TWI595101B - Cold forging and quenching and tempering after the delay breaking resistance of the wire with excellent bolts, and bolts - Google Patents
Cold forging and quenching and tempering after the delay breaking resistance of the wire with excellent bolts, and bolts Download PDFInfo
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- 230000000171 quenching effect Effects 0.000 title claims description 19
- 238000005496 tempering Methods 0.000 title claims description 13
- 238000010273 cold forging Methods 0.000 title description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 83
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
- F16B35/00—Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- General Engineering & Computer Science (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
Description
本發明係關於螺栓用鋼線及使用該鋼線製得之螺栓，詳細而言是關於冷鍛性及淬火回火後之耐延遲破壞性優異的螺栓用鋼線、以及螺栓。 The present invention relates to a steel wire for a bolt and a bolt obtained by using the steel wire, and more particularly to a steel wire for a bolt and a bolt which are excellent in cold forge resistance and delayed fracture resistance after quenching and tempering.
對於汽車和各種產業機械等所使用的螺栓，期待高強度化及提升耐延遲破壞性。雖然被指出各種關於延遲破壞的原因，但一般認為是氫脆化現象的影響。 For bolts used in automobiles and various industrial machines, it is expected to increase the strength and improve the resistance to delay damage. Although various reasons for delayed damage have been pointed out, they are generally considered to be the effects of hydrogen embrittlement.
氫脆化現象是因為鋼表面的腐蝕反應而生成的氫，滲入鋼中且擴散(以下也稱為「擴散性氫」)所產生。因此，向來以提升鋼的耐腐蝕性作為用於防止延遲破壞的有效手段。而提升耐腐蝕性後，即使為了除去銹皮而進行酸洗，仍會殘留銹皮，被指出是伸線時的缺陷或壓造時的裂痕之原因。 The phenomenon of hydrogen embrittlement is caused by hydrogen generated by a corrosion reaction on the surface of steel, which is infiltrated into steel and diffused (hereinafter also referred to as "diffusible hydrogen"). Therefore, the corrosion resistance of the steel has been conventionally used as an effective means for preventing delayed damage. When the corrosion resistance is improved, even if pickling is performed in order to remove the scale, the scale remains, and it is pointed out that it is a defect at the time of stretching or a crack at the time of extrusion.
因此，提出有增加Si添加量，使ε碳化物等過渡碳化物安定化，使擴散性氫無害化之技術等。例如專利文獻1揭示有一種螺栓，該螺栓之特徵在於：具有既定 的成分組成，螺栓軸部的沃斯田鐵結晶粒度編號為9.0以上，表示析出在螺栓軸部的沃斯田鐵結晶粒界之碳化物的比例之G值(%)係滿足(L/L0)×100≦60。該技術係使成為延遲破壞的起點之沃斯田鐵結晶粒界的強度提高，且使碳化物等的氫捕集位置減少。因此，氫量較少的環境當然能得到發揮優異的耐氫脆化特性之高強度螺栓，而在氫捕集位置全部被消耗的氫量多的環境中能也得到發揮優異的耐氫脆化特性之高強度螺栓。 Therefore, there has been proposed a technique of increasing the amount of Si added, making the transition carbide such as ε carbide stable, and making the diffusible hydrogen harmless. For example, Patent Document 1 discloses a bolt characterized in that it has an established In the component composition, the Worstian iron crystal grain size number of the bolt shaft portion is 9.0 or more, and the G value (%) of the ratio of the carbides at the Worstian iron crystal grain boundary deposited in the bolt shaft portion is satisfied (L/L0). ) × 100 ≦ 60. This technique improves the strength of the Woltian iron crystal grain boundary which is the starting point of delayed fracture, and reduces the hydrogen trapping position of carbides and the like. Therefore, in the environment where the amount of hydrogen is small, it is possible to obtain a high-strength bolt which exhibits excellent hydrogen embrittlement resistance, and it is possible to exhibit excellent hydrogen embrittlement resistance in an environment in which the amount of hydrogen consumed in the hydrogen trapping position is large. High strength bolts for the characteristics.
專利文獻2揭示有耐脫碳性及伸線加工性優異的螺栓用鋼線材，該螺栓用鋼線材之特徵在於：具有既定的成分組成，鋼線材的中心部的平均結晶粒徑Dc為80μm以下，且鋼線材的表層部的平均結晶粒徑Ds為3.0μm以上。根據該技術，熱鍛造後不須脫碳即能得到伸線加工性優異的螺栓用鋼線材。 Patent Document 2 discloses a steel wire for bolts which is excellent in decarburization resistance and wire drawing workability. The steel wire for bolts has a predetermined component composition, and the average crystal grain size Dc of the center portion of the steel wire rod is 80 μm or less. Further, the average crystal grain size Ds of the surface layer portion of the steel wire rod is 3.0 μm or more. According to this technique, it is possible to obtain a steel wire for bolts excellent in wire drawing workability without performing decarburization after hot forging.
且，專利文獻3揭示有外皮切削性優異的高強度螺栓用鋼線材，該螺栓用鋼線材之特徵在於：具有既定的成分組成，以波來鐵作為主體之組織，波來鐵團塊的粒度編號的平均值Pave係滿足6.0≦Pave≦12.0，並且表層的全脫碳層深度為0.20mm以下，且Cr系合金碳化物量為7.5%以下。根據該技術能得到一種高強度螺栓用鋼線材，除了外皮切削性及切削屑排出性良好以外，能發揮SV處理時不會產生斷線之良好的SV處理性。 Further, Patent Document 3 discloses a steel wire rod for high-strength bolts excellent in outer skin machinability, and the steel wire for bolts is characterized in that it has a predetermined composition and a structure in which ferrite is used as a main body, and the particle size of the bollite agglomerate The average value Pave of the number satisfies 6.0 ≦ Pave ≦ 12.0, and the depth of the full decarburization layer of the surface layer is 0.20 mm or less, and the amount of carbide of the Cr-based alloy is 7.5% or less. According to this technique, it is possible to obtain a steel wire for high-strength bolts, which is excellent in SV handling property in which SV processing does not cause disconnection, in addition to good outer-die machinability and chip discharge performance.
專利文獻4揭示有冷鍛造用鋼之製造方法，該冷鍛造用鋼之製造方法係將具有既定的成分組成之鋼 材，以既定的條件按照以下順序進行第1加熱保持、第2加熱保持、第1冷卻、第2冷卻之處理，使鋼材中的碳化物球狀化。根據該技術，即使Cr量為0.4%以下的鋼材也能確實地球狀化退火，而製得冷鍛造性優異的鋼材。 Patent Document 4 discloses a method for producing steel for cold forging, which is a steel having a predetermined composition. The material is subjected to the first heating, the second heating, the first cooling, and the second cooling in the following order under predetermined conditions to spheroidize the carbide in the steel material. According to this technique, even if the steel material having a Cr content of 0.4% or less can be subjected to earth-like annealing, a steel material excellent in cold forgeability can be obtained.
[專利文獻1]日本特開2013-163865號公報 [Patent Document 1] Japanese Patent Laid-Open Publication No. 2013-163865
[專利文獻2]日本特開2009-068030號公報 [Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-068030
[專利文獻3]日本特開2013-213238號公報 [Patent Document 3] Japanese Laid-Open Patent Publication No. 2013-213238
[專利文獻4]日本特開2014-201812號公報 [Patent Document 4] Japanese Patent Laid-Open Publication No. 2014-201812
例如專利文獻1的技術中，精加工輥軋後的冷卻係以通常的冷卻速度進行，脫碳率高。因此，螺栓加工後的淬火加熱時，可能因為異常粒成長而使得耐延遲破壞性降低。且，專利文獻2的技術中，輥軋後的冷卻速度慢，因此肥粒鐵-波來鐵的面積率增加，球狀化退火時的碳化物分散性差，進行冷壓造製造螺栓時會產生裂痕。 For example, in the technique of Patent Document 1, the cooling after the finish rolling is performed at a normal cooling rate, and the decarburization rate is high. Therefore, in the quenching heating after the bolt processing, the retardation destructive resistance may be lowered due to the abnormal grain growth. Further, in the technique of Patent Document 2, since the cooling rate after the rolling is slow, the area ratio of the ferrite-iron-to-iron is increased, and the carbide dispersibility during the spheroidizing annealing is inferior, and the bolt is produced by cold-pressing. crack.
專利文獻3的技術中，由於是以波來鐵作為主體的金屬組織，因此退火時的碳化物分散性差，冷壓造時會產生裂痕。且，專利文獻4的技術中，Si的添加量低，由於無法使過渡碳化物安定化，因此耐延遲破壞性的 確保有困難。 In the technique of Patent Document 3, since the metal structure mainly composed of the ferrite is used, the carbide dispersibility at the time of annealing is inferior, and cracks are generated during cold press. Further, in the technique of Patent Document 4, the amount of addition of Si is low, and since the transition carbide cannot be stabilized, the retardation resistance is delayed. Make sure you have trouble.
