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JP5171197B2 - Duplex stainless steel wire for high strength and high corrosion resistance bolts excellent in cold forgeability, steel wire and bolt, and method for producing the same - Google Patents

Duplex stainless steel wire for high strength and high corrosion resistance bolts excellent in cold forgeability, steel wire and bolt, and method for producing the same Download PDF

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JP5171197B2
JP5171197B2 JP2007264992A JP2007264992A JP5171197B2 JP 5171197 B2 JP5171197 B2 JP 5171197B2 JP 2007264992 A JP2007264992 A JP 2007264992A JP 2007264992 A JP2007264992 A JP 2007264992A JP 5171197 B2 JP5171197 B2 JP 5171197B2
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steel wire
strength
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bolt
cold forgeability
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JP2009091636A (en
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光司 高野
信二 柘植
雅之 天藤
祐司 森
好宣 多田
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Nippon Steel Stainless Steel Corp
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Nippon Steel and Sumikin Stainless Steel Corp
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Priority to TW097138890A priority patent/TWI394848B/en
Priority to KR1020107007555A priority patent/KR101248260B1/en
Priority to ES08837204T priority patent/ES2814823T3/en
Priority to PCT/JP2008/068467 priority patent/WO2009048137A1/en
Priority to EP08837204.0A priority patent/EP2199421B1/en
Priority to KR1020127031527A priority patent/KR101287772B1/en
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Description

本発明は、冷間鍛造性に優れた2相ステンレス鋼線材に係わり、例えばSUS304並の耐食性を有する高強度ボルトを安価に提供するものである。   The present invention relates to a duplex stainless steel wire excellent in cold forgeability, and provides, for example, a high-strength bolt having corrosion resistance comparable to that of SUS304 at low cost.

これまで、SUS304線材が強度700N/mmレベルの高強度・高耐食ボルトとして汎用的に使用されてきた。しかしながら、近年、自動車、家電等の分野を中心に更なるボルトの高強度化(軽量化)が求められてきた。また、SUS304ボルトは高価なNi原料を多く含有して価格が高いため、低コスト化も強く求められてきた。 Until now, SUS304 wire has been widely used as a high-strength, high-corrosion-resistant bolt with a strength of 700 N / mm 2 . However, in recent years, there has been a demand for further increasing the strength (weight reduction) of bolts mainly in the fields of automobiles, home appliances, and the like. Moreover, since SUS304 bolts contain many expensive Ni raw materials and are expensive, there has been a strong demand for cost reduction.

これまで、ボルトの高強度化は、例えば、マルテンサイト系ステンレス鋼のSUS630ボルトで対応されてきた(例えば、特許文献1)。
しかしながら、SUS630ボルトは強度に優れるものの、耐食性が十分でないばかりか、冷間鍛造性に著しく劣るため製造コストが大幅に高く、使用は非常に限定的であった。
Up to now, the strengthening of bolts has been supported by, for example, martensitic stainless steel SUS630 bolts (for example, Patent Document 1).
However, although SUS630 bolts are excellent in strength, they are not only insufficient in corrosion resistance, but are extremely inferior in cold forgeability, so that the production cost is significantly high and their use is very limited.

さらに、製造性に優れる安価な約13%Cr系のマルテンサイト系ステンレス鋼製の高力ボルトも提案されている(特許文献2)。しかしながら、耐食性が不十分であり、使用が限定されている。   Furthermore, an inexpensive high-strength bolt made of about 13% Cr martensitic stainless steel, which is excellent in manufacturability, has also been proposed (Patent Document 2). However, the corrosion resistance is insufficient and its use is limited.

また、高(C+N)量のオーステナイト系ステンレス鋼製の高力ボルトが提案されている(特許文献3)。しかしながら、冷間鍛造性に劣るため製造コストが大幅に高く、市場に受け入れられていない。   Moreover, a high strength bolt made of a high (C + N) austenitic stainless steel has been proposed (Patent Document 3). However, since it is inferior in cold forgeability, the production cost is significantly high and it is not accepted by the market.

一方、近年、高価なNiの使用を抑制した低Ni系の安価な2相ステンレス鋼(特許文献4〜6)が提案されている。
しかしながら、従来の2相ステンレス鋼では、冷間鍛造性が悪く、また、製造コストが高く、2相ステンレス鋼製のボルトは市場に存在していなかった。
On the other hand, in recent years, low Ni duplex inexpensive stainless steels (Patent Documents 4 to 6) in which the use of expensive Ni is suppressed have been proposed.
However, the conventional duplex stainless steel has poor cold forgeability and is expensive to manufacture, and duplex stainless steel bolts have not existed on the market.

以上、これまでのステンレス鋼ボルトおよびボルト用ステンレス鋼線材において、高耐食性、高強度、高冷間鍛造性、低コストを兼ね備える製品がなかった。   As described above, there has been no product having high corrosion resistance, high strength, high cold forgeability, and low cost in the conventional stainless steel bolts and stainless steel wires for bolts.

特開平9―314276号公報JP-A-9-314276 特開2005―179718号公報Japanese Patent Laid-Open No. 2005-179718 特開2006―274295号公報JP 2006-274295 A 国際公開WO2005/073422号公報International Publication WO2005 / 073422 特許第3271262号公報Japanese Patent No. 3271262 EP0337846号明細書EP0337846 specification

本発明の目的は、安価な高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材、鋼線およびボルト並びにその製造方法を提供することであり、安価な高耐食2相ステンレス鋼線の組織・成分・材質を制御することで冷間鍛造性とボルト製品の高強度化を付与することにある。   An object of the present invention is to provide an inexpensive austenite / ferritic duplex stainless steel wire for high-strength and highly corrosion-resistant bolts, a steel wire and a bolt, and a method for producing the same.・ It is to provide cold forgeability and high strength of bolt products by controlling ingredients and materials.

