KR101052008B1 - Steel pipe for high strength automobile parts and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a method for producing a steel pipe for automobile parts using press hardening, and to a steel pipe for automobile parts manufactured by the same, having excellent rigidity and shock absorbing ability.

Method for producing a steel pipe for high-strength automotive parts of the present invention, (a) at least one element selected from the group consisting of boron (B), chromium (Cr), molybdenum (Mo), vanadium (V) and nickel (Ni). Preparing a steel sheet containing the; (b) forming the steel pipe by manipulating the steel sheet; (c) heating the steel pipe to a temperature corresponding to an austenite region; (d) rapidly conveying the steel pipe to the press mold at a speed within which no pearlite, ferrite or bainite phases are formed; And (e) rapidly cooling the steel pipe in a press mold and simultaneously molding the steel pipe to have a predetermined shape along its longitudinal direction. It is possible to manufacture a high-strength steel pipe of various shapes by such a manufacturing method, the steel pipe for automobile parts produced by this has a tensile strength of 1200MPa to 1700MPa.

Steel pipes, auto parts, presses, tempering

Description

Steel pipe for high strength automotive parts and manufacturing method thereof {STEEL PIPE HAVING HIGH STRENGTH FOR AUTOMOBILE PARTS AND MANUFACTURING METHOD OF THE SAME}

1 (a), (b) and (c) are diagrams showing examples in which steel pipes are used as automobile parts.

2 is a view showing a B-pillar (pillar) and a reinforcement manufactured by the prior art.

3 is a flowchart illustrating a method of manufacturing a steel pipe for automotive parts according to an embodiment of the present invention.

4 and 5 are each a photograph of a steel pipe for automobile parts manufactured by a method for manufacturing a steel pipe for automobile parts according to an embodiment of the present invention.

The present invention relates to a steel pipe for automobile parts and a method for manufacturing the same, and more particularly, to a method for producing a steel pipe for automobile parts using press hardening, and to a steel pipe for automobile parts excellent in rigidity and shock absorbing capacity produced thereby.

Automobiles are manufactured by assembling tens of thousands of different parts such as steel, nonferrous metals, rubber, synthetic resins, glass, and textiles. In order to improve the performance of automobiles, research on the automobile parts is being actively conducted.

Among them, steel is applied to various automobile parts, and steel pipe-type parts are used to lighten the steel parts for environmental protection and fuel efficiency improvement. In addition, steel pipe-type parts are also used for reinforcement materials for passenger safety. The new steel body (NSB) project of ThyssenKrupp, a German steel company, estimates that about 40% of the parts of the car body will be converted into steel pipes.

Examples in which steel pipes are used as automobile parts are illustrated in FIGS. 1A, 1B, and 3C. As shown in (a) of FIG. 1, a steel pipe may be used in its own frame 10 having a space frame structure. Recently, steel pipes are also applied to parts requiring high strength, such as A-pillar, B-pillar, C-pillar, and side sill. As shown in FIG. 12) Steel pipes may be applied to the dash panel reinforcement 14, the side seal 16, and the floor cross member 18. And, as shown in FIG. 1C, steel pipes may be used for the torsion beam (or “torsion bar”) 22 and the trailing arm 23 of the suspension device 20.

Recently, in order to improve performance and safety of automobiles, it is required to further improve the strength and shock absorption of automobile parts using steel pipes.

However, the prior art has the following limitations in the production of steel pipes of various shapes excellent in strength and shock absorption.

According to the prior art, the steel pipe is formed by roll forming and welding a steel sheet, and press-molded the steel pipe into a predetermined shape to produce a steel pipe for automobile parts.

By the way, in the case of using a high-strength material to improve the strength of the steel pipe, the high-strength material is difficult to produce a high-strength material, even if the pipe is made, it is almost impossible to manufacture a steel pipe of various forms by modifying the cross-sectional shape.

