JP4313975B2 - Die for plate pressing in warm or hot - Google Patents
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- JP4313975B2 JP4313975B2 JP2002046265A JP2002046265A JP4313975B2 JP 4313975 B2 JP4313975 B2 JP 4313975B2 JP 2002046265 A JP2002046265 A JP 2002046265A JP 2002046265 A JP2002046265 A JP 2002046265A JP 4313975 B2 JP4313975 B2 JP 4313975B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、温間または熱間における板材プレス成形に用い得る金型に関する。
【０００２】
【従来の技術】
従来、冷間用金型として特公平３−17891 の提案がなされている。また、熱間又は温間加工用金型の複合表面処理方法として特開平11−92909 の提案がなされている。一方、ピストンリング用硬質被覆材として、特開平６−265023の提案がなされている。
【０００３】
【発明が解決しようとする課題】
しかし、特公平３−17891 の金型は冷間加工用のものであるため、熱間または温間の加工で使用すると、表面の硬質層と被加工材料が反応し金型への凝着が発生したり、表面の硬質層の摩耗や剥離により金型基材が表面に露出し被加工材料が金型に凝着し、型かじりが発生する。また、特開平11−92909 の金型の表面処理方法は、主として熱間または温間鍛造に用いることを目的としているため、一般にMoS2やＣ等の潤滑剤の塗布環境下で使用することを前提に考案されたものであるため、後処理性を損なうMoS2やＣ等の潤滑剤の使用が許されない、温間または熱間における板材プレス成形に用いると、被加工材料が金型に凝着し型かじりが発生する。また、一般に板材プレス成形においては、鍛造に比べ摺動距離が長いため、被加工材料が金型に凝着し型かじりが発生し易く、より耐久性の良い金型材料が必要となる。一方、一般にピストンリング用に発明された特開平6-265023の硬質被覆材の使用温度は200 ℃〜300 ℃と低く、摺動部にオイルが存在し、かつ面圧が低いため、温間または熱間における板材プレス成形に用いると、被加工材料が金型に凝着し型かじりが発生する。
【０００４】
本発明者は、上記問題点に鑑み、従来にない過酷な使用環境下である温間または熱間における板材プレス成形にて型かじりを起こさない金型を得るべく鋭意探索検討を行なったところ、特定の化合物を表面処理し積層した金型を使用すれば、型かじりが発生しないことを見出し、本発明を完成するに至った。
【０００５】
【課題を解決するための手段】
本発明では上記問題点を解決するための、
（１）被加工材料の温度が４００℃以上１１００℃以下の状態で板材プレス加工を行なう際に使用する金型であり、金型基材である構造用合金鋼や合金工具鋼や高速度工具鋼の表面に２０μｍ以上４０μｍ以下の窒化層を形成し、その上に１μｍ以上２μｍ以下のＣｒＮ層を形成し、その上に、４μｍ以上８μｍ以下の３〜２０重量％の酸素を固溶させたＣｒＮ層を形成させ、３〜２０重量％の酸素を固溶させたＣｒＮ層の固溶酸素濃度が、３〜２０重量％の酸素濃度範囲で、内側から外側に向かって、連続的あるいは断続的に増加しており、最表層である酸素を固溶させたＣｒＮ層の表面粗度をＲｚで２μｍ以下とすることを特徴とする温間または熱間における板材プレス成形用金型、
（２）（１）記載の金型において、酸素を固溶させたＣｒＮ層の７００℃、１０時間の大気中での酸化処理後の７００℃での高温ビッカース硬度が，６００以上１５００以下であることを特徴とする、温間または熱間における板材プレス成形用金型、
（３）（１）または（２）記載の金型において、窒化層を含む金型基材のＲｚを（１）式に従い調整することを特徴とする、温間または熱間における板材プレス成形用金型、
１≦Ｒｚ≦２（ｔa ＋ｔb ）／３ （１）
（ｔａ：ＣｒＮ層の厚さ，ｔｂ：酸素を固溶させたＣｒＮ層の厚さ，単位はμｍ）
である。
【０００６】
【発明の実施の形態】
以下に本発明を詳細に説明する。
まず、層構造を決定するための基本思想は、構成する各層間での層界面での剥離を防ぐために、1)硬度の観点からの傾斜構造、2)化学成分の傾斜する層構造、とすることにある。硬度の傾斜構造と言う観点から、本発明では、金型基材から表面に向かい、窒化層、酸素を固溶させないＣｒＮ層、酸素を固溶させたＣｒＮ層とし、金型基材から表面に向かい硬度が大きくなる傾斜構造としている。また、酸素を固溶させたＣｒＮ層について内側から表面に向かい連続的あるいは断続的に酸素濃度を増加させ、内側から表面に向かい硬度を上昇させたのも同様の観点からである。また、前記層構造とすることにより、化学成分と言う意味でも傾斜構造としている。
