Technical guide


Technical guide

Strength class material is used on the majority of standard components such as bolts, screws and nuts.

Designation indicates a yield strength of the material tensile strength (Rm), and / or yield stress (Re).

The most commonly used class of material strength: 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 10.9, 12.9, 14.9.

Informator techniczny

The bolts and screws

The bolts and screws are used in the indication of four grades of strength, consisting of a two-digit number and symbol H.

This designation corresponds to 10% of the Vickers hardness (HV) of the material.

Śruby i wkręty
Strength classHardness (HV)Strength class
14H1404.6, 4.8, 5.6, 5.8
22H2206.6, 6.8, 6.9, 8.8
33H33010.9, 12.9

The division of special steels, due to the working conditions:

  • Resistant to corrosion,
  • For operation at a reduced temperature,
  • For operation at elevated temperature,
  • Heat-resistant and heat resistant.
  • Valve,
  • Resistant to wear.
  • Thrust,
  • With special magnetic properties,
  • Highly hardenable – “maraging steel”.

21CrMoV5-7 – alloy steel for operation at elevated temperature – belonging to the heat-resistant and high-temperature creep resistant group. The advantage of this steel is resistance to hot gases and fumes, while maintaining good mechanical properties. It is used for small elements, such as nut bolts, struts, and, moreover, shafts and discs of steam turbines operating at temperatures up to 500°C.

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