TWI612149B - High-strength bolt excellent in delayed fracture resistance and fatigue characteristics, and method of producing the same - Google Patents

High-strength bolt excellent in delayed fracture resistance and fatigue characteristics, and method of producing the same Download PDF

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TWI612149B
TWI612149B TW105139497A TW105139497A TWI612149B TW I612149 B TWI612149 B TW I612149B TW 105139497 A TW105139497 A TW 105139497A TW 105139497 A TW105139497 A TW 105139497A TW I612149 B TWI612149 B TW I612149B
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bolt
less
content
fatigue
residual stress
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TW105139497A
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TW201732052A (en
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松本洋介
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神戶製鋼所股份有限公司
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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D7/00Modifying the physical properties of iron or steel by deformation
    • C21D7/02Modifying the physical properties of iron or steel by deformation by cold working
    • C21D7/04Modifying the physical properties of iron or steel by deformation by cold working of the surface
    • C21D7/06Modifying the physical properties of iron or steel by deformation by cold working of the surface by shot-peening or the like
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Recycling

Description

耐延遲破壞性及疲勞特性優異的高強度螺栓、及其製造方法 High-strength bolt excellent in delayed fracture resistance and fatigue characteristics, and method of producing the same
本發明所揭示的內容是關於:使用於汽車和各種產業機械等的螺栓。詳細地說,是有關:針對於拉伸強度為1500MPa以上的高強度螺栓,改善其耐延遲破壞性以及疲勞特性的技術。 The present invention relates to bolts for use in automobiles, various industrial machines, and the like. Specifically, it relates to a technique for improving the resistance to delayed fracture and fatigue characteristics of a high-strength bolt having a tensile strength of 1500 MPa or more.
使用於汽車和各種產業機械等的螺栓,係被寄望高強度化,而且近年來更是要求必須具有1500MPa以上的拉伸強度。 Bolts used in automobiles and various industrial machines are expected to have high strength, and in recent years, it is required to have a tensile strength of 1500 MPa or more.
對於上述螺栓也被期望能夠高強度化並且提昇耐延遲破壞性。所謂的「延遲破壞」,係指:鋼鐵材料被施加應力起經過某一時間後才發生的破壞。至於這種原因,被認為是有各種因素很複雜地糾結在一起所致,因此難以特定出其原因。亦即,左右延遲破壞現象的因子,一般是認為:回火溫度、組織、材料硬度、結晶粒度、各種合金元素的影響等。然而,就目前的實際狀況而言,還尚未確立出可防止延遲破壞的技術方案,只不過是以試行錯 誤的方式提出各種方法。但是,一般而言,大家的共識是認為:係與氫脆現象有所關連。 It is also expected that the above-mentioned bolts can be made high in strength and improved in resistance to delay damage. The so-called "delayed damage" refers to the damage that occurs after a certain period of time has elapsed since the steel material was stressed. For this reason, it is considered that various factors are complicated and complicated, so it is difficult to specify the cause. That is, the factors that delay the phenomenon of left and right delay are generally considered to be: tempering temperature, texture, material hardness, crystal grain size, and effects of various alloying elements. However, as far as the current situation is concerned, a technical solution to prevent delayed damage has not yet been established, but it is only a trial and error. Mistakes suggest various methods. However, in general, everyone's consensus is that it is related to hydrogen embrittlement.
專利文獻1以及2所揭示的技術方案,是用來改善耐延遲破壞性的技術。兩者之中,專利文獻1的高強度螺栓,係拉伸強度為1400MPa,壓縮殘留應力為拉伸強度的20~95%,表面的十點平均粗糙度是控制在10μm以下。至於其用來賦予上述壓縮殘留應力的方法,則是記載著:將脈衝雷射光束予以集光照射於螺栓表面的方法。 The technical solutions disclosed in Patent Documents 1 and 2 are techniques for improving the resistance to delay damage. Among them, the high-strength bolt of Patent Document 1 has a tensile strength of 1400 MPa, a compressive residual stress of 20 to 95% of tensile strength, and a ten-point average roughness of the surface of 10 μm or less. As for the method for imparting the above-described compressive residual stress, there is described a method in which a pulsed laser beam is collected and irradiated onto the surface of a bolt.
另一方面,專利文獻2所揭示的高強度機械構造用鋼,其組成分是含有Mo為0.2~1.2%,且拉伸強度為125kgf/mm2以上,從鋼材表面起算200μm以內的壓縮殘留應力的最大值(σr)相對於素材的拉伸強度(σB),係符合σr/σB≧0.6的關係。至於其用來賦予上述壓縮殘留應力的方法,則是記載著:實施珠擊加工。 On the other hand, the steel for high-strength mechanical structure disclosed in Patent Document 2 has a compositional component containing a Mo content of 0.2 to 1.2% and a tensile strength of 125 kgf/mm 2 or more, and a compressive residual stress of 200 μm or less from the surface of the steel material. The maximum value (σr) is in relation to the tensile strength (σB) of the material, which is in accordance with the relationship of σr/σB ≧ 0.6. As for the method for imparting the above-described compressive residual stress, it is described that the bead blasting process is performed.
〔先前技術文獻〕 [Previous Technical Literature] 〔專利文獻〕 [Patent Document]
[專利文獻1]日本特開2006-291295號公報 [Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-291295
[專利文獻2]日本特開平7-292434號公報 [Patent Document 2] Japanese Patent Laid-Open No. Hei 7-292434
上述專利文獻1所採用的賦予壓縮殘留應力的方法,是採用:將脈衝雷射光束照射於螺栓表面的方 法,因此,生產性極差,難以實施工業規模的量產。此外,上述專利文獻1的實施例,是以950℃的淬火硬化溫度來進行熱處理,因此,被認為是:螺栓的舊沃斯田鐵結晶粒變粗大化,無法充分改善耐延遲破壞性。 The method for imparting compressive residual stress used in the above Patent Document 1 is to use a method in which a pulsed laser beam is irradiated onto the surface of a bolt. Law, therefore, is extremely poor in productivity and it is difficult to implement mass production on an industrial scale. Further, in the embodiment of Patent Document 1, since the heat treatment is performed at a quench hardening temperature of 950 ° C, it is considered that the old Worth iron crystal grains of the bolt are coarsened, and the delay destructive resistance cannot be sufficiently improved.
上述專利文獻2,為了獲得鋼的淬火硬化性,並且為了具有回火軟化阻力,以400℃以上的回火溫度來獲得125kgf/mm2以上的拉伸強度,因而Mo含量為0.2~1.2%。然而,在於為了提高強度而Si含量為1.5~3.0%的鋼種中,如果Mo含量為0.2%以上的話,熱間延性會明顯下降,也難以實施工業規模的量產。 In the above Patent Document 2, in order to obtain quench hardenability of steel and to have temper softening resistance, a tensile strength of 125 kgf/mm 2 or more is obtained at a tempering temperature of 400 ° C or higher, and thus the Mo content is 0.2 to 1.2%. However, in the steel grade in which the Si content is 1.5 to 3.0% in order to increase the strength, if the Mo content is 0.2% or more, the thermal ductility is remarkably lowered, and it is difficult to carry out mass production on an industrial scale.
一般而言,延遲破壞是C含量愈高愈容易發生,因此,可以考慮例如:針對於螺栓的表層刻意進行脫碳處理。但是,對於表層進行脫碳處理的話,表層硬度會下降,因此,疲勞特性會惡化。因而難以同時將耐延遲破壞性與疲勞特性之兩者都維持在高水準。 In general, the delayed fracture is more likely to occur as the C content is higher, and therefore, for example, decarburization treatment is intentionally performed on the surface layer of the bolt. However, when the surface layer is subjected to decarburization treatment, the surface hardness is lowered, and thus the fatigue characteristics are deteriorated. Therefore, it is difficult to simultaneously maintain both the retardation destructive resistance and the fatigue characteristics at a high level.
本案所揭示的內容,係有鑒於上述的情事而開發完成的,其目的是要提供:既可確保1500MPa以上的拉伸強度,而且耐延遲破壞性及疲勞特性優異的高強度螺栓、及其製造方法。 The contents disclosed in the present invention have been developed in view of the above circumstances, and the object thereof is to provide a high-strength bolt which is excellent in tensile strength and fatigue resistance, and which is capable of ensuring tensile strength of 1500 MPa or more. method.
能夠解決上述技術課題之本案所揭示的高強度螺栓,母材的組成分以質量%計,是含有C:0.25~0.5%、Si:1.5~3.0%、Mn:0.1~1.5%、P:高於0% 且0.03%以下、S:高於0%且0.03%以下、Cr:0.05~1.5%、Mo:0%以上且低於0.2%、Al:0.01~0.1%、以及N:0.002~0.020%,並且含有Ti:0.02~0.1%、以及Nb:0.02~0.1%之中的一種或兩種,其餘部分是鐵以及不可避免的雜質之螺栓。本案所揭示的高強度螺栓的要點在於:上述螺栓的拉伸強度為1500MPa以上,螺栓之從螺紋底面起算之深度0.05mm位置處的壓縮殘留應力為拉伸強度×0.15MPa以上,將螺栓的軸部直徑視為D時,在D/4位置的舊沃斯田鐵結晶粒的平均粒徑為5~15μm。 The high-strength bolt disclosed in the present invention can solve the above-mentioned technical problems. The composition of the base material is C: 0.25 to 0.5%, Si: 1.5 to 3.0%, Mn: 0.1 to 1.5%, and P: high. At 0% And 0.03% or less, S: more than 0% and 0.03% or less, Cr: 0.05 to 1.5%, Mo: 0% or more and less than 0.2%, Al: 0.01 to 0.1%, and N: 0.002 to 0.020%, and It contains one or two of Ti: 0.02~0.1%, and Nb: 0.02~0.1%, and the rest is bolts of iron and unavoidable impurities. The main point of the high-strength bolt disclosed in the present invention is that the tensile strength of the bolt is 1500 MPa or more, and the compressive residual stress at the position of the bolt from the bottom of the thread of 0.05 mm is the tensile strength × 0.15 MPa or more. When the diameter of the portion is regarded as D, the average particle diameter of the old Worthite iron crystal grains at the D/4 position is 5 to 15 μm.
上述螺栓以質量%計,亦可以至少符合下列的(a)條件或(b)條件的方式,又含有其他的元素。 The above bolts may also contain other elements in mass %, or at least in accordance with the following conditions (a) or (b).
(a)條件是Cu:高於0%且0.5%以下、以及Ni:高於0%且1%以下之一種或兩種;(b)條件是V:高於0%且0.5%以下、以及W:高於0%且0.5%以下之一種或兩種。 (a) the condition is Cu: more than 0% and less than 0.5%, and Ni: one or two of more than 0% and less than 1%; (b) the condition is V: higher than 0% and less than 0.5%, and W: one or two of more than 0% and less than 0.5%.