【０００７】
図１に、本発明の層構成を模式的に示した。使用する金型基材としては、構造用合金鋼や合金工具鋼や高速度工具鋼を使用する必要がある。表面を硬質層で被覆しても、下にある金型基材の硬度が低いと、硬質層と金型基材の境界で硬質層が剥離するため、金型基材の硬度はビッカース硬度４００以上が好ましい。金型基材上の窒化層の厚さは、２０μｍ以上とする必要がある。２０μｍ未満だと、硬度および化学成分の傾斜構造を構成する層としての機能を果たさず、皮膜剥離が発生する。窒化層を形成する方法は、プラズマ法、ガス法、真空ガス法、塩浴法等があるが、要求に応じこれらを使いわけることができる。
【０００８】
しかし、一般に白層と呼ばれる化合物は脆弱なためクラック発生の原因となったり、ＣｒＮ層と窒化層の密着力を低下させるので、化合物層の生成しない窒化方法を選択するか、化合物層が生成した場合には、化合物層を除去する必要がある。次に、表面の硬質層は、ＣｒＮとする必要がある。表面の硬質層としてＣｒ系、Ｔｉ系、Ａｌ系、Ｚｒ系等の各種物質を金型に表面処理し、被加工材として鋼板を用い、４００〜１１００℃での板材プレス成形を実施し、耐型かじり性に優れた物質を探索した。その結果、一部の結果では、大気中での酸化温度が高いものほど耐型かじり性に優れている傾向は認められたが、酸化温度で整理できない結果も得られた。
【０００９】
ＣｒＮとＴｉＣ、ＴｉＣＮ、ＴｉＮの比較結果は、酸化温度で整理できた例である。すなわち、ＣｒＮよりも酸化温度が低いＴｉＣ、ＴｉＣＮ、ＴｉＮは、１０〜５０回の連続プレスにより型かじりが発生したのに対し、ＣｒＮは数千回の連続プレスを行なっても、型かじりが発生しなかった。型かじりの発生した金型を観察したところ、金型に被加工材である鋼板が凝着していることがわかった。
【００１０】
さらに、金型凝着部の断面をミクロに観察すると、硬質皮膜であるＴｉＣ、ＴｉＣＮ、ＴｉＮの表面に被加工材が凝着していることが判明した。しかし、特開平11-92909にあるＣｒＮよりも酸化温度が高いＴｉＡｌＮにて同様の試験を行なったところ、ＴｉＣ、ＴｉＣＮ、ＴｉＮと同様の形態の金型への被加工材の凝着が発生し型かじりが発生した。このように、酸化温度だけでは整理できず、検討を行なった硬質皮膜の中では、ＣｒＮのみが被加工材である鋼板と凝着をおこさなかった。この原因は明らかではないが、ＣｒＮが高温で被加工材である鋼板との化学的反応性が低いためではないかと推測される。
【００１１】
また，T.R.Hayward 等（Metal Forming 2000,Pietrzyk et al.(eds)2000 Balkema, Rotterdam,ISBN 90 5809 1570）は、室温の結果ではあるが、ＴｉＣ、ＴｉＮ、ＴｉＣＮに比べＣｒＮを表面処理した金型を使用した方が、摩擦係数が低くなることを示している。このような結果もＣｒＮが凝着を起こしにくいことと何らかの関係があると考えられる。
【００１２】
ＣｒＮ層の厚さは、１μｍ以上とする必要がある。１μｍ未満だと、硬度および化学成分の傾斜構造を構成する層としての機能を果たさず、皮膜剥離が発生する。酸素を固溶させたＣｒＮの厚さは、４μｍ以上とする必要がある。表面の最も硬質な層である酸素を固溶させたＣｒＮ層には、耐摩耗性を確保する役割があるため、実質上４μｍ未満だと耐摩耗性の観点から工業的意味が失われる。ＣｒＮおよび酸素を固溶させたＣｒＮは，イオンプレーティン法等のＰＶＤ法により表面処理することができる。
【００１３】
また、ＣｒＮ層が窒化層と酸素を固溶させたＣｒＮの間に存在することにより、酸素を固溶させたＣｒＮをＰＶＤにより表面処理する際に使用されるＯ 2 ガスによって下地が酸化されるのを防ぐことができる。固溶酸素の濃度は３％以上２０％以下とする必要がある。３％未満だと硬さが低く耐摩耗性が劣り、２０％を超えるとＣｒ2 Ｏ3 が生成し、皮膜靭性が劣化する。酸素を含んだＣｒＮ層の７００℃、１０時間の大気中での酸化処理後の７００℃での高温ビッカース硬度は、６００以上１５００以下である必要がある。６００未満だと、耐摩耗性に劣り、１５００を超えると下地との硬度差が大きすぎ層間剥離が発生する。
【００１４】
最表面の粗度は、Ｒｚで２μｍ以下とする必要がある。Ｒｚが２μｍを超えると、被加工材が凝着し易くなる。窒化層を含む金型基材のＲｚを（１）式に従い調整することにより、窒化層を含む金型基材とＣｒＮおよび酸素を固溶させたＣｒＮからなる硬質層の密着性を高めることができる。窒化層を含む金型基材のＲｚを大きくすることにより、窒化層を含む金型基材とＣｒＮおよび酸素を含むＣｒＮからなる硬質層の境界面積を増加し、両層の実質的密着力を上昇させる、という技術思想に基いている。
