JPH0820877A - Production of ferrous metal matrix composite material excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To impart a composite material with excellent corrosion resistance as well as wear resistance by subjecting the surface of a ferrous material subjected to nitriding treatment to oxidizing treatment under specified conditions to modify the surface part and forming an iron oxide contg. layer thereon. CONSTITUTION:The surface of a ferrous metallic material is subjected to nitriding treatment to form an iron-nitrogen compound contg. layer. This layer is subjected to oxidizing treatment at 110 to 140 deg.C by using a treating bath constituted of an aq. soln. contg. sodium hydroxide, sodium nitrate and sodium sulfite. By this treatment, at least the surface part of the iron-nitroten contg. layer is modified. Furthermore, an iron oxide-contg. layer is formed thereon. As for the compsn. of the treating soln., preferably, the concn. of sodium hydroxide is regulated to, by weight, 25 to 55%, that of sodium nitrate to 10 to 25% and that of sodium sulfite to 5 to 15%. The thickness of the iron-nitrogen compound contg. layer is preferably regulated to 10 to 20mum. The formed composite layer has excellent corrosion resistance and furthermore small in dispersion in the corrosion resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an iron-based metal composite material having excellent corrosion resistance. More specifically, the present invention provides not only mechanical properties such as wear resistance and fatigue strength, but also excellent corrosion resistance and less variation in corrosion resistance, and iron-based metal composites with significantly improved practical reliability. The present invention relates to a method for manufacturing a material.

[0002]

2. Description of the Related Art Generally, when an iron-based material such as a cold-rolled steel sheet, a carbon steel for machine structural use, or an alloy steel is used as a material for a structural member, its wear resistance and mechanical strength such as fatigue strength. It is known that the surface thereof is subjected to a nitriding treatment in order to improve the temperature. As the nitriding treatment method, a salt bath soft nitriding method (tuftride method) and a gas nitriding method are known.

It is generally known that nitriding treatment of iron-based materials also improves their corrosion resistance. However, the degree of the improvement is not sufficient. Therefore, when high corrosion resistance is required, nitriding treatment is performed. It is known to further oxidize the surface. For example, in JP-A-56-33473, the surface of an iron-based metal material is subjected to a nitriding treatment at a high temperature of about 580 to 620 ° C. in a molten salt bath containing a cyanate and a cyan compound, and the nitriding-treated surface is A molten bath (containing no water) containing an alkali metal nitrate and an alkali metal hydroxide is subjected to an oxidation treatment at a temperature of 250 to 450 ° C. to form an oxide film, and at the same time, adheres to the nitriding treated surface. There is described a method for detoxifying a cyanide compound and a cyanate salt by decomposing them. However, the iron-based metal composite material obtained by this method has a problem that its corrosion resistance does not reach a sufficiently high level, its variation is severe, and its practical reliability is lacking.

In JP-A-60-194084, the surface of free-cutting steel or ordinary steel is soft-nitrided to a depth of 10 to 20 μm using a cyanide-containing salt melting bath, and the surface of this nitriding treatment is applied. Remove oxides, scratches, and dents by polishing to a thickness of 5-15
While leaving a soft nitriding layer of μm thickness, the surface is subjected to black dyeing oxidation at a high temperature of 450 ° C. to 550 ° C. using a melting bath containing an alkali metal nitrate and an alkali metal hydroxide, and a thickness of 2 to 5 μm. The method of forming the black oxide film of is described. However, the iron-based metal composite material produced by this method also has insufficient corrosion resistance and has a large variation in the degree, and therefore the problem of low practical reliability has not been solved.

Japanese Unexamined Patent Publication (Kokai) No. 3-162559 discloses a nitride layer, an intermediate layer of oxynitride formed on the nitride layer, and a porous oxide containing iron oxide (IV) oxide as a main component. An iron-based metal sliding member having a surface portion formed by a composite layer including a material layer is disclosed. This sliding member has a surface of an iron-based metal material, ammonia gas, air,
And steam are reacted in the order described to form a nitride layer, an oxynitride layer (intermediate layer), and a ferric oxide layer (porous oxide layer). However,
The corrosion resistance of this sliding member was insufficient, and its variation was large, which was unsatisfactory in practical reliability.

[0006]

SUMMARY OF THE INVENTION The present invention is excellent not only in mechanical properties such as wear resistance but also in corrosion resistance.
An object of the present invention is to provide a method for producing an iron-based metal composite material that has little variation in corrosion resistance and is highly reliable in practical use.

