JP2009061473A - Method for manufacturing high-strength component - Google Patents

Method for manufacturing high-strength component Download PDF

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JP2009061473A
JP2009061473A JP2007231660A JP2007231660A JP2009061473A JP 2009061473 A JP2009061473 A JP 2009061473A JP 2007231660 A JP2007231660 A JP 2007231660A JP 2007231660 A JP2007231660 A JP 2007231660A JP 2009061473 A JP2009061473 A JP 2009061473A
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workpiece
heat insulating
press
strength
temperature
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Kazuo Uematsu
一夫 植松
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-strength component having a hard portion of the tensile strength of ≥980 MPa and a soft portion of the hardness smaller than that of the hard portion and having the excellent post-workability. <P>SOLUTION: In this manufacturing method, a high-strength component is manufactured by attaching a heat insulating material 3 having the heat conductivity smaller than that of a workpiece 0 to a first portion 1 of the steel-made workpiece 0 comprising the first portion 1 as a portion including a post-working scheduled part subjected to the post-working such as drilling after completing the pressing and the cooling, and a second portion 2 as a portion not including the post-working scheduled part, by charging the workpiece 0 into a heating furnace for heating the workpiece by the heat radiation by the high-temperature atmosphere therein and the heat conduction by the workpiece 0, heating the first portion 1 to the temperature below Ac<SB>3</SB>point and heating the second portion 2 to the temperature equal to or higher than the Ac<SB>3</SB>point, drawing out the workpiece 0 from the heating furnace, and charging the workpiece 0 in a press die 4 after detaching the heat insulating material 3, and starting the press-working and the cooling by the press die 4 in a state in which the temperature of the second portion 2 is the temperature equal to or higher than Ac<SB>3</SB>point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、高強度部品の製造方法に関し、具体的には、熱間プレスにより例えば980MPa以上の引張強度を有する自動車部品等の高強度部品を製造する方法に関する。   The present invention relates to a method for manufacturing a high-strength part, and specifically relates to a method for manufacturing a high-strength part such as an automobile part having a tensile strength of 980 MPa or more by hot pressing.

自動車車体の構造部材や補強部品といった自動車部品、例えばバンパーレインフォースやドアインパクトビームには、衝突安全性の向上のために高強度であることのみならず、低燃費による地球環境の保全のために軽量であることも強く要請される。一般的に、これらの自動車部品は、高張力鋼板を冷間プレスすることにより成形されて製造される。しかし、成形性、形状凍結性さらには耐遅れ破壊性等の点で、980MPa以上の高張力鋼板を素材して冷間プレスで成形する方法には問題が多い。   Automotive parts such as structural members and reinforcement parts of automobile bodies, such as bumper reinforcement and door impact beams, are not only high in strength for improving collision safety, but also for the preservation of the global environment by low fuel consumption. Light weight is also strongly demanded. Generally, these automobile parts are formed and manufactured by cold pressing a high-tensile steel plate. However, there are many problems in the method of forming a high-tensile steel plate of 980 MPa or more with a cold press in terms of formability, shape freezing property, delayed fracture resistance, and the like.

特許文献1には、素材となる鋼板であるブランクを850℃以上に加熱し、このブランクをプレス金型に装入してプレス成形し、そのまま型内で保持及び冷却して焼入れを行うことによって高強度部品を製造する熱間プレスに係る発明が開示される。   In Patent Document 1, a blank, which is a steel plate as a raw material, is heated to 850 ° C. or more, and this blank is inserted into a press die, press-molded, and held and cooled in the die as it is for quenching. An invention related to hot pressing for manufacturing high-strength parts is disclosed.

この発明によれば、焼入れにより980MPa以上の高強度を得られるだけでなく、高温の軟質状態で成形を行うために成形性が改善され、さらに熱間プレス後の製品の残留応力も低減されるために形状凍結性も良好で、遅れ破壊も抑制できるとされる。   According to the present invention, not only high strength of 980 MPa or more can be obtained by quenching, but the moldability is improved because molding is performed in a high temperature soft state, and the residual stress of the product after hot pressing is also reduced. Therefore, the shape freezing property is also good and delayed fracture can be suppressed.

しかし、一般的にプレス成形後の硬さはその強度に比例し、例えば1500MPaという高い引張強度を有するプレス成形品の硬度は450HVにも達する。このような高硬度の部品に、例えば剪断加工や穴あけ加工等の後加工を行うには大きな加工能力を有するプレス機が必要となり、仮に後加工を行うことができたとしても後加工に用いる加工工具の寿命の低下は避けられない。   However, the hardness after press molding is generally proportional to the strength, and the hardness of a press-formed product having a high tensile strength of, for example, 1500 MPa reaches 450 HV. In order to perform post-processing such as shearing and drilling on such high-hardness parts, a press machine with a large processing capacity is required, and even if post-processing can be performed, processing used for post-processing A reduction in tool life is inevitable.

そこで、プレス金型における、後加工を行う後加工部位に相当する部位に、特許文献2に記載された発明では空隙を設けること、また特許文献3に記載された発明では熱伝導率が低い素材を充填することによって、いずれも、鋼板の冷却速度を低下してマルテンサイトの生成を抑制することにより後加工部位の硬度を低下する発明が開示される。   Therefore, in the press die, a part corresponding to a post-processed part for post-processing is provided with a gap in the invention described in Patent Document 2, and a material having low thermal conductivity in the invention described in Patent Document 3. In any case, an invention is disclosed in which the hardness of the post-processed portion is reduced by reducing the cooling rate of the steel sheet and suppressing the formation of martensite by filling the steel.

しかし、特許文献2、3により開示された発明によっても後加工部位の冷却速度を十分に低下することは難しく、その硬さは焼入部の75〜80%程度とかなり硬い。熱間プレスによるプレス成形品の焼入部の硬さはHV450以上に達することを勘案すると、特許文献2、3により開示された発明によって焼入れ時の冷却速度を低下したとしてもHV340程度の硬度はあり、十分な硬度低下を図れるとはいえない。   However, even with the inventions disclosed in Patent Documents 2 and 3, it is difficult to sufficiently reduce the cooling rate of the post-processed portion, and the hardness is considerably hard, about 75 to 80% of the quenched portion. Considering that the hardness of the hardened part of the press-formed product by hot pressing reaches HV450 or more, even if the cooling rate at the time of quenching is lowered by the inventions disclosed in Patent Documents 2 and 3, there is a hardness of about HV340. It cannot be said that sufficient hardness reduction can be achieved.

そこで、特許文献4には、赤外線加熱や誘導加熱により、鋼板の一部がAr点以上となるとともに残部が室温〜Ar点未満となるように鋼板の温度を部分的に変化させて加熱を行い、一部分がオーステナイトを含む状態でプレス成形を開始することにより高強度部品を製造する発明が開示される。
特開2002−102980号公報 特開2003−328031号公報 特開2005−342776号公報 特開2005−193287号公報
Therefore, in Patent Document 4, heating is performed by partially changing the temperature of the steel sheet by infrared heating or induction heating so that a part of the steel sheet becomes Ar 1 point or higher and the remainder becomes room temperature to less than Ar 1 point. An invention is disclosed in which a high-strength part is manufactured by starting press forming in a state where a part contains austenite.
JP 2002-102980 A JP 2003-328031 A JP-A-2005-342776 JP 2005-193287 A

しかし、赤外線加熱により鋼板の温度を部分的に変化させることはエネルギー効率が非常に低く、実用的でない。また誘導加熱によると鋼板を急速加熱することとなるが、被加工材が表面処理鋼板、特に亜鉛めっき鋼板である場合には、この急速加熱によりめっき相と地鉄相との反応が進まず、また、めっきが蒸発する。   However, it is not practical to change the temperature of the steel sheet partially by infrared heating because the energy efficiency is very low. Moreover, according to induction heating, the steel sheet is rapidly heated. However, when the workpiece is a surface-treated steel sheet, particularly a galvanized steel sheet, the reaction between the plating phase and the ground iron phase does not proceed due to this rapid heating. Also, the plating evaporates.

また、赤外線加熱や誘導加熱による方法では、任意形状、例えば円形の穴あけ部位を硬化させないためにそれに合わせた円形の温度分布を付与することが困難であるので、部品の一部分の硬度を低下させることに伴って不可避的にその周囲の広い範囲の硬度も低下させてしまう。   In addition, in the method using infrared heating or induction heating, it is difficult to impart a circular temperature distribution according to an arbitrary shape, for example, a circular drilling portion, so that the hardness of a part of the component is reduced. Inevitably, a wide range of hardness around the periphery is also reduced.

さらに、通常、熱間プレスによる被加工材の加熱にはガス炉や電気炉を用いるが、この発明を行うには赤外線加熱装置や誘導加熱装置も追加して設ける必要が生じ、設備費の上昇が避けられない。   In addition, a gas furnace or an electric furnace is usually used to heat a workpiece by hot pressing. However, in order to carry out the present invention, it is necessary to additionally provide an infrared heating apparatus and an induction heating apparatus, resulting in an increase in equipment costs. Is inevitable.

本発明の目的は、熱間プレスにより例えば自動車部品等の引張強度が980MPa以上の硬質部と、この硬質部に比較して硬度が十分に小さいことから加工性が良好な軟質部とを有する高強度部品を製造する方法を提供することであり、特に、任意な形状の軟質部を形成可能であって、さらに、被加工材が亜鉛めっき鋼板である場合であっても亜鉛の蒸発を抑制することが可能な高強度部品を製造する方法を提供することである。   An object of the present invention is to provide a hard part having a tensile strength of 980 MPa or more, such as an automobile part, by hot pressing and a soft part having good workability because the hardness is sufficiently smaller than the hard part. It is to provide a method for manufacturing a strength component, and in particular, it is possible to form a soft part having an arbitrary shape, and further suppresses evaporation of zinc even when the workpiece is a galvanized steel sheet. It is to provide a method for manufacturing a high-strength part that can be used.

