A grade 8.8 can be manufactured with any material whose mechanical properties meet or exceed the requirements given in the relevant harmonized standards.
The two-digit nomenclature is not used to describe individual steel grades and only applies to metric fasteners defined under ISO 965 (as well as derived standards)
The designation system is based on two numbers e.g 8.8. The first number is the tensile strength of the bolt material (N/mm2 )/100. The second number is = 1/100. (the ratio of the Proof (or Yield ) stress and the Tensile strength expressed as a percentage = 100.[Yield (Proof stress) /Tensile strength] /100
meaning that a grade 8.8 bolt has a nominal ultimate tensile strength (UTS) of 800N/mm2 (or Mpa) and a nominal yield strength of 640N/mm2 (or Mpa).
Characteristics of Grade 8.8 Stainless Steel Fasteners
- The actual steel grade used by manufacturers may vary but in most cases, a grade 8. 8 Stainless steel fasteners (plain, black oxide, or galvanized) will be in medium alloy carbon steel, typically with 0.30- 0.50 % Carbon and alloyed with other elements such as Molybdenum, Vanadium, Manganese and sometimes Boron or Cobalt in small quantities. These alloying elements provide the required mechanical properties to reach the minimum strength set forth by the harmonized standards.
- Bare in mind that people sometimes refer to “high-tensile bolts” which are typically graded 8.8 or superior under the metric fastener system.
- Grade 8.8 and superior bolts should always have their grade permanently marked on the head to differentiate them from “low-tensile bolts” as inadvertently replacing the former with the latter could have disastrous effects.
- Grade 4.6 bolts are typically referred to as “low tensile” and are often used in the construction industry, as these bolts offer superior ductility and resilience than & high strength& bolts.
Industrial Application Grade 8.8 Stainless Steel Fasteners
- Pharmaceuticals.
- Marine.
- Aerospace.
- Construction.
- Food.
