JPH0561329B2 - - Google Patents

Description

【発明の詳細な説明】[Detailed description of the invention]

［産業上の利用分野］ 本発明は、線材コイルの焼鈍時間の大幅な短縮
化と品質の均一化に係る均一急速加熱の熱処理方
法およびその装置に関するものである。 ［従来の技術］ 球状化焼鈍に代表される焼鈍処理は、鋼材を適
当な温度に加熱して、組織中の炭化物を一旦固溶
化させた後適当な速度で冷却して、組織中の炭化
物の形状を改善し、素材としての塑性加工性、被
削性等を向上させる熱処理のことである。このと
き被処理材の品質を均一するには、固溶化させる
温度を10℃以内という狭い温度域に限定するとと
もに、その温度域で保持される時間差を小さくす
ることにより、固溶化の進行状態を均一化させる
必要がある。 しかし線材コイルの焼鈍で一般に使用される連
続焼鈍炉には、第１０図のｄ図に示すような高温
の燃焼ガスを管内に流通させるラジアントチユー
ブ２０を熱源にして間接加熱を行う雰囲気加熱方
式が採用されている。この方式では、線材コイル
の外周側は直接輻射加熱されるため雰囲気温度に
応じて比較的に速く昇温するものの、線材コイル
内部は、外周部からの熱伝導が主体であるので昇
温に長時間を要する。このため、線材コイル全体
では、昇温速度差による温度差が大きい。また、
焼鈍処理のように、目標とする均熱の温度範囲が
狭い場合には、処理時間が長時間になるばかりで
なく、保定温度での保持時間に大きな差が生じて
しまい、固溶化状態のバラツキが大きくなつてし
まう。このような状態のコイルから均一な球状化
組織にするには、炭化物の析出温度域が長時間保
定するか、Ar₁温度まで10℃／hr以下の割合で徐
冷を行つて、析出時に組織の均一化を図なければ
ならない。このため、線材コイルの球状焼鈍に
は、通常約20時間を要している。 このことから、線材コイル全体を均一に且つ急
速に加熱する技術を開発して、球状化焼鈍時間の
短縮化を実現することが永年の課題となつてい
た。これまでの改善策としては熱間圧延での圧
下、制御冷却等による焼鈍前のパーライト組織を
微細化する鋼材の改良の特開昭60−152627号、特
開昭60−255922号の公報例や、また一方、線材コ
イルを一旦ストランド状態にして特殊な加熱装置
により急速加熱した後、再びコイル状態に巻き取
る方法の特公昭60−22050号、及び特公昭61−
15930号の公報例が、さらに球状化焼鈍を熱間圧
延にオンライン化して生産性を向上させる方法の
特公昭51−33053号公報の技術が提案されている。 その他本発明に関わる公知文献として炉内雰囲
気を対流させるため炉内に攪拌フアンを設置した
特公昭57−200526号公報が、また、線材コイルの
熱処理とりわけ冷却に利用する衝風熱処理法が特
開昭55−109515号公報に、さらにまた線材コイル
への衝風供給方法について特開昭57−203724号公
報に開示がある。 ［発明が解決しようとする課題］ しかし、前記した特開昭60−152627号及び特開
昭60−255922号公報の技術は、鋼材圧延後、急冷
して、微細フエライト・パーライトとベイナイト
またはマルテンサイトの混在組織とし、これによ
りセメンタイトの球状化速度を速くしている。し
かし、このような方法ではセメンタイトが過度に
微細で、硬さが従来のものに比べてかなり高くな
り、球状化焼鈍の所期の目的を達しえない。ま
た、焼鈍時間の短縮化についても、現状の雰囲気
加熱方式で熱処理するのでは、線材コイル自体の
加熱時間は変わらず、根本的な解決手段となりえ
ないため大幅な時間短縮は望めない。 次に、特公昭60−22050号及び特公昭61−15930
号公報の一旦ストランド状態にしての熱処理方法
では、特殊な加熱設備等の設備改造が必要なだけ
でなく、この方法では生産性が著しく低下するこ
とから実用化には問題がある。 又、特公昭51−33053号公報は熱間圧延された
非同心リング状態の線材をコンベアーに載置し、
球状化処理炉内を移送して球状化処理を施す処理
炉で生産性の向上が見込まれるものの、均一に急
速加熱する方法がないため、材質のバラツキが大
きく従来の長時間焼鈍程度の品質を得るには至つ
ていない。しかも本発明が対象材とするタイトの
線材コイルには短時間の均一加熱が不可能であり
適用できない。 又、特開昭57−200526号公報では炉内に攪拌フ
アンを設置し炉内雰囲気を対流させ焼鈍時間の短
縮化を図つているが、線材コイルへの伝熱促進効
果が小さく、本発明の目的とする大幅な焼鈍時間
の短縮は期待できない。 更に、特開昭55−109515号公報は本発明の衝風
熱処理法に関わりの強いものであるが、これは、
線材コイルの一端を閉塞して、他端より線材コイ
ル内周部に気体を送り込み、線材の間隙を通過せ
しめて熱処理を行う衝風熱処理方法である。この
熱処理方法は、熱間圧延後の線材コイルを冷却す
る方法として多数の実施例がある。しかし、この
熱処理方法は、線材コイル特有の密集状態のバラ
ツキにより、通過する衝風量が局所的に偏つてし
まうため、温度バラツキは避けがたく、焼鈍工程
のように狭い温度範囲まで加熱する方法として用
いられた例はない。 また、衝風熱処理に関わる特開昭57−203724号
公報は、伝熱媒体を衝風供給用ダクトを介して接
続したフードで線材コイルの間隙に衝風を通過さ
せる方法として、線材コイル外周部より衝風を供
給して内周部より抜き取ることにより温度バラツ
キを低減するというものである。これは衝風が同
心円の中央から外周側へ向う程単位断面を通過す
る流速が順次減少するため、線材コイル内周部よ
りも線材コイル外周部の方が燃伝達率が小さいと
いう理由によるものである。しかし熱伝達率の小
さい線材コイル外周側で衝風温度を高くできるの
で、均一加熱に有利ではあるものの本発明が目的
とする均一急速加熱に対してはまだ不十分であ
り、逆に内周側の昇温が遅れるという問題が残つ
ている。 このように従来の球状化焼鈍時間の短縮化技術
には、いずれも問題があり実用化には至つておら
ず、また、本発明に大いに関わるこれまでの衝風
熱処理技術においてもまだ改善が必要であり、本
発明が目的とする線材コイル全体の短時間による
均一急速熱処理には適用できない。 ［課題を解決するための手段］ 本発明は、球状化焼鈍処理時間の短縮化の課題
に対し前述した従来技術の問題点に鑑みなされた
ものであり、その要旨とするところは (1) 線材コイル内の局所充填率（鋼材真体積／コ
イルおよび間隙部の見掛け体積）が0.2以下の
極端に小さい部位を無くするため、該線材コイ
ルの軸方向（高上方向）に該線材コイル単重の
５分の１以上の荷重でプレスする。 (2) 線材コイルの間隙に高温気体を通過させる
際、その気体の衝風速度を温度バラツキの要因
となるチヤンネリング現象の防止から見掛け速
度にして1.5m／sec以上とする。 (3) さらに線材コイル内の温度バラツキを低減す
るために、該線材コイルへの衝風供給方法とし
て、該線材コイルの内周側から外周側へと外周
側から内周側とを交互に組み合せ衝風する。そ
の際、組み合せの各々の時間帯を適度な比率と
することにより加熱時間の短縮へ寄与できる。 (4) 上述の構成要件とする球状化焼鈍処理方法の
発明を実施するための熱処理装置の提供であ
る。 以下、本発明の具体的な内容について、図を基
に詳細に説明する。 先ず、本発明の対象とするＣ成分0.1％〜0.6％
を含有する機械構造用炭素鋼、冷間圧造用炭素
鋼、低合金鋼等の球状化焼鈍の熱処理要領につい
ては、すでに周知の通りAc₁変態温度の直上
（740℃近傍）まで加熱し、組織中の炭化物を一旦
固溶させ一定時間保定し固溶調整した後、Ar₁変
態温度直下（650℃近傍）までの間を冷却速度40
℃／hr以下の徐冷で固溶炭化物を球状析出させる
ことであり、その後は空冷等で常温にする。この
炭化物を固溶させるまでの加熱に対する時間およ
び速度には全く制約はいらないが、固溶炭化物の
析出に際しては上述の冷却速度を超えると素材は
硬くなるので40℃／hr以下の徐冷は必ず守らなけ
