JP2015004370A - Fastening part with coat and process for manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fastening part in which a fastening work can be carried out within a short time and loosening after a fastening work can be effectively prevented.SOLUTION: A fastening part with coat is made such that a surface of an apex and trough part of a thread has a film of carbon fine particles peeled during a fastening process. This fastening part with coat can be realized by preparing solution including surface active agent, dispersing the carbon fine particles with the longest size being 5 μm or less in the solution under a single dispersion state, bringing solution having carbon fine particles dispersed into contact with the surfaces of an apex and trough part of a thread of the fastening part to form the coat including carbon fine particles, drying the fastening part, removing solvent in the solution and adhering the carbon fine particles to the surfaces of an apex and trough part of a thread.

Description

  The present invention relates to a fastening part such as a screw, a bolt, and a nut, and more particularly to a fastening part having a coating on the surface of a crest and trough of a screw.

  A fastening part having a coating on a thread valley is disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-291280 (Patent Document 1). This publication describes a coating that has excellent long-term corrosion resistance, excellent mechanical properties (particularly Knoop hardness, bendability, impact resistance, and coating failure), and excellent damage resistance against sliding on fastening parts such as bolts and nuts. Is disclosed.

  The coating disclosed in the above publication includes a synthetic resin binder such as phenol resin or polyamideimide, multilayer carbon nanofibers surface-treated with a non-conductive substance, and a dispersion medium.

JP 2007-291280 A

  In the industry, usually, an automatic fastening machine is used to fasten fastening parts such as screws and bolts. From the viewpoint of work efficiency, it is desirable to tighten screws and bolts in a short time. Particularly, in the case of a long screw or a long bolt having a length of about 50 to 100 mm used for a structure or a building, the fastening time greatly affects the productivity and the construction cost.

  In order to shorten the fastening time, it is conceivable to reduce the friction coefficient of the coating formed on the surface of the crests and valleys of the screw of the fastening part. However, if the coefficient of friction of the coating that is firmly adhered to the surface of the crests and valleys of the screw is reduced, the fastening parts may loosen when the structure or the building vibrates or receives an impact after fastening.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a coated fastening part that can shorten the fastening time and does not cause loosening after fastening. It is.

  The fastening component with a coating according to the present invention is characterized in that it has a carbon fine particle coating that is peeled off during the fastening process on the surface of the crest and trough of the screw. The fastening parts include not only screws and bolts having male threads but also nuts having female threads.

  The carbon fine particles forming the film preferably have a longest dimension of 5 μm or less. In the case of particulate carbon fine particles, the longest dimension is the maximum particle diameter portion, and in the case of linear carbon fine particles, the longest dimension is the maximum length portion.

  Preferably, the carbon fine particles are a minute carbon-based material selected from the group consisting of carbon black, ketjen black, carbon nanotubes, graphene, carbon nanofibers and fullerenes.

The manufacturing method of the fastening component with a film according to this invention comprises the following steps.
(A) A step of preparing a solution containing a surfactant.
(B) A step of dispersing carbon fine particles having a longest dimension of 5 μm or less in a monodispersed state in the solution.
(C) A step of bringing the solution in which the carbon fine particles are dispersed into contact with the surfaces of the crests and valleys of the screw of the fastening part to form a film containing the carbon fine particles.
(D) A step of drying the above-mentioned fastening parts to remove the solvent of the solution, and attaching carbon fine particles to the surface of the crests and valleys of the screw.

  Preferably, the carbon fine particle is a fine carbon-based material selected from the group consisting of carbon black, ketjen black, carbon nanotube, graphene, carbon nanofiber, and fullerene.

  Preferably, the drying process of the fastening part is performed within a temperature range of 80 ° C to 350 ° C. Further, the concentration of the carbon fine particles dispersed in the solution is preferably 0.05% or more.

  According to the above-mentioned fastening part with a film, since the carbon fine particle film reduces the friction coefficient in the fastening process, the fastening work can be performed in a short time with a relatively small fastening torque. Since the adhesion strength of the carbon fine particle coating to the surface of the thread valley portion is not high, the carbon fine particle coating is peeled off during the fastening process. Therefore, since the coefficient of friction is large in the loosening direction, loosening after fastening can be effectively prevented.

