Stainless steel qualities

Different inox types, more or less commonly used at Alinco and their application, sorted by AISI code:

RVS301

Austenitic, chromium-nickel stainless steel with unusually high uniform elongation under the right composition balance and deformation conditions. It is usually available as spring steel and is typically offered in thin sheets. It is applied for very strong cold forming. As a result of moderate to very strong cold deformation, tensile strength increases significantly while maintaining reasonable toughness. Type 301 is essentially non-magnetic in the soft-annealed condition but becomes magnetic through cold deformation. For very thin sheets, alternatives are not available in the classic RVS304 or RVS316, so we offer RVS301.

RVS303

Types 303 and 303Se are easy-to-machine stainless steel grades closely related to RVS304. These grades are never used in sheet metal processing but are sometimes specified on plans. In this case, we always offer standard RVS304 or RVS316.

RVS304 and RVS304L

The most used type of inox within Alinco and the sheet metal processing world. Sufficiently corrosion-resistant for most indoor and non-aggressive applications. The quality is essentially non-magnetic in the soft-annealed condition but can become slightly magnetic through cold working. It is widely used in machinery, the food and pharmaceutical sectors, and indoor construction applications such as railings. The difference between RVS304 and RVS304L is the carbon content (L stands for low carbon) and poses less risk of corrosion after welding. The distinction is less relevant for Alinco as they purchase only the L variant for sheet material. Nowadays, most sheet materials are dual-certified (both RVS304 and RVS304L). RVS304 lends itself easily to an aesthetic finish. For outdoor use, RVS316 is recommended.

RVS309

An austenitic, chromium-nickel stainless steel with high heat resistance, categorized among heat-resistant inox types. They are widely used for welding wire, but also in sheet form for ovens and such. RVS309 is the cheapest among the commonly used heat-resistant inox types. The sheets have an inox color, unlike other common heat-resistant materials which have a brown mill scale.

RVS310, RVS310S, and RVS314

Also heat-resistant inox types. They are austenitic, chromium-nickel stainless steel grades with high heat resistance and higher strength at high temperatures than type 309. They are essentially non-magnetic in both soft-annealed and cold-deformed conditions. The sheets have a brown color, leading non-experts to sometimes think it's regular steel. Previously, the standard RVS310/314 = 1.4841. Given its similarity to RVS310S = 1.4845, some manufacturers have stopped producing both grades, and the market availability leans more towards RVS310S. The expectation is that RVS310/314=1.4841 will become less common.

RVS316 and RVS316L

The more corrosion-resistant siblings of RVS304(L). The L also stands for Low Carbon and serves the same purpose as in RVS304. We only purchase L quality for sheet material, and only European origin plates. It is an austenitic, chromium-nickel-molybdenum stainless and heat-resistant steel with superior corrosion properties compared to most other chromium-nickel steel types. It finds application in aggressive environments and products, construction (outdoor applications), and is also regularly used in the pharmaceutical and chemical sectors. It is also recommended for outdoor use. It is 1/4 to 1/3 more expensive than RVS304; apart from higher corrosion resistance, this inox quality is similar to RVS304; it also lends itself well to an aesthetic finish.

RVS321 and RVS321H

Type 321 is an austenitic, chromium-nickel stainless steel similar to RVS304, with added titanium to stabilize carbon. It was initially developed as a counterpart to RVS304L, which aimed for the same goal with low carbon content. It is rarely used. This type is recommended for parts exposed to certain corrosive environments, fabricated by welding and not annealed afterward. Another advantage is its slightly better heat resistance than RVS304, making it somewhat intermediate between regular inox types and heat-resistant ones, used at temperatures between 425 and 900°C in certain corrosive environments. This RVS type is not (or less) suitable for an aesthetic finish. RVS321H is a variant with a carbon content maintained between 0.04 and 0.10 percent to improve high-temperature strength. RVS321 and 321H are also more difficult to weld.

RVS4XX

RVS4xx series belong to ferritic inox grades, which are barely used in the classic sheet metal processing sector. Therefore, they are magnetic and considered somewhat inferior because they lean more towards regular steel. They are generally more susceptible to corrosion but also cheaper. Nevertheless, they find applications in certain sectors. The only inox grade in the 400 series we occasionally use is RVS430.

RVS430

This type of inox is sufficiently corrosion-resistant for most household and kitchen applications and is widely used in standard appliances such as dishwashers, deep fryers, ovens, etc., due to its lower cost. The downside is its poor weldability. At Alinco, this inox is only used for its magnetic properties, such as when a customer explicitly requires magnetic inox, or for a magnet latch where we need a counterplate in an inox piece of furniture, using RVS430 instead of steel.