１≦Ｒｚ≦２（ｔa ＋ｔb ）／３ （１）
（ｔａ：ＣｒＮ層の厚さ，ｔｂ：酸素を固溶させたＣｒＮ層の厚さ，単位はμｍ，図２にｔａ及びｔｂの定義を図示した。）
【００１５】
窒化層を含む金型基材のＲｚが１μｍ未満だと実質上上記の効果は得られない。また、Ｒｚ＞２（ｔa ＋ｔb ）／３だと、表面に窒化層を含む金型基材が露出する可能性が高く、露出すると凝着が発生し易く、型かじりが発生し易くなる。また初期状態では、窒化層を含む金型基材が表面に露出しなくても、摩耗により露出すると型かじりが発生しやすくなるため、Ｒｚ≦２（ｔa ＋ｔb ）／３とする必要がある。
【００１６】
【実施例１】
以下に本発明を具体例で説明する。
20ｍｍ幅の780MPa級熱延ハイテンのフープを用い、図３に模式的に示した高温摺動試験機を使用し、試験材の半径（Ｒ）を30ｍｍ、加圧用ロールによる負荷荷重を２５ｋｇｆ、高周波加熱装置による鋼板の加熱温度を７００℃とし高温凝着性を評価した。表１に試験材と試験結果を示す。窒化層を含む金型基材のＲｚおよび最表面のＲｚは１μｍとした。また、酸素を固溶させたＣｒＮを表面処理した試験材については、ＣｒＮ層の厚さを１μｍ、酸素を固溶させたＣｒＮの厚さを４μｍとし、固溶酸素量を８ｗｔ％とした。ＴｉＮ、ＴｉＣＮおよびＴｉＡｌＮを表面処理した試験材は、摺動距離１０ｍ以下で表面処理皮膜上に凝着が発生したのに対し、ＣｒＮを表面処理した試験材は、摺動距離が２０ｍで表面処理皮膜が摩耗により消失した後、金型基材上に凝着が発生した。酸素を固溶させたＣｒＮを表面処理した試験材は、摺動距離が８０ｍで表面処理皮膜が摩耗により消失した後、金型基材上に凝着が発生した。
【００１７】
【実施例２】
実施例１と同様の試験機で試験材の半径（Ｒ）を３０ｍｍ、加圧用ロールによる負荷荷重を２５ｋｇｆとし、表２に示した加熱温度、試験材で、凝着性を評価した。本発明であるＡ〜Ｊは、凝着が発生した摺動距離が８０ｍ以上であるのに対し、比較例であるＫ〜Ｑは３０ｍ以下の摺動距離で凝着が発生した。
【００１８】
【実施例３】
実施例１、２と同様の試験機で試験材の半径（Ｒ）を３０ｍｍ、加圧用ロールによる負荷荷重を１０００ｋｇｆと高くし、加熱温度を７００℃、摺動距離を１００ｍとした。表３に試験条件と結果を示す。本発明であるＡ〜Ｆは、皮膜剥離、凝着とも発生せず、比較例であるＧ、I は、皮膜剥離が発生し凝着が発生し、Ｈ、Ｊは、凝着が発生した。
【００１９】
【実施例４】
板厚３．２ｍｍの７８０ＭＰａ級熱延高張力鋼板を用い、クリアランスを１０％とした打ち抜き加工によりブランク中心に２５ｍｍ直径の円形の穴をあけた１００ｍｍ角の正方形ブランクを用い、図４に模式的に示した金型により成形を行なった．円筒形状ポンチの直径を５０ｍｍとし、伸びフランジ率１００％（＝（ｄ−ｄ0 ）／ｄ０，ｄ0 ：初期のブランクの穴の直径，ｄ：成形後の穴直径）とした。しわ押さえ力（ＢＨＦ）は、１００ｋＮとした。成形直前に鋼板を高周波加熱装置で加熱し７００℃とし、表４に示すポンチを作製し、１００００個の連続成形を行なった。本発明である、Ａでは剥離や摩耗による硬質皮膜の消失がおこらず、凝着や型かじりが発生しなかったが、比較例であるＢでは、２０００個で硬質皮膜が消失し、凝着が発生し、型かじりが起こった。
尚、本発明は、温間または熱間における板材プレス成形だけでなく、冷間での板材プレス成形においても採用可能である。
【００２０】
【表１】
【表２】
【表３】
【表４】
【発明の効果】
以上説明したように、本発明により温間または熱間における板材プレス成形が可能となる。これにより、自動車部品に高強度鋼板の適用が可能となり、自動車の衝突安全性の向上および軽量化が実現できる。また高強度鋼板を自動車部品に適用することを容易にし、高強度鋼板の用途拡大に極めて有効である。
【図面の簡単な説明】
【図１】 本発明の層構成を示す模式図である。
【図２】 ＣｒＮおよび酸素を固溶させたＣｒＮ層の厚さを示す模式図である。
【図３】試験方法をあらわす模式図である。
【図４】成形方法をあらわす模式図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mold which may be used in sheet press forming between warm or hot.
[0002]
[Prior art]
