V2A, V4A, high-temperature grades – which stainless steel when.

Stainless steels are the most widely used material group in CNC turned parts manufacturing. Yet 1.4305, 1.4404 and 1.4571 are worlds apart – in price, machinability and corrosion resistance. This article walks you through the most important variants.

1.4305 (X8CrNiS18-9, a V2A variant, AISI 303) is the classic choice for easily machinable stainless steel turned parts. The sulfur addition improves chip formation significantly compared to 1.4301 – machine times and tool life both benefit. Corrosion resistance is good in non-aggressive media, but slightly reduced compared to 1.4301 due to the sulfur content. It is the standard for mechanical engineering components, sensor technology and drive components in non-aggressive environments.

1.4301 (X5CrNi18-10, V2A) is the sulfur-free variant. Better corrosion resistance, poorer machinability. It is typically used where 1.4305 is not permitted because of its sulfur content (food, pharmaceutical applications in specific cases).

1.4404 (X2CrNiMo17-12-2, AISI 316L, V4A) is the standard choice for more corrosive applications. The molybdenum addition provides significantly higher resistance to chloride corrosion. It is used in medical technology, chemical plants and seawater applications. Price is roughly 40–60 percent above 1.4305. Machinability is considerably poorer – higher machining times and tooling costs.

1.4571 (X6CrNiMoTi17-12-2, AISI 316Ti, V4A) is the titanium-stabilized variant of 1.4404. Higher corrosion resistance at elevated temperatures, better weldability. Price is roughly 60–80 percent above 1.4305. It is frequently specified on drawings as a blanket choice, although 1.4404 is technically sufficient in most cases. Rule of thumb: if there is no elevated temperature (> 400 °C) and no welding on the finished part, 1.4404 is enough.

1.4441 is the medical-grade variant (essentially 1.4404 with particularly strict purity requirements). For non-implant components in medical technology it is often the standard; for permanent implants, special materials are usually used (titanium, 1.4441 from a specific melt).

A practical recommendation from 77 years of practice: before specifying any stainless steel, clarify the functional requirement. Corrosive medium? What concentration? What temperature? What service life? Only then can the material number be chosen sensibly. Blanket specifications like 'V4A is always enough' cost money unnecessarily – and sometimes even lead time, because certain stainless steel grades have longer procurement times.

Where chloride-containing media, seawater or aggressive process chemistry meet standard austenitic materials, 1.4404 and 1.4571 reach their limits. Duplex steels such as 1.4462, with their ferritic-austenitic microstructure, then offer significantly higher resistance to pitting and stress corrosion cracking at nearly double the yield strength. Machining is more demanding: higher cutting forces, a stronger tendency to work hardening and shorter tool life. Super duplex grades go even further. We use duplex specifically where the corrosion load absolutely requires it, not as a blanket choice.

Austenitic stainless steels have a strong tendency to work hardening during turning. If a dull tool or one fed too slowly is cutting, it pushes the material rather than shearing it. The surface zone hardens, and the next tool has to work in an already hardened layer. The consequences are accelerated wear, fluctuating tool life and dimensional deviations. That is why we keep cutting parameters consistently high enough, use sharp tool geometries and avoid dwelling in the cut, to ensure reproducible results across the entire batch.

Machining alone does not complete the corrosion protection. During processing, tramp iron from tools or clamping devices reaches the surface, and thermal load creates temper colors that disrupt the protective passive layer. Passivation rebuilds this chromium oxide layer in a controlled way; pickling removes tramp iron and temper colors. Especially with the easily machinable, sulfurized 1.4305 this is worth a closer look, since the manganese sulfide inclusions already reduce corrosion resistance somewhat. We match the post-treatment to the material and the operating environment.

An often overlooked selection criterion is magnetic behavior. Austenitic grades such as 1.4305 or 1.4404 are practically non-magnetic in the as-delivered condition, which makes them ideal for sensor, measurement and medical technology; however, heavy cold forming can make them slightly magnetizable. If magnetic attraction or hardenability is required instead, martensitic steels such as 1.4021 or 1.4034 come into consideration – they can be quenched and tempered but offer less corrosion resistance. Tell us the function, and we will select the material accordingly, not the other way around.

We check feasibility, suggest optimizations and get back to you within 48 hours with a first assessment.