While ‘as strong as steel’ is still an appropriate metaphor, in real terms, its strength varies enormously. Going by as many definitions and acronyms as you’d expect in a science textbook, tested gradings are essential when it comes to application. From tensile strength to yield, to weldability and from ductility to toughness, creep and fatigue resistance, steel and especially stainless steel, can be tried and tested to exacting specifications, making it not only extremely versatile, but extremely reliable.
Understanding Tensile Strength Of Steel
A tensometer is used to measure the ‘breaking point’ as it were, of steel. Tensile strength is the term used to reference the maximum amount of stress the particular grade of steel can withstand while being pulled or stretched without breaking. Certain grades will shrink at the point of greatest stress, others hold without deforming before break point. The measurement (force per unit area- the unit being a pascal (Pa), a megapascal (MPa), a newton per square metre (N/m2) or plain old pounds-force per square inch (psi). Because steel classification terminology varies so considerably, most hold to the WorldAutoSteel format, being MPa. For example, DP 800 describes a dual phase steel with 800 MPA minimum ultimate tensile strength.
Stainless Steel’s Own Particular Performance
Under testing, increased tensile load is applied and the stress and strain relationship is plotted and measured. Bear along with us, as terms we don’t imagine are associated with steel are used to describe the results. The measurements reflected under testing are described as follows: the yield point, elastic strain, plastic strain, necking (we did warn you) and finally, fracturing.
When it comes to the yield point, mild steel will show a pronounced reaction as a sudden increase of strain without increase in stress. Stainless steel, however, often does not demonstrate any clear yield point, with the result that when it changes from ‘elastic’ behaviour to ‘permanent plastic deformation’, it is pretty difficult to detect. For design intentions, this differentiation in stainless steel may cause confusion regarding yield strength – which is taken as a 0,2 % permanent strain (offset). But its ultimate tensile strength is regular and stable ad with superior properties too.
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