AISI 4130 heat treatment 2

[Ryan Weng]

At first, please forgive my English ability. This is the first time for me to post an English article on a forum. I hope it would not be an issue for you who wants to help me figure this out.

My company manufactures tubes/pipes by centrifugal casting. Recently we've received an order its main request is hardness:HB 240-320(HRC:23-34). The difficult part for us now is we are not sure about the heat treatment conditions, and there is no specific and clear procedure in the customer specification. Before the delivery, we will have the material rough machined. So the idea now is:casting->normalization(HRC:15-20) or annealing(HRC:5-10) -> rough machined -> quenching(easier to control the hardness) or tempering.(I learned this information from a heat treatment company)

Anyone can give some advice on this issue? Thanks!

 

[metengr]

What is the thickness of the centrifugally cast pipe?

 

[RyanWengTW]

The wall thickness would be 35mm. Thank you for the mention.

 

[metengr]

I would normalize (1625 deg F for 1 hr), rough machine, normalize followed by a water quench and temper
(1080-1100 deg F for 1 hr).

 

[arunmrao]

Agree with metengr's recommendation. Careful during heat treatment, to avoid any distortion of pipe.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[RyanWengTW]

Yeah, I've read metengr's recommendation. I'll let my boss and the consultant know maybe we have a better way to deal with it. Really appreciate!

 

[RyanWengTW]

oh! So the whole procedure will be: normalization > rough machining> water quenching and tempering > normalization ?
Just want to make sure I'm not misunderstanding your suggestion.

 

[metengr]

No. Normalize -> rough machine -> re-normalize -> quench -> temper. Double normalization is common for 4130 steels.

 

[Ryan Weng]

Ohohohohoh, I got it , thank you. I misread it.

 

[redpicker]

Do you have any idea how your customer is going to use the material? That is, are they planning on performing additional machining and heat treatment? The specification you gave in your OP suggests they probably will. This is because 23-34 is a very wide hardness range to insure mechanical properties, but quite reasonable for machining purposes. Also, what kind of machining tolerances do you have to meet?

If your customer is going to perform additional heat treatment and your tolerances are wide, I would recommend to just Normalize (1700F/930C) for 1-2 hours, air cool, then temper at 1050F/560C for 2-4 hours and air cool, then rough machine. Simpler, cheaper, and should meet your requirements.

On the other hand, if you need to meet specific tensile and impact strength requirements, then the process recommended by metengr is better suited (although I would still normalize at 1700F/930C since you are dealing with an as-cast structure.

If you are going to quench the material, be sure you quench it with the axis in a vertical position.

 

[WKTaylor]

Following SAE AMS specs could be helpful for general/added guidance and info [including secondary info/specs imbedded within these basic documents]...

AMS5336 Steel, Investment Castings 0.95Cr - 0.20Mo (0.25 - 0.35C) (4130 Mod) Normalized or Normalized and Tempered

AMS2759/1 Heat Treatment of Carbon and Low-Alloy Steel Parts Minimum Tensile Strength Below 220 ksi (1517 MPa)

AMS-H-6875 Heat Treatment of Steel Raw Materials

Regards, Wil Taylor

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