Conventionally, Japanese Patent Publication No. 3-17891 has been proposed as a cold mold. Japanese Patent Laid-Open No. 11-92909 has been proposed as a composite surface treatment method for hot or warm working molds. On the other hand, JP-A-6-265023 has been proposed as a hard coating material for piston rings.
[0003]
[Problems to be solved by the invention]
However, since the mold of Japanese Patent Publication No. 3-17891 is for cold working, when used in hot or warm working, the hard layer on the surface reacts with the work material and adhesion to the mold does not occur. The mold base material is exposed to the surface due to wear or peeling of the hard layer on the surface, and the work material adheres to the mold, and mold galling occurs. In addition, since the surface treatment method of a mold disclosed in JP-A-11-92909 is mainly intended for use in hot or warm forging, it is generally used in an environment where a lubricant such as MoS 2 or C is applied. Since it was devised based on the premise, the use of lubricants such as MoS 2 and C which impair post-treatment properties is not permitted. Wearing type galling occurs. In general, plate material press molding has a longer sliding distance than forging, so that the material to be processed is likely to adhere to the mold, and mold galling is likely to occur, and a more durable mold material is required. On the other hand, the operating temperature of the hard coating material disclosed in Japanese Patent Application Laid-Open No. 6-265023, which is generally invented for piston rings, is as low as 200 ° C to 300 ° C, oil is present in the sliding portion, and the surface pressure is low. When used for hot plate material press molding, the work material adheres to the mold and mold galling occurs.
[0004]
In view of the above problems, the present inventor has conducted an extensive search and investigation to obtain a mold that does not cause mold galling in warm or hot plate material press molding under a harsh use environment that has not been conventionally used. It has been found that if a mold in which a specific compound is surface-treated and laminated is used, mold galling does not occur, and the present invention has been completed.
