High temperature compression testing and determination of warm working temperature for commercial purity aluminium

CP aluminium was subjected to axysymmetric compression testing at 303, 373, 473, 573 and 673 K. Strength coefficient and strain hardening exponent were determined from log-log plot of true stress and true strain at different temperatures. True stress vs temperature at different strains indicated that dynamic strain ageing (DSA) occurred between 473 and 673 K. Warm working is to be done between 423 K and 473 K, so that optimum substructure hardening and strain hardening can be achieved during mechanical processing.     

High strain rate torsional testing of a high manganese steel: Design and simulation

In this study, some less-discussed aspects of designing a high strain rate torsional testing machine adapted from the Kolsky bar setup are surveyed with an emphasis on the clamping system design. Dynamic torsional experiments with true strain rates in the range of ∼500–1700 /s are conducted on specimens of a high-Mn TRIP/TWIP steel. Deformation characteristics of torsional specimens with different geometries are studied through coupled field thermo-mechanical finite element analyses using ANSYS commercial software package. The effect of specimen geometry on the stress and strain distributions and accuracy of the experimental results is also studied. Using the FEM analysis, deformation temperature rise is attained over the specimen gauge zone and its influence on the stacking fault energy and mechanical behavior of the steel is investigated.     

Low-temperature fracture mechanisms in a spheroidised reactor pressure vessel steel

The micromechanisms of fracture of a spheroidised A533B reactor pressure vessel steel over the temperature range of −190°C to + 60°C were investigated by performing uniaxial tensile tests on double-notched cylindrical specimens. Failure was by quasi-cleavage at temperatures between −190°C and −145°C. Quasi-cleavage fracture surfaces are characterised by clusters of planar facets that are separated from other facets either by large voids or by clusters of microvoids. At temperatures between −145°C and −25°C failure was by mixed microvoid coalescence and cleavage while complete microvoid coalescence was observed at temperatures higher than −25°C. Over the whole temperature range studied, fracture nucleation was either from large single voids or localised regions of microvoids.     

国产T92钢高温持久过程中的显微组织演变

对某国产T92钢进行了620,650,700℃三个温度下不同时间的高温持久试验和显微组织观察试验。结果表明:在620,650℃时,随着持久试验时间的延长,T92钢基体显微组织仍保持板条状马氏体形貌特征,碳化物析出数量不断增加,尺寸也有所长大,且持久试验达到一定时间后晶界会产生微孔洞;在700℃长时间高温持久试验后,T92钢基体显微组织板条状马氏体形貌特征消失,且晶界碳化物粗化严重。     

冷拔高碳钢丝高温退火前后显微组织及织构变化

采用扫描电子显微镜（SEM）和电子背散射衍射技术（EBSD）作为分析手段,对两种变形量SWRH82B冷拔高碳钢丝在奥氏体化高温退火处理前后的显微组织和织构变化进行了表征研究。结果表明：该冷拔高碳钢丝显微组织中的珠光体经奥氏体化退火处理后由纤维状转变为等轴状;冷拔高碳钢丝主要是〈110）织构,且织构强度随着变形量的增大而增强;经奥氏体化退火处理后〈110〉织构强度明显下降,且织构强度与变形量相关性减小,同时还出现了〈112〉织构。     

Control of ductile to brittle transition temperature in ferritic pressure vessel steel

Abstract

Controlled amounts of cold work are shown to cause a minimum in the ductile to brittle transition temperature (DBTT) in a ferritic steel at a critical level of ～1·5%. Mechanical property assessments show that the hardness values exhibit the same trend. A theory is advanced for explanation of these effects, based on work hardening and Cottrell–Bilby locking models. Consideration is given to an alternative Ashby–Embury model, but it is concluded that the former approach is most successful in predicting the observed DBTT shift behaviour. Although independent of fracture surface type, the degree of plastic deformation shows some dependency on the grain boundary character. This leads to the conclusion that the matrix yield strength is the primary factor in determining the DBTT in these steels. Discussion focuses on methods for exploiting the effect to give higher toughness steels utilising knowledge of how to control matrix hardening and cleavage fracture strength.     

