JP2002088439A - Steel for damping building material excellent in low cycle fatigue characteristic and energy absorbing performance and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce steel for damping building materials excellent in low cycle fatigue characteristics to wind and earthquakes and energy absorging performance and to provide its production method. SOLUTION: This steel for damping building materials excellent in low cycle fatigue characteristics and energy absorbing performance has a structure composed of ferrite and a hard second phase of 10 to 40% by area ratio, the grain size number of the ferritic crystal grains is >=7, the hardness of the hard second phase is >=180 Hv, further, yield strength is 200 to 350 MPa, and also the work hardening exponent is 0.2 to 0.25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unbonded brace having excellent low cycle fatigue characteristics and energy absorption performance against repeated loads accompanied by plastic deformation such as wind and earthquake.
The present invention relates to a damping building material steel used for a damping wall, a damping panel, and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Various techniques for introducing energy absorbing members and devices have been put to practical use in order to reduce the response of a building-based framework such as columns and beams to wind and earthquake. Damping construction materials such as unbonded braces, damping walls, and damping panels are one of them.

[0003] The following two characteristics are particularly required as characteristics required for steel for vibration damping building materials. Excellent low cycle fatigue characteristics, that is, long rupture life against repeated plastic deformation. Excellent in energy absorption performance, that is, the yield strength of the damping construction steel is low so that the damping building material is plastically deformed before the main frame member, and the amount of energy absorption per unit volume of the damping building material is low. Be big.

[0004] The current steels for vibration damping building materials are mainly ultra-mild steels characterized by (a) reduction of strengthening elements, (b) ferrite single phase structure, and (c) tolerance of relatively large crystal grain size. The use of extremely mild steel aims at achieving the above due to extremely low yield strength and high ductility. For example, JP-A-11-3605
In Japanese Patent No. 1, the solid solution strengthening element C is limited to 0.003% or less, N is limited to 0.004% or less, and the amount of C and N dissolved is reduced by adding a small amount of Ti. A steel material characterized by improving the toughness by grain boundary strengthening by adding a small amount of B and having a ferrite single phase structure with an average grain size of 150 μm or less and a method for producing the same are disclosed.

[0005] The following points have been made clear regarding the low cycle fatigue characteristics and energy absorption performance of ultra-mild steel in the Journal of the Architectural Institute of Japan, 472, 139 and 473, 159. -Low cycle fatigue properties of extremely mild steel are comparable to those of ordinary steel. -The energy absorption performance of extremely mild steel is superior to that of ordinary steel when the variation range of strain (hereinafter referred to as strain range) is lower than 0.7%, but is higher when the strain range is higher than 0.8%. It is not better than that of ordinary steel. Therefore,
The use of steel for vibration damping building materials, which is excellent in both low cycle fatigue characteristics and energy absorption performance, is expected.

[0006]

However, in the above-mentioned Japanese Patent Application Laid-Open No. 11-36051, the average particle size is 150
Although it is stated that the deterioration in fatigue characteristics is prevented by controlling the thickness to μm to ensure uniform deformability of the members, no technique for significantly improving the low cycle fatigue characteristics as compared with ordinary steel is disclosed. Further, in this example of the invention, it is shown that a low yield strength of about 100 MPa or less has been achieved, but it is unclear whether or not the energy absorption performance is excellent because no energy absorption performance itself is shown.

[0007] As shown in the examples of the present invention, the low cycle fatigue characteristics and energy absorption performance of ultra mild steel are not necessarily superior to those of ordinary steel. Therefore, there is a strong demand for the development of steels for vibration damping building materials that are excellent in both low cycle fatigue characteristics and energy absorption performance. An object of the present invention is to solve the above problems and to provide a steel for vibration damping building materials used for unbonded braces, vibration damping walls, vibration damping panels, and the like, and a method for producing the same.

