JP3220227B2 - Cylinder rod and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to construction machines, industrial machines,
The present invention relates to a cylinder rod used for an industrial vehicle and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, cylinder rods such as piston rods have been 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. In particular,
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.

On the other hand, in industrial machines and construction machines,
There has been proposed a method of forming a predetermined pattern on a rod in order to detect the position of the rod moving forward and backward by a cylinder. For example, Japanese Unexamined Patent Publication (Kokai) No. 61-136696 discloses that in order to prevent the rod base material from being eroded, a coating layer of a synthetic resin or the like is formed on the entire surface of the rod, and a method of plating such as copper or aluminum is used. A method is disclosed in which a conductive layer is formed on the coating material, the conductive layer is removed by etching or the like to form a predetermined pattern, and a coating for surface finishing, for example, chrome plating is applied to the entire surface.

However, in the rod obtained by this method, the corrosion resistance of the chrome plating layer for surface finishing is low as described above. Therefore, the conductive layer is corroded through the chromium plating layer, the adhesion of the chromium plating layer is reduced, swelling or the like is generated, and the surface smoothness is easily reduced. Then, due to the sliding contact with the cylinder, the conductive layer formed in the predetermined pattern and the underlying coating layer are damaged, and the entire rod is corroded early.

Accordingly, an object of the present invention is to provide a hard chromium plating layer having excellent corrosion resistance even when the thickness thereof is small.
An object of the present invention is to provide a cylinder rod capable of detecting the position of a rod that moves forward and backward with respect to a cylinder.

Another object of the present invention is to provide a method capable of economically and efficiently producing a rod having the above excellent characteristics.

[0011]

The present inventors have conducted intensive studies in order to achieve the above object, and as a result, have found that when a hard chromium plating is applied and then heat treatment is performed, the corrosion resistance is remarkably improved, and the present invention has been completed. .

That is, the present invention relates to an axial direction of an iron-based rod.
To form multiple recesses and apply hard chrome plating
There is a hard area by masking the rod area except the recess.
A first plating step of applying chrome plating and the mask
Removal step and second plating for hard chrome plating
After the step and the second plating step, at least heating is performed.
And a heating step .

[0013] The present invention also relates to an iron rod in the axial direction.
This method is to form a number of recesses and apply hard chrome plating.
Masking the area of the rod except the recess
A first plating step of plating, and removing the mask
And a second plating step of applying hard chrome plating
After this second plating step, at least heating
Improve corrosion resistance of cylinder rod including heat process
Provide a way .

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as necessary.

FIG. 1 is a schematic perspective view showing an example of the cylinder rod of the present invention.

In this example, the cylinder rod 1 is
A cylindrical iron-based rod, a plurality of grooves 2 extending in the axial direction of the rod in a circumferential direction at a predetermined pitch, and a hard chromium plating layer 3 applied to the surface of the rod including the grooves 2 It is composed of The groove 2 is buried with the hard chromium plating layer 3 and the surface of the rod is covered with a hard chrome plating layer 3 having a smooth surface.

The groove 2 covered with the hard chromium plating layer 3 is not visible. A shaft 4 extends from the end surface of the rod.

In such a cylinder rod 1,
The positions of the plurality of grooves 2 formed in the circumferential direction can be detected by a position detection sensor, for example, a sensor such as an electromagnetic position detection sensor that detects a change in magnetic resistance or a potentiometer that detects a capacitance. A preferred position detection sensor is an electromagnetic position detection sensor that can detect the thickness (depth) and width of the groove 2 by magnetic means. This electromagnetic position detection sensor detects the position of the groove 2 by utilizing the fact that an eddy current flows corresponding to the groove 3. Therefore, when the rod 1 is used as a piston rod of a cylinder, the degree of advance / retreat of the piston rod 1 can be detected by counting the detection signal of the eddy current generated in response to the advance / retreat of the piston rod 1 with respect to the cylinder.

The rod is made of an iron-based material, for example,
Low carbon steel, high carbon steel, hardened steel, high speed steel, chrome steel,
Nickel steel, nickel chrome steel, nickel chrome
It can be formed of various materials such as molybdenum steel, stainless steel, and tungsten steel.

