KR102451003B1 - High strength hot-dip galvanized steel sheet having exceelent coating adhesion and spot weldability and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a high-strength hot-dip galvanized steel sheet having excellent plating adhesion and spot weldability and a method for manufacturing the same.

Description

High-strength hot-dip galvanized steel sheet with excellent plating adhesion and spot weldability and manufacturing method thereof

The present invention relates to a high-strength hot-dip galvanized steel sheet having excellent plating adhesion and spot weldability and a method for manufacturing the same.

Demand for ultra-high-strength steel sheets is rapidly increasing as a measure to respond to stricter regulations on fuel efficiency and collision stability in accordance with recently emerging environmental regulations. In addition, while improvement of fuel efficiency is required to achieve the carbon emission reduction target for each country, the weight of automobiles is continuously increasing due to high performance and the increase of various convenience devices. is increasing to Accordingly, steelmakers are focusing on the development of high-strength steel sheets such as Dual Phase (DP) steel, Transformation Induced Plasticity (TRIP) steel, and Complex Phase (CP) steel.

In order to increase the strength of the steel sheet for automobiles, it is common to add a large amount of elements such as Si, Mn, and Al to the steel to increase the strength. When the steel sheet is immersed in the hot-dip galvanizing bath, the plating property is inferior, and plating peeling may occur. In addition, in the subsequent spot welding process, liquid metal embrittlement that causes cracks by penetrating the liquid molten metal into the grain boundary of the base metal may make the spot weldability inferior.

In order to improve the plating properties of the above-mentioned Si, Mn, and Al-added steel sheet, it is necessary to suppress the oxides generated on the surface of the steel sheet. There are problems that are difficult to obtain.

Patent Document 1 is a representative technique for solving this problem. Patent Document 1 relates to a technique for suppressing formation of Si oxide on the surface by preferentially concentrating at grain boundaries through addition of trace components such as Sb to steel.

However, there is still a demand for the development of a technology capable of more reliably preventing the diffusion of alloying elements in steel when manufacturing a steel sheet.

Japanese Patent Publication No. 6222040

One aspect of the present invention is to provide a high-strength hot-dip galvanized steel sheet having excellent plating adhesion and spot weldability and a method for manufacturing the same.

One embodiment of the present invention is a base steel plate; an iron-nickel or iron-nickel alloy alloy layer formed on one or both surfaces of the base steel sheet; and an alloying inhibiting layer formed on the iron-nickel or iron-nickel alloy alloy layer. A hot-dip galvanized steel sheet comprising a hot-dip galvanized layer formed on the alloying suppression layer, wherein the base steel sheet is by weight %, carbon (C): 0.1 to 0.3%, silicon (Si): 0.1 to 2.0%, aluminum ( Al): 0.1 to 1.5%, manganese (Mn): 1.5 to 3.0%, molybdenum (Mo): 0.01 to 0.3%, the balance includes Fe and unavoidable impurities, and the sum of Si and Al satisfies 1.2 to 3.5% and the ratio of Al and Si (Al/Si) satisfies 0.5 to 2.0, and on the GDS depth profile, nickel in the region from the surface of the iron-nickel or iron-nickel alloy layer to 2 μm in the direction of the base steel sheet The area occupied by this is 2 to 10% by weight · μm, and the alloying suppression layer has 1 to 20 area% of Fe2Al5 crystals having a maximum size of 100 nm or less.

Another embodiment of the present invention is by weight, carbon (C): 0.1 to 0.3%, silicon (Si): 0.1 to 2.0%, aluminum (Al): 0.1 to 1.5%, manganese (Mn): 1.5 to 3.0% , molybdenum (Mo): 0.01 to 0.3%, the balance Fe and unavoidable impurities, the sum of Si and Al satisfies 1.2 to 3.5%, and the Al and Si ratio (Al/Si) is 0.5 to 2.0 Preparing a base steel sheet that satisfies; forming a nickel or nickel alloy coating layer on the base steel sheet so that the adhesion amount is 100 to 1000 mg/m ² ; heat-treating the base steel sheet on which the nickel or nickel alloy coating layer is formed; and immersing the heat-treated base steel sheet in an Al-containing hot-dip galvanizing bath at 440 to 460° C. to obtain a hot-dip galvanized steel sheet.

