JPH07252596A - Double-layered high damping steel - Google Patents

Abstract

PURPOSE:To sufficiently satisfy the using properties required for an ordinary steel such as strength, toughness, workability, weldability or the like in a high damping steel and simultaneously to impart excellent damping capacity thereto by forming a double-layered material in which the compsn. of the external layer part of a steel is constituted of a composition of a steel for general structures and the compsn. of the internal layer part is constituted of a one in which ferrite-austenite transformation is evaded and the crystalline grains are coarsened. CONSTITUTION:As for 5 to 20% of the total thickness of a steel, the comps. of the surface layer part in the obverse and rear faces is constituted of a composition of a steel for general structures, and the compsn. of the internal layer part is constituted of, by weight, <=0.05% C, 0.5 to 5.0% Si, <=0.5% Mn, 0.05 to 2.0% Al, 0.0003 to 0.0050% B, 0 to 5.0% Mo, 0 to 5.0% Cr, 0 to 4.0% Ni, and the balance Fe with inevitable impurities, where, as for the contents of Mo, Cr and Ni in the compsn., the cases of no addition are included, and the compsn. of the external layer part in the obverse and rear faces of the steel is not specified and is suitably decided in accordance with the using purpose and capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel having excellent vibration damping properties while sufficiently satisfying the usage properties required for ordinary steel such as strength, toughness, workability and weldability.

[0002]

2. Description of the Related Art Currently, as a steel having excellent vibration damping property,
There are two types, (1) alloy system and (2) composite system ("Iron and Steel" 60th (1974) No. 14 p.127-144.
70th (1984) No. 2 p. 16-19). The alloy system is a composite type (flake graphite cast iron, etc.) that has improved damping properties by utilizing the viscosity and plastic flow at the interface between the matrix phase and the precipitation phase, or at grain boundaries, and for irreversible movement of domain walls. Ferromagnetic type (12% Cr, pure iron, etc.) using the accompanying mechanical static history of magnetism, dislocation type (Mg, etc.) using mechanical static history due to the interaction between sliding dislocations and impurity atoms, thermoelastic martensite There is a transformation twin type in.

Further, in the composite system, a damping sheet (asphalt-rubber-inorganic filler) is adhered to steel, and a viscoelastic resin is used between steel and a non-constrained type which utilizes viscoelastic hysteresis due to its elongation deformation. There is a restraint type that utilizes sandwiching and viscoelastic hysteresis due to shear deformation of resin (see, for example, JP-A-63-188040).
Although the composite system has excellent vibration damping properties, its use performance is not sufficient and gas cutting and welding are severely restricted.

Even in alloy systems, most of them are special alloys, so that there are great restrictions on manufacturability and use performance. Pure iron can satisfy manufacturability and use performance, but is insufficient in terms of vibration damping property. In addition, JP-A-2-84
The Fe-Al alloy found in Japanese Patent No. 396 has good vibration damping properties, but when the amount of Al added is large, the toughness and workability deteriorate, and there is a problem in terms of use performance. In view of such a current situation, there is a strong demand for the production of damping steel that satisfies these performances.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a technique for manufacturing vibration-damping steel which can simultaneously satisfy sufficient vibration-damping properties, mechanical properties, gas cutting / welding properties, and the like, and which can be economically mass-produced. The purpose is to provide.

[0006]

The gist of the present invention is as follows. 5 to 20% of the total thickness of the steel material is the front and back surface layer portions, and the steel composition of the inner layer portion is% by weight, and C: 0.05.
% Or less, Si: 0.5 to 5.0%, Mn: 0.5% or less, Al: 0.05 to 2.0% or less, B: 0.0003
˜0.0050%, Mo: 0 to 5.0% (including no addition), Cr: 0 to 5.0% (including no addition), Ni: 0 to 4.0% (none) (Including the case of addition), the balance consists of iron or unavoidable impurities, and is a multilayer damping steel.

