JP2014129567A - Damping alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a damping alloy for an elastoplastic damper capable of being used with maintenance free after long cycle earthquake vibration and mass produced by lowering a bearing force and a stress amplitude after repeated tension compressive deformation and increasing the repeating number of fracture in an Fe-Mn-(Cr, Ni)-Si-based alloy.SOLUTION: There is provided an Fe-Mn-(Cr, Ni)-Si-based damping alloy containing at least one of Cr and Ni and further Al and 5 mass%≤Mn≤28 mass%, 0 mass%≤Cr≤15 mass%, 0 mass%≤Ni<15 mass%, 0 mass%<Si<6.5 mass%, 0 mass%≤Al<3 mass% and the balance Fe with inevitable impurities as a component composition, and satisfying conditions of [%Ni]+0.5[%Mn]>0.75[%Cr]+1.125[%Si]+2[%Al] and 37<[%Mn]+[%Cr]+2[%Ni]+5[%Al]<45, where [%Ni], [%Mn], [%Cr], [%Si] and [%Al] mean mass% of Ni, Mn, Cr, Si and Al respectively.

Description

  The present invention relates to a vibration damping alloy capable of elastic-plastic deformation with low stress and having excellent fatigue characteristics.

  The Great East Japan Earthquake that occurred on March 11, 2011, and the subsequent active seismic activity, have heightened awareness of disaster preparedness for huge disasters. In particular, because large metropolitan areas are included in areas where major earthquakes such as the Tokai / Tonankai / Nankai earthquakes and earthquakes directly under the Tokyo metropolitan area are expected to occur, the building structure is improved along with disaster prediction and strengthening of the disaster prevention system. Efforts are also being made to maximize industrial disaster mitigation measures such as vibration control and seismic isolation technology that protects objects from earthquake damage.

  The vibration damping damper is a vibration damping device that absorbs vibration energy input to the building due to wind or earthquake so that the vibration does not reach the structure body. The vibration dampers that have been proposed and developed so far can be broadly classified into viscous dampers (Patent Document 1), viscoelastic dampers (Patent Document 2), lead dampers (Patent Document 3), and elastic-plastic dampers (Patent Document 4). and so on.

  Among them, elasto-plastic dampers using low-yield point steel are particularly popular in recent years because they are superior in performance, cost, and maintainability as damping dampers that reduce the shaking of structures, especially during earthquakes. It is out.

  This elasto-plastic damper has a function of reducing vibration of a building by absorbing seismic energy input to a building mainly as thermal energy by plastic deformation of an alloy used as a core material for the damper.

  The plastic deformation characteristics of the damping alloy as the core material have an important influence on the performance of the damping damper. It is desirable that the yield stress or yield strength of the damping alloy is low in order to cause plastic deformation characteristics earlier than the structure body. In addition, after the earthquake occurs, the damper core itself is repeatedly elasto-plastically deformed. From the viewpoint of long-term use, changes in mechanical properties and metal fatigue due to repeated hardening are problems.

  Repeated hardening causes the start-up strength of the vibration damper to increase, causing significant damage to the vibration damping function.Furthermore, when metal fatigue progresses, the vibration damping device itself may even be damaged due to fatigue fracture. is there. In order to avoid such a situation, a damping alloy having a low repeated hardening rate and a long fatigue life is expected.

  Currently, the most widely used damping alloy is a low yield point steel whose yield stress or 0.2% proof stress has been intentionally reduced to about 100 to 225 MPa. The initial repeated hardening rate is high, and the fatigue life is naturally superior to the steel used for the main frame such as columns and beams of the structure, but there is no significant difference in fatigue characteristics and there is a clear advantage. Is hard to say.

  Therefore, conventional low-yield point steel damping dampers do not plasticize the core material (elastic range) against wind fluctuations that are exposed to many repetitions with low strain amplitude (small amplitude), and only during earthquakes. Designs that take fatigue damage into account, such as designing to be plastic, have been forced.

  In addition, after a major earthquake, inspection and replacement may be required in some cases due to performance changes due to repeated hardening and cumulative fatigue damage. As a result, disaster recovery periods and costs are incurred.

  Furthermore, in recent years, in high-rise buildings and the like, attention has been focused on the so-called long-period ground motion problem, in which buildings resonate during an earthquake and a relatively large amount of deformation continues for a long time. Therefore, there is an increasing demand for damping alloys having a longer fatigue life.

  On the other hand, the inventors have disclosed that an Fe—Mn—Si-based shape memory alloy containing NbC can be used as a damping alloy for a structure (see, for example, Patent Document 1).

  This is an invention that pays attention to the fact that the plastic strain remaining after an earthquake can be removed by the shape memory effect by heating and the initial shape can be recovered. In addition, the metallographic change of the alloy due to tensile and compressive plastic deformation is reversible between the γ-austenite phase of the FCC type crystal (face centered cubic lattice structure) and the ε martensite phase of the HCP type crystal (hexagonal close-packed structure). As a result, other effects as a damping alloy such as a low repeated hardening rate and a long fatigue life have been found (for example, see Non-Patent Document 1).

