Steel Physics 101: Min Yield Strength, Tensile Strength, and Elongation Ratio
When ordering steel coils, you might see something like this on the description label:
In this post, I will go through the definition of the Min Yield Strength, Tensile Strength, Elongation Ratio, and Hardness of steel without fancy formulas or symbols. (Right, I almost failed my high school physics).
For coatings, please read：What is AZ60? 10 Microns PE?
This article will not help you pass a physics test, but will definitely help you feel more comfortable when choosing between different steel products!
Min Yield Strength, Tensile Strength, Elongation Ratio
These concepts and inter-related, and are used to describe the physical properties of metals.
Imagine you are stretching out a piece of dough, as you keep stretching, the dough will elongate and eventually break into parts.
A piece of metal, though a lot harder, performs similar to a piece of dough.
When you stretch out a piece of metal using machines, it will also elongate but the elongation is reversible once the force is removed. However, as the force increases, the metal will eventually hit a point where the elongation is irreversible even after the force is no longer present. The force you exert at that exact point is called the minimum yield strength.
Typically materials like plastics, rubber, and metals have some degree of yield strength because they are relatively more elastic; whereas rocks, glass, and ceramics have virtually no yield strength.
If you continue to increase the force, the metal will ultimately break, and the amount of force you used to break it is called tensile strength.
When the metal is at the verge of breaking, it has already been elongated, and the ratio of its current length to its original length is called elongation ratio. A smaller elongation ratio typically suggests that the metal is brittle (Imagine a piece of caramel vs. a piece of cookie, the former has a rocket-high elongation ratio).
An elongation ratio of 0% means that the steel sheet will not elongate (or very little) when it breaks. We call it Full Hard (FH).
Hardness
Hardness is used to describe the resistance to the pressure exerted on the surface of the metal.
Steel sheets with greater hardness are more resistant to scratch and abrasion.
Typically when the Min Yield Strength is > 550 MPA and the Tensile Strength is > 570 MPA, we call it Full Hard (FH). Harder steel is also more brittle.
We use G300, G350, G400, and etc. to quantify hardness. Our company makes G300-G800, and G550 and up is FH.
Hard or soft, brittle or ductile, each kind of metal has its own use under different scenarios.
If you have more questions relating to the above concepts, or you just want to chat about your needs, please don’t hesitate to contact us.
