Failed Vickers Hardness survey
Failed Vickers Hardness survey
(OP)
I performed a test using a GMAW process in the 1G position. The matl was SA 516-70 and the plates were beveled at 37.5 each, leaving a .125 land. The root was open .093. I used a solid lincoln wire(ER70S-6). I used Argon(95%)Oxygen(5%)mix for a shielding gas. I failed my vickers hardness survey due to being above my max limit of 248HV. I did employ a temper bead technique by staggering from side to side with the last weld of each layer in the middle of the sample. Any thoughts on how I can pass this test without a PWHT process?





RE: Failed Vickers Hardness survey
6 IS HARD
RE: Failed Vickers Hardness survey
Your technique that you described in your post is not temper bead. I have several questions;
What was the thickness of the plate? Did you use preheat?
How did you conduct the hardness testing? Was the unacceptable hardness in the base metal heat affected zone, the weld metal?
What is the basis for the hardness limitation of 248 VHN?
RE: Failed Vickers Hardness survey
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Failed Vickers Hardness survey
SJones---I used a GMAW spray arc. I ran a range of 253-350 amps however most of the welds fell into a range of 290-320 amps. I used 24-25 volts. As far as the plate I believe it is capable of producing the results that I am after but I am having trouble. Any input in regards to this is greatly appreciated.
vesselfab---I will look into that wire. Thanks.
RE: Failed Vickers Hardness survey
I would use a 150 deg F preheat for a coupon of this thickness. Second, I would increase the interpass temperature to 600 deg F instead of 400 deg F.
RE: Failed Vickers Hardness survey
Voltage * Amperage * 60/Travel Speed.
You can increase this just by having the welder slow down a bit and keep your settings the same.
RE: Failed Vickers Hardness survey
I don't know if it will help hardness, but we use 75 CO2/25% argon for our shielding gas for GMAW.
RE: Failed Vickers Hardness survey
I didn't see where you answered metenger's question as to where the hardness exceeded 248. Weld? HAZ? both?
RE: Failed Vickers Hardness survey
RE: Failed Vickers Hardness survey
RE: Failed Vickers Hardness survey
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Failed Vickers Hardness survey
Another thing you may want to consider is that not all heats of 516 Gr 70 are equal and if it contains residual or intentionally added elements such as Cb, V, and Ti you may face some difficulties. NACE SP0472 and NACE 8X194 have good information on base material chemistry. One last suggestion would be to weld your test plate and cut one section to send to the lab first for a hardness traverse. If you encounter a problem, you still have the rest of your test block to run additional passes or see if a half bead technique is needed vs the temperbead before sending for the final hardenss traverse. I am spoiled here as we have our own lab for Vickers hardness traverses.