JPH08283847A - Production of graphite steel for cold forging excellent in toughness - Google Patents
Production of graphite steel for cold forging excellent in toughnessInfo
- Publication number
- JPH08283847A JPH08283847A JP8686595A JP8686595A JPH08283847A JP H08283847 A JPH08283847 A JP H08283847A JP 8686595 A JP8686595 A JP 8686595A JP 8686595 A JP8686595 A JP 8686595A JP H08283847 A JPH08283847 A JP H08283847A
- Authority
- JP
- Japan
- Prior art keywords
- cooling
- steel
- toughness
- cold forging
- graphite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Landscapes
- Metal Extraction Processes (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、冷間鍛造に焼入・焼戻
して使用される棒鋼、線材に係わり、特に冷間鍛造性
と、焼入・焼戻後の靱性に優れた黒鉛分散鋼の製造に関
わるものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel bar and a wire rod that are used after quenching and tempering in cold forging, and is particularly a graphite dispersion steel excellent in cold forgeability and toughness after quenching and tempering. Related to the manufacturing of.
【０００２】[0002]
【従来の技術】中炭素鋼中のフェライト＋パーライト組
織をフェライト＋黒鉛の２相組織にすると、その硬さは
ビッカース硬さでHv１６０からHv１１０程度まで減少す
る。そのため、特公昭６３−９５８０号公報にみられる
ように、ミクロ組織をフェライト＋黒鉛の２相組織にす
ると冷間鍛造性は著しく向上する。一方、特開平２−１
１１８４２号公報によると、黒鉛鋼分散鋼では焼入加熱
時に黒鉛の分解速度が遅く十分にオーステナイト中に溶
解しないために焼入硬さが不足する欠点があり、黒鉛を
微細化するためにＢＮを析出核として利用するのが有効
であると開示されている。2. Description of the Related Art When the ferrite + pearlite structure in medium carbon steel is made into a two-phase structure of ferrite + graphite, its hardness decreases from Hv160 to about Hv110 in Vickers hardness. Therefore, as seen in Japanese Patent Publication No. 63-9580, cold forgeability is remarkably improved when the microstructure has a two-phase structure of ferrite + graphite. On the other hand, Japanese Patent Laid-Open No. 2-1
According to 11842, graphite steel-dispersed steel has a defect that the rate of decomposition of graphite is slow at the time of quenching and heating and it is not sufficiently dissolved in austenite, so that the quenching hardness is insufficient. It is disclosed that it is effective to use it as a precipitation nucleus.
【０００３】そして、従来技術で得られる黒鉛寸法は、
特公昭５３−４６７７４号公報によれば、平均粒径はほ
ぼ３０μｍ程度である。しかし、この程度の黒鉛粒度で
は、焼入加熱時に炭素が拡散して黒鉛の存在していた箇
所が３０μｍ程度の空孔となって残存し、この空孔が起
点となって靱性値が低くなる欠点がある。微細な黒鉛を
均一に分散させるための従来技術として、特開昭４９−
６７８１７号公報では、熱延後に再加熱、急冷してマル
テンサイト変態させ、これを再々加熱して６００〜７５
０℃で焼鈍する方法が開示されている。しかし、この方
法は、熱延後に２回の加熱工程を必要とするため製造コ
ストに問題がある。さらに、加工歪みを利用する方法と
して、特開昭６３−９５８０号公報では、熱延後圧下率
３０％以上の冷間圧延による加工歪みを導入し、次いで
焼鈍する方法が開示されているが、熱延後、圧下率３０
％で冷間圧延できる工程を新たに必要とするため現実的
な製造方法といえない。さらに、特願平５−７６５７号
公報記載の製造法では、平均黒鉛粒径は５〜３０μｍで
あることが開示されているが、Ｐｂ他、Ｂｉ，Ｔｅ，Ｓ
ｅ等の特殊元素の添加を必要とし、環境およびコストの
面から実用化が困難と考えられる。The graphite size obtained by the prior art is
According to Japanese Patent Publication No. 53-46774, the average particle size is about 30 μm. However, at such a graphite particle size, carbon diffuses during quenching and heating, and the portion where the graphite was present remains as a hole of about 30 μm, and this hole serves as a starting point to lower the toughness value. There are drawbacks. A conventional technique for uniformly dispersing fine graphite is disclosed in Japanese Patent Laid-Open No. 49-
In Japanese Patent No. 67817, after hot rolling, reheating and quenching are performed to transform into martensite, and this is reheated to 600 to 75.
A method of annealing at 0 ° C is disclosed. However, this method has a problem in manufacturing cost because it requires two heating steps after hot rolling. Further, as a method of utilizing work strain, Japanese Patent Laid-Open No. 63-9580 discloses a method of introducing work strain by cold rolling with a reduction ratio of 30% or more after hot rolling and then annealing. After hot rolling, the reduction rate is 30
It cannot be said to be a realistic manufacturing method because it requires a new process capable of cold rolling in%. Further, in the manufacturing method described in Japanese Patent Application No. 5-7657, it is disclosed that the average graphite particle size is 5 to 30 μm, but Pb et al., Bi, Te, S
It is necessary to add a special element such as e, and it is considered to be difficult to put into practical use in terms of environment and cost.
