JPH01201440A - Seawater resistant non-magnetic steel material - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance to high concd. salt of the title material and to improve its durability as the steel material for concrete by reducing the amounts of Si and S in the specific compsn. of steel and adding relatively large amounts of Al and Cr thereto because of the stabilization of its nonmagnetization. CONSTITUTION:The nonmagnetic steel material contains <=1.0% C, <=0.25% Si, <=2.0% Mn, 20<Al<=37.3%, <=0.015$ P, <=0.005% S and 5.5<Cr<=15.0%, contg. at need one or more kinds among 0.01-0.5% rare earth elements such as Ce, La and Y or one or more kinds among 0.01-0.5% Ti, V, Nb, W, Co, Mo and B (where B contents are regulated to 0.0001-0.005) and the balance consisting of Fe. In the steel, the generation and growth of rust are suppressed by the lowering of Si amounts; MnS amounts, the source of rust are reduced by the lowering of S amounts to decrease the deterioration of its corrosion resistance; and the passive film on the surface of the steel material is strengthened by the relatively much auditioning of Al to prevent the generation of rust.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is applicable to steel structures and concrete structures, especially magnetic levitation high-speed railways, nuclear fusion facilities, marine equipment, and structures where non-magnetism is desired. This relates to the non-magnetic steel materials used.

That is, the purpose of the present invention is to provide a steel material suitable for the above-mentioned uses, and since the steel material itself has good corrosion resistance, it can also be used as a non-ferrous material that is useful for preventing deterioration of structures installed in oceans and coastal areas. This relates to magnetic steel materials.

(Prior Art) Recently, seed prevention methods have been proposed and put into practice in order to prevent deterioration of steel structures and concrete structures installed in oceans and coastal areas.

The biggest cause of deterioration of steel structures is corrosion caused by seawater itself,
This is due to corrosion caused by sea salt particles, etc., but the biggest cause of concrete deterioration is that the salt that permeates through concrete walls corrodes the reinforcing bars embedded in the concrete.
Since its volume is about 2.2 times that of steel, it cannot withstand the expansion force and cracks occur in the concrete along the buried reinforcing bars. If the crack is 0.2 m or more, external corrosion factors such as oxygen, salt, and carbon dioxide gas in the air can more easily penetrate through the crack to the vicinity of the buried reinforcing steel inside, further promoting corrosion of the steel layer. , which promotes the carbonation of concrete and accelerates its deterioration.

In order to prevent such deterioration of concrete, the present inventors conducted research to improve the salt resistance of the reinforcing bars themselves by controlling the chemical composition of the reinforcing bars themselves, and as a result of their research, they developed reinforcing bars for concrete with significantly improved salt resistance. (Unexamined Japanese Patent Publication No. 57-4805
4, Japanese Patent Application Laid-Open No. 59-44457).
These contents have already been published in various other areas. (
“0FFSltORE GOTEBORG '81”P
aper Na42 Goteborg 5WEDEN
1981, +1 Cement Concrete” Nα43
4 (1983) P, 23/31,
Construction (Corros tonof Re
information in concrete C
on5truction)"P 4191983,"
Architectural Technology and Construction” 1985, Nα229 January issue P
155/164. Shokokusha).

In addition, the salt resistance mechanism of the steel components of reinforcing bars at an early stage, which contributes to improving the salt resistance of reinforcing bars themselves, is also described in detail in these published papers. However, none of these can achieve nonmagnetization.

Now, recently, as mentioned above, prototype steel materials containing 15% or more of Mn have been made for the purpose of non-magnetization.
One of the disadvantages of any of these steel materials is that they rust significantly even in the presence of even a small amount of salt, and have a greater tendency to rust than current ordinary steel, and have a high corrosion rate.

(Problems to be Solved by the Invention) The present invention is based on the conventional development by the present inventors, and aims to solve the problem of corrosion of non-magnetic steel structures in coastal areas, which has recently become a particular problem, and to solve the problem of non-magnetic steel structures. The purpose is to completely prevent deterioration of buried concrete structures.

Currently, thick salt accumulates in the rust layer on the surface of steel structures that are more than 20 years old, which is a problem in various fields, and the free salt near the buried steel in concrete structures is equivalent to NaCj2 in sand. In some cases, it has reached approximately 1.0%, causing significant corrosion of buried steel materials and accompanying cracking and growth in concrete. Therefore, it is desirable to be able to almost completely stop corrosion of steel structures and cracking of concrete even when exposed to extremely high concentrations of salt.

(Means for Solving the Problems) The above objects of the present invention are achieved by providing a non-magnetic steel having the following configuration.

