US20230347444A1 - Hot-stamped article using a tailor welded blank method and a method of manufacturing the same - Google Patents
Hot-stamped article using a tailor welded blank method and a method of manufacturing the same Download PDFInfo
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- US20230347444A1 US20230347444A1 US18/206,979 US202318206979A US2023347444A1 US 20230347444 A1 US20230347444 A1 US 20230347444A1 US 202318206979 A US202318206979 A US 202318206979A US 2023347444 A1 US2023347444 A1 US 2023347444A1
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- 238000000034 method Methods 0.000 title claims abstract description 40
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 15
- 238000003466 welding Methods 0.000 claims abstract description 14
- 230000009466 transformation Effects 0.000 claims abstract description 5
- 229910000734 martensite Inorganic materials 0.000 claims description 31
- 239000002131 composite material Substances 0.000 claims description 14
- 239000011572 manganese Substances 0.000 claims description 14
- 229910001563 bainite Inorganic materials 0.000 claims description 13
- 229910000859 α-Fe Inorganic materials 0.000 claims description 13
- 239000011651 chromium Substances 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 239000012535 impurity Substances 0.000 claims description 8
- 238000002360 preparation method Methods 0.000 claims description 6
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 2
- 229910052796 boron Inorganic materials 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 229910052698 phosphorus Inorganic materials 0.000 claims description 2
- 239000011574 phosphorus Substances 0.000 claims description 2
- 229910052710 silicon Inorganic materials 0.000 claims description 2
- 239000010703 silicon Substances 0.000 claims description 2
- 229910052717 sulfur Inorganic materials 0.000 claims description 2
- 239000011593 sulfur Substances 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 28
- 238000010438 heat treatment Methods 0.000 description 18
- 239000004615 ingredient Substances 0.000 description 11
- 238000001816 cooling Methods 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 6
- 230000006355 external stress Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000007493 shaping process Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 239000002826 coolant Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/02—Stamping using rigid devices or tools
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/21—Bonding by welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/02—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of sheets
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/02—Stamping using rigid devices or tools
- B21D22/022—Stamping using rigid devices or tools by heating the blank or stamping associated with heat treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D35/00—Combined processes according to or processes combined with methods covered by groups B21D1/00 - B21D31/00
- B21D35/002—Processes combined with methods covered by groups B21D1/00 - B21D31/00
- B21D35/005—Processes combined with methods covered by groups B21D1/00 - B21D31/00 characterized by the material of the blank or the workpiece
- B21D35/006—Blanks having varying thickness, e.g. tailored blanks
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups
- B23K31/02—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups relating to soldering or welding
-
- 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
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- 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
- C21D8/0405—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 of ferrous alloys
-
- 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
- C21D8/0442—Flattening; Dressing; Flexing
-
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
- C22C38/18—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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/18—Sheet panels
- B23K2101/185—Tailored blanks
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/02—Iron or ferrous alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/18—Dissimilar materials
-
- 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 disclosure relates to a hot-stamped article using a tailor welded blank (TWB) method and a method of manufacturing the same, and more particularly to a hot-stamped article using a TWB method capable of controlling the microstructure of a weld portion to prevent fracture of the weld portion and a method of manufacturing the same.
- TWB tailor welded blank
- a sheet using a tailor welded blank (TWB) method which is a welded sheet formed as the result of two different kinds of materials having different strengths and thicknesses being welded to each other, is variously used as a vehicle part, since it is possible to achieve light weight and to reduce the number of parts.
- TWB tailor welded blank
- a hot stamping method which is a method of heating a sheet to a high temperature, pressing the sheet using a press having a coolant flowing therein, while cooling the sheet to shape the sheet, is used as a method of shaping various vehicle parts, since it is possible to perform complex shaping and to secure high dimensional precision and high strength.
- a weld portion between sheets welded to each other using the TWB method includes a heat affected zone (HAZ) and a weld zone (Weld).
- HAZ heat affected zone
- Weld weld zone
- the heat affected zone and a weld zone are heat-treated at the upper austenite transformation temperature (A3 temperature) or higher, whereby both are transformed into full austenite, and are finally transformed into martensite due to cooling at the time of hot stamping.
- the weld zone already has a fine martensite structure before heat treatment for hot stamping, is reversely transformed into austenite and is then transformed into martensite again through heat treatment for hot stamping. As a result, the weld zone has a finer martensite structure than the martensite structure of the raw material.
- the weld zone has higher hardness than the periphery thereof, therefore, external stress is concentrated on the weld zone, whereby the weld portion is frequently fractured.
- TWB tailor welded blank
- the above and other objects can be accomplished by the provision of a hot-stamped article.
- the hot stamped article is manufactured by welding a first sheet and a second sheet made of different kinds of materials to each other using a TWB method and hot-stamping a welded sheet.
