JPH0770787A - Iron based base material and production thereof - Google Patents

Abstract

PURPOSE:To enhance the corrosion resistance of an iron based base material even when the thickness of a rigid chromium plating layer is small. CONSTITUTION:In the production of a corrosion resistant member, the iron based base material such as a cylinder rod is plated with rigid chromium, and after being heat treated at >=150 deg.C by a high-frequency current heating or baking, the material is subjected to an impregnating stage by resin to a buff finish. The heat treating temp. is, for example, mostly about 170-600 deg.C. In the impregnating stage, thermosetting resin may be impregnated under reduced pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion resistant iron-based member and a method for manufacturing the same. In particular, the present invention relates to a method for producing a corrosion-resistant member capable of imparting high corrosion resistance to an iron-based base material such as a cylinder rod used in construction machines, industrial machines, industrial vehicles and the like.

[0002]

2. Description of the Related Art Conventionally, cylinder rods such as piston rods have been used in hydraulic machines for construction machines such as power shovels. The rod that slides on the cylinder is required to have characteristics such as high hardness and wear resistance, and high dimensional accuracy including surface accuracy. Therefore, the cylinder rod is usually manufactured by subjecting a rod made of an iron-based material to hard chrome plating.

However, unlike other electroplating layers, the plating layer formed by hard chrome plating has many defective portions such as cracks, pinholes and pits even if the thickness of the plating layer is about 100 μm. To generate. Therefore,
A hard chrome-plated rod is susceptible to corrosion and rust despite having various excellent characteristics. In particular,
In the presence of chloride such as sodium chloride, acid, or in a high temperature and high humidity environment, the rod is significantly corroded due to the numerous defects. When the rod is corroded, sliding on the cylinder causes scratches, which may cause oil leakage.

Incidentally, in order to prevent corrosion of the hard chrome plated product, a rust preventive agent is applied and penetrated into a defective portion such as a crack, but it cannot be said to be a fundamental solution. Further, in order to prevent corrosion of the hard chrome plated product, a plating layer having a thickness of about 0.05 to 0.1 mm is formed. However, if the thickness of the plating layer is increased, the productivity will decrease.

Japanese Patent Publication No. 3-14913 discloses a method for performing high quality mirror surface chrome plating, which uses a micro-crack type chrome plating bath to coat the surface of an iron base material with about twice as much as the finished plating layer. A thick plating layer is formed under severe conditions (40 to 6 times higher than the upper limit of standard operating temperature).
After baking at a high temperature of 0 ° C. for 40 to 50 hours,
A method of removing 40 to 50% of the plating layer by polishing, baking under mild conditions (20 to 30 hours at a temperature 10 to 20 ° C. higher than the upper limit of the standard temperature for use), and finish polishing is disclosed. There is.

However, according to this method, since it is necessary to form a thick plating layer and to remove 40 to 50% of the plating layer, it is not economical, and it takes a long time to perform the plating process and the removal of the plating layer. Requires. Moreover, it takes a long time to perform baking twice. Therefore, the productivity of drums, rolls, etc. is significantly reduced. Further, the above-mentioned prior art documents do not describe anything about corrosion resistance.

In JP-A-60-33369, a metal is chromium-plated and heated at 120 ± 10 ° C. for 15 to 30 minutes to remove hydrogen gas produced by the plating. And a method of applying a corrosion protection composition composed of a mixture of 80 to 20% by weight diallyl phthalate. However, the obtained metal member does not have sufficient corrosion resistance, as shown in a comparative example described later.

In order to improve the corrosion resistance of the cylinder rod, the present applicant proposed in Japanese Patent Laid-Open No. 4-160197 that the cylinder rod is plated with hard chrome and then baked. The present invention has been made in order to further improve the corrosion resistance of ferrous base materials such as cylinder rods plated with hard chrome.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a corrosion-resistant iron-based member having extremely high corrosion resistance even if the hard chromium plating layer has a small thickness, and a method for manufacturing the same.

Another object of the present invention is to provide a corrosion-resistant iron-based member having corrosion resistance equal to or higher than that of stainless steel, and a method for producing the same even if the iron-based substrate has corrosion resistance. is there.

Still another object of the present invention is to provide a method of manufacturing a corrosion-resistant iron-based member useful for manufacturing a cylinder rod having the above-mentioned excellent properties.

[0012]

In order to achieve the above-mentioned object, the inventors of the present invention have made earnest studies and, as a result, after applying hard chrome plating, heat treatment at a specific temperature to impregnate a resin The present invention has been completed by finding that the property is remarkably improved.

That is, in the method of the present invention, the iron-based material is plated with hard chrome, heated at a temperature of 150 ° C. or higher, and then subjected to an impregnation step with a resin or a sealant and a buffing step to obtain corrosion resistance. Manufacture parts.

In such a method, the thickness of the hard chrome plating layer formed by chrome plating is, for example,
It may be about 10 to 100 μm, and the heating temperature may be about 170 to 600 ° C., for example. A thermosetting resin can also be used as the resin and the sealant, and the resin can be impregnated under reduced pressure.

According to the method of the present invention, extremely high corrosion resistance can be imparted. For example, when a CAS test specified in JIS H8502 is carried out for 96 hours, a corrosion-resistant iron-based material having a rating number of about 9.0 to 10.0. Material, JIS H
When the salt spray test specified in 8502 is performed for 1200 hours, a corrosion-resistant iron-based member having a rating number of about 9.8 to 10.0 can be obtained. Therefore, the corrosion-resistant iron-based member is suitable as a member requiring high corrosion resistance even under severe conditions, for example, a cylinder rod such as a piston rod.