(1) C, 1.0% or less, Si; 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%,
A seawater-resistant nonmagnetic steel material containing P, 0.015% or less, s, 0.005% or less, Cr, more than 5.5 to 15.0%, and the balance consisting of iron and inevitable impurities.

(2) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, I'J; more than 20.0 to 37.3%
, P; 0.015% or less, s, 0.005% or less, Cr; more than 5.5 to 15.0%, and Ce, L
rare earth elements such as a, Y, etc. alone or in combination with 0. O1
A seawater-resistant non-magnetic steel material containing ~0.5%, with the remainder consisting of iron and inevitable impurities.

(3) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Aj; more than 20.0 to 37.3%,
Contains P, 0.015% or less, S, 0.005% or less, Cr; more than 5.5 to 15.0%, Ti,
One or two of V, Nb, W, Co, Mo, B
0.01 to 0.5% in total for elements other than B
A seawater-resistant nonmagnetic steel material containing 0.0001 to 0.005% of B, with the balance consisting of iron and inevitable impurities.

(4) C; 10% or less, Si; 0.25% or less, Mn;
2.0% or less, /V; more than 20.0 to 37.3%, P
; 0.015% or less, S; 0.005% or less,
Cr; more than 5.5 to 15.0%, Ce, La, Y
Rare earth elements such as 0.01 to 0.5 alone or in combination
%, and further contains Ti, V, Nb, W, Co
.

One or more of Mo and B, with a total of 0.01 to 0.5% of elements other than B, and 0.0001 to 0.00 of B.
A seawater-resistant non-magnetic steel material containing 5%, with the balance consisting of iron and inevitable impurities.

(5) C: 1.0% or less, Si: 0.25% or less, M
n: 2.0% or less, /u: more than 20.0 to 37.3%
, P, 0.015% or less, s, 0.005% or less, Cr; contains more than 5.5 to 15.0%, Cu,
A seawater-resistant non-magnetic steel material containing 0.1 to 5.5% of one or two types of Ni, with the balance consisting of iron and unavoidable impurities.

(6) C; 1.0% or less, 5ii 0.25% or less, Mn
; 2.0% or less, I'J; more than 20.0 to 37.3%
, P, 0.015% or less, s; 0.005% or less, Cr; contains more than 5.5 to 15.0%, Cu,
Contains 0.1 to 5.5% of one or two types of Ni, further contains 0.01 to 0.5% of rare earth elements such as Ce, La, Y, etc. alone or in combination, and the balance is iron and unavoidable A seawater-resistant non-magnetic steel material made of impurities.

(7) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, j'J; more than 20.0 to 37.3%
, P: 0.015% or less, S: 0.005% or less, Cr: more than 5.5 to 15.0%, Ti,
One or more of V, Nb, W, Co, Mo, and B, with a total of 0.01 to 0 for elements other than B.
．． 5%, B contains 0.0001 to 0.005%, and further Cu.

A seawater-resistant non-magnetic steel material containing one or two types of Ni and 1 to 5.5% O, with the balance consisting of iron and inevitable impurities.

(8) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%,
Contains P: 0.015% or less, S: 0.005% or less, Cr: more than 5.5 to 15.0%, Ti,
One or two of V, Nb, W, Co, Mo, B
For elements other than B, the total content is o, oi ~ 0.5%
, B contains 0.0001 to 0.005%, and Cu
.

Contains 0.1 to 5.5% of one or two types of Ni, further contains 0.01 to 0.5% of rare earth elements such as Ce, La, Y, etc. singly or in combination, and the balance is iron and A seawater-resistant non-magnetic steel material that contains unavoidable impurities.

The present invention will be explained in detail below.

The greatest feature of the present invention is that relatively large amounts of M and Cr are added to lower Si and Sl in the steel and to stabilize non-magnetization, and Ce + is added to improve hot workability.
The point is that a small amount of a rare earth element such as L a + Y is added. This reduces the formation of rust by lowering Sil.
MnS suppresses growth and becomes a rust generation point as sl decreases.
By significantly lowering il, the deterioration of corrosion resistance is minimized, and at the same time, 8! By making the amount of (2) relatively large, the passive film on the surface of the steel material is strengthened so that even if exposed to high concentration salt, the passive film will not be destroyed and rust will not occur.

The reasons for limiting each component in the present invention will be explained below.

The reason for limiting Cf to 1.0% or less is (Jl is 1.0%)
This is because exceeding % will cause embrittlement.

In addition, C becomes magnetic due to heat treatment etc. (Fe, jV
) Since complex carbides such as 3C are likely to be generated, a lower CI is desirable. The preferred range is C〒0.2% or less;
More preferably, it is 0.001 to 0.1%.

