How to distinguish the steel plate material is Q235 and Q345?

The appearance of Q235 and Q345 is generally invisible. 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 a rapid cooling method is used, a dense oxide layer is formed on the surface, and it will appear black.

Generally, Q345 is used in strength design, because Q345 is stronger than Q235 steel, saving steel, 15%-20% less than 235. It is better to use Q235 when designing with stability control. The price difference is 3% — -8%.

As for identification, there are several theories:

A:

1. In the factory, the method of trial welding can be used to roughly distinguish the two materials. For example, use E43 welding rods to weld a small round steel on two steel plates, and then apply shear force, and roughly distinguish the materials of the two steel plates according to the situation at the time of damage.

2. In the factory, grinding wheels can also be used to roughly distinguish the two materials. When the Q235 steel is polished with a grinding wheel, the splashed sparks are round particles and dark in color. But the spark of Q345 is bifurcated and the color is bright.

3. In addition, the two kinds of steel can be roughly distinguished according to the color difference of the shear surface of the two kinds of steel. Generally, the cutout of Q345 is whitish

B:

1. The material of Q235 and Q345 can be distinguished according to the color of the steel plate: the color of Q235 is blue, and the color of Q345 is somewhat red (this is only for the steel that has just entered the market, and it cannot be distinguished after a long time)

2. The test that can best distinguish the material is chemical analysis. The carbon content of Q235 and Q345 are different, and the chemical content is also different. (This is a foolproof method)

3. To distinguish between Q235 and Q345 materials, use the welding method: butt two steel plates of unknown material and weld them with ordinary welding rods. If the steel plate on one side with cracks appears, it is proved to be of Q345 material. (this is practical experience)