It is difficult to tell the difference between Q235 and Q345 by appearance. The color difference has nothing to do with the material of the steel, but is caused by the different cooling methods after the steel is rolled out.
Generally, the surface is red after natural cooling. If the rapid cooling method is adopted, a dense oxide layer is formed on the surface, which will appear black.
Q235 steel is an ordinary carbon structural steel. Due to its moderate carbon content, it has good comprehensive performance, and its strength, plasticity and welding properties are well matched, and it has a wide range of uses.
Q345 steel is a low-alloy high-strength structural steel with a yield point of 345MPa and a tensile strength of 470-630MPa. It is a low-alloy steel of ordinary quality and is used in bridges, vehicles, ships, buildings, pressure vessels, special equipment, etc.
Therefore, Q345 is used in general strength design because Q345 is stronger than Q235 steel and saves steel, saving 15%-20% compared to 235. It is better to use Q235 for stability control design. The price difference is 3%-8%.
Tips For Distinguishing:
◆ You can use the test welding method to roughly distinguish the two materials.
◆ You can also use grinding wheels to roughly distinguish the two materials. When Q235 steel is ground with a grinding wheel, the sparks that fly out are round particles with dark color. The sparks of Q345 are forked and bright in color.
◆ The two steels can also be roughly distinguished based on the color difference of the shear surface of the two steels. Generally, the shear surface of Q345 is whitish.
