JP4334113B2 - Method for selecting austenitic stainless steel to be used as a collision absorbing member - Google Patents

Description

【００４４】
【表２】

【００４５】
【発明の効果】
以上のように本発明により、衝突吸収部材として優れたオーステナイト系ステンレス鋼を、鉄道車両をはじめとする車両用の衝突吸収部材として提供することができたと同時に、本発明のオーステナイト系ステンレス鋼により、従来考慮されていなかった鉄道車両の衝突吸収設計を可能にした。
【図面の簡単な説明】
【図１】鋼種１の歪速度１０^-3（ｓ^-1）における応力ひずみ曲線と歪速度１０³ （ｓ^-1）における応力ひずみ曲線を示したものである。
【図２】鋼種２の歪速度１０^-3（ｓ^-1）における応力ひずみ曲線と歪速度１０³ （ｓ^-1）における応力ひずみ曲線を示したものである。
【図３】本発明によるオーステナイト系ステンレス鋼とＴＲＩＰ（Transformation-induced Plasticity ）鋼をはじめとする従来の高強度鋼の動的強度を比較した図である。
【図４】落重圧潰試験用の角筒部材を示した図である。
【図５】圧潰試験時の座屈変形過程における角筒部材の反力と変形量をプロットした荷重−変位線図である。
【図６】座屈変形過程における各変形時点での累積された吸収エネルギー量をプロットした吸収エネルギー−変位線図である。
【符号の説明】
１０ 角筒部材
１１ 圧潰方向矢印[0001]
[Technical field belonging to the invention]
The present invention relates to a method mainly used in the structural member and reinforcing member of the railway vehicles and general vehicles, to select an excellent austenitic stainless steel dynamic deformation properties used as the shock absorbing component.
[0002]
[Prior art]
With the background of environmental measures in recent years, the weight reduction of railway vehicles has been promoted, and stainless steel is used from the standpoint of maintenance-free and light weight reduction centering on non-painting and corrosion countermeasures starting from a monocoque lightweight vehicle body made of ordinary steel. The existing vehicle structure is the mainstream. In addition, with regard to the structural member strength for railway vehicles, the vehicle has been designed considering only static strength, and the dynamic strength of the structural member has not been taken into consideration at the time of designing.
[0003]
On the other hand, ensuring the safety of people who use vehicles such as automobiles, railways, and aircraft has been taken up as an important issue in all fields. There is a growing need for conventional commuter vehicles. However, conventional stainless steel for vehicles has been developed mainly for improving corrosion resistance and static strength against vehicle bending rigidity, and has not been developed from the viewpoint of collision safety. In fact, there is no legal collision safety evaluation standard for railway vehicles as in the automobile field.
[0004]
[Problems to be solved by the invention]
For example, in the case of a full vehicle collision, if a material having a high impact absorption capacity is applied to the vehicle frame member, the impact energy is absorbed by the member being crushed and buckled and the impact applied to personnel in the vehicle is mitigated. can do. When considering the impact absorption performance of the material, the strain rate experienced by each part at the time of a vehicle collision reaches about 10 ³ (s ⁻¹ ). Therefore, it is necessary to clarify the dynamic deformation characteristics in the high strain rate region. Therefore, it is necessary to develop a stainless steel having excellent dynamic deformation characteristics having conventional corrosion resistance performance after identifying the dynamic deformation characteristics.
[0005]
However, with regard to high-strength stainless steel, the dynamic deformation characteristics in the high strain rate region at the time of vehicle collision have not been elucidated, and attention is paid to the characteristics of any steel plate as a component for absorbing impact energy. It was not known in the past whether material selection and material development should be performed based on standards.
[0006]
Japanese Laid-Open Patent Publication No. 9-228000 discloses an austenitic stainless steel sheet with improved surface quality, but does not consider material properties related to collision safety performance. Moreover, in JP-A-8-176723 and JP-A-2000-17385, a steel plate for automobiles excellent in impact resistance and collision safety has been devised, but since it is a carbon steel, it is inferior in corrosion resistance. Therefore, it is impossible to apply it to a vehicle member without painting.
[0007]
[Means for Solving the Problems]
The present invention has been proposed to solve the above-described problems, and specific means are as follows.