本発明は、第1の部位と、この第1の部位とは異なる第2の部位とを少なくとも有する鋼製の被加工材のこの第1の部位に、被加工材の熱伝導率よりも小さな熱伝導率、例えば900℃において1W/(m・K)以下である熱伝導率を有する断熱材を装着し、この断熱材を装着された被加工材を所定の温度に昇温された加熱炉に装入することにより、第1の部位をAc点未満、好ましくはAr点以上Ac点未満、さらに好ましくはAr点以上Ac点とAc点との中間温度以下に加熱するとともに第2の部位をAc点以上に加熱し、次いで、被加工材を加熱炉から抽出して被加工材から断熱材を取り外した後に、この被加工材をプレス金型に装入し、第2の部位の温度がAr点以上である状態でプレス金型によるプレス加工及び冷却を開始することを特徴とする高強度部品の製造方法である。 The present invention provides a first part of a steel workpiece having at least a first part and a second part different from the first part, the thermal conductivity of the workpiece being smaller than the first part. A heating furnace in which a heat insulating material having a heat conductivity of, for example, 1 W / (m · K) or less at 900 ° C. is mounted, and the workpiece mounted with the heat insulating material is heated to a predetermined temperature. by charging the first portion of Ac less than three points, preferably 1 or more points Ac less than 3 points Ar, more preferably heated to less intermediate temperature between 1 point and the Ac 3 point or higher 1 point Ar Ac And the second part is heated to Ac 3 point or higher, and then the work material is extracted from the heating furnace and the heat insulating material is removed from the work material, and then the work material is charged into a press die. Press according to a press die in a state the temperature of the second portion is not less than the Ar 3 point A method of producing a high strength part, characterized in that to start the Engineering and cooling.

本発明では、加熱炉が、内部の高温雰囲気による熱輻射により、断熱材を装着された被加工材を加熱する型式の加熱炉であることが望ましい。
これらの本発明では、第1の部位が、プレス加工及び冷却を終了した後に例えば剪断加工や穴あけ加工等の後加工を行われる後加工予定部を含む部位であることが、望ましい。
In the present invention, it is desirable that the heating furnace is a type of heating furnace that heats a workpiece on which a heat insulating material is mounted by heat radiation from an internal high-temperature atmosphere.
In the present invention, it is desirable that the first part is a part including a post-processing scheduled portion where post-processing such as shearing or drilling is performed after the press processing and cooling are completed.

さらに、これらの本発明では、プレス加工及び冷却を終了した後に、第1の部位の少なくとも一部に上述した後加工を行うことにより、例えばバンパーレインフォースやドアインパクトビームといった自動車車体の構造部材や補強部品である高強度部品が製造される。   Further, in the present invention, after the press working and cooling are finished, the above-described post-processing is performed on at least a part of the first portion, so that, for example, a structural member of an automobile body such as a bumper reinforcement or a door impact beam, High-strength parts that are reinforcing parts are manufactured.

これらの本発明では、被加工材は、平板状の部材であってもよいし、又は平板状の部材に予成形金型により予めプレス予成形されてなる非平板状の部材であってもよい。
さらに、これらの本発明では、被加工材は、一部又は全部に亜鉛めっき層が形成され鋼板であってもよい。
In these present inventions, the workpiece may be a flat plate member, or may be a non-flat plate member that is pre-pressed into a flat plate member by a preforming mold. .
Furthermore, in these present inventions, the workpiece may be a steel plate in which a galvanized layer is partially or entirely formed.

本発明によれば、硬質のマルテンサイト組織を有する硬質部と、マルテンサイトの生成が抑制され硬質部に比べて硬度が十分に低く加工性が良好な軟質部とを有する高強度部品を製造することができる。これにより、この軟質部に対して例えば剪断加工や穴あけ加工等の後加工を容易に行うとともに、後加工に用いる工具の損耗を抑制しながら、高強度部品を製造することができる。   According to the present invention, a high-strength part having a hard part having a hard martensite structure and a soft part in which the formation of martensite is suppressed and the hardness is sufficiently lower than that of the hard part and the workability is good is manufactured. be able to. Thereby, for example, high-strength parts can be manufactured while easily performing post-processing such as shearing or drilling on the soft portion and suppressing wear of a tool used for the post-processing.

また、本発明によれば、高強度部品が亜鉛めっき鋼板からなる場合であっても亜鉛の蒸発を抑制できるので、耐食性の低下を抑制しながら高強度部品を製造することができる。
また、本発明によれば、熱間プレス後の部品における軟質部の大きさや形状を自在に設定できるとともに、軟質部の周囲に不可避的に形成される硬度低下部の範囲を最小限に抑制できる。このため、熱間プレスにより、所望の形状、寸法の軟質部を設けながらも全体として所望の高強度を有する高強度部品を確実に製造することができる。
Further, according to the present invention, since the evaporation of zinc can be suppressed even when the high-strength component is made of a galvanized steel sheet, the high-strength component can be manufactured while suppressing a decrease in corrosion resistance.
Further, according to the present invention, the size and shape of the soft part in the part after hot pressing can be freely set, and the range of the hardness reduced part inevitably formed around the soft part can be minimized. . For this reason, it is possible to reliably manufacture a high-strength part having a desired high strength as a whole while providing a soft portion having a desired shape and size by hot pressing.

さらに、本発明により、硬質部及び軟質部を高強度部品の所望の位置に配置することができるので、例えばセンターピラー等の自動車車体の構造部材の軸方向へ向けて硬質部及び軟質部を適宜設けることにより、軸方向へ向けて衝撃荷重が負荷された構造部材の座屈による塑性変形モードを制御することができ、これにより、衝撃吸収能を高めた構造部材を製造することもできる。   Further, according to the present invention, since the hard part and the soft part can be arranged at desired positions of the high-strength parts, for example, the hard part and the soft part are appropriately oriented in the axial direction of the structural member of the automobile body such as a center pillar. By providing, it is possible to control the plastic deformation mode due to buckling of the structural member to which an impact load is applied in the axial direction, and it is also possible to manufacture a structural member with improved impact absorption capability.

(実施の形態1)
はじめに、本発明の原理を簡単に説明する。
一般的に、鋼材はAc点以上に加熱されるとオーステナイト及びフェライトの二相組織となり、さらにAc点以上に加熱されるとオーステナイト単相組織となる。熱間プレスは、通常、被加工材をAc点以上に加熱してオーステナイト単相組織としてからプレス金型内で急冷してマルテンサイトを生成することにより高強度を得る加工法であるが、プレス前の加熱温度が十分には高くなくオーステナイトの割合が低い状態から急冷すると生成するマルテンサイト量も少なくなり、これに伴って熱間プレス後の製品の強度も低下する。
(Embodiment 1)
First, the principle of the present invention will be briefly described.
In general, a steel material has a two-phase structure of austenite and ferrite when heated to Ac 1 point or higher, and an austenite single-phase structure when heated to Ac 3 points or higher. Hot pressing is usually a processing method for obtaining high strength by heating a workpiece to Ac 3 point or more to form an austenite single phase structure and then rapidly cooling in a press die to generate martensite. When the heating temperature before pressing is not sufficiently high and the austenite ratio is low, the amount of martensite generated is reduced, and accordingly, the strength of the product after hot pressing also decreases.

本発明は、このような、急冷開始温度の高低に起因した強度の高低を利用するものであり、一つの被加工材において、高強度すなわち高硬度を必要とする部位はAc点以上に加熱してオーステナイト単相とするとともに低硬度を必要とする部位はAc点よりも低い温度に加熱してオーステナイトの比率を低下するか、もしくはオーステナイトを含まないようにしておき、このように温度分布を設けて加熱された被加工材をプレス金型内で急冷することにより、Ac点以上に加熱した部位を高強度化するとともに、Ac点未満に加熱した部位を低硬度とすることにより、全体としては所望の高強度を有しながら剪断加工等の後加工を行う必要がある部位に対する加工性を充分に確保するものである。 The present invention utilizes such high and low strength due to the high and low quenching start temperature, and in one workpiece, a portion requiring high strength, that is, high hardness is heated to Ac 3 points or more. As for the part which needs to be austenite single phase and requires low hardness, it is heated to a temperature lower than Ac 3 point to decrease the ratio of austenite or not to contain austenite. By rapidly cooling the heated workpiece in the press mold, the part heated to 3 or more points of Ac is strengthened, and the part heated to less than 3 points of Ac is made low hardness As a whole, sufficient workability is secured for a portion that needs to be post-processed such as shearing while having a desired high strength.

次に、本発明を実施するための最良の形態を、添付図面を参照しながら詳細に説明する。
(i)被加工材0への断熱材3a、3bの装着
図1は、加熱炉に装入される被加工材0の状況を示す説明図である。
Next, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.
(I) Mounting of heat insulating materials 3a and 3b on workpiece 0 FIG. 1 is an explanatory diagram showing the situation of the workpiece 0 inserted in the heating furnace.