本発明者らは、上記課題を解決するために種々検討した結果、高耐食の2相ステンレス鋼で高価なNi含有量を低減すると共に、成分調整にて組織を安定化させ(低M値)、フェライト相の体積分率を高目に制御し、且つ、熱処理と伸線加工にて線材、鋼線の引張強さを適正化することで、冷間鍛造性とボルト製品の高強度化を安価に両立できることを見出した。本発明は、上記知見に基づいてなされたものであり、その要旨とするところは以下の通りである。   As a result of various investigations to solve the above problems, the present inventors have reduced the expensive Ni content in a high-corrosion resistant duplex stainless steel and stabilized the structure by adjusting the components (low M value). , By controlling the volume fraction of the ferrite phase at a high level, and by optimizing the tensile strength of the wire and steel wire by heat treatment and wire drawing, cold forgeability and high strength of the bolt product are achieved. We found that both can be achieved at low cost. This invention is made | formed based on the said knowledge, The place made into the summary is as follows.

(1) 質量%で、
C;0.005〜0.05%、
Si;0.1〜1.0%、
Mn;0.1〜10.0%、
Ni;1.0〜6.0%、
Cr;19.0〜30.0%、
Cu;0.05〜3.0%、
N;0.005〜0.20%
を含有し、残部がFeおよび不可避的不純物で構成され、C+N;0.20%以下、(a)式のM値が60以下、(b)式のF値が45〜85であり、引張強さが550〜750N/mmであることを特徴とする冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材である。
M=551−462(C+N)−9.2Si−8.1Mn
−29(Ni+Cu)−13.7Cr−18.5Mo ・ ・ ・(a)
F=5.6Cr−7.1Ni+2.4Mo+15Si−3.1Mn−300C
−134N−26.6 ・ ・ ・(b)
ここで、式中の成分元素は、鋼中に含有されている成分元素の質量%であり、含有されていない成分元素は0とする。
(1) In mass%,
C; 0.005 to 0.05%,
Si: 0.1 to 1.0%,
Mn: 0.1 to 10.0%,
Ni: 1.0-6.0%,
Cr: 19.0 to 30.0%,
Cu; 0.05 to 3.0%,
N; 0.005-0.20%
Containing the balance consists of Fe and not avoidable impurities, C + N; 0.20% or less, (a) expression of M value of 60 or less, the F value is from 45 to 85 of the formula (b) There is a high strength and high corrosion resistance bolted austenitic / ferritic duplex stainless steel wire rod excellent in cold forgeability characterized by having a tensile strength of 550 to 750 N / mm 2 .
M = 551-462 (C + N) -9.2Si-8.1Mn
-29 (Ni + Cu) -13.7Cr-18.5Mo (a)
F = 5.6Cr-7.1Ni + 2.4Mo + 15Si-3.1Mn-300C
-134N-26.6 (b)
Here, the component element in the formula is mass% of the component element contained in the steel, and the component element not contained is 0.

(2) 質量%で、
Mo;1.0%以下
を含有することを特徴とする請求項1記載の冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材である。
(2) By mass%
Mo: 1.0% or less, The high-strength, high-corrosion-resistant austenitic / ferritic duplex stainless steel wire rod with excellent cold forgeability according to claim 1.

(3) 質量%で、
B;0.01%以下
を含有することを特徴とする請求項1または2記載の冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材である。
(3) In mass%,
B: The austenite-ferritic duplex stainless steel wire rod for high strength and high corrosion resistance bolts having excellent cold forgeability according to claim 1 or 2, characterized by containing 0.01% or less.

(4) 質量%で、
Al;0.1%以下、
Mg;0.01%以下、
Ca;0.01%以下
の内、1種以上を含有することを特徴とする請求項1〜3のいずれかに記載の冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材である。
(4) By mass%
Al: 0.1% or less,
Mg: 0.01% or less,
Ca: 0.01% or less, containing one or more, Austenitic ferrite for high strength and high corrosion resistance bolts with excellent cold forgeability according to any one of claims 1 to 3 It is a two-phase steel wire.

(5) 質量%で、
Nb;1.0%以下、
Ti;0.5%以下、
V;1.0%以下、
Zr;1.0%以下
の内、1種以上を含有することを特徴とする請求項1〜4のいずれかに記載の冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材である。
(5) By mass%
Nb: 1.0% or less,
Ti: 0.5% or less,
V: 1.0% or less,
The austenite-ferrite system for high strength and high corrosion resistance bolts having excellent cold forgeability according to any one of claims 1 to 4, characterized in that it contains at least one of Zr and 1.0% or less. It is a two-phase steel wire.

(6) 上記(1)〜(5)のいずれかに記載の化学組成を含有し、引張強さが700〜1000N/mmであることを特徴とする冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線である。 (6) High strength and excellent cold forgeability characterized by containing the chemical composition according to any one of (1) to (5) above and having a tensile strength of 700 to 1000 N / mm 2. This is an austenitic and ferritic duplex stainless steel wire for high corrosion resistant bolts.

(7)上記(1)〜(5)のいずれかに記載の化学組成を含有し、引張強さが700〜1200N/mmであることを特徴とする磁性を有する高強度・高耐食ボルトである。 (7) A high-strength, high-corrosion-resistant bolt having magnetism, comprising the chemical composition according to any one of (1) to (5) above, and having a tensile strength of 700 to 1200 N / mm 2 is there.

