Abstract:
This invention provides a steel sheet for structural components excellent in impact absorption property comprising, in mass %, C: 0.005 to 0.05%, N: 0.01 to 0.30%, Si: 0.1 to 2%, Mn: 0.1 to 15%, Ni: 0.5 to 8%, Cu: 0.1 to 5%, Cr: 11 to 20%, Al: 0.01 to 0.5%, and a balance of Fe and unavoidable impurities, wherein Md 30  value given by equation (A) is 0 to 100° C., and total impact energy absorption in dynamic tensile testing is 500 MJ/m 3  or greater: 
       Md 30 =551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)   (A).

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a stainless steel sheet used chiefly in structural components requiring strength and impact absorption capability, and particularly to a stainless steel sheet for automobile and bus impact absorption components such as front side members, pillars and bumpers, and for structural components such as vehicle suspension members and rims, railcar bodies and the like. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    Environmental concerns have in recent years made improvement of the fuel economy of cars, motorcycles, buses, railcars and other means of transport a critical issue. One aggressively-pursued approach to boosting fuel economy has been car body weight reduction. Car body weight reduction relies heavily on lowering the weight of the materials used to fabricate the body components, specifically on reducing the thickness of sheet steels. However, sheet metal thickness reduction has the undesirable effect of degrading rigidity and collision (crash) safety performance. As strength enhancement of the steels used for component fabrication is an effective way to increase collision safety, ordinary steels and high-strength steels are utilized in automobile impact absorption components. Ordinary steels are, however, poor in corrosion resistance and multi-coat coating is essential for their use. They cannot be used for unpainted or lightly painted components, and multi-coat painting increases cost. Although ordinary steels can be imparted with high strength by various methods such as solution hardening, precipitation hardening, dual phasing, and deformation-induced transformation, all of the methods are disadvantageous in the point that the strengthening is accompanied by a marked decline in ductility. As ductility declines, fabrication into the structural component becomes increasingly difficult, so that the degree of structural freedom is greatly degraded. 
         [0003]    Cr-containing stainless steels are far superior to ordinary steels in corrosion resistance and are therefore viewed as having the potential to reduce weight by lowering the corrosion margin (extra thickness to compensate for expected corrosion) and to eliminate the need for painting. In addition, austenitic stainless steels are excellent in strength-ductility balance and are considered capable of achieving high strength in combination with high ductility through chemical composition adjustment. Moreover, as regards collision safety improvement, utilizing a steel having high impact absorption capability in the vehicle frame makes it possible, for example, to absorb crash impact by component collapse deformation and thus to lessen the impact on passengers during a collision. In other words, considerable merits can be realized regarding fuel economy improvement through body weight reduction, painting simplification and safety enhancement. 
         [0004]    Austenitic stainless steels such as SUS301L and SUS304 are used in the structural components of railcars, for instance, because they are excellent in corrosion resistance, ductility and formability. Japanese Patent Publication (A) No. 2002-20843 teaches an austenitic stainless steel with high strain rate and excellent impact absorption capability that is intended for use mainly in structural components and reinforcing materials for railcars and ordinary vehicles. This is a steel containing 6 to 8% Ni and having an austenite structure that achieves high strength during high-speed deformation owing to the formation of deformation-induced martensite phase. This prior art defines the deformation strengths under dynamic deformation and static deformation, maximum strength, work-hardening index and other properties of the steel. However, it is inadequate on the point of impact energy absorption, which is the most important aspect from the viewpoint of safety at the time of sustaining a high-velocity impact, and even though the difference between dynamic deformation strength and static deformation strength may be great, collision performance may be inferior if the static deformation strength is low. The dynamic/static ratio is defined as the ratio between the maximum dynamic and static strengths. But strength, e.g., yield strength, in the relatively low strain range is strongly affected by the impact absorption property at the time of collision, so the definition based on the maximum strength ratio may become a problem in some cases. Moreover, when deformation occurs during a collision, not only strength but also steel ductility may be a contributing factor, and this has necessitated a design taking heavy deformation reaching the point of destruction into consideration as an absorbed energy property. In other words, the teaching of Japanese Patent Publication (A) No. 2002-20843 is insufficient regarding safety performance at the time of collision, namely, impact absorption property. In addition, the inclusion of a relatively large amount of Ni makes cost high, so that application to automobiles, motorcycles, buses and other ordinary transportation vehicles has been difficult. 
         [0005]    Further, martensitic stainless steel sheets imparted with high strength by quenching (e.g., SUS420) have very low ductility and are extremely poor in weld toughness. Since automobiles, buses and railcars have many welded structures, their structural reliability is greatly impaired by poor weld toughness. On the other hand, ferritic stainless steel sheets (e.g., SUS430) are low in strength and not suitable for members requiring strength, and they are incapable of improving collision safety performance owing to their low impact energy absorption at the time of high-velocity deformation. 
       SUMMARY OF THE INVENTION 
       [0006]    Thus no technology has been available for enabling a vehicle structural component made of stainless steel sheet to achieve good collision safety performance by improving its impact energy absorption during high-speed deformation, while simultaneously ensuring good formability of the stainless steel sheet. The present invention is directed to overcoming the foregoing issues by providing a stainless steel sheet that is both high in strength and excellent in impact absorption property during high-speed deformation. 