本發明係鑑於如上述之情事而研發者，其目的在於提供冷鍛性、及淬火回火後之耐延遲破壞性(以下稱為「耐延遲破壞性」)優異的螺栓用鋼線、以及螺栓。 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a steel wire for bolts and a bolt which are excellent in cold forgeability and delayed fracture resistance (hereinafter referred to as "delay resistance resistance" after quenching and tempering). .
能解決上述課題的冷鍛性及耐延遲破壞性優異的本發明之螺栓用鋼線，以質量%計，係含有：C：0.3~0.6%，Si：1.0~3.0%，Mn：0.10~1.5%，P：超過0%、0.020%以下，S：超過0%、0.020%以下，Cr：0.3~1.5%，Al：0.02~0.10%，N：0.001~0.02%，其餘為鐵及不可避免的雜質，在鋼線的直徑d×1/4位置之肥粒鐵結晶粒度編號為No.6~12，在鋼線的直徑d×1/4位置，長寬比2.0以下的碳化物佔碳化物全體的比例為70%以上，且在從表層算起深度0.1mm位置之C量為母材C量的60~120%。 The steel wire for bolts of the present invention which is excellent in the cold forgeability and the delayed fracture resistance of the above-mentioned problem is C: 0.3 to 0.6%, Si: 1.0 to 3.0%, and Mn: 0.10 to 1.5 in terms of % by mass. %, P: more than 0%, less than 0.020%, S: more than 0%, less than 0.020%, Cr: 0.3~1.5%, Al: 0.02~0.10%, N: 0.001~0.02%, the rest is iron and inevitable Impurities, in the diameter d × 1/4 of the diameter of the steel wire, the grain size of the ferrite grains is No. 6 to 12, and the carbides occupying carbides having an aspect ratio of 2.0 or less at the diameter d × 1/4 of the steel wire The ratio of the total amount is 70% or more, and the amount of C at a depth of 0.1 mm from the surface layer is 60 to 120% of the amount of the base material C.
在本發明之螺栓用線材，進一步含有屬於以下(A)、(B)、(C)、(D)及(E)中任一者的1種以上，亦為較佳實施態樣。(A)選自由Cu：超過0%、0.5%以下、Ni：超過0%、1.0%以下、及Sn：超過0%、0.5%以下所構成群中之至少1種，(B)選自由Ti：超過0%、0.1%以下、Nb：超過0%、0.1%以下、及Zr：超過0%、0.3%以下所構成群中之至少1 種，(C)選自由Mo：超過0%、3%以下、及W：超過0%、0.5%以下所構成群中之至少1種，(D)V：超過0%、0.5%以下，(E)選自由Mg：超過0%、0.01%以下、及Ca：超過0%、0.01%以下所構成群中之至少1種。 The wire for bolts of the present invention further contains one or more of the following (A), (B), (C), (D) and (E), and is also a preferred embodiment. (A) is at least one selected from the group consisting of Cu: more than 0%, 0.5% or less, Ni: more than 0%, 1.0% or less, and Sn: more than 0% and 0.5% or less, and (B) is selected from Ti : at least 1% of the group consisting of more than 0%, 0.1% or less, Nb: more than 0%, 0.1% or less, and Zr: more than 0% and 0.3% or less (C) is at least one selected from the group consisting of Mo: more than 0%, 3% or less, and W: more than 0% and 0.5% or less, and (D)V: more than 0% and 0.5% or less, ( E) is at least one selected from the group consisting of Mg: more than 0%, 0.01% or less, and Ca: more than 0% and 0.01% or less.
本發明亦包含螺栓，該螺栓係使用上述螺栓用鋼線而製得，拉伸強度1400MPa以上，在表層和直徑d×1/4位置的沃斯田鐵結晶粒度編號皆為No.7以上，耐延遲破壞性優異。 The present invention also includes a bolt which is obtained by using the above-mentioned steel wire for bolts, and has a tensile strength of 1400 MPa or more, and the Woltian iron crystal grain size number of the surface layer and the diameter d×1/4 position are No. 7 or more. Excellent resistance to delay damage.
本發明之鋼線係由於適當地控制化學成分組成、碳化物的球狀化度、肥粒鐵結晶粒度編號，及脫碳率，因此能以高水準兼顧冷鍛性及耐延遲破壞性。且，本發明之使用螺栓用鋼線而製得的螺栓為高強度且具有優異的耐延遲破壞性。 Since the steel wire system of the present invention appropriately controls the chemical composition, the spheroidization degree of the carbide, the grain size of the ferrite iron crystal, and the decarburization ratio, the cold forgeability and the delayed fracture resistance can be achieved at a high level. Further, the bolt obtained by using the steel wire for bolt of the present invention has high strength and excellent resistance to delay damage.
本發明者等人為了確保冷鍛性及耐延遲破壞性而反覆精心檢討。其結果，發現藉由適當地控制化學成分組成、碳化物的球狀化度、肥粒鐵結晶粒度編號、及脫碳率，能達成上述課題，而達成本發明。 The inventors of the present invention have carefully reviewed in order to ensure cold forgeability and delay destructiveness. As a result, it has been found that the above problems can be attained by appropriately controlling the chemical composition, the spheroidization degree of the carbide, the ferrite iron crystal grain size number, and the decarburization ratio, and the present invention has been achieved.
特別是本發明中，藉由提高Si含量並且降低 脫碳率而能提升耐延遲破壞性，且藉由使肥粒鐵結晶粒細微化至既定的範圍，並且提高碳化物的球狀化率，而能提升冷壓造。以下，說明本發明之螺栓用鋼線。 Especially in the present invention, by increasing the Si content and lowering The decarburization rate can improve the delayed fracture resistance, and the cold press can be improved by making the ferrite iron crystal grains fine to a predetermined range and increasing the spheroidization rate of the carbide. Hereinafter, the steel wire for bolts of the present invention will be described.
若於表層形成有C缺乏層的狀態即脫碳率高的狀態，進行淬火回火處理，則沃斯田鐵結晶物粗大化，使得耐延遲破壞性惡化。因而，為了使耐延遲破壞性提升，脫碳率儘量低為佳。因而，從表層起深度0.1mm位置之C量為母材C量的60%以上，較佳為70%以上，更佳為75%以上。另一方面，C量變得過高也會使耐延遲破壞性劣化。因而，從表層起深度0.1mm位置之C量為母材C量的120%以下，較佳為100%以下，更佳為90%以下。此外，母材的C量係基於燃燒-紅外線吸收法(JIS G 1211(2011年))測量線材之值。 When the state in which the C-deficient layer is formed in the surface layer, that is, the state in which the decarburization ratio is high, and the quenching and tempering treatment is performed, the Worthite iron crystal is coarsened, and the retardation resistance is deteriorated. Therefore, in order to improve the resistance to delay damage, the decarburization rate is preferably as low as possible. Therefore, the amount of C from the surface layer at a depth of 0.1 mm is 60% or more of the amount of the base material C, preferably 70% or more, and more preferably 75% or more. On the other hand, if the amount of C becomes too high, the retardation resistance is deteriorated. Therefore, the amount of C from the surface layer at a depth of 0.1 mm is 120% or less of the amount of the base material C, preferably 100% or less, more preferably 90% or less. Further, the C amount of the base material is a value of the wire measured based on the combustion-infrared absorption method (JIS G 1211 (2011)).
若肥粒鐵結晶粒大，則延展性降低且冷鍛性劣化。因而，鋼線的直徑d×1/4位置(以下也稱為「d/4位置」)之肥粒鐵結晶粒度編號為No.6以上，較佳為No.7以上，更佳為No.8以上。另一方面，若肥粒鐵結晶粒過細，則鋼的強度提高，冷鍛性劣化。因而，肥粒鐵結晶粒度編號為No.12以下，較佳為No.11以下，更佳為No.10以下。 If the ferrite iron crystal grains are large, the ductility is lowered and the cold forgeability is deteriorated. Therefore, the grain size of the steel wire having a diameter d × 1/4 (hereinafter also referred to as "d/4 position") is No. 6 or more, preferably No. 7 or more, and more preferably No. 8 or more. On the other hand, if the ferrite-grain crystal grains are too fine, the strength of the steel is increased, and the cold forgeability is deteriorated. Therefore, the ferrite iron crystal grain size number is No. 12 or less, preferably No. 11 or less, and more preferably No. 10 or less.
若棒狀碳化物增加，則鋼變形時由於應力集中源增加、冷鍛性降低，因此球狀化率高者為佳。因而，在d/4位置，長寬比為2.0以下的碳化物的比例為70%以上，較佳為80%以上，更佳為85%以上。球狀化率愈高愈能得到良好的冷鍛性，因此上限為100%。 When the rod-shaped carbide is increased, the stress concentration source is increased and the cold forgeability is lowered when the steel is deformed, so that the spheroidization rate is high. Therefore, at the d/4 position, the ratio of the carbide having an aspect ratio of 2.0 or less is 70% or more, preferably 80% or more, and more preferably 85% or more. The higher the spheroidization rate, the better the cold forgeability is obtained, so the upper limit is 100%.
規定本發明之螺栓用鋼線的化學成分組成之設定範圍的理由係如下述。 The reason for specifying the setting range of the chemical composition of the steel wire for bolts of the present invention is as follows.
