JP4134690B2 - Hardening heat treatment method for cast iron member and hardened heat treated cast iron member - Google Patents

Description

【００３６】
実施例１のものは全ての熱処理条件を上下限内に設定し、実施例２のものはオーステナイト化温度Ｔ１および再加熱温度Ｔ３を下限に設定し、実施例３のものはオーステナイト化温度Ｔ１を下限に設定する一方、再加熱温度Ｔ３を上限に設定し、実施例４のものはオーステナイト化温度Ｔ１を上限に設定する一方、再加熱温度Ｔ３を下限に設定し、実施例５のものはオーステナイト化離温度Ｔ１および再加熱温度Ｔ３を上限に設定し、実施例６のものは他の実施例１〜５，７のものよりも冷却速度Ｖ＝５０℃／secの速い値に設定し、実施例７のものは再加熱開始温度Ｔ２を上限に設定したものである。
【００３７】
上記[表１]から明らかなように、オーステナイト化温度Ｔ１、冷却速度Ｖ、再加熱開始温度Ｔ２、再加熱温度Ｔ３が上述の所定範囲の実施例１〜７のものは、ビッカース硬さが、Ｈｖ２００〜５００の範囲内となった。
【００３８】
これに対して比較例８のものは、オーステナイト化温度がＴ１＝９００℃と低いため、炭素の固溶不足により硬さＨｖ＝１９５と低い値になった。
また比較例９のものは、オーステナイト化温度がＴ１＝１１００℃と高いため、炭素の固溶過剰により硬さＨｖ＝５０６と高い値になった。
【００３９】
さらに比較例１０のものは冷却速度がＶ＝１０℃／secと遅いため、パーライト組織が粗大化し、これにより硬さＨｖ＝１９１と低い値になった。
比較例１１のものは、再加熱開始温度Ｔ２が６００℃と高く、５００℃以下の冷却されない時点で再加熱を開始したので、オーステナイト組織の残留と、パーライト組織の粗大化に起因して、硬さＨｖ＝１９３と低い値になった。
【００４０】
また比較例１２のものは、再加熱温度Ｔ３が５００℃と低いため、マルテンサイト組織およびベイナイト組織のパーライト変態が不足し、硬さＨｖ＝５１３と高い値になった。
さらに比較例１３のものは、再加熱温度Ｔ３が８００℃と高いため、パーライト組織の凝集、粗大化により、硬さＨｖ＝１７２と低い値になった。
【００４１】
さらにまた比較例１４のものは、再加熱処理を実行しないものであって、このように再加熱を施さないものは、冷却速度が速いことに起因して、マルテンサイト組織およびベイナイト組織の生成により、硬さＨｖ＝５６７と高い値になった。
【００４２】
すなわち、比較例８〜１４のものは何れかの条件が上記範囲外となるので、硬さはＨｖ２００〜５００の範囲内に収まることがなく、硬さが過小または過大となった。
【００４３】
図６はロータ１のアペックスシール溝部３のヘタリ量とビッカース硬さＨｖとの関係を示す特性図で、Ｈｖ２００〜５００の範囲においてヘタリ量が望ましい値となることを示している。
【００４４】
このように上記実施例の鋳鉄部材の硬化熱処理方法は、図５のその加熱パターンに示すように、黒鉛を有する鋳鉄部材(ロータ１参照)を高周波加熱により９５０〜１０５０℃のオーステナイト化温度Ｔ１に加熱した後、２０℃／sec以上の冷却速度Ｖで５００℃以下の温度Ｔ２まで冷却し、引き続き高周波加熱により５５０〜７００℃の温度Ｔ３に再加熱後冷却し、処理部５の硬さをビッカース硬度２００〜５００℃の範囲の均一なパーライト組織を得るものである。
【００４５】
上記構成によれば、まず黒鉛を有する鋳鉄部材(ロータ１参照)の処理部５(強化必要部分)が高周波加熱により９５０℃〜１０５０℃のオーステナイト化温度Ｔ１に加熱され、この加熱によって鋳鉄中の黒鉛から基地組織へ炭素の固溶を促進させる。
【００４６】
このオーステナイト化温度Ｔ１への加熱後、２０℃／sec以上の冷却速度Ｖで５００℃以下の温度Ｔ２まで冷却する。この冷却によりマルテンサイト、パーライト、フェライトの混在組織になる。また５００℃以下の温度Ｔ２まで冷却することで、粗大なパーライト組織の生成がなくなる。
【００４７】
引き続き高周波加熱により５５０℃〜７００℃の温度Ｔ３に再加熱冷却する。この再加熱により上述の冷却後の前組織がパーライト組織、ベイナイト組織、マルテンサイト組織の単層または、これらの混在組織であっても、基地組織を均一で微細なパーライト組織とし、処理部５の硬さをＨｖ２００〜５００のばらつきの僅少な安定した硬さを確保することができる(表１の実施例１〜７参照)。
なお、再加熱後の冷却は得られる組織や硬さに変化がなく、水冷のような速い冷却でも、または空冷のような遅い冷却でもよい。
【００４８】
ここで、上述のオーステナイト化温度Ｔ１が９５０℃未満の場合には、比較例８で示したように黒鉛からの炭素固溶が不足し、その後の冷却中にフェライトが生成し始め、硬さ低下を招く。逆に、オーステナイト化温度が１０５０℃を超過する場合には、比較例９で示したように黒鉛からの炭素固溶が過剰となって、冷却中にセメンタイトが析出し始め、硬さが高くなり過ぎる。このため上記オーステナイト化温度を９５０〜１０５０℃の範囲とする。
【００４９】
また冷却速度が２０℃／secよりも遅くなると、比較例１０で示したように冷却中にパーライト組織が粗大化して、硬さが低くなり過ぎ、逆に冷却速度が速くなり過ぎると、比較例１４で示したように冷却後に生成される組織はパーライト組織からベイナイト組織、マルテンサイト組織へと順次変化するので、この冷却速度Ｖはマルテンサイト組織へと変化しない所定の冷却速度が望ましい。
