Q235 and Q345 appearance is generally not visible. The color difference has nothing to do with the material of the steel, but the difference in the cooling method after the steel is rolled out. The normal, naturally cooled surface is red. If the quench method is used, the surface forms a dense oxide layer, which will appear black.

General strength design with Q345, because Q345 is higher than Q235 steel strength, steel province, than 235 province 15%- 20%. It is good to use Q235 when designing for stability control. There is a difference of 3% to 8% in price.

As for identification, there are several theories:

A:1. In the factory, trial welding can be used to roughly distinguish the two materials. For example, use E43 electrodes to weld a small round steel on each of the two steel plates, and then apply shear force to roughly distinguish the materials of the two steel plates according to the condition at the time of failure.

2. In the factory, grinding wheel can be used to roughly distinguish the two materials. When the steel of Q235 is polished with grinding wheel, the sparks flying out are round particles with dark color. Q345′s spark is bifurcated and bright.

3, there is also according to the color difference of the shear surface of two kinds of steel can be roughly distinguished between two kinds of steel. Generally, the cutting port of Q345 is white in color.

B:1. According to the color of the steel plate, the material of Q235 and Q345 can be distinguished: the color of Q235 is blue, and the color of Q345 is some red (this is only for the steel just coming into the field, and it can not be distinguished after a long time).

2, the most able to distinguish the material of the test is chemical analysis, Q235 and Q345 carbon content is not the same, at the same time the chemical content is not the same. (This is a surefire way to do it.)

3, Q235 and Q345 material distinction, with welding mode: the two unknown material of the steel plate butt, with ordinary welding rod to weld, if the crack side of the steel plate is proved to be Q345 material. (This is a practical experience)