上述螺栓之從螺紋底面起算之深度為0.05mm位置處的C含量的比率,相對於前述母材的C含量是50~110%為宜。 The ratio of the C content at the position where the depth of the bolt is 0.05 mm from the bottom surface of the screw is preferably 50 to 110% with respect to the C content of the base material.
本案所揭示的高強度螺栓,是可藉由在淬火硬化回火後,至少進行滾壓加工以及珠擊加工的其中一項來賦予壓縮殘留應力,而製造出來的。前述淬火硬化,係在碳勢相對於母材的C含量為50~110%的爐氣中來進行為宜。亦可在賦予上述壓縮殘留應力之後,又進行退火。 The high-strength bolt disclosed in the present invention can be produced by imparting compressive residual stress to at least one of rolling processing and beading processing after quench hardening and tempering. The quench hardening is preferably carried out in a furnace gas having a carbon potential of 50 to 110% with respect to the C content of the base material. Annealing may be performed after imparting the above-described compressive residual stress.
根據本案所揭示的高強度螺栓,因為是適正地控制螺栓的組成分、螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力、以及相對於螺栓軸部的直徑D之D/4位置處的舊沃斯田鐵結晶粒的平均粒徑,因此,係可提供:除了可確保1500MPa以上的拉伸強度之外,又可將耐延遲破壞性以及疲勞特性之兩者都保持在高水準的高強度螺栓。此外,根據本案所揭示的內容,亦可提供上述高強度螺栓的製造方法。 According to the high-strength bolt disclosed in the present case, the composition of the bolt is properly controlled, the compressive residual stress at the position of the bolt from the bottom of the thread is 0.05 mm, and the diameter D of the bolt portion is D/4. The average particle size of the old Worthite iron crystal grains at the position, therefore, can provide: in addition to ensuring the tensile strength of 1500 MPa or more, both the retardation resistance and the fatigue characteristics can be kept high. Standard high strength bolts. Further, according to the disclosure of the present invention, a method of manufacturing the above-described high-strength bolt can also be provided.
本發明人,為了改善拉伸強度為1500MPa以上的高強度螺栓的耐延遲破壞性以及疲勞特性,不斷努力進行檢討。其結果,找到一種創見,就是:只要將螺栓的組成分,尤其是將Si含量控制在較高的1.5~3.0%,將Mo含量控制在較低的未達0.2%,並且將螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力、以及螺栓的軸部之D/4位置處的舊沃斯田鐵結晶粒的平均粒徑做適正地控制的話,即可實現耐延遲破壞性以及疲勞特性優異的拉伸強度為1500MPa以上的高強度螺栓,因而完成了本發明。 The present inventors have made an effort to review the high-strength bolts having a tensile strength of 1500 MPa or more in terms of delayed fracture resistance and fatigue properties. As a result, a finding is found: as long as the composition of the bolt is divided, in particular, the Si content is controlled at a high 1.5 to 3.0%, the Mo content is controlled to a lower temperature of less than 0.2%, and the bolt is threaded. Delay-destructive resistance can be achieved by properly controlling the compressive residual stress at a depth of 0.05 mm from the bottom surface and the average particle size of the old Worthite iron crystal grains at the D/4 position of the shaft portion of the bolt. And a high-strength bolt having a tensile strength of 1500 MPa or more excellent in fatigue characteristics, and thus completed the present invention.
首先,說明本發明的實施方式的螺栓的母材的組成分。本發明的實施方式的螺栓,基本成分是含有C:0.25~0.5%、Si:1.5~3.0%、Mn:0.1~1.5%、P:高於 0%且0.03%以下、S:高於0%且0.03%以下、Cr:0.05~1.5%、Mo:0%以上且低於0.2%、Al:0.01~0.1%、以及N:0.002~0.020%,並且含有Ti:0.02~0.1%、以及Nb:0.02~0.1%之中的一種或兩種。在以下的說明中,組成分的%係指:質量%。 First, the composition of the base material of the bolt of the embodiment of the present invention will be described. The bolt of the embodiment of the present invention contains C: 0.25 to 0.5%, Si: 1.5 to 3.0%, Mn: 0.1 to 1.5%, and P: higher than 0% and 0.03% or less, S: higher than 0% and 0.03% or less, Cr: 0.05 to 1.5%, Mo: 0% or more and less than 0.2%, Al: 0.01 to 0.1%, and N: 0.002 to 0.020% And contains one or two of Ti: 0.02 to 0.1%, and Nb: 0.02 to 0.1%. In the following description, the % of the component means: mass%.
C是用來確保螺栓的強度之必要元素,為了使拉伸強度達到1500MPa以上,將C含量設在0.25%以上。C含量較佳是0.30%以上,更優是0.33%以上。但是,C含量過剩的話,耐延遲破壞性以及疲勞特性將會惡化,因此將C含量設在0.5%以下。C含量較佳是0.45%以下,更優是0.43%以下。 C is an essential element for securing the strength of the bolt, and the C content is set to 0.25% or more in order to achieve a tensile strength of 1500 MPa or more. The C content is preferably 0.30% or more, more preferably 0.33% or more. However, if the C content is excessive, the retardation resistance and the fatigue characteristics are deteriorated, so the C content is set to 0.5% or less. The C content is preferably 0.45% or less, more preferably 0.43% or less.
Si可作為脫氧劑,並且是用來確保螺栓的強度之必要元素。此外,Si係可抑制粗大的雪明鐵的析出,是對於提昇耐延遲破壞性有所助益的元素。此外,藉由含有Si,在實施淬火硬化回火後的滾壓加工、滾壓加工後的珠擊加工等,可對於螺栓的表層賦予高壓縮殘留應力,因此可提昇耐延遲破壞性以及疲勞特性。為了使其發揮這種效果,乃將Si含量設在1.5%以上。Si含量較佳是1.6%以上、更優是1.7%以上。但是,Si是使肥粒鐵穩定化的元素,因此過剩含有的話,在淬火硬化後,肥粒鐵將會析出,疲勞特性會惡化。從而,在本發明的實施方式中,係將Si含量設在3.0%以下。Si含量較佳是2.5%以下、更優是2.0%以下。 Si acts as a deoxidizer and is an essential element to ensure the strength of the bolt. In addition, the Si system suppresses the precipitation of coarse ferritic iron and is an element that contributes to the improvement of the resistance to delayed fracture. In addition, by containing Si, it is possible to impart high compressive residual stress to the surface layer of the bolt after the rolling process after the quench hardening and tempering, the beading process after the rolling process, and the like, thereby improving the delayed fracture resistance and the fatigue property. . In order to exert this effect, the Si content is set to 1.5% or more. The Si content is preferably 1.6% or more, more preferably 1.7% or more. However, Si is an element which stabilizes ferrite iron. Therefore, if it is contained excessively, after quenching and hardening, ferrite iron will precipitate and fatigue characteristics will deteriorate. Therefore, in the embodiment of the present invention, the Si content is set to 3.0% or less. The Si content is preferably 2.5% or less, more preferably 2.0% or less.
Mn是可提高螺栓的強度,並且可與S形成化 合物,因而可抑制會使耐延遲破壞性惡化的FeS的生成之元素。為了使其發揮這種效果,乃將Mn含量設在0.1%以上。Mn含量較佳是0.13%以上、更優是0.15%以上。但是,Mn含量過剩的話,MnS將會粗大化而成為應力集中源,耐延遲破壞性以及疲勞特性將會惡化。從而,在本發明的實施方式中,係將Mn含量設在1.5%以下。Mn含量較佳是1.3%以下、更優是1.1%以下。 Mn can increase the strength of the bolt and can form with S Therefore, it is possible to suppress the formation of FeS which deteriorates the deterioration resistance to deterioration. In order to exert such an effect, the Mn content is set to 0.1% or more. The Mn content is preferably 0.13% or more, more preferably 0.15% or more. However, if the Mn content is excessive, MnS will become coarse and become a stress concentration source, and the resistance to delayed fracture and fatigue characteristics will deteriorate. Therefore, in the embodiment of the present invention, the Mn content is set to 1.5% or less. The Mn content is preferably 1.3% or less, more preferably 1.1% or less.
P是不可避免的雜質,會濃化在結晶粒界而使得鋼的韌性延性變差,是會使螺栓的耐延遲破壞性惡化的元素。從而,在本發明的實施方式中,係將P含量設在0.03%以下。P含量較佳是0.015%以下、更優是0.010%以下。雖然P含量是愈少愈好,但是,在製造上難以將P含量達到0%,通常是含有0.003%的程度。 P is an unavoidable impurity, and is concentrated in the crystal grain boundary to deteriorate the ductility ductility of the steel, and is an element which deteriorates the resistance to delay of the bolt. Therefore, in the embodiment of the present invention, the P content is set to 0.03% or less. The P content is preferably 0.015% or less, more preferably 0.010% or less. Although the P content is as small as possible, it is difficult to achieve a P content of 0% in the production, and it is usually contained in an amount of 0.003%.
S也是與P同樣是不可避免的雜質,會濃化於結晶粒界而使得鋼的韌性延性變差,是會使螺栓的耐延遲破壞性惡化的元素。從而,在本發明的實施方式中,係將S含量設在0.03%以下。S含量較佳是0.015%以下、更優是0.010%以下。雖然S含量是愈少愈好,但是,在製造上難以將S含量達到0%,通常是含有0.003%的程度。 S is also an unavoidable impurity similar to P, and is concentrated in the crystal grain boundary to deteriorate the ductility ductility of the steel, and is an element which deteriorates the delay resistance of the bolt. Therefore, in the embodiment of the present invention, the S content is set to 0.03% or less. The S content is preferably 0.015% or less, more preferably 0.010% or less. Although the S content is as small as possible, it is difficult to achieve an S content of 0% in production, and it is usually contained in an amount of 0.003%.
Cr是用來提昇螺栓的耐腐蝕性以及改善耐延遲破壞性之必要元素。為了獲得這種效果,在本發明的實施方式中,是將Cr含量設在0.05%以上。Cr量較佳是0.10%以上、更優是0.20%以上。但是,Cr含量過剩的話,效果趨於飽和,成本會變高。從而,在本發明的實施 方式中,係將Cr含量設在1.5%以下。Cr含量較佳是1.3%以下、更優是1.1%以下。 Cr is an essential element for improving the corrosion resistance of bolts and improving the resistance to delay damage. In order to obtain such an effect, in the embodiment of the present invention, the Cr content is set to 0.05% or more. The amount of Cr is preferably 0.10% or more, more preferably 0.20% or more. However, if the Cr content is excessive, the effect tends to be saturated, and the cost becomes high. Thus, in the practice of the present invention In the mode, the Cr content is set to 1.5% or less. The Cr content is preferably 1.3% or less, more preferably 1.1% or less.
