Welding 420 Stainless (oil fieldI

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Quick question for you guys who have experience with 420 Stainless or (13 chrome.) We are currently testing the best/fastest way of manufacturing a certain piece of equipment. One of the processes includes welding a 3" OD 5/8" thick 420 SS cap on the the end of a 420 SS piece of pipe. This cap is just that, a cap. It will hold no more than 200PSI of pressure and see no more than 300 degrees Fahrenheit. The question i have is this:Is it necessary to pre or post heat the material before welding? If so what temperature do you guys get it to? Preferably we would like to NOT have to pre heat the material as this will add an additional step in the process and result in more equipment purchased but this cap can not fail and will see service for 3 years at a time minimum. Thanks for the help guys!
Reply:Due to the high hardenability of 420 I'm pretty sure you'll need both a pre heat and a post weld stress relief.
Reply:???is this 'cap' threaded onto the pipe or is it a flat plate welded to a pipe ofunknown dimensions??.....the more info.....the more appropriate the answersa 1 min. google hunt shows the below for starters:http://www.interlloy.com.au/our-prod...ess-steel-bar/..from the above '420 is not generally recommended for welding in either the annealed or hardened and tempered condition, due to its air hardening capability which can lead to the formation of brittle martensite, resulting in cold cracking due to contraction stresses within the weld and heat affected zone. The higher the carbon content the higher the hardening capability and the greater the risk of cracking.Pre heating and interpass temperature control during welding, plus very slow cooling and post-weld annealing is the best method to prevent cracking.The following welding procedure and post-weld heat treatment may be taken as a guide only if welding is necessary.'Blackbird
Reply:Originally Posted by dave powelson???is this 'cap' threaded onto the pipe or is it a flat plate welded to a pipe ofunknown dimensions??.....the more info.....the more appropriate the answersa 1 min. google hunt shows the below for starters:http://www.interlloy.com.au/our-prod...ess-steel-bar/..from the above '420 is not generally recommended for welding in either the annealed or hardened and tempered condition, due to its air hardening capability which can lead to the formation of brittle martensite, resulting in cold cracking due to contraction stresses within the weld and heat affected zone. The higher the carbon content the higher the hardening capability and the greater the risk of cracking.Pre heating and interpass temperature control during welding, plus very slow cooling and post-weld annealing is the best method to prevent cracking.The following welding procedure and post-weld heat treatment may be taken as a guide only if welding is necessary.'
Reply:Originally Posted by 4956Due to the high hardenability of 420 I'm pretty sure you'll need both a pre heat and a post weld stress relief.
Reply:oscs,What do you mean there's no requirements for this weld???   You've all ready said it could see 200 psi and 300 F. in service, has a minimum 3 year service life and can not fail.   And the fact that 420 ss is involved leads me to think that there's most likely some corrosion concerns involved also.   Also the idea of a slip on cap held on by a fillet weld doesn't sound like a very good design idea to me.  This may sound harsh but.... you're telling us that you're "hoping" to "get a way with" not preheating or post weld stress relieving when welding on 420 ss tells me that you (and your company) are most likely way in over your heads with this particular project.  At this point what I think you need most is some qualified, in house Engineering and Design support.