EP3245310A2 - Dual phase steel with improved properties - Google Patents
Dual phase steel with improved propertiesInfo
- Publication number
- EP3245310A2 EP3245310A2 EP16706031.8A EP16706031A EP3245310A2 EP 3245310 A2 EP3245310 A2 EP 3245310A2 EP 16706031 A EP16706031 A EP 16706031A EP 3245310 A2 EP3245310 A2 EP 3245310A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- steel sheet
- temperature
- manganese
- carbon
- molybdenum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 229910000885 Dual-phase steel Inorganic materials 0.000 title claims abstract description 6
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 104
- 239000010959 steel Substances 0.000 claims abstract description 104
- 238000000034 method Methods 0.000 claims abstract description 45
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 43
- 238000001816 cooling Methods 0.000 claims abstract description 38
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 18
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 13
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 238000005246 galvanizing Methods 0.000 claims description 30
- 238000005244 galvannealing Methods 0.000 claims description 26
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 16
- 229910052799 carbon Inorganic materials 0.000 claims description 16
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 14
- 229910052748 manganese Inorganic materials 0.000 claims description 14
- 239000011572 manganese Substances 0.000 claims description 14
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 13
- 229910052750 molybdenum Inorganic materials 0.000 claims description 13
- 239000011733 molybdenum Substances 0.000 claims description 13
- 229910052758 niobium Inorganic materials 0.000 claims description 13
- 239000010955 niobium Substances 0.000 claims description 13
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 13
- 229910052710 silicon Inorganic materials 0.000 claims description 12
- 239000010703 silicon Substances 0.000 claims description 12
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 11
- 229910052804 chromium Inorganic materials 0.000 claims description 11
- 239000011651 chromium Substances 0.000 claims description 11
- 238000003303 reheating Methods 0.000 claims description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims 18
- 239000012535 impurity Substances 0.000 claims 9
- 229910052742 iron Inorganic materials 0.000 claims 9
- 238000010791 quenching Methods 0.000 description 29
- 229910052751 metal Inorganic materials 0.000 description 18
- 239000002184 metal Substances 0.000 description 18
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 13
- 239000000203 mixture Substances 0.000 description 13
- 230000008569 process Effects 0.000 description 13
- 239000011701 zinc Substances 0.000 description 13
- 229910052725 zinc Inorganic materials 0.000 description 13
- 238000005275 alloying Methods 0.000 description 12
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 9
- 238000007792 addition Methods 0.000 description 9
- 239000010936 titanium Substances 0.000 description 9
- 229910052719 titanium Inorganic materials 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 8
- 229910052796 boron Inorganic materials 0.000 description 8
- 229910001563 bainite Inorganic materials 0.000 description 7
- 239000000470 constituent Substances 0.000 description 7
- 230000004048 modification Effects 0.000 description 7
- 238000012986 modification Methods 0.000 description 7
- 230000009977 dual effect Effects 0.000 description 6
- 230000009466 transformation Effects 0.000 description 6
- 229910001562 pearlite Inorganic materials 0.000 description 5
- 230000000171 quenching effect Effects 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000005496 tempering Methods 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 229910001567 cementite Inorganic materials 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 238000003618 dip coating Methods 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 2
- -1 419° C Chemical compound 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000000994 depressogenic effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
Classifications
-
- 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
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- 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
- C21D8/0478—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 involving a particular surface treatment
-
- 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
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
-
- 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
-
- 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
- C21D2211/008—Martensite
Definitions
- the present invention relates to steel compositions and processing methods for production of steel using thermal processing techniques such that the resulting steel exhibits high strength and/or cold formability.
- the present steel is produced using a composition and a modified thermal process that together produces a resulting micro structure consisting of generally ferrite and a second phase generally comprising martensite and bainite (among other constituents).
- the composition includes certain alloying additions and the thermal process includes a hot-dip
- HDG galvanizing/galvannealing
- FIGURE 1 depicts a schematic view of a HDG temperature profile with a
- quenching step performed prior to galvanizing/galvannealing.
- FIGURE 2 depicts the HDG temperature profile of FIGURE 1, with the average cooling rate of the HDG temperature profile shown in phantom.
