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Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The static CCT curve of the HG05 as-quenched-tempered seamless steel tube with high strength and toughness is measured by the Gleeble 3500 thermal simulation machine, and then the critical quenching-cooling rate of the steel is determined. The outer layer, the middle layer and the inner layer of the hot-formed HG05 seamless steel pipe are sampled and analyzed. All the said layers are of the bainite and ferrite structures, and the ferrite structure changes greatly. The size of ferrite in the middle layer is the largest, and the average size is 10 µm; and the inner ferrite volume fraction is the highest as about 12.4 vt%. The outer, the middle and the inner layers of the hot-formed steel tube are quenched with the thermal simulation method, and the critical quenching-cooling rate of the as-quenched-tempered steel, and the incompletely quenched microstructure is obtained. Since the quenched-tempered microstructure is homogeneous, there is little austenitic nucleation core, and after being heated with the thermal simulation, the austenite grain size is large, the critical quenching-cooling rate of austenite is 20 °C/s, whereas the critical quenching-cooling rate of the hot- formed microstructure is higher than that of the austenite. [ABSTRACT FROM AUTHOR]

Studied here in the essay are the physiochemical characteristics of the anti-corrosion pipe with Cr content ranging from 3% to 9%, and the effects by the contents of the alloy elements on the austenitizing temperature, phase transformation temperatures of cooling process and the micro-structures at room temperature. Results show that mixed structures of bainite/martensite are obtained, when the Cr content is no more than 5%, and the proportion of the two components depends on the cooling speed; the subtotal structures of the pipe with the Cr content more than 7% could transform to martensite at normal cooling speed. Furthermore the relations between the post-tempering micro hardness and the original structures of the pipe are also studied. The results indicate that the steel pipe with more volume fraction of martensite shows larger variation of the post-tempering micro hardness, which could be used to determine the heat treatment process, and control the mechanical properties of the anti-corrosion linepipe as well as the casings. [ABSTRACT FROM AUTHOR]

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A kinetic model of bainite isothermal transformation based on nucleation-controlled mechanism was used to study the effect of alloy design on bainite transformation kinetics. Using two kinds of high-strength bainite steels, isothermal bainite transformation experiments were conducted at 425～350 ℃ with a dilatometer. Different degrees of incomplete phase transformation phenomenon are observed. Based on nucleation-controlled mechanism, the displacive transformation kenetic model was used to describe the bainite isothermal transformation behavior of two experimental steels, where grain-boundary nucleation and autocatalytic nucleation were both considered. Finally, the difference in activation energy of nucleation, volume fraction of untransformed austenite and the nucleation rate etc between two experimental steels were comparatively analyzed, which provide theoretical guidance for the composition design and process innovation of high-strength bainite steel. [ABSTRACT FROM AUTHOR]

Microstructure transformation characteristics by continuous cooling of SA508Gr. 4N steel for next generation nuclear pressure vessels were subjected to physical simulation experiment, microstructure observation and hardness measurement. Results show that critical cooling rate of SA508Gr. 4N steel for bainitic transformation is 0.5 °C /s. When cooling rate is 1 ~30 qC/s, transformation products are lath martensite with hardness up to 470 HV. When cooling rate is 0. 5 ~0. 02 °C /s, bainite and martensite are transformation products, and as cooling rate decreases,bainite content increases gradually, granular and short rod shaped fine carbides can be seen in the bainite structure, and hardness value is as low as 400 HV. Koistinen Marburger equation is used to describe martensitic transformation kinetics of SA508Gr. 4N steel, fitting results showed that initial martensitic transformation temperature is 345.4 °C and kinetic parameter is 0. 031 4，which can accurately predict the relationship between martensitic transformation and temperature with transformed amount exceeding 20%. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The isothermal transformation kinetics of experimental steel was studied by the thermal expansion method. Uhrafine bainite was obtained by austempering at low temperature. The microstructure was quantificationally analyzed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that microstructure of the experimental steel is composed of a large number of uhrafine lath bainite ferrite and thin film austenite. The spacing of the bainitic lath is about 60 nm and the hardness is about HBW 610 by austempering at 210%. The final microstructure and properties depend on the temperature and holding time for austempering. The holding time for fully transformed bainite increases at a lower austempering temperature.

