EP1676932B1 - Tôle d'acier mince à haute résistance, possedant une résistance accrue à la fragilisation par l'hydrogène - Google Patents
Tôle d'acier mince à haute résistance, possedant une résistance accrue à la fragilisation par l'hydrogène Download PDFInfo
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- EP1676932B1 EP1676932B1 EP05028444.7A EP05028444A EP1676932B1 EP 1676932 B1 EP1676932 B1 EP 1676932B1 EP 05028444 A EP05028444 A EP 05028444A EP 1676932 B1 EP1676932 B1 EP 1676932B1
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- Prior art keywords
- steel
- residual austenite
- steel sheet
- hydrogen embrittlement
- resisting property
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
Definitions
- the present invention relates to a high strength thin steel sheet that has high hydrogen embrittlement resisting property (particularly the hydrogen embrittlement resisting property after being subjected to forming process) and high workability, especially to a high strength thin steel sheet that has high resistance against fractures due to hydrogen embrittlement such as season crack and delayed fracture that pose serious problems for steel sheets having tensile strength of 1180 MPa or higher, and has high workability.
- the TRIP steel sheet includes residual austenite structure and, when processed to deform, undergoes considerable elongation due to induced transformation of the residual austenite (residual y) into martensite by the action of stress.
- TRIP steel TRIP type composite-structure steel (TPF steel) that consists of polygonal ferrite as the matrix phase and residual austenite
- TRIP type tempered martensite steel (TAM steel) TRIP type tempered martensite steel
- TRIP type bainitic steel TBF steel
- the TBF steel has long been known (described, for example, in NISSIN STEEL TECHNICAL REPORT, No. 43, Dec. 1980, pp1-10 ), and has such advantages as the capability to readily provide high strength due to the hard bainitic ferrite structure, and the capability to show outstanding elongation because fine residual austenite grains can be easily formed in the boundary of lath-shaped bainitic ferrite in the bainitic ferrite structure.
- the TBF steel also has such an advantage related to manufacturing, that it can be easily manufactured by a single heat treatment process (continuous annealing process or plating process).
- Delayed fracture refers to the failure of high-strength steel under stress, that occurs as hydrogen originating in corrosive environment or the atmosphere infiltrates and diffuses in microstructural defects such as dislocation, void and grain boundary, and makes the steel brittle. This results in decreases in ductility and toughness of the metallic material.
- Japanese Unexamined Patent Publication (Kokai) No. 11-293383 describes a technology to improve the hydrogen embrittlement resisting property of steel sheet, where hydrogen-induced defects can be suppressed by having oxides that include Ti and Mg exist as the main components in the structure.
- this technology is intended for thick steel sheets and, although consideration is given to delayed fracture after welding with a large input heat, no consideration is given to the environment (for example, corrosive environment, etc.) in which automobile parts manufactured by using thin steel sheets are used.
- 2003-166035 describes that it is made possible to improve the ductility and delayed fracture resistance after being subjected to forming process, by controlling the mutual relationships between 1)the form (standard deviation and mean grain size) in which oxide, sulfide, composite crystallization product or composite precipitate of Mg is dispersed, 2)volumetric proportion of residual austenite and 3)strength of the steel sheet.
- the TBF steels reported in the documents described above show delayed fracture characteristic of about 1000 seconds at the most in terms of the time before crack occurrence measured in cathode charging test, indicating that these steels are not meant to endure the harsh operating environment such as that of automobile parts over a long period of time.
- the heat treatment conditions reported in the documents described above involve heating temperature being set higher, there are such problems as low efficiency of practical manufacturing process. Thus it is strongly required to develop a new species of TBF steel that provides high production efficiency as well.
- EP 1 553 202 A1 which is prior art pursuant to Art. 54(3) EPC, describes an ultra-high strength steel sheet having excellent hydrogen embrittlement resistance, which includes 0.06 to 0.6% of C, 0.5 to 3% of Si+Al, 0.5 to 3% of Mn, 0.15% of lower of P, and 0.02% or lower of S in terms of mass percentage, and also includes 3% or higher of residual austenite structure, 30% of higher of bainitic ferrite structure, and preferably 50% or lower of polygonal ferrite in terms of an area ratio to the entire structure, wherein a mean grain size of bainite blocks is smaller than 20 ⁇ m as determined by comparing observations of the same region of the bainitic ferrite structure by EBSP (electron back scatter diffraction pattern) and SEM.
- EBSP electron back scatter diffraction pattern
- the present invention has been made with the background described above, and the object of the present invention is to make available a high strength thin steel sheet that shows high hydrogen embrittlement resisting property with workability improved under the tensile strength of 1180 MPa or higher.
- Hydrogen-induced delayed fracture is believed to occur in such a steel that contains tempered martensite or martensite +ferrite, that has been commonly used as a high-strength steel ever before, because hydrogen is concentrated in grain boundaries of prior austenite thereby to form voids or other defects that become the starting points of the fracture.
- Common practice that has been employed to decrease the sensitivity to delayed fracture is to diffuse fine grains of carbide or the like uniformly as the site for trapping hydrogen, thereby to decrease the concentration of diffusive hydrogen.
- carbide grains or the like uniformly as the site for trapping hydrogen, thereby to decrease the concentration of diffusive hydrogen.
- condition (a) it is desirable to form the matrix phase of the steel structure after processing from a binary phase structure of bainitic ferrite and martensite with the bainitic ferrite acting as the main phase, instead of the single phase structure of martensite that is generally used for high strength steels.
- a carbide for example, film-like cementite
- the bainitic ferrite is easy to increase the strength of the entire structure as in the case of the single phase of martensite, because a dislocation density of the bainitic ferrite is high as it is in the form of plates, differing from polygonal ferrite used commonly.
- the hydrogen embrittlement resisting property can also be improved as much hydrogen is trapped in the dislocations. It also has such an advantage that coexistence of the bainitic ferrite and the residual austenite which will be described later prevents the generation of carbide that acts as the intergranular fracture initiating points.
- the bainitic ferrite is a hard phase and therefore it is easy to increase the strength of the entire structure. It can also absorb much hydrogen compared to the other TRIP steel as much hydrogen is trapped in the dislocations. It also has such an advantage that in the boundaries of the lath-shaped bainitic ferrite, it becomes easier to produce the lath-shaped residual austenite, thus providing an excellent elongation with it. Accordingly, it is found that it is required in the present invention that the binary structure of bainitic ferrite and martensite occupy 90% or more in order to effectively achieve the above action.
- condition (b) it is desirable to form the lath-shaped residual austenite.
- the residual austenite exerts a negative impact on its hydrogen embrittlement resisting property and fatigue.
- the present inventor has studied that although the residual austenite which is in the form of cluster in the submicron order exerts a negative impact on its hydrogen embrittlement resisting property and fatigue, if the residual austenite above described is controlled to be produced the lath-shaped residual austenite in the order of submicron, it can absorb and trap much hydrogen, thus improving the hydrogen embrittlement resisting property to a large degree due to the ability of absorbing hydrogen which the residual austenite naturally has.
