Materials know-how

How can something be called stainless if it is prone to rusting? Practical advice on protecting the surface oxide layer, on why stainless steel must never meet carbon steel, and a table of 60 chemicals with their effect on A2 and A4 grades.

An extract from ISO 683-13:1986: the chemical composition of ferritic, martensitic and austenitic stainless steels, with maximum mass percentages for carbon, silicon, manganese, phosphorus and sulphur, plus nitrogen, aluminium, chromium, molybdenum, niobium, nickel, selenium, titanium and copper, and the steel group codes that map them to the F1, C and A1–A5 grades.

According to DIN EN ISO 3506: the mechanical properties of martensitic (C1, C3, C4) and ferritic (F1) stainless fasteners — tensile strength, 0,2% yield strength, elongation at fracture and hardness in HB, HRC and HV — plus the length limits, the thread diameter range and the temperature caveats to agree with your supplier.

According to DIN EN ISO 3506: the chemical composition of austenitic (A1–A5), martensitic (C1, C3, C4) and ferritic (F1) stainless steels in mass percentages of carbon, silicon, manganese, phosphorus, sulphur, chromium, molybdenum, nickel and copper, with the twelve footnotes on sulphur, molybdenum, nickel and the stabilising titanium and niobium.

An extract from ISO 4954 : 1993: the chemical composition of ferritic, martensitic and austenitic stainless steels intended for cold forming, with mass percentages for carbon, silicon, manganese, phosphorus, sulphur, chromium, molybdenum and nickel, plus the steel group codes that map them to the A2, A4 and A5 grades.

A reference table of the stainless and acid-resistant steels used in Germany: material number, the designation under the VDEh standard that preceded DIN, indicative average analysis for carbon, silicon, manganese, chromium, nickel and molybdenum, and a typical example of use for every grade.

Austenitic stainless and acid-resistant steels belong in the category of active corrosion protection thanks to their alloying materials. Even so, they can corrode in practice. Rust contamination, surface, local, contact, stress and mechanical corrosion, and how to guard against each.

Iron is an important element of living organisms and one of our most heavily used industrial materials, especially its alloy with carbon: steel. From classification and the effect of carbon to the alloying elements behind corrosion-resistant and acid-resistant grades, here is what shapes the properties of steels.