ISO® 3506
ISO® 3506 is used to ensure that fasteners such as stainless steel screws, nuts, studs and washers meet international standards for mechanical strength and corrosion resistance in industrial applications and critical environments such as marine and chemical.
The table summarizes the mechanical specifications for each steel type and strength class provided in ISO® 3506, making it a useful tool for choosing the right material according to specific needs.
Steel types
The regulations provide for the establishment of standards for the production of stainless steel fastening systems from the following families:
- Austenitic (A): Steels with excellent corrosion resistance, non-magnetic.
- Martensitic (C): Steels with high mechanical strength, can be hardened.
- Ferritic (F): Steels with good corrosion resistance, intermediate properties.
- Duplex (D): Steels that combine the properties of austenitics and ferritics, with high mechanical strength and good corrosion resistance.
Mechanical Specifications
| Type of steel | Strength class | Tensile strength (Rm) | Yield strength (Rp02) | Minimum elongation (A) | Hardness (HV) |
|---|---|---|---|---|---|
| Austenitic (A) | A1-50, A2-50, A3-50 | 500 MPa | Not specified | 0.6 x d | 125 HV max |
| A1-70, A2-70, A3-70 | 700 MPa | 450 MPa | 0.4 x d | 190 HV max | |
| A1-80, A2-80, A3-80 | 800 MPa | 600 MPa | 0.3 x d | 250 HV max | |
| A8-70 | 700 MPa | 450 MPa | 0.4 x d | 220 HV max | |
| A8-80 | 800 MPa | 600 MPa | 0.3 x d | 270 HV max | |
| Martensitic (C) | C1-50, C3-50 | 500 MPa | 350 MPa | 0.6 x d | 255 HV max |
| C1-70, C3-70 | 700 MPa | 550 MPa | 0.4 x d | 335 HV max | |
| Ferritic (F) | F1-45, F2-45 | 450 MPa | 250 MPa | 0.6 x d | 150 HV max |
| F1-60, F2-60 | 600 MPa | 400 MPa | 0.4 x d | 220 HV max | |
| Duplex (D) | D1-80 | 800 MPa | 600 MPa | 0.3 x d | 270 HV max |
| D1-100 | 1000 MPa | 750 MPa | 0.25 x d | 320 HV max | |
| Superduplex (SD) | SD1-80 | 800 MPa | 640 MPa | 0.3 x d | 300 HV max |
| SD1-110 | 1100 MPa | 850 MPa | 0.25 x d | 350 HV max |
Additional features
Austenitic A8
A8-70, A8-80: These austenitic steels offer higher corrosion resistance than conventional A2 and A4, but with greater mechanical strength. They are used in applications requiring greater strength and reliability under high loads.
Superduplex (SD)
SD1-80, SD1-110: Superduplex steels combine enhanced corrosion resistance with extremely high mechanical strength, used for applications in highly corrosive environments such as the offshore and chemical industries.
Mechanical properties: They offer significantly higher tensile strength and yield strength than standard Duplexes, making them ideal for extreme operating conditions.
Considerations
Austenitic A8: It is particularly suitable for applications requiring corrosion resistance combined with higher mechanical strength than A2 and A4.
Superduplex (SD): offers an advanced solution for industries with exposure to very aggressive environmental conditions with high mechanical strength.
