| This paper focuses on the Q460 nuclear reactor stent steel. In order to improve the carrying capacity of nuclear reactor carriage and reduce weight, using the Q460 steel which strength and toughness are better,for the current status of nuclear reactors and other traditional support frame mostly used Q390 steel.The thick of the Q460 steel is 45 mm in this paper and a single port slope angle is 45 °. Selecting the wire of low-alloy 145230. We test the deposited metal firstly, and then subjected to heat treatment for welded joints test. Analysis of heat treatment on weld metal and welded joints from the microstructure and mechanical properties. Then analysis of heat input on the joint from microstructure and mechanical properties.Using heat input of 16 kJ/cm for performance testing of welding consumables tempering 610 ℃and incubating 29 hours to deposited metal. Through the study of deposited metal. The results show: Deposited metal microstructure are small amounts of eutectoid ferrite and ferrite side plate, and a large number of uniformly distributed acicular ferrite before and after heat treatment. before heat treatment,there is less eutectoid ferrite number, a larger number of ferrite side plate smaller size between the laths.The size of acicular ferrite is finer and the distribution is more dense. The effect of heat treatment on the strength and hardness of deposited metal is not large, and the impact toughness of deposited metal decreased after heat treatment.Using heat input of 20 kJ/cm for performance testing of welding consumables. tempering 610 ℃and incubating 29 hours to Welded joints,and studying changes in the welding joint performance before and after heat treatment. The results show: The microstructure of the weld metal is same to the deposited metal before and after heat treatment. The microstructure of welding joint are small amounts of eutectoid ferrite and ferrite side plate, and a large number of uniformly distributed acicular ferrite before and after heat treatment. before heat treatment,there is less eutectoid ferrite number, a larger number of ferrite side plate smaller size between the laths.The size of acicular ferrite is finer and the distribution is more dense. The strength and hardness of joint weld metal are decreased, and the impact toughness are increased.Doing welding test with the heat input of 12 kJ/cm、16 kJ/cm and 20 kJ/cm. Analysis the impact on the welded joints and HAZ from the mechanical properties and microstructure of thermal. The results show: a) weld: The larger heat input,the greater the number of ferrite and the fewer of ferrite side plate. The size of acicular ferrite are increased. There will precipitate M-A component and inclusions with three heat input. The yield strength, tensile strength, impact toughness and resistance to bending of weld metal can meet the performance requirements of 460 MPa low alloy steel. With the increase of heat input, weld metal yield strength, tensile strength and toughness are reduced. The hardness of weld metal is the highest with heat input of 12kJ/cm. The hardness of weld metal is slightly lower with the heat input of 16kJ/cm and 20kJ/cm, and the difference between the two is little. b) HAZ: In addition to ferrite, there is bainite in CGHAZ. There is uniformly fine ferrite and pearlite in FGHAZ. The more heat input, the greater the area of the original austenite grains in CGHAZ,and the more eutectoid ferrite precipitated. But little effect of heat input on organization in FGHAZ and incomplete phase transition zone. With the increase of heat input, the impact energy of weld line are decreased. With the increasing of heat input, the impact energy is increased and then decreased at the outer 2mm of weld line. The impact energy is maximum with the heat input of 12 kJ/cm. With the same heat input,the impact energy at the outer 2mm of weld line is higher than the impact energy of weld line.The hardness of HAZ is little difference with the three heat inputs. |