According to one aspect of the present invention, it is possible to provide a high-strength hot-dip galvanized steel sheet having excellent plating adhesion and spot weldability and a method for manufacturing the same.

1 is a schematic diagram showing a cross section of a hot-dip galvanized steel sheet according to an embodiment of the present invention.
2 is a photograph of the surface of Comparative Example 1 according to an embodiment of the present invention.
3 is a photograph of the surface of Inventive Example 1 according to an embodiment of the present invention.
4 is a photograph of an alloying inhibiting layer observed by scanning electron microscopy (SEM) after removing the galvanized layer of Comparative Example 1 according to an embodiment of the present invention.
5 is a photograph of an alloying inhibiting layer observed by scanning electron microscopy (SEM) after removing the galvanized layer of Inventive Example 1 according to an embodiment of the present invention.
6 is a GDS (Glow Discharge Spectroscopy) depth profile of Comparative Example 1 according to an embodiment of the present invention.
7 is a GDS (Glow Discharge Spectroscopy) depth profile of Inventive Example 1 according to an embodiment of the present invention.

Hereinafter, a high-strength hot-dip galvanized steel sheet excellent in plating adhesion and spot weldability according to an embodiment of the present invention will be described.

First, the alloy composition of the base steel sheet of the present invention will be described. The content of the alloy composition to be described below means wt% unless otherwise specified.

Carbon (C): 0.1-0.3%

The C is an element contributing to the stabilization of the austenite structure, and as its content increases, it is advantageous in securing the austenite structure. In order to obtain the above effect, the C content is preferably 0.1% or more. However, in the case of exceeding 0.3%, there is a problem that the cast iron defects may occur and the weldability is also deteriorated. Therefore, the content of C is preferably in the range of 0.1 to 0.3%. The lower limit of the C content is more preferably 0.15%. The upper limit of the C content is more preferably 0.25%.

Silicon (Si): 0.1~2.0%

Silicon (Si) is an element contributing to stabilization of retained austenite by suppressing precipitation of carbides in ferrite and promoting diffusion of carbon in ferrite into austenite. In order to obtain the above-described effect, it is preferable that 0.1% or more of the Si is added, but when the content exceeds 2.0%, not only the rolling performance is inferior, but also an oxide is formed on the surface of the steel sheet during the heat treatment process, resulting in poor plating properties and adhesion. may cause Accordingly, the Si content is preferably in the range of 0.1 to 2.0%. The lower limit of the Si content is more preferably 0.2%. The upper limit of the Si content is more preferably 1.8%.

Aluminum (Al): 0.1~1.5%

Aluminum (Al) is an element that deoxidizes by combining with oxygen in steel. Also, like Si, Al is an element contributing to the stabilization of retained austenite by suppressing the formation of carbides in ferrite. In order to obtain the above-described effect, it is preferable that the Al is added 0.1% or more, but when the content exceeds 1.5%, the soundness of the slab is deteriorated, and since it is an element with strong oxygen affinity, an oxide is formed on the surface of the steel sheet This may lead to deterioration of plating properties and adhesion. Therefore, the content of Al is preferably in the range of 0.1 to 1.5%. The lower limit of the Al content is more preferably 0.2%. The upper limit of the Al content is more preferably 1.4%.

Manganese (Mn): 1.5~3.0%

The Mn is an element that stabilizes the austenite structure together with carbon. If the Mn content is less than 1.5%, it becomes difficult to secure the target strength due to the occurrence of ferrite transformation. do. Therefore, the Mn content is preferably in the range of 1.5 to 3.0%. The lower limit of the Mn content is more preferably 1.7%. The upper limit of the Mn content is more preferably 2.9%.

