JP2700790B2

JP2700790B2 - Soft magnetic stainless steel for cold forging

Info

Publication number: JP2700790B2
Application number: JP61123990A
Authority: JP
Inventors: 義信本蔵; 幸二村田; 孝横山
Original assignee: Aichi Steel Corp
Current assignee: Aichi Steel Corp
Priority date: 1986-05-29
Filing date: 1986-05-29
Publication date: 1998-01-21
Anticipated expiration: 2013-01-21
Also published as: JPS62280349A

Description

【発明の詳細な説明】（産業上の利用分野）本発明は電磁バルブ、電磁クラッチおよび内燃機関の
電子燃料噴射装置等に用いられる冷間鍛造性、電磁気特
性、耐食性に優れた冷間鍛造用軟磁性ステンレス鋼に関
する。（従来技術）従来、軟磁性ステンレス鋼に要求される特性として、
磁束密度および保磁力などの電気特性と、電気抵抗、耐
食性等があり、特に優れた磁気特性を得るため2Si-13Cr
鋼、1Si-0.20Al-13Cr鋼等が開発され一部、実用に供せ
られている。近年、軟磁性ステンレス鋼の用途開発が進み、電子燃
料噴射装置のボディやコアーなどの複雑な形状を有する
部品に適用されるようになり、前記特性に加えてさらに
冷間鍛造性の優れた鋼の開発が要求されていた。上記要求に対して、たとえば、1Si-13Cr-0.2Al鋼等の
Ｃ量を0.01％程度まで低減させた鋼が開発され、一部で
使用されている。（解決しようとする問題点）しかし、これらの鋼についても引張り強さが、44.5kg
f/mm²、絞りが74％、限界加工率が47％と十分な冷間鍛
造性を得るものでなく、前記の電子燃料噴射装置のボデ
ィやコアーなどの複雑な形状を有する部品を冷間鍛造す
ることは困難であり、より優れた冷間鍛造性と電磁気特
性を有する軟磁性ステンレス鋼の開発が望まれていた。（問題点を解決するための手段）本発明はかかる従来鋼の欠点に鑑みてなしたものであ
り、本発明者等は、13Cr鋼の電磁気特性と冷間鍛造性に
及ぼす各種合金元素の影響について調査した結果、磁気
特性は、Al、Ti添加と低Ｃ＋Ｎ化によって改善され、ま
た、電気特性は、Alの添加により大幅に向上し、一方冷
間鍛造性は、Ti添加と低Ｃ＋Ｎ化および低Ｓ化によって
改善されることを見い出した。特に、TiはＣ＋Ｎ量が0.06％程度と通常の値の場合に
は冷間鍛造性は殆ど改善されず、しかも磁気特性の改善
もわずかである。ところが、Ｃ＋Ｎ量が0.025％以下と
極低減においては0.05％程度のTiの添加によって、磁気
特性、冷間鍛造性ともに大幅に向上する。 Tiのこの作用は、相当量のＣ＋Ｎ量を含む場合、すべ
てのＣ＋ＮをTiで固定すると大きなTiC、TiNの析出物が
形成されてしまい、これによって冷間鍛造性が低下して
しまうが、Ｃ＋Ｎ量が0.025％以下と非常に少ない場合
にはすべてのＣ＋ＮをTiで固定化すると無害で小さなTi
C、TiN析出物のみが形成され、もっぱらＣ＋Ｎの侵入型
の固溶強化作用のみが消滅して、冷間鍛造性、磁気特性
が大幅に向上すると考えられる。本発明はこれらの知見をもとに13Cr鋼においてＣ＋Ｎ
量を0.025％以下とするとともに0.30〜0.80％のAlと0.0
3〜0.20％のTiを含有させ、電磁気特性を大幅に改善し
たものであり、かつ、0.30〜0.80％のAlを含有させ電気
特性を改善し、さらに0.03〜0.20％のTiと、Ｃ＋Ｎ量を
0.025％以下、Ｓ量を0.002％以下とすることにより冷間
鍛造性を大幅に改善したものである。よって、本発明鋼は13000G以上の磁束密度（Ｂ₂₀）
と、1.00e以下の保磁力と優れた磁気特性を有し、か
つ、電気抵抗が65μΩ−cm以上と優れた電気特性を有
し、冷間加工性についても引張り強さが40kgf/mm²以
下、限界加工率が60％以上と、優れた冷間鍛造性を有す
る冷間鍛造用軟磁性ステンレス鋼であり、電磁バルブ、
電磁クラッチ、内燃機関の電子燃料噴射装置などに適し
た鋼である。すなわち、本発明鋼は重量比にして、C0.015％以下、
Si0.10〜0.40％未満、Mn0.40％以下、S0.002％以下、Cr
11〜13％、Ti0.03〜0.20％、N0.015％以下、Ｃ＋N0.025
％以下、Al0.30〜0.80％を含有し、残部Feならびに不純
物元素からなるもので、第２発明は第１発明にさらにBi
0.30％以下、Pb0.30％以下、S0.040％以下、Se0.040％
以下のうちの１種ないし２種以上を含有し、かつ、Ｓ、
Seを含有させる場合にはTe0.002〜0.040％、Zr0.02〜0.