In addition, low-strength materials can be easily piped, but heat treatment is required to increase the strength. In this case, there is a problem that thermal deformation occurs. In particular, curved steel pipes have severe thermal deformation, which makes it difficult to produce precise parts through heat treatment. Moreover, high strength steel pipes having different cross-sectional shapes in the longitudinal direction cannot be manufactured by the prior art.

The B-pillar 24 and the reinforcement 26 produced by the prior art are shown in FIG. 2. As shown in FIG. 2, the reinforcement 26 may be additionally mounted on the B-pillar 24 requiring high strength, but since the reinforcement 26 is manufactured by press molding, the strength of the B-pillar 24 is increased. There is a limit to the increase. In other words, the strength of the steel pipe itself forming the B-pillar is high.

As described above, in spite of the recent demand for steel pipes for automobile parts having various shapes having high strength, precision, and shock absorption, according to the prior art, the rigidity and shock absorption is maintained while maintaining the precision of the steel pipes for automobile parts. There are certain limitations in improving the capability, and in particular, a method for manufacturing the component to have a high strength and precision in the case of a curved steel pipe or a steel pipe having a different cross-sectional shape in the longitudinal direction has not been proposed.

The present invention was devised to solve the above problems, an object of the present invention is to easily form a high-strength steel pipe and can be modified in the cross-sectional shape to effectively improve the rigidity and impact absorption capacity steel pipe for automotive parts To provide a method of manufacturing and a steel pipe for automobile parts produced thereby.

In order to achieve the above object, a method for manufacturing a steel pipe for automobile parts according to the present invention includes: (a) a group consisting of boron (B), chromium (Cr), molybdenum (Mo), vanadium (V), and nickel (Ni); Preparing a steel sheet containing at least one element selected from; (b) forming the steel pipe by manipulating the steel sheet; (c) heating the steel pipe to a temperature corresponding to an austenite region; (d) rapidly conveying the steel pipe to the press mold at a speed within which no pearlite, ferrite or bainite phases are formed; And (e) rapidly cooling the steel pipe in a press mold and simultaneously molding the steel pipe to have a predetermined shape along its longitudinal direction. Accordingly, steel pipes for automobile parts can be easily manufactured in various shapes, and stiffness and shock absorbing ability can be improved.

In the step (e) it is possible to improve the rigidity and shock absorbing capacity of the steel pipe by forming a cross-sectional shape so that a different cross-sectional shape is present along the longitudinal direction of the steel pipe, bending the steel pipe along the longitudinal direction of the steel pipe It may also be molded. In this way, both the cross-sectional shape of the steel pipe and the shape in the longitudinal direction can be molded, and thus steel pipes for various types of automotive parts can be manufactured.

After the step (e) further comprises the step of tempering the steel pipe for automotive parts to 150 ℃ to 400 ℃. The tempering can further improve the shock absorbing ability of the steel pipe for automobile parts.

칭할 수 있다.In the step (e), the press mold forms the steel pipe in a state in which a cooling material is circulated therein. In this case, the steel pipe may be formed in a state in which the cooling material is injected into the steel pipe through a fine nozzle on the surface of the press mold. By this method, the steel pipe can be effectively

It can be called.

In addition, the mold and the steel pipe are immersed in a reservoir containing a cooling material or the cooling material from the outside of the mold in the mold and the steel pipe together with the cooling material circulation into the mold or the spraying method using the nozzle of the surface of the press mold. The steel pipe may be molded in this sprayed state. In this way, the cooling effect can be further improved.

In consideration of the temperature drop at the time of transfer, the steel pipe in the step (c) is preferably heated to a temperature of 800 ℃ to 1000 ℃.

In the step (c), the steel pipe may be heated in any one furnace selected from the group consisting of a high frequency induction furnace, a batch, a continuous furnace and a rotary furnace.

Steel pipe for automobile parts according to the present invention produced by the above production method is very excellent in tensile strength of 1200MPa to 1700MPa.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the manufacturing method of the steel pipe for automotive parts according to an embodiment of the present invention and the steel pipe for automobile parts manufactured thereby.