The iron-based material is made of various iron-based materials such as low carbon steel, high carbon steel, hardened steel, high speed steel, chrome steel, nickel steel, nickel chrome steel, nickel chrome molybdenum steel. , Tungsten steel, etc.
Since the method of the present invention can impart a significantly improved corrosion resistance to a corrosive member, the present invention is suitably applied to a corrosive iron-based substrate.

The shape of the iron-based substrate is not particularly limited,
It may have a flat plate shape, a curved plate shape, a polygonal cross section, a cylindrical shape, a hollow shape, or the like. The iron-based base material that is required to have high corrosion resistance includes a rod-shaped base material such as a cylindrical rod (for example, a cylinder rod such as a piston rod).

The iron-based base material is usually subjected to a pretreatment step prior to the chrome plating. In this pretreatment step, the iron-based rod may be generally subjected to a degreasing treatment with an organic solvent, alkali immersion, alkaline electrolytic degreasing, etc., and if necessary, a pickling treatment with an acid such as hydrochloric acid or sulfuric acid.

If desired, the iron-based base material may be subjected to a polishing step prior to chrome plating. The iron-based base material is polished by a conventional method, for example, cylindrical polishing (ring buff) having a large polishing force, vertical polishing, etc .; rough polishing such as emery buff polishing, belt polishing, flap wheel polishing; cotton buff, sisal buff, and combinations thereof. Further, medium polishing and finish polishing can be performed individually or in combination. The medium polishing and the final polishing may be of a closed face type, an open face type or a unit face type.

Prior to the chrome plating, the iron-based base material may be subjected to an etching treatment by anodic oxidation for adjusting the plating base. The etching treatment by anodic oxidation is carried out, for example, by electrolytically treating the iron-based material as an anode at a temperature of about 30 to 60 ° C., a current density of about 10 to 50 A / dm ² and a time of about 10 to 600 seconds. You can Instead of the etching treatment by anodic oxidation, or together with the etching treatment by anodic oxidation, an acid immersion treatment of immersing in hydrochloric acid, sulfuric acid or the like may be performed.

The iron-based base material is subjected to a hard chrome plating treatment. The composition of the chromium plating bath is not particularly limited, and a conventional plating bath can be used. The plating bath, for example, chromic acid anhydride CrO _3, Sargent bath containing sulfuric acid; chromic acid anhydride CrO _3, in addition to sulfuric acid, may be a silicofluoride bath including silicofluoride sodium or fluorosilicate of potassium reduction. Further, the chromium plating bath may contain at least one component such as silicofluoric acid, ammonium fluoride, strontium sulfate, citric acid, tartaric acid, oxalic acid and formic acid. The plating bath usually contains trivalent chromium in an amount of about 0.1 to 3 g / L.

The ratio of chromic anhydride and sulfuric acid in a plating bath such as a Sargent bath is usually about 100: 0.8 to 1.5 (g / L) chromic anhydride: sulfuric acid. Chromic anhydride 100 g / in order to improve corrosion resistance
The amount of sulfuric acid with respect to L is 0.9 to 1.3 g / L, preferably 1.0 to 1.25 g / L. As the amount of sulfuric acid decreases, the covering power improves, but the corrosion resistance tends to decrease, and as the amount of sulfuric acid increases, the corrosion resistance improves, but the adhesion and the uniformity of the plating layer tend to decrease.

The plating bath may be a high concentration bath, a standard bath or a low concentration bath, and the chromic anhydride concentration is
Usually 100 to 400 g / L, preferably 150 to 350
g / L, and more preferably about 200 to 300 g / L.

In hard chrome plating, a lead alloy, iron or the like can be appropriately arranged and used as an anode, and an auxiliary cathode, a shielding plate or the like can be used in order to make the plated portion uniform.

The plating conditions can be selected according to the composition of the bath, etc., and the plating temperature is usually 20 to 70 ° C., preferably 40.
˜65 ° C., current density 10˜100 A / dm ₂ , preferably 30˜60 A / dm ² . The plating time can be selected according to the bath temperature, current efficiency, desired plating film thickness, and the like.

The thickness of the hard chrome plated layer formed by plating can be selected within a range that does not impair the corrosion resistance.
The thickness is 200 μm, preferably 10 to 150 μm, and more preferably 10 to 100 μm. A particularly preferable thickness of the hard chrome plating layer is 15 to 75 μm (for example, 2
5 to 75 μm), especially about 15 to 60 μm. If the thickness of the hard chrome plating layer is small, the corrosion resistance tends to decrease, and if it is too thick, not only is it uneconomical, the plating requires a long time, and the productivity decreases. The plating layer having the above thickness can be formed, for example, in about 1 to 2 hours.

According to microscopic observation, the hard chrome plating layer has many cracks and pinholes which cause corrosion. Further, as described in the above-mentioned prior document, when the hard chrome plating layer is heat-treated, cracks generally grow.

However, even if the hard chrome plated layer is thin, high corrosion resistance can be imparted to the iron-based substrate by heat-treating the hard chrome-plated iron-based substrate and impregnating the resin. Furthermore, as in the above-mentioned prior art, a hard chrome plating layer having a large thickness is formed, and it is used as a cylinder piston rod of a construction machine or the like used under severe conditions without performing polishing and baking twice. However, the corrosion resistance is extremely high.

The feature of the present invention is (1) to enhance the corrosion resistance of the iron-based base material by subjecting it to a resin impregnation step after heat treatment after hard chrome plating. With such a method, the corrosion resistance is remarkably improved even if the thickness of the hard chromium plating layer is small.

As the heat treatment, various heating methods such as baking and induction heating (for example, high frequency heating) can be adopted, and the kind thereof is not particularly limited. The preferable heat treatment includes baking treatment and high frequency heat treatment.