[0008]

Means for Solving the Problems The inventors of the present invention have specified various conditions such as the structure and composition of a steel material capable of achieving both low cycle fatigue characteristics and energy absorption performance, and completed the present invention. The summary is as follows. (1) It has a structure composed of ferrite and a hard second phase having an area ratio of 10 to 40%, the ferrite crystal grains have a grain size number of 7 or more, the hardness of the hard second phase is Hv 180 or more, and a yield strength. Is 200 to 350 MPa, and has a work hardening index of 0.2 to 0.25. (2) In mass%, C: 0.05 to 0.4%, Si:
0.05 to 1.5%, Mn: 0.5 to 2%, P: 0.0
(1) characterized in that it contains not more than 3% and not more than 0.02% of S, and the balance consists of Fe and unavoidable impurities.
Steel for vibration damping building materials excellent in low cycle fatigue characteristics and energy absorption performance as described in (1). (3) Cu: 0.05 to 2%, Ni: 0.
05-2%, Cr: 0.05-2%, Mo: 0.05-
0.5%, Nb: 0.005 to 0.2%, V: 0.00
5 to 0.2%, Ca: 0.0005 to 0.006%, and rare earth element (REM): 0.0005 to 0.01%. (2) Steel for vibration damping building materials excellent in low cycle fatigue characteristics and energy absorption performance according to (2). (4) In mass%, Al: 0.005 to 0.06%, T
i: one or two of 0.005 to 0.05%, and N:
The steel for vibration damping building materials having excellent low cycle fatigue characteristics according to the above (2) or (3), further comprising 0.001 to 0.006%. (5) In producing the steel according to any one of the above (1) to (4), the slab is heated to a temperature range of Ac _{3 to} 1250 ° C., and a cumulative reduction ratio is 10% or more in a recrystallization temperature range. And then cooling at a cooling rate of 1 ° C./sec or less, the method for producing a damping building steel excellent in low cycle fatigue characteristics and energy absorption performance. (6) After hot rolling at the recrystallization zone temperature,
The low-cycle fatigue characteristics and energy according to the above (5), wherein hot rolling is performed at a cumulative rolling reduction of 40% or more in a non-recrystallization temperature range, and further cooling is performed at a cooling rate of 1 ° C / sec or less. Manufacturing method of steel for vibration damping construction materials with excellent absorption performance. (7) After cooling at a cooling rate of 1 ° C./sec or less, Ac ₁ to
(Ac ₃ -50) process for producing low-cycle fatigue characteristics and energy absorbing performance superior damping for construction steel according to (5) or (6) heating to characterized by water quenching process ℃ . (8) The method as described in (7) above, wherein after heating to Ac ₁ to (Ac ₃ -50) ° C. to perform a water quenching treatment, further to 200 ° C. to Ac ₁ to perform a tempering treatment. Method for manufacturing steel for vibration damping building materials with excellent low cycle fatigue characteristics and energy absorption performance.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. For steel materials used for building damping members and having lower strength than column and beam members, the process of low cycle fatigue fracture is generally considered to be as follows. (F1) Slip is repeated along a specific slip plane in the crystal grain, and a slip band is formed. (F2) A slip band on the surface of the steel material protrudes and penetrates, and a fine surface crack in the grain is generated. (F3) The minute surface crack in the grain penetrates through the grain boundary and propagates itself, or merges with another adjacent crack to change into a long crack, eventually leading to fracture of the member.

[0010] Here, the crystal grain boundary can be a crack propagation resistance in (F3), but there is no basis for remarkably improving the low cycle fatigue characteristics by setting the grain size to 150 µm or less. Furthermore, there is no basis for significantly improving the low cycle fatigue properties by using a ferrite single phase.

The energy absorption performance of a steel material is indicated by an area (hysteresis energy) surrounded by a hysteresis loop caused by a nominal stress and a nominal strain, and is generally considered as follows. (E1) The hysteresis energy is determined by the yield strength and the work hardening index. (E2) As the number of repetitions increases, the steel material shows a hardening or softening behavior, and the hysteresis energy changes.

The present inventors have studied in detail the controlling factors of low cycle fatigue characteristics and energy absorption performance, and have obtained the following findings. 1) Since the processes (F1) and (F2) are completed relatively early in the repetition, the low cycle fatigue life is dominated by the process (F3).

2) Refinement of crystal grains is effective in delaying the propagation of microscopic surface cracks in the grains in the process (F3), and the effect is as shown in FIG.
It is remarkable at a particle size number of 7 or more by a particle size measurement based on 0552.

