Splice plate, thermoformed part and preparation method thereof

Abstract

The invention provides a splice plate, a thermoformed component, and a method of making the same. A splice plate according to one aspect of the present invention may comprise: a first plated steel plate comprising a first base steel plate and a first Al-based plating layer on at least one surface of the first base steel plate; a second plated steel sheet comprising a second base steel sheet and a second Al-based plating layer on at least one surface of the second base steel sheet; and a welded connection section that is positioned between the first plated steel sheet and the second plated steel sheet and connects the first plated steel sheet and the second plated steel sheet, the welded connection section satisfying [relational expression 1] and [relational expression 2]: [relational expression 1] 4.44 * [C] + 0.355 * [Mn] + 0.505 * [Ni] + 0.148 * [Cr]-[Al]-1.388 gt; 0 [relational expression 2] 1.0 lt; [Cr] lt; 8.0 (In the relational expression 1] and the relational expression 2], [C], [Mn], [Ni], [Cr] and [Al] refer to the contents (wt%) of C, Mn, Ni, Cr and Al included in the welded connection part, respectively.

Description

[0001] This application is a divisional application of an application with a filing date of July 15, 2022, application number 202210839065.X, and invention name “Spliced ​​plates, thermoformed parts and preparation methods thereof”. Technical Field

[0002] The invention relates to a spliced ​​plate, a thermoforming component and a preparation method thereof. Background Art

[0003] Recently, in order to improve fuel efficiency and ensure passenger safety by reducing the weight of automobiles, attempts have been made to use ultra-high-strength hot-formed parts as structural parts of automobiles, and various studies are being conducted in related fields.

[0004] Patent Document 1 discloses such hot forming technology. According to Patent Document 1, an Al-Si plated steel sheet is heated in a temperature range of Ac1 or higher, hot formed by a press, and rapidly cooled to form the matrix structure into martensite, thereby ensuring a tensile strength of 1500 MPa or higher.

[0005] In addition, when Al-Si plated steel plates are used to prepare spliced ​​plates, the phenomenon of molten coating components mixing into the molten area may occur during laser welding. In particular, Al is a component that promotes the formation of ferrite, and Al mixed into the molten area will cause the welded joint after hot forming to fail to achieve the desired level of martensite formation, and when external force is transmitted to the final product, cracks may occur in the welded joint or the heat-affected zone adjacent to the welded joint. Patent document 2 discloses a technology for laser welding after alloying the coating to prevent the coating components from mixing into the welded joint in this way, but this technology has the limitation that even if the coating is alloyed, it cannot completely prevent the Al component of the coating from mixing into the welded joint.

[0006] Patent document 3 discloses a technique for removing a local coating near a weld before laser welding in order to prevent Al components from being mixed into the weld joint. Although such removal of the local coating near the weld can partially alleviate the phenomenon of Al components of the coating being mixed into the weld joint, additional equipment for removing the coating must be introduced, and the removal of the partial coating near the weld may result in a decrease in the corrosion resistance of the area near the weld.

[0007] Therefore, there is an urgent need to develop a technology that can effectively prevent the phenomenon of deterioration of physical properties in the welded joint or the heat-affected zone adjacent to the welded joint caused by the inflow of Al components into the welded joint, even when welding is performed without partial or complete ablation of the plating layer.

[0008] (Patent Document 1) European Patent No. EP0971044A1

[0009] (Patent Document 2) European Patent No. EP3805421A1

[0010] (Patent Document 3) Korean Patent Publication No. 10-2009-0005004 Summary of the invention

[0011] One aspect of the present invention may provide a splice plate having a welded portion capable of effectively preventing a decrease in physical properties after thermoforming, a thermoformed component, and a method for manufacturing the same. The splice plate has a welded portion capable of effectively preventing a decrease in physical properties after thermoforming.

[0012] The technical problems of the present invention are not limited to the above contents. It is not difficult for those skilled in the art to understand the additional technical problems of the present invention from the overall content of this specification.

[0013] A splicing plate according to one aspect of the present invention may include: a first plated steel plate, including a first base steel plate and a first Al-based coating on at least one side of the first base steel plate; a second plated steel plate, including a second base steel plate and a second Al-based coating on at least one side of the second base steel plate; and a welding connection portion, located between the first plated steel plate and the second plated steel plate and used to connect the first plated steel plate and the second plated steel plate, the welding connection portion satisfies the following [Relationship 1] and [Relationship 2], when the Ni content included in the welding connection portion is 2.2 weight % or more, the welding connection portion satisfies the following [Relationship 3], and when the Ni content included in the welding connection portion is less than 2.2 weight %, the welding connection portion satisfies the following [Relationship 4].

[0014] [Equation 1]

[0015] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0

[0016] [Equation 2]

[0017] 1.0<[Cr]<8.0

[0018] [Equation 3]

[0019] 0.8≤[Ni] / [Cr]≤1.2

[0020] [Equation 4]

[0021] 0.3≤[Mn] / [Cr]≤1.1

[0022] In the above [Relational Expression 1] to the above [Relational Expression 4], [C], [Mn], [Ni], [Cr], and [Al] refer to the contents (weight %) of C, Mn, Ni, Cr, and Al respectively included in the weld connection portion.

[0023] The welded connection portion may satisfy one or more of the following [Relational Expression 5] and [Relational Expression 6].

[0024] [Equation 5]

[0025] [Mn]≤4.5

[0026] [Equation 6]

[0027] [Ni]≤9.0

[0028] In the above [Relational Expression 5] and the above [Relational Expression 6], [Mn] and [Ni] refer to the contents (weight %) of Mn and Ni included in the weld connection portion.

[0029] The first Al-based plating layer may be one selected from an Al-Si-based plating layer or an Al-Fe-based alloy plating layer, and the second Al-based plating layer may be one selected from an Al-Si-based plating layer or an Al-Fe-based alloy plating layer.

[0030] The first base steel plate or the second base steel plate may include, by weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance Fe and other inevitable impurities; or, by weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S : 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, the balance is Fe and other inevitable impurities; or, in weight %, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, the balance is Fe and other inevitable impurities.

[0031] A method for preparing a spliced ​​plate according to another aspect of the present invention may include: a step of providing a first plated steel plate and a second plated steel plate, wherein the first plated steel plate has a first Al-based coating formed on at least one side of a first base steel plate, and the second plated steel plate has a second Al-based coating formed on at least one side of a second base steel plate; and a butt welding step, wherein the first plated steel plate and the second plated steel plate are arranged adjacent to each other, and a filler wire is supplied while a laser beam is irradiated to form a welded connection satisfying the following [Relationship 1] and [Relationship 2], and when the filler wire is a NiCr-based filler wire, the butt welding is performed in a manner such that the welded connection satisfies the following [Relationship 3], and when the filler wire is a CrMn-based filler wire, the butt welding is performed in a manner such that the welded connection satisfies the following [Relationship 4].

[0032] [Equation 1]

[0033] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0

[0034] [Equation 2]

[0035] 1.0<[Cr]<8.0

[0036] [Equation 3]

[0037] 0.8≤[Ni] / [Cr]≤1.2

[0038] [Equation 4]

[0039] 0.3≤[Mn] / [Cr]≤1.1

[0040] In the above [Relational Expression 1] to the above [Relational Expression 4], [C], [Mn], [Ni], [Cr], and [Al] refer to the contents (weight %) of C, Mn, Ni, Cr, and Al respectively included in the weld connection portion.