ればならない。 従つて、本発明の球状化焼鈍処理時間の短縮化
を行う上で最もポイントとなるのは、いかに線材
コイル全体を均一にして所定の保定開始温度まで
に加熱するかである。このことについて第２図の
従来の雰囲気炉の加熱によるJIS.S45C線材コイ
ルの球状化焼鈍ヒートパターン例で説明する。こ
こで図中のａ域は加熱といい線材コイルの一部
（外周部Ａ）の温度が所定温度に達するまでの時
間範囲であり、ｂ域は均熱といい線材コイル内部
Ｃの温度が外周部Ａの所定温度に近似的になるま
での間の時間範囲であり、ｃ域は保定といい炭化
物を均一固溶化に要する間の時間範囲であり、ｄ
域は徐冷といい固溶炭化物を球化析出に要する間
の時間範囲であり、ｅ域は冷却といい球状化析出
の完了後から室温までの間の空冷等の時間範囲で
ある。また、Ａの線は線材コイルの外周部、Ｃの
破線はそのコイル内部のそれぞれの位置でのヒー
トパターンである。 図示から分るように、外周部のＡは直接輻射加
熱されるため比較的早く昇温するものの、内部の
Ｃは線材と線材の輻射および熱伝導が主体である
ので、目標の保定温度に到達するまでの時間がＡ
位置に比べて数時間遅れている。従つて線材コイ
ル全体を所定温度に均一化するまでの均熱時間お
よび炭化物固溶の保定時間の延長がどうしても必
要となり、熱処理時間の短縮化の障害になつてい
る。さらにこの均熱、保定の時間延長は炭化物の
固溶化状態にバラツキを生ずる原因となり、その
固溶化のバラツキを解消するために同図でも明ら
かな如く長時間の冷却（Ac₁〜Ar₁間で10℃／Hr
以下の徐冷）で炭化物析出時の組織の均一化が必
須となり、この点からも熱処理所要時間への影響
が大きくなる。この例での球状化焼鈍時間は約19
時間を要した。 このように雰囲気加熱方式による球状化焼鈍で
は、線材コイルの外周部と内部とでどうしても温
度差が生じ、その温度差を解消するための調節時
間がかならず必要となり熱処理時間の短縮化は不
可能であつた。 そこで本発明はこの雰囲気加熱方式から線材コ
イルの間隙に高温気体を伝熱媒体として通過させ
る衝風加熱方式の熱処理法を創案した。この衝風
熱処理の基本的な構成については前記したところ
であるが、しかしそのまま本発明が目的とする線
材コイル全体の均一急速加熱へは適用することは
できない。すなわち、通常の線材コイルの特性と
して局所的に線材の密集状態にバラツキが存在
し、バラツキの大きい状態の線材コイルに高温の
衝風を送り込んでも衝風は線材の間隙を通過する
際圧力損失の小さい充填率小の部位のみに集中し
て流れ、充填率大の部位は極端に衝風量が少なく
昇温遅れとなつてしまう。第３図のａおよびｂに
その密集のバラツキ状態である通常の線材コイル
（線径：10mm、コイル外径：1.4ｍ、内径：1.0ｍ、
軸方向高さ：1.3ｍ、単重：2t）に平均流速3m／
secの割合で衝風させた模式図とその時の風量分
布の調査結果を示す。この結果から局所的な見掛
け速度は１〜８ｍ／secの範囲に分布しており、
この状態で高温の衝風を送り込んでも線材コイル
全体の均一な温度は望めない。このようなことか
ら本発明の構成要件の一つである線材コイルのプ
レス化を見出し、コイル充填率の均一化を図つ
た。 第４図にそのプレス化による効果を示すが、同
図ａの模式図は上述の密集バラツキ線材コイルを
１１のコイルプレス装置で４の衝風フードを介し
て、該線材コイル１の単重2tの５分の１にあたる
400Kgの荷重でコイルプレスをし、充填率の極端
に小さい部位がない均一化した線材コイル状態を
示し、同図のｂはこのプレスコイルに上述と同じ
平均3m／secで衝風した時の風量分布を示す図で
ある。この図の結果から衝風の局所的な見掛け速
度は1.5〜4.0m／secの範囲まで低減しプレスによ
る効果が認められる。 なお、この第３図と第４図の調査において、線
材コイルの充填率と衝風見掛け速度（以下、衝風
速度と称す）との関係を求め第６図に示した。図
より第３図で示した通常のコイルプレス無し線材
コイルではコイル内の局所充填率は0.1〜0.5の範
囲で、この0.1と密集の少ない充填率の部位の衝
風速度は8m／sec程度と大きいのに対し、0.5の
密集の多い充填率の部位では1m／sec程度であ
る。一方、第４図のコイルプレスを実施した線材
コイルは、充填率0.1から0.2未満の部位がなくな
り充填率0.2の部位で4m／sec、充填率0.5の部位
で1.5m／secの衝風速度となり、プレス化で衝風
速度のバラツキが大幅に低減することが分かる。 また、コイルプレス荷重と衝風速度の風量バラ
ツキとの関係を調査し、その結果を第５図に示
す。図から明らかのようにプレス荷重を大きくす
る程、衝風速度の風量バラツキは小さくなるが、
この風量バラツキを低減するにはプレス荷重をコ
イル単重の５分の１（0.2）以上とすることが必要
である。しかしあまりプレス荷重をかけるとその
線材コイルの材質によつては曲りや折れ等の問題
が生じることもあるので、コイル単重の15倍のプ
レス荷重にとどめておくことが望ましい。 次に、このプレス線材コイルに対する適正な衝
風速度を求めるため、上述の第４図と同じ条件の
常温プレス線材コイルを用いて、そのコイルの間
隙に高温気体の伝熱媒体（750℃）を通過させ、
均熱温度740℃±５℃まで加熱するに要する時間
への衝風速度の影響を種々変化させ調査した。第
７図にその結果を示す。図から明らかな如く均熱
までの加熱時間は衝風速度を大きくするほど短く
できるが、1.5m／sec未満では線材コイル内での
風量バラツキが生ずる、いわゆるチヤンネリング
現象が起き該線材コイル全体の温度を均一化する
までに長時間を要することが分つた。このような
ことから衝風を1.5m／sec以上の速度にすること
で、均熱終了までの加熱時間は大幅に短縮するこ
とが可能となつた。 さらに、この衝風の供給方法について調査し
た。従来の衝風供給法は前記したように第８図の
ｂに示す線材コイル１の内周側から衝風２６を送
りコイルの間隙を通過させ該線材コイルの外周側
に向け流す方法、または、その逆である第８図の
ａに示す線材コイルの外周側から内周側へ向け流
す方法のどちらか一方のみであつた。両者の内、
均一加熱からは後者の方が有利であることは最初
に述べた通りであるが、本発明の目的とする均一
急速加熱に対してはかならずしも満足するもので
はなかつた。そこで種々実験調査を行つた結果、
この両者を組合せ、それぞれの衝風供給時間を適
度な比率にすることで、さらに均一急速加熱への
処理時間の短縮化に寄与することを見出した。 第９図に全衝風加熱時間（Ａ＋Ｂ）に対するＡ
の加熱時間の比率と均熱温度に達するまでの加熱
時間との関係からその比率の最適範囲を示す。こ
こでＡはコイルの外周部側から内周側へ、Ｂは内
周部側から外周側へのそれぞれの衝風時間を表わ
す。この図から明らかな如く、Ａ／（Ａ＋Ｂ）の
比率が0.5越え1.0未満の間になるようにＡとＢを
交互に組合せて衝風すれば、均一急速加熱時間の
短縮への寄与がさらに可能である。 このように本発明は線材コイル内の密集バラツ
キをプレスによりコイル充填率を整え、そのコイ
ル間隙に衝風をチヤンネリング現象が起きない所
定量以上の速度で通過させ、またさらに衝風の供
給法として線材コイルの外周部側から、または内
周部側からの適度な比率で組合せる衝風加熱方式
である。第１図はこれら構成要件を満し、第１表
に示す成分の線材コイルについて球状化焼鈍処理
を衝風炉で行つたヒートパターンの１例である。
熱処理条件等は後述する実施例の項で記載した
（第２表の記号12）通りである。 図より明らかな如く線材コイル内部のＣ位置で
の温度は外周部のＡ位置の温度にほぼ同時間で均
一に昇温追従されており、保定開始温度までに
0.8時間ですみ、炭化物析出完了する650℃までの
総処理時間は4.0時間で大幅な短縮が得られてい
る。 次に上述の本発明法を実施するための本発明の
熱処理炉について述べる。 先ず、熱処理炉の設備構築に当つては、熱処理
の生産性及び得られる品質性はもとよりランニン
グコストも含め設備費についても充分に考慮しな
ければならない。本発明が対象とする機械構造用