Molybdenum (Mo): 0.01~0.3%

The Mo is an element that serves to improve high-temperature strength, particularly in the present invention, serves to increase the yield strength of steel, and is preferably contained in an amount of 0.01% or more in order to obtain this effect. However, when the content exceeds 0.3%, hot workability may be deteriorated, and there is a disadvantage in terms of cost competitiveness of the product. Therefore, the content of Mo is preferably in the range of 0.01 to 0.3%. The lower limit of the Mo content is more preferably 0.1%. The upper limit of the Mn content is more preferably 0.25%.

In addition to the above-described steel composition, the remainder may include Fe and unavoidable impurities. Inevitable impurities may be unintentionally mixed in a typical steel manufacturing process, and this cannot be entirely excluded, and those skilled in the ordinary steel manufacturing field can easily understand the meaning. In addition, the present invention does not entirely exclude the addition of a composition other than the steel composition mentioned above.

Meanwhile, as mentioned above, both Si and Al are elements contributing to the stabilization of retained austenite, and in order to effectively achieve this, it is preferable that the sum of the contents of Si and Al satisfies the range of 1.2 to 3.5%. When the sum of the Si and Al content is less than 1.2%, it may be difficult to sufficiently obtain the effect of increasing the elongation. On the other hand, when the sum of the content of Si and Al exceeds 3.5%, it may cause a problem in that castability and rollability are inferior. The lower limit of the sum of the Si and Al contents is more preferably 1.3%. The upper limit of the sum of the Si and Al contents is more preferably 3.4%.

In addition, the ratio of Al and Si (Al/Si) preferably satisfies 0.5 to 2.0. When the ratio of Al and Si is less than 0.5, the sensitivity of spot welding LME (Liquid Metal Embrittlement) increases due to matrixing of the Si base, which may lead to inferior weldability. On the other hand, when the ratio of Al and Si exceeds 2.0, the oxygen affinity is relatively high due to matrixing of the Al base, and as oxides are easily formed on the surface of the steel sheet, plating properties and adhesion may be deteriorated. The lower limit of the ratio of Al and Si is more preferably 0.6. The upper limit of the ratio of Al and Si is more preferably 1.9.

1 is a schematic diagram showing a cross section of a hot-dip galvanized steel sheet according to an embodiment of the present invention. As shown in Figure 1, the hot-dip galvanized steel sheet of the present invention is a base steel sheet (10); An iron-nickel or iron-nickel alloy alloy layer 20 formed on one or both surfaces of the base steel plate 10; and an alloying inhibiting layer 30 formed on the iron-nickel or iron-nickel alloy layer 20; and a hot-dip galvanizing layer 40 formed on the alloying suppression layer 30 . By forming an iron-nickel or iron-nickel alloy alloy layer on the base steel plate as described above, it is possible to suppress oxides formed by diffusion of alloying elements in the base steel plate into the surface portion of the base steel plate during annealing heat treatment, and through this, excellent plating properties can be obtained On the other hand, the hot-dip galvanizing layer further includes Al in addition to Zn, in this case, the Al content may be in a range commonly applied in the art.

The hot-dip galvanized steel sheet of the present invention has an area occupied by nickel in a region from the surface of the iron-nickel or iron-nickel alloy layer to 2㎛ in the direction of the base steel sheet on the GDS (Glow Discharge Spectroscopy) depth profile is 2 to 10 weight It is preferable that it is %*micrometer. When the area occupied by nickel is less than 2% by weight μm, nickel does not cover the entire steel sheet and as a bare Fe region exists locally, Si and Mn oxides are formed on the surface, so that the plating appearance and adhesion are inferior. . On the other hand, if it exceeds 10 wt%·㎛, nickel thickly covers the surface of the steel sheet, and as the alloying inhibiting layer becomes fine and thin, plating adhesion may be inferior. As for the lower limit of the area occupied by the said nickel, it is more preferable that it is 2.5 weight%*micrometer. As for the upper limit of the area occupied by the said nickel, it is more preferable that it is 9.5 weight%*micrometer.

