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Need stainless welding advice

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  • Need stainless welding advice

    I am in a basic stainless welding class, and am having trouble welding the horizontal groove plate position. Because of cost, they are having use mild steel coupons with stainless electrodes. We are using a 1/4" root opening with a mild steel backing plate. I passed the flat position the first try with a bend test on a face coupon and a root coupon. We are using 308L-16 electrodes. I have had three sets of coupons fail the bend test in the horizontal position. The first two broke in the middle of the weld and the first one appeared to have a slag line in it. I was running around 102 amps with an 1/8" electrode. My instructor felt that was a little cool and causing the problem. He suggested running around 113 amps which I did on the third try and felt it burned in much better. However on the bend test the root coupon cracked where it meets the mild steel, very small, hairline. The face coupon broke back in the parent metal and the weld looked very sound. I haven't showed these to my instructor yet, but even he was slightly puzzled at the first two. I tried preheating the metal slightly on the third try to see if it would help. I have felt good about all three welds and was surprised they broke, especially after passing the flat position. I feel I have enough experience to know when I may have a bad weld, but these are really stumping me. I am certified in 6G pipe but just started stainless. My question is should I be using 309 or 309L since I am welding mild steel coupons? I am letting the metal cool reasonably between passes but maybe not enough? Any suggestions would be greatly appreciated.

  • #2
    I cant understand why you would be bend testing mild steel coupons that have been welded with stainless, Trade your $20.00 lb stainless rod in and get some $2.00lb 7018 and then let me know whats happening.


    • #3
      I agree totally. This is a welding course at the local college that is an accredited AWS test facility. I have already done the course where we used all mild steel with 7018 and passed that easily. With so many students they claim that stainless steel is too cost prohibitive to use, so they have you use mild steel plate and say that it welds almost identical to stainless. I haven't welded enough stainless at work to know, but this seems difficult. That's why I'm hoping someone with more experience could help. Thanks.


      • #4
        Need stainless welding advice

        Notify your local TV station about the college not providing proper materials for class.

        All ours gave us was rusty crap to work on as we'll while the instructor and a buddy used up the nice donated armor plate to make steel targets for handgun training. I just started grabbing better materials without permission and no one said anything. This was just last summer. But I'm 60 and a little cranky so got away with it where the younger guys probably couldn't.

        I work with a guy who took his welding class at CPCC and they gave him the rusty crap routine too. He's about 50 years old and cranky too. One day he wheeled a torch cart out behind a dumpster and cut a large sheet out of the back wall of it, sliced it up and distributed it to the class. He became a hero to the other students and got a visit to the Dean's office with the instructor.

        Professors find it difficult to intimidate cranky old people. :-)

        You paid your fees. Make the *******s give you your money's worth.
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