KR20130071207A - Pillar part for vehicle - Google Patents

Abstract

The present invention relates to an automobile filler member having two strength characteristics.
Since the filler member for automobiles according to the present invention can be combined with various strengths by controlling the mold movement in the low intensity region, and the mode in which the filler member collapses can be changed according to the design specifications by adjusting the gap of the mold. Freedom of design of the body pillar member. The present invention can be implemented without an additional device for the production of a filler member having such two strength properties.

Description

Filler parts for automobiles {PILLAR PART FOR VEHICLE}

The present invention relates to an automobile filler member having two strength characteristics.

Recently, vehicle requirements have been continuously strengthened due to environmental and safety regulations. That is, in order to cope with the demand for weight reduction for improving fuel efficiency and the improvement of collision safety, the application of high strength steel including, for example, Advance High Strength Steel (AHSS) has been expanded.

High-strength parts are applied to reinforce the side impacts in the manufacturing of the body, and in the case of electric vehicles, the role of the side impact filler for the battery protection is more important than the existing internal combustion engine body. To this end, the use of ultra-high strength steel of 1000 MPa or more applied with Hot Press Forming (HPF) technology is expanding.

On the other hand, a component applied as a collision member can be classified into two types.

First, it is a member that absorbs the shock applied from the outside through the deformation as an energy absorption part.

Typically, the energy absorbing member corresponds to the front of the front side member, the rear of the rear side member and the bottom of the non-pillar.

Second, the member hardly deforms as an anti-intrusion part. For example, since a collision zone must be secured in a passenger zone, a collision member applied thereto is mostly a non-invasive member.

Typically, this is the rear of the front side member, the front of the rear side member and the top of the non-pillar.

In the case of non-invasive members, there are a growing number of cases where the impact performance is improved by applying the HPF, and the impact absorbing member uses AHSS, which has a relatively high elongation.

In the case of members such as the front side member, the rear side member and the non-pillar, the energy absorbing member and the non-penetrating member are combined. In general, the two members are molded and used.

As such, in order to solve the problem of forming and separating the two members, HPF steel and general high strength steel are made of TWB (Tailor Welded Blank) and applied, and the heat treatment characteristics are different for each part to make two strengths in one part. It has been proposed a method to realize the two strengths having. In addition, in order to eliminate deformation during collision, parts using MS-HPF (Multi Strength-Hot Press Forming) technology have been developed as a technology for implementing two areas of different strength in one side pillar.

However, when the side filler is manufactured by applying the MS-HPF technology, it is not easy to stabilize the technical system because it must be implemented through heating temperature control and cooling rate control, and requires an additional device.

One aspect of the present invention is to provide a filler member for a vehicle that overcomes the disadvantages of the conventional double-strength HPF and a method of manufacturing the same.

The present invention provides an automotive filler comprising a high strength region 101, a low intensity region 103 and a transition region 102 having an area of 5 to 50 mm between the high strength region 101 and the low intensity region 103. It is about absence.

The present invention comprises the steps of: dividing the blank into a high strength region and a low strength region; Passing the blank through a heating furnace to heat it; Moving the blank into the mold; And quenching the blank at the same time forming the blank, wherein the low-strength region of the blank is maintained in the abnormal temperature range during quenching, for 15 to 40 seconds. It is about.

In addition, the present invention is characterized by manufacturing a filler member by setting the gap (gap) of the mold to 1 ~ 50mm by using a separate mold in order to adjust the size of the transition region.

Since the filler member for automobiles according to the present invention can be combined with various strengths by controlling the mold movement in the low intensity region, and the mode in which the filler member collapses can be changed according to the design specifications by adjusting the gap of the mold. Freedom of design of the body pillar member. The present invention can be implemented without additional devices in the manufacture of filler members having these two strength properties.

1 is a view showing a vehicle filler member according to the present invention.
2 is a view showing a vehicle body structure to which the automobile filler member according to the present invention is applied.
3 is a conceptual view of a manufacturing process showing a preferred example of a method for manufacturing a vehicle filler member according to the present invention.
4 is a result of measuring the tensile strength of the filler member according to the present invention.

Hereinafter, with reference to the drawings will be described in detail a specific embodiment of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventive concept. Other embodiments falling within the scope of the inventive concept may be easily suggested, but this will also be included in the spirit of the present invention.

The pillar member is a pillar connecting the vehicle body and the roof, and not only supports the roof of the vehicle but also plays an important role in improving the rigidity and safety of the integrated vehicle body. The pillar member is provided with A-pillar, B-pillar, and C-pillar from the front of the vehicle, and the A-pillar is mounted on the windshield and side glass as the front pillar, and the B-pillar is the center pillar or the center pillar of the front and rear doors. Is mounted on. The C-pillar is also mounted as a rear filler between the rear and side glass.