The reason why the amount of Si is set to 0.25% or less is that the lower the amount of Si, the more the amount of rust formation will be dramatically reduced, but it is necessary to add Si for the purpose of guaranteeing strength and controlling inclusions. was set to 0.25% or less. A more preferable range is 0.05% or less of Si.

The reason why the Mn content is set to 2.0% or less is that if it exceeds 2.0%, hot rolling becomes difficult. From the viewpoint of rust resistance, the preferable range is 1.0% or less.

P is 0. The reason why O is 15% or less is that P is 0.015
This is because if the content exceeds %, there is no effect of suppressing rust growth in an alkaline atmosphere such as concrete, and the rust growth tends to be promoted.

/V is the most important metal element among the chemical components of the steel of the present invention. The reason why the AI was limited to more than 20.0 to 37.3% is that below 20.0%, demagnetization is incomplete.
．． This is because if it exceeds 3%, intermetallic compounds between M and Fe are likely to form, causing embrittlement of the steel and making hot rolling impossible. The most preferred range is 20.5-28.0%.

The reason why J is set to 0.005% or less is to reduce the amount of MnS, which is the source of rust.
An effect of improving corrosion resistance can also be expected by changing S to (MnCa)S or the like. In addition, it is common knowledge that the above-mentioned operations are carried out to lower the 'J' in steel, so a small amount of Ca, Ce, etc. may be mixed in, but these elements have important effects such as corrosion resistance. The presence of small amounts of Ca, Ce, etc. does not pose a problem since they do not have a negative effect on the metal.

The reason why CrN was made more than 5.5% was that the 7V amount was 20.0%.
This is because the hot rolling performance improves when the temperature exceeds 15
．． If it exceeds 0%, it has been observed that embrittlement may occur, so C
r1i was set to more than 5.5 to 15.0%. The most preferred range is 7.0-10.0%.

Rare earth elements such as Ce, La, and Y have a strong bonding force with oxygen and change the properties of the oxide on the surface of the steel material during heating, significantly improving the processing properties during hot rolling and resulting in significantly better surface properties.

This effect is not observed when the content is less than 0.01%, and no change is observed when the content exceeds 0.5%.

Therefore, the amount of these added alone or in combination is 0, O
The content was set at 1% to 0.5%.

In addition, in the present invention, Ti, V, N
b.

W, Co, Mo, B, etc. are added as known elements to improve the strength and toughness of reinforcing bars, and one or more of them are selected and added, and elements other than B are added at 0. 01-0.5%, B is 0.0001-0.005
%, which is already generally well known for the above purpose. Since these selected elements often exhibit similar addition effects, the objective can usually be achieved by adding two types together.

In addition, if necessary, one or both of Cu and Ni may be added at 0.1% to improve weather resistance before being buried in concrete.
Add ~5.5%.

Note that if necessary, for example, when free machinability is required for threaded reinforcing bars, 0.01 to 0.5% of PB can be added.

According to the present invention, the steel composed of the above chemical components is melted in a converter, electric furnace, etc., and then undergoes the steps of ingot making and blooming, or
Alternatively, after being continuously cast and rolled, it is subjected to heat treatment such as quenching, tempering, or standardization, or heat treatment such as patenting, as required, and then drawn into wire for use. The final products are supplied in the form of steel pipes, H-beams, steel sheet piles, reinforcing steel bars, wires, steel plates, etc., and can be galvanized or coated with organic coatings as required.

(Example) Example 1 Steel having the components listed in Table 1 was melted in a vacuum melting furnace, and ingot 1 was produced.
The composition and corrosion test results of hot-rolled steel and conventional steel after blooming are shown.

A sample measuring 25M in width x 60mm in length x 2III11 in thickness was taken from the center of the prepared steel plate, and the surface was polished by mechanical grinding.

On the other hand, artificial seawater was prepared as an environment to promote or reproduce the corrosion of steel in seashore areas and seawater in the laboratory.

Thereafter, the surface of the specimen was ground as described above, the side and back surfaces were coated with silicone resin, and the specimen was degreased, dried, and immediately immersed in the artificial seawater described above. This artificial seawater solution was changed every 7 days and was continuously immersed for 50 days, and the occurrence of rust was observed.

Next, in order to promote or reproduce the salt-induced corrosion of buried reinforcing bars in concrete, CaO, which is the main component of concrete, was dissolved in a 3.6% NaC12 aqueous solution to create a Ca (Of+) 2 + NaCJ aqueous solution with a pH of 12. prepared.

Thereafter, the surface of the sample was ground as described above, the side and back surfaces were coated with silicone resin, and then the sample was degreased and dried, and immediately the above Ca(OH)! + Immersed in 3.6% NaCj aqueous solution. During the test, the surface of the liquid was sealed with liquid paraffin, the liquid was replaced every 3 days, and the samples were immersed continuously for 20 days to observe the occurrence of rust. These results are shown in Table 1.

