Comparison of Chemical composition between Q245R steel and Q345R Steel

The Chemical composition of Q245R steel and Q345R steel

Q245R steel and Q345R steel have the same limiting index except silicon and manganese content. Q245R steel and Q345R steel is our mian steel .From the analysis of weldability of steel, the weldability of steel is closely related to its chemical composition, among which carbon content is the most important. Because the carbon content in the steel increases, the plasticity decreases, the hardening tendency increases, and cracks occur easily. There are many alloy elements in general steel, and their influence is comprehensive. Therefore, carbon equivalent is often used to estimate the weldability of steel. It is generally considered that the weldability of steel with Ceq < 0.45% is better  The carbon equivalents of Q245R steel and Q345R  steels are calculated as follows

Q245R steel

Ceq（%）=C+Mn/6+（Cr+Mo+V）/5+（Ni+Cu）/15

Q345R steel

Ceq（%）=C+Mn/6+（Cr+Mo+V）/5+（Ni+Cu）/15
=0.2+1.6/6=0.47

The carbon equivalent ratio of Q345R steel is higher than that of Q245R steeldue to the increase of Mn content.The height is 0.1%. The notch sensitivity of Q345R steel is larger than that of Q245R steel , and its fatigue strength is low. Therefore, in some cases, we should pay attention to the influence of medium on these two materials. For example, it is pointed out that in the wet H2S stress corrosion environment, for low carbon steel and carbon manganese steel, Ceq is less than 0.40%.Because of its lower carbon equivalent, Q245R steel  has better resistance to wet H2S stress corrosion than Q345R steel.