Alloy steel coil

Alloy steel coil is divided into low alloy steel coil, medium alloy steel coil and high alloy steel coil, as the name implies, the total amount of alloying elements to be distinguished, the total amount of less than 3.5% is called low alloy steel, 5-10% for medium alloy steel, more than 10% for high alloy steel. In the domestic customary and special quality of carbon steel and alloy steel called special steel.

Performance

(1) high strength: the general yield strength of 300MPa or more.
(2) high toughness: elongation requirements of 15% to 20%, room temperature impact toughness greater than 600kJ / m ~ 800kJ / m. For large welded components, but also requires a high fracture toughness.
(3) good welding performance and cold forming properties.
(4) low cold brittle transition temperature.
(5) good corrosion resistance.

Composition

(1) low carbon: due to the high requirements of toughness, weldability and cold forming properties, its carbon content does not exceed 0.20%.
(2) The addition of manganese based alloying elements.
(3) the addition of niobium, titanium or vanadium and other auxiliary elements: a small amount of niobium, titanium or vanadium in the steel to form fine carbide or carbonitride, which is conducive to obtaining fine ferrite grains and improve the strength and toughness of steel.
In addition, adding a small amount of copper (≤ 0.4%) and phosphorus (about 0.1%), etc., can improve corrosion resistance. Add a small amount of rare earth elements, can be desulfurized, de-gassing, so that the steel purification, improve toughness and process properties.

Heat treatment

This type of steel is generally used in the hot-rolled air-cooled state, without special heat treatment. The microstructure in the service condition is generally ferrite + sothite.

Uses

Mainly used in the manufacture of bridges, ships, vehicles, boilers, high-pressure vessels, oil and gas pipelines, large steel structures, etc.