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The measurement of thermal cycle curves of a high-strength low-alloy steel (HSLA) subjected twin-wire submerged arc welding (SAW) was introduced. The thermal simulation test was performed by using the obtained curves. The impact toughness at -50 ℃ temperature of the simulated samples was also tested. OM, SEM and TEM of the heat-affected zone (HAZ) of some simulation specimens were investigated. The results showed that the HSLA endured the twin-wire welding thermal cycle, generally, the low-temperature toughness values of each part of HAZ was lower than that of the parent materials, and the microstructure of coarse-grained zone(CGHAZ) mainly made up of granular bainite is the reason of the toughness serious deterioration. Coarse grain, grain boundary carbide extract and M-A island with large size and irregular polygon, along the grain boundary distribution, are the reasons for the toughness deterioration of CGHAZ. The research also showed that selected parameters of twin-wire SAW can meet the requirements to weld the test steel.
The measurement of thermal cycle curves of a high-strength low-alloy steel (HSLA) developed twin-wire submerged arc welding (SAW) was introduced. The thermal simulation test was performed by using the obtained curves. OM, SEM and TEM of the heat-affected zone (HAZ) of some simulation specimens were investigated. The results showed that the HSLA endured the twin-wire welding thermal cycle, generally, the low- temperature toughness values of each part of HAZ was lower than that of the parent materials, and the microstructure of coarse-grained zone (CGHAZ) mainly made up of granular bainite is the reason of the toughness serious deterioration. and MA island with large size and irregular polygon, along the grain boundary distribution, are the reasons for the toughness deterioration of CGHAZ. The research also showed that selected parameters of twin-wire SAW can meet the requirements to weld the test steel.