玩具检测用温升测试系统的设计

该文针对电玩具的温升测试,详细介绍8通道温度测量系统的硬件和软件设计。热电偶信号经AD595芯片放大调理和A/D转换,通过单片机进行处理,再连接到PC机进行显示和操作。     

超细晶粒高碳钢的研究现状及展望

晶粒超细化能同时提高材料的强度和韧性,是新一代钢铁材料研究与开发所追求的重要目标,而超细晶粒高碳钢则是新一代钢铁材料中具有重要发展前景的高性能结构材料.综述了超细晶粒高碳钢细化技术的主要研究成果,简述了高碳钢组织超细化的具体工艺、适用条件及应用情况等,并从工业应用角度分析了现有超细晶粒高碳钢制备技术的主要问题和研究方向.     

Microstructure and property evolutions of a novel Super304H steel during high temperature creeping

High-temperature creep tests of a novel Super304H steel under 650 °C/195 MPa were conducted and the evolutions of microstructure and property with creep time of the material were investigated by using optical microscope, scanning electron microscope, micro Vickers hardness tester and electrochemical workstation. The results show that M₂₃C₆ carbides precipitated along grain boundaries of austenite matrix in a chain distribution and then got coarsened with the increase of creep time. Creep cavities started to form near the surface when the steel was crept for 2500 h. Afterward creep cavities increased, developed, interconnected and finally formed micro cracks along grain boundaries till fracture at the time of 4578 h. The hardness of the steel increased dramatically at the early stage of creeping and reached a high level at 500 h, and then kept a stable state at the succedent stage till fracture. Intergranular corrosion susceptibility of the steel increased first and then declined gradually, indicating the occurrence of sensitization – desensitization process of the steel during creeping.     

Correlation between cyclic deformation behaviour and microstructure in a duplex steel between 300 and 773 K

Cyclic tests performed in the temperature range 300–773 K on duplex stainless steel DIN 1.4460 show that the cyclic stress–strain behaviour of this steel is strongly temperature dependent. At 300 and 473 K an almost constant peak tensile stress stage, is followed by a slight softening that continues up to failure in the case of 300 K, but by a secondary hardening at 473 K. Pronounced initial cyclic hardening followed by secondary hardening was the main feature of the temperature range between 573 and 723 K. At 773 K, after a weak hardening stage, a strong softening continues up to failure. The mechanical behaviour and the evolution of the microstructure were analysed, and the internal and the effective stresses were studied. It was found that the internal stress is responsible for the strong hardening that occurs in the intermediate temperature range and for the softening at 773 K.     

高温快速退火对电子束物理气相沉积制备高硅硅钢片的影响

对电子束物理气相沉积高硅硅钢片进行了高温快速退火处理.用SEM,EDS,XRD对制备态硅钢片和热处理态组织,成分,物相进行了表征,并测试了其电阻率和磁滞回线.结果表面:高温快速退火使高硅硅钢片硅成分变均匀,靠近基板侧的相由Fe3Si变成DO3;硅钢片中孔长大,电阻率从90μΩ·m增大到160μΩ·m,矫顽力减小,磁感应强度减小.     

The effect of temperature and loading rate on the crack initiation and propagation energy in carbon steel charpy specimens

The Charpy impact tests were carried out at different temperatures and loading rates. The temperature dependences of crack initiation and propagation in carbon steels 45 and St. 3 under impact testing were determined from the obtained force variation plots. The effect of the impact velocity in the range from 1 to 4.4 m/s on the fracture toughness temperature dependence is estimated. __________ Translated from Problemy Prochnosti, No. 5, pp. 120–127, September–October, 2006.     

万能试验机高温拉伸装置的改造升级

为满足高温拉伸试验标准的控温精度和温度均匀性的要求,对现有的某万能试验机的高温拉伸装置进行了技术改造升级,增加了双移动对开式电阻加热炉,改造了高温拉伸夹具,并升级了温度控制器。结果表明:改造升级后明显提高了试验机高温拉伸试验的工作效率、控温精度和温度均匀性,使其完全能满足高温拉伸试验标准的要求。     

Critical ausforming temperature to promote isothermal bainitic transformation in prior-deformed austenite

The effects of deformation temperature on phase transformation and microstructure in nanostructured bainite steel were studied. The results indicate that the deformed austenite with a strain of 0.3 at 300°C presents accelerated kinetics of bainitic transformation. However, the amount of bainite in ausformed austenite then reduces with the increase in deformation temperature. A critical deformation temperature, determining whether the bainitic transformation can be promoted, was found in deformed austenite. In addition, the thickness of bainite plate in deformed austenite reduces with the decrease in ausforming temperature. The adjacent bainite ferrite plates grow up interactively, and the intersection angle is about 60–73°. A lower ausforming temperature contributes to a more serious cross-growth phenomenon of bainite plates.     

