Forming technology of coated sheet metal

Abstract

The current article investigates production technology of holes and subsequently threads in parts from the thin steel sheets, which are coated, with layer of fireproof (fire resistant) Zn, modified by element Al (for samples of T type) and Mg element (for samples of M type). This procedure is important and well founded for the use of thin steel sheet for the threads products. However, applying protective layer in some way influences the threading technology. This issue is investigated here experimentally by combination of forming and machining technology, which conditions respect standard practice in industrial companies. In the first case we applied classical technology of drilling a hole and thread cutting with a tap. In the second case, hole was made by forming technology and thread is made by cutting tap. From the experimental results it can be derived more general conclusions related to the behaviour of the surface - coated material during threading.