[0005]
[Means for Solving the Problems]
In the present invention, in order to solve the above problems,
(1) A mold used when pressing a plate material in a state where the temperature of a work material is 400 ° C. or higher and 1100 ° C. or lower, and is a structural alloy steel, alloy tool steel or high-speed tool which is a mold base material. A nitride layer of 20 μm or more and 40 μm or less is formed on the surface of the steel, a CrN layer of 1 μm or more and 2 μm or less is formed thereon, and 3 to 20% by weight of oxygen of 4 μm or more and 8 μm or less is dissolved therein. The CrN layer formed by forming a CrN layer and solid-dissolving 3 to 20% by weight of oxygen continuously or intermittently from the inside to the outside in the oxygen concentration range of 3 to 20% by weight. The surface roughness of the CrN layer in which oxygen , which is the outermost layer, is dissolved, is 2 μm or less in terms of Rz, warm or hot plate material mold,
(2) In the mold according to (1), the high temperature Vickers hardness at 700 ° C. after oxidation treatment in the atmosphere of 700 ° C. for 10 hours of the CrN layer in which oxygen is dissolved is 600 or more and 1500 or less. A mold for hot or hot plate material press molding,
(3) In the mold according to (1) or (2), for the press molding of a warm or hot plate material, the Rz of the mold base including the nitrided layer is adjusted according to the formula (1) Mold,
1≤Rz≤2 (ta + tb) / 3 (1)
(Ta: thickness of CrN layer, tb: thickness of CrN layer in which oxygen is dissolved, unit is μm)
It is.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
First, the basic idea for determining the layer structure is 1) a gradient structure from the viewpoint of hardness, and 2) a layer structure where the chemical components are inclined, in order to prevent delamination at the layer interface between each constituting layer. There is. From the viewpoint of the hardness gradient structure, in the present invention, from the mold base to the surface, a nitride layer, a CrN layer that does not dissolve oxygen, and a CrN layer that dissolves oxygen are used. It has an inclined structure that increases the opposite hardness. Further, from the same point of view, the oxygen concentration of the CrN layer in which oxygen is dissolved is increased continuously or intermittently from the inner side to the surface, and the hardness is increased from the inner side to the surface. Further, by adopting the layer structure, an inclined structure is used also in the sense of chemical components.
[0007]
FIG. 1 schematically shows the layer structure of the present invention. As the mold base to be used, it is necessary to use structural alloy steel, alloy tool steel or high-speed tool steel. Even if the surface is coated with a hard layer, if the hardness of the underlying mold base is low, the hard layer peels off at the boundary between the hard layer and the mold base, so the hardness of the mold base is Vickers hardness 400 The above is preferable. The thickness of the nitride layer on the mold substrate needs to be 20 μm or more. When the thickness is less than 20 μm, the film does not function as a layer constituting the gradient structure of hardness and chemical components, and film peeling occurs. A method for forming the nitride layer includes a plasma method, a gas method, a vacuum gas method, a salt bath method, and the like, and these can be used as required.
[0008]
However, since a compound generally called a white layer is fragile, it may cause cracks or reduce the adhesion between the CrN layer and the nitride layer, so a nitriding method that does not generate a compound layer is selected or a compound layer is generated. In some cases, it is necessary to remove the compound layer. Next, the hard layer on the surface needs to be CrN. Various materials such as Cr-based, Ti-based, Al-based, Zr-based, etc. are surface-treated as a hard layer on the surface, a steel plate is used as a work material, and a plate material is press-formed at 400 to 1100 ° C. We searched for materials with excellent mold galling properties. As a result, some results showed that the higher the oxidation temperature in the atmosphere, the better the resistance to mold galling, but the results could not be organized by the oxidation temperature.
[0009]
The comparison results of CrN and TiC, TiCN, and TiN are examples that can be arranged by the oxidation temperature. That is, TiC, TiCN, and TiN, which have lower oxidation temperatures than CrN, generated die galling after 10 to 50 continuous presses, whereas CrN generated galling even after thousands of continuous presses. I did not. Observation of the mold with galling revealed that the steel plate as the workpiece was adhered to the mold.
