JP2001152280A - Free cutting steel - Google Patents
Free cutting steelInfo
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- JP2001152280A JP2001152280A JP33557399A JP33557399A JP2001152280A JP 2001152280 A JP2001152280 A JP 2001152280A JP 33557399 A JP33557399 A JP 33557399A JP 33557399 A JP33557399 A JP 33557399A JP 2001152280 A JP2001152280 A JP 2001152280A
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- free
- steel
- machinability
- cutting
- cutting steel
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- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、快削鋼に関し、詳
細には被削性（切り屑分断性と工具寿命）に優れるとと
もに、機械的性質のうち特に横方向衝撃値（以下横目靱
性と言う）に優れる快削鋼に関するものである。The present invention relates to a free-cutting steel, and more particularly to a steel having excellent machinability (cutting ability and tool life) and, particularly, a transverse impact value (hereinafter referred to as a transverse grain toughness) among mechanical properties. This is related to free cutting steel that excels in
【０００２】[0002]
【従来の技術】従来より、被削性はもとより機械的性質
に優れる快削鋼の提案が多くなされ、また実用されてい
る。一方、本発明者等も同様の特性を有する快削鋼の開
発を行ってきており、その開発過程で、快削鋼において
は硫化物中のMgが被削性や機械的性質のうち特に加工方
向と直角方向の延性（横目靱性）に影響を及ぼす点に注
目した。2. Description of the Related Art Conventionally, many free-cutting steels having excellent mechanical properties as well as machinability have been proposed and put into practical use. On the other hand, the present inventors have also developed a free-cutting steel having similar characteristics, and during the development process, in the free-cutting steel, Mg in sulfides is particularly difficult to work in machinability and mechanical properties. Attention was paid to the effect on ductility (transverse toughness) in the direction perpendicular to the direction.
【０００３】一方、これまで快削鋼においてMgを含有せ
しめることに注目して提案された快削鋼として、例えば
特公昭46−30935 号公報、特公昭52−7405号公報、特公
昭51−4934号公報、特開昭51−63312 号公報などがあ
る。また快削鋼ではないが、Mgを含有せしめることに注
目して提案されたものに、特開平 7−188853号公報及び
特開平 7−238342号公報などがある。On the other hand, free cutting steels which have been proposed so far with a focus on containing Mg in free cutting steels are disclosed, for example, in JP-B-46-30935, JP-B-52-7405, and JP-B-51-4934. And JP-A-51-63312. Further, although not a free-cutting steel, those proposed by focusing on containing Mg are disclosed in JP-A-7-188853 and JP-A-7-238342.
【０００４】特公昭46−30935 号公報には、Mgを0.0003
〜0.0060％添加含有せしめた快削鋼が提案されている。
この快削鋼では、Mgを含有せしめることで鋼材の機械的
性質に悪影響を及ぼすことなく、被削性の改善が期待さ
れるとされている。しかし、近年、改善が期待されてい
る機械的性質のうちの特に横目靱性については何ら記載
がなく、またその横目靱性や被削性の改善に係わる成分
組成としての S、 O、Alについても何ら規定がなく、こ
のため、十分な横目靱性値が得られないことが懸念され
る。[0004] JP-B-46-30935 discloses that Mg is 0.0003%.
Free-cutting steels containing up to 0.0060% have been proposed.
In this free-cutting steel, improvement in machinability is expected by incorporating Mg without adversely affecting the mechanical properties of the steel material. However, in recent years, among the mechanical properties expected to be improved, there is no description particularly regarding the transverse grain toughness, and there is no description about S, O, Al as a component composition related to the improvement of the transverse grain toughness and machinability. Since there is no regulation, there is a concern that a sufficient transverse grain toughness value cannot be obtained.
【０００５】特公昭52−7405号公報には、 C：0.05〜0.
75％、Si：0.05〜0.40％、Mn： 0.5〜 1.2％、Sol Al：
0.005 〜0.015 ％、O2：0.004 〜0.012 ％にMg、Baから
なる第１群元素の１種又は２種を0.1 ％以下と S、Se、
Teからなる第２群元素の１種以上を0.03〜0.5 ％含有
し、前記第１群元素と第２群元素の原子比が0.01以上に
して、残部は実質的にFeよりなる広範囲の優れた被削性
を有する機械構造用快削鋼が提案されている。この快削
鋼では、Alによる脱酸状態のもとにMgと S、Se、Teから
なる第２群元素の１種以上を原子比が0.01以上にして添
加するために、鋼中に細かく分散した快削性介在物が形
成され、被削性が向上するとされている。しかし、O2量
が0.004 〜0.012 ％と多く、このため被削性に有害な硬
質酸化物が多くなることが懸念され、必ずしも安定した
被削性が得られるとは限らないことが懸念される。また
Mgの単独添加も可能とされているものの、実施例におい
てMg単独添加の例はなくその効果が不明である。またAl
量の規定はSol Alで 0.005〜0.015 ％とされているが、
被削性への影響はアルミナなどの酸化物組成が重要なの
で、Sol Alによる規定では不十分である。In Japanese Patent Publication No. 52-7405, C: 0.05-0.