In addition, in the alloying suppression layer, it is preferable that 1 to 20 area% of Fe2Al5 crystals having a maximum size of 100 nm or less are present. In general, when the base steel sheet is immersed in the hot-dip galvanizing bath, the reaction between Al in the plating bath and Fe in the base steel sheet occurs instantaneously, so that an alloying inhibiting layer mainly containing Fe2Al5 is formed. The maximum size of a typical Fe2Al5 crystal is about 0.5-1㎛ level. However, in the present invention, by appropriately controlling the alloy composition, in particular, the content range of Mo, the size of the Fe2Al5 crystal is refined to increase the fine irregularities at the interface between the plating layer and the base steel sheet, thereby maximizing the anchoring effect to achieve plating adhesion and point Weldability can be improved. In order to sufficiently obtain the above-described effect, it is preferable that the Fe2Al5 crystal having a maximum size of 100 nm or less is 1 area% or more. However, when it exceeds 20% by area, the thickness of the alloying inhibiting layer may be excessively thin, resulting in poor plating adhesion. The lower limit of the fraction of Fe2Al5 crystals having the maximum size of 100 nm or less is more preferably 2 area%. The upper limit of the fraction of Fe2Al5 crystals having the maximum size of 100 nm or less is more preferably 18 area%.

The hot-dip galvanized steel sheet of the present invention provided as described above has a yield strength of 600 MPa or more, a tensile strength of 950 MPa or more, and an elongation of 20% or more, thereby securing excellent mechanical properties. In addition, the area of the hot-dip galvanized layer is 95% or more relative to the total area of the base steel sheet, and the plating adhesion is good, so that it can have excellent plating properties. In addition, since LME cracking does not occur, it may have excellent LME cracking resistance.

Hereinafter, a method for manufacturing a high-strength hot-dip galvanized steel sheet having excellent plating adhesion and spot weldability according to an embodiment of the present invention will be described.

First, a base steel sheet satisfying the above-described alloy composition is prepared. In the present invention, there is no particular limitation on the method for preparing the base steel sheet. However, as a preferred example, the step of preparing the base steel sheet, the step of reheating the slab at 1000 ~ 1300 ℃; obtaining a hot-rolled steel sheet by hot finish rolling the reheated slab at 800 to 950°C; winding the hot-rolled steel sheet at 630 to 700°C; and pickling the wound hot-rolled steel sheet and then cold rolling to obtain a cold-rolled steel sheet.

The slab satisfying the above alloy composition is reheated at 1000 to 1300 °C. If the slab reheating temperature is less than 1000 ℃ may cause a problem that the rolling load is significantly increased, if it exceeds 1300 ℃, the problem of excessive surface scale may occur. Therefore, the slab reheating temperature is preferably in the range of 1000 ~ 1300 ℃. The lower limit of the slab reheating temperature is more preferably 1050 ℃. The upper limit of the slab reheating temperature is more preferably 1250 ℃.

Thereafter, the reheated slab is hot finish-rolled at 800 to 950° C. to obtain a hot-rolled steel sheet. When the hot finish rolling temperature is less than 800°C, there is a problem in that the rolling load increases and the rolling becomes difficult. Therefore, the hot finish rolling temperature is preferably in the range of 800 ~ 950 ℃. The lower limit of the hot finish rolling temperature is more preferably 830°C. The upper limit of the hot finish rolling temperature is more preferably 930°C.

Then, the hot-rolled steel sheet is wound at 630 ~ 700 ℃. When the coiling temperature is less than 630 ℃, since the internal oxide layer is not formed, the formation of oxides on the surface layer of the steel sheet is promoted during the annealing heat treatment process, so that the plating property may be inferior, and if it exceeds 700 ℃, the depth of the internal oxide layer is It becomes quite deep, and oxides may be picked up on the roll during the subsequent annealing heat treatment process and cause surface defects such as dents. Therefore, the coiling temperature is preferably in the range of 630 to 700 ℃. The lower limit of the coiling temperature is more preferably 650°C. It is more preferable that the upper limit of the coiling temperature is 680°C.

