Title of Invention: Aluminum-based alloy coated steel sheet with excellent workability and corrosion resistance and its manufacturing method
technology field
[One]
The present invention relates to an aluminum-based alloy coated steel sheet having excellent workability and corrosion resistance and a manufacturing method thereof.
[2]
background art
[3]
Conventionally, aluminum (Al) plated steel sheets or zinc (Zn) plated steel sheets have been used for hot forming, but there are problems in that microcracks occur or corrosion resistance is deteriorated due to an alloy phase formed during heat treatment. In addition, there is a problem in that the coating layer is liquefied during hot forming and fused to the roll, and the temperature cannot be rapidly raised to 900 ° C., thereby reducing productivity. In addition, in the case of an aluminum-plated steel sheet, since there is no sacrificial corrosion resistance of aluminum, corrosion resistance after processing may be a problem.
[4]
In order to improve such corrosion resistance and hot formability, conventionally, an aluminum alloyed plated steel sheet in which Si is added in a plating bath at 4% or less and the plating layer is alloyed at an alloying temperature of 700 ° C. and an alloying time of 20 seconds has been disclosed.
[5]
However, since the alloying time takes a long time of 20 seconds under the above conditions, there is a problem in that there is difficulty in alloying treatment in a seal line and strong cooling is required after alloying. In addition, since the temperature of the plating bath is very high, such as about 700° C., as the Si content decreases, there is a problem in that the durability of structures such as sink rolls immersed in the plating bath is remarkably deteriorated.
[6]
(Patent Document 1) Korean Patent Publication No. 1997-0043250
[7]
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[8]
According to one aspect of the present invention, it is intended to provide an aluminum-based alloy-coated steel sheet that suppresses the generation of microcracks generated during hot forming and has excellent stickiness and corrosion resistance, and a manufacturing method thereof.
[9]
The object of the present invention is not limited to the foregoing. Anyone with ordinary knowledge in the technical field to which the present invention belongs will have no difficulty in understanding the additional objects of the present invention from the contents throughout the present specification.
[10]
means of solving the problem
[11]
One aspect of the present invention,
[12]
base grater; and
[13]
Including a single-layer alloyed plating layer formed on the base steel sheet,
[14]
The alloyed plating layer includes Fe: 35 to 50%, Zn: 1 to 20%, Mn: 5% or less, Si: less than 0.1%, the balance Al and other unavoidable impurities, by weight%,
[15]
When the distance from the center line of the surface roughness of the alloyed plating layer to the lowermost line of the alloyed plating layer is t, the ratio of the area occupied by the base steel sheet within the region from the center line of the surface roughness of the alloyed plating layer to 3/4t is 30% or more , An aluminum-based alloy coated steel sheet is provided.
[16]
[17]
On the other hand, another aspect of the present invention,
[18]
base grater;
[19]
Including an alloyed plating layer formed on the base steel sheet,
[20]
The alloyed plating layer is
[21]
A first alloyed plating layer containing Fe: 35-50%, Zn: 1-20%, Mn: 5% or less, Si: less than 0.1%, balance Al and other unavoidable impurities in weight%; and
[22]
By weight, Fe: 30 to 40%, Zn: 1 to 22%, Mn: 2% or less, Si: less than 0.1%, the balance comprising a second alloyed plating layer containing Al and other unavoidable impurities,
[23]
When the distance from the center line of the surface roughness of the alloyed plating layer to the lowermost line of the alloyed plating layer is t, the ratio of the area occupied by the base steel sheet within the region from the center line of the surface roughness of the alloyed plating layer to 3/4t is 30% or more , An aluminum-based alloy coated steel sheet is provided.
[24]
[25]
Another aspect of the present invention is,
[26]
As a method for producing an aluminum-based coated steel sheet used in hot press forming,
[27]
Preparing a base steel sheet;
[28]
immersing the base steel sheet in an aluminum plating bath containing Zn: 3 to 30%, Si: less than 0.1%, balance Al and other unavoidable impurities in weight percent to obtain an aluminum-plated steel sheet;
[29]
After aluminum plating, a cooling step of supplying air heated to 200 to 300° C. to the aluminum-coated steel sheet to form an oxide film on the surface of the aluminum-coated steel sheet; and
[30]
Obtaining an aluminum-based coated steel sheet through on-line alloying in which heat treatment is performed by continuously holding in a heating temperature range of 650 to 750 ° C. for 1 to 20 seconds after the cooling; manufacturing method of an aluminum-based coated steel sheet including provides
[31]
[32]
In addition, another aspect of the present invention provides a hot formed member obtained by hot press forming the above-described aluminum-based alloy-coated steel sheet.
[33]
Effects of the Invention
[34]
According to the present invention, it is possible to effectively provide an aluminum-based alloy-coated steel sheet and a hot-formed member using the same, which suppresses microcracks generated during hot forming and improves stickiness and corrosion resistance.
[35]
Brief description of the drawing
[36]
1 schematically shows a manufacturing apparatus in which a manufacturing method according to an aspect of the present invention is implemented.
[37]
2 is a photograph of a cross section of an aluminum-based alloy-coated steel sheet corresponding to the prior art in which Si is added at about 7% and Zn is not added, with a scanning electron microscope (SEM).
[38]
3 is a photograph of a cross-section of an aluminum-based alloy-coated steel sheet manufactured in Inventive Example 1 observed with a scanning electron microscope (SEM).
[39]
4 is a photograph taken with a scanning electron microscope (SEM) of a cross-section of an aluminum-based alloy-coated steel sheet manufactured in Inventive Example 6;
[40]
BEST MODE FOR CARRYING OUT THE INVENTION
[41]
Hereinafter, the present invention will be described in detail. First, an aluminum-based alloy-coated steel sheet, which is an aspect of the present invention, will be described in detail.
[42]
The aluminum-based alloy-coated steel sheet manufactured according to the prior art has poor hot formability, such as microcracks occurring during hot forming or fusion of rolls during hot forming, and also has a problem of insufficient corrosion resistance of the coated steel sheet.
[43]
In order to solve this problem, conventionally, Si was added to the plating bath to 4% or less to improve corrosion resistance and hot formability. However, when a small amount of Si is added to the Al plating bath, since Si is included in the Fe-Al alloy phase, there is a problem in that alloying cannot be achieved in a short time of 20 seconds or less by suppressing the diffusion of Fe, and also in the plating bath. As the temperature of the structure becomes too high, problems such as the decrease in durability of the structure could not be solved.
[44]
Accordingly, the inventors of the present invention have intensively studied to solve the above-mentioned problems of the prior art, and as a result, based on a line that becomes a specific point with respect to the distance between the surface of the alloyed plating layer and the lowermost end in contact with the base material side, the area of ​​the base steel sheet toward the upper side. By securing the area occupied by a specific amount or more, it was found that the problems of the prior art described above could be solved, and the present invention was completed.