(8)上記(1)〜(5)のいずれかに記載の化学組成を有し、引張強さが700〜1000N/mmであるオーステナイト・フェライト系2相鋼線を冷間ボルト成型後に300〜600℃で1〜100分の時効熱処理を施すことを特徴とする高強度・高耐食ボルトの製造方法である。 (8) Austenite-ferritic duplex stainless steel wire having the chemical composition described in any one of (1) to (5) above and having a tensile strength of 700 to 1000 N / mm 2 is 300 after cold bolt forming. A method for producing a high-strength, high-corrosion-resistant bolt, characterized by performing an aging heat treatment at ˜600 ° C. for 1 to 100 minutes.

本発明による冷間鍛造性に優れた高強度・高耐食ボルト用2相ステンレス鋼線材は、高価なNiをあまり含有していないにもかかわらず、優れた冷間鍛造性を確保すると共にSUS304並以上の高耐食性と高強度を付与することができ、高強度・高耐食ボルトを安価に提供する効果を発揮する。   The high-strength and high-corrosion-resistant bolt duplex stainless steel wire excellent in cold forgeability according to the present invention ensures excellent cold forgeability as well as SUS304, although it does not contain much expensive Ni. The above high corrosion resistance and high strength can be imparted, and the effect of providing high strength and high corrosion resistance bolts at low cost is exhibited.

以下に、先ず、本発明の請求項1記載の限定理由について説明する。以下、成分元素についての%は質量%である。
Below, the reason for limitation of Claim 1 of this invention is demonstrated first. Hereinafter,% for the component elements is mass%.

Cは、ボルト製品の強度を確保するために0.005%以上含有させる。しかしながら、0.05%を超えて含有させるとCr炭窒化物が生成して耐食性が劣化するばかりか、冷間鍛造性が劣化するため、0.05%以下に限定する。好ましくは、0.03%以下である。   C is contained in an amount of 0.005% or more in order to ensure the strength of the bolt product. However, if the content exceeds 0.05%, Cr carbonitride is generated and the corrosion resistance deteriorates, and the cold forgeability deteriorates, so the content is limited to 0.05% or less. Preferably, it is 0.03% or less.

Nは、固溶強化と時効硬化によりボルト製品の強度を確保するために0.005%以上含有させる。しかしながら、0.20%を超えて含有させると冷間鍛造性が著しく劣化する。そのため、上限を0.20%にする。好ましい範囲は、0.05%未満である。
C+Nは、上記の冷間鍛造性の理由から0.20%以下に限定する。好ましくは、0.10%以下である。
N is contained in an amount of 0.005% or more in order to ensure the strength of the bolt product by solid solution strengthening and age hardening. However, if it exceeds 0.20%, the cold forgeability deteriorates remarkably. Therefore, the upper limit is made 0.20%. A preferred range is less than 0.05%.
C + N is limited to 0.20% or less for the reason of the cold forgeability described above. Preferably, it is 0.10% or less.

Siは、脱酸のために0.1%以上を含有させる。しかしながら、1.0%を超えて含有させると冷間鍛造性が劣化する。そのため、上限を1.0%にする。好ましい範囲は、0.2〜0.6%である。   Si contains 0.1% or more for deoxidation. However, if it exceeds 1.0%, cold forgeability deteriorates. Therefore, the upper limit is made 1.0%. A preferable range is 0.2 to 0.6%.

Mnは、脱酸のためおよび安定なオーステナイト組織を得るための調整として0.1%以上を含有させる。しかしながら、10.0%を超えて含有させると耐銹性およびフェライト体積分率が減少し、引張強さが上昇し、冷間鍛造性が劣化する。そのため、上限を10.0%に限定する。好ましい範囲は、0.5〜5.0%である。   Mn is contained in an amount of 0.1% or more for deoxidation and as an adjustment for obtaining a stable austenite structure. However, if the content exceeds 10.0%, the weather resistance and the ferrite volume fraction decrease, the tensile strength increases, and the cold forgeability deteriorates. Therefore, the upper limit is limited to 10.0%. A preferable range is 0.5 to 5.0%.

Niは、オーステナイト組織を安定化させ、冷間鍛造性を確保するために1.0%以上含有させる。しかしながら、6.0%を超えて含有させてもその効果は飽和するし、逆にフェライト相の体積分率が45%以下になり、冷間鍛造性(工具寿命)に劣るばかりか、Niは高価なため経済性に劣る。そのため、上限を6.0%に限定する。好ましい範囲は、3.0超、5.0%以下である。   Ni is contained in an amount of 1.0% or more in order to stabilize the austenite structure and ensure cold forgeability. However, even if the content exceeds 6.0%, the effect is saturated, and conversely, the volume fraction of the ferrite phase becomes 45% or less and the cold forgeability (tool life) is inferior. Inexpensive because it is expensive. Therefore, the upper limit is limited to 6.0%. A preferable range is more than 3.0 and 5.0% or less.

Crは、耐食性を確保し、フェライト相の体積分率を増加させ、且つ、オーステナイト組織を安定化させて冷間鍛造性を確保するために、19.0%以上含有させる。しかしながら、30.0%を超えて含有させても、その効果は飽和するし、逆にフェライト相の体積分率が85%を超えるため、ボルト製品の強度が低下する。そのため、上限を30.0%にする。好ましい範囲は、22.0〜26.0%である。   Cr is contained in an amount of 19.0% or more in order to ensure corrosion resistance, increase the volume fraction of the ferrite phase, and stabilize the austenite structure to ensure cold forgeability. However, even if the content exceeds 30.0%, the effect is saturated, and conversely, the volume fraction of the ferrite phase exceeds 85%, so that the strength of the bolt product is lowered. Therefore, the upper limit is made 30.0%. A preferable range is 22.0 to 26.0%.

