I am having trouble passing bends and tensiles on 3/4" 516 Gr. 70 plate using N.S. 70S-3 filler metal, especially plates that have been heat treated. Plates that have not rerceived heat treat have barely passed tensile tests. We use N.S. Wire and I have talked to the Technicians at N.S. about our welding parameters and shielding gas (Argon 98%, 2% Oxygen) and they say we are in the heat ranges we need to be in using spray transfer on both 0.045" & 0.062" diameter wire. The tensile ranges are: 62,000 to 65,000 Ultimate Yield Strenght for the heat treated test plates that failed. I have also done tests using different filler metals, Lincoln -L50, ESAB Spool Arc 29 & 82 and got the same results using 516 Gr 70 plates heat treated and non heat treated.
Using A-36 plate with these wires provided good test results. Is there any suggestions as to what I can do to get 516 Gr 70 plates to pass tensile tests other then going to an 80S filler metal?
Ron B
Ron,
There are a couple confusing things about your post. When you say heat treated materail, are you referring to normalizing after rolling? Second, you say that the tensile range is 62-65 KSI "yeild strength". Is the 62-65 KSI referring to tensile strenght or yield strength. I am assuming that you mean tensile strength, because if it is yeild strength, you would not be failing the tests. It sounds like your tests are probably failing in the HAZ or base metal, if you use the same wire, and get passing results with A36 material. The type of materail in this case would not have enough influence over the weld to reduce its tensile strength like you are explaining. If you need assurance that your weld wire is OK, pull an all weld metal (parallel with the weld axis) tensile test. The easiest thing to check would be your base metal. Either pull an base metal tensile test, or check your CMTRs. What sort of tensile strength do you get? Due to the fact that your tensiles pass with A36, I would suspect some sort of base metal problem.
GRoberts, thanks for the reply, Sorry about the two confusing points. Yes the KSI 62-65 is reffering to the tensile strength. Second I normalized and stress relieved the test plates after welding. I have done all filler metal tests with NS and ESAB wire on 516Gr 70 plate, heat treated after welding and they failed tensile strength.
Ron B
Aaah, this makes it much more clear. It doesn't matter what you do as far as welding perameters, if a weld is normalized and tempered after welding, it will have a lower tensile strength than in the as welded, or stress relieved condition. This is because with all the base metal around the weld, it cools the weld quickly, and you end up with a different grain structure than if a weld is slowly cooled by normalizing. If you want to get the required tensile strength in a normalized weld, you will definately have to switch to a stronger filler metal. Even ER80S might not do it. You will probably need to look for a filler metal with more alloy, or higher carbon. I just completed a normalize and temper PQR myself, and just to give you an idea of how much strength you will loose, with 7018-A1, normal as-welded tensile strength might be about 87 ksi, but after normalizing, we got 65 ksi. We also did 8018-B2. Typical stress relieved tensile would be 85-90 ksi, and normalized we got 70 ksi. A lot of what electrode you pick will depend on what tempering temperature you choose also. From the results you have been getting, I would think an ER90S-1 might be the ticket, or switch to a filler with a little more alloy in it as they retain their tensile strength better after heat treatment than carbon steel electrodes. Usually the vendors are not much help in this area either, as they do not normally test their electrodes with a PWHT other than stress relief.
GRoberts,
Thanks again for the helpful information, I definately will try another filler metal and see what results I come up with.
RButler
You shouldn't have any trouble with your filler metal, but why are useing this gas.
Why not CO2 or AR/CO2?
Daon
Daon,
Although it is more expensive using the Argon/O 98/2% we have found that there is improved arc stability and better wet ability in the spray transfer mode. Radiograph of the welds on our 24" Elbows have shown almost no porosity and are extremely clean compared to using Argon/CO2 gas mixture.
You should'nt get any porosity if your technique is correct. I get excellent results this way, we're talking carbon steel.
The only time I use Ar/O 98/2 is for SS.
good luck anyways
Ron,
After reviewing your question, and helpful responses from others, my opinion is you may have lack of fusion in you test coupon. Lack of fusion will result in unacceptable test results. Using the proper spray transfer parameters and two slow or fast of a travel speed, and incorrect gun angle could couse lack of fusion. Did you have the 3/4" test coupon UT or RT before fracturing tensile bars? Did you review the fracture surface of each bar to determine if the sample broke in the base metal, HAZ, or filler material? Was it a clean break or is there evidence of lack of fusion? What was the voltage, amperage, and IPM for .045 diameter electrode? Both the base material, and the filler electrode have the same minimum tensile strength of 70 ksi.
Regards, Jinx
Hello Jinx;
Thanks for the reply. Lack of fusion in test plate was not a factor, we have the plates x-rayed before testing. Examination of the test specimans showed that the failure was in the filler metal. The voltage was 25-26 volts, amprage was:225-235 amps and the IPM was 295 using N.S. 0.045 wire. Being that the plates are heat treated after welding we are going to use a higher tensile filler metal ( 80S or 90S ) and repeat the test.
Regards,
Ron B
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