JPH08104972A - Gas nitriding method of steel die for extrusion molding of aluminum - Google Patents
Gas nitriding method of steel die for extrusion molding of aluminumInfo
- Publication number
- JPH08104972A JPH08104972A JP26311194A JP26311194A JPH08104972A JP H08104972 A JPH08104972 A JP H08104972A JP 26311194 A JP26311194 A JP 26311194A JP 26311194 A JP26311194 A JP 26311194A JP H08104972 A JPH08104972 A JP H08104972A
- Authority
- JP
- Japan
- Prior art keywords
- nitriding
- steel die
- vinyl chloride
- chloride resin
- gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、アルミ押出し用ダイス
等の鋼製ダイスの表面に均質な硬質層をガス窒化処理で
形成する方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a uniform hard layer on a surface of a steel die such as an aluminum extrusion die by a gas nitriding treatment.
【０００２】[0002]
【従来の技術】安定な窒化物を形成するＣｒ，Ｍｏ等の
合金元素を含む鋼材は、窒化処理によって著しく硬化す
る。鋼材表面に形成された窒化層は、ビッカース硬さで
１００〜１３００に達し、耐摩耗性に富み、高温硬さが
高く、再加熱によっても硬さの低下が少ない。このよう
なことから、アルミの押出し等に使用される熱間加工用
ダイスには、Ｃｒを含む熱間工具鋼を使用し、窒化処理
によって表面硬化させている。窒化処理には、塩浴窒
化，ガス窒化等がある。塩浴窒化は、短時間の処理で窒
化層が形成され、しかも低コストである。しかし、処理
温度が５５０〜５７０℃と高く、環境に悪影響を与える
シアン系の塩浴を使用することから、ガス窒化が主流と
なってきている。2. Description of the Related Art Steel materials containing alloy elements such as Cr and Mo that form stable nitrides are significantly hardened by nitriding. The nitrided layer formed on the surface of the steel material reaches a Vickers hardness of 100 to 1300, is rich in wear resistance, has high high-temperature hardness, and has little decrease in hardness due to reheating. For this reason, a hot working steel containing Cr is used for a hot working die used for extruding aluminum or the like, and the surface is hardened by nitriding. Examples of the nitriding treatment include salt bath nitriding and gas nitriding. In the salt bath nitriding, a nitride layer is formed in a short time and the cost is low. However, gas nitriding has become the mainstream because the treatment temperature is as high as 550 to 570 ° C. and a cyan salt bath that adversely affects the environment is used.
【０００３】ガス窒化では、アンモニアの気流中で鋼材
を５００〜５７０℃に１０〜１００時間加熱した後、徐
冷する。アンモニアは高温域で分解し、反応性の強い発
生基のＮ及びＨとなり、Ｆｅ，Ｃｒ等の金属元素と化合
して窒化物を作り、硬質の窒化層となる。処理温度が５
７０℃以下であることから母材の損耗が少なく、焼入れ
の必要がないため処理後の鋼材に変形が少ない。ガス窒
化処理された鋼材表面の硬化層は、最表面に数μｍ程度
のＦｅ2 Ｎ相を主成分とする白層が形成されている。白
層は、耐食性にも優れているが、比較的脆く、厚く成長
したものでは外力が加わったときに割れや剥離を起こし
易い。白層の割れや剥離は、白層の厚みを小さくするこ
とにより抑制される。白層を薄く成長させる方法として
は、通常のガス窒化を短時間で行う第１段階に続いて高
温，高ＮＨ3 解離度で窒化する２段窒化が採用されてい
る。In gas nitriding, a steel material is heated in an air stream of ammonia at 500 to 570 ° C. for 10 to 100 hours and then gradually cooled. Ammonia decomposes in a high temperature region to become N and H which are highly reactive generating groups, and combines with metal elements such as Fe and Cr to form a nitride, which forms a hard nitride layer. Processing temperature is 5
Since the temperature is 70 ° C. or less, the base material is less worn, and the steel material after treatment is not deformed because quenching is not necessary. The hardened layer on the surface of the steel material which has been subjected to the gas nitriding treatment has a white layer containing Fe 2 N phase as a main component and having a thickness of several μm on the outermost surface. The white layer is also excellent in corrosion resistance, but is relatively brittle, and if it grows thick, it tends to crack or peel when an external force is applied. Cracking and peeling of the white layer are suppressed by reducing the thickness of the white layer. As a method for growing the white layer thinly, a two-stage nitriding method is employed, in which the first step of performing normal gas nitriding in a short time is followed by nitriding with high temperature and high NH 3 dissociation degree.