1) By mass% C: 0.020 to 0.030%, Si: 0.500 to 1.00%,
Mn: 1.00 to 2.00%, P: 0.045% or less,
S: 0.030% or less, Ni: 6.00 to 8.00%,
Cr: steel containing 16.00 to 18.00%, N: 0.20% or less, with the balance being Fe and inevitable impurities, 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ) Quasi-static deformation strength σ _s in the equivalent strain range of 3 to 10% when deformed in the strain rate range of And 5 × 10 ² ~ 5 × 10 ³ Difference (σ _d −σ _{s) from the} dynamic deformation strength σd in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) ), And the maximum static strength in 3-10% of equivalent strain range when deformed at a strain rate range of ^{5 × 10 -4 ~5 × 10 -2} (s -1) σ s _max And 5 × 10 ² ~ 5 × 10 ³ Ratio σ _{d max} / σ _s of maximum dynamic strength σ _{d max} in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) _max (Σ _d −σ _s) ) Is 120 MPa or more, and the above (σ _{d max} / σ _s A method for selecting an austenitic stainless steel used as an impact absorbing member, wherein an austenitic stainless steel satisfying _max ) of 1.2 or more is selected.
2) By mass% C: 0.040-0.080%, Si: 0.40-1.00%,
Mn: 0.90 to 2.00%, P: 0.045% or less,
S: 0.030% or less, Ni: 8.00 to 10.50%,
Cr: 18.00 to 20.00%,
In which the balance is Fe and inevitable impurities, and the equivalent strain range of 3 to 10% when deformed in the strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ) Quasi-static deformation strength σ _{s in} And 5 × 10 ² ~ 5 × 10 ³ Difference (σ _d −σ _{s) from the} dynamic deformation strength σd in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) ), And the maximum static strength in 3-10% of equivalent strain range when deformed at a strain rate range of ^{5 × 10 -4 ~5 × 10 -2} (s -1) σ s _max And 5 × 10 ² ~ 5 × 10 ³ Ratio σ _{d max} / σ _s of maximum dynamic strength σ _{d max} in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) _max (Σ _d −σ _s) ) Is 100 MPa or more, and the above (σ _d −σ _s ) Is 120 MPa or more, and the above (σ _{d max} / σ _s A method for selecting an austenitic stainless steel used as an impact absorbing member, wherein an austenitic stainless steel satisfying _max ) of 1.2 or more is selected.
3) Austenitic stainless steel having a work hardening index of 0.3 or more in an equivalent strain range of 3 to 10% when deformed in a strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ). The method for selecting austenitic stainless steel used as a collision absorbing member according to 1) or 2) above, wherein steel is selected.
4) Select an austenitic stainless steel that satisfies tensile strength (MPa) × total elongation (%) ≧ 30000 when deformed in a strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ). A method for selecting an austenitic stainless steel used as a collision absorbing member according to any one of 1) to 3) above.
5) Austenite stability M _d30 shown in the following formula (1) The method of selecting an austenitic stainless steel used as a collision absorbing member according to any one of 1) to 4), wherein an austenitic stainless steel having a temperature of 0 ° C. to 60 ° C. is selected.
M _d30 = 413-462 · (% C +% N) −9.2 ·% Si−8.1 ·% Mn
-13.7% Cr-9.5% Ni-18.5% Mo (1)
[0008]
The difference (σ _d −σ _s ) between the quasi-static deformation strength σ _s and the dynamic deformation strength σ _d is a deformation rate in the range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ). The average value σ _s of the quasi-static deformation strength for each strain of 0.1% in the equivalent strain range of 3 to 10% and a strain rate range of 5 × 10 ^{2 to} 5 × 10 ³ (s ⁻¹ ) It is defined as the difference from the average value σ _d of the dynamic deformation strength for each strain of 0.1% in the equivalent strain range of 3 to 10% when deformed.
[0009]
Maximum strain rate of Shizudohi represented by static strength sigma _{s max} and maximum dynamic strength sigma _{d max} of the ratio σ _{d max} / σ _{s max} ^{is, 5 × 10 -4 ~5 × 10} -2 (s -1) The maximum static strength σ _{s max} in the equivalent strain range of 3 to 10% when deformed in the range and 3 to 10% when deformed in the strain rate range of 5 × 10 ^{2 to} 5 × 10 ³ (s ⁻¹ ) Is defined as the ratio of the maximum dynamic strength σ _{d max} in the equivalent strain range.
