WO2012043833A1 - Press forming equipment - Google Patents

Press forming equipment Download PDF

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Publication number
WO2012043833A1
WO2012043833A1 PCT/JP2011/072667 JP2011072667W WO2012043833A1 WO 2012043833 A1 WO2012043833 A1 WO 2012043833A1 JP 2011072667 W JP2011072667 W JP 2011072667W WO 2012043833 A1 WO2012043833 A1 WO 2012043833A1
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WIPO (PCT)
Prior art keywords
press
cooling
steel plate
press forming
heating furnace
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PCT/JP2011/072667
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French (fr)
Japanese (ja)
Inventor
純也 内藤
圭介 沖田
池田　周之
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株式会社神戸製鋼所
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Publication of WO2012043833A1 publication Critical patent/WO2012043833A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D37/00—Tools as parts of machines covered by this subclass
    • B21D37/16—Heating or cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • B21D22/208—Deep-drawing by heating the blank or deep-drawing associated with heat treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D35/00—Combined processes according to or processes combined with methods covered by groups B21D1/00 - B21D31/00
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets

Definitions

  • the present invention heats a steel sheet (blank) as a raw material to an austenite temperature (Ac 3 transformation point) or higher, and then press-forms it. It relates to equipment for manufacturing a press-formed product that can obtain a predetermined strength by quenching a steel sheet at the same time as shaping when forming into a predetermined shape.
  • the present invention relates to a press forming facility capable of realizing good forming with good productivity without generating.
  • a hot pressing method that simultaneously improves the strength of the component by press molding and quenching has been proposed (for example, Patent Document 1).
  • the steel sheet is heated to an austenite ( ⁇ ) region above the Ac 3 transformation point and hot pressed, and the steel sheet is simultaneously quenched by bringing it into contact with a normal temperature mold during press forming. This is a method for realizing high strength.
  • Such a hot pressing method since it is molded in a low strength state, the spring back is reduced (the shape freezing property is good), and a strength of a tensile strength of 1500 MPa class is obtained by rapid cooling.
  • a hot pressing method is called by various names such as a hot forming method, a hot stamping method, a hot stamp method, and a die quench method in addition to the hot pressing method.
  • FIG. 1 is a schematic explanatory view showing a mold configuration for carrying out hot press molding as described above (hereinafter sometimes referred to as “hot press”).
  • 3 is a blank holder
  • 4 is a steel plate (blank)
  • BHF is a crease pressing force
  • rp is a punch shoulder radius
  • rd is a die shoulder radius
  • CL is a punch / die clearance.
  • the punch 1 and the die 2 have passages 1a and 2a through which a cooling medium (for example, water) can pass, and the cooling medium is allowed to pass through the passages.
  • a cooling medium for example, water
  • Non-Patent Document 1 discloses a hot press forming facility provided with a press forming machine having a mold configuration as described above.
  • a heating furnace for heating and softening the steel plate to the Ac 3 transformation point or higher
  • a device for conveying the heated steel plate
  • a press forming machine for press forming the steel plate
  • trimming the molded product An apparatus for processing (correcting processing for making a final shape by a laser or the like) is provided (see FIG. 2 described later).
  • the steel sheet is press-cooled in the austenite region above the Ac 3 transformation point (for example, around 900 ° C.), so that the portion that contacts the mold (punch and die) and the portion that does not contact The difference in temperature is likely to occur, and strain concentrates on the relatively high temperature part.For example, in deep drawing, the shrink flange is cooled and does not shrink. It becomes difficult.
  • press molding is usually performed at around 700 to 900 ° C, and quenching is performed in the mold, so it is necessary to hold the molding at the bottom dead center (when the punch tip is at the top) for a certain period of time.
  • Productivity is worse than cold pressing.
  • the present invention has been made in view of the above circumstances, and the purpose thereof is press forming with good formability to such an extent that deep drawing can be performed without causing inconvenience due to the formation of scale on the surface of the steel sheet.
  • An object of the present invention is to provide a press molding facility for manufacturing products with high productivity.
  • the press forming equipment of the present invention that has achieved the above-mentioned object includes a heating furnace and a press forming machine. After heating a thin steel plate to a temperature of the Ac 3 transformation point or higher in the heating furnace, A press forming facility for press-molding a steel sheet to produce a molded product, wherein a cooling unit for cooling the heated thin steel sheet is provided inside the heating furnace or between the heating furnace and the press-forming machine. The point is that it is provided.
  • the cooling section has a cooling capacity higher than that of air cooling.
  • the cooling capacity higher than that of air cooling.
  • the thing provided with the gas jet cooling device or the cooled metal roll is mentioned.
  • this cooling part is configured so that the atmosphere can be controlled.
  • Examples of the press molding machine used in the press molding facility of the present invention include a punch, a die and a blank holder.
  • a cooling unit for cooling the heated thin steel plate is provided in the heating furnace or between the heating furnace and the press forming machine. Press molding can be performed with high productivity without causing inconvenience due to the formation of scale on the surface and without causing breakage or cracking during molding.
  • the temperature distribution in the steel sheet during press forming can be reduced (the temperature difference from the mold is reduced), and good formability can be secured. Further, since the press molding start temperature can be lowered, there is an advantage that the holding time at the bottom dead center of molding can be shortened.
  • Conventional hot press forming equipment generally has a configuration (equipment configuration) as shown in FIG. 2 (schematic explanatory diagram). That is, as shown in FIG. 2, the coiled steel sheet 10 is cut out by a cutting machine 11 (Blanking), heated in a heating furnace 12, and then moved to a press forming machine 13 to be a press-formed product 14. The In such an equipment configuration, between the heating furnace 12 and the press molding machine 13, the surface of the steel plate 10 is oxidized because it is in contact with the atmosphere in a high temperature state (temperature above the Ac 3 transformation point). This is an unavoidable situation.
  • Fig. 3 shows the heat pattern when press-molding using conventional press-molding equipment.
  • the heating stage heating furnace 12
  • the rate of temperature rise is about 12 ° C./second, for example.
  • a predetermined temperature 900 ° C. in FIG. 3
  • the heating time is about 75 seconds
  • a press molding machine to be press-molded. In this movement, no matter how fast it is moved, it takes about 4 seconds.
  • the number of press moldings is 3 times per minute [ 3 spm (stroke / minute): about 20 seconds / 1 press].
  • FIG. 4 is a schematic explanatory view showing an example of the press molding equipment of the present invention (in FIG. 4, the same reference numerals are assigned to the portions corresponding to FIG. 3).
  • a cooling unit 15 is provided inside the heating furnace 12 along with the heating furnace 12, and the steel plate 10 is cooled before moving from the heating furnace 12 to the press forming machine 13.
  • the cooling unit 15 may be provided between the heating furnace 12 and the press molding machine 13.
  • the cooling can be performed by the methods (1) to (4) below (or in combination) including the above-described methods.
  • a gas jet cooling device is provided for cooling.
  • a means for example, a water-cooled metal roll for bringing into contact with a metal roll as a refrigerant is provided to remove heat.
  • a means for example, a water-cooled metal roll for bringing into contact with a metal roll as a refrigerant is provided to remove heat.
  • a dry ice shot means (cooled by causing the granule dry ice to collide with the blank material) is cooled.
