BS ISO 15510:2010 pdf free download – Stainless steels – Chemical composition.
The metallurgical structure is ferrite (alpha ferrite or delta ferrite), a body-centred cubic phase that is magnetic. This structure is ductile in specific manufacturing conditions, especially in thin cross-sections.
The ferritic free-cutting grades most commonly used for bars include a sulfur addition greater than 0,15% to facilitate machining. This sulfur addition causes some reduction of corrosion resistance.
Some ferritic steels have a relatively good weldability. In general, a low heat-input is advisable to avoid embrittlement due to excessive grain growth.
C.3 Martensitic steels
Martensitic steels have the highest carbon mass fractions, typically 0,08 % to 1,00 %. Their mechanical strength is developed by heat treatment consisting of quenching and tempering. These steels are magnetic.
Some grades include sulfur additions greater than 0,15 % for improved machinability. In this case, it should be considered that corrosion resistance may be impaired.
In addition to the grades defined in this International Standard, there are grades intended for specific applications. For example, some of the steels specified for bearings are of compositions within the range of stainless steels.
C.4 Precipitation-hardening steels
Precipitation-hardening steels can have a high strength while retaining good corrosion resistance.
The high strength of these steels results from the precipitation of intermetallic compounds in the structure by a final heat treatment at relatively low temperature.
e) Super-austenitic steels
These steels are enriched in chromium and molybdenum contents and have a completely austenitic structure due to higher nickel and nitrogen contents. They have an excellent corrosion resistance in aggressive environments.
1) Comparison of methods of avoiding intergranular corrosion
Up to the 1 960s, the stabilized steel “solution” to this problem was preferred, as it was difficult, expensive and unreliable to refine extra-low-carbon steels in the electric arc furnace. However, the technological advances in stainless steelmaking since then have enabled extra-low-carbon steels to be made more cheaply, quickly and reliably than stabilized grades.
Further advice on steel selection is available from manufacturers. Whichever “solution” is chosen, the steel will be melted and processed to be free from the risk of intergranular corrosion in the delivery condition, and there should be no need to specify intergranular corrosion testing in most purchase specifications.
C.6 Austenitic-ferritic (duplex) steels
Duplex stainless steels typically have a higher chromium mass fraction (20 % to 30 %) with or without molybdenum additions up to 5 %, and a nickel mass fraction intermediate to those of ferritic and austenitic stainless steels. The metallurgical structure is typically 40 % to 60 % austenitic in a ferritic matrix. Nitrogen additions are essential to retaining toughness and corrosion resistance when these grades are welded without subsequent full annealing.
Their strength properties are higher than those of austenitic steels.
These steels have an esDeciallv aood resistance to stress corrosion.