JP4350323B2 - Ferritic stainless steel with excellent machinability - Google Patents
Ferritic stainless steel with excellent machinability Download PDFInfo
- Publication number
- JP4350323B2 JP4350323B2 JP2001145205A JP2001145205A JP4350323B2 JP 4350323 B2 JP4350323 B2 JP 4350323B2 JP 2001145205 A JP2001145205 A JP 2001145205A JP 2001145205 A JP2001145205 A JP 2001145205A JP 4350323 B2 JP4350323 B2 JP 4350323B2
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- machinability
- cao
- inclusions
- tio
- 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.)
- Expired - Lifetime
Links
Landscapes
- Treatment Of Steel In Its Molten State (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、フェライト系ステンレス鋼において、ＰｂやＳを不純物レベルとしても、被削性に優れたステンレス鋼を提供するものである。
【０００２】
【従来の技術】
ステンレス鋼は、▲１▼Ｃｒを含有する結果、熱伝導率が小さい、▲２▼特に、マルテンサイト系では強度が高い、という理由から、炭素鋼と比較して一般に切削しにくいと言われている。
ステンレス鋼の被削性は、ＰｂやＳの添加で改善されることが知られている。しかし、Ｐｂのような環境負荷物質の添加は好ましいとは言えない。
またＳの添加は、鋼中に多量のＭｎＳやＣａＳを形成するが、これらの硫化物は水溶性であるため、ステンレス鋼の孔食の起点となり、耐食性の低下が避けられない。
【０００３】
ＰｂやＳを含有せず被削性を確保する手段としては、特開平６−１４５９０８号公報に、酸化物系介在物にＣａＯを含有させる、いわゆるＣａ快削鋼が開示されている。このＣａ快削鋼の考えをステンレス鋼に適用したものとして、例えばカルシウム快削ステンレス鋼が挙げられる。本先行例では、酸化物系介在物の少なくとも２０％をゲーレナイト（２ＣａＯ・Ａｌ2 Ｏ3 ・ＳｉＯ2 ）が占めるようにすることで、ステンレス鋼の被削性が改善することが開示されている。酸化物系介在物を硬質のＡｌ2 Ｏ3 ・ＭｇＯ系から本先行例のように２ＣａＯ・Ａｌ2 Ｏ3 ・ＳｉＯ2 系に変えることで、特にオーステナイト系ステンレス鋼で被削性改善効果が得られる。
【０００４】
しかしながら、フェライト系ステンレス鋼では、工具寿命に改善の余地が大きく、現実にはＣａ快削性とＳを併用するような手段が取られている。よって、フェライト系ステンレス鋼において、ＰｂやＳを用いず、酸化物系介在物を十分に活用した被削性の改善が望まれていた。
【０００５】
【発明が解決しようとする課題】
本発明は、従来の快削ステンレス鋼が抱える問題を克服して、既存のＣａ快削ステンレス鋼を発展させ、さらに酸化物系の介在物を有効に活用することで、ＰｂやＳを用いず被削性に優れたフェライト系ステンレス鋼を提供することを課題とする。
【０００６】
【課題を解決するための手段】
本発明は、上記課題を有利に解決するものであり、その要旨とするところは、「質量％で、Ｃｒ：１０〜２０％を含有するフェライト系ステンレス鋼において、円相当径が１μｍ以上であり、質量％でＴｉＯ２ ：５〜３０％、ＣａＯ：５〜３０％、Ａｌ ２ Ｏ ３ ：２４．１〜４９．７％、ＳｉＯ ２ ：６．２〜２６．８％を含む、Ａｌ２ Ｏ３ −ＳｉＯ２ −ＣａＯ−ＴｉＯ２ 系の酸化物系介在物を任意の断面１ｍｍ×１ｍｍあたり３０個以上含有することを特徴とする被削性に優れたフェライト系ステンレス鋼」である。
【０００７】
本発明者らは、フェライト系ステンレス鋼を前提として、被削性の改善に最適な酸化物系介在物組成と存在状態を種々検討し本発明を完成するに至った。
【０００８】
【発明の実施の形態】
本発明の内容を以下に詳細に説明する。
本発明においてＣｒは、フェライト系ステンレス鋼として期待される耐食性、耐熱性、強度、加工性などの特性に応じて、１０〜２０％の範囲において任意に添加すればよい。
【０００９】
このような１０〜２０％のＣｒを含有するフェライト系ステンレス鋼において、被削性を改善するにあたって、酸化物系介在物をその組成の制御と一定量以上の数の確保が重要となる。
酸化物の組成としては、Ａｌ２ Ｏ３ −ＭｇＯ系やＡｌ２ Ｏ３−ＳｉＯ２ −ＣａＯ系から、Ａｌ２ Ｏ３ −ＳｉＯ２ −ＣａＯ−ＴｉＯ２ 系に改善することにより、被削性が著しく改善される。この理由は、ひとつには介在物の融点が切削に好ましい低融点組成を実現できるためと考えられる。
【００１０】