- hydrogen embrittlement risk index sharply decreases when the mean axis ratio (major axis/minor axis) of the residual austenite grains increases beyond 5.
- mean axis ratio major axis/minor axis
- intrinsic capability of the residual austenite to absorb hydrogen is put into full play, so that the residual austenite attains far higher capacity of trapping hydrogen than carbide and substantially neutralizes the hydrogen that infiltrates from the outside through atmospheric corrosion thereby to achieve remarkable achievement in hydrogen embrittlement resisting property.
- the present inventors conducted a research on a steel sheet to find that if it is controlled so that the below conditions are satisfied at a time, high hydrogen embrittlement resisting property is achieved even if too much alloys are not added and they brought to a completion of the present invention.
- the present inventors also found that if its average length of minor axis of the lath-shaped grains in the residual austenite is 1 ⁇ m or less (submicrometer order), the surface area (interface) of the grains in the residual austenite becomes larger, thus improving the ability of trapping hydrogen and effectively improving high hydrogen embrittlement resisting property. And it has been found that hydrogen embrittlement resisting property can be improved further by controlling the minimum distance between adjacent residual austenite grains so that it is 1 ⁇ m or less. This is supposedly because propagation of cracks is suppressed so that the structure demonstrates higher resistance against fracture, when a large number of fine lath-shape grains of residual austenite are dispersed in proximity to each other.
- a high strength thin steel sheet having high hydrogen embrittlement resisting property comprises 0.10 to 0.25% of C, 1.2 to 2.5% of Si, 1.2 to 3.5% of Mn, 0.15% or less P, 0.02% or less S, and 0.2 to 1.5% of Al, which optionally further comprises Cu: 0.003 to 0.5% and/or Ni: 0.003 to 1.0% as optional elements, Ti and/or V: 0.003 to 1.0% as optional elements, Mo: 1.0% or less (higher than 0%) and Nb: 0.1% or less (higher than 0%) as optional elements, B: 0.0002 to 0.01% as an optional element, at least one element selected from the group consisting of: Ca: 0.0005 to 0.005%, Mg: 0.0005 to 0.01% and REM: 0.0005 to 0.01% as optional elements, and Zr: 0.003 to 1.0% as an optional element, in terms of percentage by weight, with balance of iron and inevitable impurities, wherein the metal structure consists of:
- the present invention it is made possible to manufacture, with a high level of productivity, a high strength thin steel sheet having tensile strength of 1180 MPa or higher that neutralizes hydrogen that infiltrates from the outside after the steel sheet has been formed into a part thereby to maintain satisfactory hydrogen embrittlement resisting property, and demonstrates high workability during the forming process.
- Use of the high strength thin steel sheet makes it possible to manufacture high strength parts that hardly experience delayed fracture, such as bumper, impact beam and other reinforcement members and other automobile parts such as seat rail, pillar, etc.
- the metal contains 3% or more residual austenite in the area proportion to the entire structure, because residual austenite contributes not only to the improvement of hydrogen embrittlement resisting property, but also to the improvement of total elongation.
- Content of the residual austenite is preferably 5% or higher.
- the upper limit of the residual austenite content is set to 10%.
- C ⁇ R residual austenite
- the residual austenite refers to a region that is observed as FCC (face centered cubic lattice) by the FE-SEM/EBSP method which will be described later.
- Measurement by the EBSP may be done, for example, by measuring a measurement area (about 50 by 50 ⁇ m) at an arbitrarily chosen position in a surface parallel to the rolled surface at a position of one quarter of the thickness at measuring intervals of 0.1 ⁇ m.
- the measuring surface is prepared by electrolytic polishing in order to prevent the residual austenite from transforming.
- the test piece is set in the lens barrel of an FE-SEM equipped with the EBSP detector (of which details will be described later) and is irradiated with electron beam.
- An EBSP image projected onto a screen is captured by a high sensitivity camera (VE-1000-SIT manufactured by Dage-MTI Inc.) and is sent to a computer.
- the computer carries out image analysis and generates color mapping of the FCC phase through comparison with a structural pattern simulated with a known crystal system (FCC (face centered cubic lattice) phase in the case of residual austenite). Area proportion of the region that is mapped as described above is taken as the area proportion of the residual austenite.
- This analysis was carried out by means of hardware and software of OIM (Orientation Imaging MicroscopyTM) system of TexSEM Laboratories Inc.
- Fig. 1 is a graph showing the relationship between the mean axis ratio of the residual austenite grains measured by a method to be described later and hydrogen embrittlement risk index (measured by a method to be described later in an example, lower value of this index means better hydrogen embrittlement resisting property). From Fig. 1 , it can be seen that hydrogen embrittlement risk index sharply decreases when the mean axis ratio (major axis/minor axis) of the residual austenite grains increases beyond 5.
- the mean axis ratio of the residual austenite grains is preferably 10 or higher, and more preferably 15 or higher.
- the residual austenite grains are required to have certain level of thickness in order to achieve the TRIP effect during processing.
- an upper limit to 30, more preferably to 20 or less.
- the mean axis ratio was determined by observing with TEM (magnification factor of 15000) in each of three arbitrarily chosen fields of view and averaging the distances measured in the three fields of view.
- the bainitic ferrite In the case of the binary structure of bainitic ferrite and martensite (with the bainitic ferrite acting as the main phase in the binary structure), the bainitic ferrite is a hard phase and therefore it is easy to increase the strength of the entire structure.
- the hydrogen embrittlement resisting property can also be improved as much hydrogen is trapped in the dislocations. It also has such an advantage that coexistence of the bainitic ferrite and the residual austenite which will be described later prevents the generation of carbide that acts as the intergranular fracture initiating points, and it becomes easier to create the lath-shaped residual austenite in the boundaries of lath-shaped bainitic ferrite.
- the binary structure of bainitic ferrite and martensite occupy 90% or more.
- Upper limit of the proportion may be determined by the balance with residual austenite.
- the bainitic ferrite referred to in the present invention is plate-shaped ferrite having a lower structure of high density of dislocations. It is clearly distinguished from polygonal ferrite that has lower structure including no or very low density of dislocations, by SEM observation as follows.
- Area proportion of bainitic ferrite structure is determined as follows. A test piece is etched with Nital etchant. A measurement area (about 50 by 50 ⁇ m) at an arbitrarily chosen position in a surface parallel to the rolled surface at a position of one quarter of the thickness is observed with SEM (scanning electron microscope) (magnification factor of 1500) thereby to determine the area proportion.
- Bainitic ferrite is shown with dark gray color in SEM photograph (bainitic ferrite, residual austenite and martensite may not be distinguishable in the case of SEM observation), while polygonal ferrite is shown black in SEM photograph and has polygonal shape that does not include residual austenite and martensite inside thereof.