- the first sheet and the second sheet have different upper austenite transformation temperatures (A3 temperatures), the first sheet and the second sheet are welded to each other via a weld portion, each of the first sheet and the weld portion has a composite structure including ferrite, bainite, and martensite, and the second sheet has a martensite structure.
- the first sheet may include: 0.04 to 0.12 wt% of carbon (C); 0.80 wt% or less of silicon (Si); 1.60 to 2.00 wt% of manganese (Mn); 0.030 wt% or less of phosphorus (P); 0.015 wt% or less of sulfur (S); 0.10 to 0.60 wt% of chromium (Cr); 0.0008 to 0.0050 wt% of boron (B); and the remaining wt% of iron (Fe) and other inevitable impurities.
- the second sheet may include: 0.27 to 0.33 wt% of C; 0.40 wt% or less of Si; 1.10 to 1.60 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- the first sheet may have a hardness of 200 to 350 Vickers Pyramid Number (HV)
- the weld portion may have a hardness of 350 to 550 HV
- the second sheet may have a hardness of 550 to 650 HV.
- the first sheet, the weld portion, and the second sheet may be heated within a temperature range between the A3 temperature of the first sheet and the A3 temperature of the second sheet.
- Each of the first sheet and the weld portion may have a structure including 30% or less of martensite.
- Each of the first sheet and the weld portion may have a composite structure including 10 to 50% of ferrite, 10 to 50% of bainite, and 30% or less of martensite.
- a method of manufacturing a hot-stamped article includes: a preparation step of preparing a first sheet and a second sheet having different A3 temperatures; a welding step of welding the first sheet and the second sheet using a TWB method to prepare a welded sheet obtained as the result of the first sheet and the second sheet being welded to each other via a weld portion; and a hot-stamping step of hot-stamping the welded sheet heated within a temperature range between the A3 temperature of the first sheet and the A3 temperature of the second sheet.
- a sheet may be prepared as the first sheet and include: 0.04 to 0.12 wt% of C; 0.80 wt% or less of Si; 1.60 to 2.00 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- a sheet may also be prepared as the second sheet and include: 0.27 to 0.33 wt% of C; 0.40 wt% or less of Si; 1.10 to 1.60 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- the welded sheet may be heated to 810 to 880° C. in the hot-stamping step.
- each of the first sheet and the weld portion of the hot-stamped article may have a composite structure including ferrite, bainite, and martensite, and the second sheet of the hot-stamped article may have a martensite structure.
- each of the first sheet and the weld portion may have a structure including 30% or less of martensite.
- each of the first sheet and the weld portion may have a composite structure including 10 to 50% of ferrite, 10 to 50% of bainite, and 30% or less of martensite.
- the first sheet of the hot-stamped article may have a hardness of 200 to 350 HV
- the weld portion of the hot-stamped article may have a hardness of 350 to 550 HV
- the second sheet of the hot-stamped article may have a hardness of 550 to 650 HV.
- FIG. 1 A shows the results of observation of the microstructure of a Comparative Example and the hardness values thereof before hot stamping
- FIG. 1 B shows the results of observation of the microstructure of a Comparative Example and the hardness values thereof after hot stamping
- FIG. 2 A shows the results of observation of the microstructure of an Example of the present disclosure and the hardness values thereof before hot stamping
- FIG. 2 B shows the results of observation of the microstructure of an Example of the present disclosure and the hardness values thereof after hot stamping
- FIG. 3 shows the results of magnified observation of the microstructure of an Example of the present disclosure after hot stamping
- FIG. 4 A shows the results of formation of the microstructure of a weld portion according to a Comparative Example based on heat treatment temperature
- FIG. 4 B shows the results of formation of the microstructure of a weld portion according to an Example of the present disclosure based on heat treatment temperature.
- the present disclosure relates to a hot-stamped article manufactured by welding a first sheet and a second sheet made of different kinds of materials to each other using a tailor welded blank (TWB) method and hot-stamping a welded sheet and a method of manufacturing the same.
- Ingredients of the first sheet and the second sheet and a heat treatment temperature for hot stamping are controlled in order to control the microstructure of a weld portion formed as the result of the first sheet and the second sheet being welded at the time of welding using the TWB method.
- a hot-stamped article using the TWB method is formed by welding a first sheet and a second sheet, which are different kinds of sheets, to each other using the TWB method.
- the first sheet and the second sheet are welded to each other via a weld portion and heat-treated and hot-stamped.
- the structure of the weld portion is formed as a composite structure including ferrite, bainite, and martensite.
- external stress is not locally concentrated on the weld portion but is dispersed over the entire sheets, whereby fracture of the weld portion is prevented.