         [0007]    The inventors carried out a study on metal structure in relation to deformation mechanism at the time of sustaining high-speed deformation. As a result, they discovered a technique that enables improvement of impact energy absorption during high-speed deformation of an austenitic stainless steel while simultaneously achieving excellent sheet workability. Specifically, for increasing deformation resistance during ultra-high speed deformation of a strain rate of 10 3 /sec, deformation-induced transformation is positively exploited to increase work hardenability, thereby increasing impact energy absorption through a dramatic improvement in strength and ductility when the component collides. Therefore, a vehicle body fabricated using the steel sheet absorbs the impact at the time of a collision and minimizes body collapse, thereby markedly increasing the safety of passengers. 
         [0008]    The gist of the present invention is as set out in the following. 
         [0009]    A steel sheet for structural components excellent in impact absorption property comprising, in mass %, C: 0.005 to 0.05%, N: 0.01 to 0.30%, Si: 0.1 to 2%, Mn: 0.1 to 15%, Ni: 0.5 to 8%, Cu: 0.1 to 5%, Cr: 11 to 20%, Al: 0.01 to 0.5%, and a balance of Fe and unavoidable impurities, wherein Md 30  value given by equation (A) is 0 to 100° C., and total impact energy absorption in dynamic tensile testing is 500 MJ/m 3  or greater: 
         [0000]      Md 30 =551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)   (A). 
         [0010]    (2) The steel sheet for structural components excellent in impact absorption property according to (1), wherein dynamic/static ratio of yield strength is 1.4 or greater. 
         [0011]    (3) The steel sheet for structural components excellent in impact absorption property according to (1) or (2), wherein tensile strength is 600 MPa or greater and elongation at break is 40% or greater in static tensile testing. 
         [0012]    (4) A steel sheet for structural components excellent in impact absorption property comprising, in mass%, C: 0.005 to 0.05%, N: 0.01 to 0.30%, Si: 0.1 to 2%, Mn: 0.1 to 15%, Ni: 0.5 to 8%, Cu: 0.1 to 5%, Cr: 11 to 20%, Al: 0.01 to 0.5%, and a balance of Fe and unavoidable impurities, wherein Md 30  value given by equation (A) is 0 to 100° C., and impact energy absorption to 10% strain in dynamic tensile testing is 50 MJ/m 3  or greater: 
         [0000]      Md 30 =551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)   (A). 
         [0013]    (5) The steel sheet for structural components excellent in impact absorption property according to (4), wherein dynamic/static ratio of yield strength is 1.4 or greater. 
         [0014]    (6) The steel sheet for structural components excellent in impact absorption property according to (4) or (5), wherein tensile strength is 600 MPa or greater and elongation at break is 40% or greater in static tensile testing. 
         [0015]    (7) The steel sheet for structural components excellent in impact absorption property according to (4) or (5), wherein tensile strength is 700 MPa or greater and elongation at break is 5% or greater in static tensile testing. 
         [0016]    “Total impact energy absorption in dynamic tensile testing” is defined as the impact energy absorption up to break when a high-velocity tensile test is conducted at a strain rate of 10 3 /sec corresponding to that at the time of a vehicle collision, and “impact energy absorption to 10% strain” is defined as the impact energy absorption up to the 10% strain region in the high-velocity tensile test. The static tensile test is a tensile test conducted at the usual strain rate (strain rate of 10 −3 to −2 /sec). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a diagram showing the relationship between Md 30  value and total impact energy absorption in high-speed tensile testing. 
           [0018]      FIG. 2  is a diagram showing the relationship between Md 30  value and impact energy absorption to 10% strain in high-speed tensile testing. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    The reasons for the limitations of the invention are explained in the following. 
         [0020]    The important point in the present invention is the impact absorption upon incurring a high-speed impact. The impact force at the time of a vehicle collision is applied to structural components of the vehicle. The impact absorption capability of the steel constituting the components is therefore important. Up to now, no attempt has been made to provide a stainless steel that takes into account the impact energy absorption at high strain rate and high speed, nor has vehicle design with this in mind been carried out. Most vehicle structural components have angular cross-sections as typified by hat-shaped formed components. Although the strain region that absorbs impact differs among different structural components, what is important at locations that collapse during collision is the impact energy absorption up to material destruction. Total impact energy absorption is therefore used as an index. Total impact energy absorption improves as both strength and ductility are higher during high-speed deformation. However, conventional high-strength steel sheet, while high in strength, is low in fracture ductility and is therefore limited in total energy absorption. 
         [0021]    The present invention improves collision safety performance to the utmost from the material standpoint by utilizing high ductility and high work hardenability property during deformation to dramatically improve total energy absorption. Moreover, since some locations need to absorb impact up to the 10% strain region, i.e., a relatively low strain rate region, impact energy absorption to strain rate of 10% is adopted as an index. Although this depends on the component shape, it applies to automobile front side member regions and the like, as indicated in “ Report on Research Group Results Regarding High-Speed Deformation of Automotive Materials ” (compiled by The Iron and Steel Institute of Japan, p 12). 
         [0022]    The larger is the ratio between yield strength in static tensile testing and yield strength in dynamic tensile testing, the more preferable for an impact absorption structural member. Moreover, a steel with high ductility is preferable for fabrication into vehicle structural components. The elongation at break in static tensile testing was therefore used as a general material index. 
