In the process of steel production, local hardening of the surface of semi-finished products (such as thick plates) occasionally occurs. This hardening (also known as "hard spot") can cause problems or lead to component failure in advanced machining and later use of finished products such as longitudinally stitched welded pipes. As a result, in-process hardness testing of surfaces is increasingly required by relevant specifications. In the past, hardness measurements were made only on a sample basis, often using "destructive" methods in combination with laboratory analysis. Due to the growing demand for extensive surface testing of semi-finished products, Rohmann GmbH has developed and patented a new test method (EDDY+).