JPS6347773B2 - - Google Patents
Info
- Publication number
- JPS6347773B2 JPS6347773B2 JP15564782A JP15564782A JPS6347773B2 JP S6347773 B2 JPS6347773 B2 JP S6347773B2 JP 15564782 A JP15564782 A JP 15564782A JP 15564782 A JP15564782 A JP 15564782A JP S6347773 B2 JPS6347773 B2 JP S6347773B2
- Authority
- JP
- Japan
- Prior art keywords
- pearlite
- cast iron
- weight
- graphite cast
- spheroidal graphite
- 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.)
- Expired
Links
- 229910001562 pearlite Inorganic materials 0.000 claims description 39
- 229910001141 Ductile iron Inorganic materials 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 19
- 238000001816 cooling Methods 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 13
- 229910052799 carbon Inorganic materials 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 10
- 238000010791 quenching Methods 0.000 claims description 10
- 230000000171 quenching effect Effects 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 239000011159 matrix material Substances 0.000 description 10
- 239000000463 material Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 6
- 229910000859 α-Fe Inorganic materials 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000002344 surface layer Substances 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 150000001247 metal acetylides Chemical class 0.000 description 3
- 229920006395 saturated elastomer Polymers 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 238000005279 austempering Methods 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005469 granulation Methods 0.000 description 2
- 230000003179 granulation Effects 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000005480 shot peening Methods 0.000 description 2
- 238000009827 uniform distribution Methods 0.000 description 2
- 238000000137 annealing Methods 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005188 flotation Methods 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D5/00—Heat treatments of cast-iron
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Articles (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Description
本発明は、焼入性、加工性の両方に優れた球状
黒鉛鋳鉄の製造方法に関するものである。
従来より、球状黒鉛鋳鉄部品の熱処理方法は
種々提案されており、特開昭56−116853号公報に
は、Mo0.03〜0.09重量％、Cu0.3〜1.5重量％を含
有する球状黒鉛鋳鉄を焼鈍して組織をフエライト