【００５０】
さらに冷却する温度を５００℃以下とするのは、５００℃まで冷却すると、粗大なパーライト組織の生成がなく、最終的に得られる硬さに変動がなくなるためである。
【００５１】
さらにまた、上述の再加熱は均一なパーライト組織を得るものであって、混在組織、特にマルテンサイトをパーライトに変態させて均等な硬さにする処理であり、再加熱温度が５５０℃未満では比較例１２で示したように、硬さが高くなり過ぎ、再加熱温度が７００℃を超過する場合には、比較例１３で示したように硬さが低くなり過ぎる。したがってＨｖ２００〜５００の所定範囲の硬さを得るために再加熱温度を５５０℃〜７００℃の範囲とするものである。
【００５２】
またビッカース硬度を２００〜５００とするのは、図６の特性図にも示すようにＨｖ２００未満では耐へタリ性が確保できず、逆にＨｖ５００以上では硬さが高すぎて例えば仕上げ加工時の工具劣化が顕著となるので、上記範囲内とするものである。
【００５３】
このように上記構成によれば、所定の硬さ(Ｈｖ２００〜５００)を有し、均一なパーライト組織を得ることができ、被削性を確保しつつ耐疲労性、耐摩耗性、耐ヘタリ性を向上させることができ、また高周波加熱により必要とする処理部のみを連続的に処理することができて、短時間で必要とする処理部のみを効率よく熱処理することができる。
【００５４】
さらに、上記再加熱の温度を６００〜６５０℃の範囲に設定すると、鋳造された鋳鉄部材それ自体に多少のばらつきがあっても、ビッカース硬度をＨｖ２００〜５００の範囲内の中間の望ましい値と成すことができる。
【００５５】
一方、上記実施例の硬化熱処理された鋳鉄部材(ロータ１参照)は、黒鉛を有する鋳鉄部材を高周波加熱により９５０〜１０５０℃のオーステナイト化温度Ｔ１に加熱した後、２０℃／sec以上の冷却速度Ｖで５００℃以下の温度Ｔ２まで冷却し、引き続き高周波加熱により５５０〜７００℃の温度Ｔ３に再加熱後冷却し、処理部５の硬さをビッカース硬度２００〜５００℃の範囲の均一なパーライト組織にしたものである。
【００５６】
この構成によれば、所定の硬さ(Ｈｖ２００〜５００)を有し、均一なパーライト組織を得ることができ、被削性を確保しつつ耐疲労性、耐摩耗性、耐ヘタリ性を向上させることができ、また高周波加熱により短時間で、かつ必要とする処理部のみを連続的に効率よく熱処理することができる。
【００５７】
しかも、上記鋳鉄部材は球状黒鉛鋳鉄部材(ＦＣＤ４５０Ｆ参照)に設定されたものであるから、オーステナイト化温度Ｔ１とへの加熱時に球状黒鉛が均一に固溶するので、より一層均一なパーライト組織を得ることができる。
【００５８】
さらに、上記鋳鉄部材はロータリエンジンのロータ１に設定されたものである。
この構成によれば、ロータ１の頂点にはアペックスシール６を配設するアペックスシール溝部３が設けられるが、このアペックスシール溝部３を上記処理部５に設定すると、アペックスシール６との摺動により該アペックスシール溝部３が摩耗するのを防止できて、ロータ１の耐久性向上を図ることができる。
【００５９】
この発明の構成と、上述の実施例との対応において、
この発明の黒鉛を有する鋳鉄は、実施例の球状黒鉛鋳鉄に対応し、
以下同様に、
鋳鉄部材は、ロータリエンジンのロータ１に対応するも、
この発明は、上述の実施例の構成のみに限定されるものではない。
【００６０】
例えば、黒鉛を有する鋳鉄としては上述の球状黒鉛鋳鉄の他にねずみ鋳鉄や片状黒鉛鋳鉄であってもよく、鋳鉄部材としてはロータリエンジンのロータの他に高面圧下で繰り返し荷重などを受ける他の鋳鉄部材であってもよい。
【００６１】
【発明の効果】
この発明によれば、所定の硬さを有し、均一なパーライト組織を得ることができ、被削性を確保しながら耐疲労性、耐摩耗性、耐ヘタリ性を向上でき、また高周波過熱により連続的に処理することができて、短時間で必要とする処理部のみを効率よく熱処理することができる効果がある。
【００６２】
【図面の簡単な説明】
【図１】 鋳鉄部材の一例としてのロータリエンジンのロータを示す斜視図。
【図２】 処理部の説明図。
【図３】 図２のＡ−Ａ線矢視図。
【図４】 アペックスシールの説明図。
【図５】 鋳鉄部材の硬化熱処理方法を示す加熱パターンの説明図。
【図６】 ビッカース硬さとヘタリ量との関係を示す特性図。
【符号の説明】
１…ロータ
５…処理部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hardening heat treatment method for a cast iron member that receives, for example, repeated loads under high surface pressure, and a hardening iron heat-treated cast iron member.
[0002]
[Prior art]
In general, cast iron is an inexpensive material, and because of its excellent machinability due to the presence of graphite, it is frequently used as an automotive part or the like.
