STEEL QUALITY CONTROL
intended to produce the desired grade of steel. Steel-making is itself composed of two stages: the first is to obtain crude steel and the second is to refine this crude steel in order to achieve the desired composition and quality.
• CASTING OF STEEL IN A LIQUID STATE followed by solidification of the metal.
• FORMING (apart from the case of casting) which is done by rolling, either hot or cold, and which results in the production of flat products (steel sheet) or long products (bars, wires, etc.).
Fig 1: Steel operations
• NON-ALLOY STEELS
which have a very low alloy addition content, intended for general use or for heat treatment, welding, forging, etc.
• STAINLESS STEELS
that contain a minimum of 10.5% chromium by mass and a maximum of 1.2% carbon, which are resistant to corrosion and creep.
• ALLOY STEELS (not stainless)
with a higher or lower alloy addition content for hardening and tempering and for tooling.
Fig 2: Iron-cementite diagram (solid lines) and iron-graphite diagram (dotted lines)
Each of these shades is also characterised by the «thermomechanical» treatment that it may have undergone, known as the metallurgical state. The purpose of these treatments is to modify the microstructure of the steel and consequently change its mechanical properties.
=> In summary, the properties of steels depend on their chemical composition and metallurgical state. Depending on all these properties, steel’s metallographic preparation can be adjusted.
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