- a method of manufacturing a hot-stamped article includes: a preparation step of preparing a first sheet and a second sheet having different upper austenite transformation temperatures (A3 temperatures); a welding step of welding the first sheet and the second sheet using the TWB method to prepare a welded sheet obtained as the result of the first sheet and the second sheet being welded to each other via a weld portion; and a hot-stamping step of hot-stamping the welded sheet heated within a temperature range between the A3 temperature of the first sheet and the A3 temperature of the second sheet.
- A3 temperatures upper austenite transformation temperatures
- the preparation step is a step of preparing a first sheet and a second sheet having different A3 temperatures. For example, ingredients of the first sheet are adjusted such that the first sheet has an A3 temperature of 880° C., and ingredients of the second sheet are adjusted such that the first sheet has an A3 temperature of 810° C.
- a sheet is used as a first sheet, which includes: 0.04 to 0.12 wt% of C; 0.80 wt% or less of Si; 1.60 to 2.00 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- a sheet is used as the second sheet, which includes: 0.27 to 0.33 wt% of C; 0.40 wt% or less of Si; 1.10 to 1.60 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- the welding step is a step of welding the prepared first and second sheets to each other using the TWB method.
- the first sheet and the second sheet are welded to prepare a welded sheet obtained as the result of the first sheet and the second sheet being welded to each other via a weld portion.
- the ingredients of each of which are adjusted are welded to each other using the TWB method, the ingredients of the first sheet and the second sheet are mixed with each other in the weld portion.
- the A3 temperature of the weld portion is adjusted to a range of 810 to 880° C.
- the hot-stamping step is a step of hot-stamping the heated welded sheet.
- a heat treatment temperature is maintained, in one example, within a range of 810 to 880° C. in order to form a composite structure in the weld portion at the time of hot stamping.
- the second sheet is heat-treated at the A3 temperature or higher, whereby the second sheet is transformed into full austenite.
- the second sheet is cooled at the time of hot stamping, whereby the second sheet is transformed into full martensite.
- the first sheet is heat-treated at the A3 temperature or lower, whereby the first sheet is not transformed into full austenite.
- the weld portion in which the ingredients of the first sheet and the second sheet are mixed with each other, is not transformed into full austenite.
- each of the first sheet and the weld portion has a composite structure including ferrite, bainite, and martensite due to rapid cooling at the time of hot stamping.
- the second sheet has a full martensite structure, and each of the first sheet and the weld portion has a composite structure including 10 to 50% of ferrite, 10 to 50% of bainite, and 30% or less of martensite.
- the first sheet has a hardness of 200 to 350 Vickers Pyramid Number (HV)
- the weld portion has a hardness of 350 to 550 HV
- the second sheet has a hardness of 550 to 650 HV.
- a first comparative sheet having a 100 K-class tensile strength value and a second comparative sheet having a 150 K-class tensile strength value are prepared using a conventional, commonly used steel grade. These comparative sheets are welded to each other using the TWB method.
- a welded sheet obtained as the result of the first comparative sheet and the second comparative sheet being welded to each other is heat-treated at 930° C. and is then hot-stamped.
- FIG. 1 A shows the results of observation of the microstructure and the hardness values thereof before hot stamping.
- FIG. 1 B shows the results of observation of the microstructure and the hardness values thereof after hot stamping.
- the Comparative Example is heat-treated at a temperature higher than the A3 temperatures of the first comparative sheet and the second comparative sheet.
- Each of the first comparative sheet, the second comparative sheet, and the weld portion is thereby transformed into full austenite.
- the second comparative sheet has a full martensite structure
- the first comparative sheet has a martensite structure and partially a bainite structure.
- the weld portion has a full martensite structure.
- Example 2 a first sheet identical to the first comparative sheet having a 100 K-class tensile strength value, which is a conventional, commonly used steel grade, is prepared. A second sheet having higher contents of carbon (C) and manganese (Mn) than in the second comparative sheet so as to have an A3 temperature of 810° C. is also prepared. These sheets are welded to each other using the TWB method.
- a welded sheet obtained as the result of the first sheet and the second sheet being welded to each other is heat-treated at 810 to 880° C. and is then hot-stamped.
- FIG. 2 A shows the results of observation of the microstructure and the hardness values thereof before hot stamping.
- FIG. 2 B shows the results of observation of the microstructure and the hardness values thereof after hot stamping.
- the Example is heat-treated at a temperature between the A3 temperature of the first sheet and the A3 temperature of the second sheet, whereby the second sheet is transformed into full austenite.
- the second sheet has a full martensite structure.
- each of the first sheet and the weld portion is not transformed into full austenite at the time of heat treatment.
- each of the first sheet and the weld portion has a composite structure including ferrite, bainite, and martensite, although the second sheet has a full martensite structure.
- the hardness of the weld portion is between the hardness of the first sheet and the hardness of the second sheet. This result may reveal that external stress is prevented from being concentrated on the weld portion, whereby there is a low probability of the weld portion being fractured.