Here, the steel pipe for automobile parts refers to A-pillars, B-pillars, C-pillars, side seals, dash panel reinforcements, floor cross members and the like, and torsion beams, trailing arms, etc., which correspond to the skeleton of an automobile body. The steel pipe manufactured for application to the constituent parts is generically referred to.

3 is a flowchart illustrating a method of manufacturing a steel pipe for automotive parts according to an embodiment of the present invention.

As shown in Figure 3, the manufacturing method of the steel pipe for automobile parts according to the present embodiment is a steel sheet preparation step (ST10), tube manufacturing step (ST20), rapid heating step (ST30), rapid transfer step (ST40), press hardening A step ST50 and a tempering step ST60 are included. Each step is described in more detail as follows.

First, in the steel sheet preparation step (ST10), hardenability improving elements such as chromium (Cr), molybdenum (Mo), boron (B), vanadium (V), nickel (Ni), titanium (Ti), and manganese (Mn) Prepare a steel sheet containing at least one. The steel sheet may also include other elements such as carbon (C), silicon (Si), phosphorus (P), sulfur (S), and aluminum (Al).

It is preferable that content of B in a hardenability improvement element is 0.0005 weight%-0.005 weight%, respectively. It is because the hardenability improvement effect which B contains below 0.0005 weight% is not big, and when B contains more than 0.005 weight%, toughness can be reduced. More preferably, it does not exceed 0.003% by weight, because if it exceeds, precipitates called Fe ₂₃ (BC) ₆ are precipitated in large amounts to cure the material and rather the hardenability decreases.

Since Mn is an effect of improving hardenability as an element for improving hardenability, Mn should be added by 0.2 wt% or more, but when added in 2.0 wt% or more, workability deteriorates. Therefore, it is preferable that content of Mn is 0.2 weight%-2.0 weight%.

Ti should be added at least 0.005% by weight in order to prevent the precipitation of B added to improve the hardenability by precipitating nitrogen in the steel with TiN to prevent precipitation into BN, but when 0.15% by weight or more is added, precipitates other than TiN Impact impact. Therefore, it is preferable that content of Ti is 0.005 weight%-0.15 weight%.

Cr is added in an amount of 0.2% by weight or more in order to help improve the hardenability of B during quenching, but the effect is saturated and causes a cost increase even when 2.0% by weight or more is added. Therefore, it is preferable that content of Cr is 0.2 weight%-2.0 weight%.

Mo, V, and Ni are added as 0.002% by weight or more as a hardenable complement element, but even when 1.0% by weight or more is added, the effect is saturated and causes a cost increase. Therefore, it is preferable that content of Mo, V, and Ni is 0.002 weight%-1.0 weight%, respectively.

In the case of C, when the content is more than 0.60% by weight, the material may be hardened, resulting in poor weldability and weldability. When the C content is less than 0.01% by weight, hardenability is insufficient, so it is difficult to obtain the hardness or strength required after hardening and tempering.

In the case of other elements, it is generally preferable to maintain the following contents, but the present invention is not necessarily limited thereto.

Since Si has a high solid solution hardening effect and improves hardenability, it should be added in an amount of 0.01 wt% or more.

Since P causes brittleness during tempering, the impact resistance is significantly deteriorated. Therefore, the P content is preferably limited to 0.03% by weight or less.

When S is an impurity of 0.03% by weight or more, the amount of nonmetallic inclusions is increased to lower the impact resistance, so S is limited to 0.03% by weight or less.

       Al is added for the purpose of deoxidation of the steel, but if it is less than 0.005% by weight, the deoxidation effect is less. When the Al content is added in excess of 0.2% by weight or more, Al decreases the cleanliness by the formation of oxides, thereby reducing the impact resistance.

When N is added in an amount of 0.01% by weight or more, the B added for the purpose of improving the hardenability is precipitated with BN to reduce the amount of solid solution B contributing to the hardenability. Restrict.