The heating temperature can be appropriately selected from the range where the corrosion resistance can be improved, for example, 150 ° C. or higher (for example, 150 to 800 ° C.), preferably 170 to 600 ° C., particularly about 180 to 300 ° C. If the heating temperature is lower than 150 ° C., it takes a long time to improve the corrosion resistance, and if it exceeds 800 ° C., the temperature becomes excessive and the workability tends to be deteriorated.

The heating temperature can also be selected according to the heating method. For example, in the case of a baking process, the heat transfer efficiency is low, and when it is heated at a high temperature, the heat energy loss tends to increase. Therefore, the baking temperature is usually 1
50 to 400 ° C, preferably 170 to 350 ° C, more preferably 180 to 300 ° C (for example, 200 to 300).
C.) is preferably selected within the range. A particularly preferable baking temperature is 220 to 300 ° C. The baking time is, for example, 30 minutes to depending on the baking temperature.
It can be selected within a range of 12 hours, preferably 1 to 10 hours, more preferably 2 to 8 hours.

Baking can be carried out using various heating furnaces such as an infrared heating furnace, a hot air furnace, and an electric furnace.

On the other hand, in the case of induction heating, the iron-based material such as the cylinder rod can be efficiently heat-treated within a short time, so that the productivity of the corrosion-resistant iron-based member can be remarkably improved. In particular, high-frequency heating has high heat treatment efficiency. In the case of high frequency heating, the heating temperature is 150 to 800.
℃, preferably 170-600 ℃, more preferably 2
It can be appropriately selected within the range of 10 to 600 ° C, particularly 220 to 600 ° C. In the case of high frequency heating, it is difficult to directly measure the heating temperature, but the surface temperature of the iron-based base material can be used as the heating temperature.

The degree of heating by the high frequency heating is, for example,
It can be arbitrarily controlled by adjusting the inner diameter of the coil, the width of the coil, the output of the high frequency generator, the frequency, the relative feed speed between the iron-based base material and the coil, and the like. Since these factors are related to each other, it is
It is not possible to independently determine only one factor.

Hereinafter, the outer diameter of the iron-based base material is 30 to 100 m.
When using a rod of mφ, an example of high frequency heating conditions is
This will be described more specifically. As the distance between the coil and the cylinder rod increases, the induced current decreases and the rise in the surface temperature is suppressed. Therefore, the distance between the coil and the cylinder rod is, for example, 10 depending on the degree of heat treatment.
It can be selected in the range of about 50 mm, preferably about 15 to 30 mm.

The width of the coil is also related to the heat treatment time and the relative feed rate between the cylinder rod and the coil. When the coil length is short or the feed speed is high, the degree of heat generation is small. Therefore, the length of the coil can be appropriately selected in relation to the feed rate, but it is usually 1
About 0 to 50 mm is sufficient. The relative feed speed between the cylinder rod and the coil is, for example, 0.1 to 5
m / min, preferably about 0.5 to 5 m / min. Since the feeding speed can be increased by the high frequency heating as compared with the baking treatment, the cylinder rod excellent in corrosion resistance can be continuously and efficiently manufactured within a short time.

Since the output of the high frequency generator is proportional to the energy of the induced current, the higher the output, the higher the surface temperature of the cylinder rod. The output of the high frequency generator can be selected within a range of, for example, about 30 to 150 kw. When the frequency becomes smaller, the induced current flows to the deep part of the cylinder rod, and it seems that the local temperature rise is suppressed. The frequency is, for example, 3 kHz to 1 MHz, preferably 4 to 100 kHz, more preferably 4 to 10 kHz.
You can select within a range.

In the case of heat treatment by induction heating, the above conditions can be appropriately selected depending on the size of the iron-based base material such as the cylinder rod and the desired degree of heat treatment.

When the iron-based substrate is hardened steel, the heat treatment is preferably performed at a temperature that does not exceed the tempering temperature of the iron-based substrate. After the heat treatment, the plated product is usually gradually cooled.

The heating time in the present invention is significantly shorter than the baking time described in the prior art document. Moreover, in the present invention, the corrosion resistance is remarkably improved by one heat treatment. Furthermore, by combining the heat treatment process of heat-treating (baking) the hard chrome plating layer and the resin impregnation process, it is possible to impart corrosion resistance comparable to stainless steel to the iron-based base material for a long period of time, and the corrosion resistance is improved. It can be greatly improved.

In the resin impregnation step, if the resin or the sealant is impregnated, the corrosion resistance of the iron-based base material is remarkably improved, probably because many cracks and pinholes of the hard chromium plating layer are buried. The resin or sealant used as the impregnating agent in the impregnation treatment may be any resin that can impart corrosion resistance, and examples thereof include polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate. Thermoplastic resin such as copolymer, polyvinyl acetal, acrylic resin, styrene polymer, polyester, polyamide, silicone resin; thermosetting acrylic resin, epoxy resin, urethane resin, phenol resin, vinyl ester resin, unsaturated polyester, diallyl Examples thereof include phthalate resin, thermosetting silicone resin, polyimide, melamine resin, urea resin and the like. The thermosetting resin or the sealing agent may contain a curing agent or a cross-linking agent depending on the type of resin.

The preferred resin or sealant includes a resin having high corrosion resistance, for example, a thermosetting resin such as a thermosetting acrylic resin. Further, a preferable thermosetting acrylic resin can be composed of an acrylic or methacrylic oligomer and / or an acrylic or methacrylic monomer.
Examples of (meth) acrylic oligomers and monomers include polyfunctional oligomers having two or more (meth) acryloyl groups (eg, epoxy acrylate, oligoester acrylate, urethane acrylate, and methacrylates corresponding to these), and 2 or more. (Meta)
Polyfunctional monomer having an acryloyl group (for example, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol Diacrylate, tetramethylene glycol diacrylate, hexanediol diacrylate, neopentyl glycol diacrylate, 2,2-bis (4-acryloyloxyethoxyphenyl) propane, 2,2-bis (4-acryloyloxydiethoxyphenyl) propane , Trimethylolpropane triacrylate, pentaerythritol tetraacrylate And the like corresponding methacrylates to), monofunctional (meth) acrylate (e.g., methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, phenyl acrylate, benzyl acrylate and the corresponding methacrylates thereto) are included.
These compounds can be used alone or in combination of two or more.

