Classifications

• • 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
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • 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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—Hot rolling
• • 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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—Cold rolling
• • 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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0273—Final recrystallisation annealing
• • 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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
  • C21D8/0426—Hot rolling
• • 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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
  • C21D8/0436—Cold rolling
• • 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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
  • C21D8/0473—Final recrystallisation annealing
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
  • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
• • 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
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • 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
  • 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
  • C21D2211/001—Austenite
• • 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
• • 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
  • C21D2211/005—Ferrite

Definitions

• the present invention relates to a high strength cold rolled steel plate and a galvanized steel plate mainly used for the inner and outer plates of automobiles, and a method of manufacturing thereof, and more particularly, to a high strength cold rolled steel sheet and a galvanized steel plate for minimizing formability reduction that may be generated during the process of galvannealing a high strength steel plate, particularly, a thin steel plate for automobiles as well as representing excellent formability compared to conventional high strength steel plate for automobiles, and a method of manufacturing thereof.
• steel plate for automobiles requires higher level of formability as automobile parts are complicated and integrated, and also requires a better spot welding characteristic determining continuous workability during the manufacturing process of an automobile.
• a galvannealing process is performed in order to improve corrosion resistance and a spot welding characteristic.
• a galvannealing process is performed in order to improve corrosion resistance and a spot welding characteristic.
• austenite should be retained in the structure of the steel so that transformation is performed during deformation.
• austenite decomposes into carbide and ferrite and disappears.
• thin steel plate manufacturing technology for processing various deep drawing has been developed in a related art.
• Al, Si, and P have been utilized to induce transformation induced plasticity, and a method of suppressing forming of a carbide inside a structure at a temperature of 300-500 ° C has been used.
• a method of adding various alloy elements in order to improve a coating characteristic, or a method of improving a plating characteristic through suppression of segregation during a cold annealing process have been proposed.
• the present invention has been made to solve the foregoing problems with the prior art, and therefore an aspect of the present invention is to provide an alloy component system of a high strength cold rolled steel plate and a galvanized steel plate, capable of maintaining and improving workability while minimizing deterioration of material, and manufacturing conditions thereof.
• a cold rolled steel plate including: by weight%, C: 0.04-0.25%, N: 70-300 ppm, N-14/27Al: 70 ppm or more, Mn: 0.2-3.0%, Si: 0.5-2.0%, P: 0.01-0.1%, Al: 0.005% or less, Sb: 0.001-0.05%, S: 0.02% or less, including a balance of Fe and other inevitable impurities, and a galvanized steel plate obtained by performing a galvanizing process on the cold rolled steel plate.
• the cold rolled steel plate or the galvanized steel plate may further include one or two or more components selected from the group consisting of Co: 0.01-1.0%, Mo: 0.005-0.05%, Ti: 0.001-0.1%, Nb: 0.001-0.1%, V: 0.001- 0.1%, and Ca: 0.0001-0.03%.
• a method for manufacturing a cold rolled steel plate including: with respect to a slab of the steel plate of the above-described components, reheating the slab at a temperature of 1100-1250 ° C; terminating finish hot rolling at a temperature of Ar3-950 ° C; winding the slab at a temperature of
• the method may further include: with respect to the annealed steel plate, cooling the steel plate down to a temperature range of 650-750°C at a cooling rate of l-10 ° C/sec and subsequently, rapidly cooling the steel plate to a temperature range of 300-450 ° C; and galvanizing and galvannealing the cooled steel plate.
• a transformation-induced plasticity characteristic can be maintained even during a galvannealing process when a coated steel plate is manufactured using transformat ion-induced plasticity, so that a galvannealed and galvanized steel plate having excellent elongation and not causing material quality reduction can be produced. Furthermore, formability of the steel plate can be improved.
• FIG. 1 is a graph comparing retained austenite of nitrogen added steel with that of general transformat ion-induced plasticity (TRIP) steel.