炭素鋼、冷間圧造用炭素鋼、低合金鋼等Ｃ：0.1
％〜0.6％鋼の球状化焼鈍処理においては、前記
したように加熱、均熱に対する時間および昇温速
度には制約がないが、固溶化した炭化物を析出さ
せる徐冷の冷却速度では、速い（40℃／hr超）と
被熱処材の硬さが硬くなり所望の軟化が得られな
い。このような球状化焼鈍の特殊な状況をふまえ
て衝風炉と従来の雰囲気炉との設備費及びランニ
ングコストを比較すると、同一の炉長とした設備
費は送風設備を必要とした衝風炉が雰囲気炉の約
２〜５倍程になる。またランニングコストにおい
ても主に送風を行うための単位時間当りの電力費
が５〜20倍程度かかり衝風炉の方が悪い。しかし
前述したように衝風炉加熱方式では線材コイルの
全体を均一急速加熱が容易であることから、雰囲
気炉による加熱より数倍の生産性が上げられ、し
かも品質の均一化も図れる。そこで雰囲気炉で衝
風炉の同じ生産性を得るための設備費（単位炉長
当りの設備費（円／ｍ）×炉長（ｍ））で比較する
と、逆に衝風炉の方が安価な設備ともなり得る
し、また、ランニングコストの電力原単位（円／
Ｔ）にしても雰囲気炉とほぼ同程度になる。 いずれにしても最適な熱処理炉の設備構築する
上で生産性、品質性さらに設備費およびランニン
グコストとそれに設置敷地面積をできるだけ小さ
くすることも勘案した総合判断で決定するのが肝
要である。このことから本発明の線材コイルの特
殊な球状化焼鈍熱処理についての熱処理炉を調査
検討した結果、均一急速加熱を重視した加熱、均
熱を衝風炉で行い、保定を含め冷却速度の制約が
ある徐冷は従来の雰囲気炉とする衝風炉と雰囲気
炉の直結一体化に組み合せ構成した熱処理炉を創
案した。特に既設の雰囲気炉がある場合は、衝風
炉を新設するだけで直結化が可能であり経費の大
きな削減が期待できる。 本発明の熱処理炉はこのような理由に基づきな
されたものである。すなわち、線材コイルの球状
化焼鈍処理時間の短縮化を経済的に行うため、高
温気体の伝熱媒体を送風する送風装置と、媒体温
度を制御するための熱補償装置と線材コイルをプ
レスしてコイル内の充填率を均一化するためのプ
レス駆動装置とからなる衝風供給装置を１台以上
備えた衝風炉と、輻射熱源になる複数のラジアン
トチユーブと炉内雰囲気を対流させる複数の攪拌
フアンからなる雰囲気炉とを直結一体化に組み合
せ構成した熱処理炉である。また、線材コイルの
炉内搬送に際し、搬送用キヤリアー上にコンベク
ター板を設置し、該線材コイルの下端面部が搬送
用キヤリアーの接触による伝導熱損失を低減した
構造ともした。 これらについて、さらに図を基にして詳細に説
明する。 第１０図はその本発明の球状化焼鈍処理方法を
実施可能とする熱処理炉例で、同図ａは全体構成
を示す概要図である。また第１０図のｂ，ｃは衝
風炉衝風供給装置の細部を示す図でｂは側面図、
ｃは正面図である。図中、１は被熱処理材の線材
コイル、２は線材コイル１の搬送用キヤリアー、
３は搬送ローラ、１４は線材コイル１の下端面と
搬送用キヤリアー２の接触による伝導熱損失を低
減するためのコンベクター板、６は衝風供給装置
１７を複数台（本例では３台）設け加熱、均熱が
主体で保定、徐冷も可能な衝風炉、７は雰囲気に
よる保定、徐冷が主体で加熱、均熱も可能な従来
の雰囲気炉、５，５′は衝風炉６および雰囲気炉
７で還元性ガス（例えば水素、一酸化炭素などの
爆発性ガス）が使われた時、不活性ガス（例えば
Ｎ等）でパージするために設けたパージ室、１２
は衝風を通過誘導する衝風ダクト、４は端面が衝
風ダクト１２と接続している昇降ダクトジヤバラ
８と接続し、一方の端面は線材コイル１の上端部
を閉塞する衝風フード、１１は衝風フード４の昇
降と該衝風フードを介して線材コイル１をプレス
してコイルの充填率を均一化するためのプレス駆
動装置、１３は各々の炉室での処理すなわち温
度、炉内圧力、衝風量、衝風方向等を容易に可変
可能とするための上下可動の仕切扉、９は衝風ダ
クト１２の系路内に設けられた所望の温度に制御
可能な熱補償装置、１０は伝熱媒体を送風し回転
方向の変更で衝風方向を可変する送風装置、２６
は衝風方向を示すための衝風である。 第１０図のｄは第１０図ａで図示した従来の雰
囲気炉７の詳細を示す正面図である。図中、２１
は高温の燃焼ガス、２０は２１の燃焼ガスを流通
させ輻射熱の熱源として発する炉の上、下位置に
複数配設したラジアントチユーブ、２３は２４の
駆動モーターにより炉内雰囲気を対流させる攪拌
フアンである。 第１１図は第１０図で示したコンベクター板１
４の平面図である。図示の如くコンベクター板１
４は線材コイル１の下端面と搬送用キヤリアー２
の間に衝風が通過できるように桁１６を介して放
射状の溝１５を窄設したもので、搬送用キヤリア
ー２に一体化してもよく、また分離方式としても
よい。このコンベクター板の窄設により線材コイ
ルの下端面はキヤリアーとの接触面積が縮小さ
れ、また溝１５の流路を介した衝風の通過により
伝導熱損失の防止が図れる。 第１２図にそのコンベクター板の窄設有無によ
る線材コイル下端面部の温度上昇状況を示した。
図中、ａの一点破線は線材コイルの平均温度、ｂ
の線はコンベクター板を窄設した線材コイル下端
面部の温度、ｃの破線はコンベクター板を設けず
キヤリアー平板のみの時の線材コイル下端面部の
温度である。図から明らかな如くコンベクター板
を設けない線材コイルの下端面部の温度上昇は平
均温度の上昇に比べ著しく遅れるのに対し、コン
ベクター板を設けることによりその遅れは改善さ
れ、コイル下端面部の加熱と伝導により熱移動の
低減が図られることが分る。 ［作用］ 本発明の熱処理炉は被熱処理材である線材コイ
ルの全体を急速均一加熱に有利な衝風供給装置を
複数台設けた衝風炉と設備費およびランニングコ
ストの経済性に優位な雰囲気炉を保定および徐冷
用とした機能分担の組み合せ構造であり、この熱
処理により球状化焼鈍処理時間の大幅な短縮が図
られ、しかも線材コイルの品質も従来と同等のも
のが得られる。 以下、上述熱処理炉の動作について述べる。 被熱処理材の線材コイル１は搬送用キヤリアー
２上のコンベクター板１４に載置して搬送ローラ
３でパージ室５へ間欠搬送され、次の衝風炉で爆
発性の還元性ガスが使用されている場合そのパー
ジ室でＮ等の不活性ガスでパージし、衝風炉６炉
内へ送られる。炉内へ搬送された線材コイル１は
衝風フード４直下の所定位置で停止され、衝風フ
ード４がプレス駆動装置１１により降下され、所
定の荷重でプレスし線材コイル１内の充填率を均
一化する。次に線材コイルがプレス状態のままで
送風装置１０を稼動させ線材コイルの温度がAc₁
直上の740℃に到達するように衝風加熱を行うが、
その際、線材コイル内の衝風方向を交互に変える
と、コイル内の加熱がさらに均一化されるので、
前記した所定の方向割合に応じて送風装置の回転
を変更する。 衝風加熱の伝熱媒体に用いられる気体である
が、これは窒素、水素、酸素、二酸化炭素、炭化
水素ガス、不活性ガス等の単体あるいは２種類以
上の混合物よりなり、この伝熱媒体である気体は
衝風ダクト１２の系路内に配設した熱補償装置９
で所望の温度に制御される。熱補償装置は燃焼熱
を利用した直下加熱方式あるいは熱交換器による
間接加熱方式があるが、どちらを用いても何らさ
しつかえない。 第１０図で示す衝風炉６の例では３台の衝風供
給装置１７が配置しているが、この衝風炉で多数
の線材コイルを順次搬送し衝風加熱処理を行う場
合、同一線材コイルを３台の衝風供給装置で衝風
加熱を行う方が能率的であり、その加熱時間は加
熱＋均熱の所要時間を1/3づつ振分け、間欠搬送
で連続した衝風加熱を行う。少数の線材コイルを
燃処理する時は３台全数を稼動する必要はなく、
また、その後の雰囲気炉での保定、徐冷にしても
ランニングコスト面で優位であれば、衝風炉だけ
で全ヒートパターンを行つても何らさしつかえな
い。 第１０図ｂに示す衝風供給装置の動作図は、No.
１は線材コイルをプレス駆動装置１１の稼動によ
り衝風フード４を介してプレスして該線材コイル
内の充填率を均一化し、衝風２６をコイルの外周
部から内周部へ向けて通過加熱している状態、No.