Mo是在回火時會細微地析出而可提高鋼的韌性延性,是用來改善螺栓的耐延遲破壞性以及疲勞特性的元素。為了使其發揮這種效果,乃將Mo含量設在0%以上。Mo含量較佳是0.001%以上、更優是0.004%以上,最優是0.01%以上。但是,在本發明的實施方式所規定的組成分中,如果Mo含量是0.2%以上的話,熱間延性將會降低而變得無法進行製造。再者,Mo是昂貴的元素,過剩添加的話將導致成本上昇。從而,在本發明的實施方式中,係將Mo含量設在低於0.2%。Mo含量較佳是0.15%以下、更優是0.10%以下。 Mo is an element which is finely precipitated during tempering to improve the ductility of steel and is used to improve the resistance to deformation and fatigue of the bolt. In order to exert this effect, the Mo content is set to 0% or more. The Mo content is preferably 0.001% or more, more preferably 0.004% or more, and most preferably 0.01% or more. However, in the composition defined by the embodiment of the present invention, when the Mo content is 0.2% or more, the thermal coexistability is lowered and production cannot be performed. Furthermore, Mo is an expensive element, and if it is added excessively, it will lead to an increase in cost. Thus, in the embodiment of the present invention, the Mo content is set to be less than 0.2%. The Mo content is preferably 0.15% or less, more preferably 0.10% or less.
Al是可作為脫氧劑,並且可形成氮化物而利用釘扎效果來防止舊沃斯田鐵結晶粒粗大化的元素,是可提昇鋼的韌性延性,可改善耐延遲破壞性以及疲勞特性。為了使其發揮這種效果,乃將Al含量設在0.01%以上。Al含量較佳是0.015%以上、更優是0.020%以上。但是,Al含量過剩的話,將會形成粗大的氮化物而使疲勞特性惡化。從而,在本發明的實施方式中,係將Al含量設在0.1%以下。Al含量較佳是0.08%以下、更優是0.06%以下。 Al is an element which can be used as a deoxidizer and can form a nitride to prevent coarsening of the old Worthite iron crystal grain by a pinning effect, and can improve the ductility ductility of the steel, and can improve the delayed fracture resistance and the fatigue property. In order to exert such an effect, the Al content is set to 0.01% or more. The Al content is preferably 0.015% or more, more preferably 0.020% or more. However, if the Al content is excessive, coarse nitrides are formed and the fatigue characteristics are deteriorated. Therefore, in the embodiment of the present invention, the Al content is set to 0.1% or less. The Al content is preferably 0.08% or less, more preferably 0.06% or less.
N是會與Al、Ti或Nb化合而形成氮化物,而可利用釘扎效果來防止舊沃斯田鐵結晶粒粗大化的元素,係可提昇鋼的韌性延性,可改善耐延遲破壞性以及疲勞特 性。為了使其發揮這些效果,乃將N含量設在0.002%以上。N含量較佳是0.003%以上、更優是0.0035%以上。但是,N含量過剩的話,將會形成粗大的氮化物而使疲勞特性惡化。從而,在本發明的實施方式中,係將N含量設在0.02%以下。N含量較佳是0.01%以下、更優是0.008%以下。 N is an element which combines with Al, Ti or Nb to form a nitride, and can be used to prevent the coarsening of the old Worthite iron crystal grain by the pinning effect, thereby improving the ductility ductility of the steel and improving the delay destructive resistance and Fatigue Sex. In order to exert these effects, the N content is set to 0.002% or more. The N content is preferably 0.003% or more, more preferably 0.0035% or more. However, if the N content is excessive, coarse nitrides are formed and the fatigue characteristics are deteriorated. Therefore, in the embodiment of the present invention, the N content is set to 0.02% or less. The N content is preferably 0.01% or less, more preferably 0.008% or less.
Ti以及Nb是會與C以及N形成碳氮化物,而藉由釘扎效果來防止舊沃斯田鐵結晶粒粗大化的元素,因為可提昇鋼的韌性延性,所以耐延遲破壞性以及疲勞特性也提昇。Ti與Nb係可單獨採用,亦可將兩者併用。 Ti and Nb are elements which form carbonitrides with C and N, and prevent the coarsening of the old Worthite iron crystal grains by the pinning effect. Since the ductility of the steel can be improved, the delayed fracture resistance and fatigue characteristics are obtained. Also improved. The Ti and Nb systems may be used singly or in combination.
Ti含量係設在0.02%以上,較佳是0.03%以上、更優是0.05%以上。Nb含量係設在0.02%以上,較佳是0.03%以上、更優是0.05%以上。但是,Ti以及Nb含量過剩的話,將會形成粗大的碳氮化物,使得疲勞特性惡化。從而,在本發明的實施方式中,係將Ti含量設在0.1%以下,較佳是0.08%以下、更優是0.06%以下。將Nb含量設在0.1%以下,較佳是0.08%以下、更優是0.06%以下。 The Ti content is 0.02% or more, preferably 0.03% or more, more preferably 0.05% or more. The Nb content is set to 0.02% or more, preferably 0.03% or more, more preferably 0.05% or more. However, if the content of Ti and Nb is excessive, coarse carbonitride will be formed to deteriorate the fatigue characteristics. Therefore, in the embodiment of the present invention, the Ti content is set to 0.1% or less, preferably 0.08% or less, more preferably 0.06% or less. The Nb content is set to 0.1% or less, preferably 0.08% or less, more preferably 0.06% or less.
本發明的實施方式的螺栓的基本成分,係如上所述,其餘部分實質上是鐵。 The basic components of the bolt of the embodiment of the present invention are as described above, and the remainder is substantially iron.
但是,當然也可容許在鋼中含有因為原料、資材、製造設備等的狀況而夾帶進來之不可避免的雜質。 However, it is of course possible to allow the steel to contain unavoidable impurities which are entrained due to the conditions of raw materials, materials, manufacturing equipment, and the like.
本發明的實施方式的螺栓,係可因應必要而又含有下列的其他元素, (a)Cu:高於0%且0.5%以下、以及Ni:高於0%且1%以下之一種或兩種、(b)V:高於0%且0.5%以下、以及W:高於0%且0.5%以下之一種或兩種。 The bolt of the embodiment of the present invention may contain other elements as follows, as necessary. (a) Cu: more than 0% and less than 0.5%, and Ni: one or two of more than 0% and less than 1%, (b) V: more than 0% and less than 0.5%, and W: higher than One or two of 0% and 0.5% or less.
(a)Cu以及Ni係可用來提昇鋼的耐腐蝕性,而可改善螺栓的耐延遲破壞性之元素。Cu與Ni係可單獨採用,亦可將兩者併用。 (a) Cu and Ni can be used to improve the corrosion resistance of steel and improve the resistance to delay damage of bolts. The Cu and Ni systems may be used singly or in combination.
Cu含量較佳是0.05%以上、更優是0.10%以上、最優是0.13%以上。但是,Cu含量過剩的話,上述效果趨於飽和。而且過剩地含有的話,熱間延性將會降低而導致鋼的生產性變差。從而,在本發明的實施方式中,Cu含量較佳是0.5%以下、更優是0.4%以下、最優是0.35%以下。 The Cu content is preferably 0.05% or more, more preferably 0.10% or more, and most preferably 0.13% or more. However, if the Cu content is excessive, the above effects tend to be saturated. Further, if it is contained excessively, the thermal ductility will be lowered to deteriorate the productivity of steel. Therefore, in the embodiment of the present invention, the Cu content is preferably 0.5% or less, more preferably 0.4% or less, and most preferably 0.35% or less.
Ni含量較佳是0.05%以上、更優是0.10%以上、最優是0.15%以上。但是,Ni含量過剩的話,上述效果趨於飽和,成本也會上昇。從而,在本發明的實施方式中,Ni含量較佳是1%以下、更優是0.8%以下、最優是0.7%以下。 The Ni content is preferably 0.05% or more, more preferably 0.10% or more, and most preferably 0.15% or more. However, if the Ni content is excessive, the above effects tend to be saturated and the cost will increase. Therefore, in the embodiment of the present invention, the Ni content is preferably 1% or less, more preferably 0.8% or less, and most preferably 0.7% or less.
(b)V與W是會形成碳氮化物而藉由釘扎效果來防止舊沃斯田鐵結晶粒粗大化的元素,係可用來提昇耐延遲破壞性以及疲勞特性。V與W係可單獨採用,亦可將兩者併用。 (b) V and W are elements which form carbonitrides and prevent the coarsening of the old Worthite iron crystal grains by the pinning effect, and can be used to improve the resistance to delayed fracture and fatigue. The V and W systems can be used alone or in combination.
V含量較佳是0.01%以上、更優是0.03%以上、最優是0.05%以上。但是,V含量過剩的話,上述效 果趨於飽和。而且,過剩地含有的話,淬火硬化性變得太高因而導致生產性惡化。從而,在本發明的實施方式中,V含量較佳是0.5%以下、更優是0.3%以下、最優是0.2%以下。 The V content is preferably 0.01% or more, more preferably 0.03% or more, and most preferably 0.05% or more. However, if the V content is excessive, the above effect The fruit tends to be saturated. Further, if it is contained excessively, the quench hardenability becomes too high and the productivity is deteriorated. Therefore, in the embodiment of the present invention, the V content is preferably 0.5% or less, more preferably 0.3% or less, and most preferably 0.2% or less.
W含量較佳是0.01%以上、更優是0.05%以上、最優是0.1%以上。但是,W含量過剩的話,上述效果趨於飽和。而且,過剩地含有的話,淬火硬化性變得太高因而導致生產性惡化。從而,在本發明的實施方式中,W含量較佳是0.5%以下、更優是0.3%以下、最優是0.2%以下。 The W content is preferably 0.01% or more, more preferably 0.05% or more, and most preferably 0.1% or more. However, if the W content is excessive, the above effects tend to be saturated. Further, if it is contained excessively, the quench hardenability becomes too high and the productivity is deteriorated. Therefore, in the embodiment of the present invention, the W content is preferably 0.5% or less, more preferably 0.3% or less, and most preferably 0.2% or less.
以上,是說明了螺栓的母材的組成分。 The above is the composition of the base material of the bolt.
本發明的實施方式的螺栓是以拉伸強度為1500MPa以上來作為前提。拉伸強度較佳是1600MPa以上、更優是1700MPa以上。拉伸強度的上限並未特別地限定,例如可以是2200MPa的程度。 The bolt according to the embodiment of the present invention is premised on a tensile strength of 1500 MPa or more. The tensile strength is preferably 1600 MPa or more, more preferably 1700 MPa or more. The upper limit of the tensile strength is not particularly limited, and may be, for example, about 2200 MPa.
此外,本發明的實施方式的螺栓,螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力為拉伸強度×0.15MPa以上,並且將螺栓之軸部直徑視為D(mm)時,在D/4位置處的舊沃斯田鐵結晶粒的平均粒徑為5~15μm是很重要的。 Further, in the bolt of the embodiment of the present invention, the compressive residual stress at the position of the bolt from the bottom surface of the thread of 0.05 mm is the tensile strength × 0.15 MPa or more, and the diameter of the shaft of the bolt is regarded as D (mm). It is important that the average particle size of the old Worthite iron crystal grains at the D/4 position is 5 to 15 μm.
