Effect of Nonmetallic Inclusions and Impurities on the Properties and Quality Characteristics of Round Rolled Product Made of Special Alloyed Steels

Abstract

It is found from results of studying rolled steel from special alloyed steels of industrial grades 30G1R, 40Kh and laboratory grades 12KhN, 38KhGNM, 41Kh1 that a change in the ratio of Mn:S concentration in the range of 21–620, P content from 0.004 to 0.022 wt.%, non-metallic inclusions up to point 2.5 according to GOST 1778, N up to 0.010%, H up to 0.0005%, with total pressure created by gas-forming elements up to 1.05 atm, are not critical for occurrence of defects and rolling capacity for cold upsetting. Determination of the characteristics of NI, and CANI content in steel 40Kh round rolled product shows that metal corrosion resistance increases by more than a factor of three with a reduction in CANI2 content and inclusions of the system CaO–Al₂O₃–MgO containing up to 5 wt.% SiO₂, and the insignificant effect of other types of inclusions. A study of the metal of high-strength fasteners manufactured by JH (Taiwan), OF, AL (USA) shows that it has a significantly lower content of other types (corundum, calcium, aluminate, sulphide) of inclusions, and conversely better corrosion resistance.