  Usually, in order to utilize the shape memory effect, a mechanism for heating the damper member is required, but according to the above proposal, at least without providing such a heating mechanism, the curing rate due to repeated deformation is low, Because of its long fatigue life, it can be used as a high-performance damping alloy that works effectively against long-period ground motion.

  Although it is suggested in Patent Document 5 that the Fe—Mn—Si-based shape memory alloy is effective as a vibration damping alloy with almost the same composition, the progress as a result of further research has made it appropriate as a shape memory alloy. It has also become clear that the component range and the proper component range as a damping alloy are not completely consistent.

  In Patent Document 5, an alloy to which NbC is added to improve shape memory characteristics has an extremely high stress amplitude of 650 MPa or more with respect to repeated tensile compression deformation with an amplitude of 1%. If the core material for the elastoplastic damper is not elastoplastically deformed prior to the structure main body, the vibration absorbing effect for protecting the structure main body cannot be exhibited.

  That is, the strength must be lower than that of a structure body such as a building. Therefore, when a material having high material strength is used for the core material for the damper, it is necessary to reduce the cross-sectional area of the damper so as not to exceed the strength of the structure.

  However, a damper with a small cross-sectional area has a high risk of buckling during compression deformation. Therefore, in order to secure a wide applicable range as a damper, it is advantageous that the core material for the damper has a certain low material strength. .

  In order to solve this problem, the inventors further studied and attempted to control plastic deformation characteristics by adding Al based on a Fe-30Mn-6Si shape memory alloy containing no precipitate such as NbC.

  As a result, it is disclosed that an alloy containing 1 to 3% by mass of Al is useful as a damping alloy that can operate at a stress amplitude as low as about 300 MPa with respect to repeated tensile compression deformation having an amplitude of 1% (for example, , See Patent Document 6).

  On the other hand, according to Non-Patent Document 2, the addition of more than 1% by mass of Al to the Fe-30Mn-6Si shape memory alloy almost eliminates the shape memory effect. It is clear that the optimum component range of the damping alloy does not always match.

  In addition, the core material for elasto-plastic dampers can be produced at low cost by using existing mass-production steel production equipment, which is an important requirement for promoting earthquake resistance of structures at an early stage. Since the known damping alloy disclosed in Patent Document 6 contains Mn at a high concentration of 30% by mass, it is difficult to make it with equipment for producing general steel materials such as arc furnace melting.

  The reason for this is that the boiling point of Mn is very low compared to 2010 ° C and 3070 ° C of Fe, and oxides are more easily produced than Fe. This is because reaction with things is unavoidable, and it is difficult in terms of operation and cost. Therefore, in view of economic and technical demands, in order to mass-produce and put to practical use an Fe-Mn-Si vibration-damping alloy, it is essential to develop an alloy with a further lower Mn content.

  In addition, in the Fe-Mn-Si-based shape memory alloy, a component system in which a part of Mn is replaced with Cr or Ni to improve corrosion resistance is known (for example, see Non-Patent Document 3). At the same time, it suggests that substitution with Cr or Ni is effective in order to reduce the Mn content.

  However, there has been no disclosure or suggestion about the fatigue characteristics of shape memory alloys in which Mn is replaced by Cr or Ni. As described above, the proper component range of the shape memory alloy does not necessarily match the proper component range of the damping alloy. Therefore, the optimum component range of the Fe—Mn—Cr—Ni—Si system as the damping alloy is unknown. According to Non-Patent Document 4, second phases such as δ ferrite phase, silicide, and α ′ martensite phase are easily formed in the Fe—Mn—Si based alloy to which Cr or Ni is added. The effect of aging on fatigue properties is also unclear.

  On the other hand, the fatigue properties of Fe-Mn austenitic steels have been actively studied in recent years. In TWIP (Twinning Induced Plasticity) steel, which is attracting attention as a new steel sheet for automobiles with an excellent balance of strength and ductility, twin deformation of the γ austenite phase has a good effect on fatigue properties. This is because it is recognized (see, for example, Non-Patent Document 5).

  The fatigue characteristics of Fe-Mn-Cr-Ni alloys are also examined from the same viewpoint, and the relationship between the fatigue characteristics and the structure is partially publicized (see, for example, Non-Patent Document 6). However, the plastic deformation structure of these Fe-Mn alloys and Fe-Mn-Cr-Ni alloys is a complex one combining deformation twins, α 'martensite phase, ε martensite phase, stacking faults, dislocations, etc. Yes, it cannot be said that the relationship between fatigue properties and structure has been fully elucidated.

  As a result of experiments and research conducted by the inventors, it has been clarified that ε-martensite is effective in improving fatigue characteristics. However, in TWIP steel and Fe—Mn—Cr—Ni-based alloys, ε-martenite Little is known about the impact of sites on fatigue properties. Furthermore, austenitic structural steels such as TWIP steel are usually designed as components so that the yield strength is as high as possible as structural materials, and are not suitable as core materials for elastic-plastic dampers.