The pitch of the grooves can be selected within a range where the accuracy of detecting the position of the grooves 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 is not limited to the groove, but various position detecting concave parts, for example, concave parts scattered in the axial direction of the rod,
Preferably, the recesses may be formed at every predetermined pitch. The position detecting recess may be spot-shaped, but 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. Further, the groove may include a reference groove serving as a reference marker.

FIG. 2 is a schematic perspective view showing another example of the cylinder rod of the present invention. In this example, a cylinder rod in which both the position detecting concave portion and the reference concave portion are grooves is shown.

The cylinder rod 11 has a plurality of position detecting grooves 12 extending in the circumferential direction at a predetermined pitch in the axial direction of the cylindrical iron-based rod, and has a circumferentially larger pitch than the pitch of these grooves 12. It comprises a reference groove 13 formed and a hard chromium plating layer 14 provided on the surface of the rod including these grooves 12 and 13. The groove 1
2, 13 are the hard chromium plating layers 1 as described above.
4, and the surface of the rod is covered with a hard chrome plating layer 14 having a smooth surface.

In such a rod 11, the reference groove 1
3 can be used as a reference marker. That is, the detection signal from the position detection sensor that detects the reference groove 13 is used as a reference signal, and the rod 11 can be moved forward or backward from the cylinder based on the reference signal.

More specifically, when the rod 11 is advanced or retracted again from the cylinder after the rod 11 advances from the cylinder by a predetermined distance, the rod as shown in FIG. It is necessary to move the rod forward or backward while counting the detection signal based on the eddy current after returning to the above state.

On the other hand, when the rod 11 in which the reference groove 13 is formed is used, a detection signal of the eddy current generated in the reference groove 13 can be used as a reference signal, so that a stroke for returning the rod 11 to the reference position can be reduced. In addition to counting the eddy current detection signal generated in the position detection groove 12 with reference to the reference signal, the rod 11
Can be moved forward or backward by a predetermined stroke.

The reference groove is not limited to a 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.

The reference concave portion may be formed independently of the position detecting concave portion. In this case, the depth and / or width of the reference concave portion may be different from that of the position detecting concave portion. It can also be formed between recesses. Further, the reference concave portion can also be used as the position detecting concave portion. That is, for example, a concave portion in which the depth and / or width of the position detecting concave portion located at predetermined intervals is different from the other position detecting concave portions may be set as the reference concave portion. For a rod having a different depth and / or width of the reference recess, the detection signal based on the depth and / or width is different from the detection signal based on the recess for position detection, so the detection signal based on the depth and / or width can be used as the reference signal. ,
The advance / retreat degree of the rod can be controlled more precisely.

The reference recess having a depth different from that of the position detection recess can be detected by the strength of the detection signal from the position detection sensor. It can be detected by converting it into a digital signal by a converter and applying it to a differentiating circuit or an integrating circuit.

The thickness of the hard chromium plating layer from the surface of the iron-based rod can be selected within a range that does not impair the corrosion resistance, and is, for example, about 5 to 100 μm, preferably about 10 to 80 μm, and more preferably about 20 to 75 μm. is there. A particularly preferred thickness of the hard chromium plating layer is about 20 to 50 μm. Further, the thickness of the hard chrome plating layer from the concave portion can be selected according to the depth of the concave portion.
m, preferably about 25 to 125 μm. Even with such a small film thickness, the corrosion resistance can be increased by the heat treatment. Preferred cylinder rods are heat treated and buffed.

In the present invention, there is no need to apply a resin coating to the entire surface of the rod, nor to form a conductive layer, as in the above-mentioned prior art document. With this configuration, the position of the rod can be accurately detected. In particular, even when used as a cylinder piston rod of a construction machine or the like used under severe conditions, the corrosion resistance is remarkably excellent despite the thin hard chrome plating layer.

The manufacturing method according to the present invention includes a recess forming step of forming a plurality of recesses in the axial direction of the iron-based rod, and a first plating step of performing hard chrome plating by masking a region of the rod excluding the recesses. Removing the mask, a second plating step of applying hard chrome plating, and a heating step of heating at least after the second plating step.