[0010]
The work hardening index is an n value defined by the n-th power hardening equation (Hollomon equation described in the Stainless Steel Handbook edited by the Stainless Steel Association) shown in the following equation (2), and is 5 × 10 ^{−4 to} 5 × 10 ^−2. It is defined as a work hardening index in an equivalent strain range of 3 to 10% when deformed in a strain rate range of (s ⁻¹ ).
σ = C · ε ⁿ (2)
Here, σ: true stress, ε: true strain, n: work hardening index, C: constant, where n value approximates the true stress true strain curve obtained by the tensile test by the equation (2) by the least square method or the like. Can be calculated.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Details of the present invention will be described below.
The impact at the time of a vehicle collision is highly likely to be applied to the structural member, and the member itself needs to have a high shock absorption capability. However, up to now, no attempt has been made to provide high-strength stainless steel material with excellent shock absorption characteristics as an actual member in consideration of an increase in deformation stress due to an increase in strain rate. As described above, the structural member strength of the vehicle was designed in consideration of only the static strength, and the dynamic strength of the structural member was not considered.
[0012]
A structural member for a vehicle usually has a cross-sectional shape similar to that of a square tube. As a result of analyzing the high-speed crushing deformation of such a member, about 80% of the absorbed energy is absorbed in a strain region of 10% or less. The average stress σ in the range of 3 to 10% of the strain region was used as an index of the impact absorption capacity and dynamic deformation characteristics. Usually, when the static strength σ _s is moderately small, it is easy to process into a required member shape, and the larger the dynamic strength σ _d is, the better the impact absorbing ability is.
[0013]
Therefore, the quasi-static deformation strength σ _s in the equivalent strain range of 3 to 10% when deformed in the strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ), and 5 × 10 ² to The larger the difference (σ _d −σ _s ) from the dynamic deformation strength σ _d in the equivalent strain range of 3 to 10% when the deformation is in the strain rate range of 5 × 10 ³ (s ⁻¹ ), the more static it is. Excellent formability, dynamic high impact absorption capability, and equivalent strain range of 3 to 10% when deformed in a strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ) The ratio of the maximum strength σ _{s max} and the maximum strength σ _{d max} in the equivalent strain range of 3 to 10% when deformed in the strain rate range of 5 × 10 ^{2 to} 5 × 10 ³ (s ⁻¹ ) σ _{d max} / It can be said that the larger the value (static ratio) of σ _{s max} is, the better the material is as it is excellent in static formability and dynamically in terms of high impact absorption capacity. In addition, as a general material index, the work absorption index and tensile strength (MPa) x total elongation (%), which is a balance between formability and impact resistance (balance between tensile strength and elongation), are also evaluated for impact absorption characteristics. It was used as an indicator.
[0014]
As a result of investigation based on the above-mentioned material property index, it was found that an austenitic stainless steel having a predetermined component that causes a work-induced transformation at room temperature is most suitable as a steel material having excellent collision absorption characteristics. The magnitude of work hardening due to work-induced transformation of austenitic stainless steel is attributed to the stability of austenite. By adjusting the addition amount of Cr and Ni and reducing the austenite stability moderately, when subjected to processing force at room temperature, the work-induced transformation that transforms the austenite phase in the metal structure to the martensite phase is moderate. This can be used to secure a high dynamic deformation stress.
[0015]
The stability M _{d30 of} austenite can be calculated based on the calculation formula shown in the following formula (1) (described in the Stainless Steel Handbook of Stainless Steel Association). When M _d30 gives a true tensile strain of 0.3 , Which means the temperature at which 50% martensitic transformation occurs. When the collision absorption performance was evaluated using the equation (1), it was found that good collision absorption performance could be obtained by defining it within the range of the present invention.
Austenite Stability M _d30 = 413-462 ・ (% C +% N) -9.2 ・% Si-8.1 ・% Mn-13.7 ・% Cr
-9.5 ・% Ni-18.5 ・% Mo ・ ・ ・ ・ （1）
[0016]
Finally, the present invention was completed as a result of various experiments repeated in view of the above-mentioned material characteristic index, austenite stability calculation formula, and action and effect of each element.
First, the invention 1) will be described.
C is an element necessary for obtaining strength, and it is necessary to add 0.02% or more. On the other hand, if added in a large amount, formability and weldability deteriorate, so the content is made 0.030% or less.
[0017]
Si is a solid solution strengthening element and needs to be added in an amount of 0.50% or more. On the other hand, if the amount added is large, the moldability deteriorates and the static / dynamic ratio is lowered, so the content is made 1.00% or less.
