KR102312431B1 - Hot stamping parts with excellent weldability and manufacturing method - Google Patents

Abstract

Hot stamping parts according to an aspect, an interdiffusion layer sequentially formed from the surface of a base steel sheet, a first aluminum-rich layer (Al-rich Fe _x Al _y Si _z ) layer, Fe-rich (Fe-rich Fe _x Al _y Si) _z ) layer, and a multilayer plating layer comprising at least a layer of a second aluminum rich layer (Al-rich Fe _x Al _y Si _z ), wherein the plating layer has a thickness of less than 30 μm, the interdiffusion layer and the Fe-rich layer (Fe-rich, Fe _x Al _y Si _z ) The layer is an area fraction, and is 60% or less of the total plating layer.

Description

HOT STAMPING PARTS WITH EXCELLENT WELDABILITY AND MANUFACTURING METHOD

The present invention relates to a steel material and a method for manufacturing the same, and more particularly, to a hot stamping part having excellent weldability and a manufacturing method used as a vehicle member.

Joining and welding are essential in automobile assembly. The resistance spot welding process with various advantages is the most widely applied welding method because it is suitable for car body welding. The quality of the resistance spot weld is the most important management point in the body quality (rigidity and durability characteristics, etc.), and securing the welding quality is the most important task.

Recently, in a situation in which the application rate of hot stamping steel sheet is increasing in order to reduce body weight and secure stability, welding quality must also be secured along with this, but in reality, the welding characteristics of hot stamping steel for hot forming are poor. In the case of high-strength steel, the contact resistance and volume resistance are high due to high rigidity and alloy content, so the heat generation rate is high when the welding current is applied. In particular, in the case of aluminum (Al)-based plated hot stamping steel sheet, an alloying reaction occurs due to diffusion of aluminum (Al) and silicon (Si) in the plating layer and iron (Fe) in the base material in the heating furnace heat treatment process for the hot stamping method. Due to this, an interdiffusion layer and various intermetallic compound (IMC) layers are formed, which increases the surface resistance, so that expulsion occurs during welding, and the weldability is more vulnerable because the sensitivity is very high. Therefore, it is sensitive to the occurrence of intermediate expulsion and internal defects such as limiting the growth of nuggets due to the occurrence of intermediate expulsion occur, making it difficult to secure quality.

As a technology related thereto, there is Korean Patent Application Laid-Open No. 1020180095757 (Title of the Invention: Method of Manufacturing Hot Stamping Parts).

An object of the present invention is to provide a steel sheet for hot forming excellent in weldability and a method for manufacturing the same.

Hot stamping parts according to an aspect of the present invention, an interdiffusion layer sequentially formed from the surface of a base steel sheet, a first aluminum rich layer (Al-rich Fe _x Al _y Si _z ) layer, Fe-rich (Fe-rich Fe _x) Al _y Si _z ) layer, and a second aluminum-rich layer (Al-rich Fe _x Al _y Si _z ) A multilayer plating layer comprising at least a layer, wherein the plating layer has a thickness of less than 30 μm, the interdiffusion layer and Fe-rich (Fe-rich Fe _x Al _y Si _z ) layer is an area fraction, characterized in that 60% or less of the total plating layer.

The first aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer is x=30-50% by weight, y=50-70% by weight, z=0-10% by weight, and the Fe-rich (Fe- rich Fe _x Al _y Si _z ) x = 40 to 60% by weight of the layer, y = 30 to 50% by weight, z = 0 to 20% by weight, and the second aluminum-rich layer (Al-rich Fe _x Al _y Si _z ) of the layer x=30-50% by weight, y=50-70% by weight, z=0-10% by weight is preferred.

The first and second aluminum-rich (Al-rich FexAlySiz) layers are preferably 40% or more of the total plating layer in terms of area fraction.

