Fresh castables contain free and combined water. Heat-up controls the rate of dehydration: if the temperature rises too fast, water vaporizes inside the lining and builds internal pressure that cannot escape, causing the lining to explode — the mechanism behind “pop-out” incidents.
Standard curves set several holds: around 110℃ to expel free water, 350℃ for combined water, and some grades add a structural-water stage near 600℃. Hold times depend on lining thickness, density and season, typically 8–24 hours each.
Common mistakes: (1) “quick drying” at steep ramp rates, spalling the lining; (2) “heat-up equals firing” without thermocouples, judging temperature by feel; (3) ignoring ambient temperature effects on early curing in winter; (4) shutting off mid-curve, cracking the dried lining by thermal shock.
The right way: build the heat-up plan from Songrui’s standard curves, monitor lining temperature with thermocouples, control fuel for smooth ramping and hold long enough at key platforms. Precast products are pre-fired in our plant and only need a standard site heat-up.
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