Ledeburite I
The metastable eutectic microstructure of austenite and cementite formed during the solidification of iron-carbon alloys with more than two percent carbon at the eutectic temperature. It forms the backbone of white cast iron.
Ledeburite is a structure that forms when high-carbon iron solidifies. It is a brittle mixed structure of austenite and cementite. If you have to weld such a part, it's tricky because the structure transforms quickly during heating and cooling, which can lead to cracks or hard zones. It's important to preheat the workpiece and let it cool slowly and controlled to avoid stresses. Just welding away and cooling quickly won't work. Best to keep an eye on the interpass temperature and let the part cool slowly in air after welding, instead of quenching it with water.