Prior to the recess forming step, the iron-based rod 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, prior to the recess forming step, the iron-based rod may be subjected to a polishing step. The rod is polished by a conventional method, for example, cylindrical polishing (ring buff) having a large polishing power, vertical polishing, etc .; rough polishing such as emery buff polishing, belt polishing, flap wheel polishing;
Cotton buffs, sisal buffs, medium polishing or finish polishing combining these 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.

3 to 6 are views for explaining the manufacturing method of the present invention. In this example, FIG. 3 is a sectional view showing a recess forming step, and FIG. 4 is a sectional view showing a first chromium plating step. FIG. 5 and FIG. 5 are sectional views showing a removing step of removing the mask, and FIG. 6 is a sectional view showing a second chromium plating step. In this example, the grooves are formed in the recess forming step.

In the recess forming step, a resist 22 is formed on the surface of the iron-based rod 21 by a screen printing method, a photoresist method, a tape masking method or the like, leaving a portion corresponding to the recess, and thereafter, etching is performed. Thereby, the groove 23 can be formed. In this case, materials having etching resistance and chromium plating resistance can be used for the ink in the screen printing method, the photoresist in the photoresist method, and the masking tape in the tape masking method, respectively.

In the screen printing method, a plating resist and / or an etching resist can be used as the ink, and these resists may be a thermosetting resin, an ultraviolet curable resin, or the like. In the screen printing method, a groove may be formed by printing a predetermined pattern on the surface of the rod, curing the resist by a curing means corresponding to the type of the resist, and then etching.

In the photoresist method, a photoresist is applied to at least a predetermined surface of the iron-based rod, and dried if necessary. The photoresist may be applied to the entire surface of the iron-based rod. Thereafter, the rod surface is exposed to light with a predetermined pattern original, exposed by development, the resist corresponding to the groove portion is removed, and the groove is formed by the same etching as described above. The photoresist may be either a negative type or a positive type. For the development, a conventional developer, for example, an organic solvent, an aqueous alkaline solution, or the like can be used.

Furthermore, the surface of the iron-based rod may be tape-masked, leaving a portion corresponding to the groove, and the groove may be formed by etching.

The etching can be performed by a conventional method, for example, using an etching solution such as an acid such as hydrochloric acid, sulfuric acid or nitric acid, or an aqueous solution of ferric chloride. Further, the grooves may be formed by dry etching. After the etching step, the etched iron-based rod is usually subjected to cleaning, neutralization, and drying steps.

The grooves are formed without being etched.
It may be formed by mechanical processing. In this case, the surface of the rod may be covered with a coating layer having etching resistance, and a groove reaching the substrate may be formed with an iron needle or the like.

A preferred groove processing step includes a step of applying a resist to an iron-based rod, a curing step of curing the resist, and an etching step. Through these steps, the grooves can be formed accurately and efficiently.

Prior to the first chromium plating step, the iron-based rod may be subjected to an anodic oxidation etching process to adjust the plating base. The etching treatment by anodic oxidation is performed, for example, using a rod as an anode at a temperature of 3.
About 0 to 60 ° C., current density about 10 to 50 A / dm ² ,
It can be performed by performing an electrolytic treatment under the conditions of a time of about 10 to 600 seconds. 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.

In the first chromium plating step, chromium plating is performed on the iron-based rod 21 with the resist 22 remaining. This chrome plating allows the resist 22
The chrome-plated portion 24 is efficiently formed in the groove 23 in the portion where the metal is adhered.

In the first chrome plating step, the grooves 23
The area of the iron rod 21 except for the above may be masked and plated with chrome. For example, when the groove is formed by mechanical processing, the area excluding the groove 23 may be covered by tape masking and plated with chrome.

Although the thickness of the chrome plated portion 24 may be smaller than the depth of the groove 23, it is generally substantially the same as the depth of the groove 23 or bulges out of the groove 23.

