JPH0273950A - Free cutting steel excellent in hot ductility - Google Patents
Free cutting steel excellent in hot ductilityInfo
- Publication number
- JPH0273950A JPH0273950A JP22375988A JP22375988A JPH0273950A JP H0273950 A JPH0273950 A JP H0273950A JP 22375988 A JP22375988 A JP 22375988A JP 22375988 A JP22375988 A JP 22375988A JP H0273950 A JPH0273950 A JP H0273950A
- Authority
- JP
- Japan
- Prior art keywords
- less
- steel
- machinability
- hot ductility
- hot
- 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.)
- Granted
Links
- 229910000915 Free machining steel Inorganic materials 0.000 title claims abstract description 17
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 21
- 229910052796 boron Inorganic materials 0.000 claims abstract description 15
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 12
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 9
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 8
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 7
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 7
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 7
- 230000001105 regulatory effect Effects 0.000 claims abstract description 6
- 229910052797 bismuth Inorganic materials 0.000 claims description 9
- 229910052804 chromium Inorganic materials 0.000 claims description 7
- 229910052750 molybdenum Inorganic materials 0.000 claims description 6
- 229910052745 lead Inorganic materials 0.000 claims description 3
- 229910000831 Steel Inorganic materials 0.000 abstract description 43
- 239000010959 steel Substances 0.000 abstract description 43
- 229910052726 zirconium Inorganic materials 0.000 abstract description 4
- 230000002542 deteriorative effect Effects 0.000 abstract description 2
- 239000000203 mixture Substances 0.000 abstract description 2
- 230000006866 deterioration Effects 0.000 abstract 1
- 230000007423 decrease Effects 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 239000011651 chromium Substances 0.000 description 8
- 239000010936 titanium Substances 0.000 description 6
- 238000005520 cutting process Methods 0.000 description 5
- 229910052761 rare earth metal Inorganic materials 0.000 description 5
- 150000002910 rare earth metals Chemical class 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 4
- 238000005242 forging Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000005098 hot rolling Methods 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- -1 REM form nitrides Chemical class 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
（ＪＴ業上の利用分野）
本発明は、熱間延性を低下させることなく被削性を改善
した快削鋼に係り、例えば、エンジン部品や足まわり部
品などの自動車部品の素材として好適に利用される熱間
延性に優れた快削鋼に関するものである。
（従来の技術）
従来、例えば、エンジン部品や足まわり部品などの自動
車部品の素材としては１機械構造用鋼が多く使用されて
おり、浸炭焼入れ焼もどしを施して使用するものや、焼
入れ焼もどしを施すことなく非調質で使用するものなど
があった。また、被削性をより一層向上させるようにし
たり、温間加工性をさらに向上させるようにした機械構
造用鋼も開発されていた。
（発明が解決しようとする課題）
しかしながら、機械構造用鋼の被削性をより−・層内上
させるために、快削元素としてＳ、Ｓｅ。
Ｔｅ、Ｐｂ、Ｂｉ等を添加すると、熱間延性を劣化させ
ることが多く、熱間延性が劣化することによってオース
テナイト状態で行う熱間圧延、熱間鍛造等の熱間加工時
に割れや疵が発生しやすくなり、熱間加工が困難になる
ことが多いという課題があった。
（発明の目的）
本発明は、上述した従来の課題にかんがみてなされたも
のであって、熱間延性を低下させることなく被削性を改
善した、熱間延性に優れた快削鋼を提供することを目的
としている。(Field of application in the JT industry) The present invention relates to free-cutting steel that has improved machinability without reducing hot ductility, and is suitable for use as a material for automobile parts such as engine parts and suspension parts, for example. This relates to free-cutting steel with excellent hot ductility. (Prior art) Conventionally, for example, steel for machine structural use has been widely used as a material for automobile parts such as engine parts and suspension parts. There were some that were used without heat refining. In addition, steels for machine structures were developed that had further improved machinability and warm workability. (Problems to be Solved by the Invention) However, in order to further improve the machinability of steel for machine structural use, S and Se are used as free-cutting elements. Addition of Te, Pb, Bi, etc. often deteriorates hot ductility, which causes cracks and flaws during hot processing such as hot rolling and hot forging in the austenitic state. There was a problem that hot working was often difficult. (Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and provides a free-cutting steel with excellent hot ductility and improved machinability without reducing hot ductility. It is intended to.
