JP2674644B2 - Manufacturing method for machine structural parts - Google Patents

Manufacturing method for machine structural parts

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Publication number
JP2674644B2
JP2674644B2 JP62047629A JP4762987A JP2674644B2 JP 2674644 B2 JP2674644 B2 JP 2674644B2 JP 62047629 A JP62047629 A JP 62047629A JP 4762987 A JP4762987 A JP 4762987A JP 2674644 B2 JP2674644 B2 JP 2674644B2
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JPS63216920A (en
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勝典 高田
篤良 木村
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大同特殊鋼株式会社
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Description

【発明の詳細な説明】 【発明の目的】 (産業上の利用分野) この発明は、機械構造用鋼を素材とする部品、例えば
スピンドル,ジョイント,ギヤ,ボルト等の機械構造用
部品を製造するのに利用される機械構造用部品の製造方
法に関し、とくに再加熱して中間焼なまし処理を行う必
要がない機械構造用部品の製造方法に関するものであ
る。 (従来の技術) 従来、等速ジョイントやギヤ等の機械構造用部品を製
造するに際しては、熱間鍛造や冷間鍛造を採用してい
た。 これらのうち、熱間鍛造は、被鍛造材の加工性が良好
であり、鍛造型に対する負荷も小さくてすむといった利
点を有しているが、仕上がり寸法精度が悪いことや、ス
ケールおよび脱炭が発生することといった欠点があり、
熱間鍛造後に重切削を必要とすることから、材料歩留り
が悪く、工数も多く必要とするという問題点がある。 一方、冷間鍛造は、仕上がり寸法精度が良いととも
に、スケールや脱炭を生じないという利点を有している
が、被鍛造材の加工性が悪く、冷間鍛造前に焼なまし処
理を施すことが必要であるといった欠点がある。 他方、上記した熱間鍛造と冷間鍛造の中間的な加工法
として、400℃〜900℃の温度域において鍛造を行う半熱
間鍛造がある。この半熱間鍛造は温間鍛造とも称しうる
もので、熱間鍛造における低い変形抵抗と、冷間鍛造に
よる高い仕上がり寸法精度とを併せて得ることをねらっ
た加工法である。 この半熱間鍛造は、熱間鍛造と比較すれば、鍛造のた
めの加熱温度が低いことによて省エネルギーを実現でき
ると同時に被鍛造材表面のスケールや脱炭発生が少ない
こと、仕上がり寸法精度が高いために、鍛造後にアイヨ
ニング,コイニング,サイジング等の寸法出しを行う場
合の冷間加工率を低減できると同時に切削加工による仕
上げを行う場合の切削量を低減できること、などといっ
た利点を有している。また、冷間鍛造と比較すれば、被
鍛造材の変形抵抗が著しく小さいと同時に延性も向上す
るので鍛造比の大きな加工が可能であるといった利点を
有している。 このような利点を有する半熱間鍛造によって機械構造
用部品を製造するにあたっては、半熱間鍛造を行って部
品の粗成形体を加工し、中間焼なまし処理を施したの
ち、冷間仕上げ鍛造加工(アイヨニング,コイニング,
サイジング等)を行い、必要な場合には微切削加工を行
って、寸法精度の高い機械構造用部品とするようにして
いた。 (発明が解決しようとする問題点) ところが、従来の機械構造用鋼を素材として半熱間鍛
造し、その残熱を利用してそのまま中間焼なまし処理を
施すようにした場合には、硬さが十分に低下せず、その
ため、半熱間鍛造後にいったん冷却したのち再加熱して
中間焼なまし処理を施す必要があることから、冷却後再
加熱のためのエネルギー損失が多くなると共に、工程も
繁雑なものとなり、さらには半熱間鍛造後に再加熱待ち
の部品が工程間で滞溜することになるといった問題点が
あり、このような問題点は半熱間鍛造に類似する半熱間
押出などの半熱間塑性加工において生じていた。 (発明の目的) この発明は、上述した従来の問題点を解消するために
なされたもので、半熱間鍛造や半熱間押出等の半熱間加
工後に、その残熱を利用してそのまま低温焼なましを施
した際に、硬さの低下を十分に得ることが可能であり、
従来のようにいったん冷却したのち再加熱して中間燒な
まし処理を行う必要がない機械構造用部品の製造方法を
提供することを目的としているものである。 【発明の構成】 (問題点を解決するための手段) この発明に係る機械構造用部品の製造方法は、重量%
で、C:0.25〜0.65%、Si:0.15%未満、 Mn:0.60%以下、 P:0.015%以下、 S:0.010%以下、 B:0.0005〜0.0050%、 Ti:0.050%以下、 SolAl:0.015〜0.050%、 Cr:0.50%以下、 およびPb:0.01〜0.10%,Bi:0.01〜0.10%,Te:0.005〜
0.100%,Ca:0.0003〜0.0050%のうちから選ばれる1種
または2種以上を含み、 残部Feおよび不純物よりなり、より望ましくはCu:0.3
0%以下,Ni:0.20%以下,N:0.01%以下,O:0.0020以下に
規制し、結晶粒微細化のために必要に応じてNb:0.05%
以下,Ta:0.05%以下,Zr:0.05%以下の1種または2種を
添加した組成を有する鋼素材を用いて400℃〜900℃の温
度域において半熱間鍛造,半熱間押出等の半熱間加工を
行い、その残熱を利用して低温燒なましを行うことによ
り冷間鍛造等の冷間成形性を向上させて冷間鍛造等の冷
間成形ならびに適宜の切削加工により機械構造用部品を
得るようにし、半熱間加工後に再加熱して中間燒なまし
処理を行う必要がないようにしたことを特徴としている
ものである。 すなわち、この発明に係る機械構造用部品の製造方法
は、C含有量を比較的多くしたときでもSi含有量とMn含
有量を減少させることによって低温燒なまし後の硬さを
十分に低下させることができるようにして低温燒なまし
後の冷間成形性を良好なものとし、BおよびTiを添加す
ることによって上記Si含有量およびMn含有量の減少によ
る燒入性の低下を補うようにして、高周波燒入深さを確
保するようにし、さらに、B添加による結晶粒の粗大化
傾向をSolAlの添加により阻止するようにしたものであ
り、このような鋼素材を用いて400℃〜900℃の温度域に
おいて半熱間鍛造や半熱間押出等の半熱間加工を行った
後に、その残熱を利用してそのまま低温燒なましを行っ
た際に、硬さを十分に低下させることができるように
し、低温燒なまし後の冷間鍛造性(冷間塑性加工性)な
どの冷間成形性が良好なものとなるようにして、冷間鍛
造等の冷間成形ならびに適宜の切削加工により機械構造
用部品を得るようにしたことを特徴としているものであ
る。 以下、この発明に係る再加熱して中間燒なまし処理を
行う必要がない機械構造用部品の製造方法の成分範囲
(重量%)の限定理由について説明する。 C:0.25%〜0.65% Cは機械構造用部品の強度を確保するとともに高周波