(壓縮殘留應力:拉伸強度×0.15MPa以上) (Compressed residual stress: tensile strength × 0.15 MPa or more)
延遲破壞與疲勞破壞大多數並非發生在螺栓的中心部,而是表層部成為破壞的起點來發生的。因此,在本發 明的實施方式中,係進行控制螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力。具體而言,從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力是控制成:拉伸強度×0.15MPa以上。 Most of the delayed damage and fatigue damage do not occur at the center of the bolt, but the surface portion becomes the starting point of the damage. Therefore, in this issue In the embodiment of the present invention, the compressive residual stress at a position of 0.05 mm from the bottom surface of the screw is controlled. Specifically, the compressive residual stress at a position of 0.05 mm from the bottom surface of the screw is controlled to be: tensile strength × 0.15 MPa or more.
藉由對於上述深度為0.05mm的位置,賦予拉伸強度×0.15MPa以上的壓縮殘留應力,可提昇耐延遲破壞性以及疲勞特性。上述壓縮殘留應力較佳是拉伸強度×0.25MPa以上、更優是拉伸強度×0.30MPa以上。在上述深度為0.05mm位置處的壓縮殘留應力,雖然是愈高愈好,但並未高於螺栓的拉伸強度。上述壓縮殘留應力大約是拉伸強度×0.90MPa以下。 By imparting a compressive residual stress of tensile strength × 0.15 MPa or more to the above-described depth of 0.05 mm, the delayed fracture resistance and the fatigue property can be improved. The compressive residual stress is preferably a tensile strength × 0.25 MPa or more, more preferably a tensile strength × 0.30 MPa or more. The compressive residual stress at the above-mentioned depth of 0.05 mm, although the higher the better, is not higher than the tensile strength of the bolt. The above-mentioned compressive residual stress is approximately tensile strength × 0.90 MPa or less.
上述深度為0.05mm位置處的壓縮殘留應力,係可利用X射線殘留應力測定法來進行測定。 The above-described compression residual stress at a position of 0.05 mm in depth can be measured by X-ray residual stress measurement.
(平均粒徑:5~15μm) (Average particle size: 5~15μm)
將螺栓的軸部直徑視為D(mm)時,將位於D/4位置處的舊沃斯田鐵結晶粒的平均粒徑控制在15μm以下的作法也是很重要的。藉由適正地控制位於D/4位置處的金屬組織,可提昇螺栓的韌性延性,可提昇耐延遲破壞性以及疲勞特性。上述平均粒徑較佳是10μm以下、更優是8μm以下。上述D/4位置處的舊沃斯田鐵結晶粒雖然是愈小愈好,但是考慮到本發明的實施方式的組成分以及製造條件,上述平均粒徑大約是5μm以上。 When the diameter of the shaft portion of the bolt is regarded as D (mm), it is also important to control the average particle diameter of the old Worthite iron crystal grains located at the D/4 position to 15 μm or less. By properly controlling the metal structure at the D/4 position, the ductile ductility of the bolt can be improved, and the delayed destructive resistance and fatigue characteristics can be improved. The average particle diameter is preferably 10 μm or less, more preferably 8 μm or less. Although the old Worthite iron crystal grains at the above D/4 position are as small as possible, the average particle diameter is about 5 μm or more in consideration of the composition and the production conditions of the embodiment of the present invention.
本發明的實施方式的螺栓,是將螺栓之從螺 紋底面起算之深度為0.05mm位置處的C含量(質量%)的比率,相對於螺栓的母材的C含量(質量%),控制在50~110%更好。藉由將上述螺栓之從螺紋底面起算之深度為0.05mm位置處的C含量的比率,相對於前述母材的C含量,控制在50%以上,可更進一步提高表層硬度,而可更加提昇疲勞特性。上述螺栓之從螺紋底面起算之深度為0.05mm位置處的C含量(質量%)的比率,相對於前述母材的C含量(質量%),較佳是60%以上、更優是65%以上。另一方面,藉由將上述螺栓之從螺紋底面起算之深度為0.05mm位置處的C含量的比率,相對於前述母材的C含量,控制在110%以下,係可抑制表面硬度變得太硬。其結果,可更進一步改善耐延遲破壞性。上述螺栓之從螺紋底面起算之深度為0.05mm位置處的C含量(質量%)的比率,相對於前述母材的C含量(質量%),較佳是100%以下、更優是95%以下。 The bolt of the embodiment of the present invention is a bolt The ratio of the C content (% by mass) at a depth of 0.05 mm from the bottom of the groove is preferably 50 to 110% with respect to the C content (% by mass) of the base material of the bolt. By controlling the ratio of the C content at the depth of 0.05 mm from the bottom surface of the screw to the C content of the base material to 50% or more, the surface hardness can be further improved, and the fatigue can be further improved. characteristic. The ratio of the C content (% by mass) at a depth of 0.05 mm from the bottom surface of the screw is preferably 60% or more, more preferably 65% or more, based on the C content (% by mass) of the base material. . On the other hand, by controlling the ratio of the C content at the depth of 0.05 mm from the bottom surface of the screw to the C content of the base material to 110% or less, the surface hardness can be suppressed from becoming too large. hard. As a result, the delay damage resistance can be further improved. The ratio of the C content (% by mass) at a depth of 0.05 mm from the bottom surface of the screw is preferably 100% or less, more preferably 95% or less, based on the C content (% by mass) of the base material. .
此外,本發明的實施方式的螺栓,螺栓之從螺紋底面起算之深度為0.05mm位置處的舊沃斯田鐵結晶粒的平均粒徑為0.01~5μm更好。藉由將螺栓之從螺紋底面起算之深度為0.05mm位置處的舊沃斯田鐵結晶粒的平均粒徑控制在5μm以下,可提高成為延遲破壞的起點的部分之韌性延性,因此,可提昇耐延遲破壞性。上述平均粒徑更優是3μm以下、最優是2μm以下。螺栓之從螺紋底面起算之深度為0.05mm位置處的舊沃斯由鐵結晶粒,雖然是愈小愈好,但考慮到本發明的實施方式的組成分以 及製造條件的話,上述平均粒徑大約是在0.01μm以上。 Further, in the bolt of the embodiment of the present invention, the average particle diameter of the old Worthite iron crystal grain at a position where the bolt has a depth of 0.05 mm from the bottom surface of the screw is preferably 0.01 to 5 μm. By controlling the average particle diameter of the old Wolsfield iron crystal grains at a depth of 0.05 mm from the bottom surface of the screw to 5 μm or less, the ductility ductility of the portion which is the starting point of the delayed fracture can be improved, and therefore, the ductility can be improved. Durable to delay. The average particle diameter is more preferably 3 μm or less, and most preferably 2 μm or less. The Old Voss from the bottom surface of the bolt at a depth of 0.05 mm is made of iron crystal grains, although the smaller the better, the composition of the embodiment of the present invention is considered In the case of the production conditions, the above average particle diameter is approximately 0.01 μm or more.
接下來,說明本發明的實施方式的螺栓的製造方法。 Next, a method of manufacturing the bolt according to the embodiment of the present invention will be described.
首先,依循傳統方法熔製出具有上述化學成分的鋼,進行鑄造而成為鋼材,進行熱軋而製造成輥軋線材。熱軋前的鋼材的加熱溫度雖然並未特別地限定,例如係設在900~1100℃,只要進行精製輥軋製作成輥軋線材或條鋼形狀即可。精製輥軋的溫度也並未特別地限定,例如設在800~1000℃即可。 First, steel having the above chemical composition is melted according to a conventional method, cast into steel, and hot rolled to produce a rolled wire. The heating temperature of the steel material before the hot rolling is not particularly limited. For example, it is set at 900 to 1100 ° C, and may be formed into a rolled wire or a strip shape by refining and rolling. The temperature of the refining rolling is also not particularly limited, and is, for example, 800 to 1000 ° C.
接下來,針對於所製得的輥軋線材,因應必要來實施除去鏽皮處理、球狀化退火等的熱處理、皮膜處理以及最終精製伸線加工,而製造成鋼線。 Next, the obtained rolled wire is subjected to heat treatment such as stripping treatment, spheroidizing annealing, and the like, and finally subjected to a final wire drawing process to produce a steel wire.
接下來,使用所製得的鋼線,藉由冷間滾壓等的工序來成形出螺栓形狀。 Next, using the obtained steel wire, a bolt shape is formed by a process such as cold rolling.
接下來,針對於已經成形為螺栓形狀的中間製品,賦予壓縮殘留應力後,即可獲得本發明的實施方式的螺栓。 Next, the bolt of the embodiment of the present invention can be obtained by imparting compressive residual stress to the intermediate product which has been formed into a bolt shape.
在本發明的實施方式中,將上述中間製品實施淬火硬化回火後,是建議採用:從滾壓加工以及珠擊加工之中所選出的至少一種加工來對於螺栓賦予壓縮殘留應力。亦即,可以採用(a)在實施了淬火硬化回火之後,進行滾壓加工;或者採用(b)在實施了淬火硬化回火之後,進行珠擊加工;或者採用(c)在實施了淬火硬化回火之後,以不同的順序來進行滾壓加工與珠擊加工,藉以 對於螺栓賦予壓縮殘留應力。 In the embodiment of the present invention, after the intermediate product is subjected to quench hardening and tempering, it is recommended to apply at least one selected from the rolling process and the beading process to impart a compressive residual stress to the bolt. That is, (a) after the quench hardening tempering is performed, the rolling process is performed; or (b) after the quench hardening tempering is performed, the beading process is performed; or (c) the quenching is performed. After hardening and tempering, rolling and beading are performed in different orders. The compression residual stress is imparted to the bolt.
(淬火硬化Q) (Quench hardening Q)
淬火硬化時的加熱溫度,為了穩定地進行沃斯田鐵化處理起見,是設在850℃以上為佳。淬火硬化時的加熱溫度更好是880℃以上、更優是890℃以上。但是,如果是加熱到950℃以上的高溫的話,由Al、Ti、Nb等所產生的釘扎效果會變差,舊沃斯田鐵結晶粒變得粗大化,因此,變得難以改善耐延遲破壞性及疲勞特性。從而,在本發明的實施方式中,淬火硬化時的加熱溫度,是設在低於950℃為宜。淬火硬化時的加熱溫度更好是940℃以下、最優是930℃以下。 The heating temperature at the time of hardening and hardening is preferably 850 ° C or more in order to stably carry out the Worthing iron treatment. The heating temperature at the time of quench hardening is more preferably 880 ° C or more, more preferably 890 ° C or more. However, if it is heated to a high temperature of 950 ° C or higher, the pinning effect by Al, Ti, Nb or the like is deteriorated, and the old Worthite iron crystal grain becomes coarse, so that it becomes difficult to improve the retardation resistance. Destructive and fatigue properties. Therefore, in the embodiment of the present invention, the heating temperature at the time of quench hardening is preferably set to less than 950 °C. The heating temperature at the time of quench hardening is more preferably 940 ° C or lower, and most preferably 930 ° C or lower.