The composition of the chromium plating bath is not particularly limited.
Conventional plating baths 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 of 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 1.0 to 1.5 g / L, preferably 1.02 to 1.3 g / L, and more preferably 1.05 to 1.3 g / L.
About 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,
The uniformity of the plating layer tends to decrease.

The plating bath may be a high-concentration bath, a standard bath, or 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 in order to make the plated portion uniform.

The plating conditions can be selected according to the composition of the bath and the like. Usually, the plating temperature is 20 to 70 ° C., preferably 40 ° 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.

In the removing step of removing the resist 22 as a mask, the resist 22 can be removed by a mechanical method such as polishing or a chemical method of stripping the resist 22 using an acid or an alkali. A preferred removal method is a mechanical method, especially polishing. The primary plating product from which the resist 22 has been removed may be buffed. According to such a method, not only can the resist 22 be removed, but also the surfaces of the iron-based rod 21 and the chromium plating portion 24 can be smoothed, and the base for the second chromium plating can be adjusted.

After the removal step, it is preferable to adjust the base by etching. The etching can be performed using an etching solution, preferably an etching solution containing ferric chloride. The anodic oxidation etching process alone is not sufficient as a chrome plating base. That is, as shown in FIG. 5, the chromium plating portion 24 and the iron of the iron-based rod 21 coexist on the rod surface during this etching process. Therefore, when anodizing treatment is performed in this state using a chromium plating bath or a chromic acid aqueous solution as an electrolytic solution, the current is exclusively used for eluting the chromium 24, and the surface of the iron-based rod 21 is hardly etched.

On the other hand, a method of etching using an etching solution, particularly an aqueous solution of ferric chloride, is extremely effective. According to this method, the surface of the iron-based rod 21 can be efficiently etched even when the chromium plating portion 24 and the iron of the iron-based rod 21 coexist. Further, subsequently, by performing the etching treatment by the anodic oxidation, the surface of the chromium plating portion 24 is also etched, and the entire surface of the iron-based rod 21 can be cleaned and activated. Therefore, an extremely good surface can be formed as a base in the second chrome plating step.

The concentration of the aqueous solution containing ferric chloride is, for example, 10 to 600 g / L of ferric chloride, preferably 20 to 600 g / L.
It is about 100 g / L. The method for applying the etching solution may be any of a spray method, a dipping method, a brush coating method, a sponge brushing method, and the like. Etching is performed, for example, for 10 to 300 seconds, preferably 30 to 120 seconds.
Complete in about a second. After the completion of the etching, rinsing with water and, if necessary, drying, may be followed by anodizing. Note that when etching by anodic oxidation is performed after etching by the etchant, anodic oxidation may be performed for a short time.

In the second chrome plating step, chrome plating is performed in the same manner as in the first chrome plating step.
The surface of the iron-based rod 21 is covered with a hard chromium plating layer 25 together with the chrome plating portion 24 burying the groove 23. Since the groove 23 is double-plated by the second chrome plating, the rust prevention effect of the groove 23 which is easily corroded is remarkably increased.

In the second chromium plating step, the thickness of the hard chrome plating layer 25 from the surface of the iron-based rod 21 in the final product is 5 to 100 μm, preferably 10 to 80 μm, more preferably 20 to 100 μm as described above. ~ 75 μm
It is also important to perform chrome plating to a degree.
A particularly preferred thickness of the hard chromium plating layer in the final product is about 30 to 50 μm, and the plating layer having such a thickness can be formed, for example, in about 1 to 2 hours.

When the thickness of the hard chromium plating layer 25 is small, the corrosion resistance is apt to decrease. When the thickness is too large, not only is it not economical, but also the plating takes a long time and the productivity decreases.

Then, in the heating step, the plated material subjected to the chromium plating is subjected to a heat treatment. By this heat treatment, 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 type is not particularly limited. Preferred heat treatments include a baking treatment and a high-frequency heating treatment.

The heating temperature can be appropriately selected within a range in which the corrosion resistance can be improved, for example, 100 to 800 ° C., preferably 125 to 650 ° C., more preferably 150 to 600 ° C.
It is about. If the heating temperature is lower than 100 ° C., it takes a long time to enhance the corrosion resistance. If the heating temperature is higher than 800 ° C., the temperature becomes excessive, and the workability tends to be reduced.

