It is generally not possible to distinguish between Q235 and Q345 based on appearance alone. The color difference is not related to the steel material, but rather to the different cooling methods used after rolling. Normally, the surface turns red after natural cooling, but if a quenching method is used, a dense oxide layer is formed on the surface and appears black.
For general strength projects, Q345 is often used as it is stronger than Q235 and also saves 15-20% steel compared to Q235 steel. However, for stability control projects, Q235 steel is preferred. The price difference between the two materials is approximately 3-8%.
There are several methods to distinguish steel plates made from Q235 and Q345:
Distinguish method Q345 and Q235 A:
There are some methods for approximate differentiation between Q235 and Q345 materials. One method is through test welding. For example, small round steel can be welded with E43 electrode into two plates, then shear force can be applied to determine the material of the two steel plates based on the damage condition.
Another method is through grinding. The factory may use a grinding wheel to make a rough distinction between the two materials. When Q235 steel is polished with a grinding wheel, the sparks produced are round particles with dark colors, while Q345 steel sparks are bifurcated and have a bright color.
Furthermore, the color difference between the two shear surfaces of the steel can also be used to distinguish between the two types of steel. In general, the shear mouth of Q345 is white.
Distinguish method Q345 and Q235 B:
The color of the steel plate can be used to distinguish between Q235 and Q345 materials. The color of Q 235 is blue, while the color of Q345 is red (however, this method is only applicable for newly produced steel and may be unreliable over time).
The most reliable method for differentiation is chemical analysis, as the carbon content and chemical composition of Q 235 and Q345 are different.
Another practical method is through welding. When welding two steel plates of unknown materials together with common welds, the steel plates with cracks can be identified as Q345 materials.
