JPS6018132B2 - High Mn non-magnetic steel for concrete structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-Mn non-magnetic steel material for concrete structures, which has a rust-preventive property on its surface or has a coating layer having both rust-preventive property and electrical insulation property.

Non-magnetic steel is steel that cannot be magnetized by an external magnetic field.

For example, non-magnetic materials, that is, materials with small magnetic permeability peaks, are used as materials for steel frames and reinforcing bars used in concrete structures that are affected by strong external magnetic fields, such as nuclear fusion experimental facilities and the roadbed of maglev railways. is required. As a non-magnetic steel,
Conventionally widely known austenitic stainless steels are represented by 1-board R-Funai steel, but these are made of Ni.
It is expensive because it contains a large amount of carbon dioxide, and its yield strength is low, making it unsuitable as a material for steel frames, reinforcing bars, etc. for concrete reinforcement.

The present inventor previously proposed a steel containing 5 to 30% Mn as a non-magnetic steel that is inexpensive and has excellent mechanical properties (
Tokuken Showa 51-68311).

Since this steel does not contain a large amount of Ni, the Cr-N
It is not only cheaper than i-series austenitic steel, but also stable against plastic working and heat, and maintains low magnetic permeability, so it can be used widely in the above applications. Be expected. In other words, this steel is hot-rolled and processed into steel sheets, etc., and is normally subject to French SI. 02, and has sufficient performance for general non-magnetic steel applications. However, recently, special applications such as structures that deal with extremely weak magnetic changes, such as geomagnetic observation test facilities, or structures that use strong alternating magnetic fields, such as nuclear fusion experimental facilities, have recently been developed. It is now required not only that the material has a magnetic permeability of 4.0, but also that there are no problems when it is incorporated into a structure and when it is used as a structure. It's here.

The following two points can be raised as such problems. [1
} Increasing magnetic permeability due to rust occurring on the surface of non-magnetic steel, '2) Heat generation due to induced current flowing through steel incorporated in concrete, especially reinforcing bars, First of all, the problem caused by rust in {1- Even though it is a non-magnetic steel material, the rust that occurs on it is mainly composed of ferromagnetic iron oxide.

That is, the apparent magnetic permeability of the steel material from which the coin is generated is expressed by the linear equation. ．． M = 10(1-C) ``x in non-magnetic steel is extremely small (base 0,01), but compared to this, x2 is around 10, which is an order of magnitude larger.

Therefore, even if the amount of rust generated is small and C is small,
The apparent value of the steel as a whole becomes large, which, as mentioned above, causes an undesirable effect in applications where minute magnetism is a problem. However, no studies have been made regarding the effects of rust on non-magnetic steel materials, and therefore, there are no known examples of anti-rust treatment being applied to non-magnetic steel. However, some amount of rust is naturally expected when steel is stored, transported, or handled at construction sites, and even when it is embedded in concrete and used, rust may develop over many years. There's a good chance that it will. As mentioned above, even a slight amount of rust can be a big problem in the case of a special material such as non-magnetic steel. next,
Let's talk about induced current.

Even non-magnetic steel is an electrically conductive material, so if it forms an electric circuit, an induced current will be generated when it is placed in a magnetic field. There is no problem with non-magnetic steel materials embedded in concrete as long as they are isolated one by one, that is, they do not come into contact with each other. However, it is practically difficult to construct a large number of reinforcing bars etc. in a non-contact state, and an electrical closed circuit of the reinforcing bars etc. is inevitably formed within the concrete. If such a bran body is placed in a strong magnetic field generated by the use of large currents, such as in aluminum electrolytic refining equipment, or in a strong magnetic field, such as in a nuclear fusion installation, the yield current generated in the reinforcing bars will also become large. As a result, the steel material expands due to the heat generated, and the concrete is heated and becomes dangerous, which may lead to the structure being destroyed. This invention was made with the aim of solving the above-mentioned problems specific to non-magnetic steel materials.

