Heat Treating 4130 1

[Veranium]

Hello,

I am trying to meet these properties below but for some reason after performing the Heat treatment listed below, I got different results. Part is 6.6" thick. I cannot give anymore than that sorry.

UTS(Ksi)
min: 95
Max 115
Yield(.2 Offset/Ksi)
min: 80
Max: none listed
Elong(2")
Min: 20
max: none listed
RA(%)
min:45
Max: none listed
Hardness
HRC
Min: none listed
Max: 22
HBN
Min: none listed
Max: 237

Heat treatment use:
Normalize: 1650F 4hrs Min. Air cool
Austenitize: 1600F 4hrs Min. Water Quench 10min
Temper: 1225F 7hrs Min. Air cool

Results
TS: 97
Yield: 72
Elong: 25
RA: 71
HBN: 217 Avg, Hi: 229

 

[EdStainless]

Did you check the hardness as-quenched?
There are tables to use to adjust temper temperature based on the AQ hardness.
Sounds like you need to use 1175F, or something like that.
Your core properties will be lower, that is getting fairly thick for 4130.

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P.E. Metallurgy, consulting work welcomed

 

[Veranium]

No I have not checked the as quench hardness.

I set up a trial for both 1150F and 1200F. I will bring the 1150F to 1175 if it does not meet requirements.

Thank you

 

[MagBen]

you are failing only YS by a few points. Decreasing temper temp sounds a right direction, but i am afraid 1150F mgiht be too low over-shooting, failing max hardness and min EL.

if you are certifying a spec, and the spec. allows you to increase strain rate. simply using max allowed strain rate could boost your TS and YS without sacrificing too much of EL.

 

[bobjustbob]

As others have said, you will need to decrease your temper temperature. However, I don't know that I would have accepted a specification with those tensile requirements with a max hardness of 237HB. To get that 80ksi minimum yield strength, you are going to be at the top of your hardness specification. For that yield strength, our target hardness was usually 217-255 HB.

Bob

 

[EdStainless]

Ben, this is why AMS has required strain rates.
And why we threw a fit when ASTM removed them.


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P.E. Metallurgy, consulting work welcomed

 

[Veranium]

Normalize
Set point: 1700F
Min: 7 hours
Quench: Air Cool

Austenitize
Setpoint: 1650F
Min: 7 hours
Quench: Water cool, 10mins

Temper
SetPoint: 1225F
Min 2:30hrs
Quench: AIR

Here's my test. Do you guys believe I can get good properties?

Also an update

I created 2 batches and retempered them at 1175F and 1200F both came out great but now I am wondering if I can do better. 1200F gave me the highest but the range was 217-235 while 1175 gave me a consistent 229BHN.

Now I need to get them tested but I am already wondering what If I shorten the temper but elongate the Normalization and Austenitization timeframe? I want consistency overall and the best properties. As we all do.

 

[EdStainless]

The thing that I worry about the most is the quench.
On a 6.5" thick part that will take a highly agitated cold bath to assure cooling rates.
And as always with these alloys surface decarb damage is a issue to watch.
If the temper temp is correct then you should be able to make it longer by 50% without changing the properties.
You never want the temper to be time dependent.
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P.E. Metallurgy, consulting work welcomed