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
It is preferable to select within the range of about 00 to 300 ° C, preferably about 125 to 250 ° C, and more preferably about 150 to 250 ° C. The baking time can be selected, for example, in the range of 30 minutes to 12 hours, preferably about 1 to 8 hours, depending on the baking temperature.

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, since the cylinder rod can be efficiently heat-treated within a short time, the productivity of the cylinder rod 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 100 to 800 ° C, preferably 125 to 600 ° C, and more preferably 150 to 600 ° C.
It can be appropriately selected within the range of the degree. In the case of high-frequency heating, it is difficult to directly measure the heating temperature,
The surface temperature of the cylinder rod can be 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 cylinder rod and the coil, and the like. Since these factors are related to each other, it is not possible to independently determine only one factor during the heat treatment.

Hereinafter, the outer diameter of the rod is 30 to 100 mmφ.
In the case of, an example of the high-frequency heating condition will be described more specifically. As the distance between the coil and the cylinder rod increases, the induced current decreases and the rise in surface temperature is suppressed, so the distance between the coil and the cylinder rod depends on the degree of heat treatment, for example, 10 to 50 mm,
Preferably, it can be selected in a range of about 15 to 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 heat treatment is performed by induction heating, the above conditions can be appropriately selected according to the size of the cylinder rod, the desired degree of heat treatment, and the like.

When the rod is made of hardened steel, the heat treatment is preferably performed at a temperature not exceeding the tempering temperature of the iron-based body. After the baking treatment, the plated product is usually gradually cooled.

The heating time 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.

After the heat treatment, the hard chromium plating layer of the plated product 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 an open sisal buff after performing a ring buff of about # 400 to 1000 and then performing a cotton buff or sisal buff with an abrasive of about # 240 to 600. When buffing is performed by such a method, a large polishing force acts on the ring buff, and not only the protrusions and the like of the plating layer are cut off by the cotton buff and the sisal buff, but also the plastic deformation is performed, and the plating layer is deformed. Since the openings such as cracks are closed and smoothed, the corrosion resistance is improved.

The thus obtained 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.
When the corrosion resistance is evaluated by the accelerated test, 10
The plated product may be heated to about 0 to 400 ° C. and subjected to the salt spray test, or a salt water having a high temperature may be sprayed.

Preferred embodiments of the present invention are as follows.

(1) A rod in which a heat-treated hard chrome plating is applied to an iron-based rod, and a plurality of grooves extending in a circumferential direction are formed in the axial direction of the rod, and these grooves are A cylinder rod embedded in a hard chromium plating layer and having the surface of the rod covered with a buffed hard chrome plating layer.

(2) A cylinder rod in which the thickness of the hard chromium plating layer from the iron-based rod is 5 to 100 μm.

(3) A method of forming a plurality of grooves extending in the circumferential direction in the axial direction of the iron-based rod and applying hard chrome plating, wherein hard chrome plating is performed by masking the rod area excluding the grooves. A method for manufacturing a cylinder rod, comprising: a first plating step to be performed; a step of removing the mask; an etching step of etching; a second plating step of performing hard chrome plating; a heating step; and a buffing step.

(4) In the second plating step, a hard chromium plating layer having a thickness of 10 to 150 μm from the surface of the iron-based rod is formed, and heat-treated. Hard chrome plating layer thickness 5-100
Manufacturing method of cylinder rod to be μm.

(5) Baking temperature is 100 to 300 ° C.
And a baking time of 30 minutes to 12 hours.

(6) A method of manufacturing a cylinder rod in which the surface of the cylinder rod is heated to 100 to 800 ° C. by high-frequency heating.

(7) A method for manufacturing a cylinder rod in which etching is performed using an aqueous solution of ferric chloride to adjust the plating base prior to the second plating step.

The present invention can be suitably applied to various cylinder rods, for example, cylinder rods for construction machines, especially piston rods.