Thereafter, the wound hot-rolled steel sheet is pickled, and then cold-rolled to obtain a cold-rolled steel sheet. In the present invention, the pickling and cold rolling processes are not particularly limited, and all methods commonly used in the art may be used.

A nickel or nickel alloy coating layer is formed so that the adhesion amount is 100 to 1000 mg/m ² on the steel sheet prepared in this way. When the adhesion amount of the nickel or nickel alloy coating layer is less than 100 mg/m ² , nickel does not cover the entire steel sheet and as a bare Fe region exists locally, Si and Mn oxides are formed on the surface, resulting in poor plating appearance and poor adhesion. There is this. On the other hand, when it exceeds 1000mg/m ² , the intermetallic compound formation reaction between Fe in the base steel sheet and Al in the plating bath is restricted, so plating properties may be reduced, and as the size of the Fe2Al5 crystals is reduced as a whole, fine The effect of improving plating adhesion may be insignificant because the anchoring effect due to the unevenness may not be sufficiently obtained. The lower limit of the adhesion amount of the nickel or nickel alloy coating layer is more preferably 150 mg/m ² , and the upper limit is more preferably 950 mg/m ² .

Thereafter, the base steel sheet on which the nickel or nickel alloy coating layer is formed is heat-treated. Through the heat treatment, Fe of the base steel sheet is diffused into the nickel or nickel alloy coating layer to form an iron-nickel or iron-nickel alloy layer. In the present invention, any heat treatment conditions may be used as long as the iron-nickel or iron-nickel alloy layer can be formed. However, for example, the heat treatment may be performed at 750 ~ 900 ℃. When the heat treatment temperature is less than 750° C., there is a disadvantage that a non-recrystallized region may exist as a recrystallization temperature of A3 or higher cannot be secured, which may cause a deviation in mechanical properties. On the other hand, when it exceeds 900° C., it is not possible to obtain a steel sheet of excellent material by secondary recrystallization, and there is a limit in terms of heat treatment facilities.

Thereafter, the heat-treated base steel sheet is immersed in an Al-containing hot-dip galvanizing bath at 440 to 460° C. to obtain a hot-dip galvanized steel sheet. When the temperature of the hot-dip galvanizing bath is less than 440°C, the viscosity of the plating bath increases and the mobility of a roll that winds the steel sheet is reduced, causing a slip between the steel sheet and the roll, which may cause defects in the steel sheet. And, when it exceeds 460 ℃, the dissolution of the steel sheet in the plating bath is accelerated, and the generation of dross in the form of Fe-Zn compound is accelerated, which may cause surface defects.

On the other hand, after obtaining the hot-dip galvanized steel sheet, the step of alloying heat treatment of the hot-dip galvanized steel sheet at 480 ~ 600 ℃ may be further included. If the alloying heat treatment temperature is less than 480 ℃, Fe in the base material may not sufficiently diffuse into the plating layer, so that the Fe content in the plating layer may not be sufficiently secured, and if it exceeds 600 ° C, the Fe content in the plating layer is excessive. In the process, a powdering phenomenon in which the plating layer falls off may occur.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are only examples for explaining the present invention in more detail, and do not limit the scope of the present invention.

