JP2019118946A - Steel plate, butt welding member, hot press-formed product, steel pipe, hollow quench-formed product, and method of manufacturing steel plate - Google Patents

Abstract

To provide a steel plate and a steel pipe which has an excellent static strength of a joint, and provides a butt welding member having an excellent corrosion resistance after coating at a section around a weld metal part.SOLUTION: There is provided a steel plate comprising a base steel plate 12 and an Al coating layer 18 provided on both sides of the base steel plate 12. A removed section 22 where at least a part of the Al coating layer 18 is removed is formed on at least one section of both sides of peripheral end, and a remaining section 26 where the Al coating layer remains is formed on a region closer to the center of the steel plate than the removed section 22. When the boundary of the removed section 22 and the remaining section 26 is focused in a cross-sectional view, a section 100B having the shortest removal width W1 is provided at the outer side of the Al coating layer in the boundary, and a section 100D having the longest removal width W2 is provided at the side of the base steel plate rather than the outer side of the Al coating layer in the boundary.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a method for manufacturing a steel plate, a butt-welded member, a hot press-formed product, a steel pipe, a hollow quench-formed product, and a steel plate.

In recent years, weight reduction of automobile bodies is an urgent issue in the automobile field in order to reduce CO ₂ gas emissions from the viewpoint of global environment protection. On the other hand, studies to apply a high strength steel plate are actively conducted, and the strength of the steel plate is also increasing more and more.

Hot press forming (hereinafter sometimes referred to as "hot stamp") is attracting attention as one of the techniques for forming automobile parts. The hot stamp heats the steel plate to a high temperature, press-molds it in a temperature range higher than the Ar ₃ transformation temperature, rapidly cools it by heat removal from the mold, and causes transformation simultaneously with molding under a pressure applied. This is a technology capable of manufacturing a press-formed product (hereinafter, may be referred to as a “hot stamped product”) having high strength and excellent shape freezeability.

  In addition, butt welding members (hereinafter referred to as "tailored blanks") in which the end faces of at least two steel plates are butted and joined by laser welding, plasma welding or the like in order to improve the yield of pressed parts of automotive members and functionality. Material) may be applied as a material for pressing. Tailored blanks can be made to change plate thickness and strength freely in one part in order to join a plurality of steel plates according to the purpose. As a result, the tailored blank material can improve the functionality of the automotive member and reduce the number of automotive members. In addition, by hot stamping using a tailored blank material, it is possible to manufacture a high-strength press-formed product in which the thickness, strength, and the like are freely changed.

  When a tailored blank material is used as a pressing material and a member for an automobile is formed by hot stamping, the tailored blank material is heated, for example, to a temperature range of 800 ° C. to 1000 ° C. For this reason, a steel plate plated with aluminum such as Al-Si having a high plating boiling point is often used as a tailored blank for hot stamping.

  Until now, as a steel plate for forming a tailored blank material, for example, a steel plate having a plating layer has been variously studied (see, for example, Patent Documents 1 to 7).

Patent No. 5237263 gazette Patent No. 6034490 Patent No. 6053918 gazette Japanese Patent Publication No. 2015-536246 Patent No. 5316670 gazette Chinese Patent Application Publication No. 106334875 Unexamined-Japanese-Patent No. 03-094992 gazette

  However, in the conventional steel plate, the characteristics of both the static strength of the joint and the corrosion resistance after coating of the welded portion are not sufficiently satisfied, and there is room for further improvement.

  An object of the present disclosure is to provide a steel plate and a steel pipe which are excellent in static strength of a joint and can provide a butt welded member having excellent corrosion resistance after painting around a weld metal portion even after coating on a welded portion. It is a thing.

  Means for solving the above problems include the following aspects.

<1> Base steel plate,
Aluminum coating layers provided on both sides of the base steel plate,
Have
The aluminum coating layer remains on at least a part of both sides of the edge located on the periphery, in the removed part from which at least a part of the aluminum coating layer is removed, and in the region on the center side of the steel plate than the removed part Remaining part is formed,
When the boundary between the removed portion and the remaining portion is viewed from the cross section, the aluminum coating layer outer surface side of the boundary has a portion with the shortest removal width, and the base metal than the aluminum coating layer outer surface side of the boundary A steel plate that has a portion with the longest removal width on the steel plate side.
<2> The remaining part in the area on the end face side of the steel plate with respect to a virtual line extending in the direction along the thickness direction from the part having the longest removal width of the boundary among the remaining parts The steel plate as described in <1> which has a residual part which is less than 50% of the thickness of an aluminum coating layer.
The steel plate as described in <1> or <2> in which the <3> said removal part has the exposed part which the said base-material steel plate is exposed.
<4> The base steel plate is, by mass%, C: 0.02% to 0.58%, Mn: 0.20% to 3.00%, Al: 0.005% to 1.00%, Ti : 0% to 0.20%, Nb: 0% to 0.20%, V: 0% to 1.0%, W: 0% to 1.0%, Cr: 0% to 1.0%, Mo : 0% to 1.0%, Cu: 0% to 1.0%, Ni: 0% to 1.0%, B: 0% to 0.0100%, Mg: 0% to 0.05%, Ca : 0% to 0.05%, REM: 0% to 0.05%,
Bi: 0% to 0.05%, Si: 0% to 2.00%, P: 0.03% or less, S: 0.010% or less, N: 0.010% or less, and the balance: Fe and The steel plate as described in any one of <1>-<3> which has a chemical composition which consists of impurities.
<5> The aluminum coating layer has an aluminum plating layer and an intermetallic compound layer, the average thickness of the aluminum plating layer is 8 μm to 35 μm, and the average thickness of the intermetallic compound layer is 3 μm to 10 μm < The steel plate as described in any one of 1>-<4>.
<6> A butt including at least one steel plate according to any one of <1> to <5> and butt welding at least two steel plates via an end portion having the removal portion of the steel plate Welded member.
The hot press-formed article which hot-pressed the butt welding member as described in <7><6>.
The steel pipe welded through the edge part of the open pipe by the steel plate as described in any one of <8><1>-<5>.
<9> A hollow quench-formed article obtained by quenching the steel pipe according to <8>.
It is a manufacturing method of the steel plate as described in any one of <10><1>-<5>, Comprising: The manufacturing method of the steel plate which has the process of forming the said removal part by machining.

  According to the present disclosure, a steel plate and a steel pipe capable of obtaining a butt-welded member which is excellent in static strength of a joint and which is excellent in corrosion resistance after painting around a weld metal portion even after being coated around the weld metal portion. Is provided.

It is a schematic sectional drawing which shows an example of the edge part of the steel plate of this indication. It is a schematic sectional drawing which shows another example of the edge part of the steel plate of this indication. It is an expansion schematic sectional view showing an example of an end of a steel plate of this indication. It is an expansion schematic sectional view showing an example of an end of a steel plate of this indication. It is a schematic sectional drawing which shows another example of the edge part of the steel plate of this indication. It is a schematic sectional drawing which shows another example of the edge part of the steel plate of this indication. NO. FIG. 5 is an enlarged schematic cross-sectional view showing an end of a steel plate of No. 2; NO. FIG. 5 is an enlarged schematic cross-sectional view showing an end of a steel plate of No. 3; NO. FIG. 6 is an enlarged schematic cross-sectional view showing an end of a steel plate of No. 4; NO. It is an expanded sectional view showing the end of a steel plate of 5. NO. It is an expanded sectional view showing an end of a 6 steel plate. NO. It is an expanded sectional view showing an end of a 7 steel plate. NO. It is an expanded sectional view showing the end of a steel plate of eight.

Hereinafter, an example of a desirable mode of the present disclosure will be described in detail.
In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.
In the present specification, the content of the component (element) may be described as, for example, the amount of C in the case of the content of C (carbon). Moreover, it may be similarly described about content of another element.
In the present specification, the term "process" is not limited to an independent process, and may be used in this term if the intended purpose of the process is achieved even if it can not be clearly distinguished from other processes. included.

As used herein, the term "aluminum coating layer" refers to the entire aluminum plating applied to both sides of a base steel plate. That is, the aluminum coating layer represents the whole of the aluminum plating layer and the intermetallic compound layer.
In the present specification, the term "intermetallic compound layer" refers to a layer of an intermetallic compound formed between the base steel plate and the aluminum plating when the aluminum plating is performed on both sides of the base steel plate. .
In the present specification, the term "aluminum plating layer" refers to a region of the aluminum plating applied on the base steel plate except the intermetallic compound layer.
In the present specification, the term "cross section" of a steel plate refers to a cross section cut in the thickness direction.

<Steel plate>
The steel plate of the present disclosure has a base steel plate and an aluminum coating layer provided on both sides of the base steel plate.
In addition, the aluminum coating layer is formed on at least a part of both sides of the end portion located at the periphery, the removed part from which at least a part of the aluminum coating layer has been removed, and the region on the center side of the steel plate than the removed part. Remaining remaining parts are formed.
Then, when the boundary between the removed portion and the remaining portion is viewed from the cross section, the aluminum coating layer on the outer surface side of the boundary has a portion with the shortest removal width, and the boundary is more than the aluminum coating layer outer surface side A part having the longest removal width is provided on a part of the base steel plate side.
The shape of the steel plate is not particularly limited.

FIG. 1 is a schematic cross-sectional view showing an example of an end portion of a steel plate of the present disclosure. Moreover, FIG. 2 is a schematic sectional drawing which shows another example of the edge part of the steel plate of this indication.
1 and 2, 100 indicates a steel plate, 12 indicates a base steel plate, 14 indicates an aluminum plating layer, 16 indicates an intermetallic compound layer, 18 indicates an aluminum coating layer, 22 indicates a removed portion, and 26 indicates a remaining portion.
100A is the end face of the steel plate, 100B is the portion with the shortest removal width at the boundary between the removal portion 22 and the remaining portion 26, and 100D is the portion with the longest removal width at the boundary between the removal portion 22 and the remaining portion 26. Show. In FIGS. 1 and 2, the shortest removal width 100B at the boundary between the removed portion 22 and the remaining portion 26 is at the edge on the outer surface side of the aluminum coating layer at the boundary between the removed portion 22 and the remaining portion 26. positioned.