3) In the mixed structure composed of ferrite and the hard second phase, in the process (F3), the microscopic surface cracks in the grains generated by the ferrite stop or detour when hitting the hard second phase. Crack propagation speed is slowed and low cycle fatigue life is improved to longer life. On the other hand, in the ferrite single phase structure, in the process of (F3), the intergranular penetration of the small surface crack in the grain and the coalescence of the adjacent crack become easy, so that the crack propagation speed is high and the low cycle fatigue life is low. Does not bring any improvement.

4) Hard secondary phases that are effective in improving low cycle fatigue life are pearlite, bainite, martensite, and mixtures thereof. However, as shown in FIG. 2, when the hard second phase is smaller than 180 in the Vickers hardness measurement based on JIS Z 2244, the small surface crack generated by the ferrite easily penetrates the hard second phase. Low cycle fatigue life is not improved. Therefore,
The hardness of the hard second phase must be 180 or more. Further, as shown in FIG. 3, when the area ratio of the hard second phase is less than 10%, the small surface cracks generated by ferrite hardly hit the hard second phase and thus easily propagated. Not improved. Therefore, the area ratio of the hard second phase must be 10% or more. However, if the area ratio of the hard second phase is greater than 40%, the proportion of ferrite that causes slip deformation and contributes to energy absorption is small, and the energy absorption performance of the vibration damping building material is extremely reduced. Therefore, the area ratio of the hard second phase must be 40% or less.

5) There is an optimum yield strength and work hardening index for increasing the hysteresis energy in a certain strain range. As shown in FIGS. 4 and 5, a strain range of 0.5 to 5% that would be applied to the damping building material due to wind or an earthquake.
In contrast, when the yield strength is 200 to 350 MPa and the work hardening index is 0.2 to 0.25, a large hysteresis energy can be obtained. When either the yield strength or the work hardening index is out of the above range, a large hysteresis energy for wind or earthquake strain cannot be obtained.

6) The behavior of repeated hardening or softening is as follows:
The steel material having a yield strength and a work hardening index within the range shown in the above 5) is saturated at a repetition number near half of the rupture life and becomes a steady state, even before the repeated hardening or softening behavior becomes steady. High energy absorption performance even afterwards.

The present invention does not particularly limit the components and the manufacturing method as long as the requirements such as the structure are satisfied as described above. However, as the embodiment of the present invention, specific components and details of the manufacturing method are described. Is described below. First, regarding the components, each element is limited as follows.

The lower limit of 0.05% of C is the minimum amount for securing the hardness and the area ratio of the hard second phase and the yield strength of the steel material. However, when the amount of C is too large, the energy absorption performance is reduced beyond the upper limit of the area ratio of the hard second phase and the yield strength of the steel material, and the weldability and the HAZ toughness are reduced. did.

Si is a component effective for improving the yield point and deoxidizing, and its effect is exhibited by adding 0.05% or more. However, when a large amount is added, the yield strength exceeds the upper limit, the energy absorption performance is reduced, and the weldability and HA
In order to deteriorate the Z toughness, the upper limit is set to 1.5%.

Mn is an element indispensable for securing strength and toughness, and the lower limit is 0.5%. However, if added in a large amount, the hardenability increases and not only deteriorates the weldability and the HAZ toughness, but also causes the yield strength to exceed the upper limit and lower the energy absorption performance, so the upper limit of Mn was set to 2%.

The reason why the impurities P and S in the steel of the present invention are set to 0.03% and 0.02% or less, respectively, is to further improve the toughness of the base metal and the welded portion. Prevention of grain boundary fracture by reducing P, inclusion Mn by reducing S
Prevents toughness degradation due to the formation of S. Therefore, the preferable P and S contents are 0.01% and 0.005% or less.

The basic components of the steel of the present invention are as described above,
Although the purpose can be sufficiently achieved, Cu, N
By appropriately adding i, Cr, Mo, Nb, V, Ca, and REM, the weldability and the base material / HAZ toughness can be improved without impairing the excellent characteristics of the steel of the present invention. Therefore, the amount of addition is of a nature restricted by itself.

