Ananda Sarkar Responding to your query : Repair Welding Paralloy 35/45 microalloyed static cast component used Wye piece in Naphtha Cracker service First it would be interesting to do proper diaganosis how a static cast heat resistant Wye piece developed cracks in a shot run service in naptha cracker. I would tend to do this diagnosis whether it is stress related crack or both creep and cyclic temperature effect c racks or any additional stress had been caused due to hanger supports or other bearing support areas had given way to give this problem to you. Normally Wye pieces in such service are adequately designed with additional wall thickness to take care of these. Could you check whether it is an isolated case of crack or prevalent in many Wye pieces of Paralloy make. Paralloy 35/45 microalloyed static cast Wye pieces can be repair welded. successfully Pre-heat: From my experience of having repair welded similar heat resistant static or cenri cast component in naphatha cracker or Primary Reformer service. 250 deg centigrade should be adequate for repair job. I do not know why a preheat of 400 deg cent is specified by Paralloy engineers. Strictly such a high pre-heat of 400 deg centigrade may not be needed - according to me For Repair welding: Inco- 625 or Inco- 825 filler wire or electrode would be /could be chosen as alternative . Inco 617 contains higher Cobalt which may be beneficial at temperature of operation at 900 deg Cen +. Inco 617 with higher Cobalt may give rise to some problems during welding repairs unless the welder is qualified by PQR/ WPR. If he is on and off welder to use such high grade filler wire, cracking once developed with higher Cobalt based Inco 617 difficult problem to further repair welding. Since the component to be used is in naptha cracker Inco 625 with lower Co or Inco 825 would serve the purpose. First run to be TIG and subsequent runs to be SMA process on reverse polarity using inco 625 of Inco 825. I would prefer to use the above two filler /electrodes for repair welding than Inco 617. Baking the Inco electrodes - of any Inco variety - Inco 625 or Inco 825 or Inco 617 - as per guideline procedure is essential before use . Baked electrodes will give much better service usage. Inspection: Do DPT for each run. Final weld : RT to be done after repairs. Trust this answers your query Regards C.V.Srinviasan Nishi Engineers Pvt Ltd Chennai 20 India Oct 9 E-mail: nishi@vsnl.com/ nishi@hathway.com >Dear All > >this is a practical problem for which I need a quick >solution/advice..in our naphtha cracker unit there is >material of composition 35Cr45Ni(bal Fe,etc). These are >statically cast austenitic Wye pieces from Paralloy. We need >to repair weld some puctures. metallurgists from >paralloy/doncasters have advised to preheat the piece to >400degC and maintain the same interpass temp . This >condition will be highly uncomfortable for the welder. Being >a young metallurgist myself I am keen know why such high >preheat temp is reqd. Is it absolutely necessary? We will be >using Inconel 617 filler wire. In this context I would like >to mention that for centrifugally cast tubes of same >material we donot do any preheat during welding. Please >suggest some good URLs where useful informations is >available. > >Ananda Sarkar >Inspection Engineer >HPL, India >Ananda.Sarkar@hpl.co.in