２では線材コイルの搬入待ちで衝風フード４を上
昇させている状態、No.３はNo.１と同様であるが衝
風２６が線材コイルの内周部から外部へ通過し加
熱している状態を表わしている。なお、仕切扉１
３はNo.１〜No.３の各衝風供給装置炉内での熱処理
方法が異なつているので、全仕切扉とも閉鎖状態
にある。 衝風炉では上述した状況に対応した熱処理を行
うが、加熱および均熱を終了した線材コイルは、
次に雰囲気炉７へ送られ保定と徐冷が行われる。
雰囲気炉の炉内温度は入口側は保定を行うことか
ら、線材コイルの温度がAc₁の直上の740℃を所
定時間保持できるような温度炉長範囲とし、その
後は最終搬出温度のAr₁直下温度650℃まで冷却
速度40℃／hr以下となる炉長範囲でラジアントチ
ユーブからの輻射熱を制御する。このようにして
保定、徐冷を終了すると固溶炭化物の球状化は完
了するが、雰囲気炉内を爆発性の還元性ガスを使
用した場合、雰囲気炉７の後方に設けたパージ室
５′へ該線材コイルを送りＮ等の不活性ガスでパ
ージして搬出する。あとは空冷等の適宜の方法で
冷却すれば良い。 ［実施例］ 以下、上述した本発明の熱処理炉を用い、本発
明方法による線材コイルの球状化焼鈍熱処理を施
した実施例を、従来法および比較例と共に説明す
る。 被熱処理材は第１表に示す成分のJISに定めら
れた機械構造用鋼のS45Cであり、いずれも仕上
温度700〜1000℃で10mmφに圧延された後、所定
の冷却速度で冷却されたものを外径1.4ｍ、内径
1.0ｍ、高さ（軸方向）1.3ｍ、単重2tonのコイル
状に巻取つた線材コイルである。 第２表にはその線材コイルを用いて球状化焼鈍
熱処理を行つた熱処理条件と材質評価結果を併せ
て示した。材質評価は球状化焼鈍した線材コイル
の硬さおよびJIS G3539に規定される球状化度の
２点について行つた。球状化焼鈍での材質達成目
標は硬さHvが105×（％Ｃ＋％Si／３＋％Mn／６
＋％Cr／19）＋72.6（ポイント）以下、球状化度が
No.２以下の２つの条件を両方とも満足することで
ある。 表中の記号１〜12は本発明例で、記号１は衝風
速度が本発明の下限である1.5m／secとしたも
の、記号２は衝風速度を10m／secと速くしたも
の、記号３は徐冷時間を10時間の冷却速度９℃／
hrと遅くしたもの、記号４と５はコイルプレス荷
重を大きくしたもので、それぞれコイル単重の10
倍の20tonと20倍の40tonの大荷重としたものであ
るが、記号５の40ton荷重のものは材質は良好で
あつたが、線材に曲り歪が著しく製品としては不
適当であつた。記号６は衝風方向をコイルの外周
側から内周側へ一定にして衝風加熱を施したも
の、記号７は記号６とは逆の衝風方向をコイルの
内周側から外周側へと一定にして衝風加熱を施し
たもの、また記号８は衝風方向をコイルの外周側
からと内周側からの衝風比率を１：１の同一衝風
時間としたものであるが、この記号６〜８のもの
は均熱時間が他のものより0.1時間余分にかかつ
た。このことから衝風方向の本発明の比率範囲が
少なからず処理時間への短縮に寄与することが分
る。 記号９は加熱のみ衝風炉で施し、均熱以降を雰
囲気炉で処理したものであるが、均熱時間が衝風
炉で行うより1.7時間余分に要した。記号10は本
発明で最も理想的な熱処理条件で施したもの、記
号11は加熱、均熱、保定まで衝風炉で施し、徐冷
のみ雰囲気炉で処理したもの、記号12は加熱から
徐冷までの全ヒートパターンを衝風炉のみで処理
したものである。 以上が本発明方法の実施態様であるが、いずれ
も球状化焼鈍後の硬さおよび球状化度は目標通り
の満足した材質が得られた。 次に、記号13〜20は比較例で、記号13は徐冷時
間が２時間と短く冷却速度が45℃／hrと速くした
もの、記号16はコイルプレスを全く行わず、また
記号17はコイルプレスの荷重が0.2tonと本発明の
コイル単重の1/5以上（2tonコイルでは0.4ton以
上）より少ないままで衝風加熱を施したもの、記
号18及び19は衝風方向がコイルの外周側から内周
側へ一定にして、又はコイルの内周側から外周側
へ一定にして衝風加熱したが、均熱時間がこの場
合同様の本発明例の記号10，11では均熱時間が
0.4時間は必要としているのに対し0.3時間と速め
に終らしたもの、記号20はコンベクター板を使用
せず平板上に線材コイルを載せて熱処理したもの
である。このように球状化焼鈍時間の短縮を図つ
た比較例でも規定より徐冷速度を速くしたもの、
加熱衝風速度を遅くしたもの、またコイルプレス
の荷重を少なくしたもの、衝風方向による均熱時
間不足のものでは最適形状の炭化物の球状化には
ならず、従つて硬さも硬く目的とする軟質が得ら
れない。また、コンベクター板の不使用によるも
のも、線材コイルの下端部が所温不足となり目標
の品質が得られていない。 記号21，22は従来法で雰囲気炉により球状化焼
鈍熱処理を行つたものである。記号21は総処理時
間が18時間と充分に費した処理であることから、
焼鈍後の材質は本発明法のものと同等である。し
かし処理時間は本発明の約５倍である。記号22で
は焼鈍時間を短縮するために均熱および徐冷時間
を短くして総処理時間を13.5時間にしたものであ
るが、線材コイル全体の均熱が不均一となる局部
的昇温不足で球状化が不充分で所期の材質が得ら
れていない。 [Industrial Field of Application] The present invention relates to a heat treatment method and apparatus for uniform rapid heating that significantly shortens the annealing time of a wire coil and makes the quality uniform. [Prior art] In annealing treatment, typically spheroidizing annealing, steel is heated to an appropriate temperature to once dissolve carbides in the structure, and then cooled at an appropriate rate to dissolve the carbides in the structure. Heat treatment that improves the shape and improves the plastic workability, machinability, etc. of the material. At this time, in order to make the quality of the treated material uniform, the progress of solid solution treatment can be controlled by limiting the temperature for solid solution treatment to a narrow temperature range of 10°C or less, and by reducing the time difference during which the material is maintained in that temperature range. It is necessary to equalize it. However, continuous annealing furnaces commonly used for annealing wire coils have an atmosphere heating method that performs indirect heating using a radiant tube 20 that circulates high-temperature combustion gas through the tube as a heat source, as shown in Figure 10d. It has been adopted. In this method, the outer periphery of the wire coil is heated by direct radiation, so the temperature rises relatively quickly depending on the ambient temperature, but the temperature inside the wire coil takes a long time to rise because heat conduction is mainly from the outer periphery. It takes time. Therefore, the temperature difference due to the temperature increase rate difference is large in the entire wire coil. Also,
When the target soaking temperature range is narrow, as in annealing, not only does the treatment time become long, but there is also a large difference in the holding time at a fixed temperature, resulting in variations in the solution state. becomes larger. In order to create a uniform spheroidal structure from a coil in this state, the temperature range for carbide precipitation must be maintained for a long time, or slow cooling should be performed at a rate of 10°C/hr or less to the Ar ₁ temperature to improve the structure during precipitation. We must aim to equalize the For this reason, spherical annealing of a wire coil usually takes about 20 hours. For this reason, it has been a long-standing challenge to develop a technique to uniformly and rapidly heat the entire wire coil to shorten the spheroidizing annealing time. Examples of improvement measures that have been taken so far include JP-A-60-152627 and JP-A-60-255922, which are improvements to steel materials by refining the pearlite structure before annealing by reduction during hot rolling, controlled cooling, etc. , On the other hand, Japanese Patent Publication No. 60-22050 and Japanese Patent Publication No. 61-198 disclose a method of forming a wire coil into a strand, rapidly heating it with a special heating device, and then winding it into a coil again.