【０００４】しかし、ガス窒化は、塩浴窒化に比較して
処理時間が長く、窒化処理層が浅い欠点がある。また、
雰囲気中のＮと結合して硬質化合物となるＣｒ，Ａｌ，
Ｍｏ，Ｖ等を含む窒化用鋼は、窒化処理前の状態で比較
的強固な酸化皮膜が表面に形成されている。酸化皮膜
は、母材表面にＮが侵入することを抑制し、硬質窒化層
を浅くするばかりでなく、酸化皮膜で覆われていない部
分との間で窒化反応の難易度に相違が生じる。その結
果、鋼材表面に形成された窒化層が不均質になり、製品
の品質安定性が低下する。表面の酸化皮膜は、鋼材表面
に反応性の高いハロゲンガスを接触させることにより除
去される。たとえば、特公昭４５−３９９２５号公報，
特公昭４５−２５９６６号公報等で紹介されているよう
に、塩化ビニル樹脂（ＣＨ2 ＣＨＣｌ）nの分解生成ガ
スで処理するとき、鋼材表面がクリーニングされる。However, the gas nitriding has a drawback that the treatment time is long and the nitriding layer is shallow as compared with the salt bath nitriding. Also,
Cr, Al, which becomes a hard compound by combining with N in the atmosphere,
The nitriding steel containing Mo, V, etc. has a relatively strong oxide film formed on the surface before nitriding. The oxide film not only prevents N from penetrating into the surface of the base material to make the hard nitride layer shallow, but also causes a difference in the degree of difficulty of the nitriding reaction with a portion not covered with the oxide film. As a result, the nitrided layer formed on the surface of the steel material becomes inhomogeneous and the quality stability of the product deteriorates. The oxide film on the surface is removed by bringing a highly reactive halogen gas into contact with the surface of the steel material. For example, JP-B-45-39925,
As described in JP-B-45-25966, the steel material surface is cleaned when treated with a decomposition product gas of vinyl chloride resin (CH 2 CHCl) n .
【０００５】[0005]
【発明が解決しようとする課題】アルミニウム材の押出
し加工に使用される鋼製ダイスは、押出し形材の目標形
状に対応したスリットが形成されている。スリットを区
画するベアリング面は、押出し中に最も過酷な環境に曝
され、損耗の激しい箇所である。従来法に従って、樹脂
の分解生成ガスでベアリング面をクリーニングすると、
幅狭のスリットにあっては十分な量の分解生成ガスが侵
入せず、分解生成ガスとの接触反応が十分に行われな
い。その結果、ベアリング面が十分にクリーニングされ
ず、必要とする高度をもった硬質層がベアリング面に形
成されない。本発明は、このような問題を解消すべく案
出されたものであり、スリットとなる空間部に塩化ビニ
ル樹脂を詰め込むことにより、ベアリング壁面を優先的
にクリーニングし、高度が高く且つ均質な窒化層をベア
リング面に形成し、耐久性に優れた押出し加工用鋼製ダ
イスを得ることを目的とする。A steel die used for extrusion processing of aluminum material is provided with slits corresponding to the target shape of the extruded shape material. The bearing surface that divides the slit is exposed to the harshest environment during extrusion and is a point of high wear. According to the conventional method, if the bearing surface is cleaned with the decomposition product gas of the resin,
In the narrow slit, a sufficient amount of the decomposition product gas does not enter, and the contact reaction with the decomposition product gas is not sufficiently performed. As a result, the bearing surface is not sufficiently cleaned and a hard layer having the required height is not formed on the bearing surface. The present invention has been devised to solve such a problem, and by filling a vinyl chloride resin in the space that becomes the slit, the bearing wall surface is preferentially cleaned, and high-level and uniform nitriding is performed. The purpose is to form a layer on the bearing surface and obtain a steel die for extrusion with excellent durability.