Cuは、オーステナイト組織を安定化し、加工硬化を抑制して冷間鍛造性を向上させ、且つ、冷間鍛造後の時効処理時に、フェライト相の時効硬化を促進させてボルト製品を高強度化するのに有効である。そのため、0.05%以上含有させる。しかしながら、3.0%を超えて含有させるとCuの固溶限を超えて素材の熱間製造性が著しく劣化するため、上限を3.0%にする。好ましい範囲は、0.2%以上1.0%未満である。   Cu stabilizes the austenite structure, suppresses work hardening, improves cold forgeability, and promotes age hardening of the ferrite phase during aging treatment after cold forging to increase the strength of bolt products. It is effective. Therefore, 0.05% or more is contained. However, if the content exceeds 3.0%, the solid solubility limit of Cu is exceeded and the hot manufacturability of the material deteriorates remarkably, so the upper limit is made 3.0%. A preferable range is 0.2% or more and less than 1.0%.

下記(a)式のM値は、オーステナイト相の安定度に寄与し、鉄と鋼,63(1977),772頁に記載された指標であり、M値が高くなると硬質な加工誘起マルテンサイト相が生成する。二相ステンレス鋼の冷間鍛造の場合、M値が60を超えると冷間鍛造時に硬質な加工誘起マルテンサイト相が生成し、冷間鍛造性が著しく劣化する(工具寿命劣位、冷間鍛造割れ発生)。そのため、M値を60以下に限定する。好ましい範囲は、40以下である。
M=551−462(C+N)−9.2Si−8.1Mn−29(Ni+Cu)
−13.7Cr−18.5Mo ・ ・ ・(a)
The M value in the following formula (a) contributes to the stability of the austenite phase and is an index described in Iron and Steel, 63 (1977), page 772, and when the M value increases, the hard work-induced martensite phase Produces. In the case of cold forging of duplex stainless steel, if the M value exceeds 60, a hard work-induced martensite phase is generated during cold forging, and cold forgeability deteriorates significantly (tool life inferior, cold forging cracking) Occurrence). Therefore, the M value is limited to 60 or less. A preferable range is 40 or less.
M = 551-462 (C + N) -9.2 Si-8.1 Mn-29 (Ni + Cu)
-13.7Cr-18.5Mo (a)

下記(b)式のF値は、フェライト相の体積分率に寄与し、特公平7−74416号公報に記載された指標であり、F値が高くなるとフェライト相が増加する。図1は、F値と二相ステンレス鋼線材製品のフェライト相の体積分率を調査したものである。F値が45以上になると、フェライト相の体積分率が45vol.%以上になり、高耐力、低加工硬化特性を示し(図2)、製品の強度(ボルト軸部の引張強さ)を700〜1200N/mmと高強度化でき、且つ、頭部の冷間鍛造性を確保できる。そのため、F値を45以上に限定する。図2のF値に応じた加工率(%)と圧縮変形応力(N/mm)との関係に示すように、F値が45未満では、加工硬化が大きく、冷間鍛造性(圧造割れ、工具損傷)が大きく劣化する。一方、F値が85を超えると、軟質なフェライト相が85%を超えて、強度の高いオーステナイト相が減るため、ボルト製品の強度が逆に低下する。そのため、上限を85にする。好ましい範囲は50〜80である。
F=5.6Cr−7.1Ni+2.4Mo+15Si−3.1Mn−300C
−134N−26.6 ・ ・ ・(b)
The F value in the following formula (b) contributes to the volume fraction of the ferrite phase, and is an index described in Japanese Patent Publication No. 7-74416. When the F value increases, the ferrite phase increases. FIG. 1 is an investigation of the F value and the volume fraction of the ferrite phase of a duplex stainless steel wire product. When the F value is 45 or more, the volume fraction of the ferrite phase is 45 vol. %, Exhibiting high proof stress and low work hardening characteristics (Fig. 2), the strength of the product (tensile strength of the bolt shaft) can be increased to 700-1200 N / mm 2 , and the head is cooled. Inter-forgeability can be secured. Therefore, the F value is limited to 45 or more. As shown in the relationship between the processing rate (%) and the compressive deformation stress (N / mm 2 ) according to the F value in FIG. , Tool damage) is greatly deteriorated. On the other hand, when the F value exceeds 85, the soft ferrite phase exceeds 85%, and the high-strength austenite phase decreases, so that the strength of the bolt product decreases conversely. Therefore, the upper limit is set to 85. A preferred range is 50-80.
F = 5.6Cr-7.1Ni + 2.4Mo + 15Si-3.1Mn-300C
-134N-26.6 (b)

線材の引張強さは、冷間鍛造性に大きく寄与し、線材の引張強さが550N/mm未満の場合、ボルト等の冷間鍛造部品の強度が低く、高強度製品としての価値が低くなる。そのため、下限を550N/mmに限定する。一方、線材の引張強さが750N/mmを超えると冷間鍛造性が著しく劣化する(工具寿命劣化、冷間鍛造割れ発生)。そのため、上限を750N/mmにする。好ましい範囲は、600〜700N/mmである。 The tensile strength of the wire greatly contributes to cold forgeability. When the tensile strength of the wire is less than 550 N / mm 2 , the strength of cold forged parts such as bolts is low, and the value as a high strength product is low. Become. Therefore, the lower limit is limited to 550 N / mm 2 . On the other hand, when the tensile strength of the wire exceeds 750 N / mm 2 , the cold forgeability is remarkably deteriorated (tool life deterioration, cold forging crack occurrence). Therefore, the upper limit is set to 750 N / mm 2 . A preferable range is 600 to 700 N / mm 2 .