15％のうちの１種を含有し、さらにＳ＋Se＋Te0.050％
以下となし第１発明の被削性を冷間鍛造性が低下しない
よう考慮しつつ改善したもので、第３発明は第２発明に
さらにMo2.5％以下、Cu0.5％以下、Ni0.5％以下Nb0.20
％以下、V0.20％以下のうち１種ないし２種以上を含有
し、第２発明の耐食性をさらに改善したものである。以下に本発明鋼の成分限定理由について説明する。Ｃは、固溶強化作用によって冷間鍛造性を害するとと
もに磁気特性にも悪影響を与える元素であり、本発明に
おいてはできるだけ低下させることが望ましくその上限
を0.015％とした。なお、冷間鍛造性、磁気特性をさら
に向上させるためには好ましくは0.010％以下にするこ
とが望ましい。 Siは磁束密度、保磁力などの磁気特性を改善し、しか
も電気抵抗を増加させる元素であり、下限をを0.10％と
した。しかし、Siは固溶強化作用によって冷間鍛造性を害す
る元素でもあり、本発明は冷間鍛造性を最重視するもの
であり、その上限を0.40％未満とした。 MnはSiと同様に製鋼時の脱酸に必要な元素であり、磁
気特性を損なうことのない範囲とし、その上限を0.40％
とした。Ｓは被削性を改善する元素であるが、反面、冷間鍛造
性を害する元素でもあり、その上限を0.002％とした。C
rはステンレス鋼の耐食性を付与する基本的な元素であ
り、少なくとも11％以上含有させる必要がある。しかしながら、その含有量が増加すると磁束密度など
磁気特性を損なうのでその上限を13％とした。 Alは磁気特性と電気抵抗を改善する元素であり、特に
Siとの複合添加による相乗効果によって電気抵抗を大幅
に向上する元素であり、これらの効果を得るには少なく
とも0.30％以上含有させる必要があり、その下限を0.30
％とした。しかし、0.80％を越えてAlを含有すると本発明の優れ
た冷間鍛造性を損なうので上限を0.80％とした。 Tiは磁束密度、保磁力などの磁気特性を大幅に改善す
るとともにＣ＋Ｎ量が0.025％以下と極低域において
は、Ｃ＋Ｎを微細な炭窒化物に固定化することによっ
て、引張り強さ、限界加工率などの冷間鍛造性を大幅に
改善する元素であり、本発明においては重要な元素であ
る。これらの効果を得るには少なくとも0.03％以上含有さ
せる必要があり、その下限を0.03％とした。なお、より優れた磁気特性、冷間鍛造性を得るにはＣ
＋Ｎ量の３倍を目標に添加すべきであり、0.05％以上含
有させることが望ましい。しかし、0.20％以上のTiを含有させてもその効果が飽
和するので、上限を0.20％とした。ＮはＣと同様に固溶強化作用によって冷間鍛造性を損
なう元素であり、本発明においてはできるだけ低下させ
ることが望ましくその上限を0.015％以下とした。なお、冷間鍛造性をより向上させるには0.012％以下
にすることが望ましい。Ｃ＋Ｎはいずれも固溶強化作用によって冷間鍛造性を
損なう元素である。本発明においては引張り強さ40kgf/
mm²以下、限界加工率60％以上と優れた冷間鍛造性を得
ることを目的とするものであり、Ｃ＋Ｎ量をできるだけ
低下させることが必要であり、上限を0.025％とした。 Bi、Pb、Ｓ、Se、Teはいずれも被削性を改善する元素
である。しかし、Bi、Pbを多く含有させると冷間鍛造性、熱間
加工性を損なうので上限をそれぞれ0.30％とした。また、Ｓ量を多く含有させると冷間鍛造性、耐食性を
損なうので、上限を0.040％とした。さらに、Teは冷間鍛造性に及ぼすＳ、Seの悪影響を無
害化する作用を有しており、少なくとも0.02％以上含有
させる必要がある。しかし、多く含有させると、かえっ
て冷間鍛造性を損なうのでその上限を0.040％とした。
かつSeは0.040％を越えて含有させると耐食性、冷間鍛
造性を損なうので、その上限をSe0.040％とした。さらに、本発明は優れた冷間鍛造性を得ることを最大
の目的とするものであり、Ｓ＋Se＋Teの合計を0.050％
とした。 ZrはMnSを球状化して、冷間鍛造性を改善する元素で
あり、Teと同様にＳ、Seの冷鍛性に及ぼす悪影響を無害
化する効果があるので少なくとも0.02％以上含有させる
必要がある。しかし、Zrを多く含有させると介在物量が
増加し、冷間鍛造性を損なうので上限を0.15％とした。 Mo、Cu、Ni、Nb、Ｖは耐食性を改善する元素である。しかし、Moは2.5％、CuとNiはそれぞれ0.5％、Nb、Ｖ
は0.20％を越えて含有させるといずれも磁気特性、冷間
鍛造性を損なうので、その上限をMoは2.5％、Cu、Niは
0.5％、Nb、Ｖは0.20％とした。（実施例）つぎに本発明鋼の特徴を従来鋼と比べて実施例でもっ
て明らかにする。第１表はこれらの供試鋼の化学成分を示すものであ
る。第１表においてＡ〜Ｊ鋼、Ｑ〜Ｔ鋼は本発明鋼であ
り、Ｋ〜Ｐ鋼は比較鋼であり、Ｕ〜Ｗ鋼は従来鋼であ
る。第２表は第１表の供試鋼について、900℃×2Hr保持
し、ついで冷却速度100℃/Hrという熱処理を施したＡ〜
Ｗ鋼の引張り強さ、限界加工率、磁束密度、保磁力、耐
食性、電気抵抗、被削性を示したものである。引張り強さについては、JIS 4号試験片を用いて測定
