Delta ferrite can easily form in the reduced activation ferritic/martensitic (RAFM) steels after welding, leading to a change in mechanical properties. With the aim of clarifying the delta ferrite formation and its influence on the mechanical properties for the heat affected zones, the enlarged heat affected zones samples with 8–10 mm wide uniform temperature zone were prepared by the Gleeble 3800 thermal-mechanical physical simulator. Different peak temperatures and cooling rates were adopted to prepare the samples with different volumes and shapes of delta ferrite. Results show that the pebble-like delta ferrite in the RAFM steel for this study was produced at low cooling rates (1 and 10 °C/s), while the stripe-like delta ferrite and the block-like delta ferrite occurred at medium cooling rates (30, 50 and 100 °C/s) and high cooling rate (200 °C/s), respectively. The impact energies decreased gradually with the increase of peak temperature and thus, the fracture types changed from ductile fracture to brittle fracture. The impact energies existed at a relatively low level overall for the samples containing delta ferrite at high peak temperatures. Besides this, the martensite lath widths affected the mechanical properties for the samples with low peak temperatures.

焊接后，在还原活化的铁素体/马氏体（RAFM）钢中很容易形成δ铁素体，从而导致机械性能发生变化。为了弄清δ铁素体的形成及其对热影响区力学性能的影响，通过Gleeble 3800热机械物理模拟器制备了具有8-10 mm宽均匀温度区的扩大的热影响区样品。采用不同的峰值温度和冷却速率来制备具有不同体积和形状的δ铁素体的样品。结果表明，用于本研究的RAFM钢中的卵石状δ铁素体是在较低的冷却速率（1和10°C / s）下产生的，而条状δ铁素体和块状δ铁素体是在中等冷却速率下产生的。费率（30，50和100°C / s）和高冷却速率（200°C / s）。冲击能随着峰值温度的升高而逐渐降低，因此，断裂类型从韧性断裂变为脆性断裂。对于含有δ铁素体的样品，在较高的峰值温度下，其冲击能量总体上处于相对较低的水平。除此之外，马氏体板条宽度影响了峰值温度较低的样品的机械性能。