JP2758363B2 - Corrosion resistant iron-based member and method of manufacturing the same - Google Patents

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 producing the same. In particular, the present invention relates to a method for manufacturing a corrosion-resistant member capable of imparting high corrosion resistance to an iron-based substrate such as a cylinder rod used for construction machines, industrial machines, industrial vehicles, and the like.

[0002]

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

However, unlike the other electroplated layers, even if the thickness of the plated layer is about 100 μm, a large number of defective portions such as cracks, pinholes and pits are formed on the plated layer formed by hard chromium plating. Generate. Therefore,
Rods with hard chromium plating, despite having various excellent properties, are susceptible to corrosion and rust. Especially,
In the presence of chlorides and acids, such as sodium chloride, and in high-temperature and high-humidity environments, the rods are significantly corroded due to the numerous defects. If the rod is corroded, the rod will slide and damage the rod, causing oil leakage and the like.

In order to prevent corrosion of the hard chromium plating, a rust inhibitor is applied to permeate defective parts such as cracks, but this is not a fundamental solution. Further, in order to prevent corrosion of the hard chromium plating, a plating layer having a thickness of about 0.05 to 0.1 mm is formed. However, when the thickness of the plating layer is increased, productivity decreases.

Japanese Patent Publication No. 3-14913 discloses a method of applying high quality mirror chromium plating to a surface of an iron base material using a microcrack type chromium plating bath, which is about twice as large as a finished plating layer. A thick plating layer is formed under severe conditions (40 to 6 times higher than the upper limit of the standard operating temperature).
Baking at 0 ° C higher temperature for 40-50 hours)
A method is disclosed in which 40 to 50% of a plating layer is removed by polishing or the like, baked under mild conditions (at a temperature higher by 10 to 20 ° C. than the upper limit of the standard temperature used for 20 to 30 hours), and finish polished. I have.

However, in this method, it is necessary to form a plating layer having a large thickness and to remove 40 to 50% of the plating layer, which is not economical and requires a long time for plating and removing the plating layer. Cost. In addition, baking twice requires a long time. Therefore, productivity of drums, rolls, and the like is significantly reduced. Furthermore, the above-mentioned prior document does not describe anything about corrosion resistance.

Japanese Patent Application Laid-Open No. 60-33369 discloses that a metal is chromium-plated, and hydrogen gas generated by plating is removed by heating at 120 ± 10 ° C. for 15 to 30 minutes. And an anticorrosion method for applying an anticorrosion composition composed of a mixture of 80 to 20% by weight of diallyl phthalate. However, the obtained metal member has insufficient corrosion resistance as shown in a comparative example described later.

The present applicant has proposed in Japanese Patent Application Laid-Open No. 4-160197 that hardening of the cylinder rod is performed with hard chrome plating and baking to improve the corrosion resistance of the cylinder rod. The present invention has been made to further improve the corrosion resistance of a ferrous base material such as a cylinder rod plated with hard chrome.

[0009]

That is, an object of the present invention is to provide a corrosion-resistant iron-based member having extremely high corrosion resistance even if the thickness of the hard chromium plating layer is small, and a method of manufacturing the same.

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

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

[0012]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies. As a result, after performing hard chromium plating, heat treatment is performed at a specific temperature to impregnate a thermosetting acrylic resin. It was found that the corrosion resistance was remarkably improved when cured by this method, and the present invention was completed.

That is, in the method of the present invention, the iron-based substrate is hard chromium-plated, heated at a temperature of 150 ° C. or higher, and then impregnated with a thermosetting acrylic resin or a sealing agent.
The corrosion-resistant member is manufactured by being subjected to a curing step and a buffing step.

In such a method, the thickness of the hard chromium plating layer formed by chromium plating is, for example,
The heating temperature may be, for example, about 170 to 600 ° C. Further, the resin and the sealant 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 performed for 96 hours, a corrosion-resistant iron-based material having a rating number of about 9.0 to 10.0 is used. Member, 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.

