JPS6056222B2 - Sleeve for joining reinforcing bars - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to collar crimping joining of non-magnetic reinforcing bars, and relates to a sleeve for joining non-magnetic reinforcing bars that is easy to crimp and can maintain a magnetic permeability of 2.0 or less in the joined state. be.

The reinforcing bars conventionally inserted into concrete buildings are JIS G.
3l12, hot-rolled steel bars or hot-rolled deformed steel bars are used, and the material used is mild steel or carbon steel depending on the strength level.

However, in recent years, with the development of the nuclear power industry, special structures have become necessary.For example, structures that house the plasma generators and superconducting generators of large fusion reactors, or the roadbed of maglev trains using magnetic levitation, are needed. It is required that the structural objects be non-magnetic in order to minimize magnetic losses.

Therefore, since conventional reinforcing bars cannot be used for such concrete structures, so-called non-magnetic reinforcing bars with low magnetic permeability are being adopted, and along with this, research on joining methods for non-magnetic reinforcing bars is underway. is also widely practiced.
As a method for joining reinforcing bars, a so-called collar crimp joining method is considered, in which both ends of the reinforcing bars to be joined are inserted into a sleeve, and the sleeve is squeezed using a die or hydraulic jack to fit into the irregularities of the deformed reinforcing bars.

In the case of the above joining method, conventional reinforcing steel joining sleeves (JIS
Since the G3445 carbon steel pipe for mechanical structures cannot maintain low magnetic permeability in the joined state, it is not suitable as a sleeve for joining reinforcing bars inserted into non-magnetic concrete structures. Therefore, the inventors of the present invention have conducted extensive research in order to find a sleeve suitable for the above-mentioned uses. That is, the material of the sleeve for joining non-magnetic reinforcing bars is as follows: (1) Martensite or ferrite having ferromagnetic properties is not formed even when squeezed to insert the deformed reinforcing bars, and the material has low magnetic permeability in the joined state.

(2) Relatively low work hardening properties and easy construction (3) Materials must be relatively inexpensive.As a result of various studies to find an alloy that satisfies the above conditions, the composition was adjusted to the following. A sleeve made of this steel has a magnetic permeability of 2.0 or less in the joined state, and the strength of the joint part (4). 2% yield strength) was found to be 30k9/Rd or more.

That is, in the present invention, 1C: 0.15% or less, Si: 1.5%
0% or less, Mn: over 6.0 ~ 20.0%, Ni: 4
．． 0~15.0%, Cr: 13.0~! A sleeve manufactured from austenitic stainless steel with 20.0% and the remainder consisting essentially of iron and satisfying the following formula,
A sleeve for joining reinforcing bars that maintains a magnetic permeability of 2.0 or less even after cold working of 30% or less
-2C: 0.15% or less, Si: 1.50% or less,
Mn: over 6.0t~20.0%, Ni: 4.0~1
5.0%, Cr: 13.0-20.0% and CU: 4
．． 0% or less, MO: 3.0% or less, N: 0.30% or less, W: 1.0% or less, ■: 0.500.50% or less, A
l: A sleeve manufactured from austenitic stainless steel containing one or more elements selected from 0.50% or less, the remainder consisting essentially of iron, and satisfying the following formula: ( Even if cold working is performed below 2.
01). A sleeve for joining reinforcing bars characterized by maintaining a low magnetic permeability.The material of the sleeve of the present invention is compositionally adjusted to prevent the formation of ferromagnetic delta ferrite and deformation-induced martensite in practical use. Work hardening due to processing is relatively small, and the mechanical strength of the joint is comparable to or higher than that of conventional sleeves.

Next, the reason for limiting the composition range of the sleeve material of the present invention will be described below. C: Effective for stabilizing austenite and improving sleeve strength, but if added in large amounts, work hardening will increase and excessive tightening will be required during sleeve drawing, so 0.15% or less is desirable. S1: It is added as a deoxidizing element for molten steel, but if added in large quantities, work hardening will increase and the joinability of the sleeve will deteriorate, so 1.
50% or less is desirable.

Mn: Effective in deoxidizing molten steel and stabilizing austenite, and also reduces ferromagnetization due to cold working.
In order to maintain high mechanical strength as a joint, especially 6
．． Contain a large amount exceeding 0%. However, adding 20% or more is not preferable because a σ phase is formed and the magnetic permeability decreases. Ni: It is necessary to add at least 4.0% or more to stabilize austenite and maintain low magnetic permeability.

However, from the point of view of economic efficiency, it is desirable that it be 15% or less. Cr: In order to prevent the formation of ferromagnetic martensite, it is necessary to add at least 13% or more.

However, if added in a large amount, σ ferrite is formed and the magnetic permeability increases, so it is desirable that the content be 20% or less. Within the range of the above component element amounts, and in order to prevent an increase in magnetic permeability due to the formation of delta ferrite and deformation-induced martensite in practical use, the separately determined Ni equivalent is determined by the above-mentioned relational expression (
It is necessary to satisfy 1) and (2).