  As shown in FIG. 1, in the steel plate 100 of the present disclosure, an aluminum coating layer 18 is formed on both sides of a base steel plate 12. Further, the aluminum coating layer 18 has an aluminum plating layer 14 formed on both sides of the steel plate, and an intermetallic compound layer 16 formed between the base steel plate 12 and the aluminum plating layer 14.

Further, as shown in FIGS. 1 and 2, at the end of the steel plate 100, the removal portion 22 is formed on both surfaces, and the remaining portion 26 is formed in a region on the center side of the steel plate with respect to the removal portion 22. .
Furthermore, as shown in FIG. 1 and FIG. 2, when the boundary between the removal portion 22 and the remaining portion 26 is viewed from the cross section, the boundary between the removal portion 22 and the remaining portion 26 is the boundary between the removal portion 22 and the remaining portion 26. The portion 100B with the shortest removal width at the boundary protrudes toward the end face 100A of the steel plate. Further, the boundary extends from the portion 100B having the shortest removal width of the boundary toward the portion 100D having the longest removal width of the boundary. And the cross-sectional shape of this boundary inclines in the remaining part 26 side, and has a concave shape. Specifically, the boundary (that is, the end surface of the remaining portion 26) is provided on the outer surface side of the aluminum coating layer, and a protruding portion (for example, a protruding portion having 100B as a top) protruding to the end surface side of the steel plate Further, it is provided closer to the base steel plate side, and has a recessed portion (for example, a recessed portion whose bottom is 100D) which is recessed toward the center side of the steel plate. That is, the boundary between the removed portion 22 and the remaining portion 26 has the portion 100B where the aluminum coating layer outer surface side of the boundary has the shortest removal width, and is the closest to the base steel plate side than the aluminum coating layer outer surface side of the boundary. It is formed to have a portion 100D with a long removal width.

  In addition, as the steel plate of this indication is shown in FIG. 1, in the removal part 22 of the edge part of a steel plate, at least one part of the base material steel plate 12 may be removed with the aluminum coating layer 18. FIG. Further, as shown in FIG. 2, although the aluminum coating layer 18 is removed, the base steel plate 12 may not be removed.

  FIG. 3 is an enlarged schematic cross-sectional view showing an example of the end portion of the steel plate of the present disclosure. In FIG. 3, D represents the removal depth. Also, W1 represents the removal width at the edge on the outer surface side of the aluminum coating layer of the boundary, and W2 represents the removal width on the base steel plate side of the edge at the outer surface side of the aluminum coating layer at the boundary.

The removal depth represents the depth in the vertical direction from the virtual line obtained by extending the surface on the outer surface side of the aluminum plating layer (the surface of the aluminum coating layer) in the direction of the end face of the steel plate to the surface of the base steel plate.
Further, the removal width represents the length in the vertical direction from the imaginary line obtained by extending the end face of the steel plate in the thickness direction to the boundary between the removal portion and the remaining portion.

Here, referring to FIG. 3, the removal depth D is a base material steel plate from an imaginary line in which the surface of the outer surface side (the outer surface side of the aluminum plating layer 14) of the aluminum coating layer 18 is extended in the direction of the end face 100A of the steel plate. Represents the vertical depth to the surface of the.
Further, as shown in FIG. 3, the removal width has a removal width W1 and a removal width W2.
The removal width W1 represents the vertical length from the imaginary line obtained by extending the end face 100A of the steel plate in the plate thickness direction to the shortest removal width portion 100B on the outer surface of the aluminum coating layer at the boundary. That is, from the imaginary line obtained by extending the end face 100A of the steel plate in the thickness direction, the protrusion formed on the end face of the steel plate provided on the outer surface of the aluminum coating layer at the boundary protrudes most to the end face of the steel plate The vertical length to the part (in FIG. 3, the protrusion with 100B at the top) is shown.
The removal width W2 is the vertical length from the imaginary line obtained by extending the end face 100A of the steel plate in the plate thickness direction to the longest removal width 100D on the base steel plate side of the boundary from the outer surface of the aluminum coating layer. It represents. That is, from an imaginary line obtained by extending the end face 100A of the steel plate in the thickness direction, a portion of the depressions recessed toward the center side of the steel plate is provided closer to the base steel plate than the protruding portion (In FIG. 3, the vertical length to the concave part which makes 100D a bottom part) is represented.
That is, as shown in FIG. 3, in the steel plate of the present disclosure, the shortest removal width W1 is a part of the aluminum coating layer outer surface side of the boundary when the boundary between the removed portion 22 and the remaining portion 26 is viewed from the cross section. Existing. Further, the longest removal width W2 is present at a part closer to the base steel plate than the portion which becomes the shortest removal width W1.
In FIG. 3, the portion 100B having the shortest removal width at the boundary between the removal portion 22 and the remaining portion 26 is located at the edge on the outer surface side of the aluminum coating layer at the boundary between the removal portion 22 and the remaining portion 26. There is. Further, the portion 100D having the longest removal width is located at the edge on the base steel plate side at the boundary between the removed portion 22 and the remaining portion 26.

As mentioned above, although an example of an end of a steel plate of this indication was explained with reference to Drawing 1-Drawing 3, a steel plate of this indication is not limited to these. In FIGS. 1 to 3, the shortest removal width portion 100 B of the boundary is shown at the position of the edge on the surface side of the aluminum coating layer at the boundary between the removal portion and the remaining portion. It is not something that can be done. The shortest removal width portion 100B of the boundary may be formed around the edge on the surface side of the aluminum coating layer. That is, in FIG. 1 to FIG. 3, the portion 100 B which is the longest removal width of the boundary (in FIG. 1 to FIG. 3, the position of the edge on the outer surface side of the aluminum coating layer at the boundary between the removed portion 22 and the remaining portion 26) is The tip is formed in a pointed shape, but may be round or angular.
Further, in FIGS. 1 to 3, the portion 100 D having the longest removal width of the boundary is shown at the position of the base steel plate which is the end edge on the base steel plate side at the boundary between the removed portion 22 and the remaining portion 26 However, it is not limited to this part. The longest removal width portion 100D of the boundary may be the central portion of the boundary (for example, any portion of the aluminum coating layer 18).

  DESCRIPTION OF RELATED ART Conventionally, the tailored blank material which butt-welded the steel plate in which metal plating which mainly contains aluminum was given was welded by welding methods, such as laser welding and plasma welding, is known. In this tailored blank material, a large amount of aluminum resulting from the aluminum plating may be mixed into the weld metal portion. When the tailored blank material obtained in this manner is hot-stamped, the weld metal portion of the butt weld portion may be softened and the static strength may be reduced. For example, in the hot stamped molded article after the hot stamping, as a result of tensile strength test of the part including the weld metal part, an example in which fracture occurs in the weld metal part is also reported.

  In the point which avoids breakage of a weld metal part, for example, in patent documents 1, the aluminum plating layer of a welding plan part to be welded is removed, and it is considered as a steel plate which made an intermetallic compound layer remain. A butt welded tailored blank is disclosed.

  However, when a hot stamped product using a tailored blank disclosed in Patent Document 1 is coated, the post-paint corrosion resistance around the weld metal portion is low.

  In the steel plate disclosed in Patent Document 1, the shape of the boundary between the portion in which the intermetallic compound layer remains and the portion in which the aluminum plating layer is not removed is formed in the direction along the thickness direction. Therefore, a tailored blank material is formed from the steel plate disclosed in Patent Document 1, and in the hot stamped molded product using this tailored blank material, the portion where the aluminum plating layer is not removed is the intermetallic compound layer left. It does not cover the surface. Furthermore, the thickness of the remaining intermetallic compound layer is thin. Due to these, when the steel plate disclosed in Patent Document 1 is used, it is considered that the corrosion resistance after coating around the weld metal part is inferior.

  Moreover, in patent documents 2-patent document 6, in the welding plan part welded, the whole aluminum coating layer is removed and it is set as the steel plate which exposed the base material steel plate. And the tailored blank material which butt-welded the edge part of the welding plan part of this steel plate is disclosed.

  However, when painting is performed on a hot stamped molded article using a tailored blank material disclosed in Patent Literature 2 to Patent Literature 6, the post-painting corrosion resistance around the weld metal portion is low.

  In the steel plate disclosed in Patent Literature 2 to Patent Literature 6, the shape of the boundary between the portion where the base steel plate is exposed and the portion where the aluminum coating layer is not removed is 1) a direction along the thickness direction, or 2) The base steel plate side of this boundary is formed to be inclined to the end face side of the steel plate. Therefore, when the steel plates disclosed in Patent Literature 2 to Patent Literature 6 are used, a portion where the aluminum coating layer is not removed does not cover the surface of the portion where the base steel plate is exposed due to the shape of these boundaries. Thus, the base steel plate remains exposed in the portion where the base steel plate is exposed. As a result, it is considered that the hot stamped steel products using the steel plates disclosed in Patent Literature 2 to Patent Literature 6 have low post-paint corrosion resistance around the weld metal portion.

On the other hand, Patent Document 7 discloses a pipe forming method in which a plating metal is polished and removed by spraying a liquid containing abrasive grains.
However, in the technique disclosed in Patent Document 7, the removal of the plating metal formed on the plated steel plate is performed by spraying a liquid containing abrasive grains. Therefore, it is difficult to control the shape of the boundary between the portion from which the plating metal is removed and the portion not to be removed. As a result, in the pipe after pipe formation, the surface of the portion from which the plating metal is removed is not covered by the portion from which the plating metal is not removed, and the post-painting corrosion resistance around the weld is considered to be inferior.