However, in recent years, cast iron materials have been required to have higher strength due to the reduction in size and weight and the improvement in output. The parts where this strength is required are mainly local parts such as sliding parts and stress-concentrating parts.
[0003]
In order to increase the strength of the predetermined portion of the cast iron member as described above, a method capable of local heating treatment such as high-frequency heating or laser heating is generally employed. In other words, heat treatment of the entire member such as furnace heating is not only disadvantageous in terms of energy efficiency, but also strengthens parts that are not necessary, making post-processing difficult, so the above-mentioned local heat treatment is adopted. Yes.
[0004]
In local heating such as the above-mentioned high-frequency heating, the cooling rate after heating depends on the size of the heating range and is not constant, so the hardness also depends on the cooling rate and it is difficult to stably obtain the target hardness. It is.
[0005]
Conventionally, as a method for improving the hardness by raising the hardness of an as-cast or annealed cast iron member, generally normalizing treatment (normalizing treatment in which it is heated to 900 ° C. to 950 ° C. and then allowed to cool to room temperature) Is done.
[0006]
However, when only a necessary part of the cast iron member is normalized by local heating means such as high-frequency heating or laser heating, the hardness obtained varies greatly depending on the cooling rate during cooling from the austenitizing temperature to room temperature.
[0007]
That is, when the cooling rate from the austenitizing temperature is fast, the hard iron cast becomes too hard due to the formation of hard structures such as martensite and bainite structures, and the machinability in post-processing deteriorates. A point is created.
[0008]
Conversely, when the cooling rate from the austenitizing temperature is slow, the pearlite structure becomes coarse during cooling, and the hardness of the cast iron member becomes too low, and a predetermined strength cannot be obtained.
In short, in the conventional method, it is difficult to obtain a uniform pearlite structure having a predetermined hardness.
[0009]
On the other hand, there are the following methods as a heat treatment method for the spheroidal graphite cast iron member.