The Si content of the interdiffusion layer is less than 10.0 wt%, the Si content of the Fe-rich (Fe-rich Fe _x Al _y Si _z ) layer is more than 4.0 wt%, and the first aluminum-rich (Al-rich Fe _x Al) layer is more than 4.0 wt%. _{It is preferable that the Si content of the y} Si _z layer and the second aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer is less than 4.0% by weight.

A method of manufacturing a hot stamping part according to another aspect of the present invention comprises the steps of: (a) preparing a steel blank for hot stamping; (b) multi-stage heating the steel blank in a heating furnace having a plurality of different temperature maintaining sections, an interdiffusion layer sequentially formed from the surface of the blank base steel sheet, and a first aluminum rich layer (Al-rich Fe _x Al _y Si _z ) layer, Fe-rich (Fe-rich Fe _x Al _y Si _z ) layer, and a second aluminum-rich layer (Al-rich Fe _x Al _y Si _z ) layer to form a multilayer plating layer comprising at least a layer ; (c) taking out the heated blank from the heating furnace and transferring it to a press mold, followed by hot stamping to form a molded body; and (d) cooling the molded body.

The plating layer has a thickness of less than 30 μm, and the interdiffusion layer and the Fe-rich (Fe-rich, Fe _x Al _y Si _z ) layer are, in area fraction, preferably 60% or less of the total plating layer.

The first aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer is x=30-50% by weight, y=50-70% by weight, z=0-10% by weight, and the Fe-rich (Fe- rich Fe _x Al _y Si _z ) x = 40 to 60% by weight of the layer, y = 30 to 50% by weight z = 0 to 20% by weight, and the second aluminum rich layer (Al-rich Fe _x Al _y Si _z ) of the layer x=30-50% by weight, y=50-70% by weight, and z=0-10% by weight.

The step (b) preferably includes the step of heat-treating the blank at a temperature of 950 ° C. to 1000 ° C. within 360 seconds.

The Si content of the interdiffusion layer is less than 10.0 wt%, the Si content of the Fe-rich (Fe-rich Fe _x Al _y Si _z ) layer is more than 4.0 wt%, and the first aluminum-rich (Al-rich Fe _x Al) layer is more than 4.0 wt%. _{It is preferable that the Si content of the y} Si _z layer and the second aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer is less than 4.0% by weight.

According to the present invention, a multi-layered plating layer structure is formed by heating a pre-coated blank for hot stamping in a multi-stage heating method, and a hot stamping part having excellent weldability can be provided by controlling the fraction of each layer constituting the plating layer.

1 is a photograph showing traces of scattering of the melt in the hot stamping homogeneous welding site.
FIG. 2 is a photograph showing an example in which pores are formed due to scattering of the melt, resulting in a deviation in welding quality.
3 is a micrograph showing the welding process of Al-Si plated material and non-plated material.
4 is a graph showing a comparison of the dynamic resistance behavior of Al-Si plating materials before and after hot stamping.
5 is a view showing a structure of a plating layer of a hot stamping part according to an embodiment of the present invention.
6 is a process flowchart illustrating a method of manufacturing a hot stamping part according to an embodiment of the present invention.
7 is a micrograph showing a change in the structure of the plating layer according to the blank heating time.
8 is a graph showing the dynamic resistance according to the heating time.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains can easily practice it. The present invention may be embodied in several different forms, and is not limited to the embodiments described herein. The same reference numerals are assigned to the same or similar components throughout this specification. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted.

Resistance spot welding is basically a welding method in which an object to be joined is pressed with two upper and lower electrodes, then a current is passed between the electrodes while maintaining the pressure, and the object to be joined is melted using the electrical resistance heat. At this time, heat is started at the bonding surface due to the contact resistance. In the case of aluminum (Al)-silicon (Si) plating material, alloying reaction occurs due to mutual diffusion of aluminum (Al) and silicon (Si) in the plating layer and iron (Fe) in the base material in the heating furnace heat treatment process for the hot stamping method. , resulting in the formation of interdiffusion layers and various intermetallic compounds (IMCs). Therefore, the surface contact resistance of the weld is very increased, and the heat generation rate due to electrical resistance is very high at the interface of the joint where the plating layer is in contact, so molten nuggets are first generated. deepening and the welding quality deteriorates.