That is, equation (1) is an equation expressing the N1 equivalent for adjusting the amount of delta ferrite. In addition, equation (2) is an equation that expresses the Ni equivalent for adjusting the amount of deformation-induced martensite when cold working is performed, and based on many experiments by the inventors, equations (1) and (2) The Ni equivalent of the formula is -8. @). It was confirmed that the magnetic permeability sharply increases when the value is 16.0 or less, so the above limitations were made. As mentioned above, the basic components and Ni equivalent of the material for the sleeve of the present invention are limited as described above, but in addition to this, CU: 4.0
% or less, MO: 3.0% or less, N: 0.30% or less, W
: 1.0% or less, ■: 0.50% or less, Ti: 0.50
% or less, Nb: 0.50% or less, Zr: 0.50% or less, Al: 0.50% or less, it can be used satisfactorily for sleeves, but in this case, formula (1)'' and The Ni equivalent of formula (2) is −8.0 or less and 16.0 or less, respectively. (1)''
It is necessary to satisfy the formula and (2Y formula).Next, the features of the sleeve of the present invention will be explained in detail by examples.Example 1 To investigate the relationship between the amount of delta ferrite and magnetic permeability, and the amount of deformation-induced martensite and magnetic permeability. Sample materials having the component compositions shown in Table 1 were melted.

The sample materials in Table 1 were made into rods with a diameter of 3i, and then subjected to solution treatment, and then the magnetic permeability of the sample materials was measured.

As a result, various values were obtained, and when these values were organized using the relational expression (expressing the tendency of delta ferrite formation) defined in equation (1) or (1)'', the results were as shown in Figure 1. In addition, when the sum of the above relational expressions is -8 or less, the magnetic permeability tends to increase rapidly.In other words, the material for the sleeve of the present invention has a value in the above-mentioned equation (1) or (1)''. It is clearly recognized that it is necessary to adjust the amount of alloying elements so that it becomes 8 or more. Next, in order to investigate the influence of deformation-induced martensite, the sample materials in Table 1 were subjected to solution treatment with a deformation rate of 30% (the machining rate of sleeves is normally 15%).
It is about 25%. ) were subjected to cold drawing and the magnetic permeability was measured for each. As a result, various values were obtained, and these values were determined by equation (2) or (2)″ (a relational expression that expresses the formation tendency of deformation-induced martensite).
As shown in Figure 2, the sum of the above relational expressions is 16j:). At the bottom, the permeability showed a tendency to increase rapidly. In other words, the material for the sleeve of the present invention has a value of 16J in the above-mentioned formula (2) or (2)''.
．． It is clearly recognized that it is necessary to adjust the amount of alloying elements so that the

Example 2 Among the test materials in Table 1, NO. External diameter 54WfR x internal diameter 6 by cutting after solution treatment using l ~ 9, 11, 12
7. A cylindrical sleeve with a field x length of 24'' was manufactured and reinforcing bars were joined using the collar crimp joining method.

The reinforcing bars used in the experiment were 0.9C-15Mr1 series non-magnetic deformed reinforcing bars, and the frame shape was horizontal frame D32 (JlSG3ll
2).

Next, the 0.2% yield strength, joint strength, and magnetic permeability of the joint were measured.

The results are shown in Table 2. Even when magnetic reinforcing bars are used, the magnetic permeability is extremely high and it cannot be said that they are substantially non-magnetic. On the other hand, when the sleeve of the present invention is used to join, the magnetic permeability of the joint portion is maintained at 2.0 or less, so that the joint portion is substantially non-magnetic.

In addition, the sleeve No. of the present invention. l. 2.4. Comparative sleeve No. 2 had the same magnetic permeability as these by lowering the Mn content and increasing the Ni content. I made 5.6.7.

It can be seen that the sleeve of the present invention containing 6% or more of Mn has higher joint strength than these comparative sleeves.
As described above, the sleeve of the present invention is extremely suitable for joining non-magnetic reinforcing bars, and is an invention of great industrial value.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between Ni equivalent and magnetic permeability, which shows the tendency to form delta ferrite. Figure 2 is a diagram showing the relationship between Ni equivalent and magnetic permeability, which shows the tendency to form deformation-induced martensite. The numbers indicate the resistance of the sample material.

Claims (1)

[Claims] 1 C: 0.15% or less, Si: 1.50% or less, Mn
: over 6.0 ~ 20.0%, Ni: 4.0 ~ 15.0
%, Cr: 13.0 to 20.0%, the remainder is substantially iron, and the sleeve is manufactured from austenitic stainless steel that satisfies the following formula, and is subjected to cold working of 30% or less. Ni+0.5Mn+30C sleeve for joining reinforcing bars, which is characterized by maintaining a magnetic permeability of 2.0 or less
-0.9Cr -1.4Si≧-8.0 (1
) Formula Ni+0.7Mn+13.2C+0.4Cr+0.
3Si≧16.0・・・・・・(2) Formula 2 C:
0.15% or less, Si: 1.5% or less, Mn: over 6.0 to 20.0%, Ni: 4.0 to 15.0%, Cr:
13.0-20.0% and Cu: 4.0% or less, Mo
: 3.0% or less, N: 0.30% or less, W: 1.0%
Below, V: 0.50% or less, Ti: 0.50% or less, N
b: 0.50% or less, Zr: 0.50% or less, Al: 0
．． A sleeve manufactured from austenitic stainless steel containing one or more elements selected from 50% or less, with the remainder consisting essentially of iron, and satisfying the following formula, which has a cold temperature of 30% or less. A sleeve for joining reinforcing bars Ni+0.5Mn+30C+30N+0.4Cu-0. which is characterized by maintaining magnetic permeability of 2.0% or less even after processing.
9Cr-0.9Mo-1.4Si-2.1V-0.7W
-2.1Ti-0.1Nb-2.3Al≧-8.0...
・・・・・・・・・(1)′ Formula Ni+0.7Mn+5.4N
+13.2C+1.1Cu+0.4Cr+0.4Mo+
0.3Si+1, IV+0.3W+0.8Ti+1.1
Nb+0.9Al≧16.0 (2)
'formula