JPH01116072A - Surface modified steel sheet having dense chemical conversion coating and its production - Google Patents

Abstract

PURPOSE:To obtain a steel having superior corrosion resistance, wear resistance, and coloring characteristic and used for various purposes by implanting the ions of specific elements into the surface layers of various steel sheets and then forming phosphate films or chromate films on the above. CONSTITUTION:The ions of N2, Ar, O2, B, P, Cr, Zn, Ni, Ti, Al, etc., are implanted by 1X10<5>-1X10<18> doses at 10-100kV accelerating voltage under a reduced pressure of 10<-3>-10<-6>mmHg at <=200 deg.C into at least one side of a cold-rolled steel sheet, a hot-rolled steel plate, a stainless sheet, or a planted steel sheet prepared by using the above sheer or plate as a base steel sheet and plating this base steel sheet with Ti, Al, Cr, Ni, Zn, Sn, or alloys thereof by 0.01-100g/m<2> coating weight. Successively, a phosphate film of 0.1-0.5g/m<2> coating weight of phosphorus or a chromate film of 10-200mg/m<2> coating weight of chromium is formed on the above.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a steel plate that has excellent corrosion resistance, wear resistance, and coloration and can be used as a steel plate for products, a steel plate for building materials, and steel furniture. forming a nitride or oxide by ion implantation of oxygen;
Furthermore, the present invention relates to a surface-modified steel sheet having a dense chemical conversion coating by forming a phosphate coating or a chromate coating on the forming layer, and a method for manufacturing the same.

(Conventional technology) Conventional ion implantation technology is mainly used to modify the surface of tools in order to increase the surface hardness through implantation and manufacture tools that have excellent performance against mechanical wear. I've been As a published technique related to this, Japanese Patent Application Laid-Open No. 58-18.
There are publications such as Publication No. 1864. Furthermore, in recent years, it has been used as a method for forming semiconductor films, and there are many publicly available techniques.

Furthermore, as an application of ion implantation, techniques for implanting various ions with excellent corrosion resistance and wear resistance have been disclosed. For example, Japanese Patent Laid-Open No. 59-74279 discloses a metal thin film coating method in which ions are implanted after sputter-depositing a metal or metal oxide, and a steel material disclosed in Japanese Patent Laid-Open No. 80-59068. There is a method in which a colored compound film, such as aluminum nitride, is formed thereon.

However, there are few surface modification techniques for wide steel plates, which is the object of the present invention, and attempts have been made to improve coloring, wear resistance, and corrosion resistance, but no practical technique has been achieved. The present invention forms an excellent chemical conversion film by modifying the surface of a wide steel plate, which has already been used in many fields, by ion implantation and then chemical conversion treatment.
This cannot be found in conventional technology.

(Problem that the invention attempts to solve) Wide steel plates are often put into practical use after being chemically treated.

However, in recent years, the properties of steel sheets have diversified,
Steel sheets with excellent drawing properties and strength, which contain elements such as St%A1, Mn, and Ti, are being put into practical use one after another. However, these additive elements have been found to be harmful to chemical conversion treatment properties, and new equipment investment is required to solve this problem.

Regarding metal-plated steel sheets, the components of the metal plating have changed from single elements to alloy components, and there is a similar need for improvement to improve chemical conversion properties, but the main improvement is in the chemical conversion treatment method. However, from a process standpoint, a simple chemical conversion treatment method is desirable, and it is not preferable to adapt the chemical conversion treatment method to each steel type and plating component.

Furthermore, there is a strong demand for chemically coated steel sheets or plated steel sheets that are superior to those used in automobile body rust prevention applications, and improvements have been made by various means, but even higher quality is required.

(Means for Solving the Problems) The present invention solves the above-mentioned problems and provides a surface-modified steel sheet having a dense chemical conversion film that forms an even better chemical conversion film.

That is, as a result of intensive research, the present inventors succeeded in obtaining an excellent chemical conversion coating by implanting ions. Ion implantation technology can modify only the surface layer of a steel plate or plated steel plate without raising the plate temperature, and can improve chemical conversion treatment properties without changing the properties of the steel plate or plating itself. The chemical conversion coating of the present invention obtained by performing chemical conversion treatment after ion implantation has a dense structure and is homogeneous with few pinholes, making it possible to obtain a chemical conversion coated steel sheet or plated steel sheet with excellent corrosion resistance and adhesion.