In the above, the content of the steel sheet-containing element was described, but the present invention is not limited thereto. Of course, the content may be adjusted in consideration of characteristics required for steel pipes for automobile parts.

The hardenability enhancing elements such as chromium, molybdenum, boron, vanadium, nickel and the like improve the hardenability of the steel pipe so that the main structure of the steel pipe becomes martensite after the press hardening step (ST50). This will be described in more detail in the press curing step ST50.

Such steel sheet may be a hot rolled steel sheet or a cold rolled steel sheet.

Subsequently, in the tube pipe step (ST20), the steel sheet is piped by roll forming and welding to form a straight steel pipe. Then, after performing the inspection of the steel pipe defect portion is cut to a suitable size to put in the heating furnace in the rapid heating step (ST30).

Subsequently, in the rapid heating step ST30, the steel pipe is rapidly heated to a temperature corresponding to the austenite region. At this time, in consideration of the temperature drop in the rapid transfer step (ST40), it is preferable to heat to a temperature of 800 ℃ to 1000 ℃.

For rapid heating, it is preferable to use a high frequency induction heating method in which a steel pipe is placed in a high frequency induction furnace and heated. The high frequency induction heating method is a method of heating a steel pipe continuously through an induction coil, and heating the steel pipe during induction heating enables uniform heat treatment to minimize thermal deformation of the steel pipe. In addition, the high frequency induction heating method does not need to control the gas atmosphere inside the furnace, and rapid heating is possible, thereby reducing the heat treatment time.

However, the present invention is not limited thereto, and of course, a heating furnace such as a rotary furnace or a continuous furnace may be used as a batch using electricity or gas as a heat source for heating the steel pipe.

Subsequently, the steel pipe is rapidly transferred to the press hardening facility in the rapid transfer step ST40. If the transport time of the steel pipe is longer, the temperature of the steel pipe is lowered, so that the ferrite, pearlite, bainite, etc. may be generated inside the steel pipe after press hardening, thereby reducing the strength. Therefore, in consideration of the components of the steel pipe, it is preferable to transport the steel pipe at a speed that can prevent the decrease in strength.

In other words, it is preferable to transport the steel pipe at a speed within the limit where no pearlite or ferrite phase is formed, and more preferably at the fastest speed possible. Considering the cooling rate in air, it is preferable to transfer within about 10 seconds.

Here, the steel pipe may be transferred using a robot or manually. The present invention is not limited thereto, and the steel pipe may be transferred in various ways.

칭하는 것을 말하며, 당업계에서는 프레스 담금질, 프레스

칭, 다이

칭, 열간 프레스 성형, 핫 프레스 포밍 등으로 불리우기도 한다. Subsequently, in the press hardening step ST50, the steel pipe is cooled and simultaneously molded in a press mold to form a steel pipe for automobile parts. Here, press hardening refers to press forming a steel pipe at a high temperature having low strength and excellent ductility, and simultaneously forming a steel pipe by a cooled mold.

Refers to, in the art press quenching, press

Ching, die

It may also be referred to as hot pressing, hot press forming, or the like.

칭하는 방법이 개시되어 있다. 이에 개시된 것처럼 종래 프레스

칭 방법은 강판에 대한 급냉 성형 방식으로 사용되어 왔으나, 본 발명에서의 강관과 같이 프레스면으로 단순히 접촉하여 냉각할 수 없는 구조의 부품 성형에는 구조적 특성상 이러한 방법이 사용되지 못했다. Steel plate is pressed in Patent Publication No. 2002-12644 or Japanese Patent Publication No. 2003-231915

A method of calling is disclosed. Conventional press as disclosed herein

Although the quenching method has been used as a quenching method for steel sheets, such a method has not been used for forming a part having a structure that cannot be cooled simply by contacting with a press surface like a steel pipe in the present invention.

칭하기 위하여 다음과 같은 냉각 방법이 적용될 수 있다. In the present invention, the steel pipe having an inner surface not in contact with the press surface together with press molding

The following cooling method may be applied to refer to.