- the first sheet and the second sheet of Table 2 were used, wherein carbon (C) content of the first sheet was adjusted to 0.2 wt%.
- the first sheet and the second sheet of Table 2 were used, wherein carbon (C) content of the first sheet was adjusted to 0.05 wt%.
- the formation of a microstructure of a weld portion was simulated under the conditions that the first sheet and the second sheet were welded to each other using the TWB method to prepare a welded sheet and the welded sheet was heat-treated at 810 to 880° C.
- FIG. 4 A shows the results of formation of the microstructure of the weld portion according to the Comparative Example based on heat treatment temperature.
- FIG. 4 B shows the results of formation of the microstructure of the weld portion according to Example based on heat treatment temperature.
- the A3 temperature of the weld portion was lower than a range of 810 to 880° C., which is a heat treatment temperature range.
- the weld portion was transformed into full austenite during heat treatment and a full martensite structure was formed at the time of rapid cooling due to hot stamping.
- the A3 temperature of the weld portion was adjusted to a range of 810 to 880° C., which is a heat treatment temperature range.
- the weld portion was not transformed into full austenite and was partially ferrite during heat treatment, and a composite structure including ferrite, bainite, and martensite was formed at the time of rapid cooling due to hot stamping.
- ingredients of different kinds of sheets welded to each other using a TWB method are adjusted to adjust the A3 temperature of a weld portion in which the ingredients of different kinds of sheets are mixed with each other. Temperature is also controlled at the time of heat treatment for hot stamping. It is thereby possible to form a composite structure including ferrite, bainite, and martensite in the weld portion after hot stamping.
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Abstract
A hot-stamped article and a method of manufacturing same use a tailor welded blank (TWB) method capable of controlling the microstructure of a weld portion to prevent fracture of the weld portion. The method includes: preparing a first sheet and a second sheet having different upper austenite transformation temperatures (A3 temperatures); welding the first sheet and the second sheet using a TWB method to prepare a welded sheet obtained as a result of the first sheet and the second sheet being welded to each other via a weld portion; and hot-stamping the welded sheet heated within a temperature range between an A3 temperature of the first sheet and an A3 temperature of the second sheet.
Description
- This application is a divisional of U.S. Application Serial No. 17/246,214 filed Apr. 30, 2021, which claims priority to Korean Patent Application No. 10-2020-0158812, filed on Nov. 24, 2020 with the Korean Intellectual Property Office, the disclosures of which are herein incorporated by reference in their entirety.
- The present disclosure relates to a hot-stamped article using a tailor welded blank (TWB) method and a method of manufacturing the same, and more particularly to a hot-stamped article using a TWB method capable of controlling the microstructure of a weld portion to prevent fracture of the weld portion and a method of manufacturing the same.
- In general, a sheet using a tailor welded blank (TWB) method, which is a welded sheet formed as the result of two different kinds of materials having different strengths and thicknesses being welded to each other, is variously used as a vehicle part, since it is possible to achieve light weight and to reduce the number of parts.
- Meanwhile, a hot stamping method, which is a method of heating a sheet to a high temperature, pressing the sheet using a press having a coolant flowing therein, while cooling the sheet to shape the sheet, is used as a method of shaping various vehicle parts, since it is possible to perform complex shaping and to secure high dimensional precision and high strength.
- In recent years, therefore, the TWB method and the hot stamping method have been simultaneously used to manufacture vehicle parts.
- In general, when the TWB method and the hot stamping method are simultaneously used, a weld portion between sheets welded to each other using the TWB method includes a heat affected zone (HAZ) and a weld zone (Weld). When heat treatment for hot stamping is performed in this state, the heat affected zone and a weld zone are heat-treated at the upper austenite transformation temperature (A3 temperature) or higher, whereby both are transformed into full austenite, and are finally transformed into martensite due to cooling at the time of hot stamping. The weld zone already has a fine martensite structure before heat treatment for hot stamping, is reversely transformed into austenite and is then transformed into martensite again through heat treatment for hot stamping. As a result, the weld zone has a finer martensite structure than the martensite structure of the raw material.
- Since the weld zone has higher hardness than the periphery thereof, therefore, external stress is concentrated on the weld zone, whereby the weld portion is frequently fractured.
- The matters disclosed in this section are merely to enhance understanding of the general background of the disclosure and should not be taken as an acknowledgment or any form of suggestion that the matters form the related art already known to a person skilled in the art.
- It is an object of the present disclosure to provide a hot-stamped article using a tailor welded blank (TWB) method capable of controlling the microstructure of a weld portion by adjusting ingredients of different kinds of sheets welded to each other using the TWB method to prevent fracture of the weld portion and a method of manufacturing the same.