（課題を解決するための手段）
本発明に係る熱間延性に優れた快削鋼は、重￥二％で、
Ｃ：０．１５〜０．７０％、Ｓｉ：０．３５％以下、Ｍ
ｎ：２．５％以下、Ａｌ二０．００１〜０．１００％、
で、Ｃ：０．００４０〜０．０２００％、Ｎ：０．００
５０〜０ 、０２００％でかつ、％Ｎ／％で、Ｃ：０．
５〜４．０、必要に応じて、Ｎｉ：０．３〜５．０％、
Ｃｒ：０．１〜５．０％、Ｍｏ ： ０ 、０５〜３
、０％のうちから選ばれる１種または２種以上、同じく
必要に応じて、Ｐｂ：０．０５％未満、Ｂｉ ：０．０
５％未満のうちから選ばれる１種または２種を含み、Ｔ
ｉ＋Ｚｒ＋ＲＥＭ： ０．０１％以下、Ｏ： ０．００
２０％以下、Ｓ：０．０１０％以下に規制し、残部実質
的にＦｅよりなる合金成分の構成としたことを＃徴とし
ており、このような合金成分の構成を」−述した従来の
課題を解決するだめの手段としている。
次に、本発明による熱間延性に優れた快削鋼の合金成分
（重量％）の限定理由について説明する。
Ｃ（炭素） ＋０．１５〜０．７０％Ｃは例えばエン
ジン部品や足まわり部品などの自動車部品の強度を確保
するために必須の元素であり、そのためには０．１５％
以上含有させる必要があるが、多量に含有すると靭性を
低下させると共に加工性を劣化させてしまうので、０．
７０％以下とした。
Ｓｉ（ケイ素）＋０．３５％以下
Ｓｉは鋼溶製時の脱酸剤として有効な元素であり、鋼塊
の表面欠陥の発生を防止するのに有用な元素であるが、
多量に含有すると延性を低下させるので、その−４−限
を０．３５％とした。
Ｍｎ（マンガン）：２．５％以下
Ｍｎは鋼溶製時の脱酸剤および脱硫剤として有効な元素
であり、Ｍ ｎ Ｓ等の硫化物を形成することによって
Ｓによる熱間脆化を防止する効果がある。しかし、多量
に含有すると鋼の被削性を劣化させるため、その−Ｌ限
を２．５％とした。
Ａｌ（アルミニウム）：０．０Ｏ１〜０．１００％
Ａ、 ｌは鋼溶製時の脱酸剤として有効な元素であり、
鋼中の脱酸を十分なものとすることによってＢ２Ｏ３が
生成されるのを防止するのに有用であるので、このよう
な効果を得るためにｏ、ｏｏｉ％以上とした。しかし、
多量に含有すると地疵発生の原因となるので、その−Ｌ
限を０．１００％とした。
Ｂ（ホウ素）：０．００４０〜０．０２００％Ｎ（窒素
）＋０．００５０〜０．０２００％でかつ、％Ｎ／％で
、Ｃ：０．５〜４．０ＢおよびＮは鋼中において被削性
の向上に効果のあるＢＮとして析出し、鋼の被削性を向
上させるのに有効な元素である。この場合、ＢＮは鋼中
において微細に析出するので、機械的性質を低下させる
ことがなく、また熱間加工性を低下させることもない。
そして、このようなりＮの効果を上のに発揮させるため
には、Ｂを０．００４０％以−１−５Ｎを０．００５０
％以」二添加する必要がある。しかし、Ｂの含有量が０
．０２００％を超えると熱間加工性が劣化し、Ｎの含有
量が０．０２００％を超えると鋳造性が悪化してしまう
ので、Ｂについては０．００４０〜０．０２００％、Ｎ
については０．００５０〜０．０２００％の範囲とした
。
さらに、％Ｎ／％Ｂの値が０．５未満であると熱間加工
性が劣化し、前記値が４．０を超えると被削性が低下し
てしまうので、％Ｎ／％Ｂの値を０．５〜４．０％に規
制した。
Ｎｉにッケル）：０．３〜５．０％
Ｃｒ（クロム）：Ｏ，ｌ 〜５．０％
Ｍｏ（モリブデン）＋０．０５〜３．０％Ｎｉ、Ｃｒ、
Ｍｏは強度の向上に有効な元素であるので、必要に応じ
てこれらの１種または２種以上をＮｉについては０．３
％以］−１Ｃｒについては０．１％以」二、ＭＯについ
ては０．０５％以１、添加することもできるが、Ｎｉが
５．０％を超え、Ｃｒが５．０％を超え、ＭＯが３．０
％を超えても、強度向上の効果は飽和し、むしろ価格の
１−■をもたらしたり被削性が低下してしまったりする
ので、添加するとしてもＮｉは０．３〜５．０％、Ｃｒ
は０．１〜５．０％、ＭＯは０．０５〜３．０％の１種
または２種以上とするのがよい。
Ｐｂ（鉛）：０．０５％未満
Ｂｉ（ビスマス）：０．０５％未満
本発明に係る熱間延性に優れた快削鋼は、−Ｌ述したよ