  Note that an Fe—Mn—Cr—Si—Al—C alloy is disclosed as a vibration damping alloy using an ε martensite phase (see, for example, Patent Document 7). However, this damping alloy improves the internal friction in the elastic deformation region by containing 15% or more of the ε martensite phase in the γ austenite phase in the state before deformation, and the fatigue characteristics against elastoplastic deformation are disclosed. It has not been.

  Since it already contains an ε-martensite phase in a state before deformation and contains carbon having a very strong property of solid-solution hardening the γ-austenite phase, it is high in strength and is not suitable for a core material for an elastic-plastic damper. Therefore, there is no disclosure or suggestion of a component required to increase the fatigue life with a low proof stress, a low stress amplitude, and a damping alloy required.

  As described above, as a core material for an elasto-plastic damper in a damping device for a building structure, properties required for damping steel or damping alloy used mainly for the purpose of protecting the structure from earthquakes are: Low fatigue strength, low cure rate, large strain and long fatigue life (large number of repeated fractures). However, there has been no damping alloy as a core material for an elastoplastic damper having all these properties in a well-balanced manner.

JP-A-5-263858 Japanese Patent Laid-Open No. 2001-146855 JP-A-5-106367 JP-A-5-26274 JP 2006-194287 A JP 2008-56987 A JP 2011-214127 A

T. Sawaguchi, P. Sahu, T. Kikuchi, K. Ogawa, S. Kajiwara, A. Kushibe, M. Higashino, T. Ogawa, “Vibration mitigation by the reversible fcc / hcp martensitic transformation during cyclic tension-compression loading of an Fe-Mn-Si-based shape memory alloy ”Scripta Materialia, 54 (2006) 1885 M. Koyama, M. Murakami, K. Ogawa, T. Kikuchi, T. Sawaguchi, “Influence of Al on Shape Memory Effect and Twinning Induced Plasticity of Fe-Mn-Si-Al System Alloy” Mater. Trans. (2007) H. Otsuka, H. Yamada, T. Maruyama, H. Tanahashi, S. Matsuda, M. Murakami, “Effects of Alloying Additions on Fe-Mn-Si Shape Memory Alloys” Isij International, 30 (1990) 674 B. C. Maji, M. Krishnan, V. V. R. Rao, “The microstructure of an Fe-Mn-Si-Cr-Ni stainless steel shape memory alloy” Met. Mat. Trans. A, 34A (2003) 1029 T. Niendorf, F. Rubitschek, HJ Maier, J. Niendorf, HA Richard, A. Frehn, “Fatigue crack growth-Microstructure relationships in a high-manganese austenitic TWIP steel” Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing , 527 (2010) 2412 A. Glage, A. Weidner, H. Biermann, “Cyclic Deformation Behavior of Three Austenitic Cast CrMnNi TRIP / TWIP Steels with Various Ni Content” Steel Research International, 82 (2011) 1040

  The present invention eliminates the conventional problems from the background as described above, reduces the proof stress and the stress amplitude after repeated tensile and compressive deformation in Fe-Mn- (Cr, Ni) -Si based alloys, and repeats fracture. An object is to provide a damping alloy for an elasto-plastic damper that can be used without maintenance even after long-period ground motion and can be mass-produced.

  That is, the damping alloy of the present invention is characterized by the following.

  First, an Fe—Mn— (Cr, Ni) —Si vibration damping alloy containing at least one of Cr and Ni, or a vibration damping alloy further containing Al, having a component composition of 5 mass. % ≦ Mn ≦ 28 mass%, 0 mass% ≦ Cr ≦ 15 mass%, 0 mass% ≦ Ni <15 mass%, 0 mass% <Si <6.5 mass%, 0 mass% ≦ Al <3 mass%, It contains the balance Fe and inevitable impurities, [% Ni] +0.5 [% Mn]> 0.75 [% Cr] +1.125 [% Si] +2 [% Al] and 37 <[% Mn] + [% Cr] +2 [% Ni] +5 [% Al] <45 (where [% Ni], [% Mn], [% Cr], [% Si], [% Al] are Ni, Mn, Cr , Which means mass% of Si and Al).

  Secondly, the damping alloy of the first invention is characterized by containing 10 mass% ≦ Mn ≦ 20 mass%, 2 mass% ≦ Ni ≦ 10 mass%.

  Third, the damping alloy of the first or second invention contains 2% by mass ≦ Si ≦ 6% by mass.

  Fourth, in the vibration damping alloy according to any one of the first to third inventions, the metal structure of the alloy after the plastic working and the solution heat treatment is less than 15% by volume of an ε martensite phase (HCP structure). ), The balance consists only of γ-austenite phase (FCC structure), and after this state, after repeating tensile and compressive deformation with an amplitude of 1% for 100 cycles or more, an ε-martensite phase of less than 50 volume%, 3 volumes % Α 'martensite phase and the balance is γ austenite phase.

  Fifth, in the vibration-damping alloy of any one of the first to fourth inventions, the stress amplitude is 400 MPa or less after a tensile strength deformation of 280 MPa or less and an amplitude of 1% is repeated for 100 cycles or more, and the fracture. The number of repetitions is 2000 cycles or more.