In particular, as the trend toward the stability of the vehicle body continues in recent years, mounting of the B-pillar, which serves as an important energy absorbing member in a side impact, has been recognized as an essential element. Such a B-pillar is a form in which a member that absorbs energy in a collision and a non-invasive member in which deformation hardly occurs in a collision are combined.

Conventionally, two members of the B-pillar were separately formed and welded. However, in this case, there is a problem in that the two members need to be separated and molded, and the strength of the welded part is weakened, thereby easily breaking.

The present invention has been made to solve this problem, and an object of the present invention is to provide a filler member, in particular, a non-filler (B-pillar) implemented to have different strengths in one blank (material) without an additional device. More specifically, a portion where high energy absorption capacity is required in a collision is implemented as a low intensity region, while a portion where deformation is hardly generated in a collision is implemented as a high strength region. In addition, by implementing a transition region between the low-strength region and the high-strength region, the elongation is improved so that the portion where the strength is changed from low intensity to high strength does not break or break during a collision.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a view showing the structure of a vehicle filler member according to the present invention.

As shown in FIG. 1, the automotive pillar member 100 includes a high-strength region 101, a low-strength region 103, and a transition region 102 between the high-strength region 101 and the low-strength region 103. It is characterized by including.

In the filler member, the high strength region 101 has a strength of 1000 to 2000 MPa. In addition, the high intensity region 101 corresponds to the remaining portions except for the transition region 102 and the low intensity region 103.

The high strength region 101 has a strength of 1000 to 2000 MPa, in most cases, the strength of the steel capable of securing 90% or more of the martensite structure through heat treatment is 1000 MPa or more, and the high strength region of the filler member. This is because it is necessary to form at least 1000 MPa in order to secure the characteristics. In addition, the reason why the upper limit of the strength is set to 2000 MPa is that the maximum strength of the heat-treated steel that can be put into practical use is about 2000 MPa, and the steel used in the present invention may have a strength of up to 2000 MPa.

The low intensity region 103 is an area below the transition region 102 of the filler member, more specifically, an area occupying 10 to 40% by a length ratio of the entire filler, and the low intensity region 103 is 0 to 800 MPa. It is characterized by having the strength of.

The low intensity region 103 is implemented by maintaining the strength of the raw material as it is. Therefore, when realizing a low strength and high strength region using the material, a material capable of forming a high strength region 101 of 1000 to 2000 MPa strength should be used. Preferably, the material having a strength of 500 to 800 MPa can implement a high strength region 101 of 1000 to 2000 MPa through die quenching, so it is preferable to select this material. By the selection of the material, the low intensity region 103 has a strength of 500 to 800 MPa.

The low-strength region 103 of the filler member according to the present invention may be implemented to have a difference in strength by changing heat treatment characteristics when molding using a mold. The heat treatment characteristics can be largely divided into heating temperature control applying different heating conditions and cooling rate control applying different cooling conditions.

The heating temperature control is a method of controlling the phase transformation by varying the heating temperature in the high-strength region and the high-stretching region, which is advantageous in that a short cycle time can be maintained. However, have.

On the other hand, the cooling rate control includes a method of adjusting the cooling rate by setting the temperature of the mold in the high stretching region at a high level, and a method of adjusting the contact area by setting a gap or groove of the high stretching region to a large value. Although the former is advantageous in that it is easy to implement, there is a disadvantage in that it requires a device for controlling the mold temperature and an increase in cycle time, while the latter is conceptually possible but requires complicated mold processing and also increases cycle time There are disadvantages.

In the present invention, by controlling the air cooling treatment conditions of the material, that is, the pre-quenching and air cooling time, the strength of the material is controlled, and the low intensity region 103 is realized.

Therefore, the change of the strength (1000-2000 MPa) of the high strength region 101 can be implemented by the selection of the material, and the change of the strength (500-800 MPa) of the low strength region 103 can be realized. It can be realized by applying different process conditions using selected materials.

The transition region 102 formed between the high intensity region 101 and the low intensity region 103 has an area of 5 to 50 mm between the two regions.

Since the transition region 102 is formed at a portion that separates the region where the high strength is realized from the region where the low strength is implemented, the transition region 102 has strength between high strength and low strength.

2 is a view showing a vehicle body structure to which the automotive filler member 100 is applied.

As shown in FIG. 2, the high-strength region 101 of the vehicle pillar member 100 according to the present invention is connected to the roof rail rain force 201 of the vehicle body 200, and the low-strength region is a side seal rain force ( 203).

