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What Do V2A and V4A Mean – and Where Do These Terms Come From?
The abbreviations V2A and V4A originate from early experimental series in the steel industry and are not standards today but rather colloquial designations for two stainless steel groups.
The "V" stands for Versuchsschmelze (experimental melt), the "A" for Austenit (austenite). V2A stands for "Versuchsschmelze 2, Austenit" – the name given by Friedrich Krupp AG to the second austenitic alloy in their experimental series in 1912. V4A refers to the fourth experimental melt accordingly. In daily practice, these short forms have become firmly established. However, they no longer appear in any current standard.
- V2A encompasses chromium-nickel steels, primarily grade 1.4301 (AISI 304).
- V4A additionally contains approximately 2% molybdenum and includes grades such as 1.4401 (AISI 316) and 1.4404 (AISI 316L).
In terms of standards, the correct designations are material numbers according to DIN EN or AISI numbers. In practice, however, designations such as material number 1.4301 or V4A appear in virtually every enquiry and quotation.
How to Read a Stainless Steel Material Number (1.4301, 1.4404 & Co.)
Every stainless steel material number follows a fixed system. Once you understand it, you can immediately classify any grade.
Using 1.4301 as an example:
- 1 — Main material group: steel and cast steel
- 43 — Grade class: corrosion-resistant steels (chromium-nickel alloys)
- 01 — Sequential number: distinguishes materials within the same group
All stainless steel material numbers in vessel construction start with 1.4... – the last two digits differentiate the exact alloy variant. For daily work, it is important to know: 1.4301 and 1.4307 are both chromium-nickel steels of the V2A group, 1.4401 and 1.4404 are both V4A – each with minor differences in carbon content and corrosion resistance.
V2A vs V4A: What Is the Key Difference?
The key difference lies in the molybdenum content: V4A contains approximately 2% additional molybdenum, which significantly increases corrosion resistance – particularly against chlorides.
In the food, pharmaceutical or chemical sectors, V4A stainless steel is the standard choice for all product-contact surfaces. The austenitic stainless steel without molybdenum is suitable for structural elements such as frames or support legs. This saves material costs without compromising product safety.
- V2A (1.4301): Good corrosion resistance, widely used across industries, economical.
- V4A (1.4404): Enhanced resistance to chlorides, saltwater and sulphuric acid. Standard for product-contact components.
- Rule of thumb: Wherever the medium is aggressive, salty, acidic or pharma-cleaned, V4A is the right choice.
Stainless Steel Grades Compared: 1.4301, 1.4404, 1.4571 and More
Direct comparisons between individual grades are particularly frequently requested. The following tables show the most important representatives of both groups at a glance.
One physical property unites all austenitic grades: the stainless steel density ranges between 7.9 and 8.0 g/cm³. Grade 1.4301 has a density of 7.9 g/cm³, grade 1.4404 of 8.0 g/cm³. This value is relevant for vessel calculations regarding statics and weight. Beyond corrosion resistance, mechanical properties also matter: tensile strength, yield strength and elongation at break determine whether a grade is suitable for a given vessel.
V4A group grades
V4A is the upgraded version of V2A: the addition of molybdenum significantly increases corrosion resistance, especially against chlorides and sulphuric acid. Heat resistance is also higher than with the standard stainless steel AISI 304.
| Material No. | International | Key Feature |
|---|---|---|
| 1.4401 | AISI 316 | Enhanced corrosion resistance, widely used in pharma, chemical and food industries |
| 1.4404 | AISI 316L | Lower carbon content (Low Carbon), more weldable, preferred in vessel construction |
| 1.4571 | AISI 316Ti | Titanium-stabilised, particularly suited for high-temperature applications above 350 °C |
| 1.4435 | AISI 316L | Higher molybdenum and nickel content, pharma specialist, extremely pitting-resistant |
| 1.4429 | AISI 316LN | Very good corrosion resistance due to nitrogen addition |
| 1.4439 | AISI 317LMN | Resistant even at high chloride concentrations |
| 1.4539 | AISI 904L | Up to 5% molybdenum, for highly corrosive media such as phosphoric or hydrochloric acid |
Key comparisons in detail
1.4404 vs. 1.4401: Both belong to the V4A group and are almost identical in practice. The difference lies in the carbon content: 1.4404 (AISI 316L) has a lower C content, making it more weldable and marginally more resistant to intergranular corrosion. In most vessel construction applications, both are fully interchangeable.
1.4571 vs. 1.4404: 1.4571 (AISI 316Ti) additionally contains titanium as a stabiliser. This makes it particularly suited for high-temperature applications above 350 °C. Its corrosion resistance matches that of 1.4401/1.4404. Disadvantage: titanium prevents uniform surface finishing – if you want to polish your vessel to a mirror finish, 1.4571 should be avoided.
1.4541 – V2A or V4A? This question comes up regularly: 1.4541 (AISI 321) is a V2A steel that has been stabilised with a titanium addition. It offers better corrosion resistance than the standard stainless steel 1.4301 (AISI 304) but is not suited for pharmaceutical applications requiring mirror-polished surfaces.
V2A group grades
V2A encompasses all chromium-nickel steels without molybdenum addition. By far the most common representative is 1.4301 – it accounts for over 50% of the total market.
| Material No. | International | Key Feature |
|---|---|---|
| 1.4301 | AISI 304 | Very good welding properties, the most widely used stainless steel grade across all industries |
| 1.4307 | AISI 304L | Lower carbon content, enhanced resistance to intergranular corrosion |
| 1.4541 | AISI 321 | Titanium-stabilised, enhanced resistance, not suited for polishing |
Chromium-nickel steel is used across all industries: in food processing, the chemical and pharmaceutical industries, construction and automotive manufacturing. The choice of grade within the V2A group depends on the specific requirements for weldability, temperature resistance and surface quality.
Special Alloys for Extreme Conditions – When Are They Worth It?
For particularly aggressive media, even V4A reaches its limits. In such cases, special alloys with significantly higher alloying content are used.
- 1.4529 (Alloy 926): This grade contains 6.5% molybdenum. It offers excellent protection against pitting and crevice corrosion. Typical applications include marine chemistry and salt processing.
- Hastelloy: A brand name for highly alloyed nickel-molybdenum alloys with up to 30% molybdenum. This material resists even concentrated hydrochloric or sulphuric acids. However, the material cost is significantly higher.
Engineers should always base the decision for a special alloy on a media analysis and operating temperature assessment. In many cases, selective use of V4A for product-contact components offers the more economical solution. Special alloys are only used where they are technically essential.
Corrosion Resistance Overview: Which Grade for Which Medium?
Corrosion resistance is the decisive selection criterion for stainless steel grades in vessel construction. Correct matching of medium and material prevents costly damage and downtime.
- Water, food products, weak acids: V2A (1.4301) is sufficient.
- Salt-containing media, chlorides, whey, brine: V4A (1.4404) is mandatory.
- Sulphuric acid, nitric acid, phosphoric acid: V4A (1.4404 / 1.4435) recommended, depending on concentration and temperature.
- Concentrated hydrochloric acid, highly corrosive acids: Special alloys such as 1.4529 or Hastelloy.