淬火硬化加熱時的爐氣氛圍雖然並未特別地限定,例如:是將碳勢(以下稱為「CP」)控制成:相對於螺栓的母材的C含量,係為50~110%為宜。亦即,如果進行過度的脫碳的話,表層的結晶粒將會粗大化,耐延遲破壞性以及疲勞特性會惡化。而且,更進一步脫碳的話,在表層將會析出肥粒鐵,疲勞特性將會更加惡化。為了抑制過度的脫碳,乃將爐內的爐氣氛圍採用由一氧化碳與二氧化碳所混合的混合氣體,藉此,來控制爐內的碳勢為宜。CP的數值,相對於螺栓的母材的C含量,較佳是50%以上、更優是60%以上、最優是65%以上。另一方面,CP的數值太高的話,將會因為過度的滲碳而導致耐延遲破壞性惡化。從而,在本發明的實施方式中,CP的 數值,相對於螺栓的母材的C含量,是在110%以下為宜、更優是100%以下、最優是90%以下。此外,CP的數值,是測定了設置在爐內的線圈狀的高拉力鋼線(CP線圈)的含碳量的數值。 The furnace gas atmosphere during the quench hardening heating is not particularly limited. For example, the carbon potential (hereinafter referred to as "CP") is controlled so as to be 50 to 110% with respect to the C content of the base material of the bolt. . That is, if excessive decarburization is performed, the crystal grains of the surface layer will be coarsened, and the delayed fracture resistance and fatigue characteristics will be deteriorated. Moreover, if decarburization is further carried out, the ferrite iron will be precipitated on the surface layer, and the fatigue characteristics will be further deteriorated. In order to suppress excessive decarburization, it is preferable to use a mixed gas of carbon monoxide and carbon dioxide in the furnace atmosphere in the furnace, thereby controlling the carbon potential in the furnace. The value of CP is preferably 50% or more, more preferably 60% or more, and most preferably 65% or more with respect to the C content of the base material of the bolt. On the other hand, if the value of CP is too high, the resistance to delay damage will be deteriorated due to excessive carburization. Thus, in an embodiment of the invention, the CP The value is preferably 110% or less, more preferably 100% or less, and most preferably 90% or less with respect to the C content of the base material of the bolt. Further, the value of CP is a value obtained by measuring the carbon content of a coil-shaped high tensile steel wire (CP coil) provided in a furnace.
(回火T) (tempering T)
只做過淬火硬化的螺栓,韌性以及延性都很低,因此必須實施回火處理。回火溫度是設在300℃以上為宜。回火溫度更優是330℃以上、最優是350℃以上。但是,回火溫度太高的話,在舊沃斯田鐵結晶粒界將會析出粗大的雪明鐵,變得難以改善耐延遲破壞性。從而,在本發明的實施方式中,回火溫度是設在480℃以下為宜。回火溫度更優是460℃以下、最優是450℃以下。 Only hardened and hardened bolts have low toughness and ductility, so tempering must be performed. The tempering temperature is preferably set at 300 ° C or higher. The tempering temperature is more preferably 330 ° C or more, and most preferably 350 ° C or more. However, if the tempering temperature is too high, coarse snow feldspar will be precipitated in the old Wolster iron crystal grain boundary, and it becomes difficult to improve the resistance to delay damage. Therefore, in the embodiment of the present invention, the tempering temperature is preferably set to 480 ° C or lower. The tempering temperature is preferably 460 ° C or less, and most preferably 450 ° C or less.
(滾壓加工R) (rolling processing R)
在實施了淬火硬化回火之後,進行滾壓加工來形成螺紋部,藉此來賦予壓縮殘留應力。 After quench hardening and tempering, rolling processing is performed to form a threaded portion, thereby imparting compressive residual stress.
(珠擊加工SP) (bead processing SP)
在實施了淬火硬化回火之後,藉由進行珠擊加工,亦可賦予壓縮殘留應力。 After the quench hardening tempering is performed, the residual stress can be imparted by the bead blasting process.
珠擊加工的條件,雖然並未特別地限定,但是,例如:將噴珠的粒徑、投射速度以及投射時間,做下列的限制為宜。 The conditions of the beading processing are not particularly limited, but, for example, the particle size, the projection speed, and the projection time of the bead are preferably limited as follows.
噴珠粒徑是設在30~150μm為宜。噴珠粒徑小的話,可加大對於螺栓的表層之壓縮殘留應力,噴珠粒徑大的話,可將壓縮殘留應力賦予到達螺栓的深部。因此,在本發明的實施方式中,是將螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力,設為:拉伸強度×0.15MPa以上,因此,只要選擇噴珠粒徑即可。上述噴珠粒徑,較佳是30μm以上、更優是40μm以上、最優是45μm以上。但是,噴珠粒徑太大的話,螺栓的螺紋部的變形量太大,螺紋的精度將會變差。從而,在本發明的實施方式中,上述噴珠粒徑是設在150μm以下為宜。上述噴珠粒徑,更優是130μm以下、最優是120μm以下。 The particle size of the spray beads is preferably set at 30 to 150 μm. When the particle diameter of the bead is small, the compressive residual stress on the surface layer of the bolt can be increased, and if the particle diameter of the bead is large, the compressive residual stress can be applied to the deep portion of the bolt. Therefore, in the embodiment of the present invention, the compressive residual stress at a position where the depth of the bolt is 0.05 mm from the bottom surface of the screw is: tensile strength × 0.15 MPa or more, so that the bead diameter is selected. can. The particle diameter of the bead is preferably 30 μm or more, more preferably 40 μm or more, and most preferably 45 μm or more. However, if the particle diameter of the bead is too large, the amount of deformation of the thread portion of the bolt is too large, and the accuracy of the thread will be deteriorated. Therefore, in the embodiment of the present invention, the particle diameter of the bead is preferably 150 μm or less. The particle diameter of the bead is preferably 130 μm or less, and most preferably 120 μm or less.
投射速度是設在30~150m/秒為宜。投射速度大的話,可加大對於螺栓的表層之壓縮殘留應力。因此,在本發明的實施方式中,是將螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力設為:拉伸強度×0.15MPa以上,因此,只要設定投射速度即可。上述投射速度,較佳是30m/秒以上、更優是35m/秒以上、最優是40m/秒以上。投射速度,雖然是建議愈大愈好,但是因為受到設備上的制約,上限值大約是150m/秒以下。 The projection speed is preferably set at 30~150m/sec. When the projection speed is large, the compressive residual stress on the surface layer of the bolt can be increased. Therefore, in the embodiment of the present invention, the compressive residual stress at a position where the depth of the bolt is 0.05 mm from the bottom surface of the screw is: tensile strength × 0.15 MPa or more. Therefore, the projection speed may be set. The projection speed is preferably 30 m/sec or more, more preferably 35 m/sec or more, and most preferably 40 m/sec or more. The projection speed, although the recommended is larger, the upper limit is about 150 m/sec because of the constraints on the equipment.
投射時間,是設在10~60分鐘為宜。投射時間愈長的話愈可以賦予均一的壓縮殘留應力。從而,在本發明的實施方式中,投射時間是設在10分鐘以上為宜。投射時間,更好是15分以上、更優是20分以上。但是,投射時間太長的話,效果趨於飽和,因此將上限設在例 如:60分鐘以下為宜。投射時間更優是50分以下、最優是40分以下。 The projection time is set at 10~60 minutes. The longer the projection time, the more uniform compressive residual stress can be imparted. Therefore, in the embodiment of the present invention, it is preferable that the projection time is set to 10 minutes or more. The projection time is preferably 15 or more, and more preferably 20 or more. However, if the projection time is too long, the effect tends to be saturated, so the upper limit is set to the example. Such as: 60 minutes or less is appropriate. The projection time is preferably 50 or less, and the optimum is 40 or less.
珠擊加工的次數,不限定只有一次,亦可做複數次。藉由複數次進行珠擊加工,可更進一步提高螺栓的表層的壓縮殘留應力,因此可更為改善耐延遲破壞性以及疲勞特性。分成複數次來進行珠擊加工的話,可先使用粒徑相對地較大的噴珠來將壓縮殘留應力賦予到達螺栓的深部,然後,再使用粒徑相對地較小的噴珠來降低螺栓的表面粗糙度,並且可有效地對於螺栓的表層賦予較大的壓縮殘留應力。 The number of times of beading processing is not limited to one time, and can be repeated multiple times. By performing the bead blasting process a plurality of times, the compressive residual stress of the surface layer of the bolt can be further improved, so that the delayed fracture resistance and the fatigue property can be further improved. If it is divided into a plurality of times for beading processing, the beads having a relatively large particle diameter may be used to impart compressive residual stress to the deep portion of the bolt, and then the beads having a relatively small particle diameter may be used to reduce the bolt. The surface roughness is effective and gives a large compressive residual stress to the surface layer of the bolt.
(退火A) (annealing A)
將壓縮殘留應力賦予螺栓的表層之後,亦可因應必要進行退火。藉由進行退火,可使螺栓表層的變形趨於均一化,可更為提昇耐延遲破壞性以及疲勞特性。 After the compressive residual stress is applied to the surface layer of the bolt, annealing may be performed as necessary. By performing annealing, the deformation of the surface layer of the bolt tends to be uniform, and the resistance to delay damage and fatigue characteristics can be further improved.
退火條件並未特別地限定,只要將退火溫度例如:設在150~300℃的低溫,將退火時間例如:設在15~60分鐘即可。 The annealing conditions are not particularly limited as long as the annealing temperature is, for example, at a low temperature of 150 to 300 ° C, and the annealing time is, for example, 15 to 60 minutes.
經過這些工序而製得的螺栓,拉伸強度為1500MPa以上,而且耐延遲破壞性以及疲勞特性皆優異,因此,可以很適合使用於汽車、各種產業機械等。 The bolts obtained by these processes have a tensile strength of 1,500 MPa or more, and are excellent in both delayed fracture resistance and fatigue properties. Therefore, they can be suitably used in automobiles, various industrial machines, and the like.
〔實施例〕 [Examples]
以下,將舉出實施例來更具體地說明本發明 之一例,但是本發明並不受下列實施例的限制,只要是在符合前述以及後述的發明要旨的範圍內,當然都可加以變更來實施,這些變更也都被包含在本發明的技術範圍內。 Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to the following embodiments, and may be modified as long as it conforms to the scope of the invention and the scope of the invention described below, and these modifications are also included in the technical scope of the present invention. .
首先,熔製出母材是下列表1-1或表1-2所示的組成分的鋼(其餘部分是鐵以及不可避免的雜質),做成鋼錠,將製得的鋼錠進行熱軋而製造成直徑
Figure TWI612149BD00001
為14mm的輥軋線材。鋼錠的加熱溫度為1100℃、精製輥軋溫度為850℃。此外,在下列的表1-1以及表1-2當中,以「-」來表示的地方,是表示無添加。
First, the steel whose base material is the composition shown in Table 1-1 or Table 1-2 below (the rest is iron and unavoidable impurities) is melted into a steel ingot, and the obtained steel ingot is hot rolled. Made into diameter
Figure TWI612149BD00001
It is a 14mm rolled wire. The heating temperature of the ingot was 1100 ° C, and the refining rolling temperature was 850 ° C. In addition, in the following Table 1-1 and Table 1-2, the place indicated by "-" means no addition.