化し、その後オーステンパー処理し、シヨツトピ
ーニングする方法が、また特開昭57−19320号公
報には、球状黒鉛鋳鉄を焼準してパーライト化
し、その後にオーステンパー処理する方法が開示
されている。
ところで、第１図に示すように、基地組織をフ
エライト化した球状黒鉛鋳鉄Ａは、熱処理に際し
て所定の硬度に達するまでの時間、即ちオーステ
ナイト化時間に長時間を要し、焼入性が悪い問題
がある。一方、パーライト化した球状黒鉛鋳鉄Ｂ
は、オーステナイト化時間が短かく焼入性が良好
で、高周波等による迅速加熱でも十分なカーボン
濃度が得られ、硬さ深度も任意に選定でき、表面
層に疲労強度に有利な圧縮応力を与えることがで
きる利点がある。
しかしながら、第２図に示すように、加工性と
いる面からみると、パーライト地の球状黒鉛鋳鉄
Ｂでは、刃具摩耗量がフエライト地の球状黒鉛鋳
鉄Ａのものに比して著しく高く、加工性において
著しく劣る問題がある。
本発明は、かかる問題に鑑みてなされたもので
あつて、焼入性、加工性のいずれにも優れ、した
がつて高疲労強度、高耐摩耗性を有する球状黒鉛
鋳鉄部品の製造方法を提供することを目的として
いる。
このため、本発明においては、C2.6〜4.0重量
％、Si1.5〜3.5重量％、Mn0.1〜1.0重量％、P0.15
重量％以下、S0.03重量％以下、Cu0.3〜1.5重量
％又はSn0.03〜0.16重量％、Mo0.03〜0.1重量％、
Mg0.025〜0.1重量％、Fe残部からなり微細パー
ライト基地組織の球状黒鉛鋳鉄を、基地中の粒状
パーライト面積率35〜65％でかつ基地炭素量0.3
〜0.65重量％となるように、850〜1000℃の温度
下で0.5時間以上加熱した後空冷し、次いで670〜
760℃の温度下で0.5〜8.0時間加熱した後空冷又
は水冷して粒状パーライト化した後、加工し、次
いで表面硬化焼入れするようにしたことを基本的
な特徴としている。
ここで、基地炭素数0.3〜0.65重量％とは、ト
ータル炭素量から黒鉛量を減算した量をいい、フ
エライトに固溶した炭素とセメンタイト中の炭素
との合計量が0.3〜0.65重量％であることを意味
する。
この場合、球状黒鉛鋳鉄の化学組成の限定理由
は以下の通りである。
Ｃ：2.6％以下ではSiとの飽和度の関係で鋳造
欠陥特に引け巣、チルを発生する。
4.0％ではSiと飽和度の関係でざく巣、フ
ローテイシヨ等の欠陥を招く。
Si：1.5％以下ではＣとの飽和度の関係で鋳造
性（流動性）を阻害する。
3.5％以上ではＣとの飽和度の関係で流動
性は向上するがざく巣、フローテイシヨンを
招く。
Mn：Mnは必然的に溶解材料により入る量とし
て0.1％以上に、又、Mnはパーライト化の強
い元素と同時に1.0％以上では靭性を阻害す
る。
Ｐ：0.15％以上では多量のステダイドを形成
し、靭性を阻害する。
Ｓ：0.03％以上では多量のMgを要し、結果的
に酸化物等の介在物を多く発生する。
Cu：0.3％以下では焼鈍時、パーライトが分解
し基地中に均一に分布した粒状パーライトが
得られない。又、Moとの併用効果である疲
労強度、耐面圧強度特性が得られない。
1.5％以上ではCu元素による前述の効果は
飽和し、コストアツプとなる。
Sn：SnはCuの代替え元素として使用するもの
で強力なパーライト化元素である。
0.03％以下では基地中に均一に分布した粒
状パーライトが得られない。
0.16％以上では粒界に析出し、結果、強度
特性を低下する。又、効果も飽和しコストア
ツプになる。
Mo：均一に分布した粒状パーライトを得る手段
として、Moが効果的である。Moは基地中
で（Fe3・Mo）Ｃの状態で存在する。従つ
て、Cu、Snなどで基地をパーライト化され
ている部分には、Moが必ず均一に存在する
結果となる。このMoはパーライトの粒状化
において核的な役目と同時に、熱によるパー
ライト（Fe3C）の分解抵抗を発揮し、基地
中に均一に分布した粒状パーライト地を形成
する。
この均一で、かつ35％以上の粒状パーライ
トを残留させるためには、少なくとも0.03％
以上のMoを必要とする。0.03％以下では、
ち密な粒状パーライトを分布させるだけの熱
分解抵抗力を発揮せず、不均一な分布の原
因、および35％以上の残留パーライトとする
ことができず、焼入れに必要な0.3％以上の
Ｃ固溶量の基地が達成出来ない。
また、0.03％以下ではCu併用による効果
（疲労強度特性、面圧強度、耐摩耗性）も得
られない。
0.1％以上では、ち密な粒状パーライトを
均一に得る効果は飽和すると同時に、コスト
アツプとなるばかりでなく、遊離した炭化物
を析出し、炭化物による疲労強度低下、粒状
パーライトの均一分布を組害し、焼入性を悪
化させる。さらには表面焼入れ後の組織にお
いて炭化物周辺に塊状の残留オーステナイト
を形成し、強度を劣化する原因となる。
Mg：Mgは溶湯の脱流、脱酸を行い黒鉛を球状
化させるための重要な元素である。
0.025％以下ではこの効果は不十分となり
球状化が行なわれなく靭性のある球状黒鉛鋳
鉄とし難い。
0.10％以上では球状化は十分行なわれる。
しかし脱硫、脱酸時に生成した硫化物、酸化
物（Mg系）が溶湯中に残留し、靭性低下を
起す。