C是用於確保鋼的強度之有效元素。為了確保作為目標的1400MPa以上的螺栓拉伸強度，C含量為0.3%以上，較佳為0.35%以上，更佳為0.38%以上。但因為C含量過剩時會使耐延遲破壞性劣化，因此C含量為0.6%以下，較佳為0.55%以下，更佳為0.52%以下。 C is an effective element for ensuring the strength of steel. In order to secure the target tensile strength of 1400 MPa or more, the C content is 0.3% or more, preferably 0.35% or more, and more preferably 0.38% or more. However, since the C resistance is deteriorated when the C content is excessive, the C content is 0.6% or less, preferably 0.55% or less, more preferably 0.52% or less.
Si係作為脫氧劑之作用，並且是用於確保鋼的強度之有效元素。且，回火時亦發揮抑制粗大的雪明碳鐵析出，提升耐延遲破壞性之作用。為了有效地發揮該等效果，Si含量為1.0%以上，較佳為1.3%以上，更佳為1.5%以上。另一方面，若Si含量過剩，則鋼線的強度提高使得冷鍛 性惡化。Si含量為3.0%以下，較佳為2.7%以下，更佳為2.5%以下。 The Si system functions as a deoxidizer and is an effective element for securing the strength of steel. Moreover, when tempering, it also suppresses the precipitation of coarse ferritic carbon iron and improves the resistance to delayed destructiveness. In order to effectively exhibit these effects, the Si content is 1.0% or more, preferably 1.3% or more, and more preferably 1.5% or more. On the other hand, if the Si content is excessive, the strength of the steel wire is increased to make cold forging Sexual deterioration. The Si content is 3.0% or less, preferably 2.7% or less, more preferably 2.5% or less.
Mn是確保鋼的強度，並且是與S形成化合物以發揮抑制使耐延遲破壞性劣化的FeS之生成的作用之有效元素。為了發揮這種效果，Mn含量為0.10%以上，較佳為0.15%以上，更佳為0.2%以上。另一方面，若Mn含量過剩，則MnS粗大化，成為應力集中源而使得冷鍛性或耐延遲破壞性惡化。Mn含量為1.5%以下，較佳為1.3%以下，更佳為1.1%以下。 Mn is an effective element for ensuring the strength of the steel and forming a compound with S to suppress the formation of FeS which deteriorates the resistance to delayed fracture. In order to exert such an effect, the Mn content is 0.10% or more, preferably 0.15% or more, and more preferably 0.2% or more. On the other hand, when the Mn content is excessive, the MnS is coarsened, and the stress concentration source is deteriorated, and the cold forgeability or the delayed fracture resistance is deteriorated. The Mn content is 1.5% or less, preferably 1.3% or less, more preferably 1.1% or less.
P是以在結晶粒界濃化而使得鋼的韌度延展性降低且使耐延遲破壞性劣化之雜質元素。藉由使P含量減少，能提升耐延遲破壞性。P含量為0.020%以下，較佳為0.015%以下，更佳為0.010%以下。P含量為愈少愈佳，但是零在製造上有困難，有時含有0.003%左右作為不可避免的雜質。 P is an impurity element which is concentrated at a crystal grain boundary to lower the ductility of steel and to deteriorate the resistance to delayed fracture. By reducing the P content, the delay destructive resistance can be improved. The P content is 0.020% or less, preferably 0.015% or less, more preferably 0.010% or less. The smaller the P content, the better, but zero is difficult to manufacture, and sometimes contains about 0.003% as an unavoidable impurity.
S亦與P同樣，是以在結晶粒界濃化而使得鋼的韌度延展性降低且使耐延遲破壞性劣化之雜質元素。藉由使S含量減少，能提升耐延遲破壞性。S含量為0.020%以下， 較佳為0.015%以下，更佳為0.010%以下。S含量為愈少愈佳，零在製造上有困難，有時含有0.003%左右作為不可避免的雜質。 Similarly to P, S is an impurity element which is concentrated at a crystal grain boundary to lower the ductility of steel and to deteriorate the resistance to delayed fracture. By reducing the S content, the retardation resistance can be improved. The S content is below 0.020%, It is preferably 0.015% or less, more preferably 0.010% or less. The smaller the S content, the better, the zero is difficult to manufacture, and sometimes it is about 0.003% as an unavoidable impurity.
Cr是提升鋼的耐腐蝕性並且用於確保耐延遲破壞性之有效元素。且，球狀化退火時，由於Cr成為球狀化的核而促進軟質化。為了發揮這種效果，Cr含量為0.3%以上，較佳為0.4%以上，更佳為0.5%以上。另一方面，若Cr含量過剩則生成粗大的Cr系碳化物，使得韌度延展性降低。因而，Cr含量為1.5%以下，較佳為1.4%以下，更佳為1.3%以下。 Cr is an effective element for improving the corrosion resistance of steel and for ensuring resistance to delayed damage. Further, in the spheroidizing annealing, since Cr becomes a spheroidized core, softening is promoted. In order to exert such an effect, the Cr content is 0.3% or more, preferably 0.4% or more, and more preferably 0.5% or more. On the other hand, if the Cr content is excessive, coarse Cr-based carbides are formed, and the ductility of the toughness is lowered. Therefore, the Cr content is 1.5% or less, preferably 1.4% or less, more preferably 1.3% or less.
Al是作為脫氧劑之作用並且形成氮化物使結晶粒細微化之有效元素。為了發揮這種效果，Al含量為0.02%以上，較佳為0.03%以上，更佳為0.035%以上。另一方面，若Al含量過剩則生成粗大的氮化物，使得結晶粒粗大化且冷鍛性或耐延遲破壞性劣化。因而，Al含量為0.10%以下，較佳為0.08%以下，更佳為0.06%以下。 Al is an effective element that acts as a deoxidizer and forms a nitride to refine the crystal grains. In order to exert such an effect, the Al content is 0.02% or more, preferably 0.03% or more, and more preferably 0.035% or more. On the other hand, if the Al content is excessive, a coarse nitride is formed, and the crystal grains are coarsened, and the cold forgeability or the delayed fracture resistance is deteriorated. Therefore, the Al content is 0.10% or less, preferably 0.08% or less, more preferably 0.06% or less.
N是生成Al和氮化物，用於使結晶粒細微化之有效元素。為了發揮這種效果，N含量為0.001%以上，較佳 為0.003%以上，更佳為0.004%以上。另一方面，若N含量過剩則不形成化合物，成為固溶狀態的N量增加，使得冷鍛性降低。因而，N含量為0.02%以下，較佳為0.01%以下，更佳為0.008%以下。 N is an effective element for generating Al and a nitride for finening crystal grains. In order to exert such an effect, the N content is 0.001% or more, preferably It is 0.003% or more, more preferably 0.004% or more. On the other hand, when the N content is excessive, no compound is formed, and the amount of N which becomes a solid solution state increases, and the cold forgeability is lowered. Therefore, the N content is 0.02% or less, preferably 0.01% or less, more preferably 0.008% or less.
本發明之螺栓用鋼線的基本化學成分組成係如上述，其餘部實質上是鐵。但是，鋼中含有由於原料、資材、製造設備等的狀況而帶入的不可避免的雜質，當然是容許的。且，本發明之螺栓用鋼線因應需要而含有以下元素亦有效。 The basic chemical composition of the steel wire for bolts of the present invention is as described above, and the remaining portion is substantially iron. However, it is of course permissible that steel contains unavoidable impurities brought in by the conditions of raw materials, materials, manufacturing equipment, and the like. Further, the steel wire for bolts of the present invention is also effective as long as it contains the following elements.
Cu、Ni、Sn是提升鋼的耐腐蝕性並且提升耐延遲破壞性之有效元素。為了發揮這種效果，Cu含量較佳為0.03%以上，更佳為0.1%以上，再更佳為0.15%以上。且，Ni含量較佳為0.1%以上，更佳為0.2%以上，再更佳為0.3%以上。Sn含量較佳為0.03%以上，更佳為0.1%以上，再更佳為0.15%以上。 Cu, Ni, and Sn are effective elements for improving the corrosion resistance of steel and improving the resistance to delayed fracture. In order to exert such an effect, the Cu content is preferably 0.03% or more, more preferably 0.1% or more, still more preferably 0.15% or more. Further, the Ni content is preferably 0.1% or more, more preferably 0.2% or more, still more preferably 0.3% or more. The Sn content is preferably 0.03% or more, more preferably 0.1% or more, still more preferably 0.15% or more.
另一方面，若Cu含量過剩，則熱延展性降低使得鋼的生產性降低。Cu含量較佳為0.5%以下，更佳為0.4%以下，再更佳為0.35%以下。且，若Ni或Sn含量過剩則耐腐蝕性提升效果飽和。Ni含量較佳為1.0%以下，更佳為0.8%以下，再更佳為0.7%以下。Sn含量較佳為 0.5%以下，更佳為0.4%以下，再更佳為0.3%以下。 On the other hand, if the Cu content is excessive, the hot ductility is lowered to lower the productivity of steel. The Cu content is preferably 0.5% or less, more preferably 0.4% or less, still more preferably 0.35% or less. Further, if the content of Ni or Sn is excessive, the corrosion resistance improving effect is saturated. The Ni content is preferably 1.0% or less, more preferably 0.8% or less, still more preferably 0.7% or less. The Sn content is preferably 0.5% or less, more preferably 0.4% or less, still more preferably 0.3% or less.
