Abstract
	There is scarce information about the microstructure development in peritectic solidified materials. The same can be said about peritectic solidified steel, known to have a susceptibility towards surface cracking. Peritectic steel are problematic not only after continuous casting, but after welding, too. That is the main reason that the majority of structural steel is made with C content up to 0,10 %, this way not having the peritectic reaction. The problem is not only in the peritectic reaction, but also in the changes of the volume, and in the impurities solubility changes  accompanying the reaction. Simulations of the peritectic solidification must consider the macroscopic heat transport,  too.
	The aim of this work is to analyze and deal in it’s complexity with the questions of embrittlement and surface cracking in peritectic solidified steel. The high temperature properties, the types of solidified Carbon steel, processes of forming the primary microstructure, the sulphides and grain granulation are analyzed. It is supposed the most important physical-metallurgical factors of peritectic steel embrittlement are:  the coarse austenite grain, the sulphides and oxy-sulphides precipitation, and the macroscopic stress gradients built up by changes of volume during solidification.