The present invention comprises placing two heated blanks (e.g. steels) in a mold having two or more zones separated from each other and then including two or more zones having different properties by varying the cooling conditions of each zone. It is manufactured from physical parts.

The physical properties are not particularly limited as long as they change depending on the cooling rate of the steel or part, and for example, 1 selected from the group consisting of yield strength, tensile strength, elongation, toughness, plastic anisotropy index (r) and in-plane anisotropy (Δr). And species.

The blank to which the present invention is applied is not particularly limited as long as the physical properties are changed according to the cooling rate, and the blank may include an alloy or the like.

For example, in order to manufacture the blank to have two strength properties, it is preferable to use a blank having an appropriate critical cooling rate (CCR; minimum cooling rate capable of forming a martensite phase in a CCT curve).

3 shows a preferred example of a method of manufacturing a filler member for automobiles according to the present invention.

The filler material for automobiles of the present invention may be manufactured by a manufacturing method including the following steps, but is not limited thereto and may be manufactured by differently applying heat treatment characteristics as described above.

First, a blank (material) to be manufactured as a filler member for automobiles is divided into a region to be implemented at high strength and a region to be implemented at low strength.

Thereafter, the blank is heated by passing through a heating furnace.

At this time, it is preferable that the heating temperature range is sufficiently heated at about 900 ° C., which is equal to or higher than the Ac3 transformation point, so that the entire steel material is completely austenite.

After the heating is completed, the blank is extracted from the heating furnace and transferred into the mold (FIG. 3A). The time required for transferring the blank from the heating furnace into the mold is not particularly limited, but is preferably limited to 10 to 20 seconds.

The transfer time means a time until the heated blank is taken out of the heating furnace and drawn into the mold. In addition, the transfer of the heated steel can be performed directly by a worker or a robot.

At this time, it is preferable that the mold is a separate mold. This is to ensure that the finally manufactured parts have two strength characteristics, in order to obtain two strength characteristics, the mold region may be separated and the mold movement may be performed.

The present invention preferably applies a mold motion to implement a low strength region in the material, which can be performed by applying a system that can be operated by hydraulic pressure. The system can move the mold up and down depending on the presence or absence of hydraulic pressure. More specifically, in the state where the hydraulic pressure is removed, the mold in the low intensity region is raised, but when the hydraulic pressure is applied, the mold is applied to the mold by the hydraulic pressure and the mold in the low strength region is lowered.

As described above, when the mold movement of each material region is applied differently through the hydraulic system, parts having different strengths, that is, both high strength and low strength regions can be manufactured.

As such, when using a separate mold, a gap exists between two separated mold regions, in order to facilitate the mechanical movement between the two molds. Based on the gap, the blank area may be manufactured to have different strengths during molding, and a transition area in which both strengths exist may be generated in the gap part. Therefore, the size of the transition region may vary depending on the size of the gap. Although the range of the said transition area | region is not specifically limited, It is preferable to manufacture so that it may have an area | region of 5-50 mm.

When the transfer of the blank into the mold is completed, the blank is formed and at the same time, quenching (pre-quenching) is performed for phase transformation (FIG. 3B).

The molding and quenching time is not particularly limited as long as it is molded into a desired shape and a desired structure can be obtained, but is preferably limited to 1 to 5 seconds. As a result, molding may be sufficiently performed in a desired shape, and in particular, phase transformation of ferrite, perlite and bainite may easily occur in a low intensity region.

The temperature of the blank after the molding and quenching can be appropriately selected according to the purpose, and specifically, it is preferable to maintain the temperature at 500 to 700 ° C.

After forming and pre-quenching, the blank area to which the relatively low intensity area is to be obtained is air-cooled in the ideal temperature range so as not to come into contact with the mold. At this time, the blank area to obtain a high strength area is kept in contact with the mold (Fig. 3 (C)).

The abnormal range temperature range is a temperature range in which the austenite phase and the ferrite phase coexist, and air-cool the blank region for obtaining a low intensity region in the temperature range for a predetermined time.

The low-intensity region portion cooled by air without being in contact with the mold has a relatively slow cooling rate compared to the high-strength region portion in contact with the mold, and thus undergoes a phase transformation process. More specifically, the austenite produced by heating is changed to one or more of ferrite, perlite and bainite by the air cooling. The phase produced is dependent on the composition of the blank, and the amount of phase transformation is proportional to the air cooling time, which is advantageous for creating a low intensity region with a longer time.

On the other hand, the high-strength region portion that keeps in contact with the mold maintains a fast cooling rate, so that austenite is directly transformed into martensite, thereby increasing strength.