[0007]

In the present invention, the surface layer of the iron-based metallic material that has been subjected to the nitriding treatment is treated with an aqueous solution containing sodium hydroxide, sodium nitrate, and sodium nitrite at a predetermined concentration at 110 to 140 ° C. At temperature,
It was found for the first time that the above problems could be solved by applying an oxidation treatment, and based on this finding, the method of the present invention was completed.

In the method for producing an iron-based metal composite material having excellent corrosion resistance according to the present invention, the surface of a base material made of an iron-based metal material is subjected to a nitriding treatment to form an iron-nitrogen compound-containing layer, and the iron-nitrogen compound is added. The compound-containing layer is subjected to an oxidation treatment at a temperature of 110 to 140 ° C. by a treatment bath consisting of an aqueous solution containing sodium hydroxide, sodium nitrate, and sodium nitrite to cover at least the surface portion of the iron-nitrogen compound-containing layer. It is characterized in that it is modified and an iron oxide-containing layer is formed on it.

In the method of the present invention, the concentration of sodium hydroxide in the treatment bath is 25 to 55% by weight, the concentration of sodium nitrate is 10 to 25% by weight, and the concentration of sodium nitrite is 5 to 15%. It is preferably in the weight%.

In the above method of the present invention, it is preferable to form an iron-nitrogen compound-containing layer having a thickness of 10 to 20 μm by the nitriding treatment.

In the above method of the present invention, it is preferable to form an iron oxide-containing surface layer having a thickness of 1 μm or more by the oxidation treatment.

In the above method of the present invention, it is preferable that the oxidation treatment is performed in a boiling state of the aqueous solution treatment bath.

In the method of the present invention, the aqueous solution treatment bath comprises at least one selected from sodium carbonate, sodium cyanide, sodium phosphate, potassium nitrate, lead oxide, sodium thiosulfate, potassium chloride, and sodium chloride. The additive may further be contained in an amount of 1 to 5% by weight.

[0014]

In the method of the present invention, the iron-based metallic material is iron,
Steel and iron alloy materials are included, for example cold rolled steel sheets,
The method of the present invention can be applied to carbon steel for machine structure, alloy steel and the like.

In the method of the present invention, the nitriding treatment applied to the surface of the iron-based metal material may be performed by any known nitriding method. For example, the salt bath nitriding method and the gas nitriding method can be used, the salt bath nitriding method can be, for example, a tufftride method, and the gas nitriding method can be, for example, a general gas soft nitriding method. You can Whichever nitriding method is used, the thickness of the iron-nitrogen compound-containing layer formed is preferably 10 to 20 μm. If the surface of the iron-nitrogen compound-containing layer is discolored (cooling unevenness), before the oxidation treatment,
It is preferable to remove the discoloration layer by subjecting the surface portion to processing such as polishing to obtain a normal iron-nitrogen compound-containing layer.

In the method of the present invention, the iron-nitrogen compound-containing layer formed on the surface of the iron-based metal material is subjected to a specific oxidation treatment. This oxidation treatment is performed at a temperature of 110 to 140 ° C. using a treatment bath made of an aqueous solution containing sodium hydroxide, sodium nitrate, and sodium nitrite. The concentration of sodium hydroxide in the treatment liquid used in the method of the present invention is 25 to 55% by weight,
The concentration of sodium nitrate is preferably 10 to 25% by weight, and the concentration of sodium nitrite is preferably 5 to 15% by weight. The aqueous oxidation treatment bath solution may contain, in addition to the above-mentioned sodium hydroxide, sodium nitrate, and sodium nitrite, 1 to 5% by weight of an additive, and the additive may be, for example, sodium carbonate, sodium cyanide, phosphorus. It is preferable to contain at least one selected from sodium acid salt, potassium nitrate, lead oxide, sodium thiosulfate, potassium chloride, sodium chloride and the like.

In the method of the present invention, the oxidation treatment is 110
It is carried out at a temperature of 140 ° C, preferably at the boiling point of the aqueous solution for the oxidation treatment bath. If the oxidation treatment temperature is less than 110 ° C., the desired oxidation treatment will be insufficient, and the desired corrosion resistance and its uniformity cannot be achieved. Further, when the oxidation treatment temperature exceeds 140 ° C., the oxidation treatment is excessively performed, so that a part of the iron-nitrogen compound-containing layer is excessively eroded, and the appearance of the obtained product becomes reddish brown and uneven. Will be For this reason,
The obtained product is more likely to be locally corroded in the use environment.

