Abstract
The low interstitial ferritic stainless steel which has been successfully developed recently, can be uti-lized for an extensive range of applications. The use of the clad steel using the low interstitial 30Cr-2Mo steel as a cladding Plate contributes to not only reducing the material cost, but also providing the excellent corrosion resistance for devices of the chemical plants.
This study was performed for the purpose of developing the optimum welding procedure. As the first phase of the study, embrittlement in the overlay weld was investigated by means of the side-bend test and its mechanism was discussed in this report.
The main results obtained were as follows;
(1) The bending ductility in the overlay weld was dependent on C pick-up from the base metal and grain coarsening during welding and 475-C embrittlement during PWHT. In these factors, C pickup from the base metal was most detrimental, that is, crack-crack free transition temperature of the weld in the side-bend test increased by 60K with increase of C content in the first layer from 55 pp-to 135 ppm.
(2) Appearances of fractured surfaces of side-bend tested specimens for overlay welds showed typical cleavage fractured surfaces. Most initiation sites were observed in the vicinity of the weld interface of the first layer in the overlay weld when the penetration ratio of the first layer being below 35%.