燒入れ後に十分な表面硬さを得るために必要な元素であ
り、このような効果を得るためには0.25%以上含有させ
ることが必要である。しかし、多すぎると高周波燒入時
に燒割れを発生しやすくなるので0.65%以下に限定し
た。 Si:0.15%未満 Siは溶製時の脱酸剤として作用する元素であるが、通
常の脱酸剤として含有される0.15%以上の量(例えば、
JISG4052参照)であると半熱間加工後において行う低温
燒なましで硬さを十分に低下させることができず、その
後の冷間成形性(例えば冷間鍛造性)を劣化させる。そ
れゆえ、半熱間加工後にそのまま残熱を利用して低温燒
なましを行ったときでも硬さが十分に低下し、冷間成形
性(例えば冷間鍛造性)を向上させることができるよう
にするためには0.15%未満に限定する必要がある。 Mn:0.60%以下 Mnは溶製時の脱酸・脱硫剤として作用する元素であ
り、また燒入性を向上させる元素であるが、十分な燒入
性を得るために必要な量を添加すると前記Siの場合と同
様に半熱間加工後において行う低温燒なましで硬さを十
分に低下させることができず、その後の冷間成形性(例
えば冷間鍛造性)を劣化させる。それゆえ、半熱間加工
後にそのまま残熱を利用して低温燒なましを行ったとき
でも硬さが十分に低下し、冷間成形性(例えば冷間鍛造
性)を向上させることができるようにするためには0.60
%以下に限定する必要がある。 B:0.0005〜0.0050% BはSi含有量およびMn含有量を少なくしたことによる
燒入性の低下を補い、例えば高周波燒入後において必要
な燒入深さを確保するために添加する元素であって、こ
のような効果を得るためには0.0005%以上含有させるこ
とが必要である。しかし、多量に含有すると高周波燒入
時に結晶粒を粗大化し、靭性を低下させるので0.0050%
以下に限定した。 Ti:0.050%以下 TiはB添加による燒入性の向上を確保するために添加
する元素であるが、多すぎると靭性の低下をきたすので
0.050%以下に限定した。また、Tiのより望ましい含有
量は0.005〜0.050%である。 SolAl:0.015〜0.050% AlはB添加による結晶粒の粗大化傾向を防止し、B添
加鋼の高周波燒入時において結晶粒を微細化し、強度を
向上させるとともに、高周波燒入後の歪を著しく小さく
するのに有効な元素であり、このような効果を得るため
に0.015%以上含有させた。しかし多すぎるとかえって
結晶粒が粗大化し、靭性を低下させるので0.050%以下
に限定した。 Cr:0.50%以下 CrはB添加による燒入性の向上をさらに補い、高周波
燒入によって十分な燒入深さを得るのに有効な元素であ
るので添加することとしている。しかし、Cr含有量が多
すぎると半熱間加工および低温燒なまし後の冷間成形性
(例えば冷間鍛造性)を劣化させるので、0.50%以下に
限定した。 P:0.015%以下 P含有量が多すぎると靭性を害すると共に、冷間成形
性例えば冷間鍛造性を劣化させるので、0.015%以下に
規制した。 S:0.010%以下 S含有量が多すぎると冷間成形性例えば冷間鍛造性を
低下させるので、0.010%以下に規制した。 N:0.010%以下 N含有量が多すぎると変形抵抗が増大して冷間成形性
例えば冷間鍛造性を低下させるので、0.010%以下に規
制することがとくに望ましい。 O:0.0020%以下 O含有量が多すぎると鋼中の介在物量を増加して冷間
成形性例えば冷間鍛造性を低下させるので、0.0020%以
下に規制するのがより望ましい。 Cu:0.30%以下,Ni:0.20%以下 Cu,Niは基地を強化する元素であるが冷間成形性例え
ば冷間鍛造性に有害な元素であるので、Cuは0.30%以
下、Niは0.20%以下に規制するのがより望ましい。 Pb:0.01〜0.10%,Bi:0.01〜0.10%,Te:0.005〜0.100%,
Ca:0.0003〜0.0050%のうちから選ばれる1種または2
種以上 Pb,Bi,Te,Caは被削性を向上させるのに有効な元素で
あり、半熱間加工および低温燒なまし後の冷間成形性例
えば冷間鍛造性を向上させるために上記のようにS含有
量を0.010%以下にかなり抑制したときの被削性低下を
補うのに有効な元素であるので、Pbにあっては0.01%以
上,Biにあっては0.01%以上,Teにあっては0.005%以上,
Caにあっては0.0003%以上の1種または2種以上を添加
する。しかし、多すぎると冷間成形性を低下させること
となるので、Pbにあっては0.10%以下,Biにあっては0.1
0%以下,Teにあっては0.100%以下,Caにあっては0.0050
%以下とする必要がある。 Nb:0.05%以下,Ta:0.05%以下,Zr:0.05%以下のうち
の1種または2種以上 Nb,Ta,Zrは高周波燒入後の結晶粒を微細化して靭性を
向上させるのに寄与する元素であるので、必要に応じて
上記の範囲で添加するのもよい。 この発明においては、上記組成よりなる鋼素材を用い
て400℃〜900℃の温度域において半熱間鍛造や半熱間押
出等の半熱間加工を行い、その残熱を利用して低温燒な
ましを行うことにより冷間鍛造等の冷間成形性を向上さ
せて冷間鍛造等の冷間成形ならびに適宜の切削加工によ
り機械構造用部品を得るようにしているが、上記半熱間
加工において、加工温度が900℃を超えると熱間加工の
欠点を生じやすくなり、400℃よりも低いと冷間加工の
欠点を生じやすくなるので、400℃〜900℃の範囲とし
た。そして、この半熱間加工後の残熱を利用して低温焼
なましを行うが、この場合に高周波加熱や通常加熱等の
短時間加熱を併せて行ってもよい。 (実施例) 第1表に示す化学成分の鋼を溶製したのち造塊し、分
塊圧延および製品圧延を行って直径50mmの圧延剤を製造
した。 次いで、前記各圧延材を750℃で押出加工して直径を5
0mmから30mmに半熱間加工し、一部についてはそのまま
放冷し(半熱間加工まま)、他の一部については670℃
で1時間保持した後空冷する直接低温燒なましを行い、
残りについてはいったん放冷後再度加熱して720℃で1
時間保持した後空冷する通常燒なましを行った。 続いて、前記半熱間加工ままの押出材,直接低温燒な
ましを行った押出材および通常燒なましを行った押出材
からそれぞれ直径6mm,長さ9mmの試験片を加工し、各試
験片に対して据込み加工試験を行って割れが発生するま
での限界圧縮率を調べた。この結果を第2表に示す。 第2表に示す結果より明らかなように、この発明に従
って、所定の成分をもつ鋼素材に対し、半熱間加工を行
った後にそのまま残熱を利用して直接低温燒なましを行
ったNo.1,2の場合には、半熱間加工ままのものに比べて
限界圧縮率がかなり大であり、低温燒なましの効果が顕
著にあらわれており、比較のためにいった冷却後通常燒
なましを行った場合よりもむしろ限界圧縮率が高い値と
なっていることが認められ、低温燒なまし後の冷間成形
性に著しく優れたものであった。 これに対し、所定の成分を満足しない鋼素材を用いて
半熱間加工後にそのまま残熱を利用して直接低温燒なま
しを行ったNo.3の場合には、低温燒なまし後における硬
さの低下が十分でなく、限界圧縮率は上記実施例に比べ
て低いものであって、冷間成形性はあまり良くない結果
であった。 【発明の効果】 以上説明してきたように、この発明に係る機械構造用
部品の製造方法によれば、重量%で、C:0.25〜0.65%、
Si:0.15%未満、Mn:0.60%以下、P:0.015%以下、S:0.0
10%以下、B:0.0005〜0.0050%、Ti::0.050%以下、Sol