[0007]

First, in order to facilitate the use performance such as gas cutting and welding, it is not possible to bond or sandwich resin or rubber or to use a special alloy component. Therefore, we investigated the component system based on pure iron and tried to solve the above-mentioned problems in pure iron. As a result, it is possible to combine several kinds of ferrite former elements such as Si, Al, Cr and Mo and add them in a predetermined amount, and control austenite former elements such as C and Mn and other elements within an appropriate range. It was found that the vibrancy was expressed. That is, it was presumed that the crystal grains were remarkably coarsened by these component systems, the domain wall was easily moved, and the vibration damping property was improved (ferromagnetic vibration damping mechanism). In order to avoid ferrite-austenite transformation of steel and coarsen the crystal grains, if there is no other impurity element, Si
It is necessary to add about 2% or more by itself, about 1% or more by Al alone, and about 12% or more by Cr alone, and the necessary amount is further increased when an austenite former element such as C or Mn is contained.

By the way, grain coarsening is contrary to the general toughening measures for steel, and steel based on the ferromagnetic vibration damping mechanism has the drawbacks of low strength and markedly poor toughness. According to the laboratory study by the inventors, Fe-Si system, Fe-C
In the r type, the tensile strength is 300 to 400 N / mm ² , and the V Charpy impact absorption energy at 0 ° C. is about 10 J. With such a characteristic value, not only can it not be used as a structural member or a strength member, but it is expected that it will be difficult to perform light bending, and in some cases even hot working at a slightly low temperature. In view of such a situation, the inventors have invented a multi-layer steel in which a ferromagnetic vibration-damping steel is wrapped with an ordinary steel material having strength, toughness and other characteristic value levels according to the purpose of use. By forming a multi-layer structure as described above, vibration-damping steel having poor ductility can be easily subjected to strong bending and hot working at relatively low temperatures.

The reasons for limitation of the present invention will be described below. The steel composition of the front and back surface layers of the steel material is not particularly limited. This is because no special composition is required for the front and back parts, most of the various steel compositions currently used can be applied, and the steel type and composition can be selected mainly according to the use performance. For example, when the performance as a general structural steel material (SS series in JIS standard) is required, the steel composition may be applied to the front and back parts. However, in that case, when the characteristics (for example, strength) in the total thickness of the steel material are required, it is necessary to consider the thickness ratio and the characteristic value of the damping steel of the inner layer.

The thickness of the front and back surface layers is required to be 5% of the minimum total thickness of steel in order to exert the effect of multiple layers. However, if it is too thick, the most characteristic feature of the inner layer, which is the vibration damping property, will not be exhibited. The thickness of the surface layer does not necessarily have to be the same on the front and back sides, and may be 5% on the front side and 20% on the back side, for example.

Next, the reasons for limiting the composition of the inner layer, that is, the damping steel will be described. As mentioned above, Si, Al, C
It is possible to avoid the ferrite-austenite transformation of the steel and coarsen the crystal grains by using each r alone. However, when added alone, the amount added becomes very large, which increases the alloy cost. Further, it is impossible to reduce the austenite former elements C, Mn, etc. to zero, and the alloy addition amount is further increased. In the present invention, the point is that the addition amount of each element can be reduced by adding the ferrite-former element in combination.

As shown in the binary system phase diagram with iron, Si and Al can avoid the ferrite-austenite transformation with a relatively small amount. Therefore, in the present invention, it is an essential element, and it is necessary to add at least 0.5% and 0.05%, respectively. The upper limit of the added amount is limited by the effect of improving the vibration damping property with respect to the added amount, alloy cost, etc. In the present invention, Si is 5.0% and Al is 2.0%. These elements not only contribute to the coarsening of crystal grains, but also have the effect of increasing strength by solid solution strengthening.

B is added not only to fix the interstitial solid solution N which suppresses the coarsening of crystal grains but also to increase the strength. Although the strengthening mechanism by B is not clear, studies by the inventors have confirmed that the addition of B increases the strength by about ²⁰ to 100 N / mm ² . Therefore, at least 0.0 in order to exert its effect.
Addition of 003% is required. However, if it is too large, like other impurity elements, it inhibits the coarsening of crystal grains and deteriorates the vibration damping property, so the content is limited to 0.0050% or less.

Since Mo, which is one of the selective elements, is a ferrite former element, its addition improves the damping property. It is considered that this is because the crystal grains are coarsened similarly to Si. In addition to this, Mo also has the effect of increasing the strength by solid solution strengthening and increasing the toughness of the ferrite value. In order to make effective use of these effects, it is necessary to add at least 0.2%.
On the other hand, if added more than a certain amount, the problem in terms of steelmaking process and cost becomes large against the effect, so the upper limit is 5.0%.
Limited to.