That is, spheroidal graphite cast iron parts are quenched by high-frequency heating to 1173 to 1323K (900 to 1050 ° C) and then quenched, and tempered at 573 to 823K (300 to 550 ° C) for 0.5 to 2.0 hours. . Also, in a part obtained by heat treating spheroidal graphite cast iron having a form in which spheroidal graphite is dispersed in the base, the main structure of the base is a martensite structure by quenching, and the periphery of the spheroidal graphite is surrounded by a sorbite structure ( For example, see Patent Document 1).
[0010]
[Patent Document 1]
JP 2000-265210 A.
[0011]
[Problems to be solved by the invention]
In the heat treatment method according to this conventional publication, the main structure is to obtain a martensite structure by quenching, and does not have a predetermined hardness and a uniform pearlite structure.
[0012]
This invention has a predetermined hardness, can obtain a uniform pearlite structure, can improve the fatigue resistance, wear resistance, and sag resistance while ensuring machinability, and can be continuously applied by high-frequency heating. It is an object of the present invention to provide a method for hardening and heat-treating a cast iron member capable of efficiently heat-treating only a processing portion required in a short time and a cast iron member subjected to hardening and heat treatment.
[0013]
[Means for Solving the Problems]
According to the method for heat-treating a cast iron member according to the present invention, a cast iron member having graphite is heated to an austenitizing temperature of 950 to 1050 ° C. by high frequency heating, and then cooled to a temperature of 500 ° C. or less at a cooling rate of 20 ° C./sec or more. Then, it is reheated to a temperature of 550 to 700 ° C. by high-frequency heating and then cooled to obtain a uniform pearlite structure having a Vickers hardness of 200 to 500 ° C. in the treated portion.
[0014]
The cast iron having graphite having the above-described configuration may be spheroidal graphite cast iron, gray cast iron, or flake graphite cast iron.
According to the above-described configuration, first, the processing portion (required portion) of the cast iron member having graphite is subjected to high-frequency heating at an austenitizing temperature of 950 ° C. to 1050 ° C. (normal steel A, at a temperature relatively higher than the transformation point 726 ° C. Yes, this is one of the conditions of temperature and time necessary for diffusing carbon, and in the case of partial heating, the time cannot be set long, so it is a value for diffusing carbon by temperature) This heating promotes solid solution of carbon from the graphite in the cast iron to the base structure.
[0015]
After heating to this austenitizing temperature, it is cooled to a temperature of 500 ° C. or lower at a cooling rate of 20 ° C./sec or higher. This cooling results in a mixed structure of martensite, pearlite, and ferrite. Further, by cooling to a temperature of 500 ° C. or lower, generation of a coarse pearlite structure is eliminated.
[0016]
Subsequently, it is reheated and cooled to a temperature of 550 ° C. to 700 ° C. by high frequency heating. Even if the previous structure after cooling is a single layer of a pearlite structure, a bainite structure, a martensite structure, or a mixed structure thereof by this reheating, the base structure becomes a uniform and fine pearlite structure, and the hardened portion of the processing section is hardened. It is possible to secure a stable hardness with a slight variation of Hv 200 to 500.
In addition, the cooling after reheating does not change in the structure | tissue and hardness which are obtained, Fast cooling like water cooling or slow cooling like air cooling may be sufficient.
[0017]
Here, when the austenitizing temperature is less than 950 ° C., carbon solid solution from graphite is insufficient, and ferrite starts to form during the subsequent cooling, leading to a decrease in hardness. Conversely, when the austenitizing temperature exceeds 1050 ° C., carbon solid solution from graphite becomes excessive, cementite starts to precipitate during cooling, and the hardness becomes too high. For this reason, the said austenitizing temperature shall be the range of 950-1050 degreeC.
[0018]
When the cooling rate is slower than 20 ° C./sec, the pearlite structure becomes coarse during cooling, and the hardness becomes too low. Conversely, when the cooling rate becomes too fast, the structure generated after cooling is from the pearlite structure. Since the bainite structure and the martensite structure are sequentially changed, the cooling rate is preferably a predetermined cooling rate (up to about 50 ° C./sec) that does not change to the martensite structure.
[0019]
The reason why the cooling temperature is set to 500 ° C. or less is that when cooling to 500 ° C., there is no generation of coarse pearlite structure, and there is no fluctuation in the finally obtained hardness.