The present invention can be summarized in the following items (1) to (6).

(1) Ions are injected into the surface layer of at least one side of a cold-rolled steel sheet, a hot-rolled steel sheet, a stainless steel sheet, or a plated steel sheet using these as a base steel sheet, at a dose of I.times. 1-0.5 g,
/m2 phosphate film or chromium coating amount 10-20
A surface-modified steel sheet having a dense chemical conversion coating, characterized by having a chromate coating of 0 mg/rn''.

(2) The steel sheet according to item (1) above, wherein the implanted ions are nitrogen, argon, oxygen, boron, phosphorus, chromium, zinc, nickel, titanium, or aluminum.

(3) The plating film of the plated steel sheet is titanium, aluminum, chromium, nickel, zinc, tin, titanium alloy, aluminum alloy, chromium alloy, nickel alloy, zinc alloy, or tin alloy, and the coating amount of the plating film is 0. 01
The surface-modified steel sheet having a dense chemical conversion coating as described in item (1) above, which has a weight of 10 (1 g 7 m).

(4) At least one surface layer of a cold-rolled steel plate, a hot-rolled steel plate, a stainless steel plate, or a plated steel plate using these as a base steel plate is coated with a thickness of 10-3 to 10-'mm) under reduced pressure of IH. The temperature of the plating layer of the steel plate is 200℃
A method for manufacturing a surface-modified steel sheet having a dense chemical conversion film, which comprises implanting ions at an accelerating voltage of 10 to 100 kV and then performing a chemical conversion treatment.

(5) -ftnwof x 105~1 x 10”
The manufacturing method according to the above item (4), wherein F-s is injected.

(6) Phosphorus deposition amount 0.1-0,5 g as chemical conversion treatment
ird phosphate film or chromium adhesion amount 10-20
The above No. (4) forming a chromate film of 0 mg/m2
Manufacturing method described in section.

(Mechanism of Action) The mechanism of action of the present invention will be described in detail by taking as an example the phosphate treatment of a cold-rolled steel sheet into which nitrogen ions have been implanted.

Phosphate treatment of cold-rolled steel sheets is numerically used as a base coating for zinc phosphate-based paint, and its quality is extremely important. The desired phosphate film has a dense and constant adhesion (P:
0.15-0.3g/G), and its composition is “zinc phosphate” (indicated by H) and “zinc iron phosphate”.
The higher the ratio P/(H+P) (indicated by P), the better.

In order to obtain these films, the selection of steel type components,
Post-treatment is performed, and bath compositions and immersion chemical conversion treatment methods have been developed for chemical conversion treatment. In principle, this method involves suppressing segregation on the surface of the steel plate, making it homogenized, and providing nucleation points for phosphate through post-treatment, and immersion chemical conversion treatment, which efficiently converts ions eluted from the metal base into chemical conversion. Incorporated into the film,
In addition, it relies on the provision of nucleation points by substitutional precipitation of heavy metal ions. Both are chemical solution methods that provide uniform elution and a high density of precipitation points in the elution of steel sheets and phosphate aqueous solutions and the balance reaction of poorly soluble compounds9.
The present invention activates the steel plate surface by applying microscopically uniform strain to the steel plate surface by implanting nitrogen ions into the steel plate surface. By introducing nitrogen ions in an amount equivalent to at least 1010 or more per square centimeter, the surface is modified so that fine microcells are easily formed. When such a surface comes into contact with an aqueous phosphate solution, the reaction rapidly proceeds to release the energy accumulated on the surface, and a phosphate film is formed homogeneously on a plane.

That is, the present invention homogenizes the phosphate film by physical surface modification. Therefore, it is not easily affected by the 1i4 types of components, and the problems of conventional hard-to-chemically-treated steel sheets can be solved.

1() and (01) show the effect of nitrogen ion implantation on a phosphate treatment film of a cold rolled steel sheet formed using a commercially available immersion type phosphate treatment solution.

FIG. 1(A) shows a scanning electron micrograph of a phosphate film formed by treating a cold-rolled steel sheet for ultra-deep drawing (SPCO) by a known phosphate treatment process.