  • the entire steel plate may be uniformly cooled, or only a part (preferably a forming portion) of the steel plate to be press-formed may be partially cooled.
  • the steel plate position to be partially cooled is, for example, a press-formed portion such as a die shoulder portion or a punch shoulder portion of the steel plate. Since the press-formed part is the most contact area with the mold and the temperature drop of the steel plate is large, when only such an area is partially cooled, the temperature difference between the cooled part and the uncooled part is small. Thus, good moldability can be secured. Furthermore, since the strength of the center of the cooled steel plate is ensured and the ductility of the end portion of the steel plate that has not been cooled can be ensured, further excellent deep drawability can be achieved.
  • the period from ⁇ 20 to 0 means the time (transport time) during which the steel plate is transported in the heating furnace 12, and the “cooling time” after that is the time for cooling the steel plate. It means the time since the start (see Table 2 below).
  • the temperature at the center of the steel plate is lower than the temperature at the end of the steel plate, and by partially cooling the central portion of the steel plate, the temperature of the press-formed portion can be lowered efficiently. It has been shown that it can.
  • FIG. 6B even when only the central part of the steel plate is cooled, the temperature difference between the steel plate center and the steel plate end can be saturated in a certain time (about 30 seconds in the illustrated example). It is shown. This is because heat transfer occurs between the cooled portion and the non-cooled portion of the steel sheet, and the temperature difference is alleviated. From the viewpoint of improving the deep drawing formability by maintaining the strength of the press-formed part, it is desirable to perform press-molding in a state in which a certain temperature difference between the cooled part and the non-cooled part of the steel plate is secured.
  • the press forming carried out using the equipment of the present invention assumes the case where the steel sheet is heated and then applied to the method of forming after rapidly cooling to near the bainite transformation start temperature or martensite transformation start temperature.
  • the cooling section preferably has a cooling capacity equal to or higher than that of air cooling (for example, a cooling capacity equal to or higher than the critical cooling rate when cooling to the martensite transformation start temperature).
  • the atmosphere becomes easy to control, and the atmosphere is controlled (for example, nitrogen or argon atmosphere) to more effectively prevent surface oxidation of the steel sheet.
  • the atmosphere is not necessarily controlled (surface oxidation is suppressed by lowering the temperature).
  • FIG. 5 shows a heat pattern when press-molding using the press-forming equipment of the present invention.
  • the heating rate can be increased compared to the heat pattern shown in FIG. 3 (rapid heating: for example, about 20 to 60 seconds), and the mold is maintained at the bottom dead center (for example, 5 to 10 seconds). ), Die cooling, etc. can be shortened (the next press can be performed quickly), and press working of about 4 to 6 spm can be performed, and the productivity is extremely high as compared with the conventional pattern.
  • the heat pattern shown in FIG. 5 shows such a state.
  • Example 1 Using the steel sheet having the chemical composition shown in Table 1 below (thickness: 1.0 mm, circular blank with a diameter of 110 mm) and heating to 900 ° C. by the press forming equipment shown in FIG. 4 (Ac of this steel sheet) 3 transformation point: 830 ° C., martensite transformation start temperature Ms: 411 ° C.), cooled to 700 ° C. by controlled atmosphere gas jet cooling, and then cooled to about 500 ° C. by sandwiching the steel sheet, and the mold [head shape is Using a square die having a side of 45 mm (square tube die and square tube punch)] (see FIG. 1), square tube deep drawing was performed.
  • Example 2 4 using the steel plate having the same chemical composition as in Example 1 (thickness: 1.4 mm, diameter: circular steel plate having a diameter of 90 to 110 mm shown in Table 2) by the press forming equipment shown in FIG. (Ac 3 transformation point of this steel plate: 830 ° C., martensite transformation start temperature Ms: 411 ° C.) and then cooled by the following cooling means in the cooling section (in Table 2, “Cooling means”). ”And“ Cooling hold time (seconds) ”. In the case of partial cooling, a cooling unit (not shown) was provided between the heating furnace and the press molding machine for cooling.
  • the steel plate is transferred to a press molding machine (refer to “Transfer time (seconds)” in Table 2), and using a mold [punch diameter: 50 mm cylindrical mold (cylindrical die and cylindrical punch)], Cylindrical deep drawing was performed.
  • a mechanical servo press maximum pressing force 200 tons, maximum pressing 27 spm was used as a press. Further, the time from when the mold comes into contact with the steel plate until it stops at the bottom dead center of forming was set to 0.2 seconds.
  • Other press molding conditions are as follows.
  • Example 2 cylindrical deep drawing was performed in the same manner as in Example 2 using the conventional press forming equipment shown in FIG. Specifically, after heating a steel plate (blank) in a heating furnace, the steel plate was taken out from the heating furnace without being cooled and transported to a press machine (transport time: 6 seconds), and then immediately formed (in Table 2, No. 1). The results are shown in Table 2.
  • the maximum blank diameter that can be formed was the same when air-cooled and when forced-cooled. However, when forced-cooled, the effect of improving hardness could be confirmed. That is, as a result of testing the hardness of the molded product after molding (the average value of Vickers hardness measured at intervals of 5 mm from the top center to the lower end of the molded product is shown in Table 2), when air-cooled (No. 2 -1 and 2-2) have not obtained sufficient hardness of 480 Hv or more as the cooling holding time is increased, but when forced cooling (No. 3-1 to 3-3) is 480 Hv Hardness exceeding was obtained. In the case of partial cooling (Nos. 4-1 to 4-3), it was confirmed that good hardness similar to that of forced cooling could be obtained.
  • the press forming equipment of the present invention includes a heating furnace and a press forming machine, and after heating the thin steel plate to a temperature equal to or higher than the Ac 3 transformation point in the heating furnace, the thin steel plate is press formed by the press forming machine to obtain a molded product.
  • It is a press forming facility for manufacturing, and is provided with a cooling part for quenching a heated thin steel plate inside the heating furnace or between the heating furnace and the press forming machine.

Abstract

Provided is press forming equipment comprising a heating furnace and a press forming machine, for press forming a thin steel plate using the press forming machine after heating the thin steel plate in the heating furnace to a temperature at or above an Ac3 transformation point, to produce a formed article. Specifically provided is press forming equipment for producing with good productivity press formed articles that have good formability, to the extent that deep drawing is possible but without defects caused by the formation of scale on the steel plate surface, which is achieved by the provision inside the heating furnace or between the heating furnace and the press forming machine of a cooling section for rapid cooling of the heated thin steel plate.

Description

プレス成形設備Press forming equipment
　本発明は、主に自動車用車体に適用される薄鋼板成形品を製造する分野において、その素材となる鋼板（ブランク）をオーステナイト温度（Ａｃ3変態点）以上に加熱し、その後プレス成形して所定の形状に成形する際に、形状付与と同時に、鋼板を焼入れて所定の強度を得ることのできるプレス成形品を製造するための設備に関するものであり、殊にプレス成形時に破断や割れなどを発生させずに生産性良く良好な成形が実現できるプレス成形設備に関するものである。 In the field of manufacturing a thin steel sheet molded product mainly applied to an automobile body, the present invention heats a steel sheet (blank) as a raw material to an austenite temperature (Ac 3 transformation point) or higher, and then press-forms it. It relates to equipment for manufacturing a press-formed product that can obtain a predetermined strength by quenching a steel sheet at the same time as shaping when forming into a predetermined shape. The present invention relates to a press forming facility capable of realizing good forming with good productivity without generating.
