JPH07126801A - Welded structural steel with excellent vibration damping characteristics - Google Patents

Abstract

PURPOSE:To develop a steel for welding structure in which vibration and noise are controlled and having excellent vibration damping characteristics by reducing the contents of oxygen in an Fe-Cu-Al low carbon steel having a specified compsn. and high tensile strength. CONSTITUTION:As for an Fe-Cu-Al low carbon steel having a compsn. contg., by weight, <0.02% C, <0.02% Si, <0.08% Mn, 0.05 to 1.50% Cu and 1.0 to 7.0% Al or furthermore contg. 0.05 to 1.50% Ni, in which the contents of N are reduced to 0.0040%, and the balance Fe, the contents of oxygen are reduced to <=0.0015% by the addition of a deoxidizer or other methods. The steel excellent in vibration damping characteristics in which vibration and noise can be suppressed, having >=400MPa tensile strength and furthermore having weldability and toughness required as the steel for welding structures can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welded structural steel suitable for use as a member of a structure, particularly for a welded structure having a tensile strength of 400 MPa or more, which is excellent in vibration damping characteristics capable of suppressing vibration and noise. The idea is to propose steel. In recent years, there have been severe vibrations caused by the movement of heavy vehicles such as railway bridges and road bridges for automobiles. The noise that accompanies them is a social problem, which is remarkable.

As a countermeasure for this, various techniques such as using a sound absorbing material, a sound insulating material or a vibration insulating material, and increasing the rigidity of the structure to avoid resonance have been taken. In general, the vibration that is the noise source is complicated, and it is generally difficult to eliminate the cause. Therefore, a method of giving vibration damping characteristics, that is, vibration damping property to the material itself as a structural member to drastically improve the vibration and noise of the structure has been attracting attention.

[0003]

2. Description of the Related Art The present inventors previously added Cu to steel having a substantially pure iron composition in which the amount of Mn is reduced to 0.08 wt% or less, as disclosed in Japanese Patent Application Laid-Open No. 4-13847. , And Al 1.
By adding 0 to 7.0 wt%, we proposed a steel sheet that maintains high vibration damping capacity and has strength and toughness as a structural steel material.

However, the damping damping capacity of the steel sheet of the present invention is still insufficient, and further improvement in characteristics has been desired.

[0005]

The object of the present invention is that it can be mass-produced, has a high vibration damping property, and has the weldability and toughness necessary as a steel material for welded structures, and is relatively inexpensive. The purpose of this study is to propose a welded structural steel with excellent vibration damping characteristics and a tensile strength of 400 MPa or more.

[0006]

As a result of various studies to improve the vibration damping characteristics of the above-mentioned steels, the inventors of the present invention reduced the O 2 content of the above-mentioned steels to significantly reduce the vibration damping property. It has been found to improve. That is, the present invention, C: 0.02
wt% or less, Si: 0.02 wt% or less, Mn: 0.08 wt% or less, Cu: 0.05
~ 1.50wt%, Al: 1.0 ~ 7.0wt%, N: 0.0040wt% or less, O: 0.
0015 wt% or less, the balance is a steel for welded structure excellent in vibration damping characteristics consisting of Fe and unavoidable impurities, the present invention, C: 0.02 wt% or less, Si: 0.02 wt% or less, Mn: 0.0
8wt% or less, Ni: 0.05-1.50wt%, Cu: 0.05-1.50wt%,
A welded structural steel containing Al: 1.0 to 7.0 wt%, N: 0.0040 wt% or less, O: 0.0015 wt% or less, and the balance being Fe and unavoidable impurities and having excellent vibration damping characteristics.

[0007]

First, the reason why the component composition is limited to the above range in the present invention will be explained. C: 0.02 wt% or less C is contained as a strengthening component in ordinary steel, but in the steel of the present invention, the strengthening action due to the precipitation of Cu is utilized, so the amount as a strengthening component is not necessary. Rather, the C content is 0.02 wt.
When it exceeds%, the vibration damping property is deteriorated, so the content is limited to 0.02 wt% or less. Si: 0.02 wt% or less 0.02 wt% is the upper limit because addition of Si in excess of 0.02 wt% to the steel with reduced Mn content deteriorates the vibration damping property. Mn: 0.08 wt% or less Mn adversely affects toughness when strengthened by adding Cu, so the lower the content, the better.The upper limit of the content is 0.08 wt%, so 0.08 wt% or less. Limited Cu: 0.05-1.50wt% Cu is precipitated as fine ε-Cu by aging treatment,
It is a component that strengthens steel, and is used for steel with a reduced Mn content.
By including Cu, it is possible to achieve both strength and toughness without impairing the vibration damping property. Therefore, it is an essential component in this invention, but if the Cu content is less than 0.05 wt%, its effect is poor, while if it exceeds 1.50 wt%, hot cracking may occur, so 0.05-1.50 wt%
The range is%. Al: 1.0-7.0wt% Al reduces Mn to 0.08wt% or less, and improves vibration damping characteristics in steel with almost pure iron composition, but its content is
If the content is less than 1.0 wt%, the effect will not be obtained.On the other hand, if the content exceeds 7.0 wt%, the toughness of the weld will deteriorate, so the content is 1.0
The range was up to 7.0 wt%. N: 0.0040 wt% or less N content is preferably lower in terms of vibration damping and toughness, and the allowable upper limit is 0.0040 wt% or less. O: 0.0015 wt% or less In the present invention, in the Fe-Cu-Al- low N composition, it was found that O significantly deteriorates the vibration damping property, and as a result of various studies, the O content was reduced to 0.0015 wt% or less. It was found that by doing so, the vibration damping performance of the steel material is significantly improved.

