KR101637084B1 - Fillerwire and method of making taylored welded blank using thereof - Google Patents

Abstract

The present invention relates to a method of manufacturing a hot stamping molded article, which comprises nickel in an amount larger than the component system of a coated steel sheet blank, joining two or more of the steel sheet blankes by producing the joining portion and the molten portion at joining portions of two or more steel sheet blank, A filler wire for blank bonding is disclosed.

Description

FIELD OF THE INVENTION The present invention relates to a filler wire,

The present invention relates to a filler wire, a method for manufacturing a custom-made welded blank using the same, and a method for manufacturing a hot stamped formed article, and more particularly to a filler wire for preventing physical properties of a joint portion of a steel plate blank from being changed, To produce a custom welded blank.

Plated steel sheets generally used for manufacturing customized weld blanks have various materials and thicknesses, and their physical properties are different from each other. For example, in the case of a custom-welded blank used in a vehicle body, the portions to be worn by absorbing the collision energy in the event of a vehicle collision have a relatively weak strength, but in the portion securing the passenger's survival space, It has a comparatively strong strength.

A blank produced by welding a material having such a different material or a different thickness using a laser or the like is referred to as a tailored welded blank or a custom welded blank. Such customized weld blanks are mainly used for automobiles, ships, and the like, and thus are generally manufactured by using a plated steel sheet material.

However, when the plated steel sheet is welded with a laser, the components of the plated layer plated on the plated steel sheet are introduced into the fused portion of the bonded portion. In this case, the components of the plated layer are mixed with the components in the molten part, so that the physical properties of the joint part are different from those of the plated steel sheet itself. Particularly, in the case of Al-Si or Zn, which is widely used as a plating layer, there is a problem that when the plating component flows into the joint portion at the time of laser welding, the property of the weld portion of the welded blank is deteriorated.

In order to solve this problem, conventionally, the plating layer of the portion to be welded with laser is removed, and then the welding is progressed to prevent the incorporation of the welding component of the plating component. This method is a process of removing the plating layer, The process cost is increased and the equipment investment cost and the processing cost are increased. As a result, the manufacturing cost of the entire parts is increased.

Related prior arts are 'hot stamping formed article using TWB method and its manufacturing method' of Korean Patent Application No. 10-2010-0061579 (registered date May 12, 2011).

SUMMARY OF THE INVENTION The present invention provides a filler wire used for preventing changes in physical properties due to bonding of a coated steel sheet blank and a method for manufacturing a customized weld blank using the filler wire.

In one aspect, the present invention relates to a method of producing a hot stamped formed article, comprising the steps of: forming a molten portion at a joint of two or more steel sheet blankes, joining two or more of the steel sheet blankes, A filler wire for a tailored welded blank joint is provided.

The coated steel sheet blank means a material in which a plated steel sheet is in an unfinished state, and the blank can be formed into a desired product by molding.

In one embodiment, the material plated on the coated steel sheet blank is characterized by being Al, Si or Al-Si.

The joining portion refers to a portion to which a plurality of the plate steel plate blanks are joined.

The molten portion is a portion where the plated steel sheet blank and components of the filler wire melt in the joining portion, and the molten portion is solidified to bond a plurality of the coated steel sheet blank to produce a custom-welded blank.

In one embodiment, the filler wire may further include carbon (C) and manganese (Mn), and the content of carbon (C) may include an amount less than the component system of the coated steel sheet blank, The content of manganese (Mn) may be equal to or greater than the component system of the coated steel sheet blank.

In one embodiment, the filler wire may include nickel at a hot stamping temperature of 800 ° C or higher so that the content of nickel relative to aluminum in the molten portion is 5 times or more. If the content of nickel in the molten portion is 5 times or more than the content of aluminum in the molten portion, the molten portion may exist as austenite.

In one embodiment, the filler wire may include nickel at a hot stamping temperature of 900 DEG C or higher so that the content of nickel to aluminum in the molten portion is 0.5 times or more.