  On the other hand, in the steel plate of the present disclosure, when the boundary between the removed portion and the remaining portion is viewed from the cross section, the outer surface of the aluminum coating layer at the boundary has a portion with the shortest removal width. In addition, there is a portion with the longest removal width on the base steel plate side than the portion with the shortest removal width. Since the shape of the boundary between the removal portion and the remaining portion is formed in such a shape, in the hot stamped molded product obtained from the steel plate of the present disclosure, the remaining portion is a part of the surface of the removal portion It is possible to cover the periphery of the boundary with the part). It is considered that this is caused, for example, by the heat when hot stamping is performed to melt the aluminum component of the remaining part and cover a part of the surface of the removal part. Therefore, it is considered that the corrosion resistance after coating around the weld metal part is excellent. In addition, at the removal portion, at least a portion of the aluminum coating layer is removed. As a result, the amount of aluminum mixed into the weld metal is reduced, and a decrease in static strength is suppressed. Therefore, it is thought that the tailored blank material which is excellent in the static strength of a joint, and excellent in post-paint corrosion resistance around a welding metal part is obtained by using the steel plate of this indication.

  Hereinafter, the steel plate of the present disclosure will be described.

[Base steel plate]
A base material steel plate is a steel plate before providing an aluminum coating layer. The base steel plate is not particularly limited as long as it is obtained by an ordinary method. The base steel plate may be either a hot rolled steel plate or a cold rolled steel plate. Moreover, the thickness of the base material steel plate may be a thickness according to the purpose, and is not particularly limited. For example, the plate thickness of the base steel plate is a plate thickness of 0.8 mm to 4 mm as the plate thickness of the entire steel plate after the aluminum coating layer is provided, and a plate of 1 mm to 3 mm Thickness is mentioned.

  Examples of base steel sheet include, for example, various mechanical deformation and fracture properties such as high mechanical strength (e.g., tensile strength, yield point, elongation, squeezing, hardness, impact value, fatigue strength, etc.) It is good to use a steel plate formed to have a meaning.

As an example of a preferable chemical composition of a base material steel plate, the following chemical compositions are mentioned, for example.
C: 0.02% to 0.58%, Mn: 0.20% to 3.00%, Al: 0.005% to 1.00%, Ti: 0% to 0.20% by mass% Nb: 0% to 0.20%, V: 0% to 1.0%, W: 0% to 1.0%, Cr: 0% to 1.0%, Mo: 0% to 1.0%, Cu: 0% to 1.0%, Ni: 0% to 1.0%, B: 0% to 0.0100%, Mg: 0% to 0.05%, Ca: 0% to 0.05%, REM: 0% to 0.05%, Bi: 0% to 0.05%, Si: 0% to 2.00%, P: 0.03% or less, S: 0.010% or less, N: 0. 010% or less, and the balance: having a chemical composition of Fe and impurities.
In addition, "%" which shows content of a component (element) hereafter means "mass%."

(C: 0.02% to 0.58%)
C is an important element that enhances the hardenability of the steel sheet and mainly determines the strength after hardening. Further lowering the _three points A, it is an element which promotes lowering the quenching temperature. If the amount of C is less than 0.02%, the effect may not be sufficient. Therefore, the C content is preferably 0.02% or more. On the other hand, when the amount of C exceeds 0.58%, the toughness of the quenched portion significantly deteriorates. Therefore, the amount of C is preferably 0.58% or less. Preferably it is 0.45% or less.

(Mn: 0.20% to 3.00%)
Mn is a very effective element for enhancing the hardenability of the steel sheet and for stably securing the strength after hardening. If the Mn content is less than 0.20%, the effect may not be sufficient. Therefore, the Mn content is preferably 0.20% or more. Preferably, it is 0.80% or more. On the other hand, when the amount of Mn exceeds 3.00%, the effect is not only saturated, but it may be difficult to secure stable strength after quenching. Therefore, the Mn content is preferably 3.00% or less. Preferably it is 2.40% or less.

(Al: 0.005% to 1.00%)
Al functions as a deoxidizing element and has the effect of improving the integrity of the steel sheet. If the amount of Al is less than 0.005%, it may be difficult to obtain the above effects. Therefore, the amount of Al is preferably 0.005% or more. On the other hand, if the amount of Al is more than 1.00%, the effect by the above-mentioned action is saturated, which is disadvantageous in cost. Therefore, the Al content is preferably 1.00% or less.

(Ti: 0% to 0.20%, Nb: 0% to 0.20%, V: 0% to 1.0%, W: 0% to 1.0%)
Ti, Nb, V, and W are elements which promote the mutual diffusion of Fe and Al in the aluminum plating layer and the base steel plate. Therefore, at least one of Ti, Nb, V, and W may be contained in the base steel plate. However, if 1) the amount of Ti and Nb exceeds 0.20%, or 2) the amount of V and W exceeds 1.0%, the effect of the above-mentioned action is saturated and the cost is disadvantageous. Therefore, the Ti amount and the Nb amount may be 0.20% or less, and the V amount and the W amount may be 1.0% or less. The amount of Ti and Nb is preferably 0.15% or less, and the amount of V and W is preferably 0.5% or less. In order to obtain the effect by the above action more reliably, it is preferable to set the lower limit of the Ti and Nb amounts to 0.01% or more and the lower limit of the V and W amounts to 0.1% or more.

(Cr: 0% to 1.0%, Mo: 0% to 1.0%, Cu: 0% to 1.0%, Ni: 0% to 1.0%, B: 0% to 0.0100% )
Cr, Mo, Cu, Ni, and B are elements effective to enhance the hardenability of the steel plate and to stably secure the strength after hardening. Therefore, one or more of these elements may be contained. However, even if the content of Cr, Mo, Cu and Ni is more than 1.0% and the content of B is more than 0.0100%, the above effect is saturated and the cost is disadvantageous. Therefore, the content of Cr, Mo, Cu, and Ni may be 1.0% or less. The B content is preferably 0.0100% or less, and more preferably 0.0080% or less. In order to obtain the above effect more reliably, it is preferable to satisfy any of Cr, Mo, Cu, and Ni content of 0.1% or more and B content of 0.0010% or more.

(Ca: 0% to 0.05%, Mg: 0% to 0.05%, REM: 0% to 0.05%)
Ca, Mg and REM have the function of refining the form of inclusions in the steel and preventing the occurrence of cracking at the time of hot stamping due to the inclusions. Therefore, one or more of these elements may be contained. However, if it is added excessively, the effect of refining the form of inclusions in the steel is saturated, and it only causes an increase in cost. Therefore, the amount of Ca is 0.05% or less, the amount of Mg is 0.05% or less, and the amount of REM is 0.05% or less. In order to obtain the effect by the above-mentioned action more certainly, it is preferable to satisfy either the amount of Ca 0.0005% or more, the amount of Mg 0.0005% or more, and the amount of REM 0.0005% or more.

  Here, REM refers to a total of 17 elements of Sc, Y and a lanthanoid, and the content of the REM indicates the total content of these elements. In the case of lanthanides, it is industrially added in the form of misch metal.

(Bi: 0% to 0.05%)
Bi is an element having a function of suppressing segregation such as Mn which segregates in the secondary dendrite arm spacing by becoming secondary cores during the solidification process of the molten steel and reducing the secondary arm spacing of the dendrite. Therefore, Bi may be contained. In particular, in a steel plate which often contains a large amount of Mn, such as a steel plate for hot stamping, Bi is effective in suppressing the deterioration of the toughness caused by the segregation of Mn. Therefore, it is preferable to contain Bi in such a steel grade. However, even if the content of Bi exceeds 0.05%, the effect by the above action is saturated, resulting in an increase in cost. Therefore, the amount of Bi is set to 0.05% or less. Preferably it is 0.02% or less. In addition, in order to acquire the effect by the above-mentioned effect more certainly, it is preferred to make the amount of Bi into 0.0002% or more. More preferably, it is 0.0005% or more.

(Si: 0% to 2.00%)
Si is a solid solution strengthening element, and can be effectively used up to 2.00%. However, if Si is contained in excess of 2.00%, there is a concern that a defect may occur in the plating property. Therefore, when Si is contained, the amount of Si is preferably 2.00% or less. The upper limit is preferably 1.40% or less, more preferably 1.00% or less. The lower limit is not particularly limited, but is preferably 0.01% or more in order to more reliably obtain the effect by the above-mentioned action.

(P: 0.03% or less)
P is an element contained as an impurity. If P is contained in excess, the toughness of the steel sheet tends to be reduced. Therefore, the P amount is preferably 0.03% or less. Preferably it is 0.01% or less. The lower limit of the amount of P does not have to be particularly defined, but is preferably 0.0002% or more from the viewpoint of cost.

(S: 0.010% or less)
S is an element contained as an impurity, forms MnS, and has an effect of embrittling a steel plate. Therefore, the S amount is preferably 0.010% or less. A more desirable S amount is 0.004% or less. The lower limit of the amount of S need not be particularly defined, but is preferably 0.0002% or more from the viewpoint of cost.

(N: 0.010% or less)
N is an element which is contained as an impurity, forms inclusions in the steel and degrades the toughness after hot stamping. Therefore, the N amount is preferably 0.010% or less. Preferably it is 0.008% or less, More preferably, it is 0.005% or less. The lower limit of the amount of N does not have to be particularly defined, but is preferably 0.0002% or more from the viewpoint of cost.

(The rest)
Fe and impurities. Here, the term "impurity" refers to a component contained in a raw material such as ore or scrap, or a component mixed in the process of production, and refers to a component which is not intentionally contained in a steel plate.

[Aluminum coating layer]
The aluminum coating layer is composed of an aluminum plating layer formed on the outer surface side of the steel plate, and an intermetallic compound layer formed between the base steel plate and the aluminum plating layer.

  The method of forming the aluminum coating layer is not particularly limited. For example, the aluminum coating layer may be formed on both sides of the base steel plate by a hot-dip plating method in which the base steel plate is immersed in a molten metal bath mainly containing aluminum to form an aluminum coating layer.

