JPH032927B2 - - Google Patents
Info
- Publication number
- JPH032927B2 JPH032927B2 JP21617182A JP21617182A JPH032927B2 JP H032927 B2 JPH032927 B2 JP H032927B2 JP 21617182 A JP21617182 A JP 21617182A JP 21617182 A JP21617182 A JP 21617182A JP H032927 B2 JPH032927 B2 JP H032927B2
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- cast iron
- austempering
- furnace
- fluidized bed
- 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
- 229910001018 Cast iron Inorganic materials 0.000 claims description 51
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 48
- 238000005279 austempering Methods 0.000 claims description 33
- 238000010438 heat treatment Methods 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 9
- 238000001816 cooling Methods 0.000 description 23
- 229910001563 bainite Inorganic materials 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000008187 granular material Substances 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 230000009466 transformation Effects 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 229910001141 Ductile iron Inorganic materials 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 238000004781 supercooling Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000009423 ventilation Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- -1 Al 2 O 3 Chemical class 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- GEIAQOFPUVMAGM-UHFFFAOYSA-N ZrO Inorganic materials [Zr]=O GEIAQOFPUVMAGM-UHFFFAOYSA-N 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 238000005255 carburizing Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 235000000396 iron Nutrition 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000012546 transfer Methods 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)
- Crucibles And Fluidized-Bed Furnaces (AREA)
- Heat Treatments In General, Especially Conveying And Cooling (AREA)
Description
【発明の詳細な説明】
本発明は鋳鉄部品の熱処理方法に関するもので
ある。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for heat treating cast iron parts.
一般に鋳鉄部品を固溶体形成温度（830〜1000
℃）に一定時間加熱保持してオーステナイト化し
た後、急冷して例えば220〜400℃の温度に所定時
間恒温保持するいわゆるオーステンパー処理を施
すと、この鋳鉄部品がベイトナイト組織となつて
その靭性が大巾に向上することは周知である。そ
して、かかる熱処理を施した鋳鉄部品としては、
例えば強靭性を要求されるステアリングナツク
ル、コンロツド、差動機のリングギヤなどの自動
車用部品等がある。 Generally cast iron parts are heated to solid solution formation temperature (830~1000
When the cast iron parts are heated and held for a certain period of time (°C) to austenite, then rapidly cooled and kept constant at a temperature of 220 to 400°C for a specified period of time (so-called austempering treatment), this cast iron part becomes a batonite structure and its toughness increases. It is well known that there is a significant improvement in Cast iron parts subjected to such heat treatment include:
For example, there are automotive parts such as steering knuckles, connecting rods, and differential ring gears that require strong toughness.
従来、上記オーステンパー処理を施すにあたつ
ては、鋳鉄部品をオーステナイト化した後、例え
ばベイナイト生成温度に保持した塩浴中に焼入
れ、ここで組織が完全にベイナイトに変化するま
で保持する方法が一般にとられている（例えば特
公昭55−3422号公報参照）。つまり、冷却とオー
ステンパー処理とを一つの浴で行なう方式である
が、かかる方式では全体の処理時間が長くならざ
るを得ない。そこで、従来は、冷却とオーステン
パー処理とを別々の手段で行ない、冷却浴の温度
をオーステンパー処理温度よりも低くして急冷せ
しめることにより全体の処理時間を短縮すること
も行なわれている。 Conventionally, when applying the above-mentioned austempering treatment, after austenitizing a cast iron part, it is quenched in a salt bath maintained at a bainite forming temperature, and held here until the structure completely changes to bainite. This is generally adopted (for example, see Japanese Patent Publication No. 55-3422). In other words, cooling and austempering are performed in one bath, but such a method inevitably increases the overall processing time. Therefore, in the past, cooling and austempering were performed using separate means, and the temperature of the cooling bath was lowered to a temperature lower than the austempering temperature for rapid cooling, thereby shortening the overall processing time.