  Since the damping alloy of the present invention has an added amount of Mn of 28% by mass or less, it can be easily manufactured as compared with the conventional Fe-30Mn-Si-Al based damping alloy. In particular, when the amount of Mn added is less than 20% by mass, the conventional Fe-30Mn-Si-Al vibration damping alloy could only be melted in a vacuum induction heating furnace, but it could be melted in an arc furnace. Therefore, a significant cost reduction is expected.

  Furthermore, compared with the conventional low yield point steel for elastoplastic dampers, the number of repetitions of fracture is almost one digit longer, and it can be used for long-period ground motion.

  Moreover, the damping alloy under the conditions defined in the present invention has a proof stress of 280 MPa or less, a stress amplitude after repeating tensile compression deformation of 1% amplitude 100 times or more, 400 MPa or less, and a number of repeated cycles of 2000 cycles or more, Compared to conventional Fe-Mn-Si shape memory / damping alloys containing NbC, it has lower proof stress and stress amplitude and can be operated at a low strength level. Can be applied to a wide range.

It is the graph which showed the relationship of the stress and distortion of the tension compression deformation 1st cycle of Example 2 (4S). It is the graph which showed the change of the stress amplitude by the repeated tensile compression deformation of the alloy of an Example and a comparative example.

  Usually, a damping alloy refers to a structural material that absorbs mechanical vibrations in machine tools, precision equipment, automobiles, etc., mainly increasing internal friction in the elastic deformation region and achieving high strength as a metal material. .

  On the other hand, for the purpose of distinguishing from this, the term “seismic control” is sometimes used to control vibrations mainly against earthquake motions. In recent years, the notation of “vibration suppression” is becoming mainstream because it is important for vibration suppression dampers.

  Following this trend, the present invention also uses the expression “vibration suppression”, the main object of which is suppression of vibrations to structures during an earthquake. However, the suppression of relatively minute vibrations caused by wind fluctuations is included in the effect.

  The damping alloy of the present invention is an Fe-Mn- (Cr, Ni) -Si alloy, and by adjusting the contents of Mn, Cr, Ni, Si, elastic-plastic deformation is caused by γ austenite phase and ε martensite. Creates a situation that reversibly proceeds by phase interconversion and suppresses irreversible deformation such as the formation of α ′ martensite phase, and the stress amplitude after repeated tensile compression deformation with a yield strength of 280 MPa or less and an amplitude of 1%. It is a vibration-damping alloy having 400 MPa or less and having a repetition number of ruptures of 2000 cycles or more.

  The plastic deformation mechanism in an austenitic iron-based alloy is not only the lattice dislocation sliding motion, which is a general metal plastic deformation mechanism, but also the lattice dislocations decompose into two partial dislocations and a stacking fault sandwiched between them. It takes various forms such as sliding motion of moving dislocations, twin deformation, ε martensitic transformation, α 'martensitic transformation, and usually multiple plastic deformation mechanisms are developed simultaneously.

  In the damping alloy of the present invention, the structural change caused by the tensile and compressive plastic deformation is caused by repetitive hardening by creating a state in which the structural change proceeds reversibly by the bidirectional martensitic transformation of the γ austenite phase and the ε martensite phase. Increase the number of repeated fractures.

  For this purpose, it is desirable that the state before deformation is a γ-austenite single phase, and the plastic deformation mechanism proceeds mainly by ε-martensite transformation. In that case, ε martensite transformation may contain some of the twin deformation, lattice dislocation slip, and extended dislocation slip that are inevitably simultaneously generated, but α 'martensite transformation significantly hardens the alloy. The occurrence must be suppressed.

  An essential additive element that exerts a central influence on the plastic deformation mechanism of the Fe—Mn— (Cr, Ni) —Si alloy is Mn. Mn stabilizes the γ austenite phase in the iron-based alloy and lowers the stacking fault energy to create a state in which martensitic transformation from the γ austenite phase to the ε martensite phase is likely to occur.

  Therefore, during tensile compression plastic deformation, the ε martensite transformation and this reverse transformation are alternately generated from the deformation induced γ, and the formation of the α ′ martensite phase is suppressed to improve the fatigue characteristics.

  The austenite stabilizing action of Mn can be partially replaced by Ni, and the lowering effect of stacking fault energy can be partially replaced by Cr.

  In the present invention, in order to reduce the melting cost, Cr or Ni is necessarily included as an alternative additive element of Mn. Furthermore, Al having an effect of improving the damping characteristics of the Fe—Mn—Si shape memory alloy may be added as a Mn substitute element.

The effect of Mn, Cr, Ni, and Al on the plastic deformation mechanism can be represented by the mass% of Mn that gives the same effect. In the present invention, this is defined as Mn equivalent ([% Mn] eq), and the Mn equivalent is expressed by the following formula (1) using the content (% by mass) of each component element.
Mn equivalent ([% Mn] eq) = [% Mn] + [% Cr] +2 [% Ni] +5 [% Al] (1)
[% Mn], [% Cr], [% Ni], and [% Al] in the formula mean mass% of Mn, Cr, Ni, and Al as chemical components of the damping alloy.

