JP2004278930A

JP2004278930A - Continuous heat treatment device

Info

Publication number: JP2004278930A
Application number: JP2003071549A
Authority: JP
Inventors: Masaaki Koga; 正明古閑; Hisami Yajima; 久美矢島
Original assignee: Hitachi Metals Ltd
Current assignee: Proterial Ltd
Priority date: 2003-03-17
Filing date: 2003-03-17
Publication date: 2004-10-07

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous heat treatment device capable of remarkably reducing its heat treatment time and inhibiting the generation of distortion, with respect to the heat treatment device suitably used for aluminum vehicle parts, in particular, a light alloy wheel having a large diameter of more than 16 inches. <P>SOLUTION: This continuous heat treatment device for aluminum vehicle parts comprises a conveying means for conveying the aluminum vehicle parts inside, and an air blasting means capable of controlling a wind speed of the furnace atmosphere to be 15 m/s or more, a temperature rise time to a solution treatment temperature of the aluminum vehicle parts is within 30 minutes, and a control width of a work temperature after the temperature rise can be controlled to a target temperature ±2 °C or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、アルミ車両用部品の連続式熱処理装置に関するものであり、特に１６インチ以上の大口径を有する軽合金ホイールに適用するものである。
【０００２】
【従来の技術】
車両用ホイールは、鋼板を加工して製作されるものが安価であり採用されているが、近年軽量化や意匠（デザイン）性などから、アルミ鋳物で製作されてきている。またクロスメンバーや足回り部品も、軽量化を目的にアルミで製作され始めている。このためアルミ鋳物は乗用車用ホイール、クロスメンバーおよび足廻り部品等比較的小型の部品が主流であり、トラック用ホイールなど比較的大型の物にはアルミ鍛造品（例えばＪＩＳ６０６１など）が用いられてきている。
【０００３】
強度部品用として現状最も良好な性能を持つアルミ鋳物用合金はＪＩＳに定められているＡＣ４Ｃ，ＡＣ４ＣＨ材が中心であるが、この材料は機械的性質と鋳造性とのバランスのとれたアルミ合金鋳物材であり、熱処理（Ｔ６処理）を施すことにより高強度、高靭性が得られ、この性質が必要なたとえば自動車のアルミホイールとして用いられている。このＴ６処理（溶体化処理＋時効処理）は、これまで昇温に１〜２時間、保持に４〜６時間と計６〜８時間必要であったが、原価低減および省エネ等の要望により大幅な時間短縮が求められるようになっている。
【０００４】
例えば特開２００２−１７３７０８号においては高速昇温炉として循環ファンを用いた構成が開示されている。同公報によれば、ワーク搬送口が２つ重ねて備えられ、両者は開閉可能な扉を有する構造であり、かつ扉が閉状態の時に炉室の内壁と外壁との間で炉内雰囲気が循環する循環通路が確保されることが記載されている。しかしながら同公報では一般的な高速昇温炉の構造のみしか記載されておらず、しかもワークは連続式のものでなく、同搬送口からワークを出し入れするものである。特に車両用ホイールを熱処理するための最適な構造については何も記載されていない。
【０００５】
【特許文献１】
特開２００２−１７３７０８号公報（第３頁左欄４６行目〜第４頁右欄６行目、図１）
【０００６】
【発明が解決しようとする課題】
よって発明が解決しようとする課題はアルミ車両部品、特に１６インチ以上の大口径を有する軽合金ホイールに好適な連続式熱処理装置であり、その熱処理時間を大幅に短縮することができるとともに歪の発生を抑制可能な連続式熱処理装置を提供するものである。
【０００７】
【課題を解決するための手段】
上記目的を達成する方法は熱処理温度を上げその処理時間を短縮することである。しかしながらＴ６処理（溶体化処理＋時効処理）の中で特に溶体化処理温度を現行処理温度（５００〜５４０℃）より更にあげることは５７５℃近傍に存在する共晶温度直下での熱処理となり部分融解等の問題で現状実用化されていない。これまで炉では温度制御幅は±５℃程度であるが、５５５℃以上で温度を制御する場合、部分溶解および軟化による変形等が考えられ、非常に危険である。これを可能にするため鋭意検討した結果、次の連続式熱処理装置を得たものである。
つまり本発明は、アルミ車両部品用の連続式熱処理装置であって、前記連続式熱処理装置は内部で前記アルミ車両部品を搬送できる搬送手段と、炉内雰囲気の風速を１５ｍ／ｓ以上とすることが可能な送風手段を具備し、前記アルミ車両部品の溶体化処理温度までの昇温時間が３０分以内であり、かつ昇温後のワーク温度制御幅が目標温度±２℃以下で制御可能なことを特徴とするものである。
【０００８】