したものであり、限界加工率については、日本塑性加工
学会冷間鍛造分科会基準、冷間据込み性試験方法（暫定
基準）にもとづいて、試験片として直径14φ、高さ21m
m、ノッチ付を用い、圧縮試験を行い割れ発生率50％時
の据込率を測定したものである。磁気特性については、直流型BHトレーサーを用いて、
試験片として外径24φ、内径16φ、厚さ16mmのリングを
作製し、磁束密度、保磁力を測定したものである。また、耐食性については、５％NaCl、35℃水溶液にて
塩水噴霧試験を行いその発銹率を測定し、発銹率が５％
以下のものを◎、発銹率が５超〜25％のものを○とし
た。電気抵抗についてはホイーストンブッジ法により試
験片として1.2φ×500mm線を用いて測定したものであ
る。被削性については、10mm厚の試験片を用いて回転数72
5r.p.m、ドリルSKH5φ、荷重4kgで穿孔試験を行い、穴
明けに要する時間を測定したものである。第２表より知られるように、従来鋼であるＵ鋼は耐食
性については優れているが、磁束密度が12,100Gと磁気
特性については低いものであり、また、必要量のTiを含
有しないことによって引張り強さが47kgf/mm²、限界加
工率が44％と冷間鍛造性について劣るものであり、さら
に電気抵抗、被削性についても劣るものである。また、Ｖ鋼はAl量が0.20％と低く、かつ必要量のTiを
含有していないため磁束密度などの磁気特性、電気特性
については劣るものであり、かつ引張り強さが45kgf/mm
²と冷間鍛造性についても劣るものであり、さらにSi量
が高いことによって被削性についても劣るものである。
さらに、Ｗ鋼についてはＶ鋼と同様にAl量が低く、かつ
必要量のTiを含有していないので、電磁気特性、冷間鍛
造性が劣るものである。これらに対して本発明鋼であるＡ〜Ｊ鋼、Ｑ〜Ｔ鋼
は、Ｃ、Ｎ、Si等の固溶強化作用によって冷間鍛造性を
劣化させる元素の含有量を極力低下させるとともに0.03
〜0.20％のTi、0.30〜0.80％のAl、11〜13％のCrを含有
させることによって引張り強さが40kgf/mm²以下、限界
加工率が60％以上と優れた冷間鍛造性を有しており、磁
気特性についても磁束密度13000G以上、かつ保持力が1.
00e以下と優れており、さらに耐食性、電気抵抗、被削
性についても優れているものである。また、比較鋼であ
るＫ〜Ｐ鋼についても本発明鋼と同等の性能が得られる
ものである。（本発明の効果）上述のように、本発明鋼はＣ、Ｎの含有量を極力低減
させるとともに適量のTiを含有させ、かつSi、Mnの上限
を規制することによって磁気特性を損なうことなく冷間
鍛造性を改善したものであり、さらに、Ｓ、Pb、Zrの複
合添加により冷間鍛造性を損なうことなく被削性を改善
し、さらに適量のCrとTiを含有させることによって耐食
性についても優れており、本発明鋼は電磁バルブ、電磁
クラッチ、内燃機関の電子燃料噴射装置等に適した冷間
鍛造用軟磁性ステンレス鋼であり、高い実用性を有する
ものである。DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention is for cold forging excellent in cold forgeability, electromagnetic characteristics, and corrosion resistance used for an electromagnetic valve, an electromagnetic clutch, an electronic fuel injection device of an internal combustion engine, and the like. Related to soft magnetic stainless steel. (Prior art) Conventionally, as properties required for soft magnetic stainless steel,
It has electrical properties such as magnetic flux density and coercive force, electrical resistance, corrosion resistance, etc.
Steel, 1Si-0.20Al-13Cr steel, etc. have been developed and partly put to practical use. In recent years, the use of soft magnetic stainless steel has been developed, and it has been applied to parts having complicated shapes such as the body and core of an electronic fuel injection device. Development was required. In response to the above requirements, for example, steels such as 1Si-13Cr-0.2Al steel in which the C content is reduced to about 0.01% have been developed and are partially used. (Problems to be solved) However, the tensile strength of these steels is 44.5kg.