[0010]
Furthermore, when the cross section of the die adhesion part was observed microscopically, it was found that the work material adhered to the surface of TiC, TiCN, and TiN, which are hard films. However, when a similar test was performed with TiAlN having a higher oxidation temperature than CrN in JP-A-11-92909, adhesion of the work material to a mold having the same form as TiC, TiCN, and TiN occurred. Type galling occurred. Thus, the oxidation temperature alone could not be arranged, and among the hard coatings studied, only CrN did not adhere to the steel plate as the workpiece. The reason for this is not clear, but it is presumed that CrN is low in chemical reactivity with the steel sheet that is the workpiece.
[0011]
In addition, TRHayward et al. (Metal Forming 2000, Pietrzyk et al. (Eds) 2000 Balkema, Rotterdam, ISBN 90 5809 1570), although it is a result at room temperature, uses a die with surface treatment of CrN compared to TiC, TiN and TiCN. It shows that the coefficient of friction is lower when used. Such a result is also considered to have some relationship with the fact that CrN hardly causes adhesion.
[0012]
The thickness of the CrN layer needs to be 1 μm or more. When the thickness is less than 1 μm, the film does not function as a layer constituting the gradient structure of hardness and chemical composition, and film peeling occurs. The thickness of CrN in which oxygen is dissolved must be 4 μm or more. Since the CrN layer in which oxygen, which is the hardest layer on the surface, is dissolved, has a role of ensuring wear resistance, if it is substantially less than 4 μm, the industrial meaning is lost from the viewpoint of wear resistance. CrN in which CrN and oxygen are dissolved can be surface-treated by a PVD method such as an ion plating method.
[0013]
In addition, since the CrN layer exists between the nitride layer and CrN in which oxygen is dissolved, the base is oxidized by O 2 gas used when surface-treating CrN in which oxygen is dissolved by PVD. Can be prevented. The concentration of the solid solution oxygen needs to be 3% or more and 20% or less. If it is less than 3%, the hardness is low and the wear resistance is inferior. If it exceeds 20%, Cr 2 O 3 is produced and the film toughness deteriorates. The high-temperature Vickers hardness at 700 ° C. after the oxidation treatment of the CrN layer containing oxygen at 700 ° C. for 10 hours in the atmosphere needs to be 600 or more and 1500 or less. When it is less than 600, the wear resistance is poor, and when it exceeds 1500, the difference in hardness from the base is too large and delamination occurs.
[0014]
The roughness of the outermost surface needs to be 2 μm or less in terms of Rz. When Rz exceeds 2 μm, the workpiece becomes easy to adhere. By adjusting Rz of the mold base material including the nitride layer according to the formula (1), the adhesion between the mold base material including the nitride layer and the hard layer made of CrN in which CrN and oxygen are dissolved can be improved. it can. By increasing Rz of the mold base material including the nitride layer, the boundary area between the mold base material including the nitride layer and the hard layer made of CrN containing CrN and oxygen is increased, and the substantial adhesion force between both layers is increased. It is based on the technical idea of raising.
1≤Rz≤2 (ta + tb) / 3 (1)
(Ta: the thickness of the CrN layer, tb: the thickness of the CrN layer in which oxygen is dissolved, the unit is μm, and the definitions of ta and tb are shown in FIG. 2)
[0015]
If the Rz of the mold base material including the nitride layer is less than 1 μm, the above effect cannot be obtained. Further, when Rz> 2 (ta + tb) / 3, there is a high possibility that the mold base including the nitride layer is exposed on the surface, and if exposed, adhesion is likely to occur and mold galling is likely to occur. In the initial state, even if the mold base material including the nitride layer is not exposed on the surface, if it is exposed due to wear, mold galling is likely to occur. Therefore, Rz ≦ 2 (ta + tb) / 3 is required.
[0016]
[Example 1]
Hereinafter, the present invention will be described by way of specific examples.