【０００４】[0004]
【発明が解決しようとする課題】以上に述べたよう、靱
性に優れた黒鉛分散鋼を得るための知見は見出されてい
ないために、黒鉛鋼の適用先は靱性値を必要としない薄
中板に使用が限定されている。また、黒鉛鋼では鋼材硬
さを格段に低減できるため、常に工具寿命が課題となっ
ている冷間鍛造ではその適用が強く要望されているもの
の、足回り、エンジン、ミッション等の重要保安部品に
用いられることが多い冷間鍛造用棒鋼、線材分野では、
靱性が低いことが問題となって利用されるに至っていな
い。As described above, since no knowledge has been found for obtaining a graphite-dispersed steel having excellent toughness, the application of the graphite steel does not require a toughness value. Limited use for boards. In addition, since the hardness of the steel material can be significantly reduced with graphite steel, its application is strongly desired in cold forging, where tool life is always an issue, but it is an important safety component for undercarriage, engines, missions, etc. In the field of cold forging steel bars and wires that are often used,
Low toughness has not been utilized as a problem.
【０００５】[0005]
【課題を解決するための手段】そこで、本発明は、以上
の知見および課題に鑑みなされたものであり、成分及び
製造条件に改良を加えるともに、冷間鍛造前に伸線加工
ないし引抜き加工を行うことにより黒鉛を分解しておく
ことでその後の焼入れ・焼戻し後に残存する空孔を小さ
くし、靱性に優れた冷間鍛造用黒鉛棒鋼、及び鋼線の製
造方法を提供することを目的としてなされたものであ
る。Therefore, the present invention has been made in view of the above findings and problems. In addition to improving the components and manufacturing conditions, wire drawing or drawing is performed before cold forging. By decomposing the graphite by carrying out to reduce the pores remaining after the subsequent quenching and tempering, graphite rod for cold forging excellent in toughness, and made for the purpose of providing a method for manufacturing a steel wire. It is a thing.
【０００６】本発明の要旨とするところは、 （１）重量％で Ｃ ：０．３〜１．０％ Ｓｉ：０．３〜１．３％ Ｍｎ：０．４〜１．０％ Ｐ ：０．０２％以下 Ｓ ：０．０２５％以下 Ａｌ：０．０１〜０．１％ Ｂ ：０．００１〜０．００４％ Ｎ ：０．００２〜０．００８％ を基本成分とし、残部はＦｅ及び不可避的不純物からな
る熱間圧延直後の棒鋼を、その熱間圧延ラインの後に設
置した水冷却装置により、冷却開始温度をＡr1点以上、
冷却終了温度をＭｓ点以下、平均冷却速度を３０〜１０
０℃／ｓとして冷却後、さらに自然冷却し、次いで加熱
温度６００〜７２０℃で黒鉛化処理した後、減面率３０
％以上の伸線加工ないし引抜き加工を行うことを特徴と
する靱性に優れた冷間鍛造用棒鋼の製造方法。 （２）（１）記載の基本成分と残部がＦｅ及び不可避的
不純物からなる熱間圧延直後の鋼線を、その熱間圧延ラ
インの後に設置した水冷却装置により、冷却開始温度を
Ａr1点以上、冷却終了温度をＭｓ点以下、平均冷却速度
を５〜３０℃／ｓとして冷却後、さらに自然冷却し、次
いで加熱温度６００〜７２０℃で黒鉛化処理した後、減
面率３０％以上の伸線加工を行うことを特徴とする靱性
に優れた冷間鍛造用鋼線の製造方法にある。The gist of the present invention is as follows: (1) C: 0.3-1.0% Si: 0.3-1.3% Mn: 0.4-1.0% P:% by weight 0.02% or less S: 0.025% or less Al: 0.01 to 0.1% B: 0.001 to 0.004% N: 0.002 to 0.008% as a basic component, and the balance Fe And a steel bar immediately after hot rolling consisting of unavoidable impurities, with a water cooling device installed after the hot rolling line, the cooling start temperature is Ar 1 point or more,
Cooling end temperature is Ms point or less, average cooling rate is 30 to 10
After cooling at 0 ° C./s, further natural cooling, and then graphitization at a heating temperature of 600 to 720 ° C.
% Or more wire drawing or drawing is carried out, and a method for manufacturing a steel bar for cold forging excellent in toughness. (2) A steel wire immediately after hot rolling comprising the basic components described in (1) and the balance Fe and unavoidable impurities is cooled at a cooling start temperature A r1 point by a water cooling device installed after the hot rolling line. As described above, after cooling at a cooling end temperature of Ms point or less and an average cooling rate of 5 to 30 ° C./s, it is further naturally cooled, and then graphitized at a heating temperature of 600 to 720 ° C. It is a method of manufacturing a steel wire for cold forging excellent in toughness, which is characterized by performing wire drawing.