It is the photograph which shows the screw | thread which has not formed the film, and the screw which formed the ketjen black particle film side by side. It is a figure which shows the measurement condition of a fastening torque and a loosening torque. It is a figure which shows the relationship between a ketjen black particle film, a fastening torque, and fastening completion time. It is a figure which shows the relationship between a ketjen black particle film and a loosening torque. It is a figure which shows the relationship between the density | concentration of the ketjen black particle | grains in a solution, and a fastening torque.

  A feature of the embodiment of the present invention is that the fastening torque, such as screws, bolts, and nuts, can be reduced by tightening torque so that the fastening operation can be performed in a short time, and the coating prevents loosening after fastening. It is in having formed. The fastening part before the formation of the film may be one in which the metal or alloy is exposed on the surface of the crest and trough of the screw, or the surface of the crest or trough of the screw may be subjected to a corrosion-resistant coating or the like. Good.

  Specifically, the carbon fine particle film is formed almost uniformly on the surface of the crests and valleys of the fastening parts such as screws, bolts, and nuts. Since the carbon fine particle film functions to reduce the friction coefficient, the torque at the time of tightening is reduced, and the fastening operation can be performed in a short time.

  The carbon fine particles forming the above-mentioned film preferably have a longest dimension of 5 μm or less. In the case of particulate carbon fine particles, the longest dimension is the maximum particle diameter portion, and in the case of linear carbon fine particles, the longest dimension is the maximum length portion. Preferably, the carbon fine particle is a minute carbon-based material selected from the group consisting of carbon black, carbon nanotube, graphene, carbon nanofiber, and fullerene. Ketjen black, which is a kind of carbon black, is also a suitable carbon fine particle. In view of economy (cost), it is more preferable to use carbon black including ketjen black.

  An important feature is that the film is formed so that the adhesion strength of the carbon fine particle film to the surface of the crests and valleys of the screw is not so high without strongly baking the material surface of the fastening part and the carbon fine particle film. Therefore, a part or all of the carbon fine particle film is peeled off from the surface of the crests and valleys of the screw due to friction in the tightening process, that is, the tightening process. Part of the carbon fine particle film that has been peeled off functions as a resistor to prevent loosening of the screw after fastening, and the material surface of the fastening part exposed by peeling off the film exhibits a large coefficient of friction. The loosening of parts can be effectively prevented.

  The inventor of the present invention has examined the effect of the above-described film formation for long screws made of carbon steel, stainless steel, and titanium alloy materials.

  The coated fastening part that exhibits the above characteristics is manufactured through the following steps.

(A) Step of preparing a solution containing a surfactant As the surfactant, an amphoteric surfactant having hydrophilicity and hydrophobicity as disclosed in the republished patent publication WO2009 / 054309, or a neutral surfactant Alternatively, an alkaline surfactant or the like can be used.

(B) Step of dispersing carbon fine particles having a longest dimension of 5 μm or less in the above solution in a monodispersed state “Monodispersed state” means that carbon fine particles are not partially or totally entangled and aggregated. This means that the carbon fine particles are dispersed in a single state. In this case, the carbon fine particles dispersed in a single state may form a network, but this network state is also included in the “monodispersed state”. The concentration of the carbon fine particles dispersed in the solution is preferably 0.05% or more. The reason why the lower limit value of the concentration is set to “0.05%” is that the effect of reducing the tightening torque of the coating becomes remarkable from 0.05% or more. From the economical viewpoint, it is preferable to set the upper limit value of the concentration to “5%”.

(C) A step of bringing the solution in which the carbon fine particles are dispersed into contact with the surface of the crests and threads of the fastening parts to form a coating film containing the carbon fine particles. It includes immersing in the dispersion solution and spraying the carbon fine particle dispersion solution on the surface of the crests and valleys of the fastening part.

