The choice of the materials to use in the construction of industrial plants is never neither random nor it is based exclusively on the evaluation of the costs, but it is always the result of precise technical needs: reliability and safety guarantee, business continuity, durability and profitability over time and regulatory compliance. Among the different types of available stainless steel, the 316L version is the noblest metal and it represents the standard in the chemical, food, pharmaceutical and energy fields.
It belongs to the austenitic CR-Ni-Mo steel category whose chemical composition is the following:
- Carbon: C ≤ 0,03%
- Chromium: Cr 16–18%
- Nickel: Ni 10–14%
- Molybdenum: Mo 2–3%
We can consider 6 features characterizing this type of stainless steel unlike the others:
1.High resistance to corrosion thanks to molybdenum presence (2/3%)
This apparently unsignificant metallurgical detail has got concrete consequences on plants because it increases pitting, corrosion and Chloride-induced corrosion.
From an electrochemical point of view, Molybdenum promotes the self-healing of the passive film in case of local damage, reducing the risk of pitting initiation. It increases the so-called PREN (Pitting Resistance Equivalent Number).
For this reason , AISI 316L is particularly suitable for environments where the presence of chlorides, saline solutions and aggressive detergents can be found.
2. Low Carbon quantity (L= Low Carbon)
The low presence of Carbon reduces the risk of integranular corrosion after welding.
Compared to AISI 316, the version 316L contains a lower quantity of Carbon that, together with the presence of Molybdenum, enables the resistance to corrosion.
3. Excellent weldability and machinability
It boasts excellent weldability across common methods (TIG, MIG, SMAW/Stick) and good cold forming properties.
In complex industrial plants, where there are multiple welded tubes, exchangers and tanks, welding quality is crucial to guarantee plants reliability over time.
AISI 316L ensures a higher safety in this sense resulting more suitable for complex constructions.
It therefore allows maintaining metallurgical integrity in the heat-affected zones (HAZ) without the systematic need for post-weld solution treatment also reducing the precipitation of chromium carbides (Cr23C6) at the grain boundaries during thermal cycles between 450°C and 850°C.
4. High level of hygiene
AISI 316L is particularly recommended for fields where high hygiene standards, sterility and prevention of contamination must be assured and where the final product quality also depends on the integrity of contact surfaces.
The creation of the passive layer reduces the microbial adhesion and its impermeability facilitating the disinfection also in case of aggressive cleaning processes.
For this reason, it is ideal for food, biomedical and cosmetic industry.
5. Mechanical and thermal resistance
It has got a good mechanical resistance also at high temperatures, a good oxidation resistance up to 800 ° in intermittent service and a good toughness also at low temperatures; furthermore, it maintains structural stability up to approximately 800°C at intermittent service.
For these reasons, it is recommended both for under pressure applications, reactors, tanks and process lines, but also for systems subject to important temperature excursions.
6. Durability over time and maintenance costs reduction
Despite its higher cost in comparison to the other versions of stainless steel, its choice is the best solution generating economic advantages in the mid-long term: operative durability, reduced plant downtime due to corrosion or deterioration and lower replacement costs compared to less resistant materials.
In terms of price-quality ratio, AISI 304 is a good solution, but AISI 316L is surely more specific for aggressive environments and resistant applications such as in the naval, marine and industrial field. It is a sort of evolution of the basic version of AISI 304. Mistakes in the choice of the correct material can cause risks and problems with serious consequences.
Thanks to the above explained features, AISI 316L is particularly used in the following fields: pharmaceutical and medical, food&beverage, naval and offshore that is in marine contexts, for water treatment systems and in the oil&gas field where materials reliability is not an option, but rather an essential design requirement.
It is in this context that Tecra decided to specialize in the promotion of AISI 316L considered as a strategic material for your applications in a design approach focused on durability, safety, performance over time and also in off-shore and chemical aggressive circumstances ensuring reliability at the same time. We, in fact, boast solid and long-lasting partnerships with reliable producers to guarantee the maximum quality and our proven experience lets us support our customers in the choice of the best product.
In our warehouse we have got a wide variety of tubing and accessories in AISI 316L ready to be shipped. This choice promotes wide range of products, immediate availability, quick deliveries and shipment control. We have also recently added a new stock section on the website where our customers and perspective ones can easily and independently check the current stock availability.
To conclude, it can be said that AISI 316l is not simply a material nor it is chosen for a purely commercial logic: it is rather a strategic choice in the modern industrial planning and a solution among the most performing ones. It is a valid technical and engineering justified choice.