In one embodiment, the filler wire may include nickel at a hot stamping temperature of 800 ° C or higher so that the content of nickel in the molten portion is 2.25 wt% or more when the aluminum content in the molten portion is 0.42 wt% or more .

In one embodiment, the filler wire may include nickel at a hot stamping temperature of 850 or more so that the content of nickel in the molten portion is 0.45 wt% or more when the aluminum content in the molten portion is 0.42 wt% or more.

In another aspect, a method of manufacturing a hot stamping formed body using a customized weld blank of the present invention includes: preparing a coated steel sheet blank having a different strength or a different thickness; Preparing a plated steel sheet blank having a different strength or a different thickness, and a filler wire according to any one of claims 1 to 4; And hot stamping the molten portion to a hot stamping temperature of 800 to 950.

The custom welding blank means a blank produced by bonding a plurality of the steel plate blanks as necessary.

The dissimilar strength or thickness may mean that a difference in strength or thickness occurs between the plated steel sheet blanks when the composition and / or thickness of the plurality of plated steel sheet blanks are different.

In one embodiment, when the filler wire includes nickel so that the content of nickel to aluminum in the fused portion is 5 times or more, the hot stamping temperature is 800 ° C or more .

In one embodiment, the hot stamping forming method of the present invention is characterized in that when the filler wire contains nickel so that the content of nickel to aluminum in the molten portion is 0.5 times or more, the hot stamping temperature is 900 ° C or more .

In one embodiment, when the filler wire contains nickel so that the content of nickel is 2.25 wt% or more when the aluminum content in the molten portion is 0.42 wt% or more, the hot- And the stamping temperature is 800 DEG C or more.

In one embodiment, when the filler wire contains nickel so that the content of nickel is 0.45 wt% or more when the aluminum content in the molten portion is 0.42 wt% or more, the hot- And the stamping temperature is 850 DEG C or more.

In one embodiment, the hot stamping comprises heating a custom weld blank produced by the method of making a custom weld blank; And a press forming step of hot forming the heated material into a press mold to form a formed body; And a quenching step of cooling the press mold to quench the molded body.

The press die is a metallic die for producing a hot stamping formed article as required, and means a die capable of deforming the shape of the welded blank.

The hot forming means a method in which the customized weld blank is placed in the press mold and heated, and then pressure is applied thereto to perform finish molding.

The nickel, manganese, or carbon is an austenite stabilizing element, and the composition of the steel plate blank joint portion is changed so that the phase structure of the steel sheet is in austenitic state rather than ferrite structure at a certain temperature at which the steel sheet is molded. Element.

The austenitic structure means iron which solidifies carbon, that is, solid solution, and is a kind of hardened steel structure. When the austenitic structure is quenched, the austenitic structure can be stably changed to a full martensitic structure at room temperature.

The ferrite structure means a solid solution based on iron and is a solid solution in which alloy elements or impurities are dissolved in steel. The ferrite structure may be changed to martensite. The ferrite structure is unstable because the impurities are melted and the properties of the martensite are changed when the ferrite structure is rapidly cooled and changed to martensite.

The present invention provides a filler wire designed to prevent the physical properties of a welded portion from changing due to a plating layer being incorporated into a molten portion.

The filler wire includes an austenite stabilizing element to form a molten portion with the base material of the plating layer and the coated steel sheet, thereby preventing the physical properties of the welded portion from being changed by the plating layer.

