JPS5962710A - Joint of bolt - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] For construction on thick ground such as bridges and general steel structures.

As the recent trend has been for structures to become larger, the traditional gluing and welding methods require special care, so high-strength steel bolts are often used for joining in important areas where stress is concentrated. and its usage is on the rise.

This type of high-strength steel bolt connection method uses high-strength steel bolts to transfer stress at the joint by shearing the rivet, whereas the conventional glue-bet method uses high-strength steel bolts to transmit stress at the yield point. 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 paint film will greatly reduce the coefficient of friction, which in turn weakens the tightening strength. It also tends to loosen even after tightening, so it requires periodic re-tightening.

Generally, a method is employed in which mill scale, rubble, paint film, etc. are removed by grinder treatment or blast treatment such as /yotsuto blasting or sandblasting.

However, a complete bare metal surface that has been subjected to grinder treatment or blast treatment as described above has a uniform adhesiveness over the entire surface and has a lower coefficient of friction than a lightly rusted surface. It is customary to leave the material in the atmosphere for a long period of time and wait for rust to develop naturally before tightening it.

On the other hand, the current situation in the industrial world is that it is unavoidable to shorten the period from material production to tightening and assembly by a large amount. A method of applying seawater or a solution of sodium chloride, ammonium chloride, etc. to the surface after treatment to accelerate rusting has been adopted.
No. 6-175930, we proposed a method of applying a solution of ferric chloride or ferric chloride mixed with nitric acid or hexacyanic acid and a surfactant, and we proposed a method that exceeds the standards specified by the Japan Society of Civil Engineers and the Architectural Institute of Japan. These methods have been used effectively because they provide a good friction coefficient, but each method requires a double process: the removal process of mill scale, red rust, or paint film, and the rust generation process to ensure a predetermined friction coefficient. The drawbacks of the required complexity could not be imitated.

On the other hand, the method of the present invention was completed as a result of various studies in order to eliminate the drawbacks of the conventional method as described above. By applying this coating, scales such as mill scale and red rust can be effectively removed from the paint film, and after drying, a moderate amount of redness is generated on the surface within a certain period of time, resulting in friction that exceeds the specified level. Since the coefficient can be obtained, tightening can be carried out in one step, and loosening of bolts and nuts can be extremely effectively prevented even after #I plating.

Next, the present invention will be explained in detail.

Example 1 The steel plate is 15Jllt mill scale 5841
Aqueous solutions of each composition shown in Table 1 were prepared using phosphoric acid and ferric chloride, and each was applied and observed. However, the mill scale was not completely removed, but when ferric chloride was added to it.

It was confirmed that 0.5% of FeCl3.6 H20 is somewhat insufficient, but that anything between 1% and 60% promotes the exfoliation of mill scale.

Furthermore, when the N4 U treated in this way was left as is and the surface condition was observed, it was found that in the case of the comparative example of phosphoric acid alone, no red rust developed even after being left for one week. Although the conditions were inappropriate, in contrast, when an appropriate amount of ferric chloride was mixed and added according to the method of the present invention, red rust appeared uniformly over the entire surface within 24 hours, especially when the amount of ferric chloride was 1% or more. 60% or less is in a condition suitable for bolting, and is 0.4 as specified by the Architectural Institute of Japan.
It was confirmed that a friction coefficient of 5 or more could be obtained.

Example 2 Next, a shot-blasted steel plate of 23SVJ 5S41 was used as a steel plate, and a polyvinyl butyral-based and inorganic zinc-based shop primer was used.

This applies to items coated with organic zinc-based paints.

When each aqueous solution having the same formulation as in Example 1 was applied and observed, it was found that compared to the case of using only phosphoric acid as a comparative example, 2
In each case, the formulations containing 1 to 60% of the paint film were suitable for bolt tightening, both in terms of peelability of the paint film and subsequent occurrence of red rust, and were 0.45% as specified by the Architectural Institute of Japan. It was confirmed that the above friction coefficient can be obtained.

As described above, when the method of the present invention is applied to the surfaces of joints of steel materials to be joined during bolt tightening work, it is possible to effectively remove mill scale and coating Y1 coating film resistant to the surfaces of the steel materials. After drying, a moderate amount of red rust is generated on the surface within a certain period of time, and a friction coefficient higher than the specified value can be obtained.

It has the advantage of being able to be tightened as is in one process, and since it prevents bolts and nuts from loosening even after tightening, there is no need for periodic retightening after tightening. It is extremely important to note that when formulating in the present invention, it is not necessary to limit the phosphoric acid concentration, but it is practical to keep it within the range of 5 to 50%, and addition of a surfactant or the like to improve permeability is recommended. It goes without saying that addition of known thickeners such as carboxin methylcellulose, polyvinyl alcohol, and sodium alginate as anti-sagging agents is preferable in order to improve workability in the coating process.

Patent applicant: Masato Yamamoto

Claims (1)

[Claims] It is characterized by applying a solution containing 5 to 50% phosphoric acid and 1 to 60% ferric chloride to the joint surface of steel materials to be joined by the bolting method, and then bolting after drying. Bolt connection method