Hardenability

For concrete work in cold weather a specially rapid-hardening cement may be made by addition of calcium chloride to the cement. 

Photographic material containing gelatin can be hardened during manufacture the process involves cross-linking between the gelatine polypeptide chains induced by hardener. 

In case hardening C and N are introduced into the iron by heating in a Nj —NH3 atmosphere or by immersing the steel in molten NaCN/Na2C03 at about 900"C. 

Austenitic steels retain the ccp structure right down to room temperature. For this reason these steels cannot be hardened by quenching. 

Hardening per RTFOT (Rolling thin-film ouen test) NF T 66-032/ASTM D 2872... 

Once the cementation has been completed the rig will wait on cement (V OC), i.e. wait until the cement hardens prior to running in with a new assembly to drill out the plugs, float collar and shoe, all of which are made of easily drillable materials. 

The chemistry of cement slurries is complex. Additives will be used to ensure the slurry remains pumpable long enough at the prevailing downhole pressures and temperatures but sets (hardens) quickly enough to avoid unnecessary delays in the drilling of the next hole section. The cement also has to attain sufficient compressive strength to withstand the forces exerted by the formation over time. A spacer fluid is often pumped ahead of the slurry to clean the borehole of mudcake and thereby achieve a better cement bond between formation and cement. 

Fig. 1 Beginning stage of pitting origin (hardened structural steel)...

Correction for beam hardening artefacts in computerised tomography... 

Inspection of frame equipment and pipe - lines for the presence of the fatigue, hardening, and other cracks, corrosion. 

At the anode, a chemical oxidation reaction is bound to take place. In normal fixers, sulfite (SOj ) is oxidized and acid (H ) is released as a consequence of this oxidation. Due to the decrease of the sulfite concentration and the decrease in the pH, the fixing solution becomes unstable and sulfur precipitation starts to occur when the pH of the fixer decreases below 4.0. In the case of hardening fixers, there is also an upper limit to the pH, since aluminum-hydroxides starts to precipitate when the pH exceeds 5.0. 

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