The crystals are plate-shaped and heterogeneous. Figure 1 (b) shows the same cold-rolled steel plate at an accelerating voltage of 20 kV under a reduced pressure of 10 mmHH.
After irradiating with ionized nitrogen at a dose of 1X10'', a phosphate film was formed by phosphate treatment under the same conditions, and the surface was observed using a scanning electron microscope in the same manner as above. The results are shown. As is clear from Figure 1 (B), a fine, dense, and highly dense phosphate film could be obtained by ion implantation. b) In the case of the figure, it is 0.2g/m2, and the first (
b) In the case of the figure, it was 0.21 g/m', and no decrease in the adhesion amount due to conventional refinement was observed.

In addition, Figures 2 (4) and (0) show cold-rolled steel sheets for deep drawing subjected to commercially available immersion wall phosphate treatment, and Figure 2 (A) shows non-ion-implanted material and Figure 2 ( b) The figure shows argon at 1×
It was irradiated at a dose of 10'6. By injecting argon, the phosphate film was made finer and a denser film was obtained.

The amount of phosphate film deposited is 0.25 g/m2 in the case of Figure 2 (A) and 0.25 g/m2 in the case of Figure 2 (B) in terms of phosphorus.
It was 2glrd.

In the case of argon injection, activation by sputtering of the surface of the steel plate is combined at the same time as the injection, so there is an advantage that the effect can be obtained even if the amount of injection is smaller than that of nitrogen.

The ion implantation conditions will be explained below.

The ions to be implanted are not particularly limited in theory, but gas molecules such as nitrogen, argon, and oxygen are easily applicable in practice. However, B, P, Cr, and Zn heated and evaporated
, Ni%Ti, Al1, and the like can be ionized and used.

The amount of ion implantation per unit area (Ni: ions/cnf・min) is determined by the beam current density (A:llll^/c) of the following formula (1).
o? ) can be calculated from

N i =3.75xAx 10'J pieces/minute)...
- (1) In the present invention, calculations were made based on equation (1), and the ion implantation amount was expressed in dose units (pieces/C).

The practical range of the ion implantation dose is txto''' to 1xto''.For elements that are gases at room temperature and normal pressure, such as nitrogen, argon, and oxygen, the dose is txto''' to txt.
o” is desirable, and when vaporizing by reducing pressure and heating, 1
The effects of the present invention can be obtained over a wide range of x105 to lXl0''.

If the dose is less than 1Xl0', the implantation amount is small and the physical activation effect on the surface does not reach a practical level, resulting in low merit. or,
If the dose exceeds ``txto'', the refinement effect of the chemical conversion coating of the present invention will be saturated, resulting in disadvantages such as hardening of the metal surface, the need for a long time, and an increase in the size of equipment, which is not practical.

In order to implant ionized elements, it is necessary to reduce the pressure of the processing atmosphere. The range must be reduced to 10-3 maiHg or less, preferably 10-' to 10-6 m
mHg. If the pressure exceeds 10 mmHg, the implanted ions will be blocked by surrounding gas molecules, resulting in a significant drop in implantation efficiency, and the desired ion implantation will become impure due to reaction with the gas molecules, making it impractical.

In addition, in order to introduce gaseous ions, 10 ””m++
A pressure lower than +Hg is not practical because it leads to an increase in the capacity of the vacuum pump.

In order to implant other ionized elements, it is necessary to accelerate the ions. In the case of the present invention, it is preferable to carry out at 10 to 100 kV.

The lower the temperature of the steel plate is, the less influence it has on the material, so it is desirable that the temperature rises due to ion implantation be cooled to 200° C. or less. If the temperature exceeds 200°C, the surface activation effect due to injection will decrease, and furthermore, the quality of steel sheets and plated steel sheets will be affected.

Next, the chemical conversion treatment method for the upper layer will be described.

The present invention can be applied to chemical conversion treatment involving a chemical reaction between a metal surface and a solution. Phosphate treatment is widely used in practical applications.
For chromate treatment, limit the amount of adhesion.

The phosphate film is formed as a compound of zinc phosphate and zinc iron phosphate, and in the present invention, the phosphorus is 0.1 to 0.5.
g/m" is preferable. Areas outside this range are not preferable because the performance is inferior to the current non-injected materials in terms of corrosion resistance and adhesion.

Chromate treatments include coating type chromate (a method in which chromate solution is applied uniformly and then dried and baked), etching chromate (a method in which chromate is contacted with chromate solution and then washed with water,
(drying method), electrolytic chromate treatment (a method in which chromium ions are reduced by electrolyzing the sample in a chromate solution using it as a cathode, and a chromate film is obtained after washing with water and drying).