[0020]
Furthermore, the above-mentioned reheating is a process for obtaining a uniform pearlite structure and making the mixed structure uniform hardness. If the reheating temperature is less than 550 ° C., the hardness becomes too high, and the reheating temperature. When the temperature exceeds 700 ° C., the hardness becomes too low. Therefore, in order to obtain a hardness in a predetermined range of Hv 200 to 500, the reheating temperature is set to a range of 550 ° C to 700 ° C.
[0021]
Also, the Vickers hardness of 200 to 500 is that if the hardness is less than Hv200, the resistance to sag cannot be secured, and conversely if the hardness is Hv500 or more, the hardness is too high and, for example, tool deterioration during finishing is remarkable. It is intended to be inside.
[0022]
Thus, according to the above configuration, it is possible to obtain a uniform pearlite structure having a predetermined hardness, and improve fatigue resistance, wear resistance, and sag resistance while ensuring machinability. In addition, only the necessary processing unit can be continuously processed by high-frequency heating, and only the necessary processing unit can be efficiently heat-treated in a short time.
[0023]
In one embodiment of the present invention, the reheating temperature is set in a range of 600 to 650 ° C.
According to the above configuration, since the reheating temperature is 600 to 650 ° C. as an intermediate value of 550 to 700 ° C., even if there is some variation in the cast iron member itself, the Vickers hardness is Hv 200 to 500 The desired value can be in the middle of the range.
[0024]
The cast iron member subjected to hardening heat treatment according to the present invention is obtained by heating a cast iron member having graphite to an austenitizing temperature of 950 to 1050 ° C. by high frequency heating, and then cooling to a temperature of 500 ° C. or less at a cooling rate of 20 ° C./sec or more. Subsequently, it is cooled again after being reheated to a temperature of 550 to 700 ° C. by high-frequency heating, and the hardness of the treated portion is made into a uniform pearlite structure in the range of Vickers hardness 200 to 500 ° C.
[0025]
According to the said structure, it has predetermined hardness (Hv200-500), can obtain a uniform pearlite structure | tissue, and improves fatigue resistance, abrasion resistance, and sag resistance, ensuring machinability. In addition, it is possible to perform heat treatment continuously and efficiently only in a short time by using high-frequency heating.
[0026]
In one embodiment of the present invention, the cast iron member is a spheroidal graphite cast iron member.
According to the above configuration, since the spherical graphite is uniformly dissolved when heated to the austenitizing temperature, a more uniform pearlite structure can be obtained.
[0027]
In one embodiment of the present invention, the cast iron member is set to a rotor of a rotary engine.
According to the above configuration, the apex seal groove portion in which the apex seal is disposed is provided at the apex of the rotor. When the apex seal groove portion is set as the processing portion, the apex seal groove portion is worn by sliding with the apex seal. The durability of the rotor can be improved.
[0028]
【Example】
An embodiment of the present invention will be described below in detail with reference to the drawings.
The drawings show a method for hardening heat treatment of a cast iron member and a cast iron member subjected to hardening heat treatment. In this embodiment, a rotor of a rotary engine as a cast iron member is illustrated. First, the configuration of the rotor and its processing unit will be described with reference to FIGS.
[0029]
As shown in FIG. 1, the rotor 1 of the rotary engine has a three-leaf inner envelope surface 2..., Apex seal grooves 3 are provided at the top of the rotor, and a trochoid phase gear ( An internal gear) 4 is formed.
[0030]
The processing portion 5 to be heat-treated by the curing heat-treatment method of this embodiment has a depth W of 2 mm from the apex of the apex seal groove portion 3 as shown in FIG. 2 and FIG. The width L1 from the edge to the rotor side surface is 2 mm, and the length L2 from the end of the apex seal groove to the axial axis direction of the eccentric shaft is set to the corner portion of the groove 3.
[0031]
Here, an apex seal 6 as shown in FIG. 4 is disposed in the above-described apex seal groove 3 via a spring (not shown).
This apex seal 6 is a three-piece seal member consisting of a main piece 7, a second piece 8, and a side piece 9, which improves the airtightness between the working chambers formed between the rotor housing and the rotor. It is.
[0032]
The material of the rotor 1 is set to FCD450 spheroidal graphite cast iron.
The chemical composition of this FCD450F (spheroidal graphite cast iron) is as follows: C: 3.63 wt%, Si: 2.54 wt%, Mn: 0.32 wt%, Mg: 0.04 wt%, P: 0.06 wt%, S: 0 0.02 wt% and the balance Fe and other inevitable impurities are very small.
