钛对高强度钢耐延迟断裂性能的影响

在42CrMo钢中加入不同含量的微合金元素钛，研究了钛对高强度钢耐延迟断裂性能的影响。试验结果表明，钢中添加适量的钛能够改变高强度钢的耐延迟断裂性能，这种影响主要来自于析出物TiC的氢陷阱作用和晶粒细化作用。     

Correlation of Microstructure and Hydrogen Delayed Fracture for 1GPa Steels

Automobile industry tries to reduce the weight of automobile using high-strength steels.However,the high-strength steels are highly susceptible to delayed-fracture caused by hydrogen embrittlement.With increasing the strength,hydrogen embrittlement is more sensitive to diffusible hydrogen.The mechanism of delayed-fracture and the relationship with the microstructure and alloying elements are still ambiguous.This study analyzed the effect of the size and the spheroidization rate for the carbides on hydrogen-induced delayed fracture for 1GPa TS steel.     

Nb对中碳低合金耐磨钢组织和性能的影响

通过光学显微镜、扫描电镜、透射电镜、力学性能测试等手段分析了微量合金元素铌对低合金耐磨钢组织和性能的影响.加入质量分数为0.034%的Nb后,耐磨钢的硬度提高HB 9,-20℃夏比冲击功从29.4 J提高到37.6 J,耐磨性能提高3.5%.硬度和韧性提高的主要原因是组织的细化和析出强化,含Nb钢在奥氏体化过程中析出纳米级的细小NbC第二相,并且钉扎奥氏体晶界,抑制晶粒的长大,钉扎类型符合Zener模型,但不同于之前研究者所得的比例系数.     

高强度钢42CrMoVNb的氢致延迟断裂行为

采用阴极充氢、SSRT缺口拉伸和氢热分析等试验方法,研究了高强度钢42CrMoVNb在不同温度回火状态下的延迟断裂行为,并与常用的机械制造用钢42CrMo进行了对比。结果表明,随着回火温度的升高,试验钢的耐延迟断裂抗力逐渐提高;在相同回火温度下,由于42CrMoVNb钢的强度水平明显高于42CrMo钢,其耐延迟断裂抗力...     

碳含量对Mn-B钢氢致延迟断裂行为的影响

采用电化学阴极充氢、氢热分析(TDS)和慢应变速率拉伸等试验方法,研究了4种不同碳含量Mn-B钢经不同热处理制度处理后的氢致延迟断裂行为。结果表明,在低于400℃回火时,随着碳含量的增加,试验钢的氢脆敏感性升高,当碳的质量分数高于0.3%后,试验钢的氢脆敏感性几乎不再增加;碳含量一定时,试验钢的氢脆敏感性随回火温度的升高而降低,且以20MnB试验钢的降低趋势最为明显;当回火温度达到600℃时,各试验钢对氢几乎不再敏感;TDS分析表明,试验钢充氢后的氢含量明显增加,其中以可扩散性氢量的增加为主;随碳含量的增加,试验钢充入的氢量增加;当碳含量一定时,随回火温度的升高,试验钢充入的氢量减少;SEM断口观察表明,试验钢充氢后的脆性断裂倾向性增加;随着碳含量的升高,试验钢的断裂方式由韧性断裂向脆性断裂转变;碳含量一定时,随回火温度的升高,试验钢由淬火态的脆性断裂向高温回火态的韧性断裂转变。     

1300 MPa High Strength Steel for Bolt with Superior Delayed Fracture Resistance

Ｗｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｍｏｄｅｒｎｉｎｄｕｓｔｒｙ ,ｔｈｅｒｅｉｓａｉｎｃｒｅａｓｉｎｇｄｅｍａｎｄｆｏｒｈｉｇｈｓｔｒｅｎｇｔｈｓｔｅｅｌｓｗｉｔｈａｔｅｎｓｉｌｅｓｔｒｅｎｇｔｈｅｘｃｅｅｄｉｎｇ 12 0 0ＭＰａｔｏｂｅｕｓｅｄｆｏｒｈｉｇｈｅｒｓｔｒｅｎｇｔｈｂｏｌｔｓｉｎｔｈｅｃｏｎｓｔｒｕｃｔｉｏｎｉｎ ｄｕｓｔｒｙ ,ａｕｔｏｍｏｂｉｌｅ ｐａｒｔｓ ,ｌｏｎｇ ｓｐａｎｓｕｓｐｅｎｓｉｏｎｂｒｉｄｇｅｓ,ａｎｄｓｏｏｎ[1] .Ｈｏｗｅｖｅｒ ,ｆｏｒｑｕｅｎｃｈｅｄａｎｄｔｅｍｐ…     

氮-钒微合金化对低碳耐候钢强韧性的影响

利用真空感应炉冶炼氮-钒微合金化的低碳耐候钢,结合金相显微镜和透射电镜分析了耐候钢的显微组织,并通过拉伸、冲击试验和断口分析表征了实验钢的强韧性.力学试验结果表明,氮-钒微合金化耐候钢具有良好的塑性和强韧性组合.金相组织分析表明,加氮加钒耐候钢中主要组织为等轴铁素体和少量离异型珠光体(体积分数5%),体积分数约30%的铁素体晶粒中有类似粒状贝氏体组织生成;弥散析出的VN质点细化了铁素体晶粒,铁素体平均晶粒尺寸为7.8 μm.     