本発明の請求項2記載の限定理由について述べる。   The reason for limitation according to claim 2 of the present invention will be described.

Moは、耐食性を向上させるのに有効な元素であり、0.1%以上の添加で安定的に効果が得られる。しかしながら、1.0%を超えて含有させると材料のコストが上昇するばかりか、材料が硬質化し、冷間鍛造性が劣化する。そのため、上限を1.0%に限定する。好ましい範囲は、0.2%以上、0.5%未満である。   Mo is an element effective for improving the corrosion resistance, and the effect can be stably obtained by adding 0.1% or more. However, if the content exceeds 1.0%, not only the cost of the material increases, but the material becomes hard and the cold forgeability deteriorates. Therefore, the upper limit is limited to 1.0%. A preferable range is 0.2% or more and less than 0.5%.

本発明の請求項3記載の限定理由について述べる。   The reason for limitation according to claim 3 of the present invention will be described.

Bは、熱間加工性を向上させるのに有効な元素であり、0.001%以上の添加で安定的に効果が得られる。しかしながら、0.01%を超えて含有させてもボライドが生成し、耐食性および冷間鍛造性が劣化する。そのため、上限を0.01%に限定する。好ましい範囲は、0.002〜0.006%である。   B is an element effective for improving the hot workability, and an effect can be stably obtained by adding 0.001% or more. However, even if the content exceeds 0.01%, boride is generated, and corrosion resistance and cold forgeability deteriorate. Therefore, the upper limit is limited to 0.01%. A preferred range is 0.002 to 0.006%.

本発明の請求項4記載の限定理由について述べる。
Al、Mg、Caは脱酸に有効であるため、Al;0.005%以上、Mg;0.001%以上、Ca;0.001%以上の1種類以上の添加で安定的に効果が得られる。しかしながら、それぞれ、Al;0.1%、Mg;0.01%、Ca;0.01%を超えて含有させてもその効果は飽和するし、逆に粗大酸化物(介在物)が発生し、冷間鍛造性割れが発生する。そのため、それぞれ、上限をAl;0.1%、Mg;0.01%、Ca;0.01%にする。好ましい範囲は、Al;0.01〜0.06%、Mg;0.002〜0.005%、Ca;0.002〜0.005%の1種類以上を含有させることである。
The reason for limitation according to claim 4 of the present invention will be described.
Since Al, Mg, and Ca are effective for deoxidation, the effect is stably obtained by adding one or more of Al; 0.005% or more, Mg; 0.001% or more, Ca; 0.001% or more. It is done. However, even if each content exceeds Al; 0.1%, Mg; 0.01%, Ca; 0.01%, the effect is saturated and, on the contrary, coarse oxides (inclusions) are generated. Cold forgeable cracks occur. Therefore, the upper limit is made Al: 0.1%, Mg: 0.01%, Ca; 0.01%, respectively. A preferable range is to contain one or more of Al; 0.01 to 0.06%, Mg; 0.002 to 0.005%, Ca; 0.002 to 0.005%.

本発明の請求項5記載の限定理由について述べる。
Nb、Ti、V、Zrは、Cr炭窒化物の生成を抑制して耐食性を確保するのに有効であり、Nb;0.05%以上、Ti;0.02%以上、V;0.05%以上、Zr;0.05%以上の1種類以上の添加で安定的に効果が得られる。しかしながら、Nb;1.0%、Ti;0.5%、V;1.0%、Zr;1.0%を超えて含有させても、その効果は飽和するし、逆に粗大析出物が発生し、冷間鍛造性割れが発生する。そのため、各元素の上限を規定する。好ましい範囲は、Nb;0.1〜0.6%、Ti;0.05〜0.5%、V;0.1〜0.6%、Zr;0.1〜0.6%の内、1種以上を含有させる。
通常、不可避的不純物として、製造工程上、鋼は酸素を含有するが、本発明の場合、不可避的不純物として、0.01%以下の酸素とすることが好ましい。
The reason for limitation according to claim 5 of the present invention will be described.
Nb, Ti, V, and Zr are effective in suppressing the formation of Cr carbonitride to ensure corrosion resistance, and Nb: 0.05% or more, Ti: 0.02% or more, V: 0.05 % Or more, Zr; 0.05% or more of one or more additions can provide stable effects. However, even if Nb: 1.0%, Ti: 0.5%, V: 1.0%, Zr: more than 1.0%, the effect is saturated, and conversely coarse precipitates are formed. And cold forgeable cracks occur. Therefore, the upper limit of each element is specified. Preferred ranges are Nb; 0.1-0.6%, Ti: 0.05-0.5%, V: 0.1-0.6%, Zr: 0.1-0.6%, 1 type or more is contained.
Normally, steel contains oxygen as an unavoidable impurity in the manufacturing process, but in the case of the present invention, it is preferable to use 0.01% or less oxygen as an unavoidable impurity.