(Aluminum plating layer)
An aluminum plating layer is a plating layer which has aluminum as a main, and should just contain aluminum 50 mass% or more. Depending on the purpose, it may contain an element other than aluminum (e.g., Si etc.), or it may contain an impurity mixed in the process of production or the like. Specifically, the aluminum plating layer may have, for example, a chemical composition containing 5% to 12% of Si (silicon) by mass%, with the balance being aluminum and impurities. In addition, the composition may contain 5% to 12% of Si (silicon), 2% to 4% of Fe (iron) by mass%, and the balance may have a chemical composition of aluminum and impurities.
When Si is contained in the above-mentioned range, deterioration in processability and corrosion resistance can be suppressed. In addition, the thickness of the intermetallic compound layer can be reduced.

  The thickness of the aluminum plating layer is not particularly limited in the region other than the end portion of the steel plate, but for example, it may be in the range of 8 μm to 35 μm in average thickness, and in the range of 15 μm to 30 μm. preferable. In addition, the thickness of the aluminum plating layer represents the average thickness in the area | region by the side of the center of a steel plate.

  The aluminum plating layer prevents corrosion of the steel plate. Moreover, when processing a steel plate by a hot stamp, an aluminum plating layer prevents generation | occurrence | production of the scale (compound of iron) by the surface being oxidized, even if it is heated by high temperature. In addition, the aluminum plating layer has a boiling point and a melting point higher than those of the plating coating with an organic material and the plating coating with another metal material (for example, a zinc material). Therefore, when forming by hot stamping, the coating does not evaporate, so the surface protection effect is high.

  The aluminum plating layer can be alloyed with iron (Fe) in the steel sheet by heating at the time of hot-dip plating and hot-dip plating. Therefore, the aluminum plating layer is not necessarily formed as a single layer having a constant component composition, but includes a partially alloyed layer (alloy layer).

(Intermetallic compound layer)
The intermetallic compound layer is a layer formed at the boundary between the base steel plate and the aluminum plating layer when the base steel plate is subjected to aluminum plating. Specifically, the intermetallic compound layer is formed by the reaction of iron (Fe) of a base steel plate and a metal containing aluminum (Al) in a molten metal bath mainly containing aluminum. Intermetallic compound layer is formed of a plurality of kinds of mainly Fe x _{Al y (x,} y is 1 or more) is represented by compounds. If the aluminum plating layer containing Si (silicon) is, _Fe x Al _y and _{Fe x Al y Si z (x} , y, z is 1 or more) is formed by a plurality of kinds of compounds represented by.

  The thickness of the intermetallic compound layer is not particularly limited in the region other than the end portion of the steel plate, but for example, it is preferably in the range of 3 μm to 10 μm in average thickness, and in the range of 4 μm to 8 μm Is preferred. In addition, the thickness of the intermetallic compound layer represents the average thickness in the area | region by the side of the center of a steel plate. The thickness of the intermetallic compound layer can be controlled by the temperature and immersion time of the molten metal bath mainly containing aluminum.

  Here, about confirmation of a base material steel plate, an intermetallic compound layer, and an aluminum plating layer, and measurement of the thickness of an intermetallic compound layer and an aluminum plating layer, it performs by the following methods.

  Cutting is performed so that the cross section of the steel plate is exposed, and the cross section of the steel plate is polished. The section of the polished steel plate is subjected to line analysis from the surface of the steel plate to the base steel plate by an electron probe microanalyzer (FE-EPMA) to measure the aluminum concentration and the iron concentration. The measurement conditions may be an acceleration voltage of 15 kV, a beam diameter of about 100 nm, an irradiation time of 1000 ms per point, a measurement pitch of 60 nm, and a measurement distance such that the thickness of the plating layer can be measured. It is about 80 μm. The thickness of the base steel plate is preferably measured by an optical microscope.

As a measured value of the aluminum concentration of the cross section of the steel plate, the region where the aluminum (Al) concentration is less than 2 mass% is judged as the base steel plate, and the region where the aluminum concentration is 2 mass% or more as the intermetallic compound layer or the aluminum plating layer Do. Further, in the intermetallic compound layer and the aluminum plating layer, a region having an iron (Fe) concentration of more than 4% by mass is judged as an intermetallic compound layer, and a region having an iron concentration of 4% by mass or less is judged as an aluminum plating layer.
In addition, let the distance of the boundary from the boundary of a base material steel plate to an aluminum plating layer be the thickness of an intermetallic compound layer. Moreover, let the distance from the boundary of the intermetallic compound layer to the steel plate surface in which the aluminum plating layer was formed be the thickness of an aluminum plating layer. And the sum total of the thickness of the intermetallic compound layer and the thickness of the aluminum plating layer is the thickness of the aluminum coating layer.

The thickness of the aluminum plating layer and the thickness of the intermetallic compound layer are line-analyzed from the surface of the steel plate to the surface of the base steel plate (the boundary between the base steel plate and the intermetallic compound layer) and measured as follows.
The thickness of the aluminum plating layer is determined at any five positions from the surface of the steel plate having the aluminum plating layer to the intermetallic compound layer in accordance with the aforementioned judgment standard. And let the average value of the calculated | required value be the thickness of an aluminum plating layer.
The thickness of the intermetallic compound layer is the thickness from the boundary between the intermetallic compound layer and the aluminum plating layer to the boundary between the intermetallic compound layer and the base steel plate in any five positions according to the aforementioned judgment criteria. Ask. And let the average value of the calculated | required value be the thickness of the intermetallic compound layer.

[End of steel plate]
The steel plate of the present disclosure has a removal portion in which at least a portion of the aluminum coating layer is removed on at least a portion of both sides of the end portion positioned around the steel plate. Moreover, it has the remaining part in which the aluminum coating layer remains in the area | region of the center side of a steel plate rather than the removal part.

(Removal unit)
The removal part is formed on both sides of the end scheduled to weld the steel plate. Moreover, the removal part is formed in the end surface side of a steel plate rather than the remaining part. That is, the removal part is formed in the range from the edge of the end face of the steel plate to the remaining part at the end where welding is planned.

  The removal portion has the shortest removal width (hereinafter sometimes simply referred to as “removal width W1”) on the outer surface side of the aluminum coating layer of the boundary when the boundary between the removal portion and the remaining portion is viewed from the cross section It has a part. Further, there is a portion on the base steel plate side closer to the outer surface side of the aluminum coating layer at the boundary, which has a longest removal width (hereinafter, may be referred to simply as “removal width W2”).

The removal width W1 is preferably 0.2 mm to 5.0 mm on average. When the butt welding is laser welding, it is preferably 0.6 mm to 1.5 mm. When the butt welding is plasma welding, it is preferably 1.0 mm to 4.0.
The removal width W2 is preferably 0.3 mm to 5.1 mm on average. When the butt welding is laser welding, it is preferably 0.7 mm to 1.6 mm. When the butt welding is plasma welding, it is preferably 1.1 mm to 4.1.

  In addition, the removal depth D may be 15 μm to 200 μm in consideration of the static strength of the joint. The lower limit of the removal depth D may be 20 μm or more, or 25 μm or more. The upper limit of the removal depth D may be 150 μm or less, 120 μm or less, or 100 μm or less.

Here, the following methods may be mentioned as methods of measuring the removal depth D and the removal width W1 and the removal width W2 from the tailored blank material and the hot stamped molded article.
In a tailored blank and a hot stamped molded product, a steel plate having a removed portion adjacent to a weld metal portion is cut in the thickness direction, and the cut cross section is observed with a scanning electron microscope (SEM: Scanning Electron Microscope). Referring to FIG. 3, distances corresponding to W1, W2, and D in FIG. 3 may be measured.

Moreover, the measurement of the removal width W1 and the removal width W2 is an average value which observed the removal part by SEM and was measured at arbitrary five cross sections. The method of measuring the width of the exposed portion is as follows.
It cuts so that the cross section of a steel plate is exposed, embeds in resin, polishes, and it expands the cross section with SEM. Then, based on an imaginary line extending in a direction along the thickness direction from the end face of the steel plate, the distance from the imaginary line to the edge of the surface of the aluminum plating layer is measured and taken as a removal width W1. Further, the distance from this virtual line to the portion of the boundary between the removal portion and the remaining portion which is the longest removal width is measured, and this is taken as the removal width W2.

(Remaining part)
The remaining portion is a portion where the aluminum coating layer is not removed at the end where welding of the steel plate is scheduled, and is formed in a region on the center side of the steel plate than the removed portion.

  In the cross section of the steel plate, of the remaining part, a region on the end face side of the steel plate (that is, surrounded by the boundary and the imaginary line) than a virtual line extending in a direction along the thickness direction The remaining portion in the region) may have an area centroid of less than 50% of the thickness of the aluminum coating layer. When the gravity center of the area of the remaining portion in this region is less than 50% with respect to the thickness of the aluminum coating layer, the post-painting corrosion resistance around the weld metal portion becomes more excellent. The smaller the area center of gravity is preferable in that the post-painting corrosion resistance around the weld metal part is made better. Therefore, the area gravity center may be 45% or less, or 35% or less. The lower limit value is not particularly limited, but may be, for example, 25% or more in terms of facilitating retention of the shape of the remaining portion in this region.

  Here, with reference to FIG. 4, an area gravity center of the remaining portion in the vicinity of the boundary between the removed portion and the remaining portion will be described. FIG. 4 is an enlarged schematic cross-sectional view showing an example of the end portion of the steel plate, and shows the vicinity of the boundary between the removed portion and the remaining portion. In FIG. 4, the portion 100B having the shortest removal width at the boundary between the removal portion 22 and the remaining portion 26 is located at the edge on the outer surface side of the aluminum coating layer at the boundary between the removal portion 22 and the remaining portion 26. There is. Further, the portion 100D having the longest removal width is located at the edge on the base steel plate side at the boundary between the removed portion 22 and the remaining portion 26.