Therefore, the existing plating layer removing process and the re-plating process are not required, and the productivity is improved and the product unit cost is reduced.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view showing a filler wire produced by the above method. FIG.
2 is a view showing phase-dependent phase transformation according to the content of nickel contained in the filler wire.
3 is a view showing a phase transformation according to temperature according to the content of nickel contained in the filler wire.
4 is a graph for explaining the content of nickel for maintaining the austenite state according to the aluminum content in the molten part.
FIG. 5 is a graph comparing the hot stampable temperature derived from Equation (1) with the hot stampable temperature measured through simulation in FIG. 4 when filler wires having the same aluminum weight% and nickel weight percentage are used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and similarities. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having" is intended to designate the presence of stated features, elements, etc., and not one or more other features, It does not mean that there is none.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

First, an existing customized welding blank manufacturing method will be described.

Conventional custom-made blanks were prepared by welding blanks with different strengths and / or thicknesses using a laser. After the steps of welding and bonding the blanks made of different plated steel sheets, a step of molding the plated steel plate-adapted welding blank thus prepared is carried out in accordance with the application. However, the plating steel sheet blank has a large forming force during processing and molding, and it is difficult to process a complicated shape. In order to overcome this problem, a hot-stamping process has been developed in which a hot-rolled steel sheet blank heated at a high temperature of 800 to 950 占 폚 is put into a mold, molded by a press, and rapidly cooled in the mold. In order to apply such a hot stamping process, plating of a steel sheet is indispensable to prevent decarburization and oxidation of the base material. Therefore, the blanks having different strength and / or different thicknesses for producing the customized blank are plated. However, there is a problem that the plating component of the blank flows into the molten portion during welding for manufacturing a custom welded blank, thereby changing physical properties of the welded portion. Accordingly, when a custom welding blank having different physical properties of the welded portion is formed by a hot stamping process, the mechanical properties of the welded portion of the welded blank are deteriorated.

The present invention provides a filler wire and a method of manufacturing a customized weld blank using the filler wire to solve such a problem.

1. Experimental study of nickel-containing filler wire

(1) Example 1

First, a filler wire of the present invention prepared by drawing a large-diameter wire containing nickel into a series of hole dies or roller dies was prepared. The filler wire of the present invention is composed of 0.06 wt% of carbon, 0.52 wt% of silicon, 1.48 wt% of manganese, 0.002 wt% of phosphorus, 0.003 wt% of sulfur, 0.57 wt% of molybdenum, 1.75 to 4 wt% of nickel and 95.615 to 93.365 wt% ≪ / RTI > BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a filler wire of Example 1 produced by the above method. FIG.

The prepared filler wire of the present invention and two coated steel sheet blanks having different thicknesses and dissimilar strengths are prepared. The two plated steel sheet blanks were made of Al-Si plated bronze steel sheet (SABC1470). The coated steel sheet blank comprises 0.228 wt% of carbon, 0.238 wt% of silicon, 1.189 wt% of manganese, 0.183 wt% of chromium, 0.004 wt% of niobium, 0.036 wt% of titanium, 0.0023 wt% of boron, 0.0015 wt% By weight, and 98.1167% by weight of iron. Two coated steel plate blanks having a thickness of between 0.8 and 2.0 mm and including a plating layer were prepared together with the filler wires described above. It can be confirmed that the carbon content of the plated steel sheet component is 0.228 wt%, which is more than 0.06 wt%, which is the carbon content of the filler wire. In addition, it can be seen that the manganese content of the plated steel sheet component is 1.189 wt%, which is less than 1.48 wt% of the manganese content of the filler wire.

Fig. 2 is a view showing bonding of a coated steel sheet blank having a different thickness using filler wires. Fig. The two plated steel sheet blanks of Example 1 having different thicknesses are referred to as a first plated steel sheet blank and a second plated steel sheet blank for the sake of convenience.

