Rust. Is steel quality getting poorer ?
Rust. Is steel quality getting poorer ?
(OP)
Hello,
1)
As it is often the case, I am new to this "Eng-tips" forum because I have a question nobody will give me a straight answer to. Hope you guys will help.
2)
To make a long story short...
I am working for a conveyor manufacturer. To fabricate our conveyor rollers, we have been using for years ERW tubing.
In a not so distant past, we would buy this tubing in large quantities. The tubing would stay on our racks for long periods without showing real signs of corrosion. After fabrication, the rollers could be used for years before they would have to be replaced because of rust.
These days, we have to buy tubing in much smaller quantities because it will rust so fast that we don't even have the time to fabricate rollers before the raw material rust. When rollers get to our customers, rollers rust very badly within a couple of months.
3)
The most dramatic example of the above happened recently.
One of our customers asked us to lenghten an existing system. The original system is 15 years old. original rollers are still in very good condition showing little to no sign of rust.
We supplied new sections of conveyor (same specifications). Within 4 months, new rollers were all rusted and looking like crap right next to 15 years old rollers that were still looking very good!
4)
Of course, I went back to our steel supplier to find out what is going on. Nobody has clear answer to give me.
On the other end, we are hearing all kinds of rumors that China is taking over the steel industry and that the steel they provide is full of impurities (lower quality).
Is there any truth to that rumor?
Am I the only one experiencing this kind of problems?
Any explanation to suggest?
Thanks.
1)
As it is often the case, I am new to this "Eng-tips" forum because I have a question nobody will give me a straight answer to. Hope you guys will help.
2)
To make a long story short...
I am working for a conveyor manufacturer. To fabricate our conveyor rollers, we have been using for years ERW tubing.
In a not so distant past, we would buy this tubing in large quantities. The tubing would stay on our racks for long periods without showing real signs of corrosion. After fabrication, the rollers could be used for years before they would have to be replaced because of rust.
These days, we have to buy tubing in much smaller quantities because it will rust so fast that we don't even have the time to fabricate rollers before the raw material rust. When rollers get to our customers, rollers rust very badly within a couple of months.
3)
The most dramatic example of the above happened recently.
One of our customers asked us to lenghten an existing system. The original system is 15 years old. original rollers are still in very good condition showing little to no sign of rust.
We supplied new sections of conveyor (same specifications). Within 4 months, new rollers were all rusted and looking like crap right next to 15 years old rollers that were still looking very good!
4)
Of course, I went back to our steel supplier to find out what is going on. Nobody has clear answer to give me.
On the other end, we are hearing all kinds of rumors that China is taking over the steel industry and that the steel they provide is full of impurities (lower quality).
Is there any truth to that rumor?
Am I the only one experiencing this kind of problems?
Any explanation to suggest?
Thanks.





RE: Rust. Is steel quality getting poorer ?
RE: Rust. Is steel quality getting poorer ?
Have your specification requirements changed? Are you still purchasing the same grade of steel from the same supplier for this same application? What type(s) of rust preventatives are applied to the stock material when it is shipped to you? Has your supplier chosen to use a different rust preventative than was used previously? What do you require per your specification?
Maui
RE: Rust. Is steel quality getting poorer ?
I do feel the following is a plasible possibility, and perhaps an explanation, using one alloying element in a hypothetical stainless steel alloy:
- Mo is more expensive than Cr and Fe;
- An alloy has an allowable range for Mo, say 6-8%
- The allowable range was developed years ago and was based partially on the precision of metal manufacturing.
- Hence, years ago the "average" amount of Mo in this alloy was 7%
- With time manufacturing processes improve and more precision becomes practical, and the cost of allowing elements increase,
- Today, the average Mo content may be 6.2%
Any thoughts on this possibility?
RE: Rust. Is steel quality getting poorer ?
If the tubing in question is being supplied by different manufacturers, there may be a difference in surface corrosion inhibitors or lacquers etc. applied by different manufacturers, which might explain the shelf/storage performance of your material. But that wouldn't explain the performance of your finished rollers in the field- presumably these are treated the same way as always.
So if you're not getting a straight answer from us, it's that we just plain don't have sufficient evidence to make a judgment! You need to do a more detailed review of what has changed and what has absolutely remained constant to understand just exactly what is going on in this case.
RE: Rust. Is steel quality getting poorer ?
Also think about the entire system, ie. everything that touches the steel. Once dissimilar metals come into contact (even different steels) it starts to create galvonic corrosion (electrolytic cell), especially in the presence of an electrolyte. Different metals have different corrosion potential or relative positions in the galvanic series. If your current system has metals selected from further apart on the corrosion potential chart than the old system, it will corrode the high potential metal faster [(-) negative metal or anode].
In the event that you cannot determine the cause, try to add a chunk of magnesium to the steel surface and see how much difference it makes. It would become your sacrificial anode.
