JPH0314903A - Iron and steel bolt jointing - Google Patents

Abstract

PURPOSE:To form fine rust having high adhesion uniformly on the surface of an iron and steel material so as to improve friction coefficient by opposing jointed surface of the iron and steel material to be jointed to an electrode whose cloth material is impregnated with liquid such as chloride, acid for making electrolytic process. CONSTITUTION:A cotton cloth is impregnated with aqueous iron nitrate solution to cover an electrode, and is made to slide over an iron and steel joint surface to be jointed thereto and the positive pole of a d.c. power supply is connected to an iron and steel material for making electrolytic process. It is thus possible to form fine rusting high adhesion uniformly on an iron and steel surface, thus providing higher friction coefficient than a prescribed one.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in a friction welding method using high-strength steel bolts used for connecting steel members of bridges and steel frame buildings.

<Conventional technology> When constructing bridges, general steel structures, etc. on-site, with the recent trend of larger structures, the conventional gluing and welding methods require special attention, resulting in stress concentration. For important parts, high-tensile steel bolts are often used for joining, and the amount of bolts used is increasing.

This type of high-tensile-strength steel bolt joining method uses high-strength steel bolts to transfer stress at the yield point, whereas the conventional riveting method transmits joint stress by shearing the rivet. Since stress is transmitted by the frictional force generated by tightening the joints close to each other, the friction coefficient of the joint, which is an element of stress transmission, is an extremely important element. For this reason, when handling this type of bolted joint surface, the presence of mill scale, excessive red rust, or a coating of paint will greatly reduce the g-friction coefficient, which in turn may weaken the tightening strength. Since it is easy to loosen even after tightening, it requires periodic re-tightening, so it is usually treated with a grinder or by blasting. A commonly used method is to remove mill scale, red rust, paint film, etc. by blasting such as sandblasting.

However, a complete bare metal surface that has been subjected to grinder or blast treatment as described above has a lower coefficient of friction than a lightly rusted surface that is uniformly adhered to the entire surface, so it is usually exposed to the atmosphere after grinding or blasting. It is customary to leave it inside for a long time and wait for visible red rust to develop before tightening it.

On the other hand, the current situation in the industrial world is that the period from material production to tightening and assembly has been forced to be drastically shortened, and in some cases, grinding or blasting processing has traditionally been used. A method has been adopted to promote rusting by applying seawater or a solution of sodium chloride, ammonium chloride, etc. to the surface of the rust.
-175930, proposed a method of applying a solution of ferric chloride or ferric chloride mixed with nitric acid or iron nitrate and a surfactant, and the method has a friction coefficient higher than that specified by the Japan Society of Civil Engineers and the Architectural Institute of Japan. It has been implemented effectively because it provides the following benefits.

Problems to be Solved by the Invention However, the above-mentioned conventionally known methods have the following serious drawbacks. That is, in the conventional method, 11. (a) Because the method involves applying a rusting solution to the surface of the joint. There is no problem if the surface is in a horizontal position, but if the surface is vertical or sloped, the coating liquid will drip down and rust will often form on the lower part, but rust will not easily form on the upper part due to lack of liquid.

(B). Since oil and dirt adhere to the surfaces of joint parts due to bolt holes, etc., even if a temporary surfactant is added to the solution, wettability is actually poor, uneven coating occurs, and rust is unlikely to occur. There was a drawback that this occurred. In addition, in the conventional method, (2) the mechanism of rust formation is solely due to chemical reactions; Moreover, when working at high temperatures or outdoors, the coating solution may dry prematurely, impairing the rusting effect.

(mouth). Similarly, the level of atmospheric humidity has a large effect on rust formation.

(c). When the steel surfaces to be joined are placed in a horizontal state and in contact with objects or near the ground surface, rust tends to develop more easily on the upper surface, and there is a tendency for rust to develop on the lower surface.