うにＢＮの添加により被削性は確保されているが、被削
性をさらに向上させたい場合に、ＰｂおよびＢｉは被削
性の向上に有効な元素であるので、必要に応じてこれら
の１種または２種以上を不純物レベル以上添加すること
もできる。しかし、Ｐｂが０．０５％以上、Ｂｉが０．
０５％以上であると熱間加工性が低下してしまうので、
添加するとしてもＰｂはより好ましくは０．０１％以−
、ｈｏ、０５％未満、Ｂｉはより好ましくは０．０１％
以Ｊ１０．０５％未満としてこれらの１種または２種を
添加するのがよい。
Ｔｉ（チタン）＋Ｚｒ（ジルコニウム）＋ＲＥＭ（希土
類金属）：０．０１％以下
Ｔｉ 、Ｚｒ 、ＲＥＭはＮと窒化物を形成し、前述し
たＢＮの形成を阻害する元素であるため、それらの総量
を０．０１％以下に規制する必要がある。
Ｏ（酸素）：０．００２０％以下
ＯはＢと結合して酸化物（Ｂ２０３ ）を形成し、ＢＮ
の形成を阻害するため、その含有量はできるだけ少なく
するのがよく、０．００２０％以下に規制する必要があ
る。
Ｓ（いおう）：０．０１０％以下
Ｓは鋼の熱間延性を低下させ、熱間圧延や熱間鍛造など
の熱間加工性を劣化させるので、０．０１０％以下に規
制する必要がある。
（発明の作用）
本発明に係る熱間延性に優れた快削鋼においては、鋼の
溶製時にＢ、！ｌ−Ｎを含有させ、その後の凝固過程と
熱間加工工程において、被削性の向上に優れた効果を発
揮する微細なりＮ（六方晶窒化ホウ素）を析出させるよ
うにしているので、鋼の被削性は著しく良好なものとな
っており、このＢＮ析出物は、硫化物やＰｂなどの被削
性向上元素の析出物に比べるとそのサイズが小さく、非
常に微細なものであることに加えて、高温に対しても安
定なものであることから、鋼の熱間延性を劣化させるこ
となく被削性を著しく向上させる。
そして、本発明に係る熱間延性に優れた快削鋼において
は、窒化物形成傾向の強いＴｉ、ＺｒＲＥＭの含有量を
規制すると共にＢと酸化物を形成してＢＮの析出を阻害
する酸素の含有量を規制しているので、微細なりＮ介在
物が安定して析出されるようになり、熱間延性に及ぼす
悪影響が小さいＢＮによる被削性向上の作用が十分に発
揮される。
なお、通常の場合において、上記のＢとＮをＢＮ化合物
として添加しようとすると、その比重が溶鋼に比べてか
なり小さいために、溶鋼上に浮ｉ してしまうおそれが
あるので、何んらかの添加手段を考慮する必要がある場
合が多い。
（実施例）
以下、本発明の実施例を比較例とともに示す。
第１表に示す合金成分からなる組成の溶鋼を２ｔｏｎア
ーク炉で溶解しそして精錬炉で精錬することにより得た
後、それぞれインゴットとし、次いで、各インゴットを
直径９０ｍｍまで熱間圧延し、さらに直径６０ｍｍの棒
材に熱間鍛造したのち焼ならしを行った。
次に、このようにして得られた各供試鋼について、それ
ぞれ、切削試験および引張試験を行って、被削性および
熱間延性を調べた。この場合、切削試験は、工具、Ｐｌ
ｏ、切削速度；１５０ｍ／ｍｉｎ、寿命判定；逃げ面摩
耗０．２ｍｍにより行い、比較のＡ鋼の被削性を基準（
すなわち１）として、旋削における超硬工具寿命の比で
被削性を評価した。この結果を同じく第１表に示す。ま
た、引張試験は、直径６０ｍｍの鍛造材の直径方向より
試験片を採取し、試験温度；１１００℃、引張速度；５
０ｍｍ／秒の条件でグリ−プル試験を行い、熱間引張に
おける絞り値で熱間延性を評価した。この結果を同じく
第１表に示す。
第１表に示した結果において、まず、比較鋼Ａ、Ｂ、Ｃ
から明らかように、５４５Ｃ（比較鋼Ａ）にＳ（比較鋼
Ｂ）およびＰｂ（比較鋼Ｃ）を添加した場合には、被削
性は向上しているものの、熱間延性がかなり低下してい
る。
これに対して、３４５ＣにＢＮを添加した発明鋼ｌの場
合には、被剛性はかなり向上しているが、熱間延性の低
下は実質的に認められず、これにＰｂおよびＢｉを添加
したそれぞれ発明鋼２および発明鋼３の場合には被削性
はさらに向上しているものの、熱間延性の低下は実質的
に認められなかった。
また、５ＣＲ４２０（比較鋼Ｄ）にＢＮを添加した発明
鋼４の場合にも、被削性はかなり向上しているが熱間延