被加工材0は、第1の部位1と、この第1の部位の両側に設けられる第2の部位2、2とを有する鋼板である。被加工材0の第1の部位1には断熱材3a、3bが装着される。
被加工材0として、図1に示す平板状の鋼板を用いてもよいし、あるいは平板状の鋼板に予成形金型により予めプレス予成形を行って所定の形状に成形された非平板状の鋼板、例えば曲げ成形を行われた鋼板を用いてもよい。本実施の形態では被加工材0が平板状の鋼板である場合を例にとって説明し、被加工材0が曲げ成形を行われた鋼板である場合は後述する実施の形態2で説明することとする。
The workpiece 0 is a steel plate having a first part 1 and second parts 2 and 2 provided on both sides of the first part. Heat insulating materials 3a and 3b are attached to the first portion 1 of the workpiece 0.
As the workpiece 0, a flat plate-shaped steel plate shown in FIG. 1 may be used, or a non-flat plate-shaped plate formed into a predetermined shape by pre-pressing the flat plate-shaped steel plate using a preforming mold. A steel plate, for example, a bent steel plate may be used. In the present embodiment, the case where the workpiece 0 is a flat steel plate will be described as an example, and when the workpiece 0 is a bent steel plate, it will be described in Embodiment 2 described later. To do.

被加工材0である鋼板の組成は、例えば、C:0.08%以上0.45%以下(以下、本明細書では組成に関する「%」は「質量%」を意味するものとする)、Mn及び/又はCr合計で0.5%以上3.0%以下を含有し、さらに、Si:0.5%以下、P:0.05%以下、S:0.05%以下、Ni:2%以下、Cu:1%以下、Mo:1%以下、V:1%以下、Ti:1%以下、Nb:1%以下、Al:1%以下、及びN:0.01%以下の1種以上を含有し、残部Fe及び不純物である。特に高い焼入れ効果による高強度化を図る場合にはC:0.2%以上0.3%以下とすることが望ましい。   The composition of the steel sheet that is the workpiece 0 is, for example, C: 0.08% or more and 0.45% or less (hereinafter, “%” related to the composition means “mass%” in the present specification), It contains 0.5% or more and 3.0% or less in total of Mn and / or Cr, and further Si: 0.5% or less, P: 0.05% or less, S: 0.05% or less, Ni: 2 %, Cu: 1% or less, Mo: 1% or less, V: 1% or less, Ti: 1% or less, Nb: 1% or less, Al: 1% or less, and N: 0.01% or less It contains the above, and the balance is Fe and impurities. In particular, when increasing the strength by a high quenching effect, it is desirable to set C: 0.2% or more and 0.3% or less.

さらに、被加工材0として、亜鉛めっき鋼板を用いてもよい。亜鉛めっき鋼板は、上述した組成を有する鋼板を母材とし、めっき層がFeを8%以上25%以下含有し、残部がZn、Alおよび不純物からなる合金化溶融亜鉛めっき鋼板を用いることが望ましい。   Further, a galvanized steel sheet may be used as the workpiece 0. As the galvanized steel sheet, it is desirable to use an alloyed hot-dip galvanized steel sheet in which the steel sheet having the above-described composition is used as a base material, the plating layer contains 8% to 25% of Fe, and the balance is Zn, Al, and impurities. .

一方、図1に示す断熱材3a、3bは、被加工材0の熱伝導率よりも小さな熱伝導率、例えば900℃において1W/(m・K)以下である熱伝導率を有する断熱材を用いる。また、断熱材3a、3bは、オーステナイト域への加熱により燃えたり、あるいは著しく劣化したりすることがない材料からなるものであればよく、特定のものには限定されない。このような断熱材3a、3bとして、ロックウール、グラスウール、セラミックファイバーさらには耐熱煉瓦等を例示することができる。   On the other hand, the heat insulating materials 3a and 3b shown in FIG. 1 are heat insulating materials having a heat conductivity smaller than the heat conductivity of the workpiece 0, for example, a heat conductivity of 1 W / (m · K) or less at 900 ° C. Use. The heat insulating materials 3a and 3b may be made of a material that does not burn or significantly deteriorate due to heating to the austenite region, and is not limited to a specific material. Examples of the heat insulating materials 3a and 3b include rock wool, glass wool, ceramic fiber, and heat-resistant brick.

断熱材3a、3bの厚さは、その熱伝導率に基づいて決定するが、例えばセラミックファイバーを用いる場合には10mm以上、望ましくは20mm以上である。断熱材の厚さが薄過ぎると、後述する加熱炉からの輻射熱を十分に遮蔽することができなくなり、断熱材3a、3bの装着による被加工材0の温度上昇抑制効果を充分に得られなくなる。   The thickness of the heat insulating materials 3a and 3b is determined based on the thermal conductivity thereof. For example, when ceramic fibers are used, the thickness is 10 mm or more, preferably 20 mm or more. When the thickness of the heat insulating material is too thin, it becomes impossible to sufficiently shield the radiant heat from the heating furnace described later, and the effect of suppressing the temperature rise of the workpiece 0 due to the mounting of the heat insulating materials 3a and 3b cannot be sufficiently obtained. .

断熱材3a、3bの寸法、すなわち断熱材3a、3bを装着される被加工材0の範囲は、被加工材0における硬度を低く抑制したい部位を含むことができる任意の形状とすればよい。被加工材0における硬度を低く抑制したい部位に対して、断熱材3a、3bが小さ過ぎるとその周囲からの熱伝導により硬度を低く抑制したい部位の温度が上昇し過ぎる可能性があるため、断熱材3a、3bの寸法は被加工材0における硬度を低く抑制したい部位の領域よりもやや大きく設定することが望ましい。例えば、後述する実施例に示すように、被加工材0における直径20mmの円形の穴あけ予定部の硬度を低下したい場合には、この円形の穴あけ予定部の外側にさらに半径で10mmの円形、すなわち直径40mmの円形の横断面形状を有する断熱材3a、3bを装着することが望ましい。   The dimensions of the heat insulating materials 3a and 3b, that is, the range of the work material 0 to which the heat insulating materials 3a and 3b are attached may be any shape that can include a portion where the hardness of the work material 0 is desired to be kept low. If the heat insulating materials 3a and 3b are too small for the part where the hardness of the workpiece 0 is desired to be kept low, the temperature of the part where the hardness is kept low may be excessively increased due to heat conduction from the surroundings. It is desirable that the dimensions of the materials 3a and 3b be set to be slightly larger than the region where the hardness of the workpiece 0 is desired to be kept low. For example, as shown in an example described later, when it is desired to reduce the hardness of a circular drilling portion having a diameter of 20 mm in the workpiece 0, a circular shape having a radius of 10 mm is further provided outside the circular drilling portion. It is desirable to install the heat insulating materials 3a and 3b having a circular cross-sectional shape with a diameter of 40 mm.

図2(a)は被加工材0の全幅の硬度を低く抑制したい場合の断熱材3−1の配置を示す説明図であり、図2(b)は図2(a)におけるA断面図である。このような場合には、図2(a)及び図2(b)に示すように、被加工材0の側面からの加熱を抑制するために、被加工材0の側面まで覆うことができるように寸法を大きく設定した2枚の断熱材3−1a、3−1bにより被加工材0を上下から完全に覆うようにすることが望ましい。   FIG. 2A is an explanatory view showing the arrangement of the heat insulating material 3-1 when it is desired to suppress the hardness of the entire width of the workpiece 0 to be low, and FIG. 2B is a cross-sectional view taken along line A in FIG. is there. In such a case, as shown in FIGS. 2 (a) and 2 (b), the side surface of the workpiece 0 can be covered in order to suppress heating from the side surface of the workpiece 0. It is desirable that the workpiece 0 is completely covered from above and below by the two heat insulating materials 3-1a and 3-1b having large dimensions.

図1において、断熱材3a、3bの被加工材0への装着は、例えば、被加工材0の硬度を低く抑制したい部位を、断熱材3a、3bにより形成された保持治具により両側から挟み込むように保持することにより、行うことが、断熱材3を被加工材0に装着する手間を可及的少なくすることができ、望ましい。   In FIG. 1, the heat insulating materials 3 a and 3 b are attached to the workpiece 0 by, for example, sandwiching a portion where the hardness of the workpiece 0 is desired to be low from both sides by a holding jig formed by the heat insulating materials 3 a and 3 b. It is desirable to perform the holding as described above, because it is possible to reduce the labor for mounting the heat insulating material 3 on the workpiece 0 as much as possible.

このようにして、はじめに、被加工材0における硬度を低く抑制したい部位1に断熱材3a、3bを装着する。
(ii)被加工材0の加熱炉への装入
次に、このようにして断熱材3a、3bを装着された鋼板である被加工材0を、所定の雰囲気温度に昇温及び保持された加熱炉に装入することにより、硬度を低く抑制したい第1の部位をAc点未満、好ましくはAr点以上Ac点未満、さらに好ましくはAr点以上Ac点とAc点との中間温度以下に加熱するとともに、硬度を低く抑制する必要がない第2の部位をAc点以上に加熱する。
Thus, first, the heat insulating materials 3a and 3b are attached to the portion 1 where the hardness of the workpiece 0 is desired to be kept low.
(Ii) Inserting the workpiece 0 into the heating furnace Next, the workpiece 0, which is a steel plate equipped with the heat insulating materials 3a and 3b, was heated and maintained at a predetermined atmospheric temperature. By charging the heating furnace, the first part whose hardness is desired to be suppressed is less than Ac 3 points, preferably Ar 1 point or more and less than Ac 3 point, more preferably Ar 1 point or more and Ac 1 point and Ac 3 point. The second portion that does not need to be suppressed to a low hardness is heated to Ac 3 point or higher.

