ANALYSIS OF THE MECHANICAL PROPERTIES OF LONG PRODUCT ROLLING MILL ROLLS

Rolls of longproduct rolling mills, as an expendable working tool of the rolling technological operation, make up a significant share of redistribution costs and significantly affect the economic efficiency of the manufacturing process. The importance of rolls is manifested in the organization of their production at specialized enterprises, the presence of rolling menage in the workshops of metallurgical enterprises, the development and introduction of new rolling rolls materials. Therefore, the tasks of analyzing the available roll materials and their properties, choosing the optimal set of properties for the conditions of a certain state become quite actual. 
The purpose of the work is to review rolled materials and analyze the properties of rolls used in modern long-product mills. Such an analysis was performed for steel and cast-iron rolls, the use of which is most common on mills for the production of simple profiles in the form of bars and rods. 
Based on the analysis of the latest research and publications, the stages of the development of rolled materials in retrospect, the main indicators of the mechanical, technological and operational properties of the rolls have been determined. The main types of cast iron and steel rolling materials offered by leading manufacturers of rolling rolls are also established. For these groups of roll materials, an analysis of their mechanical properties, such as hardness, tensile strength, and bending strength, was performed. 
Based on the results of the analysis, a significant improvement in the mechanical and operational properties of modern rolled materials was noted. This is achieved due to alloying, improvement of their manufacturing technologies, specialized types of heat treatment aimed at forming a certain structure and properties. Conditional blurring of boundaries between cast iron and steel rolls is also established. For example, iron rolls with a ferrite structure and spheroidal graphite and graphitized steel rolls are used, which provide approximately the same mechanical strength, gripping ability and wear resistance. 
Modern rolled materials are characterized by the expansion of controlled property indicators. This applies both to the components of the chemical composition and to indicators of mechanical properties. In particular, the leading manufacturers of rolled rolls include the bending strength limit, which is 1.5 to 2 times higher than the strength limit from tensile tests, among the mandatory indicators. 
In the calculations of the rolls, the fulfillment of their strength conditions should be checked by the allowable stresses determined beyond the bending strength limit, as an indicator of the properties, which to a greater extent corresponds to the load conditions of the rolls. 
An objective assessment of the performance of the rolls according to the strength conditions can be obtained only when determining the allowable stresses based on the actual values of the properties provided by the manufacturer of the rolls, and not according to the range of values recommended in the literature. 
The results of the conducted analysis can be used for the justified selection of rolling materials, improving the control of their properties, obtaining objective assessments of their performance, increasing the efficiency of the rolling farm and technical and economic indicators of production processes.