75%, Si: 0.05 to 0.40%, Mn: 0.5 to 1.2%, Sol Al:
0.005 ~0.015%, O 2: 0.004 ~0.012% in Mg, one or two of the first group element consisting of Ba 0.1% or less and S, Se,
One or more elements of the second group consisting of Te are contained in an amount of 0.03 to 0.5%, the atomic ratio of the first group elements and the second group elements is made 0.01 or more, and the balance is substantially excellent over a wide range consisting of Fe. A free-cutting steel for machine structures having machinability has been proposed. In this free-cutting steel, Mg and one or more of the second group elements consisting of S, Se, and Te are added at an atomic ratio of 0.01 or more under the deoxidation state by Al, so that they are finely dispersed in the steel. It is described that a free-cutting inclusion is formed and the machinability is improved. However, the amount of O 2 is as large as 0.004 to 0.012%, and there is a concern that hard oxides harmful to machinability will increase, and that it is not always possible to obtain stable machinability. . Also
Although it is possible to add Mg alone, there is no example of adding Mg alone in the examples, and its effect is unknown. Also Al
Although the amount is specified as 0.005 to 0.015% in Sol Al,
Since the influence on machinability depends on the composition of the oxide such as alumina, the regulation by Sol Al is insufficient.
【０００６】特公昭51−4934号公報には、 C：0.1 〜0.
5 ％、Si：0.05〜0.4 ％、Mn： 0.5〜2.0 ％、Cu、Ni、
Cr、Moの合計が0.5 〜2.0 ％、 VまたはNbを0.01〜0.10
％、Sol Al：0.002 〜0.02％、鋼中O2：0.002 〜0.01％
に、Mg、Baからなる第１群元素の１種又は２種を0.03％
以下と S、Se、Teからなる第２群元素の１種以上を0.5
％以下を含有し、前記第１群元素と第２群元素の原子比
が0.03以上にして、残部は実質的にFeよりなる広範囲の
優れた被削性を有する快削性構造用合金鋼が提案されて
いる。この合金鋼では、Alによる脱酸状態のもとにMgと
S、Se、Teからなる第２群元素の１種以上を原子比が0.
03以上にして添加するために、鋼中に形成される球状の
快削性介在物が細かく分散し、被削性が向上するとされ
ている。しかし、O2量の規定は0.002 〜0.01％とされて
いるものの、実施例では0.004 以上と多く、このため被
削性に有害な硬質酸化物が多くなることが懸念され、必
ずしも安定した被削性が得られるとは限らないことが懸
念される。またAl量の規定はSol Alで0.002 〜0.02％と
されているが、被削性への影響はアルミナなどの酸化物
組成が重要なので、 SolAlによる規定では不十分であ
る。Japanese Patent Publication No. 51-4934 discloses that C: 0.1-0.
5%, Si: 0.05-0.4%, Mn: 0.5-2.0%, Cu, Ni,
Cr-Mo total 0.5-2.0%, V or Nb 0.01-0.10
%, Sol Al: 0.002 ~0.02% , the steel in O 2: 0.002 ~0.01%
0.03% of one or two of the first group elements consisting of Mg and Ba
And at least one of the second group elements consisting of S, Se and Te
%, The atomic ratio between the first group element and the second group element is 0.03 or more, and the balance is substantially Fe. Proposed. In this alloy steel, Mg and Mg
At least one of the second group elements composed of S, Se, and Te has an atomic ratio of 0.
It is said that since it is added at 03 or more, spherical free-cutting inclusions formed in steel are finely dispersed and machinability is improved. However, although the O 2 amount prescribed is a 0.002 to 0.01%, more and 0.004 or more in the embodiment, the order is feared to become many harmful hard oxides machinability, cutting the necessarily stable There is a concern that the property may not always be obtained. Although the Al content is specified as 0.002 to 0.02% in Sol Al, the effect on machinability is important because the composition of the oxide such as alumina is important.
【０００７】特開昭51−63312 号公報には、0.04〜0.5
％の硫黄成分を有し横方向の延性と弾性が著しく改良さ
れた快削鋼において、多くとも0.005 ％に等しく少なく
とも硫黄成分の 5／1000に等しい量のマグネシウムを含
み、且つCa、Ba、Sr、SeおよびTeの元素の１つまたはい
くつかを含む快削鋼が提案されている。この快削鋼で
は、Mgは、鋼浴の脱酸後に極少量添加されたときは、脱
酸剤としての挙動を示さず、硫化物中に残り、その形を
球状化すると同時に分布を変えるので、横方向の延性と
弾性が著しく改良される効果が期待されるものの、Ca、
Ba、Sr、SeおよびTeの元素の１つ以上との複合添加であ
ることが必須となっており、これら元素は、毒性の面
（Te、Se、Ba）、単価の高い元素であるためのコストア
ップ（Sr、Se、Te）、熱間加工性の低下（Te）、鋼中へ
の歩留りの悪さと安定製造の難しさ（全ての元素、特に
Ca）等、好ましくない条件をそれぞれ抱えているため、
実用上は使用が難しいか或いは極力使用を避けたいもの
である。また、酸素については一切記載がないので、特
段の制御がなされていないものと考えられるが、酸素が
多すぎると、硬質な酸化物が増加し被削性（工具寿命）
が低下するとともに、本発明のように硫化物形態制御の
ためにMgを添加しようとする際には鋼中へのMgの歩留り
への影響が大きく、実用上問題がある。従って、酸素量
の制御は極めて重要な問題である。[0007] JP-A-51-63312 discloses that 0.04 to 0.5
% Free-cutting steel having a significant improvement in transverse ductility and elasticity with a sulfur content of at least equal to 0.005% and at least equal to 5/1000 of the sulfur content, and containing Ca, Ba, Sr Free-cutting steels containing one or some of the elements Se, Te and Te have been proposed. In this free-cutting steel, when Mg is added in a very small amount after deoxidation of the steel bath, it does not exhibit the behavior as a deoxidizing agent, remains in the sulfide, and changes its distribution at the same time as spheroidizing its shape. Although the effect of significantly improving the ductility and elasticity in the transverse direction is expected, Ca,
It is essential that the compound be added in combination with at least one of the elements Ba, Sr, Se and Te. These elements are toxic (Te, Se, Ba), Increased cost (Sr, Se, Te), decreased hot workability (Te), poor yield in steel and difficulty in stable production (all elements, especially
Ca) and other unfavorable conditions,
It is practically difficult to use or want to avoid using as much as possible. In addition, since there is no description about oxygen, it is considered that no special control is performed. However, if there is too much oxygen, hard oxides increase and machinability (tool life) is increased.