[0016] The iron-based substrate is made of various iron-based materials, for example, low-carbon steel, high-carbon steel, hardened steel, high-speed steel, chromium steel, nickel steel, nickel-chromium steel, nickel-chromium-molybdenum steel. , And tungsten steel.
According to the method of the present invention, the corrosive member can be provided with significantly improved corrosion resistance, so that 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 be flat, curved, polygonal in cross section, cylindrical, hollow, or the like. Iron-based substrates that require high corrosion resistance include rod-shaped substrates such as cylindrical rods (for example, cylinder rods such as piston rods).

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

Further, if necessary, the iron-based substrate may be subjected to a polishing step prior to the chromium plating. Polishing of iron-based substrates is carried out by a conventional method, for example, cylindrical polishing (ring buff), vertical polishing, etc. having a large polishing power; coarse polishing such as emery buff polishing, belt polishing, flap wheel polishing; cotton buff, sisal buff, and a combination thereof Medium polishing or finish polishing can be performed alone or in combination. The medium polishing and the finish polishing may be any of a closed face, an open face, and a unit face type.

Prior to chromium plating, the iron-based substrate may be subjected to an anodic oxidation etching process to adjust the plating base. The etching treatment by anodic oxidation is performed by, for example, performing an electrolytic treatment using a ferrous base 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. Can be. Note that an acid immersion treatment of immersion in hydrochloric acid, sulfuric acid, or the like may be performed instead of or together with the etching treatment by anodic oxidation.

The iron-based substrate is subjected to hard chrome plating. 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. In addition, the chromium plating bath may include at least one component such as silicic acid, ammonium fluoride, strontium sulfate, citric acid, tartaric acid, oxalic acid, and formic acid. Usually, the plating bath often contains trivalent chromium at about 0.1 to 3 g / L.

The ratio between chromic anhydride and sulfuric acid in a plating bath, for example, a sargent bath, is usually about chromic anhydride: sulfuric acid = 100: 0.8 to 1.5 (g / L). To increase the corrosion resistance, chromic anhydride 100 g /
The amount of sulfuric acid with respect to L is 0.9 to 1.3 g / L, and preferably about 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. 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 any of a high concentration bath, a standard bath, and a low concentration bath.
Usually 100 to 400 g / L, preferably 150 to 350
g / L, more preferably about 200 to 300 g / L.

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

The plating conditions can be selected according to the composition of the bath and the like, and the plating temperature is usually from 20 to 70 ° C., preferably from 40 to 70 ° C.
The current density is about 10 to 100 A / dm ₂ , preferably about 30 to 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 chromium plating layer formed by plating can be selected within a range that does not impair the corrosion resistance.
It is about 200 μm, preferably about 10 to 150 μm, and more preferably about 10 to 100 μm. A particularly preferred thickness of the hard chromium plating layer is 15 to 75 μm (for example,
About 5 to 75 μm), and especially about 15 to 60 μm. When the thickness of the hard chromium plating layer is small, the corrosion resistance is liable to decrease. When the thickness is too large, not only is it not economical, but also it takes a long time for plating and the productivity decreases. The plating layer having such a thickness can be formed, for example, in about 1 to 2 hours.

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

However, by heating a hard chromium-plated iron base material and impregnating the resin, high corrosion resistance can be imparted to the iron base material even if the thickness of the hard chrome plating layer is small. Further, as described in the above-mentioned prior art, a hard chromium plating layer having a large thickness is formed and used as a cylinder piston rod of a construction machine used under severe conditions without performing polishing and baking twice. Even so, the corrosion resistance is extremely high.

The feature of the present invention is that (1) after the hard chromium plating treatment, heat treatment is performed, and then the resin is impregnated and cured, whereby the corrosion resistance of the iron-based substrate is enhanced.
With such a method, even if the thickness of the hard chromium plating layer is small, the corrosion resistance is significantly improved.