- In accordance with an aspect of the present disclosure, the above and other objects can be accomplished by the provision of a hot-stamped article. The hot stamped article is manufactured by welding a first sheet and a second sheet made of different kinds of materials to each other using a TWB method and hot-stamping a welded sheet. The first sheet and the second sheet have different upper austenite transformation temperatures (A3 temperatures), the first sheet and the second sheet are welded to each other via a weld portion, each of the first sheet and the weld portion has a composite structure including ferrite, bainite, and martensite, and the second sheet has a martensite structure.
- The first sheet may include: 0.04 to 0.12 wt% of carbon (C); 0.80 wt% or less of silicon (Si); 1.60 to 2.00 wt% of manganese (Mn); 0.030 wt% or less of phosphorus (P); 0.015 wt% or less of sulfur (S); 0.10 to 0.60 wt% of chromium (Cr); 0.0008 to 0.0050 wt% of boron (B); and the remaining wt% of iron (Fe) and other inevitable impurities. The second sheet may include: 0.27 to 0.33 wt% of C; 0.40 wt% or less of Si; 1.10 to 1.60 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- The first sheet may have a hardness of 200 to 350 Vickers Pyramid Number (HV), the weld portion may have a hardness of 350 to 550 HV, and the second sheet may have a hardness of 550 to 650 HV.
- At the time of hot stamping, the first sheet, the weld portion, and the second sheet may be heated within a temperature range between the A3 temperature of the first sheet and the A3 temperature of the second sheet.
- Each of the first sheet and the weld portion may have a structure including 30% or less of martensite.
- Each of the first sheet and the weld portion may have a composite structure including 10 to 50% of ferrite, 10 to 50% of bainite, and 30% or less of martensite.
- In accordance with another aspect of the present disclosure, there is provided a method of manufacturing a hot-stamped article. The method includes: a preparation step of preparing a first sheet and a second sheet having different A3 temperatures; a welding step of welding the first sheet and the second sheet using a TWB method to prepare a welded sheet obtained as the result of the first sheet and the second sheet being welded to each other via a weld portion; and a hot-stamping step of hot-stamping the welded sheet heated within a temperature range between the A3 temperature of the first sheet and the A3 temperature of the second sheet.
- In the preparation step, a sheet may be prepared as the first sheet and include: 0.04 to 0.12 wt% of C; 0.80 wt% or less of Si; 1.60 to 2.00 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities. A sheet may also be prepared as the second sheet and include: 0.27 to 0.33 wt% of C; 0.40 wt% or less of Si; 1.10 to 1.60 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- The welded sheet may be heated to 810 to 880° C. in the hot-stamping step.
- After the hot-stamping step, each of the first sheet and the weld portion of the hot-stamped article may have a composite structure including ferrite, bainite, and martensite, and the second sheet of the hot-stamped article may have a martensite structure.
- After the hot-stamping step, each of the first sheet and the weld portion may have a structure including 30% or less of martensite.
- After the hot-stamping step, each of the first sheet and the weld portion may have a composite structure including 10 to 50% of ferrite, 10 to 50% of bainite, and 30% or less of martensite.
- After the hot-stamping step, the first sheet of the hot-stamped article may have a hardness of 200 to 350 HV, the weld portion of the hot-stamped article may have a hardness of 350 to 550 HV, and the second sheet of the hot-stamped article may have a hardness of 550 to 650 HV.
- The above and other objects, features, and other advantages of the present disclosure should be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
-
FIG. 1A shows the results of observation of the microstructure of a Comparative Example and the hardness values thereof before hot stamping; -
FIG. 1B shows the results of observation of the microstructure of a Comparative Example and the hardness values thereof after hot stamping; -
FIG. 2A shows the results of observation of the microstructure of an Example of the present disclosure and the hardness values thereof before hot stamping; -
FIG. 2B shows the results of observation of the microstructure of an Example of the present disclosure and the hardness values thereof after hot stamping; -
FIG. 3 shows the results of magnified observation of the microstructure of an Example of the present disclosure after hot stamping; -
FIG. 4A shows the results of formation of the microstructure of a weld portion according to a Comparative Example based on heat treatment temperature; and -
FIG. 4B shows the results of formation of the microstructure of a weld portion according to an Example of the present disclosure based on heat treatment temperature. - Hereinafter, embodiments of the present disclosure are described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The embodiments herein are provided to make the disclosure of the present disclosure complete and to fully convey the scope of the disclosure to those skilled in the art.
- The present disclosure relates to a hot-stamped article manufactured by welding a first sheet and a second sheet made of different kinds of materials to each other using a tailor welded blank (TWB) method and hot-stamping a welded sheet and a method of manufacturing the same. Ingredients of the first sheet and the second sheet and a heat treatment temperature for hot stamping are controlled in order to control the microstructure of a weld portion formed as the result of the first sheet and the second sheet being welded at the time of welding using the TWB method.