しかるに、かかる急冷を行なう場合、鋳鉄部品
の表面温度がオーステンパー処理温度に達する前
に冷却浴から引き上げて恒温保持しないと、表面
部にマルテンサイトが多量に混在して鋳鉄部品の
機械的性質を損う結果となる。しかも、鋳鉄部品
の表面と内部では温度降下速度が異なるため、冷
却浴からの引き上げ時点で両者の温度差が例えば
200度以上にもなることがあり、この状態で鋳鉄
部品を恒温処理炉に投入しても前記温度差が解消
されるのに例えば10分以上かかることがある。そ
の間、内部では高温での変態が進行する結果、強
度の低いベイナイトが生じたり、さらにはパーラ
イト、羽毛状ベイナイトが生成することになる。
すなわち、冷却浴からの鋳鉄部品の引き上げタイ
ミングを誤まると所期のベイナイトが生成され
ず、このタイミングをはかるのが難しいという問
題がある。 However, when such rapid cooling is performed, unless the cast iron parts are removed from the cooling bath and maintained at a constant temperature before the surface temperature reaches the austempering temperature, a large amount of martensite will be mixed on the surface, which will deteriorate the mechanical properties of the cast iron parts. This will result in a loss. Moreover, since the temperature drop rate is different between the surface and the inside of cast iron parts, the temperature difference between the two at the time of removal from the cooling bath is, for example,
The temperature can reach 200 degrees or more, and even if cast iron parts are placed in a constant temperature treatment furnace in this state, it may take, for example, 10 minutes or more for the temperature difference to be resolved. During this time, transformation at high temperatures progresses inside, resulting in the production of bainite with low strength, and furthermore, the formation of pearlite and feather-like bainite.
That is, if the timing of pulling the cast iron component from the cooling bath is incorrect, the desired bainite will not be generated, and there is a problem in that it is difficult to measure the timing.
本発明は、かかる点に鑑み、オーステナイト化
温度からオーステンパー処理温度までの冷却にオ
ーステンパー処理温度よりも低い温度の流動床炉
を用い、鋳鉄部品がオーステンパー処理温度より
も上の所定温度になつた時点で流動床炉における
流動を停止し、流動用粒体の断熱効果を利用して
徐冷することにより、鋳鉄部品の表面部の過冷を
防止するとともに、該表面部と内部の温度差を短
時間でなくし、該鋳鉄部品がオーステンパー処理
温度になつた時点で流動床炉から取り出して恒温
処理炉でオーステンパー処理を行なうことによ
り、安定したベイナイト組織が得られるようにし
た鋳鉄部品の熱処理方法を提供するものである。 In view of this, the present invention uses a fluidized bed furnace at a temperature lower than the austempering temperature for cooling from the austenitizing temperature to the austempering temperature, so that the cast iron parts are heated to a predetermined temperature above the austempering temperature. By stopping the flow in the fluidized bed furnace at the point when the fluidized bed furnace cools slowly using the heat insulating effect of the fluidized granules, the surface of the cast iron part is prevented from overcooling, and the temperature of the surface and inside of the part is reduced. A cast iron part that eliminates the difference in a short time, and when the cast iron part reaches the austempering temperature, is removed from the fluidized bed furnace and subjected to austempering treatment in a constant temperature treatment furnace, thereby obtaining a stable bainite structure. The present invention provides a heat treatment method.
以下、本発明の構成を実施例につき図面に基づ
いて説明する。 DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below with reference to the drawings.
第１図は本発明で使用する流動床炉の一例を示
す。すなわち、同図の流動床炉１において、２は
炉体で下部に分流板３が取り付けられ、該分流板
３の上に流動用粒体４がある。分流板３には流動
用エアのみが通ることができる孔が分流板３の全
体にわたつて均等に開設されている。炉体２の外
周には加熱ヒータ５が設けられ、また炉体２の底
部にはエアポンプ７が通気管６で連結されてお
り、該通気管６にはバルブ８が介設されている。
９は鋳鉄部品である。 FIG. 1 shows an example of a fluidized bed furnace used in the present invention. That is, in the fluidized bed furnace 1 shown in the figure, reference numeral 2 denotes a furnace body, and a flow divider plate 3 is attached to the lower part of the furnace body. The flow dividing plate 3 has holes evenly formed throughout the flow dividing plate 3 through which only flowing air can pass. A heater 5 is provided on the outer periphery of the furnace body 2, and an air pump 7 is connected to the bottom of the furnace body 2 through a ventilation pipe 6, and a valve 8 is interposed in the ventilation pipe 6.