[0041] In the butt welding step, the butt welding may be performed so that the welded connection portion satisfies one of the following [Relational Expression 5] and [Relational Expression 6].

[0042] [Equation 5]

[0043] [Mn]≤4.5

[0044] [Equation 6]

[0045] [Ni]≤9.0

[0046] In the above [Relational Expression 5] and the above [Relational Expression 6], [Mn] and [Ni] refer to the contents (weight %) of Mn and Ni included in the weld connection portion.

[0047] The NiCr-based filler welding wire may be a filler welding wire comprising, by weight%, C: 0.15-0.40%, Ni: 40.0-50.0%, Cr: 30.0-40.0%, Mn: 0% or more and 4.5% or less, Mo: 0% or more and 8% or less, Si: 0% or more and 0.4% or less, and other inevitable impurities; the CrMn-based filler welding wire may be a filler welding wire comprising, by weight%, C: 0.1-0.25%, Cr: 30.0-40.0%, Mn: 8.0-20.0%, Ni: 5.0-15.0%, Si: 0% or more and 0.4% or less, and other inevitable impurities.

[0048] The dilution rate of the filler wire provided to the molten pool formed by the laser beam may be 5 to 20%.

[0049] The output power of the laser beam may be 2-10 kW, and the welding speed of the laser beam may be 1-6 m / min.

[0050] The first Al-based coating or the second Al-based coating may be an Al-Si-based coating formed by immersing the first base steel plate or the second base steel plate in an Al-Si-based coating bath; or may be an Al-Fe-based alloyed coating formed by alloying the Al-Si-based coating.

[0051] The butt welding may be performed without partially or completely ablating the first plating layer or the second plating layer adjacent to the welding connection portion.

[0052] The first base steel plate or the second base steel plate may include, by weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance Fe and other inevitable impurities; or, by weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S : 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, the balance is Fe and other inevitable impurities; or, in weight %, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, the balance is Fe and other inevitable impurities.

[0053] Another aspect of the hot-formed component of the present invention may include: a first plated steel plate, including a first base steel plate and a first Al-based coating on at least one side of the first base steel plate; a second plated steel plate, including a second base steel plate and a second Al-based coating on at least one side of the second base steel plate; and a welded connection portion, located between the first plated steel plate and the second plated steel plate and satisfying the following [Relationship 1] and [Relationship 2], wherein the first base steel plate and the second base steel plate respectively include more than 90 area % of martensite as a microstructure, and when the Ni content included in the welded connection portion is more than 2.2 weight %, the welded connection portion satisfies the following [Relationship 3], and when the Ni content included in the welded connection portion is less than 2.2 weight %, the welded connection portion satisfies the following [Relationship 4].

[0054] [Equation 1]

[0055] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0

[0056] [Equation 2]

[0057] 1.0<[Cr]<8.0

[0058] [Equation 3]

[0059] 0.8≤[Ni] / [Cr]≤1.2

[0060] [Equation 4]

[0061] 0.3≤[Mn] / [Cr]≤1.1

[0062] In the above [Relational Expression 1] to the above [Relational Expression 4], [C], [Mn], [Ni], [Cr], and [Al] refer to the contents (weight %) of C, Mn, Ni, Cr, and Al respectively included in the weld connection portion.

[0063] The welded connection portion may satisfy one or more of the following [Relational Expression 5] and [Relational Expression 6].

[0064] [Equation 5]

[0065] [Mn]≤4.5

[0066] [Equation 6]

[0067] [Ni]≤9.0

[0068] In the above [Relational Expression 5] and the above [Relational Expression 6], [Mn] and [Ni] refer to the contents (weight %) of Mn and Ni included in the weld connection portion.

[0069] The first Al-based plating layer and the second Al-based plating layer may be Al—Fe-based alloy plating layers.

[0070] The first base steel plate or the second base steel plate may include, by weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance Fe and other inevitable impurities; or, by weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S : 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, the balance is Fe and other inevitable impurities; or, in weight %, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, the balance is Fe and other inevitable impurities.

[0071] When the first base steel plate and the second base steel plate are the same type of steel plates, when the hardness values ​​are measured at intervals of 0.3 mm at a load of 500 gf at the center of the thickness of the welded connection, the maximum hardness value (Hv 最大 ) and the average hardness value (Hv 平均 ) between the 最大 ) and the minimum hardness value (Hv 最小 ) and the average hardness value (Hv 平均 ) between the 最小 ) can be below 70Hv, wherein the unit of the hardness value is Hv.

[0072] When the first base steel plate and the second base steel plate are different types of steel plates, when the hardness values ​​are measured at intervals of 0.3 mm at a load of 500 gf at the center of the thickness of the welded connection, the maximum hardness value (Hv 最大 ) may have an average hardness value (Hv) of the center portion of the relatively hard base steel plate in the first base steel plate and the second base steel plate. 平均 1) + 50Hv "or less hardness value, the minimum hardness value of the welded connection (Hv 最小 ) may have an average hardness value (Hv) of the center portion of the relatively soft base steel plate in the first base steel plate and the second base steel plate. 平均 2) A hardness value above -50Hv", wherein the unit of the hardness value is Hv.

[0073] A crack rate in the weld connection portion may be 0% or more and less than 3%.

[0074] Another aspect of the present invention provides a method for preparing a hot-formed component, which may include: a heating step, heating the spliced ​​plate provided by the aforementioned method for preparing the spliced ​​plate to a temperature range above the austenitizing temperature; and a hot forming step, hot forming the heated spliced ​​plate in a mold capable of water cooling, and then immediately cooling it to a temperature range below the start temperature of the martensitic phase transformation.

[0075] The solutions to the above-mentioned technical problems do not list all the technical features of the present invention. The various technical features of the present invention and the advantages and technical effects brought about thereby should be understood in more detail by referring to the following specific implementation examples and embodiments.

[0076] According to one aspect of the present invention, there is provided a spliced ​​plate which, even when welded without partial or complete ablation of the plating layer, does not produce cracks in the welded joint or the heat-affected zone adjacent to the welded joint in a tensile test after hot forming.

[0077] According to one aspect of the present invention, a thermoformed component can be provided, which has high strength characteristics and excellent collision safety and is therefore suitable for use as an anti-intrusion component, an energy absorbing component, etc. of an automobile.

[0078] The technical effects of the present invention are not limited to the above contents, and can be interpreted as including the contents that a person skilled in the art can reasonably deduce from the contents recorded in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 and Figure 2 Graphs showing the Vickers hardness measurement results of the test pieces 6 and 10 , respectively. DETAILED DESCRIPTION

[0080] The present invention relates to a spliced ​​plate, a thermoformed component and a method for preparing the same. The preferred implementation examples of the present invention are described below. The implementation examples of the present invention can be transformed into various forms, and the scope of the present invention should not be interpreted as the implementation examples described below. This implementation example is provided to enable technicians in the technical field to which the present invention belongs to understand the present invention in more detail.

[0081] Next, a splicing plate according to one aspect of the present invention will be described in detail.

[0082] A splicing plate according to one aspect of the present invention may include a first plated steel plate, a second plated steel plate, and a welding connection portion disposed between the first plated steel plate and the second plated steel plate and used to connect the first plated steel plate and the second plated steel plate. Below, a splicing plate having a structure in which two plated steel plates are connected by a welding connection portion is schematically described, but it can be interpreted that the present invention includes the concept of a splicing plate having a structure in which three or more plated steel plates are connected by a welding connection portion.