[45]
Specifically, the aluminum-based alloy-coated steel sheet according to the present invention includes a case where the alloyed plating layer is a single layer or two layers, and each case will be separately described below.
[46]
[When the alloyed plating layer is a single layer]
[47]
One aspect of the present invention,
[48]
base grater; and
[49]
Including a single-layer alloyed plating layer formed on the base steel sheet,
[50]
The alloyed plating layer includes Fe: 35 to 50%, Zn: 1 to 20%, Mn: 5% or less, Si: less than 0.1%, the balance Al and other unavoidable impurities, by weight%,
[51]
When the distance from the center line of the surface roughness of the alloyed plating layer to the lowermost line of the alloyed plating layer is t, the ratio of the area occupied by the base steel sheet within the region from the center line of the surface roughness of the alloyed plating layer to 3/4t is 30% or more , An aluminum-based alloy coated steel sheet is provided.
[52]
[53]
An aluminum-based alloy-coated steel sheet according to an aspect of the present invention may include a base steel sheet and a single or two-layer alloyed plating layer (a first alloyed plating layer and a second alloyed plating layer) formed on the base steel sheet, and the single or second alloyed plating layer. The alloyed plating layer of the layer may be formed on one side or both sides of the base steel sheet.
[54]
[55]
Meanwhile, according to one aspect of the present invention, after the base steel sheet is immersed in an aluminum plating bath and then subjected to alloying heat treatment, Fe and/or Mn of the base steel sheet diffuses into the plating layer. As a result of this diffusion, alloying occurs in the plating layer, and through this, a single-layer or two-layer alloyed plating layer having a specific composition is formed on the base steel sheet.
[56]
Hereinafter, a case in which an aluminum-based alloy-coated steel sheet according to an aspect of the present invention forms an alloyed plating layer as a single layer will be first described.
[57]
That is, when the alloyed plating layer according to one aspect of the present invention is a single layer, the alloyed plating layer, in weight%, Fe: 35 to 50%, Zn: 1 to 20%, Mn: 5% or less (including 0%), It may have a composition containing Si: less than 0.1% (including 0%), balance Al and other unavoidable impurities.
[58]
Alternatively, according to one aspect of the present invention, when the alloyed plating layer is a single layer, the composition of the alloyed plating layer is, in weight%, Fe: 35 to 50%, Zn: 1 to 20%, Mn: 5% or less (0% included), Si: less than 0.1% (including 0%), the balance Al and other unavoidable impurities.
[59]
In the single-layer alloyed plating layer according to one aspect of the present invention, the Zn not only improves stickiness and corrosion resistance of the plated steel sheet, but also serves to improve the adhesion of the alloyed plating layer after alloying treatment. Therefore, in the plated steel sheet of the present invention, it is preferable that the Zn content in the alloyed plating layer is 1 to 20%. In the present invention, if the Zn content in the alloyed plating layer is less than 1%, the effect of improving stickiness and corrosion resistance cannot be expected, and if the Zn content in the alloyed plating layer exceeds 20%, the adhesion of the plating layer after alloying is poor. there is a problem.
[60]
Meanwhile, according to one aspect of the present invention, in the single-layer alloyed plating layer, the lower limit of the Zn content may be preferably 5%, more preferably 10%. In addition, the upper limit of the Zn content may be preferably 18%. and more preferably 15%.
[61]
Further, according to one aspect of the present invention, in the single-layer alloyed plating layer, the content of Mn may be 5% or less, including the case of 0%. That is, in the present invention, Mn present in the alloyed plating layer is introduced through alloying treatment of Mn present in the base steel sheet, and the lower limit of the Mn content is not particularly limited. However, the upper limit of the Mn content is preferably 5% or less in order to secure plating properties for suppressing non-plating. Meanwhile, more preferably, the Mn content in the single-layer alloyed plating layer may be 2 to 5%.
[62]
Further, according to one aspect of the present invention, in the single-layer alloyed plating layer, the content of Si may be less than 0.1%, including the case of 0%. That is, in the present invention, elements such as Si may be included in an amount of less than 0.1% as an additional element in the molten plating bath, and since Si may not be included, the lower limit is not particularly limited. On the other hand, the Si content is preferably less than 0.1% in terms of securing resistance to cracking during the aforementioned processing. Meanwhile, more preferably, the upper limit of the Si content in the single-layer alloyed plating layer may be 0.09% (ie, 0.09% or less).
[63]
In addition, according to one aspect of the present invention, by the diffusion of Fe and / or Mn by the above-described alloying treatment, in the single-layer alloyed plating layer, the Al content is 40 to 60, and the Fe content is 35 to 50% It is desirable to be By satisfying the above-mentioned composition, it is possible to secure the stickiness and corrosion resistance that are aimed at in the present invention, and also to secure the adhesion of the plating layer.
[64]
On the other hand, according to one aspect of the present invention, in the above-described single-layer alloyed plating layer, it is more preferable in terms of ensuring plating adhesion that the Al content is 43 to 60%.
[65]
Further, according to one aspect of the present invention, the thickness of the single-layer alloyed plating layer may be 5 to 25 μm. When the thickness of the alloyed plating layer is 5 μm or more, corrosion resistance can be secured, and when it is 25 μm or less, weldability can be secured. Therefore, in the present invention, the thickness of the alloyed plating layer is preferably 5 to 25 μm, more preferably, the lower limit of the alloyed plating layer may be 10 μm, and the upper limit of the alloyed plating layer may be 20 μm.
[66]
On the other hand, according to one aspect of the present invention, the alloyed plating layer of the single layer is diffused into an aluminum plating layer having a high content of Al and Zn in the base steel sheet by alloying treatment after plating during the manufacturing process described above, As a result, an alloyed plating layer mainly composed of an intermetallic compound of Fe and Al can be formed.
[67]
Specifically, according to one aspect of the present invention, when the aforementioned alloyed plating layer is a single layer, the alloy phase of the Fe-Al-based intermetallic compound mainly constituting the alloyed plating layer is preferably Fe 2Al 5 . That is, the single-layer alloyed plating layer may include 80% or more of the Fe 2Al 5 alloy phase, and more preferably 90% or more of the Fe 2Al 5 alloy phase. Accordingly, the single-layer alloyed plating layer may be formed of an alloy phase in which Fe 2Al 5 is based (ie, 80% or more is Fe 2Al 5 ), Zn, Mn, and/or Si are dissolved.
[68]
In the present specification, being made of the alloy phase implies that other unavoidable impurities may be included, and other components may be included within a range that does not impair the object of the present invention.