9 is a cast iron part.
流動用粒体４としては、セラミツク、例えば、
Al2O3，SiO2，ZrO3，MgOなどの金属酸化物、
TiC，BaCなどの炭化物、サーメツト類が用いら
れる。流動用気体としては空気の他、窒素、アル
ゴン、炭酸ガスなどを用いてもよい。 As the fluidizing granules 4, ceramics, for example,
Metal oxides such as Al 2 O 3 , SiO 2 , ZrO 3 , MgO,
Carbides such as TiC and BaC, and cermets are used. In addition to air, nitrogen, argon, carbon dioxide, or the like may be used as the fluidizing gas.
鋳鉄部品９の熱処理工程は第２図に示されてい
る。 The heat treatment process for the cast iron part 9 is shown in FIG.
第１工程においては、鋳鉄部品９を高温加熱炉
に装入し、オーステナイト化温度（850〜1000℃）
に加熱する。高温加熱炉の雰囲気としては、大気
状態、真空状態、アルゴンや窒素などの不活性ガ
スあるいは浸炭性ガスを充満させた状態のいずれ
でもよい。 In the first step, the cast iron part 9 is charged into a high-temperature heating furnace and heated to an austenitizing temperature (850 to 1000°C).
Heat to. The atmosphere of the high-temperature heating furnace may be air, vacuum, or filled with an inert gas such as argon or nitrogen, or a carburizing gas.
第２工程においては、高温加熱炉から取り出し
た鋳鉄部品９を流動床炉１へ装入し、急冷する。
流動床炉１は炉体２内の温度がオーステンパー処
理温度（200〜400℃）よりも低い温度となるよう
に加熱ヒータ５およびエアポンプ６からのエアの
供給により調節しておく。また、流動用粒体４は
分流板３の下方からのエアの供給により浮遊流動
した状態にある。この第２工程では、鋳鉄部品９
を表面温度がオーステンパー処理温度よりも上の
所定温度（450℃以下）になるまで冷却する。こ
の所定温度については後述する。 In the second step, the cast iron parts 9 taken out from the high-temperature heating furnace are charged into the fluidized bed furnace 1 and rapidly cooled.
The fluidized bed furnace 1 is adjusted by supplying air from a heater 5 and an air pump 6 so that the temperature inside the furnace body 2 is lower than the austempering temperature (200 to 400°C). Further, the fluidizing particles 4 are in a suspended fluid state due to the supply of air from below the flow dividing plate 3. In this second step, the cast iron parts 9
is cooled until the surface temperature reaches a predetermined temperature (below 450°C) above the austempering temperature. This predetermined temperature will be described later.
第３工程においては、鋳鉄部品９の表面温度が
前記所定温度に達した時点で、炉体２内へのエア
の供給を止め、流動用粒体４の流動を停止した状
態で鋳鉄部品９の徐冷を行なう。この徐冷におい
ては、流動を停止した流動用粒体４が断熱作用を
呈し、鋳鉄部品９の表面温度の降下速度が極めて
遅くなるとともに、内部温度は比較的短時間で表
面温度と等しくなる。この第３工程では、鋳鉄部
品がオーステンパー処理温度になるまで徐冷す
る。 In the third step, when the surface temperature of the cast iron part 9 reaches the predetermined temperature, the supply of air into the furnace body 2 is stopped, and the flow of the cast iron part 9 is stopped while the flow of the fluidizing granules 4 is stopped. Perform gradual cooling. In this slow cooling, the fluidizing particles 4 that have stopped flowing exhibit an adiabatic effect, and the rate of decrease in the surface temperature of the cast iron component 9 becomes extremely slow, and the internal temperature becomes equal to the surface temperature in a relatively short time. In this third step, the cast iron part is slowly cooled to the austempering temperature.