(D) A process of drying the above-mentioned fastening part to remove the solvent of the solution, and attaching carbon fine particles to the surface of the crests and valleys of the screw. It is necessary not to be baked, but to have an adhesion strength that allows a part or the whole to be peeled off during the fastening operation. In other words, it may be a drying treatment temperature at which the solvent is scattered and removed. A preferable drying treatment temperature is in the range of 80 ° C to 350 ° C. If it is an alcohol solvent, it may be about 80 ° C, and if it is a water solvent, it may be about 100 ° C.

  The actual experiments and evaluations are described below.

[Formation of carbon fine particle film]
As carbon fine particles, inexpensive ketjen black particles (average particle size: 38 nanometers), which is a kind of carbon black, were prepared. The ketjen black particles were put into an aqueous solution containing a surfactant and dispersed uniformly in a monodispersed state in the aqueous solution using an ultrasonic stirrer. The ketjen black particle dispersion solution was a black solution such as black ink, and no aggregates of ketjen black particles were observed.

  Regarding the concentration of ketjen black particles in the solution, 0.2% and 2% were prepared.

  A plurality of the same SCM435 alloy steel screws were prepared, and the following were prepared as samples.

  Sample 1: An untreated screw on which no film was formed.

  Sample 2: 0.2% ketjen black particles that were dipped in a ketjen black particle dispersion solution of 0.2% concentration and then pulled up and then dried in an air atmosphere at 100 ° C. using an electric furnace Coated screw.

  Sample 3: A 2% ketjen black particle-coated screw that was dipped in a 2% ketjen black particle dispersion solution and pulled up and then dried in an air atmosphere at 100 ° C. using an electric furnace.

  FIG. 1A shows the untreated screw of sample 1, and FIG. 1B shows the 2% ketjen black particle-coated screw of sample 3. As shown in the photograph of (b), the ketjen black particles after drying uniformly coat the surface of the crests and valleys of the screw with good adhesion.

[Evaluation of tightening torque, loosening torque and fastening completion time]
FIG. 2 shows a measurement situation of the tightening torque and the loosening torque. With respect to the tightening torque, the torque when tightening a screw with respect to a C-type steel plate having a thickness of 1.6 mm (with a prepared hole φ2.6 mm drilled hole) was measured. Specifically, a member (C-type steel plate) was fixed, a torque analyzer was used to measure a torque transition until the sample was idle or a continuous test was impossible, and an appropriate tightening torque was set from the measured value.

  With respect to the tightening time (tightening completion time), the time during which the sample was screwed into the member (φ2.6 mm pilot hole) was measured up to the proper tightening torque determined in the preliminary test. The measurement conditions of the torque analyzer were a rotation speed of 200 rpm and a load of 100N.

  Regarding the loosening torque, the torque when the screw screwed into the 1.6 mm thick C-type steel plate (with pilot hole φ2.6 mm drilled hole) was rotated in the loosening direction was measured. Specifically, a torque analyzer was used for the test specimen for which the tightening time had been measured, and the specimen tightened on the member was rotated in the reverse direction (relaxation direction) to return about 10 mm, and the maximum torque at that time was measured. . The measurement conditions of the torque analyzer were a rotation speed of 50 rpm and a load of 100N.

  The evaluation items are tightening torque (N · m) shown in Table 1, fastening completion time (s) (tightening time) shown in Table 2, and loosening torque (N · m) shown in Table 3. The number of samples 1 (no coating), sample 2 (0.2% concentration coating), and sample 3 (2% concentration coating) is 10 respectively.

  From Table 1 showing the measurement results of the tightening torque, the tightening torque of the screw with 0.2% ketjen black particle coating is reduced by about 21% and the 2% ketjen black particle coating is based on the screw without coating. It can be seen that the tightening torque of the attached screw is reduced by about 30%.

  From Table 2, which shows the measurement results of the fastening time (fastening completion time), the fastening time of the 0.2% ketchen black particle coated screw is reduced by about 23%, based on the screw without the coating. It can be seen that the tightening time of the 2% ketjen black particle coated screw is reduced by about 34%.