When Mg is to be added for controlling the sulfide form as in the present invention, the effect on the yield of Mg in steel is large, and there is a practical problem. Therefore, controlling the amount of oxygen is a very important issue.
【０００８】特開平 7−188853号公報には、 C： 0.1〜
0.4％、Si：0.15％以下、Mn： 0.3〜 2.0％、Cr： 0.4
〜 2.0％、 P：0.03％以下、 S： 0.005〜0.03％、T.
O：0.003 ％以下を基本成分とし、更にMgをT.Mgとして
0.0015〜0.0350含有する歯車用浸炭用鋼が提案されてい
る。この歯車用浸炭用鋼では、鋼材中にMgを含有させる
ことにより酸化物系介在物（主にアルミナ）のサイズが
微細化されると共にMnSの延伸性が抑制され、面疲労強
度の飛躍的な向上及び歯曲げ疲労強度の向上が期待でき
るとされているが、被削性（切り屑分断性）や横目靱性
を改善することについては何ら言及されておらず、本発
明が対象とする快削鋼とは異なる特性を改善したもので
ある。[0008] JP-A-7-188853 discloses that C: 0.1 to
0.4%, Si: 0.15% or less, Mn: 0.3 to 2.0%, Cr: 0.4
~ 2.0%, P: 0.03% or less, S: 0.005 ~ 0.03%, T.
O: 0.003% or less as the basic component, and Mg as T.Mg
Gear carburizing steels containing 0.0015 to 0.0350 have been proposed. In this carburizing steel for gears, the inclusion of Mg in the steel material reduces the size of oxide-based inclusions (mainly alumina), suppresses the extensibility of MnS, and dramatically increases the surface fatigue strength. It is expected that the improvement of the bending strength and the tooth bending fatigue strength can be expected. However, there is no mention of improving the machinability (chip breaking property) and the transverse grain toughness, and the free cutting targeted by the present invention is not described. It is an improvement in properties different from steel.
【０００９】特開平 7−238342号公報には、上記特開平
7−188853号公報に記載の歯車用浸炭用鋼を対象とし
て、更に鋼材中に含有される酸化物及び硫化物が、個数
比として次式(MgO＋MgO ・Al2O3)個数／全酸化物個数≧
0.80---- 0.20≦(Mn ・Mg)Sの個数／全硫化物個数≦0.70----を
満たすものである高強度歯車用浸炭用鋼が提案されてい
る。この高強度歯車用浸炭用鋼では、酸化物と硫化物の
個数比を前記式とに規定することにより、面疲労強
度の飛躍的な向上及び歯曲げ疲労強度の向上が期待でき
るとされているが、被削性（切り屑分断性）や横目靱性
を改善することについては何ら言及されておらず、本発
明が対象とする快削鋼とは異なる特性を改善したもので
ある。Japanese Patent Application Laid-Open No. 7-238342 discloses the above-mentioned Japanese Patent Application Laid-Open No.
With respect to the carburizing steel for gears described in 7-188853, oxides and sulfides further contained in the steel material are represented by the following formula (MgO + MgO.Al 2 O 3 ) number / total oxide number ≧
A carburizing steel for high-strength gears that satisfies 0.80 ---- 0.20≤ (Mn.Mg) S number / total sulfide number≤0.70 ---- has been proposed. In this high-strength gear carburizing steel, it is said that by defining the number ratio of oxides and sulfides to the above formula, a dramatic improvement in surface fatigue strength and an improvement in tooth bending fatigue strength can be expected. However, there is no mention of improving the machinability (chip breaking property) or the transverse grain toughness, and it is an improvement of a property different from the free-cutting steel targeted by the present invention.
【００１０】[0010]
【発明が解決しようとする課題】ところで、快削鋼の中
で、特に自動車部品や機械部品として用いられる快削鋼
は、一般に被削性とともに機械的性質が要求される用途
に使用する場合に適した鋼材である。これらは鍛造、圧
延などによって変形加工が加えられることもあるが、こ
のような変形加工を加えた場合、材料特性に異方性を生
じることがあり、機械構造部品としての必要特性が満た
されなくなる場合がある。すなわち、一般には鍛造、圧
延などで延ばされた方向に垂直な方向の衝撃値（横目靱
性値）が問題となる場合が多い。その横目靱性に大きな
影響を与えるとして硫化物の形態があるが、これまでの
研究で提案されているMgを含有する快削鋼においては上
述した通りで、被削性（切り屑分断性と工具寿命）と機
械的性質のうち特に横目靱性の何れをも十分に改善した
ものとはなっていないのが実情であって、その改善が望
まれている。By the way, among the free-cutting steels, free-cutting steels used particularly as automobile parts and machine parts are generally used in applications requiring both machinability and mechanical properties. It is a suitable steel material. These may be deformed by forging, rolling, etc., but when such deforming is applied, the material properties may be anisotropic, and the required properties as mechanical structural parts will not be satisfied There are cases. That is, in general, the impact value (lateral grain toughness value) in the direction perpendicular to the direction extended by forging, rolling, or the like often becomes a problem. There is a form of sulfide that has a great effect on the transverse grain toughness. However, in the free-cutting steel containing Mg proposed in previous studies, as described above, the machinability (chip cutting performance and tool It is a fact that neither of the (lifetime) and the mechanical properties, particularly the transverse grain toughness, have been sufficiently improved, and it is desired to improve them.
