Simulation Optimization of Controlled Cooling Process for Suppressing Network Carbides in GCr15 Bearing Steel

The network carbides in the core of GCr15 bearing steel bars are a critical factor affecting the fatigue life and service reliability of high-end bearings. Insufficient cooling capacity within the 700–900 ℃ range after rolling significantly promotes the precipitation of network carbides at grain boundaries， while traditional physical temperature measurement methods cannot accurately to capture the temperature variation patterns within the core. To address this， a full-process simulation model for the hot continuous rolling and cooling of 40 mm bars was established using DEFORM-3D software. By precisely calculating heat transfer coefficients for air and water cooling， the simulated surface temperatures achieved high consistency with actual measured temperatures. A multi-stage water cooling process was proposed. Results indicate that the optimized cooling system rapidly reduces the core temperature from 860 ℃ to 639 ℃， effectively avoiding the temperature range where network carbide precipitation occurs， while simultaneously controlling the surface re-reddening temperature below 609 ℃. Experimental verification confirms that under this optimized water-cooling process， carbide precipitation in the core of GCr15 bearing steel bars is significantly reduced.