Although Cr is also one of the selective elements and is a ferrite former element, the effect of avoiding the ferrite-austenite transformation is smaller than that of Si, Al, etc., but the addition of multiple elements contributes to the coarsening of crystal grains and suppresses In addition to improving vibration characteristics, it contributes to the increase in strength by solid solution strengthening. In order to exert these effects, it is necessary to add at least 0.5%. As with other elements, the upper limit was limited to 5.0% due to the relationship between effect and cost.

On the other hand, the use of coarse crystal grains is contrary to the general measures for strengthening steel, and the toughness is remarkably inferior. On the other hand, according to the study by the present inventors, the addition of Ni of 2.0% or more does not impair the vibration damping property (coarse crystal grains remain),
It was confirmed that the low temperature toughness can be improved. This is Ni
Is believed to increase the stacking fault energy and facilitate cross-slip. Thus, when toughness is also required for the damping steel portion of the inner layer, it is effective to add Ni as a selective element. However, since Ni is an austenite former element, if added in a large amount, it is not only expensive, but also the austenite region in the phase diagram is expanded and the structure is refined by transformation, so the upper limit was limited to 4.0%. .

C and Mn are austenite former elements, and the smaller the ferromagnetic type damping mechanism is, the more preferable it is. Therefore, the lower limit is not particularly specified, but it is naturally limited in view of the load and cost of the steelmaking process. is there. As for the upper limit, C is 0.050 because it significantly affects the vibration damping property.
% And Mn are limited to 0.50% or less. Besides this,
The unavoidable impurities such as P, S, O, and N do not limit the range in particular, but they all hinder the coarsening of crystal grains and hinder the movement of the magnetic domain wall, which is the vibration damping mechanism. Therefore, it is clear that the lower the content, the better.

Due to the general steelmaking process capacity, P: 0.020
% Or less, S: 0.020% or less, N: 0.006% or less, O: 0.006% or less, and other unavoidable impurities.

As a method for producing the steel sheet of the present invention, as shown in Japanese Patent Laid-Open No. 63-108947, continuous casting is performed in multiple layers so that the chemical composition of the surface layer is different from that of the inner layer. Thickness, the method of rolling and forming to a predetermined thickness, the method of cladding by welding or explosive welding at the slab stage, the method of rolling and forming to a predetermined thickness, the method of cladding by explosive welding and the like at the stage of steel plate having a predetermined thickness, etc. However, any method may be used.

Although the present invention is most preferably applied to a thick plate mill, it can be widely applied to hot coils, shaped steel and the like. Further, the steel of the present invention can be used in places where vibration damping properties, vibration damping properties, etc. are required in shipbuilding, construction, bridges, industrial machinery, automobiles and the like.

[0021]

[Example] In Table 1, the surface layers of the front and back surfaces are defined by JIS standard S
The thickness ratio of the front and back surfaces of the multi-layer steel sheet having a thickness of 10 mm, which is S400 or SM490, and the damping steel composition of the inner layer are shown in Table 2, which is an index of the damping property measured by the mechanical impedance method for each steel. Coefficient, 180 ° bending workability. The steels of the present invention (multi-layered steel sheets) all have excellent vibration damping properties and, at the same time, do not crack even when bent by 180 ° and have good properties. On the other hand, in the case of a steel that is not a multi-layered steel or a steel whose multi-layered ratio deviates from the scope of the present invention, the vibration damping property or 18
There is a problem in use performance as a member having poor 0 ° bending workability and vibration damping property.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

EFFECTS OF THE INVENTION The present invention makes it possible to inexpensively provide steel having excellent vibration damping properties and use performance. As a result, it can be used as a strength member or structural member that requires vibration damping in shipbuilding, construction, bridges, construction / industrial machinery fields, factory equipment, etc., and contributes greatly to reducing noise and vibration and improving the working environment. it can.

Claims (1)

[Claims] 1. A total of 5 to 20% of the total thickness of the steel material is the front and back surface layer portions, and the steel composition of the inner layer portions is wt%, C: 0.05% or less, Si: 0.5 to 5. 0%, Mn: 0.5% or less, Al: 0.05 to 2.0% or less, B: 0.0003 to 0.0050%, Mo: 0 to 5.0% (including no addition) Cr: 0 to 5.0% (including no addition), Ni: 0 to 4.0% (including no addition), the balance being iron or inevitable impurities Layer damping steel.