Ti、Nb及Zr是與C或N形成碳氮化物，使結晶粒細微化之有效元素。且，藉由形成氮化物使得固溶狀態的N量減少，因此也是提升冷鍛性之有效元素。為了發揮該等效果，Ti含量較佳為0.02%以上，更佳為0.03%以上，再更佳為0.04%以上。Nb含量為較佳為0.02%以上，更佳為0.03%以上，再更佳為0.04%以上。且，Zr含量為0.03%以上，更佳為0.08%以上，再更佳為0.10%以上。 Ti, Nb, and Zr are effective elements for forming a carbonitride with C or N and making the crystal grains fine. Further, since the amount of N in the solid solution state is reduced by the formation of the nitride, it is also an effective element for improving the cold forgeability. In order to exert such effects, the Ti content is preferably 0.02% or more, more preferably 0.03% or more, still more preferably 0.04% or more. The Nb content is preferably 0.02% or more, more preferably 0.03% or more, still more preferably 0.04% or more. Further, the Zr content is 0.03% or more, more preferably 0.08% or more, still more preferably 0.10% or more.
另一方面，若Ti、Nb及Zr過剩，則形成粗大的碳氮化物，使得冷鍛性或耐延遲破壞性劣化。Ti含量較佳為0.1%以下，更佳為0.08%以下，再更佳為0.06%以下。Nb含量較佳為0.1%以下，更佳為0.08%以下，再更佳為0.06%以下。Zr含量較佳為0.3%以下，更佳為0.25%以下，再更佳為0.2%以下。 On the other hand, if Ti, Nb, and Zr are excessive, a coarse carbonitride is formed, and the cold forgeability or the delayed fracture resistance is deteriorated. The Ti content is preferably 0.1% or less, more preferably 0.08% or less, still more preferably 0.06% or less. The Nb content is preferably 0.1% or less, more preferably 0.08% or less, still more preferably 0.06% or less. The Zr content is preferably 0.3% or less, more preferably 0.25% or less, still more preferably 0.2% or less.
Mo、W是提高鋼的強度，並且在鋼中形成細微的析出物以提升耐延遲破壞性之有效元素。為了獲得這種效果，含有Mo及W中至少1種為佳。Mo含量較佳為0.05 %以上，更佳為0.15%以上，再更佳為0.20%以上。W含量較佳為0.03%以上，更佳為0.08%，再更佳為0.10%。另一方面，若Mo、W含量過剩則製造成本上漲。Mo含量較佳為3%以下，更佳為2%以下，再更佳為1.5%以下。W含量較佳為0.5%以下，更佳為0.4%以下，再更佳為0.35%以下。 Mo and W are effective elements for increasing the strength of steel and forming fine precipitates in the steel to improve the resistance to delayed fracture. In order to obtain such an effect, it is preferred to contain at least one of Mo and W. The Mo content is preferably 0.05 More than %, more preferably 0.15% or more, still more preferably 0.20% or more. The W content is preferably 0.03% or more, more preferably 0.08%, still more preferably 0.10%. On the other hand, if the Mo and W contents are excessive, the manufacturing cost increases. The Mo content is preferably 3% or less, more preferably 2% or less, still more preferably 1.5% or less. The W content is preferably 0.5% or less, more preferably 0.4% or less, still more preferably 0.35% or less.
V是淬火加熱時，藉由在固溶、回火時以碳化物析出而生成氫捕集位置，對提升耐延遲破壞性有效。為了發揮這種效果，V含量較佳為0.01%以上，更佳為0.05%以上，再更佳為0.08%以上。另一方面，若V含量過剩則形成粗大的碳氮化物，使得冷鍛性惡化，因此V含量較佳為0.5%以下，更佳為0.4%以下，再更佳為0.3%以下。 When V is quenched and heated, the hydrogen trapping position is formed by precipitation of carbides during solid solution or tempering, which is effective for improving the resistance to delayed fracture. In order to exert such an effect, the V content is preferably 0.01% or more, more preferably 0.05% or more, still more preferably 0.08% or more. On the other hand, if the V content is excessive, a coarse carbonitride is formed and the cold forgeability is deteriorated. Therefore, the V content is preferably 0.5% or less, more preferably 0.4% or less, still more preferably 0.3% or less.
Mg、Ca是形成碳氮化物，防止淬火加熱時的沃斯田鐵結晶粒粗大化，對提升韌度延展性、提升耐延遲破壞性有效。為了發揮這種效果，Mg含量較佳為0.001%以上，更佳為0.002%以上，再更佳為0.003%以上。Ca含量較佳為0.001%以上，更佳為0.002%以上，再更佳為0.003%以上。另一方面，若Mg、Ca含量過剩，則上述效果飽和而造成製造成本增加。Mg含量較佳為0.01%以下，更佳為 0.007%以下，再更佳為0.005%以下。Ca含量較佳為0.01%以下，更佳為0.007%以下，再更佳為0.005%以下。 Mg and Ca are carbon nitrides, which prevent the coarsening of the Worthite iron crystal grains during quenching and heating, and are effective for improving toughness ductility and improving retardation resistance. In order to exert such an effect, the Mg content is preferably 0.001% or more, more preferably 0.002% or more, still more preferably 0.003% or more. The Ca content is preferably 0.001% or more, more preferably 0.002% or more, still more preferably 0.003% or more. On the other hand, if the Mg and Ca contents are excessive, the above effects are saturated and the manufacturing cost is increased. The Mg content is preferably 0.01% or less, more preferably 0.007% or less, more preferably 0.005% or less. The Ca content is preferably 0.01% or less, more preferably 0.007% or less, still more preferably 0.005% or less.
本發明之螺栓用鋼線，可將具有上述化學成分之鋼材進行熔製、鑄造、熱鍛造而製得的螺栓用線材，因應需要而進行脫銹皮、熱處理、皮膜處理、伸線而製造。 In the steel wire for bolts of the present invention, the wire for bolts obtained by melting, casting, and hot forging the steel material having the above chemical composition can be produced by peeling, heat treatment, film treatment, and wire drawing as needed.
首先，說明螺栓用線材之製造方法。螺栓用線材之製造方法不限定下述製造方法，但為了提升酸洗性及耐延遲破壞性，期望在輥軋前的鋼胚再加熱時，加熱至950℃以上(以下，也稱為「鋼胚再加熱溫度」)，在900~1100℃的溫度範圍進行精加工輥軋成為線材或棒鋼形狀後，接著以0.5~13℃/秒的平均冷卻速度進行冷卻。 First, a method of manufacturing a wire for bolts will be described. The method for producing the wire for bolts is not limited to the following production method. However, in order to improve the pickling property and the delayed fracture resistance, it is desirable to heat the steel preform before rolling to 950 ° C or higher (hereinafter, also referred to as "steel The embryo reheating temperature ") is subjected to finishing rolling in a temperature range of 900 to 1100 ° C to form a wire or a steel bar shape, followed by cooling at an average cooling rate of 0.5 to 13 ° C / sec.
鋼胚再加熱時，為了降低熱鍛造時的變形阻力，鋼胚再加熱溫度較佳為950℃以上，更佳為1000℃以上。若該溫度未達950℃，則熱鍛造時的變形阻力增大。另一方面，若鋼胚再加熱溫度變得過高，則變成接近於鋼的熔解溫度。因而，鋼胚再加熱溫度較佳為1400℃以下，更佳為1300℃以下，再更佳為1250℃以下。 When the steel preform is reheated, in order to reduce the deformation resistance during hot forging, the reheating temperature of the steel preform is preferably 950 ° C or higher, more preferably 1000 ° C or higher. If the temperature is less than 950 ° C, the deformation resistance during hot forging increases. On the other hand, if the steel reheating temperature becomes too high, it becomes close to the melting temperature of steel. Therefore, the steel reheating temperature is preferably 1400 ° C or lower, more preferably 1300 ° C or lower, and still more preferably 1250 ° C or lower.
若精加工輥軋溫度變得過低，則變成肥粒鐵-沃斯田鐵之2相區域，被促進脫碳。且，若肥粒鐵結晶粒變得過 細則強度變高，使得冷鍛性惡化。因而，精加工輥軋溫度較佳為900℃以上，更佳為950℃以上。另一方面，若精加工輥軋溫度變得過高則肥粒鐵結晶粒粗大化，使得冷鍛性劣化。因而，精加工輥軋溫度較佳為1100℃以下，更佳為1050℃以下。 If the finishing rolling temperature becomes too low, it becomes a two-phase region of the ferrite-iron-Worstian iron, and is promoted to decarburization. And, if the ferrite iron crystal grain has become The strength of the specification becomes high, which deteriorates the cold forgeability. Therefore, the finishing rolling temperature is preferably 900 ° C or higher, more preferably 950 ° C or higher. On the other hand, if the finishing rolling temperature becomes too high, the ferrite-grain crystal grains are coarsened, and the cold forgeability is deteriorated. Therefore, the finishing rolling temperature is preferably 1100 ° C or lower, more preferably 1050 ° C or lower.