本発明においては、上記化学組成を有する球状
黒鉛鋳鉄素材の組織調整を粒状パーライト化処理
によつて行ない、粒状パーライト化率35〜65％
で、かつ基地炭素量が0.3〜0.65％となるように
粒状パーライト化する。
表面硬化焼入れの場合、基地中のＣは少なくと
も0.3％以上固溶されていないと焼入れ不良を起
こす。
0.3％以上のＣ固溶量を得るためには基地中に
少なくとも35％以上の粒状パーライトを残留させ
る必要がある。同時に、焼ムラがなく、均一な焼
入れ組織を得るためには、基地に均一に粒状パー
ライトが分布していることが必須である。
基地炭素量が0.65％以上となると、パーライト
が均一に分散しなくなり、被削性（加工性）が低
下してしまう。
上記の基地炭素量0.3〜0.65％を得るためには、
粒状パーライト面積率を上記の如く35〜65％とす
る必要がある。
この粒状パーライト化処理は、良好な焼入性と
加工性（切削性）の両方を同時に付与するため行
なうもので、具体的には、850〜1000℃の温度下
で0.5時間以上加熱した後空冷し、次いで670〜
760℃の温度下で0.5〜8.0時間加熱した後、空冷
又は水冷（徐冷可能）する２段階の熱処理によつ
て行なうことができる。
上記第１段の熱処理は、チルの分解と同時に粒
状パーライト化するためであり、粒状パーライト
を均一に分布させるためには、空冷が必要で、徐
冷（炉冷）では均一分布は得られない。また、
850℃以下では、チルの分解が行なえず、1000℃
以上では結晶粒の粗大化を招くので好ましくな
い。そして、有効なチルの分解を行なうため、
0.5時間以上は加熱を続ける必要がある。加熱後
の冷却を徐冷で行なうと、オーステナイト化処理
において粒界に不純物を晶出し、脆化の原因とな
る。
第２段の熱処理は、粒状パーライト化率を35〜
65％にコントロールするために行なう。粒状パー
ライト35％以下では加工性は良好であるが、十分
な焼入性を得るにたる炭素濃度とするに長時間を
要することとなつて好ましくない。一方、65％以
上とする、逆の傾向、即ち焼入性は向上するが加
工性が悪化する傾向を示す。
温度条件として、670℃以下では粒状パーライ
ト化が困難となり、必要な粒状化を得るためには
長時間を要することとなつて好ましくない。ま
た、760℃以上では、急速に黒鉛化が進行し、35
％以上の粒状パーライトが得られない。処理時間
は、少なくとも0.5時間必要で、８時間以上とす
ることは、生産性が悪化してコストアツプを招来
する。冷却方法は、操業時間の短縮と基地中の粒
状パーライトの均一分布の目的で空冷又は水冷と
することが好ましい。
上記の粒状パーライト化処理の後は、処理した
球状黒鉛鋳鉄部品に対し、必要な形状加工等を行
なう。例えば、ギヤ類の場合には、ラツプ代、研
削代を残した状態までの加工（シエービング加
工）を行なう。
上記の加工後においては、表面硬化焼入れ（局
部焼入れ）を行なう。この表面硬化焼入れは、高
周波等により850〜1000℃の温度で３秒以上局部
加熱を行ない、しかる後、オイル、ソルト等で焼
入れし、所定温度まで冷却した後、電気炉に移動
し、電気炉内で60秒かそれ以上の時間の間、所定
の温度に維持し、その後空冷又は水冷により冷却
することにより行なう。
この焼入れは、少なくとも部品の表面下内部に
圧縮残留応力を発生させ、耐摩耗性を向上させる
ためのもので、表面層はベーナイト地又はマルテ
ンサイト地とし、これより内部を１次熱処理（粒
状パーライト化処理）による粒状パーライト地と
したことを特徴としている。
上記電気炉において維持すべき所定温度は、目
的とする部品の負荷に応じて選択する。高負荷の
ギヤ類やシヤフト類の場合には、220〜390℃の温
度範囲として、表面層をベーナイト地とし、低負
荷のギヤ類やシヤフト類では、130〜220℃の表面
範囲としてマルテンサイト地とする。
上記のように、球状黒鉛鋳鉄部品の基地組織を
粒状パーライト地とすれば、第１図にＣで示すよ
うに、オーステナイト化時間としては、パーライ
ト地Ｂに近い特性が得られるので良好な焼入性を
確保することができると同時に、第２図にＣで示
すように、フエライト地Ａとほぼ同じ良好な加工
性を得ることができる。
なお、上記本発明による１次、２次熱処理後に
あつては、応力集中部、例えばギヤ類の場合には
歯底部、シヤフト類ではコーナ部に、シヨツトピ
ーニング又はロール加工により高い圧縮残留応力
を発生させ、疲労強度特性をより一層向上させる
ようにしてもよい。
次に、本発明の実施例を示す。
実施例