For the heat treatment, for example, 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. Preferred heat treatments include a baking treatment and a high-frequency heating treatment.

The heating temperature can be appropriately selected from a range in which the corrosion resistance can be improved, for example, 150 ° C. or more (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 increase the corrosion resistance, and if it exceeds 800 ° C., the temperature becomes excessive and the workability is liable to deteriorate.

The heating temperature can be selected according to the heating method. For example, in the case of a baking process, the heat transfer efficiency is low, and heating at a high temperature tends to increase the heat energy loss. 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)
° C). A particularly preferred baking temperature is from 220 to 300C. The baking time is, for example, 30 minutes to depending on the baking temperature.
It can be selected within a range of about 12 hours, preferably about 1 to 10 hours, and more preferably about 2 to 8 hours.

The baking can be performed using various heating furnaces such as an infrared heating furnace, a hot blast furnace, and an electric furnace.

On the other hand, in the case of induction heating, an iron-based substrate such as a cylinder rod can be efficiently heat-treated within a short time, so that the productivity of a corrosion-resistant iron-based member can be significantly 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
° C, preferably 170-600 ° C, more preferably 2
It can be appropriately selected within the range of about 10 to 600 ° C, especially about 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 substrate can be used as the heating temperature.

The degree of heating by 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 and frequency of the high-frequency generator, the relative feed speed between the iron-based substrate and the coil, and the like. Since these factors are related to each other, when heat treatment is performed,
It is not possible to determine only one factor independently.

Hereinafter, the outer diameter of the iron-based substrate is 30 to 100 m.
When using a rod of mφ, an example of the high-frequency heating condition is as follows:
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 may be, for example, 10
５０50 mm, preferably about 15-30 mm.

The width of the coil is related to the heat treatment time and the relative feed speed between the cylinder rod and the coil. When the length of the coil is short or when 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.
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. According to the high-frequency heating, the feed rate can be increased as compared with the baking process, so that a cylinder rod having excellent corrosion resistance can be continuously and efficiently manufactured in 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, for example, within a range of about 30 to 150 kW. When the frequency decreases, 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, and more preferably 4 to 10 kHz.
You can choose from a range of degrees.

When the heat treatment is performed by induction heating, the above conditions can be appropriately selected according to the size of the iron-based substrate such as a 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 not exceeding the tempering temperature of the iron-based body. After the heat treatment, the plated material is usually gradually cooled.

The heating time in the present invention is significantly shorter than the baking time described in the prior art document. In addition, in the present invention, the corrosion resistance is significantly improved by one heat treatment. Furthermore, when the heat treatment step of baking the hard chromium plating layer and the resin impregnation step are combined, it is possible to provide the iron-based substrate with corrosion resistance comparable to that of stainless steel for a long period of time, and the corrosion resistance is improved. It can be significantly improved.

In the resin impregnation step, if a thermosetting acrylic resin or a sealing agent is impregnated, many cracks and pinholes of the hard chromium plating layer are buried.
The corrosion resistance of the iron-based substrate is significantly improved. Note that the thermosetting resin or the sealing agent may include a curing agent or a crosslinking agent depending on the type of the resin.

Preferred thermosetting acrylic resins or sealants can be composed of acrylic or methacrylic oligomers and / or acrylic or methacrylic monomers.
(Meth) acrylic oligomers and monomers include, for example, polyfunctional oligomers having two or more (meth) acryloyl groups (eg, epoxy acrylate, oligoester acrylate, urethane acrylate, and corresponding methacrylates), two or more (Meta)
Polyfunctional monomers having an acryloyl group (eg, 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.

In order to increase the impregnation efficiency of the hard chromium plating layer, a liquid resin or a sealing agent, particularly a non-volatile liquid resin or a sealing agent is preferable. The resins and sealants may be used as solutions or dispersions, especially aqueous or organic solvent solutions. 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 and the like Or a mixed solvent 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, and 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, it is about 1 to 50 cps at 25 ° C., preferably about 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 coloring agent, if necessary.