A liquid resin or a sealant, particularly a non-volatile liquid resin or a sealant is preferable in order to enhance the impregnation efficiency into the hard chromium plating layer. The resin and sealant may be used as a solution or dispersion, especially as an aqueous solution or an organic solvent solution. As the solvent, depending on the type of the resin, for example, water, aliphatic or alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, esters, ketones, ethers, etc. Organic solvents and mixed solvents thereof can be used. The content of the non-volatile resin or the sealing agent in the impregnating agent is, for example, 0.1 to 100% by weight, preferably 10 to 100% by weight, more preferably 50 to 10% by weight.
It is about 0% by weight. The viscosity of the resin or sealant as the impregnating agent can be selected within a range that does not adversely affect the impregnating property,
For example, at 25 ° C., it is about 1 to 50 cps, preferably 1 to 30 cps, and more preferably about 1 to 15 cps.

The resin may contain additives such as a stabilizer, an antioxidant and a colorant, if necessary.

The resin impregnation may be carried out by a conventional method, for example, a dipping method under normal pressure, but in order to efficiently impregnate the resin, it is preferable to impregnate under reduced pressure or pressure. Impregnation is usually performed at least under reduced pressure. It is also preferable that the iron-based base material is subjected to degassing under reduced pressure prior to the impregnation treatment and then subjected to the impregnation treatment. These resin impregnation methods can be performed in combination.

The impregnation of the resin under reduced pressure includes (1) a vacuum for reducing the pressure in a predetermined container containing the iron-based base material plated with chromium and the resin or sealing agent (preferably liquid resin or sealing agent). Impregnation method: (2) Vacuum immersion impregnation method in which a container containing a chromium-plated iron-based base material is decompressed and deaerated, and a resin or a sealant is fed into the container to impregnate the resin. 3)
The inside of the container containing the chrome-plated iron-based substrate is decompressed and degassed, and the resin or sealant is sent into the container to impregnate the resin under reduced pressure, and the inside of the container is further pressurized to make the resin Alternatively, it can be carried out by a method of impregnating a sealing agent. The degree of pressure reduction during impregnation can be appropriately selected, and for example,
0.1 to 100 Torr, preferably 1 to 50 Torr, more preferably 1 to 20 Torr. The impregnation time is usually 30 seconds to 1 hour, preferably 1 to 30 minutes. Prior to impregnation, the resin or sealant is degassed under a reduced pressure equal to or less than the degree of reduced pressure in the resin impregnation step,
It is preferable to prevent the formation of bubbles.

The resin is impregnated under pressure by, for example, a pressure of 1 to 20 kg / cm ² , preferably ^{2 to} 10 kg / cm depending on the thickness of the chromium plating layer and the chromium plating conditions.
^The impregnation time is the same as above.

The resin impregnation may be carried out at room temperature, for example, under heating at about 30 to 70 ° C. When a thermosetting resin or a sealant is used, the impregnation temperature is often lower than the curing temperature of the thermosetting resin or the sealant.

The resin or sealant may be impregnated at least once, but may be impregnated multiple times. The preferred number of times the resin is impregnated is about 1 to 3. The number of times of impregnation is the number of times that a series of impregnation steps are performed once.
That is, when the resin is impregnated by combining vacuum impregnation and pressure impregnation, the impregnation steps of vacuum impregnation and pressure impregnation are performed once.

The present invention is characterized in that when the heat-treated hard chrome plated layer is impregnated with a resin or a sealant, high corrosion resistance can be imparted even when the amount of the resin or sealant impregnated is extremely small. The impregnation amount of the resin or the sealant varies depending on the number of cracks in the hard chrome plating layer, the depth of the cracks, etc., but is usually 10 per 100 g of the hard chrome plating layer.
00 mg or less (1% by weight or less), for example, 1 to 100 m
It is about g (0.001 to 0.1% by weight). The impregnation rate can be evaluated by the weight increase due to resin impregnation.

After the impregnation treatment, the chromium-plated iron-based base material may be subjected to a liquid draining step in order to remove the excess resin or sealant. Further, the drained iron-based base material may be subjected to a cleaning step. In this cleaning step, if a good solvent is used for the resin or sealant,
Since the resin impregnated in the defective portion of the hard chrome plating layer elutes, it is preferable to use a poor solvent for the resin or the sealant as the cleaning solvent. The poor solvent can be selected according to the type of resin or sealant, but usually water or the like can be used. The cleaning with the poor solvent may be carried out while heating or heating, and can be carried out by a physical method using a water flow such as bubbling or jet flow.

When a thermosetting resin is used as the resin or the sealant, the iron-based substrate is usually subjected to a curing step.
Curing of the thermosetting resin or the sealing agent is, for example, 50 to 200 ° C., preferably 80 to 15 depending on the curing temperature of the resin.
It can be performed at about 0 ° C. Further, the thermosetting resin or the sealant can be cured in hot water.

After the resin impregnation treatment, the hard chrome plated layer of the plated product is preferably subjected to a buffing process. By subjecting the hard chrome plated product to the buffing process, the corrosion resistance can be further enhanced.