【００１１】本発明は、上述したような事情に基づいて
なしたものであって、その目的は、これまでにも言われ
ているMgを含有せしめることで改善される横目靱性を、
より確かなものとするとともに、被削性（切り屑分断性
と工具寿命）に優れる快削鋼を提供するものである。The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a so-called transverse toughness improved by incorporating Mg.
It is intended to provide a free-cutting steel which is more reliable and has excellent machinability (cutting chips and tool life).
【００１２】[0012]
【課題を解決するための手段】本発明者等は、上記の課
題を解消するため調査、研究を行った。その結果、横目
靱性を安定して得るためには、鋼材中のMgの含有量はも
とより硫化物中のMgとS の原子比が極めて肝要であるこ
とを突き止めたものである。すなわち、Mgは、鋼中の硫
化物に固溶し硫化物の硬さを増し、圧延、鍛造等の加工
の際の硫化物の展伸を抑制する結果、硫化物を球状化さ
せ横目靱性を改善し得るが、硫化物の硬さが高くなりす
ぎると被削性（切り屑分断性）が劣化する。また、硬度
の高いアルミナなどの酸化物が多く生成されても被削性
（工具寿命）が劣化する。このようなことから、本発明
に係る快削鋼（請求項１）は、質量％にて S：0.01〜0.
20％、Mg：0.0005〜0.020 ％、Al：0.001 〜0.05％、O
：0.0040％未満含有するとともに、硫化物が形成され
てなる快削鋼において、前記硫化物中のMgとS の原子比
が0.01〜0.20に制御せしめることとしたものである。な
お、硫化物とはMnS を基本とするが、(Mn,Fe)S、(Mn,M
g)S、Mn(S,O) あるいはこれらの複合などのように他の
元素が含まれてもよい。また、Mgは全ての硫化物中に含
まれる必要はないが、硫化物の特性を均一化する意味で
は多くの硫化物に均一にMgが含有される方が望ましい。
また、O は0.0020％未満及びMgとS の原子比は0.05〜0.
15とすることが好ましく、この範囲であれば、横目靱性
はもとより被削性（切り屑分断性と工具寿命）に優れる
快削鋼を安定して製造し得る。Means for Solving the Problems The present inventors have conducted research and research to solve the above-mentioned problems. As a result, it has been found that the atomic ratio of Mg to S in the sulfide is extremely important, in addition to the content of Mg in the steel material, in order to stably obtain the transverse grain toughness. In other words, Mg forms a solid solution in sulfide in steel and increases the hardness of sulfide, and suppresses the expansion of sulfide during processing such as rolling and forging. Although it can be improved, if the hardness of the sulfide is too high, the machinability (cutting ability) is deteriorated. Further, even if a large amount of oxide such as alumina having high hardness is generated, machinability (tool life) is deteriorated. Therefore, the free-cutting steel according to the present invention (Claim 1) contains S: 0.01 to 0.
20%, Mg: 0.0005-0.020%, Al: 0.001-0.05%, O
: In a free-cutting steel containing less than 0.0040% and sulfides formed, the atomic ratio of Mg to S in the sulfides is controlled to 0.01 to 0.20. The sulfide is based on MnS, but (Mn, Fe) S, (Mn, M
g) Other elements such as S, Mn (S, O) or a combination thereof may be included. Further, Mg does not need to be contained in all sulfides, but it is desirable that Mg is contained uniformly in many sulfides in order to make the properties of sulfides uniform.
Further, O is less than 0.0020% and the atomic ratio of Mg to S is 0.05 to 0.1.
It is preferably set to 15, and if it is in this range, a free-cutting steel excellent in not only the transverse grain toughness but also the machinability (the chip breaking property and the tool life) can be stably manufactured.
【００１３】そして、上記本発明の快削鋼においては、
Mgの量は、下記式又は／及び式で規定される量を含
有せしめるとよく（請求項２）、この範囲を満たすこと
で、同時に含有せしめるS やO とのバランスが取れ、よ
り効果的に横目靱性はもとより被削性（切り屑分断性と
工具寿命）に優れる快削鋼を安定して製造し得る。 (S／150)＋0.75×O ≦Mg≦(S／20) ＋0.75×O ------ Mg ≧0.05×Al---------------------------------- ただし、S, Mg, O, Alはトータルの質量％である。[0013] In the free-cutting steel according to the present invention,
It is preferable that the amount of Mg be contained in the amount specified by the following formula or / and / or the formula (claim 2). By satisfying this range, the balance with S and O to be contained at the same time can be obtained, and more effectively. A free-cutting steel excellent in machinability (cutting ability and tool life) as well as transverse grain toughness can be stably manufactured. (S / 150) + 0.75 × O ≦ Mg ≦ (S / 20) + 0.75 × O ------ Mg ≧ 0.05 × Al ---------------- ------------------ Here, S, Mg, O, and Al are the total mass%.
【００１４】また、上記本発明の快削鋼においては、質
量％にて C：0.05〜1.20％、Si：0.001 〜0.40％、Mn：
0.20〜1.70％を含有する鋼であるとよく（請求項３）、
機械構造用快削鋼として広範な用途への使用が期待でき
る。なお、前記成分の他に合金元素としてNi、Cr、Mo、
Cu、V 、Nb等、あるいは積極的な添加を期待するもので
はないが快削性向上効果を期待してPbが含有されてあっ
てもよい。In the free-cutting steel of the present invention, C: 0.05 to 1.20%, Si: 0.001 to 0.40%, Mn:
The steel preferably contains 0.20 to 1.70% (claim 3),
It can be expected to be used for a wide range of applications as free-cutting steel for machine structures. In addition, Ni, Cr, Mo,
Cu, V, Nb, or the like, or Pb may be contained, although not expected to be positively added, but expected to have an effect of improving free-cutting property.