- the SEM used in the present invention is a high-resolution FE-SEM (Field Emission type Scanning Electron Microscope XL30S-FEG manufactured by Philips Inc.) equipped with an EBSP (Electron Back Scattering Pattern) detector, that has a merit of being capable of analyzing the area observed by the SEM at the same time by means of the EBSP detector.
- EBSP detection is carried out as follows. When the sample surface is irradiated with electron beam, the EBSP detector analyzes the Kikuchi pattern obtained from the reflected electrons, thereby to determine the crystal orientation at the point where the electron beam has hit upon.
- Distribution of orientations over the sample surface can be measured by scanning the electron beam two-dimensionally over the sample surface while measuring the crystal orientation at predetermined intervals.
- the EBSP detection method has such an advantage that different structures that are regarded as the same structure in the ordinary microscopic observation but have different crystal orientations can be distinguished by the difference in color tone.
- the present high strength steel is characterized in that the amount and form of residual austenite are controlled and the easy control of the amount and form of residual austenite can be achieved to provide the desired high strength steel according to the following composition.
- C is an element required to achieve a high strength of 1180 MPa or higher.
- C is an important element that can remain the desired austenite at room temperature by providing a sufficient amount of C into the phase of austenite.
- 0.10% or higher of C is contained, and 0.12% or more, preferably 0.15% or more C is contained.
- concentration of C is limited within 0.25%, preferably 0.23% or lower in the present invention.
- Si is an important element that effectively suppresses the residual austenite from decomposing and carbide from being generated, and is also effective in enhancing substitution solid solution for hardening the material.
- it is necessary to include Si in a concentration of 1.2% or higher and preferably 1.5% or higher.
- Si content is controlled within 2.5% and preferably within 2.0%.
- Mn is an element required to stabilize austenite and obtain desired residual austenite. In order to make full use of this effect, it is necessary to add Mn in concentration of 1.2% or higher, and preferably 1.5% or higher. However, adding an excessive amount Mn leads to conspicuous segregation and poor workability. Therefore upper limit to the concentration of Mn is set to 3.5% and more preferably to 3.0% or less.
- P intensifies intergranular fracture due to intergranular segregation, and the content thereof is therefore preferably as low as possible.
- Upper limit to the concentration of P is set to 0.15%, preferably 0.1% or less and more preferably to 0.05% or less.
- S intensifies the absorption of hydrogen into the steel sheet in corrosive environment, and the content thereof is therefore preferably as low as possible.
- Upper limit to the concentration of S is set to 0.02%.
- Al 0.2% or higher content of Al is included for the purpose of deoxidation.
- Al also has the effects of improving the corrosion resistance and improving hydrogen embrittlement resisting property.
- the mechanism of improving the corrosion resistance is supposedly based on the improvement of corrosion resistance of the matrix phase per se and the effect of formation rust generated by atmospheric corrosion, while the effect of the formation rust presumably has greater contribution. This is supposedly because the formation rust is denser and better in protective capability than ordinary iron rust, and therefore checks the progress of atmospheric corrosion so as to decrease the amount of hydrogen generated by the atmospheric corrosion, thereby to effectively suppress the occurrence of hydrogen embrittlement, and hence the delayed fracture.
- Al content is controlled to 0.2% or higher, preferably 0.5% or higher.
- Al content must be controlled within 1.5% in order to keep inclusions such as alumina from increasing in number and size so as to ensure satisfactory workability, ensure the generation of fine residual austenite grains, suppress corrosion from proceeding from the inclusion containing Al as the starting point, and prevent the manufacturing cost from increasing.
- constituent elements (C, Si, Mn, P, S, Al) of the steel of the present invention are as described above with the rest substantially being Fe, it may include inevitable impurities introduced into the steel depending on the stock material, production material, manufacturing facility and other circumstances, containing 0.001% or less N (nitrogen).
- N nitrogen
- other elements as described below may be intentionally added to such an extent that does not adversely affect the effects of the present invention.
- presence of Cu and Ni improves the corrosion resistance of the steel, and effectively suppresses the generation of hydrogen due to corrosion of the steel sheet.
- These elements also have the effect of promoting the generation of iron oxide, ⁇ -FeOOH, that is believed to be particularly stable thermodynamically and have protective property among various forms of rust generated in the atmosphere. By assisting the generation of this rust, it is made possible to suppress hydrogen that has been generated from infiltrating into the spring steel thereby to sufficiently improve the hydrogen embrittlement resisting property to endure in harsh corrosive environment. This effect can be achieved particularly satisfactorily when Cu and Ni are contained at the same time.
- concentration of Cu if added, should be 0.003% or higher, preferably 0.05% or higher and more preferably 0.1% or higher.
- Ti has the effect of assisting in the generation of protective rust, similarly to Cu and Ni.
- the protective rust has a very valuable effect of suppressing the generation of ⁇ -FeOOH that appears in chloride environment and has adverse effect on the corrosion resistance (and hence on the hydrogen embrittlement resisting property). Formation of such a protective rust is promoted particularly by adding Ti and V (or Zr). Ti renders the steel high corrosion resistance, and also has the effect of cleaning the steel.
- V is effective in increasing the strength of the steel sheet and decreasing the size of crystal grains, in addition to having the effect of improving hydrogen embrittlement resistance through cooperation with Ti, as described previously.
- Ti and/or V in total concentration of 0.003% or higher (more preferably 0.01% or higher).
- Ti for the purpose of improving hydrogen embrittlement resisting property, in particular, it is preferable to add more than 0.03% of Ti, more preferably 0.05% or more Ti.
- the effects described above reach saturation when an excessive amount of Ti is added, resulting in economical disadvantage.
- Excessive V content also increases the precipitation of much carbonitride and leads to poor workability and lower hydrogen embrittlement resisting property. Therefore, it is preferable to control the total concentration of Ti and/or V to within 1.0%, more preferably within 0.5%.
- Zr is effective in increasing the strength of the steel sheet and decreasing the crystal grain size, and also has the effect of improving hydrogen embrittlement resisting property through cooperation with Ti. In order to sufficiently achieve these effects, it is preferable that 0.003% or more Zr is contained. However, excessive Zr content increases the precipitation of carbonitride and leads to poor workability and lower hydrogen embrittlement resisting property. Therefore, it is preferable to control the concentration of Zr to within 1.0%.
- Mo has the effects of stabilizing austenite so as to retain the residual austenite, and suppress the infiltration of hydrogen thereby to improve hydrogen embrittlement resisting property. Mo also has the effect of improving the hardenability of the steel sheet. In addition, Mo strengthens the grain boundary so as to suppress hydrogen embrittlement from occurring. It is recommended to add 0.005% or more Mo in order to achieve these effects. More preferably 0.1% or more Mo is added. However, since the effects described above reach saturation when the Mo content exceeds 1.0%, resulting in economical disadvantage, Mo content is limited to 0.8% or less and more preferably to 0.5% or less.
