Influence of welding heat input on the HAZ of hot-rolled high strength steel

When welding the hot-rolled high strength steel manufacture by thermal-mechanical controlled process(TMCP),there has a soften zone in the heat affected zone(HAZ).Evaluate the welding quality though the research on the influence of softened zone's width,hardness,strength by the different heat input. Take the 8mm thickness QSTE700TM that produced by Baosteel as an example and used the gas metal arc welding(GMAW,the CO_2 and Ar as the shield gas) welding method choose the high strength welding wire ER76-G(GB)、ER110S-G(AWS) as the welding consumer.Adjust the welding heat input range from 6.8 kJ/cm to 43.6 kJ/cm and found that as the heat input increased the tensile strength,fatigue strength of the welding structure and the hardness of the HAZ will decreased.But when using the lower heat input the quality of the welding structure can fulfil the usage request splendidly.And give the advise to increased the welding quality in detail:when keep the heat input in the scope of Q =6.8 -20 kJ/cm the good welding quality can be achieved successful.And the further research approve that when usage the lower strength welding consumer such as the ER50-6(GB)、ER70S-G(AWS) the welding structure can also achieved high quality for which the tensile strength can get about 700 MPa when use the lower welding heat input.Thus not only keep the welding quality,but also decreased the cost.