【０００７】[0007]
【作用】以下に、本発明を詳細に説明する。請求項１に
ついては、Ｃは焼入れ後の強度を得るために必要な黒鉛
の量を確保するためにその下限値を０．３％とし、冷間
鍛造後の熱処理における焼き割れを防止するために上限
を１．０％とした。The present invention will be described in detail below. As for claim 1, C has a lower limit of 0.3% in order to secure the amount of graphite necessary for obtaining the strength after quenching, and in order to prevent quench cracking in the heat treatment after cold forging. The upper limit was 1.0%.
【０００８】Ｓｉは鋼の炭素原子との結合力が小さく、
黒鉛化を促進する有力な元素のひとつであるために必須
の元素である。焼入れ＋焼鈍処理により十分な黒鉛を析
出させて高い黒鉛化率にするにはＳｉを０．３％以上必
要とし、１．３％を超えるとフェライト相に固溶して硬
くなるため、黒鉛化による硬さ低減効果が相殺され冷間
鍛造性を損なう。Si has a small bonding force with carbon atoms of steel,
It is an essential element because it is one of the powerful elements that promotes graphitization. Si is required to be 0.3% or more in order to deposit sufficient graphite by quenching + annealing treatment to obtain a high graphitization rate. If it exceeds 1.3%, it becomes a solid solution in the ferrite phase and becomes hard, so graphitization The effect of reducing the hardness due to is offset and the cold forgeability is impaired.
【０００９】Ｍｎは、鋼中硫黄をＭｎＳとして固定、分
散されるために必要であり、またマトリクスに固溶させ
て強度を確保するためにも必要であることから、その下
限を０．４％とした。しかし、その量が多いと黒鉛化を
著しく阻害するために、上限を１．０％とした。Ｐは、
鋼中において粒界に析出し熱間加工性を著しく損なうの
でその上限を０．０２％とした。Mn is necessary to fix and disperse sulfur in the steel as MnS, and is also required to form a solid solution in the matrix to secure strength, so the lower limit is 0.4%. And However, if the amount is large, graphitization is significantly hindered, so the upper limit was made 1.0%. P is
Since it precipitates at grain boundaries in steel and the hot workability is significantly impaired, its upper limit was made 0.02%.
【００１０】Ｓは、Ｍｎと結合してＭｎＳ介在物として
存在するが、冷間鍛造時の割り発生起点となり０．０２
５％を越えると著しく冷間鍛造性を損なう。Ａｌは、鋼
中酸素を酸化物系介在物として除去し、粒径を調整する
ために０．０１％以上必要であるが、酸化物系介在物が
多すぎると靱性を損なうので上限を０．１％とした。S exists as an MnS inclusion by combining with Mn, but it becomes a crack initiation point during cold forging.
If it exceeds 5%, cold forgeability is significantly impaired. Al needs to be 0.01% or more in order to remove oxygen in the steel as oxide-based inclusions and adjust the grain size. However, if too many oxide-based inclusions impair toughness, the upper limit is set to 0. It was set to 1%.
【００１１】ＢとＮは、ＢＮを生成して黒鉛化焼鈍時間
を短縮させる。短縮効果を十分得るためには０．００１
％以上のＢを添加しなければならないが、０．００４％
を越えて添加しても焼鈍時間短縮効果は飽和する。Ｎは
０．００１〜０．００４％ＢをＢＮとするために、０．
００２〜０．００８％とした。棒鋼表面で測定した冷却
開始温度は、マルテンサイト変態歪みと圧延歪みとを同
時に発生させて黒鉛生成サイト数を多くするためＡr1点
以上でなければならない。冷却終了温度はマルテンサイ
ト変態組織を得て黒鉛生成を容易にするためにＭｓ点以
下でなければならない。平均冷却速度の下限値を３０℃
／ｓとしたのは、マルテンサイト変態組織を得るためと
加工歪みを残留させて黒鉛化を容易にするためであり、
上限を１００℃／ｓとしたのは、これ以上に急冷しても
マルテンサイト変態が増加しないためである。焼鈍温度
を６００〜７２０℃に限定したのは、この温度範囲にお
ける黒鉛化時間が最も短いためである。黒鉛化した後に
伸線加工ないし引抜き加工を行うのは、棒鋼の真円度な
らびに所定の強度を確保するとともに、黒鉛を分解さ
せ、冷間鍛造後に行う焼入れ・焼戻しの際に発生する空
孔を小さくし、靱性を向上させるためである。特に、冷
間鍛造では、デッドメタルと称される未変形部が生じ
る。この未変形部では黒鉛が分解されておらず、冷間鍛
造後の焼入れ・焼戻しで生じる空孔が大きく、靱性が低
くい。そこで冷間鍛造前に伸線ないし引抜き加工で黒鉛
を分解しておくことが必要であり、その際、減面率が３
０％より小さいと黒鉛が充分に分解されないために冷間
鍛造後の焼入れ・焼戻しで生じる空孔が大きく、靱性値
が向上しない。なお、請求項１記載の棒鋼とは、直棒な
いしバー・イン・コイルを示し、この場合、切断されず
に押出し加工されることはほとんどないが、減面率３０
％以上の押出し加工を行っても同様の効果が得られる。B and N form BN to shorten the graphitization annealing time. 0.001 to obtain sufficient shortening effect
% Or more of B must be added, but 0.004%
The effect of shortening the annealing time is saturated even if added over the range. N is 0.001 to 0.004% so that B is BN.