Cu, Ni, Cr, Mo, Nb, and V are effective in improving the strength and toughness.
It is 0.05% for Cr and Mo and 0.005% for Nb and V. However, when added in a large amount, Cu becomes Cu during hot rolling.
Cracks occur, making production difficult, Ni and Cr become extremely expensive, Mo, Nb, and V are not preferred in terms of HAZ toughness, and excessive addition of any element exceeds the upper limit of the yield point of steel. Energy absorption performance is reduced, so that the upper limit is 2% for Cu, Ni and Cr, 0.5% for Mo, 0.5% for Nb,
V was set to 0.2%.

Ca has the effect of controlling the form of inclusions MnS and improving the toughness, and the lower limit is 0.0005%.
It is. However, if it exceeds 0.006%, CaO, Ca
Since a large amount of S is formed to form large inclusions, which impair not only the toughness of the steel but also the cleanliness, and also adversely affect the weldability.
The range of the addition amount of a was 0.0005 to 0.006%.

As in the case of Ca, rare earth elements (REM) are effective when added in an amount of 0.0005% or more to control the form of MnS. The upper limit is set to 0.0
1%.

Further, when the following elements are added,
With respect to the improvement of the base material and the HAZ toughness, more favorable results are obtained. Al and Ti combine with N to form AlN, Ti
N is formed, and coarsening of γ grains during reheating is suppressed, and the structure after rolling is refined. As lower limits for obtaining these effects, 0.005% for Al and Ti and 0.001% for N are required. However, when the amount of Al, Ti, and N becomes large, the HAZ toughness is rather lowered.
%, 0.05%, and 0.006%.

Next, in order to control the crystal grain size, the hard second phase, the yield strength, and the work hardening index in appropriate ranges as described above, the following production method is recommended. First,
In any of the manufacturing methods, it is necessary to convert the slab to 100% austenite (hereinafter referred to as γ) before hot rolling. In order to obtain γ, heating to Ac ₃ or more may be performed. However, when heating exceeds 1250 ° C., γ grains are remarkably coarsened, and ferrite grains after rolling are not refined, so that low cycle fatigue life is not improved. Therefore, the reheating temperature needs to be Ac _{3 to} 1250 ° C.

Since the slab is heated to have a very large γ grain size, hot rolling is performed in a recrystallization temperature range (about 900 to 1250 ° C.) where the γ grain size can be reduced. Cumulative rolling reduction in the recrystallization region effective for refining γ grains ((h
_0- h ₁ ) × 100 / h ₀ , h ₀ : slab thickness, h ₁ : plate thickness after rolling in the recrystallization temperature range) is 10% or more, so the lower limit was set to 10%.

Further, after hot rolling in the recrystallization temperature range, the steel sheet is cooled. The cooling rate at this time must be 1 ° C./sec or less. The reason is that when the cooling rate is higher than 1 ° C./sec, the amount of solid solution C in the ferrite increases, and the energy absorption performance due to the slip deformation of the ferrite decreases.

The basic manufacturing method of the steel of the present invention is as described above, and sufficient steel material properties can be achieved. However, after rolling in the recrystallization temperature range, controlled rolling (in the non-recrystallization temperature range of about 750 to 900 ° C). Rolling) further increases the toughness. In this case, it is effective to introduce a deformation zone by rolling in the γ grains to increase the number of ferrite nuclei, and then cool at a cooling rate of 1 ° C./sec or less. In order to introduce a deformation zone, the cumulative rolling reduction in the non-recrystallized region ((h ₁ −h ₂ ) × 100 / h)
₁ , h ₁ : thickness after rolling in recrystallization temperature range or thickness before rolling in non-recrystallization temperature range, h ₂ : thickness after rolling in non-recrystallization temperature range) is 40% or more. The lower limit was set to 40%.

According to the above-mentioned production method, the hard second phase is mainly pearlite, bainite, and a mixture thereof, but it is also effective to convert the hard second phase into martensite to improve the low cycle fatigue life. . For that purpose, it is necessary to heat the steel material to Ac ₁ to (Ac ₃ -50) ° C. and quench it with water. When the heating temperature is lower than Ac ₁ , even the portion that becomes the hard second phase cannot be converted to γ, the area ratio of the hard second phase decreases, and the γ fraction increases at a temperature higher than (Ac ₃ -50) ° C. The range was set to Ac ₁ to (Ac ₃ -50) ° C. because the area ratio of the hard second phase was increased as a result.