• FIG. 2 is a graph illustrating an elongation reduction tendency by a GA process.
• FIG. 3 is a graph illustrating a change in vapor content according to a dew point .
• FIG. 4 is a graph illustrating a change in a nitrogen solid solubility during solidification of molten steel.
• FIG. 5 is a graph illustrating a change in oxygen density in molten steel during single Si deoxidation.
• FIG. 6 is a graph comparing elongation changes of the present steel and comparison steel at tensile strength of 590 MPa.
• FIG. 7 is a graph illustrating addition of nitrogen has an influence on elongation in a steel material of tensile strength of 780 MPa or more.
• FIG. 8 is a schematic graph illustrating temperature of heat treatment process according to steel of the present invention.
• FIG. 9 is a figure illustrating a difference in a coated surface depending on hydrogen content (left: hydrogen cooling (hydrogen density 60%), right: nitrogen cooling (hydrogen density 25% or less)), where black spots on the right are spot-shaped non-coated portions. [Best Mode]
• C and N are segregated into austenite during two phase region annealing, and segregated one more time into austenite during a bainite transformation process, so that martensite transformation point is lowered below room temperature or less and austenite is stably maintained at room temperature. Therefore, C is added by 0.04 weight% or more, but the upper limit of C content is limited to 0.25 weight% because when C content is excessive, a hardened structure is formed on a weld zone.
• N unlike C, has a characteristic of not forming a nitride with Fe when cooled to maintain transformation- induced plasticity. Therefore, N is added by 0.007 weight% or more.
• a steel plate can conserve transformat ion-induced plasticity even after a galvannealing process of a coated layer to maintain workability (FIG. 1).
• N gathers to an austenite portion together with dissolvable C during a dual-phase region annealing to primarily stabilize austenite.
• N is concentrated again on austenite to lower martensite transformation temperature below room temperature or less to facilitate austenite retainment.
• the upper limit of an added amount of N is limited to 0.03 weight%.
• an initially added amount of N is limited according to the present invention as described above, an actual dissolvable N amount needs to be limited separately in terms of a process or in the case where an element such as Al that reacts with N during a galvannealing process to reduce an amount of N is introduced during a manufacturing process of steel.
• an N-14/27A1 value appraising an effective dissolvable amount has been used as a standard in order to set an effective dissolvable amount.
• An effective dissolvable amount of N is set to 70 ppm or more using this standard.
• N is dissolvable up to a level of 100 ppm (FIG. 4). When Mn is added together, affinity increases and N can be added up to 300 ppm.
• an amount of dissolvable N is limited to 300 ppm or less, and preferably, 150 ppm or less.
• affinity increases and N can be added up to 300 ppm.
• Mn is an element having a solid-solution strengthening effect and an effect of suppressing the formation of an intermediate phase during a bainite process in a dual-phase region. Mn is added by 0.2 weight% or more. However, when an added amount of Mn is excessive, a hardening ability increases too much and so the strength of steel may increase excessively, so that workability and a welding characteristic may be reduced. Therefore, the upper limit of Mn is limited to 3.0 weight%.
• Si is a component inducing transformation-induced plasticity and suppresses a phenomenon whereby carbon is precipitated as carbide and exhausted from austenite during a bainite process after a coating and annealing process.
• Si is added by 0.5 weight% or more.
• excessive addition of Si has an adverse influence on a welding characteristic, and may cause segregation on the surface of a steel plate during high temperature annealing in a continuous annealing process and a continuous galvanizing process. Accordingly, since excessive addition of Si may reduce wettability of molten zinc on the surface of the steel plate during a galvanizing process, a coating characteristic may be reduced. Therefore, the upper limit of Si is limited to 2.0 weight%.
• P is a solid-solution strengthening element added for increasing strength and is added by 0.01 weight% or more.
• a welding characteristic reduces and a deviation in the material quality of steel may increase for each portion by center segregation generated during continuous casting.
• a welding characteristic may be reduced as grain boundary strength reduces after welding. Therefore, the upper limit of P is limited to 0.1 weight%.
• Al removes oxygen in molten steel to prevent an oxygen from forming a gas phase and being boiled during a solidification process.
• Al is formed as a precipitate of AlN formed by combining with N in steel to exhaust N and thus suppress a transformation-induced plasticity characteristic. Therefore, Al is limited to 0.005 weight% or less so that N may possibly remain in a dissolvable state.
• S is an element inevitably included when steel is manufactured. S is formed as MnS causing an inner defect after rolling in steel to reduce the destruction characteristic of a steel plate such as a hole expansion ratio. Therefore, an allowed range of S is limited to 0.02 weight% or less to prevent the destruction characteristic of an edge portion from reducing.