本発明の請求項6記載の限定理由について述べる。
線材を伸線加工して、引き抜き鋼線とするが、鋼線の引張強さは、冷間鍛造性とボルト製品強度に大きく寄与し、鋼線の引張強さが700N/mm未満の場合、ボルト製品の強度が低くなり、高強度製品としての価値が低くなる。そのため、下限を700N/mmに限定する。一方、鋼線の引張強さが1000N/mmを超えると冷間鍛造性が著しく劣化する(工具寿命劣化、冷間鍛造割れ発生)。そのため、上限を1000N/mmにする。好ましい範囲は、750〜900N/mmである。
The reason for limitation according to claim 6 of the present invention will be described.
When the wire rod is drawn into a drawn steel wire, the tensile strength of the steel wire greatly contributes to cold forgeability and bolt product strength, and the tensile strength of the steel wire is less than 700 N / mm 2 , The strength of the bolt product is lowered, and the value as a high strength product is lowered. Therefore, the lower limit is limited to 700 N / mm 2 . On the other hand, when the tensile strength of the steel wire exceeds 1000 N / mm 2 , the cold forgeability is remarkably deteriorated (tool life deterioration, cold forging crack occurrence). Therefore, the upper limit is set to 1000 N / mm 2 . A preferable range is 750 to 900 N / mm 2 .

本発明の請求項7記載の限定理由について述べる。
本発明の高強度ボルトの引張強さは、伸線加工と冷間鍛造後の時効熱処理に高強度化する。この時、ボルト製品の引張強さが700N/mm未満では高強度ボルト製品としての価値が低い。一方、ボルト製品の引張強さが1200N/mm以上にすると冷間鍛造割れや工具損傷等、冷間鍛造コストが著しく劣化する。そのため、ボルト製品の引張強さの上限を1200N/mmにする。経済的効果を発揮する好ましい範囲は、800〜1000N/mmである。
The reason for limitation according to claim 7 of the present invention will be described.
The tensile strength of the high-strength bolt of the present invention is increased in strength during aging heat treatment after wire drawing and cold forging. At this time, if the tensile strength of the bolt product is less than 700 N / mm 2 , the value as a high-strength bolt product is low. On the other hand, when the tensile strength of the bolt product is 1200 N / mm 2 or more, cold forging costs such as cold forging cracks and tool damage are remarkably deteriorated. Therefore, the upper limit of the tensile strength of the bolt product is set to 1200 N / mm 2 . The preferable range which exhibits an economic effect is 800-1000 N / mm < 2 >.

本発明の請求項8記載の限定理由について述べる。
本発明の鋼線を冷間鍛造によりボルトに成形後、ボルト製品の引張強さを効果的に向上させるために、300℃以上、1分保定以上の時効熱処理を施すと効果的である。一方、600℃を超えると過時効となるため、ボルト製品の引張強さが低下する。そのため、上限を600℃とする。好ましい温度範囲は400〜550℃である。また、保定時間が100分を超えると時効硬化の効果が飽和するばかりか、場合によっては過時効によりボルト製品の引張強さが低下する。そのため、保定時間の上限を100分にする。好ましい保定時間の範囲は、5〜60分である。
The reason for limitation according to claim 8 of the present invention will be described.
In order to effectively improve the tensile strength of the bolt product after the steel wire of the present invention is formed into a bolt by cold forging, it is effective to perform an aging heat treatment at 300 ° C. or more and holding for 1 minute or more. On the other hand, when it exceeds 600 ° C., it becomes over-aged, so that the tensile strength of the bolt product is lowered. Therefore, the upper limit is set to 600 ° C. A preferred temperature range is 400-550 ° C. Further, when the holding time exceeds 100 minutes, not only the effect of age hardening is saturated, but in some cases, the tensile strength of the bolt product decreases due to overaging. Therefore, the upper limit of the retention time is set to 100 minutes. The range of preferable holding time is 5 to 60 minutes.

以下に本発明の実施例について説明する。
表1−1及び1−2に実施例の鋼の化学組成を示す。
Examples of the present invention will be described below.
Tables 1-1 and 1-2 show the chemical compositions of the steels of the examples.

Figure 0005171197
Figure 0005171197

Figure 0005171197
Figure 0005171197

これらの化学組成の鋼は、300kgの真空溶解炉にて溶解し、φ180mmの鋳片に鋳造し、その鋳片をφ5.5〜6.5mmまで熱間の線材圧延を行い、1050℃で熱間圧延を終了して、引き続きインライン熱処理にて1050℃で5分保定、水冷の溶体化処理を施し、その後、酸洗を行い線材製品とした。その後、蓚酸皮膜処理を施し、φ5.2mmまで冷間で軽伸線加工を施し、冷間鍛造用の鋼線に仕上げた。   Steels of these chemical compositions are melted in a 300 kg vacuum melting furnace, cast into a slab of φ180 mm, the slab is hot-rolled to φ5.5 to 6.5 mm, and heated at 1050 ° C. After the hot rolling was finished, the solution was kept at 1050 ° C. for 5 minutes by in-line heat treatment and subjected to a water cooling solution treatment, and then pickled to obtain a wire product. Thereafter, a oxalic acid film treatment was performed, and light wire drawing was performed cold to φ5.2 mm to finish a steel wire for cold forging.

その後、冷間鍛造および転造加工により六角ボルトに約5000本加工を施した。そして、一部で300〜650℃、3〜200分保定の時効処理を施した。その後、全てのボルトで、バレル研磨・洗浄により六角ボルト製品に仕上げた。   Thereafter, about 5000 hexagon bolts were machined by cold forging and rolling. And the aging process of 300-650 degreeC and 3-200 minutes retention was performed in part. After that, all bolts were finished into hexagon bolt products by barrel polishing and washing.