[0084]

The cylinder rod of the present invention is excellent in corrosion resistance and capable of detecting the position of the rod moving forward and backward with respect to the cylinder even if the thickness of the hard chromium plating layer is small.

According to the production method of the present invention, a rod having the above-described excellent characteristics can be produced economically and with high productivity.

[0086]

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 75 mmφ was degreased, and a plating resist [DIC / UV-PR-H, manufactured by Dainippon Ink and Chemicals, Inc.] was silk screen printed. To form a groove pattern having a pitch of 100 mm and a width of 2 mm. The groove pattern includes a plurality of coated portions extending in the circumferential direction along the axial direction of the rod. After irradiating ultraviolet rays and curing the plating resist, both end surfaces of the rod are masked with tape,
An aqueous solution of ferric chloride (concentration 500 g / L) was sprayed for 20 minutes and etched. By this etching, a groove having a depth of about 100 μm was formed.

Next, the rod was washed with water, dried, and etched by a current density of 35 A / dm ² for 30 seconds by anodic oxidation using the following plating bath and the rod as an anode. Current density 35A / d
The groove of the rod was chrome-plated under the conditions of m ² and a plating time of 270 minutes.

Plating bath composition Chromic anhydride: 224 g / L Sulfuric acid: 2.5 g / L Trivalent chromium: 1.5 g / L The obtained primary plated product was polished with a grinder polishing machine.
After removing the resist film, buffing is performed with a cylindrical buff, and etching is performed for 3 minutes using an aqueous solution of ferric chloride (concentration: 50 g / L), washed with water, and dried to adjust the base of the primary plating product. did.

Then, hard chromium plating was performed under the same conditions as above except that the plating time was 90 minutes using the plating bath, and the thickness from the surface of the iron-based rod was 35 μm.
m hard chromium plating layer was formed.

The obtained secondary plating product was heated at 180 ° C. for 5 minutes.
After baking for an hour and gradually cooling, 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 # 1000 ring buff, # 320 cotton buff, # 400 cotton buff, and open sisal buff. Due to the buffing, the thickness of the hard chromium plating layer from the surface of the iron-based rod became 33 μm.

Example 2 A piston rod was produced in the same manner as in Example 1 except that the baking temperature was set to 160 ° C. and the thickness of the hard chrome plating layer from the surface of the iron-based rod by the final buffing was set to 50 μm. .

Example 3 A piston rod was produced in the same manner as in Example 1 except that the baking temperature was 230 ° C. and the thickness of the hard chrome plating layer from the surface of the iron-based rod was 25 μm by final buffing. .

Example 4 The composition of the plating bath was changed to 224 g / L of chromic anhydride, 2.3 g / L of sulfuric acid and 1.5 g / L of trivalent chromium.
A piston rod was produced in the same manner as in Example 1.

Example 5 Example 1 was repeated except that the # 600 ring buff was used instead of the # 1000 ring buff in the finishing buffing step.
A piston rod was produced in the same manner as described above.

Example 6 A piston rod was produced in the same manner as in Example 1 without subjecting the primary plated product to etching treatment with an aqueous solution of ferric chloride.

Comparative Example 1 The same procedure as in Example 1 was carried out without baking.
A piston rod was made.

Comparative Example 2 The composition of the plating bath was 224 g / L of chromic anhydride, 1.9 g / L of sulfuric acid, and 1.5 g / L of trivalent chromium. A piston rod was made.

The corrosion resistance of the piston rods obtained in each of the examples and comparative examples was evaluated by the following accelerated test method.

First, the piston rod 48 hours after the plating was heated to 400 ° C., cooled, and then subjected to JIS Z
It was subjected to a salt spray test according to 2371, and the degree of corrosion after 8 hours was evaluated according to the following criteria. The results are shown in the table.

Excellent: No occurrence of red rust Good: 5 to 10% red rust Acceptable: 10 to 20% red rust Impossible: 30% or more red rust

[0102]

[Table 1] From the table, the piston rods obtained in Examples 1 to 6 have significantly higher corrosion resistance than the piston rods obtained in Comparative Examples 1 and 2. The piston rods obtained in Examples 1 to 5 did not generate red rust even when subjected to a salt spray test for 100 hours. Further, the piston rod obtained in Example 6 showed a 5-1 to 1 in a 48-hour salt spray test.
0% red rust occurred.