칭 방법에서 일부 개시된 내용이다. 그러나, 강판과 달리 강관의 경우 그 내면이 냉각된 프레스면에 접할 수 없는 형상을 갖고 있는 경우 금형의 접촉에 의한 냉각만으로는 냉각효과를 기대하기 어렵다. 특히 길이방향에 따라 단면의 형상이 다른 강관이나 곡선형 강관의 경우 강관의 모든 면에 대한 급냉 효과를 기대하기 어렵다. 또한, 금형의 냉각효과를 높이기 위해, 냉각 물질의 순환구조를 강관의 형상에 따라 복잡하게 구성하는 것도 경제적인면이나 실질적인 면에서 바람직하지 못하다.First, there is a method of press molding while circulating a cooling material in a mold. This is a conventional press

Some of the disclosures in the method are described. However, unlike steel plates, when the inner surface of the steel pipe has a shape that cannot be in contact with the cooled press surface, it is difficult to expect a cooling effect only by cooling by contact of the mold. In particular, in the case of steel pipes or curved steel pipes having different cross-sectional shapes depending on the length direction, it is difficult to expect a quenching effect on all sides of the steel pipes. In addition, in order to increase the cooling effect of the mold, it is not economical or practical in terms of complicated configuration of the circulation structure of the cooling material according to the shape of the steel pipe.

칭한다. 이로써, 금형 표면에 형성된 다수의 작은 노즐을 통하여 냉각물질이 강관에 계속하여 분사됨으로써 냉각효과를 더욱 높일 수 있다. 이는 같은 기온하에서도 바람이 부는 곳에서 물체의 냉각속도가 더 빠른 원리와 같다고 볼 수 있다. 즉, 찬 공기 중에서 물체가 냉각되는 경우보다 찬 공기가 물체에 계속 부딪치면서 물체주위에 높아진 공기를 찬 공기로 계속 대체하는 경우가 더 빠른 냉각효과를 나타내는 것과 유사한 것이다.Therefore, in the present invention, the steel pipe is pressed while spraying the cooling material into the steel pipe through a small nozzle on the surface of the mold with circulation of the cooling material into the mold.

It is called. As a result, the cooling material is continuously injected into the steel pipe through the plurality of small nozzles formed on the mold surface, thereby further increasing the cooling effect. This is similar to the principle that the cooling rate of an object is faster in the place where the wind blows even under the same temperature. In other words, cold air continuously hits an object and cold air is replaced by cold air continuously while the object is cooled in the cold air.

In order to further improve the cooling effect, the steel pipe may be press-molded in a state in which the mold and the steel pipe are immersed in the water tank containing the cooling material together with the cooling material circulation into the mold or the spraying method through the nozzle on the surface of the mold. At this time, in the case of the structure that the cooling material of the reservoir can pass through the inner surface of the steel pipe may exhibit a uniform cooling effect of the steel pipe.

In addition, the steel pipe may be press-molded while injecting the cooling material into the steel pipe from the outside of the mold together with the cooling material circulation into the mold or the injection method through the nozzle on the surface of the mold.

In this way, the cooling effect is improved, as well as the cooling material may be in contact with the inner diameter of the steel pipe, thereby forming the entire martensitic structure.

Here, the cooling material refers to materials such as cooling water and cooling oil.

In the press molding step ST50, the steel pipe may be bent in the longitudinal direction according to the shape of the automobile part, or the cross section of the steel pipe may be formed into an appropriate shape in consideration of the rigidity and the shock absorbing ability.

Accordingly, according to the present exemplary embodiment, steel pipes for automobile parts having various shapes, such as straight or curved steel pipes having the same cross-sectional shape along the longitudinal direction and straight or curved steel pipes having different cross-sectional shapes along the longitudinal direction, can be manufactured. have.

At this time, the straight or curved steel pipes having portions having different cross-sectional shapes along the longitudinal direction are optimized to satisfy the stiffness or strength required at each portion, thereby improving the characteristics of the steel pipe for automobile parts.