第４工程においては、鋳鉄部品９が所期のオー
ステンパー処理温度の±20度の範囲になつた時点
で、該鋳鉄部品９を流動床炉１から取り出して恒
温処理炉へ入れ、該恒温処理炉でオーステンパー
処理を行なう。 In the fourth step, when the cast iron part 9 reaches the range of ±20 degrees of the intended austempering temperature, the cast iron part 9 is taken out from the fluidized bed furnace 1 and placed in a constant temperature treatment furnace, and the constant temperature treatment is performed. Perform austempering treatment in a furnace.
第５工程においては、鋳鉄部品９のオーステン
パー処理が完了した時点で、該鋳鉄部品９を恒温
処理炉から取り出し、炉外で冷却する。 In the fifth step, when the austempering of the cast iron part 9 is completed, the cast iron part 9 is taken out of the constant temperature treatment furnace and cooled outside the furnace.
なお、恒温処理炉は例えば大気、窒素あるいは
真空の雰囲気とする。 Note that the constant temperature treatment furnace has an atmosphere of air, nitrogen, or vacuum, for example.
次に、鋳鉄部品の流動床炉での冷却につき、第
３図に示す比較試験結果に基づいて説明する。 Next, cooling of cast iron parts in a fluidized bed furnace will be explained based on the comparative test results shown in FIG.
供試材は直径35mm、高さ35mmの内柱状鋳鉄部品
で、Cuを0.8重量％、Moを0.08重量％含有するダ
クタイル鋳鉄製のものである。試験は、上記鋳鉄
部品の表面と中心部とにそれぞれ熱電対を取り付
け、該鋳鉄部品を920℃から流動床炉に焼入れた
ときの冷却曲線をみるものである。比較は、流動
床炉の温度を常温（11℃）として鋳鉄部品がオー
ステンパー処理温度よりも上の所定温度で流動を
停止した本発明例と、オーステンパー処理温度
（250℃）に保持した流動床炉で焼入れした比較例
１と、流動床炉は常温で途中で流動を停止するこ
となく冷却を続行した比較例２との間で行なつ
た。第３図に示す冷却曲線において、K1，K2は
本発明例、L1，L2は比較例１、M1，M2は比較例
２にかかるもので、それぞれK1，L1，M1は表面
部、K2，L2，M2は中心部に関する。 The test material is an inner columnar cast iron part with a diameter of 35 mm and a height of 35 mm, and is made of ductile cast iron containing 0.8% by weight of Cu and 0.08% by weight of Mo. In the test, thermocouples were attached to the surface and center of the cast iron part, and the cooling curve was observed when the cast iron part was quenched from 920°C in a fluidized bed furnace. The comparison is between an example of the present invention in which the fluidized bed furnace was kept at room temperature (11°C) and the flow stopped at a predetermined temperature above the austempering temperature of the cast iron part, and a fluidized bed furnace maintained at the austempering temperature (250°C). Comparative Example 1 was quenched in a bed furnace, and Comparative Example 2 was quenched in a fluidized bed furnace at room temperature without stopping the flow midway through cooling. In the cooling curve shown in FIG. 3, K 1 and K 2 are those of the present invention example, L 1 and L 2 are those of Comparative Example 1, and M 1 and M 2 are those of Comparative Example 2 ; M 1 relates to the surface part, and K 2 , L 2 and M 2 relate to the center part.
本発明例の場合、K1で示される表面部の温度
がオーステンパー処理温度（250℃）よりも40度
程度高い時点、つまり、焼入れ後、１分強経過し
た時点ａで流動を停止している。この時点では表
面部と中心部の温度差は200度近くあるが、流動
用粒体の断熱作用により表面部の過冷が抑えられ
る結果、５分後には前記温度差が完全に解消して
いる。そして、冷却速度がゆるやかになるため、
250℃の恒温処理炉に移すタイミングも鋳鉄部品
と恒温処理炉との温度差を±５℃として60秒程度
の時間的余裕があり、タイミングをとりやすい。 In the case of the example of the present invention, the flow was stopped at the point when the temperature of the surface portion indicated by K 1 was about 40 degrees higher than the austempering temperature (250 degrees Celsius), that is, at point a, which was a little more than 1 minute after quenching. There is. At this point, the temperature difference between the surface and the center is nearly 200 degrees, but the heat insulating effect of the fluidizing particles suppresses supercooling of the surface, and the temperature difference completely disappears after 5 minutes. . And since the cooling rate becomes slower,
The timing for transferring to the constant temperature treatment furnace at 250℃ is easy to determine, as there is a margin of about 60 seconds with a temperature difference of ±5℃ between the cast iron parts and the constant temperature treatment furnace.