         [0023]    The inventors carried out a study based on the foregoing indexes, by which they learned that that the optimum stainless steel in terms of excellent impact absorption property is an austenitic stainless steel utilizing work hardening by deformation-induced transformation. They further learned that desired impact energy absorption during high-speed deformation can be achieved by adjusting the various constituents to control austenite so that deformation-induced martensite transformation occurs suitably during high-speed deformation. 
         [0024]    Austenite stability constituting an index of deformation-induced martensite transformation is calculated based on Md 30  value shown below (from the  Stainless Steel Handbook  compiled by the Japan Stainless Steel Association). The Md 30  value is the temperature at which 50% of martensite is formed at the time of imparting tensile strain to a true strain of 0.3. When impact energy absorption was assessed using this value, it was found that the excellent impact energy absorption prescribed by the present invention could be obtained. 
         [0000]      Md 30 =551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)−18.5Mo−68Nb. 
         [0025]    When Mo and Nb are not contained, the foregoing Md 30  becomes that of the following equation (A): 
         [0000]      Md 30 =551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)   (A). 
         [0026]    Explanation will be made first regarding the steel composition. 
         [0027]    C must be added to a content of 0.005% or greater to achieve high strength. On the other hand, C content is defined as 0.05% or less, because addition of a large amount degrades formability and weldability. Taking refining cost and grain boundary corrosion property into account, the more preferable content range is 0.01 to 0.02%. 
         [0028]    N, like C, is effective for strength enhancement and beneficial for improving impact energy absorption. For these purposes, it must be added to a content of 0.01% or greater. On the other hand, N content is defined as 0.30% or less, because excessive addition degrades formability and weldability. Taking refining cost, manufacturability and grain boundary corrosion property into account, the more preferable content range is 0.015 to 0.025%. 
         [0029]    Si is a deoxidizing element that is also a solution hardening element effective for achieving high strength. For these purposes, it must be added to a content of 0.1% or greater. On the other hand, Si content is defined as 2% or less, because addition of a large amount degrades formability and markedly lowers the dynamic/static ratio. Taking manufacturability into account, the more preferable content range is 0.2 to 1%. 
         [0030]    Mn is a deoxidizing element and a solution hardening element effective for achieving high strength. Mn also promotes work hardening of austenite phase during high-speed deformation. For these purposes, it must be added to a content of 0.1% or greater. On the other hand, Mn content is defined as 15% or less, because when added in a large amount, deformation-induced martensite is not formed and formation of MnS, which is a water-soluble inclusion, degrades corrosion resistance. Taking descaling property in the manufacturing process into account, the more preferable content range is 1 to 10%. 
         [0031]    Ni is an element that improves corrosion resistance. For this, and for austenite phase formation, Ni must be present at a content of 0.5% or greater. On the other hand, Ni content is defined as 8% or less, because when added in a large amount, raw material cost is markedly higher and deformation-induced martensite is not formed. Taking manufacturability, stress corrosion cracking and the like into account, the more preferable content range is 1.5 to 7.5%. 
         [0032]    Cu improves formability and contributes to dynamic/static ratio improvement. It is added to a content of 0.1% or greater. Cu also produces its effects when included from scrap or the like in the composition adjustment process. When added in excess of 5%, however, deformation-induced martensite formation no long occurs, so the content is defined as 5% or less. The more preferable range is 0.1 to 4%. 
         [0033]    Cr is an important element that must be added to a content of 11% or greater from the viewpoint corrosion resistance. On the other hand, the upper limit of Cr addition is defined as 20%, because excessive addition necessitates addition of large amounts of other elements for structure regulation. The content range is preferably 14 to 18%. 
         [0034]    Al is added as a deoxidizing element and also because it renders sulfides harmless and contributes to improvement of workability aspects such as hole expandability during component processing. These effects appear at an Al content of 0.01% or greater, so the lower limit of content is defined as 0.01%. The upper content limit is defined as 0.5%, because addition in excess of this level leads to surface flaw occurrence and manufacturability degradation. Taking cost and the like into account, the more preferable content range is 0.1 to 0.5%. 
         [0035]    When the material is impacted, it manifests deformation-induced transformation that transforms austenite phase into martensite phase, thereby effectively giving rise to work hardening during deformation. The efficient formation of martensite phase during deformation causes high strengthening and also prevents necking, thereby contributing to ductility improvement. Since martensite transformation is affected by strain and temperature, martensite formation is inhibited by the heat of deformation generated during high-speed deformation. However, in the stainless steel sheet of the present invention, it was found that martensite formation at the initial stage of deformation is sometimes promoted more during dynamic deformation than during static deformation. This is attributable to the strain rate dependence of transformation dependent on composition and the effect thereof dramatically improves impact energy absorption during high-speed deformation. 
         [0036]    Various stainless steel sheets (thickness; 1.5 mm) were subjected to dynamic tensile testing at a strain rate of 10 3 /sec. The effect of Md 30  value on total impact energy absorption and impact energy absorption to 10% strain at this time are shown in  FIGS. 1 and 2 , respectively. 
         [0037]    It can be seen that within the range of the present invention both total impact energy absorption and impact energy absorption to 10% strain exhibit excellent values. When Md 30  value is too high, ductility is thought to be lowered because cracking occurs at the boundary between austenite phase and martensite phase owing to excessive formation of martensite during deformation. Heretofore, total impact energy absorption at the time of high-speed deformation of high-strength steel has been thought to be on the order of less than 400 MJ/m 3  (see, for example, CAMP-ISIJ, Vol 9 (1996), P 1101, FIG. 4 and  Symposium on Automobile Materials , Japan Stainless Steel Association, 1997, p 71). 