【０００６】[0006]
【課題を解決するための手段】本発明のガス窒化方法
は、その目的を達成するため、狭隘なスリットが形成さ
れた鋼製ダイス素材を工具鋼で作成し、スリットに塩化
ビニル樹脂を充填した鋼製ダイス素材を密閉容器に収容
し、４００℃以上の高温に保持して塩化ビニル樹脂を熱
分解させ、分解生成ガスでスリット内壁面をクリーニン
グした後、密閉容器を窒化性雰囲気に置換して窒化処理
することを特徴とする。塩化ビニル樹脂としては、熱分
解後に残渣を残さないものが好ましく、包装用ポリ塩化
ビニルフィルム又はシート、或いは塩化ビニル樹脂系接
着剤等の１種または２種以上が使用される。この塩化ビ
ニル樹脂をスリットに充填し４００〜５００℃に３０〜
６０分間保持するとき、塩化ビニル樹脂の熱分解によっ
てハロゲンやハロゲン水素化物が発生し、スリットの内
壁面がクリーニングされる。クリーニング後、密閉容器
の雰囲気をＮＨ3 ＋Ｎ2 等に置換し、５００〜５７０℃
に３〜１２時間加熱する。このとき、スリット内壁面が
クリーニングされた活性状態にあるため、窒化反応が迅
速に且つ均一に進行し、良質の硬質窒化膜が形成され
る。In order to achieve the object, the gas nitriding method of the present invention is made by making tool steel into a steel die material having a narrow slit, and filling the slit with vinyl chloride resin. The steel die material is housed in a closed container, and the vinyl chloride resin is pyrolyzed by maintaining it at a high temperature of 400 ° C. or higher, and after cleaning the inner wall surface of the slit with a decomposition product gas, the closed container is replaced with a nitriding atmosphere. Characterized by nitriding. As the vinyl chloride resin, one that does not leave a residue after thermal decomposition is preferable, and one kind or two or more kinds of polyvinyl chloride film or sheet for packaging, vinyl chloride resin adhesive or the like is used. Fill the slit with this vinyl chloride resin, and heat it to 400-500 ° C for 30-
When it is held for 60 minutes, halogen or halogen hydride is generated by thermal decomposition of the vinyl chloride resin, and the inner wall surface of the slit is cleaned. After cleaning, the atmosphere in the closed container is replaced with NH 3 + N 2 etc., and 500 to 570 ° C.
Heat for 3-12 hours. At this time, since the inner wall surface of the slit is in the cleaned and activated state, the nitriding reaction proceeds rapidly and uniformly, and a high-quality hard nitride film is formed.