これに対し、比較例１の場合、急冷速度が遅い
ため、表面部の冷却曲線L1のｂおよび中心部の
冷却曲線L2のｃにおいてA1変態停点が明確にあ
らわれており、冷却時間が長くなるとともに焼入
れ不良を生じ易い。 On the other hand, in the case of Comparative Example 1, because the quenching rate is slow, the A1 transformation stop point clearly appears at the cooling curve L1 b at the surface and at the cooling curve L2 c at the center, and the cooling time As the length increases, quenching defects tend to occur.
比較例２の場合、冷却曲線M1で示される表面
部の温度は約５分で常温に達する。このダクタイ
ル鋳鉄のMS点（マルテンサイト組織が析出する
温度）は約200℃であり、その温度に達する前、
つまり約1.2分を経過する前に流動床炉から取り
出さなければならない。さらには、中心部にA1
変態が生じなくなる時点ｄから表面部温度がMS
点を越えない時点ｅまでの極めて短時間のうちに
鋳鉄部品を取り出さなければならない。しかも、
そのときでも表面部と中心部とでは温度差が200
度程度あるため、このまま鋳鉄部品を恒温処理炉
へ投入しても温度差は10分以上解消されず、所望
のベイナイト組織と異なる組織が生じ易い。 In the case of Comparative Example 2, the temperature of the surface portion indicated by the cooling curve M1 reaches room temperature in about 5 minutes. The MS point (temperature at which martensitic structure precipitates) of this ductile cast iron is approximately 200℃, and before reaching that temperature,
In other words, it must be removed from the fluidized bed furnace before approximately 1.2 minutes have elapsed. Furthermore, in the center A 1
From the point d when no transformation occurs, the surface temperature becomes MS
The cast iron part must be removed within a very short time up to the point e. Moreover,
Even then, there is a temperature difference of 200% between the surface and the center.
If the cast iron parts are placed in a constant temperature treatment furnace as they are, the temperature difference will not be resolved for more than 10 minutes, and a structure different from the desired bainite structure is likely to occur.
第４図は、流動停止のタイミングを変えた場合
の冷却曲線を示すもので、供試材および測温方法
は前記比較試験と同様である。 FIG. 4 shows cooling curves when the timing of stopping the flow was changed, and the sample materials and temperature measurement method were the same as those in the comparative test.
同図の冷却曲線において、P1，P2は流動停止
を表面部温度が350℃の時点で行なつた例であり、
また、Q1，Q2は流動停止をMS点の直前で行なつ
た例である。P1，Q1は表面部、P2，Q2は中心部
に関する。 In the cooling curve in the same figure, P 1 and P 2 are examples in which the flow was stopped when the surface temperature was 350°C.
Further, Q 1 and Q 2 are examples in which the flow was stopped just before the MS point. P 1 and Q 1 relate to the surface part, and P 2 and Q 2 relate to the center part.