         [0038]    The present invention provides a steel having much higher impact absorption property than the conventional high-strength steel, wherein the total impact energy absorption is defined as 500 MJ/m 3  or greater and, from  FIGS. 1 and 2 , the range of Md 30  value is defined as 0 to 100° C. In the Md 30  value range of the present invention, the impact energy absorption to 10% strain obtained is 50 MJ/m 3  or greater. Studies conducted by the inventors showed that if impact energy absorption of 50 MJ/m 3  can be obtained, that is adequate as the impact absorption property in the relatively low strain region. So the impact energy absorption to 10% strain is defined as 50 MJ/m 3  or greater. No upper limit value is defined for the impact energy absorption because the effect of the present invention can be realized without defining one. 
         [0039]    The dynamic/static ratio is an index representing the deformation rate dependence of work hardening. It is the ratio of yield strength in dynamic tensile testing to yield strength in static tensile testing and is here defined specifically as (yield strength in dynamic tensile test when conducting dynamic tensile testing at strain rate of 10 3 /sec)/(yield strength when conducting static tensile testing at strain rate of 10 −2 /sec) . Since the dynamic/static ratio indicates the degree of hardening at the time of deformation at high speed as in an automobile collision, the suitability of a steel for use in an impact absorption structural component increases in proportion as the value of the dynamic/static ratio increases. For example, “ Report on Research Group Results Regarding High-Speed Deformation of Automotive Materials ” (compiled by The Iron and Steel 
         [0040]    Institute of Japan, 2001, p 12, FIG. 6) gives dynamic/static ratios for conventional steels, with the dynamic/static ratio of a steel having a tensile strength of 600 MPa or greater shown as 1.3 or less. The present invention defines the dynamic/static ratio as 1.4 or greater and provides a steel of high strength and high dynamic/static ratio unattainable by conventional steels. No upper limit value is defined for the dynamic/static ratio because the effect of the present invention can be realized without defining one. 
         [0041]    The stainless steel of the present invention is intended for fabrication into structural components. It is therefore important for it to have good formability. As pointed out earlier, most vehicle structural components have angular cross-sections as typified by hat-shaped formed components. As the fabrication involves bending and drawing, the steel requires ductility. A study was carried out regarding methods of fabricating impact absorption components. It was found with regard to steel for which tensile strength was 600 MPa or greater in static tensile testing, adequate forming was possible if elongation at break was 40% or greater. Elongation at break in static tensile testing was therefore defined as 40% or greater. Some components require high strength of 700 MPa or greater. Such high-strength steels are adjusted in strength by cold rolling and annealing followed by temper rolling. Although no upper limit of strength is necessary from the material aspect, the upper limit is defined as 1600 MPa in view of manufacturing and practical concerns. When temper rolling is conducted, the reduction can be set in accordance with the required strength level. However, taking manufacturability into consideration, it is preferably around 1 to 70%. The steel sheet manufactured in this manner is reduced in elongation at break in static tensile testing. However, the elongation at break in static tensile testing of a steel sheet of the foregoing tensile strength level is required to be 5% or greater. It is therefore defined as 5% or greater and is preferably 10% or greater. 
         [0042]    The method of manufacturing the steel sheet of the present invention is not particularly defined and the product thickness can be decided based on requirements. The hot rolling conditions, hot rolled sheet thickness, hot rolled sheet and cold rolled sheet annealing temperature and atmosphere, and other matters can be suitably selected. No special equipment is required in connection with the pass schedule, cold rolling reduction and roll diameter in cold rolling, and efficient use of existing equipment suffices. Use/non-use of lubricant during temper rolling, the number of temper rolling passes and the like are also not particularly specified. If desired, shape correction utilizing a tension leveler can be applied after cold rolling and annealing or after temper rolling. Although the product structure is fundamentally austenite, formation of a second phase, such as of ferrite or martensite, is also acceptable. 
       EXAMPLES 
       [0043]    The present invention will be concretely explained in the following with reference to working examples. 
         [0044]    Steels having the chemical compositions shown in Table 1 were produced and cast into slabs. Each slab was hot rolled, annealed, pickled, cold rolled to a thickness of 1.5 mm, annealed, pickled, and temper rolled to obtain a product sheet. The so-obtained product sheet was subjected to the aforesaid static tensile test and dynamic tensile test. 
         [0045]    Table 1 includes examples corresponding to claims  1  to  6 . The steels having chemical compositions prescribed by the present invention were superior to the comparison steels in both total impact energy absorption to destruction and impact energy absorption in the low strain region to 10% strain, so that that they were excellent in impact absorption property. Such steels are suitable for use in impact absorption components at risk of experiencing relatively large deformation The steels were also suitable for formation into complex structural members, as evidenced by their high elongation at break and excellent ductility in static tensile testing. 
         [0046]    Table 2 includes examples corresponding to claim 7. The invention examples, whose temper rolling reduction was adjusted to achieve tensile strength of 700 MPa or greater and elongation at break is 5% or greater, exhibited high impact energy absorption to 10% strain of 50 MJ/m 3  or greater in dynamic tensile testing, as well as a dynamic/static ratio of 1.4 or greater, making them suitable for use in high-strength members required to absorb impact in the low strain region. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Static 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 yield 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Md 30   
                 strength 
               