[69]
On the other hand, when the alloyed plating layer is formed as a single layer, in the aluminum-based alloy-coated steel sheet according to the present invention, when the distance from the center line of the surface roughness of the alloyed plating layer to the lowermost line of the alloyed plating layer is t, the alloyed plating layer A ratio (As) of an area occupied by the base steel sheet within a region from the center line of surface roughness to 3/4t is 30% or more.
[70]
In the present specification, the lowermost line of the alloyed plating layer means a line drawn at the lowermost end of the alloyed plating layer in a direction perpendicular to the thickness direction of the steel sheet. Further, according to one aspect of the present invention, the lowermost line may mean a line drawn to be horizontal with the surface roughness center line.
[71]
Specifically, the case where the alloyed plating layer according to the present invention is formed as a single layer is shown in FIG. 4, and as can be seen in FIG. The interface between the alloyed plating layer and the base steel sheet is formed in a sawtooth shape so that the ratio (As) of the area occupied by the base steel sheet is 30% or more.
[72]
In the alloyed plating layer according to one aspect of the present invention, by forming the boundary with the base steel sheet, which is the base material, in a sawtooth shape as described above, it is possible to suppress the occurrence of cracks during processing, thereby ensuring excellent crack resistance. .
[73]
At this time, when the alloyed plating layer is a single layer, the upper limit may not be separately limited in that the higher the value of As, the more excellent the crack resistance effect during processing. However, more preferably, the upper limit of the value of As may be 80% (most preferably 60%).
[74]
In the present invention, the formation of the alloyed plating layer on the base steel sheet means that the alloyed plating layer is formed on the base steel sheet to be in contact with it. Also, in the present invention, that the alloyed plating layer is formed as a single layer means that a single layer is formed as the alloyed plating layer, but does not mean that other layers cannot be provided on the alloyed plating layer.
[75]
[When the alloy plating layer is two layers]
[76]
On the other hand, hereinafter, the case where the aluminum alloy-coated steel sheet according to another aspect of the present invention is formed of two alloyed plating layers will be first described.
[77]
Specifically, another aspect of the present invention,
[78]
base grater;
[79]
Including an alloyed plating layer formed on the base steel sheet,
[80]
The alloyed plating layer is
[81]
A first alloyed plating layer containing Fe: 35-50%, Zn: 1-20%, Mn: 5% or less, Si: less than 0.1%, balance Al and other unavoidable impurities in weight%; and
[82]
By weight, Fe: 30 to 40%, Zn: 1 to 22%, Mn: 2% or less, Si: less than 0.1%, the balance comprising a second alloyed plating layer containing Al and other unavoidable impurities,
[83]
When the distance from the center line of the surface roughness of the alloyed plating layer to the lowermost line of the alloyed plating layer is t, the ratio of the area occupied by the base steel sheet within the region from the center line of the surface roughness of the alloyed plating layer to 3/4t is 30% or more , An aluminum-based alloy coated steel sheet is provided.
[84]
As the case where the alloyed plating layer is two layers, the description for the case where the above-described single-layer alloyed plating layer is provided, except that the first alloyed plating layer and the second alloyed plating layer are formed, can be applied in the same way.
[85]
According to one aspect of the present invention, when the alloyed plating layer is formed of two layers including a first alloyed plating layer and a second alloyed plating layer,
[86]
The first alloyed plating layer, by weight, Fe: 35-50%, Zn: 1-20%, Mn: 5% or less (including 0%), Si: less than 0.1% (including 0%), balance Al and other unavoidable impurities;
[87]
The second alloyed plating layer, by weight, Fe: 30-40%, Zn: 1-22%, Mn: 2% or less (including 0%), Si: less than 0.1% (including 0%), balance Al and other unavoidable impurities.
[88]
Specifically, according to one aspect of the present invention, the first alloyed plating layer is an alloyed plating layer formed on the base steel sheet, in weight%, Fe: 35 to 50%, Zn: 1 to 20%, and Mn: 5 % or less (including 0%), Si: less than 0.1% (including 0%), the balance including Al, and other unavoidable impurities and other elements within a range that does not impair the object of the present invention. Alternatively, according to one aspect of the present invention, the first alloyed plating layer is, by weight%, Fe: 35 to 50%, Zn: 1 to 20%, Mn: 5% or less, Si: less than 0.1% (including 0%) ), the balance may be made of Al and other unavoidable impurities. In addition, according to one aspect of the present invention, in the first alloyed plating layer, the Al content may be 40 to 60% in weight%, more preferably It may be 43-60%. Meanwhile, in the first alloyed plating layer, by satisfying the Al content, desired stickiness, corrosion resistance, and adhesion of the plating layer can be easily secured.
[89]
Similarly, according to one aspect of the present invention, in the first alloyed plating layer, the Fe content is preferably 35 to 50% in terms of weight%, and the desired stickiness is achieved by satisfying the Fe content in the first alloyed plating layer. , corrosion resistance and adhesion of the plating layer can be easily secured.
[90]
According to one aspect of the present invention, the second alloyed plating layer is formed on the first alloyed plating layer, and is an alloyed plating layer distinct from the first alloyed plating layer, in weight%, Fe: 30 to 40%, Zn: 1 to 22%, Mn: 2% or less (including 0%), Si: less than 0.1% (including 0%), and the balance including Al, other unavoidable impurities and within a range that does not impair the object of the present invention May contain other elements. Alternatively, according to one aspect of the present invention, the second alloyed plating layer is, by weight%, Fe: 30 to 40%, Zn: 1 to 22%, Mn: 2% or less (including 0%), Si: 0.1% less than (including 0%), balance Al and other unavoidable impurities.
[91]
In addition, according to one aspect of the present invention, in the second alloyed plating layer, the Al content in weight% may be 40 to 65%, preferably 44 to 65%, more preferably 44 to 65% may be 60%. Meanwhile, in the second alloyed plating layer, by satisfying the Al content, desired stickiness, corrosion resistance, and adhesion of the plating layer can be easily secured.
[92]
Also, seen According to one aspect of the invention, in the second alloyed plating layer, the Fe content is preferably 30 to 40%, more preferably 32 to 40%, in terms of weight%. By satisfying the Fe content in the second alloyed plating layer, it is possible to easily secure desired stickiness, corrosion resistance, and adhesion of the plating layer.
[93]
That is, according to one aspect of the present invention, since the first alloyed plating layer and the second alloyed plating layer have the above-described specific composition, it is possible to improve the stickiness and corrosion resistance of the plated steel sheet, as well as the adhesion of the plating layer after alloying treatment. The desired effect of the present invention can be exhibited. Therefore, as the composition of the above-described first alloyed plating layer and the second alloyed plating layer, if any one component content is not satisfied, the effects of excellent stickiness, corrosion resistance and adhesion according to the present invention cannot be expected.
