What is the nature of the problems; tensile strength too low, fish eyes (hydrogen), slag inclusions (welder skill), incomplete fusion (welder skills), wrong material (material control), incorrect machining (surface condition), orientation of the welded joint relative to the direction of roll, ..........
thanks for the response I am doing some preliminary tensile pulls at our shop to ensure the best results before sending the test specimen to the lab. I did some bend tests as well to ensure sound welds. I preheated to 300 degrees Fahrenheit and had a max interpass temperature of 300 as well my concern is that at the time of pulling the specimens they are breaking at the weld metal and not the base metal and are coming short of the tensile requirements.
What is the nature of the failures? Do you see evidence of slag inclusions? Do you see evidence of incomplete fusion? Do you see evidence of other weld discontinuities?
Are you machining the samples that are tensile tested or are they torch cut and tested without further preparation?
Are you testing them the same day as they are welded or are "aged" for a few days? If you are performing the tensile test the same day as they are welded, are there fish eyes in the weld? Fish eyes are indications there is diffusible hydrogen in the welds. I know you said you are using 8018, but do you know whether the electrodes were removed from "new" can, a container that was opened and "laying around" for a few day, or were the electrodes used from an electrode oven? Was the oven "on" and set to the proper temperature? I have experiences were welders thought they only had to turn the oven on just before the rods had to be used. After all, storing the electrodes at the proper temperature is a waste of electricity (the welders words, not mine).
I didn't see anything in the chemistry of the SA612 that looked especially troublesome, i.e., high carbon equivalency and I didn't see anything about the mechanical properties that should be difficult to achieve. Do you have a CMTR for the base metal you used or did you pull it from stock? If the latter was the case, are you sure it was marked correctly? Who "pull" the material from stock? Did they pull the correct material from the "rack"? Do you order new base metal from a warehouse and did they provide a CMTR?
If you have a CMTR for the base metal you used, check the chemistry against the ASME SA612 specification to verify the chemistry is within the proper ranges. I have some "bad experiences" with base metals. In one case the vendor sent CMTRs for the base metal, but the plate they sent was 1 inch thick and the CMTR was for 1/2 inch plate. In another case, the chemistry of the CMTR was not within the ranges of the ASTM specification. In another case the aluminum plate was marked 6061-T6 on one side and on the other side it was marked 5052. In other cases the vendor did not provide what was ordered because he had something "better" in stock and he needed to "move" it. I've had that happen not only with bar stock, but even welding electrode!
Send us the details, only then can we begin to assess the problem and provide some suggestions that are relevant.
Umm let's see... 1. Are the tensile tests in the shop being conducted under ASTM A 370? 2. Have you examined the tensile specimen fracture surface for weld defects? What are the yield strength and elongation values of the specimens pulled thus far? 3. The 8018 C3 electrode seems appropriate for this application.
And what is the accuracy of the machining of these 'dogbones'? If they have been cut by hand, vs. machined to +/- 0.002", have a laugh & a large adult beverage.