The present invention relates to a method for manufacturing spheroidal graphite cast iron that is excellent in both hardenability and workability. Various heat treatment methods for spheroidal graphite cast iron parts have been proposed in the past, and Japanese Patent Application Laid-Open No. 116853/1985 describes a method for heat treatment of spheroidal graphite cast iron parts containing 0.03 to 0.09% by weight of Mo and 0.3 to 1.5% by weight of Cu. There is a method in which the structure is annealed to ferrite, then austempered, and then shot peened, and JP-A-57-19320 discloses a method in which spheroidal graphite cast iron is normalized to become pearlite, and then austempered. A method is disclosed. By the way, as shown in Fig. 1, spheroidal graphite cast iron A with a ferrite base structure has the problem of poor hardenability because it takes a long time to reach a predetermined hardness during heat treatment, that is, it takes a long time to austenite. There is. On the other hand, pearlitized spheroidal graphite cast iron B
has a short austenitization time and good hardenability, a sufficient carbon concentration can be obtained even with rapid heating using high frequency, etc., the hardness depth can be arbitrarily selected, and it imparts compressive stress to the surface layer that is advantageous for fatigue strength. There is an advantage that it can be done. However, as shown in Figure 2, from the perspective of workability, the amount of tool wear in pearlite-based spheroidal graphite cast iron B is significantly higher than that of ferrite-based spheroidal graphite cast iron A; There is a problem in that it is significantly inferior. The present invention has been made in view of these problems, and provides a method for manufacturing spheroidal graphite cast iron parts that have excellent hardenability and workability, and therefore have high fatigue strength and high wear resistance. It is intended to. Therefore, in the present invention, C2.6-4.0% by weight, Si1.5-3.5% by weight, Mn0.1-1.0% by weight, P0.15
Weight % or less, S 0.03 weight % or less, Cu 0.3 to 1.5 weight % or Sn 0.03 to 0.16 weight %, Mo 0.03 to 0.1 weight %,
Spheroidal graphite cast iron with a fine pearlite matrix structure consisting of 0.025 to 0.1% by weight of Mg and the remainder of Fe is used, with an area ratio of granular pearlite in the matrix of 35 to 65% and a base carbon content of 0.3.
After heating for 0.5 hours or more at a temperature of 850 to 1000℃ so that the concentration is ~0.65% by weight, it is then air cooled to a temperature of 670 to 1000℃.