An example of the publication is Japanese Patent Publication No. 15930, and Japanese Patent Publication No. 51-33053 proposes a method of improving productivity by bringing spheroidizing annealing online to hot rolling. Other known documents related to the present invention include Japanese Patent Publication No. 57-200526, in which a stirring fan is installed in the furnace to create convection in the furnace atmosphere, and Japanese Patent Publication No. 57-200526 discloses a blast heat treatment method used for heat treatment, especially cooling, of wire coils. Japanese Patent Laid-Open No. 57-203724 discloses a method of supplying air blast to a wire coil. [Problems to be Solved by the Invention] However, the techniques of the above-mentioned JP-A-60-152627 and JP-A-60-255922 involve rapid cooling after rolling of the steel material to form fine ferrite/pearlite and bainite or martensite. This makes the cementite spheroidize faster. However, in such a method, the cementite is excessively fine and the hardness is considerably higher than that in the conventional method, so that the intended purpose of spheroidizing annealing cannot be achieved. Furthermore, with regard to shortening the annealing time, if heat treatment is performed using the current atmosphere heating method, the heating time of the wire coil itself remains the same and cannot be a fundamental solution, so a significant time reduction cannot be expected. Next, Special Publication No. 60-22050 and Special Publication No. 61-15930
The method of heat treatment in which the strands are once formed into a strand as disclosed in the publication not only requires modification of equipment such as special heating equipment, but also has problems in its practical application because productivity is significantly reduced. In addition, Japanese Patent Publication No. 51-33053 discloses that hot-rolled wire rods in the form of non-concentric rings are placed on a conveyor,
Although it is expected that productivity will improve with a processing furnace that performs spheroidization treatment by transferring the inside of the spheroidization processing furnace, there is no method for uniformly rapid heating, and the quality of the material varies widely and cannot be compared to that of conventional long-time annealing. I haven't reached the point where I can get it. Furthermore, it is not possible to uniformly heat the tight wire coils to which the present invention is applied in a short period of time, and thus cannot be applied. Furthermore, in Japanese Patent Application Laid-open No. 57-200526, a stirring fan is installed in the furnace to create convection in the furnace atmosphere to shorten the annealing time, but the effect of promoting heat transfer to the wire coil is small, and the present invention is not effective. The desired significant reduction in annealing time cannot be expected. Furthermore, JP-A-55-109515 is closely related to the blast heat treatment method of the present invention;
This is a blast heat treatment method in which one end of the wire coil is closed and gas is fed into the inner circumference of the wire coil from the other end to pass through gaps in the wire to perform heat treatment. This heat treatment method has many embodiments as a method for cooling a wire rod coil after hot rolling. However, with this heat treatment method, the amount of blast air passing through the wire coil is locally uneven due to variations in the density characteristic of wire coils, so temperature variations are unavoidable, so it is not suitable for heating to a narrow temperature range as in the annealing process. There are no examples of it being used. In addition, Japanese Patent Application Laid-open No. 57-203724 related to blast heat treatment describes a method of passing blast air through gaps between wire coils using a hood connected to a heat transfer medium through an air blast supply duct. The idea is to reduce temperature variations by supplying more blast air and extracting it from the inner circumference. This is because the flow velocity passing through a unit cross section decreases as the blast moves from the center of the concentric circle toward the outer circumference, so the combustion transfer rate is lower at the outer circumference of the wire coil than at the inner circumference of the wire coil. be. However, since the blast temperature can be raised on the outer circumference side of the wire coil where the heat transfer coefficient is low, it is advantageous for uniform heating, but it is still insufficient for the uniform rapid heating that is the objective of the present invention, and on the contrary, on the inner circumference side, it is advantageous for uniform heating. The problem remains that the temperature rise is delayed. As described above, all of the conventional techniques for shortening the spheroidizing annealing time have problems and have not been put to practical use.Furthermore, the conventional blast heat treatment techniques, which are closely related to the present invention, still require improvement. Therefore, it cannot be applied to the uniform rapid heat treatment of the entire wire rod coil in a short period of time, which is the object of the present invention. [Means for Solving the Problems] The present invention has been made in view of the problems of the prior art described above with respect to the problem of shortening the spheroidizing annealing treatment time, and its gist is (1) Wire rod In order to eliminate extremely small areas in the coil where the local filling factor (true volume of steel/apparent volume of coil and gap) is 0.2 or less, the unit weight of the wire coil is Press with a load of 1/5 or more. (2) When high-temperature gas is passed through the gap between the wire coils, the blast velocity of the gas should be set to an apparent velocity of 1.5 m/sec or more to prevent channeling phenomenon that causes temperature variations. (3) In order to further reduce temperature variations within the wire coil, as a method of supplying blast to the wire coil, alternately combine the wire coil from the inner circumferential side to the outer circumferential side and from the outer circumferential side to the inner circumferential side. A blast of wind. At this time, by setting the time periods of each combination at an appropriate ratio, it is possible to contribute to shortening the heating time. (4) The present invention provides a heat treatment apparatus for carrying out the invention of the spheroidizing annealing treatment method as the above-mentioned constituent feature. Hereinafter, specific contents of the present invention will be explained in detail based on the drawings. First, the C component targeted by the present invention is 0.1% to 0.6%.
As is already well known, the heat treatment procedure for spheroidizing carbon steel for mechanical structures, carbon steel for _cold heading, low alloy steel, etc. containing Once the carbide inside is dissolved into solid solution and maintained for a certain period of time to adjust the solid solution, the cooling rate is 40°C until it reaches just below the Ar ₁ transformation temperature (around 650℃).
The solid solution carbide is precipitated into spheres by slow cooling at a temperature of ℃/hr or less, and then brought to room temperature by air cooling, etc. There is no restriction at all on the time and speed of heating to dissolve the carbide, but when the solid solution carbide is precipitated, the material becomes hard if the cooling rate exceeds the above, so slow cooling at 40℃/hr or less is always required. Must be protected. Therefore, the most important point in shortening the spheroidizing annealing treatment time of the present invention is how to uniformly heat the entire wire coil to a predetermined holding start temperature. This will be explained using an example of a spheroidizing annealing heat pattern of a JIS.S45C wire coil by heating in a conventional atmospheric furnace as shown in FIG. Here, area a in the figure is called heating, and is the time range until the temperature of a part of the wire coil (outer circumferential part A) reaches a predetermined temperature, and area b is called soaking, which is the time range when the temperature inside the wire coil C reaches the outer periphery. It is the time range until the temperature approximates the predetermined temperature in part A, c region is called retention, and it is the time range required to uniformly dissolve carbides, and d
The zone e is called slow cooling and is the time range required for spheroidizing the solid solution carbide, and the region e is cooling, which is the time range from the completion of spheroidizing precipitation to room temperature, such as air cooling. Further, the line A is the outer circumference of the wire coil, and the broken line C is the heat pattern at each position inside the coil. As can be seen from the diagram, the temperature of the outer part A increases relatively quickly because it is directly radiated, but the temperature of the inner part C is mainly due to radiation and heat conduction between the wires, so it reaches the target holding temperature. The time it takes to
It is several hours behind its current location. Therefore, it is absolutely necessary to extend the soaking time until the entire wire coil is uniformly heated to a predetermined temperature and the retention time of the carbide solid solution, which is an obstacle to shortening the heat treatment time. Furthermore, extending the soaking and holding time causes variations in the solid solution state of carbides, and in order to eliminate the variations in solid solution, as is clear from the figure, long-term cooling (between Ac ₁ and Ar ₁₎ is required. 10℃/Hr
It is essential to homogenize the structure during carbide precipitation by slow cooling (described below), and this also has a large effect on the time required for heat treatment. The spheroidization annealing time in this example is approximately 19
It took time. In this way, in spheroidizing annealing using the atmosphere heating method, a temperature difference inevitably occurs between the outer circumference and the inside of the wire coil, and adjustment time is always required to eliminate this temperature difference, making it impossible to shorten the heat treatment time. It was hot. Therefore, the present invention has devised a heat treatment method based on the blast heating method, in which high-temperature gas is passed as a heat transfer medium through the gap between the wire coils, instead of this atmosphere heating method. The basic structure of this blast heat treatment has been described above, but it cannot be directly applied to the uniform rapid heating of the entire wire coil, which is the object of the present invention. In other words, as a characteristic of a normal wire coil, there are local variations in the density of the wire, and even if a high-temperature blast is sent to a wire coil with large variations, the pressure loss will increase as the blast passes through the gaps between the wires. The flow concentrates only in areas with a small filling rate, and areas with a large filling rate have an extremely small amount of blast air, resulting in a delay in temperature rise. Figure 3 a and b show a normal wire coil (wire diameter: 10 mm, coil outer diameter: 1.4 m, inner diameter: 1.0 m,
Axial height: 1.3m, unit weight: 2t) with average flow velocity of 3m/
A schematic diagram of blasting at a rate of sec and the results of a survey of the air volume distribution at that time are shown. From this result, the local apparent velocity is distributed in the range of 1 to 8 m/sec,
Even if a high-temperature blast is sent in this state, it is not possible to achieve a uniform temperature throughout the wire coil. For this reason, we discovered that one of the constituent elements of the present invention is to press the wire coil, and attempted to make the coil filling rate uniform. Fig. 4 shows the effect of pressing. The schematic diagram in Fig. 4a shows the above-mentioned densely uneven wire rod coil being passed through 4 blast hoods with 11 coil presses, and the unit weight of the wire rod 1 is 2 tons. equivalent to one-fifth of
The wire rod is pressed under a load of 400 kg, and shows a uniform wire coil state with no areas with extremely low filling rates. b in the same figure shows the air volume when this pressed coil is blasted at the same average speed of 3 m/sec as described above. It is a figure showing distribution. From the results shown in this figure, the local apparent velocity of the blast was reduced to a range of 1.5 to 4.0 m/sec, indicating the effect of the press. In addition, in the investigation of FIGS. 3 and 4, the relationship between the filling rate of the wire coil and the blast apparent velocity (hereinafter referred to as blast velocity) was determined and is shown in FIG. 6. As shown in the figure, in the normal wire coil without coil press shown in Figure 3, the local filling factor within the coil is in the range of 0.1 to 0.5, and the blast velocity in the area where the filling factor is 0.1 and less dense is about 8 m/sec. In contrast, it is about 1 m/sec in areas with a dense packing rate of 0.5. On the other hand, in the wire coil subjected to the coil pressing shown in Fig. 4, there are no areas where the filling rate is less than 0.2 from 0.1, and the blast velocity is 4 m/sec at the area where the filling rate is 0.2, and 1.5 m/sec at the area where the filling rate is 0.5. , it can be seen that the variation in blast speed is significantly reduced by pressing. In addition, the relationship between the coil press load and the variation in blast speed and air volume was investigated, and the results are shown in FIG. As is clear from the figure, the larger the press load is, the smaller the variation in air volume in blast speed becomes.
