Now the significant number of the works devoted to the analysis of experience of development and application of improved and new materials for rolls has appeared. A wide circulation rolls from high-chromium alloys of 12-18 % Cr receive are. The contents of carbon in them is within the limits of 2,5-3 % (high-chromium iron) or 1,3-2 % (high-chromium steel).

   For shape mills finishing stands recently powder hard alloys on basis of carbide refractory metals are used. However it was found out, that for semi finishing with smaller speed rolling in some cases more preferable there may be use of high-carbon chromium-nickel steel. Ni does not form carbides. Influence of it is shown in increasing of hardenability and impact toughness, Cr raises resistance to deterioration. At addition of 3-5 % Ni the risk of occurrence of cracks of heat is reduced.

   Influence of hot plastic deformation on structure and properties was studied on samples from steel X12H4. Samples cut out from a bandage rolling, made of cast steel, subjected further to plastic deformation of 30 %, 60 %, 90 %. A microstructure, hardness and microhardness of structural components, were studied, amount austenite in structure and the period of its crystal lattice were estimated.

   The analysis of a microstructure shows that austenite grains represent very strongly ramified dendrite. Eutectic carbides are located basically between of dendrite cells and in much smaller degree on boundary borders Influence of a degree of hot plastic deformation was showed first of all in traditional change of character of structure: forming eutectic carbides in lines and crushing eutectic. Deformation with degree 30 % has affected poorly on character of structure, forming eutectic carbides in chains becomes appreciable only at 60 %, and crushing eutectic at 90 % of deformation.

   The structure was studied also on samples heated up after deformation on 1200оС. After heating the deformed samples on 1200оС in structure at 60 % and 90 % reduction traces of initial dendrite structures practically are not visible, one is observed almost austenite. In structure of a matrix rather frequently there are traces of shift transformation. (Reduction 30 % and 60 %) As it was not revealed even traces and phases, consequence martensite transformations it may not be. Presumably it is connected to allocation carbides which are allocated on creeping full dislocation those results in formation of almost flat colonies of particles - deposition strips. At reduction 90 % such traces practically are absent. Microhardness of various sites of initial and deformed samples is given in the table. It is visible, that at increase of a degree of deformation, value of microhardness grows.

   Most seriously hot plastic deformation has an effect for phase structure of a metal matrix. In process of increase of a degree of deformation up to 90 %, the quantity of austenite after cooling on air is reduced. Thus hardness of researched samples correlates with quantity of residual austenite.

   Plastic deformation influences on the content of residual austenite. That is plastic deformation reduces the stability of austenite.

   Hardness of samples confirms that the metal matrix contains of austenite plenty. The hardness grows at deformation and the above a degree of deformation, the above hardness of researched samples.

   Comparing the results of similar experiments received earlier on samples from steel Х15Н5 it is possible to sly that the degree reduction influences change of phase structure much less. Changes in morphology of structure of steel Х12Н4 it is less than changes in steel Х15Н5.

   Hot plastic deformation promotes intensive formation secondary carbides at after deformation cooling in the appropriate temperature interval that impoverish austenite by alloying elements and reduces its stability.

   At degrees of deformation of 30 and 60 % the period of a lattice rather appreciably decreases in deformed sample that is proved by a displacement of the centre of gravity of diffraction lines (311) aside the big angle. In the samples whic have been heated up on 1200оС, the period of a lattice decreases. At deformation of 90 % the period of a lattice practically does not change.

   Thus, hot plastic deformation reduces stability of austenite of researched steel due to reduction of its alloying degree. However stability austenite is reduced much less appreciably, than in more alloyed steel, for example chromium-nickel steel Х15Н5.