[94]
Further, according to one aspect of the present invention, in the first alloyed plating layer and the second alloyed plating layer, the content of Si may be less than 0.1%, including the case of 0%. That is, in the present invention, elements such as Si may be included in an amount of less than 0.1% as an additional element in the molten plating bath, and since Si may not be included, the lower limit is not particularly limited. On the other hand, the Si content is preferably less than 0.1% in terms of securing resistance to cracking during the aforementioned processing. Meanwhile, more preferably, the upper limit of the Si content in the single-layer alloyed plating layer may be 0.09% (ie, 0.09% or less).
[95]
In particular, according to one aspect of the present invention, in the first alloyed plating layer and the second alloyed plating layer, Zn not only improves the stickiness and corrosion resistance of the plated steel sheet, but also plays an important role in improving the adhesion of the plating layer after alloying treatment. do Therefore, in the plated steel sheet of the present invention, it is preferable that the Zn content in the first alloyed plating layer is 1 to 20% and the Zn content in the second alloyed plating layer is 1 to 22%. In the present invention, if the lower limit of the Zn content in the first alloyed plating layer and the second alloyed plating layer is not satisfied, the effect of improving stickiness and corrosion resistance cannot be expected. In addition, if the upper limit of the Zn content in the first alloyed plating layer and the second alloyed plating layer is not satisfied, there is a problem in that the adhesion of the plating layer after the alloying treatment is deteriorated.
[96]
According to one aspect of the present invention, the Zn content in the first alloyed plating layer is 1 to 20%, and the Zn content in the second alloyed plating layer is more preferably 1.5 to 22%.
[97]
In addition, according to one aspect of the present invention, the Zn content in the second alloyed plating layer may be greater than the Zn content in the first alloyed plating layer, which is a process of cooling and alloying treatment after immersing the base steel sheet in a plating bath. This is because Zn in the second alloyed plating layer far from the base steel sheet is concentrated as a result of diffusion of Fe in the base steel sheet during the passage of time.
[98]
Further, according to one aspect of the present invention, the Mn content in the first alloyed plating layer may be greater than the Mn content in the second alloyed plating layer. Further, according to one aspect of the present invention, the Fe content in the first alloyed plating layer may be greater than the Fe content in the second alloyed plating layer.
[99]
According to one aspect of the present invention, after immersing a base steel sheet in an aluminum plating bath during the above-described manufacturing process and performing plating, Fe and/or Mn of the base steel sheet are diffused into the aluminum plating layer by alloying heat treatment, and as a result, Fe And a first alloyed plating layer and a second alloyed plating layer mainly composed of an intermetallic compound of Al are formed.
[100]
On the other hand, although not limited to this, according to one aspect of the present invention, preferably, the first alloyed plating layer may mainly include an alloy phase of Fe 2Al 5 , and the second alloyed plating layer may include an alloy phase of FeAl 3 can mainly include. Specifically, according to one aspect of the present invention, the first alloyed plating layer may contain 80% or more of an alloy phase of Fe 2Al 5 , and the second alloyed plating layer may contain 80% or more of an alloy phase of FeAl 3 . have.
[101]
In addition, according to one aspect of the present invention, the first alloyed plating layer Fe 2Al 5 May include an alloy phase of 90% or more, and the second alloyed plating layer FeAl 3 It may include an alloy phase of 90% or more. .
[102]
In addition, according to one aspect of the present invention, the first alloyed plating layer is made of an alloy phase in which Zn, Mn and / or Si are dissolved based on Fe 2Al 5 (ie, 80% or more of Fe 2Al 5) , The second alloyed plating layer may be formed of an alloy phase in which Zn, Mn, and/or Si are dissolved based on FeAl 3 (ie, 80% or more of FeAl 3 ).
[103]
That is, in the present specification, being made of the alloy phase implies that other unavoidable impurities may be included, and other components may be included within a range that does not impair the object of the present invention.
[104]
On the other hand, when the alloyed plating layer is formed in two layers, the aluminum-based alloy-coated steel sheet according to the present invention, when the distance from the center line of the surface roughness of the alloyed plating layer to the lowermost line of the alloyed plating layer is t, the alloyed plating layer The ratio (As) of the area occupied by the base steel sheet within the area from the surface roughness center line to 3/4t is 30% or more.
[105]
In the present specification, the lowermost line of the alloyed plating layer means a line drawn at the lowermost end of the alloyed plating layer in a direction perpendicular to the thickness direction of the steel sheet. Further, according to one aspect of the present invention, the lowermost line of the alloyed plating layer may mean a line drawn to be horizontal with the center line of surface roughness.
[106]
Specifically, the case where the alloyed plating layer according to the present invention is formed in two layers is shown in FIG. 3, and as can be seen in FIG. 3, the base steel sheet is The interface between the alloyed plating layer and the base steel sheet is formed in a sawtooth shape so that the area occupied ratio (As) is 30% or more.
[107]
In the alloyed plating layer according to one aspect of the present invention, by forming the boundary with the base steel sheet, which is the base material, in a sawtooth shape as described above, it is possible to suppress the occurrence of cracks during processing, thereby ensuring excellent crack resistance. .
[108]
In this case, the upper limit of the value of As may not be separately limited in that the larger the value, the more excellent the crack resistance effect during processing. However, more preferably, the upper limit of the value of As may be 80%.
[109]
On the other hand, when the alloyed plating layer is formed in two layers, the meaning of the boundary between the alloyed plating layer and the base steel sheet described above is that the first alloyed plating layer is formed on the base steel sheet as a base material, specifically, the first alloyed plating layer and the base steel sheet. It may mean the boundary of the steel plate.
[110]
Further, according to one aspect of the present invention, the thickness of the first alloyed plating layer may be 1 ~ 25㎛, the thickness of the second alloyed plating layer may be 3 ~ 20㎛. According to one aspect of the present invention, by setting the thickness of the first alloyed plating layer to 1 μm or more, the effect of corrosion resistance is exhibited, and by setting the thickness of the first alloyed plating layer to 25 μm or less, adhesion can be secured. In addition, by setting the thickness of the second alloyed plating layer to 3 μm or more, the effect of corrosion resistance is exhibited, and by setting the thickness of the second alloyed plating layer to 25 μm or less, adhesion can be secured.
[111]
Meanwhile, in the present invention, the formation of the second alloyed plating layer on the first alloyed plating layer means that the second alloyed plating layer is formed on the first alloyed plating layer to be in contact with it.