- Nb is very effective in increasing the strength of the steel sheet and decreasing the grain size of the structure. Nb achieves these effects particularly effectively in cooperation with Mo. In order to achieve these effects, it is recommended to include 0.005% or more Nb. More preferably 0.01% or more Nb is added. However, since the effects described above reach saturation when an excessive Nb content is included, resulting in economical disadvantage, Nb content is limited to 0.1% or less and more preferably to 0.08% or less.
- B is effective in increasing the strength of the steel sheet, and it is preferable that 0.0002% or more (more preferably 0.0005% or more) B is contained in order to achieve these effects.
- 0.0002% or more (more preferably 0.0005% or more) B is contained in order to achieve these effects.
- an excessive content of B leads to poor hot processing property. Therefore, it is preferable to control the concentration of B to within 0.01% (more preferably within 0.005%).
- ⁇ At least one kind selected from among a group consisting of Ca: 0.0005% to 0.005%, Mg: 0.0005% to 0.01% and REM: 0.0005% to 0.01%)
- Ca, Mg and REM are effective in suppressing an increase in hydrogen ion concentration, that is, a decrease in pH in the atmosphere of the interface due to corrosion of the steel sheet surface, thereby to improve the corrosion resistance of the steel sheet. It is also effective in controlling the form of sulfide in the steel and improving the workability of the steel.
- concentrations of Ca within 0.005%, Mg and REM each within 0.01%.
- the recommended procedure is to keep the steel the composition described above at a temperature (T1) in a range from A3 point to (A3 point + 50°C) for a period of 10 to 1800 seconds (t1), cool down the steel at a mean cooling rate of 3°C/s or higher to a temperature (T2) in a range from Ms point to Bs point and keep the material at this temperature for a period of 60 to 3600 seconds (t2).
- the temperature T1 becomes higher than (A3 point + 50°C) or the period t1 is longer than 1800 seconds, in which case austenite grains grow resulting in poor workability (elongation flanging property).
- the temperature T1 is lower than A3 point, on the other hand, desirable bainitic ferrite structure cannot be obtained.
- the period t1 is shorter than 10 seconds, austenitization does not proceed sufficiently and therefore cementite and other alloy carbides remain.
- the period t1 is preferably in a range from 30 to 600 seconds, more preferably from 60 to 400 seconds.
- the steel sheet is cooled down.
- the steel is cooled at a mean cooling rate of 3°C/s or higher, for the purpose of preventing pearlite structure from being generated while avoiding the pearlite transformation region.
- the mean cooling rate should be as high as possible, and is preferably 5°C/s or higher, and more preferably 10°C/s or higher.
- the steel After quenching to the temperature between Ms point and Bs point at the rate described above, the steel is subjected to isothermal transformation so as to transform the matrix phase into binary phase structure of bainitic ferrite and martensite.
- T2 heat retaining temperature
- Bs heat retaining temperature
- much pearlite that is not desirable for the present invention is formed, thus hampering the formation of the predetermined bainitic ferrite structure.
- T2 is below Ms, on the other hand, the amount of residual austenite decreases.
- t2 When the temperature holding period t2 is longer than 1800 seconds, density of dislocations in bainitic ferrite becomes low, the amount of trapped hydrogen decreases and the desired residual austenite cannot be obtained. When t2 is less than 60 second, on the other hand, desired bainitic ferrite structure cannot be obtained.
- the length of t2 is preferably from 90 to 1200 seconds, and more preferably from 120 to 600 seconds. There is no restriction on the method of cooling after maintaining the heating temperature, and air cooling, quenching or air-assisted water cooling may be employed.
- the annealing process described above can be carried out easily by employing a continuous annealing facility or a batch annealing facility.
- the heat treatment process may be replaced by the plating process by setting the plating conditions so as to satisfy the heat treatment conditions.
- the plating may also be alloyed.
- the hot rolling process may be carried out in such a procedure as, after hot rolling at a temperature above Ar3 point, the steel sheet is cooled at a mean cooling rate of about 30°C/s and is wound up at a temperature from about 500 to 600°C.
- cold rolling may be applied in order to rectify the appearance. It is recommended to set the cold rolling ratio in a range from 1 to 70%. Cold rolling beyond 70% leads to excessive rolling load that makes it difficult to carry out the cold rolling.
- While the present invention is addressed to thin steel sheet, there is no limitation to the form of product, and may be applied, in addition to steel sheet made by hot rolling or steel sheet made by cold rolling, to those subjected to annealing after hot rolling or cold rolling, followed by chemical conversion treatment, hot-dip coating, electroplating, vapor deposition, painting, priming for painting, organic coating treatment or the like.
- the plating process may be either galvanizing or aluminum plating.
- the method of plating may be either hot-dip coating or electroplating, and the plating process may also be followed by alloying heat treatment or multi-layer plating.
- a steel sheet, that is plated or not plated, may also be laminated with a film.
- the coating material may be a known resin that can be used in combination with a known hardening agent such as epoxy resin, fluorocarbon resin, silicone acrylic resin, polyurethane resin, acrylic resin, polyester resin, phenol resin, alkyd resin, or melamine resin.
- epoxy resin, fluorocarbon resin or silicone acrylic resin is preferably used in consideration of corrosion resistance.
- additives that are added to coating materials such as coloring agent, coupling agent, leveling agent, sensitization agent, antioxidant agent, anti-UV protection agent, flame retarding agent or the like may be used.
- Desired coating layer of the coating material described above can be formed on the steel by a known technique such as dipping, roll coater, spraying, or curtain flow coater.
- the coating layer may have any proper thickness.
- the high strength thin steel sheet of the present invention may be applied to high-strength automotive components such as bumper, door impact beam, pillar and other reinforcement members and interior parts such as seat rail, etc.
- Automobile components that are manufactured by forming process also have sufficient properties (strength) and high hydrogen embrittlement resisting property.
- ⁇ Mean length of minor axes of the residual austenite grains is 1 ⁇ m or less>
- hydrogen embrittlement resisting property can be effectively improved by dispersing fine grains of residual austenite of lath shape.
- hydrogen embrittlement resisting property can be surely improved by dispersing the lath-shape grains of residual austenite having sizes of 1 ⁇ m or less (submicrometer order). This is supposedly because surface area of the residual austenite grains (interface) increases resulting in larger hydrogen trapping capability, when larger number of fine lath-shape grains of residual austenite having smaller mean length of minor axis are dispersed.
- Mean length of minor axes of the residual austenite grains is preferably 0.5 ⁇ m or less, more preferably 0.25 ⁇ m or less.
- hydrogen trapping capability of the fine lath-shape grains of residual austenite can be made far greater than that in the case of dispersing carbide, and thereby to substantially neutralize hydrogen that infiltrates from the outside through atmospheric corrosion, even when the same proportion by volume of residual austenite is contained, by controlling the mean axis ratio and mean length of minor axes of the residual austenite grains as described above.
- hydrogen embrittlement resisting property can be improved further by controlling the minimum distance between adjacent residual austenite grains, in addition to the above.