Moreover, in this invention, the range of Mn equivalent for expressing the bi-directional martensitic transformation between (gamma) austenite phase-epsilon martensite phases is made into the conditions represented by Formula (2) below.
37 <[% Mn] eq <45 (2)
When the Mn equivalent is not more than 37% by mass, the thermodynamic stability of the ε-martensite phase becomes very high. Therefore, even if the ε-martensite phase induced by deformation once deforms in the reverse direction, it becomes a γ-austenite phase. No reverse transformation.

  As a result, the volume fraction of the ε-martensite phase monotonously increases due to repeated tensile and compressive deformation, and when the volume fraction reaches 50% by volume or more, the probability of crack occurrence and cracks at the locations where the formed ε-martensite phases collide with each other. The extension speed increases and the number of repeated ruptures decreases.

  Further, when the Mn equivalent is 30% by mass or less, when the solution heat treatment temperature is cooled to room temperature, an ε-martensite phase having a volume fraction of 15% by volume or more is already formed, and the subsequent deformation-induced ε-martensite phase is formed. The number of repetitions of breakage is reduced.

  On the other hand, when the Mn equivalent is 45% by mass or more, the stacking fault energy increases and ε martensite is not formed.

  On the other hand, Si, which is another essential additive element, hardly affects the Mn equivalent, but improves the reversibility of the bi-directional martensitic transformation between the γ-austenite phase and the ε-martensite phase and improves the number of repetitions of fracture. It was clarified by experiment. Even when Si is not added, the number of repetitions of breakage of about 2000 cycles can be achieved. However, the addition of Si greatly increases the number of repetitions of breakage, and is most effective in the vicinity of 4% by mass.

  However, when Si is added excessively, the number of repetitions of fracture is decreased, and particularly when 6.5% by mass or more is added, the alloy may be remarkably hardened, resulting in a problem that the stress amplitude of repeated tensile compression deformation increases. .

  Regarding the addition amount of Mn, Cr, Ni, Si, the total amount of Ni, Mn, which is an austenite stabilizing element, and Cr, which is a ferrite stabilizing element, so that the metal structure before deformation is a γ-austenite single phase. The balance adjustment of the total amount of Si and Al is important. The higher the ferrite stabilizing element concentration and the lower the austenite stabilizing element concentration, the more easily the δ ferrite phase is formed. When both the ferrite stabilizing element concentration and the austenite stabilizing element concentration are low, the α ′ martensite phase is easily formed. Become.

As a result of experiments by the inventors, in the alloy system of the present invention, in order to obtain a γ-austenite single phase by suppressing formation of δ-ferrite phase when water-cooled after solution heat treatment at 1000 ° C. for 1 hour. It was found that the condition that the addition amount should be satisfied is given by the following formula (3).
[% Ni] +0.5 [% Mn]> 0.75 [% Cr] +1.125 [% Si] +2 [% Al] (3)
[% Ni], [% Mn], [% Cr], [% Si], and [% Al] in the formula are the masses of Ni, Mn, Cr, Si, and Al as chemical components of the damping alloy. Means%.

In addition to the above conditions, the amount of each component element of Mn, Cr, Ni, Si, and Al is limited due to manufacturing restrictions and the like. This will be described in detail below.
<Mn>
Mn is an essential additive element that has two effects of stabilizing austenite and lowering stacking fault energy. However, in the damping alloy of Patent Document 6 in which as much as 30% by mass of Mn is added, the Mn yield due to evaporation or oxidation of Mn. It is difficult to melt at a cost that can be put to practical use.

  In the present invention, in order to reduce the dissolution cost, the addition amount of Mn is set to 28% by mass or less by adding Cr or Ni. Further, if the amount of Mn added is less than 20% by mass, an alloy can be produced by melting in an arc furnace suitable for mass production.

  On the other hand, when the amount of Mn added is less than 10% by mass, both Cr, which is effective in reducing stacking fault energy, and Ni, which is an austenite stabilizing element, must be added in a large amount, but the dissolution cost decreases. Material costs increase.

Furthermore, if the amount of Mn added is less than 5% by mass, the formation of an α ′ martensite phase that is harmful to fatigue characteristics cannot be avoided no matter how the amount of Cr and Ni added is adjusted. From the above, in the present invention, the amount of Mn added is 5 mass% ≦ Mn ≦ 28 mass%, more preferably 10 mass% ≦ Mn ≦ 20 mass%.
<Cr>
Cr is an element that reduces the stacking fault energy of the γ austenite phase and promotes the martensitic transformation to the ε martensite phase to improve the fatigue characteristics of the vibration damping alloy of the present invention. Furthermore, it contributes to improving corrosion resistance and high-temperature oxidation resistance. However, when the amount of Cr added is 15% by mass or more, it becomes difficult to suppress the formation of the α 'martensite phase no matter how other components are adjusted, and further, Si and a low-melting intermetallic compound are formed. This makes it difficult to melt the alloy. From the above, in the present invention, the amount of Cr added is in the range of 0% by mass ≦ Cr ≦ 15% by mass.
<Ni>
Ni is an element that substitutes for the austenite stabilizing action of Mn. In particular, when the addition amount of Mn is less than 20% by mass, a γ-austenite single phase cannot be obtained as a state before deformation unless Ni as an austenite stabilizing element is added by 2% by mass or more.