【０００７】[0007]
【作用】塩化ビニル樹脂を高温加熱すると、２００℃付
近で分解反応が開始し、ハロゲンガス，ハロゲン水素化
物等のガスが発生する。しかし、塩化ビニル樹脂で鋼製
ダイス素材を単にラッピングして加熱するだけでは、狭
隘なスリットに持ち込まれるハロゲンガス，ハロゲン水
素化物等の分圧が不足し、所期のクリーニング作用が得
られない。この点、本発明にあっては、スリットに塩化
ビニル樹脂を詰め込んでいるので、分解生成ガスがスリ
ット内に暫定的に充満し、クリーニング作用に必要な分
圧が得られる。また、分解反応終了後にはスリット内に
分解残渣が残らないため、後続する窒化処理工程に悪影
響を与えることがない。したがって、雰囲気を窒化性と
することにより、分解生成ガスによってクリーニングさ
れたベアリング面が均一に窒化処理される。その結果、
ベアリング面に均質な窒化膜が形成され、品質が高位に
安定した押出し加工用鋼製ダイスが得られる。塩化ビニ
ル樹脂の熱分解により塩化水素を発生させるため、２０
０℃以上の温度で塩化ビニル樹脂を加熱する必要があ
る。しかし、５００℃を越える温度に加熱すると、ＮＨ
3 が分解し易くなる。したがって、塩化ビニル樹脂の熱
分解は、ＮＨ3 の導入を伴う窒化の前処理として５００
℃以下で行う必要がある。When the vinyl chloride resin is heated at a high temperature, the decomposition reaction starts at around 200 ° C. and a gas such as a halogen gas or a halogen hydride is generated. However, merely lapping the steel die material with vinyl chloride resin and heating it does not provide the desired cleaning action because the partial pressure of halogen gas, halogen hydride, etc. brought into the narrow slit is insufficient. In this respect, in the present invention, since the slit is filled with the vinyl chloride resin, the decomposition product gas temporarily fills the slit, and the partial pressure required for the cleaning action is obtained. Further, after the decomposition reaction is completed, no decomposition residue remains in the slits, so that the subsequent nitriding treatment step is not adversely affected. Therefore, by making the atmosphere nitriding, the bearing surface cleaned by the decomposition product gas is uniformly nitrided. as a result,
A homogeneous nitride film is formed on the bearing surface, and a steel die for extrusion processing with high quality and stability can be obtained. In order to generate hydrogen chloride by the thermal decomposition of vinyl chloride resin, 20
It is necessary to heat the vinyl chloride resin at a temperature of 0 ° C or higher. However, when heated above 500 ° C, NH
3 becomes easy to disassemble. Therefore, the thermal decomposition of vinyl chloride resin is carried out as a pretreatment for nitriding with the introduction of NH 3 as much as 500
It is necessary to do it below ℃.
【０００８】[0008]
【実施例】工具鋼ＳＫＤ６１を押出し加工用ダイス形状
に成形し、スリット厚みが０．３ｍｍ，０．５ｍｍ及び
１ｍｍで、ベアリング長さが３０ｍｍのスリットを形成
した。シート状の塩化ビニル樹脂を細かく裁断したもの
をスリットに詰め込み、密閉容器に装入した。密閉容器
内で工具鋼を５００℃に４０分間加熱することによって
塩化ビニル樹脂を熱分解し、分解生成ガスでスリットの
内壁面をクリーニングした。加熱後のスリットには、分
解残渣は全く見られなかった。次いで、容器内の雰囲気
をＮＨ3 ＋Ｎ2 の混合ガスに代え、昇温速度１００℃／
時で５５０℃まで昇温し、５５０℃に６時間保持した
後、放冷した。常温まで降温した段階で、窒化処理され
た工具鋼を密閉容器から取り出した。EXAMPLE Tool steel SKD61 was formed into an extrusion die shape, and slits having slit thicknesses of 0.3 mm, 0.5 mm and 1 mm and a bearing length of 30 mm were formed. A sheet-shaped vinyl chloride resin finely cut was packed in a slit and placed in a closed container. The vinyl chloride resin was thermally decomposed by heating the tool steel to 500 ° C. for 40 minutes in the closed container, and the inner wall surface of the slit was cleaned with the decomposition product gas. No decomposition residue was found in the slit after heating. Next, the atmosphere in the container was changed to a mixed gas of NH 3 + N 2 , and the temperature rising rate was 100 ° C. /
After that, the temperature was raised to 550 ° C., the temperature was kept at 550 ° C. for 6 hours, and then the mixture was allowed to cool. When the temperature was lowered to room temperature, the nitriding-treated tool steel was taken out from the closed container.
