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为了分析电磁纯铁DT4在850~1150℃区间锻造时经常出现开裂的原因,选用DT4拉伸试样和压缩试样,在Gleeble1500上分别进行高温热模拟拉伸试验和压缩试验,同时完成了DT4从α-Fe向γ-Fe相变点检测。试验发现:DT4从α-Fe向γ-Fe的相变温度为900℃,在高于相变点温度(912,920和950℃)进行拉伸时出现双颈缩,颈缩点温度接近相变温度,在900和950℃进行压缩试验,在试样两端出现异常流动。在850~1150℃区间内,变形集中在α-Fe向γ-Fe同素异构转变温度区,压缩应力应变曲线显示两相转变区强度比相邻高温区和低温区均低,导致锻造时在相变区出现变形集中而开裂。因此,在锻造过程中避开α-Fe向γ-Fe相变温度区可避免锻造开裂。
In order to analyze the cause of cracking of DT4 in the range of 850 ~ 1150 ℃ forging, DT4 tensile specimen and compressive specimen were selected to carry out high temperature thermal simulation tensile test and compression test on Gleeble1500 respectively. At the same time, DT4 From α-Fe to γ-Fe transition point detection. It is found that the phase transition temperature of DT4 from α-Fe to γ-Fe is 900 ℃. When the temperature is higher than the transformation temperature (912, 920 and 950 ℃), the dual-neck shrinkage occurs. The neck-in temperature is close to the phase transition temperature , Compression tests were performed at 900 and 950 ° C with anomalous flow across the sample. In the range of 850-1150 ℃, the deformation is concentrated in the alloying temperature range of α-Fe to γ-Fe. The compressive stress-strain curve shows that the strength of the two-phase transformation zone is lower than that of the adjacent high-temperature zone and low-temperature zone, Deformation in the phase transition zone concentrated and cracking. Therefore, forging cracking can be avoided by avoiding the α-Fe to γ-Fe transformation temperature zone during forging.