FTM 179: Can the sulphur % in steel be too high?

Fastener Training Minute 179

This edition of the Fastener Training Minute with Carmen Vertullo was originally published August 18th, 2022 as “the chemical analysis requirements for SAE J429 fasteners, in particular Grade 5“, during episode 179 of Fully Threaded Radio.

Hi everyone this is Carmen Vertullo coming to you from the Fastener Training Institute and the AIM Testing Laboratory in beautiful El Cajon California.

This Fastener Training Minute, like many or most of our Fastener Training Minutes, was precipitated by a very good question from one of our clients.

And that question was regarding the chemical analysis requirements for a particular fastener, a Grade 5 Bolt from SAE J429. And there was one particular element that was causing a problem and that element was sulfur. When we return we’re going to talk about sulfur. There’s a lot to know about chemistry when it comes to steel in bolts, but in particular sulfur is one of those things that we run into problems with. When we return, I will tell you how to solve some of those problems or maybe how to avoid them and identify them. But in the meanwhile while we are on the break, if you have the ability to go and get out your IFI Fastener Standards book (inch version), and if you happen to have the latest version which is 2021 you can turn to page 241 and on that page you will see the chemical composition table for SAE J29, it’ll be helpful to have it in front of you. You don’t need it or any other version of SAE J429, but it will help.

Well, welcome back everyone this is Carmen Vertullo with your Fastener Training Minute and today we’re talking about the chemical analysis requirements for SAE J429 fasteners, in particular Grade 5 and specifically the requirement for sulfur. Now the chemistry requirements for SAE J429 are very similar to many other fasteners. Grade 5 is a heat-treated material so is Grade 8 a heat treated material. Grade 5 is typically going to be medium carbon steel and it turns out that just like many other standards, SAE J429 does not dictate a particular alloy, it simply gives us some requirements for the constituents of the various elements that are in the alloy. Now mostly it’s going to be Iron, because it’s Steel.

So this is going to be far north of ninety some percent steel, and because we’re talking about medium carbon steel here not alloy steel, it’s going to be somewhere north of 98% Iron by weight. So in this particular case it turns out that our Grade 5 material has a sulfur requirement which is actually a maximum. Usually when we see requirements where there’s a maximum it means that having too much of this product or this element will have a negative effect or a deleterious effect of some sort of the performance of the finished alloy. In this case SAE J29 requires that we have a maximum of 0.025% by weight of sulfur and that’s not very much. That’s a very small amount.

That is a similar requirement for example for phosphorus, which also can have a deleterious effect. But in some cases we intentionally add sulfur to steel because it can have a positive effect on one property which is machinability. It makes the steel or even in some cases stainless steel easy to cut and machine. But when we’re making Grade 5 bolts we’re not machining anything, that part is made by hot forming or cold forming in most cases. Almost always cold forming. But in the case I need to talk to you about it was hot formed and so we have a situation here where we don’t want the sulfur and we don’t need the sulfur, and we’re going to hold it at that maximum.

Now in this particular case a very astute end-user looked at the material test reports, the mill test reports that came with the product, and noticed that the sulfur was at 0.027%, so it was 0.002% higher than that allowed by the standard. And I can tell you right now that 0.002% would have absolutely no impact or make any difference whatsoever on the performance of this alloy. But it’s on the paper, so we have to deal with it. So, we have a couple of choices here, and it turns out that SAE J429 gives us a little bit of wiggle room, For example, what it tells us in one of the notes to Table 2, which is on the next page, probably, Note 10 says that alloy steel used to make fasteners by hot forging or machining may have a maximum content weight of 0.03% for phosphorus and a 0.04% for sulfur. So if we’re going to use alloy steel and we’re going to hot forge it or machine it, then we can bump that up. Because one of the things that too much sulfur can give us problems with is cold forming. So we’re hot forming, we’re machining, so we don’t need to worry too much about that. It turns out when I was looking at this product, it was in a weird size it was like 7/16 x 14 1/2 inches long.