【０００９】窒化処理された工具鋼について、図１に示
すようにスリットの長さ方向及びベアリング面の深さ方
向に関して複数の測定点でベアリング面の硬度を測定し
た。スリット厚み０．３ｍｍのベアリング面では、図２
に示すように、ベアリング面の長手方向に関してほぼ均
一の硬度分布になっていた。また、スリット厚みが０．
５ｍｍ及び１ｍｍのものでも、同様に均一な硬度分布を
もつベアリング面が窒化処理後に得られた。比較のた
め、同じスリット厚み０．３ｍｍを持つ鋼製ダイスを、
スリットに塩化ビニル樹脂を詰め込むことなく同一条件
下でガス窒化した。窒化処理後のベアリング面は、図３
に示すようにスリット両側に位置するベアリング面の硬
度が低下していた。この対比から明らかなように、スリ
ットに充填した塩化ビニル樹脂を熱分解させ、分解生成
ガスによってベアリング面が均質にクリーニングされ、
後続する窒化処理工程で硬度分布が一定した窒化膜が生
成することが判る。窒化処理された鋼製ダイスは、部分
的に硬度が不足することなくベアリング面が均一に硬質
化されているため、品質が高位に安定し、耐久性に優れ
たものとなる。With respect to the tool steel subjected to the nitriding treatment, the hardness of the bearing surface was measured at a plurality of measurement points in the length direction of the slit and the depth direction of the bearing surface as shown in FIG. In the bearing surface with a slit thickness of 0.3 mm,
As shown in, the hardness distribution was almost uniform in the longitudinal direction of the bearing surface. The slit thickness is 0.
Even with 5 mm and 1 mm, bearing surfaces having a uniform hardness distribution were obtained after nitriding. For comparison, a steel die with the same slit thickness of 0.3 mm,
Gas nitriding was performed under the same conditions without filling the slit with vinyl chloride resin. The bearing surface after nitriding is shown in Fig. 3.
As shown in, the hardness of the bearing surfaces located on both sides of the slit was reduced. As is clear from this comparison, the vinyl chloride resin filled in the slits is thermally decomposed, and the decomposition surface gas uniformly cleans the bearing surface.
It can be seen that a nitride film having a uniform hardness distribution is formed in the subsequent nitriding process. Since the bearing surface of the nitriding steel die is uniformly hardened without a partial lack of hardness, the quality is stable at a high level and the durability is excellent.
【００１０】[0010]
【発明の効果】以上に説明したように、本発明において
は、狭隘な間隙をもつスリットに塩化ビニル樹脂を充填
した状態で加熱することにより、塩化ビニル樹脂の熱分
解で生じたハロゲンやハロゲン水素化物でベアリング面
をクリーニングした後、窒化処理によって均質な硬質膜
を形成している。この方法によるとき、クリーニング不
足等に起因した窒化不良な部分が生じることなく、均質
な硬度分布にベアリング面を硬質化することが可能とな
る。そのため、窒化処理された鋼製ダイスは、高位に安
定した品質をもち、耐久性に優れたダイスとしてアルミ
ニウム材料の熱間押出しに使用される。また、この鋼製
ダイスを使用して熱間押出しするとき、ベアリング面の
硬度が高いことから、長期間に渡って形状精度に優れた
押出し成形品が得られる。As described above, in the present invention, the halogen or halogen hydrogen generated by the thermal decomposition of the vinyl chloride resin is heated by heating the slit having the narrow gap with the vinyl chloride resin. After cleaning the bearing surface with a compound, a uniform hard film is formed by nitriding. According to this method, it is possible to harden the bearing surface with a uniform hardness distribution without causing a defective nitriding portion due to insufficient cleaning or the like. Therefore, the nitriding steel die has a highly stable quality and is used for hot extrusion of an aluminum material as a die having excellent durability. Further, when hot extruding using this steel die, the hardness of the bearing surface is high, so that an extruded product having excellent shape accuracy over a long period of time can be obtained.
【図１】 鋼製ダイスの硬度を測定した測定点[Fig. 1] Measurement points for measuring the hardness of steel dies
【図２】 本発明実施例で窒化処理された鋼製ダイスの
硬度分布FIG. 2 is a hardness distribution of a steel die subjected to a nitriding treatment in an example of the present invention.
