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141.
T. Michler Dr.‐Ing. 《Materialwissenschaft und Werkstofftechnik》2007,38(1):32-35
The formation of martensite in metastable austenitic stainless steels was investigated. The results showed that the formation of martensite in 304 grade stainless steels due to the exposure to cryogenic temperatures is negligible. The amount of formed martensite is dependent on the chemical composition of the actual heat but for standard grades the amount is not expected to exceed a very few percent. In welds the formation of martensite is not promoted by the presence of δ‐ferrite. The formation of martensite due to cold forming at room temperature can reach around 20 %. Cold forming with subsequent exposure to cryogenic temperatures does not lead to additional formation of martensite due to the exposure to low temperatures. Cold forming at low temperatures leads to the highest amount of martensite formed in metastable stainless steels. 相似文献
142.
143.
《Baosteel Technical Research》2010,(Z1):89
Nickel-base superalloys are high performance materials subject to severe operating conditions in the high temperature turbine section of gas turbine engines.Turbine blades in modern engines are fabricated from Ni-base alloy single crystals which are strengthened by ordered g’ precipitates.Turbine disks are made from polycrystal line Ni-base alloys because these components have higher strength requirements(due to higher stresses).By increasing the upper temperature limit for the next generation of disk materials,the aviation industry will see significant environmental as well as cost benefits. Researchers in the High Temperature Materials Center of the National Institute of Materials Science of Japan have recently completed their work on a new kind of disk alloys.The new disk alloys,a kind of nickel-coble-base superalloys processed by a normal cast and wrought(C & W) route,can withstand temperatures in excess of 725 degree centigrade,a 50-degree increase over C&W disks currently in operation. In this presentation,the author shows the design idea,workability and properties of these Ni-Co-base superalloys. Furthermore,the evaluation of the processing and microstructure on a full-scale processing of Ni-Co-base superalloy turbine disk are described,which demonstrated the advantages and possibility of the Ni-Co-base disc alloys at the component level. 相似文献
144.
The work shows the results obtained in recognition of different types of austenitic steels with an ultrasonic system that provides the necessary data towards two different neural networks. One of the neural networks (RNAU) used as input a vector containing processed data (propagation velocity and ultrasonic attenuation). The second neural network (AUFRAN) used the amplitude of digitized radio-frequency signal and its numerical Fourier transform as input vector.Two thirds of data obtained from three kinds of steels (W.1.4541, W.1.6903 and HP50) were used in the learning process. The last third of acquired data on these samples were used in the testing process. The obtained classification probabilities were above 98.3%. As a supplement, the testing process was extended to three other types of austenitic steels having different chemical compositions than those used in the learning process. 相似文献
145.
Jung-Suk Lee Jeong-Yong Park Byung-Kwon Choi Bong Guen Hong Ki-Jung Jung Yong Hwan Jeong 《Metals and Materials International》2009,15(3):465-470
One of the main research and development issues concerning the test blanket module (TBM) is the development of joining technologies
for fabrication of the first wall. The objectives of the present study are to investigate the effects of thermal history corresponding
to the TBM fabrication process on reduced activation ferritic martensitic (RAFM) steel microstructure, and to establish the
appropriate hot isostatic pressure (HIP) conditions for the fabrication of RAFM/RAFM steels and beryllium (Be)/RAFM steels
joints without degradation of the mechanical properties of the RAFM steel or delamination of the joined interface. In this
study, RAFM and RAFM steels were joined by HIPing at 1050 °C under 100 MPa for 2 h. During the HIP process, the thermally
altered microstructure and mechanical properties were recovered to the as-received state by subsequent normalizing at 950
°C for 2 h and tempering at 750 °C for 2 h. Be and RAFM steels were also bonded successfully by the application of Ti/Cu interlayers
and HIPing at 850 °C under 100 MPa for 2 h. 相似文献
146.
针对45类钢变流的问题,分析了浇注变流的机理,提出了解决与防止的方法,同时对防止其它钢种浇注变流提供了一个新思路。 相似文献
147.
The effect of seawater on fracture mode transition in fatigue 总被引:1,自引:0,他引:1
The fracture mode transition for two steels fatigued in air and seawater was investigated by measuring the crack growth rates and by examining the fractured surfaces using scanning electron microscopy. It was found that the transition from normal to shear fracture mode did not always occur in seawater under the same fatigue conditions as in air. Three possible mechanisms, based on the effective stress intensity factor range, the threshold stress intensity factor range and environmentally assisted brittle fracture, are proposed to account for this behaviour and their validity is discussed. 相似文献
148.
Applications in plastics processing bear increased requirements for the used materials, especially with respect to their corrosion and wear resistance. For this reason, special powder metallurgical tools steels were developed that fulfil these demands. The common processing route for their production is hot isostatic pressing (HIP) of pre‐alloyed powders which is followed by hot working if semi‐finished parts are to be produced. As an alternative to HIP, super solidus liquid phase sintering (SLPS) permits the consolidation of pre‐alloyed tool steel powders to near net‐shape parts. It can be performed in different sintering atmospheres. In this work, the plastic mould steel X190CrVMo20‐4 was processed by SLPS in vacuum as well as under nitrogen atmosphere. The resulting materials were analysed with respect to their microstructure, tempering behaviour and corrosion resistance in 0.5 molar sulphuric acid in dependence of the heat treatment. As a reference, the HIPed and the HIPed and worked state were also investigated. The results show that different heat treatments alter the ranking of the sintered and the HIPed state with respect to corrosion resistance. As expected, a high tempering for maximum secondary hardness causes a significant loss of corrosion resistance. The experimental findings were supported by thermodynamic calculations based on slight alterations in chemical composition that result from the different manufacturing processes. 相似文献
149.
The knowledge of mechanical long term behaviour under static and cyclic loading for high temperature components requires methodologies for life assessment in order to employ the full potential of materials. A phenomenological life time prediction concept which was developed for multi‐stage creep fatigue loading demonstrates the applicability of rules for synthesis of stress strain path and relaxation including an internal stress concept, as well as mean stress effects. Further, a creep fatigue interaction concept which was also developed covers a wide range of creep dominant loading as well as fatigue dominant loading. Service‐type experiments conducted at different strain rates and hold times for verification purposes demonstrate the acceptability of life prediction method for variation of conventional 1 %Cr‐steels as well as modern high chromium 9‐10 %Cr‐steels. Generally, the service life of components is influenced by multi‐axial behaviour. Multi‐axial experiments with e.g. notched specimens and with cruciform specimens accompanied by advanced methods for calculation of stress strain path and life time prediction stress conditions are of future interest. 相似文献
150.
The use of stainless steel bars in reinforced concrete structures may be an effective method to prevent corrosion in aggressive environments where high amounts of chlorides may penetrate in the concrete cover. For an estimation of the service life of structures where stainless steel bars are used, the chloride threshold for these rebars should be defined, and the influence of chemical composition and metallurgical factors that may affect the corrosion resistance (strengthening, welding, etc.) should be assessed. To reduce the cost of stainless steel reinforcement, duplex stainless steels with low nickel content have been recently proposed as an alternative to traditional austenitic steels, even though, few results are available regarding their corrosion performance in chloride contaminated concrete. This paper deals with the corrosion resistance of low‐nickel duplex stainless steel rebars (1.4362 and 1.4162) as a function of the chloride content. Comparison is made with traditional austenitic steels. An attempt to define a chloride threshold for the different stainless steels is made by comparing the results of several test procedures both in concrete and in solution. 相似文献