The method for reducing the amount of O 2 in the steel to 0.0015 wt% or less is not particularly limited, but a small amount of a deoxidizing element such as Ti may be added to fix O 2, or various methods such as vacuum degassing may be used.
In addition to the above components, the steel of the present invention may further contain
Ni can be contained in an amount of 0.05 to 1.50 wt%. Ni: 0.05 to 1.50 wt% Ni can suppress the tendency of hot cracking due to the addition of Cu without impairing the vibration damping property. If the Ni content is less than 0.05%, the effect is poor, while if it exceeds 1.50%, it is not economical. Therefore, the Ni content is 0.05 to 1.50.
The range was wt%.

In addition to the above components, P and S of 0.01 wt% and 0.005 wt%, respectively, are acceptable as impurity components in the present invention. Although P deteriorates the vibration damping property as the content of P increases, it is acceptable up to 0.01 wt%, so the upper limit is made 0.01 wt%. S, like P, is a component that is unfavorable to vibration damping properties, and if its content exceeds 0.005 wt%, the vibration damping properties deteriorate particularly. Therefore, the upper limit of S content is 0.005 wt%.

The material of the present invention can be formed into a thick steel plate by ordinary melting, casting and rolling. Further, not only thick steel plates but also thin steel plates, shaped steels, steel bars, wire rods and the like can be used. In addition, it is preferable to perform normal tempering for the precipitation of Cu.

[0011]

EXAMPLE Steels having various compositional compositions shown in Table 1 were melted and cast by a conventional method, and further subjected to ordinary hot rolling.
mm, annealed at 850 ℃ ~ 1000 ℃, and further
As a Cu precipitation aging treatment, heat treatment was performed at 575 ° C for 1 hour. In order to reduce the amount of O to 0.0015% or less, V
It was OD treated.

In Table 1, symbols A to E represent the steels of the present invention.
It is a steel sheet that has a component composition. On the other hand, symbols F to I are comparative examples.
And the amount of O 2 is high. J is the conventional steel described above
Of the composition of Japanese Patent Application Laid-Open No. 4-13847, and the symbol K is
The conventional steel is SS400 steel. Now for these steel sheets
The internal friction (Q
^-1) Was measured and the obtained results are also shown in Table 1.

[0013]

[Table 1]

As is clear from the table, all of the steels A to E which fall within the composition range of the present invention satisfy the tensile strength of 400 MPa or more required as a structural steel sheet. In addition, the internal friction value is far superior to the conventional SS400 steel, and the vibration damping property is improved. Moreover, it can be seen that the internal friction value is further improved and the vibration damping property is improved as compared with the comparative example of Japanese Patent Application Laid-Open No. 4-13847 which does not satisfy the component composition range of the present invention.

[0015]

EFFECTS OF THE INVENTION The welded structural steel excellent in vibration damping characteristics of the present invention is a steel having a composition of almost pure iron in which the amount of Mn is reduced to 0.08 wt% or less, Cu is added, and Al is 1.0 to 7.0. By reducing the O content to 0.0015 wt% or less for low N steel with added wt% to improve vibration damping properties, it is possible to obtain better vibration damping properties and sufficiently high tensile strength of 400 MPa or more as a structural material. It has an industrially useful property of having good vibration damping performance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Morikage 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Division (72) Inventor Shinichi Amano Kawasaki-cho, Chiba-shi, Chiba No. 1 Kawasaki Steel Co., Ltd. Technical Research Division

Claims (2)

[Claims] 1. C: 0.02 wt% or less, Si: 0.02 wt% or less, Mn:
0.08wt% or less, Cu: 0.05-1.50wt%, Al: 1.0-7.0wt%,
N: 0.0040wt% or less, O: 0.0015wt% or less, the balance is
Welded structural steel with excellent vibration damping characteristics consisting of Fe and inevitable impurities. 2. C: 0.02 wt% or less, Si: 0.02 wt% or less, Mn:
0.08wt% or less, Ni: 0.05-1.50wt%, Cu: 0.05-1.50wt%
, Al: 1.0-7.0wt%, N: 0.0040wt% or less, O: 0.0015wt%
A welded structural steel that contains the following, with the balance being Fe and inevitable impurities, with excellent vibration damping characteristics.