Ｔｈｅ ｅｆｆｅｃｔ ｏｆ ｄｉｆｆｅｒｅｎｔ ａｕｓｔｅｍｐｅｒｉｎｇ ｐｒｏｃｅｓｓｅｓ ｏｎ ｍｉｃｒｏｓｔｒｕｃｔｕｒｅ ｅｖｏｌｕｔｉｏｎ ａｎｄ ｍｅｃｈａｎｉｃａｌ ｐｒｏｐｅｒｔｙ ｏｆ ｌｏｗ ｃａｒｂｏｎ ｕｌｔｒａ-ｈｉｇｈ ｓｔｒｅｎｇｔｈ ｂａｉｎｉｔｉｃ ｓｔｅｅｌｓ ｗａｓ ｓｔｕｄｉｅｄ. Ｔｈｅ ｒｅｓｕｌｔｓ ｓｈｏｗ ｔｈａｔ ｃｏｍｐａｒｅｄ ｗｉｔｈ ｔｈｅ ｏｎｅ-ｓｔａｇｅ ａｕｓｔｅｍｐｅｒｉｎｇ ｐｒｏｃｅｓｓꎬ ｔｈｅ ａｍｏｕｎｔ ｏｆ ｂａｉｎｉｔｅ ｉｎｃｒｅａｓｅｓ ａｎｄ ｔｈｅ ｃｏｎｔｅｎｔ ｏｆ ｍａｒｔｅｎｓｉｔｅ ｄｅｃｒｅａｓｅｓ ｉｎ ｔｈｅ ｔｗｏ-ｓｔａｇｅ ｐｒｏｃｅｓｓꎬ ｗｈｉｃｈ ｒｅｓｕｌｔ ｔｈａｔ ｔｈｅ ｙｉｅｌｄ ｓｔｒｅｎｇｔｈ ｏｆ ｔｈｅ ｅｘｐｅｒｉｍｅｎｔａｌ ｓｔｅｅｌ ｉｎｃｒｅａｓｅｓ ５８％ ａｎｄ ｉｓ ｕｐ ｔｏ １ １７８ ＭＰａꎬ ｔｈｅ ｅｌｏｎｇａｔｉｏｎ ｉｎｃｒｅａｓｅｓ ｆｒｏｍ ７􀆰 ７％ ｔｏ １４􀆰 ４％ ａｎｄ ｔｈｅ ｉｍｐａｃｔ ｔｏｕｇｈｎｅｓｓ ｉｎｃｒｅａｓｅｓ １６％ ａｎｄ ｒｅａｃｈｅｓ ６６ Ｊ / ｃｍ２. Ｃｏｍｐａｒｉｎｇ ｔｈｅ ｓｔｒｅｎｇｔｈ ａｎｄ ｐｌａｓｔｉｃｉｔｙ ｍａｔｃｈｉｎｇ ｏｆ ｔｈｅ ｃｏｒｒｅｓｐｏｎｄｉｎｇ ｅｘｐｅｒｉｍｅｎｔａｌ ｓｔｅｅｌｓ ｕｎｄｅｒ ｄｉｆｆｅｒｅｎｔ ｈｅａｔ ｔｒｅａｔｍｅｎｔｓꎬ ｉｔ ｉｓ ｆｏｕｎｄ ｔｈａｔ ｔｈｅ ｐｒｏｄｕｃｔ ｏｆ ｓｔｒｅｎｇｔｈ ａｎｄ ｅｌｏｎｇａｔｉｏｎ ｏｆ ｔｈｅ ｓｔｅｅｌ ｃａｎ ｒｅａｃｈ ２１ ８８８ ＭＰａ􀅰％ ｕｎｄｅｒ ｔｈｅ Ａ３(２４０ ℃ ｆｏｒ ２ ｈ ａｎｄ ｔｈｅｎ ２７０ ℃ ｆｏｒ １ ｈ) ｔｗｏ-ｓｔａｇｅ ｐｒｏｃｅｓｓ ｃｏｎｄｉｔｉｏｎ. Ｕｎｄｅｒ ｔｈｅ ｔｗｏ-ｓｔａｇｅ ｐｒｏｃｅｓｓ ｃｏｎｄｉｔｉｏｎｓꎬ ｔｈｅ ｍａｒｔｅｎｓｉｔｅ ｂａｎｄ ｄｕｅ ｔｏ Ｍｎ ｓｅｇｒｅｇａｔｉｏｎ ｉｎ ｔｈｅ ｓｔｅｅｌ ｃａｎ ｂｅ ｅｌｉｍｉｎａｔｅｄ ａｎｄ ａ ｒｅｌａｔｉｖｅｌｙ ｕｎｉｆｏｒｍ ｂａｉｎｉｔｅ ｓｔｒｕｃｔｕｒｅ ｃａｎ ｂｅ ｏｂｔａｉｎｅｄꎬ ｓｏ ｔｈａｔ ｔｈｅ ｓｔｒｅｎｇｔｈ ａｎｄ ｔｏｕｇｈｎｅｓｓ ｏｆ ｔｈｅ ｅｘｐｅｒｉｍｅｎｔａｌ ｓｔｅｅｌ ｃａｎ ｂｅ ｉｍｐｒｏｖｅｄ ｓｉｍｕｌｔａｎｅｏｕｓｌｙ. [ABSTRACT FROM AUTHOR]