　地球環境保護の観点から、低燃費化を目的とした自動車の軽量化が強く望まれており、車両を構成する部品に鋼板が使用される場合には、高強度鋼板を適用し、この鋼板の板厚を薄くすることによって、軽量化が図られている。その一方で、自動車の衝突安全性を向上させるために、ピラー等の自動車部品には、更なる高強度化が要求されており、引張強度がより高い超高強度鋼板に対するニーズも高まっている。 From the viewpoint of protecting the global environment, it is strongly desired to reduce the weight of automobiles for the purpose of reducing fuel consumption. When steel plates are used for the parts that make up vehicles, high-strength steel plates are used. Weight reduction is achieved by reducing the plate thickness. On the other hand, in order to improve the collision safety of automobiles, automobile parts such as pillars are required to have higher strength, and there is an increasing need for ultra-high strength steel sheets having higher tensile strength.
　しかしながら、薄鋼板の強度をより高くすると、伸びＥＬやｒ値（ランクフォード値）が低下し、プレス成形性や形状凍結性が劣化することになる。 However, if the strength of the thin steel plate is further increased, the elongation EL and the r value (Rankford value) are lowered, and the press formability and the shape freezeability are deteriorated.
　こうした状況の下、高強度の自動車用構造部品を実現するために、プレス成形と焼入れによる部品の強度向上を同時に行なう熱間プレス方法（いわゆる「ホットプレス法」）が提案されている（例えば、特許文献１）。この技術は、鋼板をＡｃ3変態点以上のオーステナイト（γ）領域まで加熱して、熱間でプレス成形すると共に、プレス成形時に常温の金型と接触させることによって鋼板の焼入れを同時に行い、超高強度化を実現する方法である。 Under these circumstances, in order to realize a high-strength automotive structural component, a hot pressing method (so-called “hot pressing method”) that simultaneously improves the strength of the component by press molding and quenching has been proposed (for example, Patent Document 1). In this technology, the steel sheet is heated to an austenite (γ) region above the Ac 3 transformation point and hot pressed, and the steel sheet is simultaneously quenched by bringing it into contact with a normal temperature mold during press forming. This is a method for realizing high strength.
　こうした熱間プレス方法によれば、低強度状態で成形されるので、スプリングバックも小さくなると共に（形状凍結性が良好）、急冷によって引張強度が１５００ＭＰａ級の強度が得られることになる。尚、このような熱間プレス方法は、ホットプレス法の他、ホットフォーミング法、ホットスタンピング法、ホットスタンプ法、ダイクエンチ法等、様々な名称で呼ばれている。 According to such a hot pressing method, since it is molded in a low strength state, the spring back is reduced (the shape freezing property is good), and a strength of a tensile strength of 1500 MPa class is obtained by rapid cooling. Such a hot pressing method is called by various names such as a hot forming method, a hot stamping method, a hot stamp method, and a die quench method in addition to the hot pressing method.
　図１は、上記のような熱間プレス成形（以下、「ホットプレス」で代表することがある）を実施するための金型構成を示す概略説明図であり、図中１はパンチ、２はダイ、３はブランクホルダー、４は鋼板（ブランク）、ＢＨＦはしわ押え力、ｒｐはパンチ肩半径、ｒｄはダイ肩半径、ＣＬはパンチ／ダイ間クリアランスを夫々示している。また、これらの部品のうち、パンチ１とダイ２には冷却媒体（例えば水）を通過させることができる通路１ａ，２ａが夫々の内部に形成されており、この通路に冷却媒体を通過させることによってこれらの部材が冷却されるように構成されている。 FIG. 1 is a schematic explanatory view showing a mold configuration for carrying out hot press molding as described above (hereinafter sometimes referred to as “hot press”). In FIG. Die, 3 is a blank holder, 4 is a steel plate (blank), BHF is a crease pressing force, rp is a punch shoulder radius, rd is a die shoulder radius, and CL is a punch / die clearance. Of these components, the punch 1 and the die 2 have passages 1a and 2a through which a cooling medium (for example, water) can pass, and the cooling medium is allowed to pass through the passages. These members are configured to be cooled.
　こうした金型を用いてホットプレス（例えば、熱間深絞り加工）するに際しては、ブランク（鋼板４）をＡｃ3変態点以上に加熱して軟化させた状態で成形を開始する。即ち、高温状態にある鋼板４をダイ２とブランクホルダー３間に挟んだ状態で、パンチ１によってダイ２の穴内（図１の２，２間）に鋼板４を押し込み、鋼板４の外径を縮めつつパンチ１の外形に対応した形状に成形する。また、成形と並行してパンチ１およびダイ２を冷却することによって、鋼板４から金型（パンチおよびダイ）への抜熱を行なうと共に、成形下死点（パンチ先端が最上部に位置した時点：図１に示した状態）で更に保持冷却することによって素材の焼入れを実施する。こうした成形法を実施することによって、寸法精度の良い１５００ＭＰａ級の成形品を得ることができ、しかも冷間で同じ強度クラスの部品を成形する場合に比較して、成形荷重が低減できることからプレス機の容量が小さくて済むことになる。 When hot pressing (for example, hot deep drawing) using such a mold, molding is started in a state where the blank (steel plate 4) is heated to the Ac 3 transformation point or more and softened. That is, in a state where the steel plate 4 in a high temperature state is sandwiched between the die 2 and the blank holder 3, the steel plate 4 is pushed into the hole of the die 2 (between 2 and 2 in FIG. 1) by the punch 1, and the outer diameter of the steel plate 4 is reduced. A shape corresponding to the outer shape of the punch 1 is formed while shrinking. Further, by cooling the punch 1 and the die 2 in parallel with the forming, heat is removed from the steel plate 4 to the mold (punch and die) and the bottom dead center of the forming (when the punch tip is located at the top) : The material is quenched by further holding and cooling in the state shown in FIG. By carrying out such a molding method, it is possible to obtain a 1500 MPa class molded product with good dimensional accuracy and to reduce the molding load compared to the case of molding parts of the same strength class in the cold. The capacity of the can be small.
　上記のような金型構成を有するプレス成形機を備えた熱間プレス成形設備は、例えば非特許文献１に開示されている。この設備では、鋼板をＡｃ3変態点以上に加熱して軟化させるための加熱炉、加熱した鋼板を搬送するための装置、鋼板をプレス成形するためのプレス成形機、および成形した成型品をトリミング加工（レーザ等によって最終形状にするための補正加工）するための装置等を備えたものである（後記図２参照）。 Non-Patent Document 1, for example, discloses a hot press forming facility provided with a press forming machine having a mold configuration as described above. In this facility, a heating furnace for heating and softening the steel plate to the Ac 3 transformation point or higher, a device for conveying the heated steel plate, a press forming machine for press forming the steel plate, and trimming the molded product An apparatus for processing (correcting processing for making a final shape by a laser or the like) is provided (see FIG. 2 described later).
