Welding 440 stainless
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  1. #1
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    Default Welding 440 stainless

    Had a welder who used to do this for us, retired and out of the picture. We make heated metering pumps (medical) and have to plug and weld the ends of fluid lines. Pump bodies are 440C stainless, plugs made from 440C, about 3/8 diameter, 1/2 inch long press fit into the holes. . We put a .06 chamfer on the plug and the hole to fill with weld. We have had cracking problems in the past, so now we stress relieve after welding, then do our finish machining , then vacuum heat treat , then surface grind. TIG welding, what rod would you use? Tried laser welding, and found micro cracks. Can not change material (FDA approved process).

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    Info from the internet regarding 440c

    About 44C Stainless steel - Grade 44c -
    Quote from the above article:
    "Welding - If welding is necessary pre-heat at 250C and follow welding with a full anneal. Grade 420 filler will give a high hardness weld (not as high as the 440C). Generally welding of 440C is not recommended due to its hardening capability which can lead to the formation cracks within or near the weld."


    Welding guide for Stainless Steels from Lincoln Electric:
    www.lincolnelectric.com/assets/global/Products/Consumable_StainlessNickelandHighAlloy-Excalibur-Excalibur316316L-17/c64000.pdf

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  4. #3
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    Preheat, as Fabworks noted. Note that's 250C=482F, not 250F. Slow cooling (fiberglass blankets, tub of vermiculite, etc) if you can't put the part directly in an annealing oven.

    Better yet, get your retired guy to write down his proven procedure for you. Pay him for a day's consultation, if needed.

    The pre-weld preheat and post-weld anneal has absolutely nothing to do with your final product HT. The post-weld anneal can be considered your stress relief prior to final machining.

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