Brittle crack carbon steel

As the result of a heater failure, the temperature of the vessel, designed for -29°C, fell to -60°C by evaporative cooling (see Section 10.5.2) at this temperature carbon steel becomes brittle, and cracking may have started. 

Although the majority of the hydrogen produced on the cathodic areas is evolved as gas and assists the removal of scale, some of it diffuses into the steel in the atomic form and can render it brittle. With hardened or high-carbon steels the brittleness may be so pronounced that cracks appear during pickling. Austenitic steels, however, are not so subject to embrittlement. 

Brittle Failure (8). Brittleness is a principal consideration in selecting construction materials for liquid hydrogen service. Brittle fracture can result in the essentially instantaneous release of a vessel s contents, the hazard being a combined one of PV energy release and the possibility of fire and/or explosion. Three conditions must exist for a brittle fracture to occur 1) a stress riser, a crack, notch, or other discontinuity, 2) a section where the actual stress exceeds the yield stress of the material, and 3) a temperature below which failure occurs without appreciable plastic deformation. Metals that are satisfactory for liquid hydrogen service include aluminum, stainless steels, brass, and copper. Carbon steel is not suitable. 

Brittle Failure. Below some limiting temperature steel pipe is notch sensitive and can crack at lower-than-yield-point stress with little or no deformation or absorption of energy. Do not use carbon steel pipe at temperatures even as low as 0°F unless the service is completely non-hazardous or you have specific evidence that a particular lot of pipe is resistant to brittle failure at the service temperature. 

Dry hydrogen sulfide is satisfactorily handled under pressure at normal ambient temperatures in carbon steel or black iron piping. Carbon steels in wet applications are known to be subject to sulfide stress cracking and low-temperature brittle fracture under some conditions of temperature, stress, and pressure. While hydrogen sulfide itself is relatively noncorrosive to steel in many uses, factors such as impurities, pH, erosive con-... 

The carbon content in plain carbon and low steels is restricted to 0.30 and 0.15%, respectively. The cooling rates and carbon contents are controlled during the welding of carbon steels to maximize the formation of soft a-ferrite and minimize the formation of pearlite and cemen-tite which are hard components. Similarly in low alloy chromium steels, the formation of brittle martensite is minimized. Martensite is sensitive to hydrogen-induced cracking and ferrite is... 

Titanium carbonitride that may be found in 4340 steel or 18 Ni maraging, are so brittle that break under very low deformation of the matrix crystals in which they are contained. Once broken or debonded, an inclusion nucleates a micro crack. Manganese-sulhde inclusions, MnS, are quite common in low-medium strength carbon steel, but they are less brittle. They may be long and sharp representing points of high stress concentration that may also activate a slip band. Figure 3.20... 

Punches manufactured from high carbon/high chromium steel may exhibit improved wear resistance characteristics, however under extreme compression force, the cup may crack due to the brittle nature of the steel. Steels with lower carbon and chromium levels will act conversely. While these steels may be useful in some applications, the majority will require a more moderate balance of toughness and wear resistance. Steel selection for dies is not as critical. In most cases, high wear resistance steel is preferred. 

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