特開２００２－１０２９８０号公報JP 2002-102980 A
　これまでのホットプレスでは、鋼板をＡｃ3変態点以上（例えば、９００℃付近）のオーステナイト領域でプレス冷却することになるので、金型（パンチおよびダイ）と接触する部分と接触しない部分とで温度差がつきやすくなり、相対的に高温となる部分に歪みが集中することや、例えば深絞り成形では縮みフランジが冷却されて縮まなくなることなどによって、成形性が悪くなり、特に深絞り成形が難しくなる。 In the conventional hot press, the steel sheet is press-cooled in the austenite region above the Ac 3 transformation point (for example, around 900 ° C.), so that the portion that contacts the mold (punch and die) and the portion that does not contact The difference in temperature is likely to occur, and strain concentrates on the relatively high temperature part.For example, in deep drawing, the shrink flange is cooled and does not shrink. It becomes difficult.
　また、ホットプレスでは、通常７００～９００℃付近でプレス成形を行い、金型内で焼入れを行うので、成形下死点（パンチ先端が最上部に位置した時点）で一定時間保持する必要があり、冷間プレス加工と比べて生産性が悪くなる。 Also, in hot pressing, press molding is usually performed at around 700 to 900 ° C, and quenching is performed in the mold, so it is necessary to hold the molding at the bottom dead center (when the punch tip is at the top) for a certain period of time. , Productivity is worse than cold pressing.
　一方、鋼板をＡｃ3変態点以上（例えば、９００℃）のオーステナイト領域まで加熱すると、加熱炉からプレス成形機へ移動するときに、大気中に数秒間曝されることになり、鋼板表面に酸化層（スケール）が形成されることになる。このスケールは、プレス成形時に剥がれ、プレス疵等が生じる原因となる。また、このようなスケールの存在は、耐食用塗膜の塗装性を悪くするので、プレス成形後にピーニング処理等によってスケール除去が必要となる。 On the other hand, when the steel sheet is heated to the austenite region above the Ac 3 transformation point (for example, 900 ° C.), it is exposed to the atmosphere for several seconds when moving from the heating furnace to the press molding machine, and the steel sheet surface is oxidized. A layer (scale) will be formed. This scale peels off during press molding and causes press wrinkles and the like. In addition, the presence of such a scale deteriorates the paintability of the corrosion-resistant coating film, so that it is necessary to remove the scale by a peening process or the like after press molding.
　スケールが形成されることによる不都合を回避する対策として、プレス成形素材（ブランク）に、アルミめっき、亜鉛めっき、合金化溶融亜鉛めっき等の表面処理鋼板を用いることも行われているが、表面処理をすることによって、コストアップとなるばかりか、加熱の段階で所要時間が長くなる（めっき保持と合金化のために急速加熱できない）という不都合もある。また、加熱炉内やプレス成形機の周囲の雰囲気を制御してスケールが生じないようにすることも考えられるが、装置が大規模になってしまい、非現実的である。 As measures to avoid inconvenience due to the formation of scale, surface-treated steel sheets such as aluminum plating, galvanizing, and alloyed hot dip galvanizing are also used for press forming materials (blanks). This not only increases the cost, but also has the disadvantage that the required time becomes longer in the heating stage (rapid heating is not possible due to plating retention and alloying). Further, it is conceivable to control the atmosphere in the heating furnace or around the press molding machine so as not to generate scale, but the apparatus becomes large and unrealistic.
　本発明は上記事情に鑑みてなされたものであって、その目的は、鋼板表面にスケールが形成されることによる不都合を招くことなく、深絞り加工が可能な程度に成形性が良好なプレス成形品を生産性良く製造するためのプレス成形設備を提供することにある。 The present invention has been made in view of the above circumstances, and the purpose thereof is press forming with good formability to such an extent that deep drawing can be performed without causing inconvenience due to the formation of scale on the surface of the steel sheet. An object of the present invention is to provide a press molding facility for manufacturing products with high productivity.
　上記目的を達成することのできた本発明のプレス成形設備とは、加熱炉とプレス成形機を備え、前記加熱炉で薄鋼板をＡｃ3変態点以上の温度に加熱した後、プレス成形機によって薄鋼板をプレス成形して成形品を製造するためのプレス成形設備であって、前記加熱炉内部、または前記加熱炉とプレス成形機の間には、加熱された薄鋼板を冷却するための冷却部が備えられたものである点に要旨を有する。 The press forming equipment of the present invention that has achieved the above-mentioned object includes a heating furnace and a press forming machine. After heating a thin steel plate to a temperature of the Ac 3 transformation point or higher in the heating furnace, A press forming facility for press-molding a steel sheet to produce a molded product, wherein a cooling unit for cooling the heated thin steel sheet is provided inside the heating furnace or between the heating furnace and the press-forming machine. The point is that it is provided.
　本発明のプレス成形設備においては、前記冷却部は、空冷以上の冷却能力を有するものであることが好ましい。例えば、マルテンサイト変態開始温度まで冷却する際には、臨界冷却速度以上の冷却能力を有するものである。また、冷却部における具体的な構成としては、ガスジェット冷却装置、または冷却した金属ロールを備えたものが挙げられる。更に、この冷却部は、雰囲気制御できるように構成されたものであることが好ましい。 In the press molding equipment of the present invention, it is preferable that the cooling section has a cooling capacity higher than that of air cooling. For example, when cooling to the martensitic transformation start temperature, it has a cooling capacity higher than the critical cooling rate. Moreover, as a specific structure in a cooling part, the thing provided with the gas jet cooling device or the cooled metal roll is mentioned. Furthermore, it is preferable that this cooling part is configured so that the atmosphere can be controlled.
　本発明のプレス成形設備で用いるプレス成形機は、パンチ、ダイおよびブランクホルダーを備えたものが挙げられる。 Examples of the press molding machine used in the press molding facility of the present invention include a punch, a die and a blank holder.
　本発明によれば、前記加熱炉内部、または前記加熱炉とプレス成形機の間に、加熱された薄鋼板を冷却するための冷却部を備えたので、この設備によってプレス成形を行えば、鋼板表面にスケールが形成することによる不都合を招くことなく、また成形時に破断や割れなどを発生させることなく、生産性良くプレス成形が可能である。 According to the present invention, a cooling unit for cooling the heated thin steel plate is provided in the heating furnace or between the heating furnace and the press forming machine. Press molding can be performed with high productivity without causing inconvenience due to the formation of scale on the surface and without causing breakage or cracking during molding.
熱間プレス成形を実施するための金型構成を示す概略説明図である。It is a schematic explanatory drawing which shows the metal mold | die structure for implementing hot press molding. 従来の熱間プレス成形設備の構成例を示す概略説明図である。It is a schematic explanatory drawing which shows the structural example of the conventional hot press molding equipment. 従来のプレス成形設備を用いてプレス成形したときのヒートパターンを示すグラフである。It is a graph which shows a heat pattern when it press-molds using the conventional press molding equipment. 本発明のプレス成形設備の一例を示す概略説明図である。It is a schematic explanatory drawing which shows an example of the press molding equipment of this invention. 本発明のプレス成形設備を用いてプレス成形したときのヒートパターンを示すグラフである。It is a graph which shows a heat pattern when it press-molds using the press molding equipment of this invention. 鋼板の中央部を部分冷却したときの鋼板中心と鋼板端部の温度パターンを示すグラフである。It is a graph which shows the temperature pattern of a steel plate center and a steel plate edge part when the center part of a steel plate is partially cooled. 鋼板の中央部を部分冷却したときの鋼板中心と鋼板端部の温度差を示すグラフである。It is a graph which shows the temperature difference of the steel plate center and steel plate edge part when the center part of a steel plate is partially cooled.
