What are the differences between Q345B steel and Q345C steel？

Q345B steel is a standardized low-alloy medium tensile strength steel in China. Q345B steel is made by hot rolling and used for various manufacturing purposes. Q345B steel is a kind of steel whose composition is less than 0.2% composed of carbon, and less than 0.55% composed of silicon and several impurities (mainly sulfur, chromium and nickel). This special grade of steel is a "universal" manufacturing steel in the field of construction equipment. For example, Q345B steel is the basic material for manufacturing excavator buckets and long arms of excavators.

Q345C steel is low-alloy high-strength steel. Compared with Q345A and Q345B steel, Q345C steel has a lower temperature impact and better performance. In addition, the content of harmful substances P and S is low, and the market price of Q345C steel is higher than that of Q345A and Q345B steel.

Steel Grade	Chemical Composition
Steel Grade	C≤	Mn	Si≤	P≤	S≤	V	Nb	Ti	Al≥
Q345B	0.020	1.00~1.60	0.55	0.040	0.040	0.02~0.15	0.015~0.060	0.20	-
Q345C	0.020	1.00~1.60	0.55	0.035	0.035	0.02~0.15	0.015~0.060	0.20	0.015

Steel Grade	Yield Strength Mpa	Tensile Stregth Map	Elongation%
Q345B	345	470~630	21
Q345C	345	470~630	22

Q345C steel has good comprehensive mechanical properties, good weldability, hot and cold workability and corrosion resistance. Q345C steel also has good low temperature toughness. Q345C steel is mainly used for high-load welding structural parts such as ships, boilers, pressure vessels, petroleum storage tanks, bridges, power station equipment, and lifting and transporting machinery.