- hydrogen embrittlement resistance can be surely improved when the minimum distance between residual austenite grains is 1 ⁇ m or less. This is supposedly because propagation of cracks is suppressed so that the structure demonstrates higher resistance against fracture, when a large number of fine lath-shape grains of residual austenite are dispersed in proximity to each other.
- Minimum distance between adjacent residual austenite grains is preferably 0.8 ⁇ m or less, and more preferably 0.5 ⁇ m or less.
- Sample steels A-1 through Y-1 having the compositions described in Table 1 were melt-refined in vacuum to make test slabs.
- the slabs were processed in the following procedure (hot rolling ⁇ cold rolling ⁇ continuous annealing) thereby to obtain hot-rolled steel plates measuring 3.2 mm in thickness.
- the steel plates were pickled to remove scales from the surface and then cold rolled so as to reduce the thickness to 1.2 mm.
- Rolling ratio 50% ⁇ Continuous annealing>
- Each steel specimen was kept at a temperature of A3 point + 30°C for 120 seconds, then cooled in air at a mean cooling rate of 20°C/s to temperature T0 shown in Table 2, and was kept at T0 for 240 seconds, followed by air-assisted water cooling to the room temperature.
- No. 116 shown in Table 2 was made by heating a cold-rolled steel sheet to 830°C, keeping at this temperature for 5 minutes followed by quenching in water and tempering at 300°C for 10 minutes, thereby to form a martensite steel as a comparative example of the high-strength steel of the prior art.
- No. 120 was made by heating a cold-rolled steel sheet to 800°C, keeping at this temperature for 120 seconds, cooling down at a mean cooling rate of 20°C/s to 350°C and keeping at this temperature for 240 seconds.
- test pieces Metal structures of the test pieces were observed before and after the processing as follows. A measurement area (about 50 by 50 ⁇ m) at an arbitrarily chosen position in a surface parallel to the rolled surface at a position of one quarter of the thickness was photographed at measuring intervals of 0.1 ⁇ m, and area proportions of bainitic ferrite (BF), martensite (M) and residual austenite (residual ⁇ ) were measured by the method described previously. Then similar measurements were made in two fields of view that were arbitrarily selected, and the measured values were averaged. Area proportions of other structures (ferrite, pearlite, etc.) were subtracted from the entire structure. Mean axis ratio of the residual austenite grains of the steel sheet before and after the processing were measured by the method described previously. Test pieces having mean axis ratio of 5 or higher were regarded to satisfy the requirements of the present invention (o), and those having mean axis ratio of lower than 5 were regarded to fail to satisfy the requirements of the present invention (x).
- BF bainitic
- Tensile test was conducted on the JIS No. 5 test piece before processing, so as to measure the tensile strength (TS) and elongation (E1). Stretching speed of the tensile test was set to 1 mm/sec. Among the steel sheets having tensile strength of 1180 MPa as measured by the method described previously, those which showed elongation of 10% or more were evaluated as high in elongation property.
- the JIS No. 5 test piece was stretched. Then after bending with a radius of curvature of 15 mm, load of 1000 MPa was applied and the test piece was immersed in 5% solution of hydrochloric acid, and the time before crack occurred was measured.
- Hydrogen-charged 4-point bending test was also conducted for some steel species. Specifically, a rectangular test piece measuring 65 mm by 10 mm made of each steel sheet elongated by 3% was immersed in a solution of 0.5 mol of H 2 SO 4 and 0.01 mol of KSCN and was subjected to cathode hydrogen charging. Maximum stress endured without breaking for 3 hours was determined as the critical fracture stress (DFL).
- DFL critical fracture stress
- the test on weldability was conducted on the test pieces made according to the procedures of JIS Z 3136 and JIS Z 3137. And then spot welding was conducted on these pieces under the following conditions. Then tensile shear test (in which ultimate load was measured in the tensile velocity of 20mm/min) and cross tension test (in which ultimate load was measured in the tensile velocity of 20mm/min) was conducted on these pieces, so as to measure the tensile shear strength (TSS) and cross tension strength (CTS). And if the ductibility ratio(CTS/TSS) of cross tension strength (CTS) to the tensile shear strength (TSS) is 0.2 or higher, it was evaluated that the test piece has a better weldability.
- No.101 (not belonging to the scope of the invention) is better than No.114 (prior art) in reference to weldability because the ratio of ductibility in sample No.114 is.0.19 while that in sample No.101 is 0.22
- Tables 1 and 2 can be interpreted as follows (numbers in the following description are test Nos. in Table 2).
- Test pieces Nos. 122 through 125 (inventive steel sheets 1) that satisfy the requirements of the present invention have high strength of 1180 MPa or higher, and high hydrogen embrittlement resisting property in harsh environment after the forming process. They also have high elongation property required of the TRIP steel sheet, thus providing steel sheets best suited for reinforcement parts of automobiles that are exposed to corrosive atmosphere.
- Test pieces Nos. 114 through 120 and 126 that do not satisfy the requirements of the present invention, in contrast, have the following drawbacks.
- No. 114 made of steel species N-1 that includes excessive amounts of C content does not have good weldability.
- No. 115 made of steel species O-1 that includes insufficient Mn content does not retain sufficient residual austenite and is inferior in hydrogen embrittlement resisting property after the processing.
- martensite steel that is a conventional high strength steel made of steel species P-1 that includes insufficient Si content, hardly contains residual austenite and is inferior in hydrogen embrittlement resisting property. It also does not show the elongation property required of a thin steel sheet.
- No. 118 made of steel species R-1 that includes excessive Nb content and No. 119 made of steel species S-1 that includes excessive Mo content are inferior in forming workability. Nos. 118 and 119 could not undergo the processing, making it impossible to investigate the property after the processing.
- No. 126 includes Al content higher than that specified for the inventive steel sheet 1. As a result, although the predetermined amount of residual austenite is retained, the residual austenite does not have the mean axis ratio specified in the present invention, the desired matrix phase is not obtained and inclusions such as AlN are generated thus resulting in poor hydrogen embrittlement resisting property.
- the part 1 (hat channel as test piece) shown in Fig. 3 was made by using reference steel species A-1 shown in Table 1 and the comparative steel sheet, and was subjected to pressure collapse test.
- the part was spot welded at the positions 2 of the part shown in Fig. 3 at 35 mm intervals as shown in Fig. 3 by supplying electric current of a magnitude less than the expulsion generating current by 0.5 kA from an electrode measuring 6 mm in diameter at the distal end.
- a die 3 was pressed against the part 1 from above the mid portion thereof in the longitudinal direction as shown in Fig. 4 , and the maximum tolerable load was determined. Absorbed energy was determined from the area under the load-deformation curve. The results are shown in Table 3.
- the part (test piece) made from the steel sheet of the reference steel species A-1 has higher load bearing capability and absorbs greater energy than a part made of the conventional steel sheet having lower strength, thus showing high pressure collapse resistance.