しかし、これだけではＡｌ2 Ｏ3 −ＳｉＯ2 −ＣａＯ系介在物との差が説明できない。Ａｌ2 Ｏ3 −ＳｉＯ2 −ＣａＯ−ＴｉＯ2 系介在物による被削性の改善は、切削工具に超硬材料を採用したときに顕著に確認されることから、酸化物をＡｌ2 Ｏ3 −ＳｉＯ2 −ＣａＯ−ＴｉＯ2 系にすることにより、すなわちＣａＯに加えてＴｉＯ2 を含有することで、介在物が切削時に軟化・溶融して形成される工具上の一種の保護皮膜がより安定した、密着性の良好なものになるためと解釈している。
【００１１】
このようなＡｌ２ Ｏ３ −ＳｉＯ２ −ＣａＯ−ＴｉＯ２ 系介在物の中に、ＴｉＯ２ とＣａＯを質量％で、ＴｉＯ２：５〜３０％、ＣａＯ：５〜３０％の範囲で含有することが被削性の改善に有効である。ＴｉＯ２ が５％未満では、工具上の保護性の良い皮膜が形成されにくい。一方、ＴｉＯ２ が３０％を超えると介在物の融点が上昇して硬質化するので、被削性が低下する。ＣａＯについては、ＴｉＯ２ を５〜３０％の範囲で含有するＡｌ２ Ｏ３ −ＳｉＯ２ −ＣａＯ−ＴｉＯ２ 系介在物において、切削に好ましい軟質・低融点介在物を得るために、その質量％は５〜３０％であることが必要である。
その際のＡｌ ２ Ｏ ３ 及びＳｉＯ ２ の含有量は、実施例に示すようにＡｌ ２ Ｏ ３ が２４．１〜４９．７％、ＳｉＯ ２ が６．２〜２６．８％であり、この酸化物の範囲でＣａＯ及びＴｉＯ ２ との組合わせで好ましい切削性が付与される。
【００１２】
以上述べたＡｌ2 Ｏ3 −ＳｉＯ2 −ＣａＯ−ＴｉＯ2 系介在物の存在により被削性の改善効果が現れるには、一定量以上の介在物の存在が必要であり、円相当径で１μｍ以上の介在物を任意の断面１ｍｍ×１ｍｍあたり３０個以上含有する必要がある。
ここで存在個数は、鏡面研磨した試験片をＥＰＭＡで分析し、数百倍程度の組成像で認識できる程度の分解能で求められる。測定方法の精密化により分解能を上げれば、より多くの介在物を検出することができるであろうが、本発明では、少なくとも１ｍｍ×１ｍｍあたり３０個以上の介在物が存在すればよく、分析精度の向上により数えられる介在物個数が増大することは問題とはならない。
介在物の円相当径を１μｍ以上としたのは、工具表面に保護的な皮膜を形成し得るだけの介在物の体積を必要とするためで、サブミクロンの微細な介在物は、軟化・溶融しても、保護皮膜の形成には十分に寄与しない。
【００１３】
【実施例】
表１に成分を示す鋼組成を溶製した後、脱酸条件を変化させて、含有する介在物を変化させた。得られた鋳片を熱間加工した後焼鈍・酸洗して鋼板を得た（板厚５ｍｍ）。鋼板の圧延方向に垂直な断面を鏡面研磨した後、ＥＰＭＡの分析に供した。ＥＰＭＡサンプルの採取箇所は各鋼板について、５箇所とした。
ＥＰＭＡの各サンプルから、任意に選択した３視野について、５００倍の組成像で確認できる円相当径１μｍ以上の酸化物系介在物を計数すると共に、各介在物を５０００倍に拡大した視野で定量分析した。以上の介在物調査に基づき、表２の結果を得た。
【００１４】
被削性試験は、１０枚の超硬切削刃からなる工具を用いて回転旋削を連続して行った。被削材１個あたりの切削長さは約３００ｍｍで、切削深さは１ｍｍである。無潤滑のドライ切削と油潤滑の両方について、焼き付きで工具寿命に到達するまでの工具１個あたりの連続旋削可能数を比較した。なお、被削材の平均硬さはいずれの介在物条件でも等しく、８４ＨＲＢである。
表３に示すように、本発明に属する酸化物系介在物を有する場合は、比較例と比較して優れた被削性を有することが分かる。
【００１５】
【表１】
【表２】
【表３】
【発明の効果】
本発明によって、ＰｂやＳを用いず、被削性に優れたフェライト系ステンレス鋼を提供することができるので、その工業価値は大きい。[0001]
BACKGROUND OF THE INVENTION
The present invention provides a ferritic stainless steel having excellent machinability even when Pb and S are impurity levels.
[0002]
[Prior art]
Stainless steel is said to be generally harder to cut than carbon steel because of its low thermal conductivity as a result of containing (1) Cr, and (2) high strength especially in martensite systems. Yes.
It is known that the machinability of stainless steel is improved by the addition of Pb and S. However, it cannot be said that addition of an environmentally hazardous substance such as Pb is preferable.
Addition of S forms a large amount of MnS and CaS in the steel, but since these sulfides are water-soluble, they become the starting point of stainless steel pitting corrosion, and a reduction in corrosion resistance is inevitable.
