Inspection of bar stock

[mshop27]

Hi All,

Sorry if this post doesn't belong in this group. I couldn't find a relatable post.

The place I work at receives in lots of round bar stock: SS, Aluminum, Brass material. We are trying to implement an incoming inspection for the raw bar stock. I know we can confirm size/length, check mill certs, and the only other thing we can try to control right now is doing a visual inspection on the raw material. My question here is what would be the key things to look for visually?.. Cracks, pitting corrosion....?

I'm not trying to make this process overly complicated. Just need accountability at receiving inspection to prevent making bad parts and having to start all over.

Any help is greatly appreciated. Thank you.

 

[eKretz]

Not much you can do other than size and certs. If there are defects, they usually aren't easily visible. Obviously you can bounce severely rusted material but you aren't likely to receive that in the first place. If the defects are internal the time in which you discover them isn't super critical. It's not like you can just slap a cold seam or a crack into a rolled bar at will. The only time that can happen is during manufacture. If you find one after delivery and acceptance a reputable supplier will make it right.

 

[Mike1974]

Also, regarding round stock... *Usually* tool steels are a bit rough'ish finish, brass should be pretty smooth and shiny, ss not sure, aluminum should have a uniform finish, similar to rectangle stock, not completely round. What I would look for if you use TGP, this should be on size, nice finish, and very uniform, like feeding thru a bushing close tolerance...

 

[DDoug]

Not much you can do other than size and certs. If there are defects, they usually aren't easily visible. Obviously you can bounce severely rusted material but you aren't likely to receive that in the first place. If the defects are internal the time in which you discover them isn't super critical. It's not like you can just slap a cold seam or a crack into a rolled bar at will. The only time that can happen is during manufacture. If you find one after delivery and acceptance a reputable supplier will make it right.

You can set up a system with waist high rails, rollers, for the ease of moving the material.
Hire inspectors, install correct lighting, use ultrasound, magna flux station, etc.

 

[eKretz]

You can set up a system with waist high rails, inspectors, correct lighting, ultrasound, etc.

Better have some of that gub'mint cheese then...

But yes, that is occasionally necessary for certain kinds of work. Not commonplace though.

 

[DDoug]

Better have some of that gub'mint cheese then...

But yes, that is occasionally necessary for certain kinds of work. Not commonplace though.

OP did not indicate qty's, tolerances, quality standards etc.
So how can YOU Assume otherwise.

There are people inspecting every day.
To the levels they need.

If your keeping 50 Swiss fed, and running lights out, you want to have good stock, and asking an incoming inspector to climb up on a stock rack
to glance at some bars is not happening.

 

[eKretz]

OP did not indicate qty's, tolerances, quality standards etc.
So how can YOU Assume otherwise.

There are people inspecting every day.
To the levels they need.

If your keeping 50 Swiss fed, and running lights out, you want to have good stock, and asking an incoming inspector to climb up on a stock rack
to glance at some bars is not happening.

I guess I can assume whatever I please. The fault with that doesn't lie with me, it is with the lack of complete information. All one can do in such a case is make guesses or assumptions. I have been in a good number of shops, and very few barring those doing aerospace work are doing anything like ultrasound testing on incoming stock. I've seen a few do magnetic particle inspection (MagnaFlux, etc.) but not very common on raw stock. And how likely exactly is it that an inspector is to do more advanced inspection but can't be bothered to take a quick initial look? I think there may be a flaw in your logic.

 

[gbent]

Depending on your quality requirements, a PMI (positive material identification) could be required. This would involve scanning the material with a device such as a Niton gun that will give an element readout to compare with the material certification.

 

[Shipp]

I work in aerospace with rocket fuel components and we don't ultrasound material, we just go off of certs. In the few extremely rare cases we find issues in our material, we never have any problem getting it replaced. Of course, that doesn't account for the time of shipping back and forth and paying for the guy to make a batch of parts only to have to scrap the whole lot due to material concerns. We keep track of which batch of material each part came from and mark it on the parts for just that eventuality.

 

[eKretz]

I work in aerospace with rocket fuel components and we don't ultrasound material, we just go off of certs. In the few extremely rare cases we find issues in our material, we never have any problem getting it replaced. Of course, that doesn't account for the time of shipping back and forth and paying for the guy to make a batch of parts only to have to scrap the whole lot due to material concerns. We keep track of which batch of material each part came from and mark it on the parts for just that eventuality.

That's exactly how I'm used to seeing it happen... Although certain suppliers will cover some lost time if you are a high volume customer and have a very good relationship, often I believe it is written into the fine print of the sales contracts that they will not bear responsibility for that.

