Red-short
Encyclopedia
Red-short, hot-short or Sulfur embrittlement is the quality possessed by carbon steel that suffers from having too much sulfur
as an impurity
.
Iron
or steel
, when heated to above 900 °F (480 °C), glows with a red
color. The colour of any heated object changes predictably (due to black body radiation) from dull red through orange and yellow to white, and can be a useful indicator of its temperature. Good quality iron or steel at and above this temperature becomes increasingly malleable and plastic. Iron or steel having too much sulfur, on the other hand, becomes crumbly and brittle. This is due to the sulfur forming iron sulfide/iron mixtures in the grain boundaries of the metal which have a lower melting point than the steel.
When the steel is heated up and worked, the mechanical energy added to the workpiece increases the temperature further. The Iron Sulfide (FeS) or Iron/Iron Sulfide alloy (which has an even lower melting point) begins to melt, and the steel starts to separate at the grain boundaries. Steelmakers add Manganese (Mn) to the steel when it is produced, to form Manganese Sulfide (MnS). Manganese sulfide inclusions have a higher melting point and do not concentrate at the grain boundaries. Thus, when the steel is later heated up and worked, the melting at the grain boundaries does not occur.
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
as an impurity
Impurity
Impurities are substances inside a confined amount of liquid, gas, or solid, which differ from the chemical composition of the material or compound.Impurities are either naturally occurring or added during synthesis of a chemical or commercial product...
.
Iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
or steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, when heated to above 900 °F (480 °C), glows with a red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
color. The colour of any heated object changes predictably (due to black body radiation) from dull red through orange and yellow to white, and can be a useful indicator of its temperature. Good quality iron or steel at and above this temperature becomes increasingly malleable and plastic. Iron or steel having too much sulfur, on the other hand, becomes crumbly and brittle. This is due to the sulfur forming iron sulfide/iron mixtures in the grain boundaries of the metal which have a lower melting point than the steel.
When the steel is heated up and worked, the mechanical energy added to the workpiece increases the temperature further. The Iron Sulfide (FeS) or Iron/Iron Sulfide alloy (which has an even lower melting point) begins to melt, and the steel starts to separate at the grain boundaries. Steelmakers add Manganese (Mn) to the steel when it is produced, to form Manganese Sulfide (MnS). Manganese sulfide inclusions have a higher melting point and do not concentrate at the grain boundaries. Thus, when the steel is later heated up and worked, the melting at the grain boundaries does not occur.