Novel Fine Grain Austenitic Stainless Steel (NFG) Strong and formable alternative to AISI 304 and AISI 316
General characteristics
Novel fine grain stainless steels are a group of 300-series stainless steels. They are a stronger, yet formable alternative for general stainless steels such as 1.4307 (AISI 304L) and 1.4404 (AISI 316L). Their yield strength levels can be varied from 350 MPa up to 800 MPa and their elongation properties range from 20% up to 50%.
The phenomena behind the properties of these unique stainless steels is based on grain refining. The grain size of novel fine grain stainless steel is between 1–6 µm (typical 2 µm) compared to 15–30 µm in conventional. Small grain size gives the steels excellent surface quality, which is especially prominent after cold forming.
The steels can be used in applications where extra strength is needed or where surface quality is important. The steels can be used as an alternative to existing 300-series steels in many applications as their composition complies with standard EN10088-2.
The product is supplied in cold rolled and annealed condition. Various chemical and mechanical surface treatments are available.
Possible thicknesses range from 0.05 mm up to 3.5 mm in coil and sheet forms.
Typical applications:
- Heat Exchangers
- Cookware and kitchen appliances
- Medical and hygienic applications
- Pressure vessels
- Architectural structures
Chemical composition
The chemical composition of the steels vary depending on the grade, but they are compatible with the EN10088-2 standard.
| C | Mn | Cr | Ni | N | |
|---|---|---|---|---|---|
| Typical | 0.02 | 18.5 | 9 | ||
| EN 10088-2 | ≤0.03 | ≤2.0 | 17.5–19.5 | 8.0–10.5 | ≤0.10 |
| C | Mn | Cr | Ni | Mo | N | |
|---|---|---|---|---|---|---|
| Typical | 0.02 | 17.2 | 10.1 | 2.1 | ||
| EN 10088-2 | ≤0.03 | ≤2.0 | 16.5–18.5 | 10.0–13.0 | 2.0–3.0 | ≤0.10 |
Mechanical properties
Mechanical properties of the steels may be varied by grain size and composition. Typical mechanical properties and stress-strain curve for type 304/304L are presented below.
| Rp0.2 [MPa] | Rm [MPa] | A80 [%] | |
|---|---|---|---|
| Typical | 450–500 | 750–780 | 37–40 |
| EN 10088-2 (1.4301) | ≥230 | <750 | ≥45 |
Rp0.2 492 MPa • Rm 773 MPa • Ag 33% • A50 40.3%
Fabrication
The materials can be formed with all standard cold forming methods. They are not suitable for hot forming.
The materials are suitable for deep-drawing, having a limiting drawing ratio (LDR) of 2.1 for grade AISI304. Materials also stretch formable, as its Erichsen Index (IE) for 1,5 mm thickness AISI 304 is 12,1 mm.
The steels have good weldability using methods like MIG/MAG, MIG-laser hybrid, laser and TIG. Materials are suited for autogenous welding. A care must be taken when welding as the strength of the material may be reduced in the heat affected zone (HAZ). Therefore, methods with low heat input are recommended. Post weld heat treatment is not recommended as the heat reduces the material strength.
pWPS is available for MIG/MAG welding.
Please contact NextInox for more detailed information about welding.