In the oxidation treatment of the method of the present invention, the sodium hydroxide contained in the treatment bath is iron-based on the surface of the material to be treated.
It has a function of etching the nitrogen compound-containing layer to elute iron ions in the treatment bath. Further, sodium nitrate in the treatment bath has a function of oxidizing iron ions eluted in the treatment bath and converting it into iron oxide (mainly Fe ₃ O ₄ ). Further, sodium nitrite in the treatment bath has a function of forming iron oxide (mainly Fe ₃ O ₄ ) on the surface of the material to be treated with good adhesion. Further, due to the combined action of sodium hydroxide, sodium nitrate, and sodium nitrite, at least the surface portion of the iron-nitrogen compound-containing layer is modified and has a uniform black appearance, and Fe ₃ O
_An iron oxide-containing layer containing ₄ as a main component is formed. In addition, the composite layer formed on the iron-based metal material has excellent corrosion resistance due to the synergistic effect of the modification of the surface portion of the iron-nitrogen compound-containing layer, and the formation of the iron oxide-containing layer, and This variation in corrosion resistance is significantly reduced.

In the method of the present invention, when the concentration of sodium hydroxide in the oxidation treatment bath is less than 25% by weight, the etching power of the treatment bath is insufficient and the elution rate and elution amount of iron ions are insufficient. For this reason, modification of the surface portion of the iron-nitrogen compound-containing layer and formation of the iron oxide-containing layer may become insufficient. When the concentration of sodium hydroxide exceeds 55% by weight, the etching power of the treatment bath is usually saturated, which is economically disadvantageous.

In the method of the present invention, when the concentration of sodium nitrate in the oxidation treatment bath is less than 10% by weight, the oxidizing power for converting iron ions into iron oxides may be insufficient, and it may be insufficient. If it exceeds 25% by weight, the color (black) of the obtained iron oxide-containing layer may be poor and non-uniform. In the method of the present invention, when the concentration of sodium nitrite in the oxidation treatment bath is less than 5% by weight, the adhesion of the iron oxide formed on the surface of the material to be treated may be insufficient. If it exceeds 15% by weight, the effect is usually saturated, which is economically disadvantageous.

The iron oxide-containing layer formed by the method of the present invention is preferably formed to a thickness of 1 μm or more, and this thickness is more preferably 1 to 3 μm.

By subjecting the surface of the iron-nitrogen compound-containing layer to the specific oxidation treatment bath at a specific temperature in the method of the present invention, the corrosion resistance of the obtained iron-based metal composite material is remarkably improved, and its dispersion is varied. The reason or the mechanism of the significant reduction of γ is still not clear enough.
However, the iron-nitrogen compound-containing layer is treated at a predetermined temperature (110 to 140 ° C.) with an aqueous solution containing sodium hydroxide, sodium nitrate and sodium nitrite at predetermined concentrations. The surface portion is modified to be densified, and as a result, the pinhole existing in the iron-nitrogen compound-containing layer is closed, and the crystalline oxidation mainly composed of Fe ₃ O ₄ is formed. It is speculated that the iron-containing layer is further densified due to the influence of the modified layer.

A solid lubricant such as M ₀ S ₂ and / or a lubricant such as wax is adhered to the black surface of the iron-based metal composite material produced by the method of the present invention, whereby its wear resistance and corrosion resistance are improved. Can be further improved.

[0024]

The present invention will be further described by the following examples. Example 1 An iron-based metal composite material was manufactured by subjecting the iron-based metal material described below to nitriding treatment and oxidation treatment according to the following steps. (1) Test material: JIS SPCC-SB plate material (70 mm
X 150 mm x 0.8 mm)

(2) Treatment process Surface cleaning: Trichloroethane vapor is used. Nitriding treatment (Tufftride salt bath soft nitriding method) Treatment salt bath composition CNO ⁻ : 34.6% by weight CN ⁻ : 2.2% by weight Treatment temperature × time: 570 ° C. × 60 minutes Thickness of iron-nitrogen compound-containing layer: 10 μm Water cooling (washing with water): Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Oxidation treatment bath aqueous solution composition Sodium hydroxide 50% by weight Sodium nitrate 23% by weight Sodium nitrite 12% by weight Water balance Treatment temperature × time: 138 ° C. × 10 minutes Thickness of iron oxide containing layer: 1.5 μm outside View: Uniform deep black water Washing: Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Example 2 (1) Test material: JIS S45C plate (dimension: 70 mm
(150 mm × 5 mm) (2) Treatment process Cleaning: Nitriding treatment with trichloroethane vapor (gas soft nitriding method) Gas composition: 50% NH ₃ -50% Endo gas Treatment temperature × time: 570 ° C × 90 minutes Iron-nitrogen compound Containing layer thickness: 15 μm