The resin impregnation may be carried out by a conventional method, for example, an immersion method under normal pressure. However, in order to impregnate the resin efficiently, it is preferable to impregnate the resin under reduced pressure or under pressure. The impregnation is usually performed at least under reduced pressure. Prior to the impregnation, it is also preferable that the iron-based substrate is subjected to a degassing treatment under reduced pressure and subjected to the impregnation treatment. These resin impregnation methods can be performed in combination.

The impregnation of the resin under reduced pressure is performed by (1) vacuuming the inside of a predetermined container containing a chromium-plated iron base material and a resin or a sealing agent (preferably a liquid resin or a sealing agent). Impregnation method; (2) Vacuum immersion method of depressurizing and degassing the inside of the container containing the chromium-plated iron-based substrate, and sending resin or sealing agent into the container to impregnate the resin; 3)
The inside of the container containing the chromium-plated iron-based substrate is depressurized and degassed, and a resin or a sealant is fed into the container to impregnate the resin under reduced pressure. Alternatively, it can be performed by a method of impregnating with a sealing agent. The degree of reduced pressure during the impregnation can be appropriately selected, for example,
It is about 0.1 to 100 Torr, preferably about 1 to 50 Torr, and more preferably about 1 to 20 Torr. Further, the impregnation time is usually about 30 seconds to 1 hour, preferably about 1 to 30 minutes. Prior to impregnation, the resin or sealant is degassed under reduced pressure equal to or less than the degree of reduced pressure in the resin impregnation step,
Preferably, the formation of bubbles is prevented.

The impregnation of the resin under pressure is carried out, for example, at a pressure of 1 to 20 kg / cm ² , preferably ^{2 to} 10 kg / cm ² depending on the thickness of the chromium plating layer and the chromium plating conditions.
^{About 2} can be performed, and the impregnation time is the same as described above.

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

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

According to the present invention, when the hard chromium plating layer subjected to the heat treatment is impregnated with a resin or a sealing agent, a high corrosion resistance can be imparted even when the impregnation amount of the resin or the sealing agent is extremely small. The impregnation amount of the resin or the sealing agent varies depending on the number of cracks in the hard chromium plating layer and the depth of the cracks.
00 mg or less (1% by weight or less), for example, 1 to 100 m
g (0.001 to 0.1% by weight). In addition, the impregnation rate can be evaluated based on the weight increase accompanying the resin impregnation.

After the impregnation, the chromium-plated iron-based substrate may be subjected to a draining step to remove excess resin or sealant. The drained iron-based substrate may be subjected to a washing step. In this washing step, if a good solvent is used for the resin or the sealing agent,
Since the resin impregnated in the defective portion of the hard chromium plating layer is eluted, it is preferable to use a poor solvent for the resin or the sealant as a cleaning solvent. The poor solvent can be selected according to the type of the resin or the sealing agent, but usually, water or the like can be used. The washing with the poor solvent may be performed under heating or heating, and can be performed by a physical method using a water flow such as bubbling or jet flow.

After the impregnation, the iron-based substrate is usually subjected to a curing step. Curing of thermosetting resin or sealant
Depending on the curing temperature of the resin, it can be carried out, for example, at 50 to 200 ° C, preferably about 80 to 150 ° C. Further, the curing of the thermosetting resin or the sealing agent can be performed in hot water.

After the resin impregnation treatment, the hard chromium plating layer of the plating is preferably subjected to a buffing step. By subjecting the hard chromium plating to a buffing process, the corrosion resistance can be further increased.