That is, in this embodiment, both bending and longitudinal cross-sectional forming of the steel pipe can be performed, and thus steel pipes for automobile parts having various shapes can be manufactured while having high strength.

In this embodiment, the press hardening is applied to form a steel pipe at a high temperature having low strength and excellent ductility, so that a high strength steel pipe can be easily formed. That is, it is possible to manufacture a steel pipe for automotive parts using a high-strength steel pipe can improve the rigidity and impact absorption capacity of the steel pipe for automotive parts. In addition, the cross-sectional shape of the steel pipe can be modified to further improve the rigidity and shock absorbing ability of the steel pipe for automobile parts.

칭하여, 자동차 부품용 강관의 주조직이 높은 강도의 마르텐사이트가 되도록 한다. 이에 자동차 부품용 강관의 강성과 충격 흡수 능력을 보다 향상시킬 수 있다. In this embodiment, a steel pipe having excellent hardenability is

In other words, the main structure of the steel pipe for automobile parts is a high strength martensite. Therefore, the rigidity and shock absorbing ability of the steel pipe for automobile parts can be further improved.

칭 시 강관의 외경부는 금형에 접촉되지만 강관의 내경부는 금형에 접촉되지 않으므로, 강관의 내경부의 냉각 속도가 상대적으로 느려 강관의 내경부에 마르텐사이트가 아닌 조직이 생성될 수 있다. 이러한 현상은 강관의 두께가 두꺼울수록 나타나기 쉬우므로 강관의 두께가 두꺼울수록 경화능이 우수한 강관을 사용하거나 상술한 우수한 냉각 효과를 나타낼 수 있는 방법으로 프레스 경화를 진행하는 것이 바람직하다.

When the outer diameter portion of the steel pipe is in contact with the mold, but the inner diameter portion of the steel pipe is not in contact with the mold, the cooling rate of the inner diameter portion of the steel pipe is relatively slow, a non-martensite structure may be generated in the inner diameter of the steel pipe. This phenomenon is more likely to appear as the thickness of the steel pipe is thicker, it is preferable to use the steel pipe with excellent hardenability or press hardening in a manner that can exhibit the excellent cooling effect as the thickness of the steel pipe is thicker.

칭이 이루어지므로 금형이 자동차 부품용 강관의 열변형 및 이에 따른 뒤틀림을 효과적으로 방지한다. 결과적으로 본 실시예에 따르면 우수한 형상의 자동차 부품용 강관을 제조할 수 있다. When press hardening is completed, the steel pipe for automobile parts is taken out from the mold of the press hardening facility. In this embodiment, inside the mold

As the mold is made, the mold effectively prevents heat deformation and consequent warpage of the steel pipe for automobile parts. As a result, according to this embodiment, it is possible to manufacture a steel pipe for automotive parts of excellent shape.

Although it is preferable to take out from a metal mold after a steel pipe for auto parts reaches room temperature, it is also possible to take out a steel pipe for auto parts under the temperature which the transformation from austenite to martensite is completed for productivity improvement.

Subsequently, the steel pipe for automobile parts is tempered in the tempering step ST60. Steel pipes for automotive parts immediately after press hardening are brittle, so they are tempered at a relatively low temperature to improve shock absorbing ability. The tempering temperature is preferably 150 ° C. to 400 ° C. so as to increase toughness without a large decrease in strength. However, the present invention is not limited thereto, and the tempering temperature can be appropriately adjusted according to the components of the steel pipe for automobile parts.

The tensile strength of the steel pipe for automobile parts according to the present invention manufactured as described above shows 1500MPa to 1700MPa. That is, about 3 to 5 times the tensile strength of the steel pipe for automobile parts manufactured by the prior art. As such, it can be seen that the steel pipe for automobile parts according to the present invention has excellent rigidity and shock absorbing ability.

4 and 5 show photographs of steel pipes for automobile parts manufactured by the method for manufacturing steel pipes for automobile parts according to the present embodiment.