1 is a photograph showing traces of scattering of the melt in the same type of hot stamping welding, and FIG. 2 is a photograph showing an example in which the weld quality is varied due to the formation of pores due to the scattering of the melt. As such, there is a great difficulty in securing and managing the quality of hot stamping parts due to scattering of the melt.

This is to show the effect of the Al-Si plating layer on the welding resistance heating and the nugget growth. It is a graph showing the comparison of the dynamic resistance behavior of plating materials before and after hot stamping.

Referring to FIG. 3 , in the case of the plating material, heat generation on the surface of the plating layer starts in 2-cycle, and a seal is not formed in the weld zone in 3-cycle due to heat generation, and heat generation is further increased in 4-cycle and 5-cycle shows that it is getting worse. On the other hand, in the case of a non-plated material, a seal is gradually formed as the 2, 3, and 4-cycles proceed, and the melting of the bonding surface begins in the 5-cycle, thereby forming a stable bonding.

Also, referring to FIG. 4 , it can be seen that the dynamic resistance 10 before hot stamping is observed to be lower than that after hot stamping 20 , and therefore heat generation during resistance welding before hot stamping is low.

As such, in the case of non-plated materials, in the case of plated materials, due to the alloyed aluminum (Al)-silicon (Si) plated layer after heat treatment, the heating pattern and pattern in which excessive heat is rapidly generated locally during welding, and the melting rate of the welded portion due to this will change This phenomenon is due to the alloyed plating layer, unlike the aluminum (Al) plating layer before heat treatment, and it was confirmed that the control of the IMC formed during the Fe-Si alloying process of the plating layer is the most important factor in weldability.

The present invention analyzes the cause of weldability inferiority in the plating layer, identifies the IMC that is unfavorable to welding, and proposes a method of manufacturing a hot stamping part for controlling this and optimizing the welding process and the structure of a steel sheet for hot stamping accordingly. .

hot stamping parts

One aspect of the present invention relates to a hot stamped part having excellent weldability. In a preferred embodiment, the hot stamping part includes an aluminum (Al)-based plating layer formed to prevent corrosion of the surface of the base material, and the plating layer is intermetallic alloying, austenitizing and hot stamping in a heat treatment process for hot stamping. It has a multi-layered structure made through, and the multi-layered plating layer structure is composed of at least four layers and has a structure in which the fraction of each layer is controlled so as to have excellent weldability.

5 is a view showing a structure of a plating layer of a hot stamping part according to an embodiment of the present invention.

Referring to FIG. 5 , the plating layer of the hot stamping part is formed from an interdiffusion layer 31 , a first aluminum-rich layer 32 , a Fe-rich layer 33 , and a second layer from the base material 30 . An aluminum-rich layer 34 is sequentially disposed. Another layer may be further disposed on the second Al-rich layer 34 .

The first aluminum-rich (Al-rich FexAlySiz, x=30-50wt%, y=50-70wt.%, z=0-10wt%) layer 32 is Fe: 30-50 wt%, Al: 50- 70% by weight, Si: has a composition of 0 to 10% by weight.

Fe-rich (Fe-rich FexAlySiz, x=40-60wt%, y=30-50wt.%, z=0-20wt%) layer 33 is Fe: 40-60 wt%, Al: 30-50 wt% %, Si: A layer having a composition of 0 to 20% by weight.

The second aluminum-rich (Al-rich FexAlySiz, x=30-50wt%, y=50-70wt.%, z=0-10wt%) layer 34 is Fe: 30-50 wt%, Al: 50- 70% by weight, Si: A layer having a composition of 0 to 10% by weight.