- FIGURE 3 depicts a schematic view of an alternative HDG temperature profile with a quenching step performed after galvanizing/galvannealing.
- FIG. 1 shows a schematic representation of a combination of a typical hot-dip galvanizing thermal profile and a modified hot-dip galvanizing thermal profile.
- the modified thermal cycle is used to achieve high strength and good formability in a dual phase steel sheet (described in greater detail below).
- the steel sheet generally comprises two phases after the thermal cycles - a first phase of predominantly ferrite and a second phase.
- first phase of predominantly ferrite
- second phase is generally used to refer to a phase generally comprising predominately martensite with some bainite.
- such a second phase may also include any one or more of cementite and/or residual austenite.
- FIG. 1 is shown in connection with hot-dip galvanizing, in other embodiments a galvannealing or other hot-dip coating process can be used. In still other embodiments, hot-dip coating processes are omitted entirely and the steel sheet is merely subjected to the thermal profile as shown.
- the solid line in FIG. 1 shows a schematic view of the typical hot-dip galvanizing or galvannealing thermal profile (10).
- the typical thermal profile (10) involves heating the steel sheet to a peak metal temperature (12) and optionally holding the steel sheet at the peak metal temperature (12) for a first predetermined period of time.
- the peak metal temperature (12) is at least above the austenite transformation temperature (AO (e.g., dual phase austenite + ferrite region).
- AO austenite transformation temperature
- the peak metal temperature may also include temperatures above the temperature at which ferrite completely transforms to austenite (A 3 ) (e.g., the single phase, austenite region).
- a 3 austenite
- the steel sheet is held at the peak metal temperature (12) for a first predetermined amount of time. It should be understood that the particular amount of time that the steel sheet is held at the peak metal temperature (12) may be varied by a number of factors such as the particular chemistry of the steel sheet, or the desired volumetric quantity of the second phase in the steel sheet at the conclusion of the thermal cycle.
- the time held at the peak metal temperature (12) may be reduced to zero or near zero.
- the peak metal temperature can be increased to compensate for such a reduction.
- the profile (10) involves rapidly cooling the steel sheet to an intermediate temperature (14).
- the steel sheet is then held at the intermediate temperature (14) for a second predetermined period of time.
- the steel sheet is held at the intermediate temperature (14) for a sufficient amount of time to permit the steel sheet to reach a temperature that is near the temperature of the zinc bath.
- the steel sheet is next inserted into a liquid zinc galvanizing tub or galvannealing apparatus.
- the temperature of the steel sheet is slightly reduced to a bath temperature (16) that is below the intermediate temperature (14).
- the bath temperature (16) is generally below the intermediate temperature (14) to avoid dross formation upon entry of the steel sheet into the liquid zinc.
- the steel sheet remains at the bath temperature (16) for the duration of the
- the steel sheet is removed from the bath at some period of time and then elevated to an annealing temperature.
- the particular temperature of the bath temperature (16) is at least above the melting point of zinc (e.g., 419° C, 787° F).
- the bath temperature (16) may be even higher depending on the particular configuration of the galvanizing bath or galvannealing apparatus.
- the intermediate temperature (14) may remain the same as shown, be correspondingly raised, or even lowered.
- the steel sheet is cooled below the martensite start temperature (M s ), thereby transforming at least some austenite into martensite.
- M s martensite start temperature
- other constituents may form such as bainite, pearlite, or retained austenite.
- the second phase may contain one or more of martensite, bainite, pearlite and/or retained austenite, it should be understood that the second phase is generally characterized by formation of predominately martensite.
- the average cooling rate from the peak metal temperature (12) to the martensite start temperature (M s ) may be insufficient to form a desirable volumetric quantity of martensite - instead forming non- martensitic transformation products (e.g., bainite, cementite, pearlite, and/or etc.). This may be the case regardless of how quickly the steel sheet is cooled after galvanizing or galvannealing.
- conventional dual phase steels used in such a process often includes high alloy content to increase hardenability and thereby avoid formation of non- martensitic transformation products.
- the typical thermal profile (10) described above can be any thermal profile (10) described above.