　本発明者らは、薄鋼板をＡｃ3変態点以上の温度に加熱した後プレス成形するに際して、スケールが形成されることによる不都合を発生させることなく、成形性が良好なプレス成形品を生産性良く製造するために、様々な角度から検討した。その結果、薄鋼板をＡｃ3変態点以上の温度に加熱した後、そのまま成形を開始するのではなく、薄鋼板をベイナイト変態開始温度やマルテンサイト変態開始温度付近まで冷却し、その温度からプレス成形を開始するようにすれば、スケール形成による不都合を発生させることなく、良好な成形性が確保できるとの知見が得られた。 When the present inventors press-mold after heating a thin steel plate to a temperature equal to or higher than the Ac 3 transformation point, the productivity of a press-formed product having good formability without causing a disadvantage due to the formation of a scale. In order to manufacture well, it examined from various angles. As a result, after heating the thin steel plate to a temperature above the Ac 3 transformation point, the forming is not started as it is, but the thin steel plate is cooled to near the bainite transformation start temperature or the martensitic transformation start temperature, and press forming from that temperature. As a result, it was found that good formability could be secured without causing any inconvenience due to scale formation.
　上記のような構成を採用することによって、プレス成形中の鋼板内での温度分布を小さくでき（金型との温度差が少なくなる）、良好な成形性が確保できたのである。また、プレス成形開始温度を低くできるので、成形下死点での保持時間も短くできるという利点もある。 By adopting the above configuration, the temperature distribution in the steel sheet during press forming can be reduced (the temperature difference from the mold is reduced), and good formability can be secured. Further, since the press molding start temperature can be lowered, there is an advantage that the holding time at the bottom dead center of molding can be shortened.
　しかしながら、従来のプレス成形設備では、冷却に際して加熱炉から取り出してから、プレス成形機内で行う（例えば、金型による冷却）必要があり、加熱炉からプレス成形機に移動する際に、いかに迅速に移動させても、若干の表面酸化が生じることは回避できない。 However, in the conventional press molding equipment, it is necessary to take out from the heating furnace for cooling and then perform it in the press molding machine (for example, cooling by a mold), and how quickly when moving from the heating furnace to the press molding machine. Even if it is moved, some surface oxidation cannot be avoided.
　従来の熱間プレス成形設備では、図２（概略説明図）に示すような構成（設備構成）となっているのが一般的である。即ち、図２に示すように、コイル状態の鋼板１０を、切り出し機１１によって切り出しされ（Ｂｌａｎｋｉｎｇ）、加熱炉１２内で加熱された後、プレス成形機１３に移動されてプレス成形品１４とされる。このような設備構成では、加熱炉１２とプレス成形機１３の間では、高温状態（Ａｃ3変態点以上の温度）で大気と接触することになるので、鋼板１０の表面が酸化されることは避けがたい状況である。 Conventional hot press forming equipment generally has a configuration (equipment configuration) as shown in FIG. 2 (schematic explanatory diagram). That is, as shown in FIG. 2, the coiled steel sheet 10 is cut out by a cutting machine 11 (Blanking), heated in a heating furnace 12, and then moved to a press forming machine 13 to be a press-formed product 14. The In such an equipment configuration, between the heating furnace 12 and the press molding machine 13, the surface of the steel plate 10 is oxidized because it is in contact with the atmosphere in a high temperature state (temperature above the Ac 3 transformation point). This is an unavoidable situation.
　従来のプレス成形設備を用いてプレス成形したときのヒートパターンを図３に示す。まず、加熱の段階では（加熱炉１２）、めっき等の表面処理鋼板を用いた場合には、めっき保持と合金化のために急速加熱できないことから、昇温速度を例えば１２℃／秒程度にして所定の温度（図３では、９００℃）まで加熱され（従って加熱時間は７５秒程度）、その温度で所定時間保持（図３では、３～５分）される。その後、プレス成形機に移動されてプレス成形されるが、この移動の際には、いかに迅速に移動させても４秒程度必要となる。また、成形時間（例えば、２秒程度）や成形下死点での保持（例えば、１０～１５秒）、金型冷却等に要する時間を考慮すれば、プレス成形回数は１分当り３回［３ｓｐｍ（ストローク／ｍｉｎｕｔｅ）：２０秒／１プレス］程度となる。 Fig. 3 shows the heat pattern when press-molding using conventional press-molding equipment. First, in the heating stage (heating furnace 12), when a surface-treated steel sheet such as plating is used, rapid heating is not possible due to plating retention and alloying, so the rate of temperature rise is about 12 ° C./second, for example. Then, it is heated to a predetermined temperature (900 ° C. in FIG. 3) (therefore, the heating time is about 75 seconds) and held at that temperature for a predetermined time (3 to 5 minutes in FIG. 3). After that, it is moved to a press molding machine to be press-molded. In this movement, no matter how fast it is moved, it takes about 4 seconds. Further, considering the molding time (for example, about 2 seconds), holding at the molding bottom dead center (for example, 10 to 15 seconds), and the time required for mold cooling, the number of press moldings is 3 times per minute [ 3 spm (stroke / minute): about 20 seconds / 1 press].
　図４は、本発明のプレス成形設備の一例を示す概略説明図である（図４において、図３に対応する部分には同一の参照符号が付してある）。本発明のプレス成形設備においては、加熱炉１２の内部に、加熱炉１２に付随して冷却部１５が備えられ、鋼板１０を加熱炉１２からプレス成形機１３に移動するまでに冷却される。この冷却部１５は、加熱炉１２とプレス成形機１３の間に備えるようにしても良い。冷却部１５で行う冷却では、上記した方法も含め、例えば下記（１）～（４）等の方法で（或は併用して）冷却を実施することができる。
　（１）ガスジェット冷却装置を設けて冷却する。
　（２）冷媒としての金属ロールと接触させる手段（例えば、水冷した金属ロール）を設けて抜熱する。
　（３）ミスト冷却手段を設けて冷却する。
　（４）ドライアイスショット手段（顆粒ドライアイスをブランク材に衝突させて冷却する）を設けて冷却する。 FIG. 4 is a schematic explanatory view showing an example of the press molding equipment of the present invention (in FIG. 4, the same reference numerals are assigned to the portions corresponding to FIG. 3). In the press forming facility of the present invention, a cooling unit 15 is provided inside the heating furnace 12 along with the heating furnace 12, and the steel plate 10 is cooled before moving from the heating furnace 12 to the press forming machine 13. The cooling unit 15 may be provided between the heating furnace 12 and the press molding machine 13. In the cooling performed by the cooling unit 15, the cooling can be performed by the methods (1) to (4) below (or in combination) including the above-described methods.
(1) A gas jet cooling device is provided for cooling.
(2) A means (for example, a water-cooled metal roll) for bringing into contact with a metal roll as a refrigerant is provided to remove heat.
(3) Provide mist cooling means for cooling.
(4) A dry ice shot means (cooled by causing the granule dry ice to collide with the blank material) is cooled.