Example 7 A rod made of low carbon steel (S43C) having an outer diameter of 65 mmφ (entire rod length 590 m) was used instead of the rod of Example 1.
m, a shaft length of 120 mm) and a hard chromium plating layer having a thickness of 30 μm from the surface of the iron-based rod 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 subjected to high-frequency heating at 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 180 ° C.

The piston rod subjected to the heat treatment was subjected to a final buffing to produce a cylinder rod having a thickness of 27 μm with a hard chromium plating layer from the surface of the iron-based rod.

Then, the corrosion resistance of the obtained piston rod was subjected to the following acceleration test. That is, the piston rod is heated at 175 ° C. for 90 minutes using a baking furnace, cooled, and then cooled at 50 ° C. according to JIS Z2371.
Was subjected to a salt spray test in which heated salt water was sprayed, and the degree of corrosion after 48 hours was evaluated according to the same criteria as described above.
As a result, generation of red rust was not recognized.

Example 8 Using the coil of Example 7, high-frequency heating was performed at a voltage of 46
0V, high frequency generator output 80kw, frequency 6.0kHz
A cylinder rod was produced in the same manner as in Example 7, except that z and the feed speed of the coil were 3.3 m / min.

The surface temperature of the piston rod when the high-frequency heat treatment was performed under the above conditions was measured.
It was 0 ° C.

Then, the obtained piston rod was subjected to the same accelerated test as in Example 7 and the corrosion resistance was evaluated. As a result, generation of red rust was not recognized.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an example of a cylinder rod of the present invention.

FIG. 2 is a schematic perspective view showing another example of the cylinder rod of the present invention.

FIG. 3 is a sectional view showing a recess forming step.

FIG. 4 is a sectional view showing a first chrome plating step.

FIG. 5 is a cross-sectional view showing a removing step of removing the mask.

FIG. 6 is a sectional view showing a second chromium plating step.

[Explanation of symbols]

 1,11 ... Cylinder rod 2,12 ... Groove 3,14 ... Chrome plating layer 13 ... Reference groove 21 ... Iron rod 22 ... Resist 23 ... Groove 24 ... Chrome plating part 25 ... Chrome plating layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-35202 (JP, A) JP-A-62-44603 (JP, A) JP-A-62-8010 (JP, A) 60853 (JP, A) JP-A 1-197055 (JP, A) JP-A 61-137001 (JP, A) JP-A 62-42003 (JP, A) JP-A 51-99557 (JP, A) JP-A-54-117335 (JP, A) JP-B-27-2960 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25D 7/00

Claims (7)

(57) [Claims] 1. A method of forming a plurality of recesses in an axial direction of an iron-based rod and performing hard chrome plating, wherein a first chrome plating step is performed by masking a region of the rod excluding the recesses and performing hard chrome plating. And a step of removing the mask, a second plating step of applying hard chromium plating, and a heating step of heating at least after the second plating step. 2. Prior to the second plating step, the manufacturing method according to claim 1, wherein the cylinder rod is etched by ferric chloride rods. 3. In the hard chromium plating step, sulfuric acid is added in an amount of 1.0 to 1.5 g / 100 g / L of chromic anhydride.
The process according to claim 1, wherein the cylinder rod using L containing plating bath. 4. The process for producing the cylinder rod of claim 1, wherein performing heating in baking or high-frequency heating. 5. The process for producing a cylinder rod of claim 1, wherein the heating temperature is 100 to 800 ° C.. 6. After heating, the production method according to claim 1, wherein the cylinder rod to buffing. 7. A plurality of recesses are formed in an axial direction of an iron rod.
And a method of applying hard chrome plating, wherein the recess is
Hard chrome plating with masking rod area except
A first plating step, a step of removing the mask,
A second plating step of applying high-quality chrome plating,
Including a heating step of heating at least after the plating step
A method for improving the corrosion resistance of cylinder rods.