流動停止が早い場合は、冷却曲線P2上でｆで
示される如く中心部にA1変態が観察される。ま
た、流動停止が遅い場合は、表面部と中心部との
温度差が解消される時点でMS点以下の温度とな
つている。従つて、流動停止のタイミングは、所
期のオーステンパー処理温度よりも高温でしかも
その温度より上方100度未満がよい。つまり、所
期のオーステンパー処理温度よりも100度以上の
時点で流動停止すると、所期のオーステンパー処
理温度に達するのに長時間を要するとともに、高
温での変態が進行する結果、強度の低いベイナイ
トが混在することになり、さらに中心部ではパー
ライトや羽毛状ベイナイトが生成し易くなり好ま
しくない。また、所期のオーステンパー処理温度
よりも低い温度で流動を停止すると、恒温処理炉
において所期のオーステンパー処理温度に到達す
るのに時間がかかり、さらに、所期のベイナイト
組織よりも硬くてもろいベイナイトが混在する結
果となり好ましくない。 When the flow stops quickly, A1 transformation is observed in the center as shown by f on the cooling curve P2 . In addition, if the flow stops slowly, the temperature is below the MS point at the time when the temperature difference between the surface part and the center part is eliminated. Therefore, the timing of stopping the flow is preferably higher than the intended austempering temperature and less than 100 degrees above that temperature. In other words, if the flow stops at 100 degrees or more above the intended austempering temperature, it will take a long time to reach the desired austempering temperature, and as a result of the transformation at high temperatures, the strength will be low. Bainite will be mixed, and pearlite and feather-like bainite will be likely to be generated in the center, which is undesirable. Furthermore, if the flow is stopped at a temperature lower than the desired austempering temperature, it will take time to reach the desired austempering temperature in the constant temperature treatment furnace, and the structure will be harder than the desired bainite structure. The result is that brittle bainite is mixed, which is not desirable.
また、鋳鉄部品を流動床炉から引き上げるタイ
ミングは、鋳鉄部品各部の温度がオーステンパー
処理温度の±20度の範囲にあるときである。例え
ば、大気を雰囲とする恒温処理炉では、塩浴と違
つて熱伝達量が非常に小いため、鋳鉄部品が恒温
処理炉の温度と等しくなるのに時間がかかる。従
つて、鋳鉄部品の温度が恒温処理炉の温度にでき
るだけ近くなつた時点で引き上げるのが良く±20
度を越えると直径25mm、高さ25mm程度の小さなも
のでも恒温処理炉の温度に達するまでに180秒程
度かかり好ましくない。 Furthermore, the timing for lifting the cast iron parts from the fluidized bed furnace is when the temperature of each part of the cast iron parts is within ±20 degrees of the austempering temperature. For example, in a constant-temperature treatment furnace using air as an atmosphere, unlike a salt bath, the amount of heat transfer is very small, so it takes time for the cast iron parts to equalize the temperature of the constant-temperature treatment furnace. Therefore, it is best to raise the temperature by ±20° when the temperature of the cast iron parts is as close as possible to the temperature of the constant temperature treatment furnace.
If the temperature is exceeded, even a small item as small as 25 mm in diameter and 25 mm in height will take about 180 seconds to reach the temperature of the constant temperature processing furnace, which is undesirable.
なお、ダクタイル鋳鉄としてはFCD45相当の
ものやこれにMo，Niなどの合金元素を含有した
ものでもよく、また、本発明はダクタイル鋳鉄以
外の他の鋳鉄にも適用することができる。 Note that the ductile cast iron may be one equivalent to FCD45 or one containing alloying elements such as Mo and Ni, and the present invention can also be applied to other cast irons other than ductile cast iron.
また、本発明が鋳鉄部品全体を均一な組織にす
る場合だけでなく、表面より所定深さまでの層に
のみオーステンパー処理を施す場合にも適用でき
ることはもちろんである。 Furthermore, it goes without saying that the present invention can be applied not only to the case where the entire cast iron part has a uniform structure, but also to the case where the austempering treatment is applied only to a layer from the surface to a predetermined depth.
以上のように、本発明によれば、鋳鉄部品がオ
ーステンパー処理温度よりも上の所定温度になつ
た時点で流動床炉における流動を停止して徐冷す
るようにしたから、鋳鉄部品表面部の過冷を流動
用粒体の断熱作用により抑えつつ、表面部と内部
との温度差を短時間で解消することができ、ま
た、過冷が抑えられる結果、流動床炉から鋳鉄部
品を恒温処理炉に移すタイミングもとり易くな
り、恒温処理炉でのオーステンパー処理により所
期の金属組織が得易くなるという優れた効果が得
られる。 As described above, according to the present invention, when the cast iron part reaches a predetermined temperature higher than the austempering temperature, the flow in the fluidized bed furnace is stopped and the cast iron part is gradually cooled. The temperature difference between the surface and the inside can be eliminated in a short time while suppressing supercooling due to the insulating effect of the fluidized granules. Also, as a result of suppressing supercooling, cast iron parts can be kept at a constant temperature from the fluidized bed furnace. The timing of transferring to a processing furnace becomes easier, and the austempering treatment in a constant temperature processing furnace makes it easier to obtain the desired metal structure, which is an excellent effect.