[112]
In addition, according to one aspect of the present invention, in all cases where the alloyed plating layer is formed in one layer or two layers, the base steel sheet included in the aluminum-based coated steel sheet is a steel sheet for hot press forming, and is not particularly limited as long as it is used for hot press forming. don't
[113]
However, if one non-limiting example is given, a steel sheet containing Mn in the range of 1 to 25% may be used as the base steel sheet. Or, more preferably, as a base steel sheet, in weight%, C: 0.05 to 0.3%, Si: 0.1 to 1.5%, Mn: 0.5 to 8%, B: 50 ppm or less, the balance including Fe and other unavoidable impurities A base steel plate can be used.
[114]
That is, according to the present invention, it is possible to provide a plated steel sheet having excellent corrosion resistance and adhesion of the plated layer while suppressing seizure of the plated layer attached to the press die or the roll, which occurs during hot forming.
[115]
[Method of manufacturing aluminum-based alloy coated steel sheet]
[116]
Hereinafter, one example of a method for manufacturing an aluminum-based alloy-coated steel sheet used in hot press forming according to an aspect of the present invention is described as follows. However, the manufacturing method of the aluminum-based alloy-coated steel sheet for hot press forming described below is an example, and the aluminum-based alloy-coated steel sheet for hot press forming of the present invention does not necessarily have to be manufactured by the present manufacturing method.
[117]
Another aspect of the present invention is a method for manufacturing an aluminum-based coated steel sheet used in hot press forming,
[118]
Preparing a base steel sheet;
[119]
immersing the base steel sheet in an aluminum plating bath containing Zn: 3 to 30%, Si: less than 0.1%, balance Al and other unavoidable impurities in weight percent to obtain an aluminum-plated steel sheet;
[120]
After aluminum plating, a cooling step of supplying air heated to 200 to 300 ° C. to the aluminum-coated steel sheet to form an oxide film on the surface of the aluminum-coated steel sheet; and
[121]
Obtaining an aluminum-based plated steel sheet through on-line alloying of heat treatment by continuously maintaining a heating temperature range of 650 to 750 ° C. for 1 to 20 seconds after the cooling; manufacturing method of an aluminum-based plated steel sheet including provides
[122]
First, a base steel sheet is prepared to manufacture an aluminum alloy coated steel sheet. The above description can be equally applied to the base steel sheet.
[123]
Next, the present invention An aluminum-based coated steel sheet according to one aspect is subjected to molten aluminum plating using an aluminum plating bath containing Zn: 3 to 30%, Si: less than 0.1%, the balance Al and other unavoidable impurities, by weight% on the surface of the base steel sheet. It can be obtained by performing an on-line alloying treatment in which heat treatment is performed immediately after cooling in succession to the plating step.
[124]
Specifically, plating is performed by immersing the base steel sheet in a molten aluminum plating bath. On the other hand, according to one aspect of the present invention, the composition of the plating bath may be a molten aluminum alloy plating bath including Zn: 3 to 30%, Si: less than 0.1%, the balance Al and other unavoidable impurities, more preferably Zn: 3 to 30%, Si: less than 0.1%, and Al: 70 to 97% may be included, and other unavoidable impurities may also be included.
[125]
In addition, according to one aspect of the present invention, additional elements may be further added to the aluminum plating bath within a range that does not impair the object of the present invention.
[126]
In addition, according to one aspect of the present invention, the molten aluminum alloy plating bath may be made of Zn: 3 to 30%, Si: less than 0.1%, Al: 70 to 97% and other unavoidable impurities.
[127]
According to one aspect of the present invention, the amount of Zn added to the aluminum plating bath is preferably 3 to 30% by weight. When the Zn content exceeds 30%, a large amount of ash is generated in the plating bath, resulting in poor workability due to generation of dust. In addition, if the Zn content is less than 3%, the melting point of the plating bath is not greatly reduced, and corrosion resistance cannot be improved because Zn does not remain in the plating layer due to evaporation of Zn during alloying.
[128]
However, in order to further maximize the effects of the present invention, the lower limit of the Zn content is preferably 5% and more preferably 10%. Similarly, in order to further maximize the effect of the present invention, the upper limit of the Zn content is preferably 25%, more preferably 20%.
[129]
On the other hand, according to one aspect of the present invention, it is preferable to manage the temperature of the plating bath as high as 20 to 50 ° C (ie, in the range of Tb + 20 ° C to Tb + 50 ° C) compared to the melting point (Tb) of the plating bath. . By controlling the temperature of the plating bath to Tb + 20 ° C or higher, it is possible to control the coating amount due to the fluidity of the plating bath, and by controlling the temperature of the plating bath to Tb + 50 ° C or lower, structural erosion in the plating bath is prevented. It can be prevented.
[130]
In addition, according to one aspect of the present invention, during the plating, the coating amount per side (attachment amount per side of the plating layer) may be 20 to 100 g / m 2 , which is after immersing the base steel sheet in a molten aluminum plating bath, air It can be controlled by applying an air wipping process. During the plating, when the plating amount per side is 20 g/m 2 or more, the corrosion resistance effect is exhibited, and when the plating amount per side is 100 g/m 2 or less during the plating, the effect of securing adhesion can be exhibited.
[131]
Subsequently, after aluminum plating, air heated to 200 to 300° C. may be supplied to the aluminum-coated steel sheet to be cooled to form an oxide film on the surface of the aluminum-coated steel sheet. This cooling step is important in the present invention in that it is a means of forming a uniform alloy layer. That is, by supplying and exposing air heated to 200 to 300° C. to the aluminum-coated steel sheet during cooling, an oxide film (aluminum oxide film; AlO x ) is formed on the surface of the aluminum-coated steel sheet.
[132]
According to one aspect of the present invention, as described above, before the alloying treatment, an oxide film may be formed on the surface of the aluminum-coated steel sheet by 10% or more (more preferably 10% or more and 20% or less) of the total thickness of the hot-dip aluminum plating layer. have. As described above, by forming an oxide film of 10% or more, volatilization of Zn included in the plating layer during the alloying process can be prevented, and thus excellent stickiness, corrosion resistance, and adhesion of the plating layer can be secured.
[133]
Next, an on-line alloying treatment in which heat treatment is performed immediately after the cooling described above may be performed. Through this alloying heat treatment, Fe and/or Mn of the base steel sheet are diffused into the aluminum plating layer, whereby the plating layer can be alloyed.
[134]
Specifically, in the present invention, the alloying heat treatment temperature is in the range of 650 ~ 750 ℃, the holding time may be 1 ~ 20 seconds.