- Preferably, a hot-stamped article using the TWB method according to an embodiment of the present disclosure is formed by welding a first sheet and a second sheet, which are different kinds of sheets, to each other using the TWB method. The first sheet and the second sheet are welded to each other via a weld portion and heat-treated and hot-stamped.
- At this time, the structure of the weld portion is formed as a composite structure including ferrite, bainite, and martensite. In the case in which the structure of the weld portion is formed as a composite structure, as described above, external stress is not locally concentrated on the weld portion but is dispersed over the entire sheets, whereby fracture of the weld portion is prevented.
- Next, a method of manufacturing a hot-stamped article having the structure described above is described.
- A method of manufacturing a hot-stamped article according to an embodiment of the present disclosure includes: a preparation step of preparing a first sheet and a second sheet having different upper austenite transformation temperatures (A3 temperatures); a welding step of welding the first sheet and the second sheet using the TWB method to prepare a welded sheet obtained as the result of the first sheet and the second sheet being welded to each other via a weld portion; and a hot-stamping step of hot-stamping the welded sheet heated within a temperature range between the A3 temperature of the first sheet and the A3 temperature of the second sheet.
- The preparation step is a step of preparing a first sheet and a second sheet having different A3 temperatures. For example, ingredients of the first sheet are adjusted such that the first sheet has an A3 temperature of 880° C., and ingredients of the second sheet are adjusted such that the first sheet has an A3 temperature of 810° C.
- In other words, a sheet is used as a first sheet, which includes: 0.04 to 0.12 wt% of C; 0.80 wt% or less of Si; 1.60 to 2.00 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- In addition, a sheet is used as the second sheet, which includes: 0.27 to 0.33 wt% of C; 0.40 wt% or less of Si; 1.10 to 1.60 wt% of Mn; 0.030 wt% or less of P; 0.015 wt% or less of S; 0.10 to 0.60 wt% of Cr; 0.0008 to 0.0050 wt% of B; and the remaining wt% of Fe and other inevitable impurities.
- The welding step is a step of welding the prepared first and second sheets to each other using the TWB method. The first sheet and the second sheet are welded to prepare a welded sheet obtained as the result of the first sheet and the second sheet being welded to each other via a weld portion.
- When the first sheet and the second sheet, the ingredients of each of which are adjusted, are welded to each other using the TWB method, the ingredients of the first sheet and the second sheet are mixed with each other in the weld portion. The A3 temperature of the weld portion is adjusted to a range of 810 to 880° C.
- The hot-stamping step is a step of hot-stamping the heated welded sheet.
- At the time of heat treatment before hot stamping, a heat treatment temperature is maintained, in one example, within a range of 810 to 880° C. in order to form a composite structure in the weld portion at the time of hot stamping.
- As a result, the second sheet is heat-treated at the A3 temperature or higher, whereby the second sheet is transformed into full austenite. The second sheet is cooled at the time of hot stamping, whereby the second sheet is transformed into full martensite.
- However, the first sheet is heat-treated at the A3 temperature or lower, whereby the first sheet is not transformed into full austenite. Also, the weld portion, in which the ingredients of the first sheet and the second sheet are mixed with each other, is not transformed into full austenite. As a result, each of the first sheet and the weld portion has a composite structure including ferrite, bainite, and martensite due to rapid cooling at the time of hot stamping.
- Meanwhile, in the case in which the first sheet and the second sheet having the above composition are used, and the heat-treatment temperature is maintained within 810 to 880° C. in the hot-stamping step, the second sheet has a full martensite structure, and each of the first sheet and the weld portion has a composite structure including 10 to 50% of ferrite, 10 to 50% of bainite, and 30% or less of martensite.
- As the result of formation of the structures described above, the first sheet has a hardness of 200 to 350 Vickers Pyramid Number (HV), the weld portion has a hardness of 350 to 550 HV, and the second sheet has a hardness of 550 to 650 HV.
- Next, the present disclosure is described based on a Comparative Example and an Example according to the present disclosure (i.e., the Example).
- In the Comparative Example, a first comparative sheet having a 100 K-class tensile strength value and a second comparative sheet having a 150 K-class tensile strength value are prepared using a conventional, commonly used steel grade. These comparative sheets are welded to each other using the TWB method.
- Ingredients of the first comparative sheet and the second comparative sheet are shown in Table 1.
-
TABLE 1 Classification C Si Mn P S Cr B A3 temperature (°C) First comparative sheet 0.057 0.53 1.86 0.013 0.001 0.20 0.0023 880 Second comparative sheet 0.23 0.26 1.22 0.009 0.002 0.19 0.0044 850 - A welded sheet obtained as the result of the first comparative sheet and the second comparative sheet being welded to each other is heat-treated at 930° C. and is then hot-stamped.