  On the other hand, when the added amount of Ni is 15% by mass or more, Si and a low-melting intermetallic compound are formed, so that the hot workability of the alloy is deteriorated.

  Further, from the viewpoint of material cost, Ni which is an expensive element is desirably less than 10% by mass. From the above, in the present invention, the amount of Ni added is in the range of 0 mass% ≦ Ni <15 mass%, more preferably 2 mass% ≦ Ni ≦ 10 mass%.

In addition, about said Cr and Ni, at least any one is contained in the damping alloy of this invention, and both do not become 0 mass%.
<Si>
Si is an essential element of the Fe—Mn—Si based shape memory alloy, and its component range is 3.5 to 8% by mass, but the Si concentration range of industrially available alloys is 5 to 6% by mass. It is as follows.

On the other hand, in the damping alloy of the present invention, Si is an element that plays an important role for improving the number of fracture repetitions, but the optimum component concentration is different from that of the shape memory alloy. As a result of the experiments and researches by the inventors, in the present invention, the amount of Si to be added is 0 mass% <Si <6.5 mass%, more preferably 2 mass% ≦ Si in order to make the number of fracture repetitions 2000 cycles or more. ≦ 6 mass%.
<Al>
Since Al is an element that affects the Mn equivalent by a factor of 5, it may be added as an alternative element for Mn. However, since it is also a ferrite stabilizing element, if an excessive amount of Al is added, a δ ferrite phase is likely to be formed. When heat-treated in the atmosphere, Al having a high affinity with nitrogen may form nitrides and embrittle the alloy.

Thus, while Al is effective in adjusting the Mn equivalent even in a small amount, there is a harmful effect when excessively added, so the addition amount is in the range of 0 mass% ≦ Al <3 mass%.
<Others>
In the present invention, in addition to the above, Co, Cu, C, N may be added as an element having an effect of substituting Mn. However, since addition of Co and Cu leads to an increase in material cost, in the present invention, Co <0.2 mass% and Cu <2 mass% are set.

  Further, C and N have a function to solidify and harden the alloy, and increase the yield strength and impair the performance as a core material for an elastoplastic damper. %, N <0.08% by mass.

  In addition, for the purpose of removing interstitial elements C and N that are dissolved in the iron-based matrix, elements such as Nb, Ta, V, Ti, and Mo that have a high affinity with C and N are added to form carbides and nitrides. Forming objects is widely practiced in the field.

  In the vibration damping alloy of the present invention, it is necessary to reduce the influence of solid solution strengthening of the matrix phase by the interstitial elements C and N as much as possible in order to reduce the proof stress and the stress amplitude in repeated tensile and compressive deformation. Therefore, in the present invention, Nb, Ta, V, Ti, and Mo may be added to remove solid solution C or solid solution N by applying a conventional method.

  However, if the amount of each element added is too large, the yield strength and the stress amplitude increase due to precipitation hardening of the formed carbides and nitrides. In order to avoid this, in the present invention, Nb <0.05 mass%, Ta <0.05 mass%, V <0.05 mass%, Ti <0.05 mass%, Mo <0.05 mass%. And

  The state before deformation is preferably a single γ-austenite phase, but may contain an ε-martensite phase if the amount is small. An alloy adjusted to a state in which ε martensite transformation is likely to be induced by deformation may cause an ε martensite phase to be formed unintentionally due to environmental temperature changes or processing effects.

  These unintentionally formed ε-martensite phases, unlike the ε-martensite phases, whose crystallographic orientation is usually subsequently induced by deformation, serve as a barrier to the growth of deformation-induced ε-martensite phases, so their volume fraction Is less than 15% by volume.

  The tensile and compressive plastic deformation of the damping alloy of the present invention is mainly performed by alternately generating a martensitic transformation from the γ austenite phase to the ε martensite phase and its reverse transformation. The ε-martensite phase induced during tensile deformation reversely transforms into a γ-austenite phase when the deformation direction is reversed to compression.

  On the other hand, compressive deformation produces a new ε-martensite phase with a crystal orientation different from that at the time of tensile deformation simultaneously with the reverse transformation of the tensile-induced ε-martensite phase. This compression-induced ε martensite phase also reversely transforms into a γ austenite phase when the deformation is reversed again to tension. As described above, the tensile-induced ε and the compression-induced ε are alternately generated and disappeared by repeated tensile compression, so that the cumulative volume fraction increase of the ε martensite phase due to repeated tensile compression deformation is small. This is the reason why the damping alloy is excellent in fatigue characteristics.

  However, as the strain amplitude and the number of cycles increase, the volume fraction of the ε-martensite phase gradually increases, but when it exceeds 50% by volume, the probability of crack generation and crack extension rate increase, leading to fracture. There is. Therefore, in order to set the number of repetitions of breakage to 2000 cycles or more with respect to a tensile compression deformation with an amplitude of 1%, it is desirable that the volume ratio of ε-martensite after 2000 cycles deformation is less than 50% by volume.