特にアルミ車両部品用が車両用ホイールである場合、本発明の連続式熱処理装置は内部で前記軽合金ホイールを搬送できる搬送手段と、炉内雰囲気の風速を１５ｍ／ｓ以上とすることが可能な送風手段を具備し、前記搬送手段は前記軽合金製ホイールの軸を垂直方向のまま搬送可能な構造であるとともに、炉内雰囲気の風向きを実質的に垂直方向にしたものが好適である。ここで軽合金ホイールの軸を垂直方向のまま搬送させるのは通常よりも高い溶体化処理温度（４５５〜４６５℃）まで短時間加熱するために軽合金ホイールを回転軸を平行にして積載・搬送するとリムの部分で歪が発生するためである。
【０００９】
熱媒体である炉内空気の流速を一般的に５ｍ／ｓ程度であったものを、その流速を１５ｍ／ｓ以上とすることで温度のバラツキを±２℃に抑えることが可能となり、共晶温度直下の温度を狙っても部分融解の可能性が工業生産レベルでも起きなくなった。また熱媒体である炉内空気の流速を速くすることにより昇温速度も向上し熱処理時間短縮に大幅に寄与する。特にアルミホイールを処理する場合、１５ｍ／ｓの送風では、ホイール側面（タイヤ面側）より送風すると均一な昇温がされず、最も厚肉部で且つ平らであるデザイン面方向より送風することが実験の結果必要であることが解った。これらの技術を織込んだ本特許記載の熱処理炉を使うことにより初めてＴ６処理を２時間という非常に短い時間での処理が可能となる。非熱処理品が１６インチ以上の軽合金ホイールではホイールリムの歪を抑制することが重要課題である。この熱処理炉の構成を用いることで熱処理中に歪みの発生を従来よりも格段に少なくすることができる。
【００１０】
また、搬送手段は上下方向に複数備えられるとともに通風可能であり、炉内雰囲気の風向きが上側から下側である部分と、下側から上側である部分とを具備するものであれば設置面積が同じ熱処理炉でも大容量の被熱処理品を処理可能であり、かつ被熱処理品の必要部分を均一に昇温することが可能である。溶体化処理を行う装置内の位置において風向きが上側から下側である部分と、下側から上側である部分とを具備することが好ましい。
【００１１】
前記被熱処理品は、搬送方向での炉断面におけるの積載個数が４ヶ以下かつ並列に並び、実質的に１ヶ流しである構造であればライン管理上好ましい。
【００１２】
搬送手段はアルミ車両部品のみを搬送できる機構が好ましい。アルミ車両部品のみを搬送できる機構とは、ラックなどの積載用部材が不用であることを意味する。例えば歪防止用のジグ的なものなど、熱処理品と比べて小さく熱容量の小さいものであれば本願発明の均等の範囲である。熱処理時間を大幅に短縮することおよびワークを積載するトレーを使用しないことが好ましい。トレーを昇温する必要が無くなるために省エネの効果も期待できる。
【００１３】
【発明の実施の形態】
以下に本発明の実施の形態を説明する。
本発明の熱処理炉の一例を図１，２の模式図で説明する。
図１は本発明の熱処理装置の要部断面の模式図である。熱処理装置１は装置内の雰囲気を循環するための循環器２を備えており、その循環器の傍には装置内の雰囲気温度を昇温する為の熱源３が備えられている。図中、破線の矢印は装置内の雰囲気の風向きを示すものである。５ａ、５ｂは循環器と連結されたダクトである。ここでは循環器２から熱風がダクト５ｂに送られ、そこから装置内を上方に向けて熱風を送風している。この熱風は装置内で搬送される軽合金ホイール３０を昇温し、その後ダクト５ａから循環器２に戻る構造が取られている。軽合金ホイール３０は搬送手段４ａ，ｂによって図の紙面上奥に向い搬送される。図中１０は車両用ホイールを搬送手段４から離れた位置に備えられる浴槽８に出すための窓である。
【００１４】
図２は図１のＡ−Ａ断面である。図中６は軽合金ホイールの搬入口、７が搬出口である。搬入口より搬入された軽合金ホイール３０は搬送手段により図中右方向に移動する。まず上記に示したように循環器から送られた熱風がダクト５ｂから５ａに向って送風され、この間は下から上の風向きの熱風により昇温される。このダクト５ａ、５ｂの間を通過するのに要する時間は０．５時間であり、その間に軽合金ホイールは５６０℃±２℃にまで昇温される。
さらにその後、図中３０ｂの位置に搬送された軽合金ホイールはダクト５ｃからダクト５ｄの方向の熱風により先程とは反対方向の送風で昇温される。このダクト５ｃ、５ｄの間を通過するのに要する時間は０．５Ｈであり、その間軽合金ホイールは５６０℃±２℃の範囲で保持にまで昇温される。この装置内の場所により風向きを変えることで車両用ホイールが複数段で垂直方向に積載される形態の連続式熱処理装置であっても車両用ホイール全体が均一に昇温・保持される。
【００１５】
その後、この車両用ホイールを昇降アーム９により窓１０介してを搬送手段から降ろし、浴槽８の水中に埋没させて急冷する。二重破線にてその車両用ホイールの移動ルートを示す。その後、時効処理として車両用ホイールは再度搬送手段に積載される。ダクト５ｅからダクト５ｆの方向に熱風を送風し、その間に車両用ホイールを１８０℃まで昇温・保持する。この時効処理に要する時間は１Ｈとした。その後熱処理（Ｔ６処理）が施された車両用ホイールは搬出口７より装置外に出され、次の加工工程に搬送される。搬入からここまでに必要な処理時間は１Ｈ以内である。
【００１６】
アルミ車両用部品としてアルミホイールを用い実験を行った。図３に示す代表的な４ヶ所（▲１▼湯口近傍、▲２▼フロントフランジ、▲３▼タイヤ面中央、▲４▼インナーフランジ）にその厚さ中央部まで穴をあけて熱伝対を取付けた。その後、上記した本発明の熱処理装置に挿入し装置内の雰囲気の循環風速を変えて、その昇温状況および昇温後の温度制御状況を確認した。昇温時間は最も昇温が遅い部位が目標温度に到達するのに必要な時間とする。
昇温速度は、ワークの形状および重量によっても異なるが装置内の循環風速が早いほど短くなり、流速１５ｍ／ｓを超えると実質的に３０分以下となる。また温度制御状況も、炉内風速が１５ｍ／ｓをこえると温度制御幅±２℃に収まる。装置内での処理時間と各測定位置での温度との関係を図４にしめす。また各風速（６，１０，１７ｍ／ｓ）毎の昇温時間および昇温後の温度制御状況を表１にしめす。ここでの風速とは軽合金ホイールが搬送される位置で測定したものを指す。
【００１７】
【表１】

