Steel Glossary
Technical terms from steel trading, materials science and plant engineering – explained briefly and clearly. From the material number to the PREN value.
Materials & Grades
Material number
Five-digit code to EN 10027-2 for the unambiguous identification of a material. Examples: 1.0038 for S235JR, 1.0577 for S355J2, 1.4301 for stainless chromium-nickel steel. The first digit denotes the main material group (1 = steel).
Structural steel (S235, S355)
Non-alloy structural steel to EN 10025-2. The "S" stands for structural steel, the number for the minimum yield strength in MPa. S355 allows slimmer cross-sections for the same load, while S235 is cheaper to buy and sufficient for lightly loaded parts.
S235JR (1.0038) · S355J2 (1.0577) · EN 10025-2Creep-resistant steel
Steel for use at elevated temperatures, for example in steam and superheated-steam lines. Chromium-molybdenum alloyed grades such as 16Mo3, 13CrMo4-5 and 10CrMo9-10 retain their strength and creep rupture strength under heat and internal pressure.
16Mo3 (1.5415) · 13CrMo4-5 (1.7335) · 10CrMo9-10 (1.7380)Stainless steel
Alloy steel with at least 10.5% chromium, which forms a protective passive layer. Austenitic grades such as 1.4301 (V2A) and 1.4571/1.4404 (V4A, molybdenum-alloyed) are readily formable and weldable. 1.4571 is additionally titanium-stabilised.
1.4301 · 1.4404 · 1.4571 · EN 10088Duplex and superduplex steel
Stainless steel with a roughly half ferritic and half austenitic microstructure. Duplex 1.4462 and superduplex 1.4410 combine high strength with very good resistance to pitting and stress corrosion cracking – typical for petrochemicals and offshore.
1.4462 Duplex · 1.4410 SuperduplexNickel-base alloy
Alloy with nickel as its main constituent, extremely resistant to corrosion and high temperatures. Alloy 625, 825 and C276 are used in the chemical industry, flue-gas cleaning and aggressive media, where stainless steel reaches its limits.
Alloy 400 · 625 · 825 · C276Properties & Testing
Yield strength
Stress in MPa (N/mm²) up to which a material deforms elastically and beyond which it remains permanently stretched. The number in the short name (S235, S355) indicates the minimum yield strength for the smallest product thickness; as thickness increases, the guaranteed value drops in steps.
Tensile strength
The maximum stress a material withstands in the tensile test up to fracture. Together with the yield strength, it describes the strength behaviour and is the basis of every structural design.
Impact toughness
Resistance to brittle fracture, tested in the Charpy impact bending test. The suffixes on the short name stand for the test temperature: JR = +20 °C, J0 = 0 °C, J2 = -20 °C. The lower the service temperature, the higher the required toughness should be.
JR · J0 · J2 · K2PREN value
Pitting Resistance Equivalent Number – a characteristic value for the pitting resistance of stainless steels. Calculated from the chromium, molybdenum and nitrogen content (PREN = %Cr + 3.3 × %Mo + 16 × %N). The higher the value, the better the resistance in chloride-containing media.
Pipes & Flanges
DN — nominal diameter
Diamètre Nominal, a dimensionless figure for the approximate inside diameter of a pipe or valve (e.g. DN 100). It serves to match related components and does not correspond exactly to the millimetre dimension.
PN — pressure rating
Pression Nominale, a dimensionless figure for the permissible nominal pressure of a component at reference temperature (e.g. PN 16 = 16 bar). As the temperature rises, the permissible operating pressure decreases.
Schedule (Sch.)
A figure standardised to ASME B36.10 (steel) or B36.19 (stainless steel) for the pipe wall thickness, such as Sch. 40 or Sch. 80. A higher Schedule number means a greater wall thickness at the same outside diameter.
Flange to EN 1092-1
Standardised connecting element for piping. Types include weld-neck flange, blind flange and lap-joint flange, among others; the sealing face (e.g. form B1) and the pressure rating (PN) must match between the connected parts.
Standards & Certificates
Inspection certificate 3.1
Inspection certificate 3.1 to EN 10204 with the specific test results for the delivered batch, confirmed by an inspection body independent of the manufacturing department. The standard certificate for safety-relevant applications. Steel Line supplies it on request with every batch.
Certificate 2.2
Certificate 2.2 to EN 10204: the manufacturer confirms compliance with the order and states test results based on non-specific testing. Sufficient for less critical applications, without batch-specific traceability.
EN 10025 / EN 10028 / EN 10088
European material standards: EN 10025 for hot-rolled structural steels, EN 10028 for pressure vessel and boiler steels, EN 10088 for stainless steels. They define chemical composition, mechanical properties and the scope of testing.
Traceability
Seamless assignment of a delivered material to its batch, heat and test certificate. A prerequisite for quality assurance and documentation in plant, power plant and apparatus construction.
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