Example 2 After grinding the surface of a hot-rolled steel plate made of the ingredients shown in Table 1, it was exposed to a beach area for one year, and the state of rusting was investigated.

In addition, hot-rolled reinforcing bars (9 mmφ) made of the ingredients shown in Table 1 were embedded in a concrete mortar made of sand containing 1.0% NaCl, Portland cement, water, and gravel, and after curing at room temperature for 28 days, they were placed in a seaside area for one year. exposed.

The water-cement ratio of the concrete was 0.60, and the fog thickness was 2 cm.

After one year of exposure, the concrete was crushed and the rusting status of the reinforcing bars was investigated. The results of these investigations are shown in Table 1.

The results in Table 1 show that the steel of the present invention does not cause any damage even in seawater, and the salt content in the concrete is 1.0% in terms of Na in sand (calculated as 1.0% in terms of j).
It was clearly observed that no rust occurred even at a high concentration of 3.6% NaClt in water, and it was found that the deterioration of concrete caused by rust occurrence and rust growth could be completely stopped. Therefore, it is presumed that the deterioration of both steel structures and concrete structures can be completely suppressed even in extremely harsh marine environments.

(Effects of the Invention) The present invention is useful as a steel material and concrete steel material that is extremely effective in maintaining the durability of non-magnetic steel materials exposed to salt damage and concrete structures in which non-magnetic steel materials are buried. It can be used in a wide range of applications that require non-magnetism, such as magnetic levitation railways that are exposed to salt damage such as coastal areas.

Claims (8)

[Claims] (1) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%, P;
0.015% or less, S; 0.005% or less, Cr;5.
A seawater-resistant nonmagnetic steel material containing more than 5% to 15.0%, with the balance consisting of iron and inevitable impurities. (2) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%, P;
0.015% or less, S; 0.005% or less, Cr;5.
A seawater-resistant nonmagnetic steel material containing more than 5% to 15.0% and 0.01 to 0.5% of rare earth elements such as Ce, La, and Y, singly or in combination, with the balance being iron and inevitable impurities. (3) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%, P;
0.015% or less, S; 0.005% or less, Cr;5.
Contains more than 5 to 15.0% of Ti, V, Nb, W, Co
, Mo, and B, the total content of elements other than B is 0.01 to 0.5%, and B is 0.0001 to 0.00%.
A seawater-resistant non-magnetic steel material containing 5%, with the balance consisting of iron and inevitable impurities. (4) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%, P;
0.015% or less, S; 0.005% or less, Cr;5.
5 to 15.0%, rare earth elements such as Ce, La, Y, etc. alone or in combination 0.01 to 0.5%, and further T
Contains one or more of i, V, Nb, W, Co, Mo, and B, with a total of 0.01 to 0.5% of elements other than B, and 0.0001 to 0.005% of B. , a seawater-resistant non-magnetic steel material consisting of the balance iron and unavoidable impurities. (5) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%, P;
0.015% or less, S; 0.005% or less, Cr;5.
A seawater-resistant non-magnetic steel material containing more than 5% to 15.0%, 0.1 to 5.5% of one or both of Cu and Ni, and the balance consisting of iron and inevitable impurities. (6) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%, P;
0.015% or less, S; 0.005% or less, Cr;5.
5 to 15.0%, one or both of Cu and Ni to 0.1 to 5.5%, and rare earth elements such as Ce, La, Y, etc. alone or in combination. A seawater-resistant nonmagnetic steel material containing 01 to 0.5%, with the remainder consisting of iron and unavoidable impurities. (7) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%, P;
0.015% or less, S; 0.005% or less, Cr;5.
Contains more than 5 to 15.0% of Ti, V, Nb, W, Co
, Mo, and B, the total content of elements other than B is 0.01 to 0.5%, and B is 0.0001 to 0.00%.
5%, and further contains one or two of Cu and Ni at 0.1%.
A seawater-resistant non-magnetic steel material containing ~5.5%, with the balance consisting of iron and inevitable impurities. (8) C: 1.0% or less, Si: 0.25% or less, Mn
; 2.0% or less, Al; more than 20.0 to 37.3%, P;
0.015% or less, S; 0.005% or less, Cr;5.
Contains more than 5 to 15.0% of Ti, V, Nb, W, Co
, Mo, and B, the total content of elements other than B is 0.01 to 0.5%, and B is 0.0001 to 0.00%.
5%, and further contains one or two of Cu and Ni at 0.1%.
~5.5%, and further contains 0.01~0.5% of rare earth elements such as Ce, La, and Y, singly or in combination, with the balance consisting of iron and unavoidable impurities. .