- Fig. 5 The parts 4 (hat channel as test piece) shown in Fig. 5 were made by using reference steel species A-1 shown in Table 1 and the comparative steel sheet, and were subjected to impact resistance test.
- Fig. 6 is a sectional view along A-A of the part 4 shown in Fig. 5 .
- a weight 6 (weighing 10kg) was dropped onto the part 4 from a height of 11 meters, and the energy absorbed before the part 4 underwent deformation of 40 mm in the direction of height.
- Table 4 Steel sheet used Evaluation of test piece Steel species Symbol TS EL Residual ⁇ Energy absorbed (MPa) (%) (Area %) (kJ)
- TEM photograph of the test piece made in this example is shown as reference.
- Fig. 8 is a photograph of TEM observation of No. 101. From Fig. 8 , it can be seen that the high strength thin steel sheet contains lath-shaped residual austenite (black portion of bar shape in Fig. 8 ) specified in the present invention dispersed therein.
- Fig. 9 is a photograph of TEM observation of No. 120 of a comparative example. From Fig. 9 , it can be seen that the high strength thin steel sheet of No. 120 contains residual austenite (black portion of somewhat round shape in Fig. 9 ), although the residual austenite has a block shape that does not satisfy the requirements of the present invention.
- test slabs were produced under the same requirements as that in Example 1(hot rolling, cold rolling and continuous annealing).
- No.217 in Table 6 was prepared by the procedure of No.116 in Table 2 according to Example 1 to produce a known high strength martensite steel as a comparative example.
- No. 220 was prepared by the procedure of No.120 in Table 2 according to Example 1.
- test pieces were produced by the same procedures as in Example 1. Then the test pieces were immersed in the same solution of hydrochloric acid as that in Example 1, and the time before crack occurred was measured.
- the bent test pieces prepared as described in Example 1 were subjected to accelerated exposure test in which 3% solution of NaCl was sprayed once every day for 30 days simulating the actual operating environment, and the number of days before crack occurred was determined.
- hydrogen-charged 4-point bending test was also conducted for some steel species as is the case with Example 1. Maximum stress endured without breaking for 3 hours was determined as the critical fracture stress (DFL). Then the ratio (DFL ratio) of this value to the value of DFL of test No. 202 (steel species B-2 not belonging to the scope of the invention) shown in Table 6 was determined.
- No.201 and No.215 which are representative steel species. As a result, it was found that No.201 (not belonging to the scope of the invention) is better than No.215(prior art) in reference to weldability because the ratio of ductibility in sample No.215 is 0.19 while that in sample No.201 is 0.22.
- Table 5 Steel species Symbol Chemical composition (mass%)* Ac3 (°C) Bs (°C) Ms (°C) C Si Mn P S Al Cu u Ni Ti V Nb Mo Others A-2 0.24 2.04 2.01 0.012 0.002 0.033 0.3 - - - - - - 857.0 584.3 380.9 B-2 0.
- Test pieces Nos. 222 through 225 (inventive steel sheets 1) that satisfy the requirements of the present invention have high strength of 1180 MPa or higher, and high hydrogen embrittlement resisting property in harsh environment after the forming process. They also have high elongation property required of the TRIP steel sheet, thus providing steel sheets best suited for reinforcement parts of automobiles that are exposed to corrosive atmosphere.
- No. 215 made of steel species O-2 that includes excessive C content fails to show the required level of hydrogen embrittlement resisting property of the present invention.
- No. 216 made of steel species P-2 that includes insufficient Mn content does not retain sufficient residual austenite and is inferior in hydrogen embrittlement resisting property after the processing.
- martensite steel that is a conventional high strength steel made of steel species Q-2 that includes insufficient Si content, hardly contains residual austenite and is inferior in hydrogen embrittlement resisting property. It also does not show the elongation property required of a thin steel sheet.
- No. 218 made of steel species R-2 that includes insufficient C content is inferior in both the forming workability and the hydrogen embrittlement resisting property after processing.
- No. 226 includes Al content higher than that specified for the inventive steel sheet 1. As a result, although the predetermined amount of residual austenite is retained, the residual austenite does not have the mean axis ratio specified in the present invention, the desired matrix phase is not obtained and inclusions such as AlN are generated thus resulting in poor hydrogen embrittlement resisting property.
- the part (test piece) made from the steel sheet of the reference steel species A-2 has higher load bearing capability and absorbs greater energy than a part made of the conventional steel sheet that has lower strength, thus showing higher pressure collapse resistance.
- TEM photograph of the test piece made in this example is shown as reference.
- Fig. 10 is a photograph of TEM observation of No. 201. From Fig. 10 , it can be seen that the high strength thin steel sheet contains lath-shaped residual austenite (black portion of bar shape in Fig. 10 ) specified in the present invention dispersed therein.
- Fig. 11 is a photograph of TEM observation of No. 220 of a comparative example. From Fig. 11 , it can be seen that the high strength thin steel sheet of No. 220 contains residual austenite (black portion of somewhat round shape in Fig. 11 ), although the residual austenite has a block shape that does not satisfy the requirements of the present invention.
- test slabs were produced under the same conditions as that in Example 1(hot rolling, cold rolling and continuous annealing).
- No.312 in Table 10 was prepared by the procedure of No.116 in Table 2 according to Example 1 to produce a known high strength martensite steel as a comparative example.
- No. 313 was prepared by the procedure of No.120 in Table 2 according to Example 1.
- E0 represents the elongation before rupture of a steel test piece that does not substantially contain hydrogen
- E1 represents the elongation before rupture of a steel test piece that has been charged with hydrogen electrochemically in sulfuric acid.
- Hydrogen charging was carried out by immersing the steel test piece in a mixed solution of H 2 SO 4 (0.5 mol/L) and KSCN (0.01 mol/L) and supplying constant current (100A/m 2 ) at room temperature.
- a steel sheet having hydrogen embrittlement risk index higher than 50% is likely to undergo hydrogen embrittlement during use.
- steel sheets having hydrogen embrittlement risk index not higher than 50% were evaluated to have high hydrogen embrittlement resisting property. Results of the test are shown in Table 10.
- Test pieces Nos. 315 through 318 that satisfy the requirements of the present invention have high strength of 1180 MPa or higher, and show high hydrogen embrittlement resisting property in harsh environment after the forming process. They also have high elongation property required of the TRIP steel sheet, thus providing steel sheets best suited for reinforcement parts of automobiles that are exposed to corrosive atmosphere.
- No. 311 made of steel species K-3 that includes excessive C content has carbide precipitated and residual austenite of longer mean length of minor axis, thus resulting poor performance in both workability and hydrogen embrittlement resisting property after processing.
- martensite steel that is a conventional high strength steel made of steel species L-3 that includes insufficient Si content, hardly contains residual austenite and is inferior in hydrogen embrittlement resisting property. It also does not show the elongation property required of a thin steel sheet.
