Discs with round hole DIN 440 Form R-steel 100 HV hot-dip galvanized

The combination of strength classes for flat washers with those for bolts and nuts is governed by ISO 898-3:2018, Table 1. Washers with a hardness of 100 HV are suitable for applications with unhardened bolts up to strength class 5.8 and nuts up to class 5. Applications involving bolts of strength class 6.8 and nuts of class 6 must be checked during installation. Combinations with higher strength classes must not be used.

Steel is an iron-carbon alloy with a maximum carbon content of 2% by mass. The steels achieve their intended physical and mechanical properties through various hardening, annealing and tempering processes. It is also possible to harden the edge zone by surface hardening, case hardening or nitriding. Well-known steel grades are structural steels, free-machining steels, case-hardening steels, nitriding steels, tempering steels, tool steels and stainless steels.

In hot-dip galvanising, a zinc coating is applied to the component by immersing it in molten zinc and then spinning it off. DIN EN ISO 10684 restricts its application to steel fasteners with standard threads ranging from M8 to M64, as well as strength classes up to 10.9 for bolts and 12 for nuts. The average coating thickness for fasteners is 50 micrometres, which ensures corrosion protection for many years.