what test is there to check if steel has been normalised. 1

[SteelBloke]

I don't know if I'm been led down the garden path or not but what test's are there to see if L.C.S has been normalised or stress relieved, and where can I get info on the subject thats worthy.

any help would be appreciated.

 

[metengr]

Steelbloke;
Can you provide some additional information regarding your specific problem? This could help provide a specific answer to your question. Normalizing and stress relief are two completely different concepts.

Normalizing is a heat treatment method that involves heating carbon steel to about 1500-1600 deg F and cooling in air. A stress relief heat treatment, by comparison, involves heating the steel at lower temperature (below 1300 deg F) and also cooling in air.

The specific difference between these two methods is that normalization is a heat treatment that will affect the mechanical properties of the steel, whereas a stress relief operation typically removes residual stress induced by welding or machining operations. Stress relief will affect the hardness of the steel if it has been welded because stress relief can also be called post weld heat treatment. This is designed to reduce residual stresses and the hardness of the weld metal and the heat affected zone - stress relief temperature is normally selected so it will not affect the bulk mechanical properties of the steel. If the steel has not been welded and your objective is to remove residual stresses from machining, a stress relief operation should not result in change of hardness or mechanical properties of the steel.

 

[rnd2]

Steelbloke, you would need to take a squizz at the grain structure under a microsope.
For example I beam material will present elongated grains.
The grains would not to be elongated if the I beam was normalised. I have no idea why anyone would want to normalise an I beam.

 

[SteelBloke]

sorry for not enough info, I understand both processes as in temps, duration in furnace ect. We cold bend a few items which is allowable only if you normalise them afterwards and then other items are stress relived. My boss has said "we'll heat them for such & such and leave them in there(furnace) for an hour" which according to my knowledge that will anneal the components making them weaker, I said this to him and now he's said that the furnace only gets to about 650 C up the top of the furnace and 450 C at the bottom, which is fine for stress relief. So I got a thermal crayon which was rated 825 C and that smeared on the outside of the funace and it wasn't fully crancked up. I am now convinced that it can get to 900 C to normalise. What i'm worried about is if these items fail under pressure and lots of cash is lost we will be liable, is there a test to reveal if there was any heat treatment if any.

 

[unclesyd]

As metengr requested come back with more information especially the material in question.

 

[SteelBloke]

the steel is low carbon, 75 x 12 flat bar about 520mm long, one fold is 90 degrees and is done cold. Other material is all the same low carbon steel, 50 x 3, 50 x 8, ect.

 

[metengr]

If you are concerned about changes in tensile strength to the flat bar that was required to be stress relieved at 1202 deg F (650 deg C) versus normalized, I would perform hardness testing. Hardness testing of certain steels can provide an indirect correlation to tensile strength. Comparison of hardness data should enable you to evaluate the affects of normalizing versus lower temperature stress relief heat treatment.

Select a sample of flat bar, prior to cold bending, to obtain a baseline hardness. After cold bending, perform the stress relief at 650 deg C, and conduct hardness testing at a location adjacent to and away from the outer radius of the bend on the flat bar. Perform hardness testing at the same locations on a second flat bar after cold bending that you suspect was heated to 850 deg C to 900 deg C, and air cooled (normalized).

If a normalization heat treatment did occur it should result in uniform hardness adjacent to and away from the outer bend radius of the flat bar. The hardness of the normalized flat bar away from the bend may also be affected, which is the reason for obtaining the baseline hardness. The flat bars that were cold bent and subjected to only a lower temperature stress relief operation should see some variation in hardness along the outer bend radius.

I would strongly suggest you send out your test pieces for hardness testing to a reputable metallurgical test lab.

 

[grampi1]

Normalizing can achieve several goals
1) Grain refine, ASTM 6 or larger would be typical
2) Homogenize through the phase transformation process
3) Relieve residual stress if present
4) Improve fracture toughness

Having a fine grain size is not proof of normalizing, but having large grains is proof of not-normalizing.

Meeting impacts is much more likley if normalized, but failure to meet impacts is not proof of failing to normalize.