Al:0.015〜0.050%、Cr:0.50%以下、およびPb:0.01〜
0.10%,Bi:0.01〜0.10%,Te:0.005〜0.100%,Ca:0.0003
〜0.0050%のうちから選ばれる1種または2種以上を含
み、残部Feおよび不純物よりなり、より望ましくは不純
物中において、N:0.010%以下、O:0.0020%以下に規制
した組成を有する鋼素材を用いて400℃〜900℃の温度域
において半熱間鍛造や半熱間押出等の半熱間加工を行
い、その残熱を利用して低温燒なましを行うことにより
冷間鍛造等の冷間成形性を向上させて冷間鍛造等の冷間
成形ならびに適宜の切削加工により機械構造用部品を得
るようにしたものであるから、C含有量を比較的多くし
たときでもSi含有量とMn含有量とを減少させることによ
って低温燒なまし後の硬さを十分に低下させることが可
能であり、それゆえ低温燒なまし後の冷間鍛造等の冷間
成形性を良好なものとすることができるようになる。ま
た、P含有量およびS含有量を低く規制していることに
よっても冷間鍛造等の冷間成形性をより一層良好なもの
とすることができるようになる。さらに、上記Si含有量
およびMn含有量の減少による燒入性の低下をBおよびTi
の添加によって補うようにして高周波燒入深さを確保す
るようにし、さらにB添加による結晶粒の粗大化傾向を
SolAlの添加により阻止するようになすことができ、こ
のような鋼素材を半熱間加工したのち、その残熱を利用
してそのまま低温燒なましを施した際に、硬さの低下を
十分なものとすることができ、従来のようにいったん冷
却しのち再加熱して中間燒なまし処理を行う必要がない
ためエネルギー効率を十分高いものとすることが可能で
あり、このように低温燒なまし後の硬さ低下が大きいこ
とからその後の冷間鍛造等の冷間成形性が良好であり、
そのため切削加工よりも歩留り良くかつ高い生産性で機
械構造用部品を製作することができ、高周波燒入性に優
れているため機械構造用部品の耐摩耗性,強度とくに疲
労強度,転動寿命などを向上させることができ、燒入層
における結晶粒が微細であるため燒入歪を小さなものと
することができる。さらにまた、被削性の向上に寄与す
るS含有量をかなり低く規制して冷間鍛造等の冷間成形
性が良好なものとなるようにしているものの、ほかに被
削性向上元素を必須で適量含有させることとしているこ
とから、S含有量がかなり低いにもかかわらず、被削性
にも優れたものであるため、冷間鍛造等の冷間成形後の
切削加工(例えば、軽微な仕上げ加工,穴あけ加工等)
も良好に行うことが可能であるという非常に優れた効果
がもたらされる。
DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention manufactures parts made of steel for machine structure, for example, machine structure parts such as spindles, joints, gears and bolts. The present invention relates to a method for manufacturing a machine structural part used for, especially to a method for manufacturing a mechanical structural part that does not need to be reheated and subjected to an intermediate annealing treatment. (Prior Art) Conventionally, hot forging and cold forging have been adopted when manufacturing mechanical structural parts such as constant velocity joints and gears. Of these, hot forging has the advantages that the workability of the material to be forged is good and that the load on the forging die can be small, but the finished dimensional accuracy is poor, and scale and decarburization do not occur. There are drawbacks such as occurrence,
Since heavy cutting is required after hot forging, there are problems that the material yield is low and a large number of man-hours are required. On the other hand, cold forging has the advantage that the finished dimensional accuracy is good and scale and decarburization do not occur, but the workability of the material to be forged is poor, and an annealing treatment is performed before cold forging. Has the disadvantage that it is necessary. On the other hand, as an intermediate processing method between the hot forging and the cold forging described above, there is a semi-hot forging in which the forging is performed in the temperature range of 400 ° C to 900 ° C. This semi-hot forging can also be referred to as warm forging, and is a processing method aimed at obtaining low deformation resistance in hot forging and high finish dimensional accuracy by cold forging. Compared with hot forging, this semi-hot forging can realize energy saving due to the lower heating temperature for forging, and at the same time, less scale and decarburization on the surface of the material to be forged, finish dimensional accuracy Has a merit of being able to reduce the cold working rate when performing dimensioning such as ironing, coining, and sizing after forging, and