Oil cold washing: Trichloroethane vapor oxidation treatment bath composition sodium hydroxide 30% by weight sodium nitrate 15% by weight sodium nitrite 8% by weight water balance treatment temperature × time: 118 ° C. × 20 minutes Thickness of iron oxide containing layer : 2.0 μm Washing with water: Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Example 3 (1) Test material: JIS SS400 plate material (dimensions: same as in Example 2) (2) Treatment process Washing: Trichloroethane vapor nitriding treatment (ion nitriding treatment method) Gas composition: 20% N ₂ -80% H ₂ treatment temperature × time: 550 ° C. × 120 minutes Thickness of nitrided layer: 20 μm

Furnace Cold Oxidation Treatment Bath Composition: Sodium hydroxide 45% by weight Sodium nitrate 20% by weight Sodium nitrite 10% by weight Sodium chloride 2% by weight Water balance Treatment temperature x time: 132 ° C x 10 minutes Thickness of iron oxide containing layer Size: 1.2 μm Washing with water: Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Example 4 (1) Test material: JIS S45C plate material (dimensions: the same as in Example 2) (2) Treatment process Washing: Trichloroethane vapor nitriding treatment (salt bath soft nitriding treatment: Tufftride treatment method) (Treatment) Change the time to 90 minutes and change the thickness of the nitride layer to 15 μm.
The same as in Example 1 except that the above) was used. Water cooling (washing): room temperature x 1 minute Hot air drying: approximately 80 ° C x 2 minutes

Oxidation treatment Bath composition: Sodium hydroxide 40% by weight Sodium nitrate 17% by weight Sodium nitrite 9% by weight Sodium carbonate 3% by weight Water balance Treatment temperature x time: 129 ° C x 10 minutes Thickness of iron oxide containing layer: 1.2 μm Washing with water: Room temperature × 1 minute Hot air drying: About 80 ° C. × 2 minutes

Example 5 (1) Test material: JIS SPCC-SB plate material (dimensions:
(Same as Example 1) (2) Treatment step Washing: Trichloroethane vapor Nitriding treatment (salt bath soft nitriding treatment: Tufftride method) (Treatment time was changed to 120 minutes and the thickness of the nitrided layer was 20 μm.
The same as in Example 1 except that the above was used) Furnace Cold polishing: Dry lapping by hand polishing (abrasive amount: about 1 μm) using # 1000 abrasive paper

Oxidation treatment Bath composition: Sodium hydroxide 45% by weight Sodium nitrate 20% by weight Sodium nitrite 10% by weight Water balance Treatment temperature × time: 131 ° C. × 15 minutes Thickness of iron oxide containing layer: 1.8 μm Washing with water : Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Comparative Example 1 (1) Test material: JIS SPCC-SB plate material (dimensions:
(Same as Example 1) (2) Treatment step Washing: Trichloroethane vapor Nitriding treatment (salt bath soft nitriding treatment: Tufftride treatment method) Same as Example 1 Water cooling (washing): room temperature x 1 minute Hot air drying: about 80 ° C x 2 minutes

Oxidation treatment Bath composition: Sodium hydroxide 65% by weight Sodium nitrate 25% by weight Sodium nitrite 5% by weight Water balance Treatment temperature × time: 146 ° C. × 10 minutes Thickness of iron oxide containing layer: 1.5 μm Washing with water : Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Comparative Example 2 (1) Test material: JIS S45C plate material (dimensions: same as in Example 2) (2) Treatment process Washing: Trichloroethane vapor nitriding treatment (gas soft nitriding treatment method) Same as Example 2 Oil Cold trichloroethane steam cleaning

Oxidation treatment Bath composition: Sodium hydroxide 20% by weight Sodium nitrate 8% by weight Sodium nitrite 3% by weight Water balance Treatment temperature x time: 106 ° C x 10 minutes Thickness of iron oxide containing layer: 0.3 μm Washing with water : Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Comparative Example 3 (1) Test material: JIS SPCC-SB plate material (dimensions:
(Same as in Example 1) (2) Treatment process Alkaline degreasing: Fine Cleaner-4360 (trademark) strong alkaline cleaner manufactured by Nippon Parkerizing Co., Ltd.)
Use, 20g / l, dipping in water at 60 ° C for 3 minutes Washing at room temperature for 1 minute