[0018]
Mn is a solid solution strengthening element and needs to be added in an amount of 1.00% or more. On the other hand, when the addition amount is increased as in the case of Si addition, the moldability deteriorates and the static / dynamic ratio is lowered, so the content is made 2.00% or less.
[0019]
P is an impurity, and when the content increases, the grain boundary becomes weak and impact resistance and moldability deteriorate.
[0020]
Since S is also an impurity and the content increases, the formability deteriorates, so the content was made 0.030% or less.
[0021]
If the amount of Ni added is increased, corrosion resistance is exhibited even in a non-oxidizing environment. Therefore, Ni is contained at 6.00% or more. On the other hand, in order to suppress the amount of expensive Ni added as much as possible and keep the metal structure in an austenite single phase, the content is made 8.00% or less.
[0022]
If the amount of Cr added is increased, the corrosion resistance is remarkably improved, so Cr is contained at 16.00% or more. On the other hand, if it exceeds 18.00%, more expensive Ni must be added in order to keep the metal structure in an austenite single phase, which is limited to the above range.
[0023]
N, which is an impurity, contributes to the improvement of the static ratio, but if it exceeds 0.20%, the formability is deteriorated and there is a risk of causing intergranular corrosion, so the content is made 0.20% or less. In order to improve the static ratio, the content is preferably 0.002% or more.
[0024]
In the above component system, the quasi-static deformation strength σ _s in the equivalent strain range of 3 to 10% when deformed in the strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ), and 5 The difference (σ _d −σ _s ) from the dynamic deformation strength σ _d in the equivalent strain range of 3 to 10% when deformed in the strain rate range of × 10 ^{2 to} 5 × 10 ³ (s ⁻¹ ) is a large value. more preferred the crash absorbing structural members but, as a result of various materials tested, if sigma _d - [sigma] _s is 120MPa or more, the indicate the characteristics was found stable in the material composition, sigma _d -Σ _s is limited to 120 MPa or more. The upper limit of σ _d −σ _s is not particularly defined, and the effect of the present invention can be obtained.
[0025]
Next, the invention 2) will be described. Regarding the invention of 2), material design was performed on the premise that temper rolling was not performed with emphasis on cost.
C is an element necessary for obtaining strength, and it is necessary to add 0.040% or more. On the other hand, if added in a large amount, formability and weldability deteriorate, so 0.080% or less.
[0026]
If the Ni addition amount is increased, corrosion resistance is exhibited even in a non-oxidizing environment. Therefore, Ni is contained at 8.00% or more. On the other hand, in order to suppress the amount of expensive Ni added as much as possible and keep the metal structure in an austenite single phase, the content is made 10.50% or less.
[0027]
If the amount of Cr added is increased, the corrosion resistance is remarkably improved, so Cr is contained at 18.00% or more. On the other hand, if it exceeds 20.00%, more expensive Ni must be added in order to keep the metal structure in the austenite single phase, and the range is limited to the above range.
[0028]
The reasons for limitation of Si, Mn, P, and S are the same as in the first aspect of the invention.
[0029]
In the above component system, the quasi-static deformation strength σ _s in the equivalent strain range of 3 to 10% when deformed in the strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ), and 5 The difference (σ _d −σ _s ) from the dynamic deformation strength σ _d in the equivalent strain range of 3 to 10% when deformed in the strain rate range of × 10 ^{2 to} 5 × 10 ³ (s ⁻¹ ) is a large value. more preferred the crash absorbing structural members but, as a result of various materials tested, if sigma _d - [sigma] _s is 100MPa or more, the indicate the characteristics was found stable in the material composition, sigma _d -Σ _s is limited to 100 MPa or more. The upper limit of σ _d −σ _s is not particularly defined, and the effect of the present invention can be obtained.
[0030]
Next, the inventions 1) and 2) will be further described.
The maximum static strength σs in the equivalent strain range of 3 to 10% when deformed in the strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ), and 5 × 10 ² ~ 5 × 10 ³ Ratio σ _{d max} of maximum dynamic strength σ _{d max} in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) / Σ _{s max} The larger the static ratio represented by is, the more preferable it is for the impact absorbing structure member. However, as a result of repeated various material tests, σ _{d max} / Σ _{s max} Is 1.2 or more, it has been found that the material composition stably exhibits the characteristics, so the static ratio σ _{d max} / Σ _{s max} Is limited to 1.2 or more. There is no particular upper limit for the static ratio, and the effect of the present invention can be obtained, so no upper limit is set.