(Example)

The molten metal having the alloy composition shown in Table 1 was prepared as an ingot having a width of 175 mm and a thickness of 90 mm in a vacuum melting furnace, and then reheated at 1200° C. for 1 hour to homogenize, and hot finish rolled at 900° C., which is a temperature of Ar3 or higher. Then, it was maintained at 680° C. for 1 hour to simulate hot-rolled winding. Then, the hot-rolled steel sheet was immersed in a pickling solution of 15% HCl for 40 seconds to simulate the pickling process. Thereafter, cold rolling was performed at a cold rolling reduction of 50 to 60% to prepare a cold rolled steel sheet. This cold-rolled steel sheet was subjected to annealing heat treatment in a gas atmosphere of 5 vol% H + 95 vol% N in a reduction furnace at 800 ° C. Heat treatment was performed. Thereafter, after being immersed in a hot-dip galvanizing bath at 460° C. for 5 seconds, the plating adhesion amount was adjusted to a level of 60 g/m ² based on one side through air wiping to prepare a hot-dip galvanized steel sheet.

Mechanical properties of the hot-dip galvanized steel sheet prepared in this way, the distribution of nickel in the region from the surface of the iron-nickel or iron-nickel alloy layer to 2㎛ in the direction of the base steel sheet, and Fe2Al5 crystals with a maximum size of 100 nm or less in the alloying suppression layer After measuring the area fraction, plating property and LME crack resistance, the results are shown in Table 2 below.

Mechanical properties: Cut a hot-dip galvanized steel sheet in the vertical direction in the rolling direction to a size of 40mm × 200mm, mill the sides, and prepare a tensile specimen in accordance with JIS No. 5 standard. (TS) and elongation (EL) were measured.

In order to confirm the distribution of Ni present at the interface between the plating layer and the base steel sheet, on the GDS (Glow Discharge Spectroscopy) depth profile, from the surface of the iron-nickel or iron-nickel alloy layer to the base steel sheet, the amount of nickel in the region up to 2㎛ area was obtained.

The area fraction of Fe2Al5 crystals having a maximum size of 100 nm or less in the alloying suppression layer was measured by using an image analyzer after removing the hot-dip galvanized layer formed on the hot-dip galvanized steel sheet and photographing the alloying suppression layer at a magnification of ×10,000 using SEM. .

The plating property is measured by measuring the area of the hot-dip galvanized layer with respect to the total area of the hot-dip galvanized steel sheet by image analysis to measure the fraction, and after applying a structural adhesive on the hot-dip galvanized steel sheet, hardening at 175°C for 20 minutes, When bending at 90°, it was evaluated by checking whether or not it came out on the sealer (plating adhesion).

The LME crack resistance was evaluated by whether or not LME cracking occurred at the upper limit current after welding the hot-dip galvanized steel sheet. At this time, welding was carried out under the conditions of 16 cycles of energization time and 15 cycles of holding time with a pressing force of 2.6 kN using a Cu-Cr electrode with a tip diameter of 6 mm. When the thickness of the steel sheet is t, the welding current at the point where the nugget diameter becomes smaller than 4√t is set as the lower limit current, and the welding current at the point in time when the blow-off phenomenon occurs is set as the upper limit current (expulsion current).

Kang type No. Alloy composition (wt%) C Si Al Mn Mo Al+Si Al/Si Invention lecture 1 0.23 0.73 0.60 2.5 0.14 1.33 0.82 Invention lecture 2 0.21 0.65 0.75 2.8 0.15 1.40 1.15 Invention lecture 3 0.2 0.40 1.10 2.7 0.18 1.20 2.00 Invention lecture 4 0.22 0.60 0.70 2.5 0.13 1.30 1.17 Invention River 5 0.22 0.75 0.70 2.8 0.19 1.45 0.93 Invention lecture 6 0.2 0.60 0.80 2.7 0.11 1.40 1.33 Comparative lecture 1 0.22 0.96 0.24 2.7 0.13 1.20 0.25 Comparative lecture 2 0.23 0.52 0.55 2.9 0.10 1.07 1.06