評価は、鋼線の引張強さ、鋼線のフェライト相の体積分率、冷間鍛造性(割れ有無、工具の欠損有無)、ボルト製品の引張強さ、耐食性を評価した。その評価結果を表2−1及び2−2に示す。   The evaluation was performed on the tensile strength of the steel wire, the volume fraction of the ferrite phase of the steel wire, the cold forgeability (with or without cracking, with or without a tool defect), the tensile strength of the bolt product, and the corrosion resistance. The evaluation results are shown in Tables 2-1 and 2-2.

Figure 0005171197
Figure 0005171197

Figure 0005171197
Figure 0005171197

機械的性質は、JIS Z 2241の引張試験での引張強さと破断絞りにて評価した。本発明例の鋼線では、全て650〜1000N/mmの範囲であり、本発明例のボルト製品では、全て700〜1200N/mmの範囲にあり、高強度に優れていた。 The mechanical properties were evaluated by the tensile strength and breaking drawing in the tensile test of JIS Z 2241. The steel wire of the present invention embodiment, all the range of 650~1000N / mm 2, the bolt products of the present invention example, the range of all 700~1200N / mm 2, was excellent in strength.

鋼線のフェライト相の体積分率は、鋼線の縦断面を鏡面研磨し、村上試薬にてフェライト相を着色し、画像解析により面積率を算出して体積分率を求めた。本発明例の鋼線はフェライト分率は、45〜85vol.%の範囲にあった。   The volume fraction of the ferrite phase of the steel wire was obtained by mirror-polishing the longitudinal section of the steel wire, coloring the ferrite phase with Murakami reagent, and calculating the area ratio by image analysis. The steel wire of the example of the present invention has a ferrite fraction of 45 to 85 vol. % Range.

冷間鍛造性は、3段ヘッダーにより六角頭に5000本圧造加工を施し、圧造割れの有無と工具損傷について評価した。工具損傷が発生しない場合を工具寿命○、工具損傷が発生する場合を工具寿命×として評価した。本発明例の線材は、冷間割れ発生無し、工具寿命○で冷間鍛造性に優れていた。   The cold forgeability was evaluated on the presence of forging cracks and tool damage by subjecting 5000 hexagon heads to forging with a three-stage header. The case where tool damage did not occur was evaluated as tool life ○, and the case where tool damage occurred was evaluated as tool life x. The wire of the example of the present invention was excellent in cold forgeability with no occurrence of cold cracking, tool life ○.

ボルト製品の耐食性は、JIS Z 2371の塩水噴霧試験に従い、各ボルト製品10本づつに対し、100時間の噴霧試験を実施して発銹するか否かで評価した。無発銹および僅かな点錆レベルであれば耐食性を○、流れ錆、全面発銹の場合は耐食性を×として評価した。本発明例のボルト製品の耐銹性は全て○であった。   Corrosion resistance of the bolt products was evaluated according to whether or not the bolt products were sprinkled by carrying out a spray test for 100 hours for each 10 bolt products according to the salt spray test of JIS Z 2371. Corrosion resistance was evaluated as ◯ for non-fogging and slight spot rust levels, and corrosion resistance was evaluated as x for flow rust and full surface rusting. The weather resistance of the bolt products of the examples of the present invention was all good.

一方、比較例No.34〜57は、本発明の範囲外にあり、冷間鍛造性、ボルト製品の強度、耐食性等、劣っており、本発明の優位性は明らかである。   On the other hand, Comparative Example No. 34 to 57 are outside the scope of the present invention, and are inferior in cold forgeability, bolt product strength, corrosion resistance, etc., and the superiority of the present invention is clear.

以上の各実施例から明らかなように、本発明の高価なNiをあまり含有しない高耐食性の2相ステンレス鋼線材は、優れた冷間鍛造性を有すると共にボルト製品の高強度化が可能であり、高強度・高耐食ボルトを安価に提供することができ、更に、ナットにも適用が可能であり、産業上極めて有用である。   As is clear from the above examples, the highly corrosion-resistant duplex stainless steel wire material that does not contain much expensive Ni of the present invention has excellent cold forgeability and can increase the strength of bolt products. It is possible to provide a high-strength, high-corrosion-resistant bolt at a low cost, and it is also applicable to nuts, which is extremely useful in the industry.

F値と線材製品のフェライト相の体積分率との関係を示す図である。It is a figure which shows the relationship between F value and the volume fraction of the ferrite phase of a wire product. F値に応じた鋼線(15%伸線材)の加工率(%)と圧縮変形応力(N/mm)との関係を示す図である。It is a figure which shows the relationship between the processing rate (%) and the compressive deformation stress (N / mm < 2 >) of the steel wire (15% wire drawing material) according to F value.

Claims (8)