【００１８】
（参考例）
図２に示す熱処理装置において、循環器からの熱風の風向きを軽合金ホイールの搬送方向に対して水平方向として（図２の紙面上、手前から奥）熱処理を施した。他、熱処理の送風条件、搬送条件は実施例１と同様にしている。この条件で行った場合の軽合金ホイールの昇温時間を表１に参考例として併記する。送風を１５ｍ以上としてもリムのアウターフランジ側とインナーフランジ側とで昇温に必要な時間が３分以上異なることが解る。これは厚肉部となる意匠面では部分的に熱容量が多いことによるものと思われる。前記したように車両用ホイールは搬送する際には回転軸を垂直方向にして運ぶ必要が有るため、送風の方向はこの軸に平行にし、熱風が車両用ホイールのリムで遮られないような垂直方向の送風が好ましいことが解った。これにより強度のバラツキも抑制可能である。
【００１９】
本発明の高温、短時間での熱処理を施した場合、熱処理後の機械的性質が少なくとも従来の熱処理条件と最低でも同程度である必要がある。そこで本発明の熱処理装置を用いた軽合金ホイールから試験片を切りだして供試材を作製し、従来熱処理条件品との比較で引張試験を実施した。結果を表２に示す。従来の熱処理条件と本熱処理装置を用いて高温、短時間で処理したものとの間を比較すると、高温での熱処理が可能となったために機械的性質は向上していることが認められる。また図５に従来と本発明の熱処理装置で熱処理した車両用ホイールのミクロ組織写真を示す。両者ともアウターフランジ部のものである。本発明で熱処理したものは熱処理時間がトータル１Ｈ程と短いにも係わらず両者の間に有意差は認められない。
【００２０】
【表２】

