Acier inoxydable is an indispensable material in modern manufacturing, playing a crucial role in applications ranging from heavy industry to domestic cutlery. While many grades exist, the most commonly encountered for consumer goods and general purpose manufacturing are the 18/8, 18/10, et 18/0 varieties. These designations, which indicate the primary alloying elements, define the material’s performance, coût, and suitability for specific environments.
Understanding the subtle yet significant differences between these three grades is essential for making informed sourcing and design decisions, optimizing both product lifespan and budget.
Qu'est-ce que 18/8 Acier inoxydable (Most Commonly Grade 304)?
18/8 stainless steel is arguably the most ubiquitous grade worldwide, primarily recognized by its common industry designation, Grade 304.
Composition and Structure
The numerical designation clearly reveals its composition: approximately $\mathbf{18\%}$ Chrome ($\texte{Cr}$) and $\mathbf{8\%}$ Nickel ($\texte{Dans}$). The remainder is predominantly $\mathbf{\sim 67\%}$ Fer ($\texte{Fe}$), along with a trace amount of carbon (about $\mathbf{0.07\%}$).
This grade is a fundamental member of the austenitic steel family. The presence of nickel stabilizes the austenitic crystal structure at room temperature, granting it several distinct advantages:
Résistance à la corrosion: It possesses good resistance to general corrosion and oxidation due to the chromium, which forms a thin, passif, self-healing oxide layer on the surface.
Propriétés mécaniques: It exhibits high strength, excellent ductility, and is relatively easy to weld.
Durcissement: A key characteristic of the austenitic family is that it cannot be hardened through traditional heat treatments; only cold working can increase its tensile strength.
Applications et limites
18/8 is deemed food safe and is extensively used in the food preparation and service industries, including restaurant-grade worktops, industrial pipes for fluids, batterie de cuisine, ustensiles, and general household cutlery.
Cependant, its corrosion resistance has limits. C'est not ideal for continuous exposure to high-salinity environments (saltwater), high chloride concentrations, harsh industrial chemicals, or strong acids, where pitting corrosion is a high risk.
Processus de fabrication
The production involves melting all raw ingredients and alloying elements in an electric furnace, typically a process lasting 8–12 hours. This is followed by decarburization—a step critical for reducing excess carbon (which can compromise corrosion resistance) using gases like argon or oxygen. Enfin, the liquid steel is poured into molds to harden into the required shape and size.
Qu'est-ce que 18/10 Acier inoxydable?
18/10 stainless steel represents a premium upgrade over 18/8, driven by a higher nickel content that significantly enhances performance characteristics.
Composition and Properties
The composition is approximately $\mathbf{18\%}$ Chrome ($\texte{Cr}$) and $\mathbf{10\%}$ Nickel ($\texte{Dans}$). This extra $\mathbf{2\%}$ boost in nickel content is the critical difference, offering major advantages:
Résistance supérieure à la corrosion: The higher nickel percentage provides high résistance à la rouille, oxydation, et, crucially, better performance against acidic or corrosive foods and liquids. This makes it ideal for items routinely cleaned with strong detergents or used with high-acidity foods (par exemple., vinegar or citrus).
Esthétique: The increased nickel content results in a much shinier and more aesthetically pleasing surface finish that retains its polish well.
High Temperature Performance: It demonstrates reliable stability and structural integrity in high-temperature environments.
Magnetic Status: 18/10 steel maintains non-magnetic properties, which is typical of high-nickel austenitic grades, though this may not be suitable for all applications (par exemple., induction cooking).
Inconvénients
While superior in performance, 18/10 est généralement plus cher que 18/8 due to the higher nickel proportion. En outre, the higher alloying content can make it less easily machinable, requiring more time and specialized effort during fabrication. It also shares 18/8’s vulnerability to extended exposure in saltwater environments.
Processus de fabrication
The process mirrors that of 18/8—melting scrap in a furnace followed by decarburization—with the primary difference being the slightly greater proportion of nickel included in the batch.
Qu'est-ce que 18/0 Acier inoxydable?
18/0 stainless steel is defined by a singular, cost-saving feature: the complete absence of nickel.
Composition and Characteristics
Its composition is approximately $\mathbf{18\%}$ Chrome ($\texte{Cr}$) and $\mathbf{0\%}$ Nickel ($\texte{Dans}$), often with slightly varying chromium levels (16–18%). This absence fundamentally alters its physical and mechanical properties:
Cost and Budget: It is the most budget-friendly grade available among the three, making it attractive for large-scale, cost-sensitive production.
Résistance à la corrosion: Due to the lack of nickel (and often molybdenum), its resistance to corrosion and oxidation is faible. It has a high susceptibility to staining compared to the other grades.
Magnétisme: Unlike the austenitic 18/8 et 18/10, 18/0 l'acier est magnetic, which can be an advantage for specific applications like certain kitchen appliances or induction cooktops.
Brittleness and Welding: The lack of nickel causes the material to be more brittle and prone to cracking. It is also challenging to weld because it retains heat, has a high melting point, is prone to distortion.