[0083] The first plated steel sheet may include a first base steel sheet and a first plated layer formed on at least one side of the first base steel sheet, and the second plated steel sheet may include a second base steel sheet and a second plated layer formed on at least one side of the second base steel sheet.

[0084] The first plating layer and the second plating layer may be Al-based plating layers, and may be one of Al-Si-based plating layers and Al-Fe-based plating layers. The first plating layer and the second plating layer may be provided as plating layers of the same type or different types.

[0085] As a non-limiting example, the Al-based plating layer may include 3-15% Si in weight %, the remainder Al, and impurities that inevitably flow in. Impurities that inevitably flow into the Al-based plating layer may be interpreted as a concept including components that flow in from the base material iron.

[0086] The thickness of the first plating layer and the second plating layer is not particularly limited, and the first plating layer and the second plating layer may have a thickness corresponding to that of the plating layer of the plated steel sheet used in the preparation of a conventional spliced ​​plate.

[0087] The first base steel sheet and the second base steel sheet provided in the present invention are not particularly limited as long as they are steel sheets that can be cured by hot forming.

[0088] As a non-limiting example, the first base steel plate and the second base steel plate may be steel plates set with a component of one steel plate selected from the following steel plates 1 to 3, and the first base steel plate and the second base steel plate may be set with the same or different components.

[0089] Steel plate 1: includes, by weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other inevitable impurities.

[0090] Steel plate 2: includes, by weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance Fe and other inevitable impurities.

[0091] Steel plate 3: includes, by weight%, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance Fe and other inevitable impurities.

[0092] Illustratively, the steel plate 1 may have a tensile strength of about 500 MPa to 1000 MPa after hot forming, the steel plate 2 may have a tensile strength of about 1500 MPa after hot forming, and the steel plate 3 may have a tensile strength of about 1800 MPa to 2000 MPa after hot forming.

[0093] The thickness of the first base steel plate and the second base steel plate may be the same or different, and the first base steel plate and the second base steel plate may have a thickness corresponding to that of the base steel plate of the plated steel plate used in the conventional splicing plate preparation. For example, the first plated steel plate and the second plated steel plate may satisfy a thickness of 0.8 mm to 2.8 mm.

[0094] The inventors of the present invention conducted in-depth research on the conditions under which cracks would not appear in the welded joint or the heat-affected zone adjacent to the welded joint in a tensile test after hot forming even if a part of the Al component of the plating layer flows into the welded joint. The inventors realized that the collision safety of the hot-formed part can be ensured by controlling the content of a specific alloy component included in the welded joint within a prescribed range, and derived the present invention.

[0095] Next, the welded connection included in the spliced ​​plate according to one aspect of the present invention will be described in more detail.

[0096] The spliced ​​plate of one aspect of the present invention can satisfy [Relationship 1] and [Relationship 2] at the same time.

[0097] [Equation 1]

[0098] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0

[0099] [Equation 2]

[0100] 1.0<[Cr]<8.0

[0101] In the above [Relational Expression 1] and the above [Relational Expression 2], [C], [Mn], [Ni], [Cr], and [Al] refer to the contents (weight %) of C, Mn, Ni, Cr, and Al respectively included in the weld connection portion.

[0102] The inventors of the present invention have recognized that stable austenitization of the welded joint is a major factor in suppressing the crack rate of the welded joint when heating for hot forming is performed, and derived [Relationship 1]. Even if the ferrite-forming element Al flows into the welded joint, by controlling the relative content range of C, Mn, Ni, Cr and Al included in the welded joint to [Relationship 1], the welded joint can be stably austenitized during the hot forming process, and uniform martensite can be formed in the welded joint. That is, the present invention controls the alloy composition of the welded joint to [Relationship 1], and can control the crack rate of the welded joint to less than 3% in the tensile test after hot forming. The preferred crack rate of the welded joint can be 1% or less, and the more preferred crack rate of the welded joint can be 0%. In addition, the present invention does not particularly limit the upper limit of [Relationship 1], but in order to ensure economic efficiency, the upper limit of [Relationship 1] can also be limited to 5.0.

[0103] The inventors of the present invention have found that not only the relative contents of C, Mn, Ni, Cr and Al included in the welded joint, but also the individual content range of Cr included in the welded joint is also a factor that mainly affects the crack rate of the welded joint, and derived [Relationship 2]. Cr is a component that helps to ensure the strength of the welded joint, so as shown in [Relationship 2], 1.0 weight % or more of Cr may be included in the welded joint. The preferred content of Cr may be 2.0 weight % or more, and the more preferred content of Cr may be 2.5 weight %. On the other hand, Cr is a component that promotes the formation of ferrite, so the content of Cr included in the welded joint may be limited to 8.0 weight % or less. The preferred content of Cr may be 7 weight % or less, and the more preferred content of Cr may be 5 weight % or less.

[0104] The splicing plate of one aspect of the present invention may further satisfy one of the following [Relationship 3] or [Relationship 4] depending on the Ni content included in the welded connection portion. When the Ni content included in the welded connection portion is 2.2 wt % or more, the welded connection portion may satisfy the following [Relationship 3], and when the Ni content included in the welded connection portion is less than 2.2 wt %, the welded connection portion satisfies the following [Relationship 4].

[0105] [Equation 3]

[0106] 0.8≤[Ni] / [Cr]≤1.2

[0107] [Equation 4]

[0108] 0.3≤[Mn] / [Cr]≤1.1

[0109] In the above [Relational Expression 3] and the above [Relational Expression 4], [Mn], [Ni], and [Cr] refer to the contents (weight %) of Mn, Ni, and Cr respectively included in the weld connection portion.

[0110] The inventors of the present invention found that when the content of Ni included in the welded connection portion is 2.2 wt % or more, the relative contents of Ni and Cr included in the welded connection portion are main factors for ensuring the physical properties of the welded connection portion, and derived [Relational Expression 3].

[0111] In the case where the content of Ni included in the welded connection is 2.2% by weight or more, when the ratio of the content of Ni included in the welded connection to the content of Cr is too low, the austenite forming ability of the welded connection is reduced and soft ferrite remains at room temperature, which may cause the physical properties of the welded connection to deteriorate. Therefore, in the case where the content of Ni included in the welded connection is 2.2% by weight or more, in order to ensure the physical properties of the welded connection, as shown in [Relational Formula 3], the ratio of the content of Ni to the content of Cr ([Ni] / [Cr]) may be limited to 0.8 or more, more preferably 0.85 or more. On the other hand, in the case where the content of Ni included in the welded connection is 2.2% by weight or more, when the ratio of the content of Ni included in the welded connection to the content of Cr is too high, the austenite of the welded connection is too stable, and austenite may also remain at room temperature, which may cause the physical properties of the welded connection to deteriorate. Therefore, when the content of Ni included in the welded connection is 2.2 wt % or more, in order to ensure the physical properties of the welded connection, as shown in [Relationship 3], the ratio of the Ni content to the Cr content ([Ni] / [Cr]) can be limited to less than 1.2, and more preferably limited to less than 1.1.