性の低下は実質的に認められず、これにＰｂおよびＢｉ
を添加したそれぞれ発明鋼５および発明鋼６の場合には
被削性はさらに向上しているものの、熱間延性の低下は
実質的に認められなかった。
さらに、ＳＣＭ４２０（比較鋼Ｅ）にＢＮを添加した発
明鋼７の場合にも、被削性はかなり向」二しているが熱
間延性の低下は実質的に認められず、これにＰｂおよび
Ｂｉを添加したそれぞれ発明鋼８および発明鋼９の場合
には被削性はさらに向上しているものの、熱間延性の低
下は実質的に認められなかった。
さらにまた、５ＮＣ８３１（比較鋼Ｆ）にＢＮを添加し
た発明鋼１０の場合にも、被削性はかなり向上している
が熱間延性の低下は実質的に認められず、これにＰｂお
よびＢｉを添加したそれぞれ発明鋼１１および発明鋼１
２の場合には被削性はさらに向上しているものの、熱間
延性の低下は実質的に認められなかった。
ざラニマタ、ＳＮ０Ｍ２２０ （比較鋼Ｇ）にＢＮを添
加した発明鋼重３の場合にも、被削性はかなり向」ニジ
ているが熱間延性の低下は実質的に認められず、これに
ＰｂおよびＢｉを添加したそれぞれ発明鋼１４および発
明鋼１５の場合には被削性はさらに向上しているものの
、熱間延性の低下は実質的に認められず、本発明鋼は熱
間延性を低下させることなく被削性が大幅に改善されて
いることが確かめられた。(Means for solving the problem) The free-cutting steel with excellent hot ductility according to the present invention has a weight of 2%,
C: 0.15-0.70%, Si: 0.35% or less, M
n: 2.5% or less, Al2 0.001 to 0.100%,
So, C: 0.0040-0.0200%, N: 0.00
50-0, 0200% and %N/%, C: 0.
5 to 4.0, if necessary, Ni: 0.3 to 5.0%,
Cr: 0.1-5.0%, Mo: 0, 05-3
, 0%, one or more selected from 0%, and also as necessary, Pb: less than 0.05%, Bi: 0.0
Contains one or two types selected from less than 5%, T
i+Zr+REM: 0.01% or less, O: 0.00
20% or less, S: 0.010% or less, and the balance is essentially Fe. It is used as a last resort to solve the problem. Next, the reasons for limiting the alloy components (weight %) of the free-cutting steel with excellent hot ductility according to the present invention will be explained. C (carbon) +0.15-0.70%C is an essential element to ensure the strength of automobile parts such as engine parts and suspension parts, and for that purpose 0.15%
It is necessary to contain more than 0.0.
It was set to 70% or less. Si (silicon) +0.35% or lessSi is an effective element as a deoxidizing agent during steel melting, and is an element useful in preventing the occurrence of surface defects in steel ingots.