f / mm ² , drawing of 74% and critical working ratio of 47% do not provide sufficient cold forgeability. Forging is difficult, and the development of a soft magnetic stainless steel having better cold forgeability and electromagnetic properties has been desired. (Means for Solving the Problems) The present invention has been made in view of the drawbacks of the conventional steel, and the present inventors have studied the effects of various alloying elements on the electromagnetic properties and cold forgeability of 13Cr steel. As a result of investigation, the magnetic properties were improved by adding Al and Ti and lowering C + N, and the electrical properties were significantly improved by adding Al. On the other hand, the cold forgeability was improved by adding Ti and lowering C + N and It was found that it was improved by lowering S. In particular, when the C + N content of Ti is an ordinary value of about 0.06%, the cold forgeability is hardly improved, and the magnetic properties are slightly improved. However, when the amount of C + N is extremely reduced to 0.025% or less, the magnetic properties and the cold forgeability are greatly improved by adding about 0.05% of Ti. The effect of Ti is that, when a considerable amount of C + N is contained, when all C + N are fixed with Ti, large precipitates of TiC and TiN are formed, thereby reducing the cold forgeability. When the amount is very small, 0.025% or less, all C + N is immobilized with Ti and harmless and small Ti
It is considered that only C and TiN precipitates are formed, and only the interstitial solid solution strengthening action of C + N disappears, and the cold forgeability and magnetic properties are greatly improved. The present invention is based on these findings, and
The content should be 0.025% or less and 0.30 ~ 0.80% of Al and 0.0
It contains 3 to 0.20% Ti and greatly improves the electromagnetic characteristics. It also contains 0.30 to 0.80% Al to improve the electric characteristics, and further reduces the amount of Ti and C + N from 0.03 to 0.20%.
