S275JR steel is a relatively common low-carbon micro-alloy structural steel, and its thin-gauge (generally less than 18mm in thickness) steel coil production process has been relatively mature.
The production process of S275JR steel produced by BBN is: 3001 converter→300tCAS→slab continuous casting→slab off-line inspection→heating furnace→high pressure water descaling→width setting→rough rolling→insulation cover heat preservation→high pressure water descaling→finish rolling→ Laminar cooling → coiling.
The liquidus line of S275JR steel is about 1515°C, the temperature range of this batch of tundish is 1535~1548°C, and the corresponding superheat range is 20~32°C. The heat is not conducive to the improvement of the longitudinal cracks of the slab.
In the next step of producing S275JR steel, the superheat control target is 15~25℃. However, the same as the effect of MSC on the defect rate, among the 29 furnaces, the defect rate of 15 furnaces whose superheat is 20~25℃ is also about 10%, which shows that the influence of superheat on the surface crack defect of S275JR steel is not the main one.
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