Low alloy steel & high alloy steel, Fe-C & C-Mn Steel

Hi Experts,
What is difference between Low alloy steel & high alloy steel and Fe-C Steel & C-Mn Steel ? Thank

Hi @Hieu_Thai,
Good explainatoion in Section 17 CSWIP WIS5-90516b:

Classification of Steels

Alloy steels:

  • Low Alloy Steels <7% alloying elements.
  • High Alloy Steels >7% alloying elements.
    Alloy steels are considered the type of steels that predominantly contain extra alloying elements other than iron and carbon.

Types of weldable C, C-Mn and low alloy steels

Carbon steels

  • Carbon contents up to about ~ 0.25%.
  • Manganese up to ~ 0.8%.
  • Low strength and moderate toughness.

Carbon-manganese steels
Manganese up to ~ 1.6%.
Carbon steels with improved toughness due to additions of manganese.