               
                   
                 No. 
                 C 
                 Si 
                 Mn 
                 Ni 
                 Cr 
                 Cu 
                 Al 
                 N 
                 (° C.) 
                 (MPa) 
               
               
                   
               
               
                 Invention 
                 1 
                 0.020 
                 0.6 
                 1.1 
                 7.1 
                 17.4 
                 0.2 
                 0.03 
                 0.129 
                 16 
                 364 
               
               
                 Examples 
                 2 
                 0.023 
                 0.5 
                 8.6 
                 5.0 
                 14.5 
                 2.5 
                 0.03 
                 0.046 
                 29 
                 280 
               
               
                   
                 3 
                 0.030 
                 0.6 
                 1.5 
                 5.1 
                 17.7 
                 1.0 
                 0.02 
                 0.131 
                 41 
                 325 
               
               
                   
                 4 
                 0.029 
                 0.6 
                 1.5 
                 6.1 
                 17.7 
                 1.0 
                 0.05 
                 0.129 
                 12 
                 312 
               
               
                   
                 5 
                 0.021 
                 0.5 
                 1.0 
                 7.4 
                 17.3 
                 0.2 
                 0.02 
                 0.115 
                 18 
                 319 
               
               
                   
                 6 
                 0.019 
                 0.5 
                 3.4 
                 3.6 
                 17.3 
                 3.5 
                 0.03 
                 0.122 
                 12 
                 330 
               
               
                   
                 7 
                 0.021 
                 0.5 
                 6.6 
                 3.5 
                 17.4 
                 0.2 
                 0.03 
                 0.118 
                 82 
                 378 
               
               
                   
                 8 
                 0.022 
                 0.5 
                 6.0 
                 3.5 
                 17.4 
                 2.4 
                 0.01 
                 0.120 
                 23 
                 345 
               
               
                   
                 9 
                 0.021 
                 0.5 
                 3.4 
                 3.6 
                 17.2 
                 1.5 
                 0.02 
                 0.119 
                 73 
                 359 
               
               
                   
                 10 
                 0.021 
                 0.5 
                 3.4 
                 3.5 
                 17.1 
                 2.0 
                 0.04 
                 0.119 
                 60 
                 363 
               
               
                   
                 11 
                 0.021 
                 0.5 
                 3.4 
                 5.2 
                 17.1 
                 2.0 
                 0.03 
                 0.117 
                 12 
                 317 
               
               
                   
                 12 
                 0.021 
                 0.5 
                 6.3 
                 3.5 
                 17.2 
                 1.0 
                 0.07 
                 0.122 
                 62 
                 352 
               
               
                   
                 13 
                 0.021 
                 0.5 
                 6.3 
                 3.5 
                 17.1 
                 1.5 
                 0.03 
                 0.121 
                 50 
                 346 
               
               
                   