Further, in order to improve the toughness of the steel material and to prevent dimensional deviation due to residual stress and dehydrogenation treatment, tempering treatment after quenching may be necessary in production. If the tempering temperature is lower than 200 ° C., such prevention is not expected. If the tempering temperature exceeds the Ac ₁ point, transformation starts and the strength is significantly reduced. Therefore, the tempering temperature is 200 ° C. to Ac
₁ point.

Even if the composition of the steel material and the manufacturing method are limited, the low cycle fatigue characteristics and the energy absorption performance are not improved unless the structure, the yield strength, and the work hardening index of the manufactured steel material are all appropriate. . The present invention is intended to reliably improve low cycle fatigue characteristics and energy absorption performance, and the steel for vibration damping building materials provided by the present invention is not limited to thick steel plates, but can be used for thin steel plates, shaped steel, rods, and steel pipes. The same can be applied.

[0035]

EXAMPLE A steel plate was manufactured by a converter, continuous casting, and thick plate processes, and its metal structure, yield point, work hardening index, low cycle fatigue characteristics, energy absorption performance, and the like were investigated. Tables 1 to 15 show the chemical compositions of the steels of the present invention, and 16 to 31 show the chemical compositions of the comparative steels. Table 2 shows the steel sheet production conditions of the steel of the present invention and the comparative steel and their mechanical properties. Table 3 shows the results of the strain control low cycle fatigue test using the steel of the present invention and the comparative steel.

The strain control low cycle fatigue test was performed by the following method. A round bar fatigue test piece having a total length of 150 mm, a parallel portion length of 22 mm, and a parallel portion diameter of 10 mm was collected from each steel plate. An extensometer having a gauge length of 21 mm was fixed to the parallel portion, and a low cycle fatigue test in which the parallel portion strain range (maximum strain−minimum strain) was controlled was performed using a computer-controlled electrohydraulic fatigue tester. Distortion waveform is triangle wave, distortion ratio (minimum distortion / maximum distortion)
−1, the strain rate was 0.5% / sec, and two typical strain ranges were 0.5% (corresponding to wind vibration) and 5% (corresponding to earthquake motion). During the test, record the nominal stress-strain relationship of the parallel part of the test piece at any time, and if the test piece breaks or the maximum load during the test decreases to 75% of the maximum load at the beginning of the test, the test piece fracture Considered.

The steels 1 to 15 of the present invention have ferrite grain size, hardness and area ratio of hard second phase, yield strength and work hardening index within appropriate ranges, and have excellent low cycle fatigue life and excellent energy absorption performance. I have.

On the other hand, the comparative steel 16 has a shortage of C,
Since the area ratio of the hard second phase is low, the low cycle fatigue life is not improved. Conversely, the comparative steel 17 has an excessive C content and an excessively large area ratio of the hard second phase, so that the low cycle fatigue life is improved, but the energy absorption performance is not improved.
In Comparative Steels 18 to 24, the yield strength exceeds 350 MPa and the work hardening index is less than 0.20 due to the excess of the specific elements, and as a result, the energy absorption performance is not improved. In Comparative Steel 25, the ferrite grain size did not reach 7, so that the low cycle fatigue life was not improved. In addition, since the V content was too large, the yield hardness was too large and the work hardening index was insufficient, so that the energy absorption performance was improved. Not done. In Comparative Steel 26, the reheating temperature of the slab is too high, and in Comparative Steel 27, the cumulative rolling reduction in the recrystallization temperature range rolling is small, so that the ferrite grain size does not reach 7, and the low cycle fatigue life is not improved. Further, the energy absorption performance of the comparative steel 27 is not improved because the yield hardness is excessive and the work hardening index is insufficient. Since the cooling rate of the comparative steel 28 after the hot rolling is high, the yield hardness is excessive, the work hardening index is insufficient, and the energy absorption performance is not improved. Comparative steel 29
Since the quenching temperature is low, the area ratio of the hard second phase is too low, and the low cycle fatigue life is not improved. On the other hand, since the comparative steel 30 has a high quenching temperature, the area ratio of the hard second phase is too large, the yield hardness is excessive, and the work hardening index is insufficient,
Energy absorption performance is not improved. The comparative steel 31 has a coarse ferrite single structure because the reheating temperature is too high in addition to the lack of the C content. As a result, neither low cycle fatigue life nor energy absorption performance is improved.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

As is clear from the above embodiments, the present invention can provide a steel for vibration damping building materials having good low cycle fatigue characteristics and good energy absorption performance. Therefore,
The industrial value of the present invention can be said to be extremely high.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the ferrite grain size number of a steel material and low cycle fatigue life.