[0003]
As a means for ensuring machinability without containing Pb and S, Japanese Patent Application Laid-Open No. 6-145908 discloses so-called Ca free cutting steel in which CaO is contained in oxide inclusions. As an example of applying the idea of this Ca free-cutting steel to stainless steel, for example, calcium free-cutting stainless steel can be cited. In this prior example, it is disclosed that the machinability of stainless steel is improved by making gehlenite (2CaO · Al 2 O 3 · SiO 2 ) occupy at least 20% of oxide inclusions. . By changing the oxide inclusions from hard Al 2 O 3 · MgO type to 2CaO · Al 2 O 3 · SiO 2 type as in the previous example, machinability improvement effect is obtained especially in austenitic stainless steel It is done.
[0004]
However , in ferritic stainless steel, there is a lot of room for improvement in tool life, and in reality, measures are taken to use both Ca free-cutting properties and S. Therefore , in ferritic stainless steel, it has been desired to improve machinability by fully utilizing oxide inclusions without using Pb or S.
[0005]
[Problems to be solved by the invention]
The present invention overcomes the problems of conventional free-cutting stainless steel, develops existing Ca-free-cutting stainless steel, and effectively uses oxide inclusions, so that Pb and S are not used. providing a ferritic stainless steel excellent the machinability to an object.
[0006]
[Means for Solving the Problems]
The present invention advantageously solves the above-described problems, and the gist of the present invention is that “ in ferritic stainless steel containing 10% to 20% by mass, the equivalent circle diameter is 1 μm or more. , TiO 2 in weight%: 5~30%, CaO: 5~30 %, Al 2 O 3: 24.1~49.7%, SiO 2: containing 6.2~26.8%, Al 2 O 3 Is -SiO 2 -CaO-TiO 2 based oxide inclusions and any cross-section 1mm × ferritic was excellent in machinability, characterized in that it contains 30 or more per 1mm stainless steel ".
[0007]
Based on the premise of ferritic stainless steel, the present inventors have studied various oxide inclusion compositions and existing conditions optimal for improving machinability and have completed the present invention.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The contents of the present invention will be described in detail below.