The area gravity center y is determined as follows. First, at the boundary between the removal portion 22 and the remaining portion 26, an imaginary line extending in the direction along the thickness direction is drawn from the portion 100D having the removal width W2 (the longest removal width). The distance in the vertical direction from the imaginary line to the portion 100B where the shortest removal width W1 (shortest removal width) of the boundary between the removal portion 22 and the remaining portion 26 is a is a. In this imaginary line, the boundary between the removed portion 22 and the remaining portion 26 from the boundary between the base steel plate 12 and the aluminum coating layer 18 (that is, the boundary between the base steel plate 12 and the intermetallic compound layer 16). The distance in the vertical direction up to is b. Furthermore, the total thickness of the aluminum coating layer 18 is h. At this time, the end face of the steel plate than the imaginary line extending in the direction along the thickness direction from the remaining portion in the region surrounded by the boundary between the removal portion 22 and the remaining portion 26 and the imaginary line The area gravity center y of the remaining part located in the side area is expressed by the following equation.
(Formula) y = (h (a + 2b)) / (3 (a + b))
The above equation is applied, for example, when obtaining the area gravity center y in the case of a shape (including a triangle) belonging to a trapezoid as shown in FIG. 4.

  In order to make the post-painting corrosion resistance of the weld metal portion more excellent, a should be 150 μm or less, and 100 μm or less. In addition, b is preferably 80 μm or less and 40 μm or less from the same point.

  In the case where the cross-sectional shape of the boundary between the removed portion and the remaining portion is a shape other than a shape belonging to a trapezoid such as non-linear or zigzag, it becomes difficult to calculate the geometrical cross-sectional center of gravity. Therefore, when the cross-sectional shape at the boundary between the removed portion and the remaining portion is such a shape, the area gravity center y may be calculated by image processing from the cross-sectional observation photograph.

  In addition, what is necessary is just to obtain | require the measurement of the thickness h of said aluminum coating layer by the cross-sectional observation photograph by SEM. Moreover, what is necessary is just to measure the said measuring method of the distance a and the distance b by the cross-sectional observation photograph by SEM.

  In the steel plate of the present disclosure, at the end of the portion to be welded, at least the removed portion from which the aluminum coating layer is removed is formed. If there is more aluminum coating layer remaining in the removal width W1 range (specifically, the area on the end face side of the steel plate than the top of the protruding part provided on the outer surface side of the aluminum coating layer in the removal part) The amount of aluminum mixed into the metal increases and the static strength becomes inferior. In this respect, for example, as shown in FIGS. 1 and 2, the removal portion may be removed so as to have an exposed portion to which the base steel plate is exposed.

  In the removal portion within the range of the removal width W1, the outer surface of the removal portion facing in the thickness direction may be inclined with respect to the surface direction of the base steel plate in the region on the center side of the steel plate. Moreover, the direction parallel to the surface of the base material steel plate in the area | region of the center side of a steel plate may be sufficient. The outer surface of the removal portion in the range of removal width W1 facing the thickness direction is a direction along the direction parallel to the surface of the base steel plate on the center side of the steel plate in that the corrosion resistance after painting around the weld metal portion is excellent. It is good. In addition, the removal width W2 is preferably present at the edge on the base steel plate side of the boundary (for example, at the position 100D shown in FIG. 1 and FIG. 2) in terms of excellent post-painting corrosion resistance around the weld metal part. .

Here, from the point of corrosion resistance after coating around the weld metal part, the angle formed by the following imaginary line A and the following imaginary line B, and the angle at the remaining part side may be in the following range. This angle may be greater than 90 °. Also, specifically, this angle may be in the range of 100 ° to 150 °. The lower limit is preferably 120 ° or more, and more preferably 125 ° or more. The upper limit is preferably 135 ° or less and 140 ° or less.
For example, referring to FIG. 2, this angle is an angle formed by the surface of the base steel plate 12 and the boundary between the removed portion 22 and the remaining portion 26, and represents the angle formed on the remaining portion 26 side.
Virtual line A: A virtual line in the direction along the surface of the base steel plate in the remaining portion.
An imaginary line B: a portion having the shortest removal width on the outer surface side of the aluminum coating layer at the boundary between the removed portion and the remaining portion (a protrusion provided on the outer surface side of the aluminum coating layer at the boundary and protruding to the end surface of the steel Among them, a portion which most protrudes to the end face side of the steel plate), and a portion where the longest removal width on the side of the base steel plate is more than the outer surface side of the aluminum coating layer at the boundary (a virtual line From the above, an imaginary line connecting the most concave portion of the steel plate to the center side of the steel plate, which is provided on the base steel plate side with respect to the protruding portion and is recessed to the center side of the steel plate.

  When the portion with the shortest removal width at the boundary between the removal portion and the remaining portion is a continuous portion, the portion on the outermost surface side of the aluminum coating layer is adopted as the shortest removal width. Also, in the case where the longest removal width of the above-mentioned boundary has, for example, a plurality of places or continuous locations, the outermost surface side in the thickness direction is adopted as the longest removal width. It shall be.

  In addition, if it is a range which a fracture does not produce in a weld metal part when it is considered as a tailored blank material and a hot stamped molded article, at least a part of aluminum coating layer remains within the range of removal width W1. There may be cases. Specifically, the following relationship may be satisfied as an acceptable range of at least a part of the aluminum coating layer. The ratio of the cross-sectional area Sp to the cross-sectional area Sb when the cross-sectional area of the half of the plate thickness of the base steel plate is Sb and the cross-sectional area of the remaining aluminum coating layer is Sp within the range of the removal width W1 / Sb) should be in the range of 3.5% or less. The ratio of Sp / Sb is preferably smaller, and may be 2.0% or less, or 1.0% or less.

  The method of measuring the cross-sectional area Sb of the half thickness of the base steel plate and the cross-sectional area Sp of the remaining aluminum coating layer in the range of the removal width W1 may be measured by a cross-sectional observation photograph by SEM.

  Here, referring to FIG. 5, at the end of the steel plate shown in FIG. 5, the intermetallic compound layer 16 remains in the removing portion 22. (Sp / Sb) in the range on the end face 100A side of the steel plate (that is, within the removal width W1) of the shortest removal width 100B on the outer surface side of the aluminum coating layer at the boundary between the removal portion 22 and the remaining portion 26 The intermetallic compound layer 16 may remain in the removal portion 22 if the content of the intermediate layer 16 is 3.5% or less. For example, when the thickness of the base steel plate 12 is 1.6 mm and the thickness of the remaining intermetallic compound layer 16 is 20 μm at the end of the steel plate shown in FIG. The ratio of the area Sp (Sp / Sb) is 2.5%.

  Further, referring to FIG. 6, at the end of the steel plate shown in FIG. 6, the removing portion 22 is an exposed portion where the base steel plate is exposed and a remaining portion where at least a portion of the aluminum coating layer 18 remains. And 24. The remaining portion 24 is in a region in contact with the edge of the end face 100A of the steel plate. Ratio of the cross-sectional area Sp to the above-mentioned cross-sectional area Sb in the range of the end face 100A side of the steel plate with respect to the shortest removal width 100B on the outer surface side of the aluminum coating layer at the boundary between the removed portion 22 and the remaining portion 26 (Sp If / Sb) is 3.5% or less, it may have an exposed portion and a remaining portion. In this case, for example, as in the end portion of the steel plate illustrated in FIG. 6, the remaining portion 24 and the remaining portion 26 may be provided apart from each other across the exposed portion.

  In addition, for example, when punching a steel plate to obtain a punching member, sag may occur by a cutting means such as a shear in a region including the edge of the steel plate among the end portions positioned around the steel plate. In the portion where the sag occurs, the thickness of the steel plate gradually decreases toward the edge of the steel plate. Therefore, when the intermetallic compound layer and the aluminum plating layer are removed by cutting, grinding or the like at the end of the steel plate, for example, at least the intermetallic compound layer remains in the portion where the sag occurs. There is something to do. The portion where at least the intermetallic compound layer remains is the remaining portion.

That is, in the present specification, “a removed portion from which at least a part of the aluminum coating layer is removed” has a ratio (Sp / Sb) of the cross-sectional area Sp to the above-described cross-sectional area Sb is 3.5% or less The following forms are concepts included.
(1) It is a form which has only an exposed part which a base material steel plate has exposed, and a form by which at least one copy of a base material steel plate is removed (for example, refer to Drawing 1). Or the form which has an exposed part, but a base-material steel plate is not removed (for example, refer FIG. 2).
(2) A form having a remaining portion in which at least a portion of the aluminum coating layer remains and not having an exposed portion to which the base steel plate is exposed (see, for example, FIG. 5).
(3) A form having both the exposed part and the residual part described above (see, for example, FIG. 6).

Next, an example of the preferable manufacturing method of the steel plate of this indication is demonstrated. An example of a preferred method of manufacturing the steel sheet of the present disclosure includes the step of forming a removal portion. The formation of the removal portion is not particularly limited, and may be either laser processing or mechanical processing. As an example of a more preferable manufacturing method, it has the process of forming a removal part by machining. Hereinafter, an example of the preferable method of removing at least one part of both surfaces of the edge part located around the steel plate about a removal part is demonstrated.
In the following description, as an example, the removal portion will be described taking an example in which only the exposed portion where the base steel plate is exposed is described.

  There is a step of removing the aluminum coating layer formed on both sides of the base steel plate by cutting or grinding at least a part of the end portion located around the steel plate to form an exposed portion where the base steel plate is exposed (It may be referred to as formation method A).

  Formation method A is, for example, a method of forming an exposed portion at the end of a steel plate as follows. First, a steel plate cut to a desired size is prepared as a steel plate before forming a tailored blank material. Next, the aluminum coating layer formed on both sides of the base steel plate is removed by cutting or grinding on at least a part of both sides of the end portion of the steel plate after cutting. And an exposed part is formed in the edge part of a steel plate.

  The method of removal by cutting or grinding is not particularly limited. The method of cutting or grinding may be, for example, a method of machining with a grinding stone, a cutting tool, a slicing machine, an end mill, a metal saw or the like. Furthermore, these methods may be combined to remove the aluminum coating layer to form an exposed portion to which the base steel plate is exposed. The tools used in the machining may be selected so that the boundary between the removal portion and the remaining portion has a desired concave shape.