By setting the S content to 0.025% or less and the S content to 0.002% or less, the cold forgeability is greatly improved. Therefore, the steel of the present invention has a magnetic flux density (B ₂₀ ) of 13000 G or more.
With excellent coercive force and excellent magnetic properties of 1.00e or less, and having excellent electric properties of electric resistance of 65μΩ-cm or more, and tensile strength of cold workability of 40kgf / mm ² or less , Is a soft magnetic stainless steel for cold forging with an excellent cold forgeability with a critical working rate of 60% or more, electromagnetic valves,
This steel is suitable for electromagnetic clutches, electronic fuel injection devices for internal combustion engines, and the like. That is, the steel of the present invention is expressed as a weight ratio of C 0.015% or less,
Si 0.10 to less than 0.40%, Mn 0.40% or less, S0.002% or less, Cr
11-13%, Ti 0.03-0.20%, N 0.015% or less, C + N 0.025
% Or less, containing 0.30 to 0.80% of Al, the balance being Fe and impurity elements.
0.30% or less, Pb 0.30% or less, S0.040% or less, Se0.040%
Containing one or more of the following, and S,
When Se is contained, Te 0.002 to 0.040% and Zr 0.02 to 0.
Contains one of 15% and S + Se + Te 0.050%
The following is an improvement of the machinability of the first invention, taking into account that the cold forgeability does not decrease. The third invention further includes Mo2.5% or less, Cu0.5% or less, Ni0. 5% or less Nb0.20
% Or less and V0.20% or less, which further improves the corrosion resistance of the second invention. The reasons for limiting the components of the steel of the present invention will be described below. C is an element that impairs the cold forgeability and also adversely affects the magnetic properties due to the solid solution strengthening action. In the present invention, it is desirable to reduce as much as possible, and the upper limit is made 0.015%. In order to further improve the cold forgeability and magnetic properties, the content is preferably set to 0.010% or less. Si is an element that improves magnetic properties such as magnetic flux density and coercive force, and also increases electric resistance. The lower limit is set to 0.10%. However, Si is also an element that impairs cold forgeability due to the solid solution strengthening action, and the present invention places the highest priority on cold forgeability, and its upper limit is set to less than 0.40%. Mn is an element necessary for deoxidation during steelmaking, similar to Si. The upper limit is set to 0.40% without impairing magnetic properties.
And S is an element that improves machinability, but is also an element that impairs cold forgeability, and its upper limit is made 0.002%. C
r is a basic element that imparts corrosion resistance to stainless steel, and must be contained at least 11% or more. However, if the content increases, magnetic properties such as magnetic flux density are impaired, so the upper limit is set to 13%. Al is an element that improves the magnetic properties and electric resistance.
It is an element that greatly improves the electrical resistance due to the synergistic effect of complex addition with Si. To obtain these effects, it is necessary to contain at least 0.30% or more, and the lower limit is 0.30%.