at the same time, the amount of cutting when finishing by cutting can be reduced. There is. Further, compared with cold forging, the deformation resistance of the material to be forged is remarkably small, and at the same time, the ductility is improved, so that there is an advantage that processing with a large forging ratio is possible. When manufacturing machine structural parts by semi-hot forging having such advantages, the semi-hot forging is performed to process the rough formed body of the parts, the intermediate annealing process is performed, and then the cold finishing is performed. Forging process (Ioning, coining,
Sizing, etc.) and, if necessary, fine cutting to obtain a machine structural component with high dimensional accuracy. (Problems to be solved by the invention) However, when the conventional structural steel is used as a raw material for semi-hot forging and the residual heat is used for intermediate annealing, the Does not decrease sufficiently, therefore, it is necessary to cool once after half-hot forging and then reheat to perform an intermediate annealing treatment, so that the energy loss for reheating after cooling increases, and The process becomes complicated, and there is a problem that parts waiting for reheating after the half-hot forging are accumulated between the processes, and such problems are similar to the half-hot forging. It occurred in semi-hot plastic working such as hot extrusion. (Object of the Invention) The present invention has been made to solve the above-mentioned conventional problems, and after semi-hot working such as semi-hot forging and semi-hot extrusion, the residual heat is utilized as it is. When subjected to low temperature annealing, it is possible to obtain a sufficient decrease in hardness,
It is an object of the present invention to provide a method for manufacturing a machine structural component that does not require intermediate annealing treatment by cooling once and then reheating as in the conventional case. (Means for Solving Problems) The method for manufacturing a machine structural component according to the present invention is
, C: 0.25 to 0.65%, Si: less than 0.15%, Mn: 0.60% or less, P: 0.015% or less, S: 0.010% or less, B: 0.0005 to 0.0050%, Ti: 0.050% or less, SolAl: 0.015 to 0.050%, Cr: 0.50% or less, and Pb: 0.01 to 0.10%, Bi: 0.01 to 0.10%, Te: 0.005 to
0.100%, Ca: 0.0003 to 0.0050%, containing one or more selected from the balance Fe and impurities, more preferably Cu: 0.3
0% or less, Ni: 0.20% or less, N: 0.01% or less, O: 0.0020 or less, Nb: 0.05% if necessary for grain refinement
In the temperature range of 400 ℃ ~ 900 ℃, using steel materials with the addition of one or two of Ta: 0.05% or less and Zr: 0.05% or less, semi-hot forging, semi-hot extrusion, etc. Semi-hot working is performed, and the residual heat is used to perform low-temperature annealing to improve cold formability such as cold forging, and cold forming such as cold forging and appropriate cutting It is characterized in that a structural part is obtained so that it is not necessary to reheat after semi-hot working to perform intermediate annealing treatment. That is, in the method for manufacturing a machine structural component according to the present invention, the hardness after low-temperature annealing