[0031]
Next, the invention 3 ) will be described.
A larger work hardening index in the equivalent strain range of 3 to 10% when deformed in a strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ) is preferable for the impact absorbing structure member. As a result of repeating various material tests, it has been found that if the work hardening index is 0.3 or more, the material composition stably shows the characteristics, so the work hardening index is limited to 0.3 or more. In the component system of 2), since workability is an important component on the premise that temper rolling is not performed, the work hardening index is more preferably 0.4 or more. The upper limit of the work hardening index is not particularly determined, and the effect of the present invention can be obtained, so the upper limit is not determined.
[0032]
Next, the invention 4 ) will be described.
Tensile strength (MPa) x total elongation (%) when deformed in a strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ) is a balance between formability and impact resistance (tensile strength and elongation A larger value is preferable for a collision-absorbing structural member. However, as a result of repeated various material tests, if tensile strength (MPa) × total elongation (%) ≧ 30000, the material composition is stable. Therefore, the tensile strength (MPa) × total elongation (%) ≧ 30000 is limited. In the component system 2), since workability is an important component on the premise that temper rolling is not performed, it is preferable to satisfy tensile strength (MPa) × total elongation (%) ≧ 40000.
The upper limit of tensile strength (MPa) × total elongation (%) is not particularly defined, and the effect of the present invention can be obtained, so the upper limit is not defined.
[0033]
Next, the invention 5 ) will be described.
The magnitude of work hardening due to work-induced transformation of austenitic stainless steel is attributed to the stability of austenite. By adjusting the addition amount of Cr and Ni and reducing the austenite stability moderately, when subjected to processing force at room temperature, the work-induced transformation that transforms the austenite phase in the metal structure to the martensite phase is moderate. This can be used to secure a high dynamic deformation stress. The stability of austenite can be calculated based on the calculation formula shown in the formula (1).
[0034]
The austenite stability M _d30 shown in the formula (1) expresses a work-induced transformation in which the austenite phase in the metal structure is transformed into the martensite phase when subjected to working force and impact force at room temperature, and high dynamic deformation stress. In order to ensure this, the temperature is set to 0 ° C. or higher, and preferably 10 ° C. or higher in consideration of the processing temperature. In order to prevent cracking during deformation due to excessive work hardening, the austenite stability shown in the formula (1) is set to 60 ° C. or lower, preferably 40 ° C. or lower.
[0035]
Excellent impact absorption performance by casting steel with such components and directly or heating the obtained hot piece slab or hot piece billet, or by reheating the cold piece and hot rolling, hot extrusion, etc. Austenitic stainless steel materials are manufactured. In addition, about the invention of said 1), temper rolling is given.
In addition to the above, the steel of the present invention can contain 0.03% by mass or less of one or more of Al, Nb, Mo, Ti and the like.
[0036]
【Example】
The present invention will be specifically described below with reference to examples and comparative examples for selecting an austenitic stainless steel used for the impact absorbing member of the present invention, but the technical scope of the present invention is not limited to this example.
Austenitic stainless steels with various chemical components shown below were produced by casting and hot rolling with actual machines.
[Steel Type 1] By mass% C: 0.030%, Si: 1.00%, Mn: 2.00%,
P: 0.045%, S: 0.030%, Ni: 7.00%,
Cr: 17.00%, N: 0.20%
The balance is Fe and inevitable impurities (3 to 10% average stress static difference: 138 MPa, tensile strength: 1106 MPa)
[Steel Type 2] By mass% C: 0.080%, Si: 1.00%, Mn: 2.00%,
P: 0.045%, S: 0.030%, Ni: 9.50%,
Cr: 19.00%
The balance is Fe and inevitable impurities (3 to 10% average stress static difference: 125 MPa, tensile strength: 716 MPa)
[0037]
A static tensile test and a dynamic tensile test were carried out using a JIS No. 5 test piece using the above steel type plate-like test pieces. FIG. 1 shows a stress strain curve at a strain rate of 10 ⁻³ (s ⁻¹ ) and a stress strain curve at a strain rate of 10 ³ (s ⁻¹ ). ^-3 (s ^-1 ) stress strain curve and strain rate 10 ³
The stress-strain curve in (s ^<-1> ) is shown.