　また冷却部１５で行う冷却では、鋼板全体を均一に冷却してもよいし、プレス成形する鋼板の一部（好ましくは成形部分）のみを部分的に冷却してもよい。部分的に冷却する鋼板位置としては、例えば鋼板のダイ肩部分やパンチ肩部分などのプレス成形部分である。プレス成形部分は金型に最も接触し、鋼板の温度低下が大きい領域であるため、このような領域のみを部分的に冷却した場合、冷却した部分と冷却しなかった部分との温度差が少なくなり、良好な成形性が確保できる。さらに、冷却した鋼板中央の強度が確保されるとともに、冷却しなかった鋼板の端部の延性を確保できるため、より一層優れた深絞り成形性が達成できる。 In the cooling performed by the cooling unit 15, the entire steel plate may be uniformly cooled, or only a part (preferably a forming portion) of the steel plate to be press-formed may be partially cooled. The steel plate position to be partially cooled is, for example, a press-formed portion such as a die shoulder portion or a punch shoulder portion of the steel plate. Since the press-formed part is the most contact area with the mold and the temperature drop of the steel plate is large, when only such an area is partially cooled, the temperature difference between the cooled part and the uncooled part is small. Thus, good moldability can be secured. Furthermore, since the strength of the center of the cooled steel plate is ensured and the ductility of the end portion of the steel plate that has not been cooled can be ensured, further excellent deep drawability can be achieved.
　図６Ａ、図６Ｂには、円筒深絞り成形において、鋼板の中央部（パンチ肩部分を含むｒ＝３０ｍｍまでの部分）を部分冷却したときの鋼板中心（ｒ＝０ｍｍ）と、冷却しなかった鋼板端部（ｒ＝６０ｍｍ）の温度パターンを示す。尚、図６Ａ、図６Ｂに示した－２０から０までの間は、加熱炉１２内で鋼板が搬送される時間（搬送時間）を意味し、それ以後の「冷却時間」は鋼板の冷却が開始されてからの時間を意味する（後記表２参照）。 In FIG. 6A and FIG. 6B, in the cylindrical deep drawing, the center of the steel plate (the portion up to r = 30 mm including the punch shoulder portion) was partially cooled and the steel plate center (r = 0 mm) was not cooled. The temperature pattern of a steel plate edge part (r = 60mm) is shown. 6A and 6B, the period from −20 to 0 means the time (transport time) during which the steel plate is transported in the heating furnace 12, and the “cooling time” after that is the time for cooling the steel plate. It means the time since the start (see Table 2 below).
　図６Ａに示すように鋼板中心の温度は鋼板端部の温度と比べて低い温度となっており、鋼板の中央部を部分冷却することによって、効率的にプレス成形部分の温度を低下させることができることが示されている。一方、図６Ｂには、鋼板の中央部のみを冷却した場合であっても、鋼板中心と鋼板端部との温度差はある一定の時間（図示例では約３０秒程度）で飽和することが示されている。これは鋼板の冷却部分と非冷却部分との間で熱移動が生じて温度差が緩和されるためである。プレス成形部分の強度を維持して深絞り成形性を向上させる観点からは、鋼板の冷却部分と非冷却部分との温度差を一定以上確保した状態でプレス成形することが望ましい。 As shown in FIG. 6A, the temperature at the center of the steel plate is lower than the temperature at the end of the steel plate, and by partially cooling the central portion of the steel plate, the temperature of the press-formed portion can be lowered efficiently. It has been shown that it can. On the other hand, in FIG. 6B, even when only the central part of the steel plate is cooled, the temperature difference between the steel plate center and the steel plate end can be saturated in a certain time (about 30 seconds in the illustrated example). It is shown. This is because heat transfer occurs between the cooled portion and the non-cooled portion of the steel sheet, and the temperature difference is alleviated. From the viewpoint of improving the deep drawing formability by maintaining the strength of the press-formed part, it is desirable to perform press-molding in a state in which a certain temperature difference between the cooled part and the non-cooled part of the steel plate is secured.
　本発明の設備を用いて実施されるプレス成形は、鋼板を加熱した後、一旦ベイナイト変態開始温度やマルテンサイト変態開始温度付近まで急冷してから成形する方法に適用する場合を想定したものであるが、こうした点を考慮すれば、冷却部は、空冷以上の冷却能力（例えば、マルテンサイト変態開始温度まで冷却する際には、臨界冷却速度以上の冷却能力）を有するものであることが好ましい。また、冷却部では、比較的低い温度に設定されることによって、その雰囲気は制御しやすくなり、その雰囲気を制御（例えば、窒素やアルゴン雰囲気）して、鋼板の表面酸化をより効果的に防止できるようすることも有効であるが、必ずしも雰囲気制御されている必要はない（低温にすることによって表面酸化が抑制される）。 The press forming carried out using the equipment of the present invention assumes the case where the steel sheet is heated and then applied to the method of forming after rapidly cooling to near the bainite transformation start temperature or martensite transformation start temperature. However, in consideration of these points, the cooling section preferably has a cooling capacity equal to or higher than that of air cooling (for example, a cooling capacity equal to or higher than the critical cooling rate when cooling to the martensite transformation start temperature). In addition, by setting the cooling section at a relatively low temperature, the atmosphere becomes easy to control, and the atmosphere is controlled (for example, nitrogen or argon atmosphere) to more effectively prevent surface oxidation of the steel sheet. Although it is effective to be able to do this, the atmosphere is not necessarily controlled (surface oxidation is suppressed by lowering the temperature).
　上記のような構成のプレス成形設備を用い、薄鋼板をベイナイト変態開始温度やマルテンサイト変態開始温度付近まで冷却（好ましくは急冷）してから成形することによって、（１）プレス成形中の鋼板内での温度分布を小さくでき（金型との温度差が少なくなる）、良好な成形性が確保できること、（２）プレス成形開始温度を低くできるので、成形下死点での保持時間も短くできるという利点の他、下記（Ａ）～（Ｃ）のような利点も発揮される。
　（Ａ）急速加熱が可能となって、生産性が向上する（加熱炉による加熱は通常電気炉による加熱であるが、めっき等の表面処理を施した鋼板を用いなくてもよいので、通電加熱や誘導加熱が採用できる）。
　（Ｂ）鋼板の表面酸化が回避できる（加熱炉１２からプレス成形機１３に移動する段階では比較的低い温度となっているので、高温による表面酸化が回避できる）。
　（Ｃ）９００℃程度の高温から急冷できるので、焼入れ性の低い材料（安価な鋼板）を用いても高強度化が達成される。 (1) Inside the steel sheet during press forming by using the press forming equipment configured as described above and cooling the thin steel sheet to near the bainite transformation start temperature or martensite transformation start temperature (preferably rapid cooling). The temperature distribution at can be reduced (the temperature difference from the mold is reduced), good moldability can be ensured, and (2) the press molding start temperature can be lowered, so the holding time at the bottom dead center of molding can also be shortened. In addition to the advantages described above, the following advantages (A) to (C) are also exhibited.
(A) Rapid heating is possible, and productivity is improved (heating by a heating furnace is usually heating by an electric furnace, but it is not necessary to use a steel sheet that has been subjected to surface treatment such as plating, so that heating by energization is possible. Or induction heating).
(B) Surface oxidation of the steel sheet can be avoided (because the temperature is relatively low at the stage of moving from the heating furnace 12 to the press molding machine 13, surface oxidation due to high temperature can be avoided).