Effects of Niobium and Vanadium on Hydrogen-Induced Delayed Fracture in High Strength Spring Steel

 Influence of vanadium and/or niobium additions on delayed fracture behavior in high strength spring steel was studied by hydrogen permeation method and slow strain rate technique (SSRT), and its mechanism was analyzed. The results show that apparent diffusion coefficient of hydrogen in microalloyed spring steels Nb V steel and Nb steel is lower than that in non microalloyed steel 60Si2MnA. Percentage of strength reduction in SSRT in air after precharged hydrogen of the microalloyed steels is smaller than that of 60Si2MnA. Addition of the microalloys changes the fracture characteristics. Thence, vanadium and/or niobium additions are a very effective and economy means to improve the hydrogen induced delayed fracture resistance of high strength spring steel.     

Delayed Fracture Behavior of CrMo Type High Strength Steel Containing Vanadium

The quenchedandtemperedlowalloysteelswithtensilestrengthexceeding 12 0 0MPaaresus ceptibletohydrogen induceddelayedfracture(HIDF )wheninuse[1,2 ] .Despitetheenormousamountofresearchworkperformedondelayedfrac tureofhighstrengthsteelintheseyears ,thesolu tiontothisproblemstillhasnotbeenobtained .TheresistanceofanalloytoHIDFisstronglyaffectedbytheinteractionofhydrogenwithmicrostructuralhet erogeneitiesthatactashydrogentraps ,andthere foreinasearlyas 1980s ,GMPressouyre[3 ] suggest edtheappli…     

Nb微合金化在EAF-CSP流程管线钢生产的技术应用

通过研究Nb的固溶、析出规律;EAF-CSP流程对含Nb钢影响;Nb,Ti微合金化的第2相粒子的固溶析出和奥氏体晶粒长大规律;成功开发出Nb,Ti微合金化的管线钢,且消除了含Nb钢的混晶问题,避免了Nb钢的铸坯裂纹,其产品的组织和性能均能满足用户要求.     

Microstructure Development for Brittle Fracture Control in Nb Microalloyed Line Pipe Steel

EBSD characterization of density and dispersion of high angle boundaries was carried out in niobium microalloyed steels of HTP base chemistry with 0.09 wt % Nb,which were thermo-mechanically processed under laboratory conditions.Similar studies were carried out in higher grade (X-100 and above) line pipe steels with different chemistries,which were processed under simulation of industrial rolling conditions.The twin objectives are (i) to understand the effect of chemistry and processing parameters on the density and dispersion of high angle boundaries,and (ii) to correlate the microstructure and density of high angle boundaries with strength and fracture properties.The present studies confirm that refinement of austenite grain size prior to pancaking,large strain accumulation in austenite conditioning,alloy design with high hardenability and high cooling rates are essential to control high density and uniformity of dispersion of high angle boundaries in the final microstructure in order to achieve high strength,toughness,low DBTT and consistently 100% ductile shear in DWTT in thermo-mechanically rolled higher grade line pipe steels.     

Delayed Fracture Behavior of CrMo-Type High Strength Steel Containing Titanium

Generally ,thequenchedandtemperedlowalloysteelswithtensilestrengthabove 12 0 0MPaaresus ceptibletohydrogen induceddelayedfracture(HIDF) [1,2 ] .Extensivestudiesonthedelayedfracturebehaviorofhighstrengthsteelshavebeenperformedtheseyears,butthesatisfactorys…     

超高强度热冲压用钢中H的扩散与氢致滞后开裂行为

采用阴极充H、恒载荷拉伸和电化学H渗透等试验方法,研究了超高强度钢22MnB5Nb的H扩散行为及氢致滞后开裂性能,并与常用热冲压钢22MnB5进行了对比。结果表明,H在22MnB5Nb钢中的扩散系数为3.02×10-7 cm2/s,显著低于22MnB5钢;与22MnB5钢相比,22MnB5Nb钢具有较好的耐氢致滞后开裂性能;这是由于22MnB5Nb钢晶粒较细小,增加了晶界的有效面积,使H陷阱分布更均匀,进而抑制H向裂纹尖端扩展,避免了局部H的富集。     

Effect of Boron on Delayed Fracture Resistance of Medium-Carbon High Strength Spring Steel

The delayed fracture behavior of medium-carbon high strength spring steel containing different amounts of boron (0.000 5%, 0.001 6%) was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron content from 0.000 5% to 0.001 6%. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350 ℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initiation area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3(C, B) phase.     