The basic feature is that it is heated at a temperature of 760°C for 0.5 to 8.0 hours, then cooled in air or water to form granular pearlite, processed, and then surface hardened and quenched. Here, the base carbon number of 0.3 to 0.65% by weight refers to the amount obtained by subtracting the amount of graphite from the total carbon amount, and the total amount of carbon dissolved in ferrite and carbon in cementite is 0.3 to 0.65% by weight. It means that. In this case, the reason for limiting the chemical composition of the spheroidal graphite cast iron is as follows. C: Below 2.6%, casting defects, especially shrinkage cavities and chills, occur due to the saturation level with Si. At 4.0%, defects such as cavities and floatation occur due to the relationship between Si and saturation. Si: At 1.5% or less, castability (fluidity) is inhibited due to the saturation degree with C. If it exceeds 3.5%, the fluidity will improve due to the saturation level with C, but this will lead to stagnation and flotation. Mn: Mn inevitably enters the melted material in an amount of 0.1% or more, and Mn is a strong pearlitizing element and inhibits toughness if it exceeds 1.0%. P: If it is 0.15% or more, a large amount of stedide is formed and the toughness is impaired. When S: 0.03% or more, a large amount of Mg is required, resulting in the generation of many inclusions such as oxides. If Cu: 0.3% or less, pearlite decomposes during annealing and granular pearlite uniformly distributed in the matrix cannot be obtained. In addition, the fatigue strength and surface pressure resistance properties that are the effects of combined use with Mo cannot be obtained. If the content exceeds 1.5%, the above-mentioned effect of the Cu element will be saturated and the cost will increase. Sn: Sn is used as a replacement element for Cu and is a strong pearlitizing element. If it is less than 0.03%, granular pearlite uniformly distributed in the matrix cannot be obtained. If it exceeds 0.16%, it will precipitate at grain boundaries, resulting in a decrease in strength properties. Moreover, the effect becomes saturated and the cost increases. Mo: Mo is effective as a means to obtain uniformly distributed granular pearlite. Mo exists in the (Fe 3 Mo) C state in the base. Therefore, in the part where the base is pearlitized with Cu, Sn, etc., Mo is always uniformly present. This Mo plays a core role in the granulation of pearlite, and at the same time exerts resistance to decomposition of pearlite (Fe 3 C) due to heat, forming a granular pearlite base uniformly distributed throughout the matrix. In order to maintain this uniform granular pearlite of 35% or more, at least 0.03%
or more Mo is required. Below 0.03%,
It does not exhibit enough thermal decomposition resistance to distribute dense granular pearlite, which causes uneven distribution, and it is not possible to achieve a residual pearlite of 35% or more, and the C solid solution of 0.3% or more required for quenching. The amount of base cannot be achieved. Further, if Cu is less than 0.03%, the effects (fatigue strength characteristics, surface pressure strength, wear resistance) of Cu in combination cannot be obtained. If it exceeds 0.1%, the effect of uniformly obtaining dense granular pearlite will be saturated, and at the same time, the cost will not only increase, but also free carbides will precipitate, reducing the fatigue strength due to carbides, damaging the uniform distribution of granular pearlite, and reducing the hardness of quenching. make sex worse. Furthermore, in the structure after surface quenching, residual austenite is formed around the carbides, causing deterioration in strength. Mg: Mg is an important element for draining and deoxidizing the molten metal and making graphite spheroidal. If it is less than 0.025%, this effect will be insufficient and spheroidization will not occur, making it difficult to obtain tough spheroidal graphite cast iron. At 0.10% or more, spheroidization is sufficiently achieved.
However, sulfides and oxides (Mg-based) generated during desulfurization and deoxidation remain in the molten metal, causing a decrease in toughness. In the present invention, the structure of the spheroidal graphite cast iron material having the above chemical composition is adjusted by a granular pearlite treatment, and the granular pearlite conversion rate is 35 to 65%.