図3は、このようにして所定の温度分布に加熱された被加工材0を示す説明図である。
図3に示すように、被加工材0は、断熱材3a、3bを装着された第1の部位1がAc点未満に加熱されるとともに、硬度を低く抑制する必要がない第2の部位2、2がAc点以上に加熱される。
FIG. 3 is an explanatory view showing the workpiece 0 heated to a predetermined temperature distribution in this way.
As shown in FIG. 3, the workpiece 0 is a second portion where the first portion 1 to which the heat insulating materials 3 a and 3 b are attached is heated to less than Ac 3 and the hardness does not need to be suppressed low. 2 and 2 are heated to 3 or more points of Ac.

被加工材0の加熱に用いる加熱炉は、内部の高温雰囲気による熱輻射と、内部に配置される被加工材0における熱伝導とにより、断熱材3a、3bを装着された被加工材0を加熱する型式の加熱炉を用いることが望ましい。また、この加熱炉は、被加工材0を効率よく加熱するとともに被加工材0の表面の品質を良好に保つため、密閉もしくは雰囲気を保持できる加熱炉であることが望ましい。スケールの発生を抑制するため、加熱炉の内部を窒素やアルゴン等の不活性ガス雰囲気とするか、ガス炉の場合では空燃比制御により還元雰囲気とすることが望ましい。このような加熱炉としては、例えば電気炉やガス炉が例示される。   The heating furnace used for heating the workpiece 0 uses the workpiece 0 on which the heat insulating materials 3a and 3b are mounted by heat radiation from the internal high temperature atmosphere and heat conduction in the workpiece 0 disposed inside. It is desirable to use a heating furnace of the heating type. In addition, this heating furnace is desirably a heating furnace that can be hermetically sealed or can maintain an atmosphere in order to efficiently heat the workpiece 0 and to keep the surface quality of the workpiece 0 good. In order to suppress the generation of scale, it is desirable that the inside of the heating furnace be an inert gas atmosphere such as nitrogen or argon, or in the case of a gas furnace, a reducing atmosphere is formed by air-fuel ratio control. Examples of such a heating furnace include an electric furnace and a gas furnace.

この加熱炉の内部に被加工材0を配置して加熱すると、被加工材0は、加熱炉内の高温雰囲気による熱輻射と、被加工材0の内部の熱伝導とによって、昇温される。この昇温の初期段階では、炉内雰囲気からの輻射による割合が圧倒的に高いので、被加工材0の熱伝達率よりも低い熱伝達率を有する断熱材3a、3bを装着された被加工材0の第1の部位1の温度は、この断熱材3a、3bを装着されない第2の部位2の温度よりも、大幅に低下する。   When the workpiece 0 is placed inside the heating furnace and heated, the workpiece 0 is heated by heat radiation from the high-temperature atmosphere in the heating furnace and heat conduction inside the workpiece 0. . In the initial stage of the temperature increase, since the ratio of radiation from the furnace atmosphere is overwhelmingly high, the work to which the heat insulating materials 3a and 3b having a heat transfer coefficient lower than the heat transfer coefficient of the work material 0 is attached. The temperature of the first part 1 of the material 0 is significantly lower than the temperature of the second part 2 where the heat insulating materials 3a and 3b are not attached.

このため、このような型式の加熱炉を用いて断熱材3a、3bを装着された被加工材0を加熱することによって、第1の部位1の硬度を低く抑制して軟質部として形成することができ、また、被加工材0が亜鉛めっき層を形成された鋼板である場合には加熱に伴う亜鉛の蒸発を、充分に抑制することが可能である。   For this reason, by heating the workpiece 0 on which the heat insulating materials 3a and 3b are mounted using such a type of heating furnace, the hardness of the first portion 1 is suppressed to be low and formed as a soft portion. In addition, when the workpiece 0 is a steel plate on which a galvanized layer is formed, it is possible to sufficiently suppress evaporation of zinc accompanying heating.

第2の部位2をオーステナイト単相組織とするために加熱炉の炉内温度はAc点以上に設定するが、過剰に高く設定すると断熱材3a、3bを装着された第1の部位1までもAc点以上に加熱されるおそれがあるので、加熱炉はAc点以上(Ac点+100℃)以下の温度に設定することが望ましい。 In order to make the second part 2 an austenite single phase structure, the furnace temperature of the heating furnace is set to Ac 3 point or higher, but if it is set too high, the first part 1 to which the heat insulating materials 3a and 3b are attached is set. since it may also be heated above the Ac 3 point, the heating furnace is desirably set to a temperature below Ac 3 point or more (Ac 3 point + 100 ° C.).

被加工材0の加熱温度については、高強度化したい第2の部位2は、オーステナイト単相からの急冷によりマルテンサイトを充分に生成するためにAc点以上に加熱する。一方、高硬度化を阻止したい第1の部位1については、急冷後のマルテンサイトの生成を充分に抑制する観点から、非オーステナイト組織を含んだ状態である必要があり、そのためにはAc点未満に加熱する。望ましくは、オーステナイト比率が非オーステナイト比率より低い状態であるので、Ac点とAc点との中間温度以下であることが望ましい。さらに、オーステナイトが存在しない温度域、すなわちAc点以下であることが望ましい。つまり、高硬度化を阻止したい第1の部位1の硬度を低くするためには、この第1の部位1の温度は低いほど望ましい。 Regarding the heating temperature of the workpiece 0, the second portion 2 to be increased in strength is heated to Ac 3 points or more in order to sufficiently generate martensite by rapid cooling from the austenite single phase. On the other hand, the first part 1 to be prevented high hardness, from sufficiently suppressing the generation of martensite after quenching, must be in a state containing a non-austenitic structure, in order that the Ac 3 point Heat to less than Desirably, since the austenite ratio is lower than the non-austenite ratio, it is desirable that the temperature is not higher than the intermediate temperature between the Ac 1 point and the Ac 3 point. Furthermore, it is desirable that the temperature range in which austenite does not exist, that is, Ac is 1 point or less. That is, in order to reduce the hardness of the first portion 1 where it is desired to prevent the increase in hardness, the temperature of the first portion 1 is preferably as low as possible.

しかし、実際には、被加工材0を加熱炉から取り出してプレスを開始するまでにある程度の時間を要するので、第1の部位1が過剰に低温であると、被加工材0を加熱炉から取り出してプレスを開始するまでの間に第2の部位2から第1の部位1への熱伝導によって第2の部位2の熱を奪ってしまい、結果的に製品全体として所望の高強度を有することが難しくなるおそれがある。一方、材料の相変態のメカニズムを考察すると、第1の部位1の温度がAr点以上であっても、本発明が目的とする第1の部位1の部分的な硬度の低下は十分に達成でき、かつ第2の部位2の温度低下も最小限に抑制することができる。このため、第1の部位1の温度はAr点以上Ac点未満が望ましく、さらに望ましくはAr点以上Ac点とAc点との中間温度以下、一層望ましくはAr点以上Ac点以下である。 However, in practice, since it takes a certain amount of time to take out the workpiece 0 from the heating furnace and start pressing, if the first portion 1 is excessively cold, the workpiece 0 is removed from the heating furnace. The heat of the second part 2 is taken away by heat conduction from the second part 2 to the first part 1 until the press is started after taking out, and as a result, the entire product has a desired high strength. Can be difficult. On the other hand, considering the phase transformation mechanism of the material, even if the temperature of the first part 1 is not less than Ar 1 point, the partial decrease in hardness of the first part 1 targeted by the present invention is sufficiently This can be achieved, and the temperature drop of the second portion 2 can be minimized. For this reason, the temperature of the first part 1 is preferably Ar 1 point or more and less than Ac 3 point, more preferably Ar 1 point or more and less than or equal to the intermediate temperature between Ac 1 point and Ac 3 point, and more preferably Ar 1 point or more Ac. 1 point or less.

このようにして、被加工材0を、所定の雰囲気温度に昇温及び保持された加熱炉に装入し、被加工材0の第1の部位をAc点未満、好ましくはAr点以上Ac点未満、さらに好ましくはAr点以上Ac点とAc点との中間温度以下、一層好ましくはAr点以上Ac点以下に加熱するとともに、硬度を低く抑制する必要がない第2の部位をAc点以上に加熱する。
(iii)被加工材0の加熱炉からの抽出、及び断熱材3a、3bの取り外し
このようにして加熱された被加工材0を加熱炉から抽出し、被加工材0から断熱材3a、3bを取り外す。これらの操作には特段の特徴はないので、これ以上の説明は省略する。
(iv)被加工材0のプレス金型4への装入及びプレス加工の開始
図4は、断熱材3a、3bを取り外された被加工材0にプレス加工を行う状況を示す説明図である。
In this way, the workpiece 0 is charged into a heating furnace heated and maintained at a predetermined atmospheric temperature, and the first portion of the workpiece 0 is less than Ac 3 points, preferably Ar 1 points or more. Less than Ac 3 point, more preferably Ar 1 point or more and Ac 1 point and Ac 3 point or less, more preferably Ar 1 point or more and Ac 1 point or less, and it is not necessary to suppress hardness low The part 2 is heated to 3 or more points of Ac.
(Iii) Extraction of workpiece 0 from heating furnace and removal of heat insulating materials 3a, 3b The workpiece 0 thus heated is extracted from the heating furnace, and the workpiece 0 is insulated from the heat insulating materials 3a, 3b. Remove. Since these operations have no particular characteristics, further explanation is omitted.
(Iv) Inserting Work Material 0 into Press Die 4 and Starting Press Work FIG. 4 is an explanatory diagram showing a situation where press work is performed on the work material 0 from which the heat insulating materials 3a and 3b have been removed. .

