Defects of low-carbon engineering steels 18Kh2N4MA, 25Kh2N4MA, 25G2S2N2MA reducing the operational durability of the parts were studied. The most common defects of metallurgical processing are: non-metallic inclusions, microstructure banding, internal cracks and pores. It has been established that the inclusion of titanium carbonitride significantly reduces the operational durability of heavily loaded parts. The defects formed during heat treatment and chemical-thermal processing of parts were also considered.