This buffing can be performed in the same manner as in the polishing step. A preferable method is a method in which polishing is performed by applying a large polishing force, and fine buffing is sequentially performed. In particular, it is preferable to perform a ring buff of about # 400 to 1000, and then perform a cotton buff or sisal buff with an abrasive of about # 240 to 600, and then it is also preferable to perform an open sisal buff. When buffing is performed by such a method, a large abrasive force acts on the ring buff, and a cotton buff or sisal buff causes
Not only are the projections and the like of the plating layer cut, but also plastically deformed, and the openings such as cracks in 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 including the plating step, the heat treatment step, the impregnation step, the hardening step, and the finishing step, if the impregnation step is repeated at least two times, Can be enhanced. In such a method, even if the iron-based substrate is corrosive, extremely high corrosion resistance can be imparted by one heat treatment, and the iron-based member hardly corrodes.

Further, when the cycle including the plating step, the heat treatment step, the impregnation step, the curing step, and the finishing step is repeated at least twice, even if the heat treatment temperature in the heat treatment step is low, Very high corrosion resistance can be imparted to iron-based members. That is, when heat treatment is performed at a temperature of about 150 to 200 ° C. in the heat treatment step, if the thickness of the hard chromium plating layer is small and the number of repetitions of the cycle is one, corrosion resistance is lower than that of the heat treatment at about 200 to 500 ° C. The properties may be slightly inferior. However, if the cycle is
When repeated more than once, the iron-based member hardly corrodes. In addition, when heat treatment is performed at about 200 to 500 ° C., an iron-based member that hardly corrodes even in one cycle can be obtained. By repeating the cycle a plurality of times, even if the thickness of the hard black plating layer is thin, extremely high corrosion resistance is obtained. Can be reliably provided. In the process of repeating the processing cycle, the heat treatment temperature can be selected, for example, from a range of about 150 to 600 ° C. In many cases, the impregnation step is performed at least under reduced pressure or, if necessary, in combination with under pressure.

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

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

The final thickness of the hard chromium plating layer thus formed is, for example, 5 to 100 μm, preferably 10 to 80 μm, and more preferably 15 to 75 μm.
m. A particularly preferred thickness of the hard chromium 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 cracks are present in the plating layer, even under severe conditions, for example, when subjected to a salt spray test.

For example, JIS H 8502 (198
Even if the cas test specified in 8) is performed for 96 hours, the rating number serving as an index of the corrosion area is 9.0 to 1
0.0 (for example, 9.3 to 10.0), preferably 9.5
To 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 SH8502 was performed for 1200 hours, the rating number was 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, a high corrosion resistance can be imparted to a corrosive iron-based substrate. Therefore, the present invention
The present invention can be applied to various corrosive iron-based substrates, for example, iron-based members used in a corrosive environment or an environment in which corrosion is accelerated, in particular, sliding members whose corrosion resistance tends to be reduced due to sliding contact or the like. In particular, the present invention 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 to control the advance and retreat 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 the plurality of grooves formed in the circumferential direction are determined by position detection sensors (for example, an electromagnetic position detection sensor that detects a change in magnetic resistance, a potentiometer that detects a capacitance, etc.). Sensor). Preferable sensors include an electromagnetic position detection sensor capable of detecting the thickness (depth) and width of the groove by magnetic means by utilizing the flow of an eddy current 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 peripheral surface of the rod, or a groove extending at least partially in the circumferential direction along the axial direction of the rod.
Particularly preferred position detecting grooves extend in a region extending in the axial direction of the rod in a circumferential direction orthogonal to the axial direction of the rod.

The pitch of the groove can be selected within a range where the accuracy of detecting the position of the groove does not decrease.
It is preferably about 0.5 to 25 mm. The depth of the groove
It can be selected appropriately as long as the grooving workability does not decrease,
For example, 1 to 200 μm, preferably 10 to 150 μm
m, more preferably about 25 to 100 μm.

The rod groove 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, a plurality of position detection grooves extending in the circumferential direction at a predetermined pitch, and formed in the circumferential direction at a pitch larger than the pitch of these grooves. Reference groove.