It was set to 002-0.008%. The cooling start temperature measured on the surface of the steel bar must be A r1 point or higher in order to simultaneously generate martensitic transformation strain and rolling strain and increase the number of graphite formation sites. The cooling end temperature must be below the Ms point in order to obtain a martensitic transformation structure and facilitate graphite formation. Lower limit of average cooling rate is 30 ℃
/ S is used to obtain a martensitic transformation structure and to retain work strain to facilitate graphitization.
The upper limit is set to 100 ° C./s because the martensitic transformation does not increase even if it is rapidly cooled. The annealing temperature is limited to 600 to 720 ° C. because the graphitization time is the shortest in this temperature range. Performing wire drawing or drawing after graphitizing ensures that the roundness and the specified strength of the steel bar are ensured, and that the graphite is decomposed and voids generated during quenching / tempering performed after cold forging are performed. This is to reduce the size and improve the toughness. Particularly, in cold forging, an undeformed portion called dead metal occurs. In this undeformed portion, graphite is not decomposed, the voids generated by quenching and tempering after cold forging are large, and the toughness is low. Therefore, it is necessary to decompose graphite by wire drawing or drawing before cold forging.
If it is less than 0%, graphite is not sufficiently decomposed, so that the voids generated by quenching and tempering after cold forging are large and the toughness value is not improved. The steel bar described in claim 1 means a straight bar or a bar-in-coil, and in this case, it is hardly extruded without being cut, but the surface reduction rate is 30.
The same effect can be obtained even if the extrusion processing is performed at a rate of not less than%.
【００１２】請求項２は熱間圧延線材の製造法であり、
線材表面で測定される冷却開始温度、冷却終了温度は棒
鋼と同様にそれぞれＡr1点以上、Ｍｓ点以下であるが、
平均冷却速度は直径の太い棒鋼より遅く、５〜３０℃／
ｓとした。下限値を５℃／ｓとしたのは、マルテンサイ
ト変態組織を得るためと加工歪みを残留させて黒鉛化を
容易にするためであり、上限を３０℃／ｓとしたのは、
これ以上に急冷してもマルテンサイト変態が増加しない
ためである。なお、線材では、真円度ならびに所定の強
度を確保するために伸線加工が行われ、切断することな
く引抜き加工ないし押出し加工を受けることはほとんど
ない。しかし、減面率３０％以上の引抜き加工、押出し
加工を行っても同様の靱性向上効果が得られる。[0012] Claim 2 is a method for producing a hot rolled wire rod,
The cooling start temperature and the cooling end temperature measured on the surface of the wire are A r1 point or higher and Ms point or lower, respectively, as in the case of the steel bar.
Average cooling rate is slower than thick steel bar,
s. The lower limit is set to 5 ° C./s in order to obtain a martensitic transformation structure and to make work strain remain to facilitate graphitization, and the upper limit is set to 30 ° C./s.
This is because the martensite transformation does not increase even if it is cooled more rapidly. The wire rod is subjected to wire drawing in order to ensure roundness and predetermined strength, and is rarely subjected to drawing or extrusion without cutting. However, the same toughness improving effect can be obtained even if the drawing process and the extrusion process with a surface reduction rate of 30% or more are performed.
【００１３】[0013]
【実施例】次に実施例により本発明の効果をさらに具体
的に示す。表１および表２に供試棒鋼の化学成分と製造
条件及び黒鉛化率を示す。EXAMPLES Next, the effects of the present invention will be more specifically illustrated by the following examples. Tables 1 and 2 show the chemical composition, manufacturing conditions and graphitization rate of the test steel bars.
【００１４】[0014]
【表１】 [Table 1]
【００１５】[0015]
【表２】 [Table 2]
【００１６】本実施例に用いた棒鋼は直径２０mm以上の
直棒ないしバーインコイルであり、熱延ラインの延長線
上に設置した冷却装置により棒鋼表面の全面に単位面積
当たり０．３〜０．５トン／ｍ2 の冷却水を均一に散水
することにより冷却した。冷却装置は、長さ２０ｍで、
円周上に多数の冷却水を供給するための孔を有するパイ
プで、棒鋼はパイプ中心線上を通過する際に冷却され
る。冷却開始温度、冷却終了温度は、鋼材の表面温度を
放射温度計で測定した値である。また、平均冷却速度
は、冷却開始温度と冷却終了温度との差を冷却時間で除
することにより求めた。その後、自然冷却させ、さらに
オフラインの焼鈍炉で黒鉛化した。The steel bar used in this example is a straight bar or a bar-in coil having a diameter of 20 mm or more, and a cooling device installed on the extension line of the hot rolling line covers the entire surface of the steel bar to 0.3 to 0.5 per unit area. It was cooled by uniformly spraying cooling water of ton / m 2 . The cooling device is 20m long,
A pipe having holes for supplying a large number of cooling water on the circumference, and the steel bar is cooled when passing through the pipe center line. The cooling start temperature and the cooling end temperature are values obtained by measuring the surface temperature of the steel material with a radiation thermometer. Further, the average cooling rate was obtained by dividing the difference between the cooling start temperature and the cooling end temperature by the cooling time. Then, it was naturally cooled and graphitized in an off-line annealing furnace.