FIG. 2 is a diagram showing the relationship between the hardness of a hard second phase of steel and low cycle fatigue life.

FIG. 3 is a diagram showing a relationship between the area ratio of a hard second phase of a steel material and a low cycle fatigue life.

FIG. 4 is a diagram showing the relationship between the yield strength of steel and energy absorption performance.

FIG. 5 is a diagram showing a relationship between a work hardening index of a steel material and energy absorption performance.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shuji Awaiihara 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Atsushi Watanabe 2-6-3 Otemachi, Chiyoda-ku, Tokyo Nippon Steel Corporation (72) Inventor Eiichiro Saeki 2-6-3 Otemachi, Chiyoda-ku, Tokyo F-term within Nippon Steel Corporation (reference) 4K032 AA01 AA04 AA05 AA08 AA11 AA12 AA14 AA15 AA16 AA19 AA21 AA22 AA23 AA24 AA27 AA29 AA31 AA32 AA35 AA36 AA40 BA01 CA01 CA02 CA03 CB02 CC04 CD01 CF01 CF02 CF03

Claims (8)

[Claims] 1. A structure comprising a ferrite and a hard second phase having an area ratio of 10 to 40%, wherein a grain size number of ferrite crystal grains is 7 or more, and a hardness of the hard second phase is Hv 180 or more. The yield strength is 200-350MPa, and
A vibration-damping building material steel having a low work cycle index of 0.2 to 0.25 and excellent in low cycle fatigue characteristics and energy absorption performance. 2. In mass%, C: 0.05 to 0.4%, Si: 0.05 to 1.5%, Mn: 0.5 to 2%, P: 0.03% or less, S: The steel for vibration damping building materials according to claim 1, wherein the steel contains 0.02% or less, and the balance consists of Fe and inevitable impurities. 3. In mass%, Cu: 0.05 to 2%, Ni: 0.05 to 2%, Cr: 0.05 to 2%, Mo: 0.05 to 0.5%, Nb: 0 0.005 to 0.2%, V: 0.005 to 0.2%, Ca: 0.0005 to 0.006%, Rare earth element (REM): 0.0005 to 0.01%
The steel for vibration-damping building materials excellent in low cycle fatigue characteristics and energy absorption performance according to claim 2, further comprising one or more types. 4. One or two kinds of Al: 0.005 to 0.06%, Ti: 0.005 to 0.05%, and N: 0.001 to 0.006% by mass%. The steel for vibration damping building materials having excellent low cycle fatigue characteristics and energy absorption performance according to claim 2 or 3, further containing. 5. The steel according to claim 1, wherein the slab is heated to a temperature range of Ac _{3 to} 1250 ° C., and has a cumulative rolling reduction of 10% or more in a recrystallization temperature range. A method for producing a damping building material steel having excellent low cycle fatigue characteristics and energy absorption performance, wherein the steel is cooled at a cooling rate of 1 ° C./sec or less after hot rolling. 6. After hot rolling at a recrystallization temperature range, hot rolling is performed at a cumulative rolling reduction of 40% or more in a non-recrystallization temperature range, and further cooling at a cooling rate of 1 ° C./sec or less. The method for producing a steel for vibration damping building materials according to claim 5, which is excellent in low cycle fatigue characteristics and energy absorption performance. 7. After cooling at a cooling rate of 1 ° C./sec or less, Ac
₁ ~ (Ac ₃ -50) low cycle fatigue properties and a manufacturing method of the vibration damping building material steel excellent in energy absorption performance according to claim 5 or 6 heated, characterized in that water quenching process ° C.. 8. The method according to claim 7, wherein after heating to Ac ₁ to (Ac ₃ -50) ° C. to perform a water quenching treatment, further heating to 200 ° C. to Ac ₁ to perform a tempering treatment. A method for producing a damping building material steel having excellent low cycle fatigue characteristics and energy absorption performance as described above.