Delayed Fracture Resistance and Mechanical Properties of 30MnSi High Strength Steel

To investigate the effect of heat treatment on mechanical properties and delayed fracture resistance of high strength steel, 30MnSi prestressed concrete (PC) steel bars are quenched and tempered. Tensile results show that, after 950 °C quenching and about 430 °C tempering, 30MnSi PC steel bars have superior mechanical properties and delayed fracture resistance. Microstructural observation shows that 30MnSi steel bar is mainly composed of fine tempered sorbite (troostite) with carbide distributed along the lath martensite boundaries. It can be concluded that thermal refining is an effective way to improve mechanical properties and delayed fracture resistance of 30MnSi PC steel bar.     

亚稳奥氏体和微合金元素对冷轧高强汽车钢性能的影响

介绍了亚稳奥氏体和微合金元素（Nb、V）对TRIP钢、TWIP钢和Q＆P钢等冷轧高强汽车钢性能的影响。主要包括调控冷轧高强汽车钢亚稳奥氏体组织的成分体系和连续退火工艺、亚稳奥氏体组织特征及测量方法,及其对高强汽车钢强塑积、拉伸曲线形状等性能的影响等。同时介绍了微合金元素（V、Nb）对冷轧高强汽车钢成形性、强度等级、延迟断裂等个性化性能的影响。     

Formability of High Strength Dual‐phase Steels

The application of ferritic‐martensitic dual‐phase (DP) steels has become an increasing trend in the automotive industry due to the possibility to achieve significant weight reduction and fuel efficiency with improved crash performance while keeping the manufacturing costs at affordable levels. In order to meet the different design requirements of individual auto‐body components, a wide variety of DP grades exhibiting different strength and ductility levels is currently industrially produced. Despite the numerous studies on the relationship between the mechanical properties and the microstructural characteristics of DP steels over the last decades, it is still a challenge to increase their formability at a constant strength level (or equivalently increasing the strength while maintaining a high ductility). One of the possibilities to increase strength is grain refinement. Ultrafine‐grained ferritic‐martensitic microstructures were produced by intercritical annealing of a cold‐rolled, pre‐processed dual‐phase steel. Ferrite mean grain sizes in the order of ~ 1.5 μm were obtained. The mechanical properties of these steels are studied, revealing the beneficial effect of grain refinement. Ultimate tensile strength above 800 MPa is achievable, while reaching remarkable high uniform and total elongations, which are only slightly affected by the martensite volume fraction. Moreover, the yield to tensile strength ratio can be adjusted between 0.4 and 0.5. Light and electron microscopy investigations, fracture profile and fracture surface analyses, hole expansion tests and additional ultramicrohardness measurements are used for the interpretation of the results and for the correlation of the mechanical properties and the formability characteristics with the microstructure of the steel.     

Effect of Heat Treatment on Delayed Fracture Resistance of High Strength Steel 30CrMnSi2NiNb

Ｔｈｅｄｅｌａｙｅｄｆｒａｃｔｕｒｅｉｓｏｎｅｏｆｔｈｅｍｏｓｔｉｍｐｏｒ ｔａｎｔｆａｉｌｕｒｅｍｏｄｅｓｆｏｒｈｉｇｈｓｔｒｅｎｇｔｈｓｔｅｅｌｓａｐｐｌｉｅｄｔｏｈｅａｖｙｄｕｔｙｍａｃｈｉｎｅｃｏｍｐｏｎｅｎｔｓｓｕｃｈａｓｈｉｇｈｓｔｒｅｎｇｔｈｂｏｌｔｓ[1] .Ｉｎｐｒｅｖｉｏｕｓｉｎｖｅｓｔｉｇａｔｉｏｎｓ ,ｉｔｗａｓｓｈｏｗｎｔｈａｔｔｈｅｄｅｌａｙｅｄｆｒａｃｔｕｒｅｒｅｓｉｓｔａｎｃｅｏｆｈｉｇｈｓｔｒｅｎｇｔｈｓｔｅｅｌｉｓｉｎｔｅｎｓｉｖｅｌｙｄｅｐｅｎｄｅｎｔｏｎｉｔｓｃｈ…     

Influence of Microalloying Elements (Nb,V, Ti) on Yield Strength in Bainitic Steels

In order to study the influence of microalloying elements in bainitic high strength steels, seven steels with different contents of V, Ti, Nb and N were investigated. The steel 35 CrMo 4 (C=0.38; Mn=0.82; Si= 0.25; Cr=0.83; Mo=0.17, all in wt.%) was used as reference steel. CCT diagrams were determined by dilatometric tests at different cooling rates, and the maximum and minimum cooling rates for bainite formation were determined. With regard to tensile tests, the presence of precipitates in the bainitic microstructure contributed to raising their yield strength, as was found by comparing the results for all the steels with the reference steel which did not contain microalloying elements. The yield strength can be predicted by an Orowan expression.