【００１７】黒鉛化率は、（１）式により算出した。 （鋼中黒鉛含有量／鋼の炭素含有量）×１００ （％） ・・・（１） 鋼の炭素含有量は化学成分により定量した。黒鉛含有量
は平均黒鉛粒子径、密度、及び黒鉛粒子数から算出し
た。表１および表２より、本発明の製造方法による棒鋼
の黒鉛化率は焼鈍時間が１０時間前後と短いにも係わら
ず、１００％と著しく優れた結果である。これに対し、
比較製造方法であるＡ−１４〜Ａ−１８の場合には、黒
鉛化率は５０％程度と低い。The graphitization rate was calculated by the equation (1). (Graphite content in steel / carbon content in steel) × 100 (%) (1) Carbon content in steel was quantified by chemical composition. The graphite content was calculated from the average graphite particle size, density, and the number of graphite particles. From Table 1 and Table 2, the graphitization ratio of the steel bar manufactured by the manufacturing method of the present invention is remarkably excellent as 100% even though the annealing time is as short as about 10 hours. In contrast,
In the case of A-14 to A-18, which are comparative manufacturing methods, the graphitization ratio is as low as about 50%.
【００１８】黒鉛析出状態の直径４０mmの供試棒鋼を表
１に示す減面率で引抜加工を行い、さらに直径２５mmに
旋削した。その後、高周波により１０００℃まで３sec
で加熱し水冷却する高周波焼入れ、及び焼戻し（６００
℃×６min →水冷）を行った。焼入れ・焼戻した後に、
ＪＩＳ Ｚ ２２０２ ３号−２mmＵノッチ衝撃試験片
を切り出し、２０℃でシャルピー試験を行った。表１お
よび表２にシャルピー試験時の吸収エネルギーを併記す
る。本発明で製造された鋼材の靱性はいずれも１０kgfm
／cm2 以上であり、比較鋼に比べ著しく靱性が高いこと
がわかる。また、本発明鋼Ａ−１については、引抜加工
前後で直径１４mm×高さ２１mmの円柱試験片を切り出
し、圧縮率７５％まで圧縮試験（試験温度２０℃）を行
った。その結果、引抜き加工前後で圧縮試験成形荷重は
それぞれ４２tonfと４１tonfであり、引抜き加工付与に
よる冷間鍛造性の低下もなかった。さらに、同様の圧縮
試験を冷間鍛造可能な鋼材の上限の硬さとされているＪ
ＩＳ Ｇ ４０５１ Ｓ４８Ｃの球状化焼鈍材について
も行った。その成形荷重は６２tonfであり、従来不可能
とされていた高炭素鋼の冷間鍛造成形が、本発明法によ
り工具への負担を減らすことで可能となることがわかっ
た。A sample steel bar having a diameter of 40 mm in the state of precipitation of graphite was drawn at the area reduction ratio shown in Table 1 and further turned to a diameter of 25 mm. After that, 3 seconds up to 1000 ℃ by high frequency
Induction hardening that heats with water and cools with water, and tempering (600
℃ × 6 min → water cooling) was performed. After quenching and tempering,
A JIS Z 2203 No. 2-2 mm U notch impact test piece was cut out and subjected to a Charpy test at 20 ° C. Tables 1 and 2 also show the absorbed energy during the Charpy test. The toughness of the steel materials manufactured by the present invention is 10 kgfm
/ Cm 2 or more, indicating that the toughness is significantly higher than that of the comparative steel. Further, for the steel A-1 of the present invention, a cylindrical test piece having a diameter of 14 mm and a height of 21 mm was cut out before and after the drawing process, and a compression test (test temperature 20 ° C.) was performed up to a compression rate of 75%. As a result, the compression test forming loads before and after the drawing process were 42 tonf and 41 tonf, respectively, and there was no reduction in cold forgeability due to the application of the drawing process. Furthermore, the same compression test is used as the upper limit hardness of the steel material that can be cold forged.
A spheroidized annealed material of IS G 4051 S48C was also performed. The forming load was 62 tonf, and it was found that cold forging of high carbon steel, which has been impossible in the past, can be performed by reducing the load on the tool by the method of the present invention.
【００１９】表３および表４には、供試線材の化学成分
と製造条件及び黒鉛化率を示す。Tables 3 and 4 show the chemical composition, production conditions and graphitization rate of the test wire.