- No. 319 includes Al content higher than that specified for the inventive steel sheet 1. As a result, although the predetermined amount of residual austenite is retained, the residual austenite does not have the mean axis ratio specified in the present invention, the desired matrix phase is not obtained and inclusions such as AlN are generated thus resulting in poor hydrogen embrittlement resisting property.
- the part (test piece) made from the steel sheet of the reference steel species A-3 has higher load bearing capability and absorbs greater energy than a part made of the conventional steel sheet having lower strength, thus showing high pressure collapse resistance.
- Fig. 12 is a photograph of TEM observation (magnification factor 15000) of No. 301.
- Fig. 13 is a photograph of TEM observation (magnification factor 60,000) of a portion shown in the photograph of Fig. 12 . From Figs. 12 , 13 , it can be seen that the high strength thin steel sheet contains fine residual austenite grains (black portion of bar shape in Figs. 12 , 13 ) specified in the present invention dispersed therein, and that the residual austenite has the lath shape specified in the present invention.
- Fig. 14 is a photograph of TEM observation of No. 313 of a comparative example. From Fig. 14 , it can be seen that the high strength thin steel sheet of No. 313 contains residual austenite (black portion of somewhat round shape in Fig. 14 ), although the residual austenite has a block shape that does not satisfy the requirements of the present invention.
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- Heat Treatment Of Sheet Steel (AREA)
Claims (1)
- Tôle d'acier mince à haute résistance possédant une propriété élevée de résistance à la fragilisation par l'hydrogène, qui comprend :C : 0,10 à 0,25 % ;Si : 1,2 à 2,5 % ;Mn : 1,2 à 3,5 % ;P : 0,15 % ou moins ;S : 0,02 % ou moins ;Al : 0,2 à 1,5 % ;qui en outre comprend facultativement du Cu : 0,003 à 0,5 % et/ou du Ni : 0,003 à 1,0 % comme éléments facultatifs, du Ti et/ou du V : 0,003 à 1,0 % comme éléments facultatifs, du Mo : 1,0 % ou moins (plus que 0 %) et du Nb : 0,1 % ou moins (plus que 0 %) comme éléments facultatifs, du B : 0,0002 à 0,01 % comme un élément facultatif, au moins un élément choisi dans le groupe constitué de : Ca : 0,0005 à 0,005 %,Mg : 0,0005 à 0,01 % et de métaux de terres rares : 0,0005 à 0,01 % comme éléments facultatifs, et de Zr : 0,003 à 1,0 % comme un élément facultatif, en termes de pourcentage en poids, le reste étant du fer et des impuretés inévitables ;dans laquelle la structure du métal consiste en :austénite résiduelle : 3 % par zone ou plus en proportion de la structure globale ;une phase binaire de ferrite bainitique et de martensite avec la ferrite bainitique agissant en tant que phase principale : 90 % ou plus au total,alors que le ratio de l'axe moyen (le grand axe/le petit axe) des grains de ladite austénite résiduelle est supérieur ouégal à 5, et que l'acier possède une résistance à la traction supérieure ou égale à 1180 MPa,dans laquelle la structure du métal satisfait en outre aux exigences suivantes :la longueur moyenne des plus petits axes des grains de ladite austénite résiduelle est inférieure ou égale à 1 µm ; etla distance minimale entre les grains de ladite austénite résiduelle est inférieure ou égale à 1 µm.
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
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JP2004381232 | 2004-12-28 | ||
JP2004381231 | 2004-12-28 | ||
JP2004381230 | 2004-12-28 | ||
JP2005147240A JP4684002B2 (ja) | 2004-12-28 | 2005-05-19 | 耐水素脆化特性に優れた超高強度薄鋼板 |
JP2005147239A JP4553372B2 (ja) | 2004-12-28 | 2005-05-19 | 耐水素脆化特性に優れた超高強度薄鋼板 |
JP2005147238A JP4868771B2 (ja) | 2004-12-28 | 2005-05-19 | 耐水素脆化特性に優れた超高強度薄鋼板 |
Publications (2)
Publication Number | Publication Date |
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EP1676932A1 EP1676932A1 (fr) | 2006-07-05 |
EP1676932B1 true EP1676932B1 (fr) | 2015-10-21 |
Family
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Application Number | Title | Priority Date | Filing Date |
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EP05028444.7A Expired - Fee Related EP1676932B1 (fr) | 2004-12-28 | 2005-12-23 | Tôle d'acier mince à haute résistance, possedant une résistance accrue à la fragilisation par l'hydrogène |
Country Status (4)
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US (1) | US20060137768A1 (fr) |
EP (1) | EP1676932B1 (fr) |
KR (1) | KR100723092B1 (fr) |
CA (1) | CA2531615A1 (fr) |
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JP3764411B2 (ja) * | 2002-08-20 | 2006-04-05 | 株式会社神戸製鋼所 | 焼付硬化性に優れた複合組織鋼板 |
US7314532B2 (en) * | 2003-03-26 | 2008-01-01 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) | High-strength forged parts having high reduction of area and method for producing same |
JP4716359B2 (ja) * | 2005-03-30 | 2011-07-06 | 株式会社神戸製鋼所 | 均一伸びに優れた高強度冷延鋼板およびその製造方法 |
JP4716358B2 (ja) * | 2005-03-30 | 2011-07-06 | 株式会社神戸製鋼所 | 強度と加工性のバランスに優れた高強度冷延鋼板およびめっき鋼板 |
KR100990772B1 (ko) * | 2005-12-28 | 2010-10-29 | 가부시키가이샤 고베 세이코쇼 | 초고강도 박강판 |
JP4217245B2 (ja) * | 2006-01-20 | 2009-01-28 | 株式会社神戸製鋼所 | 耐水素脆性に優れた高強度鋼 |