同図に示すように、断熱材3a、3bを取り外された被加工材0をプレス金型4a、4bに装入し、第2の部位2、2の温度がAr以上である状態で、プレス金型4a、4bにより所定の断面形状へのプレス加工及び冷却を開始する。 As shown in the figure, the workpiece 0 from which the heat insulating materials 3a and 3b have been removed is inserted into the press dies 4a and 4b, and the temperature of the second parts 2 and 2 is Ar 3 or higher. Press processing and cooling to a predetermined cross-sectional shape are started by the press dies 4a and 4b.

このプレス成形の際に、第2の部位2、2はオーステナイト域から急冷されるので硬質のマルテンサイトが形成される。一方、断熱材3a、3bを装着された第1の部位は、マルテンサイトの生成が防止される。   During the press molding, the second portions 2 and 2 are quenched from the austenite region, so that hard martensite is formed. On the other hand, generation of martensite is prevented in the first part to which the heat insulating materials 3a and 3b are attached.

本発明では、プレス成形後に急冷することにより第2の部位2、2を焼入れるが、加熱炉から抽出してからプレス成形を開始するまでの間を空冷により徐冷されると、第2の部位2の硬度低下を生じる。このため、加熱炉から抽出した後は、出来るだけ速やかにプレス成形を開始することが望ましい。しかし、加熱炉から抽出して第1の部位1に装着された断熱材3a、3bを取り外してからこの被加工材0をプレス金型4まで搬送する必要があるので一定時間を要するが、時間が経つにつれて熱伝導により第1の部位1と第2の部位2との間の温度差が小さくなってしまう。そして、さらに温度低下が進んでプレス開始前に第2の部位2がAr点を下回ってしまうと、第2の部位2の強度を所望の高強度とすることができなくなる。例えば、被加工材0の板厚が1.6mmである場合には900℃からの空冷における被加工材0の冷却速度が15℃/秒以上20℃/秒以下であることに鑑み、加熱炉から抽出してからプレス成形を開始するまでの時間は、12秒以内であることが望ましい。 In the present invention, the second parts 2 and 2 are quenched by quenching after press molding. However, when the part is extracted from the heating furnace until the press molding is started, the second part 2 and 2 are quenched. The hardness of the part 2 is reduced. For this reason, it is desirable to start press molding as soon as possible after extraction from the heating furnace. However, since it is necessary to transport the workpiece 0 to the press die 4 after removing the heat insulating materials 3a and 3b extracted from the heating furnace and mounted on the first part 1, it takes a certain time. As time passes, the temperature difference between the first part 1 and the second part 2 becomes smaller due to heat conduction. The second site 2 is the fall below the 3-point Ar, can not be the second intensity of the portion 2 of the desired high strength before further temperature decrease willing press start. For example, in the case where the plate thickness of the workpiece 0 is 1.6 mm, in view of the fact that the cooling rate of the workpiece 0 in air cooling from 900 ° C. is 15 ° C./second or more and 20 ° C./second or less. It is desirable that the time from the extraction to the start of press molding is within 12 seconds.

なお、プレス金型4a、4bは、プレス成形及び下死点保持により冷却焼入を行うが、プレス金型4a、4bへの抜熱により焼入を行うことから、プレス成形時のプレス金型4a、4bの温度はその材質のMs点よりも低温でなければならず、十分な冷却速度を得るためにはプレス金型4a、4bのプレス加工時における温度は、100℃以下に保たれていることが望ましい。例えば、プレス金型4a、4bの内部に水管を配し、冷却水を通水することで金型の温度を100℃以下に保つことができるような冷却機構を設けることが望ましい。   The press dies 4a and 4b are cooled and quenched by press molding and holding the bottom dead center. Since the quenching is performed by removing heat from the press dies 4a and 4b, the press dies at the time of press molding are used. The temperatures of 4a and 4b must be lower than the Ms point of the material. In order to obtain a sufficient cooling rate, the temperature during pressing of the press dies 4a and 4b is kept below 100 ° C. It is desirable. For example, it is desirable to provide a cooling mechanism that can keep the temperature of the mold at 100 ° C. or lower by arranging water pipes inside the press molds 4 a and 4 b and passing cooling water.

プレス加工では、プレスストロークの下死点で所定時間保持した後、被加工材0にプレス加工を行われて得られた成形品をプレス金型から取り出す。
成形後すぐに成形品をプレス金型から取り出してしまうと、熱収縮の不均一により、成形品の形状精度が低下するおそれがあるからである。成形後はプレスストロークの下死点で成形品の温度が200℃以下に低下するまで保持冷却することが望ましい。また、第2の部位2の硬度を十分高くする観点より、加熱炉から抽出してからMs点以下に冷却されるまでの間の冷却速度は30℃/秒以上であることが望ましい。
In press working, after holding for a predetermined time at the bottom dead center of the press stroke, a molded product obtained by performing press working on the workpiece 0 is taken out from the press die.
This is because if the molded product is taken out of the press die immediately after molding, the shape accuracy of the molded product may be reduced due to non-uniform heat shrinkage. After molding, it is desirable to hold and cool until the temperature of the molded product drops to 200 ° C. or lower at the bottom dead center of the press stroke. Further, from the viewpoint of sufficiently increasing the hardness of the second portion 2, it is desirable that the cooling rate from the extraction from the heating furnace to the cooling to the Ms point or less is 30 ° C./second or more.

図5は、このようにして製造された高強度部品5を示す説明図である。図5に示すように、この高強度部品5は、硬質のマルテンサイト組織を有する硬質部2、2と、マルテンサイトの生成が抑制され、硬質部2に比較して硬度が十分に小さい軟質部1とを有する。この軟質部1には、例えば剪断加工や穴あけ加工等といった後加工を行われる後加工予定部が含まれている。   FIG. 5 is an explanatory view showing the high-strength component 5 manufactured as described above. As shown in FIG. 5, the high-strength component 5 includes the hard portions 2 and 2 having a hard martensite structure, and a soft portion in which the generation of martensite is suppressed and the hardness is sufficiently smaller than that of the hard portion 2. 1. The soft portion 1 includes a post-processing scheduled portion where post-processing such as shearing or drilling is performed.

このため、この高強度部品は、軟質部1に対しては例えば剪断加工等の後加工を容易に行うことができ、かつ後加工に用いる工具の損耗を抑制することができる。
また、この高強度部品5は、内部の高温雰囲気による熱輻射と、内部に配置される被加工材の内部の熱伝導とにより被加熱物を昇温する形式の加熱炉により加熱されてからプレス加工に供されて製造されるので、その素材である被加工材0が亜鉛めっき層を形成された鋼板からなる場合であっても亜鉛の蒸発を抑制でき、これにより耐食性の低下を防止できる。
For this reason, this high-strength part can easily perform post-processing such as shearing on the soft portion 1 and can suppress wear of a tool used for the post-processing.
Further, the high-strength component 5 is heated after being heated by a heating furnace that raises the temperature of the object to be heated by heat radiation from the internal high-temperature atmosphere and heat conduction inside the workpiece disposed inside. Since it is used for processing and manufactured, even if the workpiece 0, which is the raw material, is made of a steel plate on which a galvanized layer is formed, the evaporation of zinc can be suppressed, thereby preventing a decrease in corrosion resistance.

さらに、この高強度部品3は、断熱材3の形状や寸法を適宜調整するだけでプレス後の部品における軟質部1の大きさや形状を自在に設定できるとともに、軟質部1の周囲に不可避的に形成される硬度低下部の範囲を最小限に抑制できる。よって、熱間プレスにより、所望の形状の軟質部1を設けながらも全体として所望の超高強度を確実に有する。   Further, the high-strength component 3 can freely set the size and shape of the soft part 1 in the pressed part by adjusting the shape and dimensions of the heat insulating material 3 as appropriate, and inevitably around the soft part 1. The range of the hardness fall part formed can be suppressed to the minimum. Therefore, the desired ultrahigh strength is reliably obtained as a whole while the soft portion 1 having a desired shape is provided by hot pressing.

さらに、この高強度部品3は、断熱材3の形状や寸法を適宜調整するだけで硬質部2及び軟質部1を高強度部品5の所望の位置に配置することができるので、例えばセンターピラー等の自動車車体の構造部材の軸方向へ向けて硬質部2及び軟質部1を適宜設けることにより、軸方向へ向けて衝撃荷重が負荷された構造部材の座屈による塑性変形モードを制御することができ、これにより、衝撃吸収能を高めた構造部材を製造することもできる。
(実施の形態2)
次に、実施の形態2を説明する。本実施の形態が実施の形態1と相違するのは、熱間プレスに供される被加工材0が、平板が曲げ成形された非平板状の部材である点である。そこで、以降の説明では上述した実施の形態1と相違する部分を説明し、共通する部分については同一の符号を付することにより重複する説明を適宜省略する。
Furthermore, the high-strength component 3 can arrange the hard portion 2 and the soft portion 1 at desired positions of the high-strength component 5 simply by adjusting the shape and dimensions of the heat insulating material 3 as appropriate. By appropriately providing the hard part 2 and the soft part 1 in the axial direction of the structural member of the automobile body, the plastic deformation mode by buckling of the structural member loaded with the impact load in the axial direction can be controlled. Thus, it is possible to manufacture a structural member having improved shock absorption capability.
(Embodiment 2)
Next, a second embodiment will be described. The present embodiment is different from the first embodiment in that the workpiece 0 to be subjected to hot pressing is a non-flat plate member formed by bending a flat plate. Therefore, in the following description, portions that are different from the above-described first embodiment will be described, and common portions will be denoted by the same reference numerals, and redundant description will be omitted as appropriate.