Using a 780MPa class hot rolled high tensile hoop with a width of 20mm, using the high-temperature sliding tester schematically shown in Fig. 3, the radius (R) of the test material is 30mm, the load applied by the pressure roll is 25kgf, high frequency The heating temperature of the steel sheet by the heating device was set to 700 ° C., and the high temperature adhesion was evaluated. Table 1 shows the test materials and test results. The Rz of the mold base including the nitride layer and the Rz of the outermost surface were 1 μm. In addition, regarding the test material in which CrN in which oxygen was dissolved was surface-treated, the thickness of the CrN layer was 1 μm, the thickness of CrN in which oxygen was dissolved was 4 μm, and the amount of dissolved oxygen was 8 wt%. The test material with the surface treatment of TiN, TiCN and TiAlN showed adhesion on the surface treatment film at a sliding distance of 10 m or less, whereas the test material with the surface treatment of CrN had a surface treatment of 20 m at the sliding distance. After the film disappeared due to wear, adhesion occurred on the mold substrate. The test material on which CrN in which oxygen was dissolved was subjected to surface treatment, and after the sliding distance was 80 m and the surface treatment film disappeared due to wear, adhesion occurred on the mold substrate.
[0017]
[Example 2]
Using the same tester as in Example 1, the radius (R) of the test material was 30 mm, the load applied by the pressure roll was 25 kgf, and the adhesion was evaluated using the heating temperature and test material shown in Table 2. In the present invention, A to J had a sliding distance of 80 m or more, whereas in Comparative Examples K to Q, adhesion occurred at a sliding distance of 30 m or less.
[0018]
[Example 3]
In the same testing machine as in Examples 1 and 2, the radius (R) of the test material was increased to 30 mm, the load applied by the pressure roll was increased to 1000 kgf, the heating temperature was 700 ° C., and the sliding distance was 100 m. Table 3 shows the test conditions and results. In the present invention, A to F did not cause film peeling and adhesion, and in Comparative Examples G and I, film peeling occurred and adhesion occurred, and H and J produced adhesion.
[0019]
[Example 4]
A 100 mm square square blank with a 25 mm diameter circular hole in the center of the blank by punching with a clearance of 10% using a 3.2 mm thick 780 MPa class hot rolled high strength steel sheet is shown schematically in FIG. Molding was performed using the mold shown in Fig. 1. The diameter of the cylindrical punch was 50 mm, and the stretch flange ratio was 100% (= (d-d0) / d0, d0: diameter of the hole in the initial blank, d: hole diameter after molding). The wrinkle pressing force (BHF) was 100 kN. Immediately before forming, the steel plate was heated with a high-frequency heating device to 700 ° C., punches shown in Table 4 were produced, and 10,000 pieces were continuously formed. In the present invention, A, the hard coating did not disappear due to peeling or abrasion, and no adhesion or mold galling occurred, but in the comparative example B, the hard coating disappeared after 2000 pieces, and the adhesion did not occur. Occurred and type galling occurred.
The present invention can be applied not only to hot or hot plate press forming, but also to cold plate press forming.
[0020]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
【The invention's effect】
As described above, the present invention enables warm or hot plate pressing. As a result, it is possible to apply a high-strength steel sheet to the automobile part, and it is possible to improve the collision safety and reduce the weight of the automobile. Moreover, it is easy to apply the high-strength steel sheet to automobile parts, and it is extremely effective for expanding the application of the high-strength steel sheet.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a layer structure of the present invention.
FIG. 2 is a schematic diagram showing the thickness of a CrN layer in which CrN and oxygen are dissolved.
FIG. 3 is a schematic diagram showing a test method.
FIG. 4 is a schematic view showing a molding method.
Claims (3)
１≦Ｒｚ≦２（ｔa ＋ｔb ）／３ （１）
（ｔａ：ＣｒＮ層の厚さ，ｔｂ：酸素を固溶させたＣｒＮ層の厚さ，単位はμｍ） 3. The mold for hot plate material press molding according to claim 1, wherein Rz of the mold base including the nitrided layer is adjusted according to the formula (1).
1≤Rz≤2 (ta + tb) / 3 (1)
(Ta: thickness of CrN layer, tb: thickness of CrN layer in which oxygen is dissolved, unit is μm)
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| EP1918421B1 (en) | 2006-09-27 | 2017-03-15 | Hitachi Metals, Ltd. | Hard-material-coated member excellent in durability |
| JP6162217B2 (en) * | 2012-04-16 | 2017-07-12 | マグナ インターナショナル インコーポレイテッド | Laser support tool production and repair method |
| JP6198244B2 (en) * | 2014-08-21 | 2017-09-20 | 株式会社神戸製鋼所 | Evaluation method of mold resistance |
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