Black Steel and Carbon Steel Terminology

[IanVG]

This is probably going to get me some links to other posts, mil-spec's and standards, but can anyone define the difference creation, use and alloy-wise between black steel and carbon steel? I've heard they are different, but as far as my understanding goes, black steel is just a kind of carbon steel that has undergone blackening. I know there are literally hundreds of different kinds of steels, but is black steel just the name for the kinds of steel pipe that have undergone blackening? I'm assuming that blackening can be/is only applied to certain kinds of steel for chemical and economic reasons. And I see that ASTM A53 refers to black steel and that ASTM 7XX (I forgot which) refers to the different ways that steel can be blackened. Are there any other "popular" or "common" standards that define black steel? Lol, random googling has got me a handful of manufacturing websites which give some pretty half-ass definitions.

 

[LittleInch]

A rose by any other name would smell as sweet...

In other words what's in a name?

"Black steel" is usually what you get if you walk into a plumbers merchants and ask for some "steel pipe"

Many times you don't really know what you're getting and as for it being made to a specification... Blank looks all round.

ASTM A53 is a recognised standard with two grades, but only rarely will you know exactly what it is you're buying. As for getting test certificates....

So use in low pressure water, gas, air, all screwed not welded connections, you're OK. Any serious piping design, welded flanges or fittings, you need something a lot better than A53.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[HVAC-Novice]

Steel is an iron-carbon alloy. So any steel contains carbon in different %. The % of carbon (and other elements like chromium), the heating/cooling process etc. determine the type of steel.

"black" is just what they call regular steel has the blackening as a protection process (in lieu of galvanizing, or making it stainless). You will have to specific a certain ASTM or other standard to know exactly what you get.

 

[IanVG]

Okay , so black steel ... is just steel that's gone through blackening (or generic term for who knows what type/quality steel!). It's interesting that you added, all screwed not welded connections, as our campus construction standards have typically specified welded schedule 40 black steel. If I wanted to be nit-picky about getting the right kind of "black steel" pipe, I guess I could call out more specifically, "schedule 40 steel (ASTM A53) that has undergone blackening (ASTM D769), i.e. black steel." I feel satisfied now that I have sufficiently over-engineered this spec.

If black steel has been included on some construction standards for many years, I'm sure at one point in time, there was someone who saw fit to differentiate between non-blackened steel (plain ol' ASTM A53 steel) and black steel (ASTM A53 + ASTM D769). Do you think that's an appropriate assumption?

 

[LittleInch]

Remove the brackets and add which grade, A or B.

Welding needs welding procedures and testing so you need to know what you're welding so that it doesn't break, crack or fail. Hence why screwing is better to avoid these issues.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[HVAC-Novice]

If you don't specify in detail and enforce the specs, you will get whatever is the cheapest or was at hand at the time. If you just specify "black", I'm sure someone will go around with black paint if you demand black steel.

 

[IanVG]

Thanks for the guidance LittleInch. I've since updated our master spec in-house with some of this information! And haha, I'm sure that happened at least once or twice before here, if I had to guess. Based on a spool piece of black steel that just arrived to our job-site (from Ukraine no less!), it looks like the ASTM A53/A53M standard is called out pretty clearly, but I don't see any mention of the blackening process standard ASTM D769. I have a feeling that the only way to verify if the steel pipe was blackened via ASTM D769 would be to reach out to the manufacturing plant of the pipe, and that sounds like way too much work for too little reward!

Oh - and it gives me great pleasure to have found all the silly emojis you can use on this forum.

 

[LittleInch]

You need to find the animated ones....



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.