2, the filler wire 3 is positioned between the bonding portion of the first coated steel sheet blank 1 and the bonding portion of the second coated steel sheet blank 2, and then the first coated steel sheet blank 1 is placed, , The joining portion of the second coated steel sheet blank (2) and the filler wire (3) were laser welded to produce a molten portion (4). The melted portion 4 has a composition of the first coated steel sheet blank 1, the second coated steel sheet blank 2, and the filler wire 3, respectively. The components of the Al-Si plated layer 5 plated on the first plated steel sheet blank 1 and the second plated steel sheet blank 2 are also mixed with the molten portion 4. In this case, the nickel content in the fused portion 4 was maintained to be 0.45 to 3.45 wt% as described above. The first plated steel sheet blank 1 and the second plated steel sheet blank 2 were bonded to each other while the molten portion 4 solidified to produce a custom welding blank of the present invention.

The thus prepared customized weld blank of the present invention was formed through a hot stamping process. The steps of the hot stamping process are as follows. First, the custom welding blank of the present invention is heated to a temperature of 800 캜 to 950 캜. Then, the formed welded blank blank according to the present invention was formed through the hot forming in which the heated customized weld blank of the present invention was placed in a press mold and subjected to pressure and finish molding. Thereafter, the press mold was rapidly cooled to rapidly cool the formed article to produce a hot stamping molded article of the present invention.

(2) Comparative Example

In the comparative example, a filler wire having no nickel component alone was prepared from the filler wire of Example 1. In the comparative example, a hot stamping formed body was produced in the same manner as in Example 1, except that the nickel-free filler wire was used.

(3) Result 1 (comparison of molten Al content of a hot stamping formed article to exist as austenite at hot stamping process temperature)

Fig. 3 is a view showing a molten part phase transformation diagram of a hot stamping formed article according to whether or not the filler wire contains nickel. Fig.

3, when the hot-stamping formed body was produced using the nickel-added filler wire of Example 1 as compared with the case where the hot-stamping formed body was produced using the filler wire of Comparative Example in which nickel was not added, It can be confirmed that the area is widened. Particularly, when checking the hot stamping process temperature range of 800 ° C. to 950 ° C., in the case of the comparative example, the molten portion may be present as austenite when Al is contained in an amount of 0 to 1 wt%, but in the case of Example 1, It was confirmed that the molten portion could be present in the austenite state until it contained 2.5% by weight.

The austenite structure means iron which solidifies carbon, that is, solid solution. When the austenite structure is rapidly cooled, it changes from normal temperature to full martensite. When the austenite structure is changed to full martensite, the strength of the molten portion is higher than that of the custom welding blank. On the other hand, the ferrite structure means a solid solution based on iron, and the solid solution is a form in which alloy elements or impurities are dissolved in steel. Since the ferrite structure has impurities dissolved therein, it is unstable because rapid cooling may not change the properties of the martensite to full martensite and may change the properties of the martensite.

3, when hot-stamping the tailored weld blank according to Example 1 of the present invention at 800 ° C to 950 ° C, even if more aluminum is contained in the molten portion than in the comparative example, it can easily exist in the austenite state Respectively.

(4) Result 2 (Comparison of Strength of Hot Stamping Molded Body)

No YS (MPa) TS (MPa) EL (%) Rupture portion Example 1 940 1430 4.8 Base material Comparative Example 890 1000 1.5 Weld

Table 1 shows the yield strength and tensile strength of the hot-stamping formed article produced using the filler wire of Example 1 containing nickel of the present invention and the hot-stamped formed article prepared using the filler wire of the comparative example containing no conventional nickel , An elongation percentage, and a breaking portion.

In Table 1, the comparative example refers to a conventional hot stamping molded article to which a filler wire to which Mn was added without adding Ni was applied. In Example 1, the hot stem of the present invention, to which filler wires containing both Ni and Mn were applied, &Quot;

Referring to Table 1, the yield strength, tensile strength and elongation of the hot stamping molded product of the comparative example were measured to be 890 MPa, 1000 MPa and 1.5%, respectively. In contrast, the yield strength, tensile strength and elongation of the hot stamping molded body of Example 1 were measured to be 940 MPa, 1430 MPa and 4.8%, respectively. It was confirmed that the hot stamping molded article of Example 1 showed high yield strength, tensile strength and elongation.