%. However, if the Al content exceeds 0.80%, the excellent cold forgeability of the present invention is impaired, so the upper limit was made 0.80%. Ti significantly improves the magnetic properties such as magnetic flux density and coercive force, and in the extremely low range where the C + N content is 0.025% or less, by fixing C + N to fine carbonitride, tensile strength and critical processing It is an element that greatly improves cold forgeability, such as the rate, and is an important element in the present invention. To obtain these effects, it is necessary to contain at least 0.03% or more, and the lower limit is set to 0.03%. In order to obtain better magnetic properties and cold forgeability, C
Three times the amount of + N should be added as a target, and it is desirable to contain 0.05% or more. However, the effect is saturated even if 0.20% or more of Ti is contained, so the upper limit is set to 0.20%. N is an element that impairs the cold forgeability due to the solid solution strengthening effect, like C, and in the present invention, it is desirable to lower it as much as possible, and its upper limit is made 0.015% or less. In order to further improve the cold forgeability, the content is desirably 0.012% or less. C + N is an element that impairs cold forgeability due to solid solution strengthening. In the present invention, the tensile strength is 40 kgf /
The purpose of the present invention is to obtain an excellent cold forgeability of not more than mm ² and a critical working ratio of not less than 60%, and it is necessary to reduce the amount of C + N as much as possible. Bi, Pb, S, Se, and Te are all elements that improve machinability. However, if a large amount of Bi and Pb is contained, the cold forgeability and the hot workability are impaired, so the upper limits are each set to 0.30%. Further, if a large amount of S is contained, the cold forgeability and corrosion resistance are impaired, so the upper limit was made 0.040%. Further, Te has a function of detoxifying the adverse effects of S and Se on cold forgeability, and it is necessary to contain at least 0.02% or more. However, if a large amount is contained, the cold forgeability is impaired, so the upper limit is made 0.040%.
Further, if Se is contained in excess of 0.040%, the corrosion resistance and the cold forgeability are impaired, so the upper limit is made Se 0.040%. Further, the present invention aims at obtaining excellent cold forgeability, and the total of S + Se + Te is 0.050%.
And Zr is an element that improves the cold forgeability by spheroidizing MnS. Like Zr, Zr has the effect of detoxifying the adverse effects of S and Se on the cold forgeability, so it must be contained at least 0.02% or more. . However, when a large amount of Zr is contained, the amount of inclusions increases and the cold forgeability is impaired, so the upper limit was made 0.15%. Mo, Cu, Ni, Nb, and V are elements that improve corrosion resistance. However, Mo is 2.5%, Cu and Ni are each 0.5%, Nb, V
If the content exceeds 0.20%, the magnetic properties and cold forgeability are all impaired. Therefore, the upper limit is 2.5% for Mo and 2.5% for Cu and Ni.
0.5%, Nb and V were 0.20%. (Examples) Next, the characteristics of the steel of the present invention will be clarified by examples in comparison with conventional steels. Table 1 shows the chemical composition of these test steels. In Table 1, A to J steels, Q to T steels are steels of the present invention, K to P steels are comparative steels, and U to W steels are conventional steels. Table 2 shows that the test steels in Table 1 were held at 900 ° C for 2 hours and then heat-treated at a cooling rate of 100 ° C / Hr.
It shows the tensile strength, critical working ratio, magnetic flux density, coercive force, corrosion resistance, electric resistance, and machinability of W steel. Tensile strength is measured using JIS No. 4 test piece, and critical working ratio is based on the cold forging subcommittee standard of the Japan Society for Plastic Working and the cold upsetting test method (provisional standard). 14mm in diameter and 21m in height as a test piece
A compression test was performed using a notch with a notch of m, and the upsetting rate at a crack occurrence rate of 50% was measured. Regarding magnetic properties, using a DC type BH tracer,
A ring having an outer diameter of 24φ, an inner diameter of 16φ, and a thickness of 16mm was prepared as a test piece, and the magnetic flux density and the coercive force were measured. For corrosion resistance, a salt spray test was performed with a 5% NaCl aqueous solution at 35 ° C., and the rust rate was measured.
The following were rated as ◎, and those with a rust rate of more than 5 to 25% were rated as ○. The electric resistance was measured by a Wheatstone budge method using a 1.2 φ × 500 mm wire as a test piece. The machinability was measured using a 10 mm thick test piece at 72 rpm.