[0033]
The processing section 5 of the rotor 1 described above was subjected to curing heat treatment according to the heating pattern shown in FIG.
That is, the above-described processing unit 5 is heated to an austenitizing temperature T1 = 950 to 1050 ° C. over t1 = 10 seconds by a heating coil (not shown) of a high-frequency heating apparatus, and then a cooling rate V = 20 ° C./sec or more. Then, it is naturally cooled to a temperature of 500 ° C. or lower (see reheating start temperature T2) over t2 = 10 to 25 seconds, and then reheated temperature T3 over t3 = 5 seconds by a heating coil (not shown) of the high frequency heating device. After reheating to a temperature of 550 to 700 ° C., cooling treatment was performed by water cooling or air cooling.
[0034]
Here, any one of the cast iron members (see rotor 1) of Examples 1 to 7 in which the austenitizing temperature T1, the cooling rate V, the reheating start temperature T2, and the reheating temperature T3 are slightly different within the above-described range. The following [Table 1] shows the results of actual measurement of Vickers hardness with the cast iron members of Comparative Examples 8 to 14 whose conditions are out of the above range, together with various heat treatment conditions.
The above-mentioned hardness is obtained by measuring the cross section of the processing section 5 with Vickers hardness (load 5 kgf).
[0035]
[Table 1]

[0036]
In Example 1, all heat treatment conditions are set within the upper and lower limits, in Example 2, the austenitizing temperature T1 and reheating temperature T3 are set to the lower limits, and in Example 3, the austenitizing temperature T1 is set. While the lower limit is set, the reheating temperature T3 is set to the upper limit, and in Example 4, the austenitizing temperature T1 is set to the upper limit, while the reheating temperature T3 is set to the lower limit, and in Example 5, the austenite is set. The upper limit is set at the separation temperature T1 and the reheating temperature T3, and the example 6 is set to a faster cooling rate V = 50 ° C./sec than those of the other examples 1 to 5 and 7. In Example 7, the reheating start temperature T2 is set to the upper limit.
[0037]
As is clear from the above [Table 1], the austenitizing temperature T1, the cooling rate V, the reheating start temperature T2, and the reheating temperature T3 in Examples 1 to 7 in the above-described predetermined ranges have Vickers hardness. It became in the range of Hv200-500.
[0038]
On the other hand, since the austenitizing temperature of the comparative example 8 is as low as T1 = 900 ° C., the hardness Hv = 195 is low due to insufficient solid solution of carbon.
In Comparative Example 9, since the austenitizing temperature was as high as T1 = 1100 ° C., the hardness Hv = 506 was high due to excessive solid solution of carbon.
[0039]
Furthermore, since the cooling rate of Comparative Example 10 was as low as V = 10 ° C./sec, the pearlite structure was coarsened, and thus the hardness Hv = 191 was low.
In Comparative Example 11, since the reheating start temperature T2 was as high as 600 ° C. and reheating was started when the temperature was not cooled below 500 ° C., the hardness of the austenite structure remained and the pearlite structure became coarse. Hv = 193, which is a low value.
[0040]
Moreover, since the reheating temperature T3 was as low as 500 degreeC, the thing of the comparative example 12 lacked the pearlite transformation of a martensite structure and a bainite structure, and became hardness Hv = 513 and a high value.
Furthermore, since the reheating temperature T3 of the comparative example 13 is as high as 800 ° C., the hardness Hv = 172 is low due to the aggregation and coarsening of the pearlite structure.
[0041]
Furthermore, the thing of the comparative example 14 is what does not perform a reheating process, and what does not give a reheating in this way originates in the production | generation of a martensite structure | tissue and a bainite structure | tissue due to a high cooling rate. The hardness Hv = 567 was a high value.
[0042]
That is, since any of the conditions of Comparative Examples 8 to 14 was outside the above range, the hardness did not fall within the range of Hv 200 to 500, and the hardness was too small or too large.
[0043]
FIG. 6 is a characteristic diagram showing the relationship between the amount of stickiness of the apex seal groove 3 of the rotor 1 and the Vickers hardness Hv, and shows that the amount of stickiness is a desirable value in the range of Hv 200 to 500.