division Kang type No. Ni
adhesion amount
(mg/m ² ) surrender
burglar
(MPa) Seal
burglar
(MPa) elongation
(%) The area occupied by nickel in the region up to 2 μm from the surface of the iron-nickel or iron-nickel alloy layer to the base steel sheet on the GDS depth profile
(%·㎛) within the alloying inhibition layer
Fe2Al5 with a maximum size of 100 nm or less
crystal fraction
(area%) Plating LME
crack
Whether plating layer
area fraction
(%) Plated
adhesion Invention Example 1 Invention lecture 1 202 656 1051 21.1 4.8 12.7 96 non-peel uncracked Invention Example 2 Invention lecture 2 354 765 1047 23.2 2.6 13.5 95 non-peel uncracked Invention example 3 Invention lecture 3 178 770 1080 23.5 9.4 10.8 98 non-peel uncracked Invention Example 4 Invention lecture 4 430 654 1055 21.4 6.9 18.2 97 non-peel uncracked Comparative Example 1 Invention River 5 25 754 1043 23.0 0.1 0.2 91 peeling uncracked Comparative Example 2 Invention lecture 6 1320 768 1052 22.8 22.8 34 87 peeling crack Comparative Example 3 Comparative lecture 1 255 672 1059 21.5 3.5 11.2 98 non-peel crack Comparative Example 4 Comparative lecture 2 303 525 943 19.2 4.4 14.3 99 non-peel uncracked

As can be seen from Tables 1 and 2, in the case of Inventive Examples 1 to 4 satisfying the alloy composition and manufacturing conditions proposed by the present invention, the surface of the iron-nickel or iron-nickel alloy alloy layer to be obtained by the present invention It can be seen that the nickel distribution in the region up to 2㎛ in the direction of the base steel sheet and the area fraction of Fe2Al5 crystals with a maximum size of 100 nm or less in the alloying suppression layer are secured, and thus it has excellent plating properties and LME cracking resistance.

On the other hand, in Comparative Example 1, the alloy composition proposed by the present invention is satisfactory, but the amount of Ni adhered does not fall within the scope of the present invention, so that the present invention is obtained from the surface of the iron-nickel or iron-nickel alloy layer in the direction of the base steel sheet. It can be seen that the plating adhesion is poor as the nickel distribution in the region up to 2 μm and the area fraction of the Fe2Al5 crystal having the maximum size in the alloying suppression layer of 100 nm or less cannot be secured.

In Comparative Example 2, the alloy composition proposed by the present invention is satisfactory, but the Ni adhesion amount exceeds the scope of the present invention, and the present invention wants to obtain 2㎛ from the surface of the iron-nickel or iron-nickel alloy alloy layer in the direction of the base steel sheet. As the area fraction of the Fe2Al5 crystals having the maximum size of 100 nm or less in the nickel distribution in the region up to and including the alloying suppression layer was not secured, non-plating occurred, and it can be seen that the plating adhesion and LME crack resistance were also poor.

Comparative Example 3 was at a level lower than the ratio of Al and Si proposed by the present invention, indicating that LME cracking occurred.

Comparative Example 4 does not satisfy the sum of Si and Al suggested by the present invention, and thus it can be seen that the mechanical properties are at a low level.

2 is a photograph of the surface of Comparative Example 1, and FIG. 3 is a photograph of the surface of Invention Example 1. As can be seen from FIGS. 2 and 3 , it can be seen that the plating quality of Inventive Example 1 is good because there are almost no unplated areas, whereas Comparative Example 1 has many unplated areas and thus the plating quality is inferior.

4 and 5 are photographs of the alloying inhibitory layer observed by SEM (Scanning Electron Microscopy) after removing the galvanized layer of Comparative Example 1 and Inventive Example 1, respectively. As can be seen from FIGS. 4 and 5, in Comparative Example 1, Fe2Al5 crystals having a maximum size of 100 nm or less were hardly formed, whereas in Inventive Example 1, Fe2Al5 crystals having a maximum size of 100 nm or less were formed in an appropriate fraction. It can be seen that there is

6 and 7 are GDS (Glow Discharge Spectroscopy) depth profiles of Comparative Example 1 and Inventive Example 1, respectively. As can be seen from FIGS. 6 and 7, in the case of Inventive Example 1, nickel is appropriately distributed within a region from the surface of the iron-nickel or iron-nickel alloy layer to 2㎛ in the direction of the base steel sheet, whereas the comparative In the case of Example 1, it can be seen that nickel is not distributed. On the other hand, although it seems that Ni is present in a very small amount in the GDS depth profile disclosed in FIG. 6, this is an error of the measuring device.