                 14 
                 0.025 
                 0.5 
                 3.5 
                 3.5 
                 17.3 
                 0.2 
                 0.02 
                 0.210 
                 65 
                 362 
               
               
                   
                 15 
                 0.020 
                 0.3 
                 6.5 
                 3.5 
                 17.3 
                 0.2 
                 0.01 
                 0.240 
                 31 
                 367 
               
               
                   
                 16 
                 0.015 
                 0.5 
                 6.5 
                 3.5 
                 17.6 
                 1.0 
                 0.04 
                 0.240 
                  4 
                 321 
               
               
                   
                 17 
                 0.009 
                 0.8 
                 3.5 
                 1.0 
                 17.3 
                 3.5 
                 0.04 
                 0.210 
                 47 
                 331 
               
               
                   
                 18 
                 0.045 
                 0.5 
                 11.0  
                 0.8 
                 19.5 
                 0.5 
                 0.05 
                 0.280 
                  2 
                 335 
               
               
                   
                 19 
                 0.006 
                 0.9 
                 11.6  
                 3.1 
                 11.5 
                 0.5 
                 0.05 
                 0.280 
                 55 
                 367 
               
               
                 Comparative 
                 20 
                 
                   0.004 
                 
                 0.5 
                 0.3 
                 
                   0.1 
                 
                 
                   10.5 
                 
                   0.04   
                 0.03 
                 
                   0.007 
                 
                   391   
                 228 
               
               
                 Examples 
                 21 
                 
                   0.057 
                 
                 0.5 
                 0.2 
                 
                   0.1 
                 
                 16.2 
                   0.02   
                 0.03 
                 
                   0.009 
                 
                   289   
                 308 
               
               
                   
                 22 
                 
                   0.003 
                 
                 0.1 
                 0.1 
                 
                   0.1 
                 
                 16.6 
                   0.02   
                 0.02 
                 0.010 
                   313   
                 210 
               
               
                   
                 23 
                 0.007 
                 0.4 
                 1.0 
                 
                   0.1 
                 
                 18.3 
                   0.02   
                 0.05 
                 0.013 
                   277   
                 351 
               
               
                   
                 24 
                 
                   0.346 
                 
                 0.8 
                 0.6 
                 
                   0.2 
                 
                 13.4 
                   0.02   
                 0.02 
                 0.019 
                   180   
                 408 
               
               
                   
                 25 
                 0.016 
                 0.5 
                 0.7 
                 7.2 
                 
                   25.4 
                 
                   0.05   
                 0.03 
                 0.144 
                   −91   
                 717 
               
               
                   
                 26 
                 
                   0.055 
                 
                 0.4 
                 1.1 
                 
                   8.1 
                 
                 18.1 
                  0.19 
                 0.03 
                 0.041 
                  6 
                 301 
               
               
                   
                 27 
                 
                   0.051 
                 
                 0.6 
                 0.9 
                 
                   9.1 
                 
                 18.2 
                  0.18 
                 0.01 
                 0.015 
                 
                   −11 
                 
                 273 
               
               
                   
                 28 
                 0.008 
                 0.4 
                 2.7 
                 7.9 
                 17.1 
                 2.7 
                 0.02 
                 0.012 
                   −26   
                 175 
               
               
                   
                 29 
                 0.048 
                 0.5 
                 0.9 
                   12.6   
                 16.8 
                  0.26 
                 0.04 
                 0.032 
                   −99   
                 306 
               
               
                   
                 30 
                 
                   0.085 
                 
                 0.5 
                 11.4  
                 6.6 
                 17.9 
                  0.10 
                 0.03 
                 
                   0.302 
                 
                   −163   
                 448 
               
               
                   
                 31 
                 0.040 
                 0.4 
                 1.1 
                 6.4 
                 17.4 
                 2.2 
                 0.07 
                 0.059 
                  4 
                 292 
               
               
                   
                 32 
                 0.021 
                 0.5 
                 1.0 
                 3.6 
                 17.3 
                  0.21 
                 0.03 
                 0.116 
                   129   
                 997 
               
               
                   
                 33 
                 0.020 
                 0.5 
                 3.5 
                 3.5 
                 17.4 
                 0.2 
                 0.02 
                 0.118 
                   108   
                 401 
               
               
                   
                 34 
                 0.026 
                 0.9 
                 1.8 
                 7.1 
                 16.0 
                 1.9 
                 0.01 
                 0.010 
                 33 
                 266 
               
               
                   
                 35 
                 0.021 
                 0.5 
                 1.0 
                 5.2 
                 17.3 
                  0.21 
                 0.04 
                 0.116 
                 82 
                 722 
               
               
                   
                 36 
                 0.020 
                 0.5 
                 1.0 
                 3.6 
                 17.2 
                 3.6 
                 0.04 
                 0.121 
                 30 
                 757 
               
               
                   