In order to reduce this variation in air volume, it is necessary to set the press load to one-fifth (0.2) or more of the coil unit weight. However, if too much press load is applied, problems such as bending or breaking may occur depending on the material of the wire coil, so it is desirable to limit the press load to 15 times the unit weight of the coil. Next, in order to find the appropriate blast speed for this pressed wire coil, we used a room-temperature pressed wire coil under the same conditions as in Figure 4 above, and injected a high-temperature gas heat transfer medium (750°C) into the gap between the coils. Let it pass;
The influence of the blast speed on the time required to heat up to the soaking temperature of 740°C ± 5°C was investigated by varying the blast speed. Figure 7 shows the results. As is clear from the figure, the heating time until uniform heating can be shortened by increasing the blast speed, but if it is less than 1.5 m/sec, the so-called channeling phenomenon occurs in which the air volume varies within the wire coil, and the temperature of the entire wire coil increases. It was found that it took a long time to make the particles uniform. For this reason, by increasing the blast speed to 1.5 m/sec or higher, it became possible to significantly shorten the heating time until the end of soaking. Furthermore, we investigated the method of supplying this blast. Conventional blast supply methods include, as described above, a method in which the blast 26 is sent from the inner periphery of the wire coil 1 as shown in FIG. Only one of the opposite methods, ie, the method of flowing from the outer circumferential side to the inner circumferential side of the wire coil shown in FIG. 8a, was available. Of both,
As mentioned above, the latter method is more advantageous in terms of uniform heating, but it is not always satisfactory for uniform rapid heating, which is the objective of the present invention. As a result of various experimental investigations,
It has been found that by combining the two and adjusting the blast supply time to an appropriate ratio, it can further contribute to shortening the processing time for uniform rapid heating. Figure 9 shows A for the total blast heating time (A+B).
The optimal range of the ratio is shown from the relationship between the ratio of heating time and the heating time until the soaking temperature is reached. Here, A represents the blast time from the outer circumferential side of the coil to the inner circumferential side, and B represents the blast time from the inner circumferential side to the outer circumferential side. As is clear from this figure, if A and B are alternately combined and blasted so that the ratio of A/(A+B) is between more than 0.5 and less than 1.0, it is possible to further contribute to shortening the uniform rapid heating time. It is. In this way, the present invention corrects the density variation in the wire coil by adjusting the coil filling rate by pressing, passes the blast air through the coil gap at a speed higher than a predetermined amount that does not cause the channeling phenomenon, and further provides a method for supplying the blast air. This is a blast heating method that combines wire coils from the outer circumferential side or from the inner circumferential side at an appropriate ratio. FIG. 1 is an example of a heat pattern obtained by performing a spheroidizing annealing process in a blast furnace on a wire coil having the components shown in Table 1, which satisfies these structural requirements.
The heat treatment conditions, etc. are as described in the Examples section below (symbol 12 in Table 2). As is clear from the figure, the temperature at position C inside the wire coil uniformly follows the temperature at position A on the outer periphery in almost the same time, and by the retention start temperature.
It took only 0.8 hours, and the total processing time to reach 650°C to complete carbide precipitation was 4.0 hours, a significant reduction. Next, a heat treatment furnace of the present invention for implementing the above-described method of the present invention will be described. First, when constructing equipment for a heat treatment furnace, it is necessary to fully consider not only the productivity of heat treatment and the quality obtained, but also the equipment cost, including running costs. Carbon steel for machine structures, carbon steel for cold heading, low alloy steel, etc. targeted by the present invention C: 0.1
In the spheroidizing annealing treatment of % to 0.6% steel, as mentioned above, there are no restrictions on the time and temperature increase rate for heating and soaking, but the cooling rate of slow cooling to precipitate solid solution carbides is fast ( 40℃/hr), the hardness of the material to be heat treated becomes hard and the desired softening cannot be achieved. Considering the special circumstances of spheroidizing annealing, we compare the equipment costs and running costs between a blast furnace and a conventional atmosphere furnace. It will be about 2 to 5 times the size of the furnace. Also, in terms of running costs, blast furnaces are worse because the electricity cost per unit time for blowing air is about 5 to 20 times higher. However, as mentioned above, with the blast furnace heating method, it is easy to uniformly and rapidly heat the entire wire coil, so productivity can be increased several times as much as heating with an atmosphere furnace, and quality can also be made uniform. Therefore, if we compare the equipment cost (equipment cost per unit furnace length (yen/m) x furnace length (m)) to obtain the same productivity with an atmosphere furnace as a blast furnace, on the contrary, a blast furnace is cheaper equipment. It can also be
Even if T) is used, it will be almost the same as that of an atmospheric furnace. In any case, when constructing the optimal heat treatment furnace equipment, it is important to make a comprehensive decision that takes into consideration productivity, quality, equipment costs, running costs, and minimizing the installation site area. Based on this, as a result of researching and considering heat treatment furnaces for the special spheroidizing annealing heat treatment of the wire rod coil of the present invention, it was found that heating and soaking with emphasis on uniform rapid heating are performed in a blast furnace, and there are restrictions on the cooling rate including retention. For slow cooling, we devised a heat treatment furnace that is a direct combination of a blast furnace and an atmosphere furnace, which are conventional atmosphere furnaces. In particular, if you have an existing atmosphere furnace, you can directly connect it by simply installing a new blast furnace, and you can expect a significant cost reduction. The heat treatment furnace of the present invention was developed based on this reason. In other words, in order to economically shorten the spheroidizing annealing time for wire coils, a blower device for blowing a high-temperature gaseous heat transfer medium, a heat compensator for controlling the medium temperature, and a wire coil are pressed. A blast furnace equipped with one or more blast supply devices consisting of a press drive device to equalize the filling rate in the coil, multiple radiant tubes that serve as a radiant heat source, and multiple stirring fans that cause convection of the atmosphere inside the furnace. This is a heat treatment furnace that is directly connected and integrated with an atmospheric furnace consisting of: In addition, when the wire coil is transported in the furnace, a convector plate is installed on the transport carrier, and the lower end surface of the wire coil is structured to reduce conduction heat loss due to contact with the transport carrier. These will be further explained in detail based on the drawings. FIG. 10 shows an example of a heat treatment furnace in which the spheroidizing annealing method of the present invention can be carried out, and FIG. 10a is a schematic diagram showing the overall configuration. In addition, b and c in Fig. 10 are views showing details of the blast furnace blast supply device, and b is a side view;
c is a front view. In the figure, 1 is a wire coil of the material to be heat treated, 2 is a carrier for transporting the wire coil 1,
3 is a conveyance roller, 14 is a convector plate for reducing conduction heat loss due to contact between the lower end surface of the wire coil 1 and the conveyance carrier 2, and 6 is a plurality of blast supply devices 17 (three in this example). 7 is a conventional atmosphere furnace that mainly performs heating and uniform heating but also can be heated and gradually cooled; 5 and 5' are blast furnaces 6 and 5'; A purge chamber 12 provided for purging with an inert gas (for example, N, etc.) when a reducing gas (for example, an explosive gas such as hydrogen or carbon monoxide) is used in the atmosphere furnace 7;
4 is a blast duct that guides the blast through the air; 4 is a blast hood connected to a lifting duct bellows 8 whose end face is connected to the blast duct 12; one end face is a blast hood that closes the upper end of the wire coil 1; A press drive device for raising and lowering the blast hood 4 and pressing the wire rod coil 1 through the blast hood to equalize the filling rate of the coil; 13 is for controlling the processing in each furnace chamber, that is, temperature and pressure in the furnace; , a vertically movable partition door for easily changing the blast amount, blast direction, etc., 9 a heat compensator installed in the blast duct 12 and capable of controlling the temperature to a desired temperature; A blower device that blows a heat transfer medium and changes the blast direction by changing the rotation direction, 26
is a wind blast to indicate the wind direction. FIG. 10d is a front view showing details of the conventional atmosphere furnace 7 shown in FIG. 10a. In the figure, 21
20 is a high-temperature combustion gas, 21 is a radiant tube disposed in multiple positions above and below the furnace to circulate the combustion gas and emit it as a radiant heat source, and 23 is a stirring fan that causes convection of the atmosphere inside the furnace by a drive motor 24. be. Figure 11 shows the convector plate 1 shown in Figure 10.