- this alternative procedure is generally identical to the procedure described above with the exception of the portion of the procedure related to the intermediate temperature (14).
- the steel sheet is quenched from the peak metal temperature (12) to a quench temperature (20).
- the cooling rate from the peak metal temperature (12) to the quench temperature (20) is generally high enough to transform at least some of the austenite formed at the peak metal temperature (12) to martensite.
- the cooling rate is rapid enough to transform austenite to martensite instead of other non-martensitic transformation products such as ferrite, pearlite, or bainite which form at relatively lower cooling rates.
- the quench temperature is below the martensite start temperature (M s ).
- the difference between the quench temperature (20) and the martensite start temperature (M s ) can vary depending on the individual composition of the steel sheet being used. However, in many embodiments the difference between quench temperature (20) and M s is sufficiently great to form a predominately martensitic second phase.
- the temperature of the steel sheet is maintained at the quench temperature for a predetermined quench time. Because formation of martensite is nearly instantaneous, the particular amount of time during which the steel sheet is at the quench temperature is generally insignificant.
- the steel sheet is reheated to the intermediate temperature (14) or to another temperature at or near the bath temperature (16). In the present example, reheating is relatively quick and may be performed using various methods such as induction heating, torch heating, and/or other methods known in the art. Once reheated, the steel sheet is inserted into a zinc bath.
- the steel sheet In the zinc bath, the steel sheet will reach the bath temperature (16), as described above, where the steel sheet will remain for the remainder of the galvanizing.
- the particular amount of time during which the steel sheet is in the zinc bath is largely determined by the galvanizing/galvannealing process.
- the martensite is tempered to thereby improve the mechanical properties of the steel sheet.
- the steel sheet may be heated to an annealing temperature after removal from the bath.
- the reheating step is described herein as being in connection with a coating step, such as galvanizing or galvannealing, it should be understood that no such limitation is intended.
- the reheating step may merely be performed and then the process may proceed as described below.
- the steel sheet is held at the intermediate temperature (14) or the bath temperature (16) despite not actually being subjected to a galvanizing or galvannealing treatment.
- the steel sheet may be held at a lower temperature (e.g., 400° C) relative to the bath temperature (16) because heating the steel sheet to the melting point of zinc is not necessary without application of zinc.
- the steel sheet may be held at such a temperature for any suitable time as will be apparent to those of ordinary skill in the art in view of the teachings herein.
- the steel sheet is cooled to room temperature, as similarly described above. Accordingly, in the present example, the steel sheet is first heated to a peak metal temperature (12) to form austenite and optionally ferrite. Next the steel sheet is cooled from the peak metal temperature (12) to the quench temperature (20) to form martensite or other constituents of the second phase. After quenching, the steel sheet is reheated to approximately the zinc bath temperature for galvanizing and optionally galvannealing. Finally, the steel sheet is cooled to ambient temperature.
- FIG. 2 shows a comparison of the average cooling rate (30) of the typical thermal profile (10) versus the average cooling rate (32) of the typical thermal profile (10) modified to include the quench step (18).
- the quench step (18) substantially reduces the average cooling rate of the typical thermal profile (10).
- average cooling rate may depend at least partially on the feed speed of the galvanizing/galvannealing line. For instance, where feed speeds of about 30 meters per minute are used, the average cooling rate using the typical thermal profile (10) is about 17° C per second, while the average cooling rate using the modifications described herein is about 48° C per second.
- the average cooling rate using the typical thermal profile (10) is about 6° C per second, while the average cooling rate using the modifications described herein is about 16° C per second. In yet other examples where feed speeds of about 120 meters per minute are used, the average cooling rate using the typical thermal profile (10) is about 4° C per second, while the average cooling rate using the modifications described herein is about 12° C per second.
- the quench step (18) may be performed after galvanizing/galvannealing instead of before.
- the quench step (18) may be performed as similarly described above with a rapid cooling of the steel sheet below the martensite start temperature (M s ).
- M s martensite start temperature
- the average cooling rate from the peak metal temperature (12) to the intermediate temperature (14) or bath temperature (16) is similar to the average cooling rate (30) for the typical thermal profile (10) shown in FIG. 2.