In the present invention, Cr may be arbitrarily added in a range of 10 to 20% depending on properties such as corrosion resistance, heat resistance, strength, and workability expected as a ferritic stainless steel.
[0009]
In such a ferritic stainless steel containing 10 to 20% Cr, in order to improve machinability, it is important to control the composition of oxide inclusions and to secure a certain amount or more.
As the composition of the oxide, Al 2 O 3 From —MgO system and Al 2 O 3 —SiO 2 —CaO system, Al 2 O 3 By improving the -SiO 2 -CaO-TiO 2 system, machinability is remarkably improved. One reason for this is considered to be that the melting point of the inclusion can realize a low melting point composition preferable for cutting.
[0010]
However, this alone cannot explain the difference from Al 2 O 3 —SiO 2 —CaO inclusions. Al 2 O 3 -SiO 2 improved machinability by -CaO-TiO 2 based inclusions, the remarkably be verified when employing the superhard material to the cutting tool, an oxide Al 2 O 3 - By using SiO 2 —CaO—TiO 2 system, that is, containing TiO 2 in addition to CaO, a kind of protective film on the tool formed by inclusions being softened and melted during cutting is more stable. It is interpreted that it will have good adhesion.
[0011]
Such Al 2 O 3 -SiO 2 It is effective for improving machinability to contain TiO 2 and CaO in the mass percentage of TiO 2 and CaO in the range of TiO 2 : 5 to 30% and CaO: 5 to 30% in the -CaO-TiO 2 inclusions. is there. When TiO 2 is less than 5%, it is difficult to form a protective film on the tool. On the other hand, if TiO 2 exceeds 30%, the melting point of the inclusions increases and becomes hard, so that the machinability decreases. For CaO, Al 2 O 3 containing TiO 2 in a range of 5 to 30%. In the —SiO 2 —CaO—TiO 2 -based inclusion, in order to obtain a soft and low-melting-point inclusion preferable for cutting, the mass% needs to be 5 to 30%.
Al 2 O 3 at that time And SiO 2 content is Al 2 O 3 as shown in the examples. Is 24.1 to 49.7% and SiO 2 is 6.2 to 26.8%, and a preferable machinability is imparted in combination with CaO and TiO 2 within the range of this oxide .
[0012]
In order for the machinability improving effect to appear due to the presence of the Al 2 O 3 —SiO 2 —CaO—TiO 2 inclusions described above, the presence of a certain amount or more of inclusions is necessary, and the equivalent circle diameter is 1 μm. It is necessary to contain 30 or more inclusions per 1 mm × 1 mm in cross section.
Here, the existing number is determined with a resolution that can be recognized by a composition image several hundred times larger by analyzing the mirror-polished test piece with EPMA. If the resolution is increased by refinement of the measurement method, more inclusions can be detected. However, in the present invention, at least 30 inclusions per 1 mm × 1 mm may be present, and the analysis accuracy is improved. It is not a problem that the number of inclusions to be counted increases due to the improvement.
The reason why the equivalent circle diameter of inclusions is set to 1 μm or more is because the volume of inclusions that can form a protective film on the tool surface is required, and submicron inclusions are softened and melted. However, it does not contribute sufficiently to the formation of the protective film.
[0013]
【Example】
After melting the steel composition which shows a component in Table 1, the deoxidation conditions were changed and the inclusion to contain was changed. The obtained slab was hot worked and then annealed and pickled to obtain a steel plate (plate thickness 5 mm). The cross section perpendicular to the rolling direction of the steel plate was mirror-polished and then subjected to EPMA analysis. EPMA samples were collected at five locations for each steel plate.
Counting oxide inclusions with an equivalent circle diameter of 1 μm or more, which can be confirmed with a 500-fold composition image, from three samples of EPMA, and quantifying each inclusion in a field of view magnified 5000 times analyzed. Based on the above inclusion investigation, the results in Table 2 were obtained.
[0014]
In the machinability test, rotary turning was continuously performed using a tool composed of ten cemented carbide cutting blades. The cutting length per work material is about 300 mm, and the cutting depth is 1 mm. For both dry lubrication and oil lubrication, the number of continuous turnings per tool until the tool life was reached due to seizure was compared. Note that the average hardness of the work material is the same for all inclusion conditions, and is 84 HRB.