If contained in a large amount, the ductility decreases, so the -4- limit was set at 0.35%. Mn (manganese): 2.5% or less Mn is an effective element as a deoxidizing agent and desulfurizing agent during steel melting, and prevents hot embrittlement due to S by forming sulfides such as M n S. It has the effect of However, if contained in a large amount, the machinability of steel deteriorates, so the -L limit was set at 2.5%. Al (aluminum): 0.0O1~0.100% A, l are elements effective as deoxidizing agents during steel melting,
Since it is useful for preventing the formation of B2O3 by sufficiently deoxidizing the steel, in order to obtain such an effect, the content is set to o, ooi% or more. but,
If it is contained in a large amount, it may cause ground scratches, so -L
The limit was set at 0.100%. B (boron): 0.0040-0.0200% N (nitrogen) + 0.0050-0.0200% and %N/%, C: 0.5-4.0B and N are It precipitates as BN, which is effective in improving the machinability of steel, and is an effective element in improving the machinability of steel. In this case, since BN is finely precipitated in the steel, it does not reduce mechanical properties or hot workability. In order to maximize the effect of N, B should be 0.0040% or more - 1-5N should be 0.0050%
% or more must be added. However, the content of B is 0
．． If the N content exceeds 0.0200%, hot workability will deteriorate, and if the N content exceeds 0.0200%, the castability will deteriorate.
The range was 0.0050% to 0.0200%. Furthermore, if the value of %N/%B is less than 0.5, hot workability deteriorates, and if the value exceeds 4.0, machinability decreases. The value was regulated to 0.5-4.0%. Ni): 0.3 to 5.0% Cr (chromium): O, l to 5.0% Mo (molybdenum) + 0.05 to 3.0% Ni, Cr,
Since Mo is an effective element for improving strength, one or more of these may be added as necessary to 0.3% of Ni.
% or more] -1 Cr can be added by 0.1% or more, MO can be added by 0.05% or more, but if Ni exceeds 5.0%, Cr exceeds 5.0%, MO is 3.0
Even if Ni exceeds 0.3% to 5.0%, the strength improvement effect will be saturated and the price will increase by 1-■ or the machinability will decrease. Cr
is preferably 0.1 to 5.0%, and MO is preferably one or more of 0.05 to 3.0%. Pb (lead): less than 0.05% Bi (bismuth): less than 0.05% The free-cutting steel with excellent hot ductility according to the present invention has -L As mentioned above, machinability is ensured by the addition of BN. However, if you want to further improve machinability, Pb and Bi are effective elements for improving machinability, so if necessary, one or more of these can be added above the impurity level. You can also. However, Pb is 0.05% or more and Bi is 0.05% or more.
If it is more than 0.05%, hot workability will decrease, so
Even if Pb is added, it is more preferably 0.01% or more.
, ho, less than 0.05%, Bi is more preferably 0.01%
It is preferable to add one or two of these in an amount of less than 10.05%. Ti (titanium) + Zr (zirconium) + REM (rare earth metal): 0.01% or less Ti, Zr, and REM form nitrides with N and are elements that inhibit the formation of BN as described above, so their total amount is It is necessary to regulate it to 0.01% or less. O (oxygen): 0.0020% or less O combines with B to form oxide (B203), and BN
In order to inhibit the formation of , its content should be kept as low as possible, and should be regulated to 0.0020% or less. S (sulfur): 0.010% or less S reduces the hot ductility of steel and deteriorates hot workability in hot rolling, hot forging, etc., so it needs to be regulated to 0.010% or less. . (Action of the invention) In the free-cutting steel with excellent hot ductility according to the present invention, B,! By incorporating l-N, fine N (hexagonal boron nitride), which has an excellent effect on improving machinability, is precipitated during the subsequent solidification process and hot working process, so the steel The machinability is extremely good, and this BN precipitate is small in size and extremely fine compared to the precipitates of machinability-improving elements such as sulfide and Pb. In addition, since it is stable even at high temperatures, it significantly improves the machinability of the steel without deteriorating its hot ductility. In the free-cutting steel with excellent hot ductility according to the present invention, the content of Ti and ZrREM, which have a strong tendency to form nitrides, is controlled, and the content of oxygen, which forms oxides with B and inhibits the precipitation of BN, is controlled. Since the content is regulated, fine N inclusions are stably precipitated, and the machinability-improving effect of BN, which has little adverse effect on hot ductility, is fully exhibited. In addition, in normal cases, if you try to add the above B and N as a BN compound, there is a risk that it will float on the molten steel because its specific gravity is quite small compared to the molten steel. In many cases, it is necessary to consider the means of addition. (Example) Examples of the present invention will be shown below together with comparative examples. Molten steel having the alloy composition shown in Table 1 is melted in a 2 ton arc furnace and refined in a refining furnace. Each ingot is made into an ingot. Then, each ingot is hot rolled to a diameter of 90 mm, and then After hot forging into a 60 mm bar, it was normalized. Next, each of the sample steels thus obtained was subjected to a cutting test and a tensile test to examine machinability and hot ductility. In this case, the cutting test consists of the tool, Pl
o, cutting speed: 150 m/min, life judgment: carried out with flank wear of 0.2 mm, based on the machinability of comparative steel A (
That is, as 1), machinability was evaluated based on the ratio of carbide tool life in turning. The results are also shown in Table 1. In addition, for the tensile test, a test piece was taken from the diametrical direction of a forged material with a diameter of 60 mm, the test temperature was 1100°C, and the tensile speed was 5.
