Steel’s chemical composition is referred to as 8.8-grade steel. Carbon is the most common alloying element, accounting for over 98% of all alloying elements. 8.8 steel is characterized by an average silicon content of 0.08 to 0.18 percent, a manganese content of 0.13 to 0.2 percent, and an Aluminium content of 0.3 to 0.48 percent. It works by manipulating the steel’s harden-able, weld-able, and tough properties.
A material whose mechanical qualities satisfy or surpass the criteria of the applicable harmonized standards can be used to make a Carbon Steel 8.8 Fasteners. Individual steel grades are not described using the two-digit nomenclature, which is exclusively applicable to metric fasteners.
There are two digits in the bolt numbering system, such as 8.8. It represents the tensile strength of the bolt material (N/mm2/100). In other words, the second number represents a ratio of Proof (or Yield) stress to Tensile strength of one-hundredth of one hundredth (100 [Proof stress] / Tensile strength) x 100.
The nominal ultimate tensile strength of a grade 8.8 bolt is 800N/mm2 (or Mpa), while the nominal yield strength is 640N/mm2 (or Mpa).
Neither Kg/mm2 nor PSI are valid SI units since they are, respectively, an expression of mass and weight by surface area, and neither is a measure of mass or weight.
A fastener grade of 8.8 (self-colored, black-oxidized, or zinc-plated) is usually produced or manufactured from a medium-alloyed medium carbon steel alloyed with other elements such as Molybdenum, Vanadium, Manganese, and occasionally Boron or Cobalt. Generally, harmonized standards require at least a minimum level of strength provided by these alloying elements.
Grade 8.8 and higher bolts should always have their grade permanently stamped on the head to distinguish them from “low-tensile bolts,” since replacing the former with the latter can have devastating consequences.
