O.K., I have received a second sample. Like the first, I won't reveal the welder user name unless he wants to identify himself. However, I would like to apologize to him because I have had this sample for some time and it has taken a while for me to get around to looking at it. Furthermore, the quality of the images is not great but I have been short on time to rework them.

The sample and joint configuration is almost identical to the first sample examined except this sample was gas tungsten arc welded (TIG) The joint type consisted of a a notched tube to tube T type assembly which utilizes a fillet type weld joint. The material is 1 ½" O.D. ERW (seam welded) carbon steel tubing. The welder believed it was 1020 carbon steel and from the hardness it is close. The welder thought the filler metal was ER70S.

First, a visual inspection was performed on the as received sample using the unaided eye and a low magnification stereomicroscope at approximately 10 X. Photos are attached that show the typical features of the joint assembly and weld features.

The general appearance of the weld lacked the uniformity of many TIG welds when performed by experienced welders. However, the weld appeared suitable for its intended application. Some weld spatter and possible tungsten inclusions were noted on the surface of the weld face. Splatter is usually an outgassing reaction from contamination and/or insufficient shielding gas. The tungsten inclusions occur when the electrode makes contact with the weld pool. Determination as to whether these indications are tungsten requires either an x-ray inspection or cross sectioning through the actual indication and examining microscopically (usually this is a random occurrence).

One other potential issue noted by the visual examine was evidence of slight undercut. Undercut is the localized melting of the adjacent base material (usually at the toe of the weld) which reduces the overall thickness of the base material member (in this case, wall thickness). Most specifications due make allowance for this condition if not excessive. Typically no more than 10% of the total base material member thickness is allowed.

Like the first sample, two cross sections were taken from the joint. One to show a perpendicular type joint and one to show tapered fillet type joint (90 degrees to the first). The sections were each metallographically prepared by mounting, polishing and etching. The samples were then examined using a metallograph.

Both samples exhibited complete joint penetration and fusion at the root. Thinner base materials often result in incomplete root penetration, however, this sample shows good fusion-not only in the root but in the leg size (length of fusion) in both the horizontal and vertical members. This fusion can be attributed to a high level of heat input. Although the heat imput provides good fusion characteristics it can compromise the joint integrity in other ways as evident by both slight undercut and fusion at the opposite side of the weld. In both instances observed, the extent of the condition noted is negligible and would typically be within spec limits. Fusion at the opposing size of the base material is usually not critical in this type of application. It becomes more of an issue when welding tubing for flow applications (ie, head pipes, etc.). Fusion like this not only restricts airflow by reducing the diameter, but often results in diversion of the airflow direction which can really compromise efficiency.

The internal quality of the weld looks very good in that there are no cracks, hot tears, cold shuts, voids, porosity or present. None of the suspect tungsten inclusions were observed in the cross section so this condition is non-conclusive from this examination.

A microhardness survey was performed to show the typical hardness variations in the base material, heat affected zone and weld filler metal. I also indicated the approximate tensile strength of these zones based on the hardness readings. For this particular sample the heat affected zone was the softest region in the weld joint (on alloy steels it is often the hardest, requiring annealing or the need for a structural stress relief).

In conclusion, other than cosmetic appearance, the weld appears sound in processing, exhibiting good penetration/fusion and being free from defects or conditions determined to be detrimental to weld performance. As with most things in life, experience will lend it self to improving the overall appearance, but from a structural standpoint the weld looks good.

So far we have looked at both MIG and TIG type welds in carbon steel. I would be happy to evaluate another sample but would like to find a TIG weld using 4130 (chrome-moly) for comparison. This is where the microstructure of the weld and heat affected zone is more critical in the quality of the weld.


'Bob

Someones been practicing. Reveal to us the masked man!!!

Ok, I admit it,..it wasn't me...

<----not me

C'mon Yosh, I knew those were not YOUR welds!!

Just razzin ya!

King?

Thats awesome

Very cool, congrats to the welder and thanks for your time in examining the samples.

Can you test any welds on anything? I sure would like to see all of the builders step up to this test on something that already done. I am sure half of them would fail, but that just my opinion............

What do we have to do to get a weld looked at? I had to cut several tudes out of the chassis I am building and I would like to know the quality of the welding.

What does it mean when you have a small amount of fluid comeing from the weld?

Yah,
But how often does a weld fail on a sandcar chassis?

words.....words...
words....words...
uh more words... words..

so, is it good or not?






just giving you crap for the long but educational post.

im sure that weld would be strong enough for 90% of the sand cars out there.

For those who got the MEGO effect. before the end:

Great analysis, good weld!








If he ever posts pics of 2 pieces of mild steel held together by Bubble Yum, we'll know that's Yoshi's sample.

What would be different to address the remaining 10% of the cars? Is your comment related to something about the weld itself or related to the noted approximate tensile strengths of the base material and weld area?

Yeah, but it'd be artistic Bubble Yum!!! And then we'd see 45 pictures of it!!!

He'd start a project log about it and post daily updates.