質量%で、
C;0.005〜0.05%、
Si;0.1〜1.0%、
Mn;0.1〜10.0%、
Ni;1.0〜6.0%、
Cr;19.0〜30.0%、
Cu;0.05〜3.0%、
N;0.005〜0.20%
を含有し、残部がFeおよび不可避的不純物で構成され、C+N;0.20%以下、(a)式のM値が60以下、(b)式のF値が45〜85であり、引張強さが550〜750N/mmであることを特徴とする冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材。
M=551−462(C+N)−9.2Si−8.1Mn
−29(Ni+Cu)−13.7Cr―18.5Mo ・ ・ ・(a)
F=5.6Cr−7.1Ni+2.4Mo+15Si−3.1Mn−300C
−134N−26.6 ・ ・ ・(b)
ここで、式中の成分元素は、鋼中に含有されている成分元素の質量%であり、含有されていない成分元素は0とする。
% By mass
C; 0.005 to 0.05%,
Si: 0.1 to 1.0%,
Mn: 0.1 to 10.0%,
Ni: 1.0-6.0%,
Cr: 19.0 to 30.0%,
Cu; 0.05 to 3.0%,
N; 0.005-0.20%
Containing the balance consists of Fe and not avoidable impurities, C + N; 0.20% or less, (a) expression of M value of 60 or less, the F value is from 45 to 85 of the formula (b) A high-strength, high-corrosion-resistant austenitic-ferritic duplex stainless steel wire rod excellent in cold forgeability, having a tensile strength of 550 to 750 N / mm 2 .
M = 551-462 (C + N) -9.2Si-8.1Mn
-29 (Ni + Cu) -13.7Cr-18.5Mo (a)
F = 5.6Cr-7.1Ni + 2.4Mo + 15Si-3.1Mn-300C
-134N-26.6 (b)
Here, the component element in the formula is mass% of the component element contained in the steel, and the component element not contained is 0.
質量%で、
Mo;1.0%以下
を含有することを特徴とする請求項1記載の冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材。
% By mass
Mo: 1.0% or less, The austenitic / ferritic duplex stainless steel wire rod for high strength and high corrosion resistance bolts having excellent cold forgeability according to claim 1.
質量%で、
B;0.01%以下
を含有することを特徴とする請求項1または2記載の冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材。
% By mass
The austenite-ferritic duplex stainless steel wire rod for high strength and high corrosion resistance bolts having excellent cold forgeability according to claim 1 or 2, characterized by containing B: 0.01% or less.
質量%で、
Al;0.1%以下、
Mg;0.01%以下、
Ca;0.01%以下
の内、1種以上を含有することを特徴とする請求項1〜3のいずれかに記載の冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材。
% By mass
Al: 0.1% or less,
Mg: 0.01% or less,
Ca: 0.01% or less, containing one or more, Austenitic ferrite for high strength and high corrosion resistance bolts with excellent cold forgeability according to any one of claims 1 to 3 Duplex steel wire.
質量%で、
Nb;1.0%以下、
Ti;0.5%以下、
V;1.0%以下、
Zr;1.0%以下
の内、1種以上を含有することを特徴とする請求項1〜4のいずれかに記載の冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線材。
% By mass
Nb: 1.0% or less,
Ti: 0.5% or less,
V: 1.0% or less,
The austenite-ferrite system for high strength and high corrosion resistance bolts having excellent cold forgeability according to any one of claims 1 to 4, characterized in that it contains at least one of Zr and 1.0% or less. Duplex steel wire.
請求項1〜5のいずれかに記載の化学組成を有し、引張強さが700〜1000N/mmであることを特徴とする冷間鍛造性に優れた高強度・高耐食ボルト用オーステナイト・フェライト系2相鋼線。 A high-strength, high-corrosion-resistant austenite bolt with excellent cold forgeability, having the chemical composition according to any one of claims 1 to 5 and having a tensile strength of 700 to 1000 N / mm 2 Ferritic duplex steel wire. 請求項1〜5のいずれかに記載の化学組成を有し、引張強さが700〜1200N/mmであることを特徴とする高強度・高耐食ボルト。 It has a chemical composition according to any one of claims 1 to 5, high strength and high corrosion resistance bolts tensile strength characterized in that it is a 700~1200N / mm 2. 請求項1〜5のいずれかに記載の化学組成を有し、引張強さが700〜1000N/mmであるオーステナイト・フェライト系2相鋼線を冷間ボルト成型後に300〜600℃で1〜100分の時効熱処理を施すことを特徴とする高強度・高耐食ボルトの製造方法。 An austenitic ferritic two-phase steel wire having the chemical composition according to any one of claims 1 to 5 and having a tensile strength of 700 to 1000 N / mm 2 is applied at 300 to 600 ° C after cold bolt molding. A method for producing a high-strength, high-corrosion-resistant bolt, characterized by performing an aging heat treatment for 100 minutes.
JP2007264992A 2007-10-10 2007-10-10 Duplex stainless steel wire for high strength and high corrosion resistance bolts excellent in cold forgeability, steel wire and bolt, and method for producing the same Active JP5171197B2 (en)

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JP2007264992A JP5171197B2 (en) 2007-10-10 2007-10-10 Duplex stainless steel wire for high strength and high corrosion resistance bolts excellent in cold forgeability, steel wire and bolt, and method for producing the same
TW097138890A TWI394848B (en) 2007-10-10 2008-10-09 Two-phase stainless steel wire rod, steel wire, bolt and manufacturing method thereof
ES08837204T ES2814823T3 (en) 2007-10-10 2008-10-10 Duplex stainless steel wire material, steel wire, bolt and manufacturing method thereof
PCT/JP2008/068467 WO2009048137A1 (en) 2007-10-10 2008-10-10 Duplex stainless steel wire material, steel wire, bolt, and method for production of the bolt
KR1020107007555A KR101248260B1 (en) 2007-10-10 2008-10-10 Duplex stainless steel wire material, steel wire, bolt, and method for production of the bolt
EP08837204.0A EP2199421B1 (en) 2007-10-10 2008-10-10 Duplex stainless steel wire material, steel wire, bolt, and method of manufacturing the same
KR1020127031527A KR101287772B1 (en) 2007-10-10 2008-10-10 Duplex stainless steel wire material, steel wire, bolt, and method for production of the bolt
CN2008801102255A CN101815803B (en) 2007-10-10 2008-10-10 Duplex stainless steel wire material, steel wire, bolt, and method for production of the bolt

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