Also, in Examples 1 and 2, the tensile force was applied to the limit at which fracture occurred, and the fracture site was confirmed. As a result, the hot stamping formed article of the comparative example broke at the welded portion of the formed article, whereas the hot stamped formed article of Example 1 broke at the parent material itself of the formed article. This means that the welded portion strength of Example 1 is higher than that of the base material itself of the hot stamping formed body. That is, it has been confirmed that the molten portion of the above-mentioned Embodiment 1 has properties equal to or greater than the physical properties of the custom-welded blank base material. Thus, it can be seen from Table 1 that the welded portion strength of the hot stamping formed body of the present invention of Example 1 is higher than the welded portion strength of the conventional hot stamped formed body containing no Ni in the comparative example.

2. Optimum nickel content in filler wire

(1) Determination of Al content in the molten part

Experiments to produce a molten portion by laser welding to bond the filler wire of Example 1, the first coated steel sheet blank and the second coated steel sheet blank were repeated many times. Further, in order to confirm the Al content contained in the plurality of molten portions generated through the above-mentioned experiment, the Al content was examined according to the positions of each of the plurality of molten portions.

The Al content in the molten part was examined through a number of experiments. As a result, it was found that the maximum content of Al was 0.78 wt% and the minimum content of Al was 0.42 wt%.

(2) Determination of proper nickel content according to Al contents in molten part through simulation

4 is a graph showing the content of nickel for maintaining the austenite state according to the aluminum content in the molten part through simulation.

Referring to Fig. 4, the graph on the left is a graph of the state when 0.42 wt% of aluminum is contained in the molten portion, and the graph on the right is a graph of the state when 0.78 wt% of aluminum is contained in the molten portion. As a result of repeated tests for determining the Al content in the molten portion, it was confirmed that the maximum content of Al was 0.78% by weight and the minimum content was 0.42% by weight. Therefore, the content of nickel in the molten portion was determined Respectively.

Referring to the left graph of FIG. 4, when the molten portion contains aluminum at a temperature of 800 ° C or more at which the hot stamping process starts, the nickel content should be 2.25 wt% or more so that the molten portion is in austenite state It can be confirmed that it is maintained. Also, in the graph on the left, it can be confirmed that when the hot stamping temperature is 850 DEG C or higher, the molten portion remains in the austenite state when the nickel content is 0.45 wt% or more.

4, when 0.78 wt% aluminum is contained in the fused portion and the temperature is 800 ° C or higher at which the hot stamping process can be started, if the content of nickel is at least 3.45 wt%, the melt portion austenite Quot; state. ≪ / RTI > Also, in the graph on the right side, when the hot stamping temperature is 850 DEG C or higher, it can be confirmed that the molten portion remains in the austenite state when the nickel content is 1.74 wt% or more. Similarly, when the hot stamping temperature is 900 ° C. or higher in the right graph, it can be confirmed that the molten portion is maintained in the austenite state when nickel is contained in an amount of 0.45 wt% or more.

(3) Determination of nickel content relative to Al in molten zone by temperature by simulation

4, when the hot stamping temperature is 800 ° C. or higher and the content of aluminum in the molten portion is 0.42 wt%, the content of nickel in the molten portion is 2.25 wt% or more It was confirmed that the filler wire contained nickel, and in this case, the molten portion was maintained in the austenite state. Also, when the hot stamping temperature is 800 ° C or higher and the content of aluminum in the molten portion is 0.78wt%, the filler wire includes nickel so that the content of nickel in the molten portion is 3.45wt% or more. In this case, It was confirmed that the molten part was maintained in the austenite state. As a result of analyzing the nickel content with respect to aluminum, it was confirmed that when the content of nickel relative to aluminum in the molten portion was 5 times or more at a hot stamping temperature of 800 ° C or higher, the molten portion was maintained in austenite state.