• Co is an element added for improving the strength of steel. Co suppresses the formation of an oxide during high temperature annealing and is added by 0.01 weight% or more in order to improve wettability with respect to a steel plate of molten zinc during galvanizing. However, when Co is added excessively, the elongation of steel may greatly reduce. Therefore, the upper limit of Co is limited to 1.0 weight%.
• Mo is an element suppressing brittleness in workability and improving a coating characteristic, and is added by 0.005 weight% or more.
• Mo content exceeds 0.05 weight% or more, not only an improvement effect may greatly reduce but also economical efficiency may be reduced. Therefore, Mo content is limited to 0.005-0.05 weight%.
• Sb is added by 0.001 weight% or more, preferably 0.005 weight% or more in order to improve a caoting characteristic by suppressing, on the whole, an oxide formed on the surface of a steel material. When Sb is not added, an oxide is formed on an entire surface, so that wettability reduces during galvanizing and thus there is a high possibility that non-coated portions may be generated.
• the upper limit of Sb is limited to 0.1 weight%, preferably, 0.05 weight%.
• V, Ti and/or Nb are elements useful for increasing the strength of a steel plate and refining grain diameter.
• N can form a precipitate in preference to C inside a steel material, so that these elements have the effect of refining crystal grains and conserving carbon.
• these elements are added by 0.001 weight%.
• the content of these elements exceeds 0.1 weight%, manufacturing costs increase and ductility of ferrite may reduce due to an excessive precipitate. Therefore, the upper limit of these elements is limited to 0.1 weight%.
• V plays a similar role to Nb. When V is added alone, V content of 0.04% or more should be secured so that it is precipitated. In the case where V is added in a composite form with Nb, V can be precipitated in a composite form. In this case, the addition range of V is limited to 0.001-0.1%.
• Ca forms a compound with a non-metallic inclusion such as MnO, MnS, etc. inside molten steel to spherodize the non-metallic inclusion and increase the destruction strength of a columnar crystal grain boundary, and also suppresses a crack generation of a steel plate, and increases the hole expansion ratio of a steel plate. Therefore, Ca is added by a level of 0.0001-0.03 weight%, preferably 0.0005-0.003 weight%.
• the fine structure of the steel formed of the above-described component system is characterized by ferrite of 70% or more, and a composite structure, of bainite-austenite (partially carbide) around crystalline grains surrounding the ferrite for a remainder. Austenite in the composite structure plays an important role in improving workability. At this point, the austenite structure may have a long shape whose axis ratio is 2 or more.
• Al content in steel is low in a manufacturing process of molten steel before solidification, a CO gas boils during solidification and continuous casting becomes difficult. Therefore, Al is basically added to a general kind of steel to form oxygen and aluminum in a molten steel state, so that generation of a CO gas is suppressed. Also, remaining Al that does not combine with oxygen combines with N inside steel after solidification to form AlN. Such a reaction removes an aging characteristic from general steel, so that a surface after process becomes elegant, but the steel material of the present invention should make a sufficient use of a dissolvable N effect. Therefore, the introduced amount of Al after solidification should be reduced.
• minimizing Al content after solidification is very important as a formability improvement method.
• Such a method is difficult to use during a process of producing a general steel material, but can be used for transformation-induced plasticity steel containing a large amount of Si where oxygen disappears by combining with Si in the form of Si ⁇ 2 (FIG. 5).
• Al should not be added or, even if Al is added, Al needs to be used in a limited range of 0.005% or less, which is an amount not leaving oxygen of 5 ppm or more after solidification during a steel manufacturing process.
• a steel slab formed of the above-described configuration is reheated at a temperature of 1100-1250 ° C .
• the reheating temperature is less than 1100°C , uniform structure and re-dissolvable Ti and Nb are not sufficient.
• the reheating temperature is greater than 1250 ° C, oxidized scale and a large amount of oxides such as S1O2, MnO, and AI2O3 are generated on a boundary with metal and inside metal, so that surface quality may be deteriorate. Therefore, the reheating temperature is limited within a range of 1100-1250 ° C.
• finish hot rolling is ended at a temperature ranging from Ar3 transformation point to 950 ° C.
• a temperature less than Ar 3 transformation point there is the high possibility that hot transformation resistance rapidly increases and a problem may be generated during a manufacturing process.
• a temperature greater than 950 ° C too thick an oxidized scale may be generated and the structure of the steel plate may be coarsened.
• the steel plate After the finish hot rolling is performed, the steel plate is wound at a temperature of 450-700 ° C. When the winding temperature condition exceeds 700 ° C, an amount of an oxide on the surface of the hot rolled material increases and so the surface quality may reduce. When winding is performed at a temperature less than 450 ° C, the material quality of the hot rolled material is too hardened, so that a load may increase too much during a cold rolling process, which is the next process.
