.0cr6mn13ni10moti/1cr5mo Heterogeneous Joints Aging Organizational Structure Change And The Carbon Diffusion Behavior

Presently, austenitic stainless steel welding rods are widely used to weld Cr-Mo low alloy heat-resistant steels in petrochemical plants and power stations. During aging the carbon-depleted belt and the carbon-enriched belt form in matrix and weld respectively. The strength decreases in the carbon-depleted belt, at the same time the rigidity increases and the toughness decreases or low-temperature brittleness appears in the carbon-enriched belt. In addition, heat-expandability coefficient between the matrix and the weld doesn't match. Both of the above two aspects result in that the early failure of dissimilar metal welded joints takes place, which brings huge economic loss and ill social effect. In order to settle the failure problem, the weld materials laboratory of Dalian University of Technology declared and acquired the National "95" Key Project of Science and Technology: The application and exploitation of the low-Cr austenitic weld materials. And in 2000, OCr6Mn13Ni10MoTi was developed and exploited to replace the past austenitic stainless steel. These weld materials can settle the early-failure problem and are on stream. From the former research result, we know that the structure transformation, the carbon and alloy elements diffusion behavior and their diffusion mechanism need to be analyzed and researched more deeply.This work chooses 1Cr5Mo and OCr6Mnl3NilOMoTi wire as matrix and weld materials, respectively. After different heat treatment, we know the structure transformation and the carbon and alloy elements diffusion behavior in aging 0Cr6Mn13Ni10MoTi/1Cr5Mo dissimilar welded joints. The results show that:(1) Initially, the carbon-enriched zone, to a certain extent, forms in austenitic steel adjacent to the weld interface in the fusion zone. The carbon-enriched zone width increases with increasing aging time. After it reaches the maximum, it begins to decreases and disappears finally.(2) TEM analysis shows that the main carbides in the carbon-enriched zone in aging 0Cr6Mn13Ni10MoTi/1Cr5Mo dissimilar welded joints are M3C, which are different from M23C6 in aging A302/lCr5Mo dissimilar welded joints. The M3C are instable and they would decompose and dissolute with increasing aging time.(3) M3C carbides decompose and dissolute after aging for a longer time. C and Cr from the M3C carbides anti-diffusion and the Mn, Ni assemblage and dissolution are the new diffusion mechanism.(4) Set up a carbon diffusion model and it can describe the carbon diffusion behavior in aging 0Cr6Mn13Ni10MoTi/1Cr5Mo dissimilar welded joints.