The interdiffusion layer 31 formed on the surface of the base material 30 and the Fe-rich FexAlySiz layer 33 located in the middle is a layer having a high resistance phase, which is disadvantageous in weldability due to high resistance during welding, The Al-rich FexAlySiz layers 32 and 34 are layers having a low resistance phase, and are advantageous in weldability. The electrical resistance of the plating layer, that is, the contact resistance, is closely related to the electrical properties and fraction of the composition. Accordingly, the high resistance layers 31 and 33 and the low resistance layers 32 and 34 can maximize the weldability of the hot stamping part by optimizing the fraction. According to a preferred embodiment of the present invention, in order to maximize the weldability of the hot stamping part, in the multi-layered plating layer structure, the low-resistance Al-rich FexAlySiz layers 32 and 34 are the area fraction, 40% of the total plating layer. Including the above, it is preferable that the total area fraction of the high-resistance interdiffusion layer 31 and the Fe-rich FexAlySiz layer 33 is controlled to be about 60% or less of the total plating layer.

The factors constituting the multi-layer plating layer are expressed as follows.

40% < V _{Al-rich FexAlySiz} , 60%> V _{interdiffusion layer} + V _{Fe-rich FexAlySiz} = 1- V _{Al-rich FexAlySiz}

40% < V _{Al-rich FexAlySiz} (50wt% < y < 70wt%, 30wt% < x+z < 50wt% in Al-rich FexAlySiz)

60% > V _{interdiffusion layer} + V _{Fe-rich FexAlySiz} (30wt% < y < 50wt%, 50wt% < x+z < 70wt% in Fe-rich FexAlySiz)

On the other hand, the inventors of the present invention confirmed that the electrical resistance of the plating layer is closely related to the content of silicon (Si) in the plating layer. That is, the plating layer has a silicon (Si) content of 4.0 regardless of the number of layers. The Fe-Al-Si plating layer exceeding the weight % and the Fe-Al-Si plating layer in which the content of silicon (Si) is less than 4.0 weight %, in this case, Fe in which the content of silicon (Si) exceeds 4.0 weight % When the thickness ratio of the -Al-Si plating layer is less than 60% of the total plating layer, preferably 35 to 55% or 40 to 50%, good weldability may be exhibited. It is preferable to control the thickness ratio of the Fe-Al-Si plating layer having a silicon (Si) content of less than 4.0% by weight to 40% or more. When the thickness ratio of the Fe-Al-Si plating layer in which the content of silicon (Si) exceeds 4.0% by weight is less than 60%, the electrical resistance of the plating layer is prevented from increasing, spatter is reduced in the spot welding process, and welding strength can be obtained

Also, preferably, in the present invention, the silicon (Si) content of the interdiffusion layer is less than 10.0 wt%, the Fe-rich (Fe-rich Fe _x Al _y Si _z ) Si content of the layer is more than 4.0 wt%, The Si content of the first aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer and the second aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer is preferably controlled to be less than 4.0 wt%.

In addition, the plating layer of the hot stamping part of the present invention consists of at least four or more layers, and the thickness of the entire plating layer is preferably less than 30 μm. When the blank heating temperature and heating time for hot stamping are excessively increased, the growth of the interdiffusion layer 31 and the Fe-rich layer 33 is promoted due to overheating, and the total plating layer thickness is increased, which leads to poor weldability. Therefore, the total thickness of the plating layer is preferably controlled to be less than 30㎛. When the total thickness of the plating layer is controlled to be less than 30 μm, it is possible to easily increase the temperature, enter a rapid phase transformation, and prevent overheating, and, in addition, it is possible to reduce the adhesion of foreign substances in the plating layer to the hot stamping mold.

A hot stamping part having excellent weldability including the above-described plating layer can be obtained by a manufacturing process for having a multi-layer plating layer by heating the blank in multiple stages for hot stamping. Hereinafter, a method of manufacturing a hot stamping part having excellent weldability according to an example will be described in detail.