[0112] In the case where the content of Ni included in the welded connection is less than 2.2 wt%, when the ratio of the content of Mn to the content of Cr included in the welded connection is too low, the austenite forming ability of the welded connection is reduced and soft ferrite remains at room temperature, which may cause the physical properties of the welded connection to deteriorate. Therefore, in the case where the content of Ni included in the welded connection is less than 2.2 wt%, in order to ensure the physical properties of the welded connection, as shown in [Relational Formula 4], the ratio of the content of Mn to the content of Cr ([Mn] / [Cr]) may be limited to 0.3 or more, more preferably 0.4 or more. On the other hand, in the case where the content of Ni included in the welded connection is less than 2.2 wt%, when the ratio of the content of Mn to the content of Cr included in the welded connection is too high, the austenite of the welded connection is too stable, and austenite may also remain at room temperature, which may cause the physical properties of the welded connection to deteriorate. Therefore, when the content of Ni included in the welded connection is less than 2.2 wt %, in order to ensure the physical properties of the welded connection, as shown in [Relationship 4], the ratio of the Mn content to the Cr content ([Mn] / [Cr]) can be limited to less than 1.1, and more preferably limited to less than 1.0.

[0113] The spliced ​​plate according to one aspect of the present invention may satisfy one or more of the following [Relational Expression 5] and [Relational Expression 6].

[0114] [Equation 5]

[0115] [Mn]≤4.5

[0116] [Equation 6]

[0117] [Ni]≤9.0

[0118] In the above [Relational Expression 5] and the above [Relational Expression 6], [Mn] and [Ni] refer to the contents (weight %) of Mn and Ni included in the weld connection portion.

[0119] Ni and Mn are representative elements for stabilizing austenite, and are elements that effectively contribute to uniform austenitization of the welded joint when heated for hot forming. However, when the content of Ni and Mn exceeds the specified range, austenite is too stable and austenite may remain in the welded joint at room temperature, which may cause the physical properties of the welded joint to deteriorate. Therefore, as shown in [Relational Formula 5] and [Relational Formula 6], the content of Mn and Ni included in the welded joint can be limited to 4.5% by weight or less and 9.0% by weight or less, respectively.

[0120] Since the splicing plate of one aspect of the present invention controls the alloy composition of the welded connection as described above, even if the welding of the plated steel sheets is carried out without partial or complete ablation of the coating, the degradation of physical properties caused by the influx of the Al component of the coating into the welded connection can be effectively suppressed, and cracks in the welded connection or the heat-affected zone adjacent to the welded connection can be effectively prevented in the tensile test after hot forming.

[0121] Next, a method for preparing a spliced ​​plate according to one aspect of the present invention is described in more detail.

[0122] A method for preparing a spliced ​​plate according to one aspect of the present invention may include the steps of providing a plated steel plate and performing butt welding.

[0123] In the step of providing a plated steel plate, a first plated steel plate and a second plated steel plate may be provided, wherein the first plated steel plate has a first Al-based coating formed on at least one side of a first base steel plate, and the second plated steel plate has a second Al-based coating formed on at least one side of a second base steel plate.

[0124] The first Al-based plating layer and the second Al-based plating layer may be Al-Si-based plating layers formed by immersing the base steel sheet in an Al-Si-based plating bath, or may be Al-Fe-based alloyed plating layers provided by alloying after forming the Al-Si-based plating layer. The Al-Si-based plating bath may include 3 to 15 wt % Si, the remainder Al, and other inevitable impurities.

[0125] The specific contents about the first base steel plate and the second base steel plate, the first coating and the second coating correspond to the corresponding contents in the aforementioned plated steel plate, so the aforementioned description of the plated steel plate replaces the description of the plated steel plate provided in the preparation of the spliced ​​plate.

[0126] In the butt welding step, the end of the first plated steel sheet and the end of the second plated steel sheet may be brought into abutment with each other, and a laser beam may be irradiated while supplying a filler wire to form a welded connection. At this time, butt welding may be performed after partially or completely ablating the first or second plated layer in the adjacent region, or may be performed without partially or completely ablating.

[0127] The filler wire used in the butt welding of the present invention may be a NiCr-based filler wire or a CrMn-based filler wire. The NiCr-based filler wire may refer to a filler wire including Ni and Cr as main components. As a non-limiting example, the NiCr-based filler wire may include, by weight%, C: 0.15-0.40%, Ni: 40.0-50.0%, Cr: 30.0-40.0%, Mn: 0% or more and 4.5% or less, Mo: 0% or more and 8% or less, Si: 0% or more and 0.4% or less, and other inevitable impurities. The CrMn-based filler wire may refer to a filler wire including Cr and Mn as main components. As a non-limiting example, the CrMn-based filler wire may include, in weight %, C: 0.1-0.25%, Cr: 30.0-40.0%, Mn: 8.0-20.0%, Ni: 5.0-15.0%, Si: 0% or more and 0.4% or less, and other inevitable impurities.

[0128] In the butt welding step, laser welding can be performed so that the welded connection formed by butt welding satisfies the following [Equation 1] and [Equation 2]. When butt welding is performed using a NiCr-based filler wire, laser welding is performed in a manner that satisfies the following [Equation 3]. When butt welding is performed using a CrMn-based filler wire, laser welding is performed in a manner that satisfies the following [Equation 4].

[0129] [Equation 1]

[0130] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0

[0131] [Equation 2]

[0132] 1.0<[Cr]<8.0

[0133] [Equation 3]

[0134] 0.8≤[Ni] / [Cr]≤1.2

[0135] [Equation 4]

[0136] 0.3≤[Mn] / [Cr]≤1.1

[0137] In the above [Relational Expression 1] to the above [Relational Expression 4], [C], [Mn], [Ni], [Cr], and [Al] refer to the contents (weight %) of C, Mn, Ni, Cr, and Al respectively included in the weld connection portion.

[0138] The reasons for limiting [Relational Expression 1] to [Relational Expression 4] correspond to the reasons for limiting the relational expressions of the aforementioned spliced ​​plate, and therefore the specific description of [Relational Expression 1] to [Relational Expression 4] is replaced by the aforementioned description.

[0139] In the butt welding step, laser welding may be performed so that the welded joint portion satisfies one or more of the following [Relational Expression 5] and [Relational Expression 6].

[0140] [Equation 5]

[0141] [Mn]≤4.5

[0142] [Equation 6]

[0143] [Ni]≤9.0

[0144] In the above [Relational Expression 5] and the above [Relational Expression 6], [Mn] and [Ni] refer to the contents (weight %) of Mn and Ni included in the weld connection portion.

[0145] The reasons for limiting [Relational Expression 5] and [Relational Expression 6] correspond to the reasons for limiting the relational expression of the aforementioned spliced ​​plate, and therefore the specific description of [Relational Expression 5] and [Relational Expression 6] is replaced by the aforementioned description.

[0146] The alloy composition of the welded joint may be somewhat affected by the alloy composition of the base steel plate and the alloy composition of the coating, but is more affected by the laser welding conditions. That is, the alloy composition of the welded joint can be controlled by the alloy composition of the filler wire used in laser welding, the dilution ratio of the filler wire in the molten pool, the output power of the laser beam, and the welding speed of the laser beam.

[0147] The method for preparing a spliced ​​plate according to one aspect of the present invention can limit the filler wire used in laser welding to a NiCr-based filler wire or a CrMn-based filler wire, so that the welded connection formed by butt welding satisfies the aforementioned [Equation 1] to [Equation 6], and the ratio of the filler wire diluted in the molten pool formed by the laser beam is limited to a range of 5 to 20%. At this time, the output power of the laser beam can satisfy the range of 2 to 10 kW, and the welding speed of the laser beam can satisfy the range of 1 to 6 m / min. During butt welding, in order to prevent oxidation of the molten metal and remove fume, etc., inert gases such as He and Ar can be used as shielding gases, but are not necessarily limited to this.