and the base carbon content is 0.3 to 0.65%. In the case of surface hardening and quenching, if at least 0.3% of C in the matrix is not dissolved as a solid solution, quenching defects will occur. In order to obtain a C solid solution content of 0.3% or more, it is necessary to leave at least 35% or more of granular pearlite in the matrix. At the same time, in order to obtain a uniform hardened structure without uneven heating, it is essential that granular pearlite be uniformly distributed in the matrix. If the base carbon content is 0.65% or more, pearlite will not be uniformly dispersed, and machinability (workability) will decrease. In order to obtain the above base carbon content of 0.3 to 0.65%,
The area ratio of granular pearlite needs to be 35 to 65% as mentioned above. This granular pearlite treatment is performed to simultaneously impart both good hardenability and workability (cutting ability). Specifically, it is heated at a temperature of 850 to 1000°C for 0.5 hours or more, then air cooled. and then 670～
The heat treatment can be carried out in two steps: heating at a temperature of 760° C. for 0.5 to 8.0 hours, and then cooling in air or water (slow cooling is possible). The first heat treatment described above is to simultaneously decompose the chill and turn it into granular pearlite.In order to uniformly distribute the granular pearlite, air cooling is necessary, and gradual cooling (furnace cooling) cannot achieve uniform distribution. . Also,
Chill cannot be decomposed at temperatures below 850℃, and at temperatures below 1000℃
The above is not preferable because it causes coarsening of crystal grains. In order to effectively decompose chill,
It is necessary to continue heating for 0.5 hours or more. If cooling after heating is performed slowly, impurities will crystallize at grain boundaries during austenitizing treatment, causing embrittlement. The second stage heat treatment increases the granular pearlite conversion rate to 35~
Performed to control to 65%. If the granular pearlite is less than 35%, the workability is good, but it is not preferable because it takes a long time to reach a carbon concentration sufficient to obtain sufficient hardenability. On the other hand, when it is set to 65% or more, the opposite tendency is shown, that is, the hardenability improves but the workability tends to deteriorate. As for the temperature condition, if it is below 670°C, it becomes difficult to form granular pearlite and it takes a long time to obtain the necessary granulation, which is not preferable. In addition, at temperatures above 760°C, graphitization progresses rapidly and 35
% or more of granular pearlite cannot be obtained. Processing time is required to be at least 0.5 hours, and if it is longer than 8 hours, productivity will deteriorate and costs will increase. The cooling method is preferably air cooling or water cooling for the purpose of shortening operating time and uniformly distributing granular pearlite in the base. After the above-mentioned granular pearlite treatment, the treated spheroidal graphite cast iron parts are subjected to necessary shape processing and the like. For example, in the case of gears, machining (shaving) is performed to a state where lapping and grinding allowances are left. After the above-mentioned processing, surface hardening quenching (local quenching) is performed. In this surface hardening process, local heating is performed at a temperature of 850 to 1000°C for 3 seconds or more using high frequency, etc., and then hardened with oil, salt, etc., cooled to a predetermined temperature, and then transferred to an electric furnace. The temperature is maintained at a predetermined temperature for 60 seconds or more, and then cooled by air or water. This hardening is to generate compressive residual stress at least inside the surface of the part and improve its wear resistance.The surface layer is made of bainite or martensite, and the inside is subjected to primary heat treatment (granular pearlite). It is characterized by being made into a granular pearlite ground by a chemical treatment. The predetermined temperature to be maintained in the electric furnace is selected depending on the target load on the parts. For high-load gears and shafts, the surface layer is made of bainitic material with a temperature range of 220 to 