Performance Of CLAM Steel With TIG Welding And Corrosion Behavior Of Weldment In Liquid Lithium-Lead

CLAM steel is used in the manufacture of China's fusion reactor first wall and other structural. Welding techniques and processes related to the test blanket module (TBM) can be created successfully, is a key technology for the practical application of CLAM steel. Therefore, researching on the performance of CLAM steel with TIG welding and corrosion behavior of weldment in liquid lithium-lead, is benefit to practical application of CLAM steel, to improve the performance of CLAM steel structure in liquid metal corrosion.In this study, Tungsten Insert Gas (TIG) welding on China Low Activation Martensitic (CLAM) steel (5mm thick) under identical conditions was performed, a) using the original CLAM composition filler metal and b) using the modified composition (9.8Cr2W0.5Ta). Microhardness test, tensile test, Charpy impact test and microstructure measurements were carried out on TIG welded joints after post weld heat-treatment. Using the original CLAM composition filler, the microhardness and ultimate tensile stress of weld metal decreased when the temperature of PWHT increased. Absorbed energy increased with PWHT temperature rising, until PWHT was done at 760℃/30min, the specimen ductile fractured in local area. The microstructure of the weld metal was found to be tempered martensite with a little of delta ferrite. M23C6 particles are the predominant type of carbides, the composition of M is Cr, Fe, W and Mn. Using the modified composition (9.8Cr2W0.5Ta), the mechanical properties of welded joints is consistent with that by using the original CLAM composition filler:the microhardness and ultimate tensile stress of weld metal decreased when the temperature of PWHT increased. Absorbed energy increased with PWHT temperature rising, until PWHT was done at 760℃/30min, the specimen ductile fractured in local area. However, compared with the matrix material filled, the number ofδferrite is less than that by using original CLAM composition filler. The compostion of M is Cr, Fe, W and V.Three-dimensional finite element numerical model of CLAM steel TIG welded butt joint was established using finite element analysis software-ANSYS, double ellipsoid heat source model is chosen for thermal simulation. Transient temperature distribution and weld pool changes in welding process were analysized by numerical simulation, welding residual stress and deformation after welding were also simulated. The temperature distribution under different welding speed and referenced value of the welding process thermal efficiency were caculated, It shows that 2mm/s of welding speed andηreferenced value in the range of 0.78 to 0.85 were reasonable to obtain fine weld width and penetration depth, were good agreement with the actual welding conditions. It also shows that transverse residual stress is tensile stress at the center of joint, is compressive stress at both ends of joint. Along the vertical direction, transverse residual stress is tensile stress at the center of joint and mainly caused by the longitudinal stress. The longitudinal residual stress is tensile stress near joint, with increasing distance from the weld, gradually transformed into compressive stress.Under 480℃,0.08m/s liquid lithium lead corrosion, the easily corrosive areas of CLAM steel joints existenced, its influence on corrosion was analysized, and established a basic structural model. The results show that:as the M23C6 carbides segregated in the original austenite grain boundaries and martensite lath, Cr content significantly reduced in this place, and formed easily corrosive area, reduced the resistance corrosion performance in liquid lithium lead. Under such conditions, CLAM steel joints were seriously corroded, after 500h and1000h corroded, weight loss was respectively 0.491mg/cm2 (average corrosion depth is 0.55μm) and 0.641mg/cm2 (average corrosion depth is 0.72μm), much higher than tempered CLAM steel corrosion. With time increased, the corrosion rate of the sample decreased significantly. By corrosion, the elements in the surface of weld zone did not significant changed, no lithium-lead penetrated is inside, corrosion layer became more uniform.