4 is a plan view of FIG. Convector board 1 as shown
4 is the lower end surface of the wire coil 1 and the conveying carrier 2
A radial groove 15 is provided through the beam 16 so that a blast of air can pass through between the two, and it may be integrated into the transport carrier 2 or may be of a separate type. By narrowing the convector plate, the contact area of the lower end surface of the wire coil with the carrier is reduced, and conductive heat loss can be prevented by passing the blast through the flow path of the groove 15. FIG. 12 shows the temperature rise at the lower end surface of the wire coil depending on whether the convector plate is constricted or not.
In the figure, the dashed line a is the average temperature of the wire coil, b
The line c is the temperature of the lower end surface of the wire coil with the convector plate narrowed, and the broken line c is the temperature of the lower end surface of the wire coil when no convector plate is provided and only the carrier flat plate is provided. As is clear from the figure, the temperature rise at the lower end surface of the wire coil without a convector plate is significantly delayed compared to the average temperature rise, but by providing a convector plate, this delay is improved, and the temperature rise at the lower end surface of the coil It can be seen that heat transfer is reduced by conduction. [Function] The heat treatment furnace of the present invention is a blast furnace equipped with a plurality of blast supply devices that are advantageous for rapidly and uniformly heating the entire wire rod coil that is the material to be heat treated, and an atmosphere furnace that is advantageous in terms of economy in equipment costs and running costs. This is a combination structure in which the functions are divided into holding and slow cooling, and this heat treatment significantly shortens the spheroidizing annealing processing time, and the quality of the wire rod coil is also the same as that of the conventional method. The operation of the heat treatment furnace described above will be described below. The wire rod coil 1 of the material to be heat treated is placed on a convector plate 14 on a conveyance carrier 2, and is intermittently conveyed to a purge chamber 5 by a conveyance roller 3, where an explosive reducing gas is used in the next blast furnace. If there is, it is purged with an inert gas such as N in the purge chamber, and then sent to the blast furnace 6. The wire rod coil 1 conveyed into the furnace is stopped at a predetermined position directly under the blast hood 4, and the blast hood 4 is lowered by the press drive device 11 and pressed with a predetermined load to make the filling rate inside the wire rod coil 1 uniform. become Next, while the wire coil remains in the pressed state, the blower 10 is operated to raise the temperature of the wire coil to Ac ₁
Blast heating is performed to reach 740℃ directly above the
At that time, by alternating the direction of the blast inside the wire coil, the heating inside the coil will be made more uniform.
The rotation of the blower device is changed according to the predetermined directional ratio described above. The gas used as a heat transfer medium for blast heating is composed of a single substance or a mixture of two or more of nitrogen, hydrogen, oxygen, carbon dioxide, hydrocarbon gas, inert gas, etc. A certain gas is caused by a heat compensator 9 installed in the system of the blast duct 12.
The temperature is controlled to the desired temperature. There are two types of heat compensation devices: a direct heating method using combustion heat, and an indirect heating method using a heat exchanger, but there is no problem in using either method. In the example of the blast furnace 6 shown in FIG. 10, three blast supply devices 17 are arranged, but when a large number of wire rod coils are sequentially conveyed and subjected to blast heating treatment in this blast furnace, the same wire coils are It is more efficient to perform blast heating using three blast supply devices, and the heating time is divided into 1/3 of the time required for heating + soaking, and continuous blast heating is performed with intermittent conveyance. When burning a small number of wire coils, there is no need to operate all three units.
Further, if the running cost is advantageous even after the subsequent holding and slow cooling in an atmospheric furnace, there is no problem even if the entire heat pattern is performed only in a blast furnace. The operational diagram of the blast supply device shown in Fig. 10b is No.
1 presses the wire coil through the blast hood 4 by operating the press drive device 11 to equalize the filling rate in the wire coil, and heats the wire by passing blast 26 from the outer circumference to the inner circumference of the coil. State of being, No.
In No. 2, the blast hood 4 is raised while waiting for the wire coil to be carried in, and in No. 3, it is the same as No. 1, but the blast air 26 passes from the inner circumference of the wire coil to the outside and heats it. represents the state. In addition, partition door 1
In No. 3, all the partition doors are in a closed state because the heat treatment methods in the blast supply apparatus furnaces of No. 1 to No. 3 are different. In the blast furnace, heat treatment is performed in accordance with the above-mentioned conditions, but the wire coil after heating and soaking is
Next, it is sent to an atmospheric furnace 7 where it is held and slowly cooled.
Since the temperature inside the atmosphere furnace is maintained at the inlet side, the temperature range for the furnace length is such that the temperature of the wire coil can be maintained at 740℃ just above Ac ₁ for a specified period of time, and after that it is kept at just below Ar ₁ , the final discharge temperature. The radiant heat from the radiant tube is controlled within the furnace length range where the cooling rate is 40°C/hr or less up to a temperature of 650°C. When the retention and slow cooling are completed in this way, the spheroidization of the solute carbides is completed, but if an explosive reducing gas is used in the atmosphere furnace, the purge chamber 5' provided at the rear of the atmosphere furnace 7 The wire coil is sent, purged with an inert gas such as N, and carried out. All that is left to do is to cool it using an appropriate method such as air cooling. [Example] Hereinafter, an example in which a wire rod coil was subjected to spheroidizing annealing heat treatment according to the method of the present invention using the above-described heat treatment furnace of the present invention will be described together with a conventional method and a comparative example. The material to be heat treated is S45C, a mechanical structural steel specified by JIS, with the components shown in Table 1. All materials are rolled to a diameter of 10 mm at a finishing temperature of 700 to 1000°C, and then cooled at a specified cooling rate. Outer diameter 1.4m, inner diameter
It is a wire coil that is 1.0m long, 1.3m high (in the axial direction), and has a unit weight of 2 tons. Table 2 also shows the heat treatment conditions and material evaluation results when the wire coil was subjected to spheroidizing annealing heat treatment. The material quality was evaluated based on two points: the hardness of the spheroidally annealed wire coil and the degree of spheroidization specified in JIS G3539. The target material quality achieved by spheroidizing annealing is hardness Hv of 105 x (%C + %Si/3 + %Mn/6
+%Cr/19) +72.6 (points) or less, the degree of spheroidization is
Both of the two conditions below No. 2 must be satisfied. Symbols 1 to 12 in the table are examples of the present invention. Symbol 1 is an example in which the blast speed is 1.5 m/sec, which is the lower limit of the present invention, and symbol 2 is an example in which the blast velocity is increased to 10 m/sec. 3 is a slow cooling time of 10 hours and a cooling rate of 9℃/
hr and slower ones, symbols 4 and 5 are those with larger coil press loads, each with 10 of the coil unit weight.
The load was twice as large as 20 tons and 20 times as large as 40 tons, and although the material of the 40-ton load with symbol 5 was good, the wire had significant bending strain and was unsuitable as a product. Symbol 6 applies blast heating with the blast direction constant from the outer circumference side to the inner circumference side of the coil, and symbol 7 applies blast heating with the blast direction constant from the inner circumference side to the outer circumference side of the coil, which is the opposite of symbol 6. Symbol 8 is the one in which blast heating is applied at a constant rate, and symbol 8 is the one in which the blast direction is from the outer circumference of the coil and the blast ratio from the inner circumference is 1:1 and the blast time is the same. The soaking time for samples with numbers 6 to 8 took 0.1 hour more than the others. This shows that the ratio range of the present invention in the blast direction contributes to a considerable reduction in processing time. In case of symbol 9, only heating was performed in a blast oven, and the soaking process was performed in an atmosphere furnace, but the soaking time was 1.7 hours longer than in the blast oven. Symbol 10 is heat treatment performed under the most ideal conditions of the present invention, symbol 11 is heat treatment performed from heating, soaking, and holding in a blast furnace, and only slow cooling is performed in an atmosphere furnace, and symbol 12 is heat treatment from heating to slow cooling. The entire heat pattern was processed using only the blast furnace. The above are the embodiments of the method of the present invention, and in all cases, materials with satisfactory hardness and degree of spheroidization after spheroidizing annealing were obtained as targeted. Next, symbols 13 to 20 are comparative examples. Symbol 13 has a short annealing time of 2 hours and a fast cooling rate of 45°C/hr, symbol 16 has no coil pressing at all, and symbol 17 has a coil press. Items subjected to blast heating with the press load being 0.2 tons, which is less than 1/5 of the unit weight of the coil of the present invention (0.4 tons or more for 2 ton coils), and symbols 18 and 19 indicate that the blast direction is the outer periphery of the coil. Blast heating was carried out constant from the side to the inner circumference or from the inner circumference to the outer circumference of the coil.