When the hot stamping temperature is 850 DEG C or higher, when the filler wire contains nickel so that the content of nickel in the molten portion becomes 0.45 wt% or more when the content of aluminum in the molten portion is 0.42 wt% It was confirmed that the molten part was maintained in the austenite state. Similarly, when the hot stamping temperature is 850 DEG C or higher, when the filler wire contains nickel so that the content of nickel in the molten portion is 1.74 wt% or more when the content of aluminum in the molten portion is 0.78 wt% It can be confirmed that the additional austenite state is maintained. As a result of analyzing the content of nickel with respect to aluminum, it was confirmed that when the content of nickel was more than 2 times as high as that of aluminum in the molten portion at a hot stamping temperature of 850 ° C. or more, the molten portion was maintained in austenite state.

Likewise, when the hot stamping temperature is 900 ° C. or higher and the content of aluminum in the molten portion is 0.78 wt%, the filler wire includes nickel so that the content of nickel in the molten portion is 0.45 wt% or more. In this case, It was confirmed that the molten part was maintained in the austenite state. As a result of analyzing the nickel content with respect to aluminum, it was confirmed that when the content of nickel relative to aluminum in the molten portion was 0.5 times or more at a hot stamping temperature of 900 ° C or more, the molten portion was maintained in austenite state.

The simulation results of FIG. 4 were analyzed to derive the relationship between the hot stampable temperature, aluminum weight%, and nickel weight% by the following relational expression 1.

<Relation 1>

Hot stampable temperature = 810 + 125 * Aluminum weight% - 31.4 * Nickel weight%

The range of the weight percent of aluminum means the weight percentage of any aluminum measured in parts in the fused part. The nickel weight% refers to the weight percentage of nickel determined according to the hot stampable temperature and aluminum weight percent.

Through the above equation (1), the hot stampable temperature may be arbitrarily selected, for example, preferably in the range of 800 ° C to 900 ° C. Thus, through the above formula (1), it is possible to determine the weight percentage of nickel at a desired hot stamping temperature of 800 ° C to 900 ° C, even when the aluminum weight percentage has an arbitrary value between 0.42 and 0.78 wt%.

FIG. 5 is a graph comparing the hot stampable temperature derived from Equation (1) with the hot stampable temperature measured through simulation in FIG. 4 when filler wires having the same aluminum weight% and nickel weight percentage are used. Referring to FIG. 5, it can be seen that the hot stampable temperature measured in Equation 1 and the hot stampable temperature measured through simulation are 98.87%.

Claims (16)

Claims [1] A filler wire for a tailored welded blank joint, which is used in hot stamping at a temperature of 800 DEG C or higher by joining two or more of the steel sheet blankes by producing a molten portion at a joining portion of two or more steel plate blankes, Wherein said molten portion maintains the austenite state including nickel so that the content of nickel relative to aluminum is 5 times or more. The method according to claim 1,
Characterized in that the filler wire further comprises carbon (C) and manganese (Mn).
Filler wire for custom welded blank joints. delete delete delete delete delete delete delete The method according to claim 1,
Characterized in that the plating is Al, Si and Al-Si plating.
Filler wire for custom welded blank joints. Preparing a coated steel sheet blank having a different strength or a different thickness, and a filler wire according to any one of claims 1 to 10;
A joining step of joining the plated steel sheet blank by welding the joining portion of the plated steel sheet blank and the filler wire; And
And hot stamping the molten portion to a hot stamping temperature of 800 DEG C to 950 DEG C. [
A method of manufacturing a hot stamped formed article using a customized weld blank. delete delete delete delete 12. The method of claim 11,
The hot stamping step
Heating the custom welding blank produced by the custom welding blank manufacturing method; And a press forming step of hot forming the heated material into a press mold to form a formed body; And a quenching step of cooling the press mold to quench the formed body,
A method of manufacturing a hot stamped formed article using a customized weld blank.

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