利用Gleeble热模拟以及电子背散射衍射(EBSD)技术，研究了高强管线钢焊接临界再热粗晶区(ICCGHAZ)中逆转奥氏体(γ_r)在不同第二道次峰值温度(760、800和840℃)下的逆相变规律及其晶体学关系。结果表明，在3个峰值温度下形成的γ_r体积分数依次为4.1%、8.9%和25.2%，γ_r优先在第一道次粗晶区的原奥氏体晶界(PAGB)处形核，其次是原奥氏体晶粒(γ_p)内板条束(block)的交界处。在极快的焊接加热速率下，γ_r倾向于以块状形式长大。晶体学研究表明，γ_r在PAGB处的逆相变不是自由形核，而是依托于PAGB一侧γ_p的晶体学取向按照近似K-S关系通过逆相变而形成，而与另一侧的γ_p没有确定的晶体学关系。第二道次峰值温度较低(760℃)时，γ_r在PAGB处形核后向非K-S关系一侧的晶粒内部长大，γ_r呈链状分布于PAGB处。随峰值温度的升高(800和840℃)，γ_r向PAGB两侧同时生长。分析表明，γ_r在第二道次加热过程中的逆相变行为对其在后续冷却过程中的相变过程、终态组织及其韧性等有重要影响。

Low carbon microalloyed high-strength pipeline steels processed by the thermomechanical controlled process have a good strength-toughness combination. However, after welding, the microstructure and mechanical properties of the heat-affected zone (HAZ) become deteriorated. Previous studies show that martensite-austenite (M-A) constituent formed in the HAZ is a key factor that lowers the toughness, especially necklace-type M-A constituent formed in the intercritically reheated coarse-grained HAZ (ICCGHAZ). However, the phase transformation mechanism of necklace-type M-A constituent in the ICCGHAZ is unclear. In this study, the crystallography of reverted austenite (γ_r) during the reversion phase transformation upon heating the ICCGHAZ of a high-strength pipeline steel was studied using Gleeble thermal simulation and electron backscatter diffraction (EBSD) technique. Two thermal cycles with peak temperatures of 1300^oC and 760^oC/800^oC/840^oC were conducted to simulate the phase transformation process in the ICCGHAZ. The samples were directly quenched to room temperature after been reheated to the second peak temperature, and the reversion behavior, distribution, and crystallography of γ_r were studied. The results showed that the volume fraction of γ_r formed at 760, 800, and 840^oC was 4.1%, 8.9%, and 25.2%, respectively. γ_r preferred to nucleate along prior austenite grain boundaries (PAGB), and posterior the block boundaries within the prior austenite grains. γ_r preferred to grow to blocky type along the PAGB, and the acicular type γ_r between bainite laths was suppressed. The crystallographic study showed that the formation of γ_r at PAGB was not free nucleation. However, γ_r was formed based on the crystallographic orientation of PAGB alongside prior austenite grain complying with Kurdjuov-Sachs (K-S) relationship, while having non K-S relationship with the prior austenite grain on the other side. After nucleation at PAGB, and at a low second peak temperature (760^oC), γ_r transformed to prior austenite grain with non K-S relationship, and the γ_r formed in blocky and necklace-type along the PAGB. With an increase in the second peak temperature (800-840^oC), γ_r transformed to the prior austenite grains on both sides. The analysis showed that the reversion behavior and crystallography of γ_r during the second pass reheating have a big impact on the phase transformation upon cooling and the corresponding microstructure and mechanical properties.