Esthétique: It generally has a duller, less reflective finish than its nickel-containing counterparts.
Applications
Despite its lower resistance, 18/0’s rust resistance is still adequate for basic kitchen equipment and utensils. Its most notable advantage is its nickel-free composition, le rendre idéal pour Équipement médical, bijoux, and kitchen tools used by individuals with nickel allergies.
Processus de fabrication
It is melted and cast similarly to the other grades, without the addition of nickel. Après le casting, it often undergoes processes like recuit or other finishing techniques to optimize its modest properties.
Comprehensive Comparison of All Three Steels
The choice between the three grades must be a careful calculation based on the required material characteristics, the product’s intended environment, and the manufacturing budget.
The following table summarizes the key property differences:
| Propriété | 18/8 Acier inoxydable | 18/10 Acier inoxydable | 18/0 Acier inoxydable |
| Teneur en nickel | 8-10.5% | 10-14% | 0% |
| Contenu en chrome | 18-20% | 16-18% | 16-18% |
| Résistance à la corrosion | Modéré | Haut | Faible |
| Force | Bien | Excellent | Modéré |
| Coût | Modéré | Plus haut | Inférieur |
| Staining Susceptibility | Modéré | Faible | Haut |
| Magnetic Property | Non-Magnetic | Non-Magnetic | Magnétique |
En bref, $\mathbf{18/10}$ offers the highest performance for premium, high-contact, or acidic food applications but carries the highest cost. $\mathbf{18/8}$ is the versatile, cost-effective standard for general-purpose, food-safe applications. $\mathbf{18/0}$ is the budget-conscious choice, sacrificing durability and corrosion resistance for cost savings and necessary applications involving magnetism or nickel-allergy concerns.
Conclusion and Manufacturing Availability
The composition, particularly the nickel percentage, fundamentally determines the cost, résistance à la corrosion, and magnetic properties of stainless steel. By assessing the necessary characteristics—such as whether the part requires superior resistance to acids (18/10) or must be budget-friendly and magnetic (18/0)—manufacturers can select the optimal grade.
Specialized manufacturing services, like those offered by Xometry, utilize these popular stainless steel grades (y compris le 304 et 316 variants) across diverse processes such as CNC machining, fabrication de tôle, and custom sheet cutting, providing immediate access to the right material for any custom part requirement.
FAQ
T1: Why are 18/8 et 18/10 Non-Magnetic, alors que 18/0 is Magnetic?
UN: The difference lies in their internal crystalline structure. 18/8 et 18/10 stainless steels are austenitic due to their high nickel content (8% à 14%). Nickel stabilizes the austenite phase, which is a face-centered cubic structure that is inherently non-magnetic. En revanche, 18/0 stainless steel contains no nickel, placing it in the ferritic ou martensitic steel family. These families have a body-centered cubic structure, which is ferromagnetic and therefore highly magnetic.
T2: Est 18/10 Stainless Steel the same as Grade 316?
UN: Non, they are not the same, cependant 18/10 is often used as a general term for high-nickel austenitic steel. Grade 316 (which typically has a composition close to 18% Cr / 10% Dans) contains an additional crucial alloying element: Molybdène ($\texte{Mo}$). The addition of Molybdenum provides vastly superior resistance to pitting corrosion, especially in chloride and marine environments, making Grade 316 the standard choice for saltwater exposure, traitement chimique, and surgical instruments.
T3: Why is 18/0 more prone to cracking and brittleness compared to 18/8 ou 18/10?
UN: This is a direct consequence of the zero nickel content. Nickel is a potent stabilizer of the ductile (austenitic) structure. Without nickel, 18/0 steel exists in the ferritic or martensitic state, which generally has lower toughness and higher susceptibility to embrittlement, particularly when subjected to thermal stress or impact. The lack of nickel means the material is inherently less pliable, making it brittle and more likely to crack or distort under strain compared to its high-nickel counterparts.
T4: When designing for a humid or coastal environment, which grade is the absolute minimum standard?
UN: For humid or general outdoor environments, 18/8 (Grade 304) is usually the minimum standard due to its good general corrosion resistance. Cependant, if the environment is coastal or marine (involving contact with saltwater or airborne chlorides), 18/8 is insufficient due to the risk of pitting. In chloride-rich environments, a grade containing Molybdenum, tel que Grade 316 (not explicitly 18/10, but a further alloyed version), should be used to provide adequate resistance.
Q5: How does the higher cost of 18/10 justify its use over 18/8 in professional kitchens?
UN: The increased cost of 18/10 is justified by its superior resistance to corrosion and staining caused by acides. Professional kitchens frequently deal with high-acidity foods (par exemple., tomato sauce, citrus juices, vinegars) and strong commercial cleaning detergents containing chlorides. The extra nickel in 18/10 provides the necessary passivation and stability to prevent these substances from causing long-term staining, piqûre, and degradation, ensuring the utensils and equipment maintain their aesthetic quality and longevity.