is sufficiently reduced by reducing the Si content and the Mn content even when the C content is relatively increased. In order to improve the cold formability after low-temperature annealing, the addition of B and Ti compensates for the decrease in the injectability due to the decrease in the Si content and the Mn content. In order to secure a high-frequency penetration depth, and to prevent the crystal grain coarsening tendency due to the addition of B by the addition of SolAl, 400 ° C to 900 After performing semi-hot working such as semi-hot forging and semi-hot extrusion in the temperature range of ℃, the residual heat is used to lower the hardness sufficiently when performing low temperature annealing as it is. Allows cold forging after low temperature annealing Characterized by making it possible to obtain good cold formability such as (cold plastic workability), and to obtain machine structural parts by cold forming such as cold forging and appropriate cutting There is something. Hereinafter, the reason for limiting the component range (% by weight) of the method for manufacturing a machine structural component that does not need to be reheated and subjected to an intermediate annealing treatment according to the present invention will be described. C: 0.25% to 0.65% C is an element necessary to secure the strength of machine structural parts and to obtain sufficient surface hardness after high frequency annealing, and in order to obtain such effects, 0.25% or more It is necessary to include it. However, if the amount is too large, scab cracking is likely to occur during high-frequency sintering, so the content was limited to 0.65% or less. Si: less than 0.15% Si is an element that acts as a deoxidizer during melting, but an amount of 0.15% or more contained as a normal deoxidizer (for example,
If it is JIS G4052), the hardness cannot be sufficiently lowered by the low temperature annealing performed after the semi-hot working, and the subsequent cold formability (for example, cold forgeability) is deteriorated. Therefore, even if low-temperature annealing is performed using the residual heat as it is after the semi-hot working, the hardness is sufficiently reduced and the cold formability (for example, cold forgeability) can be improved. In order to achieve this, it is necessary to limit it to less than 0.15%. Mn: 0.60% or less Mn is an element that acts as a deoxidizing / desulfurizing agent at the time of melting, and is an element that improves the injectability, but if added in an amount necessary to obtain sufficient injectability Similar to the case of Si described above, the hardness cannot be sufficiently reduced by the low temperature annealing performed after the semi-hot working, and the subsequent cold formability (for example, cold forgeability) is deteriorated. Therefore, even if low-temperature annealing is performed using the residual heat as it is after the semi-hot working, the hardness is sufficiently reduced and the cold formability (for example, cold forgeability) can be improved. 0.60 to
%. B: 0.0005 to 0.0050% B is an element added in order to compensate for the decrease in the introducibility due to the reduction of the Si content and the Mn content, and for example to ensure the required infiltration depth after high-frequency infiltration. In order to obtain such effects, it is necessary to contain 0.0005% or more. However, if contained in a large amount, the crystal grains will become coarse and the toughness will be reduced during high frequency induction.