This buffing can be performed in the same manner as the polishing step. A preferable method is a method in which a large polishing force is applied to perform polishing, and fine buffing is sequentially performed. In particular, it is preferable to perform a ring buff of about # 400 to 1000 and then a cotton buff or sisal buff with an abrasive of about # 240 to 600, and then perform an open sisal buff. When buffing is performed by such a method, a large polishing force acts on the ring buff, and a cotton buff or sisal buff causes
Not only the protrusions and the like of the plating layer are cut, but also the plastic layer is plastically deformed, and the openings such as cracks of the plating layer are closed and smoothed, so that the corrosion resistance is improved.

In the method for producing a corrosion-resistant iron-based member through a cycle consisting of the plating treatment step, the heat treatment step, the impregnation step, and the finishing step, if the impregnation step is repeated at least twice, the corrosion resistance is improved. Can be increased. In such a method, even if the iron-based base material is corrosive, extremely high corrosion resistance can be imparted by one heat treatment, and the iron-based member is hardly corroded.

Furthermore, when the cycle consisting of the plating process, the heat treatment process, the impregnation process and the finishing process is repeated at least twice, the corrosion resistance is extremely high even if the heat treatment temperature in the heat treatment process is low. The property can be imparted to the iron-based member. That is, in the heat treatment step, the temperature is 150 to 2
When the heat treatment is performed at about 00 ° C., if the thickness of the hard chrome plating layer is thin and the number of times the cycle is repeated is 1,
The corrosion resistance may be slightly inferior to the heat treatment at about 00 to 500 ° C. However, if the above cycle is repeated twice or more, the iron-based member is hardly corroded. In addition, from 200
When heat-treated at about 500 ° C, an iron-based member that hardly corrodes even in one cycle is obtained, but by repeating the cycle a plurality of times, extremely high corrosion resistance is surely given even if the hard chromium plating layer is thin. it can. In the process of repeating the treatment cycle, the heat treatment temperature can be selected from the range of about 150 to 600 ° C, for example. The impregnation step is often performed at least under reduced pressure or, if necessary, in combination with increased pressure.

The number of repetitions of the above cycle may be 2 or more, but usually it is about 2 to 3 times in many cases. When performing hard chrome plating a plurality of times, the thickness of the hard chrome plated layer by each plating treatment can be appropriately selected from the above range of 10 to 200 μm according to the number of plating, for example, 10 to 100 μm, preferably 15 to. It is about 50 μm.

When performing hard chrome plating a plurality of times, it is usually difficult to form a uniform hard chrome plated layer with the impregnated resin when the hard chrome plating treatment is performed after impregnating the resin. However, in the above-mentioned cycle, since the buffing is performed after the resin impregnation step, a uniform hard chrome plating layer can usually be formed even if the hard chrome plating treatment is performed a plurality of times.

The final thickness of the hard chrome plating layer thus formed is, for example, 5 to 100 μm, preferably 10 to 80 μm, more preferably 15 to 75 μm.
It is about m. The particularly preferable thickness of the hard chrome plating layer in the final product is 10 to 50 μm (for example, 20 to 5 μm).
0 μm). The obtained iron-based member such as a cylinder rod does not corrode even if the plating layer has cracks or the like even under severe conditions, for example, when subjected to a salt spray test.

For example, JIS H8502 (198
Even if the Cass test specified in 8) is performed for 96 hours, the rating number as an index of the corroded area is 9.0 to 1
0.0 (for example, 9.3 to 10.0), preferably 9.5
~ 10.0, more preferably about 9.8 to 10.0,
In particular, it is about 10.0 and hardly corrodes. Also, JI
Even if the salt spray test specified in SH 8502 is conducted for 1200 hours, the rating number is 9.5 to 1
0.0, preferably about 9.8 to 10.0, particularly 10.
It is about 0 and hardly corrodes.

According to the method of the present invention, high corrosion resistance can be imparted to the corrosive iron-based substrate. Therefore, the present invention is
It can be applied to various corrosive iron-based base materials, for example, iron-based members used in a corrosive environment or an environment in which corrosion is promoted, particularly sliding members whose corrosion resistance is likely to decrease due to sliding contact or the like. Especially, it can be suitably applied to various cylinder rods, for example, cylinder rods for construction machines, particularly piston rods.

The cylinder rod is provided with a position detecting recess in the axial direction of the cylindrical rod in order to control the forward / backward movement of the rod.
For example, recesses scattered in the axial direction of the rod, preferably a plurality of grooves extending in the circumferential direction at a predetermined pitch may be formed.

In such a cylinder rod, the positions of a plurality of grooves formed in the circumferential direction are determined by a position detection sensor (for example, an electromagnetic position detection sensor that detects a change in magnetic resistance, a potentiometer that detects a capacitance, etc.). Sensor). A preferable sensor includes an electromagnetic position detection sensor that can detect the thickness (depth) and width of the groove by magnetic means by utilizing the fact that eddy current flows corresponding to the groove. Therefore, when the rod is used as the piston rod of the cylinder, the degree of advance / retreat of the piston rod can be detected by counting the detection signal of the eddy current generated in response to the advance / retreat of the piston rod with respect to the cylinder.

The position detecting recess is preferably an annular groove or a spiral groove formed over the entire circumferential surface of the rod, or a groove extending at least partially in the circumferential direction along the axial direction of the rod.
Particularly preferable position detecting grooves extend in a region extending in the axial direction of the rod in the circumferential direction orthogonal to the axial direction of the rod.

The pitch of the groove can be selected within a range in which the accuracy of detecting the position of the groove is not deteriorated, for example, 0.1 to 50 mm,
It is preferably about 0.5 to 25 mm. The depth of the groove
It can be appropriately selected within the range that does not lower the grooving workability,
For example, 1 to 200 μm, preferably 10 to 150 μm
m, and more preferably about 25 to 100 μm.

The groove of the rod may include a reference groove serving as a reference marker. The cylinder rod including the reference marker is formed in the axial direction of the cylindrical iron-based rod with a plurality of position detecting grooves extending in the circumferential direction at a predetermined pitch and in the circumferential direction at a pitch larger than the pitch of these grooves. And a reference groove.