EP1832667A1 (fr) | 2006-03-07 | 2007-09-12 | ARCELOR France | Procédé de fabrication de tôles d'acier à très hautes caractéristiques de résistance, de ductilité et de tenacité, et tôles ainsi produites |
CN100510143C (zh) * | 2006-05-29 | 2009-07-08 | 株式会社神户制钢所 | 延伸凸缘性优异的高强度钢板 |
JP4974341B2 (ja) * | 2006-06-05 | 2012-07-11 | 株式会社神戸製鋼所 | 成形性、スポット溶接性、および耐遅れ破壊性に優れた高強度複合組織鋼板 |
JP5030200B2 (ja) * | 2006-06-05 | 2012-09-19 | 株式会社神戸製鋼所 | 伸び、伸びフランジ性および溶接性に優れた高強度鋼板 |
JP4282731B2 (ja) | 2006-08-11 | 2009-06-24 | 新日本製鐵株式会社 | 疲労特性に優れた自動車足回り部品の製造方法 |
JP4164537B2 (ja) * | 2006-12-11 | 2008-10-15 | 株式会社神戸製鋼所 | 高強度薄鋼板 |
US8465806B2 (en) * | 2007-05-02 | 2013-06-18 | Tata Steel Ijmuiden B.V. | Method for hot dip galvanizing of AHSS or UHSS strip material, and such material |
EP1990431A1 (fr) | 2007-05-11 | 2008-11-12 | ArcelorMittal France | Procédé de fabrication de tôles d'acier laminées à froid et recuites à très haute résistance, et tôles ainsi produites |
JP4445522B2 (ja) * | 2007-06-20 | 2010-04-07 | 豊田鉄工株式会社 | 車両用センターピラーの補強部材 |
JP5365217B2 (ja) * | 2008-01-31 | 2013-12-11 | Jfeスチール株式会社 | 高強度鋼板およびその製造方法 |
JP5365216B2 (ja) * | 2008-01-31 | 2013-12-11 | Jfeスチール株式会社 | 高強度鋼板とその製造方法 |
JP5394709B2 (ja) | 2008-11-28 | 2014-01-22 | 株式会社神戸製鋼所 | 耐水素脆化特性および加工性に優れた超高強度鋼板 |
JP5412182B2 (ja) | 2009-05-29 | 2014-02-12 | 株式会社神戸製鋼所 | 耐水素脆化特性に優れた高強度鋼板 |
JP6027302B2 (ja) * | 2009-12-22 | 2016-11-16 | 株式会社神戸製鋼所 | 高強度焼戻し省略ばね用鋼 |
JP5327106B2 (ja) | 2010-03-09 | 2013-10-30 | Jfeスチール株式会社 | プレス部材およびその製造方法 |
KR101315568B1 (ko) * | 2010-03-24 | 2013-10-08 | 제이에프이 스틸 가부시키가이샤 | 고강도 전봉 강관 및 그 제조 방법 |
JP5771034B2 (ja) | 2010-03-29 | 2015-08-26 | 株式会社神戸製鋼所 | 加工性に優れた超高強度鋼板、およびその製造方法 |
JP5662902B2 (ja) * | 2010-11-18 | 2015-02-04 | 株式会社神戸製鋼所 | 成形性に優れた高強度鋼板、温間加工方法、および温間加工された自動車部品 |
JP5662903B2 (ja) * | 2010-11-18 | 2015-02-04 | 株式会社神戸製鋼所 | 成形性に優れた高強度鋼板、温間加工方法、および温間加工された自動車部品 |
US9475112B2 (en) | 2011-06-10 | 2016-10-25 | Kobe Steel, Ltd. | Hot press-formed product and process for producing same |
US9745639B2 (en) * | 2011-06-13 | 2017-08-29 | Kobe Steel, Ltd. | High-strength steel sheet excellent in workability and cold brittleness resistance, and manufacturing method thereof |
CN104185690A (zh) * | 2012-04-23 | 2014-12-03 | 新日铁住金株式会社 | 钢轨 |
WO2016001708A1 (fr) * | 2014-07-03 | 2016-01-07 | Arcelormittal | Procédé de production d'une tôle d'acier revêtue à haute résistance présentant une résistance, une aptitude au formage améliorées et tôle ainsi obtenue |
DE102014016073A1 (de) | 2014-10-23 | 2016-04-28 | Vladimir Volchkov | Stahl |
CN105039851B (zh) * | 2015-08-17 | 2017-03-01 | 攀钢集团攀枝花钢铁研究院有限公司 | 钛合金化tam钢及其制造方法 |
WO2017109539A1 (fr) | 2015-12-21 | 2017-06-29 | Arcelormittal | Procédé de fabrication d'une tôle d'acier à haute résistance présentant une résistance et une formabilité améliorées et tôle d'acier à haute résistance obtenue par ce procédé |
CN105755376A (zh) * | 2016-03-31 | 2016-07-13 | 苏州睿昕汽车配件有限公司 | 一种耐高温汽车配件合金钢材料及其制备方法 |
DE102016005532A1 (de) | 2016-05-02 | 2017-11-02 | Vladimir Volchkov | Stahl |
BR112018073110A2 (pt) | 2016-08-08 | 2019-03-06 | Nippon Steel & Sumitomo Metal Corp | chapa de aço |
WO2019189842A1 (fr) * | 2018-03-30 | 2019-10-03 | Jfeスチール株式会社 | Tôle d'acier galvanisée à résistance élevée, élément à résistance élevée et leurs procédés de fabrication |
US11828698B2 (en) | 2018-11-30 | 2023-11-28 | Nsk Ltd. | Ambient-hydrogen-level assessment method and white-structure-damage-likelihood prediction method |
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JP3241897B2 (ja) * | 1993-10-12 | 2001-12-25 | 新日本製鐵株式会社 | 引張強度、疲労強度および被削性に優れる熱間鍛造用非調質鋼 |
JPH11293383A (ja) | 1998-04-09 | 1999-10-26 | Nippon Steel Corp | 水素性欠陥の少ない厚鋼板およびその製造方法 |
JP2001020030A (ja) * | 1999-07-02 | 2001-01-23 | Kobe Steel Ltd | 伸びフランジ性に優れた高強度熱延鋼板 |
JP3924159B2 (ja) | 2001-11-28 | 2007-06-06 | 新日本製鐵株式会社 | 成形加工後の耐遅れ破壊性に優れた高強度薄鋼板及びその製造方法並びに高強度薄鋼板により作成された自動車用強度部品 |
JP4091894B2 (ja) * | 2003-04-14 | 2008-05-28 | 新日本製鐵株式会社 | 耐水素脆化、溶接性、穴拡げ性および延性に優れた高強度薄鋼板およびその製造方法 |
JP4102281B2 (ja) * | 2003-04-17 | 2008-06-18 | 新日本製鐵株式会社 | 耐水素脆化、溶接性および穴拡げ性に優れた高強度薄鋼板及びその製造方法 |
EP1553202A1 (fr) * | 2004-01-09 | 2005-07-13 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) | Acier à très haute résistance mécanique ayant une excellente résistance à la fragilisation par l'hydrogène et son procédé de production |
DE602005013442D1 (de) * | 2004-04-22 | 2009-05-07 | Kobe Steel Ltd | Hochfestes und kaltgewaltzes stahlblech mit hervorragender verformbarkeit und plattiertes stahlblech |
-
2005
- 2005-12-23 CA CA002531615A patent/CA2531615A1/fr not_active Abandoned
- 2005-12-23 EP EP05028444.7A patent/EP1676932B1/fr not_active Expired - Fee Related
- 2005-12-27 US US11/317,174 patent/US20060137768A1/en not_active Abandoned
- 2005-12-28 KR KR1020050131831A patent/KR100723092B1/ko active IP Right Grant
Also Published As
Publication number | Publication date |
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KR100723092B1 (ko) | 2007-05-30 |
US20060137768A1 (en) | 2006-06-29 |
CA2531615A1 (fr) | 2006-06-28 |
KR20060076744A (ko) | 2006-07-04 |
EP1676932A1 (fr) | 2006-07-05 |
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