  Also, since the α ′ martensite phase hardens the alloy, its volume fraction should be less than 3% by volume. When the volume fraction of the α ′ martensite phase is 3% by volume or more, the stress amplitude increases due to hardening, and the increase in the stress amplitude induces further α ′ martensite phase transformation in a chain, and therefore, the stress level increases. Not only does this reduce the damper performance, but it also leads to a reduction in the number of repeated fractures.

  The yield strength of the damping alloy of the present invention is 280 MPa or less. If the yield strength is higher than this, the cross-sectional area of the damper core material for optimizing the operation start strength of the damper becomes too small, and it becomes easy to buckle at the time of elastic-plastic deformation. In order to avoid buckling, a buckling stiffening jig must be installed. However, the installation of the buckling stiffening jig increases the manufacturing cost of the damper member.

  In addition, when the tensile and compressive deformation is repeated, the stress amplitude increases due to repeated curing. From the viewpoint of long-term use, it is desirable that the stress amplitude after repeating the tensile and compressive deformation with an amplitude of 1% 100 times or more is 400 MPa or less. .

  When the stress amplitude exceeds 400 MPa, the yield strength of the core material for the damper rises after the occurrence of a large earthquake and exceeds the strength of the building body, and it becomes difficult to operate as a damper in the subsequent earthquake. The damping alloy of the present invention is intended to be used for damping devices such as high-rise buildings as a core material for damping dampers that can cope with long-period ground motions. The number of repetitions is 2000 cycles or more.

  Hereinafter, the present invention will be specifically described based on examples. Of course, the present invention is not limited to these examples.

  10 kg of each of the chemical compositions of Examples 1 to 6 and Comparative Examples 1 to 8 shown in Table 1 were prepared in a vacuum induction melting furnace, subjected to hot forging and hot rolling at 1100 ° C., and then argon. An ingot was obtained by heating in an atmosphere at 1000 ° C. for 1 hour and then cooling with water. In addition, the addition amount of each component of Table 1 represents the mass%.

  In Table 1, in order to facilitate understanding of the characteristics of the blending components of Examples and Comparative Examples, Examples 1 to 6 are also indicated as symbols 2S, 4S, 6S, 2A, 25M8N, and 25M15C, and Comparative Examples 1 to 8 are used. Are also shown as symbols 0S, 8S, 5M, 25M, 2N, 15N, PRE, 30M1A.

  From each ingot of Examples 1 to 6 and Comparative Examples 1 to 8, low cycle fatigue test pieces with a parallel part diameter of 8 mm were prepared by lathe processing, and 0.1 Hz triangular wave, 1% amplitude strain control in room temperature atmosphere. A low cycle fatigue test was conducted.

  FIG. 1 shows the relationship between stress and strain in the first cycle of tensile compression deformation of Example 2 (4S). When the tensile strain is increased from the state O without deformation, plastic deformation is generated following the elastic deformation OA, and the point B reaches a tensile strain of 1%.

  Thereafter, when the deformation is reversed to compression, the tensile plastic strain also decreases following the elastic deformation portion BC in which the tensile elastic stress decreases in proportion to the decrease in tensile strain, and the strain becomes zero at point D.

  Furthermore, compressive plastic strain is generated as compression deformation proceeds. When the compressive strain reaches the E point of -1%, the deformation again turns from compression to tension, and then the elastic deformation EF and plastic deformation FG are followed, and the first cycle is completed. The second cycle starts along the curve GB ′ represented by a dotted line, and thereafter the same deformation as the first cycle is repeated.

  Work energy equal to the area drawn by the stress-strain curve in one cycle of deformation is converted into thermal energy and absorbed, and the vibration is attenuated.

  The point at which plastic deformation starts during tensile deformation was evaluated by 0.2% proof stress. Further, the stress amplitude in the tensile compression deformation was obtained from the maximum stress on the tension side as shown in FIG. The same evaluation was performed on all the alloys of Examples 1 to 6 and Comparative Examples 1 to 8. 2 shows Example 1 (2S), Example 2 (4S), Example 3 (6S), Comparative Example 1 (0S), Comparative Example 3 (5M), Comparative Example 4 (25M), and Comparative Example 5. (2N) shows changes in stress amplitude due to repeated tensile compression deformation of the alloys of Comparative Example 7 ((PRE), Comparative Example 8 (30M1A)).

  Many alloys exhibit a generally stable stress amplitude after repeated hardening in the first 10 cycles. However, 5M repeatedly cured after 10 cycles. Moreover, the initial curing of the PRE was small, and after showing remarkable curing from 10 to 200 cycles, the stress amplitude became stable. In order to evaluate the change of the stress amplitude due to repeated tensile and compressive deformation, the stress amplitude (σa) at the 100th cycle was obtained, and the curing rate was calculated by the following formula (4).