Manufacturing method of hot stamping parts

6 is a process flowchart illustrating a method of manufacturing a hot stamping part according to an embodiment of the present invention. Referring to FIG. 6 , the method of manufacturing a hot stamping part according to an embodiment of the present invention includes the steps of preparing a steel blank for hot stamping (S110), heating the blank (S120), and heating the blank Hot stamping with a press mold to form a molded body (S130), and cooling the molded body to form a hot stamping part (S140).

Preparing a blank for hot stamping (S110)

The step of preparing the blank for hot stamping ( S110 ) is a step of preparing a plate for forming hot stamping parts, cutting the plate into a desired shape according to the purpose, and forming a blank.

In the process of preparing the plate, a steel slab having a known composition applied for hot stamping is prepared, and the steel slab is subjected to at least one of known hot rolling and cold rolling, followed by annealing heat treatment to manufacture a steel plate It can proceed as a process. After the annealing heat treatment, an Al-Si-based plating layer or a Zn plating layer may be formed on the steel sheet material by a known method. In a specific example, an Al-Si-based plating layer is formed on the steel sheet material, but the thickness of the entire plating layer is less than 30 µm, preferably 20 to 29 µm. If the plating layer is too thick, the amount of heat required for the alloying heat treatment process may increase and the time to reach the cracking temperature may be delayed, which may lead to an increase in heating time and overheating. In addition, if the plating layer is thick, there is a possibility that foreign materials in the plating layer may stick to the mold during hot stamping molding.

Step of heating the blank (S120)

In an embodiment of the present invention, the heating of the blank may be performed as a multi-step heating process in a heating furnace having a plurality of different temperature maintaining sections. The blank is mounted on a roller and moved to pass through the inside of the heating furnace. The blank may be heated while passing through the inside of the heating furnace after being introduced into the inlet side of the heating furnace, and may be drawn out to the exit shaft of the heating furnace. In this case, each temperature of the plurality of different temperature sections may be set to increase from an inlet through which the blank is introduced to an outlet direction at which the blank is drawn out.

In one embodiment, the heating of the blank may be carried out to include the step of heat-treating the blank at a temperature of 950 ℃ ~ 1,000 ℃ crack. When the cracking heat treatment temperature is less than 950 ° C, after the heated blank is withdrawn from the heating furnace, the press forming start temperature is excessively lowered by the air cooling exposure time, so that the elongation of the heated blank decreases, resulting in a reduction in thickness during molding or fracture may occur. In addition, by cooling during the air cooling exposure time, the strength of the blank is increased, and a large force is required to simultaneously form a plurality of blanks, thereby overloading the press equipment. On the other hand, when the cracking heat treatment temperature exceeds 1,000° C., carbide-forming elements or nitride-forming elements such as Ti, V, Nb, and Mo in the blank are dissolved into the base material, making it difficult to suppress grain coarsening.

In an embodiment, the heating of the blank may be performed in a state in which the inside of the heating furnace is maintained at a dew point of 0° C. or less.

In an embodiment, heating the blank may include allowing the blank to stay in the heating furnace for 180 seconds to 360 seconds. When the residence time is less than 180 seconds, it is difficult to have a sufficient soaking time at the desired soaking temperature. When the residence time exceeds 360 seconds, the amount of hydrogen penetrating into the blank increases, thereby increasing the risk of delayed fracture, and corrosion resistance after hot stamping may be reduced.

As the blank heating step (S130) proceeds, an alloying reaction occurs due to internal diffusion of Al and Si of the plating layer and Fe of the steel sheet material, and as a result, the plating layer is formed in a multi-layer structure of four or more layers, as described with reference to FIG. 4 . can be Specifically, as shown in FIG. 4 , the plating layer includes an interdiffusion layer 31 , a first aluminum-rich layer 32 , a Fe-rich layer 33 , and a second layer from the base material 30 . Two aluminum-rich (Al-rich) layers 34 are sequentially disposed, and another layer may be further disposed on the second aluminum-rich (Al-rich) layer 34 .