[0044]
Thus, the hardening heat treatment method of the cast iron member of the above-described embodiment is, as shown in the heating pattern of FIG. 5, the cast iron member having graphite (see rotor 1) is heated to an austenitizing temperature T1 of 950 to 1050 ° C. by high frequency heating. After heating, it is cooled to a temperature T2 of 500 ° C. or less at a cooling rate V of 20 ° C./sec or more, then reheated to a temperature T3 of 550 to 700 ° C. by high frequency heating and then cooled, and the hardness of the processing unit 5 is reduced to Vickers A uniform pearlite structure having a hardness in the range of 200 to 500 ° C. is obtained.
[0045]
According to the said structure, the process part 5 (strengthening required part) of the cast iron member (refer rotor 1) which has graphite is first heated by the high frequency heating to the austenitizing temperature T1 of 950 degreeC-1050 degreeC, and this heating WHEREIN: Promotes solid solution of carbon from graphite to the matrix structure.
[0046]
After heating to this austenitizing temperature T1, it is cooled to a temperature T2 of 500 ° C. or lower at a cooling rate V of 20 ° C./sec or higher. This cooling results in a mixed structure of martensite, pearlite, and ferrite. Further, by cooling to a temperature T2 of 500 ° C. or less, generation of a coarse pearlite structure is eliminated.
[0047]
Subsequently, it is reheated and cooled to a temperature T3 of 550 ° C. to 700 ° C. by high frequency heating. Even if the previous structure after cooling is a single layer of a pearlite structure, a bainite structure, a martensite structure, or a mixed structure thereof by this reheating, the base structure is a uniform and fine pearlite structure, It is possible to ensure a stable hardness with a slight variation of Hv 200 to 500 (see Examples 1 to 7 in Table 1).
In addition, the cooling after reheating does not change in the structure | tissue and hardness which are obtained, Fast cooling like water cooling or slow cooling like air cooling may be sufficient.
[0048]
Here, when the austenitizing temperature T1 is less than 950 ° C., the carbon solid solution from graphite is insufficient as shown in Comparative Example 8, and ferrite starts to form during the subsequent cooling, resulting in a decrease in hardness. Invite. Conversely, when the austenitizing temperature exceeds 1050 ° C., the carbon solid solution from graphite becomes excessive as shown in Comparative Example 9, and cementite begins to precipitate during cooling, resulting in an increase in hardness. Pass. For this reason, the said austenitizing temperature shall be the range of 950-1050 degreeC.
[0049]
When the cooling rate is slower than 20 ° C./sec, the pearlite structure becomes coarse during cooling as shown in Comparative Example 10 and the hardness becomes too low. On the contrary, when the cooling rate becomes too high, the comparative example Since the structure generated after cooling sequentially changes from a pearlite structure to a bainite structure and a martensite structure as indicated by 14, this cooling rate V is preferably a predetermined cooling rate that does not change to a martensite structure.
[0050]
The reason why the cooling temperature is set to 500 ° C. or less is that when cooling to 500 ° C., there is no generation of coarse pearlite structure, and there is no fluctuation in the finally obtained hardness.
[0051]
Furthermore, the above-mentioned reheating is to obtain a uniform pearlite structure, and is a process of transforming the mixed structure, particularly martensite, to pearlite to obtain a uniform hardness. When the reheating temperature is less than 550 ° C., the comparison is made. As shown in Example 12, when the hardness becomes too high and the reheating temperature exceeds 700 ° C., the hardness becomes too low as shown in Comparative Example 13. Therefore, in order to obtain a hardness in a predetermined range of Hv 200 to 500, the reheating temperature is set to a range of 550 ° C to 700 ° C.
[0052]
Further, the Vickers hardness of 200 to 500 is that, as shown in the characteristic diagram of FIG. 6, the hardness resistance is not secured when it is less than Hv200, and conversely the hardness is too high at Hv500 or more. Since tool deterioration becomes remarkable, it is within the above range.
[0053]
As described above, according to the above-described configuration, a uniform pearlite structure can be obtained with a predetermined hardness (Hv 200 to 500), and fatigue resistance, wear resistance, and sag resistance are ensured while ensuring machinability. In addition, it is possible to continuously process only the processing unit required by high-frequency heating, and it is possible to efficiently heat-treat only the processing unit required in a short time.
[0054]
Further, when the reheating temperature is set in the range of 600 to 650 ° C., the Vickers hardness is set to an intermediate desired value in the range of Hv 200 to 500 even if there is some variation in the cast iron member itself. be able to.