(C) Since rapid cooling can be performed from a high temperature of about 900 ° C., high strength can be achieved even if a material with low hardenability (inexpensive steel plate) is used.
　本発明のプレス成形設備を用いてプレス成形したときのヒートパターンを図５に示す。このヒートパターンでは、前記図３に示したヒートパターンに比べて、昇温速度を速くできると共に（急速加熱：例えば２０～６０秒程度）、成形下死点での保持（例えば、５～１０秒）、金型冷却、等を短くでき（次のプレスが早くできる）、４～６ｓｐｍ程度のプレス加工ができ、従来パターンと比べて生産性が極めて高いものとなる。図５に示したヒートパターンはこうした状態を示したものである。 FIG. 5 shows a heat pattern when press-molding using the press-forming equipment of the present invention. In this heat pattern, the heating rate can be increased compared to the heat pattern shown in FIG. 3 (rapid heating: for example, about 20 to 60 seconds), and the mold is maintained at the bottom dead center (for example, 5 to 10 seconds). ), Die cooling, etc. can be shortened (the next press can be performed quickly), and press working of about 4 to 6 spm can be performed, and the productivity is extremely high as compared with the conventional pattern. The heat pattern shown in FIG. 5 shows such a state.
　以下、本発明の効果を実施例によって更に具体的に示すが、下記実施例は本発明を限定するものではなく、前・後記の趣旨に徴して設計変更することはいずれも本発明の技術的範囲に含まれるものである。 Hereinafter, the effects of the present invention will be described more specifically by way of examples. However, the following examples are not intended to limit the present invention, and any design changes in accordance with the gist of the preceding and following descriptions are technical aspects of the present invention. It is included in the range.
　（実施例１）
　前記図４に示したプレス成形設備によって、下記表１に示す化学成分組成を有する鋼板を用い（厚さ：１．０ｍｍ、直径：１１０ｍｍの円形ブランク）、９００℃に加熱し（この鋼板のＡｃ3変態点：８３０℃、マルテンサイト変態開始温度Ｍｓ：４１１℃）、雰囲気制御されたガスジェット冷却で７００℃まで冷却し、その後５００℃付近まで鋼板挟持によって冷却し、金型［頭部形状が一辺４５ｍｍの角形の金型（角筒ダイおよび角筒パンチ）］を用い（前記図１参照）、角筒深絞り成形を行った。 Example 1
Using the steel sheet having the chemical composition shown in Table 1 below (thickness: 1.0 mm, circular blank with a diameter of 110 mm) and heating to 900 ° C. by the press forming equipment shown in FIG. 4 (Ac of this steel sheet) 3 transformation point: 830 ° C., martensite transformation start temperature Ms: 411 ° C.), cooled to 700 ° C. by controlled atmosphere gas jet cooling, and then cooled to about 500 ° C. by sandwiching the steel sheet, and the mold [head shape is Using a square die having a side of 45 mm (square tube die and square tube punch)] (see FIG. 1), square tube deep drawing was performed.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　このとき、金型がブランクに接触してから、成形下死点で停止するまでの時間は０．７５秒とした。その他のプレス成形条件は下記の通りである。 At this time, the time from when the mold comes into contact with the blank until it stops at the bottom dead center of molding was set to 0.75 seconds. Other press molding conditions are as follows.
　（他のプレス成形条件）
　しわ押え力：３トン
　ダイ肩半径ｒｄ：５ｍｍ
　パンチ肩半径ｒｐ：５ｍｍ
　パンチ－ダイ間クリアランスＣＬ：１．３２／２＋１．４（鋼板厚さ）ｍｍ
　成形高さ：３７ｍｍ (Other press molding conditions)
Wrinkle presser force: 3 tons Die shoulder radius rd: 5mm
Punch shoulder radius rp: 5mm
Punch-die clearance CL: 1.32 / 2 + 1.4 (steel plate thickness) mm
Molding height: 37mm
　その結果、良好な成形性が達成され、成形下死点まで深絞りができた（前記図１に示した状態）。また、成形品はその表面にスケールが形成されることによる不都合も発生することは無かった。 As a result, good moldability was achieved, and deep drawing was achieved up to the bottom dead center of the molding (the state shown in FIG. 1). In addition, the molded article did not suffer from inconvenience due to the formation of scale on the surface.
　（実施例２）
　前記図４に示したプレス成形設備によって、実施例１と同じ化学成分組成を有する鋼板を用い（厚さ：１．４ｍｍ、直径：表２に示す直径９０～１１０ｍｍの円形鋼板）を、９００℃に加熱して５分間保持した後（この鋼板のＡｃ3変態点：８３０℃、マルテンサイト変態開始温度Ｍｓ：４１１℃）、冷却部において以下の冷却手段で冷却した（表２中、「冷却手段」、「冷却保持時間（秒）」参照）。尚、部分冷却する場合は、加熱炉とプレス成形機の間に冷却部（図示せず）を設けて冷却を行った。 (Example 2)
4 using the steel plate having the same chemical composition as in Example 1 (thickness: 1.4 mm, diameter: circular steel plate having a diameter of 90 to 110 mm shown in Table 2) by the press forming equipment shown in FIG. (Ac 3 transformation point of this steel plate: 830 ° C., martensite transformation start temperature Ms: 411 ° C.) and then cooled by the following cooling means in the cooling section (in Table 2, “Cooling means”). ”And“ Cooling hold time (seconds) ”. In the case of partial cooling, a cooling unit (not shown) was provided between the heating furnace and the press molding machine for cooling.
　空冷：加熱炉からブランクを取り出したまま保持して所定の温度になるまで空冷した。
　強制冷却：鋼板両面全体をスポットクーラーで冷却した。
　部分冷却：鋼板中央部（パンチ肩部分を含むｒ＝３０ｍｍまでの範囲内）にエアを噴きつけて部分的に冷却した。 Air cooling: The blank was taken out from the heating furnace and held until it reached a predetermined temperature.
Forced cooling: The entire steel sheet was cooled with a spot cooler.
Partial cooling: Air was blown onto the central part of the steel sheet (within the range up to r = 30 mm including the punch shoulder) to partially cool.
　冷却後、鋼板をプレス成形機に移送して（表２中、「移送時間（秒）」参照）、金型［パンチの直径：５０ｍｍの円筒金型（円筒ダイおよび円筒パンチ）］を用い、円筒深絞り成形を行った。プレス成形では、プレス機として、メカニカルサーボプレス機（最大押圧力２００トン、最大プレス加工２７ｓｐｍ）を用いた。また、金型が鋼板に接触してから、成形下死点で停止するまでの時間は０．２秒とした。その他のプレス成形条件は下記の通りである。 After cooling, the steel plate is transferred to a press molding machine (refer to “Transfer time (seconds)” in Table 2), and using a mold [punch diameter: 50 mm cylindrical mold (cylindrical die and cylindrical punch)], Cylindrical deep drawing was performed. In press molding, a mechanical servo press (maximum pressing force 200 tons, maximum pressing 27 spm) was used as a press. Further, the time from when the mold comes into contact with the steel plate until it stops at the bottom dead center of forming was set to 0.2 seconds. Other press molding conditions are as follows.
