Development of a Continuous Cooling Technology for Rolled Stock of ShKh15 Steel to Obtain a Fine Pearlitic Structure

To obtain a homogeneous pearlitic microstructure in coil‑rolled product made of ShKh15 steel, a continuous heat‑treatment regime with two‑stage cooling was developed on the Stelmor line of a 370/150 wire‑rod mill. Wire rod 5.5–18.5 mm in diameter, after homogenizing annealing of NLZ with a cross‑section of 250 × 300 mm, was investigated. The initial cooling temperature in the coil‑former zone was taken as 870 ± 20°C. Thereafter the rod was cooled on the Stelmor roller conveyor with subsequent holding under thermally insulating covers. The developed regime guarantees diffusional transformation of austenite and produces a ferrite–cementite mixture of sorbitic pearlite with minor (less than 5%) areas of fine‑ and medium‑lamellar pearlite. Subsequent spheroidizing annealing of the rod meets the requirements of State standard GOST 801–2022 with respect to microstructure quality indicators and mechanical properties.