【００１５】また、上記本発明の快削鋼においては、質
量％にてBi：0.01〜0.30％、Ti：0.01〜0.10％、Zr：0.
001 〜0.20％、REM ：0.0003〜0.050 ％、Ca：0.0003〜
0.010 ％のうちの１種、あるいは２種以上を含有せしめ
てもよく（請求項４）、これらのうちの成分を更に含有
することで、横目靱性を害することなく被削性（切り屑
分断性と工具寿命）の改善が期待される。In the free-cutting steel of the present invention, Bi: 0.01 to 0.30%, Ti: 0.01 to 0.10%, Zr: 0.
001 to 0.20%, REM: 0.0003 to 0.050%, Ca: 0.0003 to
One or more of 0.010% may be contained (Claim 4), and by further containing these components, the machinability (chip breaking property) is not impaired. And tool life) are expected to improve.
【００１６】以下、化学成分等の数値限定の理由につい
て詳述する。S は硫化物を形成し被削性を向上させる元
素ではあるが、その含有量が0.01％未満では十分な被削
性が得られず、また0.20％を超えると機械的性質、特に
横目靱性が劣化するので、 S：0.01〜0.20％とした。Hereinafter, the reasons for limiting the numerical values of chemical components and the like will be described in detail. S is an element that forms sulfides and improves machinability. However, if its content is less than 0.01%, sufficient machinability cannot be obtained, and if it exceeds 0.20%, mechanical properties, especially transverse toughness, will deteriorate. S: 0.01 to 0.20% because of deterioration.
【００１７】Mgは、硫化物中に固溶する、並びにMg含有
酸化物が硫化物形成の核となることにより、硫化物形態
を制御して横目靱性と被削性の両立を可能とする。特
に、硫化物中に固溶するMg量の制御が重要で、Mg含有量
が0.0005％未満では硫化物中の固溶Mg量が十分でなく、
十分な硫化物形態制御が得られない。またMg含有量が0.
020 ％を超えると硫化物が硬くなりすぎて被削性（切り
屑分断性）が低下する。従って、Mg：0.0005〜0.020 ％
とした。また、硫化物中への固溶に必要なMg量は硫化物
中のS 量とO 量によっても変化するので、下記式を満
たす量のMgを鋼中に含有させるとよい。 (S／150)＋0.75×O ≦Mg≦(S／20) ＋0.75×O ------ ただし、S, Mg, Oはトータルの質量％である。Mg forms a solid solution in the sulfide, and the Mg-containing oxide serves as a nucleus for the formation of the sulfide, thereby controlling the sulfide morphology and making it possible to achieve both transverse grain toughness and machinability. In particular, it is important to control the amount of Mg dissolved in the sulfide. If the Mg content is less than 0.0005%, the amount of dissolved Mg in the sulfide is not sufficient.
Sufficient sulfide morphology control cannot be obtained. The Mg content is 0.
If it exceeds 020%, the sulfide becomes too hard and the machinability (cutting ability) decreases. Therefore, Mg: 0.0005-0.020%
And Further, since the amount of Mg necessary for solid solution in sulfide varies depending on the amount of S and O in the sulfide, the amount of Mg satisfying the following equation is preferably contained in steel. (S / 150) + 0.75 × O ≦ Mg ≦ (S / 20) + 0.75 × O ------ However, S, Mg and O are the total mass%.
【００１８】O は酸化物を形成し、その酸化物が硫化物
の核となる効果を有するが、多すぎると硬質な酸化物が
増し、被削性（工具寿命）が低下するので、その鋼中の
含有量をO ：0.0040％未満とした。また、より効果を期
待するのであればO ：0.0020％未満で含有せしめること
が望ましい。O forms an oxide, which has the effect of forming nuclei of sulfides. However, if it is too much, hard oxides increase and machinability (tool life) decreases. The content of O was set to O: less than 0.0040%. If more effect is expected, it is desirable to make O: less than 0.0020%.
【００１９】Alは、脱酸元素であるが、その含有量が0.
001 ％未満であると、脱酸が不十分であり、酸素量の制
御ができない。また、Mgとの複合酸化物を形成して硫化
物の核となり、硫化物の形態制御に寄与する効果も期待
できない。一方、含有量が0.05％を超えると、硬質なア
ルミナ系酸化物が主となり被削性（工具寿命）を低下さ
せる、また硫化物中のMg量を低下させるなどの不具合を
生じる。従って、Al：0.001 〜0.05％とした。また、硫
化物中のMg量を低下させないようにするためには、下記
式を満たすようにAlを鋼中に含有させるとよい。 Mg ≧0.05×Al------ ただし、Mg, Alはトータルの質量％である。Al is a deoxidizing element, but its content is 0.1%.
If it is less than 001%, the deoxidation is insufficient and the oxygen content cannot be controlled. Further, an effect of forming a complex oxide with Mg to form a sulfide nucleus and contributing to the control of sulfide morphology cannot be expected. On the other hand, if the content exceeds 0.05%, hard alumina-based oxides are mainly used to cause problems such as a decrease in machinability (tool life) and a decrease in the amount of Mg in the sulfide. Therefore, the content of Al is set to 0.001 to 0.05%. Further, in order not to reduce the amount of Mg in the sulfide, it is preferable to include Al in steel so as to satisfy the following formula. Mg ≧ 0.05 × Al- However, Mg and Al are the total mass%.
