High Temperature Mechanical Properties Of FTSC Extreme Low Carbon Steel

According to statistics, crack takes up 50% or more in all kinds of defects of thin slab. Crack formation is the integrative action because of mechanics behavior and metallurgical property in continuous casting. In order to prevent and decrease the occurrence of crack, it is of great significance to analyse the high temperature mechanical properties and simulate the temperature and thermal stress field of thin slab.High temperature mechanical properties of SPHC steel is tested with Gleeble thermal simulation testing machine. The variance of rupture strengthσb and the shrinkage rate R.A on the cross section in different temperatures are analyzed so as to find the temperature areas of brittleness. The test results show that there are two temperature areas of brittleness for slab produced within 600～1350℃, the first temperature area of brittlenessâ… is 1200℃～solidus, the second temperature area of brittlenessâ…¢is 600～850℃, and the steel is plastic within 850～1200℃.Based on the solidification process of SPHC steel in H2 mould, the introduction of element birth and death in ANSYS software which alters states of thin slab elements along with residence time in continuous casting mould, is to simulate the thermal and mechanical states in 2D transient mode. When casting speed is 4.0 m·min^-1, temperature and thermal stress distributions of thin slab in different parts of H₂ mould are obtained. The results show that the closer solidified slab shell approachs to the outlet of mould, the easier crack of thin slab which occurs in the center of bloom surface will take place. As the superheat increases, it indicates that the external temperature of slab ascends, the solidified slab shell thickness at end of mould lessens, but it is nothing to do with thermal stress field of thin slab; when casting speed rises, slab shell thickness at end of mould lessens as well, the cracking index tendency in the center of bloom surface decreases, as well as the cracking index tendency in corner of slab at the beginning of solidification, so casting speed will be raised appropriately.It is under the circumstances of 4.4 m ? min?1 casting speed that heat transmitting and thermal stress situations are simulated in secondary cooling zone by the finite-element method software ANSYS. The results reveal that once thin slab enters the secondary cooling zone, cooling intensity is relative minimum, bloom surface temperature rebounds at first, later goning down by degrees; the crack is less likely to occur in the center of bloom surface on account of cracking index R <1. Owing to cracking index R >1 in corner of thin slab, crack will be more possible to take palce from the end of seg.4 to seg.9. On the condition that temperature and thermal stress field of thin slab are not changed, the optimized secondary cooling scheme makes the total water flow-rate decrease and improve reasonably.