JP2801635B2 - High toughness welded structural steel with high vibration damping capacity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a steel material used for various types of machinery and structures, and in particular, has high vibration damping characteristics for suppressing vibration and noise, and has strength, toughness and welding. The present invention relates to a material for welded structures having excellent properties.

2. Description of the Related Art In recent years, vibrations of transportation engines, bridges, machine shops, and the like or noise generated from them have been regarded as a problem, and improvement thereof has been strongly demanded. In order to reduce the vibration and noise, various measures have been taken in terms of implementation such as increasing the rigidity of the structure to avoid resonance and using a vibration insulating material, a sound insulating material and a sound absorbing material.

However, the vibration which is an actual noise source is complicated, and it is difficult to eliminate the vibration only by the above means.

(Prior Art) Therefore, a so-called material damping method, which uses a material having a high vibration damping characteristic for a mechanical structure portion or the like that is a source of vibration and seeks a fundamental improvement, has attracted attention.

Wherein the alloy damping performance are often generally expressed by the magnitude of the internal friction (Q ^-1), which is an indicator of the magnitude of the energy lost to the strain amplitude per cycle, Q ^-1 The greater the ratio, the greater the rate of converting vibration energy into heat inside the alloy and the movement of the domain wall.

As a vibration damping steel sheet, for example, a sandwich type steel sheet in which a resin is sandwiched between thin steel sheets as described in JP-A-59-52644 is widely used, but this kind of steel sheet has a very high damping. Although it has performance, it has drawbacks in strength, rigidity and solubility, and is not suitable as a material for machine structural use.

Graphite cast iron is well known as a structural material having vibration damping properties, but its use is limited due to poor workability, toughness and weldability.

On the other hand, as an alloy type vibration damping material, a Mn-Cu alloy (JP-A-57
Ferromagnetic material utilizing domain wall motion in a low C-low N system or a material in which inclusions or Pb are mixed in a ferromagnetic material (Japanese Patent Publication No. 59-45748 or 59-27377).
References have been made, but there is a problem in strength, weldability, reliability in forming a structure, and the like, and it has not been put to practical use for structures.

(Problems to be Solved by the Invention) The present invention proposes a steel material having high vibration damping characteristics and excellent strength, toughness, workability and weldability required for a material for a welded structure. With the goal.

It is a further object of the present invention to propose a steel material that can be easily manufactured stably on an industrial scale.

(Means for Solving the Problems) The inventors have newly found that a soft austenite phase is precipitated in a steel material, thereby significantly improving the vibration damping characteristics, and have completed the present invention.

That is, the present invention is a steel material containing C: 0.01 to 0.50 wt% and having a Ceq. Represented by the following formula of 0.70 wt% or less, and further having austenite having a volume ratio of 3% or more. Steel material for high toughness welded structures with high vibration damping capacity It is.

The present invention relates to a rolled steel material for general structure (JIS G
It is advantageously applicable to 41kgf / mm2 class ² steel such as SS41 of 3101 standard and rolled steel for welded structure (SM41 of JIS G3106).

(Operation) Next, the experimental results on which the present invention is based will be described.

C: 0.01 to 1.00 wt%, Si: 0.05 to 2.50 wt%, Mn: 0.50 to 3.
00wt%, Ni: 0 ~ 15.0wt%, Cr: 0 ~ 30.0wt%, Cu: 0 ~ 3.0w
t%, Mo: 0 to 5.0 wt%, Nb: 0 to 0.10 wt%, V: 0 to 0.10 wt
%, Ti: 0 to 0.80 wt%, Al: 0.01 to 5.00 wt% and B: 0 to 0.
Each steel slab of various component compositions in the component range of 08 wt% is subjected to various heat histories, such as hot rolling, or cooling treatment after hot rolling, and similarly reheating quenching treatment or tempering treatment. When a large number of samples were manufactured in which the amount of austenite was changed by manufacturing, and Q- ¹ of each sample was measured, Q- ¹ was proportional to the increase in the amount of austenite, especially as shown in FIG. It became larger at 3vol%.

Naturally, depending on the steel composition, heat treatment method and manufacturing method,
Although the Q ^{−1 of} the samples and the strength and toughness were different, the Q ⁻¹ increased in each sample due to the precipitation of austenite, and the vibration damping performance was improved.

From the above experiments, it was found that in a general structural material, high vibration damping ability can be imparted by precipitating or mixing 3% or more by volume of austenite.
Moreover, it was confirmed that the weldability and the mechanical properties were not impaired by the increase in the amount of austenite.

The reason why the vibration damping property is improved by having austenite having a volume ratio of 3% or more is considered that vibration energy is absorbed by viscous flow at the interface between the mother phase and the austenite phase and shear deformation in the soft phase. .

Next, the reason for limiting the component composition range in the present invention will be described.