(Atmospheric oxygen is indispensable for the reaction of cartilage formation, and it is thought that chain formation is delayed on the bottom surface where air circulation is poor, and that chain formation is accelerated on the top surface due to sufficient exposure to oxygen in the air.) ( two). Generally, the reaction rate of this kind of rusting caused by chemical reactions is slow, and it takes several hours to more than 10 hours for the rust to develop, resulting in inconveniences such as being forced to have time constraints when tightening bolts. <Means for Solving the Problems> The present invention is proposed in view of the drawbacks of the above-mentioned known methods. The steel material is connected to one pole of an AC power supply or the anode of a DC power supply, and the opposite pole connected to the other pole of each power supply is coated with a cloth-like substance made of natural or synthetic fiber, and this coating material is Iron chloride, sodium chloride. Chlorides such as ammonium chloride and potassium chloride, or iron nitrate. After being impregnated with an aqueous solution containing one or more of nitrates such as sodium nitrate, ammonium nitrate, and potassium nitrate, or one or more of hydrochloric acid, sulfuric acid, or nitric acid, the opposite electrodes are opposed and energized, and then the joining members are tightened with bolts. The bolt joint force method for steel materials is characterized by the following.

Effect> Generally, the rusting phenomenon of metals is promoted by surface activation. In the method of the present invention, an anodic dissolution effect is produced by direct current electrolysis or alternating current electrolysis using the material to be treated as an anode, rapidly activating the surface, and reducing oxidation by the oxygen generated during electrolysis. Because it has an extremely effective effect on rust formation, the phenomenon of rust formation is observed immediately after electrolytic treatment, and the formation of dense rust is observed over the entire surface.

The method of the present invention does not use an electrolytic bath and is manual, so it is possible to perform electrolysis regardless of whether the surface of the material to be treated is horizontal, vertical, or sloped, and it also eliminates uneven rust formation due to dripping. Even when the current is applied, wet areas will be chained extremely reliably and uniformly.

Furthermore, even if oil is attached to the material to be treated, the wettability of the electrolytic solution is improved by the electrolytic degreasing action, and rusting does not occur unevenly.

Furthermore, since the present invention is an electrochemical method, it is naturally unaffected by temperature and humidity, and can generate dense rust with good adhesion to the base material in an extremely short time (within 10 minutes at the latest). This makes it possible to perform bolting work on steel structural members at any time and place.

<Example> S541m whose surface was treated with a grinder to remove black skin
A plate (19 mm thick; splint plate 12 mm thick) was formed to the standard test piece dimensions specified by JIS, and each joint surface was anodic electrolyzed using direct current. Iron nitrate aqueous solution (10% by weight) is used as the electrolyte, and the counter electrode is made of SUS304 material.
This was fabricated, covered with real cotton cloth and impregnated with the above electrolyte solution, and electrolytically treated by applying electricity while sliding on each of the above bonded surfaces (slide slowly over the same area several times). The surface that had undergone electrolytic degreasing had good wettability with the electrolyte, and rust appeared uniformly over the entire surface. After the standard test pieces that had been subjected to these chain-starting processes were tightened to a predetermined torque value using high-strength steel bolts (FIOTIM20), tension was applied using a tensile tester, and the slip coefficient μ (friction coefficient) was calculated. 0.53, which fully satisfies the industry standard value.

In addition to direct current electrolysis, we also tried alternating current electrolysis and obtained almost the same results. Also, as an electrolyte. In addition to the above, chlorides such as iron chloride, sodium chloride, ammonium chloride, potassium chloride, nitrates such as iron nitrate, sodium nitrate, ammonium nitrate, potassium nitrate, and -14 or two or more of hydrochloric acid, nitric acid, and sulfuric acid are mixed. Almost the same results as above could be obtained with the aqueous solution.

<Effects of the Invention> In short, according to the method of the present invention, since an electrochemical method is used to deal with the damage caused by the bolting method on the joint surfaces of steel materials, it is not affected by seasonal or climate changes, and Regardless of the surface contamination or surface orientation of the treated material, extremely dense rust with good adhesion to the base material is generated evenly and in a very short time, meeting civil engineering and construction regulations. We succeeded in easily realizing a bolt joint surface that can obtain the above friction coefficient, and it is extremely useful in the construction of friction welding methods using high-tensile steel bolts.

Claims (1)

[Claims] 1. Connect the steel materials to one pole of an AC power source or the anode of a DC power source to the surface of the joint of steel materials to be joined by bolting method, and connect the opposite electrode to the other pole of each power source. A cloth-like substance made of natural or synthetic fibers is coated, and this coating material is coated with chlorides such as iron chloride, sodium chloride, ammonium chloride, potassium chloride, nitrates such as iron nitrate, sodium nitrate, ammonium nitrate, potassium nitrate, or hydrochloric acid. A bolt joint method for steel materials, characterized in that the joining members are bolted after being impregnated with an aqueous solution containing one or more of sulfuric acid or nitric acid, and then energized with opposing electrodes.