西气东输二线工程用X80螺旋埋弧焊管热影响区性能分析

对西气东输二线工程用X80级φ1219 mm×18.4 mm螺旋埋弧焊管热影响区夏比冲击韧性和维氏硬度进行了统计分析.结果表明:X80螺旋埋弧焊管热影响区具有优良的力学性能,不同钢厂产品之间性能差异较小;热影响区夏比冲击功低于管体母材130 J;硬度低于母材15～24 HV10,存在明显的热影响区"软化"现象.随着钢级...     

舰船结构钢的夏比冲击韧性与断口形貌

论述了从夏比冲击韧性分解出来的断裂扩展功与断口形貌的关系，指出冶金因素对夏比冲击韧性α＿ｋ值和扩展功的影响不完全是一致的，提出采用α＿ｋ，值和断口纤维率作为韧性指标的互补性，建议在我国的舰船结构钢韧性指标中增加断口纤维率的要求。     

3D analyses of the effect of weld orientation in Charpy specimens

Three dimensional transient analyses of Charpy impact specimens are carried out. The material response is characterized by an elastic-viscoplastic constitutive relation for a porous plastic solid, with adiabatic heating due to plastic dissipation and the resulting thermal softening accounted for. The onset of cleavage is taken to occur when the average of the maximum principal stress over a specified volume attains a critical value. The weld analyzed here is overmatched, so that the yield strength for the weld is larger than that of the base material. Analyses are carried out for specimens where the notch is cut parallel to the surface of the test piece, as well as more complex geometries where the notched surface of the specimen is rotated relative to the surface of the test piece. It is found that even for a homogeneous material the brittle-ductile transition can be much affected by three dimensional effects; for example, curvature of the deformed free surface gives rise to a stress increase that promotes cleavage. Furthermore, for the rotated specimens the weld geometry relative to the notched specimen surface is so complex that only a full 3D analysis is able to account for the interaction of failure in the weld material, base material and heat affected zone (HAZ). For these rotated specimens the location where the notch crosses the thin layer of HAZ, i.e. whether this location is near the center of the specimen or near the free specimen edge, makes a large difference in the response.     

Influence of the specimen configuration and the insert material on fracture toughness characterisation with reconstituted specimens

Specimen reconstitution techniques offer the possibility to obtain fracture toughness measurements when only small amounts of material are available. In order to obtain extra information from charpy specimens, an electron-beam weld reconstitution method is established to obtain compact tension specimens (CT) from the broken halves of the charpy ones. Three types of reconstituted CT specimens with different weld configurations are tested in order to analyse the influence of specimen configuration on fracture toughness evaluation. The validity of the fracture toughness characterisation is analysed by comparing J-integral resistance curves (J–R curves) of specimens with insert and those of reference specimens without insert.     

Influence of thermal aging on cast stainless steels used in JAEA's nuclear reactor Fugen

The influence of thermal aging on cast stainless steels used in JAEA's advanced thermal prototype reactor “Fugen” that were exposed to 275°C for about 15 years was investigated. The degree and mechanism of thermal embrittlement were evaluated on the basis of Charpy impact test results and the three-dimensional atom probe (3DAP) analysis of the microstructural changes in the spinodal decomposition using materials obtained from Fugen. The results revealed early signs of a thermal aging effect over a long period at the low temperature.     

Influence of microstructure and notch fabrication on impact bending properties of tungsten materials

Refractory materials, in particular tungsten base materials are considered as primary candidates for high heat load applications in future nuclear fusion power plants. Promising design outlines make use of the high heat conductivity and strength of W-1%La₂O₃ (WL10) as structural material. Here, the lower temperature range is restricted by the transition to a steel part and the upper operation temperature limit is defined by the onset of recrystallization and/or loss of strength, respectively. The most critical issue of tungsten materials in connection with structural applications, however, is the ductile-to-brittle transition. Another problem consists in the fact that especially refractory alloys show a strong correlation between microstructure and their manufacturing history. Since mechanical properties are defined by the underlying microstructure, refractory alloys can behave quite different, even if their chemical composition is the same. Therefore, the fracture behavior of several tungsten based alloys was characterized by standard Charpy tests which have been performed up to 1100 °C in vacuum. Due to their fabrication history (powder mixing, pressing, sintering, rolling or swaging) all materials had specific microstructures which often led to typical delamination fractures. The influence of the microstructure characteristics like grain size, anisotropy, texture, or chemical composition as well as the effect of notch machining was investigated. All results are discussed and assessed with respect to the optimization of future component fabrication for high temperature nuclear fusion applications.     