【００２０】[0020]
【表３】 [Table 3]
【００２１】[0021]
【表４】 [Table 4]
【００２２】本実施例に用いた棒鋼は直径１８〜１９mm
で、熱延ラインの延長線上に設置した水槽内で冷却し
た。仕上げスタンドから水槽までの距離は約４５mm、圧
延速度は１０〜１００mm／sec で、圧延終了から水槽に
至るまでの所要時間は約１〜３sec である。線材をコイ
ル状に巻いて水温２０〜１００℃の水槽に挿入した。水
槽内の滞留時間は２０〜２００秒である。冷却開始温
度、冷却終了温度は、線材の表面温度を放射温度計で測
定した値である。また、平均冷却速度は、冷却開始温度
と冷却終了温度との差を冷却時間で除することにより求
めた。その後、自然冷却させ、さらにオフラインの焼鈍
炉で黒鉛化した。黒鉛化率は、前記（１）式により算出
した。棒鋼の場合と同様に鋼の炭素含有量は化学成分に
より定量し、黒鉛含有量は平均黒鉛粒子径、密度、及び
黒鉛粒子数から算出した。The steel bar used in this embodiment has a diameter of 18 to 19 mm.
Then, it was cooled in a water tank installed on the extension of the hot rolling line. The distance from the finishing stand to the water tank is about 45 mm, the rolling speed is 10 to 100 mm / sec, and the time required from the end of rolling to the water tank is about 1 to 3 seconds. The wire rod was wound into a coil and inserted into a water tank having a water temperature of 20 to 100 ° C. The residence time in the water tank is 20 to 200 seconds. The cooling start temperature and the cooling end temperature are values obtained by measuring the surface temperature of the wire with a radiation thermometer. Further, the average cooling rate was obtained by dividing the difference between the cooling start temperature and the cooling end temperature by the cooling time. Then, it was naturally cooled and graphitized in an off-line annealing furnace. The graphitization rate was calculated by the above formula (1). As in the case of steel bar, the carbon content of steel was quantified by the chemical composition, and the graphite content was calculated from the average graphite particle size, density, and the number of graphite particles.
【００２３】表２より、本発明の製造方法での黒鉛化率
は焼鈍時間が１０〜１３時間と短いにも係わらず、１０
０％と著しく優れた結果である。これに対し、比較製造
方法であるＢ−１２〜Ｂ−１６の場合には、黒鉛化率は
６０％以下と低い。黒鉛析出状態の直径１８〜１９mmの
線材を表３および表４に示す各減面率で伸線加工した
後、切断後、高周波により１０００℃まで３sec で加熱
し水冷却する高周波焼入れ、及び焼戻し（６００℃×６
min →水冷）を行った。焼入れ・焼戻し後、ＪＩＳ（Ｚ
２２０２）３号−２mmＵノッチ衝撃試験片を切り出
し、２０℃でシャルピー試験を行った。その結果を表３
および表４に併記する。本発明で製造された鋼材の靱性
はいずれも１０kgfm／cm2 以上であり、比較鋼に比べ著
しく靱性が高いことがわかる。また、本発明鋼Ｂ−１に
ついては伸線加工前後で、直径１０mm×高さ１５mmの円
柱試験片を切り出し圧縮率７５％まで圧縮試験（試験温
度２０℃）を行った。その結果、伸線加工前後で圧縮試
験成形荷重はそれぞれ２１tonfと２２tonfであり、伸線
加工付与による冷間鍛造性の低下もなかった。さらに、
同様の圧縮試験を冷間鍛造可能な鋼材の上限の硬さとさ
れているＳ４８Ｃの球状化焼鈍材についても行った。そ
の成形荷重は６０tonfであり、従来不可能とされていた
高炭素鋼の冷間鍛造成形が、本発明法により工具への負
担を減らすことで可能となることがわかった。From Table 2, the graphitization ratio in the manufacturing method of the present invention is 10 even though the annealing time is as short as 10 to 13 hours.
This is a very excellent result of 0%. On the other hand, in the case of B-12 to B-16 which are comparative manufacturing methods, the graphitization rate is as low as 60% or less. After wire-drawing a wire having a diameter of 18 to 19 mm in the state of graphite precipitation at each area reduction ratio shown in Tables 3 and 4, after cutting, induction hardening is performed by heating to 1000 ° C. for 3 seconds by high frequency and water cooling, and tempering ( 600 ° C x 6
min → water cooling). After quenching and tempering, JIS (Z
2202) No. 3-2 mm U notch impact test pieces were cut out and subjected to a Charpy test at 20 ° C. The results are shown in Table 3.
And also shown in Table 4. The toughness of each of the steel materials produced by the present invention is 10 kgfm / cm 2 or more, which shows that the toughness is significantly higher than that of the comparative steel. Further, with respect to the steel B-1 of the present invention, a cylindrical test piece having a diameter of 10 mm and a height of 15 mm was cut out and subjected to a compression test (test temperature 20 ° C.) up to a compression rate of 75% before and after wire drawing. As a result, the compression test forming loads before and after the wire drawing were 21 tonf and 22 tonf, respectively, and the cold forgeability was not deteriorated by the wire drawing. further,
The same compression test was also performed on the S48C spheroidized annealed material, which has the upper limit hardness of the steel material that can be cold forged. The forming load was 60 tonf, and it was found that the cold forging of high carbon steel, which was hitherto impossible, can be performed by reducing the load on the tool by the method of the present invention.