The adhesion amount of the chromate treatment film is 10 to 200 as Cr.
mg/m2 is preferred. If it is less than 10IIIg/m2, corrosion resistance will be insufficient, which is not preferable. Also, Cr200mg
If it exceeds /rn'', the problem arises that cohesive failure of the chromate film tends to occur during processing and adhesion tends to deteriorate, which is undesirable.

Steel plates targeted by the present invention are cold-rolled steel plates, hot-rolled steel plates, stainless steel plates, and plated steel plates.

The amount of coating on plated steel sheets varies depending on the type of plating, ranging from 1 to 100 g/m'' for general rust-preventing steel sheets, and 0.01 to t glrd for use as a base for painting and primary rust prevention.
It can be applied to either.

(Example) Examples of the present invention will be described below.

Example 1 Cold-rolled steel sheet for ultra-deep drawing (C40p) manufactured by a known method
pm or less, TiO, 08%) was degreased with alkali, dried, and heated with nitrogen at an accelerating voltage of 20 k under a reduced pressure of 10 mmHg.
V to the surface of the steel plate at a calculated ion density of 1X10'' dose. The plate temperature reached was 90°C or less. Thereafter, a commercially available immersion type zinc phosphate treatment was applied to obtain the steel plate of the present invention. Separately, a comparison steel plate was obtained by phosphate treatment using ion powder injection after drying.The phosphate treatment conditions were alkaline degreasing (4
0°C 1 minute), preconditioning (20°C 10 seconds), phosphate treatment (
The experiment was conducted at a bath temperature of 40° C. for 2 minutes with a free acid concentration of 0.9 to 1.1, a preacidity of 22 to 24, and an accelerator of 2.9 to 3.1 g/j2.

The weight of the resulting phosphate-treated film was measured using fluorescent X-rays, and the results showed that the injected material had phosphorus: 0.21 g/ni" and the uninjected material had 0.
．． It was 20g/rri'. In addition, the appearance of the phosphate film was observed using scanning electron micrographs, and the results are shown in Figure 1 (a) of the comparative example (no injection), Figure 1 (b) of the present invention.
(Nitrogen injection). As these photos show,
A dense phosphate film crystal with fine crystals was obtained by nitrogen injection.

Example 2 Cold-rolled steel plate for drawing (C: 50 ppm or less, TiO,0
Argon ionized under a reduced pressure of 10-' mmHg was implanted at a calculated density of 1 x 105 to 1 x 1018 doses at an accelerating voltage of 20 kV.

The plate temperature was 80°C or lower. Next, phosphate treatment was performed under the conditions of Example 1.

The amount of phosphorus deposited was 0.22 g/m2 for the uninjected material and 0.25 g/m2 for the injected material. Furthermore, as shown in Figure 2 (a) of the photograph of the comparative example (non-injected plate) and Figure 2 (b) of the photograph of the present invention (argon implantation), the crystals on the surface are fine crystals due to injection. Obtained.

Example 3 A high tensile strength steel plate (SiO, 5%, Mn 0.6%) was treated with argon under the conditions of Example 2 under the conditions of implanting a lXl0'' dose. Obtained.

Example 4 2 x 10-'mmHg on Cr-containing steel plate (C "5%)"
Nitrogen was implanted in a txto'' dose at an accelerating voltage of 30 kV under a reduced pressure of No phosphate was formed, whereas a film with a phosphorus coverage of [1.10 g/m'' was obtained on the injection material.

Example 5 The high-strength steel plate of Example 3 was subjected to the phosphate treatment of Example 1 after a t x t o' dose of nickel was implanted at an accelerating voltage of 90 kV under a reduced pressure of 10-'maHg.

As a result, the injected steel plate had phosphorus: 0.21g/rf
A phosphate film with granular microcrystals was obtained.

In addition, when a steel plate in which phosphorus was implanted at a dose of 1 x 105 at an accelerating voltage of 30 kV under a reduced pressure of 10-'ma + A film was obtained. The plate temperature at the time of injection was 120°C or lower.