In order to solve problem 1' above, the inventors of the present invention have proposed a protective coating on the surface of non-magnetic steel that will not increase the apparent magnetic permeability of the steel and can effectively prevent the occurrence of rust. It was found that applying an electrically insulating coating to the surface of the non-magnetic steel material is effective in solving the problem (2).

In particular, it is extremely desirable to apply a coating that is non-magnetic and has both rust prevention and insulation properties. A coating with . First, coatings for the purpose of rust prevention include metal coatings such as Zn, aluminum, Sn, coatings mainly composed of inorganic compounds such as phosphates and oxalates, organic coatings such as synthetic resins, oils and fats, Rust inhibitors such as petroleum refining by-products can be used.

It goes without saying that the metal coating must itself be a non-magnetic metal.

As a coating method, a method of impregnating a non-magnetic steel material into molten metal, an electroplating method, or in the case of A, a thermal spraying method, a colorizing method, etc. can be used. These coating methods can be performed using the same processes as those used for general steel materials, but since they are intended for non-magnetic steel, descaling must be done thoroughly and thoroughly before coating. That is essential. Next, we will discuss coatings for the purpose of insulation.

As mentioned earlier, the insulation coating is used to keep reinforcing bars embedded in a concrete structure electrically insulated even if they come into contact with each other. Therefore, electrical insulation can be achieved by coating only the parts where contact is expected, but rust prevention is also required, so the entire surface of the non-magnetic steel is coated. As the covering material having both rust prevention and electrical insulation properties, rubber, cotton cloth, linen cloth, jute, paper, materials impregnated with grease or tar, various synthetic resins, etc. can be used.

These coatings are applied to the entire surface of the steel material using normal coating methods. Of the above-mentioned coating materials, synthetic resin coatings have excellent properties as rust prevention and insulating materials, and the coating method is relatively simple, and the strength of the coating layer is low.
It is also excellent in terms of ease of handling the steel material after coating. As synthetic resin coating materials, vinyl chloride resin, epoxy resin, polyolefin resin, such as polyethylene,
Polypropylene or the like can be used, and coating methods include powder coating baking method, liquid resin coating method, melt extrusion coating method, etc.

There is no particular limitation on the material of the non-magnetic steel to be coated.

However, since the non-magnetic steel material having the coating layer of the present invention is intended for the above-mentioned uses, it is possible to use a high-Mn steel material that is inexpensive and has the most practical properties in terms of mechanical properties and other aspects.
It is best to target non-magnetic steels. Furthermore, as a high Mn non-magnetic steel,
The steel invented by the applicant according to CO. 2-1
．． 5%, Mn5-30%, Sio. Contains 1 to 1.5%,

[c] Steel that satisfies +2 plates ≧ 25, or 15% of this
A steel containing the following Cr, 5% or less Ni, 1% or less Cu, 5% or less Mo, and small amounts of Ti, Nb, V, W, Zr, etc. is desirable. That is, as stated in the specification of the above-mentioned application, this coin has many excellent properties, especially as a non-magnetic reinforcing bar for concrete structures. There is no need to particularly limit the shape of the non-magnetic steel material.

Forms used for concrete structures include reinforcing bars,
There are many products such as steel steel, deformed steel steel, and shaped steel that are used for steel frames, but there are also various products such as wire strips and fibers, and even in these products, by forming a coating layer on the surface,
The effects of this invention are similarly exhibited. Hereinafter, specific examples of coatings and their effects will be explained with reference to Examples.

Using non-magnetic steel with the composition shown in Table 1, various coatings and
Tests were conducted regarding its rust prevention and insulation effects.

Table 1 Sample material composition Phosphorus *Magnetic permeability at a magnetic field strength of 1000e after solution treatment at 1050°C Rust prevention test Steels A to F in Table 1 were hot rolled to the 10th straight edge. After being left to cool naturally, the surface coating shown in Table 2 was applied.
Tested in air and artificial seawater.