The first aluminum-rich (Al-rich FexAlySiz) layer 32 is a layer having a composition of Fe: 30-50 wt%, Al: 50-70 wt%, Si: 0-10 wt%, and Fe-rich (Fe -rich FexAlySiz) layer 33 is a layer having a composition of Fe: 40 to 60% by weight, Al: 30 to 50% by weight, Si: 0 to 20% by weight, and the second aluminum-rich (Al-rich FexAlySiz) layer (34) is a layer having a composition of Fe: 30 to 50% by weight, Al: 50 to 70% by weight, Si: 0 to 10% by weight.

In this case, the high-resistance layers 31 and 33 and the low-resistance layers 32 and 34 can maximize the weldability of the hot stamping part by optimizing their area fractions, respectively. According to a preferred embodiment, in order to maximize the weldability of the hot stamping part, in the multi-layered plating layer structure, the low-resistance Al-rich FexAlySiz layers 32 and 34 include 40% or more of the total plating layer as an area fraction. and the sum of the high-resistance interdiffusion layer 31 and the Fe-rich FexAlySiz layer 33 can be controlled to be about 60% or less of the total plating layer as an area fraction.

The structure of the plating layer is closely related to the blank heat treatment time.

7 is a micrograph showing the change of the plating layer structure according to the blank heating time, and FIG. 8 is a graph showing the dynamic resistance according to the heating time. At this time, using a blank of 22MnB5 material in which an Al-based pre-coating layer containing Si: 5 to 10% by weight was formed of 100 g/cm 2 ㅁ 20 was used, and the blank was heated at 950° C. using a multi-stage heating method.

7 and 8, from the raw material before the first heat treatment, when 60 seconds elapsed, an Al-rich FexAlySiz layer was formed, and it was observed that the resistance decreased as the fraction increased. From about 120 seconds on, the resistance rapidly increases as the interdiffusion layer and the Fe-rich FexAlySiz layer are formed. After 600 seconds, the thickness fraction of the interdiffusion layer and the Fe-rich FexAlySiz layer increases significantly, resulting in very high resistance and poor weldability.

Therefore, in order to realize a plating layer advantageous for weldability, the fraction of the Al-rich FexAlySiz layer must be secured at a certain level or more. In addition, it is preferable to limit the heating time to within 360 seconds at a heating temperature of 950° C., and it is preferable to set the lower limit temperature and heating time in consideration of the physical properties of the material.

Hot stamping step (S130) and cooling step (S140)

The blank heated to the above conditions is transferred to the press mold. After being molded into a final part shape in a press mold for hot stamping, the molded body is cooled to form a final product. A cooling channel through which a refrigerant circulates may be provided in the press mold. It is possible to rapidly cool the heated blank by circulation by the refrigerant supplied through the provided cooling channel. At this time, in order to prevent a spring back phenomenon of the steel and maintain a desired shape, rapid cooling may be performed while the press mold is closed while pressing. In forming and cooling the heated blank, the average cooling rate can be cooled to at least 10° C./s or more to the martensite end temperature. The blank may be maintained in the press mold for 3 to 20 seconds. When the holding time in the mold is less than 3 seconds, it is difficult to secure mechanical properties because a sufficient amount of martensite is not generated. When the holding time in the mold exceeds 20 seconds, a significant difference does not occur, so a cooling holding time of 3 to 20 seconds can be set in terms of productivity.

As described above, according to the present invention, a multi-layered plating layer structure is formed by heating a pre-coated blank for hot stamping in a multi-stage heating method, and a hot stamping part with excellent weldability is obtained by controlling the fraction of each layer constituting the plating layer. can provide

Although the above description has been focused on the embodiments of the present invention, various changes or modifications may be made at the level of those skilled in the art. Such changes and modifications can be said to belong to the present invention without departing from the scope of the present invention. Accordingly, the scope of the present invention should be judged by the claims described below.

