Scale
Scale is a thick, brittle oxide layer on steel that forms at high temperatures and low oxygen. It prevents welding by blocking metal ions and can cause porosity.
Physikalisch-chemischer Wirkmechanismus
Scale forms on the steel surface by the reaction of iron with oxygen at high temperatures. This process is a chemical oxidation that leads to a brittle oxide layer.
Metallurgical Relevance & Welding Risks
Scale prevents welding because it blocks metal ions and hinders the diffusion of carbon and other metals. This can cause porosity and affect the strength of the weld. In addition, scale can lead to hot cracking and grain coarsening in the structure if it is not removed.
Werkstattpraxis & Handlungsanweisungen
To remove scale, clean the steel parts thoroughly. This can be done with chemical cleaners or mechanical methods like grinding or polishing. Before welding, let the steel sit dry for at least 24 hours to form a thin natural oxide layer that promotes welding.