図6は、本実施の形態において用いる被加工材0−1の形状を示す説明図である。
図6に示すように、本実施の形態において用いる被加工材0−1は、平板状の鋼板を予成形金型(図示しない)により所定の断面形状に冷間でプレス予成形することにより、得られるものである。この被加工材0−1には、図6中にハッチングして示す、後加工を行うために硬化を阻止したい部位がある。
FIG. 6 is an explanatory diagram showing the shape of the workpiece 0-1 used in the present embodiment.
As shown in FIG. 6, the workpiece 0-1 used in the present embodiment is obtained by cold-pressing a flat steel plate into a predetermined cross-sectional shape with a preforming die (not shown). It is obtained. The workpiece 0-1 has a portion which is indicated by hatching in FIG.

なお、プレス予成形に用いる予成形金型は、プレス成形に用いるプレス金型と同じ断面形状のものでもよく、また、異なる断面形状のものであってもよい。
図7は、加熱炉に装入される被加工材0−1の状況を示す説明図である。
The pre-molding die used for press pre-molding may have the same cross-sectional shape as the press die used for press molding, or may have a different cross-sectional shape.
FIG. 7 is an explanatory diagram showing the situation of the workpiece 0-1 charged in the heating furnace.

図7に示すように、次いで、この被加工材0−1における、図6中にハッチングして示す、後加工を行うために硬化を阻止したい部位を含む第1の部位1に、断熱材3−2a、3−2bを装着してから、所定の雰囲気温度に設定された、実施の形態1で用いた加熱炉に装入し、加熱する。   Next, as shown in FIG. 7, in the workpiece 0-1, the heat insulating material 3 is applied to the first portion 1 including the portion that is desired to be prevented from hardening in order to perform post-processing, which is hatched in FIG. 6. -2a and 3-2b are mounted, and then charged into the heating furnace used in the first embodiment set to a predetermined atmospheric temperature and heated.

図8は、加熱時の被加工材0−1を示す説明図である。
これにより、断熱材3−2a、3−2bを装着された被加工材0−1は、図8に示すように、第1の部位1がAc点未満の温度に加熱されるとともに、第1の部位1を除く第2の部位2がAc点以上となる温度に加熱される。
FIG. 8 is an explanatory diagram showing the workpiece 0-1 during heating.
Thereby, as shown in FIG. 8, the workpiece 0-1 fitted with the heat insulating materials 3-2a and 3-2b is heated to a temperature less than Ac 3 points as shown in FIG. the second site 2 is being heated to a temperature at which the Ac 3 point or more, excluding the portion 1 of 1.

図9は、断熱材3−2a、3−2bを取り外された被加工材0−1にプレス加工を行う状況を示す説明図である。
次いで、この被加工材0−1を加熱炉から抽出し、断熱材3−2a、3−2bを取り外した後に、図9に示すように、第2の部位2がオーステナイトを含む状態でプレス金型6a、6bに装入し、プレス金型6a、6bにより所定の断面形状にプレス成形する。そして、プレスストロークの下死点で所定時間保持した後、プレス金型6a、6bから取り出す。
FIG. 9 is an explanatory diagram illustrating a state in which press working is performed on the workpiece 0-1 from which the heat insulating materials 3-2a and 3-2b have been removed.
Next, after extracting the workpiece 0-1 from the heating furnace and removing the heat insulating materials 3-2a and 3-2b, as shown in FIG. 9, the second portion 2 is pressed with austenite. The molds 6a and 6b are inserted and press-molded into a predetermined cross-sectional shape by the press molds 6a and 6b. And after hold | maintaining for a predetermined time at the bottom dead center of a press stroke, it takes out from press metal mold | die 6a, 6b.

プレス成形の際に、第2の部位2はオーステナイト域から急冷却され硬質のマルテンサイトが形成される。一方、断熱材3−2a、3−2bを装着された第1の部位1は、マルテンサイトの生成が防止される。   During the press molding, the second portion 2 is rapidly cooled from the austenite region to form hard martensite. On the other hand, the 1st site | part 1 with which heat insulating material 3-2a, 3-2b was mounted | worn prevents the production | generation of a martensite.

図10は、このようにして製造された高強度部品7を示す説明図である。
これにより、図10に示すように、硬質のマルテンサイト組織を有する硬質部2、2と、マルテンサイトの生成が抑制され硬質部2に比較して硬度が十分に低く加工性が良好な軟質部1とを有する高強度部品7が得られる。軟質部1は後加工を行うために硬化を阻止したい部位を含むため、この軟質部1に対して剪断加工等の後加工を容易に行うことができる。
FIG. 10 is an explanatory view showing the high-strength component 7 manufactured as described above.
Accordingly, as shown in FIG. 10, the hard portions 2 and 2 having a hard martensite structure, and the soft portion having sufficiently low hardness and good workability compared to the hard portion 2 in which the generation of martensite is suppressed. 1 is obtained. Since the soft part 1 includes a portion where it is desired to prevent hardening in order to perform post-processing, the soft part 1 can be easily subjected to post-processing such as shearing.

実施の形態1では、熱間プレスにおいて、特に絞り成形では絞り成形部の壁の耐力の低下に伴って絞り成形時に壁の破断が起こり易くなり、成形限界の低下を招くおそれがある。これに対し、実施の形態2では、冷間状態でのプレス予成形においては絞り成形部の壁の耐力が高いため、壁の破断を生じることなく複雑な絞り成形を行うことができる。   In the first embodiment, in hot pressing, particularly in the case of drawing, the wall tends to break during drawing with a decrease in the proof stress of the wall of the drawing portion, which may lead to a reduction in the forming limit. On the other hand, in the second embodiment, since the proof strength of the wall of the drawn portion is high in the cold press pre-forming, complicated drawing can be performed without causing the wall to break.

また、実施の形態2では、加熱後のプレス成形の主たる目的は、成形ではなく抜熱冷却による急冷であり、実施の形態1に比較するとプレス金型6a、6bに作用する負荷を小さくすることができる。このため、本実施の形態では、プレス金型6a、6bの材質を、例えば銅合金といった、軟質ではあるものの熱伝導率が高い材料を使用することが可能となり、これにより、実施の形態1よりも冷却効率を高めて生産能率を高めることができる。   In the second embodiment, the main purpose of press molding after heating is not quenching but rapid cooling by heat removal cooling, and compared with the first embodiment, the load acting on the press dies 6a and 6b is reduced. Can do. For this reason, in this embodiment, it is possible to use a soft material having high thermal conductivity, such as a copper alloy, for example, as the material of the press dies 6a and 6b. Even cooling efficiency can be increased to increase production efficiency.

実施例を参照しながら、本発明をさらに具体的に説明する。
図1に示すように、C:0.21%、Si:0.25%、Mn:1.20%を含有する板厚1.6mm、長さ280mm、幅80mmの合金化溶融亜鉛めっき鋼板(Ac点:
823℃程度、Ac点:728℃程度、Ar点:600℃程度)からなる被加工材0の長手方向の中央部の両面に、厚さ20mm、幅40mmのセラミックファイバー(900℃における熱伝導率0.25W/m・K)を断熱材3a、3bとして巻き付けて装着し、900℃に設定した電気炉に装入して210秒間加熱した。
The present invention will be described more specifically with reference to examples.
As shown in FIG. 1, an alloyed hot-dip galvanized steel sheet having a plate thickness of 1.6 mm, a length of 280 mm, and a width of 80 mm containing C: 0.21%, Si: 0.25%, and Mn: 1.20% ( Ac 3 points:
Ceramic fibers (heat at 900 ° C.) having a thickness of 20 mm and a width of 40 mm are formed on both sides of the longitudinal center portion of the workpiece 0 consisting of about 823 ° C., Ac 1 point: about 728 ° C., Ar 3 points: about 600 ° C. Wrapped with 0.25 W / m · K) as the heat insulating materials 3a and 3b, mounted in an electric furnace set at 900 ° C. and heated for 210 seconds.

加熱後、図3に示す、断熱材3a、3bを装着された第1の部位1の温度は700℃であり、第2の部位2、2の温度はいずれも900℃であった。
この被加工材0を加熱炉から抽出した後およそ5秒間以内に断熱材3を取り外し、図4に示す金型4a、4b(深さd:70mm、頭部幅w:80mm)で、図5に示すハット状部材5にプレス成形した。下死点でプレスを止めそのまま20秒間保持し、その後金型4aを上死点に戻して成形品5を取り出した。取り出し後の温度はおおむね100℃以下であった。なお、炉出しからプレス開始までは空冷とした。
After the heating, the temperature of the first part 1 to which the heat insulating materials 3a and 3b are attached as shown in FIG. 3 was 700 ° C., and the temperature of the second part 2 and 2 was 900 ° C.
The insulating material 3 is removed within about 5 seconds after the workpiece 0 is extracted from the heating furnace, and the molds 4a and 4b (depth d: 70 mm, head width w: 80 mm) shown in FIG. The hat-shaped member 5 shown in FIG. The press was stopped at the bottom dead center and held for 20 seconds, and then the mold 4a was returned to the top dead center and the molded product 5 was taken out. The temperature after removal was approximately 100 ° C. or less. Air cooling was performed from the start of the furnace to the start of pressing.

このようにして得られた成形品の硬度を測定したところ、図5に示すように、第2の部位2の硬度はHV450以上(引張強度1500MPa相当)であったのに対し、第1の部位1の硬度はHV170(引張強度570MPa相当)であった。   When the hardness of the molded product thus obtained was measured, the hardness of the second part 2 was HV450 or higher (equivalent to a tensile strength of 1500 MPa) as shown in FIG. The hardness of No. 1 was HV170 (equivalent to a tensile strength of 570 MPa).