此外，於含有Ti或Nb等添加元素之情形，也是在與上述精加工輥軋溫度同樣的溫度範圍為佳。若精加工輥軋溫度較佳為900℃以上，更佳為950℃以上，則添加元素能以細微之碳、氮化物析出於鋼中。另一方面，若精加工輥軋溫度較佳為1100℃以下，更佳為1050℃以下，則能充分地析出碳、氮化物。 Further, in the case of containing an additive element such as Ti or Nb, it is also preferable to have the same temperature range as the above-described finishing rolling temperature. If the finishing rolling temperature is preferably 900 ° C or higher, more preferably 950 ° C or higher, the added element can be precipitated into the steel with fine carbon or nitride. On the other hand, if the finishing rolling temperature is preferably 1100 ° C or lower, more preferably 1050 ° C or lower, carbon and nitride can be sufficiently precipitated.
若精加工輥軋後的平均冷卻速度變得過快，則表層生成麻田散鐵，使得酸洗性惡化。因而，精加工輥軋後的平均冷卻速度較佳為13℃/秒以下，更佳為8℃/秒以下。另一方面，若輥軋後的平均冷卻速度變得過慢，則生產性惡化。因而，精加工輥軋後的平均冷卻速度較佳為0.5℃/秒以上，更佳為1.0℃/秒以上。 If the average cooling rate after finishing rolling becomes too fast, the surface layer generates granulated iron, which deteriorates the pickling property. Therefore, the average cooling rate after finishing rolling is preferably 13 ° C / sec or less, more preferably 8 ° C / sec or less. On the other hand, if the average cooling rate after rolling becomes too slow, productivity will deteriorate. Therefore, the average cooling rate after finishing rolling is preferably 0.5 ° C / sec or more, more preferably 1.0 ° C / sec or more.
接著，說明從所得到的線材製造本發明之螺栓用鋼線之製造方法。本發明之螺栓用鋼線不限定於下述製造方法，但為了提升冷鍛性及耐延遲破壞性，對上述線材可因應需要而組合進行(A)脫銹皮步驟、(B)熱處理步驟、(C)皮膜處理步驟、(D)伸線步驟而製造。從更進一步 提升冷鍛性的觀點而言，特別是(B)熱處理步驟的控制為重要。 Next, a method of manufacturing the steel wire for bolts of the present invention from the obtained wire material will be described. The steel wire for bolts of the present invention is not limited to the following production method. However, in order to improve the cold forgeability and the delayed fracture resistance, the wire material may be combined with (A) a peeling step and a (B) heat treatment step as needed. (C) a film treatment step and (D) a wire drawing step. From further From the viewpoint of improving the cold forgeability, in particular, the control of the (B) heat treatment step is important.
上述線材表面有時會附著有銹皮。銹皮是造成伸線時的缺陷或壓造時的裂痕之原因，因此線材附著有銹皮的情形，必須藉由鹽酸或硫酸等化學方法或珠擊、彎曲等物理方法除去銹皮。本發明可採用眾所周知的任何化學方法、物理方法。例如藉由化學方法將線材進行脫銹皮處理時，將線材在濃度25%左右、液溫70℃左右的鹽酸溶液中浸漬10分鐘左右進行酸洗為佳。未特別限定處理次數，反覆進行至可完全除去銹皮為佳。 The surface of the above-mentioned wire may sometimes have a scale attached thereto. The scale is the cause of the defect at the time of stretching or the crack at the time of extrusion. Therefore, in the case where the wire adheres to the scale, it is necessary to remove the scale by a chemical method such as hydrochloric acid or sulfuric acid or a physical method such as beading or bending. The present invention can employ any chemical method or physical method well known. For example, when the wire is subjected to descaling by a chemical method, it is preferred to immerse the wire in a hydrochloric acid solution having a concentration of about 25% and a liquid temperature of about 70 ° C for about 10 minutes for pickling. The number of treatments is not particularly limited, and it is preferably repeated until the scale can be completely removed.
熱處理步驟不僅是將鋼軟化，也調整結晶組織並且抑制過度的脫浸碳。尤其本發明是控制熱處理條件，使對於耐延遲破壞性造成不良影響的粗大的雪明碳鐵熔解，並且抑制成為球狀碳化物的核之含Cr之雪明碳鐵、V或Ti的碳氮化物之熔解。且，若藉由熱處理過度地進行脫碳，則表層的沃斯田鐵結晶粒徑因為淬火回火處理而粗大化，使得耐延遲破壞性惡化，因此控制熱處理條件以抑制脫碳。具體的的熱處理條件係於下述(i)~(v)表示。 The heat treatment step not only softens the steel, but also adjusts the crystal structure and suppresses excessive desorption of carbon. In particular, the present invention controls the heat treatment conditions to melt coarse ferritic carbon iron which adversely affects the delayed destructive property, and suppresses the carbon-containing nitrogen of Cr-containing swarf carbon iron, V or Ti which becomes the nucleus of the spheroidal carbide. Melting of the compound. When the decarburization is excessively performed by the heat treatment, the Worthite iron crystal grain size of the surface layer is coarsened by the quenching and tempering treatment, and the retardation resistance is deteriorated. Therefore, the heat treatment conditions are controlled to suppress decarburization. The specific heat treatment conditions are shown in the following (i) to (v).
(i)熱處理溫度：為了熔解粗大的雪明碳鐵，熱處理溫度為700℃以上，較佳為715℃以上，更佳為 720℃以上。另一方面，若溫度為變得過高，則成為球狀碳化物的核之碳化物熔解。因而，熱處理溫度為800℃以下，較佳為780℃以下，更佳為770℃以下。此外，熱處理溫度只要是在上述範圍內則不需要均熱。 (i) Heat treatment temperature: in order to melt coarse ferritic carbon, the heat treatment temperature is 700 ° C or higher, preferably 715 ° C or higher, more preferably Above 720 °C. On the other hand, if the temperature is too high, the carbide which becomes a nucleus of the spherical carbide melts. Therefore, the heat treatment temperature is 800 ° C or lower, preferably 780 ° C or lower, more preferably 770 ° C or lower. Further, the heat treatment temperature does not require soaking as long as it is within the above range.
(ii)熱處理時間：為了使粗大的雪明碳鐵熔解，於上述熱處理溫度保持的時間為2小時以上，較佳為3小時以上，更佳為3.5小時以上。另一方面，若熱處理時間變得過長，則成為球狀碳化物的核之碳化物熔解。因而，若熱處理時間為15小時以下，較佳為12小時以下，更佳為10小時以下。 (ii) Heat treatment time: The time for maintaining the heat treatment temperature is 2 hours or longer, preferably 3 hours or longer, more preferably 3.5 hours or longer, in order to melt the coarse snowy carbon. On the other hand, if the heat treatment time becomes too long, the carbide which becomes a nucleus of the spherical carbide melts. Therefore, when the heat treatment time is 15 hours or shorter, it is preferably 12 hours or shorter, more preferably 10 hours or shorter.
(iii)平均冷卻速度：上述熱處理時間保持後，進行冷卻。為了在冷卻過程中使碳化物球狀化，平均冷卻速度較佳為20℃/hr以下，更佳為15℃/hr以下。另一方面，若平均冷卻速度變得過慢則生產性惡化，因此是3℃/hr以上，較佳為4℃/hr以上，更佳為5℃/hr。 (iii) Average cooling rate: After the above heat treatment time is maintained, cooling is performed. In order to spheroidize the carbide during cooling, the average cooling rate is preferably 20 ° C / hr or less, more preferably 15 ° C / hr or less. On the other hand, if the average cooling rate becomes too slow, productivity is deteriorated, and therefore it is 3 ° C / hr or more, preferably 4 ° C / hr or more, and more preferably 5 ° C / hr.
(iv)抽出溫度：為了使碳化物充分地球狀化，必須控制熱處理爐的抽出溫度。抽出溫度較佳為750℃以下，更佳為720℃以下。另一方面，若抽出溫度變得過低則生產性惡化。因而，抽出溫度較佳為650℃以上，更佳為680℃以上。 (iv) Extraction temperature: In order to make the carbide sufficiently earthy, it is necessary to control the extraction temperature of the heat treatment furnace. The extraction temperature is preferably 750 ° C or lower, more preferably 720 ° C or lower. On the other hand, if the extraction temperature becomes too low, productivity is deteriorated. Therefore, the extraction temperature is preferably 650 ° C or higher, more preferably 680 ° C or higher.