 

[mshop27]

I guess I can assume whatever I please. The fault with that doesn't lie with me, it is with the lack of complete information. All one can do in such a case is make guesses or assumptions. I have been in a good number of shops, and very few barring those doing aerospace work are doing anything like ultrasound testing on incoming stock. I've seen a few do magnetic particle inspection (MagnaFlux, etc.) but not very common on raw stock. And how likely exactly is it that an inspector is to do more advanced inspection but can't be bothered to take a quick initial look? I think there may be a flaw in your logic.

Sorry I didn't mention, but we work to aerospace standards. We're not looking to dive deep at initial incoming (knowing most flaws happen during manufacturing), just a general idea of what can be seen straight from a visual inspection. I appreciate the help.

 

[boslab]

Visual inspection, surface and ends, things ro see, skin lamination, stop marks ( extrusion) porosity, rolled in slag, that’s about all you can do, next up metrology, diameter length, straightness, next up chemistry then mechanical testing, ether a slice on a OES spectrometer or XRF or even plasma injection spectrometers if that kind of kit is available, usually not and limited to a thermo XRF gun ( or cheap imitations!)
If your iso 9001 then punched numbers to tie to certs
If that’s what you actually say your going to do.
I don’t think ultrasound or radiographs would be feasible but I’ve been to places that do,
It can be as easy or as hard ar you want to make it, from expirence the biggest failure of goods in was right diameter wrong material, second was right material wrong diameter!,
Mark

 

[dian]

imho such inspection doesnt make much sence if the bar is going to get machined. the main thing with bar stock is how dendritic it has become in the center. either you believe the spec or you slice a piece off, grind, polish, etch, etc. optical should be enough.

 

[boslab]

If it’s a big cast billot a handy method of getting a look at dendritic and equiaxed crystal structure, 1/4 band corner cracks ( square billot) as received off a billot caster is the lowley sulphur print.
To achieve a picture of the internal solidification structure the following is very easy and reliable.
Take a slice, mill, grind ( even a saw cut works) etch with 10% nitric acid, sponge and wash bottle, sponge off the brown smut as it forms ( bath sponge is fine) after about 2-3 minutes wash and dry with an airline or hairdryer.
Soak a sheet of emulsion photographic paper ( B&W) in 10% sulphuric acid solution for 4-5 minutes
Whilst still wet, slap it on the steel or iron sample, bit of rubber mat and a weight helps, be gentle it’s a bit slick
You don’t want a double image.
Wait 5 - 7 mins, lift it off to reveal the entire structure including cracks, segregation, porosity and dendritic growth from skin to core obviously.
Manganese sulphide and such gets driven to the core of the cast product.
If you want to keep the image, wash and dump in a fix bath then dry.
The process ( used to be called the baumann process) works on any carbon steel or iron, will not work on non ferrous or ultra low carbons including IF titanium steels ( if in deed they are steel!)
IF = interstitial free btw
Mark

 

[dian]

is that regular photographic paper? surface roughness doesnt matter?

 

[jscpm]

Oh, man, I thought this thread was going to be about liquor.

 

[boslab]

Smooth finish is better obviously however a good saw cut will print, when I started doing it in the 80s we ground the sample on a vertical spindle surface grinder, it broke and we just used the milled finish, it broke then we tried the saw cut, they all worked!
Though the milled was good, I even prepped a 5m slab on a big open side planer.
The paper was old stock black and white multi grade paper, light exposed or otherwise, it’s the silver your after, they do get slimy in the acid wash and slip a bit
But being gentle and squeegee the paper down your good.
You can even shove the paper in a blender to make paper machy and slap it on funny shaped castings to see cracks, old school I know
( original ndt was kerosine and whitewash, also very effective)
Mark

 

[partsproduction]

Years ago we got some 303 round bar in that got stuck in the collet. We hammered it out backwards a bit with a copper slug and found the brights marks the collet smeared, and miked it, right on size! But I noticed the marks were at three areas 120 degrees apart, the bar was lobed from the rolling or whatever they did at the mill. The only way to tell would be a three anvil mike or a simple quick ring gage a few thousandths larger inside than nominal. Bent bars have been common and complaining begets finger pointing, supplier says the shipper, and visa versa. Crates of bars made of pine break open in shipment and scratch the heck out of the sides of bars sliding on the trucks floor.
I finally got to where I gave the vendor notice of the problems and if they continue sending us their bad bars I find another vendor.