The paper presents a study on the mechanism of steel hardening, focusing on the transformation of austenite into martensite during cooling. It describes the formation of partially martensitic austenite crystals through slow cooling and subsequent quenching. The transformation involves changes upon heating, and the regular orientation of tetragonal and α-iron crystals towards austenite. The paper also discusses surface dislocations and their description through a 24-fold lattice. Simple shear mechanisms are proposed as the basis for the transformation. Carbon precipitation occurs during heating. The paper notes that the mechanism of this "martensitic transformation" is not yet fully understood. Bain suggests that a tetragonal body-centered unit cell of austenite transforms into a body-centered cubic α-iron structure through contraction in one direction and expansion in the others. However, this has not been confirmed. Jeffries proposes a fusion of octahedral faces of austenite with dodecahedral faces of α-iron, similar to what occurs in nickel-iron alloys. Attempts to confirm this have not yielded definitive results. Independent observations showed that in coarse-grained austenite near 111 facets, 011 facets of tetragonal or α-iron phases often appear, suggesting they are parallel. The paper proposes that the transformation occurs through mechanical shear along the octahedral face, which, after additional distortion, converts the face-centered lattice into a body-centered one (tetragonal or cubic). This explains why the transformation is significantly influenced by mechanical processes. Further investigations are needed to clarify the exact mechanism.The paper presents a study on the mechanism of steel hardening, focusing on the transformation of austenite into martensite during cooling. It describes the formation of partially martensitic austenite crystals through slow cooling and subsequent quenching. The transformation involves changes upon heating, and the regular orientation of tetragonal and α-iron crystals towards austenite. The paper also discusses surface dislocations and their description through a 24-fold lattice. Simple shear mechanisms are proposed as the basis for the transformation. Carbon precipitation occurs during heating. The paper notes that the mechanism of this "martensitic transformation" is not yet fully understood. Bain suggests that a tetragonal body-centered unit cell of austenite transforms into a body-centered cubic α-iron structure through contraction in one direction and expansion in the others. However, this has not been confirmed. Jeffries proposes a fusion of octahedral faces of austenite with dodecahedral faces of α-iron, similar to what occurs in nickel-iron alloys. Attempts to confirm this have not yielded definitive results. Independent observations showed that in coarse-grained austenite near 111 facets, 011 facets of tetragonal or α-iron phases often appear, suggesting they are parallel. The paper proposes that the transformation occurs through mechanical shear along the octahedral face, which, after additional distortion, converts the face-centered lattice into a body-centered one (tetragonal or cubic). This explains why the transformation is significantly influenced by mechanical processes. Further investigations are needed to clarify the exact mechanism.