Limited to the following. Ti: 0.050% or less Ti is an element added to ensure the improvement of the penetration property by the addition of B, but if it is too much, the toughness decreases.
It was limited to 0.050% or less. Further, the more desirable content of Ti is 0.005 to 0.050%. SolAl: 0.015 to 0.050% Al prevents the crystal grains from becoming coarse due to the addition of B, refines the crystal grains at the time of high frequency induction of B addition steel, improves the strength, and remarkably reduces the strain after high frequency induction. It is an effective element for reducing the content, and 0.015% or more was contained to obtain such an effect. However, if the amount is too large, the crystal grains become coarser and the toughness decreases, so the content was limited to 0.050% or less. Cr: 0.50% or less Cr is added because it is an element effective for supplementing the improvement of the penetration property by adding B and obtaining a sufficient penetration depth by high frequency induction. However, if the Cr content is too high, the cold formability (for example, cold forgeability) after semi-hot working and low temperature annealing is deteriorated, so the content is limited to 0.50% or less. P: 0.015% or less If the P content is too large, the toughness is impaired and the cold formability, for example, cold forgeability is deteriorated, so the content is regulated to 0.015% or less. S: 0.010% or less Since S content is too large, cold formability, for example, cold forgeability is deteriorated, so the content is regulated to 0.010% or less. N: 0.010% or less If the N content is too large, the deformation resistance increases and the cold formability, for example, cold forgeability is deteriorated. Therefore, it is particularly desirable to regulate the content to 0.010% or less. O: 0.0020% or less If the O content is too large, the amount of inclusions in the steel increases and the cold formability, for example, cold forgeability, decreases. Therefore, it is more preferable to regulate the content to 0.0020% or less. Cu: 0.30% or less, Ni: 0.20% or less Cu and Ni are elements that strengthen the matrix, but since they are elements harmful to cold formability such as cold forgeability, Cu is 0.30% or less and Ni is 0.20% or less. The following restrictions are more desirable. Pb: 0.01 to 0.10%, Bi: 0.01 to 0.10%, Te: 0.005 to 0.100%,
Ca: One or two selected from 0.0003 to 0.0050%
More than one species Pb, Bi, Te, Ca are effective elements to improve the machinability, and in order to improve the cold formability after semi-hot working and low temperature annealing such as cold forgeability, It is an element that is effective in compensating the machinability deterioration when the S content is considerably suppressed to 0.010% or less, so that it is 0.01% or more for Pb, 0.01% or more for Bi, and Te In that case, 0.005% or more,
For Ca, 0.0003% or more of one kind or two or more kinds is added. However, if the amount is too large, the cold formability is deteriorated, so 0.10% or less for Pb and 0.1% for Bi.
