"Mystery" A36 plate...

[hankj]

Last trip to the steel store, I picked up a 100# hunk of 3/8" plate scrap just to have some around. The first O/A cut I made on it was kinda ragged. I chalked it up to the fact that I hadn't cut any thicker stuff for a while, so I was probably just rusty. Two weeks ago, I cut off another slice, and had the same trouble! The grinder took care of it, but I was feeling sorta confused, 'cause I know I cut better than that!

Yesterday, the Polish fella who is my neighbor came up with a hunk of 1/2" he wanted me to make into two pieces for him. Not without a little trepidation, I fired up the torch, and cut it slick as a whistle!

Coincidentially, I had to move the hunk of 3/8" off it's resting place so I could paint some door runners. When I stood it up, there was a bunch of stenciling on the side I had facing down. It had a heat # and a batch #, A-36, MADE IN THAILAND!

Wonder what the **** they think constitutes A36? This stuff cuts like it's closer to stainless! Anyone else had this kind of experience?

Hank

[TJJ]

Hank

Sounds like a piece of low alloy plate.

Now you have an excuse to get that Spectrum 625.



Tom

[hankj]

Tom,

Yeah, it CUTS like it is! BUT it is CLEARLY marked "A36"!

I'll use it up pretty soon, and I intend to play with some different settings on the O/A just for drill, and maybe I'll jump up to a #1 tip 'n see what happens. All I know is it sure don't CUT like A36!

Hank

[TJJ]

Yea I know it's marked A-36. But remember, that mark was put on by someone with a spray can and stencil......that probably no speaka d englese.


Tom

[Zrexxer]

A36 doesn't tell you what the actual properties of the plate are, only that it meets the minimum standards set by ASTM for that particular grade. The actual strength and/or alloy composition could be quite different.

[TOMWELDS]

In other words Hank, time to break out the "argoff"....

[Hotfoot]

Perhaps he could determine its makeup with a Dilmer Soddik edge blow tester. I might have one out in the shop I can snap a picture of tomorrow...seems like I saw it over by where I store my Blasto Rods.

[hankj]

Yeah, I'll bet it ain't no 1010! It has a funky mill scale, too - almost red. Looks like the old "red lead" paint, and it doesn't come off easily with the grinder. Do you suppose it could have some nickel in it? A 23xx steel? I don't have any way of testing it, but the sparks look just like mild steel to me!


Hank

[JTMcCracken]

A36 doesn't tell you what the actual properties of the plate are, only that it meets the minimum standards set by ASTM for that particular grade. The actual strength and/or alloy composition could be quite different.

A36 does specify chemical and mechanical properties.

JTMcC.

[aametalmaster]

Yeah, I'll bet it ain't no 1010! It has a funky mill scale, too - almost red.


Hank

We used that same description plate at work we called it AR plate. It was a deep red color also. I welded it with a submurged arc welder, then i had to turn it in a lathe. Thats where i found it to be different than regular carbon steel. It left a shiny smooth finish like stainless vrs a dull rougher finish from reg plate. I can't say about burning it as it was cut with a cnc torch but the guy cutting it never said anything different. I also have some of it in my shop for projects and it turns the same way, shiny...Bob

[Zrexxer]

A36 does specify chemical and mechanical properties.

JTMcC.

It specifies minimums, if I'm not mistaken. The material can exceed those standards. For example, "A36" indicates a 36 ksi yield strength at face value, but the average yield strength of most A36 steel these days is about 48 ksi, with an ultimate strength of about 70 ksi.

At any rate I'm not going to belabor the point, because I know you've seen a copy of the ASTM standards a lot more recently than I have, it's been 20 years for me.

[JTMcCracken]

It specifies minimums, if I'm not mistaken. The material can exceed those standards. For example, "A36" indicates a 36 ksi yield strength at face value, but the average yield strength of most A36 steel these days is about 48 ksi, with an ultimate strength of about 70 ksi.

At any rate I'm not going to belabor the point, because I know you've seen a copy of the ASTM standards a lot more recently than I have, it's been 20 years for me.

All mechanical specs call for a minimum, some call for a maximum. The minimums are whats used for design purpose. There isn't any metal that's spec'ed to a specific set of mechanicals, they all come in a range. That's why we have to furnish Material Test Reports, they show the chemical and mechanical properties for a particular heat of metal.
A36 is quickly becoming obsolete. Since the 80's almost all A36 has in reality been 50 ksi material. Now whats called A36 is usually a dual grade or more, meaning the material meets the spec for grade 50 and A36 and sometimes one or two more specs.
A36 (or any of the other structural specs) does indeed tell you what the properties of the material are, that's the only reason the standards exist.

JTMcC.

[hankj]

Well, thanks for the disussion, guys. I'll just have to deal with it the best I can. Mr. 7" Grinder fixes my boo-boos, so I guess I'm OK!


Hank

[TOMWELDS]

Hank, ive been noticing some of these strange metals myself. I had some a while back that would leave a thin green line next to the weld. Ive had some cut easier than others. Who know's where the stuff comes from...LOL

[OldSparks]

hankj

Heavy mill scale and natural reddish colouring would lead me to think corten steel. I think it has copper and other alloys added to it to slow down oxidation...possibly you have a high enough content to cause weird burning. If you suspect AR plate you might want to do a weld and hammer test. Weld a small piece of 3/8" mild steel scrap along one edge...heavy fillet approx. 2" long...with 1/8" 7018. Let cool and then beat over towards weld to see how it breaks. You know that normal mild to mild should take several back and forth hits before the weld lets go. Some AR plates will break right away by simply tearing a chunk out of the plate. Not very scientific but may be good to know when you put this piece of plate to use.