- a tempering step (40) may also be performed, where the steel sheet is heated to a predetermined temperature above or below the martensite start temperature (M s ) for a predetermined period of time after the quench step (18).
- M s martensite start temperature
- the average cooling rate is also similar to the average cooling rate (30) for the typical thermal profile (10) shown in FIG. 2.
- HER hole expansion ratio
- the steel sheet may include various alloying elements typically present in
- carbon provides increased strength.
- increasing carbon concentration generally lowers the M s temperature, lowers transformation temperatures for other non-martensitic constituents (e.g., bainite, ferrite, pearlite), and increases the time required for non-martensitic products to form.
- increased carbon concentrations may improve the hardenability of the material thus retaining formation of non-martensitic constituents near the core of the material where cooling rates may be locally depressed.
- carbon additions may be limited as significant carbon concentrations can lead to detrimental effects on weldability.
- carbon can have a detrimental effect of formability. Therefore, the carbon content is generally kept around 0.067- 0.14% by weight.
- manganese provides increased strength by lowering
- Manganese can further improve the propensity of the steel sheet to form martensite by increasing hardenability. Manganese can also increase strength through solid solution strengthening. However, the presence of manganese in large concentrations can degrade formability. Therefore the manganese content is generally present in the concentration of about 1.65-2.9% by weight.
- aluminum is generally present in the concentration of about 0.015-0.07% by weight.
- silicon can be added to promote a dual phase structure consisting of predominately ferrite and martensite.
- silicon is generally present in the concentration of about 0.1-0.25% by weight.
- niobium is added to refine ferrite grains. Such grain
- refinement is desirable to improve formability and improve weld quality.
- niobium is generally present in the concentration of about 0-0.045% by weight. Alternatively, in some examples niobium is present in the concentration of about 0.015-0.045% by weight.
- vanadium is added to increase hardenability and/or refine ferrite grains.
- vanadium is generally included in a concentration less than or equal to 0.05% by weight.
- chromium is added to improve formability and weld quality.
- chromium may be included in the concentration of about 0-0.67%, or 0.2-0.67% by weight.
- molybdenum may be used to increase hardenability.
- molybdenum can be included in a concentration of about 0.08-0.45% by weight. In other embodiments the lower limit concentration of molybdenum is reduced further, or even eliminated entirely.
- titanium and boron are added to increase strength. It should be understood that in some embodiments titanium and boron may be used together, separately in lieu of the other, or neither element may be used. When titanium is used, titanium is present in the concentration of about 0.01-0.03% by weight. When boron is used, boron is present in the concentration of about 0.0007-0.0013% by weight.
- titanium is added together.
- titanium may be included to combine with nitrogen prior to the nitrogen combining with boron.
- titanium is included in concentrations of about 3.43 times the weight percent of nitrogen. When included in this concentration, titanium generally combines with nitrogen, thereby preventing boron from forming nitrides.
- Embodiments of the steel sheet made with the compositions set forth above in Table 1 were subjected to mechanical testing. Mechanical properties for a selected number of the compositions set forth in Table 1 are set forth below in Table 2.
- Embodiments of the steel sheet were made with the compositions set forth in Table 3 below.
- the particular compositions shown in Table 3 are based on the compositional ranges set forth in Table 1.
- Embodiments of the steel sheet made with the compositions set forth above in Table 3 were subjected to mechanical testing. Mechanical properties for each of the compositions set forth in Table 3 are set forth below in Tables 4 through 15.