A Greeple test was conducted under the condition of 0 mm/sec, and the hot ductility was evaluated by the reduction of area in hot tension. The results are also shown in Table 1. In the results shown in Table 1, first, comparative steels A, B, and C
As is clear from the above, when S (comparative steel B) and Pb (comparative steel C) were added to 545C (comparative steel A), machinability improved, but hot ductility decreased considerably. There is. On the other hand, in the case of the invention steel 1, which is made by adding BN to 345C, the stiffness is considerably improved, but there is no substantial decrease in hot ductility. Although the machinability was further improved in the case of Invention Steel 2 and Invention Steel 3, respectively, no decrease in hot ductility was substantially observed. Furthermore, in the case of Inventive Steel 4, in which BN was added to 5CR420 (Comparative Steel D), the machinability was considerably improved, but no substantial decrease in hot ductility was observed.
In the case of Inventive Steel 5 and Inventive Steel 6, respectively, which had the addition of , the machinability was further improved, but no substantial decrease in hot ductility was observed. Furthermore, in the case of Inventive Steel 7, which is made by adding BN to SCM420 (comparative steel E), the machinability is considerably improved, but no substantial decrease in hot ductility is observed. Although the machinability was further improved in the case of Invention Steel 8 and Invention Steel 9 to which Bi was added, there was substantially no decrease in hot ductility. Furthermore, in the case of Inventive Steel 10, in which BN was added to 5NC831 (Comparative Steel F), the machinability was considerably improved, but there was virtually no decrease in hot ductility. Invention steel 11 and invention steel 1, respectively, with the addition of
In the case of No. 2, although the machinability was further improved, there was virtually no decrease in hot ductility. In the case of invention steel 3, which is made by adding BN to Zaranimata, SN0M220 (comparative steel G), the machinability is considerably improved, but there is no substantial decrease in hot ductility. In the case of Invention Steel 14 and Invention Steel 15, in which Bi was added, the machinability was further improved, but no substantial decrease in hot ductility was observed; It was confirmed that machinability was significantly improved without causing any damage.
本発明に係る快削鋼は、重量％で、Ｃ：ｏ、ｉｓ〜０．
７０％、Ｓｊ：０．３５％以下Ｍ ｎ ： ２ 、５％
以下、Ａｌ：Ｏ，０Ｏ１−０，１００％、で、Ｃ： ０
．００４０〜０．０２００％、Ｎ：０．００５０〜０．
０２００％でかつ、％Ｎ／％で、Ｃ：０．５〜４．０、
必要に応じて、Ｎｉ：０．３−５．０％、Ｃｒ：０．１
〜５．０％、Ｍｏ：０．０５〜３．０％のうちから選ば
れる１種または２種以上、同じく必要に応じて、Ｐｂ：
０．０５％未満、Ｂｉ：０．０５％未満のうちから選ば
れる１種または２種を含み、Ｔｉ＋Ｚｒ＋ＲＥＭ：０．
０１％以下、０：０．００２０％以下、Ｓ：０．０１０
％以下に規制し、残部実質的にＦｅよりなる合金成分の
構成としていることから、熱間延性を低下させることな
く被削性を著しく改善した、熱間延性に債れた快削鋼で
あり、オーステナイト状態で行う熱間圧延、熱間鍛造等
の熱間加工時に割れや疵が発生しがたいものであって、
熱間加工を良好に行うことができると共に、切削加工に
おいても被削性が良好であるため、切削加工性の向上、
工具寿命の増大をはかることができ、自動車部品および
その他各種機械構造物用部品の品質および製造性を著し
く向上させることかでざるようになるという著大なる効
果がもたらされる。The free-cutting steel according to the present invention has C:o, is~0.