First, C is one of the components contributing to stabilization of retained austenite, and 0.01% by weight or more is required to obtain a desired amount of austenite and a desired strength. However
If the content exceeds 0.50 wt%, toughness and weldability deteriorate, so the upper limit is 0.50 wt%.

To increase the amount of retained austenite, it is advantageous to add austenite stabilizing elements such as Mn, Cr, Ni, Mo, Cu and V, in addition to the above-mentioned C, but the addition of a large amount of these components is uneconomical. Not only that, but also the deterioration of weldability.

It is important to ensure that the weldability is reduced to 0.70 wt% or less.

The components of Mn, Cr, Ni, Mo, Cu, and V can be added in the following ranges after satisfying the above-mentioned limit of Ceq. In other words, Mn improves hardenability and secures the strength of steel materials.
0.50% by weight or more is necessary, but if it exceeds 3.00% by weight, toughness and weldability deteriorate. Therefore, it is desirable to set the range of 0.50 to 3.00% by weight.

Ni and Cr increase the hardenability and corrosion resistance and stabilize austenite, and thus have the effect of increasing the strength without impairing the vibration damping performance. However, if added in a large amount, the toughness, hot workability, weldability and economy are reduced. Therefore, it is preferable that the upper limit of Ni is 15.0 wt% and the upper limit of Cr is 30.0 wt%.

Mo improves the hardenability and is effective in increasing the strength of the steel material, but when added in large amounts, the toughness and weldability decrease,
It is desirable to set the upper limit to 5.0%.

Although Cu has an effect of increasing corrosion resistance and strength, if added in a large amount, surface cracks are likely to occur during ingot production, and toughness and weldability are deteriorated. Therefore, it is desirable to set the upper limit to 3.0 wt%.

V has the effect of increasing the strength by precipitation strengthening,
If the amount is too large, toughness and weldability will decrease.
Desirably, it is 0.5 wt%.

Further, as described above, the vibration damping ability can be improved by increasing the amount of austenite to 3 vol% or more. However, when the amount of retained austenite exceeds 60 vol%, a tensile strength of 41 kgf / mm ² or more can be secured. Since it is difficult and economically disadvantageous, the upper limit of the amount of austenite is preferably set to 60 vol%. However, in the case of a steel material that secures various characteristics required as a product, for example, strength, toughness, weldability, etc., although the amount of austenite varies depending on the type of the steel material, the upper limit is naturally determined for each steel material.

The production conditions for precipitating austenite vary depending on the composition of the steel, but the addition of Cr or Ni as a component is advantageous for austenite precipitation, and the heat treatment is for the precipitation of residual austenite such as two-phase region heating and tempering. It is preferable to select advantageous conditions.

(Examples) Steels having the component compositions shown in Table 1 were melted by a conventional method, and heat treatment was performed for each steel type under the following conditions (A) or (B) to obtain steel plates having a thickness of 15 mm.

Note (A): After the hot-rolled steel sheet is heated to 950 ° C., 800 to 700
C., rapidly cooled to 400.degree. C., and held for 2 hours to perform multi-stage quenching to change the amount of austenite.

(B): As hot rolled (commercial general structural steel sheet-SS41
Material) Table 1 also shows the results obtained by examining the amount of austenite, tensile properties, impact properties, workability, weldability, and internal friction Q- ¹ of each steel sheet thus obtained.

As can be seen from the table, any steel sheet having an austenite amount of less than 3 vol% has a low Q- ¹ and has a poor damping property. In accordance with the present invention, steel sheets having an austenite content of 3 vol% or more have excellent vibration damping ability, and have sufficient strength (tensile strength of 41 kgf / mm ² or more) as a material for welded structures and toughness. It can be seen that they have good workability and weldability.

(Effects of the Invention) The steel material according to the present invention can improve vibration damping characteristics while ensuring sufficient strength, toughness, workability and weldability, which are not afraid of conventional structural materials, and thus can be used in mechanical structures. It is possible to replace conventional steel materials in any part of the structure, and it is possible to reliably reduce vibration and noise of the entire structure, which is extremely useful in industry.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of austenite and the internal friction Q- ¹ .

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shuzo Ueda 1 Kawasaki-cho, Chiba City, Chiba Prefecture Kawasaki Steel Engineering Co., Ltd. Technology Research Division (56) References JP-A-54-123517 (JP, A) JP-A Sho 55-2743 (JP, A) JP-A-56-116861 (JP, A) JP-A-3-500305 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 -38/60

Claims (1)

(57) [Claims] 1. A steel material containing C: 0.01 to 0.50 wt% and having a Ceq. Represented by the following formula of 0.70 wt% or less, and further having austenite having a volume ratio of 3% or more. High toughness welded structural steel with high vibration damping capacity.