Example 6 When performing chromate treatment on an electrogalvanized steel sheet (zinc plating amount: 20 g/m2), a temperature of 10-4 mmHg (
7) Accelerating nitrogen under reduced pressure with a voltage of 20 kV1' I
A dose of 1012 was implanted. The plate temperature during injection was kept at 80°C or lower. Chromate is chromic anhydride 10g/42. It was carried out using a coating type chromate with 20 g/l of silica sol, and 30 to 40 mg/m2 of Cr was deposited. The resulting plated steel sheet was treated in boiling water for 3 minutes, and the Cr elution rate of the chromate film was measured; the non-injected material was 60%, while the injected material had a poorly soluble film of less than 30%. improved.

Example 7 10% Ni-Zn alloy plated steel plate (plating amount 20 g/m
2), nitrogen was implanted under a reduced pressure of 5 x 10-'ma + Hg at an accelerating voltage of 20 kV at a 1 x 10'' dose (plate temperature: 8 o'clock).
℃ or below), and then the phosphate treatment of Example 1 was performed.

In the injected plated steel sheet, fine crystals with a crystal size approximately % smaller than that of the non-injected material were obtained.

Example 8 10-6 mmHg on a stainless steel plate with SV5304 composition
Nitrogen was injected at an acceleration voltage of 20 kV at a dose of 1X10'' under a reduced pressure of .

(Effect of the invention) The present invention can be applied in principle to a chemical reaction system between a metal and a solution, and as an effect of the present invention, the chemical conversion properties of steel sheets or plated steel sheets that are difficult to undergo chemical conversion treatment can be improved by ion implantation. I can do it. Therefore, a chemical conversion film that does not depend on the surface composition of the metal can be obtained. Ion implantation also improves surface wear resistance and lubricity. Furthermore, metal-based ion implantation materials can be expected to have the combined effect of improving the corrosion resistance of the steel sheet itself and forming an excellent chemical conversion film. Especially for applications that require uniform appearance color tone such as chromate treatment,
The wetting and spreading properties of the chromate solution are improved and the uniformity effect is significant.

[Brief explanation of the drawing]

Figure 1 (A) is an embodiment of the present invention in which a steel plate for ultra-deep drawing is subjected to phosphate treatment after ion implantation of nitrogen, and Figure 2 (A) is a steel plate for deep drawing without ion implantation of argon. A comparative example is shown in which a steel plate for deep drawing is subjected to a phosphate treatment, and FIG. Agent Patent attorney Masaaki Akizawa Mitsunobu 1 person ゛Signboard F, (I) r ¥1

Claims (6)

[Claims] (1) Apply 1 x 10^5 to 1 x 10^1^8 ions to the surface layer of at least one side of a cold-rolled steel plate, hot-rolled steel plate, stainless steel plate, or a plated steel plate using these as the base steel plate.
The dose is injected, and the amount of phosphorus deposited is 0.1 to 0.5 g/
Phosphate film of m^2 or chromium deposition amount 10-20
A surface-modified steel sheet having a dense chemical conversion film, characterized by having a chromate film of 0 mg/m^2. (2) The steel sheet according to claim (1), wherein the implanted ions are nitrogen, argon, oxygen, boron, phosphorus, chromium, zinc, nickel, titanium, or aluminum. (3) The plating film of the plated steel sheet is titanium, aluminum, chromium, nickel, zinc, tin, titanium alloy, aluminum alloy, chromium alloy, nickel alloy, zinc alloy, or tin alloy, and the coating amount of the plating film is 0. 01
A surface-modified steel sheet having a dense chemical conversion coating according to claim (1), which has a surface-modified coating of ~100 g/m^2. (4) At least one surface layer of a cold-rolled steel plate, a hot-rolled steel plate, a stainless steel plate, or a plated steel plate made of these as a base steel plate is coated under a reduced pressure of 10^-^3 to 10^-^6 mmHg. The temperature of the plating layer of the plated steel plate is 2
A method for manufacturing a surface-modified steel sheet having a dense chemical conversion film, which comprises implanting ions at an acceleration voltage of 10 to 100 kV at 00° C. or lower, and then performing a chemical conversion treatment. (5) The manufacturing method according to claim (4), wherein ions are implanted at a dose of 1×10^5 to 1×10^1^8. (6) Phosphorus deposition amount 0.1 to 0.5 g/m as chemical conversion treatment
Phosphate film of ^2 or chromium adhesion amount 10-200
The manufacturing method according to claim (4), wherein a chromate film of mg/m^2 is formed.