As shown in Table 3, it can be seen that the oxide inclusions belonging to the present invention have excellent machinability as compared with the comparative example.
[0015]
[Table 1]
[Table 2]
[Table 3]
【The invention's effect】
The present invention, without using Pb and S, it is possible to provide a superior ferritic stainless steels machinability, the greater its industrial value.
Claims (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001145205A JP4350323B2 (en) | 2001-05-15 | 2001-05-15 | Ferritic stainless steel with excellent machinability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001145205A JP4350323B2 (en) | 2001-05-15 | 2001-05-15 | Ferritic stainless steel with excellent machinability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2002339045A JP2002339045A (en) | 2002-11-27 |
| JP4350323B2 true JP4350323B2 (en) | 2009-10-21 |
Family
ID=18991055
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2001145205A Expired - Lifetime JP4350323B2 (en) | 2001-05-15 | 2001-05-15 | Ferritic stainless steel with excellent machinability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4350323B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4822248B2 (en) * | 2005-04-25 | 2011-11-24 | 新日鐵住金ステンレス株式会社 | Martensitic stainless steel sheet for automobile structure |
-
2001
- 2001-05-15 JP JP2001145205A patent/JP4350323B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JP2002339045A (en) | 2002-11-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP2779164B2 (en) | Tool steel | |
| CN1989263A (en) | Steel for steel pipes | |
| JP5461929B2 (en) | BN free-cutting steel with excellent chip disposal | |
| JP6828557B2 (en) | Seamless steel pipe for low alloy wells | |
| TWI310054B (en) | ||
| JP2001131684A (en) | Steel for machine structure excellent in treatment of chip | |
| EP1431412B1 (en) | Free cutting alloy | |
| EP2679698B1 (en) | Cold-work tool steel exhibiting superior machinability | |
| JP4350323B2 (en) | Ferritic stainless steel with excellent machinability | |
| JP2005256135A (en) | High strength steel for welding having excellent corrosion resistance and machinability and method for producing high strength steel sheet for welding | |
| JP2008231517A (en) | Stainless steel material for cutting tool and its manufacturing method | |
| JP4655437B2 (en) | Martensitic stainless steel with excellent workability | |
| JP2631262B2 (en) | Manufacturing method of cold die steel | |
| JP2991923B2 (en) | Austenitic stainless steel with excellent machinability | |
| JP3703008B2 (en) | Free-cutting stainless steel | |
| JP6814655B2 (en) | Ferritic free-cutting stainless steel wire | |
| EP1520912A3 (en) | Steel excellent in toughness of weld heat-affected zone | |
| JP2000144339A (en) | High corrosion resistance free cutting stainless steel | |
| JP7469612B2 (en) | Steel bar for machine structure and cutting method thereof | |
| JP3270035B2 (en) | Lead-free mechanical structural steel with excellent machinability and low strength anisotropy | |
| JP3791664B2 (en) | Austenitic Ca-added free-cutting stainless steel | |
| JP4108493B2 (en) | Austenitic S free-cutting stainless steel | |
| JP2000045042A (en) | H SHAPE STEEL FOR TUNNEL SUPPORT, HAVING TENSILE STRENGTH OF 490 N/mm2 AND ABOVE AND EXCELLENT IN BENDABILITY, AND ITS MANUFACTURE | |
| JP3448541B2 (en) | Ferritic stainless steel sheet with excellent ductility | |
| JP2003221654A (en) | Free-cutting stainless steel |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A711 | Notification of change in applicant |
Free format text: JAPANESE INTERMEDIATE CODE: A712 Effective date: 20050216 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A821 Effective date: 20050225 |
|
| RD02 | Notification of acceptance of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7422 Effective date: 20050225 |
|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20051020 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20071011 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20080205 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20080328 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20090721 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20090722 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120731 Year of fee payment: 3 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 4350323 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120731 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130731 Year of fee payment: 4 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| R371 | Transfer withdrawn |
Free format text: JAPANESE INTERMEDIATE CODE: R371 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| EXPY | Cancellation because of completion of term |