將製得的輥軋線材,依循一般方法,依序進行:除去鏽皮處理、球狀化退火、除去鏽皮處理、皮膜處理、伸線加工、球狀化退火、除去鏽皮處理、皮膜處理、精製伸線加工,將金屬組織以及線徑予以一致化,而製成直徑
Figure TWI612149BD00002
為11.8mm的鋼線。
The obtained rolled wire material is sequentially carried out according to the general method: removing the scale treatment, spheroidizing annealing, removing the scale treatment, coating treatment, wire drawing processing, spheroidizing annealing, removing the scale treatment, and treating the film. , refined wire drawing processing, metal structure and wire diameter are consistent, and made into diameter
Figure TWI612149BD00002
It is a steel wire of 11.8 mm.
使用多段成型模,藉由冷加滾壓工序而從鋼線製作出M12mm×P1.25mm以及軸桿長度L70mm的凸緣螺栓。此處的M是表示軸部的直徑,P是表示螺距。 Using a multi-stage molding die, a flange bolt of M12 mm × P1.25 mm and a shaft length L 70 mm was produced from a steel wire by a cold addition rolling process. Here, M denotes the diameter of the shaft portion, and P denotes the pitch.
針對於所製得的凸緣螺栓,改變其:淬火硬化Q、回火T、滾壓加工R、珠擊加工SP、退火A的條件以及加工順序來進行處理。在下列的表2中,顯示其條件與工序的順序。在下列的表2中,Q是表示淬火硬化,T是表示回火,R是表示滾壓加工,SP是表示珠擊加工,A是表示退火之意。 For the obtained flange bolt, the treatment is performed by changing the conditions of quench hardening Q, tempering T, rolling process R, beading process SP, annealing A, and processing sequence. In Table 2 below, the order of the conditions and the processes is shown. In the following Table 2, Q means quench hardening, T means tempering, R means rolling, SP means beading, and A means annealing.
淬火硬化Q,是進行加熱至下列的表2所示 的溫度,將淬火硬化加熱時的碳勢(CP)控制成如下列的表2所示的條件,來進行淬火硬化。淬火硬化的加熱時間設為20分鐘,淬火硬化是以60℃的油冷方式來進行的。 Quench hardening Q, which is heated to the following table 2 At the temperature, the carbon potential (CP) at the time of quench hardening heating was controlled to be quench-hardened under the conditions shown in Table 2 below. The heating time for quench hardening was set to 20 minutes, and quench hardening was carried out by oil cooling at 60 °C.
回火T,是加熱到下列的表2所示的溫度來進行的。回火的加熱時間是設為45分鐘。 The tempering T is carried out by heating to the temperatures shown in Table 2 below. The heating time for tempering is set to 45 minutes.
珠擊加工SP,係組合了下列的SP1或SP2的條件來進行的。在下列的表2中顯示出珠擊加工SP的具體組合方式。 The bead processing SP is carried out by combining the following conditions of SP1 or SP2. The specific combination of the beading process SP is shown in Table 2 below.
SP1=噴珠粒徑:100μm、投射速度:50m/秒、投射時間:10分鐘。 SP1 = bead diameter: 100 μm, projection speed: 50 m/sec, projection time: 10 minutes.
SP2=噴珠粒徑:50μm、投射速度:50m/秒、投射時間:10分鐘。 SP2 = particle diameter of the beads: 50 μm, projection speed: 50 m/sec, projection time: 10 minutes.
珠擊加工SP之後,因應必要,以加熱溫度:190℃以及加熱時間:30分鐘的條件進行退火A。 After the SP was processed, the annealing A was performed under the conditions of a heating temperature of 190 ° C and a heating time of 30 minutes as necessary.
針對製得的螺栓,依照以下的步驟,測定了(1)拉伸強度、(2)從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力、(3)從螺紋底面起算之深度為0.05mm位置處的C含量、(4)D/4位置處的舊沃斯田鐵結晶粒的平均粒徑、以及(5)從螺紋底面起算之深度為0.05mm位置處的舊沃斯田鐵結晶粒的平均粒徑。 For the obtained bolts, according to the following steps, (1) tensile strength, (2) compressive residual stress at a depth of 0.05 mm from the bottom of the thread, and (3) depth from the bottom of the thread of 0.05 were measured. The C content at the mm position, the average particle size of the old Worthite iron crystal grains at the (4) D/4 position, and (5) the old Worthite iron crystal at a depth of 0.05 mm from the bottom of the thread. The average particle size of the granules.
(1)螺栓的拉伸強度是依據日本工業規格JIS B1051(2009年)來進行測定的。將結果顯示於下列的表3-1或表3-2。本發明之一例是將拉伸強度為1500MPa以上視為合格。 (1) The tensile strength of the bolt was measured in accordance with Japanese Industrial Standard JIS B1051 (2009). The results are shown in Table 3-1 or Table 3-2 below. An example of the present invention is that a tensile strength of 1,500 MPa or more is regarded as acceptable.
(2)針對於螺栓的螺紋部,進行電解研磨,以使其露出從螺紋底面起算之深度為0.05mm的位置,露出面的壓縮殘留應力,則是根據下列的條件,利用X射線殘留應力測定法來進行了測定。將結果顯示於下列的表3-1或表3-2。 (2) Electrolytic polishing is performed on the threaded portion of the bolt so that the depth from the bottom surface of the screw is 0.05 mm, and the compressive residual stress on the exposed surface is measured by X-ray residual stress according to the following conditions. The method was measured. The results are shown in Table 3-1 or Table 3-2 below.
X射線入射方向:螺栓圓周方向 X-ray incident direction: bolt circumferential direction
輸出能量:40kV、40mA Output energy: 40kV, 40mA
照射時間:60sec Irradiation time: 60sec
縫隙:1.0mm Gap: 1.0mm
並且,計算出相對於上述拉伸強度之上述壓縮殘留應力的比值(壓縮殘留應力/拉伸強度),將結果顯示於下列的表3-1或表3-2。在本發明的一例中,係將上述比值為0.15以上視為合格。 Then, the ratio (compressive residual stress/tensile strength) of the above-mentioned compressive residual stress with respect to the above tensile strength was calculated, and the results are shown in Table 3-1 or Table 3-2 below. In an example of the present invention, the above ratio is regarded as 0.15 or more as a pass.
(3)將螺栓的螺紋部從縱斷面(對螺栓的軸保持平行的斷面)切斷,在從螺紋底面起算的深度方向上,進行EPMA(Electron Probe Micro Anlyzer)線分析,而測定了從螺紋底面起算之深度為0.05mm位置處的C含量。將結果顯示於下列的表3-1或表3-2。 (3) The threaded portion of the bolt was cut from the longitudinal section (the section in which the axis of the bolt was kept parallel), and the EPMA (Electron Probe Micro Anlyzer) line analysis was performed in the depth direction from the bottom surface of the screw. The depth from the bottom of the thread is the C content at a position of 0.05 mm. The results are shown in Table 3-1 or Table 3-2 below.
此外,計算出相對於母材的C含量之從螺紋底面起算之深度為0.05mm位置處的C含量的比率。將結果顯示於下列的表3-1或表3-2。並且,使用表1-1或表1-2所示的C含量來作為螺栓的母材的C含量,以計算出上述比率。 Further, the ratio of the C content at the position of 0.05 mm from the bottom surface of the thread with respect to the C content of the base material was calculated. The results are shown in Table 3-1 or Table 3-2 below. Further, the C content shown in Table 1-1 or Table 1-2 was used as the C content of the base material of the bolt to calculate the above ratio.
(4)將螺栓的軸部從橫斷面(對螺栓的軸保 持垂直的斷面)切斷,將軸部的直徑視為D時,利用光學顯微鏡以400的觀察倍率對於D/4位置處之任意的0.039mm2的領域進行了觀察。利用圖像解析來測定出位於D/4位置處的舊沃斯田鐵結晶粒的粒徑,求出其平均值。將結果顯示於下列的表3-1或表3-2。 (4) When the shaft portion of the bolt is cut from the cross section (a cross section perpendicular to the axis of the bolt), and the diameter of the shaft portion is regarded as D, the observation magnification of 400 with an optical microscope is at the D/4 position. Any of the fields of 0.039 mm 2 was observed. The particle size of the old Worthite iron crystal grains located at the D/4 position was measured by image analysis, and the average value thereof was determined. The results are shown in Table 3-1 or Table 3-2 below.
(5)將螺栓的螺紋部從縱斷面(對螺栓的軸保持平行的斷面)切斷,使用掃描型電子顯微鏡,以5000倍的觀察倍率,來觀察從螺紋底面起算之深度為0.05mm的位置,利用電子射線後方散亂繞射法(Electron Backscatter Diffraction:EBSD),測定了在觀察視野內的舊沃斯田鐵結晶粒的粒徑,求出其平均值。利用EBSD法時的測定條件如下所示。將結果顯示於下列的表3-1或表3-2。 (5) Cut the threaded portion of the bolt from the longitudinal section (the section parallel to the axis of the bolt), and observe the depth from the bottom of the thread to 0.05 mm using a scanning electron microscope at an observation magnification of 5000 times. The position of the old Worthite iron crystal grain in the observation field was measured by Electron Backscatter Diffraction (EBSD), and the average value was determined. The measurement conditions when using the EBSD method are as follows. The results are shown in Table 3-1 or Table 3-2 below.
裝置名稱:TSL製OIM結晶方位解析裝置(EBSD) Device Name: TIM OIM Crystal Orientation Analysis Device (EBSD)
加速電壓:15kV Acceleration voltage: 15kV
分析範圍:寬50μm×縱52.5μm Analysis range: width 50μm × vertical 52.5μm
步進寬度:0.15μm Step width: 0.15μm
接下來,針對於所製得的螺栓進行(6)耐延遲破壞性以及(7)疲勞特性評比。 Next, (6) delayed fracture resistance and (7) fatigue characteristic evaluation were performed for the obtained bolts.
