JPH059572B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) This invention is directed to the corrosion-resistant coating that is received from underground rocks when the anti-corrosion coated steel used for civil engineering and construction is cast into the ground. It concerns the shape of the anti-corrosion coating to prevent damage.

(Prior Art) Conventionally, the durability of steel materials used for structures built on coasts and river banks has been determined by increasing or decreasing the thickness of the steel materials based on the amount of corrosion per year. However, in recent years, it has become clear that the amount of corrosion in the splash zone near the water surface is much larger than initially expected, and that it is not possible to design based on the annual amount of corrosion. Therefore, in recent years, the use of especially thick and high-performance organic heavy corrosion protection coatings (e.g. polyethylene, urethane, etc.), as shown in Japanese Patent Application Laid-open No. 59-197466, has been increasing as a means of preventing corrosion in this area. . Since these organic materials have extremely low water absorption, they are extremely stable against seawater and lake/river water, and can be expected to have a long-term anticorrosion effect, meeting the modern demand for maintenance-free materials. However, recently there has been a movement to apply this organic heavy corrosion protection coating not only underwater but also underground, such as in highly corrosive acidic soil.

(Problems to be Solved by the Invention) Under these circumstances, the problem is that the heavy corrosion protection coating is damaged by underground rocks, etc., and the corrosion protection of that part is impaired. Since the heavy corrosion protection coating is made of organic material, it is naturally weaker than rock and is easily damaged. Of course, this problem can be solved by providing a harder layer on the surface of the anticorrosive coating, but this method increases the cost considerably and is unlikely to be put to practical use. Therefore, the present invention aims to provide the same effect as having a hard protective layer by changing the shape of this heavy organic anti-corrosion coating.

(Means for Solving the Problems) The present inventors have found from numerous pouring results that when there is a convex part on the surface of the coating layer, scratches caused by rocks are concentrated on the convex part, and other parts are It was found that the scars were smaller and shallower. Therefore, a pouring test was carried out by changing the height of the convex part, and the relationship between the height of the convex part and the flaw depth in other parts was determined. The results are shown in FIG. Note that the convex portion was provided in a spiral shape on the surface of the steel pipe as shown in FIG. The heavy-duty anti-corrosion coating material used in this pouring test was polyethylene, and the pouring ground contained gravel of 10 mm to 40 mm in the middle 12 to 14 m section, as shown in Figure 3. Many scratches occur in some areas. From this result, the height of the convex part is
If it is 0.3 mm, the scratch depth can be kept to about 1.0 mm, which is sufficient considering that the thickness of the organic heavy corrosion protection material is set at 2.5 mm, but the height of the convex part is It has been found that it is almost perfect if the thickness is desirably 1.0 mm or more.

The method of providing the convex portions differs depending on the coating material, but
In the case of a polyethylene-coated steel pipe produced by the T-die method, spiral convex portions can be easily formed by increasing the overlapping margin between sheets. Further, in the case of urethane-coated steel materials made by spraying, if the urethane material is flowed down through a small nozzle, it is possible to apply it to the desired shape, either spirally or concentrically. In the case of powdered polyethylene, both a spiral shape and a concentric circular shape can be easily formed by flowing the powdered polyethylene material down from a small nozzle.

Based on the above results, an example in which a pouring test was conducted using Examples and Example steel materials will be shown below.

(Example) Example 1 Steel material... Steel pipe 600 x 12 x 24000 (12000 2 pieces jointed) Covering material... Polyethylene (T-die method) thickness 2.5
mm Convex part...height 1.4mm 20mm width spiral shape (pitch 250mm) Casting ground...N value Max35 Gravel layer flaw depth...0.1~0.3mm Example 2 Steel material...Sheet pile FSP- 18m length Covering material ...Urethane (spray method) thickness 2.0mm Convex part...Height 0.8mm Width 40mm Linear at 500mm pitch (horizontal to the ground) Casting ground...N value 30 Clay and gravel layer scratch depth...0.2~ It was effective not only on 0.5mm steel pipes but also on sheet piles, and urethane showed the same effect as polyethylene.

Comparative example 1 Steel material... Steel pipe 800φ x 15 x 18000 Coating material... Polyethylene (T-die method) thickness 2.5
mm Convex portion...height 0.1 mm Width 30 mm Spiral shape (pitch 300 mm) Casting ground...N value 30 Clay and gravel layer scratch depth...1.6 to 1.8 mm A small height of the convex portion will prevent scratches Comparative example where the effect is small 2 Steel material: H-shaped steel 294×200×8/12×15000 Coating material: polyethylene (powder) thickness 2.5mm Convex portion: height 1.0mm 20mm width 500mm pitch Figure 4 Line shown in (horizontal to the ground, flange only) Casting ground...N value 25 Sand and gravel layer flaw depth...Flange part 0.15~0.3mm Web part
The flange portion with a 1.5 to 1.8 mm convex portion had few scratches, but the web portion had many deep scratches. From this result, it is important that the convex parts are continuous without any breaks, and if there are some discontinuous parts, the anticorrosion material will be deeply scratched.

(Effects of the Invention) From the above, according to the present invention, even if the organic material is relatively soft, if continuous convex portions are provided, scratches during pouring can be effectively prevented.
Even when installed in corrosive soil, it can be used without impairing the corrosion protection properties of the heavy corrosion protection coating.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the height of the convex part and the depth of scratches caused by rocks in areas other than the convex part, Figure 2 a is a side view showing the shape of the provided convex part, and Figure 2 b is a partial cross-sectional view. , FIGS. 3a and 3b are explanatory diagrams of the ground for the casting test, and FIG. 4 is a diagram showing the convex portion of the H-shaped steel in Comparative Example 2. 1: steel pipe, 2: protrusion, 3: protrusion height, 4: polyethylene, 5: protrusion width, 6: flange, 7: web.

Claims (1)

[Claims] 1. A heavy-duty anti-corrosion coated steel material for pouring into the ground, which is characterized by having a continuous band-shaped convex portion of 0.3 mm or more in height on the outer peripheral surface of the coat.