Characterization of the fracture behavior of glass fiber reinforced thermoplastics based on PP,PE‐HD,and PB‐1

This article deals with the influence of the polymeric matrix, such as isotactic polypropylene (iPP), polyethylene (PE‐HD), and isotactic polybutene‐1 (iPB‐1), and the glass fiber content on the material behavior of short glass fiber reinforced thermoplastics. The glass fiber content of all materials ranged between 0 and 50 wt %, which corresponds to a volume content between 0 and approx. 0.264. To describe the mechanical properties of all materials, the stiffness, strength, hardness, and toughness behavior were determined. The crack toughness behavior regarding unstable crack propagation was also assessed by applying fracture mechanics concepts. It was found that the energy‐determined J‐values for the PP material system reach their maximum at a glass fiber content of 0.135. In contrast, the crack toughness of the PE‐HD materials increases continuously with increasing glass fiber content due to the unchanged deformation ability at simultaneously increasing strength. The toughness level of the PB‐1 materials is nearly the same independent of the glass fiber content due to the opposite trend of the load and the deformation ability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

聚丙烯材料简支梁缺口冲击性能的时温效应研究

将聚丙烯(PP)树脂在一定注塑工艺条件下制备成用于简支梁冲击测试的样条,分别为ISO注塑A型缺口冲击样条和无缺口样条(然后通过铣缺口机机械加工成A型缺口冲击样条),通过摆锤冲击试验仪进行简支梁缺口冲击强度测试,研究共聚型PP材料注塑缺口和铣缺口冲击性能的时温效应.结果表明,共聚型PP材料铣缺口在标准环境下调节,简支梁缺...     

Influence of Ti/N ratio on simulated CGHAZ microstructure and toughness in X70 steels

Abstract

Three API 5L X70 steels with different Ti and N contents and otherwise identical chemistry were selected to investigate the effect of Ti/N ratio on the toughness in coarse grained heat affected zone (CGHAZ). A Gleeble 3500 thermomechanical simulator was used to simulate the thermal profile of CGHAZ of double submerged arc welding process. The microstructure was examined by optical microscopy. Statistics of CGHAZ grain coarsening were compiled by measuring the prior austenite grain size. Toughness of the simulated CGHAZ regions was evaluated by Charpy V-notch testing at ?20 and ?40°C. Morphology of the impact fracture surface was investigated using SEM. Steel B with Ti/N ratio of 3·22 (slightly below stoichiometric) showed slightly higher toughness in the simulated CGHAZ due to higher volume fraction of austenite grains less than 80 μm in diameter.     

Effect of cooling rate on microstructure and properties of microalloyed HSLA steel weld metals

Abstract

Two high strength Nb/Ti microalloyed S690QL steels were welded with identical filler material, varying welding parameters to obtain three cooling rates: slow, medium and fast cooling. As cooling rate increased, the predominantly acicular ferrite in Nb weld metal (WM) is substituted by bainite, with a consequence of obvious hardness increase, but in Ti WM, no great variation of acicular ferrite at all cooling rates contributed to little increment of hardness. The transition between bainite and acicular ferrite has been analysed from the point view of inclusions characteristics, chemical composition and cooling rate. Excellent Charpy toughness at 233?K was obtained with acicular ferrite as predominantly microstructure. Even with bainite weld of high hardness, the toughness was nearly enough to fulfill the minimal requirements. WM for Ti steel showed to be markedly less sensitive to the variations of cooling rate than that for Nb steel.