The effect of different process parameters on the microstructure and mechanical properties of marine engineering H-beam steel(SM490YB) were studied through the hot rolling and ultra-fast cooling experiments. The mechanisms of strengthening and toughening of SM490YB steel were analyzed. The results showed that with decreasing temperature of the final cooling， the contents of bainite and acicular ferrite increase at the same position in thickness direction of the tested steel， in contrast to those of polygonal ferrite and pearlite. Moreover， the strength and low-temperature toughness of the steel increase with the decrease of the final cooling temperature. When the final cooling temperature is 480°C and the heat return temperature is 554°C， the performance of mechanical property is the best. The increase of the cooling rate can improve the strength of the tested steel， however the excessive cooling rate can deteriorate the toughness. [ABSTRACT FROM AUTHOR]

The microstructure,martensite/austenite(M/A) islands,precipitated phases,high-angle grain boundaries and effective grain size of hot rolled and tempered low carbon bainitic steel AH80 DB were studied by scanning electron microscopy(SEM),transmission electron microscopy(TEM) and electron back-scattered diffraction(EBSD). The reason for the improvement in impact toughness of the low carbon bainitic steel after tempering was discovered. The results show that the microstructures of both the samples mainly consist of lath bainite,granular bainite and acicular ferrite. There is more acicular ferrite in the tempered steel. Coarse M/A islands are found in the hot rolled steel and its distribution is directional,the ratio of large-angle grain boundaries is 17.33%,and the average effective grain size is 3.57 μm. Nevertheless,the size of M/A islands decreases after tempering. Besides,the ratio of largeangle grain boundaries increases by 3.43% and the average effective grain size decreases by 0.56 μm after tempering. The precipitated phase of the hot rolled steel is(Nb,Ti) C with the size of 50-150 nm,while much small and spherical precipitates with the size of about 10 nm appear after tempering.

Composition design of low cost V-N microalloying steel was studied without adding Mo， Cr， Ni. The thermo-mechanical control process (TMCP) test was conducted. The phase transition mechanism and precipitation behavior were discussed. The microstructure and comprehensive mechanical properties of the hot-rolled Bainitic steel were systematically studied by optical microscopy， scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that the microstructure is consisted of acicular ferrite， quasi-polygonal ferrite and granular bainite and small triangular M/A island. The fine precipitates present disks and distribute dispersedly in the ferrite matrix. The yield strength， tensile strength and elongation of the steel are 618MPa， 701MPa and 19%， respectively. The property of cold bending is qualified， the hold-expansion ratio reaches 94%， and strentch-flangeability and the low temperature impact performance is good. The above results can meet the demand of the automotive wheel disc. The fine grain strengthening， solid solution strengthening， precipitation strengthening and phase transformation strengthening are the main strengthening mechanisms. [ABSTRACT FROM AUTHOR]

The effect was investigated by means of continuous cooling torsion test (CCT) using conventional controlled rolling (CCR), recrystallizaiton controlled rolling (RCR) and dynamic recrystallization controlled rolling (DRCR) at 1 200~400 °C. It is found that the austenite grains are refined by three rolling schedules, the refinement degree of which is DRCR, RCR and CCR. At the same cooling rate, the bainite transformation temperature of deformed specimens with the three schedules is different. The final structure obtained from the CCR is ferrite and some little compounds, whereas the bainite structure is obtained by the schedules of RCR and DRCR which takes the morphology of plate like. The size and fraction of bainite structure are changed with cooling rate. [ABSTRACT FROM AUTHOR]