[0038]
When the stress strain diagram of steel type 1 in FIG. 1 is analyzed in detail, the quasi-static deformation strength σ _s in an equivalent strain range of 3 to 10% at a strain rate of 10 ⁻³ (s ⁻¹ ) and 10 ³ (s The difference (σ _d −σ _s ) from the dynamic deformation strength σ _d in the equivalent strain range of 3 to 10% at the strain rate of ⁻¹ ) is 138 MPa, and the deformation is performed at the strain rate of 10 ⁻³ (s ⁻¹ ). The maximum static strength σ _{s max in} the equivalent strain range of 3 to 10% and the maximum dynamic strength σ in the equivalent strain range of 3 to 10% when deformed in the strain rate range of 10 ³ (s ⁻¹ ) _The static ratio expressed by the ratio σ _{d max} / σ _{s max} of the _{d max} is 1.2, and the work hardening index in the equivalent strain range of 3 to 10% at the strain rate of 10 ⁻³ (s ⁻¹ ) is 0. The tensile strength (MPa) × total elongation (%) at a strain rate of 10 ⁻³ (s ⁻¹ ) was 43,000.
[0039]
On the other hand, when the stress strain diagram of steel type 2 in FIG. 2 is analyzed in detail, the quasi-static deformation strength σ _s in the equivalent strain range of 3 to 10% at a strain rate of 10 ⁻³ (s ⁻¹ ) and 10 ³ The difference (σ _d −σ _s ) from the dynamic deformation strength σ _d in the equivalent strain range of 3 to 10% at the strain rate of (s ⁻¹ ) is 125 MPa, and the strain rate of 10 ⁻³ (s ⁻¹ ). Maximum static strength σ _{s max in} the equivalent strain range of 3 to 10% when deformed at a maximum dynamic range in the equivalent strain range of 3 to 10% when deformed in the strain rate range of 10 ³ (s ⁻¹ ) The static ratio represented by the ratio σ _{d max} / σ _{s max} of the strength σ _{d max} is 1.26, and the work hardening index in the equivalent strain range of 3 to 10% at a strain rate of 10 ⁻³ (s ⁻¹ ) is obtained. The tensile strength (MPa) × the total elongation (%) at a strain rate of 10 ⁻³ (s ⁻¹ ) was 46000. Both show high dynamic strength.
[0040]
Incidentally, FIG. 3 is a diagram comparing the dynamic strength of conventional high-strength steels including austenitic stainless steel according to the present invention and TRIP (Transformation-induced Plasticity) steel. The components of TRIP steel are shown in Table 1, and the components of conventional steel are shown in Table 2.
[0041]
Static difference (σ _d) which is the difference between dynamic stress and static stress -Σ _s ) That is, the strain rate dependence of stress generally tends to decrease with increasing static strength of steel, but steel grade 1 and grade 2 are vehicle structural members with high static strength and static difference. The ideal steel was selected .
[0042]
In addition, in order to confirm the impact absorption energy performance, a rectangular tube member 11 shown in FIG. 4 is manufactured using the steel material 1 and TRIP steel (quoting No. 1 in Table 1), and the length direction of the member (the direction of the arrow 10). A drop weight crush test analysis was performed in which a weight of 400 kg was collided at a speed of 15 m / sec. FIG. 5 is a load-displacement diagram plotting the reaction force and deformation amount of the rectangular tube member in the buckling deformation process during the crushing test, and FIG. 6 is the accumulated absorbed energy amount at each deformation time point in the buckling deformation process. It is the absorbed energy-displacement diagram which plotted.
In FIG. 5, steel type 1 maintains a higher load value than TRIP steel after the maximum load elapses, and in FIG. 6, steel type 1 shows an absorption energy about 1.2 times that of TRIP steel in each displacement process. It was found that the austenitic stainless steel of the present invention has high absorbed energy performance.
[0043]
[Table 1]

[0044]
[Table 2]

[0045]
【The invention's effect】
As described above, according to the present invention, the austenitic stainless steel excellent as a collision absorbing member can be provided as a collision absorbing member for a vehicle including a railway vehicle, and at the same time, by the austenitic stainless steel of the present invention, It has made possible the collision absorption design of railway vehicles, which has not been considered before.
[Brief description of the drawings]
FIG. 1 shows a stress strain curve of a steel type 1 at a strain rate of 10 ⁻³ (s ⁻¹ ) and a stress strain curve at a strain rate of 10 ³ (s ⁻¹ ).