【００２１】
共晶温度直下で熱処理を実施するためワークの歪状況を確認する必要がある。そこで従来の送風を行わない熱処理条件との比較で歪発生状況を確認した。測定方法は、アウターフランジ部９点を定め、その各点の熱処理前後での相対的な差異をとり絶対値で評価した。本発明の熱処理装置を用いた結果を表３に、従来の熱処理装置を用いた結果を表４に示す。本発明で熱処理したものは熱処理時間がトータル１Ｈ程と短いにも係わらず最大変位量および平均変位量ともに従来の５Ｈ以上もかかって処理していたものと同程度の車両用ホイールを得ることができている。
【００２２】
【表３】

【００２３】
【表４】

【００２４】
【発明の効果】
これによりアルミ車両部品、特に１６インチ以上の大口径を有する軽合金ホイールに好適な熱処理装置を提供できた。熱処理時間を大幅に短縮することができるとともに車両用ホイールにおいては歪の発生を抑制可能な連続式の熱処理設備を提供できた。
【図面の簡単な説明】
【図１】本発明の連続式熱処理装置の要部を示す模式断面図である。
【図２】図１のＡ−Ａ断面図である。
【図３】測定ヶ所を示す図である。
【図４】本発明の連続式熱処理装置を使用した再の車両用ホイールの昇温の状態を示す図である。
【図５】熱処理後の車両用ホイールのミクロ写真である。
【符号の説明】
１連続式熱処理装置、２循環器、３熱源、４搬送手段、５ダクト、６搬入口、７搬出口、８浴槽、９昇降手段、１０窓[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuous heat treatment apparatus for aluminum vehicle parts, and more particularly to a light alloy wheel having a large diameter of 16 inches or more.
[0002]
[Prior art]
Vehicle wheels manufactured by processing a steel plate are inexpensive and employed. However, in recent years, aluminum wheels have been manufactured from aluminum casting due to weight reduction and design (design) properties. Cross members and undercarriage parts have also begun to be made of aluminum to reduce weight. For this reason, relatively small parts such as wheels for passenger cars, cross members and undercarriage parts are mainly used for aluminum castings, and forged aluminum parts (for example, JIS6061) have been used for relatively large parts such as truck wheels. I have.
[0003]
Currently, aluminum casting alloys with the best performance for strength parts are mainly AC4C and AC4CH materials specified in JIS, but this material is an aluminum alloy casting with a balance between mechanical properties and castability. It is a material that can be subjected to heat treatment (T6 treatment) to provide high strength and high toughness, and is used as, for example, an aluminum wheel of an automobile that requires this property. This T6 treatment (solution treatment + aging treatment) required a temperature rise of 1 to 2 hours and a holding time of 4 to 6 hours, a total of 6 to 8 hours. It is required to reduce the time.
[0004]
For example, JP-A-2002-173708 discloses a configuration using a circulation fan as a high-speed heating furnace. According to the publication, two work transfer ports are provided so as to overlap each other, both of which have a door that can be opened and closed, and when the door is in a closed state, the furnace atmosphere is formed between the inner wall and the outer wall of the furnace chamber. It is described that a circulation passage for circulation is ensured. However, this publication describes only the structure of a general high-speed heating furnace, and the work is not of a continuous type, and works are put in and out of the transfer port. In particular, nothing is described about an optimum structure for heat-treating a vehicle wheel.
[0005]
[Patent Document 1]
JP-A-2002-173708 (page 3, left column, line 46 to page 4, right column, line 6, FIG. 1)
[0006]
[Problems to be solved by the invention]
Therefore, the problem to be solved by the present invention is a continuous heat treatment apparatus suitable for aluminum vehicle parts, particularly for light alloy wheels having a large diameter of 16 inches or more, which can significantly reduce the heat treatment time and generate distortion. It is intended to provide a continuous heat treatment apparatus capable of suppressing the heat treatment.
[0007]
[Means for Solving the Problems]
A method of achieving the above object is to increase the heat treatment temperature and shorten the treatment time. However, in the T6 treatment (solution treatment + aging treatment), raising the solution treatment temperature more than the current treatment temperature (500 to 540 ° C) is a heat treatment just below the eutectic temperature existing near 575 ° C and causes partial melting. At present, it is not practically used due to such problems. So far, the furnace has a temperature control range of about ± 5 ° C. However, if the temperature is controlled at 555 ° C. or higher, deformation due to partial melting and softening is considered, which is extremely dangerous. As a result of intensive studies to make this possible, the following continuous heat treatment apparatus was obtained.
In other words, the present invention is a continuous heat treatment apparatus for aluminum vehicle parts, wherein the continuous heat treatment apparatus has a conveying means capable of conveying the aluminum vehicle parts therein, and a wind speed in a furnace atmosphere of 15 m / s or more. Air blowing means capable of controlling the temperature of the aluminum vehicle component up to the solution heat treatment temperature within 30 minutes, and the work temperature control width after the temperature rise can be controlled at the target temperature ± 2 ° C. or less. It is characterized by the following.
[0008]
