JPH0381013B2 - - Google Patents

Description

[Detailed description of the invention]

When constructing bridges, general steel structures, etc. on-site, the recent trend has been to increase the size of the structures, and conventional riveting and welding methods require special attention. In many cases, joint construction methods using high-tensile steel bolts are often used, and the amount used is also on the rise. The above-mentioned joint method using high-tensile steel bolts uses high-strength steel bolts that are tightened to near their yield point, whereas the conventional riveting method transmits joint stress by shearing the rivets. As a result, stress is transmitted by the frictional force generated on the joint surfaces of the joint, so the friction coefficient of the joint surfaces of the joint, which is an element of stress transmission, is an extremely important factor. For this reason, if mill scale, uneven red rust, foreign matter, etc. are present on the joint surfaces of the above-mentioned joints, the coefficient of friction will be extremely reduced, which will weaken the tightening strength and also cause loosening after tightening. Since it is easy to tighten and requires periodic retightening, it is usually necessary to remove mill scale, red rust, etc. by grinding or blasting such as shot blasting or sandblasting. However, on the other hand, a lightly rusted surface that is uniformly formed over the entire surface has a much larger friction coefficient than the bare metal surface that has been subjected to the above-mentioned grinder treatment or blasting treatment, so it is usually It is customary to leave it inside 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 necessary to significantly shorten the period from material production to tightening and assembly. In addition, even if exposed outdoors, the desired red rust often does not develop before tightening, and conversely, at construction sites, etc., which last for an extremely long period of time, depending on the exposure period and corrosive environment conditions, the desired red rust may not develop. Because the rust has progressed to the point where the desired red rust cannot be obtained, the rust must be removed again using a wire brush or the like before tightening and finished to an appropriate level of rust. At present, many problems remain regarding surface treatment of bonding surfaces. In response to this current situation, some conventional methods have been adopted in which seawater or salt water is applied to the surface after grinding or blasting, and the surface is exposed outdoors to promote the formation of rust. However, it still takes a considerable amount of time to produce the desired rust, and the rust produced is not uniform, resulting in irregularities. The present invention has been proposed in view of the above, and is a treatment agent that improves friction by applying it after grinding or blasting the joint surfaces of joints in bolt joint construction method, and comprises 0.1wt%
The present invention relates to a friction improving treatment agent characterized by being composed of an aqueous solution containing the above ferric chloride and 0.5 to 2 wt% of an anionic surfactant, and the friction improving treatment agent of the present invention can be used in seawater or common salt as described above. By applying it to the steel material of the joint instead of water and drying it, a desired amount of uniform rust can be generated within a very short time, and bolts can be tightened. Further, by applying the friction improving treatment agent of the present invention to the treated surface after grinder or blasting treatment and drying it, rust can be generated within a very short time.
It has extremely good adhesion to the metal base surface, and has a coefficient of friction that is even greater than that of rust that occurs in the natural environment, so it is possible to increase the bonding strength. In the friction improving treatment agent of the present invention, the amount of ferric chloride is 0.1 wt% or more, but if it is too small, it will take a long time for rust to develop, which will impede workability. Practically speaking, the amount of ferric chloride may be determined depending on the allowable time from application to tightening. The anionic surfactant is added to make the surface of the steel material on the joint surface of the joint hydrophilic and cause uniform rust to occur on the surface, and the amount usually added is 0.5 to 2 wt%. The friction improving treatment agent of the present invention is prepared by dissolving the above-mentioned ferric chloride and anionic surfactant in water, but other solvents, additives, etc. may be added. Next, the friction improving agent of the present invention will be explained with reference to Examples. Example 1 As shown in Table 1, ferric chloride was converted into FeCl ₃ 6H ₂
The aqueous solutions Nos. 1 to 6 were adjusted to have an O concentration of 0.1 wt% or more, and 1% each of anionic surfactants were added to the solutions, and then sandblasted.
When comparing the application to the joint surfaces of joints made of S381, it was observed that when the concentration was high, rust began to form already during drying, and as the ferric chloride concentration decreased, the time for rust formation slowed. However, even at 0.1wt%
After 24 hours, rust was observed to have formed.

[Table] In addition, in the above test, the test was conducted indoors and observed.
It was found that almost the same effect can be obtained even when left outdoors. Example 2 The joint surface of the joint in Example 1 was tightened using high-tensile steel bolts (90Kg/mm ² ), and the friction coefficient was measured and compared with untreated and naturally occurring rust. However, as shown in Table 2, 0.1 of No. 1
%, the friction coefficient is slightly lower than that of a naturally occurring moderately rusted surface, but when it is about 1.0% or more for Nos. 3, 5, and 6, a friction coefficient higher than that of a naturally occurring moderately rusted surface is obtained. It was also observed that these values far exceeded the friction coefficient of 0.45 specified by the architectural academia.

[Table] As described above, during bolt tightening construction, after removing mill scale by grinder or blasting, the friction improving treatment agent of the present invention is applied to the joint surface of the joint in the bolted joint method and dried. Rust with extremely good adhesion to the metal base surface can be rapidly and uniformly generated. In addition, by adjusting the amount of ferric chloride in the friction improving treatment agent of the present invention, the time for rust to occur can be set, and excessive rust can be scraped off with a wire brush or the like as in the conventional method. No work required. Furthermore, since the rusted surface obtained by the friction improving treatment agent of the present invention has a higher coefficient of friction than a naturally generated rusted surface, it becomes easier to tighten, increases the joint strength, and improves the strength of bolts and nuts after tightening. It has the advantage of being able to prevent loosening and eliminating the need for periodic retightening after construction, making it extremely useful industrially.

Claims (1)

[Scope of Claims] 1. A treatment agent that improves friction by applying it after grinding or blasting the joint surface of a joint in a bolt joint construction method, which comprises 0.1 wt% or more of ferric chloride, and 0.5 to 0.5 wt% of ferric chloride. A friction improving treatment agent comprising an aqueous solution containing 2wt% of an anionic surfactant.