- At this time, the microstructures of a weld portion and the periphery thereof before and after hot stamping were observed, and the hardness of each area was measured. The results are shown in
FIGS. 1A and 1B . -
FIG. 1A shows the results of observation of the microstructure and the hardness values thereof before hot stamping.FIG. 1B shows the results of observation of the microstructure and the hardness values thereof after hot stamping. - As can be seen from
FIGS. 1A and 1B , the Comparative Example is heat-treated at a temperature higher than the A3 temperatures of the first comparative sheet and the second comparative sheet. Each of the first comparative sheet, the second comparative sheet, and the weld portion is thereby transformed into full austenite. At the time of rapid cooling due to hot stamping, the second comparative sheet has a full martensite structure, and the first comparative sheet has a martensite structure and partially a bainite structure. The weld portion has a full martensite structure. - As a result, as shown in
FIG. 1B , it can be seen that the hardness of the weld portion is higher than the hardness of the first comparative sheet and the hardness of the second comparative sheet. This result may reveal that external stress is concentrated on the weld portion, whereby there is a high probability of the weld portion fracturing. - In the Example, on the other hand, a first sheet identical to the first comparative sheet having a 100 K-class tensile strength value, which is a conventional, commonly used steel grade, is prepared. A second sheet having higher contents of carbon (C) and manganese (Mn) than in the second comparative sheet so as to have an A3 temperature of 810° C. is also prepared. These sheets are welded to each other using the TWB method.
- Ingredients of the first sheet and the second sheet are shown in Table 2.
-
TABLE 2 Classification C Si Mn P S Cr B A3 temperature (°C) First sheet 0.057 0.53 1.86 0.013 0.001 0.20 0.0023 880 Second sheet 0.31 0.22 1.4 0.013 0.002 0.2 0.0026 810 - A welded sheet obtained as the result of the first sheet and the second sheet being welded to each other is heat-treated at 810 to 880° C. and is then hot-stamped.
- At this time, the microstructures of a weld portion and the periphery thereof before and after hot stamping were observed, and the hardness of each area was measured. The results are shown in
FIGS. 2A and 2B . -
FIG. 2A shows the results of observation of the microstructure and the hardness values thereof before hot stamping.FIG. 2B shows the results of observation of the microstructure and the hardness values thereof after hot stamping. - The microstructure of the weld portion after hot stamping was observed in a magnified state. The results are shown in
FIG. 3 . - As can be seen from
FIGS. 2A and 2B , the Example is heat-treated at a temperature between the A3 temperature of the first sheet and the A3 temperature of the second sheet, whereby the second sheet is transformed into full austenite. At the time of rapid cooling due to hot stamping, the second sheet has a full martensite structure. However, each of the first sheet and the weld portion is not transformed into full austenite at the time of heat treatment. At the time of rapid cooling due to hot stamping, therefore, each of the first sheet and the weld portion has a composite structure including ferrite, bainite, and martensite, although the second sheet has a full martensite structure. These results can be confirmed fromFIG. 3 . - As a result, as shown in
FIG. 2B , it can be seen that the hardness of the weld portion is between the hardness of the first sheet and the hardness of the second sheet. This result may reveal that external stress is prevented from being concentrated on the weld portion, whereby there is a low probability of the weld portion being fractured. - Next, experiments were performed in order to observe a change in A3 temperature of the weld portion based on carbon (C) content of the first sheet and a change in microstructure thereof due thereto.
- In the Comparative Example, the first sheet and the second sheet of Table 2 were used, wherein carbon (C) content of the first sheet was adjusted to 0.2 wt%. In the Comparative Example, the first sheet and the second sheet of Table 2 were used, wherein carbon (C) content of the first sheet was adjusted to 0.05 wt%.
- The formation of a microstructure of a weld portion was simulated under the conditions that the first sheet and the second sheet were welded to each other using the TWB method to prepare a welded sheet and the welded sheet was heat-treated at 810 to 880° C.
- The simulation results are shown in
FIGS. 4A and 4B . -
FIG. 4A shows the results of formation of the microstructure of the weld portion according to the Comparative Example based on heat treatment temperature.FIG. 4B shows the results of formation of the microstructure of the weld portion according to Example based on heat treatment temperature. - As can be seen from
FIG. 4A , in the case in which carbon (C) content of the first sheet exceeded the range presented in the present disclosure, the A3 temperature of the weld portion was lower than a range of 810 to 880° C., which is a heat treatment temperature range. As a result, the weld portion was transformed into full austenite during heat treatment and a full martensite structure was formed at the time of rapid cooling due to hot stamping. - As can be seen from
FIG. 4B , on the other hand, in the case in which carbon (C) content of the first sheet was within the range presented in the present disclosure, the A3 temperature of the weld portion was adjusted to a range of 810 to 880° C., which is a heat treatment temperature range. As a result, the weld portion was not transformed into full austenite and was partially ferrite during heat treatment, and a composite structure including ferrite, bainite, and martensite was formed at the time of rapid cooling due to hot stamping. - As is apparent from the above description, according to an embodiment of the present disclosure, ingredients of different kinds of sheets welded to each other using a TWB method are adjusted to adjust the A3 temperature of a weld portion in which the ingredients of different kinds of sheets are mixed with each other. Temperature is also controlled at the time of heat treatment for hot stamping. It is thereby possible to form a composite structure including ferrite, bainite, and martensite in the weld portion after hot stamping.