【００２４】[0024]
【発明の効果】以上の実施例からも明らかなように本発
明によれば、靱性の優れた冷間鍛造黒鉛鋼を製造するこ
とが可能であり、靱性を必要とする自動車重要保安部品
への適用が可能となるとともに、従来その製造が不可能
と考えられていた高炭素鋼の冷間鍛造成形が可能とな
り、産業上の効果は極めて顕著なものがある。As is apparent from the above examples, according to the present invention, it is possible to produce a cold forged graphite steel having excellent toughness, and to obtain an important automobile safety component requiring toughness. In addition to being applicable, cold forging of high carbon steel, which has been considered impossible in the past, is possible, and the industrial effect is extremely remarkable.
Claims (2)
る熱間圧延直後の棒鋼を、その熱間圧延ラインの後に設
置した水冷却装置により、冷却開始温度をＡr1点以上、
冷却終了温度をＭｓ点以下、平均冷却速度を３０〜１０
０℃／ｓとして冷却後、さらに自然冷却し、次いで加熱
温度６００〜７２０℃で黒鉛化処理した後、減面率３０
％以上の伸線加工ないし引抜き加工を行うことを特徴と
する靱性に優れた冷間鍛造用棒鋼の製造方法。1. C: 0.3-1.0% Si: 0.3-1.3% Mn: 0.4-1.0% P: 0.02% or less S: 0.025 % Or less Al: 0.01 to 0.1% B: 0.001 to 0.004% N: 0.002 to 0.008% as a basic component, and the balance immediately after hot rolling consisting of Fe and unavoidable impurities The steel bar of No. 1 was cooled by a water cooling device installed after the hot rolling line, and the cooling start temperature was Ar 1 point or more,
Cooling end temperature is Ms point or less, average cooling rate is 30 to 10
After cooling at 0 ° C./s, further natural cooling, and then graphitization at a heating temperature of 600 to 720 ° C.
% Or more wire drawing or drawing is carried out, and a method for manufacturing a steel bar for cold forging excellent in toughness.
び不可避的不純物からなる熱間圧延直後の鋼線を、その
熱間圧延ラインの後に設置した水冷却装置により、冷却
開始温度をＡr1点以上、冷却終了温度をＭｓ点以下、平
均冷却速度を５〜３０℃／ｓとして冷却後、さらに自然
冷却し、次いで加熱温度６００〜７２０℃で黒鉛化処理
した後、減面率３０％以上の伸線加工を行うことを特徴
とする靱性に優れた冷間鍛造用鋼線の製造方法。2. A steel wire immediately after hot rolling, which comprises the basic components according to claim 1 and the balance Fe and unavoidable impurities, is cooled to a cooling start temperature of A by a water cooling device installed after the hot rolling line. After r1 point or more, the cooling end temperature is Ms point or less, and the average cooling rate is 5 to 30 ° C./s, the material is further cooled naturally, and then graphitized at a heating temperature of 600 to 720 ° C., and the area reduction rate is 30%. A method for producing a steel wire for cold forging excellent in toughness, which is characterized by performing the above wire drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8686595A JPH08283847A (en) | 1995-04-12 | 1995-04-12 | Production of graphite steel for cold forging excellent in toughness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8686595A JPH08283847A (en) | 1995-04-12 | 1995-04-12 | Production of graphite steel for cold forging excellent in toughness |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH08283847A true JPH08283847A (en) | 1996-10-29 |
Family
ID=13898721
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8686595A Withdrawn JPH08283847A (en) | 1995-04-12 | 1995-04-12 | Production of graphite steel for cold forging excellent in toughness |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH08283847A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999045162A1 (en) * | 1998-03-04 | 1999-09-10 | Nippon Steel Corporation | Steels for cold forging and process for producing the same |
| FR2788821A1 (en) * | 1999-01-12 | 2000-07-28 | Ntn Toyo Bearing Co Ltd | Power transmission shaft using constant velocity universal joint has induction hardened surface layer and comprises carbon steel including silicon, manganese, aluminum and boron |
| EP1178126A1 (en) * | 1999-12-24 | 2002-02-06 | Nippon Steel Corporation | Bar or wire product for use in cold forging and method for producing the same |
| KR100605722B1 (en) * | 2004-11-24 | 2006-08-01 | 주식회사 포스코 | Method of manufacturing graphite steel rod for machine structural use having excellent free cutting characteristics and cold forging characteristics |
| WO2007086215A1 (en) * | 2006-01-26 | 2007-08-02 | Jfe Steel Corporation | Constant velocity universal joint having excellent rolling fatigue property, power transmission shaft having excellent torsional fatigue property, and processes for producing them |
| JP2007197772A (en) * | 2006-01-26 | 2007-08-09 | Jfe Steel Kk | Transmission shaft superior in torsion fatigue characteristic and manufacturing method therefor |
| JP2007197771A (en) * | 2006-01-26 | 2007-08-09 | Jfe Steel Kk | Constant-velocity universal joint excellent in rolling fatigue characteristic, and manufacturing method therefor |
| JP2008163458A (en) * | 2006-12-08 | 2008-07-17 | Jfe Steel Kk | Steel material for machine structural use excellent in machinability and fatigue characteristic |
-
1995
- 1995-04-12 JP JP8686595A patent/JPH08283847A/en not_active Withdrawn