In particular, when the aluminum vehicle parts are used for vehicle wheels, the continuous heat treatment apparatus of the present invention is capable of transporting the light alloy wheel therein, and the wind speed of the furnace atmosphere can be set to 15 m / s or more. It is preferable that a blower is provided, and the transporter has a structure in which the axis of the light alloy wheel can be transported in a vertical direction and the atmosphere in the furnace has a substantially vertical wind. Here, when the light alloy wheel is transported in the vertical direction, the light alloy wheel is loaded and transported with the rotation axis parallel to heat the solution alloy processing temperature (455-465 ° C.) for a short time to a higher temperature than usual. Then, distortion occurs at the rim.
[0009]
The flow rate of the air in the furnace, which is a heating medium, was generally about 5 m / s, but by setting the flow rate to 15 m / s or more, the temperature variation can be suppressed to ± 2 ° C. The possibility of partial melting no longer occurs at the industrial production level even when aiming at a temperature just below the temperature. In addition, increasing the flow rate of the furnace air, which is a heating medium, increases the temperature rise rate, which greatly contributes to shortening the heat treatment time. In particular, when processing aluminum wheels, if the air is blown from the side of the wheel (tire side), the temperature rise is not uniform when the air is blown at 15 m / s, and the air is blown from the direction of the thickest and flat design surface. As a result of the experiment, it was found necessary. Only by using the heat treatment furnace described in this patent incorporating these technologies, the T6 treatment can be performed in a very short time of 2 hours. For light alloy wheels whose non-heat treated product is 16 inches or more, it is an important issue to suppress distortion of the wheel rim. By using this heat treatment furnace configuration, the occurrence of distortion during heat treatment can be significantly reduced as compared with the conventional case.
[0010]
In addition, a plurality of transport means are provided in the vertical direction and are capable of ventilating, and the installation area is as long as the furnace atmosphere includes a portion where the wind direction of the atmosphere in the furnace is from the upper side to the lower side and a part where the wind direction from the lower side is the upper side. Even in the same heat treatment furnace, a large-capacity heat-treated product can be processed, and a required portion of the heat-treated product can be uniformly heated. It is preferable to include a portion where the wind direction is from the upper side to the lower side and a portion where the wind direction is from the lower side to the upper side at a position in the apparatus for performing the solution treatment.
[0011]
It is preferable from the viewpoint of line management that the heat-treated product has a structure in which the number of stacked pieces in the furnace cross section in the transport direction is four or less and arranged in parallel, and is substantially one stream.
[0012]
The transporting means is preferably a mechanism capable of transporting only aluminum vehicle parts. The mechanism capable of transporting only aluminum vehicle parts means that a loading member such as a rack is unnecessary. For example, if the heat capacity of the heat-treated product is smaller than that of the heat-treated product, such as a jig for preventing distortion, the present invention is within the equivalent range. It is preferred that the heat treatment time be significantly reduced and that no tray for loading the work be used. Since there is no need to raise the temperature of the tray, energy saving effects can be expected.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
An example of the heat treatment furnace of the present invention will be described with reference to the schematic diagrams of FIGS.
FIG. 1 is a schematic diagram of a cross section of a main part of the heat treatment apparatus of the present invention. The heat treatment apparatus 1 includes a circulator 2 for circulating the atmosphere in the apparatus, and a heat source 3 for increasing the ambient temperature in the apparatus is provided beside the circulator. In the drawing, broken arrows indicate the wind direction of the atmosphere in the apparatus. 5a and 5b are ducts connected to the circulator. Here, hot air is sent from the circulator 2 to the duct 5b, from which hot air is blown upward in the apparatus. This hot air raises the temperature of the light alloy wheel 30 conveyed in the apparatus, and then returns to the circulator 2 from the duct 5a. The light alloy wheel 30 is conveyed by the conveying means 4a, b toward the back of the drawing. In the figure, reference numeral 10 denotes a window through which a vehicle wheel is put out of a bathtub 8 provided at a position distant from the conveying means 4.
[0014]
FIG. 2 is a sectional view taken along line AA of FIG. In the drawing, reference numeral 6 denotes a carry-in port of a light alloy wheel, and 7 denotes a carry-out port. The light alloy wheel 30 carried in from the carry-in port is moved rightward in the figure by the carrying means. First, as described above, the hot air sent from the circulator is sent from the ducts 5b to 5a, and during this time, the temperature is increased by the hot air from the bottom to the top. The time required to pass between the