[0148] Next, a thermoformed component and a method for preparing the same according to one aspect of the present invention will be described in more detail.

[0149] The thermoformed component of one aspect of the present invention can be provided by thermoforming the aforementioned spliced ​​plate. That is, the thermoformed component of one aspect of the present invention can be prepared through the following steps: a heating step of heating the aforementioned spliced ​​plate to a temperature range above the austenitizing temperature; and a thermoforming step of thermoforming the heated spliced ​​plate in a water-coolable mold, and then immediately cooling it to a temperature range below the martensitic transformation start temperature.

[0150] The hot-formed component according to one aspect of the present invention may include a first plated steel plate, a second plated steel plate, and a welded connection portion for connecting the first plated steel plate and the second plated steel plate. The hot-formed component according to one aspect of the present invention is provided by hot-forming the aforementioned spliced ​​plates, and therefore, there may be differences in shape, coating composition, and microstructure of the base steel plate relative to the aforementioned spliced ​​plates. Alloying of the coating can be achieved during the hot-forming process, and some components of the base steel plate can flow into the coating. Through the heating and rapid cooling process during the hot-forming process, martensitization of the base steel plate can be achieved, and the base steel plate of the formed component may include martensite of about 90% by area or more and less than 100% by area.

[0151] As the hot forming process is carried out, the welded connection part also undergoes martensite transformation, but the alloy composition of the welded connection part does not change significantly before and after the hot forming process. Therefore, the welded connection part of the formed component according to one aspect of the present invention also satisfies the aforementioned [Relationship 1] to [Relationship 6].

[0152] The formed component of one aspect of the present invention alleviates local physical property deviations between the base steel plate and the welded joint, so that when the formed component is subjected to a tensile test, the crack rate of the welded joint can be controlled to be 0% or more and less than 3%.

[0153] When the first base steel plate and the second base steel plate of the molded component are the same steel plates, when the hardness value (Hv) is measured at a 0.3 mm interval from the thickness center of the welded connection portion with a load of 500 gf, the maximum hardness value (Hv) of the welded connection portion is 最大 ) and the average hardness value of the base steel plate (Hv 平均 ) between the 最大 ) absolute value and the minimum hardness value of the welded joint (Hv 最小 ) and the average hardness value of the base steel plate (Hv 平均 ) between the 最小 ) can be less than 70Hv respectively.

[0154] In addition, when the first base steel plate and the second base steel plate of the molded component are different steel plates, when the hardness value (Hv) is measured at an interval of 0.3 mm from the thickness center of the welded connection portion with a load of 500 gf, the maximum hardness value (Hv) of the welded connection portion is 最大 ) may have a "relatively hard base steel plate" in the first base steel plate and the second base steel plate. The average hardness value (Hv 平均 1) Hardness value below +50Hv, minimum hardness value of welded joint (Hv 最小 ) may have an average hardness value (Hv) of the center portion of the relatively soft base steel plate in the first base steel plate and the second base steel plate. 平均 2) Hardness value above -50Hv”.

[0155] Therefore, the molded component of one aspect of the present invention not only has high strength characteristics but also has excellent collision safety, and thus can have physical properties suitable for use as an anti-intrusion component, an energy absorbing component, etc. of an automobile.

[0156] The following is a more detailed description of the splicing plate, the thermoformed component and the preparation method thereof of the present invention through specific embodiments. It should be noted that the following embodiments are only used to understand the present invention and are not used to limit the scope of protection of the present invention. The scope of protection of the present invention can be determined by the contents recorded in the claims and the contents reasonably deduced therefrom.

[0157] Using the welding conditions listed in Table 1, spliced ​​plate test pieces were produced.

[0158] The base steel plate A in Table 1 represents a base steel plate which includes, in weight %, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance Fe and other inevitable impurities. The base steel plate A can ensure a tensile strength of about 1000 MPa after hot forming. The base steel plate B represents a base steel plate which includes, in weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the remainder of Fe and other inevitable impurities, and the base steel plate B can ensure a tensile strength of approximately 1500 MPa after hot forming. The base steel sheet C refers to a base steel sheet including, by weight%, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, the balance Fe and other inevitable impurities, and the base steel sheet C can ensure a tensile strength of about 1800 MPa after hot forming. The prepared base steel sheets A to C respectively meet the thicknesses described in Table 1.

[0159] After each base steel sheet is immersed in an aluminum plating bath containing 4 to 15% by weight of Si, a single-side plating amount of 10 to 40 g / m 2 The plating is performed in a manner of, and alloying treatment is further performed on a portion. Regarding pre-alloying, the "○" mark indicates that alloying treatment of the plating layer is performed before laser welding, and the "X" mark indicates that alloying treatment of the plating layer is not performed before laser welding.

[0160] Before laser welding, ablation treatment was performed on some of the test pieces to remove the plating layer on the end side of the plated steel sheet. Regarding the ablation treatment, the "○" mark indicates the case where the ablation treatment was performed, and the "X" mark indicates the case where the ablation treatment was not performed.

[0161] Butt welding was performed at a welding speed of 1 to 3 m / min using a laser beam whose output was adjusted to a range of 3 to 5 kW, and a filler wire was supplied to a molten pool formed by the laser beam at a dilution rate described in Table 1. The NiCr-based filler wire in the filler wire described in Table 1 refers to a filler wire containing, by weight %, C: 0.15 to 0.40%, Ni: 40.0 to 50.0%, Cr: 30.0 to 40.0%, Mn: 0% to 4.5%, Mo: 0% to 8%, Si: 0% to 0.4%, and other inevitable impurities, and the CrMn-based filler wire refers to a filler wire containing, by weight %, C: 0.1 to 0.25%, Cr: 30.0 to 40.0%, Mn: 8.0 to 20.0%, Ni: 5.0 to 15.0%, Si: 0% to 0.4%, and other inevitable impurities.

[0162] [Table 1]

[0163]

[0164] For each test piece in Table 1, each test piece was heated to a temperature range of 870 to 950°C and maintained for five minutes, and press quenching was performed using a mold that can be water-cooled inside to simulate hot forming. Each test piece was cut to form a cross section perpendicular to the welding direction, and EPMA (electron probe microanalyzer) and SEM (scanning electron microscope) were used for EDS (dispersion spectrum) quantitative analysis to analyze the alloy composition of the welded connection in the cross section of each test piece. In the cross section of each test piece, the welded part except the weld heat affected part was divided into 8 to 12 areas, and each area was analyzed, and the average value of the component content measured in each area was recorded in Table 2. In addition, after substituting the contents of these components into Relational Formulas 1, 3, and 4, the results are recorded together in Table 2. In each test piece, a plurality of tensile test pieces (ISO 6892-1 Type 1, the welded portion is located in the center of the parallel portion in the direction perpendicular to the tensile load) were taken and subjected to a tensile test, and after calculating the ratio of the number of tensile test pieces with cracks in the welded portion to the number of tensile tests (the number of tensile test pieces with cracks in the welded portion / the total number of tensile test pieces), the weld crack rate of each test piece was measured as described in Table 2. The hardness value (Hv) was measured at a load of 500 gf at intervals of 0.3 mm in the center of the thickness of the welded connection using a Vickers hardness tester, and the maximum hardness value (Hv) of the welded connection was calculated. 最大 ) and the average hardness value of the base steel plate (Hv 平均 ) between the 最大 ) and the minimum hardness value of the welded joint (Hv 最小 ) and the average hardness value of the base steel plate (Hv平均 ) between the 最小 ) and recorded together in Table 2. In addition, Figure 1 and Figure 2 6 and 10 are graphs showing the Vickers hardness measurement results of the test piece 6 and the test piece 10, respectively. Figure 1 As shown in FIG. 6 , it can be confirmed that the average hardness of the base material of the first plated steel plate of the test piece 6 is about 490 Hv, the average hardness of the base material of the second plated steel plate is about 390 Hv, and the average hardness of the welded connection is 446 Hv to 474 Hv. Figure 2 As shown in FIG. 1 , it can be confirmed that the average hardness of the base material of the first plated steel plate of the test piece 10 is about 488 Hv, the average hardness of the base material of the second plated steel plate is about 563 Hv, and the average hardness of the welded connection is 525 Hv to 551 Hv. That is, it can be confirmed that the maximum hardness value (Hv 最大 ) satisfies the "average hardness value (Hv 平均 1) +50Hv” range, and the minimum hardness value of the welded joint (Hv 最小 ) satisfies the "average hardness value (Hv 平均 2) -50Hv” or above, so the weld crack rate is less than 3%.