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999045162A1 (en) * | 1998-03-04 | 1999-09-10 | Nippon Steel Corporation | Steels for cold forging and process for producing the same |
| US6419761B1 (en) | 1998-03-04 | 2002-07-16 | Nippon Steel Corporation | Steels for cold forging and process for producing the same |
| FR2788821A1 (en) * | 1999-01-12 | 2000-07-28 | Ntn Toyo Bearing Co Ltd | Power transmission shaft using constant velocity universal joint has induction hardened surface layer and comprises carbon steel including silicon, manganese, aluminum and boron |
| EP1178126A1 (en) * | 1999-12-24 | 2002-02-06 | Nippon Steel Corporation | Bar or wire product for use in cold forging and method for producing the same |
| EP1178126A4 (en) * | 1999-12-24 | 2004-04-14 | Nippon Steel Corp | Bar or wire product for use in cold forging and method for producing the same |
| KR100605722B1 (en) * | 2004-11-24 | 2006-08-01 | 주식회사 포스코 | Method of manufacturing graphite steel rod for machine structural use having excellent free cutting characteristics and cold forging characteristics |
| WO2007086215A1 (en) * | 2006-01-26 | 2007-08-02 | Jfe Steel Corporation | Constant velocity universal joint having excellent rolling fatigue property, power transmission shaft having excellent torsional fatigue property, and processes for producing them |
| JP2007197772A (en) * | 2006-01-26 | 2007-08-09 | Jfe Steel Kk | Transmission shaft superior in torsion fatigue characteristic and manufacturing method therefor |
| JP2007197771A (en) * | 2006-01-26 | 2007-08-09 | Jfe Steel Kk | Constant-velocity universal joint excellent in rolling fatigue characteristic, and manufacturing method therefor |
| JP2008163458A (en) * | 2006-12-08 | 2008-07-17 | Jfe Steel Kk | Steel material for machine structural use excellent in machinability and fatigue characteristic |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR102021216B1 (en) | Wire rods for bolts with excellent delayed fracture resistance after pickling and quenching tempering, and bolts | |
| WO2013151009A1 (en) | Steel wire rod or steel bar having excellent cold forgeability | |
| JP6226086B2 (en) | Rolled steel bar or wire rod for cold forging parts | |
| JP5407178B2 (en) | Steel wire rod for cold forging excellent in cold workability and manufacturing method thereof | |
| JP2012041587A (en) | Wire for machine part excellent in high strength and hydrogen embrittlement resistance characteristic, steel wire, and the machine part and method for manufacturing the same | |
| JP6226085B2 (en) | Rolled steel bar or wire rod for cold forging parts | |
| Kandpal et al. | Effect of heat treatment on properties and microstructure of steels | |
| WO2015146331A1 (en) | Steel for high strength bolts having excellent delayed fracture resistance and high strength bolt | |
| JP3879459B2 (en) | Manufacturing method of high hardenability high carbon hot rolled steel sheet | |
| WO2016158343A1 (en) | Steel wire for use in bolts that has excellent cold headability and resistance to delayed fracture after quenching and tempering, and bolt | |
| CN109790602B (en) | Steel | |
| JPH08283847A (en) | Production of graphite steel for cold forging excellent in toughness | |
| JP2001131635A (en) | Method for producing non-oriented silicon steel sheet excellent in workability and magnetic property after annealing | |
| JPS6137334B2 (en) | ||
| JP2005120397A (en) | High strength forged parts with excellent drawability | |
| JP3249700B2 (en) | High carbon hot rolled steel sheet excellent in hardenability and punching workability and method for producing the same | |
| JP2016074951A (en) | Manufacturing method of case hardened steel | |
| KR20090057564A (en) | A wire rod free from heat treament having high toughness for cold forging and method for manufacturing the same | |
| JP3602602B2 (en) | Method for producing fine graphite uniformly dispersed steel bar for cold working with excellent toughness | |
| JP4517459B2 (en) | Manufacturing method of steel material having ultrafine martensite structure | |
| JP3339795B2 (en) | Method for manufacturing linear motion bearing member | |
| JP2001011571A (en) | Steel for machine structure excellent in machinability, cold forgeability and hardenability | |
| JPH0243319A (en) | Production of case hardening cr-mo steel | |
| JP2024001480A (en) | Steel | |
| JP3282491B2 (en) | Steel for mechanical structure excellent in cold workability and method for producing the same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A300 | Withdrawal of application because of no request for examination |
Free format text: JAPANESE INTERMEDIATE CODE: A300 Effective date: 20020702 |