And I’m thinking: it’s not very likely that this part was cold formed because a lot of cold formers can’t make a part that long, and secondly the quantity was very low only a hundred pieces, and I also knew who the manufacturer was. And it turns out they are a hot header, so I knew the part was hot-headed. Then the next question was: did they use alloy steel or not? because if they did then we’re out of jail free. In this case, it turns out they did not use alloy steel. However there is a note, Note 7 in the table that gives us a definition of what alloy steel would be for the purposes of this standard, and it’s a very complicated note. I’m going to read it to you, and you’re going to get a headache, and you are not going to understand it I am sure, unless you read it yourself, because I had to read it three or four times before I figured it out, but I finally did figure it out. I’m not going to explain it to you though because I’ll get a headache so here’s Note 7.

Welcome to the world of Fastener standards.
Note 7 says:

Alloy steel shall contain at least one of the following elements in the minimum quantity given: chromium 0.30%, nickel 0.30%, molybdenum 0.20%, Vanadium 0.10% ,manganese 1.65%, where elements are specified in combinations of two three four or five and have alloy contents less than those given above, the limit value may be applied for steel class determination is 70% of the sum of the individual limit values shown above for the two three four or five elements concerned.

OK, go get your Advil. Now, this actually is a very cool passage in that it just kind of gives you some insight into how metallurgists think, especially when it comes to things like cold forming, hot forming, and fasteners. And it’s basically just saying hey you can get away with calling an alloy steel an alloy steel when it’s not, if some combination of two or three or four or five depending on how you add them up comes to a certain amount of limit of the some of those alloys even though it’s not the amount that’s required for any given one. That’s the best way I can explain it, though there’s probably a better way. Anyway, so I’m looking at our table and I’m looking at this and we were almost there with manganese so if we would have had one of those elements above one of those amounts we could have been there, but we weren’t.

So it turns out that this was pretty close to meeting the definition of alloy steel, even though it was medium carbon steel. But not close enough. So where are we at now? Well I’m thinking I will just write an opinion that it can’t matter. But there’s also another note and this is the note that really got us out of jail free. And that’s Note 1. And it says all values are for product analysis percent by weight. For cast or heat analysis use standard permissible variations as shown in SAE J409. SAE J409 is a material standard or an analysis standard, not a fastener standard, but it allows us to fudge some elements a little bit, and sulphur is one of them. So we were able to accept this product based on the variations allowed from SAE J409. And so it was an easy to solve problem. It took a little bit of going back and forth, however what I would like to see us do is change SAE J429 to up that sulfur off of the 0.025% or simply say what the variation of SAE J09 is, so that the product can be accepted without having to dig into SAE J409. The other elements can have similar things like ” we’re just not quite there does it really matter?”

Another solution would have been: “let’s go do a subsequent chemical analysis”. Which would have required what’s called an OES or Optical Emission Spectrometer test, because sulfur is not visible in our PMI x-ray diffraction tests, so we need to put that in the OES machine. It’s a little bit more expensive and perhaps the sulfur would come in where we needed it to come in. But on the other side it could come out higher. So we don’t really know where it would be but when you’re talking about 0.025% compared 0.027%, I’m pretty sure you should do several tests and they would all be somewhere, not exactly the same, but within probably more than 0.002% for sure on that.

The lesson here is: first off, I was very impressed that the end user found that. Most people don’t really look at their Mill test reports to see that the alloy constituents comply with the standard. This end user did. And secondly: there are two or three suppliers in between. There was a manufacturer, a distributor, and an end-user. And between them and me, we were able to come to a good conclusion of this product with their help. Everyone sort of contributed a little bit of intellect to the solving of this problem. And of course we had a good end user who wanted to keep the parts in place. So that always helps as well.

Well that’s a little bit to know about sulfur. There are probably about five other elements we could give a similar Fastener Training Minute on, and whenever we have a problem with one of those, I will do that.

Thank you for listening this has been Carmen Vertullo with your Fastener Training Minute.

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