There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

http://digilib.its.ac.id/public/ITS-Undergraduate-10957-Paper.pdf

Carbon partitioning into austenite after martensite transformation

Effects of Chemical Composition, Heat Treatment, and Microstructure in Splittable Forged Steel Connecting Rods

This chapter introduces the quenching and partition process, a thermal treatment that is designed to employ carbon partitioning from martensite into untransformed austenite, with the purpose of generating austenite-containing microstructures in low-alloy steels with attractive performance characteristics. Some physical metallurgy fundamentals of the process and associated mechanisms are introduced. Applications for a variety of steel product forms are presented, with selected data from property measurements available to date.

Quenched and Partitioned Steels

A double-twist torsion testing technique has been developed using a 316 stainless steel as an exemplar material to experimentally assess recrystallization behavior and determine the non-recrystallization temperature (Tnr). This new method was compared to the traditional methods of double-hit compression and multi-step hot torsion testing. The double-twist torsion test allows Tnr to be related to the extent of austenite recrystallization through measurements of fractional softening while accommodating multiple deformation and recrystallization steps with a single specimen. The double-twist torsion test resulted in average Tnr values similar to those determined with multi-step hot torsion, and a partially recrystallized microstructure was observed in the vicinity of the calculated Tnr for all three methods. The ability of the double-twist torsion test to relate the experimental Tnr to the evolution of austenite recrystallization via fractional softening measurements while incorporating effects of multiple deformation steps offers an advantage over traditional methods for quantifying changes in austenite recrystallization during thermomechanical processing.

/pdf/double-twist-torsion-testing-to-determine-the-non-4d89vf7nwn.pdf

Double twist torsion testing to determine the non recrystallization temperature.

The present invention refers to a rolled steel article consisting essentially of by weight percent: 0.0005 to less than 0.1 % carbon; between zero and up to 2.5 % manganese; between zero and up to 0.5 % aluminium; between zero and up to 0.5 % of a nitride forming element selected from the group consisting of boron, zirconium and titanium; between zero and less than 0.04 % nitrogen; between 0.005 and less than 0.6 % vanadium; between zero and up to 1.0 % silicon and between zero and up to 0.25 % phosphorus; with the balance being iron and inevitable impurities, characterized in that the ratio of vanadium to carbon is 10 or above. Moreover the application is directed to a method for producing the same.

Method for producing bake hardenable vanadium containing steel product and its products

Medium carbon steels alloyed with two levels each of V and Si were heat treated to form tempered martensite and bainite, followed by nitriding to evaluate their effects on case hardness and residual stress. Microstructures were quantitatively characterized with Vickers microhardness testing, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), conventional transmission electron microscopy (CTEM), and scanning transmission electron microscopy (STEM). Measurements of subgrain size, cementite size, dislocation density, and volume fractions of nitride precipitates were combined in a strength model to predict the contributions of V and Si to maximum case hardness after nitriding. Higher V contents lead to increases in maximum case hardness by increasing the volume fraction of MX precipitates. Increases in Si content lead to increased maximum case hardness by increasing the volume fraction of amorphous (Si and Mn)-containing nitride precipitates; the presence of Mn in these precipitates has not been previously reported. Higher Si contents also lead to increases in solid solution strengthening because the majority of Si remains in solution in the ferrite matrix. Greater volume fractions of MX and (Si and Mn)-containing nitrides both lead to higher magnitudes of compressive residual stress. The results presented here demonstrate that alloying can improve the properties after nitriding, providing insight into advanced nitriding steel grades and potentially enabling a wider range of steel microstructures to be nitrided without a debit in performance.

John G. Speer

Papers

Effects of Chemical Composition, Heat Treatment, and Microstructure in Splittable Forged Steel Connecting Rods

Quenched and Partitioned Steels

Double twist torsion testing to determine the non recrystallization temperature.

Method for producing bake hardenable vanadium containing steel product and its products

Influences of Vanadium and Silicon on Case Hardness and Residual Stress of Nitrided Medium Carbon Steels