Influence of deformation degree on grains size and borders between them in metal alloys during cold rolling of sheets

The internal structure of metal products was investigated and it was identified that it affects quality and workability of equipment parts. Changes that occur in metal products structure during cold treatment by pressure, which lead to changes in physical and mechanical properties of products, have been analyzed. It was established that grains and borders between them, which determine internal structure of metal products, change their shape and size during cold rolling, depending on percentage reduction value. It is offered to consider grain borders as amorphous layer. Methodology has been developed to study influence of deformation degree during cold rolling to grain size of metal internal structure and intergranular layer volume. Intergranular surface area, its volume and part of surface volume from metal volume were determined. Parameters of internal structure of low-carbon steel were calculated depending on reduction value during cold rolling. According to study results, interconnection between grains size and deformation degree was established; and percentage reduction influence to grain size and borders between them was determined, obtaining a minimum standard grain size with percentage reduction of over 80 %; yield strength and its growth for metal alloy during cold rolling are established, which allows controlling the strength of steel by adjusting the grain size and their junction surface. It is shown that with an increase in deformation degree, yield strength of metal product material increases in hyperbolic dependence, and fraction of amorphous layer and strength properties of low-carbon steel change almost equally in exponential functions. It is revealed that during cold rolling, it is possible to control internal properties of obtained product by adjusting reduction value.