                 37 
                 0.020 
                 1.6 
                 1.1 
                 7.2 
                 17.4 
                 0.2 
                 0.05 
                 0.129 
                  5 
                 476 
               
               
                   
                 38 
                 0.020 
                 0.8 
                   18    
                 7.3 
                 16.2 
                 0.2 
                 0.03 
                 0.030 
                   −65   
                 235 
               
               
                   
                 39 
                 0.020 
                 0.8 
                   18    
                 
                   0.2 
                 
                 16.2 
                 7.3 
                 0.02 
                 0.030 
                   −65   
                 216 
               
               
                   
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                 Total 
                   
               
               
                   
                   
                 Static 
                 Static 
                 Dynamic 
                 Total 
                 impact 
               
               
                   
                   
                 elongation 
                 tensile 
                 yield 
                 impact 
                 energy to 
                 Dynamic/ 
               
               
                   
                   
                 at break 
                 strength 
                 strength 
                 energy 
                 10% strain 
                 static 
               
               
                   
                 No. 
                 (%) 
                 (MPa) 
                 (MPa) 
                 (MJ/m 3 ) 
                 (MJ/m 3 ) 
                 ratio 
               
               
                   
               
               
                 Invention 
                 1 
                 55 
                 745 
                 687 
                 541 
                 56 
                 1.9 
               
               
                 Examples 
                 2 
                 54 
                 796 
                 516 
                 517 
                 55 
                 1.8 
               
               
                   
                 3 
                 41 
                 826 
                 576 
                 594 
                 54 
                 1.8 
               
               
                   
                 4 
                 55 
                 700 
                 670 
                 535 
                 56 
                 2.1 
               
               
                   
                 5 
                 56 
                 710 
                 640 
                 571 
                 56 
                 2.0 
               
               
                   
                 6 
                 55 
                 682 
                 670 
                 523 
                 56 
                 2.0 
               
               
                   
                 7 
                 51 
                 806 
                 740 
                 545 
                 61 
                 2.0 
               
               
                   
                 8 
                 50 
                 649 
                 678 
                 508 
                 54 
                 2.0 
               
               
                   
                 9 
                 46 
                 834 
                 736 
                 558 
                 56 
                 2.1 
               
               
                   
                 10 
                 44 
                 637 
                 678 
                 528 
                 55 
                 1.9 
               
               
                   
                 11 
                 60 
                 637 
                 650 
                 503 
                 52 
                 2.1 
               
               
                   
                 12 
                 58 
                 712 
                 710 
                 523 
                 53 
                 2.0 
               
               
                   
                 13 
                 56 
                 715 
                 728 
                 508 
                 56 
                 2.1 
               
               
                   
                 14 
                 47 
                 1013  
                 688 
                 532 
                 62 
                 1.9 
               
               
                   
                 15 
                 53 
                 816 
                 692 
                 519 
                 56 
                 1.9 
               
               
                   
                 16 
                 54 
                 722 
                 650 
                 512 
                 59 
                 2.0 
               
               
                   
                 17 
                 62 
                 882 
                 635 
                 506 
                 53 
                 1.9 
               
               
                   
                 18 
                 50 
                 715 
                 670 
                 550 
                 55 
                 2.0 
               
               
                   
                 19 
                 46 
                 856 
                 610 
                 576 
                 65 
                 1.7 
               
               
                 Comparative 
                 20 
                 
                   36 
                 
                 
                   398 
                 
                 550 
                 
                   256 
                 
                 
                   46 
                 
                 2.4 
               
               
                 Examples 
                 21 
                 
                   31 
                 
                 
                   480 
                 
                 514 
                 
                   274 
                 
                 
                   47 
                 
                 1.7 
               
               
                   
                 22 
                 
                   37 
                 
                 
                   384 
                 
                 489 
                 
                   251 
                 
                 
                   40 
                 
                 2.3 
               
               
                   
                 23 
                 
                   31 
                 
                 
                   520 
                 
                 672 
                 
                   267 
                 
                 
                   47 
                 
                 1.9 
               
               
                   
                 24 
                 
                   25 
                 
                 642 
                 661 
                 
                   282 
                 
                 54 
                 1.6 
               
               
                   
                 25 
                 
                   26 
                 
                 806 
                 889 
                 
                   408 
                 
                 81 
                 
                   1.2 
                 
               
               
                   
                 26 
                 50 
                 682 
                 547 
                 525 
                 
                   48 
                 
                 1.8 
               
               
                   
                 27 
                 52 
                 628 
                 427 
                 510 
                 
                   37 
                 
                 1.6 
               
               
                   
                 28 
                 52 
                 
                   507 
                 
                 380 
                 
                   475 
                 
                 
                   31 
                 
                 2.2 
               
               
                   
                 29 
                 45 
                 622 
                 473 
                 
                   486 
                 
                 
                   45 
                 
                 1.5 
               
               
                   