【００２０】本発明は、特に横目靱性と被削性を改善す
ることを目的としてなしたもので、その場合に必要な鋼
中の成分を上記のように限定したものである。以下は上
記の成分を含む上で、前記横目靱性と被削性を好ましい
状態で得られる請求項３及び４に限定した鋼の成分につ
いて説明する。The object of the present invention is to improve the transverse grain toughness and the machinability, and the components in the steel required in such a case are limited as described above. In the following, a description will be given of the steel components limited to the third and fourth aspects in which the above-described components are included and the above-mentioned transverse grain toughness and machinability are obtained in a preferable state.
【００２１】C は、その含有量が鋼の機械的強度を向上
させるために最低0.05％は必要であるが、1.2 ％を超え
ると加工性が低下することから、その上限を1.2 ％とし
た。The content of C is required to be at least 0.05% in order to improve the mechanical strength of steel, but if it exceeds 1.2%, the workability is reduced. Therefore, the upper limit is set to 1.2%.
【００２２】Siは、脱酸剤として溶鋼中に添加され少な
くとも0.001 ％は必要であるが、多量に添加すると靱性
と被削性が低下することから、その上限を0.40％とし
た。Si is added to molten steel as a deoxidizing agent and at least 0.001% is required. However, if added in a large amount, toughness and machinability are reduced, so the upper limit was made 0.40%.
【００２３】Mnは、固溶硬化作用が大きく機械的性質を
向上させるため、並びにS の熱間脆性を抑制するために
最低0.20％は必要であるが、多量の添加では過度に硬化
し、圧延、鍛造などの加工性が低下するので、その上限
を1.7 ％とした。Mn is required to have a minimum content of 0.20% in order to improve the mechanical properties and to suppress the hot brittleness of S. Since the workability of forging and the like deteriorates, the upper limit is set to 1.7%.
【００２４】Biは、更なる被削性の向上効果を期待して
添加することができる。その含有量は0.01％以上を必要
とするも、多すぎると熱間脆性を起こすので、その上限
を0.30％とした。Bi can be added in expectation of a further effect of improving machinability. Although its content is required to be 0.01% or more, if it is too large, hot embrittlement occurs, so its upper limit was made 0.30%.
【００２５】Ti、Zr、Ca、REM は、更なる硫化物の形態
制御による被削性向上のために含有されてあってもよ
く、その含有量はTi：0.01〜0.10％、Zr：0.001 〜0.20
％、REM ：0.0003〜0.050 ％、Ca：0.0003〜0.010 ％と
するが、それぞれの下限値未満の含有では前記被削性向
上効果が期待できず、また上限値を超えての含有では前
記被削性向上効果が飽和してしまうので、それぞれ前記
の含有量とするものである。なお、REM とはLa、Ce、P
r、Nd等であって、それぞれ単独あるいは複合での含有
であってもよい。Ti, Zr, Ca, and REM may be contained for further improving the machinability by controlling the form of the sulfide, and the contents thereof are 0.01 to 0.10% for Ti and 0.001 to 0.001 for Zr. 0.20
%, REM: 0.0003 to 0.050%, and Ca: 0.0003 to 0.010%. However, if the content is less than the lower limit, the machinability improving effect cannot be expected. Since the effect of improving the properties is saturated, the contents are respectively set as described above. REM is La, Ce, P
r, Nd, etc., each of which may be contained alone or in combination.
【００２６】[0026]
【実施例】高周波溶解炉を用い表１に示す化学成分の鋼
材を溶製した。この溶製の際、Mgの歩留りを制御するた
めにフラックスの組成や、合金元素の添加時期、順番な
どに留意した。具体的には、溶鋼にまずカーボンを添加
し、続いてFe−Mn合金、Fe−Si合金を添加し、更にFe−
S 合金を添加した。その後、Alを添加した。更にその
後、CaO-SiO2-MgO-Al2O3系フラックスを添加すると共に
Ni−Mg合金でMg及びNiを添加した。Ni−Mg合金を添加す
る前の溶存酸素量は 3〜10ppm とし、溶鋼の温度は1550
℃〜1600℃とした。添加後少なくとも 5分以内に鋳造し
た。鋳造はφ140mm のインゴットに鋳造した。なお、Ni
−Mg合金の添加方法としては、約 1mm程度の粒状のもの
を鉄パイプにつめて溶鋼の中に押し込む方法で実施し
た。EXAMPLES Steel materials having the chemical components shown in Table 1 were melted using a high-frequency melting furnace. At the time of this smelting, attention was paid to the composition of the flux, the timing of adding the alloying elements, the order, and the like in order to control the yield of Mg. Specifically, first, carbon is added to molten steel, then an Fe-Mn alloy and an Fe-Si alloy are added, and then Fe-
S alloy was added. Thereafter, Al was added. After that, a CaO-SiO 2 -MgO-Al 2 O 3 type flux is added and
Mg and Ni were added in a Ni-Mg alloy. The dissolved oxygen content before adding the Ni-Mg alloy is 3 to 10 ppm, and the temperature of the molten steel is 1550 ppm.
C. to 1600C. Cast at least within 5 minutes after addition. Casting was carried out into a φ140 mm ingot. Note that Ni
The method of adding the Mg alloy was a method in which a granular material of about 1 mm was packed in an iron pipe and pressed into molten steel.
【００２７】[0027]
【表１】 [Table 1]
【００２８】上記で鋳造された各成分値のφ140mm イン
ゴットをφ80mmの鋼材に熱間鍛造した。この時の鍛造開
始温度は約1190℃、鍛造終了温度は約1140℃で行った。
そして、この鍛造後の鋼材について、それぞれをφ80mm
×30mmに切断・旋削加工した後に焼き入れ焼き戻しを施
して、ヴィッカース硬さ 270±10にそろえて試験材を得
た。この試験材をもとに、以下の要領で硫化物中のMgと
S の原子比（Mg／S 比）を測定調査、被削性の評価、及
び横方向衝撃値の試験を行った。The 140 mm ingot of each component value cast as described above was hot forged into a 80 mm steel material. The forging start temperature at this time was about 1190 ° C, and the forging end temperature was about 1140 ° C.
