Nonmetallic inclusion

Laminations. A lamination is a separation within the metal wall caused hy the presence of a highly elongated nonmetallic inclusion. Laminations generally are aligned parallel to the surfaces. 

Seams. As a defect, a seam is distinct from the seam resulting from a welding process. Seam defects can be found in nonwelded (seamless) tubes. They can originate from blow holes or nonmetallic inclusions in the ingot and are caused by crevices that have been closed by some rolling process but remain unfused. At times, they will appear in a spiral pattern in tubes. Seams can be very tight and appear as hairlines on the surface. They can cause failure when the component is pressurized. 

Metallic materials consist of one or more metallic phases, depending on their composition, and very small amounts of nonmetallic inclusions. In the metallic state, atoms donate some of their outer electrons to the electron gas that permeates the entire volume of the metal and is responsible for good electrical conductivity (10 S cm ). Pure elements do not react electrochemically as a single component. A mesomeric state can be approximately assumed... 

This potential depends on the interfacial tension am of a passivated metal/electrolyte interface shifting to the lower potential side with decreasing am. The lowest film breakdown potential AEj depends on the surface tension of the breakdown site at which the film-free metal surface comes into contact with the electrolyte. A decrease in the surface tension from am = 0.41 J m"2 to metal surface, will cause a shift of the lowest breakdown potential by about 0.3 V in the less noble direction. 

The presence of nonmetallic inclusions tends to increase the extent of blistering damage. When steel contains segregated impurities, stringer-type inclusions or laminations, hydrogen or methane accumulations in these areas may cause severe blistering.10... 

The fracture mode of both forgings was by the microvoid nucleation and growth process (Figure 4). Microvoids nucleate at nonmetallic inclusions in the steel (sulfides, oxides, etc) and grow under strain until they coalesce at fracture (10). While the CF heats had a fairly uniform microvoid size distribution on the fracture surface, the HERF steel fracture surface had a bimodal distribution of microvoids with large microvoids surrounded by clusters of fine microvoids. 

M.M. Shenoy et al Modeling effects of nonmetallic inclusions on LCF in DS nickel-base superalloys. Int. J. Fatigue 27, 113-127 (2005)... 

Hydrogen blistering blister formation, originating at nonmetallic inclusions. 

Instrumental neutron activation analysis was used to determine concentrations of several major and trace elements in samples of heavily corroded residues found in crucible fragments excavated at Tel Dan, Israel. The residues were mostly hard, metallic phases admixed with nonmetallic inclusions that appeared to be ceramic material from the loose porous interior of the crucible itself The objective was to identify the metals that had been melted in these crucibles. A method is described that attempts to separate nonmetallic and metallic phase data. In comparison to previous reports on analyses of source materials thought to have been used at Dan in this period (Late Bronze II Age-Early Iron I Age 1400-1000 B.C.), high gold concentrations were found. These appear to be correlated to arsenic and antimony concentrations. This finding is discussed in relation to possible changes in the source of tin at this period. 

In its simplest form, steel is an alloy of iron and carbon. In general, there are other alloying elements present. Steel wires can vary in composition enormously, from simple C-Mn steel to alloy steels containing more than ten alloy additions. Control of impurities (mostly nonmetallic inclusions), chemical segregation,... 

Metal Fatigue Effects of Small Defects and Nonmetallic Inclusions ISBN 008-044064-9... 

Flexsil [Ametek]. TM for for a high silica refractory cloth filter designed to extract dross, slag, refractory particles, and nonmetallic inclusions from molten metals. An important property is its chemically active surface. 

This chapter sums up the investigations performed by the author for years on establishing the scientific basics of the ultrasonic treatment of melts of light alloys with the aim to improve purity of the melt in nonmetallic inclusions and to control the structure of as-cast and deformed metal. 

Table 1. Effect of Content of Hydrogen (H2) and Nonmetallic Inclusions (Al203) on Cavitation Threshold Pc in a Melt of Commercially Pure Aluminum3...

To better appreciate the role of ultrasonic treatment of aluminum melts, it is necessary to consider the presence of solid nonmetallic inclusions within liquid aluminum (nonwettable by the melt). 

The data show that melt fluidity increases by 30% due to ultrasonic degassing of the melt, which is very important for a shape-casting production. Bondarek [18] has confirmed these results, according to his data the ultrasonic treatment in a 45-kg crucible of an AL9 grade alloy not only decreases the hydrogen content and volume proportion of nonmetallic inclusions but disperses the latter (Table 7). 

For example, the determining factors for the filtration are the initial rate of liquid movement (6 to 8 cm s l) and the rate of the liquid rises to several centimeters during the first seconds of the ultrasonic action. On the other hand, due to adhesion of dispersed particles of solid nonmetallic inclusions onto the walls of a capillary, the effective cross-section of the latter continuously changes in the process of filtration. Finally, with actual filtration we deal not with the regularities of the flow through a capillary channel but with the statistics of melt movement through a porous medium with a host of channels. 

But the practice shows that only a small part of the submicroscopic particles (or so-called plankton ) are active. Most of the nonmetallic particles do not participate in the solidification process. Only the particles with deep cracks filled with a matrix alloy are sufficiently stable to serve as solidification sites [60]. The melting temperature of such an alloy appears to be significantly higher than that of the equilibrium liquidus. Filling of imperfections on the surface of nonmetallic inclusions is hampered by the presence of a gas phase within the imperfections, which does not allow the particles to serve as nucleation sites for the matrix and intermetallics. 

It should be noted that the activation and wetting of noncontrolling nonmetallic inclusions in an acoustic cavitation field can occur due to the action of cumulative jets forming when cavitation bubbles collapse (see Section 2.4). 

These processes involve crack formation by the precipitation of dissolved hydrogen onto lamellar nonmetallic inclusions. They are a particular problem... 

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