In such a rod, the reference groove is used as a reference marker, and a detection signal from a position detection sensor for detecting the reference groove is used as a reference signal. Based on the reference signal, the rod is moved forward or backward from the cylinder. Can be made.

When the rod having the reference groove is used, the detection signal of the eddy current generated in the reference groove can be used as the reference signal. Therefore, after returning the rod once to the reference point in the cylinder, the rod is moved forward or backward. The stroke for returning the rod to the reference position can be reduced. Moreover, the rod can be moved forward or backward by a predetermined stroke while counting the detection signal of the eddy current generated in the position detection groove with reference to the reference signal.

The reference groove is not limited to the groove shape and can be formed in the same manner as the position detecting recess. Similar to the above, the preferable reference recess is a groove that extends at least partially in the circumferential direction along the axial direction of the rod. A particularly preferred reference groove is
The region extending in the axial direction of the rod extends in the circumferential direction orthogonal to the axial direction of the rod.

In such a cylinder rod, the position detecting recess and the reference recess are filled with the hard chrome plating layer, and the surface of the rod is covered with the hard chrome plating layer having a smooth surface. .

The cylinder rod can be manufactured by forming a plurality of recesses in the axial direction of the iron-based rod and then forming a hard chromium plating layer in the same manner as described above. The concave portion of the cylinder rod can be formed by screen-printing method, photoresist method, tape masking method or the like to form a resist by leaving a portion corresponding to the concave portion, and then etching.

Further, when forming the hard chrome plating layer, it is preferable that the region of the rod excluding the recess is masked and hard chrome plated, the mask is removed, and hard chrome plated again. In this case, after each hard chrome plating, along with buffing if necessary, the resin impregnation and heat treatment may be performed in an appropriate combination,
After performing the second hard chrome plating treatment, finally,
The resin impregnation, the heat treatment, and the buffing as required may be combined.

After the mask is removed, even if the chromium-plated portion and iron of the iron-based rod coexist, in order to efficiently etch the surface of the iron-based rod, an etching solution, preferably chloride It is preferable to perform etching by using an etching solution containing ferric iron to prepare the base. Further, subsequently, by performing the etching treatment by the anodic oxidation, the surface of the chromium plated portion is also etched, and the entire surface of the iron-based rod can be cleaned and activated.

[0075]

According to the method of the present invention, hard chrome plating is combined with heat treatment and resin impregnation,
Even if the thickness of the hard chrome plated layer is small, it is possible to obtain a corrosion-resistant iron-based member having excellent corrosion resistance. Further, it is possible to impart corrosion resistance equal to or higher than that of stainless steel to the iron-based base material having corrosiveness. Further, the cylinder rod having the above-mentioned excellent properties can be manufactured economically and with high productivity.

[0076]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example 1 A rod made of low carbon steel (S43C) having an outer diameter of 25 mmφ was degreased and buffed with # 320 ring buffs, # 600 ring buffs, # 800 ring buffs and sisal buffs. Etching was carried out for 3 minutes at a current density of 35 A / dm ² using a plating bath and an anodizing method with the rod as an anode.

Plating bath composition Chromic anhydride: 250 g / L Sulfuric acid: 2.5 g / L Trivalent chromium: 1.0 g / L Then, the plating bath temperature was 50 ° C. and the current density was 35 A /
The rod was chromium-plated under conditions of dm ² and plating time of 100 minutes to form a hard chromium-plated layer having a thickness of 35 μm.

The obtained hard chrome-plated product was heated to a temperature of 18
It was baked at 0 ° C. for 5 hours, gradually cooled, and then subjected to a resin impregnation step. This resin impregnation step was performed using an impregnating solution containing an acrylic resin-based impregnating agent (DIAKITE PF-1900, manufactured by Diafloc Co., Ltd.) and a curing agent (A-1, manufactured by Diafloc Co., Ltd.).

That is, the inside of the vacuum container accommodating the hard chrome-plated rod is adjusted to 10 at 5 Torr by a vacuum pump.
It is degassed for a minute, and the impregnating liquid is sent into the container, and it is 1
After impregnating with vacuum immersion for 0 minute, it was opened under atmospheric pressure. Next, the inside of the container is pressurized to 10 at a pressure of 5 kg / cm ² .
After impregnating under pressure for a minute, the rod was taken out, excess impregnating liquid was drained off, placed in a drying oven and heated at 150 ° C. for 30 minutes to cure the resin, and a hard chrome plated rod impregnated with the resin was obtained.

Then, after gradually cooling the rod, it was subjected to a finishing buffing process to prepare a hard chromium plated piston rod. The finishing buffs were performed in the order of # 800 ring buff and sisal buff. The thickness of the hard chrome plating layer was 30 μm by buffing.

Example 2 A hard chrome plated product was baked at 230 ° C. for 5 hours,
A piston rod was obtained in the same manner as in Example 1 except that a hard chromium plating layer having a thickness of 25 μm was formed by buffing.

Example 3 A low carbon steel rod similar to that in Example 1 was pretreated by degreasing, buffing and etching, and the plating bath of Example 1 was used at a temperature of 50 ° C. and a current density of 35 A / dm. ² ,
Plating time 60 minutes, chromium plating, thickness 20
A μm hard chrome plating layer was formed.

The obtained hard chrome-plated product was heated at 180 ° C.
5 hours of baking treatment and resin impregnation treatment similar to that of Example 1, the excess impregnating liquid was drained, placed in a drying oven and heated at 150 ° C. for 30 minutes to cure the resin, and the resin was impregnated. A hard chrome plated rod was obtained.

After gradually cooling the rod, it was subjected to a finishing buffing process in the same manner as in Example 1 to form a hard chrome plating layer having a thickness of 15 μm.

