A514 gr K quenched and tempered alloy steel chemical composition (melting analysis)%C: 0.10-0.20, Si: 0.15-0.30, Mn: 1.10-1.50, P max.: 0.035, S max.: 0.035, Mo: 0.45-0.6.0, B: 0.001-0.005The mechanical properties in thickness (mm)T≤65Yield strength (≥Mpa): 690Tensile strength (Mpa):760-895Elongation in ≥, %: 18
The sulfur element (S element) comes from the ore and fuel coke of steelmaking. It is a harmful element in A709 Gr 50 low alloy steel sheet etc. steel. Sulfur exists in steel in the form of iron sulfide (FeS). FeS and Fe form a low melting point (985℃) compound. The hot working temperature of steel is generally above 1150 - 1200℃, so when the steel is hot working, the premature melting of FeS compound causes the workpiece to crack, which is called "hot brittleness". It reduces ductility and toughness of steel and causes cracks during forging and rolling. Sulfur is also detrimental to welding performance and reduces corrosion resistance.
Quenching is a heat treatment process in which steel parts are heated to above the critical temperature, and after proper heat preservation, the parts are quickly cooled to room temperature in water or oil, so that martensite transformation occurs. The hardness of the quenched A709 Gr 50 low alloy steel sheet increases sharply. Quenching is to prepare the organization for adjusting and improving the performance of A709 Gr 50 low alloy steel sheet during tempering, while tempering determines the performance and life of the workpiece.
Normalizing is a heat treatment that improves the toughness of steel. After the steel components are heated to 30-50°C above the Ac3 temperature, they are kept for a period of time and then air cooled. The main feature is that the cooling rate is faster than annealing but lower than quenching. During normalizing, the crystal grains of the steel A709 Gr 50 low alloy steel sheet can be refined in a slightly faster cooling. Not only can satisfactory strength be obtained, but also the toughness (AKV value) can be significantly improved and reduced The tendency of the component to crack.
