ASTM A513 grade? type? Ult tensile

By Kix

Date 02-19-2008 19:08

I just got back from the lab wit the results for my box tubing procedure. I was told that all of our box tubing was made from ASTM A500 gr.-B, which has a min tensile of 58ksi in the D1.1 code. My results where well below the min requirements of A500 gr.-B which leads me to believe I tested with a different material. I'm trying to do some research on ASTM A513 and it is looking like it's tensile can vary anywhere from 30ksi to 80ksi. Does this sound correct?
I welded a 3"X2"X.31" and a 4"x3"X.31" box tube. Tensiles for the smaller tube where 56,000 and 60,000psi ruffly, welded with an ER80S-D2 mig wire. One specimen went above the min A500 gr.-b requirements. Hmmm The larger 4x3" tube tensiles were 47,000 and 48,000psi ruffly, welded with the same wire and procedure. All specimens broke in ductile base material. I'm digging for mill certs for the past couple years to kinda see what kind of tube we are actually getting in here. I did some hardness tests at the end of the specimens and next to the weld and they were always real close. Sometimes it was actually harder next to the weld then it was at the end of the specimen, but not by much. Like I said they were always pretty close. Thanks for any info you guys can help me with.

Thanks, Ray C .

By GRoberts (***)

Date 02-19-2008 20:18

It may or may not be your issue, but one thing to watch with A500 tubing, is that it can sometimes derive some of it's strength from cold-working. Welding erases the cold work hardening in the HAZ, so the HAZ can be softer than the parent metal. The soft zone gets wider with higher heat input/lower thickness, and narrower with lower heat input/thicker sections. If heat input gets low enough, and the critical cooling rate is exceeded (martensite formed), then the weld can also have a hard zone in the HAZ right next to the weld, but it will also have the softer zone a little further away from the weld.

By Kix

Date 02-19-2008 20:46

That's why I did the hardness tests next to the weld and out at the end of the specimen to see if my procedure was getting the part to hot or not hot enough. If I was making it harder then I might of got the #'S I wanted to see like how one specimen went to 60ksi. Keep in mind that every piece of tubing was supposed to be A500 gr.-B. I almost guarantee I have a problem with purchasing. Come to find out a few minutes ago that the engineers are specking out A513 on the prints, but I don't know what type. The guy in purchasing says he is buying A500 gr.-B. I think we have a problem of well it's stronger and costs just as much and they don't have any A513 available right now so I'll by the stronger stuff for the same price without asking the engineers. So the scrap I cut the coupons out of are probably a mix of some type of A513 and maybe a section of A500 gr.-b.