Referring to Figure 4, it can be seen that according to the method for manufacturing a steel pipe for automotive parts according to the present invention can produce a steel pipe 30, 32 for a variety of shapes.

FIG. 5 is a photograph of the steel pipe 38 and the trailing arm 40 applied as the torsion beam of the suspension device 36. The cross section CA at the A line and the cross section CB at the B line of the steel pipe 38. ), The cross section CC on the C line, the cross section CD on the D line, and the cross section CE on the E line are different from each other.

Thus, according to the present invention, it can be seen that the cross-section of the steel pipe for automotive parts can be molded into various shapes, and the steel pipe for automotive parts can be manufactured so that some cross-sections have different shapes from other parts along the longitudinal direction. .

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

As described above, according to the manufacturing method of the steel pipe for automobile parts according to the present invention, the high strength steel pipe can be easily formed into various shapes because the steel pipe can be formed at a high temperature having low strength and excellent ductility by using press hardening. That is, the steel pipe for automobile parts having various cross sections and shapes can be manufactured as a high strength steel pipe, thereby improving the rigidity and shock absorbing ability of the steel pipe for automobile parts. In addition, the cross-sectional shape of the steel pipe may be modified to further improve the rigidity and shock absorbing ability of the steel pipe for automobile parts.

칭함으로써 자동차 부품용 강관의 주 조직이 마르텐사이트가 되도록 하여 자동차 부품용 강관의 강성 및 충격 흡수 능력을 좀더 향상시킬 수 있다. 프레스 경화 이후에 템퍼링을 수행하여 해당 자동차 부품용 강관의 충격 흡수 능력을 더욱 향상시킬 수 있다. In addition, the steel pipe with excellent hardenability

By making the main structure of the steel pipe for automotive parts become martensite, the rigidity and shock absorbing ability of the steel pipe for automotive parts can be further improved. Tempering may be performed after press hardening to further improve the shock absorbing ability of the steel pipe for the automotive part.

칭하므로 강관의 열변형 현상 을 방지하여 우수한 형상의 자동차 부품용 강관을 제조할 수 있다. Steel pipe inside the mold of press hardening equipment

Therefore, it is possible to prevent the heat deformation of the steel pipe to manufacture a steel pipe for automotive parts of excellent shape.

In addition, various cooling methods can be applied to uniformly cool even the inner surface that is not in contact with the press surface, and by obtaining a uniform martensite structure, the strength of the steel pipe for parts can be further improved.

On the other hand, the steel pipe for automobile parts manufactured by the manufacturing method of this invention is very excellent in rigidity and shock absorption ability. Accordingly, it can be applied to a vehicle body, a reinforcement, etc., which requires rigidity and shock absorbing ability, and can improve the characteristics of the vehicle and protect the safety of the occupants.

Claims (12)