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- Crystallography & Structural Chemistry (AREA)
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- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
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US201562103286P | 2015-01-14 | 2015-01-14 | |
PCT/US2016/013338 WO2016115303A2 (en) | 2015-01-14 | 2016-01-14 | Dual phase steel with improved properties |
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US (1) | US20160201159A1 (en) |
EP (1) | EP3245310A2 (en) |
JP (1) | JP2018508653A (en) |
KR (2) | KR20170095363A (en) |
CN (2) | CN110218942A (en) |
AU (1) | AU2016206736B2 (en) |
BR (1) | BR112017014686A2 (en) |
CA (1) | CA2972470C (en) |
CO (1) | CO2017006995A2 (en) |
MX (1) | MX2017009192A (en) |
PH (1) | PH12017501293A1 (en) |
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JPS56146853A (en) * | 1980-04-11 | 1981-11-14 | Nippon Steel Corp | Dual-phase steel plate for car with superior weldability and high corrosion resistance |
JP2761096B2 (en) * | 1990-11-05 | 1998-06-04 | 株式会社神戸製鋼所 | Manufacturing method of high ductility and high strength alloyed hot-dip galvanized steel sheet |
JPH0693340A (en) * | 1992-09-14 | 1994-04-05 | Kobe Steel Ltd | Method and equipment for manufacturing high strength galvannealed steel sheet having stretch flanging formability |
JP3126911B2 (en) * | 1995-12-27 | 2001-01-22 | 川崎製鉄株式会社 | High strength galvanized steel sheet with good plating adhesion |
CN100471982C (en) * | 2002-11-26 | 2009-03-25 | Uec科技有限责任公司 | Method for the production of dual phase sheet steel |
JP4681290B2 (en) * | 2004-12-03 | 2011-05-11 | 本田技研工業株式会社 | High strength steel plate and manufacturing method thereof |
US11155902B2 (en) * | 2006-09-27 | 2021-10-26 | Nucor Corporation | High strength, hot dip coated, dual phase, steel sheet and method of manufacturing same |
ES2387040T3 (en) * | 2007-08-15 | 2012-09-12 | Thyssenkrupp Steel Europe Ag | Double phase steel, flat product of a double phase steel of this type and process for manufacturing a flat product |
ATE516380T1 (en) * | 2007-08-15 | 2011-07-15 | Thyssenkrupp Steel Europe Ag | DUAL PHASE STEEL, FLAT PRODUCT FROM SUCH A DUAL PHASE STEEL AND METHOD FOR PRODUCING A FLAT PRODUCT |
EP2123786A1 (en) * | 2008-05-21 | 2009-11-25 | ArcelorMittal France | Method of manufacturing very high-resistance, cold-laminated dual-phase steel sheets, and sheets produced thereby |
JP5304522B2 (en) * | 2009-08-03 | 2013-10-02 | 新日鐵住金株式会社 | High-strength steel sheet with excellent workability and method for producing the same |
KR100958019B1 (en) * | 2009-08-31 | 2010-05-17 | 현대하이스코 주식회사 | Dual phase steel sheet and method for manufacturing the same |
CN102021482B (en) * | 2009-09-18 | 2013-06-19 | 宝山钢铁股份有限公司 | Cold-rolled galvanized duplex steel and manufacturing method thereof |
TWI560279B (en) * | 2013-05-17 | 2016-12-01 | Ak Steel Properties Inc | High strength steel exhibiting good ductility and method of production via in-line heat treatment downstream of molten zinc bath |
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KR20170095363A (en) | 2017-08-22 |
TWI605137B (en) | 2017-11-11 |
WO2016115303A2 (en) | 2016-07-21 |
CN107109586A (en) | 2017-08-29 |
JP2018508653A (en) | 2018-03-29 |
BR112017014686A2 (en) | 2018-01-09 |
RU2017123566A3 (en) | 2019-02-14 |
TW201641715A (en) | 2016-12-01 |
AU2016206736B2 (en) | 2019-02-14 |
CA2972470C (en) | 2019-10-22 |
CO2017006995A2 (en) | 2017-09-20 |
TWI653342B (en) | 2019-03-11 |
CN110218942A (en) | 2019-09-10 |
WO2016115303A3 (en) | 2016-09-09 |
AU2016206736A1 (en) | 2017-07-13 |
UA119189C2 (en) | 2019-05-10 |
RU2017123566A (en) | 2019-02-14 |
KR20200003264A (en) | 2020-01-08 |
TW201812053A (en) | 2018-04-01 |
US20160201159A1 (en) | 2016-07-14 |
CA2972470A1 (en) | 2016-07-21 |
PH12017501293A1 (en) | 2018-01-29 |
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