図面は本発明の実施態様を例示し、第１図は流
動床炉の全体構成図、第２図は熱処理工程図、第
３図は本発明方法と他の熱処理方法との冷却曲線
を示すグラフ図、第４図は流動停止時期を変えた
場合を示すグラフ図である。
１……流動床炉、４……流動用粒体、７……エ
アポンプ、８……バルブ、９……鋳鉄部品。
The drawings illustrate embodiments of the present invention; FIG. 1 is an overall configuration diagram of a fluidized bed furnace, FIG. 2 is a heat treatment process diagram, and FIG. 3 is a graph showing cooling curves between the method of the present invention and other heat treatment methods. 4 are graphs showing the case where the flow stop timing is changed. 1... Fluidized bed furnace, 4... Fluidized granules, 7... Air pump, 8... Valve, 9... Cast iron parts.
Claims (1)
次いで該鋳鉄部品をオーステンパー処理温度より
も低い温度の流動床炉に入れ、該鋳鉄部品がオー
ステンパー処理温度よりも上の所定温度になつた
時点で流動を停止して徐冷し、該鋳鉄部品がオー
ステンパー処理温度になつた時点で該鋳鉄部品を
流動床炉から取り出して恒温処理炉へ入れ、該恒
温処理炉でオーステンパー処理を行なうことを特
徴とする鋳鉄部品の熱処理方法。1 Heating the cast iron part to the austenitizing temperature,
Next, the cast iron part is placed in a fluidized bed furnace at a temperature lower than the austempering temperature, and when the cast iron part reaches a predetermined temperature above the austempering temperature, the flow is stopped and the cast iron is gradually cooled. A method for heat treating cast iron parts, which comprises taking out the cast iron part from a fluidized bed furnace and placing it in a constant temperature treatment furnace when the part reaches an austempering temperature, and performing austempering treatment in the constant temperature treatment furnace.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21617182A JPS59107018A (en) | 1982-12-08 | 1982-12-08 | Heat treatment of cast iron parts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21617182A JPS59107018A (en) | 1982-12-08 | 1982-12-08 | Heat treatment of cast iron parts |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS59107018A JPS59107018A (en) | 1984-06-21 |
| JPH032927B2 true JPH032927B2 (en) | 1991-01-17 |
Family
ID=16684394
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21617182A Granted JPS59107018A (en) | 1982-12-08 | 1982-12-08 | Heat treatment of cast iron parts |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS59107018A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59157221A (en) * | 1983-02-25 | 1984-09-06 | Hitachi Metals Ltd | Manufacture of spheroidal graphite cast iron |
| JPS6024318A (en) * | 1983-02-25 | 1985-02-07 | Hitachi Metals Ltd | Manufacture of spheroidal graphite cast iron |
| JPS61136620A (en) * | 1984-12-08 | 1986-06-24 | Japan Steel Works Ltd:The | Subzero treatment of steel stock |
| JPS6247424A (en) * | 1985-08-23 | 1987-03-02 | Mazda Motor Corp | Heat treatment device for casting |
| JP2632678B2 (en) * | 1987-02-13 | 1997-07-23 | 森川産業株式会社 | Cooling method for casting products |
| JP2685965B2 (en) * | 1990-06-18 | 1997-12-08 | 本田技研工業株式会社 | Heat treatment method for spheroidal graphite cast iron material |
| JP6445897B2 (en) * | 2015-02-24 | 2018-12-26 | 浜松ヒートテック株式会社 | Cooling system |
-
1982
- 1982-12-08 JP JP21617182A patent/JPS59107018A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59107018A (en) | 1984-06-21 |
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