390°C, and for low-load gears and shafts, the surface layer is made of martensite material with a temperature range of 130 to 220°C. shall be. As mentioned above, if the base structure of the spheroidal graphite cast iron part is a granular pearlite base, as shown by C in Figure 1, the austenitization time will be close to that of the pearlite base B, resulting in good quenching. At the same time, as shown by C in FIG. 2, it is possible to obtain almost the same good workability as ferrite material A. After the primary and secondary heat treatment according to the present invention, high compressive residual stress is applied to stress concentrated areas, such as tooth bottoms in gears and corner areas in shafts, by shot peening or rolling. The fatigue strength characteristics may be further improved. Next, examples of the present invention will be shown. Example
【表】
上記化学組成から成る球状黒鉛鋳鉄素材を高周
波大気溶解炉にて鋳造により製造し、切削性、お
よび焼入れ性確保の目的で電気炉によりチル分解
を兼ねた920℃×2.0Hr加熱後、冷却は粒界に不
純物を析出させないために炉冷は避け空冷した。
空冷後720±10℃から予め用意された750℃の電気
炉にて約2.5Hr加熱後処理時間短縮のため空冷し
た。ワークが室温になつたのちブラストにより表
面のスケールを除去し、仕上加工を行つた。次い
で高周波加熱を890℃、約15秒間行い予め用意さ
れた260℃のソルト炉へ約2.0Hr浸漬し、ベーナ
イト化を行なつた。処理完了後、約80℃の温水に
て洗浄した。
得られた本発明にかかる試験片の仕上加工後お
よびベーナイト化後の組織を夫々、第３図、第４
図に示す。
本発明方法は、第５図および第６図に夫々示す
ように、リングギヤ１，２を夫々一体に形成する
FF用およびFR用デイフアレンシヤルギヤケース
３，４の製造に有利に適用することができる。
この場合には、リングギヤ１，２を形成するフ
ランジ部５，６をギヤケース３，４と一体に形成
しておき、ギヤを加工するフランジ部外周部には
シエービング加工の後、局所焼入れを施すように
すればよい。この場合の局所焼入れは、オーステ
ンパー処理とし、高負荷を受合うリングギヤ１，
２に対しては、焼入れ後に、シヨツトピーニング
処理を施し、耐疲労強度をより一層向上させるこ
とが好ましい。[Table] A spheroidal graphite cast iron material with the above chemical composition was manufactured by casting in a high-frequency atmospheric melting furnace, and heated at 920℃ for 2.0 hours in an electric furnace that also served as chill decomposition for the purpose of ensuring machinability and hardenability. For cooling, furnace cooling was avoided and air cooling was used to prevent impurities from precipitating at grain boundaries.
After air cooling, the mixture was heated from 720±10°C to 750°C in an electric furnace prepared in advance for about 2.5 hours to shorten the post-treatment time. After the workpiece reached room temperature, surface scale was removed by blasting and finishing was performed. Next, high-frequency heating was performed at 890°C for about 15 seconds, and the material was immersed in a previously prepared salt furnace at 260°C for about 2.0 hours to form bainite. After the treatment was completed, it was washed with warm water at about 80°C. The structures of the obtained test piece according to the present invention after finishing processing and after bainiticization are shown in FIGS. 3 and 4, respectively.
As shown in the figure. In the method of the present invention, the ring gears 1 and 2 are integrally formed, as shown in FIGS. 5 and 6, respectively.
It can be advantageously applied to manufacturing differential gear cases 3 and 4 for FF and FR. In this case, the flange portions 5 and 6 forming the ring gears 1 and 2 are formed integrally with the gear cases 3 and 4, and the outer periphery of the flange portion where the gears are machined is subjected to local hardening after shaving. Just do it. In this case, the local hardening is austempering treatment, and the ring gear 1, which receives high loads,
For No. 2, it is preferable to perform shot peening treatment after quenching to further improve the fatigue strength.
第１図は球状黒鉛鋳鉄の基地組織の相違に基づ
く焼入性の相違を示す特性図、第２図は球状黒鉛
鋳鉄の基地組織の相違に基づく加工性の相違を示
す特性図、第３図、第４図は本発明の実施例に示
した本発明材にかかる２次熱処理後およびオース
テンパー処理後の試験片の組織を夫々倍率（×
400）の図面代用顕微鏡写真、第５図、第６図は
夫々本発明方法の適用例を示す、リングギヤを一
体に形成した車両用デイフアレンシヤルギヤケー
スの各断面図である。
Figure 1 is a characteristic diagram showing differences in hardenability due to differences in matrix structure of spheroidal graphite cast iron, Figure 2 is a characteristic diagram showing differences in workability due to differences in matrix structure of spheroidal graphite cast iron, Figure 3 , FIG. 4 shows the structure of the test piece after the secondary heat treatment and the austempering treatment of the material of the present invention shown in the examples of the present invention, respectively, at a magnification (×
400), and FIGS. 5 and 6 are cross-sectional views of a differential gear case for a vehicle in which a ring gear is integrally formed, each showing an example of application of the method of the present invention.