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

If a rod having a reference groove is used, a detection signal of an eddy current generated in the reference groove can be used as a reference signal. Therefore, the rod is once returned to the reference point in the cylinder, and then the rod is moved forward or backward. There is no need to make the rod return, and 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 detecting groove with reference to the reference signal.

The reference groove is not limited to the groove, but can be formed in the same manner as the position detecting recess. The preferred reference recess is a groove that extends at least partially in the circumferential direction along the axial direction of the rod, as described above. Particularly preferred reference grooves are
In the region extending in the axial direction of the rod, it extends in the circumferential direction orthogonal to the axial direction of the rod.

In such a cylinder rod, the position detecting concave portion and the reference concave portion are buried with the hard chrome plating layer, and the surface of the rod is covered with a smooth hard chrome plating layer. .

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. Note that the concave portion of the cylinder rod can be formed by forming a resist by using a screen printing method, a photoresist method, a tape masking method, or the like, excluding a portion corresponding to the concave portion, and then performing etching.

In forming the hard chromium plating layer, it is preferable that hard chrome plating is performed by masking the area of the rod excluding the recess, the mask is removed, and hard chrome plating is performed again. In this case, after each hard chromium 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 process, finally,
The resin impregnation, heat treatment, and, if necessary, buffing may be performed in combination.

After the mask is removed, even if the chrome-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 a chloride solution, is used. It is preferable to perform etching using an etching solution containing ferric iron to adjust the base. Further, by subsequently performing the etching treatment by the anodic oxidation, the surface of the chromium plating 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, since the hard chromium plating and the heat treatment, the resin impregnation and the curing steps are combined, even if the thickness of the hard chromium plating layer is small, the corrosion resistance is excellent. An iron-based member can be obtained. Further, the corrosion resistance can be imparted to a ferrous base material having corrosion resistance equal to or higher than that of stainless steel. Further, a cylinder rod having the above-mentioned excellent characteristics can be manufactured economically and with high productivity.

[0076]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments.

Example 1 A rod made of low carbon steel (S43C) having an outer diameter of 25 mmφ was degreased and buffed with a # 320 ring buff, a # 600 ring buff, a # 800 ring buff and a sisal buff. Using a plating bath, etching was performed at a current density of 35 A / dm ² for 3 minutes by anodic oxidation using 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 temperature of the plating bath was 50 ° C. and the current density was 35 A / L.
Under a condition of dm ² and a plating time of 100 minutes, the rod was chromium-plated to form a hard chromium plating layer having a thickness of 35 μm.

The obtained hard chrome plated product was heated at a temperature of 18
After baking at 0 ° C. for 5 hours and slowly cooling, it was subjected to a resin impregnation step. In the resin impregnating step, a thermosetting acrylic resin impregnating agent (DIAKITE, manufactured by Diafloc Co., Ltd.)
PF-1900) and curing agent (Diafloc Co., Ltd.)
And A-1).

That is, the inside of the vacuum vessel containing the hard chromium-plated rod is pumped at 10 Torr at 5 Torr by a vacuum pump.
Degas for 1 minute, send the impregnating liquid into the container,
After impregnation for 0 minutes in a vacuum, it was opened under atmospheric pressure. Then, the inside of the container is pressurized, and the pressure is 5 kg / cm ² for 10 minutes.
After pressure impregnation for 1 minute, the rod was taken out, the excess impregnating liquid was drained, and the resin was cured by heating in a drying oven at 150 ° C. for 30 minutes to obtain a hard chrome plated rod impregnated with the resin.

After the rod was gradually cooled, it was subjected to a finishing buffing step to produce a hard chromium-plated piston rod. The finishing buff was performed in the order of # 800 ring buff and sisal buff. Due to the buffing, the thickness of the hard chromium plating layer became 30 μm.