(a) preparing a steel sheet containing at least one element selected from the group consisting of boron (B), chromium (Cr), molybdenum (Mo), vanadium (V), and nickel (Ni); (b) forming the steel pipe by manipulating the steel sheet; (c) heating the steel pipe to a temperature corresponding to an austenite region; (d) rapidly conveying the steel pipe to the press mold at a speed within which no pearlite, ferrite or bainite phases are formed; And (e) rapidly cooling the steel pipe in a press mold and simultaneously forming the steel pipe to have a predetermined shape along its longitudinal direction; Including; The method of manufacturing a steel pipe for high-strength automotive parts, characterized in that for forming the cross-sectional shape so that there is a portion different in cross-sectional shape along the longitudinal direction of the steel pipe in the step (e). delete (a) preparing a steel sheet containing at least one element selected from the group consisting of boron (B), chromium (Cr), molybdenum (Mo), vanadium (V), and nickel (Ni); (b) forming the steel pipe by manipulating the steel sheet; (c) heating the steel pipe to a temperature corresponding to an austenite region; (d) rapidly conveying the steel pipe to the press mold at a speed within which no pearlite, ferrite or bainite phases are formed; And (e) rapidly cooling the steel pipe in a press mold and simultaneously forming the steel pipe to have a predetermined shape along its longitudinal direction; Including; The method of manufacturing a high-strength automotive parts steel pipe, characterized in that for bending the steel pipe along the longitudinal direction of the steel pipe in the step (e). The method according to claim 1 or 3, After step (e), The method of manufacturing a high-strength automotive parts steel pipe further comprises the step of tempering the steel pipe for automotive parts at 150 ℃ to 400 ℃. The method according to claim 1 or 3, In the step (e), the press mold is a method of manufacturing a steel pipe for high-strength automotive parts, characterized in that for forming the steel pipe in a state that the cooling material is circulated therein. (a) preparing a steel sheet containing at least one element selected from the group consisting of boron (B), chromium (Cr), molybdenum (Mo), vanadium (V), and nickel (Ni); (b) forming the steel pipe by manipulating the steel sheet; (c) heating the steel pipe to a temperature corresponding to an austenite region; (d) rapidly conveying the steel pipe to the press mold at a speed within which no pearlite, ferrite or bainite phases are formed; And (e) rapidly cooling the steel pipe in a press mold and simultaneously forming the steel pipe to have a predetermined shape along its longitudinal direction; Including; In the step (e), the press mold is a high strength, characterized in that for forming the steel pipe in the state that the cooling material is circulated therein, the cooling material is injected into the steel pipe through a fine nozzle on the surface of the press mold Method for manufacturing steel pipe for automotive parts. (a) preparing a steel sheet containing at least one element selected from the group consisting of boron (B), chromium (Cr), molybdenum (Mo), vanadium (V), and nickel (Ni); (b) forming the steel pipe by manipulating the steel sheet; (c) heating the steel pipe to a temperature corresponding to an austenite region; (d) rapidly conveying the steel pipe to the press mold at a speed within which no pearlite, ferrite or bainite phases are formed; And (e) rapidly cooling the steel pipe in a press mold and simultaneously forming the steel pipe to have a predetermined shape along its longitudinal direction; Including; In the step (e), the press mold has a cooling material circulated therein or the cooling material is injected into the steel pipe through a fine nozzle on the surface of the press mold, and the mold and the steel pipe in the reservoir containing the cooling material. Method for producing a high-strength automotive parts steel pipe, characterized in that for forming the steel pipe in the locked state. (a) preparing a steel sheet containing at least one element selected from the group consisting of boron (B), chromium (Cr), molybdenum (Mo), vanadium (V), and nickel (Ni); (b) forming the steel pipe by manipulating the steel sheet; (c) heating the steel pipe to a temperature corresponding to an austenite region; (d) rapidly conveying the steel pipe to the press mold at a speed within which no pearlite, ferrite or bainite phases are formed; And (e) rapidly cooling the steel pipe in a press mold and simultaneously forming the steel pipe to have a predetermined shape along its longitudinal direction; Including; In the step (e), the cooling die is circulated therein or the cooling material is injected into the steel pipe through a fine nozzle on the surface of the pressing die, and the cooling material is injected from the outside of the mold into the mold and the steel pipe. Method for producing a high-strength automotive parts steel pipe, characterized in that for molding the steel pipe in the sprayed state. The method according to claim 1 or 3, In the step (c), the steel pipe is a method of manufacturing a high-strength automotive parts steel pipe, characterized in that heated to a temperature of 800 ℃ to 1000 ℃. The method according to claim 1 or 3, In the step (c), the steel pipe is a high frequency induction heating furnace, batch (batch), a method of manufacturing a high-strength automotive parts steel pipe, characterized in that the heating in any one of the heating furnace selected from the group consisting of a rotary furnace. . delete The steel pipe for high strength automotive parts manufactured by the manufacturing method of the steel pipe for automobile parts of any one of Claims 1, 3, and 6-8, and whose tensile strength is 1500MPa-1700MPa.

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