

Thus, as shown in Tables 4 and 5, specimens targeted by the present invention (hereinafter referred to as "examples of the present invention") and specimens not covered by the present invention (hereinafter referred to as "comparative examples"). "
And) were prepared. In Table 4, Nos. 1 to 21 are examples of the present invention, and Nos. 22 to 38 are comparative examples. Also,
In Table 5, Nos. 39 to 59 are examples of the present invention, and No. 60
To 76 are comparative examples. Tables 4 and 5 also show the results of examining the phosphating property of the inventive examples and comparative examples by the following.

[0057]

[Table 4]

[0058]

[Table 5]

Evaluation of Phosphate Treatability: Initial number of nuclei of phosphate crystals after treatment for 10 seconds using PB3030 treatment liquid manufactured by Japan Parkerizing Co., and completed phosphoric acid after treatment for 2 minutes The crystal size of the salt film was examined by a scanning electron microscope, and thereby the phosphating property was evaluated.

As is clear from Table 4, the invention sample No. 1
From No. 21 to 21, in the phosphating treatment, since the initial number of nuclei at the time of film formation is large and the crystal size is fine, the finished film is densified and the phosphating property is good. It was

On the other hand, even though the chemical composition of the steel sheet is within the range of the present invention, Comparative Example Nos. 22 to 29 in which the Ni metal layer is outside the scope of the present invention and the Ni metal layer is Even in the scope of the invention, in Comparative Example No. 30 to 38, the chemical composition of the steel sheet is outside the scope of the present invention, in each case, the initial number of each film formation in the phosphate treatment is small, and However, due to the large crystal size, the finished film had a gap and the phosphating property was poor.

Further, as is clear from Table 5, examples of the present invention
In Nos. 39 to 59, in the phosphating treatment, the number of initial nuclei at the time of film formation was large, and the crystal size was fine, so that the completed film was densified and the phosphating property was high. It was good.

On the other hand, even though the chemical composition of the steel sheet is within the range of the present invention, the Ni-P alloy layer is outside the scope of the present invention, Comparative Examples Nos. 60 to 67 and the Ni-P alloy layer. Even within the range of the present invention, in Comparative Example Nos. 68 to 76 in which the chemical composition of the steel sheet is outside the range of the present invention, in any case, in the phosphate treatment, the initial nucleus number at the time of film formation is Due to the small number and the large crystal size, the finished film was a source of scaling and the phosphating property was poor.

[0064]

As described above, according to the cold-rolled steel sheet of the present invention, whatever its manufacturing method,
Its phosphatability is good and excellent, and the quality level of high-strength cold-rolled steel sheets with various types manufactured by various methods is
It has an industrially useful effect that it can be constantly maintained in a good condition.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of the relationship between the distribution density of particles in the Ni metal layer and the Ni deposition amount on the phosphating property.

FIG. 2 is a graph showing the effect of the relationship between the distribution density of particles in the Ni-P alloy layer and the Ni deposition amount on the phosphating property.

FIG. 3 is a graph showing a heat treatment process.

Front Page Continuation (72) Inventor Yoshihiro Hosoya Marunouchi 1-2-2 Nihon Steel Tube Co., Ltd., Chiyoda-ku, Tokyo (72) Inventor Masaaki Yamashita Marunouchi 1-2-2 Nihon Steel Pipe Co., Ltd. In the company

Claims (2)

[Claims] 1. Carbon: 0.001 to 0.25 wt.%, Silicon: 0.1 to 1.5 wt.%, Manganese: 0.2 to 3.0 wt.%, At least one element selected from the group consisting of: Copper: 0.5 to 1.5 wt.%, nickel: 0.5 to 1.5 wt.%, molybdenum: 0.2 to 1.0 wt.%, chromium: 0.1 to 2.5 wt.%, vanadium: 0.01 to 0.1 wt.%, boron: 0.0005 to 0.003 wt.%, titanium : 0.01 to 0.20 wt.%, Niobium: 0.01 to 0.20 wt.%, And a cold-rolled steel sheet consisting of the balance iron and unavoidable impurities, and granular adhesion forms are formed on at least one surface of the cold-rolled steel sheet. And a nickel metal layer in which nickel metal particles are deposited at a distribution density of 1 × 10 ¹² pieces / m ² to 1 × 10 ¹⁶ pieces / m ² , and the adhesion amount of the nickel metal layer is characterized in that the per side 5 of the steel sheet is in the range of 60 mg / m ² High-strength cold-rolled steel sheet excellent in phosphating properties. 2. Carbon: 0.001 to 0.25 wt.%, Silicon: 0.1 to 1.5 wt.%, Manganese: 0.2 to 3.0 wt.%, At least one element selected from the group consisting of: Copper: 0.5 to 1.5 wt.%, nickel: 0.5 to 1.5 wt.%, molybdenum: 0.2 to 1.0 wt.%, chromium: 0.1 to 2.5 wt.%, vanadium: 0.01 to 0.1 wt.%, boron: 0.0005 to 0.003 wt.%, titanium : 0.01 to 0.20 wt.%, Niobium: 0.01 to 0.20 wt.%, And a cold-rolled steel sheet consisting of the balance iron and unavoidable impurities, and granular adhesion forms are formed on at least one surface of the cold-rolled steel sheet. And a nickel-phosphorus alloy layer in which nickel-phosphorus alloy particles are deposited at a distribution density of 1 × 10 ¹² particles / m ² to 1 × 10 ¹⁶ particles / m ² , wherein the nickel-phosphorus alloy particles are 0 .
It contains phosphorus in the range of 01 to 16.0 wt.%, And the amount of the nickel-phosphorus alloy layer deposited is in the range of 5 to 60 mg / m ² per one side of the cold rolled steel sheet as the amount of nickel deposited. A high-strength cold-rolled steel sheet with excellent phosphating properties.