(6)首先,將所製得的螺栓安裝到具有荷重計的夾具,利用螺帽動力扳手來將螺栓旋轉以將夾具夾緊,藉此,可以獲得螺栓的旋轉角度與軸力的關係。然後,根據這種關係,分別求出:加諸在螺栓上的軸力到達降伏點時的旋轉角度,以及加諸於螺栓的軸力趨於最大軸 力時的旋轉角度。接下來,進行下列的2種水準的延遲破壞試驗。下列的延遲破壞試驗2的條件是較之下列的延遲破壞試驗1的條件更為嚴酷的條件,因此,下列的延遲破壞試驗1中被視為不合格的螺栓,就不再實施下列的延遲破壞試驗2。在本發明的一例中,是將下列的延遲破壞試驗1中被視為合格(○)的螺栓,予以評比為耐延遲破壞性優異,將下列的延遲破壞試驗2中被視為合格(○)的螺栓,予以評比為耐延遲破壞性極優異。 (6) First, the obtained bolt is attached to a jig having a load meter, and a nut is rotated by a nut to clamp the jig, whereby the relationship between the rotation angle of the bolt and the axial force can be obtained. Then, based on this relationship, it is determined separately: the angle of rotation when the axial force applied to the bolt reaches the point of undulation, and the axial force applied to the bolt tends to the maximum axis The angle of rotation of the force. Next, the following two levels of delayed damage tests were carried out. The following conditions of the delayed damage test 2 are more severe conditions than those of the following delayed damage test 1, and therefore, the following delayed damage is not performed for the bolts which are regarded as unqualified in the following delayed damage test 1. Test 2. In the example of the present invention, the bolts which are considered to be acceptable (○) in the following delayed fracture test 1 are evaluated as excellent in resistance to delayed fracture, and are considered to be acceptable in the following delayed fracture test 2 (○). The bolts are rated as excellent in resistance to delay damage.
(延遲破壞試驗1) (Delayed damage test 1)
旋轉螺栓直到加諸於螺栓的軸力到達降伏點時的旋轉角度為止,以將夾具鎖緊之後,將每一個夾具浸泡在濃度為1%的HCl中達到200小時,對其耐延遲破壞性進行評比。螺栓是以每組10支來進行評比。10支當中完全都沒有斷裂的話,就視為合格,在下列的表3-1以及表3-2中,係標示為○。10支當中只要有1支斷裂的話,就視為不合格,在下列的表3-1以及表3-2中,係標示為×。 Rotate the bolt until the axial force applied to the bolt reaches the angle of rotation at the point of the drop. After the clamp is locked, each fixture is immersed in 1% HCl for 200 hours to delay the damage resistance. Rating. Bolts are rated in groups of 10 each. If none of the 10 pieces are broken, it is regarded as pass, and in the following Table 3-1 and Table 3-2, it is marked as ○. As long as one of the 10 breaks is considered to be unsatisfactory, it is marked as × in Tables 3-1 and 3-2 below.
(延遲破壞試驗2) (Delayed damage test 2)
在上述延遲破壞試驗1中,是將螺栓的旋轉量旋轉至加諸於螺栓的軸力到達降伏點時的旋轉角度為止,以將夾具鎖緊,而在延遲破壞試驗2中,則是將螺栓的旋轉量旋轉至加諸於螺栓的軸力到達最大軸力(螺栓旋轉角度-軸力線關係圖中的最大軸力)時旋轉角度為止,以將夾具鎖 緊之後,再更加鎖緊+90°,除此之外,其他的條件都是與上述延遲破壞試驗1相同的條件來進行試驗,根據相同的基準來評比耐延遲破壞性。將結果標示於下列表3-1以及表3-2。 In the above-described delayed fracture test 1, the rotation amount of the bolt is rotated until the rotation angle of the bolt applied to the point at which the bolt reaches the drop point to lock the clamp, and in the delayed damage test 2, the bolt is The amount of rotation is rotated until the axial force applied to the bolt reaches the maximum axial force (the maximum axial force in the bolt rotation angle - the axial force line diagram), so that the clamp is locked After that, it was further locked to +90°, and other conditions were tested under the same conditions as the above-described delayed fracture test 1, and the delayed fracture resistance was evaluated based on the same criteria. The results are shown in Table 3-1 below and Table 3-2.
(7)使用油壓伺服脈衝產生機,進行下列的2種水準的疲勞試驗。下列的疲勞試驗2的條件是較之下列的疲勞試驗1的條件更為嚴酷的條件,因此,在下列的疲勞試驗1中被視為不合格的螺栓,就不再實施下列的疲勞試驗2。在本發明之一例中,是將在下列的疲勞試驗1中被視為合格(○)的螺栓,予以評比為疲勞特性優異,將在下列的疲勞試驗2中被視為合格(○)的螺栓,予以評比為疲勞特性極優異。 (7) The following two levels of fatigue tests were performed using a hydraulic servo pulse generator. The conditions of the following fatigue test 2 are more severe conditions than those of the following fatigue test 1, and therefore, the following fatigue test 2 is not performed in the case of the bolt which is regarded as unacceptable in the following fatigue test 1. In the example of the present invention, the bolt which is regarded as the pass (○) in the following fatigue test 1 is evaluated as a bolt which is excellent in fatigue characteristics and is regarded as qualified (○) in the following fatigue test 2 It is rated as excellent in fatigue characteristics.
(疲勞試驗1) (Fatigue test 1)
將螺栓的拉伸強度之0.5倍視為平均應力,以平均應力的16%視為振幅應力,實施至2×106次為止,來評比疲勞特性。螺栓是以每組為5支來進行評比,5支當中沒有任何一支斷裂的話,就視為合格,在下列的表3-1以及表3-2中,標示為○。5支當中只要有任何一支斷裂的話,就視為不合格,在下列的表3-1以及表3-2中,標示為×。 0.5 times of the tensile strength of the bolt was regarded as the average stress, and 16% of the average stress was regarded as the amplitude stress, and the fatigue characteristics were evaluated until 2×106 times. Bolts are evaluated in groups of five, and none of the five rods are considered to be acceptable. In Tables 3-1 and 3-2 below, they are marked as ○. As long as any one of the five branches is broken, it is regarded as unqualified. In the following Table 3-1 and Table 3-2, it is marked as ×.
(疲勞試驗2) (Fatigue test 2)
在上述疲勞試驗1中,是以螺栓的拉伸強度之0.5倍 視為平均應力,而在疲勞試驗2中,則是以螺栓的拉伸強度之0.6倍視為平均應力,除此之外,都是以相同的條件來進行試驗,以相同的基準來評比疲勞特性。將結果標示在下列的表3-1以及表3-2。 In the above fatigue test 1, it is 0.5 times the tensile strength of the bolt. It is regarded as the average stress, and in the fatigue test 2, the average stress is regarded as 0.6 times the tensile strength of the bolt. In addition, the test is performed under the same conditions, and the fatigue is evaluated on the same basis. characteristic. The results are shown in Table 3-1 and Table 3-2 below.
由下列的表1-1、表1-2、表2、表3-1、以及表3-2可以獲得以下的考察結果。 The following findings can be obtained from Table 1-1, Table 1-2, Table 2, Table 3-1, and Table 3-2 below.
No.1~23、42~44是符合本發明規定的要件之例子,可以得知是具有高強度,並且可發揮優異的耐延遲破壞性以及疲勞特性。亦即,No.1~23、42~44都是在延遲破壞試驗1以及疲勞試驗1的基準下,合格的例子。尤其是No.42、43與No.1~23、44進行比較的話,可以得知:其是藉由將螺栓之從螺紋底面起算之深度為0.05mm的位置處的C含量的比率,予以調整成:相對於母材的C含量,是50~110%,而可更為提昇耐延遲破壞性以及疲勞特性。亦即,No.1~23、44即使是在延遲破壞試驗2以及疲勞試驗2的基準下,也是合格的例子。 No. 1 to 23 and 42 to 44 are examples in accordance with the requirements of the present invention, and it is known that they have high strength and exhibit excellent resistance to retardation and fatigue. In other words, No. 1 to 23 and 42 to 44 are all qualified examples under the criteria of the delayed damage test 1 and the fatigue test 1. In particular, when No. 42, 43 is compared with No. 1 to 23, 44, it can be known that it is adjusted by the ratio of the C content at a position where the depth of the bolt is 0.05 mm from the bottom surface of the screw. Cheng: Compared with the C content of the base metal, it is 50~110%, which can improve the resistance to delayed damage and fatigue. That is, No. 1 to 23, and 44 are acceptable examples even in the case of the delayed damage test 2 and the fatigue test 2.
相對於此,No.24~41是不符合本發明所規定的要件之其中任一項要件的例子,不是無法製造成螺栓,就是即使製造成螺栓之後,在強度、耐延遲破壞性、以及疲勞特性之中,至少有一項特性表現不佳。 On the other hand, No. 24 to 41 are examples of any one of the requirements not required by the present invention, and it is not impossible to manufacture a bolt, that is, strength, resistance to delay damage, and fatigue even after being manufactured into a bolt. At least one of the characteristics is underperforming.
在這些當中,No.24~26的例子,是在滾壓之後,實施了淬火硬化和回火,因此,是屬於:在螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力,在其與拉伸強度的關係上,太低的例子。其結果,無法改 善耐延遲破壞性以及疲勞特性。 Among these, the example No. 24 to 26 is quench hardened and tempered after rolling, and therefore belongs to the compressive residual stress at a depth of 0.05 mm from the bottom surface of the bolt. In its relationship with tensile strength, it is an example that is too low. The result cannot be changed Good resistance to delayed destructive and fatigue characteristics.
No.27是C含量太少的例子,即使將回火溫度提高到300℃,也無法確保1500MPa以上的拉伸強度。 No. 27 is an example in which the C content is too small, and even if the tempering temperature is raised to 300 ° C, the tensile strength of 1500 MPa or more cannot be secured.
No.28是C含量太多的例子,鋼的韌性延性都變差,因此,無法改善耐延遲破壞性以及疲勞特性。 No. 28 is an example in which the C content is too large, and the ductility ductility of the steel is deteriorated, so that the delay destructive resistance and the fatigue characteristics cannot be improved.
No.29是Si含量太少的例子,有粗大的雪明鐵析出於結晶粒界,因此,無法改善耐延遲破壞性以及疲勞特性。 No. 29 is an example in which the Si content is too small, and the coarse snow-smelting iron is precipitated in the crystal grain boundary, and therefore, the delayed fracture resistance and the fatigue property cannot be improved.
No.30是Si含量太多的例子,因為有肥粒鐵析出,因而無法改善疲勞特性。 No. 30 is an example in which the Si content is too large, and since the ferrite is precipitated, the fatigue characteristics cannot be improved.
No.31是Mn含量太多的例子,因為有粗大的MnS生成,因而無法改善耐延遲破壞性以及疲勞特性。 No. 31 is an example in which the Mn content is too large, and since coarse MnS is formed, the delayed fracture resistance and the fatigue characteristics cannot be improved.
No.32是P含量太多的例子,因為P在結晶粒界濃化,鋼的韌性延性降低,因而無法改善耐延遲破壞性。 No. 32 is an example in which the P content is too large, since P is concentrated at the crystal grain boundary, and the ductility ductility of the steel is lowered, so that the delayed fracture resistance cannot be improved.
No.33是S含量太多的例子,與P同樣地,S會在結晶粒界濃化,鋼的韌性延性降低,因而無法改善耐延遲破壞性。 No. 33 is an example in which the S content is too large. Similarly to P, S is concentrated at the crystal grain boundary, and the ductility of the steel is lowered, so that the retardation resistance cannot be improved.
