“Stainless steel” is a general term. Behind it are grades that differ markedly in welding, turning and contact with salt. This overview adds the grades you will find with us as semi-finished products to our article “V2A or V4A”.
Problem
The problem: “stainless steel” is not enough as a specification
An order for a “stainless steel round bar 20 mm” leaves open whether the part will later be welded, turned or used outdoors with road salt. That is exactly why there are different grades. The wrong choice only shows later: as rust at the weld seam, as a blunt tool or as pitting.
Cause
The cause: chromium, nickel, molybdenum, sulphur
According to EN 10088, stainless steels contain at least 10.5% chromium. The chromium forms a thin passive layer on the surface that protects the steel. Nickel makes the material austenitic, i.e. easy to form and practically non-magnetic.
The additions determine the strengths: molybdenum (1.4571) protects against chlorides. Sulphur (1.4305) makes the chip short but impairs weldability and resistance. Little carbon (1.4307) prevents intergranular corrosion after welding.
| Grade | Known as | Strength | Weakness | Semi-finished forms at MVG |
|---|---|---|---|---|
| 1.4301 (X5CrNi18-10) | V2A, AISI 304 | Standard: weldable, polishable, food-safe | not for chlorides | Round, flat, square bar, tubes, angles, threaded rod |
| 1.4305 (X8CrNiS18-9) | AISI 303 | excellent machinability | not weldable, slightly less resistant | Round and hexagonal bar |
| 1.4307 (X2CrNi18-9) | 304L | low carbon, weld seam resistant without post-treatment | not for chlorides | brushed structural tubes |
| 1.4571 (X6CrNiMoTi17-12-2) | V4A, AISI 316Ti | resistant to chlorides, road salt, sea air | more expensive than 1.4301 | Round bar |
Standard values to EN 10088; tensile strength of all four grades about 500 to 700 N/mm² (1.4305 up to 750 N/mm²). The certificate of the delivery is binding.
Solution
The solution: choose by the next work step
Ask first what happens to the part next. If it is turned and not welded, 1.4305 is the economical choice. If it is welded and polished, take 1.4301, or 1.4307 for welded tube structures. If it comes into contact with salt, there is no way around 1.4571.
Like 1.4571, 1.4404 (X2CrNiMo17-12-2) is one of the molybdenum-alloyed V4A grades. Our article “V2A or V4A” describes the differences between V2A and V4A and how to choose by environment.
- Use tools and brushes that have never been in contact with mild steel – otherwise extraneous rust forms.
- Saw slowly and cool generously: stainless steel conducts heat poorly and work-hardens during machining.
- Pickle or brush temper colours after welding, otherwise the resistance is lost there.
Remember: Order with the material number, not just “stainless steel”.
At a glance
- State the next work step: welding, turning, polishing
- Describe the environment: indoors, outdoors, road salt, swimming pool, coast
- State the material number in the order
- If required, request an inspection certificate 3.1 in advance
Matching products
Frequently asked questions
Why does stainless steel sometimes rust after all?
Often it is extraneous rust from mild steel particles from tools or brushes. With 1.4301, chloride (road salt, swimming pool, sea air) can also cause pitting; there 1.4571 is the right choice.
Can I weld 1.4305?
No, 1.4305 is not suitable for welding. For welded parts, choose 1.4301 or 1.4307.
Is stainless steel magnetic?
The austenitic grades 1.4301, 1.4305, 1.4307 and 1.4571 are practically non-magnetic. Cold forming can make them slightly magnetic.