[135]
In the present invention, as can be seen in the schematic diagram shown in Figure 1, the online alloying treatment means a process of heat treatment by raising the temperature after molten aluminum plating. In the online alloying heat treatment method according to the present invention, alloying is possible in a short time because heat treatment for alloying starts before the plating layer is cooled and hardened after molten aluminum plating. In the conventionally known coating layer components of aluminum-coated steel sheet, since the alloying rate is slow and sufficient alloying cannot be completed in a short time, it is difficult to apply an on-line alloying method in which heat treatment is performed immediately after plating. However, in the present invention, alloying of the aluminum plating layer can be achieved despite a relatively short heat treatment time of 1 to 20 seconds by controlling the composition of the plating bath and manufacturing conditions that affect the alloying rate.
[136]
On the other hand, the alloying heat treatment temperature is based on the surface temperature of the steel sheet to be heat treated, and if the heat treatment temperature is less than 650 ° C, a problem of insufficient alloying of the plating layer may occur, whereas if the heat treatment temperature exceeds 750 ° C, the plated steel sheet There is a problem in that the cooling of the coating is deteriorated due to a problem.
[137]
On the other hand, according to one aspect of the present invention, the composition of the alloyed plating layer is changed by adjusting the alloying heat treatment temperature. When the alloying heat treatment temperature is 650 to 680 ° C, the alloyed plating layer is formed in two layers (the aforementioned first alloyed plating layer and the second alloyed plating layer). Corresponding to the plating layer), whereas at 680 to 750 ° C, the alloyed plating layer is formed as a single layer.
[138]
In addition, according to one aspect of the present invention, the holding time during the alloying heat treatment may be performed in the range of 1 to 20 seconds. In the present invention, the holding time means the time during which the heating temperature (including deviation ±10°C) is maintained in the steel sheet. By setting the holding time to 1 second or more, sufficient alloying is possible, and by setting the holding time to 20 seconds or less, there is an effect of securing productivity.
[139]
According to one aspect of the present invention, in order to further improve the effect of the present invention, the lower limit of the holding time during the alloying heat treatment may be 1 second, more preferably 3 seconds. Similarly, the upper limit of the holding time during the alloying heat treatment may be 20 seconds, more preferably 10 seconds.
[140]
As described above, in the prior art, since the diffusion of Fe is suppressed by the inclusion of Si, it was impossible to achieve alloying in a short time of 20 seconds or less, whereas according to the present invention, the composition of the plating bath and the conditions during alloying heat treatment are controlled By doing so, alloying can be achieved in a relatively short time of 20 seconds or less.
[141]
Meanwhile, the method for manufacturing an aluminum alloy coated steel sheet according to an aspect of the present invention may further include cooling after the alloying treatment.
[142]
According to one aspect of the present invention, the cooling may cool the steel sheet discharged from the alloying process to 300 ° C or less at an average cooling rate of 15 to 25 ° C / s. Meanwhile, the cooling may be air cooling or mist cooling, and most preferably, the cooling may be air cooling or mist cooling. According to one aspect of the present invention, by setting the average cooling rate to 15° C. or more, the temperature of the steel sheet is cooled to 300° C. or less to prevent adsorption to the roll, and the average cooling rate to 25° C./s or less. This has the effect of increasing the operating speed.
[143]
In addition, according to one aspect of the present invention, the cooling can be carried out for 6 to 30 seconds, and the effect of cooling to the desired steel sheet temperature is exhibited by setting the cooling time to 6 seconds or more, and the cooling time to 30 seconds Seconds or less can exert an effect of cooling the steel sheet temperature to a desired temperature while maximizing productivity.
[144]
Meanwhile, according to one aspect of the present invention, in the plated steel sheet manufactured through the present invention, the Fe content in the alloyed plating layer can be represented by the following relational expression 1, and the heat treatment temperature during alloying and the Zn content in the plating bath are appropriately By controlling within the range, the effect of excellent stickability, corrosion resistance and/or coating layer adhesion can be easily exhibited.
[145]
[Relationship 1]
[146]
150 - 0.4×[T]+3.3×10-4×[T] 2 - 0.38×[wt%Zn] ≤ [wt%Fe] ≤ 180 - 0.4×[T]+3.3×10-4×[T] 2 - 0.38 × [wt%Zn]
[147]
(In the above relational expression 1, [T] represents the alloying heat treatment temperature (° C.), [wt%Zn] represents the Zn weight% content in the plating bath, and [wt%Fe] represents the Fe weight% content in the alloyed plating layer indicates.)
[148]
On the other hand, another aspect of the present invention provides a hot formed member obtained by hot press forming the above-described aluminum alloy plated steel sheet.
[149]
The hot press molding may use a method generally used in the art. For example, after heating a plated steel sheet in a temperature range of 800 to 950° C. for 3 to 10 minutes, the heated steel sheet may be hot-formed into a desired shape using a press, but is not limited thereto.
[150]
In addition, the composition of the base steel sheet of the hot press-formed member may be the same as the composition of the above-described base steel plate.
[151]
Mode for Carrying Out the Invention
[152]
Hereinafter, the present invention will be described in more detail through examples. However, it should be noted that the following examples are only for exemplifying and specifying the present invention, and are not intended to limit the scope of the present invention. The scope of the present invention is the patent claims This is because it is determined by the matters described above and those reasonably inferred from them.
[153]
(Experimental Example 1)
[154]
First, after preparing a cold-rolled steel sheet for hot press forming having a thickness of 1.2 mm having a composition shown in Table 1 as a base steel sheet, the base steel sheet was immersed and ultrasonically washed to remove substances such as rolling oil present on the surface.
[155]
Thereafter, after heat treatment at an annealing temperature of 800 ° C. and an annealing time of 50 seconds in a furnace maintained in a reducing atmosphere, the base steel sheet is immersed in a plating bath under the plating bath composition and plating bath temperature conditions shown in Table 2 below Then, aluminum plating was performed. During immersion in the plating bath, the immersion temperature was maintained at the same temperature as that of the plating bath, and the temperature of the plating bath was maintained at a temperature raised by 40° C. collectively with respect to the melting point (Tb) of each plating component system. The coating weight was kept constant at 60 g/m 2 on one side using air wiping to compare alloying.
[156]
Subsequently, the aluminum-plated steel sheet was cooled by supplying air heated to 200 to 300 ° C. to the aluminum-plated steel sheet, and then, alloying heat treatment was performed under the alloying heat treatment conditions shown in Table 2, and the aluminum alloy plating was cooled by air cooling. A steel plate was prepared.
[157]
[Table 1]
element C Si Mn Al Ti B Fe
Content (%) 0.22 0.25 1.3 0.03 0.03 25ppm bal.
