What is the reason for the blue color on the shear surface of hot-rolled medium and thick steel plates?

1. Production process of hot-rolled medium and thick steel plates

Hot rolled medium thick steel plates are made by continuous rolling at high temperatures, and the phenomenon of blueness on the cutting surface is mainly due to the influence of high temperatures on the steel plates during heating and rolling. During this process, the surface of the steel plate will react with oxygen in the air, producing oxides. These oxides will adhere to the surface of the steel plate, forming a thin film. This thin film is the main reason for the blueness of the cutting surface.

2.In addition to the influence of oxides, the blueness of the cutting surface may also be related to the composition of the steel plate

Some specific elements in the steel material undergo chemical reactions at high temperatures, causing color changes on the surface of the steel plate. For example, steel plates with high manganese content often exhibit a dark blue cut surface. This is because manganese oxide formed by the reaction of manganese element with oxygen at high temperature has a blue color characteristic.

3. The mechanical action during the cutting process can also affect the color of the cutting surface

When cutting steel plates, the cutting machine will apply a large force, causing the metal grains on the surface to fracture and deform. This mechanical action will change the original glossiness and color of the steel plate surface, thereby causing the cutting surface to turn blue.

Although blueing of the cutting surface is a common phenomenon, it is not necessarily a negative situation, but can serve as a reference indicator for judging the quality of steel plates.