Oxidation treatment Bath composition: Sodium hydroxide 45% by weight Sodium nitrate 20% by weight Sodium nitrite 10% by weight Water balance Treatment temperature × time: 131 ° C. × 10 minutes Thickness of iron oxide containing layer: 1.2 μm Washing with water : Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Comparative Example 4 (1) Test material: JIS S45C plate material (dimensions: same as in Example 2) (2) Treatment process Washing: Trichloroethane vapor nitriding treatment (salt bath soft nitriding treatment: Tufftride treatment method) (Treatment) Change the time to 90 minutes and change the thickness of the nitride layer to 15 μm.
The same as in Example 1 except that the above was used) Water cooling (washing): room temperature x 1 minute Hot air drying: approximately 80 ° C x 2 minutes No oxidation treatment

Comparative Example 5 (1) Test Material: JIS SPCC-SB Plate Material (Dimension:
(Same as Example 1) (2) Treatment step Washing: Trichloroethane vapor Nitriding treatment (salt bath soft nitriding treatment: Tufftride treatment method) (Treatment time was changed to 120 minutes, and the thickness of the nitrided layer was 20 μm.
Same as in Example 1 except that m was used.) Water cooling (washing): room temperature x 1 minute Hot air drying: about 80 ° C x 2 minutes Surface grinding: grinding depth: 5 μm

Oxidation treatment (nitrate type salt bath treatment method) Bath composition: Sodium nitrate 65 wt% Sodium nitrite 15 wt% Sodium hydroxide 20 wt% Treatment temperature x time: 500 ° C x 30 minutes Thickness of iron oxide containing layer : 2.0 μm Washing with water: Room temperature x 1 minute Hot air drying: About 80 ° C x 2 minutes

Performance Test The corrosion resistance of the iron-based metal composite material test pieces obtained in each of the above Examples and Comparative Examples was evaluated by a salt spray test. 1. Corrosion resistance evaluation method: Salt spray test according to JIS Z 2371 (1) Equipment used: Salt spray test chamber manufactured by Suga Test Instruments (Dimension:
(Height: 5000 mm x 4000 mm x 2000 mm) (2) Test time: 1000 hours (3) Number of test pieces: 100

2. Abrasion resistance evaluation method: Thrust color friction wear tester (1) Friction speed 1.0 m / s (2) Lubrication method Nisseki Gear Oil EP90 (immersion 20
0cc) (3) Surface pressure 5kg / cm ² step by step every 1 minute (4) Counterpart material: SUJ-2 (hardness H _R C60)

The test results are shown in Table 1.

[Table 1]

[0047]

According to the method of the present invention, it is possible to efficiently manufacture an iron-based metal composite material which has excellent corrosion resistance as well as mechanical properties such as wear resistance and has no variation in corrosion resistance.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C23C 28/02

Claims (6)

[Claims] 1. An iron-nitrogen compound-containing layer is formed by subjecting a surface of a base material made of an iron-based metal material to nitriding treatment, and the iron-nitrogen compound-containing layer is provided with sodium hydroxide, sodium nitrate, and nitrous acid. Oxidation treatment is performed at a temperature of 110 to 140 ° C. by a treatment bath composed of an aqueous solution containing sodium to modify at least the surface portion of the iron-nitrogen compound-containing layer and form the iron oxide-containing layer thereon. A method for producing an iron-based metal composite material having excellent corrosion resistance, comprising: 2. The concentration of sodium hydroxide in the treatment bath is 25 to 55% by weight, the concentration of sodium nitrate is 10 to 25% by weight, and the concentration of sodium nitrite is 5 to 15% by weight. The manufacturing method according to claim 1, wherein 3. The manufacturing method according to claim 1, wherein the nitriding treatment forms an iron-nitrogen compound-containing layer having a thickness of 10 to 20 μm. 4. The manufacturing method according to claim 1, wherein the iron oxide-containing layer having a thickness of 1 μm or more is formed by the oxidation treatment. 5. The manufacturing method according to claim 1, wherein the oxidation treatment is performed in a boiling state of the aqueous solution treatment bath. 6. The aqueous solution treatment bath is sodium carbonate,
The additive according to claim 1, further comprising at least one additive selected from sodium bromide, sodium phosphate, potassium nitrate, lead oxide, sodium thiosulfate, potassium chloride, and sodium chloride in an amount of 1 to 5% by weight. The manufacturing method described in.