• the steel plate manufactured as described above passes through a pickling process and a cold rolling process for an object thickness, and is then annealed at a temperature of 750-830°C for recrystallization and fine structure control.
• carbon and oxygen in the steel are primarily concentrated on an austenite portion.
• 750-830°C an effect suppressing surface segregation of a Si component, which is most problematic in coating of Si- added steel, can be obtained.
• the annealing temperature is less than 750 ° C, re-solution of a carbide is not properly performed during the annealing, so that C cannot be sufficiently utilized to represent a sufficient transformation-induced plasticity.
• atmosphere control in an annealing section and a heat treatment section prior to coating after the annealing section is also required, which means a reduction atmosphere should be applied after the annealing process.
• the reduction atmosphere can be controlled by hydrogen density and moisture content (dew point) inside a heat treatment furnace. Partial water vapor pressure changes depending on a dew point (FIG. 3). Also, reduction tendency can be appraised using Math Figure 1. [Math Figure 1]
• G G"+RTLn(P 11 /P Hp )
• a steel plate formed of components and structures according to the present invention is hot-dip galvanized and galvannealed using heat treatment meeting the above conditions.
• FIG. 9 Therefore, a steel plate formed of components and structures according to the present invention is hot-dip galvanized and galvannealed using heat treatment meeting the above conditions.
• general steel of transformation-induced plasticity should be galvanized (preferably, zinc coat ing-galvannealing process) at a low temperature of 520 ° C or less in order to maintain a transformat ion-induced plasticity characteristic serving as an elongation improving mechanism, but the present invention extends a region where workability is excellent to a galvannealing process temperature of 560 ° C .
• the annealed steel plate is slowly cooled at a cooling rate of 1-10O /sec to a temperature region of 650-750 ° C so that a problem is not generated to coat shape control, and rapidly cooled to a temperature range of 300-450 ° C , preferably, 350-400 ° C, and the temperature is maintained, so that C inside the steel material is secondarily collected to an austenite region.
• an isothermal bainite reaction is performed under the temperature condition of 300-450 ° C. By this isothermal bainite reaction, the martensite transformation temperature of the steel material falls below room temperature or less, so that the steel material of the present invention has a fine structure where austenite remains.
• an annealing pre-treatment of one or two or more selected from the group consisting of a brushing process, a pickling process using hydrochloric acid solution of 80-85%, and an S-coating process at a density of 4-12% can be performed after a degreasing process at an entry side of an annealing furnace.
• an effect of reducing galvannealing temperature by 15 ° C or more is obtained to assist securing elongation even during galvannealing.
• a coating bath temperature and a galvannealing process temperature serve as factors reducing a transformation-induced plasticity effect, it is required to minimize thermal history as small as possible.
• a steel slab formed as in Table 1 below is heated to a temperature range of 1200 ° C to extract the same, and the steel slab is processed under the above-described conditions. Also, to appraise an influence on high strength, a nitrogen adding effect has been derived from the component system of Table 2.
• FIG. 6 Results of embodiments for the respective steel plates of Table 1 are shown in FIG. 6, and the results of embodiments for the respective steel plates of Table 2 are shown in FIG. 7.
• invention steels can secure elongation of about 30% or more under tensile strength of about 590 MPa even in the case where the hot-dip galvanizing(GI) temperature is 560 ° C .
• FIG. 7 illustrates that in case of a nitrogen-processed steel plate, the elongation level is high compared to a temperature increase, or the falling width in elongation is small compared to comparison steel.
• Nb-processed steel of FIG. 7 is an example illustrating the reaction characteristic of an invention steel 7 of Nb-processed invention steels. In case of using nitrogen, an excellent characteristic is shown in comparison with a component system where nitrogen is not used during a high temperature galvannealing process.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Coating With Molten Metal (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=40801347

Family Applications (1)

Country Status (4)

Cited By (6)

Families Citing this family (6)

Citations (4)

Family Cites Families (6)

• 2007
  • 2007-12-20 KR KR1020070134236A patent/KR100957981B1/ko active IP Right Grant
• 2008
  • 2008-08-08 JP JP2010539276A patent/JP5564432B2/ja active Active
  • 2008-08-08 CN CN200880124797.9A patent/CN101910441B/zh active Active
  • 2008-08-08 WO PCT/KR2008/004642 patent/WO2009082078A1/en active Application Filing

Patent Citations (4)

Also Published As

Similar Documents

Legal Events