Primary Cementite in Ledeburite

Massive carbide phases that form as primary precipitates during the solidification of hypoeutectic cast iron melts. They impart high hardness but reduce the impact toughness of the material.

Primary cementite is a hard, brittle microstructural constituent that can form during solidification of hypoeutectic cast iron. When welding, it is critical because it embrittles the weld and can lead to cracks, especially if the weld is mechanically loaded. To get the problem under control, you have to keep the heat input low and slow down the cooling. This prevents too much of the hard carbide from forming. If you let the weld cool slowly after welding, the structure becomes much tougher.

MetallurgieSchweißtechnik