FIG. 2 shows a stress strain curve of steel type 2 at a strain rate of 10 ⁻³ (s ⁻¹ ) and a stress strain curve at a strain rate of 10 ³ (s ⁻¹ ).
FIG. 3 is a diagram comparing the dynamic strength of conventional high-strength steels including austenitic stainless steel according to the present invention and TRIP (Transformation-induced Plasticity) steel.
FIG. 4 is a view showing a rectangular tube member for a drop weight crushing test.
FIG. 5 is a load-displacement diagram in which reaction force and deformation amount of a rectangular tube member in a buckling deformation process during a crush test are plotted.
FIG. 6 is an absorption energy-displacement diagram in which accumulated absorption energy amounts at respective deformation points in the buckling deformation process are plotted.
[Explanation of symbols]
10 Square tube member 11 Crush direction arrow

Claims (5)

C: 0.020 to 0.030% in mass%,
Si: 0.500 to 1.00%,
Mn: 1.00 to 2.00%,
P: 0.045% or less,
S: 0.030% or less,
Ni: 6.00 to 8.00%,
Cr: 16.00-18.00%,
N: steel containing 0.20% or less, the balance being Fe and inevitable impurities, 3 when deformed in a strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ) Quasi-static deformation strength σ _s in the equivalent strain range of -10% And 5 × 10 ² ~ 5 × 10 ³ Difference (σ _d −σ _{s) from the} dynamic deformation strength σd in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) ), And the maximum static strength in 3-10% of equivalent strain range when deformed at a strain rate range of ^{5 × 10 -4 ~5 × 10 -2} (s -1) σ s _max And 5 × 10 ² ~ 5 × 10 ³ Ratio σ _{d max} / σ _s of maximum dynamic strength σ _{d max} in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) _max (Σ _d −σ _s) ) Is 120 MPa or more, and the above (σ _{d max} / σ _s A method for selecting an austenitic stainless steel used as an impact absorbing member, wherein an austenitic stainless steel satisfying _max ) of 1.2 or more is selected. C: 0.040% to 0.080% in mass%,
Si: 0.40 to 1.00%,
Mn: 0.90 to 2.00%
P: 0.045% or less,
S: 0.030% or less,
Ni: 8.00 to 10.50%,
Cr: 18.00 to 20.00%,
In which the balance is Fe and inevitable impurities, and the equivalent strain range of 3 to 10% when deformed in the strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ) Quasi-static deformation strength σ _{s in} And 5 × 10 ² ~ 5 × 10 ³ Difference (σ _d −σ _{s) from the} dynamic deformation strength σd in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) ), And the maximum static strength in 3-10% of equivalent strain range when deformed at a strain rate range of ^{5 × 10 -4 ~5 × 10 -2} (s -1) σ s _max And 5 × 10 ² ~ 5 × 10 ³ Ratio σ _{d max} / σ _s of maximum dynamic strength σ _{d max} in the equivalent strain range of 3 to 10% when deformed in the strain rate range of (s ⁻¹ ) _max (Σ _d −σ _s) ) Is 100 MPa or more, and the above (σ _d −σ _s ) Is 120 MPa or more, and the above (σ _{d max} / σ _s A method for selecting an austenitic stainless steel used as an impact absorbing member, wherein an austenitic stainless steel satisfying _max ) of 1.2 or more is selected. An austenitic stainless steel satisfying a work hardening index of 0.3 or more in an equivalent strain range of 3 to 10% when deformed in a strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ). The method for selecting an austenitic stainless steel used as a collision absorbing member according to claim 1 or 2. Select an austenitic stainless steel that satisfies tensile strength (MPa) × total elongation (%) ≧ 30000 when deformed in a strain rate range of 5 × 10 ^{−4 to} 5 × 10 ⁻² (s ⁻¹ ). A method for selecting an austenitic stainless steel used as a collision absorbing member according to any one of claims 1 to 3. Austenite stability M _d30 shown in the following formula (1) The method for selecting austenitic stainless steel used as a collision absorbing member according to any one of claims 1 to 4, wherein an austenitic stainless steel having a temperature of 0 to 60 ° C is selected.
M _d30 = 413-462 · (% C +% N) −9.2 ·% Si−8.1 ·% Mn
-13.7% Cr-9.5% Ni-18.5% Mo (1)

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