  From Table 3 showing the measurement results of the loosening torque, the uncoated screw, the 0.2% ketjen black particle coated screw, and the 2% ketjen black particle coated screw have almost the same values. It can be seen that there is no significant difference between them.

  In Fig. 3, the horizontal axis represents the screw without coating, the screw with 0.2% concentration coating, the screw with 2% concentration coating, the tightening torque (N · m) on the left vertical axis, and the tightening time on the right vertical axis It is the figure which took (s). “◯” indicates the average value of the tightening torque of each sample, and “Δ” indicates the average value of the tightening time of each sample. As shown in FIG. 3, it is recognized that the tightening torque and the tightening time are decreased by forming the ketjen black particle coating, and the decrease rate is larger as the concentration of the ketjen black particles is higher. Is recognized.

  FIG. 4 is a diagram in which the abscissa represents the uncoated screw, the 0.2% concentration coated screw, and the 2% concentration coated screw, and the left ordinate represents the loosening torque (N · m). “◇” indicates the average value of each sample. As shown in FIG. 4, it is recognized that the 0.2% concentration coated screw and the 2% concentration coated screw have a loosening torque equivalent to that of the coated non-screw.

  From Table 1 to Table 3, FIG. 3 and FIG. 4, it is recognized that the screw formed with the ketjen black particle coating of the predetermined concentration on the surface of the thread crest portion reduces the tightening torque and reduces the tightening time. On the other hand, it is recognized that the loosening torque is about the same as that of the film-free screw and can effectively prevent loosening after fastening.

[Relationship between ketjen black particle concentration and tightening torque]
The inventor of the present application investigated the relationship between the concentration of ketjen black particles dispersed in the solution and the tightening torque. The results are shown in Table 4 and FIG.

  As shown in Table 4 and FIG. 5, it is recognized that when the concentration of the ketjen black particles is 0.05% or more, the tightening torque of the screw with the ketjen black particles coating is rapidly reduced. Therefore, the concentration of ketjen black particles in the solution is preferably 0.05% or more.

  The present invention has been described based on the embodiments (examples). However, the present invention is not limited to the described embodiments, and various modifications and variations can be made within the same or equivalent scope as the invention. Can be added. For example, other carbon blacks, carbon nanotubes, graphene, carbon nanofibers, fullerenes and the like can be used instead of ketjen black as the fine carbon-based material constituting the carbon fine particles.

  The present invention can be advantageously used as a fastening part that can perform fastening work in a short time and can effectively prevent loosening after fastening.

Claims (9)

A fastening part with a coating, which has a carbon fine particle coating that peels off during the fastening process on the surface of the thread valley. The coated part according to claim 1, wherein the carbon fine particles have a longest dimension of 5 μm or less. The said carbon microparticle is a fastening component with a film | membrane of Claim 2 which is a micro carbon type material selected from the group which consists of carbon black, Ketjen black, a carbon nanotube, a graphene, a carbon nanofiber, and fullerene. The said fastening component is a fastening component with a film in any one of Claims 1-3 which has an external thread. The said fastening component is a fastening component with a film | membrane in any one of Claims 1-3 which has an internal thread. Preparing a solution containing a surfactant;
A step of dispersing carbon fine particles having a longest dimension of 5 μm or less in a monodispersed state in the solution;
A step of bringing the solution in which the carbon fine particles are dispersed into contact with the surface of the crests and threads of the fastening part to form a film containing the carbon fine particles;
Drying the fastening part to remove the solvent of the solution, and attaching the carbon fine particles to the surface of the crest and trough of the screw. The method for producing a coated fastening part according to claim 6, wherein the carbon fine particle is a minute carbon-based material selected from the group consisting of carbon black, ketjen black, carbon nanotube, graphene, carbon nanofiber, and fullerene. The manufacturing method of the fastening components with a film of Claim 6 or 7 which performs the drying process of the said fastening components within the temperature range of 80 to 350 degreeC. The method for manufacturing a coated fastening part according to any one of claims 6 to 8, wherein the concentration of the carbon fine particles dispersed in the solution is 0.05% or more.