With the increase of carbon content in the steel material, the yield point and tensile strength increase, but the plasticity and impact decrease. When the carbon content is more than 0.23%, the welding performance of the steel material becomes worse. Therefore, the carbon content of low alloy structural steel used for welding is generally less than 0.20%. The high carbon content can also reduce the atmospheric corrosion resistance of steel material, and the high carbon steel in the open air is easy to rust; in addition, carbon can increase the cold brittleness and aging sensitivity of A709 Gr 50 carbon steel plate etc. steel material.
Laser cutting is that the horizontal laser beam emitted by the laser changes into a vertical downward laser beam through the 45° total reflector, and then focuses through the lens, forming a tiny spot at the focal point. When the spot hits the material, the material is heated to the vaporization temperature quickly, and evaporates to form a hole. With the movement of the beam on the material such as A709 Gr 50 carbon steel plate, the auxiliary gas (carbon dioxide gas, oxygen, Nitrogen, etc.) blow away the melted slag, make the hole continuously form a very narrow width (such as about 0.1mm) cutting seam, and complete the cutting of materials.
The carbon content of A709 Gr 50 carbon steel plate, hot rolled steel plate is slightly higher than that of cold rolled steel plate. Hot rolled steel plate has low hardness, easy processing and good ductility. Cold rolled steel plate has high hardness and is difficult to process, but it is not easy to deform and has high strength. The strength of hot-rolled steel plate is relatively low, the surface quality (oxidation finish) is low, but the plasticity is good, and it is generally medium thick plate.
According to the new report of the World Steel Association (worldsteel), the world crude steel production for the 64 countries has reached to143.3 million tonnes (Mt) in February 2020, a 2.8% increase compared to February 2019. China’s A709 Gr 50 carbon steel plate, crude steel production for February 2020 was 74.8 Mt, an increase of 5.0% compared to February 2019. India produced 9.6 Mt of crude steel in February 2020, up 1.5% on February 2019. Japan produced 7.9 Mt of crude steel in February 2020, up 2.2% on February 2019.
