Steel mechanical conditions affecting

Mechanical Conditions Affecting Vessel Steel in Hydrogen... 

Structural Properties at Low Temperatures It is most convenient to classify metals by their lattice symmetiy for low temperature mechanical properties considerations. The face-centered-cubic (fee) metals and their alloys are most often used in the construc tion of cryogenic equipment. Al, Cu Ni, their alloys, and the austenitic stainless steels of the 18-8 type are fee and do not exhibit an impact duc tile-to-brittle transition at low temperatures. As a general nile, the mechanical properties of these metals with the exception of 2024-T4 aluminum, improve as the temperature is reduced. Since annealing of these metals and alloys can affect both the ultimate and yield strengths, care must be exercised under these conditions. 

The resistivity of the soil in any particular location will be a function of moisture content, soil temperature and presence of dissolved salts. At a site where climatic conditions vary considerably throughout the year, earth electrodes should be buried at a depth where such changes will not affect the resistivity. Grounding rods are generally made of copper bonded onto a steel core. The copper provides a good connection to earth and offers a high corrosion resistance, while the steel core gives the mechanical... 

The preparation of surfaces to receive epoxy compounds is as important as the selection of the proper system for bonding. Concrete surfaces must be freshly exposed, free of loose and unsound material and should be at proper surface temperatures at the time of epoxy application. Among the methods for preparation of concrete surfaces are sandblasting, mechanical scarification and acid etching. The same procedures may be followed for preparation of steel surfaces. Temperature conditions for epoxy application should be in the range of 50°F. to 90 f. Temperature conditions v ill also affect pot life of mixed compounds, as well as curing time. 

The wear map of Figure 10.21 corresponds to a particular case, that is, a non-lubricated steel to steel contact in a pin-on-disk apparatus. This situation is of little practical interest, because most metal to metal contacts are lubricated. Furthermore, much of the parameter space covered in the map refers to extreme conditions, far from typical engineering situations. The wear map shown is nevertheless interesting because it provides an overview of how a combination of different variables can affect the wear mechanism and the wear rate. 

Factors that influence SCC response will generally affect one of four basic variables in the process the material or alloy system, the chemical service environment, the electrochemical state of the system relative to surroundings, and the state of mechanical stress. Nearly all structural alloy systems can be found susceptible to SCC under certain alloy chemistry, metallurgical condition, and service environmental conditions. SCC behavior relative to alloy system was detailed in an American Society for Metals (ASM) publication [6], for a broad range of structural alloys, and has also been covered extensively for aluminum, titanium, and high-strength steels [8]. 

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