(v)熱處理氛圍：若過度的脫碳進行則表層的結晶粒粗大化，使得耐延遲破壞性或疲勞特性惡化。為了抑制過度的脫碳，將爐內氛圍設定為一氧化碳和二氧化碳的混合氣，且必須控制爐內的碳位能(以下稱為「CP 值」)。CP值是母材C量的60%以上，較佳為65%以上，更佳為70%以上。另一方面，若CP值變得過高則滲碳而使得耐延遲破壞性惡化。因而，CP值為母材C量的120%以下，較佳為100%以下，更佳為90%以下。此外，CP值是測量設置在爐內的線圈狀的鋼琴線(以下稱為「CP線圈」)的碳量之值。 (v) Heat treatment atmosphere: If excessive decarburization is carried out, the crystal grains of the surface layer are coarsened, so that the delayed fracture resistance or the fatigue property is deteriorated. In order to suppress excessive decarburization, the atmosphere in the furnace is set to a mixture of carbon monoxide and carbon dioxide, and the carbon potential energy in the furnace must be controlled (hereinafter referred to as "CP" value"). The CP value is 60% or more of the amount of the base material C, preferably 65% or more, and more preferably 70% or more. On the other hand, if the CP value becomes too high, carburization causes the deterioration resistance to deterioration. Therefore, the CP value is 120% or less, preferably 100% or less, and more preferably 90% or less of the amount of the base material C. Further, the CP value is a value for measuring the amount of carbon of a coil-shaped piano wire (hereinafter referred to as "CP coil") provided in the furnace.
皮膜處理步驟中，為了防止伸線加工或冷壓造時的焦化或缺陷而施以潤滑性塗布。本發明中可使用各種眾所周知的皮膜劑。在1400MPa以上的高強度螺栓例示鈣皮膜、非磷皮膜，及磷酸鹽皮膜等。皮膜處理方法亦未有特別限定，在潤滑劑溶液或皮膜劑溶液例如浸漬3~15分鐘左右為佳。 In the film treatment step, lubricity coating is applied in order to prevent coking or defects during wire drawing or cold press forming. Various well-known coating agents can be used in the present invention. High-strength bolts of 1400 MPa or more are exemplified by a calcium film, a non-phosphorus film, and a phosphate film. The film treatment method is also not particularly limited, and it is preferably immersed in the lubricant solution or the film solution for about 3 to 15 minutes.
在伸線步驟藉由模具等反覆進行冷伸線，對具有目的的線徑、性能之線進行精加工。伸線加工藉由各種眾所周知的方法進行即可，未有特別限定。 In the step of stretching, the cold drawing line is repeatedly formed by a mold or the like, and the wire having the desired wire diameter and performance is finished. The wire drawing processing is carried out by various well-known methods, and is not particularly limited.
上述(a)~(d)的各步驟亦可因應需要而反覆進行，且，組合亦可因應要求特性等而適當選擇。藉由上述製造方法製得的鋼線係具有拉伸強度1400MPa以上，化學成分組成被適當地控制，並且鋼線的脫碳、浸碳也被適當地控制，因此具有優異的耐延遲破壞性。且，肥粒鐵結 晶粒度和球狀化率被適當地控制，因此具有優異的冷鍛性。 The steps (a) to (d) above may be repeated as needed, and the combination may be appropriately selected depending on the required characteristics and the like. The steel wire obtained by the above-described production method has a tensile strength of 1400 MPa or more, and the chemical composition is appropriately controlled, and the decarburization and carbon immersion of the steel wire are also appropriately controlled, so that it has excellent retardation resistance. And fat iron knot The grain size and the spheroidization rate are appropriately controlled, and thus have excellent cold forgeability.
本發明之螺栓，可藉由冷壓造等將上述鋼線成型為螺栓，進一步藉由進行淬火回火處理而製造螺栓。為了控制沃斯田鐵結晶粒徑，期望淬火前的加熱溫度較佳為930℃以下，更佳為920℃以下，進一步更佳為910℃以下。另一方面，若淬火前加熱溫度過低則淬火時無法充分地進行麻田散鐵變態，而無法得到必要的強度。因而，淬火前的加熱溫度較佳為870℃以上，更佳為880℃以上，進一步更佳為890℃以上。其他的淬火前加熱條件未有特別限定，以下條件為例示。 In the bolt of the present invention, the steel wire can be formed into a bolt by cold pressing or the like, and the bolt can be further produced by quenching and tempering. In order to control the grain size of the Worthite iron, it is desirable that the heating temperature before quenching is 930 ° C or less, more preferably 920 ° C or less, still more preferably 910 ° C or less. On the other hand, if the heating temperature before quenching is too low, the numb iron can not be sufficiently deformed at the time of quenching, and the necessary strength cannot be obtained. Therefore, the heating temperature before quenching is preferably 870 ° C or higher, more preferably 880 ° C or higher, and still more preferably 890 ° C or higher. Other pre-quenching heating conditions are not particularly limited, and the following conditions are exemplified.
淬火前加熱時間：10~45分鐘 Heating time before quenching: 10~45 minutes
冷卻方法：油冷，溫度：室溫~70℃ Cooling method: oil cooling, temperature: room temperature ~ 70 ° C
爐內氛圍：一氧化碳(RX氣體)和二氧化碳的混合氛圍、氮氛圍、大氣氛圍等。 Furnace atmosphere: a mixed atmosphere of carbon monoxide (RX gas) and carbon dioxide, a nitrogen atmosphere, an atmospheric atmosphere, and the like.
溫度、時間等回火條件可因應必要的強度而適當變更。藉由使用本發明之鋼線，可得到顯示1400MPa以上的拉伸強度和優異的耐破壞性之螺栓。 The tempering conditions such as temperature and time can be appropriately changed depending on the necessary strength. By using the steel wire of the present invention, a bolt exhibiting tensile strength of 1400 MPa or more and excellent fracture resistance can be obtained.
本發明之螺栓的沃斯田鐵結晶粒已細微化。沃斯田鐵結晶粒是愈細微則其韌度延展性愈提升，且耐延遲破壞性提升。為了藉由本發明之化學成分組成、拉伸強度確保耐延遲破壞性，表層及在d/4位置的沃斯田鐵結晶粒度編號皆較佳為No.7以上，更佳為No.9以上。沃斯田鐵結晶粒愈細微愈佳，於通常的熱處理大致No.14以 下。 The Worthite iron crystal grains of the bolt of the present invention have been refined. The finer the Woustian iron crystal grain is, the more the ductility is enhanced, and the resistance to delayed damage is improved. In order to ensure the delayed fracture resistance by the chemical composition and the tensile strength of the present invention, the surface layer and the Worstian iron crystal grain size number at the d/4 position are preferably No. 7 or more, and more preferably No. 9 or more. The finer and finer the Worthite iron crystal grain, the general heat treatment is roughly No.14. under.
本申請案係基於2015年3月27日提出的日本專利申請案第2015-066204號而主張優先權之利益。日本專利申請案第2015-066204號的說明書之全部內容，被援用於作為本申請案之參考。 The present application claims the benefit of priority based on Japanese Patent Application No. 2015-066204 filed on March 27, 2015. The entire contents of the specification of Japanese Patent Application No. 2015-066204 are hereby incorporated herein by reference.
以下，舉出實施例更具體地說明本發明，本發明原本就不受下述實施例限制，當然也可以在能適合前、後述之趣旨之範圍內加以適當地變更而實施，該等皆包含於本發明之技術範圍。 In the following, the present invention will be more specifically described by the following examples, and the present invention is not limited to the following examples, and may be appropriately modified and implemented within the scope of the present invention. It is within the technical scope of the present invention.
將下述表1所示之化學成分組成的鋼材予以熔煉，進行鑄造、熱輥軋，製造出直徑12mmΦ或9.3mmΦ的線材。此時，以表2所示之條件，進行鋼胚再加熱、精加工輥軋、以精加工輥軋後的平均冷卻速度進行而得到線材。在該線材以表2所示之組合進行(A)脫銹皮步驟、(B)熱處理步驟、(C)皮膜處理步驟、(D)伸線步驟而製造成直徑9.06mm的鋼線。各步驟之條件如下述。 A steel material having the chemical composition shown in Table 1 below was melted, cast, and hot rolled to produce a wire having a diameter of 12 mm Φ or 9.3 mm Φ. At this time, the steel material was reheated, finished, and rolled under the conditions shown in Table 2, and the wire was obtained by the average cooling rate after finishing rolling. The wire was subjected to (A) derusting step, (B) heat treatment step, (C) film treatment step, and (D) wire drawing step in the combination shown in Table 2 to produce a steel wire having a diameter of 9.06 mm. The conditions of each step are as follows.
(A)脫銹皮步驟：「P」 (A) Descaling step: "P"
在25%鹽酸(70℃)浸漬10分鐘而除去銹皮。 The scale was removed by dipping in 25% hydrochloric acid (70 ° C) for 10 minutes.
(B)熱處理步驟：「SA」 (B) Heat treatment step: "SA"
(i)熱處理溫度、(ii)熱處理時間、(iii)平均冷卻速度係以表2所示之條件進行。(iv)抽出溫度為690℃，(v)熱處理氛圍係一氧化碳(RX氣體)和二氧化碳的混合氣。 (i) heat treatment temperature, (ii) heat treatment time, and (iii) average cooling rate were carried out under the conditions shown in Table 2. (iv) The extraction temperature was 690 ° C, and (v) the heat treatment atmosphere was a mixture of carbon monoxide (RX gas) and carbon dioxide.
(C)皮膜處理步驟：「L」 (C) Film treatment step: "L"
鈣皂槽浸漬10分鐘進行鈣皮膜處理。 Calcium soap bath was immersed for 10 minutes for calcium film treatment.