L80 pipe steel microstructure assessment using ultrasonic testing

The potential exists to use ultrasonic shear velocity for real-time microstructure assessment of the quenching step in the heat treatment of L80 steel pipe. L80 steel samples were austenitised and subsequently cooled in different quench mediums (water, oil, heated oil, air and furnace) to produce microstructures ranging from primarily martensite to coarse ferrite/pearlite mixed structures. Following heat treatment, the samples were ultrasonically tested, tensile and hardness tested and metallographically examined. The shear wave velocity was observed to increase as the underlying microstructure of each sample changed from primarily martensite, to primarily bainite and finally to coarse ferrite + pearlite. The measured shear wave velocity exhibited an inverse linear dependence on both yield strength and microhardness.     

High temperature crack initiation and defect assessment of P22 steel weldments using time dependent failure assessment method

High temperature deformation and crack resistance of low alloy ferritic grade P22 steel weldments applied in power plants are reported. The creep crack initiation (CCI) and creep crack growth (CCG) data were determined using compact type (C(T)) and C-Shape (CS(T)) fracture mechanics specimens at 550 °C. The deformation and crack growth behaviour of similar weldment zones and significance of CCI and CCG in defect assessment of components were addressed. The weldments with industrially relevant properties were produced in butt welded pipe joint from which test specimens are sampled. The studied material covers a spectrum of microstructures and ductility over the weldment zones to give representative for a welded component. The emphasis is placed on the measurement and particularly analysis of crack initiation for failure assessment in P22 steel weldments. The particular importance of construction of isochronous curves for time dependent failure assessment diagram (TDFAD) method is reported. It is aimed to contribute to establishing guidelines for acceptable methodologies for testing, analysis and assessment of welded components using TDFAD for high temperature service.     

J型高温高速染色机常见缺陷与检测要点

对染色工艺中最常用的设备——J型高温高速染色机的常见缺陷类型、各类缺陷产生的原因以及对其进行检验检测时需注意的要点进行了归纳总结,并给出了相应的预防措施及建议。重点阐述了在J型高温高速染色机使用过程中经常出现的应力腐蚀裂纹和疲劳裂纹等危险性缺陷,并指出产生这些缺陷的主要原因是柒液中存在氯离子、染色机存在应力集中、振动及频繁启动等因素;检验时应采用金相检验、无损探伤等方法措施,以便能够及早发现此类危险性缺陷,消除安全隐患。     

The effect of high temperature carburization upon the ambient temperature ductility of Alloy 800H

This paper presents the results of a series of tests designed to assess the changes in ambient temperature ductility of Alloy BOOH, a 20%Cr-32%Ni austenitic steel, resulting from exposure to an aggressive carburizing environment at 10000°C. A gas mixture of H₂-CH₄ with 0.8 carbon activity has been used as the corrosive medium and postexposure compression testing of the carburized tubular specimens has enabled the significant reduction in ductility accompanying the uptake of carbon to be demonstrated and understood.     

一种新型980MPa高强钢在不同温度下的拉伸断裂试验

本文通过在不同温度下,对一种轧制而成的贝氏体高强钢在三个相互垂直的方向进行了拉伸实验,结合宏观力学性能参数及微观断口形貌的观察,分析了这种高强钢在不同温度下的拉伸断裂行为。结果表明:此种钢在三个方向上的宏观力学性能参数基本相同(在室温下屈服强度为950MPa,抗拉强度为1000MPa;-196℃下,屈服强度达到1260MPa,抗拉强度高达1400MPa)。但沿不同方向的拉伸断口差异却很大。沿轧制方向和宽度方向的试样,不同温度下断口形貌相似,在温度较低的试样中都出现了纵向裂纹,在-196℃均出现"Z"型断裂路径;但沿板厚方向的试样,在不同温度下其断口形态都为典型的拉伸断口。     

高温正火消除85Cr2Mn2Mo钢组织遗传的研究

在研究８５Ｃｒ２Ｍｎ２Ｍｏ钢的组织遗传的基础上,着重研究了该钢组织遗传的消除,采用高温正火工艺,使８５Ｃｒ２Ｍｎ２Ｍｏ钢经重结晶,奥氏体再结晶有效地细化了奥氏体晶粒,切断了组织遗传,并对８５Ｃｒ２Ｍｎ２Ｍｏ钢的奥氏体再结晶温度做了有益的探析。