Différance and Paranoia

This exploratory essay aims to open différance to a form of enquiry it has not seen coming. A consideration of the complex temporality that attends its historical emergence leads to a specifically différantial articulation of spatio-temporality. A residual element of spacing before/behind spati­otemporality provokes further consideration. The notion of verbality is introduced to provide analytical purchase. Analysis identifies a fundamen­tal mannerism in différance; a participative and orchestrative spacance. Dif­férance participates too determinately in this spacing, as this spacing. The paper thus urges différance to rewrite this element quasimetaphorically. In the ensuing drama, différance can rewrite the metaphor of spacing only by relying again on the spacing of metaphor. Unable to rewrite itself quickly enough, nonetheless compelled, an unexpected dimension opens.

Influence of Diffusion in the Underlying Metal during Oxidation of Iron Containing Small Amounts of Copper and Nickel

The residual element copper in recycled steels embrittles grain boundaries, causing a surface cracking phenomenon known as hot shortness. Embrittlement is caused by a copper-rich liquid phase that forms at the oxide/metal interface during steel oxidation. Another residual element, nickel, enriches along with copper and reduces hot shortness cracking. The mechanisms by which nickel affects copper enrichment behavior have not yet been adequately studied. This work examines the effects of nickel and copper on the oxidation behavior and oxide/metal interface microstructure of iron. Iron-0.3 wt% copper alloys containing 0.1 wt% nickel and 0.05 wt% nickel were compared. Pure iron was used as a reference material. Alloy samples were oxidized in air at 1150°C. The parabolic oxidation rates for both alloys were found to decrease by a factor of two from that of pure iron. Both alloys had perturbed oxide/metal interfaces consisting of alternating solid/liquid regions. The interface development is due to stabilization of perturbations in the solid/liquid interface. The interface morphology can also explain the observed decrease in oxidation rate.

Population Studies of Titanium-Bearing Inclusions in AISI 316l using Automated Image Analysis with Scanning Electron Microscopy/Electron Dispersion Spectroscopy (SEM/EDS)

Titanium is used in the manufacture of AISI 316L austenitic stainless steel as a deoxidizer. Titanium is considered a residual element, and limits are often not specified. As a residual element, titanium most often appears in complex oxide inclusions, usually in conjunction with aluminum and other deoxidizers. Titanium-bearing inclusions have been found to initiate pitting during electropolishing. The present work was performed to evaluate the acceptable upper limit for titanium as a residual element in AISI 316L.Metallographic specimens were prepared from seven commercial heats of AISI 316L (Table 1) with titanium contents varying from 0.003 % to 0.014 %. A quantitative metallographic analysis of each specimen was performed using an SEM/EDS system with an automated stage. Operating parameters are given in Table 2. Data was obtained with the system in the backscatter (BS) mode, producing a high-contrast image based on differences in chemical composition. Once each inclusion was identified by its difference in gray scale, it was also analyzed by EDS for elements present.

The effects of residual elements and deoxidation practice on the mechanical properties and stress relief cracking susceptibility of ½%CrMoV turbine castings

The effects of residual element content on the mechanical properties and stress relief cracking susceptibility have been investigated for basic electric arc melted ½%CrMoV steel castings deoxidized by using either aluminium or titanium practices. The residual element contents ranged from the lowest readily available in commercial practice to levels substantially higher than those common at present. In normalized and tempered material, deoxidation by the use of aluminium resulted in lower creep rupture ductility than deoxidation by using titanium, regardless of residual element content. Only in one cast did low purity appear to correlate with low ductility. Similarly, in simulated heat-affected zone material, the susceptibility to stress relief cracking was less in casts deoxidized with titanium. Increasing the residual element content had a slightly deleterious effect on stress relief cracking susceptibility, but austenite grain size refinement gave significant improvement. It is concluded that adoption of the titanium deoxidation practice used in the present work would improve the creep rupture ductility and stress relief cracking resistance of ½%CrMoV steel, but that at present there is no need for very low residual element contents. Regardless of deoxidation practice, sound welds should be obtainable when adequate grain refinement can be produced by control of the welding process.

The effects of residual elements on the properties of engineering steels

The effect of a variety of residual elements on the tensile and toughness properties of special carbon and low alloy engineering steels has been determined. The major objective of this work has been to identify the extent to which residual element contents can be allowed to rise without infringing the specification and in-service performance requirements of these steels. In C-Mn and C-Mn-B steels, the main effect of the residual elements, chromium, molybdenum, nickel and copper, is to raise hardenability and tensile strength with a concurrent reduction in ductility. The effects on toughness are dependent upon the microstructural changes accompanying the increase in hardenability and can be either beneficial or detrimental. A statistical approach has been adopted in quantifying the influence of these elements on hardenability. In many cases, naturally occurring levels of chromium, molybdenum, nickel and copper can be used to advantage as the basis for providing cheaper alternatives to low alloy steels. However, it might be necessary to compensate for very high residual element levels by reducing the carbon and/or manganese levels in order to maintain the currently specified hardenability limits. In low alloy steels, phosphorus, arsenic and tin were found to exhibit the greatest influence on toughness and this effect was most detrimental in the Cr and Ni-Cr steels. The presence of molybdenum reduced the susceptibility to embrittlement. In most of the low alloy steel grades examined, it has been concluded that there would be no foreseeable violations of property specifications, even if the residual content were allowed to rise much above the current levels. Only in certain cases, e.g. 815H17, was it concluded that the phosphorus, arsenic and tin contents must be maintained at the current levels produced by electric arc steelmaking in order to satisfy user requirements.