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

The obtained hard chrome plated product was heated at 180 ° C.
And then subjected to a baking treatment for 5 hours and a resin impregnation treatment similar to that in Example 1. The excess impregnating liquid was drained off, put 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 the rod was gradually cooled, it was subjected to a finishing buffing step in the same manner as in Example 1 to form a hard chromium plating layer having a thickness of 15 μm.

Next, the hard chromium plated rod is subjected to the same chromium plating step as above to form a 20 μm thick hard chromium plating layer (total thickness 35 μm) on the plating layer. The piston rod was subjected to a time baking step, a resin impregnating step, and a finishing buffing step to obtain a 30 mm thick hard chromium plating layer formed on the piston rod.

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 190 ° C.

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

Comparative Example 2 A piston rod having a 30 μm-thick hard chromium plating layer 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 chromium plating layer having a thickness of 30 μm was obtained in the same manner as in Example 1 without performing the baking treatment and the 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 mm (the entire length of the rod is 590 m)
m, and a shaft length of 120 mm), and a hard chromium plating layer having a thickness of 30 μm was formed in the same manner as in Example 1.

Next, a coil (inner diameter 86 mm, width 20
mm), the rod was arranged in a hollow portion, and high-frequency heating 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 speed of 2.8 m / min. The surface temperature of the piston rod measured under the above conditions was 220 ° C.

The piston rod subjected to the heat treatment was used in Example 1.
Subjected to the resin impregnation step in the same manner as described above, after impregnating the resin,
Used for final buffing, hard chrome plating layer thickness 27
A μm cylinder rod was prepared.

Example 6 Using the coil of Example 5, high-frequency heating conditions were
0V, high frequency generator output 80kw, frequency 6.0kHz
A cylinder rod was produced in the same manner as in Example 5, except that z and the feed speed of the coil were 3.3 m / min. In addition,
The surface temperature of the piston rod when subjected to the high-frequency heating under the above conditions was 500 ° C.

Then, 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 lapse of the spraying time. Was evaluated using 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 performed at 50 ° C. Table 1 shows the results.

In the corrosion test, although the degree of corrosion was small, rust flowed from the corroded portion and apparently,
The degree of corrosion may be overestimated. for that reason,
In the table, the result of the test time of 48 hours indicates the degree of corrosion of the piston rod itself subjected to the test, and also the degree of corrosion after wiping and cleaning the rod surface.

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 numerical value, the higher the corrosion resistance.

Total corrosion area (%) Rating number 0 100 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 0.507 7 0.50 to 1.00 6 1.00 to 2.50 5 2.50 to 5.00 4 5.00 to 10.0 310 0.0-25.0 2 25.0-50.0 1

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[Table 1] As shown in Table 1, the corrosion resistance of the piston rod of each example is significantly higher than that of the rod of the comparative example which was not subjected to the heat treatment or the resin impregnation treatment. In addition, the combination of the heat treatment and the resin impregnation greatly improves the corrosion resistance of the piston rod. In particular, when the plating process, the heating process, and the resin impregnation process are performed a plurality of times, the corrosion resistance of the piston rod is significantly improved.

Comparative Example 4 Stainless steel having an outer diameter of 40 mmφ (SUS304)
Chromium plating was carried out in the same manner as in Example 1 except that the plating time was lengthened using a rod made of stainless steel to form a hard chromium plating layer having a thickness of 50 μm.

Comparative Example 5 A hard chromium was formed 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 plating layer thickness of 25 μm was obtained.

Example 7 A hard chromium plating layer having a thickness of 30 μm was formed on a low carbon steel (S43C) rod having an outer diameter of 40 mmφ, and heat treatment was performed at 250 ° C. for 4 hours and 30 minutes.
A piston rod having a hard chrome plating layer thickness of 25 μm was obtained.

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

Example 9 A 30 μm-thick hard chromium plating layer 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 30 mm thick piston rod having a hard chromium plating layer 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
A / dm ² was chromium plated to form a 30 μm thick hard chrome plating layer.