[158]
[Table 2]
Remarks Plating Bath Composition (wt%) Alloying
Al Zn Temperature [℃] Time [sec]
Comparative Example 1 100 - 750 20
Inventive example 1 bal. 3 700 7
Comparative Example 2 bal. 5 630 30
Inventive example 2 bal. 5 650 10
Inventive example 3 bal. 5 680 10
Inventive example 4 bal. 5 750 5
Comparative Example 3 bal. 20 630 20
Inventive example 5 bal. 20 650 10
Inventive example 6 bal. 20 680 5
Inventive Example 7 bal. 20 750 3
Comparative Example 4 bal. 30 630 15
Inventive example 8 bal. 30 650 10
Inventive example 9 bal. 30 680 7
Inventive example 10 bal. 30 750 3
Comparative Example 5 bal. 32 630 25
Comparative Example 6 bal. 32 650 25
Comparative Example 7 bal. 32 680 20
Comparative Example 8 bal. 32 750 10
[159]
[Table 3]
Note When the alloyed plating layer is a single layer or the first alloyed plating layer and the second alloyed plating layer As*
Component [wt%] Thickness
[㎛] Component [wt%] Thickness
[μm]
Al Zn Mn Fe Al Zn Mn Fe
Comparative Example 1 bal 2 45 10 bal 0.0 1.5 0 12 18
Inventive example 1 bal 1 0 46 10 bal 1.5 1 38 5 80
Comparative Example 2 bal 2 0.3 44 10 bal 1.0 0.1 0 15 15
Inventive Example 2 bal 2 1 44 1 bal 4.0 0.3 39 20 70
Inventive Example 3 bal 2 1 45 5 bal 3.5 0.5 40 15 65
Inventive Example 4 bal 1 2 50 15 bal - - - 60
Comparative Example 3 bal 17 0.5 37 10 bal 19.0 1 0 15 27
Inventive Example 5 bal 15 1 38 15 bal 17.0 1.2 34 5 50
Inventive example 6 bal 12 2 39 17 bal 14.0 1.5 35 3 45
Inventive Example 7 bal 10 3 48 20 bal - - - 40
Comparative Example 4 bal 23 1.5 35 5 bal 25.0 1 0 10 24
Inventive example 8 bal 20 2 35 20 bal 22.0 1.5 32 4 42
Inventive Example 9 bal 18 3 36 15 bal 20.0 2 33 3 36
Inventive example 10 bal 15 5 40 25 bal - - - 31
Comparative Example 5 bal 27 2 33 10 bal 29.0 1 0 20 17
Comparative Example 6 bal 25 4 34 10 bal 27.0 2 30 18 10
Comparative Example 7 bal 23 5 35 12 bal 25.0 3 31 16 27
Comparative Example 8 bal 22 6 35 30 - - - - 25
[160]
As*: Ratio of the area occupied by the base steel sheet within the region from the center line of the surface roughness of the alloyed plating layer to 3/4t, when the distance from the center line of the surface roughness of the alloyed plating layer to the lowermost line of the alloyed plating layer is t [ %]
[161]
On the other hand, in the aluminum alloy plated steel sheet manufactured by the above method, when the alloyed plating layer is a single layer or two layers, the content and thickness of each component in the first alloyed plating layer and the second alloyed plating layer are measured and shown in Table 3 above. was Components in the plating layer were measured by point analysis using EDS (Energy Dispersive Spectroscopy), and the thickness was measured by an electron microscope.
[162]
In addition, the alloy phase of the alloyed plating layer formed of a single layer of Example 4 was analyzed by XRD (X-Ray Diffraction) method, and it was confirmed that the alloyed plating layer consisted of an alloy phase of Fe 2 Al 5 or more by 80%.
[163]
In addition, the alloy phase analysis was performed on the alloyed plating layer formed of the two layers of the invention example 1 by way of XRD (X-Ray Diffraction) and EDS analysis, and the first alloyed plating layer was mainly composed of an alloy phase of Fe 2 Al 5 , It was confirmed that the second alloyed plating layer consisted of 80% or more of the FeAl 3 alloy phase.
[164]
With respect to the plated steel sheet manufactured in this way, the ratio of the upper plating layer to the total plating layer was measured using a SEM (scanning electron microscope) and the ratio of the cross-sectional thickness is shown in Table 4 below. In addition, in order to evaluate the physical properties of the plated steel sheet, the plating layer upper ratio, stickiness, corrosion resistance, and plating adhesion were evaluated in the following manner.
[165]
[Adherence]
[166]
The plated steel sheet thus manufactured was heated at 900° C. for 5 minutes to evaluate the physical properties of the plating, and then visually observed whether the alloyed plating layer was fused to a die, and evaluated according to the following criteria.
[167]
○: no sticking
[168]
×: die adsorption caused by melting of the plating layer
[169]
[corrosion resistance]
[170]
After the salt spray experiment was performed on the coated steel sheet, it was allowed to stand for 720 hours, and then the corrosion product formed on the surface was removed to measure the maximum depth of the corrosion product formed on the surface.
[171]
Corrosion resistance: After 720 hours of salt spray experiment, corrosion products formed on the surface were removed, and the depth of corrosion formed by corrosion was measured.
[172]
○: 70 μm or less
[173]
×: more than 70 μm
[174]
[Plating Adhesion]
[175]
The plating adhesion was measured by converting the degree of peeling using a tape into weight when shear stress was applied to the plating layer through a one-sided friction test after alloying. Evaluated based on
[176]
○: 0.5 g/m2 or less
[177]
×: more than 0.5 g/m 2
[178]
[Table 4]
Top ratio of plating layer (%) Stickiness Corrosion resistance Plating adhesion Composition of plating layer
Comparative Example 1 55% × × ○ double layer
Inventive Example 1 33% ○ ○ ○ double layer
Comparative Example 2 60% × × ○ double layer
Inventive Example 2 95% ○ ○ ○ double layer
Inventive Example 3 75% ○ ○ ○ Double layer
Inventive Example 4 0% ○ ○ ○ single layer
Comparative Example 3 60% × ○ ○ double layer
Inventive Example 5 25% ○ ○ ○ double layer
Inventive Example 6 15% ○ ○ ○ double layer
Inventive Example 7 0% ○ ○ ○ Single layer
Comparative Example 4 67% × ○ ○ double layer
Inventive Example 8 17% ○ ○ ○ Double layer
Inventive Example 9 17% ○ ○ ○ Double layer
Inventive example 10 0% ○ ○ ○ single layer
Comparative Example 5 67% × ○ × double layer
Comparative Example 6 64% ○ ○ × double layer
Comparative Example 7 57% ○ ○ × double layer
Comparative Example 8 0% ○ ○ × single phase
[179]
As shown in Tables 1 to 4, in the case of Inventive Examples 1 to 10 satisfying the composition and alloying conditions of the plating bath specified in the present invention, all of the stickiness, corrosion resistance and coating adhesion were good, and accordingly, occurrence during hot forming It was possible to prevent the plating layer from sticking to the press die or roll to be used or the occurrence of microcracks.