In addition, removing by laser processing, such as laser gouging, is also mentioned as another method other than machining. However, when forming an exposed portion by laser processing such as laser gouging, heat is applied depending on the heat input to the base steel plate of the portion where the exposed portion is formed due to water vapor in the atmosphere. Hydrogen may be mixed. In addition, when the base steel plate of the portion where the exposed portion is formed is quenched after the laser processing, martensite is generated in the metal structure of the base steel plate of this portion. As a result, delayed fracture may occur at the end face of the steel plate before welding.
On the other hand, when forming an exposed part by machining, the base steel plate of the part in which an exposed part is formed suppresses a temperature rise, and martensite does not arise. In addition, since hydrogen does not enter either, the occurrence of delayed destruction is suppressed. In this respect, as a method for forming the exposed portion, it is preferable to adopt machining cutting or grinding.
Furthermore, when forming an exposed part by machining, there is no need to take measures to shield the laser light when performing laser processing such as laser gouging, which is advantageous in terms of cost and the like.
When the shape of the boundary between the removed portion and the remaining portion is inclined toward the remaining portion by laser processing to form a concave shape, the heat of the laser processing heats the aluminum coating layer. Therefore, the heat of the laser processing may cause the aluminum coating layer to be easily melted, and it may be difficult to control the shape of the boundary to be a concave shape by inclining toward the remaining portion side.

The order of forming the exposed portions at the ends is not limited to the forming method A as long as the exposed portions are formed on at least a part of both surfaces of the ends located around the steel plate.
As an example of another preferable method of forming an exposed part in at least one part of the both surfaces of the edge part located around the steel plate, the following method is mentioned, for example.

  The aluminum plating layer and the intermetallic compound layer formed on both sides of the base steel plate were removed by cutting or grinding in at least a part of the both sides of the steel plate except for the end portion of the steel plate to expose the base steel plate And a step of forming an exposed portion, and cutting the steel plate so that the exposed portion of the base steel plate is at an end portion of the steel plate, and exposing the base steel plate to at least a part of both sides of the end portion of the steel plate. And B. (step of forming method B).

  Specifically, the formation method B is, for example, the following method. First, a punching process is performed to prepare a steel plate cut into a desired size. Next, with respect to the cut steel plate, the aluminum coating layer formed on the base steel plate is removed by cutting or grinding to form an exposed portion in which the base steel plate is exposed. The exposed portion is formed to extend in one direction, for example, in an area other than the end of the steel plate. Then, in the steel plate after cutting, the exposed portion of the base steel plate is cut such that the exposed portion is along the edge of the end face of the steel plate. The steel plate obtained by cutting is a steel plate before forming a tailored blank material.

In the case of the forming method B, among the widths of the exposed portion formed by removing the aluminum coating layer, the removal width (removal width before cutting) when the boundary between the removal portion and the remaining portion is viewed from the cross section is It is good to be a range.
The removal width of the portion where the removal width is the shortest is preferably 0.4 mm to 10.0 mm, and preferably 1.2 mm to 8.0 mm. In addition, the removal width of the portion where the removal width is the longest is preferably 0.6 mm to 10.2 mm, and preferably 1.4 mm to 8.2 mm. The position at which the exposed portion is cut may be cut at a position near the center line of the exposed portion so as to have a target width.

Of the width of the exposed portion of the base steel plate formed by the above formation method A, the removal width of the portion where the removal width is the shortest is the width of the melted region (welded metal portion) after butt welding of the steel plate. 10% to 50% larger than half is good.
Of the width of the exposed portion of the base steel plate before cutting of the steel plate formed as in the above formation method B, the removal width of the portion where the removal width is shortest is the melting range after welding the steel plate (welding 10% to 50% larger than half of the width of the metal part).
Since the mixing of aluminum is suppressed to the weld metal part after butt welding of a steel plate as it is these ranges, the fall of static strength is controlled.

<Butt welding member>
Next, the butt welding member (tailored blank material) will be described.
The tailored blank material is a welded member having at least one steel plate of the present disclosure and having at least two steel plates butt-welded via an end portion having the removal portion of the steel plate of the present disclosure. As long as at least one steel plate of the present disclosure is included, welding may be performed in a state in which the end faces of two steel plates are butted, and welding may be performed in a state in which end faces of three steel plates are butted. For example, the tailored blank material may be a welded member welded in a state in which the end face of the end of the steel plate of the present disclosure having the removal portion and the end face of the end of the welding scheduled portion of another steel plate are butted. In addition, the tailored blank material may be welded, for example, in a state in which the end faces of the end portions having the removal portions in the two steel plates of the present disclosure are butted, the end having the removal portions in the three steel plates of the present disclosure The welding may be performed in a state where the end faces of the parts are butted.

  That is, the tailored blank material includes a steel plate including at least one steel plate of the present disclosure and in which the ends of at least two steel plates are disposed to face each other, and a welded metal portion joining the ends of at least two steel plates. And a weld metal portion provided adjacent to the removal portion of the steel plate of the present disclosure. For example, specifically, the removal portion is provided on both sides of the two steel plates joined by the weld metal portion, which are located around the weld metal portion.

Two or more steel plates for obtaining a tailored blank may be used in combination according to the purpose. As two or more steel plates for obtaining a tailored blank, for example, steel plates of the same strength class may be used, or steel plates of different strength classes may be used. Further, as the two or more steel plates, steel plates having the same thickness may be used, or steel plates having different thicknesses may be used.
Furthermore, two or more steel plates for obtaining a tailored blank material may have the same width as the removal width W1 and the removal width W2 of the removal portion formed at the end of the steel plate, or may be different steel plates. Further, the shape of the boundary between the removed portion and the remaining portion of the steel plate may be the same or different. Furthermore, the aspect of the removal part of a steel plate may be the same steel plate, and a different steel plate may be sufficient. For example, as a combination in which the mode of the removal part of a steel plate differs, the combination of the mode with which a removal part has an exposed portion and a residual part, and the mode with only a removal part is mentioned.

The welding method for performing butt welding is not particularly limited, and examples thereof include laser welding (laser beam welding), arc welding, electron beam welding and the like. Moreover, as arc welding, plasma welding, TIG (Tungsten Inert Gas) welding, MIG (Metal Inert Gas) welding, MAG (Metal Active Gas) welding, etc. may be mentioned, and as suitable arc welding, plasma welding may be mentioned. . The welding conditions may be selected according to the desired conditions such as the thickness of the steel plate used.
Also, welding may be performed while supplying the filler wire, if necessary.

  The tailored blank material performs butt welding in a state where the end faces of the end portion having the removal portion are butted as described above. Therefore, in the weld metal portion, the mixing amount of aluminum resulting from the intermetallic compound layer and the aluminum plating layer is small. Moreover, since the removal part in which the intermetallic compound layer does not exist is adjacent to a welding metal part, the fall of the tensile strength (static strength) of a joint is suppressed.

<Hot pressed parts>
Next, a hot press-formed product (hot stamped product) will be described.
The hot stamped molded article is a molded article obtained by hot stamping a butt-welded member (tailed blank material) having at least one steel plate of the present disclosure. That is, a hot stamped molded product obtained by hot stamping includes at least one steel plate of the present disclosure, and at least two steel plates arranged opposite to each other and an end of at least two steel plates. A weld metal part joining the parts, the weld metal part being provided adjacent to the removed part of the steel plate of the present disclosure. For example, specifically, the removal portion is provided on both sides of the two steel plates joined by the weld metal portion, which are located around the weld metal portion.
The hot stamped molded article is a welded member in which at least two steel plates of the present disclosure are butt-welded through an end portion having a removal portion in terms of static strength of the joint and corrosion resistance after coating around the weld metal portion. It is good that it is a molded article obtained by hot stamping.

The hot stamped article can be manufactured as follows.
First, the tailored blank material is heated to a high temperature to soften the tailored blank material. Then, using a mold, the softened tailored blank material is formed and cooled by a hot stamp, and quenched to obtain a hot stamped article having a desired shape. The hot stamped molded product is quenched by heating and cooling, and a molded product having high tensile strength of, for example, about 1500 MPa or more can be obtained.

  As a heating method at the time of hot stamping, it is possible to adopt a heating method by infrared heating, electric heating, induction heating or the like in addition to a normal electric furnace or radiant tube furnace.

  Hot-stamped articles are converted to intermetallic compounds in which the aluminum-plated layer of the steel sheet provides protection against oxidation of the steel sheet upon heating. For example, when silicon (Si) is contained in the aluminum plating layer as an example, when the aluminum plating layer is heated, the Al phase becomes an intermetallic compound, ie, an Al-Fe alloy phase, by interdiffusion with Fe. , Al-Fe-Si alloy phase. The melting points of the Al-Fe alloy phase and the Al-Fe-Si alloy phase are high, and are 1000 ° C. or more. There are a plurality of types of Al-Fe alloy phase and Al-Fe-Si alloy phase, and when heated at a high temperature or for a long time, it changes to an alloy phase having a higher Fe concentration. These intermetallic compounds prevent the oxidation of the steel sheet.

  The maximum ultimate temperature for hot stamping is not particularly limited, but is preferably 850 ° C. to 1000 ° C., for example. In hot stamping, since the highest ultimate temperature is heated in the austenite region, a temperature of about 900 ° C. to about 950 ° C. is usually adopted in many cases.

  In hot stamping, a tailored blank material heated to a high temperature is press-formed by a mold cooled by water cooling or the like, and simultaneously quenched by cooling by the mold. In addition, water may be directly sprayed onto the blank material from the gaps of the mold as needed, and water cooled. And the hot stamped molded article of the target shape is obtained. The hot stamped molded product may be used as it is as a part, or may be used after being subjected to a descaling treatment such as shot blasting, brushing, laser cleaning or the like on the welded portion as necessary.

