A new criterion for hot cracking of P91 high-alloy steel based on peritectic reaction characteristics
摘要
Quantitatively determining the effect of volume shrinkage during the peritectic reaction on hot cracking formation is crucial. P91 high-alloy steel was taken as the research object. The solidification process was observed in-situ using a high-temperature confocal laser scanning microscope, and the liquid phase feeding capacity and solidification shrinkage behavior during the phase precipitation and transformation stages of the peritectic reaction were analyzed. A hot cracking susceptibility criterion related to solid–liquid density changes and mushy zone permeability during the peritectic reaction was established to quantitatively calculate the solidification shrinkage volume (Vs) and liquid phase feeding volume (Vf). Theoretical calculations show that Vs reaches the maximum value of 0.601 mm3 when the solid fraction (fs) is 0.839, with the difference between Vf and Vs being approximately 2.52 mm3. Experimental results indicate that Vs peaks at 0.764 mm3 when fs is 0.828, and the difference between Vf and Vs is about 2.69 mm3. The maximum theoretical Vs is 0.163 mm3 lower than the experimental result. The probability of hot cracking is the highest when fs is about 0.99, where Vf is approximately 0.366 mm3, Vs is about 0.118 mm3, and the difference is around 0.248 mm3. Under the experimental cooling rate (10 °C/min), Vf is always greater than Vs, which is consistent with the in-situ observation result of no cracks.