10: Soji steel plate
20: iron-nickel or iron-nickel alloy alloy layer
30: alloying suppression layer
40: hot-dip galvanized layer

Claims (6)

Soji steel plate; an iron-nickel or iron-nickel alloy alloy layer formed on one or both surfaces of the base steel sheet; and an alloying suppression layer formed on the iron-nickel or iron-nickel alloy layer; A hot-dip galvanized steel sheet comprising a hot-dip galvanized layer formed on the alloying suppression layer,
The base steel sheet is, by weight, carbon (C): 0.1 to 0.3%, silicon (Si): 0.1 to 2.0%, aluminum (Al): 0.1 to 1.5%, manganese (Mn): 1.5 to 3.0%, molybdenum ( Mo): 0.01 to 0.3%, including the remainder Fe and unavoidable impurities, the sum of Si and Al satisfies 1.2 to 3.5%, and the Al and Si ratio (Al/Si) satisfies 0.5 to 2.0, and ,
On the GDS depth profile, the area occupied by nickel in the area from the surface of the iron-nickel or iron-nickel alloy layer to 2㎛ in the direction of the base steel sheet is 2 to 10% by weight ·㎛,
In the alloying suppression layer, 1 to 20 area% of Fe2Al5 crystals having a maximum size of 100 nm or less are present,
The surface of the iron-nickel or iron-nickel alloy layer is a high-strength hot-dip galvanized steel sheet having excellent plating adhesion and spot weldability, which is a surface in contact with the alloying suppression layer.
The method according to claim 1,
The hot-dip galvanized steel sheet has a yield strength of 600 MPa or more, a tensile strength of 950 MPa or more, and an elongation of 20% or more.
The method according to claim 1,
The hot-dip galvanized steel sheet is a high-strength hot-dip galvanized steel sheet having excellent plating adhesion and spot weldability in which the area of the hot-dip galvanized layer is 95% or more of the total area of the base steel sheet.
By weight%, carbon (C): 0.1-0.3%, silicon (Si): 0.1-2.0%, aluminum (Al): 0.1-1.5%, manganese (Mn): 1.5-3.0%, molybdenum (Mo): 0.01 -0.3%, including the remainder Fe and unavoidable impurities, the sum of Si and Al satisfies 1.2-3.5%, and the ratio of Al and Si (Al/Si) satisfies 0.5-2.0 to do;
forming a nickel or nickel alloy coating layer on the base steel sheet so that the adhesion amount is 100 to 1000 mg/m ² ;
heat-treating the base steel sheet on which the nickel or nickel alloy coating layer is formed; and
A method of manufacturing a high-strength hot-dip galvanized steel sheet excellent in plating adhesion and spot weldability, comprising the step of immersing the heat-treated base steel sheet in an Al-containing hot-dip galvanizing bath at 440 to 460° C. to obtain a hot-dip galvanized steel sheet.
5. The method according to claim 4,
The step of preparing the base steel sheet, the step of reheating the slab at 1000 ~ 1300 ℃; obtaining a hot-rolled steel sheet by hot finish rolling the reheated slab at 800 to 950°C; winding the hot-rolled steel sheet at 630 to 700°C; and pickling the wound hot-rolled steel sheet and then cold rolling to obtain a cold-rolled steel sheet.
5. The method according to claim 4,
After obtaining the hot-dip galvanized steel sheet, the method of manufacturing a high-strength hot-dip galvanized steel sheet excellent in plating adhesion and spot weldability further comprising the step of alloying heat treatment at 480 ~ 600 ℃ the hot-dip galvanized steel sheet.

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