- Consequently, external stress is prevented from being concentrated on the weld portion, whereby fracture of the weld portion is prevented.
- Although the disclosed embodiments of the present disclosure have been described above with reference to the accompanying drawings, those having ordinary skill in the art should appreciate that the present disclosure can be implemented in various other embodiments without changing the technical ideas or features thereof.
Claims (8)
1. A method of manufacturing a hot-stamped article, the method comprising:
a preparation step of preparing a first sheet and a second sheet having different upper austenite transformation temperatures (A3 temperatures);
a welding step of welding the first sheet and the second sheet using a tailor welded blank (TWB) method to prepare a welded sheet obtained as a result of the first sheet and the second sheet being welded to each other via a weld portion; and
a hot-stamping step of hot-stamping the welded sheet heated within a temperature range between an A3 temperature of the first sheet and an A3 temperature of the second sheet.
2. The method according to claim 1 , wherein, in the preparation step,
a sheet comprising 0.04 to 0.12 wt% of carbon (C), 0.80 wt% or less of silicon (Si), 1.60 to 2.00 wt% of manganese (Mn), 0.030 wt% or less of phosphorus (P), 0.015 wt% or less of sulfur (S), 0.10 to 0.60 wt% of chromium (Cr), 0.0008 to 0.0050 wt% of boron (B), and a remaining wt% of iron (Fe) and other inevitable impurities is prepared as the first sheet, and
a sheet comprising 0.27 to 0.33 wt% of C, 0.40 wt% or less of Si, 1.10 to 1.60 wt% of Mn, 0.030 wt% or less of P, 0.015 wt% or less of S, 0.10 to 0.60 wt% of Cr, 0.0008 to 0.0050 wt% of B, and a remaining wt% of Fe and other inevitable impurities is prepared as the second sheet.
3. The method according to claim 2 , wherein the welded sheet is heated to 810 to 880° C. in the hot-stamping step.
4. The method according to claim 1 , wherein, after the hot-stamping step,
each of the first sheet and the weld portion of the hot-stamped article has a composite structure comprising ferrite, bainite, and martensite, and
the second sheet of the hot-stamped article has a martensite structure.
5. The method according to claim 4 , wherein, after the hot-stamping step, each of the first sheet and the weld portion has a structure comprising 30% or less of martensite.
6. The method according to claim 5 , wherein, after the hot-stamping step, each of the first sheet and the weld portion has a composite structure comprising 10 to 50% of ferrite, 10 to 50% of bainite, and 30% or less of martensite.
7. The method according to claim 1 , wherein, after the hot-stamping step,
the first sheet of the hot-stamped article has a hardness of 200 to 350 Vickers Pyramid Number (HV),
the weld portion of the hot-stamped article has a hardness of 350 to 550 HV, and
the second sheet of the hot-stamped article has a hardness of 550 to 650 HV.
8. The method according to claim 1 , wherein, in the welding step, the weld portion is a volume between the first sheet and the second sheet where the composition of the first sheet is mixed with the composition of the second sheet.
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US17/246,214 US11724338B2 (en) | 2020-11-24 | 2021-04-30 | Hot-stamped article using a tailor welded blank method and a method of manufacturing the same |
US18/206,979 US20230347444A1 (en) | 2020-11-24 | 2023-06-07 | Hot-stamped article using a tailor welded blank method and a method of manufacturing the same |
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EP2374910A1 (en) | 2010-04-01 | 2011-10-12 | ThyssenKrupp Steel Europe AG | Steel, flat, steel product, steel component and method for producing a steel component |
JP5971004B2 (en) * | 2012-07-24 | 2016-08-17 | 新日鐵住金株式会社 | Hot press-formed product having a low-strength part and method for producing the same |
KR101448473B1 (en) | 2012-12-03 | 2014-10-10 | 현대하이스코 주식회사 | Tailor welded blnk and hot stamping parts using the same |
JP6073154B2 (en) * | 2013-02-21 | 2017-02-01 | 株式会社神戸製鋼所 | Manufacturing method of hot press-formed product |
CN106350741B (en) | 2016-10-24 | 2017-12-19 | 大连理工大学 | A kind of warm working preparation method of laser assembly solder high-strength steel |
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2020
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2021
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US11724338B2 (en) | 2023-08-15 |
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