Grade Identity and Standard Context
13MnNi6-3 is a nickel alloy steel plate for pressurised equipment, and it carries the material number 1.6217 in the European designation system that pairs a short grade name with a numeric identifier. The grade belongs to the family of nickel alloy steels for low temperature service and is covered by the European flat product standard for pressure purposes that deals with steels with specified low temperature properties, EN 10028-4. In that system the chemistry and the guaranteed low temperature impact values are defined together, so a purchaser buys a strength class and a toughness class in a single designation.
The plate is intended for pressurised equipment, boilers and pressure vessels, and it is a common choice where the design metal temperature is below the range that ordinary carbon and carbon-manganese vessel steels can handle safely.
Mechanical Properties
| Property | Thickness range | Requirement |
|---|---|---|
| Yield strength | up to 30 mm | 355 MPa minimum |
| Yield strength | over 30 to 50 mm | 345 MPa minimum |
| Yield strength | over 50 to 80 mm | 335 MPa minimum |
| Tensile strength | all sizes | 490 to 610 MPa |
| Elongation after fracture | all sizes | 22 % minimum |
The step-down in yield strength with increasing thickness is normal for quenched, normalised or thermomechanically treated plate: thicker material cools more slowly and receives less reduction, so the achievable strength falls slightly. The tensile window of 490 to 610 MPa with elongation of at least 22 percent indicates a steel that is ductile rather than purely strong, which is exactly what low temperature pressure equipment needs. Dimensions, shape, mass and permissible deviations are ordered in accordance with the flat product requirements of EN 10028-1.
Why Nickel Is Added
Nickel is the element that makes this grade work. Dissolved in the ferrite matrix it lowers the ductile-to-brittle transition temperature, so the steel keeps absorbing energy in a Charpy test and resists brittle crack initiation at low temperature. In practical terms, the nickel addition allows a vessel to be designed for cold service without resorting to austenitic stainless steel or aluminium, both of which carry a substantial cost and fabrication penalty. Manganese contributes strength and hardenability, and the carbon level is kept low to preserve toughness and weldability.
Applications
The main application is the manufacture of spherical storage tanks with a capacity above 50 cubic metres, where the geometry and the low temperature duty together demand a plate with predictable toughness. The grade is also used for single layer coil-welded containers, multilayer hot-sleeve coil-welded containers and multilayer wrapped containers, as well as general low temperature pressure vessels. Typical industries are petroleum, chemical, power station and boiler construction, with components such as reactors, heat exchangers, separators, spherical tanks, oil and gas tanks, liquefied gas tanks, boiler drums, liquefied petroleum gas cylinders, high pressure penstocks for hydroelectric stations and turbine spiral cases.
Fabrication and Quality Control
Forming: suitable for cold forming within agreed limits and for hot forming with a subsequent restoring heat treatment.
Welding: low hydrogen consumables matched to the base metal strength, controlled preheat and interpass temperature, and moderate heat input to protect heat affected zone toughness.
Heat treatment: post-weld heat treatment where thickness or service conditions require it, with test pieces optionally tested after simulation.
Inspection: ultrasonic testing sheet by sheet and dimensional checks, with the acceptance criteria agreed in the order.
Documentation: material certificate with heat number, chemical analysis and mechanical test results for full traceability.
Frequently Asked Questions
Q: What is the material number of 13MnNi6-3?
A: It is 1.6217 in the European designation system.
Q: What is the yield strength of the grade?
A: At least 355 MPa up to 30 mm, 345 MPa over 30 to 50 mm and 335 MPa over 50 to 80 mm.
Q: Which standard covers the plate?
A: The European flat product standard for pressure purposes covering steels with specified low temperature properties, EN 10028-4, with dimensions per EN 10028-1.
Q: What is the grade mainly used for?
A: Spherical storage tanks above 50 cubic metres, multilayer and coil-welded containers and cryogenic pressure vessels.
Q: What is the tensile strength range?
A: 490 to 610 MPa, with elongation after fracture of at least 22 percent.