[180]
On the other hand, in the case of Comparative Examples 1 to 8, which did not satisfy the Zn content of the plating bath stipulated in the present invention or did not satisfy the alloying conditions, one or more physical properties of stickiness, corrosion resistance and coating adhesion were not good, and accordingly, hot Problems such as adhesion of the plating layer to the press die or roll or generation of microcracks occurred during linearization.
[181]
Meanwhile, FIG. 1 shows a photograph of a cross section of an aluminum-based coated steel sheet observed with a scanning electron microscope for an additional experimental example in which 7% Si was added to an aluminum plating bath according to the prior art. In this case, the ratio of the area occupied by the base steel sheet within the region from the center line of the surface roughness of the alloyed plating layer to 3/4t was less than 30%.
[182]
On the other hand, FIG. 2 is a photograph of a cross-section of an aluminum alloy-coated steel sheet prepared in Inventive Example 1 observed with a scanning electron microscope, in which a two-layer alloyed plating layer is formed, and an alloyed plating layer by adding Zn and a base material The boundary of the steel sheet was formed in a sawtooth shape, and accordingly, it was confirmed that the ratio of the area occupied by the base steel sheet within the area from the center line of the surface roughness of the above-described alloyed plating layer to 3/4t was 30% or more.
[183]
In addition, FIG. 3 is a scanning electron microscope photograph of a cross section of an aluminum-based alloy-coated steel sheet manufactured in Inventive Example 6, and the boundary between the alloyed plating layer and the base steel sheet is formed in a sawtooth shape by the addition of Zn, Accordingly, the ratio of the area occupied by the base steel sheet within the region from the center line of the surface roughness of the above-described alloyed plating layer to 3/4t was 30% or more.
[184]
[185]
1: heat treatment furnace
[186]
2: aluminum plating bath
[187]
3: cooling device
[188]
4: alloying heat treatment device
claims
[Claim 1]
base grater; and a single-layer alloyed plating layer formed on the base steel sheet, wherein the alloyed plating layer, by weight, Fe: 35-50%, Zn: 1-20%, Mn: 5% or less, Si: less than 0.1%, balance Al and other inevitable Area occupied by the base steel sheet within a region from the center line of the surface roughness of the alloyed plating layer to 3/4t, including impurities, when the distance from the centerline of the surface roughness of the alloyed plating layer to the lowermost line of the alloyed plating layer is t An aluminum-based alloy-coated steel sheet having a ratio of 30% or more.
[Claim 2]
base grater; An alloyed plating layer formed on the base steel sheet, wherein the alloyed plating layer, by weight, Fe: 35-50%, Zn: 1-20%, Mn: 5% or less, Si: less than 0.1%, the balance Al and others A first alloyed plating layer containing unavoidable impurities; and a second alloyed plating layer containing Fe: 30-40%, Zn: 1-22%, Mn: 2% or less, Si: less than 0.1%, balance Al and other unavoidable impurities, by weight%, wherein the alloying When the distance from the center line of the surface roughness of the plating layer to the lowermost line of the alloyed plating layer is t, the ratio of the area occupied by the base steel sheet within the area from the center line of the surface roughness of the alloyed plating layer to 3/4t is 30% or more. based alloy coated steel sheet.
[Claim 3]
The aluminum-based alloy-coated steel sheet according to claim 1, wherein the thickness of the alloyed plating layer is 5 to 25 μm.
[Claim 4]
The aluminum-based alloy-coated steel sheet according to claim 1, wherein the alloyed plating layer contains 80% or more of an alloy phase of Fe 2 Al 5 .
[Claim 5]
The aluminum-based alloy-coated steel sheet according to claim 1, wherein the content of Al in the alloyed plating layer is 40 to 60%.
[Claim 6]
The aluminum-based alloy-coated steel sheet according to claim 2, wherein the Zn content in the second alloyed plating layer is greater than the Zn content in the first alloyed plating layer.
[Claim 7]
The aluminum-based alloy-coated steel sheet according to claim 2, wherein the Zn content in the first alloyed plating layer is 1 to 20%, and the Zn content in the second alloyed plating layer is 1.5 to 22%.
[Claim 8]
The aluminum-based alloy-coated steel sheet according to claim 2, wherein the Al content in the first alloyed plating layer is 40 to 60%, and the Al content in the second alloyed plating layer is 40 to 65%.
[Claim 9]
[Claim 3] The aluminum-based alloy-coated steel sheet according to claim 2, wherein the first alloyed plating layer has a thickness of 1 to 25 µm and the second alloyed plating layer has a thickness of 4 to 20 µm.
[Claim 10]
The aluminum-based alloy-coated steel sheet according to claim 2, wherein the first alloyed plating layer contains 80% or more of an alloy phase of Fe 2Al 5 , and the second alloyed plating layer contains 80% or more of an alloy phase of FeAl 3 .
[Claim 11]
The base steel sheet according to claim 1 or 2, by weight, C: 0.05-0.3%, Si: 0.1-1.5%, Mn: 0.5-8%, B: 50 ppm or less, the balance of Fe and other unavoidable impurities Containing, an aluminum-based alloy coated steel sheet.
[Claim 12]
A method of manufacturing an aluminum-based alloy coated steel sheet used for hot press forming, comprising: preparing a base steel sheet; immersing the base steel sheet in an aluminum plating bath containing Zn: 3 to 30%, Si: less than 0.1%, balance Al and other unavoidable impurities in weight percent to obtain an aluminum-plated steel sheet; After aluminum plating, a cooling step of supplying air heated to 200 to 300° C. to the aluminum-coated steel sheet to form an oxide film on the surface of the aluminum-coated steel sheet; And obtaining an aluminum-based plated steel sheet through on-line alloying of heat treatment by continuously holding in a heating temperature range of 650 to 750 ° C. for 1 to 20 seconds after the cooling; manufacturing method.
[Claim 13]
The method of claim 12, wherein the alloying temperature is controlled to satisfy the following relational expression 1. [Relationship 1] 150 - 0.4 × [T] + 3.3 × 10-4 × [T] 2 - 0.38 × [wt%Zn] ≤ [wt% Fe] ≤ 180 - 0.4 × [T] + 3.3 × 10-4 × [T] 2 - 0.38 × [wt%Zn] (in the above relational expression 1, [T] represents the alloying heat treatment temperature (° C.), [wt%Zn] represents the Zn weight% content in the plating bath, [ wt% Fe] represents the Fe wt% content in the alloyed plating layer.)
[Claim 14]
13. The method of claim 12, wherein the oxide film is formed on the surface by 10% or more with respect to the total thickness of the hot-dip aluminum plating layer.
[Claim 15]
A hot formed member obtained by hot press forming the aluminum-based alloy-coated steel sheet according to claim 1 or 2.