0% or less, 0.100% or less for Te, 0.0050 for Ca
% Or less. One or more of Nb: 0.05% or less, Ta: 0.05% or less, Zr: 0.05% or less Nb, Ta, Zr contributes to improve the toughness by refining the crystal grains after high frequency induction. Since it is an element to be added, it may be added in the above range if necessary. In the present invention, a steel material having the above composition is used to perform semi-hot working such as semi-hot forging and semi-hot extrusion in the temperature range of 400 ° C to 900 ° C, and the residual heat is used for low temperature firing. By improving the cold formability such as cold forging by carrying out annealing, machine structural parts are obtained by cold forming such as cold forging and appropriate cutting. In the above, when the working temperature exceeds 900 ° C, the defects of hot working tend to occur, and when the working temperature is lower than 400 ° C, the defects of cold working tend to occur, so the range was set to 400 ° C to 900 ° C. Then, low-temperature annealing is performed using the residual heat after the semi-hot working, but in this case, short-time heating such as high-frequency heating or normal heating may be performed together. (Example) Steels having the chemical composition shown in Table 1 were melted, then ingot-cast, and slab-rolled and product-rolled to produce a rolling agent having a diameter of 50 mm. Then, each rolled material was extruded at 750 ° C. to have a diameter of 5
Semi-hot working from 0mm to 30mm, part of it is left to cool as it is (semi-hot working), other part is 670 ℃
After holding for 1 hour at room temperature, perform direct low temperature annealing with air cooling,
For the rest, let it cool once and reheat it to 1 at 720 ° C.
Normal annealing was carried out by holding for a time and then air cooling. Then, a test piece with a diameter of 6 mm and a length of 9 mm was processed from each of the extruded material as it was in the semi-hot working, the extruded material directly subjected to low temperature annealing, and the extruded material subjected to normal annealing An upsetting test was performed on one piece to examine the critical compressibility until cracking occurred. Table 2 shows the results. As is clear from the results shown in Table 2, according to the present invention, a steel material having a predetermined composition was directly subjected to low temperature annealing using residual heat after semi-hot working No. In the case of .1 and 2, the critical compression rate is considerably larger than that of the as-hot-worked product, and the effect of low-temperature annealing is remarkable. It was recognized that the critical compressibility was higher than that when annealing was performed, and the cold formability after low-temperature annealing was remarkably excellent. On the other hand, in the case of No. 3 in which the low temperature annealing was performed directly using the residual heat after the semi-hot working using the steel material which does not satisfy the predetermined composition, the hardness after the low temperature annealing was performed. The decrease in thickness was not sufficient, the critical compressibility was lower than that in the above examples, and the cold formability was not so good. As described above, according to the method for manufacturing a machine structural component according to the present invention, C: 0.25 to 0.65% by weight%,
Si: less than 0.15%, Mn: 0.60% or less, P: 0.015% or less, S: 0.0
10% or less, B: 0.0005 to 0.0050%, Ti :: 0.050% or less, Sol
Al: 0.015 to 0.050%, Cr: 0.50% or less, and Pb: 0.01 to
0.10%, Bi: 0.01 to 0.10%, Te: 0.005 to 0.100%, Ca: 0.0003
Steel material containing one or more selected from 0.0050% to 0.0050%, the balance being Fe and impurities, and more preferably having a composition regulated to N: 0.010% or less and O: 0.0020% or less in the impurities. Is used to perform semi-hot working such as semi-hot forging and semi-hot extrusion in the temperature range of 400 ° C to 900 ° C, and the residual heat is used to perform low-temperature annealing and cold forging. Since the cold-formability is improved to obtain the machine structural parts by cold forming such as cold forging and appropriate cutting, even if the C content is relatively increased, the Si content and It is possible to sufficiently reduce the hardness after low-temperature annealing by reducing the Mn content, and therefore, to obtain good cold formability such as cold forging after low-temperature annealing. You will be able to. Further, by controlling the P content and the S content to be low, it becomes possible to further improve the cold formability such as cold forging. In addition, the decrease of the injectability due to the decrease of the Si content and the Mn content described above was
Is added to secure a high-frequency penetration depth, and the tendency of crystal grains to coarsen due to the addition of B is increased.