Then, the rod plated with hard chrome is subjected to the same chrome plating process as described above to form a hard chrome plated layer having a thickness of 20 μm (total thickness 35 μm) on the plated layer, and the rod is plated at 5 ° C. at 180 ° C. It was subjected to a baking treatment step, a resin impregnation step and a finishing buffing step for a long time to obtain a piston rod having a hard chrome plated layer with a thickness of 30 μm.

Example 4 A piston rod was obtained in the same manner as in Example 3 except that the baking temperature in each of the two baking treatment steps was set to 190 ° C.

Comparative Example 1 A piston rod having a hard chromium plating layer with a thickness of 30 μm was obtained in the same manner as in Example 1 without performing baking treatment.

Comparative Example 2 A piston rod having a hard chrome plated layer with a thickness of 30 μm was obtained in the same manner as in Example 1 without performing the resin impregnation treatment.

Comparative Example 3 A piston rod having a hard chrome plated layer with a thickness of 30 μm was obtained in the same manner as in Example 1 without performing baking treatment and resin impregnation treatment.

Example 5 Instead of the rod of Example 1, a rod made of low carbon steel (S43C) having an outer diameter of 65 mmφ (entire rod length 590 m
m, shaft length 120 mm) and in the same manner as in Example 1 to form a hard chrome plating layer having a thickness of 30 μm.

Next, a coil (inner diameter 86 mmφ, width 20
mm), the rod was placed in the hollow portion, and high frequency heat treatment was performed under the conditions of a voltage of 300 V, an output of a high frequency generator of 50 kw, a frequency of 5.0 kHz and a coil feed rate of 2.8 m / min. The surface temperature of the piston rod when treated under the above conditions was measured and found to be 220 ° C.

The heat-treated piston rod was used as in Example 1.
After being subjected to the resin impregnation step in the same manner as above and impregnated with the resin,
Used for final buffing, and hard chrome plating layer thickness 27
A μm cylinder rod was prepared.

Example 6 Using the coil of Example 5, a high frequency heating condition was set to a voltage of 46.
0V, output of high frequency generator 80kw, frequency 6.0kH
A cylinder rod was produced in the same manner as in Example 5 except that the feeding rate of z and the feeding rate of the coil were 3.3 m / min. In addition,
The surface temperature of the piston rod when subjected to the high frequency heat treatment under the above conditions was 500 ° C.

The piston rods obtained in the respective examples and comparative examples were subjected to the Cass test method specified in JIS H8502 (1988), and the corrosion defects (corrosion resistance) of the rods with the passage of the spraying time. Was evaluated by a rating number standard chart. The test solution in the Cass test was obtained by dissolving 0.268 g of cupric chloride dihydrate in an aqueous solution having a sodium chloride concentration of 40 g / L and adjusting the pH to 3.0 with acetic acid. Also,
The Cass test was conducted at 50 ° C. The results are shown in Table 1.

In the corrosion test, although the degree of corrosion was small, rust seemed to flow from the corroded portion,
The degree of corrosion may be overestimated. for that reason,
In the table, in the result of the test time of 48 hours, the degree of corrosion of the piston rod itself subjected to the test is shown, and the degree of corrosion after the rod surface is wiped and cleaned is also evaluated.

The rating number standard chart corresponds to the total corrosion area ratio (%), and the relationship between the total corrosion area and the rating number is as follows: the larger the value, the higher the corrosion resistance.

Total corrosion area (%) Rating number 0 10 0 to 0.02 9.8 0.02 to 0.05 9.5 0.05 to 0.07 9.3 0.07 to 0.10 9. 0 0.10 to 0.25 8 0.25 to 0.50 7 0.50 to 1.00 6 1.00 to 2.50 5 2.50 to 5.00 4 5.00 to 10.0 3 10 .0 to 25.0 2 25.0 to 50.0 1

[0099]

[Table 1] From Table 1, the piston rods of the respective examples have significantly higher corrosion resistance than the rods of the comparative examples which are not heat-treated or resin-impregnated. Further, the combination of heat treatment and resin impregnation treatment greatly improves the corrosion resistance of the piston rod. Particularly, when the plating treatment, the heat treatment and the resin impregnation treatment are performed a plurality of times, the corrosion resistance of the piston rod is significantly improved.

Comparative Example 4 Stainless steel with an outer diameter of 40 mmφ (SUS304)
A hard chrome plated layer having a thickness of 50 μm was formed by chrome plating in the same manner as in Example 1 except for using a rod made of aluminum and prolonging the plating time.

Comparative Example 5 Hard chromium was prepared in the same manner as in Example 1 except that a hard chromium plating layer having a thickness of 30 μm was formed on a rod made of low carbon steel (S43C) having an outer diameter of 40 mmφ and heat-treated at 120 ° C. for 30 minutes. A piston rod having a plated layer thickness of 25 μm was obtained.

Example 7 In the same manner as in Example 1 except that a hard chromium plating layer having a thickness of 30 μm was formed on a rod made of low carbon steel (S43C) having an outer diameter of 40 mmφ and heat-treated at 250 ° C. for 4 hours and 30 minutes.
A piston rod having a hard chromium plating layer with a thickness of 25 μm was obtained.

Example 8 A piston rod having a hard chromium plating layer with a thickness of 25 μm was obtained in the same manner as in Example 7 except that the heat treatment was carried out at 250 ° C. for 6 hours.

Example 9 A hard chrome plating layer having a thickness of 30 μm was formed on a rod made of low carbon steel (S43C) having an outer diameter of 40 mmφ, heat treated at 250 ° C. for 6 hours, and then impregnated with resin twice. In the same manner as in Example 1, a hard chromium plating layer having a thickness of 30 μm was obtained.