[0165] [Table 2]

[0166]

[0167] As can be seen from Tables 1 and 2, the weld crack rate of the test pieces satisfying the conditions of the present invention is less than 3% by area, whereas the weld crack rate of the test pieces not satisfying the conditions of the present invention significantly exceeds 3% by area.

[0168] Therefore, the spliced ​​plate of one aspect of the present invention can provide a thermoformed component that will not produce cracks in the welded connection or the heat-affected zone adjacent to the welded connection in a tensile test after thermoforming even if the thermoformed component is welded without partial or complete ablation of the coating.

[0169] This application also involves the following aspects:

[0170] 1. A splicing plate, comprising:

[0171] A first plated steel sheet, comprising a first base steel sheet and a first Al-based coating on at least one side of the first base steel sheet;

[0172] a second plated steel sheet comprising a second base steel sheet and a second Al-based coating on at least one side of the second base steel sheet; and

[0173] A welding connection portion is located between the first plated steel plate and the second plated steel plate and is used to connect the first plated steel plate and the second plated steel plate. The welding connection portion satisfies the following [Relationship 1] and [Relationship 2]:

[0174] When the Ni content included in the weld connection portion is 2.2 wt % or more, the weld connection portion further satisfies the following [Relationship 3], and when the Ni content included in the weld connection portion is less than 2.2 wt %, the weld connection portion further satisfies the following [Relationship 4],

[0175] [Equation 1]

[0176] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0

[0177] [Equation 2]

[0178] 1.0<[Cr]<8.0

[0179] [Equation 3]

[0180] 0.8≤[Ni] / [Cr]≤1.2

[0181] [Equation 4]

[0182] 0.3≤[Mn] / [Cr]≤1.1

[0183] In the [Relationship 1] to the [Relationship 4], [C], [Mn], [Ni], [Cr] and [Al] refer to the contents of C, Mn, Ni, Cr and Al respectively included in the weld connection portion, wherein the contents are expressed in weight %.

[0184] 2. The splicing plate according to aspect 1, wherein:

[0185] The first Al-based plating layer is one selected from an Al-Si-based plating layer or an Al-Fe-based alloyed plating layer.

[0186] The second Al-based plating layer is one selected from an Al-Si-based plating layer or an Al-Fe-based alloy plating layer.

[0187] 3. The splicing plate according to aspect 1, wherein:

[0188] The first base steel plate or the second base steel plate comprises:

[0189] In terms of weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance is Fe and other unavoidable impurities; or

[0190] In terms of weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other unavoidable impurities; or

[0191] In terms of weight%, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other inevitable impurities.

[0192] 4. A method for preparing a spliced ​​plate, comprising:

[0193] The step of providing a first plated steel sheet and a second plated steel sheet, wherein the first plated steel sheet has a first Al-based plated layer formed on at least one side of a first base steel sheet, and the second plated steel sheet has a second Al-based plated layer formed on at least one side of a second base steel sheet; and

[0194] The butt welding step comprises placing the first plated steel sheet and the second plated steel sheet adjacent to each other, supplying a filler wire and irradiating a laser beam to form a welded connection portion satisfying the following [Relationship 1] and [Relationship 2],

[0195] When the filler wire is a NiCr-based filler wire, butt welding is performed in a manner such that the welded connection further satisfies the following [Relationship 3]; when the filler wire is a CrMn-based filler wire, butt welding is performed in a manner such that the welded connection further satisfies the following [Relationship 4],

[0196] [Equation 1]

[0197] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0

[0198] [Equation 2]

[0199] 1.0<[Cr]<8.0

[0200] [Equation 3]

[0201] 0.8≤[Ni] / [Cr]≤1.2

[0202] [Equation 4]

[0203] 0.3≤[Mn] / [Cr]≤1.1

[0204] In the [Relationship 1] to the [Relationship 4], [C], [Mn], [Ni], [Cr] and [Al] refer to the contents of C, Mn, Ni, Cr and Al respectively included in the weld connection portion, wherein the contents are expressed in weight %.

[0205] 5. The method for preparing a spliced ​​plate according to aspect 4, wherein:

[0206] The NiCr-based filler wire is a filler wire comprising, by weight%, C: 0.15-0.40%, Ni: 40.0-50.0%, Cr: 30.0-40.0%, Mn: 0% to 4.5%, Mo: 0% to 8%, Si: 0% to 0.4%, and other inevitable impurities.

[0207] The CrMn-based filler wire is a filler wire containing, by weight%, C: 0.1-0.25%, Cr: 30.0-40.0%, Mn: 8.0-20.0%, Ni: 5.0-15.0%, Si: 0% or more and 0.4% or less, and other inevitable impurities.

[0208] 6. The method for preparing a spliced ​​plate according to aspect 4, wherein:

[0209] The dilution rate of the filler wire provided to the molten pool formed by the laser beam is 5 to 20%.

[0210] 7. The method for preparing a spliced ​​plate according to aspect 4, wherein:

[0211] The output power of the laser beam is 2 to 10 kW.

[0212] The welding speed of the laser beam is 1-6 m / min.

[0213] 8. The method for preparing a spliced ​​plate according to aspect 4, wherein:

[0214] The first Al-based coating or the second Al-based coating is an Al-Si-based coating formed by immersing the first base steel plate or the second base steel plate in an Al-Si-based coating bath; or is an Al-Fe-based alloyed coating formed by alloying the Al-Si-based coating.

[0215] 9. The method for preparing a spliced ​​plate according to aspect 4, wherein:

[0216] The butt welding is performed without partially or completely ablating the first plating layer or the second plating layer adjacent to the welded connection portion.

[0217] 10. The method for preparing a spliced ​​plate according to aspect 4, wherein:

[0218] The first base steel plate or the second base steel plate comprises:

[0219] In terms of weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance is Fe and other unavoidable impurities; or

[0220] In terms of weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other unavoidable impurities; or

[0221] In terms of weight%, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other inevitable impurities.