The coating method is as follows. No treatment... Zn plating after pickling and descaling... After pickling and descaling, molten Zn corrosion prevention Rust Oil... After pickling and descaling, water-soluble rust preventive oil coating Epoxy resin coating... After shot blast descaling , electrostatic powder coating of anhydride-curing bisphenolepoxy resin 24,000 x 30 minutes, film thickness 170-200〃 Vinyl chloride resin coating...After washing and descaling, 100℃
Electrostatic powder coating of polyvinyl chloride resin at 220 qo x 30 minutes with a coating thickness of approximately 170 mm.The test results are shown in Table 2.

Leopard 2 drum scale scale wiping results The amount of rust generated is determined by measuring the weight of the sample (IQ Misaki J) before the test, and after the test, removing the rust with an aqueous ammonium citrate solution and measuring the weight. The difference was converted to the average diameter reduction (fence) of the sample.

The magnetic permeability was measured using a magnetic balance using 10 x 3 mosquito samples.

From the results in Table 2, it can be seen that the uncoated product is 1 in the atmosphere.
It can be seen that the number of piles due to rust has already increased by more than 1.02 after being left unused for a long time.

Furthermore, although coating with anti-corrosion oil is quite effective in the atmosphere, it has almost no effect in artificial seawater. On the contrary,
Zn plating, epoxy resin, and pinyl chloride resin coating materials show good results both in the atmosphere and in artificial seawater, and the latter two in particular do not rust at all, so an increase in magnetic permeability is completely prevented. I can see that 'Raw Insulation Test D22 deformed reinforcing bars are produced by hot rolling from steels A, C, and D listed in Table 1, and after applying the surface coating shown in Table 3,
Electrical resistance was measured by the test method shown in FIGS.

That is, as shown in Fig. 1, the 700-side sail piece 1 and the 90-W ship side piece 1' are assembled in a jigeta shape at 500-kite intervals, and the intersection points 2 to 4 are tied with mild steel wire or nylon rope. 5 was insulated with a rubber tube. This was embedded in a concrete slab 6 (800 x 800 x 5 Qianqiao) shown in FIG. 2, and the electrical resistance between the A machine and the B end was measured using a resistance meter 7. In addition, the test was conducted by producing 5 concrete slabs for each type. The test results are shown in Table 3.

It can be seen that in the as-rolled reinforcing bars, the electrical resistance at the intersection points is small, and there is an extremely high possibility that an electrical closed circuit will be formed due to mutual contact between the reinforcing bars.

Furthermore, tar painting is not suitable as an insulating coating, considering the actual construction method, as the coating layer may be destroyed by twisting the mild steel wire, resulting in poor insulation. In contrast, all synthetic resin coatings had infinite electrical resistance, that is, were completely insulated, confirming their excellent performance.

Table 3 Insulation test results Combined with the results of the rust prevention test mentioned above, it is clear that the synthetic resin coating is extremely excellent for both rust prevention and insulation purposes.

In the above examples, epoxy resin and vinyl chloride resin were exemplified as representatives, but it has been confirmed that the various synthetic resin coatings described above also have such effects, and such synthetic resin coatings are suitable for bending. Also, because it has excellent mechanical properties against impact, etc., it is the most excellent coating for non-magnetic steel materials.

[Brief explanation of the drawing]

Figure 1 is a plan view showing a part of a non-magnetic reinforcing bar grid using surface-coated non-magnetic steel according to the present invention, and Figure 2 is for measuring the electrical resistance of a concrete slab having the reinforcing bar grid shown in Figure 1. FIG. In the figure 1... specimen, 2, 3, 4, 5... intersection, 6...
・Concrete slab, 8... Electric resistance meter. Figure 1 Figure 2

Claims (1)

[Claims] 1. A high-Mn non-magnetic steel material for concrete structures, characterized by having a surface having rust prevention properties or a coating layer having both rust prevention properties and electrical insulation properties.