CODE
www.assda.asn.au/asp/index.asp?pgid=18533 corrosion chart
www.ocean.udel.edu/seagrant/publications/corrosion.html
According to the last link, you can measure the potential difference with a volt meter. If you can isolate the correct metals you can measure and compare the old to new systems. I hope this helps.
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RE: Rust. Is steel quality getting poorer ?
RE: Rust. Is steel quality getting poorer ?
You need to be treating material that you recieve with a rust inhibitor. Better yet your supplier should, but they cut that out to save money and now it is your problem.
Once there is some surface corrosion the surface is pitted. Even if you clean it off the pits will resume corroding easily.
This could be a function of inclusions in the steel, but more likely someone changed a process that effects the surface condition.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: Rust. Is steel quality getting poorer ?
Is the loss of corrosion protection also an environmental issue? It seems that years ago, we'd receive sheet/bar steel with a light oil coating as a matter of course, whereas now it comes "dry" from the supplier. Somebody told me this was an environmental issue to reduce the amount of oil dripping on the floor/ground and from there into drains.
RE: Rust. Is steel quality getting poorer ?
RE: Rust. Is steel quality getting poorer ?
1)
Wow, I am overwhelmed by how many and how good a response I am getting for my post.
2)
I am sorry I have not provided answers to your questions at this point. I have been working on other projects away from my computer.
3)
keep the good stuff coming, I should be able to answer back this afternoon.
Thanks again.
RE: Rust. Is steel quality getting poorer ?
RE: Rust. Is steel quality getting poorer ?
To be honest, I have no idea how they would know the steel would be from asia, but they want north american steel only.
RE: Rust. Is steel quality getting poorer ?
Re "Within 4 months, new rollers were all rusted and looking like crap right next to 15 years old rollers that were still looking very good!"
-- Coatings are irrelevant here since worn off during use (unless going high end, e.g., chrome plating). A different chemistry or heat treatment may cause a difference in microstructure or resdiual stress. Some pearlitic steels 'flash rust' very quickly in the presence of moisture due to galvanic corrosion of the ferrite matrix (anodic vs. carbide).
Asia produces more 'good' steel than the US. Also, more crappy stuff. The volume of imports wouldn't be so high (see 'Imports Hit Second Highest Monthly Total in U.S. History' [in July 2006] at http://www.steel.org
Problems arise when buying on the basis of price alone from bottom feeding distributors -- may sell reject material. Need a reputable supplier, and it is difficult for small buyers to know what is going on overseas.
RE: Rust. Is steel quality getting poorer ?
1)
Like I said earlier, I am overwhelmed by the number and the quality of the replies I revceived for my post. For this reason, it will be impossible for me to answer specifically to all the questions I received. Nevertheless, I see a lot of commonalities between some of your comments. I will try to answer to those.
2)
First, I guess I already have the answer to my question: "Is steel quality getting poorer?".
Although this is the feeling I am getting from comments I get from suppliers, customer, competitors, it seems it is not as generalized a problem as I would have expected.
Very few of you actually considered the GENERAL steel quality as the problem. Sure the specific quality I bought probably has something to do with my problem but it does NOT seem like this is a GENERALIZED problem.
If any one of you has comments on the GENERAL quality of steel these days, please keep comments coming.
2)
Now with the specifics of my problem
Tube is carbon steel (not stainless or fancy alloy)
When we purchase, we specify ASTM A513 type 2.
If I am not mistaking, this implies I am getting C1010 steel which is rolled into the shape of a tube using a cold rolling process.
There is no surface treatment on the tubing other than a light film of rust inhibitor when tubing is delivered to us. This films washes away very quickly once rollers are used by customer.
There is no machining done to the tube other than cut it to the proper lenght. Nothing done to the face of the tube.
3)
Before I put up my post, I was also of the opinion that the 2 better places to look were: supplier and composition of steel.
Supplier:
I am currently going through the tedious job of tracing back all the purchase orders of steel tubing for the last couple of years.
First news, suppliers vary a lot. Although it is +/- always the same 4 suppliers, we do not consitently buy from the same supplier. Purchasing criteria is usually price and availability.
According to my production people, no matter which supplier is picked or tubing size bought, they all have a rust problem. By that I mean: their tubing rusts a lot more quickly than it use to rust years ago.
Does that indicate that it is a generalized problem? Caused by the general quality of steel? or by the general change in manufacturing processes? or environmental constraints?
One thing for sure, going to cheapest bidder probably does not help our case!
Composition of steel:
I can get samples of the old and the new. I am presently in contact with a lab to get composition analysis. Furthermore, a local corrosion engineer has offered me to look at the result to help me identify what could be the cause of the problem.
4)
This is all I have to say for now. If you can comment about general quality of steel these days and/or manufacturing process changes and new environmental contraints, please do.
Thanks again,
EAllard.
RE: Rust. Is steel quality getting poorer ?
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Rust. Is steel quality getting poorer ?
Bingo - you are headed in the proper direction.
RE: Rust. Is steel quality getting poorer ?
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Rust. Is steel quality getting poorer ?
