Comportamento mecânico de tubos cladeados : avaliação experimental e modelamento numérico

Abstract

This work presents results obtained from tensile testing where one bimetallic, with base metal in carbon steel grade API 5L X-70 metallurgically clad with Inconel 625, breaks in a load below the loads needed to break both materials if isolated. The design criteria adopted for clad pipes is based on established international standards through the oil and gas industry, which specify that just mechanical strength from base metal is considered for design purposes, disregarding the effects of the clad coating. The present work studies the mechanisms that lead the early rupture of the clad coating to extend data base for the international standards to re-evaluate the design criteria currently adopted. Physical phenomena were evaluated through tensile and hardness testing and a numeric model implemented through finite elements software is proposed as a way to reproduce the curve obtained through tensile testing. The different hardening rates between the carbon steel grade API 5L X-70 and the Inconel 625, the different instants in which the plastic deformation of each is initiated and the triaxial stress state are factors that lead the clad coating to break in a load below the base metal. The numeric model proposed to the bimetallic indicates that the effects of the clad coating are negligible up to 2% deformation, used as operational limit through the oil and gas industry.