(D)伸線步驟：「Dr」 (D) Stretching step: "Dr"
Φ12.0mm的輥軋材：試驗No.1~3、6、7、10、11、16、17、19~22、27、28、31~34、37~40、42~45： Rolled material of Φ12.0mm: Test No. 1~3, 6, 7, 10, 11, 16, 17, 19~22, 27, 28, 31~34, 37~40, 42~45:
使用伸線模具以伸線速度1m/秒從Φ12.0mm伸線至Φ9.3mm，然後實施熱處理、酸洗、皮膜處理後，實施精加工伸線至Φ9.06mm。 Using a wire drawing die, the wire is stretched from Φ12.0 mm to Φ9.3 mm at a wire speed of 1 m/sec, and then subjected to heat treatment, pickling, and film treatment, and then the finished wire is stretched to Φ9.06 mm.
Φ9.3mm的輥軋材：試驗No.4、5、8、9、12~15、18、23~26、29、30、35、36、41： Rolled Φ9.3mm: Test No. 4, 5, 8, 9, 12~15, 18, 23~26, 29, 30, 35, 36, 41:
使用伸線模具以伸線速度1m/秒伸線至Φ9.06mm。 Using a wire drawing die, the wire was stretched at a speed of 1 m/sec to Φ 9.06 mm.
測量上述各鋼線的肥粒鐵結晶粒度、球狀化率，從表層起深度0.1mm位置之C量。 The grain size and spheroidization ratio of the ferrite iron of each of the above steel wires were measured, and the amount of C at a depth of 0.1 mm from the surface layer was measured.
對鋼線的軸沿著垂直的剖面(以下稱為「橫剖面」)切斷後，將該橫剖面的直徑d×1/4位置(以下稱為「d/4位置」)的任意0.039mm2之區域，藉由倍率400倍的光學顯微鏡觀察，按照JIS G 0551(2015)規定的「鋼-結晶粒度之顯微鏡試驗方法」測量肥粒鐵結晶粒度。在各4個視野測量且將其平均值作為肥粒鐵結晶粒度編號。 When the axis of the steel wire is cut along a vertical cross section (hereinafter referred to as "cross section"), the diameter of the cross section is d × 1/4 (hereinafter referred to as "d/4 position") of any 0.039 mm 2 . In the region, the grain size of the ferrite iron crystal was measured in accordance with the "microscopic test method for steel-crystal grain size" prescribed in JIS G 0551 (2015) by an optical microscope at a magnification of 400 times. The average value was measured in each of the four fields of view and the average value was taken as the grain size of the ferrite iron crystal.
在切斷的鋼線的橫剖面之d/4位置的任意部位，藉由 倍率4000倍、觀察視野30μm×23μm的掃描型電子顯微鏡觀察，拍攝10張照片。將各照片進行圖像解析，算出長寬比相對於碳化物的總數為2.0以下的碳化物的個數比例，將10張照片的結果進行算術平均者，作為各採樣的球狀化率。此外，掃描型電子顯微鏡觀察時，係以具有可測量的0.0025μm2左右以上的面積之碳化物作為對象。 Ten photographs were taken at any position at the d/4 position of the cross section of the cut steel wire by a scanning electron microscope at a magnification of 4000 times and an observation field of 30 μm × 23 μm. Each photograph was subjected to image analysis, and the ratio of the number of carbides having an aspect ratio to the total number of carbides of 2.0 or less was calculated, and the results of the ten photographs were arithmetically averaged as the spheroidization ratio of each sample. Further, in the observation by a scanning electron microscope, a carbide having an measurable area of about 0.0025 μm 2 or more is targeted.
從表層起深度0.1mm位置之C量為，藉由EPMA(Electron Probe Micro Analyzer)線分析而測定。且，使用該測量值算出相對於表1記載的母材C量之比例。 The amount of C from the surface layer at a depth of 0.1 mm was measured by EPMA (Electron Probe Micro Analyzer) line analysis. Further, the ratio of the amount of the base material C described in Table 1 was calculated using the measured value.
使用多段模具藉由冷壓造，從上述各鋼線製作M10mm×P1.5mm、長度80mm的凸緣螺栓。此外，M意指軸部之直徑，P意指間距。 A flange bolt of M10 mm × P 1.5 mm and a length of 80 mm was produced from each of the above steel wires by cold press using a multi-stage mold. Further, M means the diameter of the shaft portion, and P means the pitch.
上述冷壓造時，根據凸緣裂痕之有無而評價冷鍛性。冷鍛性係於未產生裂痕時評價為合格「P」(Pass)，產生裂痕時為不合格「F」(Failure)。 At the time of the above cold press forming, the cold forgeability was evaluated based on the presence or absence of the crack of the flange. The cold forgeability was evaluated as "P" (Pass) when no crack occurred, and "F" (Failure) when cracking occurred.
在上述製作的螺栓，以表3所示之條件施行淬火、回火處理。此時，淬火的加熱時間為15分鐘，爐內氛圍為大氣氛圍，淬火為25℃之油冷。且，回火的加熱時間為45分鐘。此外，冷鍛性不合格的情形除外。 The bolts produced above were subjected to quenching and tempering treatment under the conditions shown in Table 3. At this time, the heating time of the quenching was 15 minutes, the atmosphere in the furnace was atmospheric, and the quenching was oil cooling at 25 °C. Moreover, the heating time for tempering is 45 minutes. In addition, the case where the cold forgeability is unqualified is excluded.
評價各螺栓的沃斯田鐵結晶粒徑、拉伸強度、耐延遲破壞性。 The Worthite iron crystal grain size, tensile strength, and retardation resistance of each bolt were evaluated.
在螺栓的軸部，相對於螺栓的軸沿著垂直的剖面(以下稱為橫剖面)切斷後，在該橫剖面的直徑d×1/4位置、及最表層的任意0.039mm2之區域，藉由倍率400倍的光學顯微鏡觀察，按照JIS G 0551(2015)規定的「鋼-結晶粒度之顯微鏡試驗方法」測量舊沃斯田鐵結晶粒度編號。在各4個視野測量且將其平均值作為沃斯田鐵結結晶粒度編 號。沃斯田鐵結晶粒度編號No.7以上為合格，未達No.7為不合格。 The shaft portion of the bolt is cut along a vertical cross section (hereinafter referred to as a cross section) with respect to the axis of the bolt, and is in a region of the diameter d×1/4 of the cross section and an arbitrary 0.039 mm 2 of the outermost layer. The old Worthite iron crystal grain size number was measured by an optical microscope observation at a magnification of 400 times in accordance with the "Microscopic test method for steel-crystal grain size" prescribed in JIS G 0551 (2015). The average value was measured in each of the four fields of view and the average value was taken as the Wolsfield iron crystal grain size number. The Worthite iron crystal grain size No. 7 or above was acceptable, and the No. 7 was unqualified.
按照JIS B 1051(2014)進行拉伸試驗以測量螺栓的拉伸強度。1400MPa以上為合格，未達1400MPa為不合格。 A tensile test was conducted in accordance with JIS B 1051 (2014) to measure the tensile strength of the bolt. 1400MPa or more is qualified, and less than 1400MPa is unqualified.
將螺栓治以降伏點為目標緊固於治具後，(a)各治具在1%HCl浸漬15分鐘，(b)在大氣中暴露24小時，(c)確認有無破斷，作為1循環，將此反覆10循環以進行評價。螺栓是對於1水準各評價10支，評價為1支都未破斷的情形為合格「P」，只要有1支破斷的情形為不合格「F」。 After tightening the bolt to the jig with the target of the drop point, (a) each jig is immersed in 1% HCl for 15 minutes, (b) exposed to the atmosphere for 24 hours, (c) confirmed whether there is any break, as 1 cycle This was repeated for 10 cycles for evaluation. The bolts are evaluated for each of the 10 levels, and the evaluation is that the one is not broken, and the condition is "P". If there is one break, the condition is "F".
從該等之結果可考察如下。試驗No.1~18、22、29、43~45係滿足本發明中規定的要件之發明例。該等皆為高強度且冷鍛性及耐延遲破壞性優異。 The results from these can be examined as follows. Test Nos. 1 to 18, 22, 29, and 43 to 45 are examples of the invention satisfying the requirements specified in the present invention. These are all high strength, and are excellent in cold forgeability and retardation resistance.
試驗No.19~21、23~28、30~42係未滿足本發明中規定的要件之例。 Test Nos. 19 to 21, 23 to 28, and 30 to 42 are examples in which the requirements specified in the present invention are not satisfied.
試驗No.19係退火時的溫度低之例。該例中，複合碳化物的熔解不充分，且球狀化率亦低，冷鍛性差。 Test No. 19 is an example in which the temperature at the time of annealing is low. In this example, the melting of the composite carbide is insufficient, the spheroidization rate is also low, and the cold forgeability is poor.
試驗No.20係退火時的溫度高之例。該例中，成為球狀碳化物的核之碳化物熔解，球狀化率變低且冷鍛性差。 Test No. 20 is an example in which the temperature at the time of annealing is high. In this example, the carbide which is a nucleus of the spherical carbide is melted, the spheroidization ratio is lowered, and the cold forgeability is inferior.
