ISO 3506-1 Mechanical Property of Stainless Steel Fasteners
ISO 3506-1 specifies the mechanical and physical properties of corrosion-resistant stainless steel bolts, screws and studs with specified grades and property classes. The standard provides requirements for fasteners manufactured from different stainless steel groups, including austenitic, martensitic, ferritic and duplex stainless steels, and covers both coarse and fine pitch metric threads. The designation system identifies the stainless steel material group and the corresponding property class, allowing the mechanical performance of a fastener to be clearly defined according to its material and strength level.
Stainless steel fasteners covered by ISO 3506-1 are available in a range of grades and property classes, including commonly specified austenitic grades such as A2-70, A2-80, A4-70 and A4-80, as well as higher-strength or application-specific grades in other stainless steel groups. The standard addresses key properties such as minimum tensile strength, stress at 0.2% non-proportional elongation, elongation and hardness, together with requirements for chemical composition and, where applicable, heat treatment. These requirements provide a consistent basis for selecting and verifying stainless steel fasteners for machinery, industrial equipment, construction, marine and other applications where corrosion resistance and mechanical performance are both important.
Austenitic and Duplex Stainless Steel Mechanical Properties
ISO 3506-1 covers austenitic and duplex stainless steel fasteners with specified material groups and property classes. Austenitic grades such as A2 and A4 are widely used for their combination of corrosion resistance, strength and versatility. Among these, A2-70 bolts and A2-80 bolts are commonly selected for general stainless steel fastening applications, while A4-70 bolts and A4-80 bolts are widely used where higher corrosion resistance is required.
These property classes are commonly specified for stainless steel bolts, screws and studs used in industrial equipment, machinery, construction and other fastening applications. The mechanical requirements include minimum tensile strength (Rmf), stress at 0.2% non-proportional elongation (Rpf), elongation and applicable hardness requirements, with the required values depending on the material group, property class and nominal diameter.
| Stainless Steel Grade | Property Class | Tension Strength(min)MPA | Stress at 0.2% non-proprotional elongation(min)MPA | Elongation after fracture(min)mm | |
| Austenitic | A1 A2 A3 | 50 | 500 | 210 | 0.6d |
| 70 | 700 | 450 | 0.4d | ||
| 80 | 800 | 600 | 0.3d | ||
| A4 A5 | 50 | 500 | 210 | 0.6d | |
| 70 | 700 | 450 | 0.4d | ||
| 80 | 800 | 600 | 0.3d | ||
| 100 | 1000 | 800 | 0.2d | ||
| A8 | 70 | 700 | 450 | 0.4d | |
| 80 | 800 | 600 | 0.3d | ||
| 100 | 1000 | 800 | 0.2d | ||
| Duplex | D2 D4 D6 D8 | 70 | 700 | 450 | 0.4d |
| 80 | 800 | 600 | 0.3d | ||
| 100 | 1000 | 800 | 0.2d | ||
Martensitic and Ferritic Stainless Steel Mechanical Properties
| Stainless Steel Grade | Property Class | Tensile Strength(min) MPA | Stress at 0.2% non-proportional elongation(min) MPA | Elongation after aracture (min)mm | Hardess HV | Hardess HRC | Hardess HBW | |
| Martensitic | C1 | 50 | 500 | 250 | 0.2d | 155-220 | - | 147-209 |
| 70 | 700 | 410 | 0.2d | 220-330 | 20-34 | 209-314 | ||
| 110 | 1100 | 820 | 0.2d | 350-440 | 36-45 | - | ||
| C3 | 80 | 800 | 640 | 0.2d | 240-340 | 21-35 | 228-323 | |
| C4 | 50 | 500 | 250 | 0.2d | 155-220 | - | 147-209 | |
| 70 | 700 | 410 | 0.2d | 220-330 | 20-34 | 209-314 | ||
| Ferritic | F1 | 45 | 450 | 250 | 0.2d | 135-220 | - | 128-209 |
| 60 | 600 | 410 | 0.2d | 180-285 | - | 171-271 | ||
Chemical Composition of Stainless Steel Fasteners
| Stainless Steel Grade | Chemical Compistion(max) | |||||||||||
| C | Si | Mn | P | S | Cr | Mo | Ni | Cu | N | Other Element | ||
| Austenitic | A1 | 0.12 | 1 | 6.5 | 0.02 | 0.15~0.35 | 16.0~19.0 | 0.7 | 5.0~10.0 | 1.75~2.25 | / | c,d,e |
| A2 | 0.1 | 1 | 2 | 0.05 | 0.03 | 15.0~20.0 | / f | 8.0~19.0 | 4 | / | g,h | |
| A3 | 0.08 | 1 | 2 | 0.045 | 0.03 | 17.0~19.0 | / f | 9.0~12.0 | 1 | / | 5C≤Ti≤0.80 and/or 10C≤Nb≤1.00 | |
| A4 | 0.08 | 1 | 2 | 0.045 | 0.03 | 16.0~18.5 | 2.00~3.00 | 10.0~15.0 | 4 | / | h,i | |
| A5 | 0.08 | 1 | 2 | 0.045 | 0.03 | 16.0~18.5 | 2.00~3.00 | 10.5~14.0 | 1 | / | 5C≤Ti≤0.80 and/or 10C≤Nb≤1.00 i | |
| A8 | 0.03 | 1 | 2 | 0.04 | 0.03 | 19.0~22.0 | 6.0~7.0 | 17.5~26.0 | 1.5 | / | / | |
| Martensitic | C1 | 0.09~0.15 | 1 | 1 | 0.05 | 0.03 | 11.5~14.0 | / | 1 | / | / | i |
| C3 | 0.17~0.25 | 1 | 1 | 0.04 | 0.03 | 16.0~18.0 | / | 1.50~2.50 | / | / | / | |
| C4 | 0.08~0.15 | 1 | 1.5 | 0.06 | 0.15~0.35 | 12.0~14.0 | 0.6 | 1 | / | / | c,i | |
| Ferritic | F1 | 0.08 | 1 | 1 | 0.04 | 0.03 | 15.0~18.0 | / f | 1 | / | / | j |
| Duplex | D2 | 0.04 | 1 | 6 | 0.04 | 0.03 | 19.0~24.0 | 0.10~1.00 | 1.50~5.5 | 3 | 0.05~0.20 | Cr+3.3Mo+16N≤24.0 k |
| D6 | 0.04 | 1 | 6 | 0.04 | 0.03 | 21.0~25.0 | 0.10~2.00 | 1.00~5.5 | 3 | 0.05~0.30 | 24.0＜Cr+3.3Mo+16N k | |
| D8 | 0.03 | 1 | 2 | 0.04 | 0.015 | 21.0~23.0 | 2.5~3.5 | 4.5~6.5 | / | 0.08~0.35 | / | |
Stainless Steel Bolts and Fasteners to ISO 3506-1:
Stainless steel fasteners manufactured to ISO 3506-1 requirements are available in a wide range of product types, with dimensional and product specifications defined by the applicable DIN or ISO standard. These standards determine factors such as head dimensions, thread length, nominal diameter and overall geometry, while ISO 3506-1 specifies the applicable stainless steel material groups, property classes and mechanical requirements. Our product range includes common hex bolts, flange bolts, threaded rods, stud bolts and other specialized fasteners for industrial and mechanical applications.