[0222] 11. A thermoformed component, comprising:

[0223] A first plated steel sheet, comprising a first base steel sheet and a first Al-based coating on at least one side of the first base steel sheet;

[0224] a second plated steel sheet comprising a second base steel sheet and a second Al-based coating on at least one side of the second base steel sheet; and

[0225] The welded connection portion is located between the first plated steel plate and the second plated steel plate and satisfies the following [Relationship 1] and [Relationship 2],

[0226] The first base steel plate and the second base steel plate each include 90% by area or more of martensite as a microstructure,

[0227] When the Ni content included in the weld connection portion is 2.2 wt % or more, the weld connection portion further satisfies the following [Relationship 3], and when the Ni content included in the weld connection portion is less than 2.2 wt %, the weld connection portion further satisfies the following [Relationship 4],

[0228] [Equation 1]

[0229] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0

[0230] [Equation 2]

[0231] 1.0<[Cr]<8.0

[0232] [Equation 3]

[0233] 0.8≤[Ni] / [Cr]≤1.2

[0234] [Equation 4]

[0235] 0.3≤[Mn] / [Cr]≤1.1

[0236] In the [Relationship 1] to the [Relationship 4], [C], [Mn], [Ni], [Cr] and [Al] refer to the contents of C, Mn, Ni, Cr and Al respectively included in the weld connection portion, wherein the contents are expressed in weight %.

[0237] 12. The thermoformed component according to aspect 11, wherein:

[0238] The first Al-based plating layer and the second Al-based plating layer are Al—Fe-based alloy plating layers.

[0239] 13. The thermoformed component according to aspect 11, wherein:

[0240] The first base steel plate or the second base steel plate comprises:

[0241] In terms of weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance is Fe and other unavoidable impurities; or

[0242] In terms of weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other unavoidable impurities; or

[0243] In terms of weight%, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other inevitable impurities.

[0244] 14. The thermoformed component according to aspect 13, wherein:

[0245] When the first base steel plate and the second base steel plate are the same type of steel plates, when the hardness values ​​are measured at the thickness center of the welded connection portion at a load of 500 gf at intervals of 0.3 mm, the maximum hardness value Hv of the welded connection portion is 最大 and the average hardness value Hv of the base steel plate 平均 The difference between △H 最大 The absolute value of the minimum hardness value Hv of the welded connection 最小 and the average hardness value Hv of the base steel plate 平均 The difference between △H 最小 The absolute value of the hardness is below 70Hv, where the unit of the hardness value is Hv.

[0246] 15. The thermoformed component according to aspect 13, wherein:

[0247] When the first base steel plate and the second base steel plate are different types of steel plates, when the hardness values ​​are measured at a load of 500 gf at intervals of 0.3 mm at the center of the thickness of the welded connection, the maximum hardness value Hv of the welded connection is 最大 The average hardness value Hv of the center portion of the relatively hard base steel plate in the first base steel plate and the second base steel plate is 平均1+50Hv” or less, the minimum hardness value of the welded connection is Hv 最小 The average hardness value Hv of the center portion of the relatively soft base steel plate is Hv 平均 2-50Hv" or above hardness value, wherein the unit of the hardness value is Hv.

[0248] 16. The thermoformed component according to aspect 11, wherein:

[0249] The crack rate in the welded connection portion is 0% or more and less than 3%.

[0250] 17. A method for preparing a thermoformed part, comprising:

[0251] A heating step, heating the spliced ​​plate provided by the preparation method according to any one of aspects 4 to 10 to a temperature range above the austenitizing temperature; and

[0252] In the hot forming step, the heated spliced ​​plate is hot formed in a water-coolable mold, and then immediately cooled to a temperature range below the martensitic transformation start temperature.

[0253] The present invention is described in detail above by using the embodiments, but other forms of embodiments may also be adopted. Therefore, the technical concept and scope of the claims in the appended claims are not limited to the embodiments.

Claims

1. A splicing plate, comprising: A first plated steel sheet, comprising a first base steel sheet and a first Al-based coating on at least one side of the first base steel sheet; A second plated steel sheet, comprising a second base steel sheet and a second Al-based coating on at least one side of the second base steel sheet; and A welding connection portion is located between the first plated steel plate and the second plated steel plate and is used to connect the first plated steel plate and the second plated steel plate. The welding connection portion satisfies the following [Relationship 1] and [Relationship 2]: [Equation 1] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0 [Equation 2] 1.0<[Cr]<8.0 In the [Relational Formula 1] to the [Relational Formula 2], [C], [Mn], [Ni], [Cr], and [Al] refer to the contents of C, Mn, Ni, Cr, and Al respectively included in the weld connection portion, wherein the contents are expressed in weight %.

2. The splice plate according to claim 1, wherein: The first Al-based plating layer is one selected from an Al-Si-based plating layer or an Al-Fe-based alloyed plating layer. The second Al-based plating layer is one selected from an Al-Si-based plating layer or an Al-Fe-based alloy plating layer.

3. The splice plate according to claim 1, wherein: The first base steel plate or the second base steel plate comprises: In terms of weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance is Fe and other unavoidable impurities; or In terms of weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other unavoidable impurities; or In terms of weight%, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other inevitable impurities.

4. The splice plate according to claim 1, wherein: When the Ni content included in the weld connection portion is 2.2 wt % or more, the weld connection portion further satisfies the following [Relationship 3], and when the Ni content included in the weld connection portion is less than 2.2 wt %, the weld connection portion further satisfies the following [Relationship 4], [Equation 3] 0.8≤[Ni] / [Cr]≤1.2 [Equation 4] 0.3≤[Mn] / [Cr]≤1.1 In the [Relational Expression 3] to the [Relational Expression 4], [Mn], [Ni], and [Cr] refer to the contents of Mn, Ni, and Cr respectively included in the weld connection portion, wherein the contents are expressed in weight %.

5. The splice plate according to claim 1, wherein: The welded connection portion satisfies at least one of the following [Relationship 5] and [Relationship 6]: [Equation 5] [Mn]≤4.5 [Equation 6] [Ni]≤9.0 In the [Relational Expression 5] to the [Relational Expression 6], [Mn] and [Ni] refer to the contents of Mn and Ni respectively included in the weld connection portion, wherein the contents are expressed in wt %.

6. A method for preparing a spliced ​​plate, comprising: The step of providing a first plated steel sheet and a second plated steel sheet, wherein the first plated steel sheet has a first Al-based plated layer formed on at least one side of a first base steel sheet, and the second plated steel sheet has a second Al-based plated layer formed on at least one side of a second base steel sheet; and The butt welding step comprises placing the first plated steel sheet and the second plated steel sheet adjacent to each other, supplying a filler wire and irradiating a laser beam to form a welded connection portion satisfying the following [Relationship 1] and [Relationship 2], [Equation 1] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0 [Equation 2] 1.0<[Cr]<8.0 In the [Relational Formula 1] to the [Relational Formula 2], [C], [Mn], [Ni], [Cr], and [Al] refer to the contents of C, Mn, Ni, Cr, and Al respectively included in the weld connection portion, wherein the contents are expressed in weight %.

7. The method for preparing a spliced ​​plate according to claim 6, wherein: The filler wire is a NiCr-based filler wire or a CrMn-based filler wire. The NiCr-based filler wire is a filler wire comprising, by weight%, C: 0.15-0.40%, Ni: 40.0-50.0%, Cr: 30.0-40.0%, Mn: 0% to 4.5%, Mo: 0% to 8%, Si: 0% to 0.4%, and other inevitable impurities. The CrMn-based filler wire is a filler wire containing, by weight%, C: 0.1-0.25%, Cr: 30.0-40.0%, Mn: 8.0-20.0%, Ni: 5.0-15.0%, Si: 0% or more and 0.4% or less, and other inevitable impurities.

8. The method for preparing a spliced ​​plate according to claim 6, wherein: The dilution rate of the filler wire provided to the molten pool formed by the laser beam is 5 to 20%.