[0055]
On the other hand, the hardened and heat-treated cast iron member of the above example (see rotor 1) is obtained by heating a cast iron member having graphite to an austenitizing temperature T1 of 950 to 1050 ° C. by high frequency heating, and then a cooling rate of 20 ° C./sec or more. V is cooled to a temperature T2 of 500 ° C. or less, and then reheated to a temperature T3 of 550 to 700 ° C. by high-frequency heating and then cooled, and the hardness of the processing unit 5 is a uniform pearlite structure having a Vickers hardness of 200 to 500 ° C. It is a thing.
[0056]
According to this structure, it has predetermined hardness (Hv200-500), can obtain a uniform pearlite structure, and improves fatigue resistance, wear resistance, and settling resistance while ensuring machinability. In addition, it is possible to perform heat treatment continuously and efficiently only in a short time by using high-frequency heating.
[0057]
Moreover, since the cast iron member is set to be a spheroidal graphite cast iron member (see FCD450F), since the spheroidal graphite is uniformly dissolved when heated to the austenitizing temperature T1, a more uniform pearlite structure is obtained. be able to.
[0058]
Further, the cast iron member is set to the rotor 1 of the rotary engine.
According to this configuration, the apex seal groove portion 3 in which the apex seal 6 is disposed is provided at the apex of the rotor 1. When the apex seal groove portion 3 is set as the processing portion 5, the apex seal groove portion 3 is slid with the apex seal 6. The wear of the apex seal groove 3 can be prevented, and the durability of the rotor 1 can be improved.
[0059]
In the correspondence between the configuration of the present invention and the above-described embodiment,
The cast iron having graphite of the present invention corresponds to the spheroidal graphite cast iron of the example,
Similarly,
The cast iron member corresponds to the rotor 1 of the rotary engine,
The present invention is not limited to the configuration of the above-described embodiment.
[0060]
For example, the cast iron having graphite may be gray cast iron or flake graphite cast iron in addition to the above-mentioned spheroidal graphite cast iron, and the cast iron member may be subjected to repeated load under high surface pressure in addition to the rotor of a rotary engine. The cast iron member may be used.
[0061]
【The invention's effect】
According to the present invention, a uniform pearlite structure having a predetermined hardness can be obtained, fatigue resistance, wear resistance, and sag resistance can be improved while securing machinability. Since it can process continuously, only the process part required in a short time can be heat-processed efficiently.
[0062]
[Brief description of the drawings]
FIG. 1 is a perspective view showing a rotor of a rotary engine as an example of a cast iron member.
FIG. 2 is an explanatory diagram of a processing unit.
FIG. 3 is a view taken along the line AA in FIG. 2;
FIG. 4 is an explanatory diagram of an apex seal.
FIG. 5 is an explanatory diagram of a heating pattern showing a hardening heat treatment method for a cast iron member.
FIG. 6 is a characteristic diagram showing the relationship between Vickers hardness and amount of settling.
[Explanation of symbols]
1 ... Rotor 5 ... Processing section

Claims (5)

After heating the cast iron member having graphite to an austenitizing temperature of 950 to 1050 ° C. by high frequency heating, the cast iron member is cooled to a temperature of 500 ° C. or less at a cooling rate of 20 ° C./sec or more,
Subsequently, it is cooled after reheating to a temperature of 550 to 700 ° C. by high frequency heating,
A hardening heat treatment method for a cast iron member that obtains a uniform pearlite structure having a Vickers hardness of 200 to 500 ° C. in the hardness of the processing portion. The method of hardening heat treatment of a cast iron member according to claim 1, wherein the reheating temperature is set in a range of 600 to 650 ° C. After heating the cast iron member having graphite to an austenitizing temperature of 950 to 1050 ° C. by high frequency heating, the cast iron member is cooled to a temperature of 500 ° C. or less at a cooling rate of 20 ° C./sec or more,
Subsequently, it is cooled after reheating to a temperature of 550 to 700 ° C. by high frequency heating,
A hardened and heat-treated cast iron member having a uniform pearlite structure with a Vickers hardness in the range of 200 to 500 ° C. in the processing portion. The hardened and heat-treated cast iron member according to claim 3, wherein the cast iron member is a spheroidal graphite cast iron member. The hardened and heat-treated cast iron member according to claim 3 or 4, wherein the cast iron member is set in a rotor of a rotary engine.

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