　（他のプレス成形条件）
　しわ押え力：３トン
　ダイ肩半径ｒｄ：５ｍｍ
　パンチ肩半径ｒｐ：５ｍｍ
　パンチ－ダイ間クリアランスＣＬ：０．１５／２＋１．４（鋼板厚さ）ｍｍ
　成形高さ：４０．０ｍｍ (Other press molding conditions)
Wrinkle presser force: 3 tons Die shoulder radius rd: 5mm
Punch shoulder radius rp: 5mm
Punch-die clearance CL: 0.15 / 2 + 1.4 (steel plate thickness) mm
Molding height: 40.0mm
　比較のため、図２に示した従来のプレス成形設備を使用し、実施例２と同様にして円筒深絞り成形を行った。具体的には、鋼板（ブランク）を加熱炉で加熱した後、鋼板を冷却することなく加熱炉から取り出してプレス機まで搬送した後（搬送時間：６秒）、直ちに成形した（表２中、Ｎｏ．１）。結果を表２に示す。 For comparison, cylindrical deep drawing was performed in the same manner as in Example 2 using the conventional press forming equipment shown in FIG. Specifically, after heating a steel plate (blank) in a heating furnace, the steel plate was taken out from the heating furnace without being cooled and transported to a press machine (transport time: 6 seconds), and then immediately formed (in Table 2, No. 1). The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　実験の結果、従来のプレス成形設備を使用したＮｏ．１では、冷却が不十分だったため、直径９５ｍｍ以上の成形ができなかった。一方、加熱炉内の冷却部、または加熱炉とプレス成形機の間に設けた冷却部において急冷した本発明例（Ｎｏ．２－１～４－３）では、良好な成形性が達成され、成形下死点まで深絞りができた。また、成形品はその表面にスケールが形成されることによる不都合も発生することは無かった。特に、部分冷却を行った４－１～４－３では、直径１００ｍｍ以上でも良好な成形性が達成された。 As a result of the experiment, No. using conventional press forming equipment. In No. 1, since the cooling was insufficient, molding with a diameter of 95 mm or more could not be performed. On the other hand, in the present invention example (Nos. 2-1 to 4-3) rapidly cooled in the cooling part in the heating furnace or in the cooling part provided between the heating furnace and the press molding machine, good formability is achieved, Deep drawing was possible to the bottom dead center of molding. In addition, the molded article did not suffer from inconvenience due to the formation of scale on the surface. In particular, in 4-1 to 4-3 subjected to partial cooling, good moldability was achieved even with a diameter of 100 mm or more.
　空冷した場合と強制冷却した場合とで成形可能な最大ブランク径は同じであったが、強制冷却した場合は、硬度向上効果が確認できた。即ち、成形後に成形品に硬さを試験した結果（成形品の頂部中央部から下端部までを５ｍｍ間隔で測定したビッッカース硬さの平均値を表２に示す）、空冷した場合（Ｎｏ．２－１、２－２）は冷却保持時間の増大に伴い、４８０Ｈｖ以上の十分な硬さが得られていないのに対し、強制冷却した場合（Ｎｏ．３－１～３－３）は４８０Ｈｖを超える硬さが得られた。尚、部分冷却した場合（Ｎｏ．４－１～４－３）も、強制冷却と同程度の良好な硬さが得られることが確認できた。 The maximum blank diameter that can be formed was the same when air-cooled and when forced-cooled. However, when forced-cooled, the effect of improving hardness could be confirmed. That is, as a result of testing the hardness of the molded product after molding (the average value of Vickers hardness measured at intervals of 5 mm from the top center to the lower end of the molded product is shown in Table 2), when air-cooled (No. 2 -1 and 2-2) have not obtained sufficient hardness of 480 Hv or more as the cooling holding time is increased, but when forced cooling (No. 3-1 to 3-3) is 480 Hv Hardness exceeding was obtained. In the case of partial cooling (Nos. 4-1 to 4-3), it was confirmed that good hardness similar to that of forced cooling could be obtained.
　本発明のプレス成形設備は、加熱炉とプレス成形機を備え、前記加熱炉で薄鋼板をＡｃ3変態点以上の温度に加熱した後、プレス成形機によって薄鋼板をプレス成形して成形品を製造するためのプレス成形設備であって、加熱炉内部、または前記加熱炉とプレス成形機の間には、加熱された薄鋼板を急冷するための冷却部が備えられたものであり、鋼板表面にスケールが形成されることによる不都合を招くことなく、深絞り加工が可能な程度に成形性が良好なプレス成形品を生産性良く製造できる。 The press forming equipment of the present invention includes a heating furnace and a press forming machine, and after heating the thin steel plate to a temperature equal to or higher than the Ac 3 transformation point in the heating furnace, the thin steel plate is press formed by the press forming machine to obtain a molded product. It is a press forming facility for manufacturing, and is provided with a cooling part for quenching a heated thin steel plate inside the heating furnace or between the heating furnace and the press forming machine. Thus, it is possible to produce a press-molded product having good formability to the extent that deep drawing can be performed without causing inconvenience due to the formation of a scale.
１　パンチ
２　ダイ
３　ブランクホルダー
４，１０　ブランク（鋼板）
１１　切り出し機
１２　加熱炉
１３　プレス成形機
１４　プレス成形品
１５　冷却部 1 Punch 2 Die 3 Blank holder 4, 10 Blank (steel plate)
11 Cutting Machine 12 Heating Furnace 13 Press Molding Machine 14 Press Molded Product 15 Cooling Section

Claims (6)

  1. 　加熱炉とプレス成形機を備え、前記加熱炉で薄鋼板をＡｃ3変態点以上の温度に加熱した後、プレス成形機によって薄鋼板をプレス成形して成形品を製造するためのプレス成形設備であって、前記加熱炉内部、または前記加熱炉とプレス成形機の間には、加熱された薄鋼板を冷却するための冷却部が備えられたものであることを特徴とするプレス成形設備。 A press forming facility for manufacturing a molded product by heating a thin steel plate to a temperature equal to or higher than the Ac 3 transformation point in the heating furnace and then press-forming the thin steel plate with a press forming machine. A press forming facility characterized in that a cooling unit for cooling the heated thin steel sheet is provided in the heating furnace or between the heating furnace and the press forming machine.
  2. 　前記冷却部は、空冷以上の冷却能力を有するものである請求項１に記載のプレス成形設備。 The press molding facility according to claim 1, wherein the cooling section has a cooling capacity equal to or higher than air cooling.
  3. 　前記冷却能力は、臨界冷却速度以上の冷却能力である請求項２に記載のプレス成形設備。 The press forming equipment according to claim 2, wherein the cooling capacity is a cooling capacity equal to or higher than a critical cooling rate.
  4. 　前記冷却部は、ガスジェット冷却装置、または冷却した金属ロールを備えたものである請求項１に記載のプレス成形設備。 The press forming facility according to claim 1, wherein the cooling unit includes a gas jet cooling device or a cooled metal roll.
  5. 　前記冷却部は、雰囲気制御できるように構成されたものである請求項１に記載のプレス成形設備。 The press molding facility according to claim 1, wherein the cooling unit is configured to be able to control an atmosphere.
  6. 　前記プレス成形機は、パンチ、ダイおよびブランクホルダーを備えたものである請求項１～５のいずれかに記載のプレス成形設備。
          The press molding equipment according to any one of claims 1 to 5, wherein the press molding machine includes a punch, a die, and a blank holder.
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