                 30 
                 44 
                 785 
                 1008  
                 550 
                 72 
                 2.3 
               
               
                   
                 31 
                 58 
                 617 
                 505 
                 
                   173 
                 
                 
                   47 
                 
                 1.7 
               
               
                   
                 32 
                   9   
                 1265  
                 1287  
                 
                   207 
                 
                 90 
                 
                   1.3 
                 
               
               
                   
                 33 
                 
                   26 
                 
                 1013  
                 722 
                 583 
                 
                   49 
                 
                 1.8 
               
               
                   
                 34 
                 54 
                 673 
                 356 
                 511 
                 
                   37 
                 
                 
                   1.3 
                 
               
               
                   
                 35 
                 
                   21 
                 
                 1146  
                 1234  
                 
                   440 
                 
                 89 
                 1.7 
               
               
                   
                 36 
                 
                   20 
                 
                 1118  
                 1261  
                 
                   348 
                 
                 66 
                 1.7 
               
               
                   
                 37 
                 
                   36 
                 
                 950 
                 533 
                 505 
                 
                   43 
                 
                 
                   1.1 
                 
               
               
                   
                 38 
                 50 
                 
                   374 
                 
                 310 
                 
                   436 
                 
                 
                   41 
                 
                 
                   1.3 
                 
               
               
                   
                 39 
                 53 
                 
                   362 
                 
                 285 
                 
                   415 
                 
                 
                   38 
                 
                 
                   1.3 
                 
               
               
                   
               
               
                 Remarks: Chemical constituents are expressed in mass %. 
               
               
                 Underlining indicates that value is outside invention range. 
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Total 
                   
               
               
                   
                   
                 Temper 
                 Static 
                 Static 
                 Static 
                 Dynamic 
                 impact 
               
               
                   
                   
                 rolling 
                 yield 
                 elongation 
                 tensile 
                 yield 
                 energy to 
                 Dynamic/ 
               
               
                   
                   
                 reduction 
                 strength 
                 at break 
                 strength 
                 strength 
                 10% strain 
                 static 
               
               
                   
                 No. 
                 (%) 
                 (MPa) 
                 (%) 
                 (MPa) 
                 (MPa) 
                 (MJ/m 3 ) 
                 ratio 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Invention 
                 1 
                 2 
                 399 
                 54 
                   
                 710 
                 57 
                 1.8 
               
               
                 Examples 
                 1 
                 10 
                 656 
                 33 
                 925 
                 998 
                 59 
                 1.5 
               
               
                   
                 1 
                 20 
                 739 
                 30 
                 985 
                 1120 
                 81 
                 1.5 
               
               
                   
                 1 
                 44 
                 1106 
                 12 
                 1263 
                 1612 
                 82 
                 1.5 
               
               
                   
                 1 
                 60 
                 1412 
                  5 
                 1502 
                 1970 
                 83 
                 1.4 
               
               
                   
                 6 
                 20 
                 753 
                 32 
                 1005 
                 1180 
                 80 
                 1.6 
               
               
                   
                 7 
                 1 
                 405 
                 53 
                 795 
                 780 
                 57 
                 1.9 
               
               
                   
                 7 
                 20 
                 758 
                 31 
                 1035 
                 1180 
                 84 
                 1.6 
               
               
                   
                 7 
                 45 
                 1200 
                 15 
                 1295 
                 1685 
                 90 
                 1.4 
               
               
                   
                 15 
                 5 
                 405 
                 35 
                 800 
                 743 
                 60 
                 1.8 
               
               
                   
                 16 
                 15 
                 735 
                 30 
                 905 
                 1064 
                 73 
                 1.4 
               
               
                 Comparative 
                 1 
                 75 
                 1535 
                   1   
                 1615 
                 2010 
                 
                   48 
                 
                 
                   1.3 
                 
               
               
                 Examples 
                 6 
                 75 
                 1580 
                   4   
                 1820 
                 2040 
                 
                   45 
                 
                 
                   1.3 
                 
               
               
                   
                 7 
                 72 
                 1593 
                   2   
                 1850 
                 2053 
                 
                   44 
                 
                 
                   1.3 
                 
               
               
                   
                 8 
                 80 
                 1635 
                   1   
                 1686 
                 1964 
                 
                   40 
                 
                 
                   1.2 
                 
               
               
                   
                 16 
                 85 
                 1785 
                   1   
                 1765 
                 2035 
                 
                   32 
                 
                 
                   1.1 
                 
               
               
                   
               
               
                 Remark: Underlining indicates that value is outside invention range. 
               
             
          
         
       
     
         [0047]    As is clear from the foregoing explanation, the present invention enables provision of a high-strength stainless steel sheet excellent in impact absorption capability even without addition of large amounts of alloying elements. The stainless steel sheet manifests outstanding industrial usefulness, including environmental protection through weight reduction and improved collision safety, especially when utilized in the structural components of transport means such as automobiles, buses and railcars.