A piercing test was performed with a drill SKH5φ and a load of 4 kg at 5 rpm, and the time required for drilling was measured. As can be seen from Table 2, U steel, which is a conventional steel, has excellent corrosion resistance, but has a low magnetic flux density of 12,100G and low magnetic properties. With a tensile strength of 47 kgf / mm ² and a critical working ratio of 44%, it is inferior in cold forgeability, and is also inferior in electrical resistance and machinability. In addition, since V steel has a low Al content of 0.20% and does not contain a necessary amount of Ti, it has poor magnetic and electrical properties such as magnetic flux density, and a tensile strength of 45 kgf / mm.
Are those inferior about ² and the cold forgeability, but also poor machinability by high further amount of Si.
Further, the W steel has a low Al content as in the V steel and does not contain a necessary amount of Ti, so that its electromagnetic properties and cold forgeability are inferior. On the other hand, the steels A to J and Q to T, which are the steels of the present invention, reduce the content of elements that degrade cold forgeability due to the solid solution strengthening action of C, N, Si, etc.
0.20% of Ti, Yes 0.30 to 0.80% of Al, tensile strength by containing 11 to 13% of Cr is 40 kgf / mm ² or less, the limit working ratio is excellent cold forgeability and 60% As for the magnetic properties, the magnetic flux density is more than 13000G and the coercive force is 1.
It is excellent at not more than 00e and also excellent in corrosion resistance, electric resistance and machinability. In addition, the same performance as that of the steel of the present invention can be obtained for the comparative steels K to P. (Effects of the present invention) As described above, the steel of the present invention reduces the contents of C and N as much as possible, contains an appropriate amount of Ti, and regulates the upper limits of Si and Mn without impairing magnetic properties. It improves cold forgeability, and further improves the machinability without impairing cold forgeability by adding S, Pb, and Zr in combination, and further improves corrosion resistance by adding appropriate amounts of Cr and Ti. The steel of the present invention is a soft magnetic stainless steel for cold forging suitable for an electromagnetic valve, an electromagnetic clutch, an electronic fuel injection device of an internal combustion engine, and the like, and has high practicality.

Claims

(57) [Claims] By weight ratio C 0.015% or less, Si 0.10 to less than 0.40%, Mn 0.40% or less, S 0.002% or less, Cr 11 to 13%, Ti
0.03 to 0.20%, N 0.015% or less, C + N 0.025% or less, Al
A soft magnetic stainless steel for cold forging characterized by containing 0.30 to 0.80% and the balance being Fe and impurity elements. 2. C 0.015% or less by weight, Si 0.10 to less than 0.40%, Mn 0.40% or less, Cr 11 to 13%, Ti 0.03 to 0.20%, N
0.015% or less, C + N 0.025% or less, Al 0.30 to 0.80%, Bi 0.30% or less, Pb 0.30% or less, S 0.04%
0% or less, Se 0.040% or less of one or more, and when one or more of S and Se is contained,
A soft magnetic stainless steel for cold forging, characterized by containing one of 0.002 to 0.040% of Te and 0.02 to 0.15% of Zr, containing S + Se + Te of 0.050% or less, and the balance of Fe and impurity elements. 3. C 0.015% or less by weight, Si 0.10 to less than 0.40%, Mn 0.40% or less, Cr 11 to 13%, Ti 0.03 to 0.20%, N
0.015% or less, C + N 0.025% or less, Al 0.30 to 0.80%, Bi 0.30% or less, Pb 0.30% or less, S 0.04%
0% or less, Se 0.040% or less of one or more, and when one or more of S and Se is contained,
One of Te 0.002 to 0.040% and Zr 0.02 to 0.15%, S + Se + Te 0.050% or less, and Mo2.
It is characterized by containing one or more of 5% or less, Cu 0.5% or less, Ni 0.5% or less, Nb 0.20% or less, and V0.20% or less, with the balance being Fe and impurity elements. Soft magnetic stainless steel for hot forging.