And about this forged steel material, each φ80mm
After cutting and turning to a size of × 30 mm, quenching and tempering were performed to obtain a test material having a Vickers hardness of 270 ± 10. Based on this test material,
The atomic ratio of S (Mg / S ratio) was measured and investigated, the machinability was evaluated, and the lateral impact value was tested.
【００２９】硫化物中のMg／S 比は、硫化物をランダム
に50個以上選択し、ＥＰＭＡで測定して平均値を求め
た。幅 1μm 以上の硫化物だけを測定の対象とした。Mg
／S 比を求めているのは、MnS 中のMg濃度の測定は、Mn
S のサイズの影響を受け、正確な値が得られないケース
が多いためである。また、アスペクト比は、光学顕微鏡
を用いて倍率100 倍で１視野当たり 0.5mm× 0.5mmの面
積を100 視野ずつ画像解析装置で測定し、幅 1μm 以上
の硫化物だけに限定して平均値を求めた。As for the Mg / S ratio in the sulfide, 50 or more sulfides were selected at random and measured by EPMA to obtain an average value. Only sulfides with a width of 1 μm or more were measured. Mg
/ S ratio is determined by measuring the Mg concentration in MnS
This is because in many cases, an accurate value cannot be obtained due to the influence of the size of S. The aspect ratio was measured using an optical microscope at a magnification of × 100 and an area of 0.5 mm × 0.5 mm per visual field in 100 visual fields at a time, and the average value was limited to sulfides with a width of 1 μm or more. I asked.
【００３０】被削性評価は、ハイス製φ10mmのストレー
トドリルを用いて穴あけ試験を行い、切り屑の単位ｇ当
たりの個数をカウントして切り屑性指数を評価した。切
削条件は、速度Ｖ＝20m ／min 、送りｆ＝0.2mm ／rev
、穴深さ10mm、乾式の条件で行った。工具寿命は、速
度Ｖ＝50m ／min に変化した以外の条件は前記と同じ条
件で切削不能になるまでのトータルの穴深さを求めて評
価した。For the evaluation of the machinability, a drilling test was carried out using a straight drill of φ10 mm made of HSS, and the number of chips per unit g was counted to evaluate the chipability index. The cutting conditions are as follows: speed V = 20 m / min, feed f = 0.2 mm / rev
The test was performed under dry conditions with a hole depth of 10 mm. The tool life was evaluated by obtaining the total hole depth until cutting became impossible under the same conditions as described above except that the speed V was changed to 50 m / min.
【００３１】衝撃試験は、衝撃試験片を鍛造で展伸させ
た方向と直角に切り出してシャルピー衝撃試験を実施し
た。In the impact test, a Charpy impact test was performed by cutting out the impact test piece at right angles to the direction in which it was extended by forging.
【００３２】それぞれの調査、試験結果を表２及び図１
に示す。なお、図１において数字は試験No. を示し、○
数字と△数字は本発明例、枠のない数字は比較例を示
す。Table 2 and FIG.
Shown in In FIG. 1, the numbers indicate the test No.
Numerals and Δ numerals indicate examples of the present invention, and numerals without frames indicate comparative examples.
【表２】 [Table 2]
【００３３】上記表２及び図１から、本発明例（試験N
o.1, 2, 4, 6 〜8, 12, 14, 22 〜27）は比較例（試験N
o.3, 5, 9〜11, 13, 15〜21）に比べて、横目靱性と切
り屑個数のバランスが向上していることがわかる。な
お、試験No.26 と27の本発明例は請求項１の要件を満た
すものの、請求項２の要件を満たさない例である。ま
た、比較例である試験No.20 は、O 量が本発明で限定す
る0.0040％未満を超えて含有したものであり、工具寿命
が低下している。From the above Table 2 and FIG. 1, the example of the present invention (test N
o.1, 2, 4, 6 to 8, 12, 14, 22 to 27) are comparative examples (test N
o.3, 5, 9-11, 13, 15-21), it can be seen that the balance between the transverse grain toughness and the number of chips is improved. The test examples Nos. 26 and 27 of the present invention satisfy the requirements of claim 1 but do not satisfy the requirements of claim 2. In Test No. 20, which is a comparative example, the O 2 content was more than 0.0040%, which is limited in the present invention, and the tool life was shortened.
【００３４】[0034]
【発明の効果】以上説明したように、本発明に係る快削
鋼であれば、被削性（切り屑分断性、工具寿命）はもと
より機械的性質のうち特に横目靱性に優れており、この
ように横目靱性と被削性が大きく改善されたことで、こ
の快削鋼を用いることにより機械構造部品の靱性の安全
係数を小さくとることができ、引いては加工歩留りの向
上が期待される。As described above, the free-cutting steel according to the present invention is excellent not only in machinability (cutting chip breaking property, tool life) but also in mechanical properties, in particular, in side grain toughness. As described above, the transverse grain toughness and machinability have been greatly improved, and by using this free-cutting steel, the safety factor of the toughness of machine structural parts can be reduced, which is expected to improve the machining yield. .
【図１】快削鋼の横目靱性と切り屑個数の関係を示す説
明図である。FIG. 1 is an explanatory diagram showing the relationship between the lateral grain toughness of free-cutting steel and the number of chips.
