Investigation of heat treatment effect on micro- structure and hardness map of 4130 alloy steel welds

The microstructure distribution and mechanical properties variation through welded structure is inhomogeneous and not suitable for certain applications. 4130 steel is classified in chrome-molybdenum steels and has wide usage in marine industry. In this work a series of welds have been fabricated in 4130 steel tube by gas tungsten arc and resistance spot welding. The tube was subjected to quench-tempered heat treatment. the macrostructure and microstructure of samples were observed. Hardness maps were then determined over the large area of weld zone, including the heat affected zone and base plate. Results show good relations between the various microstructures, macrostructures and hardness values. It is proved that this method is precise, applicable and consistent to correlate hardness and the microstructural phases.

Keywords:

Microstructure , Macrostructure , hardness , Martensite , HAZ