The air cooling time of the low intensity region is not particularly limited, but is preferably performed for 15 to 40 seconds. As a result, a part of the blank forming the low intensity region may be transformed into ferrite.

In this case, unlike the high strength region continuously quenched, the low intensity region cooled by air is maintained at a high temperature of 400 ℃ or more.

After completion of the air cooling, the post quenching process is performed to quench the entire area by contacting the mold in order to complete shape distortion and martensite transformation due to the temperature deviation of each area of the blank (FIG. 3 (d)).

The post quenching process time may vary depending on the ejection temperature of the final part and the material of the mold, and it is preferable to carry out for 10 to 60 seconds.

By completing the post quenching, the blank region in which the high strength region is formed may be transformed to 90% or more martensite structure, and the blank region in which the low intensity region is formed may be transformed into ferrite and martensite structure. In this case, the low intensity region may transform the martensite structure to 30% or less.

In addition, a blank having completed all the above steps may generate a transition region between the regions in addition to the high strength region and the low intensity region.

The transition region may be generated in a gap portion that distinguishes the high strength region and the low intensity region to be formed.

More specifically, the high strength region is continuously quenched while being in contact with the mold throughout the process, while the gap portion is slowly cooled while being in contact with the air throughout the process. Therefore, the portion of the gap portion adjacent to the high strength region is relatively quick in cooling, and the portion of the gap portion adjacent to the high intensity region is in a relatively slow cooling state. As a result, a transition region having an intermediate level of strength between the high strength region and the low strength region is generated in the gap portion in which the forming and quenching is completed.

However, if the size of the gap (gap) is less than a certain size may be more affected by the cooling in the high-strength region, in this case the cooling rate of the gap (gap) can maintain a faster state than the low-strength region have.

In the case of the conventional two-strength HPF, the design was carried out in the direction of changing the thickness or the steel type to satisfy the side impact characteristics. In particular, since the size of the transition region located in the middle of the high strength and low intensity region cannot be enlarged, there is a limit in controlling the mode in which the pillar member collapses during side impact. That is, when the transition region is too narrow, there is a problem that breakage can easily occur due to the rapid change in strength between the high strength and low strength region.

However, since the filler member for automobiles according to the present invention can adjust the size of the transition region located between the low strength and high strength region, the mode in which the filler member collapses can be changed according to the design specification, thereby increasing the design freedom of the vehicle filler member. It can increase.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example  1. Automotive filler  Member manufacturing and The tensile strength  Measure

The blank having the composition of the components shown in Table 1 was prepared using a separate mold material, and a filler member having two strength properties under the conditions of Table 2 below. A specific manufacturing method may be performed as shown in FIG. At this time, the gap between the high intensity region and the low intensity region was set to 2 mm.

As a result, 960 mm of high strength region, 280 mm of low intensity region, and 30 mm of transition region between high strength and low intensity region were produced | generated among all the filler members.

Ingredient composition Steel grade
C Si Mn P S Al Mo Ti Nb Cu B N W Sb 0.127 0.159 1.649 0.015 0.0011 0.048 0.0639 0.0024 0.0006 0.0104 0.0019 0.0072 0.0009 0.0005

High strength zone Low intensity zone Total machining time Transfer time Forming and quenching Transfer time Prequenching Air cooling Postquenching 10 seconds 37 seconds 10 seconds 2 seconds 20 seconds 15 seconds 47 seconds

The tensile strength of the filler member manufactured by the above was measured, and the measurement results are shown in FIG. 4.

As a result, it was confirmed that the tensile strength was about 1300 MPa at maximum in the high strength region, and about 700 MPa at the low strength region. In addition, it was confirmed that in the transition region formed between the high strength region and the low strength region, the tensile strength is changed from high strength to low strength.

Therefore, the present invention facilitates the production of filler members having distinctive strength properties.

100: automotive filler member
101: high strength region
102: transition area
103: low intensity region
200:
201: LoopRail Reinforce
202: A-pillar rain force
203: side seal rain force

Claims (5)

An automotive filler member comprising a high strength region (101), a low intensity region (103) and a transition region (102) having an area of 5 to 50 mm between the high strength region (101) and the low intensity region (103).
The method of claim 1,
The high strength region 101 is a vehicle filler member, characterized in that having a strength of 1000 to 2000 MPa.
The method of claim 1,
The low intensity region 103 is a vehicle filler member, characterized in that having a strength of 500 to 800 MPa.
The method of claim 1,
The low-intensity region (103) is an area below the transition region of the filler member and occupies 10 to 40% by the ratio of the length of the whole filler member.
The method of claim 1,
The pillar member for automobiles, characterized in that the non-pillar (B-pillar).

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