The heat treatment was completed in 0.3 hours instead of the required 0.4 hours, and symbol 20 was heat-treated by placing the wire coil on a flat plate without using a convector plate. In this comparative example, which aimed to shorten the spheroidizing annealing time, the annealing speed was faster than the specified one.
If the heating blast speed is slow, the coil press load is reduced, or the soaking time is insufficient depending on the blast direction, the carbide will not be spheroidized in the optimal shape, and the hardness will not be as high as the target. Softness cannot be obtained. In addition, when a convector plate is not used, the lower end of the wire coil becomes insufficiently warm and the target quality cannot be obtained. Symbols 21 and 22 are those in which spheroidizing annealing heat treatment was performed in an atmosphere furnace using the conventional method. Symbol 21 means that the total processing time is 18 hours, which is a sufficient amount of time.
The material after annealing is the same as that of the method of the present invention. However, the processing time is about five times that of the present invention. In order to shorten the annealing time, code 22 shortened the soaking and slow cooling times to make the total processing time 13.5 hours, but due to insufficient local temperature rise, which resulted in uneven heating of the entire wire coil. Spheroidization is insufficient and the desired material cannot be obtained.

【表】【table】

【表】【table】

【表】 ［発明の効果］ 以上説明したように本発明は永年の課題であつ
た線材コイルままでの球状化焼鈍の熱処理時間短
縮化を、品質的にも安定した均一急速加熱の衝風
方法により従来の処理時間の約1/5に短縮した。 また、この衝風加熱を施す衝風炉を従来の雰囲
気炉に組み合せ直結し、ヒートパターン内の熱処
理工程部分を各炉の優位特性に見合つた炉に振り
分け分担とする設備費およびランニングコストの
省エネルギー上の効果も考慮した熱処理炉を見出
したなど、工業上の利用価値の極めて高いもので
ある。[Table] [Effects of the Invention] As explained above, the present invention solves the long-standing problem of shortening the heat treatment time for spheroidizing annealing of wire rod coils by providing a uniform rapid heating blasting method that is stable in terms of quality. This reduced processing time to approximately 1/5 of conventional processing time. In addition, the blast furnace that performs blast heating can be directly connected to a conventional atmosphere furnace, and the heat treatment process part in the heat pattern can be distributed to the furnaces that match the advantageous characteristics of each furnace, resulting in energy savings in equipment costs and running costs. We have discovered a heat treatment furnace that takes into account the effects of

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明による球状化焼鈍のヒートパタ
ーン例、第２図は従来の雰囲気炉による球状化焼
鈍のヒートパターン例、第３図ａは通常の線材コ
イルままの密集バラツキ状態で衝風している模式
図、第３図ｂはその時の風量分布を示す図、第４
図ａは通常の線材コイルにプレスした状態で衝風
している模式図、第４図ｂはその時の風量分布を
示す図、第５図はコイルプレス荷重と衝風風量バ
ラツキとの関係を示す図、第６図は線材コイル内
の局所充填率と衝風速度の関係を示す図、第７図
は衝風速度と加熱、均熱に要する時間の関係を示
す図、第８図は、衝風を線材コイルの外周側から
ａ、または内周側からｂの衝風方式を示す模式
図、第９図は衝風方向比率と加熱時間の関係を示
した図、第１０図は本発明の熱処理炉の一例を示
す図で、同図のａはその全体構成を示す概要図
で、ｂは衝風炉の衝風供給装置の細部を示す側面
図、ｃはその正面図であり、ｄは従来の雰囲気炉
の細部を示す正面図、第１１図はコンベクター板
設置例の模式図、第１２図はコンベクター板設置
による線材コイル下端面温度上昇効果を示す図で
ある。 １……線材コイル、２……搬送用キヤリアー、
３……搬送ローラ、４……衝風フード、５，５′
……パージ室、６……衝風炉、７……雰囲気炉、
８……昇降ダクトジヤバラ、９……熱補償装置、
１０……送風装置、１１……プレス駆動装置、１
２……衝風ダクト、１３……仕切扉、１４……コ
ンベクター板、１７……衝風供給装置、２０……
ラジアントチユーブ、２３……攪拌フアン、２５
……炉壁、２６……衝風。 Fig. 1 shows an example of a heat pattern for spheroidizing annealing according to the present invention, Fig. 2 shows an example of a heat pattern for spheroidizing annealing using a conventional atmosphere furnace, and Fig. 3a shows an example of a heat pattern for spheroidizing annealing using a conventional atmosphere furnace. Fig. 3b is a schematic diagram showing the airflow distribution at that time, Fig. 4
Figure a is a schematic diagram of a normal wire coil being pressed and blasted, Figure 4 b is a diagram showing the air volume distribution at that time, and Figure 5 shows the relationship between coil press load and blast air volume variation. Figure 6 is a diagram showing the relationship between the local filling rate in the wire coil and the blast velocity, Figure 7 is a diagram showing the relationship between the blast velocity and the time required for heating and soaking, and Figure 8 is a diagram showing the relationship between the blast velocity and the local filling rate in the wire coil. A schematic diagram showing the blasting method in which the wind is applied from the outer circumference side of the wire coil (a) or from the inner circumference side (b), FIG. 9 is a diagram showing the relationship between the blast direction ratio and heating time, and FIG. In the figure, a is a schematic diagram showing the overall configuration, b is a side view showing details of the blast supply device of the blast furnace, c is a front view thereof, and d is a conventional one. FIG. 11 is a schematic diagram of an example of installing a convector plate, and FIG. 12 is a diagram showing the effect of increasing the temperature on the lower end face of a wire coil by installing a convector plate. 1...Wire coil, 2...Transportation carrier,
3...Transport roller, 4...Blast hood, 5,5'
...Purge chamber, 6...Blast furnace, 7...Atmosphere furnace,
8... Lifting duct bellows, 9... Heat compensation device,
10...Blower device, 11...Press drive device, 1
2... Blast duct, 13... Partition door, 14... Convector board, 17... Blast supply device, 20...
Radiant tube, 23...Stirring fan, 25
... Furnace wall, 26... Blast.

Claims (1)

【特許請求の範囲】 １ 線材コイルの焼鈍熱処理方法において、前記
線材コイルの単重の５分の１以上の荷重でコイル
軸方向にプレスした状態で、該線材コイルの間隙
に高温気体を伝熱媒体とした衝風を通過させ、該
衝風の見かけ速度を1.5m／sec以上とすることを
特徴とする線材コイルの熱処理方法。 ２ 衝風の方向が、線材コイルの外周側から内周
側へをＡ、内周側から外周側へをＢとして、該衝
風の全時間（Ａ＋Ｂ）に対するＡの時間比率Ａ／
（Ａ＋Ｂ）が0.5越え1.0未満でＡとＢを交互に組
み合せて衝風する請求項１記載の線材コイルの熱
処理方法。 ３ 高温気体の伝熱媒体を送風する送風装置と、
媒体温度を制御するための熱補償装置と線材コイ
ルをプレスしてコイル内の充填率を均一化するた
めのプレス駆動装置とからなる衝風供給装置を１
台以上備えた衝風炉と、輻射熱源になる複数のラ
ジアントチユーブと炉内雰囲気を対流させる複数
の攪拌フアンからなる雰囲気炉とを直結一体化に
組み合せ構成したこを特徴とする熱処理炉。 ４ 線材コイルの炉内搬送に際し、搬送用キヤリ
アー上にコンベクター板を設置し、該コンベクタ
ー板に前記線材コイルを載置する請求項３記載の
熱処理炉。[Claims] 1. In an annealing heat treatment method for a wire coil, the wire coil is pressed in the axial direction with a load of one-fifth or more of the unit weight of the wire coil, and a high-temperature gas is transferred into the gap between the wire coils. 1. A method for heat treatment of a wire coil, characterized by passing through blast air as a medium and setting the apparent velocity of the blast air to 1.5 m/sec or more. 2 The direction of the blast is A from the outer circumference to the inner circumference of the wire coil, and B is from the inner circumference to the outer circumference, and the time ratio of A to the total time (A + B) of the blast is A/
2. The method for heat treating a wire coil according to claim 1, wherein A and B are alternately combined and blasted so that (A+B) is more than 0.5 and less than 1.0. 3. A blower device that blows a high-temperature gas heat transfer medium;
The blast supply device consists of a heat compensator for controlling the medium temperature and a press drive device for pressing the wire coil to equalize the filling rate in the coil.
A heat treatment furnace is characterized in that it is configured by directly connecting and integrating a blast furnace with at least one blast furnace, an atmosphere furnace consisting of a plurality of radiant tubes serving as a radiant heat source, and a plurality of stirring fans for causing convection of the atmosphere inside the furnace. 4. The heat treatment furnace according to claim 3, wherein a convector plate is installed on a carrier for conveying the wire rod coil in the furnace, and the wire rod coil is placed on the convector plate.