  When the tailored blank is heated to a high temperature, the metallographic structure of the base steel plate becomes an austenite single phase structure at least partially, preferably entirely. Thereafter, when press-formed with a mold, the austenite is transformed into at least one of martensite and bainite by cooling under a target cooling condition. And, in the obtained hot stamped molded product, the metallographic structure of the base steel plate is any of martensite, bainite or martensite-bainite.

Here, an example of the process from manufacture of a steel plate to manufacture of a hot stamped molded article is as follows. In addition, the case where a removal part has only the exposed part which a base material steel plate exposes is mentioned as an example, and is demonstrated.
First, an aluminum coating layer is formed on both sides of a base steel plate to obtain a steel plate. At this time, an aluminum plating layer is formed on the base steel plate, and an intermetallic compound layer is formed between the base steel plate and the aluminum plating layer.

  Next, the steel plate subjected to aluminum plating on both sides of the base steel plate is wound into a coil. Next, the steel plate wound in a coil shape is drawn out and subjected to punching processing to obtain a punching member.

The aluminum coating layer is then removed on at least a portion of both sides of the edge located around the steel plate to form an exposed portion of the base steel plate to obtain the steel plate of the present disclosure.
Here, the exposed portion formed at the end of the steel plate may be formed in a state where the steel plate wound in a coil shape is drawn out after the steel plate is wound in a coil shape. In this case, after forming the exposed portion, punching is performed so that the exposed portion is at the end of the steel plate to obtain a punching member.
The exposed portion formed at the end portion of the steel plate may be formed after the steel plate wound in a coil shape is drawn out and the drawn steel plate is punched to form a punched member. In this case, an exposed portion may be formed at the end of the punching member. Further, after forming an exposed area so as to extend in one direction, for example, in a portion other than the end of the punching member, the exposed area of the punching member is cut so that an exposed portion is formed at the end of the steel plate. May be

Next, at least one punching member having an exposed portion formed at the end of the steel plate is prepared. For example, one punching member or two punching members in which the exposed portion is formed may be prepared.
Next, in a state where the end portions of the punching members are butted, butt welding is performed to obtain a tailored blank. Specifically, when two punched members having an exposed portion formed are prepared, butt welding is performed in a state where the end portions having the exposed portion are butted to obtain a tailored blank material.

Next, the tailored blank material is heated in a heating furnace.
Next, the heated tailored blank material is pressed, shaped and hardened by a pair of upper and lower molds.
Then, by removing it from the mold, the intended hot stamped molded article can be obtained.

  Hot-stamped molded articles are useful, for example, for application to various members of industrial machines as well as various automobile members such as automobile bodies.

<Steel pipe>
Next, a steel pipe will be described.
The steel pipe is welded through the end of the open pipe of the steel plate of the present disclosure. That is, a steel pipe is a steel pipe obtained by making the steel plate of this indication into an open pipe, and welding in the state which abuts the end faces of the end part which has a removal part. That is, the steel pipe has at least one weld metal part (that is, a weld metal part that joins the open pipe end of the steel sheet), and is removed on both sides of the tubular body by the steel sheet of the present disclosure adjacent to the weld metal part. Have a department.

Examples of the steel pipe include those obtained as follows.
1) A first removal section is provided at the first end, and one steel plate provided with a second removal section at the second end is prepared. This single steel plate is formed into a tube to form an open tube. Thereafter, in the obtained open pipe, a steel pipe obtained by welding in a state where the end face of the end provided with the first removal portion and the end face of the end provided with the second removal portion may be abutted.
2) A first removal portion is provided at the first end, and two or more steel plates provided with a second removal portion at the second end are prepared. When the number of steel plates is two, the end face of the end of the first steel plate provided with the first removal portion and the end face of the second steel plate of the end provided with the second removal portion are butted together Weld to make a tailored blank. Then, this tailored blank material is formed into a tubular shape to form an open pipe. Thereafter, in the obtained open pipe, the second steel plate provided with the end face of the end portion of the first steel plate portion provided with the second removal part not welded and the first removal part not welded It may be a steel pipe obtained by welding in a state where the end faces of the end portions of the portions are abutted.

  When forming a steel pipe from a tailored blank, two or more steel plates forming the tailored blank for forming a steel pipe are not limited to the above, and may be used in combination according to the purpose. The combination of two or more steel plates is, for example, the same combination as the steel plate described in the steel plate for forming the tailored blank material described above.

The method of forming into a tubular shape is not particularly limited, but any method such as UOE method, bending roll method, etc. may be used.
Also, welding after forming into a tubular shape is not particularly limited, and examples thereof include laser welding; plasma welding; electric resistance welding or electric resistance welding or electric resistance welding or high frequency induction heating welding.

<Hollow hardening form>
Next, the hollow quench-formed product will be described.
A hollow quench-formed product (hereinafter sometimes referred to as "hollow hot stamped product") is a steel pipe formed from the steel plate of the present disclosure or a tailored blank material obtained by butt welding of the steel plate of the present disclosure. Is a hollow shaped article obtained by quenching.
That is, the hollow quench-formed product obtained by hot-stamping a steel pipe has at least one weld metal portion (that is, a weld metal portion joining the ends of the steel plate) and is adjacent to the weld metal portion It has a removal part on both sides of the hollow molded object by the steel plate of this indication.

The hollow quench-formed product is obtained, for example, as follows.
The steel pipe obtained using the steel plate of the present disclosure is formed by a bender. Next, heating is performed by a heating furnace, electric heating, or high frequency induction heating. As a temperature which heats a steel pipe, since it is necessary to set it as an austenite field, it is good to set it as 850 ° C-1000 ° C, for example, and it is good to set it as a temperature of about 900 ° C-950 ° C. Next, the heated steel pipe is cooled by water cooling or the like to perform quenching.
In addition, you may perform shaping | molding and hardening simultaneously. This is called three-dimensional hot bending and quenching (3DQ), and for example, while heating a steel pipe, it is deformed by applying a load, and is quenched immediately by cooling with water cooling or the like. By going through these processes, the desired hollow hardened formed article can be obtained. The hollow quench-formed product may be used as a part as it is. In addition, if necessary, the weld may be subjected to a descaling treatment (for example, shot blasting, brushing, laser cleaning, etc.) before use.

  Although it does not specifically limit as a use of the hollow-quenched molded article of this indication, For example, various auto members, such as a car body, etc., various members of an industrial machine are mentioned. Specific examples of automobile members include various pillars; reinforcements such as stabilizers, door beams, roof rails, and bumpers; frames; and various parts such as arms.

Examples of the present disclosure are illustrated below, but the present disclosure is not limited to the following examples.
It is obvious that those skilled in the art can conceive of various modifications or alterations within the scope of the idea described in the claims, and it is natural that the technical scope of the present disclosure It is understood to belong to

<Example>
As a test material to be described below, a steel plate having a strength class after hot stamping of 1470 MPa, a square shape of 15 cm per side, and a thickness of 1.6 mm was used.
Test Material 1: A test material 1 having a plating weight of 80 g / m ² per one side was prepared. The thickness of the aluminum plating layer of the test material 1 is 28 μm, and the thickness of the intermetallic compound layer is 4 μm. The chemical composition of the base steel plate of the test material 1 is as shown in Table 1.
Specimen 2: Specimen 2 having a plating weight of 60 g / m ² per side was prepared. The thickness of the aluminum plating layer of the test material 2 is 22 μm, and the thickness of the intermetallic compound layer is 4 μm. The chemical composition of the base steel plate of the test material 2 is the same as that of the test material 1.

  Next, on both sides of the end of the steel plate, the aluminum coating layer was cut off and removed by an end mill over only one side of four sides for a total length of 15 cm. As a tool of the end mill, a reverse taper-shaped carbide cutter was used. The blade diameter is φ5 mm and the blade length is 1 mm. The removal depth was adjusted in the range of 26 μm to 60 μm. The removal width is the removal width of the portion on the outer surface side of the aluminum coating layer of the boundary (removal width W1 in Table 2) and the outer surface side of the aluminum coating layer of the boundary when the boundary between the removed portion and the remaining portion is viewed in cross section. It adjusted so that the removal width (removal width W2 in Table 2) by the side of a base material steel plate may become a value shown in Table 2 rather than. Moreover, the shape of the single-sided part when the boundary of a removal part and a remaining part was seen from a cross section was made into the shape shown in FIGS. 7-13. The prepared steel plates are shown in Table 2. No. No. 5 is the test material 2, No. Test materials 1 were used except 5 respectively.

Next, two steel plates subjected to each removal treatment were prepared, the end faces of the end portions of the steel plates subjected to the above removal treatment were butted together, butt welding was performed by laser welding to produce a tailored blank material. The conditions of the laser welding were a fiber laser as the oscillator, a spot diameter of 0.9 mm, a laser output of 3.2 kW, and a laser scanning speed of 3 m / min, without using a filler wire.
Next, the tailored blank material was held for 4 minutes in a furnace heated to 920 ° C., and then molded with a water-cooled mold and quenched to produce a flat flat stamped product. As a result, the hot stamped molded article has a tensile strength of 1470 MPa.
Here, the number of revolutions of the end mill used for cutting and removing was set to 10000 rpm.

  The a (distance a), b (distance b) and h (thickness h of the aluminum coating layer) of the remaining portion in Table 2 were measured by SEM observation to determine the area gravity center y.

[Evaluation]
(Post-paint corrosion resistance test)
After subjecting the hot stamped molded product obtained above to chemical conversion treatment, electrodeposition coating was performed, and a post-coating corrosion resistance test was performed. The chemical conversion treatment was performed with a chemical processing solution PB-SX35T manufactured by Nihon Parkerizing Co., Ltd. Thereafter, as the electrodeposition paint, cathodic electrodeposition paint Powernics 110 manufactured by Nippon Paint Co., Ltd. was used, and electrodeposition coating was performed with an electrodeposition thickness of about 15 μm as a target. After washing with water, the film was baked at 170 ° C. for 20 minutes to prepare a test plate. The size of the test plate was 65 mm long and 100 mm wide (there is a weld at the center of the width).
Using this test plate, the post-paint corrosion resistance was evaluated in the state of corrosion after 360 cycles (120 days), using an automobile part appearance corrosion test JASO M610-92.

