JPS6018743B2 - non-magnetic reinforcing bar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to non-magnetic reinforcing bars used in reinforced concrete structures that are required to be non-magnetic.

Since all the reinforcing bars used in conventional reinforced concrete are made of ferritic steel, they inevitably exhibit ferromagnetic properties.

However, in order to prevent problems such as signal disturbances and reductions in car body levitation force, there is a growing demand for the roadbeds of maglev superhigh-speed railways that have been developed in recent years to have a non-magnetic reinforced concrete structure. In contrast, it is extremely difficult to make conventional reinforcing bars non-magnetic. On the other hand, as a non-magnetic steel material, there is austenitic stainless steel, but this has an extremely low yield point, so its yield point is insufficient to be used as reinforcing steel, and it is also a very expensive material, so it cannot be used as reinforcing steel. Mass consumption at low prices is not economically viable. Therefore, there has been a desire for a reinforcing bar that has non-magnetism comparable to conventional austenitic stainless steel, has a high yield point, and does not contain expensive Ni. The steel of the present invention has a CO. 2% or more and less than 1.0%, Mn6.9~
30%, Sio. 1 to 1.5%, and the C and Mn components have the formula 100/9 [C] + 2 [Mn] and 25 (C,
The base is made non-magnetic by adjusting the Mn content (% by weight) to a satisfactory value.

The inventor of the present invention pointed out that reinforcing bars have a larger length relative to their cross-sectional area than steel plates, making it relatively difficult to carry out water-toughening treatment, which involves water cooling after solution heating, and resulting in large cost losses. In addition to the fact that the cooling rate is fast and the reduction rate is large, and austenite grains become pongee grains during rolling,
It has been found that the yield strength required as a reinforcing bar can be secured within the C, Si, and Mn component ranges of the present application range, while maintaining nonmagnetic properties during rolling. The reinforcing bars of the present invention have tensile strength,
The yield point, elongation, reduction of area, and bending properties exceed the required limits for reinforcing steel, but if the diameter of the steel is extremely large, it will not be possible to cool it by natural cooling. The speed is small and the grain boundaries become arms, which may reduce the ductility and bending workability of the steel.

In such a case, it is extremely easy to increase the cooling rate and ensure the required ductility and bendability by employing an appropriate cooling means such as water cooling or forced air cooling. If it is necessary to further increase the strength, the required strength can be ensured by reheating the steel material that has been naturally cooled after hot rolling to 800oC or higher, and then forcedly cooling it by the above-mentioned means. The reason why the components of the steel are limited in the present invention is as follows.

C: If it is less than 0.2%, the yield point will be lower than 30k9/iso, which is not preferable.

On the other hand, when C increases, the yield strength increases and the fineness becomes stable, and it remains non-magnetic even when heated and bent.
If it exceeds 0%, carbide precipitation occurs at grain boundaries during the cooling process after hot rolling at a cooling rate comparable to the cooling of reinforcing bars, and the steel becomes significantly vertical. Mn: An element necessary to keep steel non-magnetic, but since the non-magnetism disappears when Mn reaches 6.9%, the lower limit was set at 6.9%. If it exceeds 30%, the furnace wall bricks that come into contact with molten steel during steelmaking will be seriously damaged, and the steelmaking cost will increase significantly, which is not preferable.

Si: It is necessary to contain 0.1% or more as a deoxidizing agent for steel. Furthermore, although the content of Si is effective in raising the yield point of steel, if it exceeds 1.5%, it becomes difficult to maintain stable non-magnetic properties of the steel, so the upper limit was set at 1.5%. C10Mm: 10
0/9 [C] + 2 [Mn] ≧ 25 (C, Mh' weight%
) was used to stabilize the steel as non-magnetic.
When the C and Mn components are outside this range, the magnetic permeability increases and non-magnetism disappears.

Next, examples of the present invention will be described.

Table 1 shows the conventional steel (Samples 1, 2) and the invention steel (Samples 3, 4,
5, 6) components, mechanical properties, and physical properties.

All of these six samples were melted into ingots using a low-frequency induction furnace in the atmosphere, and after hot forging into billets on the 113th side, they were heated to 1100 qo and heated to over 900°C. It was obtained by hot rolling into a DIO deformed reinforcing bar in a temperature gauge, rolling it, and allowing it to cool naturally.

Regarding the test method, after straightening these samples into a straight shape, for tensile test and bending test, follow JIS G311.
2, and the magnetic permeability was measured using a magnetic balance. Sample 1 is SUS301 stainless steel, and Sample 2 is high manganese steel. Sample 3, 4, 5,
6 shows a typical example of the reinforcing bar of the present invention. Sample 1 fully satisfies the performance of non-magnetic reinforcing bars in terms of bendability and magnetic permeability, but has a yield point of only 22 kg/ground, and is insufficient in strength as a reinforcing bar. Sample 2 satisfies the performance as a reinforcing bar in terms of bending strength, but has high magnetic permeability and is not a non-magnetic reinforcing bar. Samples 3, 4, 5, and 6 were all completely non-magnetic, and satisfied the performance as reinforcing bars in terms of strength and bendability. Table 1 Sample components and mechanical and physical properties As mentioned above, the present invention is a completely new material that imparts non-magnetism to reinforcing bars without adding expensive materials such as Nj, and maintains mechanical properties equivalent to conventional reinforcing bars. However, it brought about the appearance of reinforcing bars, and has made an extremely large contribution to the construction of non-magnetic reinforced concrete structures.

Claims (1)

[Claims] 1% by weight, C0.2% or more and less than 1.0%, Mn6.
9 to 30%, Si 0.1 to 1.5%, the remainder substantially consists of Fe, and the content of C and Mn is of the formula 100.
/9[C]+2[Mn]≧25 (C and Mn are weight%) A non-magnetic reinforcing bar adjusted to satisfy the following.