Claims (1)
〜1.0重量％、P0.15重量％以下、S0.03重量％以
下、Cu0.3〜1.5重量％又はSn0.03〜0.16重量％、
Mo0.03〜0.1重量％、Mg0.025〜0.1重量％、Fe残
部からなり微細パーライト基地組織の球状黒鉛鋳
鉄を、基地中の粒状パーライト面積率35〜65％で
かつ基地炭素量0.3〜0.65重量％となるように、
850〜1000℃の温度下で0.5時間以上加熱した後空
冷し、次いで670〜760℃の温度下で0.5〜8.0時間
加熱した後空冷又は水冷して粒状パーライト化し
た後、加工し、次いで表面硬化焼入れするように
したことを特徴とする球状黒鉛鋳鉄部品の製造
法。1 C2.6~4.0wt%, Si1.5~3.5wt%, Mn0.1
~1.0 wt%, P0.15 wt% or less, S0.03 wt% or less, Cu0.3~1.5 wt% or Sn0.03~0.16 wt%,
Spheroidal graphite cast iron with a fine pearlite base structure consisting of Mo0.03~0.1% by weight, Mg0.025~0.1% by weight, and Fe balance, with a granular pearlite area ratio in the base of 35~65% and a base carbon content of 0.3~0.65% by weight. %,
After heating at a temperature of 850-1000℃ for 0.5 hours or more, air cooling, then heating at a temperature of 670-760℃ for 0.5-8.0 hours, air cooling or water cooling to form granular pearlite, processing, and then surface hardening. A method for manufacturing spheroidal graphite cast iron parts, characterized by quenching them.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15564782A JPS5943816A (en) | 1982-09-06 | 1982-09-06 | Manufacture of spheroidal graphite cast iron parts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15564782A JPS5943816A (en) | 1982-09-06 | 1982-09-06 | Manufacture of spheroidal graphite cast iron parts |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5943816A JPS5943816A (en) | 1984-03-12 |
| JPS6347773B2 true JPS6347773B2 (en) | 1988-09-26 |
Family
ID=15610536
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15564782A Granted JPS5943816A (en) | 1982-09-06 | 1982-09-06 | Manufacture of spheroidal graphite cast iron parts |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5943816A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61219566A (en) * | 1985-03-25 | 1986-09-29 | Toshiba Corp | Material for polishing surface plate |
| JPS62224573A (en) * | 1986-03-24 | 1987-10-02 | Toshiba Corp | Manufacture of lapping surface table |
| JP3172337B2 (en) * | 1993-07-29 | 2001-06-04 | 株式会社日立製作所 | Compressor |
| JP4495800B2 (en) * | 1999-07-07 | 2010-07-07 | 電気興業株式会社 | Induction hardening of cast iron |
| JP4801799B2 (en) * | 2001-08-10 | 2011-10-26 | アイシン高丘株式会社 | Method for producing spheroidal graphite cast iron with excellent strength, elongation and machinability |
| JP5208175B2 (en) * | 2010-09-02 | 2013-06-12 | アイシン高丘株式会社 | Vehicle cast iron parts |
| CN113322369B (en) * | 2021-05-31 | 2022-02-18 | 东风商用车有限公司 | Normalizing-strengthening cast iron, and normalizing-strengthening method and application thereof |
-
1982
- 1982-09-06 JP JP15564782A patent/JPS5943816A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5943816A (en) | 1984-03-12 |
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