ducts

5a and 5b is 0.5 hour, during which time the temperature of the light alloy wheel is raised to 560 ° C. ± 2 ° C.
Thereafter, the light alloy wheel conveyed to the position 30b in the figure is heated by hot air in the direction from the duct 5c to the duct 5d by blowing air in the direction opposite to the previous direction. The time required to pass between the

ducts

5c and 5d is 0.5H, during which time the temperature of the light alloy wheel is raised to a holding temperature in the range of 560 ° C. ± 2 ° C. By changing the wind direction depending on the location in the apparatus, even in a continuous heat treatment apparatus in which the vehicle wheels are stacked vertically in a plurality of stages, the entire vehicle wheel is uniformly heated and held.
[0015]
Thereafter, the vehicle wheel is lowered from the transport means through the window 10 by the lifting arm 9 and buried in the water in the bathtub 8 to be rapidly cooled. The traveling route of the vehicle wheel is indicated by a double dashed line. Thereafter, the vehicle wheel is loaded again on the transport means as aging processing. Hot air is blown from the duct 5e in the direction of the duct 5f, during which the temperature of the vehicle wheel is raised and maintained at 180 ° C. The time required for this aging treatment was 1H. Thereafter, the vehicle wheel that has been subjected to the heat treatment (T6 treatment) is taken out of the apparatus through the carry-out port 7, and is conveyed to the next processing step. The processing time required from loading to here is within 1H.
[0016]
An experiment was conducted using aluminum wheels as parts for aluminum vehicles. At the four typical locations shown in Fig. 3 ((1) near the gate, (2) the front flange, (3) the center of the tire surface, (4) the inner flange), drill holes up to the center of the thickness and insert a thermocouple. Installed. After that, it was inserted into the above-described heat treatment apparatus of the present invention, and the circulating wind speed of the atmosphere inside the apparatus was changed, and the temperature rising state and the temperature control state after the temperature rising were confirmed. The temperature raising time is a time required for the slowest temperature to reach the target temperature.
The heating rate depends on the shape and weight of the work, but becomes shorter as the circulating wind speed in the apparatus becomes faster, and becomes substantially 30 minutes or less when the flow velocity exceeds 15 m / s. In addition, the temperature control condition falls within the temperature control range ± 2 ° C. when the in-furnace wind speed exceeds 15 m / s. FIG. 4 shows the relationship between the processing time in the apparatus and the temperature at each measurement position. Table 1 shows the heating time for each wind speed (6, 10, 17 m / s) and the temperature control status after the heating. The wind speed here refers to a value measured at a position where the light alloy wheel is transported.
[0017]
[Table 1]