Claims (9)

The interdiffusion layer sequentially formed from the surface of the base steel sheet, the first aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer, the Fe-rich (Fe-rich Fe _x Al _y Si _z ) layer, and the second aluminum-rich ( Al-rich Fe _x Al _y Si _z ) comprising a multilayer plating layer comprising at least a layer,
The plating layer has a thickness of less than 30㎛,
The interdiffusion layer and the Fe-rich (Fe-rich FexAlySiz) layer is an area fraction, less than 60% of the total plating layer,
x = 30 to 50 wt%, y = 50 to 70 wt%, z = 0 to 10 wt% of the first aluminum-rich (Al-rich FexAlySiz) layer,
x = 40 to 60% by weight of the Fe-rich (Fe-rich FexAlySiz) layer, y = 30 to 50% by weight, z = 0 to 20% by weight,
The second aluminum-rich (Al-rich FexAlySiz) layer of x = 30-50 wt%, y = 50-70 wt%, z = 0-10 wt%, characterized in that the hot stamping part. delete According to claim 1,
The first and second aluminum-rich (Al-rich FexAlySiz) layers are an area fraction, characterized in that 40% or more of the total plating layer,
hot stamping parts. According to claim 1,
The Si content of the interdiffusion layer is less than 10.0% by weight,
The Fe-rich (Fe-rich Fe _x Al _y Si _z ) Si content of the layer exceeds 4.0% by weight,
The first aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer and the second aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer are characterized in that the Si content is less than 4.0% by weight,
hot stamping parts. (a) preparing a steel blank for hot stamping;
(b) an interdiffusion layer sequentially formed from the surface of the blank base steel sheet by heating the steel blank in multiple stages in a heating furnace having a plurality of different temperature maintaining sections, a first aluminum-rich (Al-rich FexAlySiz) layer, Fe- at least a rich (Fe-rich FexAlySiz) layer, and a second aluminum-rich (Al-rich FexAlySiz) layer, wherein x=30-50 wt% of the first aluminum-rich (Al-rich FexAlySiz) layer, y=50 ~70% by weight, z = 0 ~ 10% by weight, and x = 40 ~ 60% by weight of the Fe-rich (Fe-rich FexAlySiz) layer, y = 30 ~ 50% by weight, z = 0 ~ 20% by weight, and , allowing the second aluminum-rich (Al-rich FexAlySiz) layer to form a multi-layer plating layer of x=30-50 wt%, y=50-70 wt%, z=0-10 wt%;
(c) taking out the heated blank from the heating furnace and transferring it to a press mold, followed by hot stamping to form a molded body; and
(d) characterized in that it comprises the step of cooling the molded body,
A method of manufacturing hot stamping parts. 6. The method of claim 5,
The plating layer has a thickness of less than 30㎛,
The interdiffusion layer and the Fe-rich (Fe-rich Fe _x Al _y Si _z ) layer is characterized in that the area fraction is 60% or less of the total plating layer,
A method of manufacturing hot stamping parts. delete 6. The method of claim 5,
Step (b) is
Characterized in that it comprises the step of heat-treating the blank within 360 seconds at a temperature of 950 ℃ ~ 1000 ℃,
A method of manufacturing hot stamping parts. 6. The method of claim 5,
The Si content of the interdiffusion layer is less than 10.0% by weight,
The Fe-rich (Fe-rich Fe _x Al _y Si _z ) Si content of the layer exceeds 4.0% by weight,
The first aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer and the second aluminum-rich (Al-rich Fe _x Al _y Si _z ) layer are characterized in that the Si content is less than 4.0% by weight,
A method of manufacturing hot stamping parts.

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