You may need to consider adding a cleaning and surface treating step to your operation, since your suppliers have dropped it from theirs.
Over all steel quality (surface finish, chemistry control, mechanical properties, corrosion resistance) is better than it ever was. It is still true that the junk is junk, but the material from the good sources has continued to benifit from tighter process controls.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: Rust. Is steel quality getting poorer ?
1)
Many of you suggested I get an analysis of both the old material and the new to highlight any potential differences.
2)
I followed this advice and I got the results.
SAMPLE A:
Carbon = 0.10%
Manganese = 0.51%
Silicon = <0.01%
Phosphorus = 0.008%
Sulphur = 0.011%
Chrominium = 0.04%
Nickel = 0.05%
Molybdenum = 0.01%
Grade: Lab says it is AISI 1010
SAMPLE B:
Carbon = 0.07%
Manganese = 0.38%
Silicon = 0.02%
Phosphorus = 0.006%
Sulphur = 0.006%
Chrominium = 0.02%
Nickel = 0.02%
Molybdenum = <0.01%
Grade: Lab says it is AISI 1006 (Supplier says 1008)
3)
Let's make this fun.
For now, I won't tell you which of the 2 samples is the old tube (not rusting) or which is the new (rusting a lot).
Let's see what you have to say.
I your opinion, which of the 2 samples should experience more corrosion if subject to the same "normal" atmospheric conditions? and why?
Would you expect the difference to as dramatic as what I have been experiencing? and why?
Thanks again.
RE: Rust. Is steel quality getting poorer ?
RE: Rust. Is steel quality getting poorer ?
RE: Rust. Is steel quality getting poorer ?
You will need to look at surface contamination and surface protection practices (phosphating, oiling, etc.).
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Rust. Is steel quality getting poorer ?
RE: Rust. Is steel quality getting poorer ?
Ask your supplier, you might be able to get steel treated for better storage life.
Otherwise you need to clean and treat the steel yourself.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: Rust. Is steel quality getting poorer ?
Now, as to why the new one looks rustier than the old in service, I would think there might indeed be a reason(s) for this, but I don’t know what it is/they are. You mentioned that the rollers were somehow “washed”. Is the tubing by any chance in electrical contact with another material, e.g. some sort of steel trunnions or inner bearing rods etc. and exposed in some sort of manner to a fluid or moisture that might be acting as a corrosion agent or electrolyte? I would e.g. expect a carbon steel with even a little less intentional or unintentional “alloying” (of nickel, copper, chrome etc.) to be some “anodic”, and perhaps corrode at least a little more relative to another that is more cathodic (with even a little more of such alloying) steel, if immersed in an electrolyte etc. as in a galvanic cell. Though I personally would not have expected such very minor chemistry variations like you show here to cause much current flow, I think various tests can nevertheless be run to diagnose such relationships/tendencies.
In any case, you or your customer might eventually have to bite the bullet and go to some sort of special surface treatment or maybe even some special alloy steel material (of course probably at a little more initial material cost) to get a more consistent appearance (particularly if the “looking like crap” represents something more than an aesthetic problem in the application!)
RE: Rust. Is steel quality getting poorer ?
In what we buy we see a great number of suppliers who are meeting specifications as written but who are running around the non-written parts to cut costs. More and more we are writing specifications for ourselves and our customers defining the specifications in terms of composition, manufacture and use.
Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com
RE: Rust. Is steel quality getting poorer ?
With regard to the prior/good comments of kenvlach, it certainly might not be a bad idea to look at (have a detailed "microstructure examination" as well performed?) on samples of the two materials.
RE: Rust. Is steel quality getting poorer ?
Maui
RE: Rust. Is steel quality getting poorer ?
1)
I am sorry I have been away from this thread for so long and left you hanging with my "teaser".
Here is the answer to the question you have been waiting for...
Sample A is the "old" material. The one that shows much better resistance to corrosion.
Sample B is the "new" material. The one that is causing me a lot of trouble.
2)
The general concensus seem to be that the difference in steel composition is so small that it probably cannot justify such a difference in corrosion behavior. I have to look somewhere else.
3)
I think a lot of you have hit the nail right on the head. My main purchasing criteria being "price" I open myself to all those suppliers who are ready to cut corners to lower their prices. I could try to force them into a very precise specification but my purchasing volume being relatively low (not high volume), I probably would end up paying an arm and a leg, get forced into buying greater quantities with longer deliveries...not a very good deal.
4)
Conclusion (because at one point we have to draw conclusion):
In those applications where looks are not important, we are going to use the tube we have on hand and alert the customer to the possibility that roller tube may rust without affecting the functionnality of the roller.
In those applications where looks are important, we will propose that tube be electro-galvanized.
For future purchase of tubing, we will strongly consider the purchase of pre-galvanized (mill galvanized) tubing. Sure it will cost more but it is going to insure a quality product to our customer and eliminate a lot of aggravation with manufacturing and engineering (me).
5)
I won't be able thank to you enough for all the valuable input everybody put in my basic question. Thank you all.