試驗No.21係退火時的冷卻速度快之例。該例中，球狀化率變低且冷鍛性差。 Test No. 21 is an example in which the cooling rate at the time of annealing is fast. In this example, the spheroidization rate is low and the cold forgeability is poor.
試驗No.23係退火時的時間短之例。該例中，軟質化未充分地進行，球狀化率變低且冷鍛性差。 Test No. 23 is an example in which the time during annealing is short. In this example, the softening was not sufficiently performed, the spheroidization ratio was lowered, and the cold forgeability was poor.
試驗No.24係退火時的時間長之例。該例中，成為球狀碳化物的核之碳化物熔解，且球狀化率變低且冷鍛性差。 Test No. 24 is an example of a long time during annealing. In this example, the carbide which is a nucleus of the spherical carbide is melted, and the spheroidization ratio is lowered and the cold forgeability is inferior.
試驗No.25係退火時的CP值低之例。該例中，表層產生過度的脫碳，由於淬火時沃斯田鐵結晶粒粗大化，因此耐延遲破壞性差。 Test No. 25 is an example in which the CP value at the time of annealing is low. In this example, the surface layer is excessively decarburized, and the Worthite iron crystal grains are coarsened at the time of quenching, so that the retardation resistance is poor.
試驗No.26係退火時的CP值高之例。該例中，表層產生過度的滲碳，由於表層的韌性延性降低，因此耐延遲破壞性劣化。 Test No. 26 is an example in which the CP value at the time of annealing is high. In this example, the surface layer is excessively carburized, and since the ductility ductility of the surface layer is lowered, the retardation resistance is deteriorated.
試驗No.27係精加工輥軋溫度低，在肥粒鐵-沃斯田鐵的2相區域輥軋之例。該例中，由於脫碳促進且表層的沃斯田鐵結晶粒粗大化，因此耐延遲破壞性惡化。 Test No. 27 is an example in which the finishing rolling temperature is low and rolling is performed in the 2-phase region of the ferrite-iron-Worstian iron. In this example, since the decarburization is promoted and the Worstian iron crystal grains in the surface layer are coarsened, the retardation resistance is deteriorated.
試驗No.28係精加工輥軋溫度高之例。該例中，肥粒鐵結晶粒粗大化且冷鍛性劣化。 Test No. 28 is an example in which the finishing rolling temperature is high. In this example, the ferrite iron crystal grains are coarsened and the cold forgeability is deteriorated.
試驗No.30係使用C含量低於本發明之下限的鋼種A1之例。該例中，未能確保1400MPa以上的拉伸強度。 Test No. 30 is an example in which steel type A1 having a C content lower than the lower limit of the present invention is used. In this example, the tensile strength of 1400 MPa or more was not secured.
試驗No.31係使用C含量高於本發明之上限的鋼種B1之例。該例中，由於韌度延展性降低，因此耐延遲破壞性差。 Test No. 31 is an example in which the steel type B1 having a C content higher than the upper limit of the present invention is used. In this example, since the ductility is lowered, the delay resistance is poor.
試驗No.32係使用Si含量低於本發明之下限的鋼種C1之例。該例中，由於回火時粗大的雪明碳鐵析出，因此耐延遲破壞性差。 Test No. 32 is an example in which steel type C1 having a Si content lower than the lower limit of the present invention is used. In this example, since the coarse ferritic carbon is precipitated during tempering, the retardation resistance is poor.
試驗No.33係使用Si含量高於本發明之上限的鋼種D1之例。該例中，鋼線的強度變得過高，冷鍛性劣化。 Test No. 33 is an example in which steel type D1 having a Si content higher than the upper limit of the present invention is used. In this example, the strength of the steel wire becomes too high, and the cold forgeability deteriorates.
試驗No.34係使用Mn含量低於本發明之下限的鋼種E1之例。該例中，生成大量FeS，因此耐延遲破壞性差。 Test No. 34 is an example in which steel type E1 having a Mn content lower than the lower limit of the present invention is used. In this example, a large amount of FeS is generated, and thus the delay resistance is poor.
試驗No.35係使用Mn含量高於本發明之上限的鋼種F1之例。該例中，由於MnS粗大化，因此冷鍛性差。 Test No. 35 is an example in which steel type F1 having a Mn content higher than the upper limit of the present invention is used. In this example, since the MnS is coarsened, the cold forgeability is poor.
試驗No.36係使用P含量高於本發明之上限的鋼種G1之例。該例中，由於韌度延展性降低，因此耐延遲破壞性差。 Test No. 36 is an example in which the steel type G1 having a P content higher than the upper limit of the present invention is used. In this example, since the ductility is lowered, the delay resistance is poor.
試驗No.37係使用S含量高於本發明之上限 的鋼種H1之例。該例中，由於韌度延展性降低，因此耐延遲破壞性差。 Test No. 37 uses an S content higher than the upper limit of the present invention. An example of a steel type H1. In this example, since the ductility is lowered, the delay resistance is poor.
試驗No.38係使用Cr添加量低於本發明之下限的鋼種I1之例。該例中，軟質化無法充分地進行，冷鍛性差。 Test No. 38 is an example in which the steel type I1 in which the Cr addition amount is lower than the lower limit of the present invention is used. In this example, the softening cannot be sufficiently performed, and the cold forgeability is poor.
試驗No.39係使用Cr含量高於本發明之上限的鋼種J1之例。該例中，粗大的Cr碳化物生成且耐延遲破壞性差。 Test No. 39 is an example in which the steel type J1 having a Cr content higher than the upper limit of the present invention is used. In this example, coarse Cr carbide is formed and the retardation resistance is poor.
試驗No.40係使用Al含量低於本發明之下限的鋼種K1之例。該例中，肥粒鐵結晶粒粗大化且冷鍛性差。 Test No. 40 is an example in which the steel type K1 having an Al content lower than the lower limit of the present invention is used. In this example, the ferrite iron crystal grains are coarsened and the cold forgeability is poor.
試驗No.41係使用Al含量高於本發明之上限的鋼種L1之例。該例中，粗大的AlN生成，因此冷鍛性差。 Test No. 41 is an example in which the steel type L1 having an Al content higher than the upper limit of the present invention is used. In this example, coarse AlN is formed, so cold forgeability is poor.
試驗No.42係使用N含量高於本發明之上限的鋼種M1之例。該例中，由於固溶N量增加，因此冷鍛性差。 Test No. 42 is an example in which the steel type M1 having a N content higher than the upper limit of the present invention is used. In this example, since the amount of solid solution N is increased, cold forgeability is poor.
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| CN111910124A (en) * | 2020-07-31 | 2020-11-10 | 深圳市润安科技发展有限公司 | Anti-stretch-fold component in wrist strap and preparation method thereof |
| CN112011742B (en) * | 2020-10-22 | 2021-01-22 | 江苏省沙钢钢铁研究院有限公司 | Wire rod for 5000MPa grade diamond wire and production method thereof |
| CN114058974B (en) * | 2021-11-30 | 2022-09-13 | 马鞍山钢铁股份有限公司 | 15.9-grade corrosion-resistant high-strength bolt steel and production method and heat treatment method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| TW201339325A (en) * | 2012-01-11 | 2013-10-01 | 神戶製鋼所股份有限公司 | Steel for bolt, bolt and manufacturing method of bolt |
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| JP2002235149A (en) * | 2001-02-07 | 2002-08-23 | Daido Steel Co Ltd | Bar wire rod and production method therefor |
| CN101624679B (en) * | 2007-07-20 | 2011-08-17 | 株式会社神户制钢所 | Steel wire material for spring and its producing method |
| KR20110075319A (en) * | 2009-12-28 | 2011-07-06 | 주식회사 포스코 | Ultra high strength steel wire rod having high resistance of delayed fracture, and method for manufacturing the same |
| JP5600502B2 (en) * | 2010-07-06 | 2014-10-01 | 株式会社神戸製鋼所 | Steel for bolts, bolts and methods for producing bolts |
| JP5707177B2 (en) * | 2011-03-02 | 2015-04-22 | 新日鐵住金株式会社 | Manufacturing method of steel wire for cold forging |
| JP5796549B2 (en) * | 2012-06-21 | 2015-10-21 | 新日鐵住金株式会社 | Steel material for weatherproof bolts |
| JP6034605B2 (en) * | 2012-07-09 | 2016-11-30 | 株式会社神戸製鋼所 | Boron-added steel for high strength bolts and high strength bolts with excellent delayed fracture resistance |
| JP5824443B2 (en) * | 2012-11-22 | 2015-11-25 | 株式会社神戸製鋼所 | Method of manufacturing steel wire for spring |
| JP5913214B2 (en) * | 2013-07-05 | 2016-04-27 | 株式会社神戸製鋼所 | Bolt steel and bolts, and methods for producing the same |
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| TW201339325A (en) * | 2012-01-11 | 2013-10-01 | 神戶製鋼所股份有限公司 | Steel for bolt, bolt and manufacturing method of bolt |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2016186098A (en) | 2016-10-27 |
| WO2016158343A1 (en) | 2016-10-06 |
| JP6461672B2 (en) | 2019-01-30 |
| TW201704499A (en) | 2017-02-01 |
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