比較例として、断熱材3a、3bを装着せずに加熱すること以外の条件は実施例1と同じ条件で、成形品を製造した。900℃に設定した電気炉中で210秒間加熱したところ、被加工材0全体が900℃に達し、加熱炉から取り出した後速やかにプレス成形し、下死点にて20秒間保持してから取り出し、得られた成形品の硬度を測定したところ、全域でHV450以上であった。   As a comparative example, a molded product was manufactured under the same conditions as in Example 1 except that heating was performed without mounting the heat insulating materials 3a and 3b. When heated in an electric furnace set at 900 ° C. for 210 seconds, the entire workpiece 0 reached 900 ° C., and after being removed from the heating furnace, it was immediately press-molded, held at the bottom dead center for 20 seconds, and then removed. When the hardness of the obtained molded product was measured, it was HV450 or more in the entire region.

実施例1と同じ鋼板(C:0.21%、Si:0.25%、Mn:1.20%を含有する板厚1.6mm、長さ280mm、幅80mmの合金化溶融亜鉛めっき鋼板、Ac点:
823℃)を被加工材0として用いた。
The same steel plate as in Example 1 (C: 0.21%, Si: 0.25%, Mn: 1.20% plate thickness 1.6 mm, length 280 mm, width 80 mm alloyed hot dip galvanized steel plate, Ac 3 points:
823 ° C.) was used as workpiece 0.

図11は、加熱炉に装入される被加工材0の状況を示す説明図である。
被加工材0の長手方向の中央部を、図11に示すように、厚さ20mm、半径20mm(直径40mm)のセラミックファイバー(900℃における熱伝導率0.25W/m.K)からなる円柱状の断熱材3−3a、3−3bにより挟み込むことによって、被加工材0に断熱材3−3a、3−3bを装着し、この状態で900℃に設定した電気炉に装入して210秒間加熱した。
FIG. 11 is an explanatory view showing the situation of the workpiece 0 charged in the heating furnace.
As shown in FIG. 11, the center part in the longitudinal direction of the workpiece 0 is a circle made of ceramic fiber (thermal conductivity at 900 ° C. of 0.25 W / m · K) having a thickness of 20 mm and a radius of 20 mm (diameter 40 mm). By sandwiching between the columnar heat insulating materials 3-3a and 3-3b, the heat insulating materials 3-3a and 3-3b are mounted on the workpiece 0, and charged in an electric furnace set at 900 ° C. in this state. Heated for 2 seconds.

なお、断熱材3−3a、3−3bに断熱材3−3a、3−3bを装着した部分の中心から半径10mmの円形の部位8が、円形の穴あけ加工を行われる後加工予定部である。
図12は、加熱時の被加工材0を示す説明図である。
A circular portion 8 having a radius of 10 mm from the center of the portion where the heat insulating materials 3-3a and 3-3b are attached to the heat insulating materials 3-3a and 3-3b is a post-processing scheduled portion where circular drilling is performed. .
FIG. 12 is an explanatory diagram showing the workpiece 0 during heating.

加熱後、断熱材3−3a、3−3bを装着された第1の部位1は、図12に示すように中心部が700℃であり、中心から半径10mmの部位8が720℃であり、さらに、第2の部位2は900℃に達していた。   After heating, the first part 1 to which the heat insulating materials 3-3a and 3-3b are attached has a center part at 700 ° C. as shown in FIG. 12, and a part 8 having a radius of 10 mm from the center is 720 ° C. Furthermore, the 2nd site | part 2 had reached 900 degreeC.

図13は、断熱材3−3a、3−3bを取り外された被加工材0にプレス加工を行う状況を示す説明図である。
加熱炉から取り出し後5秒間程度で、図13に示すプレス金型9a、9b(深さd:70mm、頭部幅w:80mm)で、図14に示すハット状部材10にプレス成形し、下死点にて20秒間保持してから取り出した。取り出し後のハット状部材10の温度はおおむね100℃以下であった。なお、炉出しからプレス開始までは空冷とした。
FIG. 13 is an explanatory diagram illustrating a state in which press working is performed on the workpiece 0 from which the heat insulating materials 3-3a and 3-3b have been removed.
About 5 seconds after taking out from the heating furnace, press-molding is performed on the hat-shaped member 10 shown in FIG. 14 with the press dies 9a and 9b (depth d: 70 mm, head width w: 80 mm) shown in FIG. After holding at the dead point for 20 seconds, it was taken out. The temperature of the hat-shaped member 10 after taking out was approximately 100 ° C. or less. Air cooling was performed from the start of the furnace to the start of pressing.

このようにして得られたハット状部材10の硬度を測定したところ、図14に示す第1の部位1の中心部の硬度はHV170であり、中心から半径10mmの部位8の硬度はHV190であり、第2の部位2の硬度はHV450以上であった。   When the hardness of the hat-shaped member 10 thus obtained was measured, the hardness of the central portion of the first portion 1 shown in FIG. 14 was HV170, and the hardness of the portion 8 having a radius of 10 mm from the center was HV190. The hardness of the second part 2 was HV450 or more.

実施例1と同じ鋼板を冷間にて図4に示すプレス金型4a、4b(深さd:70mm、頭部幅w:80mm)により、ハット状部材にプレス予成形することにより得られる、図6に示す被加工材0−1に対して、頭部の中央部に図7に示すように厚さ20mm、幅40mmのセラミックファイバー(900℃における熱伝導率0.25W/m・K)を断熱材3−2a、3−2bとして巻き付けて装着し、900℃に設定した電気炉に装入して210秒間加熱した。   The same steel sheet as in Example 1 is obtained by press-molding into a hat-shaped member by press dies 4a and 4b (depth d: 70 mm, head width w: 80 mm) shown in FIG. For the workpiece 0-1 shown in FIG. 6, a ceramic fiber having a thickness of 20 mm and a width of 40 mm (thermal conductivity at 900 ° C. of 0.25 W / m · K) as shown in FIG. Was wound and mounted as heat insulating materials 3-2a and 3-2b, charged in an electric furnace set at 900 ° C., and heated for 210 seconds.

加熱後、図8に示す、断熱材3−2a、3−2bを装着された第1の部位1の温度は700℃に達し、装着されなかった第2の部位2は900℃に達していた。
この被加工材0−1を加熱炉から抽出した後、すみやかに図9に示すようにプレス金型6a、6bによりプレス成形して、図10に示す成形品7とし、下死点にて20秒間保持した後取り出した。取り出し後の成形品7の温度はおおむね100℃以下であった。
After the heating, the temperature of the first part 1 attached with the heat insulating materials 3-2a and 3-2b shown in FIG. 8 reached 700 ° C., and the second part 2 not attached reached 900 ° C. .
After the workpiece 0-1 is extracted from the heating furnace, it is immediately press-molded by the press dies 6a and 6b as shown in FIG. 9 to obtain a molded product 7 shown in FIG. After holding for 2 seconds, it was removed. The temperature of the molded product 7 after taking out was approximately 100 ° C. or less.

このようにして得られた成形品7の硬度を測定したところ、図10に示す第2の部位2の硬度はHV450以上であったのに対し、第1の部位1の中央の硬度はHV170であった。   When the hardness of the molded product 7 thus obtained was measured, the hardness of the second part 2 shown in FIG. 10 was HV450 or more, whereas the hardness of the center of the first part 1 was HV170. there were.

実施例1と同じ鋼板を冷間にて図4に示すプレス金型4a、4b(深さd:70mm、頭部幅w:80mm)によりハット状部材にプレス予成形することにより得られる、図15に示す被加工材0−2の、頭部の中央部であって直径20mmの穴あけ予定部11を含む領域12を、図16に示すように厚さ20mm、半径20mm(直径40mm)のセラミックファイバー(900℃における熱伝導率0.25W/m.K)からなる円柱状の断熱材3−4a、3−4bにより挟み込むことによって、被加工材0−2に断熱材3−4a、3−4bを装着し、900℃に設定した電気炉に装入して210秒間加熱した。   FIG. 4 is a diagram obtained by pre-forming a hat-shaped member into the hat-shaped member by pressing the same steel plate as in Example 1 with the press dies 4a and 4b (depth d: 70 mm, head width w: 80 mm) shown in FIG. A region 12 of the work piece 0-2 shown in Fig. 15 that is the central portion of the head and includes the planned drilling portion 11 having a diameter of 20 mm is a ceramic having a thickness of 20 mm and a radius of 20 mm (diameter 40 mm) as shown in Fig. 16. The heat insulating materials 3-4a, 3- in the workpiece 0-2 are sandwiched between cylindrical heat insulating materials 3-4a, 3-4b made of fibers (thermal conductivity at 900 ° C. of 0.25 W / m.K). 4b was mounted, charged in an electric furnace set at 900 ° C. and heated for 210 seconds.

加熱後、図17に示したように第1の部位1の中心部である穴あけ予定部11の温度は700℃であり、この中心から半径10mmの領域12の温度は720℃であり、さらに第2の部位2は900℃であった。   After heating, as shown in FIG. 17, the temperature of the drilled portion 11 that is the center of the first part 1 is 700 ° C., the temperature of the region 12 having a radius of 10 mm from this center is 720 ° C., and The 2 part 2 was 900 degreeC.