9. The method for preparing a spliced ​​plate according to claim 6, wherein: The output power of the laser beam is 2 to 10 kW. The welding speed of the laser beam is 1-6 m / min.

10. The method for preparing a spliced ​​plate according to claim 6, wherein: The first Al-based coating or the second Al-based coating is an Al-Si-based coating formed by immersing the first base steel plate or the second base steel plate in an Al-Si-based coating bath; or is an Al-Fe-based alloyed coating formed by alloying the Al-Si-based coating.

11. The method for preparing a spliced ​​plate according to claim 6, wherein: The butt welding is performed without partially or completely ablating the first plating layer or the second plating layer adjacent to the welded connection portion.

12. The method for preparing a spliced ​​plate according to claim 6, wherein: When the Ni content included in the weld connection portion is 2.2 wt % or more, the weld connection portion further satisfies the following [Relationship 3], and when the Ni content included in the weld connection portion is less than 2.2 wt %, the weld connection portion further satisfies the following [Relationship 4], [Equation 3] 0.8≤[Ni] / [Cr]≤1.2 [Equation 4] 0.3≤[Mn] / [Cr]≤1.1 In the [Relational Expression 3] to the [Relational Expression 4], [Mn], [Ni], and [Cr] refer to the contents of Mn, Ni, and Cr respectively included in the weld connection portion, wherein the contents are expressed in weight %.

13. The method for preparing a spliced ​​plate according to claim 6, wherein: The welded connection portion satisfies at least one of the following [Relationship 5] and [Relationship 6]: [Equation 5] [Mn]≤4.5 [Equation 6] [Ni]≤9.0 In the [Relational Expression 5] to the [Relational Expression 6], [Mn] and [Ni] refer to the contents of Mn and Ni respectively included in the weld connection portion, wherein the contents are expressed in wt %.

14. The method for preparing a spliced ​​plate according to claim 6, wherein: The first base steel plate or the second base steel plate comprises: In terms of weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance is Fe and other unavoidable impurities; or In terms of weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other unavoidable impurities; or In terms of weight%, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other inevitable impurities.

15. A thermoformed component comprising: A first plated steel sheet, comprising a first base steel sheet and a first Al-based coating on at least one side of the first base steel sheet; a second plated steel sheet comprising a second base steel sheet and a second Al-based coating on at least one side of the second base steel sheet; and The welded connection portion is located between the first plated steel plate and the second plated steel plate and satisfies the following [Relationship 1] and [Relationship 2], The first base steel plate and the second base steel plate each include 90% by area or more of martensite as a microstructure, [Equation 1] 4.44×[C]+0.355×[Mn]+0.505×[Ni]+0.148×[Cr]-[Al]-1.388>0 [Equation 2] 1.0<[Cr]<8.0 In the [Relational Formula 1] to the [Relational Formula 2], [C], [Mn], [Ni], [Cr], and [Al] refer to the contents of C, Mn, Ni, Cr, and Al respectively included in the weld connection portion, wherein the contents are expressed in weight %.

16. The thermoformed part according to claim 15, wherein: The first Al-based plating layer and the second Al-based plating layer are Al—Fe-based alloy plating layers.

17. The thermoformed part according to claim 15, wherein: The first base steel plate or the second base steel plate comprises: In terms of weight%, C: 0.01-0.15%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: 0.05% or less, S: 0.01% or less, Al: 0.5% or less, Ti: 0.1% or less, Cr: 0.5% or less, Mo: 0.5% or less, B: 0.01% or less, and the balance is Fe and other unavoidable impurities; or In terms of weight%, C: more than 0.15% and less than 0.25%, Si: 0.1-0.5%, Mn: 0.5-2.5%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other unavoidable impurities; or In terms of weight%, C: more than 0.25% and less than 0.45%, Si: 0.3-1.0%, Mn: 0.3-1.2%, P: less than 0.05%, S: less than 0.01%, Al: less than 0.5%, Ti: less than 0.1%, Cr: less than 0.5%, Mo: less than 0.5%, B: less than 0.01%, and the balance is Fe and other inevitable impurities.

18. The thermoformed part according to claim 17, wherein: When the first base steel plate and the second base steel plate are the same type of steel plates, when the hardness values ​​are measured at the thickness center of the welded connection portion at a load of 500 gf at intervals of 0.3 mm, the maximum hardness value Hv of the welded connection portion is 最大 and the average hardness value Hv of the base steel plate 平均 The difference between △H 最大 The absolute value of the minimum hardness value Hv of the welded connection 最小 and the average hardness value Hv of the base steel plate 平均 The difference between △H 最小 The absolute value of the hardness is below 70Hv, where the unit of the hardness value is Hv.

19. The thermoformed part according to claim 17, wherein: When the first base steel plate and the second base steel plate are different types of steel plates, when the hardness values ​​are measured at a load of 500 gf at intervals of 0.3 mm at the center of the thickness of the welded connection, the maximum hardness value Hv of the welded connection is 最大 The average hardness value Hv of the center portion of the relatively hard base steel plate in the first base steel plate and the second base steel plate is 平均 1+50Hv” or less, the minimum hardness value of the welded connection is Hv 最小 The average hardness value Hv of the center portion of the relatively soft base steel plate in the first base steel plate and the second base steel plate is 平均 2-50Hv" or above hardness value, wherein the unit of the hardness value is Hv.

20. The thermoformed part of claim 15, wherein: The crack rate in the welded connection portion is 0% or more and less than 3%.

21. The thermoformed part of claim 15, wherein: When the Ni content included in the weld connection portion is 2.2 wt % or more, the weld connection portion further satisfies the following [Relationship 3], and when the Ni content included in the weld connection portion is less than 2.2 wt %, the weld connection portion further satisfies the following [Relationship 4], [Equation 3] 0.8≤[Ni] / [Cr]≤1.2 [Equation 4] 0.3≤[Mn] / [Cr]≤1.1 In the [Relational Expression 3] to the [Relational Expression 4], [Mn], [Ni], and [Cr] refer to the contents of Mn, Ni, and Cr respectively included in the weld connection portion, wherein the contents are expressed in weight %.

22. The thermoformed part of claim 15, wherein: The welded connection portion satisfies at least one of the following [Relationship 5] and [Relationship 6]: [Equation 5] [Mn]≤4.5 [Equation 6] [Ni]≤9.0 In the [Relational Expression 5] to the [Relational Expression 6], [Mn] and [Ni] refer to the contents of Mn and Ni respectively included in the weld connection portion, wherein the contents are expressed in wt %.

23. A method for preparing a thermoformed part, comprising: A heating step of heating the spliced ​​plate provided by the preparation method according to any one of claims 6 to 14 to a temperature range above an austenitizing temperature; and In the hot forming step, the heated spliced ​​plate is hot formed in a water-coolable mold, and then immediately cooled to a temperature range below the martensitic transformation start temperature.

24. A NiCr-based filler welding wire, comprising, in weight %, C: 0.15-0.40%, Ni: 40.0-50.0%, Cr: 30.0-40.0%, Mn: 0% to 4.5%, Mo: 0% to 8%, Si: 0% to 0.4% and other inevitable impurities.

25. A CrMn-based filler welding wire, comprising, in weight %, C: 0.1-0.25%, Cr: 30.0-40.0%, Mn: 8.0-20.0%, Ni: 5.0-15.0%, Si: more than 0% and less than 0.4%, and other inevitable impurities.

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