TEM Observation for the Heated-affected Zone of HQ130 Super-high Strength Steel

摘要

Fine structure in the heat-affected zone (HAZ) of HQ130 super-high strength steel was researched by means of SEM, TEM and electron diffraction technique. Test results indicated that the HAZ of HQ130 steel main was lath martensite (ML), in which there were a lot of dislocations in the sub-structure inside ML lath, the dislocation density was about (0.3 - 0.9) • 10~(12)/cm~2. No obvious twin was discovered in the HAZ under the condition of normal weld heat input. The cause of the toughness decrease in the HAZ was related to the gather of carbide distributed along lath direction at the gain boundary. By controlling weld heat input (E ≤ 20 kJ/cm), the gather of carbide in the HAZ can be removed and the impact toughness in the HAZ can be assured. HQ130 super-high strength steel; heat-affected zone; microstructure; fine structure