加熱炉から取り出し後5秒間程度で図18に示すようにプレス金型13a、13bでプレス成形して成形品14とし、下死点にて20秒間保持した後取り出した。取り出し後の成形品14の温度はおおむね100℃以下であった。なお、炉出しからプレス開始までは空冷とした。   About 5 seconds after taking out from the heating furnace, as shown in FIG. 18, it was press-molded with press dies 13a and 13b to form a molded product 14, which was held for 20 seconds at the bottom dead center and taken out. The temperature of the molded product 14 after taking out was approximately 100 ° C. or less. Air cooling was performed from the start of the furnace to the start of pressing.

このようにして得られた成形品14の硬度を測定したところ、図19に示す第1の部位1の中心の穴あけ予定部11の硬度はHV170であり、中心から半径10mmの領域12の硬度はHV190であり、さらに、第2の部位2の硬度はHV450以上であった。   When the hardness of the molded product 14 thus obtained was measured, the hardness of the planned drilling portion 11 at the center of the first part 1 shown in FIG. 19 was HV170, and the hardness of the region 12 having a radius of 10 mm from the center was The hardness of the second portion 2 was HV450 or higher.

図1は、実施の形態1において加熱炉に装入される被加工材の状況を示す説明図である。FIG. 1 is an explanatory diagram illustrating a state of a workpiece to be charged in a heating furnace in the first embodiment. 図2(a)は、実施の形態1において被加工材の全幅の硬度を低く抑制したい場合の断熱材の配置を示す説明図であり、図2(b)は、図2(a)におけるA断面図である。FIG. 2 (a) is an explanatory view showing the arrangement of the heat insulating material when it is desired to suppress the hardness of the entire width of the work material to be low in the first embodiment, and FIG. 2 (b) is an illustration of A in FIG. 2 (a). It is sectional drawing. 図3は、実施の形態1において所定の温度分布に加熱された被加工材を示す説明図である。FIG. 3 is an explanatory diagram showing a workpiece heated to a predetermined temperature distribution in the first embodiment. 図4は、実施の形態1において断熱材を取り外された被加工材にプレス加工を行う状況を示す説明図である。FIG. 4 is an explanatory diagram illustrating a state in which press working is performed on the workpiece from which the heat insulating material has been removed in the first embodiment. 図5は、実施の形態1により製造された高強度部品を示す説明図である。FIG. 5 is an explanatory view showing a high-strength part manufactured according to the first embodiment. 図6は、実施の形態2において用いる被加工材0−1の形状を示す説明図である。FIG. 6 is an explanatory diagram showing the shape of the workpiece 0-1 used in the second embodiment. 図7は、実施の形態2において加熱炉に装入される被加工材の状況を示す説明図である。FIG. 7 is an explanatory diagram showing a state of a workpiece to be charged in a heating furnace in the second embodiment. 図8は、実施の形態2において加熱時の被加工材を示す説明図である。FIG. 8 is an explanatory diagram showing the workpiece during heating in the second embodiment. 図9は、実施の形態2において断熱材を取り外された被加工材にプレス加工を行う状況を示す説明図である。FIG. 9 is an explanatory diagram illustrating a state in which press working is performed on the workpiece from which the heat insulating material has been removed in the second embodiment. 図10は、実施の形態2において製造された高強度部品を示す説明図である。FIG. 10 is an explanatory view showing a high-strength part manufactured in the second embodiment. 図11は、実施例2において加熱炉に装入される被加工材の状況を示す説明図である。FIG. 11 is an explanatory diagram illustrating a state of a workpiece to be charged in a heating furnace in the second embodiment. 図12は、実施例2において加熱時の被加工材を示す説明図である。FIG. 12 is an explanatory view showing a workpiece during heating in Example 2. 図13は、実施例2において断熱材を取り外された被加工材にプレス加工を行う状況を示す説明図である。FIG. 13 is an explanatory diagram illustrating a state in which press working is performed on the workpiece from which the heat insulating material has been removed in the second embodiment. 図14は、実施の形態2において製造された高強度部品を示す説明図である。FIG. 14 is an explanatory view showing a high-strength part manufactured in the second embodiment. 図15は、実施の形態4における被加工材を示す説明図である。FIG. 15 is an explanatory diagram showing a workpiece in the fourth embodiment. 図16は、実施の形態4において加熱炉に装入される被加工材の状況を示す説明図である。FIG. 16 is an explanatory diagram illustrating a state of a workpiece to be charged into a heating furnace in the fourth embodiment. 図17は、実施例4において加熱時の被加工材を示す説明図である。FIG. 17 is an explanatory diagram showing the workpiece during heating in Example 4. 図18は、実施例4において断熱材を取り外された被加工材にプレス加工を行う状況を示す説明図である。FIG. 18 is an explanatory diagram illustrating a state in which press working is performed on the workpiece from which the heat insulating material has been removed in the fourth embodiment. 図19は、実施例4において断熱材を取り外された被加工材にプレス加工を行う状況を示す説明図である。FIG. 19 is an explanatory diagram illustrating a state in which press working is performed on the workpiece from which the heat insulating material has been removed in the fourth embodiment.

符号の説明Explanation of symbols

0、0−1、0−2 被加工材
1 第1の部位
2 第2の部位
3a、3b、3−1、3−2a、3−2b、3−3a、3−3b、3−4a、3−4b 断熱材
4、4a、4b、6a、6b、9a、9b、13a、13b プレス金型
5 高強度部品
7 高強度部品
8 円形の部位
10 ハット状部材
11 穴あけ予定部
12 領域
14 成形品
0, 0-1, 0-2 Workpiece material 1 First part 2 Second part 3a, 3b, 3-1, 3-2a, 3-2b, 3-3a, 3-3b, 3-4a, 3-4b Heat insulating material 4, 4a, 4b, 6a, 6b, 9a, 9b, 13a, 13b Press die 5 High strength component 7 High strength component 8 Circular part 10 Hat-shaped member 11 Planned hole portion 12 Region 14 Molded product

Claims (9)

第1の部位と、該第1の部位とは異なる第2の部位とを少なくとも有する鋼製の被加工材の当該第1の部位に、該被加工材の熱伝導率よりも小さな熱伝導率を有する断熱材を装着し、該断熱材を装着された被加工材を所定の温度に昇温された加熱炉に装入することにより、前記第1の部位をAc点未満に加熱するとともに前記第2の部位をAc点以上に加熱し、次いで、前記被加工材を前記加熱炉から抽出して該被加工材から前記断熱材を取り外した後に、該被加工材をプレス金型に装入し、前記第2の部位の温度がAr点以上である状態で前記プレス金型によるプレス加工及び冷却を開始することを特徴とする高強度部品の製造方法。 The first part of the steel workpiece having at least a first part and a second part different from the first part has a thermal conductivity smaller than the thermal conductivity of the workpiece. The first part is heated to less than Ac 3 points by inserting a heat-insulating material having the heat-insulating material, and charging the work piece equipped with the heat-insulating material into a heating furnace heated to a predetermined temperature. The second part is heated to Ac 3 or more points, and then the work material is extracted from the heating furnace and the heat insulating material is removed from the work material. A method for manufacturing a high-strength component, comprising charging and starting the press working and cooling with the press die in a state where the temperature of the second part is at least Ar 3 . 前記加熱炉は、内部の高温雰囲気による熱輻射により、前記断熱材を装着された被加工材を加熱する請求項1に記載された高強度部品の製造方法。   The said heating furnace is a manufacturing method of the high intensity | strength components described in Claim 1 which heats the workpiece with which the said heat insulating material was mounted | worn with the thermal radiation by internal high temperature atmosphere. 前記第1の部位は、前記プレス加工及び冷却を終了した後に後加工を行われる後加工予定部を含む部位である請求項1又は請求項2に記載された高強度部品の製造方法。   3. The method for manufacturing a high-strength part according to claim 1, wherein the first part is a part including a post-processing scheduled portion that is subjected to post-processing after finishing the pressing and cooling. 前記プレス加工及び冷却を終了した後に、前記第1の部位の少なくとも一部に後加工を行う請求項1から請求項3までのいずれか1項に記載された高強度部品の製造方法。   The method for manufacturing a high-strength part according to any one of claims 1 to 3, wherein after the pressing and cooling are finished, post-processing is performed on at least a part of the first part. 前記被加工材は、平板状の部材である請求項1から請求項4までのいずれか1項に記載された高強度部品の製造方法。   The method for manufacturing a high-strength component according to any one of claims 1 to 4, wherein the workpiece is a flat plate member. 前記被加工材は、平板状の部材に予成形金型により予めプレス予成形されてなる非平板状の部材である請求項1から請求項4までのいずれか1項に記載された高強度部品の製造方法。   5. The high-strength component according to claim 1, wherein the workpiece is a non-plate member formed by press-preforming a plate-like member in advance with a preforming mold. 6. Manufacturing method. 前記第1の部位を、前記加熱炉によりAr点以上に加熱する請求項1から請求項6までのいずれか1項に記載された高強度部品の製造方法。 The method for manufacturing a high-strength component according to any one of claims 1 to 6, wherein the first part is heated to one or more Ar points by the heating furnace. 前記断熱材の900℃における熱伝導率は、1W/(m・K)以下である請求項1から請求項7までのいずれか1項に記載された高強度部品の製造方法。   The method for manufacturing a high-strength component according to any one of claims 1 to 7, wherein the thermal conductivity of the heat insulating material at 900 ° C is 1 W / (m · K) or less. 前記被加工材は、一部又は全部に亜鉛めっき層が形成された鋼板である請求項1から請求項8までのいずれか1項に記載された高強度部品の製造方法。   The method for manufacturing a high-strength component according to any one of claims 1 to 8, wherein the workpiece is a steel plate in which a galvanized layer is formed in part or in whole.
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