Example 10 A rod made of low carbon steel (S43C) having an outer diameter of 40 mmφ was
Pretreatment by degreasing, buffing and etching,
Using the plating bath of Example 1, a temperature of 50 ° C. and a current density of 35
Chrome plating was performed at A / dm ² to form a hard chromium plating layer having a thickness of 30 μm.

The obtained hard chrome-plated product is heated to 200 ° C.
Subjected to a baking treatment for 4 hours and 30 minutes and a resin impregnation treatment similar to that in Example 1, washing the excess impregnation liquid with water and 90 ° C.
It is removed by washing with hot water at 30 ° C and put in a drying oven at 150 ° C for 30
The resin was hardened by heating for a minute to obtain a hard chrome plated rod impregnated with the resin.

After gradually cooling the rod, it was subjected to a finishing buffing process in the same manner as in Example 1 to form a hard chrome plating layer having a thickness of 20 μm.

Then, the hard chrome plated rod is subjected to the same chrome plating step as described above to form a hard chrome plated layer having a thickness of 30 μm (total thickness 50 μm) on the plated layer and the same as above. Was subjected to a baking treatment step (4 hours and 30 minutes at 200 ° C.), a resin impregnation step and a finishing buff step to obtain a piston rod on which a hard chrome plated layer having a thickness of 35 μm was formed.

Example 11 3 hours at 250 ° C. in 2 baking steps
A piston rod was obtained in the same manner as in Example 10 except that baking was performed for 0 minutes.

Example 12 A piston rod was obtained in the same manner as in Example 10 except that a hard chrome plating layer having a thickness of 15 μm was formed in each chrome plating step and baking was performed at 250 ° C. for 6 hours in each baking treatment step.

The piston rods obtained in Comparative Examples 4 and 5 and Examples 7 to 12 were subjected to the same Cass test as described above, and the degree of rod corrosion defects (corrosion resistance) at 96 hours and 480 hours was evaluated. The rating number was evaluated by a standard chart. In addition, it was subjected to the neutral salt spray test method (concentration 40 g / L at the time of preparation of sodium chloride, pH 6.5 to 7.2) specified in JIS H8502, and the corrosion defect (corrosion resistance) at 1200 hours of salt spray was confirmed. The degree was evaluated by a rating number standard chart. Further, as a reference, the corrosion resistance of the piston rod obtained in the same manner as in Comparative Example 3 was examined. The results are shown in Table 2.
Shown in.

[0112]

[Table 2] As is clear from Table 2, when the heat treatment temperature is increased, the impregnation treatment is performed a plurality of times, and the plating step, the heat treatment step, the impregnation step, and the like are repeated a plurality of times, a piston rod that hardly corrodes can be obtained. In addition, the piston rod of the embodiment,
All of them maintained high gloss and water repellency. In particular,
The piston rods of Examples 8 to 12 showed corrosion resistance equal to or higher than that of the stainless steel of Comparative Example 4, the corrosion resistance was remarkably improved, and no corrosion occurred. In addition,
In the piston rod of Comparative Example 4, chromium was corroded and white rust was generated in 480 hours (20 cycles) of the cass test, and slight red rust was generated in the salt spray test.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // C25D 3/04

Claims (9)

[Claims] 1. A corrosive iron-based base material is plated with hard chrome,
A method for producing a corrosion-resistant member, which comprises buffing after impregnating a resin or a sealing agent after heat treatment at a temperature of 150 ° C. or higher. 2. A cylindrical rod coated with hard chrome
A plating treatment step of forming a hard chromium plating layer of 0 to 100 μm, a heat treatment step of heat treatment at 170 to 600 ° C., an impregnation step of impregnating a thermosetting resin or a sealant under reduced pressure, and an impregnated resin. Alternatively, the method for producing a corrosion-resistant member according to claim 1, comprising a curing step of curing the sealant and a finishing step of buffing. 3. The method for producing a corrosion resistant member according to claim 1, wherein the iron-based base material is a cylinder rod. 4. The method for producing a corrosion-resistant iron-based member according to claim 1, wherein the heat treatment is performed at a temperature of 180 to 300 ° C. for 30 minutes to 12 hours. 5. An acrylic or methacrylic oligomer or monomer having a viscosity at 25 ° C. of 1 to 50 c.
The method for manufacturing a corrosion resistant member according to claim 1, wherein a thermosetting resin or a sealant having a ps is used. 6. The method for producing a corrosion-resistant iron-based member according to claim 1, wherein the impregnation is performed under a reduced pressure of 0.1 to 100 Torr. 7. The method for producing a corrosion-resistant iron-based member according to claim 2, wherein a hard chrome plating layer having a thickness of 5 to 95 μm is formed by buffing. 8. An iron-based base material is plated with hard chrome for 15 to 15.
A plating treatment step of forming a hard chromium plating layer of 60 μm, and a heat treatment step of heat treatment at 180 to 300 ° C.
Viscosity at 25 ° C under reduced pressure of 1 to 50 Torr 1 to 15 cp
impregnation step of impregnating the thermosetting resin or the sealing agent of s,
A method for producing a corrosive iron-based substrate, comprising a curing step of curing an impregnated resin or a sealant, and a finishing step of buffing. 9. A corrosive iron-based cylindrical rod is plated with hard chrome, the plated rod is heat-treated at a temperature of 150 ° C. or higher, and the heat-treated rod is impregnated with a thermosetting resin or a sealing agent, followed by an impregnation treatment. Corrosion-resistant iron-based member obtained by buffing the formed rod according to JIS H
When the CAS test specified in 8502 was performed for 96 hours, the rating number was 9.0 to 10.0, JIS
When the salt spray test specified in H8502 was conducted for 1200 hours, the rating numbers were 9.8 to 10.
Corrosion-resistant iron-based member that is 0.