Development of technology and testing of boron microalloyed steel production in the conditions of a casting and rolling complex

The requirements for increasing the complex properties of steel, along with ensuring low cost of finished products, determine the need to search for effective alloying components. In the conditions of the casting and rolling complex of JSC “VMZ”, pilot production of rolled products from manganese-boron steel was carried out, used in the manufacture of electric-welded straightseam casing and pump-compressor pipes of strength group from J55 and higher for the construction of oil, gas condensate and gas wells in normal or complicated geological conditions with intensive crushing loads on the pipe body, as well as for the extraction and injection of liquids and gases from them. Optimal conditions of the out-of-furnace treatment technology and continuous casting of steel on a thin-slab continuous casting machine for obtaining defect-free products with specified properties have been determined experimentally. The results obtained in finished tubular products confirm the effectiveness of using boron in increasing hardenability by up to 10 times compared to similar steel without adding boron. During the experimental work, a negative effect of increased boron content in steel on the formation of a defect in the macrostructure of a thin slab in the form of a “nest” crack was revealed. The performed studies of the macro and microstructure of a continuously cast slab made it possible to establish the nature of the occurrence of a “nest” crack due to excessive boron content in steel and the formation of a low-melting eutectic of boron compounds with iron. Studies of the microstructure of rolled products confirmed the effect of a certain boron content in steel on increasing homogeneity and reducing the grain size.K. S. Smetanin, O. S. Khlybov, Cand. Eng., took part in the work, Viksa OMK, Vyksa, Russia.