【図３】 塩化ビニル樹脂を使用しない比較例で窒化処
理された鋼製ダイスの硬度分布[Fig. 3] Hardness distribution of steel dies nitrided in a comparative example not using vinyl chloride resin
Claims (5)
素材を工具鋼で作成し、スリットに塩化ビニル樹脂を充
填した鋼製ダイス素材を密閉容器に収容し、４００℃以
上の高温に保持して塩化ビニル樹脂を熱分解させ、分解
生成ガスでスリット内壁面をクリーニングした後、密閉
容器を窒化性雰囲気に置換して窒化処理するアルミニウ
ム材押出し加工用鋼製ダイスのガス窒化方法。1. A steel die material in which a narrow slit is formed is made of tool steel, and a steel die material in which a slit is filled with vinyl chloride resin is housed in a closed container and kept at a high temperature of 400 ° C. or higher. A method of gas nitriding a steel die for extruding aluminum material, in which vinyl chloride resin is pyrolyzed and the inner wall surface of the slit is cleaned with a decomposition product gas, and then the airtight container is replaced with a nitriding atmosphere for nitriding.
ニルフィルム又はシート，或いは塩化ビニル樹脂系接着
剤を使用する請求項１記載のガス窒化方法。2. The gas nitriding method according to claim 1, wherein a polyvinyl chloride film or sheet for packaging or a vinyl chloride resin adhesive is used as the vinyl chloride resin.
することにより、塩化ビニル樹脂を熱分解させる請求項
１記載のガス窒化方法。3. The gas nitriding method according to claim 1, wherein the vinyl chloride resin is thermally decomposed by holding it at 400 to 500 ° C. for 30 to 60 minutes.
スである請求項１〜３の何れかに記載のガス窒化方法。4. The gas nitriding method according to claim 1, wherein the nitriding atmosphere is a mixed gas of NH 3 and N 2 .
０〜５７０℃に３〜１２時間加熱する請求項１〜４の何
れかに記載のガス窒化方法。5. A steel die material is made of 50 in a nitriding atmosphere.
The gas nitriding method according to claim 1, wherein heating is performed at 0 to 570 ° C. for 3 to 12 hours.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26311194A JPH08104972A (en) | 1994-10-03 | 1994-10-03 | Gas nitriding method of steel die for extrusion molding of aluminum |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26311194A JPH08104972A (en) | 1994-10-03 | 1994-10-03 | Gas nitriding method of steel die for extrusion molding of aluminum |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH08104972A true JPH08104972A (en) | 1996-04-23 |
Family
ID=17384986
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26311194A Pending JPH08104972A (en) | 1994-10-03 | 1994-10-03 | Gas nitriding method of steel die for extrusion molding of aluminum |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH08104972A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1030164A (en) * | 1996-07-18 | 1998-02-03 | Nippon Light Metal Co Ltd | Treatment for nitriding die for aluminum extrusion and die for aluminum extrusion |
| JP2005256165A (en) * | 2004-02-09 | 2005-09-22 | Honda Motor Co Ltd | Passive film removal method |
| US8414710B2 (en) | 2004-02-04 | 2013-04-09 | Honda Motor Co., Ltd. | Method for surface treatment of metal material |
-
1994
- 1994-10-03 JP JP26311194A patent/JPH08104972A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1030164A (en) * | 1996-07-18 | 1998-02-03 | Nippon Light Metal Co Ltd | Treatment for nitriding die for aluminum extrusion and die for aluminum extrusion |
| US8414710B2 (en) | 2004-02-04 | 2013-04-09 | Honda Motor Co., Ltd. | Method for surface treatment of metal material |
| JP2005256165A (en) * | 2004-02-09 | 2005-09-22 | Honda Motor Co Ltd | Passive film removal method |
| JP4494996B2 (en) * | 2004-02-09 | 2010-06-30 | 本田技研工業株式会社 | Passivation membrane removal method |
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