フロントページの続き (72)発明者 金丸 守賀 兵庫県神戸市西区高塚台１丁目５番５号 株式会社神戸製鋼所神戸総合技術研究所内 (72)発明者 工藤 高裕 兵庫県神戸市西区高塚台１丁目５番５号 株式会社神戸製鋼所神戸総合技術研究所内 (72)発明者 染川 雅実 兵庫県神戸市灘区灘浜東町２番地 株式会 社神戸製鋼所神戸製鉄所内 (72)発明者 安部 聡 兵庫県神戸市灘区灘浜東町２番地 株式会 社神戸製鋼所神戸製鉄所内Continued on the front page (72) Inventor Moriga Kanamaru 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Inside Kobe Steel Research Institute Kobe Research Institute (72) Inventor Takahiro Kudo 1-chome Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture No. 5-5 Kobe Steel, Ltd.Kobe Research Institute (72) Inventor Masami Somegawa 2 Nadahama-Higashi-cho, Nada-ku, Kobe City, Hyogo Prefecture Inside Kobe Steel Co., Ltd.Kobe Works (72) Inventor Satoshi Abe Kobe, Hyogo Prefecture 2 Nadahama-Higashicho, Nadahama-ku, Kobe Steel Corporation Kobe Steel Works Kobe Steel Works
Claims (4)
05〜0.020 ％、Al：0.001 〜0.05％、O ：0.0040％未満
含有するとともに、硫化物が形成されてなる快削鋼にお
いて、前記硫化物中のMgとS の原子比が0.01〜0.20に制
御されてなることを特徴とする快削鋼。1. In mass%, S: 0.01 to 0.20%, Mg: 0.00
In a free-cutting steel containing 0.05 to 0.020%, Al: 0.001 to 0.05%, O: less than 0.0040%, and a sulfide formed, the atomic ratio of Mg to S in the sulfide is controlled to 0.01 to 0.20. Free-cutting steel characterized by being made.
される量を含有してなる請求項１に記載の快削鋼。 (S／150)＋0.75×O ≦Mg≦(S／20) ＋0.75×O ------ Mg ≧0.05×Al---------------------------------- ただし、S, Mg, O, Alはトータルの質量％である。2. The free-cutting steel according to claim 1, wherein the amount of Mg includes an amount defined by the following formula and / or: (S / 150) + 0.75 × O ≦ Mg ≦ (S / 20) + 0.75 × O ------ Mg ≧ 0.05 × Al ---------------- ------------------ Here, S, Mg, O, and Al are the total mass%.
i：0.001 〜0.40％、Mn：0.20〜1.70％を含有する請求
項１又は２に記載の快削鋼。3. In addition, in mass%, C: 0.05 to 1.20%, S
3. The free-cutting steel according to claim 1, wherein i: 0.001 to 0.40% and Mn: 0.20 to 1.70%.
i：0.01〜0.10％、Zr：0.001 〜0.20％、REM ：0.0003
〜0.050 ％、Ca：0.0003〜0.010 ％のうちの１種、ある
いは２種以上を含有する請求項１乃至３の何れかに記載
の快削鋼。4. Further, Bi: 0.01 to 0.30% by mass%, T
i: 0.01 to 0.10%, Zr: 0.001 to 0.20%, REM: 0.0003
The free-cutting steel according to any one of claims 1 to 3, which contains one or more of 0.050% to 0.050% and Ca: 0.0003% to 0.010%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33557399A JP3442706B2 (en) | 1999-11-26 | 1999-11-26 | Free-cutting steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33557399A JP3442706B2 (en) | 1999-11-26 | 1999-11-26 | Free-cutting steel |
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| Publication Number | Publication Date |
|---|---|
| JP2001152280A true JP2001152280A (en) | 2001-06-05 |
| JP3442706B2 JP3442706B2 (en) | 2003-09-02 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP33557399A Expired - Lifetime JP3442706B2 (en) | 1999-11-26 | 1999-11-26 | Free-cutting steel |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004052099A (en) * | 2002-05-31 | 2004-02-19 | Jfe Steel Kk | Steel member for machine structural |
| US7195736B1 (en) | 2000-02-10 | 2007-03-27 | Sanyo Special Steel Co., Ltd. | Lead-free steel for machine structural use with excellent machinability and low strength anisotropy |
| US8980022B2 (en) | 2009-01-16 | 2015-03-17 | Nippon Steel & Sumitomo Metal Corporation | Case hardening steel, carburized component, and manufacturing method of case hardening steel |
| CN112063916A (en) * | 2020-05-12 | 2020-12-11 | 上海大学 | Preparation method of magnesium-based high-sulfur free-cutting steel |
| CN114107820A (en) * | 2021-11-26 | 2022-03-01 | 宝武集团鄂城钢铁有限公司 | Steel plate with elongation rate more than 30% and good cutting performance and production method thereof |
-
1999
- 1999-11-26 JP JP33557399A patent/JP3442706B2/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7195736B1 (en) | 2000-02-10 | 2007-03-27 | Sanyo Special Steel Co., Ltd. | Lead-free steel for machine structural use with excellent machinability and low strength anisotropy |
| US7445680B2 (en) | 2000-02-10 | 2008-11-04 | Sanyo Special Steel Co., Ltd. | Lead-free steel for machine structural use with excellent machinability and low strength anisotropy |
| JP2004052099A (en) * | 2002-05-31 | 2004-02-19 | Jfe Steel Kk | Steel member for machine structural |
| US8980022B2 (en) | 2009-01-16 | 2015-03-17 | Nippon Steel & Sumitomo Metal Corporation | Case hardening steel, carburized component, and manufacturing method of case hardening steel |
| CN112063916A (en) * | 2020-05-12 | 2020-12-11 | 上海大学 | Preparation method of magnesium-based high-sulfur free-cutting steel |
| CN114107820A (en) * | 2021-11-26 | 2022-03-01 | 宝武集团鄂城钢铁有限公司 | Steel plate with elongation rate more than 30% and good cutting performance and production method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3442706B2 (en) | 2003-09-02 |
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