Curing rate (H) = (σa100−σa1) / σa1 (4)
Table 2 shows the yield strength, the first cycle stress amplitude, the 100th cycle stress amplitude, the curing rate, and the final number of repetitions obtained from these results.

  In all of Examples 1 to 6 (2S, 4S, 6S, 2A, 25M8N, 25M15C), the proof stress is 280 MPa or less, the stress amplitude of the 100th cycle is 400 MPa or less, and the final number of repetitions is 2000 cycles or more. In Comparative Example 1 (0S) without addition of Si, the number of repetitions of fracture was slightly less than 2000.

  In Comparative Example 2 (8S) in which Si was added in a larger amount than the component range of the present invention, a sample could not be prepared due to rolling cracks. The occurrence of cracking is thought to be due to the formation of a low melting intermetallic compound.

  In Comparative Example 3 (5M) in which the Mn equivalent was reduced to 31, repeated curing was remarkable, and the number of repeated fractures was 1000 or less. It is considered that the repeated curing is caused by the deformation-induced α 'martensite phase.

  In Comparative Example 4 (25M) in which the Mn equivalent was increased to 51, ε was not formed by deformation, and the number of repetitions of fracture was 1000 or less.

  In Comparative Example 5 (2N), in which the amount of Ni added was reduced to 2% by mass as compared with the inventive material, and as a result, the Mn equivalent was reduced to 29, repetitive curing was remarkably high, and the number of repeated fractures was 1000 or less. This is considered to be due to the formation of 50 volume% or more of the ε martensite phase and the α ′ martensite phase.

  In Comparative Example 6 (15N) containing 15% by mass of Ni and higher in concentration than the Examples, cracks occurred during hot rolling, and a test piece could not be produced. This is considered to be because Ni formed a low melting point intermetallic compound with Si.

  Comparative Example 7 (PRE) is an NbC precipitate-added vibration damping alloy disclosed in Patent Document 5. The number of repetitions of fracture is excellent at 3000 cycles or more, but the stress amplitude is extremely high at 620 MPa.

  Comparative Example 8 (30M1A) is an Al-added vibration damping alloy disclosed in Patent Document 6. Although the number of repeated fractures is 2000 or more and the stress amplitude is low, Mn is contained in an amount of 30% by mass, so that it is not suitable for mass production.

  From these results, the damping alloys of Examples 1 to 6 under the conditions defined in the present invention have lower proof stress and stress amplitude after repeated tensile and compressive deformation than the alloys of Comparative Examples 1 to 8 that are out of the conditions. It was confirmed that the damping alloy can be used without maintenance even after long-period ground motion and can be mass-produced.

  By using the damping alloy of the present invention, it is an elasto-plastic damper that suppresses the vibration of building structures due to earthquakes, wind fluctuations, etc., operates at low stress, and can be used maintenance-free even when repeatedly exposed to large earthquakes It becomes possible to manufacture a simple low-cost vibration damping device.

As a high-performance damper that does not impair the damping performance even if a large-amplitude vibration such as long-period ground motion continues for a long time, it can be used especially for damping high-rise buildings. In addition, building structures are places that are repeatedly deformed with large strains in all forms such as chemical plants, power plants, halls, towers, fuel tanks, elevated railways / roads, bridges, pipelines, tunnels, wind power generation facilities, etc. It is expected to be effective in suppressing vibrations.

Claims (5)

  An Fe-Mn- (Cr, Ni) -Si vibration damping alloy containing at least one of Cr and Ni, or a vibration damping alloy further containing Al, and having a component composition of 5 mass% ≦ Mn ≦ 28% by mass, 0% by mass ≦ Cr ≦ 15% by mass, 0% by mass ≦ Ni <15% by mass, 0% by mass <Si <6.5% by mass, 0% by mass ≦ Al <3% by mass, balance Fe and inevitable [% Ni] +0.5 [% Mn]> 0.75 [% Cr] +1.125 [% Si] +2 [% Al] and 37 <[% Mn] + [% Cr] +2 [% Ni] +5 [% Al] <45 (where [% Ni], [% Mn], [% Cr], [% Si], [% Al] are Ni, Mn, Cr, Si, Al A damping alloy characterized by satisfying the following condition:   2. The damping alloy according to claim 1, comprising 10 mass% ≦ Mn ≦ 20 mass%, 2 mass% ≦ Ni ≦ 10 mass%.   3. The damping alloy according to claim 1, comprising 2 mass% ≦ Si ≦ 6 mass%.   The metal structure of the alloy after plastic working and solution heat treatment consists of less than 15% by volume of ε martensite phase (HCP structure) and the balance is γ austenite phase (FCC structure). The state after repeating 100% cycles of 1% tensile and compressive deformation is less than 50% by volume of ε martensite phase, less than 3% by volume of α ′ martensite phase, and the balance is γ austenite phase. The damping alloy according to any one of claims 1 to 3. 5. The stress amplitude after proof stress is 280 MPa or less, the tensile compression deformation of 1% amplitude for 100 cycles or more, and the stress amplitude is 400 MPa or less, and the number of repeated fractures is 2000 cycles or more. The damping alloy according to one item.

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