It can be prevented by adding SolAl, and after such steel material is semi-hot worked, the remaining heat is used to perform low-temperature annealing as it is, and the decrease in hardness is sufficient. Since it is not necessary to cool and then reheat to perform intermediate annealing treatment as in the conventional case, it is possible to make energy efficiency sufficiently high. Since the decrease in hardness after annealing is large, the cold formability such as cold forging after that is good,
Therefore, it is possible to manufacture machine structural parts with higher yield and higher productivity than cutting, and because of their excellent high-frequency injectability, wear resistance, strength, especially fatigue strength, rolling life, etc. of machine structural parts Can be improved, and since the crystal grains in the penetration layer are fine, the penetration strain can be made small. Furthermore, although the S content, which contributes to the improvement of machinability, is regulated to be considerably low so that the cold formability such as cold forging becomes good, other machinability improving elements are essential. Since it is supposed to be contained in an appropriate amount, since it has excellent machinability even though the S content is considerably low, it is possible to perform cutting work after cold forming such as cold forging (for example, a slight Finishing, drilling, etc.)
Also has a very excellent effect that it can be performed well.

Claims (1)

  1. (57)【特許請求の範囲】 1.重量%で、C:0.25〜0.65%、 Si:0.15%未満、 Mn:0.60%以下、 P:0.015%以下、 S:0.010%以下、 B:0.0005〜0.0050%、 Ti:0.050%以下、 SolAl:0.015〜0.050%、 Cr:0.50%以下、 およびPb:0.01〜0.10%,Bi:0.01〜0.10%,Te:0.005〜0.
    100%,Ca:0.0003〜0.0050%のうちから選ばれる1種ま
    たは2種以上を含み、 残部Feおよび不純物よりなる組成を有する鋼素材を用い
    て400℃〜900℃の温度域において半熱間鍛造や半熱間押
    出等の半熱間加工を行い、その残熱を利用して低温焼な
    ましを行うことにより冷間鍛造等の冷間成形性を向上さ
    せて冷間鍛造等の冷間成形ならびに適宜の切削加工によ
    り機械構造用部品を得ることを特徴とする再加熱して中
    間焼なまし処理を行う必要がない機械構造用部品の製造
    方法。 2.不純物中において、N:0.010%以下、O:0.0020%以
    下に規制した組成を有する鋼素材を用いることを特徴と
    する特許請求の範囲第(1)項に記載の再加熱して中間
    焼なまし処理を行う必要がない機械構造用部品の製造方
    法。
    (57) [Claims] % By weight, C: 0.25 to 0.65%, Si: less than 0.15%, Mn: 0.60% or less, P: 0.015% or less, S: 0.010% or less, B: 0.0005 to 0.0050%, Ti: 0.050% or less, SolAl: 0.015 to 0.050%, Cr: 0.50% or less, and Pb: 0.01 to 0.10%, Bi: 0.01 to 0.10%, Te: 0.005 to 0.
    Semi-hot forging in the temperature range of 400 ℃ to 900 ℃ using a steel material containing one or more selected from 100% and Ca: 0.0003 to 0.0050% with the balance Fe and impurities. Cold forming such as cold forging by improving the cold formability such as cold forging by performing low temperature annealing using the residual heat. And a method for manufacturing a machine structural part which does not require intermediate heating treatment by reheating, characterized by obtaining a machine structural part by appropriate cutting. 2. In the impurities, a steel material having a composition regulated to N: 0.010% or less and O: 0.0020% or less is used, and reheating and intermediate annealing according to claim (1) are performed. A method for manufacturing a machine structural component that does not require treatment.
JP62047629A 1987-03-04 1987-03-04 Manufacturing method for machine structural parts Expired - Lifetime JP2674644B2 (en)

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US5279688A (en) * 1989-12-06 1994-01-18 Daido Tokushuko Kabushiki Kaisha Steel shaft material which is capable of being directly cut and induction hardened and a method for manufacturing the same
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