70%, Sj: 0.35% or less M n : 2, 5%
Below, Al:O,0O1-0,100%, C: 0
．． 0040-0.0200%, N: 0.0050-0.
0200% and %N/%, C: 0.5 to 4.0,
Ni: 0.3-5.0%, Cr: 0.1 as necessary
-5.0%, Mo: one or more selected from 0.05 to 3.0%, Pb:
Ti+Zr+REM: less than 0.05%, Bi: less than 0.05%, and Ti+Zr+REM:0.
01% or less, 0:0.0020% or less, S:0.010
It is a free-cutting steel with excellent hot ductility that has significantly improved machinability without reducing hot ductility. , which is unlikely to cause cracks or flaws during hot processing such as hot rolling or hot forging in an austenitic state,
In addition to being able to perform hot working well, it also has good machinability in cutting, improving machinability.
This has the great effect of increasing tool life and significantly improving the quality and manufacturability of automobile parts and other parts for various mechanical structures.
Claims (1)
：０．００１〜０．１００％、 Ｂ：０．００４０〜０．０２００％、Ｎ： ０．００５０〜０．０２００％でかつ、％Ｎ／％Ｂ：０
．５〜４．０を含み、Ｔｉ＋Ｚｒ＋ＲＥＭ：０．０１％
以下、Ｏ：０．００２０％以下、Ｓ：０．０１０％以下
に規制し、残部実質的にＦｅよりなることを特徴とする
熱間延性に優れた快削鋼。 （２）重量％で、Ｃ：０．１５〜０．７０ ％、Ｓｉ；０．３５％以下、Ｍｎ：２．５％以下、Ａｌ
：０．００１〜０．１００％、 Ｂ：０．００４０〜０．０２００％、Ｎ： ０．００５０〜０．０２００％でかつ、％Ｎ／％Ｂ：０
．５〜４．０、およびＮｉ：０．３〜５．０％、Ｃｒ：
０．１〜５．０％、Ｍｏ：０．０５〜３．０％のうちか
ら選ばれる１種または２種以上を含み、Ｔｉ＋Ｚｒ＋Ｒ
ＥＭ：０．０１％以下、Ｏ：０．００２０％以下、Ｓ：
０．０１０％以下に規制し、残部実質的にＦｅよりなる
ことを特徴とする熱間延性に優れた快削鋼。 （３）重量％で、Ｃ：０．１５〜０．７０ ％、Ｓｉ：０．３５％以下、Ｍｎ：２．５％以下、Ａｌ
：０．００１〜０．１００％、 Ｂ：０．００４０〜０．０２００％、Ｎ： ０．００５０〜０．０２００％でかつ、％Ｎ／％Ｂ：０
．５〜４．０、およびＰｂ：０．０５％未満、Ｂｉ：０
．０５％未満のうちから選ばれる１種または２種を含み
、Ｔｉ＋Ｚｒ＋ＲＥＭ：０．０１％以下、Ｏ：０．００
２０％以下、Ｓ：０．０１０％以下に規制し、残部実質
的にＦｅよりなることを特徴とする熱間延性に優れた快
削鋼。 （４）重量％で、Ｃ：０．１５〜０．７０ ％、Ｓｉ：０．３５％以下、Ｍｎ：２．５％以下、Ａｌ
：０．００１〜０．１００％、 Ｂ：０．００４０〜０．０２００％、Ｎ： ０．００５０〜０．０２００％でかつ、％Ｎ／％Ｂ：０
．５〜４．０、およびＮｉ：０．３〜５．０％、Ｃｒ：
０．１〜５．０％、Ｍｏ：０．０５〜３．０％のうちか
ら選ばれる１種または２種以上、Ｐｂ：０．０５％未満
、Ｂｉ：０．０５％未満のうちから選ばれる１種または
２種を含み、Ｔｉ＋Ｚｒ＋ＲＥＭ：０．０１％以下、Ｏ
：０．００２０％以下、Ｓ：０．０１０％以下に規制し
、残部実質的にＦｅよりなることを特徴とする熱間延性
に優れた快削鋼。[Claims] (1) In weight%, C: 0.15 to 0.70%, Si: 0.35% or less, Mn: 2.5% or less, Al
: 0.001 to 0.100%, B: 0.0040 to 0.0200%, N: 0.0050 to 0.0200%, and %N/%B: 0
．． Contains 5 to 4.0, Ti+Zr+REM: 0.01%
Hereinafter, a free-cutting steel with excellent hot ductility, characterized in that O: 0.0020% or less, S: 0.010% or less, and the remainder substantially consists of Fe. (2) In weight%, C: 0.15 to 0.70%, Si: 0.35% or less, Mn: 2.5% or less, Al
: 0.001 to 0.100%, B: 0.0040 to 0.0200%, N: 0.0050 to 0.0200%, and %N/%B: 0
．． 5 to 4.0, and Ni: 0.3 to 5.0%, Cr:
0.1 to 5.0%, Mo: 0.05 to 3.0%, including one or more selected from Ti+Zr+R
EM: 0.01% or less, O: 0.0020% or less, S:
A free-cutting steel with excellent hot ductility, characterized in that the content is regulated to 0.010% or less, and the remainder essentially consists of Fe. (3) In weight%, C: 0.15 to 0.70%, Si: 0.35% or less, Mn: 2.5% or less, Al
: 0.001 to 0.100%, B: 0.0040 to 0.0200%, N: 0.0050 to 0.0200%, and %N/%B: 0
．． 5 to 4.0, and Pb: less than 0.05%, Bi: 0
