Doubling (metallurgy)

When duplication is called a fault in the rolled steel in the form of a splitting of the material.

It is created by cavities in the cast semi-finished product, especially by blowholes .

During later processing - for example by forging or rolling - these cavities are pressed flat. The doubling is in the middle of the cross-section for sheet metal, in the rail head for rails and in the web for double T-beams . Sheets in which doublings are present are rather unsuitable for further processing by welding. Irregularities can occur in the area of ​​the seam preparation. Furthermore, duplications are weak points in a welded construction, for example the weld seam may fail if it is loaded in the Z direction. Therefore, welding should be avoided in areas of duplication.

Such errors in the structure of the material can mean weak points in statically important areas of a profile. Semi-finished products such as sheet metal and profiles can be checked fully automatically and reliably for duplication using ultrasound- based testing methods with water gap coupling.