No.34是Cr含量太少的例子,因為鋼的耐腐蝕性變差,因而無法改善耐延遲破壞性。 No. 34 is an example in which the Cr content is too small, and since the corrosion resistance of steel is deteriorated, the delay destructive resistance cannot be improved.
No.35是Mo含量太多的例子,因為熱間延性變差,甚至於線材本身都無法被製造出來。 No. 35 is an example in which the Mo content is too large, because the thermal ductility is deteriorated, and even the wire itself cannot be manufactured.
No.36是Al含量太多的例子,因為形成了粗大的氮化物,因而無法改善疲勞特性。 No. 36 is an example in which the Al content is too large, and since the coarse nitride is formed, the fatigue characteristics cannot be improved.
No.37是N含量太多的例子,因為形成了粗大的氮化物,因而無法改善疲勞特性。 No. 37 is an example in which the N content is too large, and since the coarse nitride is formed, the fatigue characteristics cannot be improved.
No.38~40是Ti含量以及Nb含量低於本發明所規定的範圍,是Ti含量以及Nb含量太少的例子,因為在D/4位置處的舊沃斯田鐵結晶粒變粗大化,因此,無法改善耐延遲破壞性以及疲勞特性。 No. 38 to 40 are examples in which the Ti content and the Nb content are lower than the range defined by the present invention, and the Ti content and the Nb content are too small, because the old Worthite iron crystal grains at the D/4 position become coarse, Therefore, the resistance to delay damage and the fatigue characteristics cannot be improved.
No.41是因為淬火硬化溫度太高,因此,在D/4位置處的舊沃斯田鐵結晶粒變粗大化,鋼的韌性延性變差的例子。其結果,無法改善耐延遲破壞性以及疲勞特性。 No. 41 is an example in which the quench hardening temperature is too high, and the old Worth iron crystal grains at the D/4 position are coarsened, and the ductility ductility of the steel is deteriorated. As a result, the delayed fracture resistance and the fatigue characteristics cannot be improved.
Figure TWI612149BD00003
Figure TWI612149BD00003
Figure TWI612149BD00004
Figure TWI612149BD00004
Figure TWI612149BD00005
Figure TWI612149BD00005
Figure TWI612149BD00006
Figure TWI612149BD00006
Figure TWI612149BD00007
Figure TWI612149BD00007
本說明書的揭示內容係包含下列的態樣。 The disclosure of this specification contains the following aspects.
態樣:1 Aspect: 1
一種耐延遲破壞性及疲勞特性優異的高強度螺栓,其特徵為:母材的組成分,以質量%計,係含有C:0.25~0.5%、Si:1.5~3.0%、Mn:0.1~1.5%、P:高於0%且0.03%以下、S:高於0%且0.03%以下、Cr:0.05~1.5%、Mo:0%以上且低於0.2%、Al:0.01~0.1%、以及N:0.002~0.020%,並且又含有Ti:0.02~0.1%、以及Nb:0.02~0.1%之中的一種或兩種,其餘部分是鐵以及不可避免的雜質,拉伸強度是1500MPa以上,螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力是拉伸強度×0.15MPa以上,將螺栓的軸部的直徑視為D時,在D/4位置處的舊沃斯田鐵結晶粒的平均粒徑是5~15μm。 A high-strength bolt excellent in delayed fracture resistance and fatigue characteristics, characterized in that the composition of the base material, in mass%, contains C: 0.25 to 0.5%, Si: 1.5 to 3.0%, and Mn: 0.1 to 1.5. %, P: higher than 0% and 0.03% or less, S: higher than 0% and 0.03% or less, Cr: 0.05 to 1.5%, Mo: 0% or more and less than 0.2%, Al: 0.01 to 0.1%, and N: 0.002~0.020%, and further contains one or two of Ti: 0.02~0.1%, and Nb: 0.02~0.1%, the rest is iron and unavoidable impurities, the tensile strength is 1500MPa or more, bolt The compressive residual stress at a position of 0.05 mm from the bottom of the thread is tensile strength × 0.15 MPa or more, and when the diameter of the shaft portion of the bolt is regarded as D, the old Worthite iron crystal at the D/4 position The average particle size of the particles is 5 to 15 μm.
態樣2: Aspect 2:
一種如態樣1所述的高強度螺栓,其中,以質量%計,又含有下列的其他元素,Cu:高於0%且0.5%以下、以及Ni:高於0%且1%以下之一種或兩種。 A high-strength bolt according to aspect 1, wherein, in mass%, further contains the following other elements, Cu: more than 0% and less than 0.5%, and Ni: more than 0% and less than 1% Or two.
態樣3: Aspect 3:
一種如態樣1或2所述的高強度螺栓,其中,以質量%計,又含有下列的其他元素,V:高於0%且0.5%以下、以及W:高於0%且0.5%以下之一種或兩種。 A high-strength bolt according to aspect 1 or 2, wherein, in mass%, further contains the following other elements, V: more than 0% and less than 0.5%, and W: more than 0% and less than 0.5% One or two.
態樣4: Aspect 4:
一種如態樣1至3之任一種態樣所述的高強度螺栓,其中,螺栓之從螺紋底面起算之深度為0.05mm位置處的C含量的比率,相對於前述母材的C含量,是50~110%。 A high-strength bolt according to any one of the aspects 1 to 3, wherein a ratio of a C content at a depth of 0.05 mm from a bottom surface of the screw is relative to a C content of the base material. 50~110%.
態樣5: Aspect 5:
一種如態樣1至4之任一種態樣所述的高強度螺栓的製造方法,其特徵為:在淬火硬化回火後,執行從滾壓加工以及珠擊加工所選出的至少一種加工,藉此,對於螺栓賦予壓縮殘留應力。 A method for manufacturing a high-strength bolt according to any one of the aspects 1 to 4, characterized in that after quenching hardening and tempering, at least one type of processing selected from rolling processing and beading processing is performed, Thus, a compressive residual stress is imparted to the bolt.
態樣6: Aspect 6:
一種如態樣5所述的高強度螺栓的製造方法,其中,前述淬火硬化,是在相對於母材的C含量,碳勢為50~110%的爐氣氛圍中進行的。 A method for producing a high-strength bolt according to aspect 5, wherein the quench hardening is carried out in a furnace atmosphere having a carbon potential of 50 to 110% with respect to the C content of the base material.
態樣7: Aspect 7:
一種如態樣5或6所述的高強度螺栓的製造方法,其中,是在賦予壓縮殘留應力之後,進行退火處理。 A method for producing a high-strength bolt according to aspect 5 or 6, wherein the annealing treatment is performed after imparting a compressive residual stress.
本申請案是以2015年12月1日在日本申請發明專利的日本國特許出願之特願第2015-235196號作為基礎申請案來主張優先權。該特願第2015-235196號的內容係被引用到本說明書中。 The present application claims priority on Japanese Patent Application No. 2015-235196, the entire disclosure of which is incorporated herein by reference. The contents of the Japanese Patent Application No. 2015-235196 are incorporated herein by reference.

Claims (6)

  1. 一種耐延遲破壞性及疲勞特性優異的高強度螺栓,其特徵為:母材的組成分,以質量%計,係含有C:0.25~0.5%、Si:1.5~3.0%、Mn:0.1~1.5%、P:高於0%且0.03%以下、S:高於0%且0.03%以下、Cr:0.05~1.5%、Mo:0%以上且低於0.2%、Al:0.01~0.1%、以及N:0.002~0.020%,並且又含有Ti:0.02~0.1%、以及Nb:0.02~0.1%之中的一種或兩種,其餘部分是鐵以及不可避免的雜質,拉伸強度是1500MPa以上,螺栓之從螺紋底面起算之深度為0.05mm位置處的壓縮殘留應力是拉伸強度×0.15MPa以上,將螺栓的軸部的直徑視為D時,在D/4位置處的舊沃斯田鐵結晶粒的平均粒徑是5~15μm。 A high-strength bolt excellent in delayed fracture resistance and fatigue characteristics, characterized in that the composition of the base material, in mass%, contains C: 0.25 to 0.5%, Si: 1.5 to 3.0%, and Mn: 0.1 to 1.5. %, P: higher than 0% and 0.03% or less, S: higher than 0% and 0.03% or less, Cr: 0.05 to 1.5%, Mo: 0% or more and less than 0.2%, Al: 0.01 to 0.1%, and N: 0.002~0.020%, and further contains one or two of Ti: 0.02~0.1%, and Nb: 0.02~0.1%, the rest is iron and unavoidable impurities, the tensile strength is 1500MPa or more, bolt The compressive residual stress at a position of 0.05 mm from the bottom of the thread is tensile strength × 0.15 MPa or more, and when the diameter of the shaft portion of the bolt is regarded as D, the old Worthite iron crystal at the D/4 position The average particle size of the particles is 5 to 15 μm.
  2. 如請求項1所述的高強度螺栓,其中,以質量%計,係以至少符合下列的(a)條件或(b)條件的方式, 又含有其他的元素,(a)條件是Cu:高於0%且0.5%以下、以及Ni:高於0%且1%以下之一種或兩種;(b)條件是V:高於0%且0.5%以下、以及W:高於0%且0.5%以下之一種或兩種。 The high-strength bolt according to claim 1, wherein, in mass%, in a manner that at least conforms to the following condition (a) or (b), Further containing other elements, (a) the condition is Cu: higher than 0% and less than 0.5%, and Ni: one or two of higher than 0% and less than 1%; (b) condition is V: higher than 0% And 0.5% or less, and W: one or two of more than 0% and 0.5% or less.
  3. 如請求項1或2所述的高強度螺栓,其中,螺栓之從螺紋底面起算之深度為0.05mm位置處的C含量的比率,相對於前述母材的C含量,是50~110%。 The high-strength bolt according to claim 1 or 2, wherein a ratio of the C content of the bolt at a depth of 0.05 mm from the bottom surface of the screw is 50 to 110% with respect to the C content of the base material.
  4. 一種如請求項1或2所述的高強度螺栓的製造方法,其特徵為:在淬火硬化回火後,執行從滾壓加工以及珠擊加工所選出的至少一種加工,藉此,對於螺栓賦予壓縮殘留應力。 A method of manufacturing a high-strength bolt according to claim 1 or 2, characterized in that after quench hardening and tempering, at least one of the processes selected from the rolling process and the beading process is performed, thereby imparting a bolt Compress residual stress.
  5. 如請求項4所述的製造方法,其中,前述淬火硬化,是在相對於母材的C含量,碳勢為50~110%的爐氣氛圍中進行的。 The production method according to claim 4, wherein the quench hardening is carried out in a furnace atmosphere having a carbon potential of 50 to 110% with respect to the C content of the base material.
  6. 如請求項4所述的製造方法,其中,是在賦予壓縮殘留應力之後,進行退火處理。 The manufacturing method according to claim 4, wherein the annealing treatment is performed after the compressive residual stress is applied.
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