The obtained hard chrome plated product was heated at 200 ° C.
And a baking treatment for 4 hours and 30 minutes and a resin impregnation treatment similar to that in Example 1.
In a drying oven at 150 ° C for 30 minutes.
The resin was cured by heating for a minute to obtain a hard chromium-plated rod impregnated with the resin.

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

Next, the hard chromium-plated rod is subjected to the same chromium plating step as above to form a 30 μm-thick hard chromium plating layer (total thickness 50 μm) on the plating layer. (4 hours and 30 minutes at 200 ° C.), a resin impregnating step and a finishing buffing step to obtain a piston rod having a 35 μm thick hard chromium plating layer formed thereon.

Example 11 4 hours at 250 ° C. in two baking treatment 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 chromium plating layer having a thickness of 15 μm was formed in each chromium plating step and baked 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 corrosion defects (corrosion resistance) of the rods at 96 hours and 480 hours was determined. The rating was evaluated using a standard chart of rating numbers. Further, it was subjected to a neutral salt spray test method (concentration of sodium chloride at the time of preparation of 40 g / L, pH 6.5 to 7.2) specified in JIS H8502, and the corrosion defect (corrosion resistance) at a salt spray time of 1200 hours was measured. The degree was evaluated by a rating number standard chart. Further, for reference, the corrosion resistance of a piston rod obtained in the same manner as in Comparative Example 3 was also examined. Table 2 shows the results
Shown in

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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C25D 5/00-5/56 C23C 26/00

Claims (9)

(57) [Claims] 1. A hard chromium plating of a corrosive iron-based substrate,
After a heat treatment at a temperature of 150 ° C. or more, a thermosetting acrylic resin or a sealing agent is impregnated, and the impregnated resin or the sealing agent is
A method of manufacturing a corrosion-resistant member that is cured and buffed. 2. The method according to claim 1, wherein the cylindrical rod is hard chromium plated.
A plating step of forming a hard chromium plating layer 0～100Myuemu, the heat treatment step of heat-treating at one hundred seventy to six hundred ° C., a step of impregnating a tree butter or sealant at least vacuo impregnated resin or sealing The method for producing a corrosion-resistant member according to claim 1, comprising a curing step of curing the stopper and a finishing step of buffing. 3. The method according to claim 1, wherein the iron-based substrate is a cylinder rod. 4. The method 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 producing a corrosion-resistant member according to claim 1, wherein a thermosetting acrylic resin or a sealant of ps is used. 6. The method according to claim 1, wherein the impregnation is performed under a reduced pressure of 0.1 to 100 Torr. 7. The method according to claim 2, wherein a hard chromium plating layer having a thickness of 5 to 95 μm is formed by buffing. 8. A hard chromium-plated iron-based substrate,
A plating step of forming a hard chromium plating layer of 60 μm, a heat treatment step of heat treatment at 180 to 300 ° C.,
Under reduced pressure of 1 to 50 Torr, viscosity at 25 ° C is 1 to 15
Manufacture of a corrosive iron-based substrate composed of an impregnation step of impregnating a thermosetting acrylic resin or a sealing agent of cps, a curing step of curing the impregnated resin or the sealing agent, and a finishing step of buffing Method. 9. corrosive iron cylindrical rod and hard chrome plating, the plating rods were heat-treated at a temperature 0.99 ° C. or higher, is impregnated with a thermosetting acrylic resin or sealant to heat-treated rods, impregnated Cured resin or sealant
This is a corrosion-resistant iron-based member obtained by buffing a rod that has been subjected to a buffing process. When a cas test specified in JIS H8502 is performed for 96 hours, a rating number of 9.0 to 10.0 and JIS H8502 is satisfied. A corrosion-resistant iron-based member having a rating number of 9.8 to 10.0 when subjected to a prescribed salt spray test for 1200 hours.