Austenite formation during intercritical annealing was studied in a cold-rolled dual-phase (DP) steel based on a low-carbon DP780 composition processed in the mill. Two heating rates, 10 and 50 K/s, and a range of annealing temperatures from 1053 K to 1133 K (780 °C to 860 °C) were applied to study their effects on the progress of austenitization. The effect of these process parameters on the final microstructures and mechanical properties was also investigated using a fixed cooling rate of 10 K/s after corresponding annealing treatments. It was found that the heating rate affects the austenite formation not only during continuous heating, but also during isothermal holding, and the effect is more pronounced at lower annealing temperatures. Faster heating delays the recrystallization kinetics of the investigated steel. The rate of austenite formation and its distribution are strongly influenced by the extent of overlapping of the processes of recrystallization and austenitization. It appeared that the heating rate and temperature of intercritical annealing have a stronger effect on the final tensile strength (TS) of the DP steel than holding time. Both higher annealing temperatures and long holding times minimize the strength difference caused by a difference in heating rate.
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机译：基于在轧机中加工的低碳DP780成分，研究了冷轧双相（DP）钢在临界退火过程中的奥氏体形成。研究了两种加热速率10和50 K / s，退火温度范围从1053 K到1133 K（780°C到860°C），以研究它们对奥氏体化过程的影响。在相应的退火处理后，使用10 K / s的固定冷却速率，还研究了这些工艺参数对最终组织和机械性能的影响。发现加热速率不仅影响连续加热期间的奥氏体形成，而且还影响等温保持期间的奥氏体形成，并且在较低的退火温度下该影响更加明显。更快的加热会延迟所研究钢的重结晶动力学。奥氏体的形成速率及其分布受到重结晶和奥氏体化过程重叠程度的强烈影响。看来，临界退火的加热速率和温度对DP钢的最终拉伸强度（TS）的影响要比保温时间长。较高的退火温度和较长的保持时间都使由加热速率差异引起的强度差异最小。
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