[0018]
(Reference example)
In the heat treatment apparatus shown in FIG. 2, the heat treatment was performed with the direction of the hot air from the circulator horizontal to the transport direction of the light alloy wheel (on the paper surface in FIG. 2, from the front to the back). In addition, the blowing conditions and transport conditions of the heat treatment are the same as those in the first embodiment. The heating time of the light alloy wheel under these conditions is also shown in Table 1 as a reference example. It can be seen that the time required for raising the temperature differs by 3 minutes or more between the outer flange side and the inner flange side of the rim even when the air blowing is 15 m or more. This is considered to be due to the fact that the heat capacity is partially large on the design surface which is a thick portion. As described above, when transporting the vehicle wheel, it is necessary to carry the rotating axis in the vertical direction, so the direction of the air blow is parallel to this axis, so that the hot air is not blocked by the rim of the vehicle wheel. It has been found that directional blowing is preferred. Thereby, the variation in strength can be suppressed.
[0019]
When the heat treatment of the present invention is performed at a high temperature for a short time, the mechanical properties after the heat treatment need to be at least about the same as the conventional heat treatment conditions. Therefore, a test piece was prepared by cutting a test piece from a light alloy wheel using the heat treatment apparatus of the present invention, and a tensile test was performed in comparison with a conventional heat treatment product. Table 2 shows the results. A comparison between the conventional heat treatment conditions and the heat treatment performed at a high temperature for a short time using the present heat treatment apparatus shows that the mechanical properties have been improved because the heat treatment at a high temperature has become possible. FIG. 5 shows microstructure photographs of a vehicle wheel heat-treated by the heat treatment apparatuses of the related art and the present invention. Both are of the outer flange. In the case of the heat treatment in the present invention, no significant difference is observed between the two, even though the heat treatment time is as short as about 1H in total.
[0020]
[Table 2]

[0021]
Since the heat treatment is performed just below the eutectic temperature, it is necessary to confirm the strain state of the work. Therefore, the state of occurrence of strain was confirmed by comparison with a conventional heat treatment condition in which air was not blown. As a measurement method, nine points of the outer flange portion were determined, and the relative difference between before and after the heat treatment at each point was evaluated by an absolute value. Table 3 shows the results using the heat treatment apparatus of the present invention, and Table 4 shows the results using the conventional heat treatment apparatus. Although the heat treatment time of the present invention is shorter than the total heat treatment time of about 1H, it is possible to obtain a vehicle wheel having a maximum displacement and an average displacement of about 5H or more, which is the same as that of the conventional vehicle wheel. is made of.
[0022]
[Table 3]

[0023]
[Table 4]

[0024]
【The invention's effect】
As a result, a heat treatment apparatus suitable for aluminum vehicle parts, particularly light alloy wheels having a large diameter of 16 inches or more, could be provided. A continuous heat treatment facility capable of greatly reducing the heat treatment time and suppressing the occurrence of distortion in a vehicle wheel could be provided.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a main part of a continuous heat treatment apparatus of the present invention.
FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a diagram showing measurement points.
FIG. 4 is a diagram showing a state in which the temperature of a vehicle wheel is raised again using the continuous heat treatment apparatus of the present invention.
FIG. 5 is a microphotograph of a vehicle wheel after heat treatment.
[Explanation of symbols]
Reference Signs List 1 continuous heat treatment apparatus, 2 circulator, 3 heat source, 4 transfer means, 5 duct, 6 carry-in, 7 carry-out, 8 bathtub, 9 elevating means, 10 windows

Claims

A continuous heat treatment apparatus for aluminum vehicle parts, wherein the continuous heat treatment apparatus has a conveying means capable of conveying the aluminum vehicle parts therein, and a blowing means capable of controlling a wind speed of a furnace atmosphere to 15 m / s or more. Wherein the temperature raising time to the solution heat treatment temperature of the aluminum vehicle component is within 30 minutes, and the work temperature control width after the temperature raising can be controlled at the target temperature ± 2 ° C. or less. Continuous heat treatment equipment.

A continuous heat treatment apparatus for a light alloy wheel, wherein the continuous heat treatment apparatus has a conveying means capable of conveying the light alloy wheel therein, and a blowing means capable of setting a wind speed of a furnace atmosphere to 15 m / s or more. A continuous heat treatment apparatus, wherein the transport means has a structure capable of transporting the axis of the light alloy wheel in the vertical direction, and the wind direction of the furnace atmosphere is substantially vertical. .

The said heat-alloy wheel is 16 inches or more, The continuous heat processing apparatus of Claim 2 characterized by the above-mentioned.

The said conveyance means is provided with two or more by the up-down direction, and is able to ventilate, Comprising: The wind direction of an atmosphere in a furnace is provided with the part where the wind direction is from the upper side to the lower side, and the part from the lower side to the upper side. The continuous heat treatment apparatus according to any one of claims 1 to 3.

5. The continuous heat treatment apparatus according to claim 4, wherein the number of aluminum vehicle parts loaded in the furnace cross section in the transport direction is four or more. 6.