．． Contains one or two selected from less than 0.05%, Ti + Zr + REM: 0.01% or less, O: 0.00
A free-cutting steel with excellent hot ductility, characterized in that S: 0.010% or less, and the remainder substantially consists of Fe. (4) In weight%, C: 0.15 to 0.70%, Si: 0.35% or less, Mn: 2.5% or less, Al
: 0.001 to 0.100%, B: 0.0040 to 0.0200%, N: 0.0050 to 0.0200%, and %N/%B: 0
．． 5 to 4.0, and Ni: 0.3 to 5.0%, Cr:
0.1 to 5.0%, Mo: one or more selected from 0.05 to 3.0%, Pb: less than 0.05%, Bi: less than 0.05% Ti + Zr + REM: 0.01% or less, O
A free-cutting steel with excellent hot ductility, characterized in that S: 0.0020% or less, S: 0.010% or less, and the remainder substantially consists of Fe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63223759A JP2733989B2 (en) | 1988-09-06 | 1988-09-06 | Free cutting steel with excellent hot ductility |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63223759A JP2733989B2 (en) | 1988-09-06 | 1988-09-06 | Free cutting steel with excellent hot ductility |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0273950A true JPH0273950A (en) | 1990-03-13 |
| JP2733989B2 JP2733989B2 (en) | 1998-03-30 |
Family
ID=16803269
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63223759A Expired - Lifetime JP2733989B2 (en) | 1988-09-06 | 1988-09-06 | Free cutting steel with excellent hot ductility |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2733989B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000192962A (en) * | 1998-12-25 | 2000-07-11 | Ntn Corp | Rolling bearing |
| JP2011052299A (en) * | 2009-09-04 | 2011-03-17 | Jfe Bars & Shapes Corp | Bn free-cutting steel having excellent cutting chip treatability |
| CN109680216A (en) * | 2017-10-19 | 2019-04-26 | 株式会社Posco | The excellent middle carbon easy-cutting steel of hot rolling and its manufacturing method |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01191764A (en) * | 1988-01-26 | 1989-08-01 | Daido Steel Co Ltd | Free cutting steel for carburization quenching |
-
1988
- 1988-09-06 JP JP63223759A patent/JP2733989B2/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01191764A (en) * | 1988-01-26 | 1989-08-01 | Daido Steel Co Ltd | Free cutting steel for carburization quenching |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000192962A (en) * | 1998-12-25 | 2000-07-11 | Ntn Corp | Rolling bearing |
| JP2011052299A (en) * | 2009-09-04 | 2011-03-17 | Jfe Bars & Shapes Corp | Bn free-cutting steel having excellent cutting chip treatability |
| CN109680216A (en) * | 2017-10-19 | 2019-04-26 | 株式会社Posco | The excellent middle carbon easy-cutting steel of hot rolling and its manufacturing method |
| KR20190043790A (en) * | 2017-10-19 | 2019-04-29 | 주식회사 포스코 | Medium carbon free cutting steel having excellent hot workability and method for manufacturing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2733989B2 (en) | 1998-03-30 |
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