The evaluation of the corrosion resistance after coating was performed with the ratio of red rust as the red rust occurrence rate (rounded value), and visually evaluated around the weld metal portion and the weld metal portion. Up to evaluation B (o) is acceptable.
-Judgment criteria-
A (◎): Red rust rate 25% or less B (○): Red rust rate 26% to 50%
C (△): 51% to 75% red rust rate
D (×): Red rust rate 76% to 100%

(Joint static strength)
From the obtained hot stamped molded product, a test piece in the shape of a dumbbell having a welded portion was collected as a test piece for a tensile strength test. The test piece had a parallel part distance of 50 mm and a parallel part width of 25 mm, and was cut out so as to have a weld in the central part of the parallel part across the entire width so as to be perpendicular to the longitudinal direction. The static tensile strength test was performed using this test piece. It judged by the following judgment criteria. Up to evaluation B (o) is acceptable.
-Judgment criteria-
A (◎): 1500 MPa or more B (○): 1400 MPa or more and less than 1500 MPa C (Δ): 1300 MPa or more and less than 1400 MPa D (×): less than 1300 MPa

  In addition, in Table 2, the description of "A"-"G" of a removal part type column represents the following shapes in the cross section of the edge part of a steel plate in the shape of the boundary of a removal part and a remaining part.

"A": No removal part (Aluminum coating layer is not removed; Sample 1 remains as it is).
"B": See FIG. The removal portion is removed to a part of the base steel plate, and the base steel plate has an exposed portion where the base steel plate is exposed. The boundary between the removed portion and the remaining portion extends in the direction along the thickness direction. The removal width (W1) on the surface side of the aluminum coating layer and the removal width (W2) on the base steel plate side are the same (W1 = W2).
"C": see FIG. The removal portion is removed to a part of the base steel plate, and the base steel plate has an exposed portion where the base steel plate is exposed. The boundary between the removed portion and the remaining portion is inclined, the edge on the aluminum coating layer side of the boundary is located on the center side of the steel plate, and the edge on the base steel plate side of the boundary is located on the end surface side of the steel plate There is. The removal width (W1) on the surface side of the aluminum coating layer is larger than the removal width (W2) on the base steel plate side (W1> W2).

"D": see FIG. The removal portion is removed to a part of the base steel plate, and the base steel plate has an exposed portion where the base steel plate is exposed. In the boundary between the removed portion and the remaining portion, the edge on the outer surface side of the aluminum coating layer has a protruding portion that most protrudes on the end surface side of the steel plate. The apex of the protrusion is the portion that has the shortest removal width (W1). Moreover, the edge by the side of a base material steel plate has the most dented recessed part in the center side of a steel plate. The bottom of the recess is the portion with the longest removal width (W2). W1 is smaller than W2 (W1 <W2).
"E": see FIG. The removal part is removed to the intermetallic compound layer, and it has the exposed part to which the base-material steel plate is exposed. In the boundary between the removed portion and the remaining portion, the edge on the outer surface side of the aluminum coating layer has a protruding portion that most protrudes on the end surface side of the steel plate. The apex of the protrusion is the portion that has the shortest removal width (W1). In addition, the central portion of the boundary between the removed portion and the remaining portion is the aluminum plating layer portion, and has a concave portion that is most recessed on the central side of the steel plate. The bottom of the recess is the portion with the longest removal width (W2). Furthermore, in the boundary between the removed portion and the remaining portion, a step is formed on the base steel plate side with respect to the portion of the removal width W2. W1 is smaller than W2 (W1 <W2).
"F": See FIG. The removal portion is removed to a part of the base steel plate, and the base steel plate has an exposed portion where the base steel plate is exposed. The boundary between the removed portion and the remaining portion has a protruding portion where the edge on the surface side of the aluminum coating layer most protrudes on the end surface side of the steel plate. The apex of the protrusion is the portion that has the shortest removal width (W1). Moreover, the edge by the side of a base material steel plate has the most dented recessed part in the center side of a steel plate. The bottom of the recess is the portion with the longest removal width (W2). However, W2 is shorter than W2 of removal part type "D". W1 is smaller than W2 (W1 <W2).
"G": See FIG. The removal portion is removed to a part of the base steel plate, and the base steel plate has an exposed portion where the base steel plate is exposed. The boundary between the removed portion and the remaining portion has a protruding portion where the edge on the surface side of the aluminum coating layer most protrudes on the end surface side of the steel plate. The apex of the protrusion is the portion that has the shortest removal width (W1). In addition, the central portion of the boundary between the removed portion and the remaining portion is the aluminum plating layer portion, and has a concave portion that is most recessed on the central side of the steel plate. The bottom of the recess is the portion with the longest removal width (W2). Furthermore, the boundary between the removed portion and the remaining portion is inclined toward the end face side of the steel plate on the base steel plate side with respect to the portion where the longest removal width is to be obtained. W1 is smaller than W2 (W1 <W2).

"H": See FIG. The removal portion is removed to a part of the base steel plate, and the base steel plate has an exposed portion where the base steel plate is exposed. The boundary between the removed portion and the remaining portion has a protruding portion in which the periphery of the edge on the surface side of the aluminum coating layer protrudes to the end surface side of the steel plate. The protruding portion is formed continuously in the thickness direction. The protrusion has a portion with the shortest removal width (W1). Moreover, it has the recessed part indented in the center side of the steel plate in the range covering an aluminum plating layer, an intermetallic compound layer, and a base material steel plate in the base material steel plate side rather than a protrusion part. The recessed portion is continuously formed in the plate thickness direction. The recess has a portion that has the longest removal width (W2). W1 is smaller than W2 (W1 <W2).

As shown in Tables 2 and 3, no. In the case of Sample 1 in 1, the corrosion resistance after painting around the weld metal portion is excellent. However, the static tensile strength was inferior because the amount of aluminum mixed into the weld metal increased.
As shown in Tables 2 and 3, no. 2 and No. No. 3 has removed the aluminum plating layer in the edge part of a steel plate. Therefore, the amount of aluminum mixed into the weld metal decreases, and the static tensile strength is excellent. However, when the boundary between the removed portion and the remaining portion is viewed from the cross section, the cross-sectional shape of the boundary is formed as shown in FIGS. 7 and 8, respectively. Therefore, the corrosion resistance after painting around the weld metal part was inferior.

  On the other hand, as shown in Tables 2 and 3, no. 4-No. 8, when the boundary between the removed portion and the remaining portion is viewed from the cross section, the sectional shape of the boundary is such that the aluminum coating layer outer surface side of the remaining portion protrudes to the end surface side of the steel plate, and the base steel plate side is the center side of the steel plate It's recessed. Therefore, a part of the remaining part is considered to cover a part of the surface of the removal part, and the post-painting corrosion resistance around the weld metal part is excellent. In addition, since the aluminum plating layer is removed, the amount of aluminum mixed into the weld metal is small, and the static tensile strength is excellent.

  12 base steel plate 14 aluminum plating layer 16 intermetallic compound layer 18 aluminum coating layer 22 removed portion 26 remaining portion 100 steel plate

Claims (10)

Base steel plate and
Aluminum coating layers provided on both sides of the base steel plate,
Have
The aluminum coating layer remains on at least a part of both sides of the edge located on the periphery, in the removed part from which at least a part of the aluminum coating layer is removed, and in the region on the center side of the steel plate than the removed part Remaining part is formed,
When the boundary between the removed portion and the remaining portion is viewed from the cross section, the aluminum coating layer outer surface side of the boundary has a portion with the shortest removal width, and the base metal than the aluminum coating layer outer surface side of the boundary A steel plate that has a portion with the longest removal width on the steel plate side.   The remaining portion in the area on the end face side of the steel plate relative to a virtual line extending in the direction along the thickness direction from the portion having the longest removal width of the boundary, wherein the area gravity center is the aluminum coating layer The steel plate according to claim 1, having a remaining portion that is less than 50% of the thickness of the steel sheet.   The steel plate according to claim 1 or 2, wherein the removal portion has an exposed portion where the base steel plate is exposed. The base steel plate is in mass%,
C: 0.02% to 0.58%,
Mn: 0.20% to 3.00%,
Al: 0.005% to 1.00%,
Ti: 0% to 0.20%,
Nb: 0% to 0.20%,
V: 0% to 1.0%,
W: 0% to 1.0%,
Cr: 0% to 1.0%,
Mo: 0% to 1.0%,
Cu: 0% to 1.0%,
Ni: 0% to 1.0%,
B: 0% to 0.0100%,
Mg: 0% to 0.05%,
Ca: 0% to 0.05%,
REM: 0% to 0.05%,
Bi: 0% to 0.05%,
Si: 0% to 2.00%,
P: 0.03% or less,
S: 0.010% or less,
The steel plate according to any one of claims 1 to 3, having a chemical composition consisting of N: 0.010% or less, and the balance: Fe and impurities.   The aluminum coating layer has an aluminum plating layer and an intermetallic compound layer, and the average thickness of the aluminum plating layer is 8 μm to 35 μm, and the average thickness of the intermetallic compound layer is 3 μm to 10 μm. The steel plate according to any one of claims 4.   A butt-welding member comprising at least one steel plate according to any one of claims 1 to 5 and butt-welding at least two steel plates via an end portion having the removal portion of the steel plate.   The hot press-formed article which hot-press-formed the butt welding member of Claim 6.   The steel pipe welded through the edge part of the open pipe by the steel plate of any one of Claims 1-5.   A hollow quench-formed article obtained by quenching the steel pipe according to claim 8. It is a manufacturing method of the steel plate of any one of Claims 1-5,
The manufacturing method of the steel plate which has the process of forming the said removal part by machining.