Thread: Soft Aluminium Alloy

I just hit it with a hammer. Makes a different sound if its soft. Bush mechanics trick.

Cheers Rod

Originally Posted by loanrangie

Yes tested in front of me, brinell scale I think around 95 and tested in 3 places.

That`s part of what i don`t get with the tests 3 places doesn`t seem enough .

The link Tombie gave also says 3 places and they then use the average .

Places that only test metals give minimum spacings for the testing which maybe 2mm or 5 mm or 10mm they also say they discount the highest and lowest and then average the rest to get the number .

They`re not talking about cylinder heads but do mention blocks .

Originally Posted by 67hardtop

I just hit it with a hammer. Makes a different sound if its soft. Bush mechanics trick.

Cheers Rod

That i have heard of and done for a crack but it`s still guesstimation .

What do you gauge it against ?

The casting gives different thickness , does that affect the ping from the hammer and is it a ping ?

Do you think a tuning fork could give a similar out come ?

My hearing is such that i don `t have the luxury of doing these types of things .

I actually just tried it with a small peen hammer and a V8 cylinder head that has been bashed by a loose liner so can`t be damaged much more by marks .

I can`t discern the noises well enough to be any value .

You have to hold the head in ur hand (lets not be naughty) and let it sorta hang down. Tap it with a hammer and if it sorta rings then its ok but if it just thunks then its soft. Harder heads bounce the hammer back and soft heads absorb the blow sorta thing.

Cheers Rod

Might be talking out of school, but I don't think that a small number of non-destructive tests on a cylinder head would be that big a concern? Like half a dozen 0.5mm2 indents from a rockwell test or similar.... as long as it's not peppered 300 times.

As for averaging the measurements, yes taking outliers out of any measurement is a good idea, as long as you can justify that they are not valid test results! Furthermore, an average is only as good as the sample size and the accuracy of the measurement tool. Which sort of works against my first paragraph... but anyway...
If you were to observe uniform hardness on any material, you'd think it would follow a normal distribution. But reality is that heat cycles and casting imperfections and all that other funky metallurgy stuff might give other results. And with that, the devil is in the detail.
I've contradicted myself 3 times in the paragraphs above, but as they say, there are lies, damn lies, and statistics.

Originally Posted by Toxic_Avenger

Might be talking out of school, but I don't think that a small number of non-destructive tests on a cylinder head would be that big a concern? Like half a dozen 0.5mm2 indents from a rockwell test or similar.... as long as it's not peppered 300 times.

As for averaging the measurements, yes taking outliers out of any measurement is a good idea, as long as you can justify that they are not valid test results! Furthermore, an average is only as good as the sample size and the accuracy of the measurement tool. Which sort of works against my first paragraph... but anyway...
If you were to observe uniform hardness on any material, you'd think it would follow a normal distribution. But reality is that heat cycles and casting imperfections and all that other funky metallurgy stuff might give other results. And with that, the devil is in the detail.
I've contradicted myself 3 times in the paragraphs above, but as they say, there are lies, damn lies, and statistics.

I think approx 99.9% of this place fits the talking out of school phrase so there`s no concern that i see and i know very little about this subject .

I agree that on a cylinder head face in certain places it would be of no concern with the slight indents and have always been of the thinking the gaskets are there for a reason .

The places that need testing in my opinion are where the fire ring is positioned and near to where the bolts pass through as well as where the linked coolant passages are because these are places that don`t want to be softer .

Where the bolts pass wouldn`t be of concern and possibly the coolant but i wouldn`t want pock marks near where the combustion happens because even a small mark can grow .

Deciding that it is the norm for places that check heads for softness and only doing 3 test spots will need some more searching . It is hard on the net to find much detail on cylinder head testing , there is plenty of basic stuff but little detail .

There is information on aluminium cast testing in general but even some of that is obviously from the same source , even retailers of the test machines will have information from the same source at times .

With as you say the variables in casting etc and so few test positions if it is the norm it is very hard to accept that there is much point in even doing it or taking note of the test outcome .

I appreciate you words .

Maybe off topic, but even if you get a whole bunch of accurate hardness test data - what next?
Does one soft reading around a fire ring mean a scrapped head? What even IS considered soft.
My thought has always been that the tests are an indication of general condition - ie obvious if it's soft, but from there it's more a judgement call based on application and cost. Unless cost isn't a concern, it's likely the same call would be made on a lesser result set.

Steve

Originally Posted by steveG

Maybe off topic, but even if you get a whole bunch of accurate hardness test data - what next?
Does one soft reading around a fire ring mean a scrapped head? What even IS considered soft.
My thought has always been that the tests are an indication of general condition - ie obvious if it's soft, but from there it's more a judgement call based on application and cost. Unless cost isn't a concern, it's likely the same call would be made on a lesser result set.

Steve

Don`t know who decides what`s off topic but i would think as a thread evolves so does the topic . The heading says Soft Aluminium Alloy the first question is about testers , which gives the greater direction .

I`m guessing your questions are mostly rhetorical and if so i can understand what your getting at .

As i understand the explanation , aluminium alloy uses an accepted/agreed scale mostly relating to or transferred to the brinell scale . I bit like i find sometimes i need to use imperial to picture or relate a length .

A reading under 65 HB or BHN or HBN and probably others depends who`s doing the talking is considered too soft for use in an aluminium alloy cylinder head as i understand it has little to do with the alloy make up , if that number is achieved it is considered soft .

A reading of 85 brinell is as far as i have read considered a number which says the aluminum alloy is hardened .

Pure aluminium is 15 brinell , i`ve read .

As i understand once soft the alloy can`t by itself return to its harder state but can get softer .

As i understand the general running temp of engines now is given as in the paddock of 100 C , twice that and the alloy will be near its brink of softness , thrice and it is well on the way of being unusable . The reading i`ve done sort of indicates that up to 250 C there is still hope for alloy but not specifically cylinder heads .

Does anyone know the temperatures reached when an engine is overheated as in looses its coolant and is still run , i don`t mean till it stops but when the driver is aware of and pulls up at the time when the softening of the heads is said to occur ?

I understand its relative so any general type temperatures , i can`t find any .

I know sensors don`t read steam and when the gauge drops back down that is the reason .

Edit ... yes , your right it should be sender not sensor .